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  Subjects -> CHEMISTRY (Total: 845 journals)
    - ANALYTICAL CHEMISTRY (51 journals)
    - CHEMISTRY (595 journals)
    - CRYSTALLOGRAPHY (21 journals)
    - ELECTROCHEMISTRY (25 journals)
    - INORGANIC CHEMISTRY (41 journals)
    - ORGANIC CHEMISTRY (45 journals)
    - PHYSICAL CHEMISTRY (67 journals)

CHEMISTRY (595 journals)                  1 2 3 | Last

Showing 1 - 200 of 735 Journals sorted alphabetically
2D Materials     Hybrid Journal   (Followers: 8)
Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement     Hybrid Journal   (Followers: 26)
ACS Catalysis     Full-text available via subscription   (Followers: 34)
ACS Chemical Neuroscience     Full-text available via subscription   (Followers: 18)
ACS Combinatorial Science     Full-text available via subscription   (Followers: 23)
ACS Macro Letters     Full-text available via subscription   (Followers: 24)
ACS Medicinal Chemistry Letters     Full-text available via subscription   (Followers: 39)
ACS Nano     Full-text available via subscription   (Followers: 248)
ACS Photonics     Full-text available via subscription   (Followers: 11)
ACS Synthetic Biology     Full-text available via subscription   (Followers: 21)
Acta Chemica Iasi     Open Access   (Followers: 2)
Acta Chimica Sinica     Full-text available via subscription   (Followers: 1)
Acta Chimica Slovaca     Open Access   (Followers: 1)
Acta Chromatographica     Full-text available via subscription   (Followers: 9)
Acta Facultatis Medicae Naissensis     Open Access  
Acta Metallurgica Sinica (English Letters)     Hybrid Journal   (Followers: 5)
Acta Scientifica Naturalis     Open Access   (Followers: 2)
adhäsion KLEBEN & DICHTEN     Hybrid Journal   (Followers: 5)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 8)
Adsorption Science & Technology     Full-text available via subscription   (Followers: 5)
Advanced Functional Materials     Hybrid Journal   (Followers: 51)
Advanced Science Focus     Free   (Followers: 3)
Advances in Chemical Engineering and Science     Open Access   (Followers: 56)
Advances in Chemical Science     Open Access   (Followers: 13)
Advances in Chemistry     Open Access   (Followers: 15)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 18)
Advances in Drug Research     Full-text available via subscription   (Followers: 22)
Advances in Enzyme Research     Open Access   (Followers: 9)
Advances in Fluorine Science     Full-text available via subscription   (Followers: 8)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 16)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 9)
Advances in Materials Physics and Chemistry     Open Access   (Followers: 21)
Advances in Nanoparticles     Open Access   (Followers: 15)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 15)
Advances in Polymer Science     Hybrid Journal   (Followers: 41)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 17)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 20)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 5)
Advances in Science and Technology     Full-text available via subscription   (Followers: 12)
African Journal of Bacteriology Research     Open Access  
African Journal of Chemical Education     Open Access   (Followers: 2)
African Journal of Pure and Applied Chemistry     Open Access   (Followers: 7)
Agrokémia és Talajtan     Full-text available via subscription   (Followers: 2)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 3)
AMB Express     Open Access   (Followers: 1)
Ambix     Hybrid Journal   (Followers: 3)
American Journal of Biochemistry and Biotechnology     Open Access   (Followers: 67)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 14)
American Journal of Chemistry     Open Access   (Followers: 27)
American Journal of Plant Physiology     Open Access   (Followers: 14)
American Mineralogist     Hybrid Journal   (Followers: 14)
Analyst     Full-text available via subscription   (Followers: 40)
Angewandte Chemie     Hybrid Journal   (Followers: 194)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 221)
Annales UMCS, Chemia     Open Access   (Followers: 1)
Annals of Clinical Chemistry and Laboratory Medicine     Open Access   (Followers: 4)
Annual Reports in Computational Chemistry     Full-text available via subscription   (Followers: 3)
Annual Reports Section A (Inorganic Chemistry)     Full-text available via subscription   (Followers: 4)
Annual Reports Section B (Organic Chemistry)     Full-text available via subscription   (Followers: 8)
Annual Review of Chemical and Biomolecular Engineering     Full-text available via subscription   (Followers: 12)
Annual Review of Food Science and Technology     Full-text available via subscription   (Followers: 15)
Anti-Infective Agents     Hybrid Journal   (Followers: 3)
Antiviral Chemistry and Chemotherapy     Hybrid Journal  
Applied Organometallic Chemistry     Hybrid Journal   (Followers: 7)
Applied Spectroscopy     Full-text available via subscription   (Followers: 23)
Applied Surface Science     Hybrid Journal   (Followers: 28)
Arabian Journal of Chemistry     Open Access   (Followers: 6)
ARKIVOC     Open Access   (Followers: 2)
Asian Journal of Biochemistry     Open Access   (Followers: 1)
Atomization and Sprays     Full-text available via subscription   (Followers: 4)
Australian Journal of Chemistry     Hybrid Journal   (Followers: 7)
Autophagy     Hybrid Journal   (Followers: 2)
Avances en Quimica     Open Access   (Followers: 1)
Biochemical Pharmacology     Hybrid Journal   (Followers: 10)
Biochemistry     Full-text available via subscription   (Followers: 309)
Biochemistry Insights     Open Access   (Followers: 6)
Biochemistry Research International     Open Access   (Followers: 6)
BioChip Journal     Hybrid Journal  
Bioinorganic Chemistry and Applications     Open Access   (Followers: 9)
Bioinspired Materials     Open Access   (Followers: 5)
Biointerface Research in Applied Chemistry     Open Access   (Followers: 2)
Biointerphases     Open Access   (Followers: 1)
Biology, Medicine, & Natural Product Chemistry     Open Access   (Followers: 1)
Biomacromolecules     Full-text available via subscription   (Followers: 19)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 10)
Biomedical Chromatography     Hybrid Journal   (Followers: 6)
Biomolecular NMR Assignments     Hybrid Journal   (Followers: 3)
BioNanoScience     Partially Free   (Followers: 5)
Bioorganic & Medicinal Chemistry     Hybrid Journal   (Followers: 119)
Bioorganic & Medicinal Chemistry Letters     Hybrid Journal   (Followers: 91)
Bioorganic Chemistry     Hybrid Journal   (Followers: 10)
Biopolymers     Hybrid Journal   (Followers: 18)
Biosensors     Open Access   (Followers: 2)
Biotechnic and Histochemistry     Hybrid Journal   (Followers: 1)
Bitácora Digital     Open Access  
Boletin de la Sociedad Chilena de Quimica     Open Access  
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 2)
Bulletin of the Chemical Society of Japan     Full-text available via subscription   (Followers: 24)
Bulletin of the Korean Chemical Society     Hybrid Journal   (Followers: 1)
C - Journal of Carbon Research     Open Access   (Followers: 3)
Cakra Kimia (Indonesian E-Journal of Applied Chemistry)     Open Access  
Canadian Association of Radiologists Journal     Full-text available via subscription   (Followers: 3)
Canadian Journal of Chemistry     Hybrid Journal   (Followers: 10)
Canadian Mineralogist     Full-text available via subscription   (Followers: 4)
Carbohydrate Research     Hybrid Journal   (Followers: 26)
Carbon     Hybrid Journal   (Followers: 66)
Catalysis for Sustainable Energy     Open Access   (Followers: 7)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 8)
Catalysis Science and Technology     Free   (Followers: 7)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 3)
Catalysts     Open Access   (Followers: 8)
Cellulose     Hybrid Journal   (Followers: 7)
Cereal Chemistry     Full-text available via subscription   (Followers: 4)
ChemBioEng Reviews     Full-text available via subscription   (Followers: 1)
ChemCatChem     Hybrid Journal   (Followers: 8)
Chemical and Engineering News     Free   (Followers: 14)
Chemical Bulletin of Kazakh National University     Open Access  
Chemical Communications     Full-text available via subscription   (Followers: 72)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 24)
Chemical Research in Chinese Universities     Hybrid Journal   (Followers: 3)
Chemical Research in Toxicology     Full-text available via subscription   (Followers: 20)
Chemical Reviews     Full-text available via subscription   (Followers: 181)
Chemical Science     Open Access   (Followers: 22)
Chemical Technology     Open Access   (Followers: 16)
Chemical Vapor Deposition     Hybrid Journal   (Followers: 5)
Chemical Week     Full-text available via subscription   (Followers: 8)
Chemie in Unserer Zeit     Hybrid Journal   (Followers: 58)
Chemie-Ingenieur-Technik (Cit)     Hybrid Journal   (Followers: 26)
ChemInform     Hybrid Journal   (Followers: 8)
Chemistry & Biodiversity     Hybrid Journal   (Followers: 6)
Chemistry & Biology     Full-text available via subscription   (Followers: 30)
Chemistry & Industry     Hybrid Journal   (Followers: 5)
Chemistry - A European Journal     Hybrid Journal   (Followers: 149)
Chemistry - An Asian Journal     Hybrid Journal   (Followers: 15)
Chemistry and Materials Research     Open Access   (Followers: 20)
Chemistry Central Journal     Open Access   (Followers: 4)
Chemistry Education Research and Practice     Free   (Followers: 5)
Chemistry in Education     Open Access   (Followers: 9)
Chemistry International     Hybrid Journal   (Followers: 2)
Chemistry Letters     Full-text available via subscription   (Followers: 44)
Chemistry of Materials     Full-text available via subscription   (Followers: 253)
Chemistry of Natural Compounds     Hybrid Journal   (Followers: 9)
Chemistry World     Full-text available via subscription   (Followers: 22)
Chemistry-Didactics-Ecology-Metrology     Open Access   (Followers: 1)
ChemistryOpen     Open Access   (Followers: 2)
Chemkon - Chemie Konkret, Forum Fuer Unterricht Und Didaktik     Hybrid Journal  
Chemoecology     Hybrid Journal   (Followers: 4)
Chemometrics and Intelligent Laboratory Systems     Hybrid Journal   (Followers: 15)
Chemosensors     Open Access  
ChemPhysChem     Hybrid Journal   (Followers: 9)
ChemPlusChem     Hybrid Journal   (Followers: 2)
ChemTexts     Hybrid Journal  
CHIMIA International Journal for Chemistry     Full-text available via subscription   (Followers: 2)
Chinese Journal of Chemistry     Hybrid Journal   (Followers: 6)
Chinese Journal of Polymer Science     Hybrid Journal   (Followers: 10)
Chromatographia     Hybrid Journal   (Followers: 24)
Clay Minerals     Full-text available via subscription   (Followers: 10)
Cogent Chemistry     Open Access  
Colloid and Interface Science Communications     Open Access  
Colloid and Polymer Science     Hybrid Journal   (Followers: 10)
Colloids and Surfaces B: Biointerfaces     Hybrid Journal   (Followers: 7)
Combinatorial Chemistry & High Throughput Screening     Hybrid Journal   (Followers: 4)
Combustion Science and Technology     Hybrid Journal   (Followers: 18)
Comments on Inorganic Chemistry: A Journal of Critical Discussion of the Current Literature     Hybrid Journal   (Followers: 2)
Composite Interfaces     Hybrid Journal   (Followers: 6)
Comprehensive Chemical Kinetics     Full-text available via subscription   (Followers: 2)
Comptes Rendus Chimie     Full-text available via subscription  
Comptes Rendus Physique     Full-text available via subscription   (Followers: 1)
Computational and Theoretical Chemistry     Hybrid Journal   (Followers: 9)
Computational Biology and Chemistry     Hybrid Journal   (Followers: 12)
Computational Chemistry     Open Access   (Followers: 2)
Computers & Chemical Engineering     Hybrid Journal   (Followers: 9)
Coordination Chemistry Reviews     Full-text available via subscription   (Followers: 3)
Copernican Letters     Open Access   (Followers: 1)
Critical Reviews in Biochemistry and Molecular Biology     Hybrid Journal   (Followers: 5)
Crystal Structure Theory and Applications     Open Access   (Followers: 4)
CrystEngComm     Full-text available via subscription   (Followers: 13)
Current Catalysis     Hybrid Journal   (Followers: 2)
Current Metabolomics     Hybrid Journal   (Followers: 5)
Current Opinion in Colloid & Interface Science     Hybrid Journal   (Followers: 9)
Current Opinion in Molecular Therapeutics     Full-text available via subscription   (Followers: 17)
Current Research in Chemistry     Open Access   (Followers: 8)
Current Science     Open Access   (Followers: 61)
Dalton Transactions     Full-text available via subscription   (Followers: 23)
Detection     Open Access   (Followers: 2)
Developments in Geochemistry     Full-text available via subscription   (Followers: 2)
Diamond and Related Materials     Hybrid Journal   (Followers: 12)
Dislocations in Solids     Full-text available via subscription  
Doklady Chemistry     Hybrid Journal  
Drying Technology: An International Journal     Hybrid Journal   (Followers: 4)
Eclética Química     Open Access   (Followers: 1)
Ecological Chemistry and Engineering S     Open Access   (Followers: 3)
Ecotoxicology and Environmental Contamination     Open Access  
Educación Química     Open Access   (Followers: 1)
Education for Chemical Engineers     Hybrid Journal   (Followers: 5)
EJNMMI Radiopharmacy and Chemistry     Open Access  
Elements     Full-text available via subscription   (Followers: 3)
Environmental Chemistry     Hybrid Journal   (Followers: 7)
Environmental Chemistry Letters     Hybrid Journal   (Followers: 5)
Environmental Science & Technology Letters     Full-text available via subscription   (Followers: 5)

        1 2 3 | Last

Journal Cover Angewandte Chemie
  [194 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0044-8249 - ISSN (Online) 1521-3757
   Published by John Wiley and Sons Homepage  [1579 journals]
  • A Supramolecular Capsule for Reversible Polysulfide Storage/Delivery in
           Lithium-Sulfur Batteries
    • Authors: Jin Xie; Hong-Jie Peng, Jia-Qi Huang, Wen-Tao Xu, Xiang Chen, Qiang Zhang
      Abstract: Supramolecular materials, in which small organic molecules are assembled into regular structures by non-covalent interactions, attract tremendous interests because of their highly tunable functional groups and porous structure. Supramolecular adsorbents are expected to fully expose their abundant adsorptive sites in a dynamic framework. In this contribution, we introduced cucurbit[6]uril as a supramolecular capsule for reversible storage/delivery of mobile polysulfides in lithium-sulfur (Li-S) batteries to control undesirable polysulfide shuttle. The Li-S battery equipped with the supramolecular capsules retains a high Coulombic efficiency and shows a large increase in capacity from 300 to 900 mAh g−1 at a sulfur loading of 4.2 mg cm−2. The implementation of supramolecular capsules offers insights into intricate multi-electron-conversion reactions and manifests as an effective and efficient strategy to enhance Li-S batteries and analogous applications that involve complex transport phenomena and intermediate manipulation.Smarter Energiespeicher: Lösungen für die effektive Transportkontrolle von Polysulfiden in Li-S-Batterien befassen sich mit dem Shuttle. Eine supramolekulare Kapsel mit der Fähigkeit der reversiblen Polysulfid-Speicherung/Lieferung wurde in Li-S-Batterien verwendet.
      PubDate: 2017-11-20T05:52:32.466391-05:
      DOI: 10.1002/ange.201710025
       
  • 7%+Efficiency&rft.title=Angewandte+Chemie&rft.issn=0044-8249&rft.date=2017&rft.volume=&rft.aulast=Liu&rft.aufirst=Shengjian&rft.au=Shengjian+Liu&rft.au=Yuliar+Firdaus,++Simil+Thomas,++Zhipeng+Kan,++Federico+Cruciani,++Sergei+Lopatin,++Jean-Luc++M.+Bredas,++Pierre++M.+Beaujuge&rft_id=info:doi/10.1002/ange.201709509">Isoindigo-3,4-Difluorothiophene Polymer Acceptors Yield "All-Polymer" BHJ
           Solar Cells with>7% Efficiency
    • Authors: Shengjian Liu; Yuliar Firdaus, Simil Thomas, Zhipeng Kan, Federico Cruciani, Sergei Lopatin, Jean-Luc M. Bredas, Pierre M. Beaujuge
      Abstract: Poly(isoindigo-alt-3,4-difluorothiophene) (PIID[2F]T) analogues used as "polymer acceptors" in bulk-heterojunction (BHJ) solar cells achieve>7% efficiency when used in conjunction with the polymer donor PBFTAZ (model system). Considering that most efficient polymer acceptor alternatives to fullerenes (e.g. PC61BM or its C71 derivative) are based on perylenediimide (PDI) or naphthalenediimide (NDI) motifs thus far, branched alkyl-substituted PIID[2F]T polymers are remarkably promising nonfullerene candidates for "all-polymer" BHJ solar cells.
      PubDate: 2017-11-20T05:52:13.859266-05:
      DOI: 10.1002/ange.201709509
       
  • GOx@ZIF-8(NiPd) Nanoflower: An Artificial Enzyme System for Tandem
           Catalysis
    • Authors: Qingqing Wang; Xueping Zhang, Liang Huang, Zhiquan Zhang, Shaojun Dong
      Abstract: We report a facile approach to prepare an artificial enzyme system for tandem catalysis. NiPd hollow nanoparticles and glucose oxidase (GOx) were simultaneously immobilized on the zeolitic imidazolate framework 8 (ZIF-8) via a co-precipitation method. The as-prepared GOx@ZIF-8(NiPd) nanoflower not only exhibited the peroxidase-like activity of NiPd hollow nanoparticles but also maintained the enzymatic activity of GOx. A colorimetric sensor for rapid detection of glucose was realized through the GOx@ZIF-8(NiPd) based multi-enzyme system. Moreover, the GOx@ZIF-8(NiPd) modified electrode showed good bioactivity of GOx and high electrocatalytic activity for the oxygen reduction reaction (ORR), which could also be used for electrochemical detection of glucose.Flower Power: Hohle NiPd-Nanopartikel und Glucose-Oxidase (GOx) wurden durch gemeinsame Fällung in einem Metall-organischen Gerüst (ZIF-8) immobilisiert. Das resultierende System verbindet GOx-Aktivität mit Sauerstoffreduktionsfähigkeit und schlägt somit eine Brücke zwischen natürlichen Enzymen und Nanozymen.
      PubDate: 2017-11-20T05:45:24.387412-05:
      DOI: 10.1002/ange.201710418
       
  • Adsorption-Induced Structural Phase Transformation in Nanopores
    • Authors: Bogdan Kuchta; Ege Dundar, Filip Formalik, Philip L. Llewellyn, Lucyna Firlej
      Abstract: We report a new type of structural transformation occurring in methane adsorbed in micropores. The observed methane structures are defined by probability distributions of molecular positions. The mechanism of the transformation has been modeled using Monte Carlo method. The transformation is totally determined by a reconstruction of the probability distribution functions of adsorbed molecules. The methane molecules have some freedom to move in the pore but most of the time they are confined to the positions around the high probability adsorption sites. The observed high-probability structures evolve as a function of temperature and pressure. The transformation is strongly discontinuous at low temperature and becomes continuous at high temperature. The mechanism of the transformation is influenced by a competition between different components of the interaction and the thermal energy. The methane structure represents a new state of matter, intermediate between solid and liquid.Zwischen fest und flüssig: Ein neuartiger Strukturübergang, dessen Mechanismus auf einer Wahrscheinlichkeitsverteilung beruht, wurde in einem Modell für adsorbierte Methanmoleküle in Mikroporen des Metall-organischen Gerüsts IRMOF-1 entdeckt. Die Methanstruktur in den Poren wird durch die eingeschränkte Beweglichkeit bestimmt und stellt eine Mischung aus festem und flüssigem Zustand dar.
      PubDate: 2017-11-20T05:41:56.482405-05:
      DOI: 10.1002/ange.201708993
       
  • Gold-Catalyzed Asymmetric Intramolecular Cyclization of N-Allenamides for
           the Synthesis of Chiral Tetrahydrocarbolines
    • Authors: Yidong Wang; Peichao Zhang, Xiaoyu Di, Qiang Dai, Zhan-Ming Zhang, Junliang Zhang
      Abstract: Highly enantioselective gold-catalyzed intramolecular cyclization of N-allenamides was implemented by utilizing a designed chiral sulfinamide phosphine ligand (PC-Phos). This represents the first example of highly enantioselective intramolecular cyclization of N-allenamides. The practicality of this reaction was validated in the total synthesis of (R)-desbromoarborescidine A and formal synthesis of (R)-desbromoarborescidine C and (R)-deplancheine. Moreover, the catalyst system PC-Phos/AuNTf2 proved to be specifically efficient to promote the desymmetrization of N-allenamides in excellent yields with satisfactory ee values.Dritter Ring: Eine hoch enantioselektive goldkatalysierte intramolekulare Cyclisierung von N-Allenamiden unter Verwendung von PC-Phos-Liganden wurde entwickelt und in der Totalsynthese von (R)-Debromarborescidin A verwendet.
      PubDate: 2017-11-20T05:36:01.319272-05:
      DOI: 10.1002/ange.201709595
       
  • The MOF+ Technique: A Significant Synergic Effect Enables High Performance
           Chromate Removal
    • Authors: Ming Biao Luo; Yang Yang Xiong, Hui Qiong Wu, Xue Feng Feng, Jian Qiang Li, Feng Luo
      Abstract: A significant synergic effect between a metal–organic framework (MOF) and Fe2SO4, the so-called MOF+ technique, is exploited for the first time to remove toxic chromate from aqueous solutions. The results show that relative to the pristine MOF samples (no detectable chromate removal), the MOF+ method enables super performance, giving a 796 Cr mg g−1 adsorption capacity. The value is almost eight-fold higher than the best value of established MOF adsorbents, and the highest value of all reported porous adsorbents for such use. The adsorption mechanism, unlike the anion-exchange process that dominates chromate removal in all other MOF adsorbents, as unveiled by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), is due to the surface formation of Fe0.75Cr0.25(OH)3 nanospheres on the MOF samples.Poren machen Pause: Die MOF+-Methode nutzt statt des Porensystems eines Metall-organischen Gerüsts dessen Oberfläche und ermöglicht die hoch effiziente Entfernung von Chromat aus wässrigen Lösungen von bis zu 796 mg(Cr) g−1. Chromat wird durch FeSO4 reduziert, wobei FeIII- und CrIII-Ionen entstehen; anschließend induziert die MOF-Oberfläche die Bildung von Fe0.75Cr0.25(OH)3-Nanopartikeln.
      PubDate: 2017-11-20T02:56:01.33252-05:0
      DOI: 10.1002/ange.201709197
       
  • Die direkte katalytische Oxidation von Methan zu Methanol – eine
           kritische Beurteilung
    • Authors: Manoj Ravi; Marco Ranocchiari, Jeroen A. van Bokhoven
      Abstract: Es gibt vielzählige direkte, selektive Ansätze, um Methan partiell zu oxidieren, jedoch ist noch keiner von ihnen zur industriellen Reife gelangt. In diesem Zusammenhang ist die Oxidation von Methan zu Methanol eine schwierige, aber lohnende Aufgabe, da sie eine wirkungsvolle Methode ist, um das Abfackeln von Erdgas, das als Nebenprodukt in der Erdölindustrie anfällt, zu unterbinden, und zugleich die Möglichkeit bietet, Methan zu valorisieren. Dieser Aufsatz berücksichtigt die Synthese von Methanol und seinen Derivaten ausgehend von Methan durch homogen- und heterogenkatalytische Methoden. Er zeigt die starken Einschränkungen der direkten katalytischen Synthese von Methanol aus Methan auf und unterstreicht dabei die enorme Überlegenheit von Systemen, die Methanolderivate produzieren oder sich durch Besonderheiten wie die Verwendung von Mehrkomponenten-Katalysatoren zur Methanolstabilisierung auszeichnen. Für die zukünftige Forschung erweist sich die Stabilisierung von Methanol in der homogenen und heterogenen Katalyse als unentbehrlich.Die selektive Oxidation von Methan zu Methanol in hoher Ausbeute ist derzeit schwer umsetzbar, hat aber ein immenses Potential. Dieser Aufsatz veranschaulicht die homogenen und heterogenen katalytischen Wege für diesen Prozess und erläutert die vielversprechendsten Ansätze, welche die Petroindustrie revolutionieren könnten.
      PubDate: 2017-11-20T02:55:42.478614-05:
      DOI: 10.1002/ange.201702550
       
  • Synthesis and reactivity of nickel-stabilised µ2:η2,η2-P2,
           As2 and PAs units.
    • Authors: Gabriele Hierlmeier; Alexander Hinz, Robert Wolf, Jose Manuel Goicoechea
      Abstract: The reactivity of two paramagnetic nickel(I) compounds, CpNi(NHC) (where Cp = cyclopentadienyl; NHC = 1,3-bis(2,4,6-trimethylphenyl)-imidazol-2-ylidene (IMes) or 1,3-bis(2,6-diisopropylphenyl)-imidazol-2-ylidene (IPr)), towards [Na(dioxane)x][PnCO] (Pn = P, As) is described. These reactions afford symmetric bimetallic compounds (µ2:η2,η2-Pn2){Ni(NHC)(CO)}2. Several novel intermediates en route to such species are identified and characterised, including a compound containing the PCO- anion in an unprecedented µ2:η2,η2-binding mode. Ultimately, on treatment of the (µ2:η2,η2-Pn2){Ni(NHC)(CO)}2 compounds with carbon monoxide the Pn2 units can be released, affording P4 in the case of the phosphorus-containing species, and elemental arsenic in the case of (µ2:η2,η2-As2){Ni(IMes)(CO)}2.
      PubDate: 2017-11-20T01:50:36.395393-05:
      DOI: 10.1002/ange.201710582
       
  • Mono- and Bis-Imidazolidinium Ethynyl Cations and the Reduction of the
           Latter to give an Extended Bis-1,4-([3]Cumulene)-p-Carbo-Quinoid System
    • Authors: Brain Barry; Graeme Soper, Juha Hurmalainen, Akseli Mansikkamäki, , Katherine N Robertson, William L McClennan, Alex J. Veinot, Tracey L. Roemmele, Ulrike Werner-Zwanziger, René T Boeré, Heikki M. Tuononen, Jason Clyburne, Jason Masuda
      Abstract: An extended π-system containing two [3]cumulene fragments separated by a p-carbo-quinoid and stabilized by two capping N-heterocyclic carbenes (NHCs) has been prepared. Mono- and bis-imidazolidinium ethynyl cations have also been synthesized from the reaction of an NHC with phenylethynyl bromide or 1,4-bis(bromoethynyl)benzene. Cyclic voltammetry coupled with synthetic and structural studies showed that the dication is readily reduced to a neutral, singlet bis-1,4-([3]cumulene)-p-carbo-quinoid due to the π-accepting properties of the capping NHCs.
      PubDate: 2017-11-19T21:51:09.908256-05:
      DOI: 10.1002/ange.201711031
       
  • Dynamic Cross-Exchange in Halophosphonium Species: First Direct
           Observation of Stereochemical Inversion in the Course of an SN2 Process
    • Authors: Kirill Nikitin; Elizabeth V. Jennings, Sulaiman Al Sulaimi, Yannick Ortin, Declan G Gilheany
      Abstract: The complex fluxional interconversions between, otherwise very similar, phosphonium bromides and chlorides R3PX+X- (R = Alk, Ar, X = Cl or Br) was studied by NMR techniques. Their energy barriers are typically ca. 11 kcal/mol but rise rapidly as bulky groups are attached to phosphorus, revealing the importance of steric factors. In contrast, electronic effects, as measured by Hammett analysis, are modest (rho 1.46) but still clearly indicate negative charge flow towards phosphorus in the transition state. Most significantly, detailed analysis of the exchange pathways unequivocally, and for the first time in any such process, shows that nucleophilic attack of the nucleophilic anion on the tetrahedral centre results in inversion of configuration.
      PubDate: 2017-11-17T14:55:24.543288-05:
      DOI: 10.1002/ange.201708649
       
  • A redox-activated G-quadruplex DNA binder based on a platinum(IV)-salphen
           complex
    • Authors: Ramon Vilar; Stephane Bandeira, Jorge Gonzalez Garcia, Evangelina Pensa, Tim Albrecht
      Abstract: There has been increasing interest in the development of small molecules that can selectively bind to G-quadruplex DNA structures. The latter have been associated to a number of key biological processes and therefore are proposed to be potential targets for drug development. In this paper we report the first example of a reduction-activated G-quadruplex DNA binder. We show that a new octahedral platinum(IV)-salphen complex does not interact with DNA in aqueous media at pH 7.4; however, upon addition of bio-reductants such as ascorbic acid or glutathione, the compound readily reduces to the corresponding square planar platinum(II) complex. In contrast to the parent platinum(IV) complex, the in situ generated platinum(II) complex binds to HTelo and c-Myc G-quadruplex DNA with affinity constants up to 106 M-1.
      PubDate: 2017-11-17T13:00:25.046695-05:
      DOI: 10.1002/ange.201709968
       
  • The Weakly Coordinating Tris(trichlorosilyl)silyl Anion
    • Authors: Marian Olaru; Maxie F. Hesse, Elena Rychagova, Sergey Ketkov, Stefan Mebs, Jens Beckmann
      Abstract: Closely following the procedure for the preparation of the base-stabilized dichlorosilylene complex NHCDipp∙SiCl2 by Roesky and Stalke et al. (Angew. Chem. Int. Ed. 2009, 48, 5683-5686), besides the reported by-product [NHCDipp-H+∙∙∙Cl−], few crystals of the salt [NHCDipp-H∙∙∙Cl∙∙∙H-NHCDipp]Si(SiCl3)3 were isolated and characterized by X-ray crystallography (NHCDipp = N,N-di(2,6-isopropylphenyl)-imidazo-2-ylidene). They feature the weakly-coordinating anion Si(SiCl3)3−, which was more rationally obtained in high yields upon deprotonation of conjugate Brønsted acid HSi(SiCl3)3 with NHCDipp or PMP (PMP = 1,2,2,6,6-pentamethylpiperidine). The acidity of HSi(SiCl3)3 estimated by DFT calculations is substantially higher than those of other H-silanes. The electronic structure of Si(SiCl3)3− studied by DFT calculations including the electrostatic potential and the electron localizability confirms the low basicity and nucleophilicity in comparison to other silyl anions.
      PubDate: 2017-11-17T10:55:22.087893-05:
      DOI: 10.1002/ange.201710416
       
  • Controlled Sol-Gel Transitions of a Thermoresponsive Polymer in a
           Photoswitchable Azobenzene Ionic Liquid as a Molecular Machine
    • Authors: Masayoshi Watanabe; Caihong, Wang, Kei Hashimoto, Ryota Tamate, Hisashi Kokubo
      Abstract: Producing ionic liquids (ILs) that function as molecular machines for macroscopic change is a challenging issue. We report that photoisomerization of an azobenzene IL at the molecular level could evoke a macroscopic response (light-controlled mechanical sol-gel transitions) for ABA triblock copolymer solutions. The A endblocks, poly(2-phenylethyl methacrylate), show a low critical solution temperature in the IL mixture containing azobenzene while the B midblock, poly(methyl methacrylate), is compatible with the mixture. In a concentrated polymer solution, we observed different gelation temperatures in it under dark and UV conditions. In this temperature range, light-controlled sol-gel transitions were achieved by a photoresponsive solubility change of the A endblocks upon photoisomerization of the azobenzene IL. Therefore, an azobenzene IL as a molecular switch can tune the self-assembly of a thermoresponsive polymer, leading to macroscopic light-controlled sol-gel transitions.
      PubDate: 2017-11-17T10:25:46.775562-05:
      DOI: 10.1002/ange.201710288
       
  • Control of N-Heterocyclic Carbene Catalyzed Switchable Linear and
           Cycloaddition Reactions of Enals: Asymmetric Synthesis of
           Oxindole-γ-Amino Acid Derivatives
    • Authors: Dieter Enders; Xiang-Yu Chen, Jia-Wen Xiong, Qiang Liu, Sun Li, He Sheng, Carolina von Essen, Kari Rissanen
      Abstract: A strategy to control the switchable linear and cycloaddition reactions of enals through NHC catalyisis has been developed. The new scalable protocol leads to γ-amino acid esters bearing a tetrasubstituted stereocenter in good yields and high stereoselectivities via homo-Mannich reactions of enals and isatin-derived ketimines. By simply changing the N-ketimine substituent to an ortho-hydroxy phenyl group, the corresponding spirocyclic oxindolo-γ-lactams are obtained.
      PubDate: 2017-11-17T09:25:54.76112-05:0
      DOI: 10.1002/ange.201708994
       
  • Can coordination-driven supramolecular self-assembly reactions be
           conducted from fully aliphatic linkers '
    • Authors: Christophe Lescop; Mehdi Elsayed Moussa, Sloane Evariste, Barbara Kräemer, Régis Réau, Manfred Scheer
      Abstract: A series of fully aliphatic cyano-capped ditopic linkers with increasing lengths were reacted with a pre-assembled Cu(I) bimetallic molecular clip bearing short intermetallic distances. It is shown that, depending on the length of the ditopic linkers, a rational design of unprecedented supramolecular compact metallacycles bearing fully aliphatic walls is possible. The specific pre-organized molecular arrangement of the molecular clip used favors stabilizing interlinker London dispersion interactions allowing, as the linkers' lengths increase, the selective formation of discrete compact metallacycles at the expense of 1D coordination polymers. The generalizability of this approach is demonstrated by reacting fully aliphatic cyano-capped linkers with two other types of pre-assembled Cu(I) bimetallic molecular clips also having short intermetallic distances.
      PubDate: 2017-11-17T08:26:25.235598-05:
      DOI: 10.1002/ange.201709119
       
  • Dual Functionalization of White Phosphorus: Formation, Characterization,
           and Reactivity of Rare-Earth-Metal Cyclo-P3 Complexes
    • Authors: Shanshan Du; Jianhao Yin, Yue Chi, Ling Xu, Wen-Xiong Zhang
      Abstract: The [3+1] fragmentation reaction of rare-earth metallacyclopentadienes 1 a–c with 0.5 equivalents of P4 affords a series of rare-earth metal cyclo-P3 complexes 2 a–c and a phospholyl anion 3. 2 a–c demonstrate an unusual η3 coordination mode with one P−P bond featuring partial π-bonding character. 2 a–c are the first cyclo-P3 complexes of rare-earth metals, and also the first organo-substituted polyphosphides in the category of Group 3 and f-block elements. Rare-earth metallacyclopentadienes play a dual role in the combination of aromatization and Diels–Alder reaction. Compounds 2 a–c can coordinate to one or two [W(CO)5] units, yielding 4 a–c or 5 c, respectively. Furthermore, oxidation of 2 a with p-benzoquinone produces its corresponding phospholyllithium and regenerated P4.Die Fragmentierung von P4 liefert cyclo-P3-Seltenerdmetallkomplexen mit ungewöhnlicher η3-Koordination, wobei eine P-P-Bindung π-Anteile aufweist. Durch Oxidation des cyclo-P3-Komplexes mit p-Benzochinon sind Phospholylanionen zugänglich; bei diesem Prozess wird zusätzlich P4 regeneriert.
      PubDate: 2017-11-17T05:36:32.397334-05:
      DOI: 10.1002/ange.201708897
       
  • Double Regioselective Asymmetric C-Allylation of Isoxazolinones: Iridium
           Catalyzed N-Allylation Followed by an Aza-Cope-Rearrangement
    • Authors: Stefan Rieckhoff; Jan Meisner, Johannes Kästner, Wolfgang Frey, René Peters
      Abstract: Isoxazolinones are biologically and synthetically interesting densely functionalized heterocycles, which for a long time were not accessible in enantioenriched form by asymmetric catalysis. Next to the deficit of enantioselective methods, the functionalization of isoxazolinones is often plagued by regioselectivity issues due to the competition of various nucleophilic centers within the heterocycles. Here we report the first regio- and enantioselective C-allylations of isoxazolinones. They also allowed for high regioselectivity in favor of the linear allylation products, although Ir phosphoramidite catalysts were used, which commonly result in branched isomers. Our studies suggest that this outcome is the result of a reaction cascade via an initial regio- and enantioselective N-allylation providing a branched allyl intermediate, followed by a spontaneous [3,3]-rearrangement permitting a chirality transfer.
      PubDate: 2017-11-17T05:25:54.583372-05:
      DOI: 10.1002/ange.201710940
       
  • Shunai Che
    • PubDate: 2017-11-17T05:16:07.771887-05:
      DOI: 10.1002/ange.201711485
       
  • Access to α-Amino Acid Esters through Palladium-Catalyzed Oxidative
           Amination of Vinyl Ethers with Hydrogen Peroxide as the Oxidant and Oxygen
           Source
    • Authors: Lu Ouyang; Jianxiao Li, Jia Zheng, Jiuzhong Huang, Chaorong Qi, Wanqing Wu, Huanfeng Jiang
      Abstract: A novel and convenient palladium catalytic system for the synthesis of α-amino acid esters from simple starting materials is reported. Hydrogen peroxide not only acts as the green oxidant, but also as the oxygen source. This strategy for the conversion of amines and vinyl ethers into highly functionalized and structurally diverse α-amino acid esters is characterized by the simplicity of the experimental procedure, mild reaction conditions, high atom economy, scalability, and practicability.Beginnen wir mit etwas Einfachem: Ein praktisches Palladiumkatalysesystem, in dem Wasserstoffperoxid zugleich als Oxidationsmittel und Sauerstoffatomquelle fungiert, überführt leicht verfügbare Amine und Vinylether in hoch funktionalisierte α-Aminosäureester (siehe Schema). Die vielseitige Strategie zeichnet sich durch ein einfaches Syntheseprotokoll, milde Reaktionsbedingungen und hohe Atomökonomie aus.
      PubDate: 2017-11-17T05:15:41.492383-05:
      DOI: 10.1002/ange.201709285
       
  • Efficient Water Reduction with sp3-sp3 Diboron(4) Compounds: Application
           to Hydrogenations, H–D Exchange Reactions, and Carbonyl Reductions
    • Authors: Mathias Flinker; Hongfei Yin, René W. Juhl, Espen Z. Eikeland, Jacob Overgaard, Dennis U. Nielsen, Troels Skrydstrup
      Abstract: A series of crystalline sp3-sp3 diboron(4) compounds were synthesized and shown to promote the facile reduction of water with dihydrogen formation. The application of these diborons as simple and effective dihydrogen and dideuterium sources was demonstrated by conducting a series of selective reductions of alkynes and alkenes, and hydrogen–deuterium exchange reactions using two-chamber reactors. Finally, as the water reduction reaction generates an intermediate borohydride species, a range of aldehydes and ketones were reduced by using water as the hydride source.BH-Chemie: sp3-sp3-Diborane(4) können Wasser reduzieren und dadurch Wasserstoff für eine Reihe von Umsetzungen zur Verfügung stellen. Ausgewählte Aldehyde und Ketone wurden in Gegenwart dieser Diborane in Wasser durch intermediäre Borhydridspezies reduziert.
      PubDate: 2017-11-17T05:10:43.29944-05:0
      DOI: 10.1002/ange.201709685
       
  • Ring-Size-Modulated Reactivity of Putative Dicobalt-Bridging Nitrides:
           C−H Activation versus Phosphinimide Formation
    • Authors: Peng Cui; Qiuran Wang, Samuel P. McCollom, Brian C. Manor, Patrick J. Carroll, Neil C. Tomson
      Abstract: Dicobalt complexes supported by flexible macrocyclic ligands were used to target the generation of the bridging nitrido species [(nPDI2)Co2(μ-N)(PMe3)2]3+ (PDI=2,6-pyridyldiimine; n=2, 3, corresponding to the number of catenated methylene units between imino nitrogen atoms). Depending on the size of the macrocycle and the reaction conditions (solution versus solid-state), the thermolysis of azide precursors yielded bridging phosphinimido [(2PDI2)Co2(μ-NPMe3)(PMe3)2]3+, amido [(nPDI2)Co2(μ-NH2)(PMe3)2]3+ (n=2, 3), and C−H amination [(3PDI2*-μ-NH)Co2(PMe3)2]3+ products. All results are consistent with the initial formation of [(nPDI2)Co2(μ-N)(PMe3)2]3+, followed by 1) PMe3 attack on the nitride, 2) net hydrogen-atom transfer to form N−H bonds, or 3) C−H amination of the alkyl linker of the nPDI2 ligand.Produkte von C-H-Aminierung, Wasserstoffatomtransfer und Phosphinimid-Bildung wurden nach thermischer Aktivierung von azidverbrückten Dicobaltkomplexen mit flexiblen makrocyclischen Liganden erhalten. Die Größe des Makrocyclus beeinflusst dabei die Produktverteilung.
      PubDate: 2017-11-17T05:05:40.427537-05:
      DOI: 10.1002/ange.201708966
       
  • Polycyclische, polyprenylierte Acylphloroglucinole – eine Klasse
           nicht-peptidbasierter MRSA- und VRE-aktiver Antibiotika
    • Authors: Claudia Guttroff; Aslihan Baykal, Huanhuan Wang, Peter Popella, Frank Kraus, Nicole Biber, Sophia Krauss, Friedrich Götz, Bernd Plietker
      Abstract: In den vergangenen 20 Jahren wurden peptidbasierte Antibiotika wie Vancomycin, Teicoplanin oder Daptomycin als Reserveantibiotika betrachtet. In den letzten Jahren erschienen jedoch vermehrt Berichte über Vancomycin-resistente Krankheitserreger, was die Entwicklung neuartiger Leitstrukturen für neue wirksame Antibiotika motivierte. Hier wird über die Totalsynthese einer definierten endo-Typ-B-PPAP-Bibliothek und deren antibiotische Aktivität gegen multiresistente Staphylococcus-aureus- und diverse Vancomycin-resistente Enterococcus-Stämme berichtet. Es wurden vier neue Strukturen identifiziert, die zeigen, dass das PPAP-Grundgerüst eine neue nicht-peptidbasierte Leitstruktur in der Antibiotika-Forschung werden könnte, die sich durch die Kombination von hoher Aktivität und geringer Zytotoxizität auszeichnet.Eine definierte endo-Typ-B-PPAP-Bibliothek wurde synthetisiert und auf ihre antibiotische Aktivität gegen multiresistente Staphylococcus-aureus- und Vancomycin-resistente Enterococci-Stämme untersucht. Vier neue Strukturen wurden identifiziert (Beispiel siehe Bild), die zeigen, dass PPAPs in der Antibiotikaforschung eine neue Leitstruktur mit hoher Aktivität und geringer Zytotoxizität werden könnten. PPAP=polycyclisches, polyprenyliertes Acylphloroglucinol.
      PubDate: 2017-11-17T04:31:14.945732-05:
      DOI: 10.1002/ange.201707069
       
  • Visible-Light-Mediated Metal-Free Hydrosilylation of Alkenes through
           Selective Hydrogen Atom Transfer for Si-H Activation
    • Authors: Rong Zhou; Yi Yiing Goh, Haiwang Liu, Hairong Tao, Lihua Li, Jie Wu
      Abstract: Although developments on the transition-metal-catalyzed hydrosilylation of alkenes have achieved great progress over the past several decades, metal-free hydrosilylation is still rare and highly desirable. Herein, we report a convenient visible-light-driven metal-free hydrosilylation of both electron-deficient and electron-rich alkenes via selective hydrogen atom transfer for Si-H activation. By the synergistic combination of an organo-photocatalyst 4CzIPN and quinuclidin-3-yl acetate catalyst, the hydrosilylation of electron-deficient alkenes exclusively occurred with Si-H activation. Additionally, the hydrosilylation of electron-rich alkenes was achieved by merging photoredox and polarity-reversal catalysis.
      PubDate: 2017-11-16T21:55:48.823482-05:
      DOI: 10.1002/ange.201711250
       
  • Controlled radical polymerization of ethylene using organotellurium
           compounds
    • Authors: Franck D'Agosto; Arne Wolpers, Bastian Ebeling, Yasuyuki Nakamura, Shigeru Yamago, Vincent Monteil
      Abstract: The first successfully controlled radical polymerization (CRP) of ethylene is reported using several organotellurium chain-transfer agents (CTAs) under mild conditions (70 °C, 200 bar of ethylene) within the concept of organotellurium-mediated radical polymerization (TERP). In contrast to preceding works on CRPs of ethylene applying reversible addition-fragmentation chain-transfer (RAFT), the organotellurium-mediated system provided a high livingness and chain-end functionalization of polyethylene chains. Molar-mass distributions with dispersities between 1.3 and 2.1 were obtained up to average molar masses of 5000 g mol−1. As in the RAFT system, the high reactivity of the growing polyethylenyl radical led to an inherent side reaction. However, for the presented TERP systems, this side reaction did not result in dead chains, while it could even be effectively suppressed by a good choice of the CTA.
      PubDate: 2017-11-16T11:56:20.458125-05:
      DOI: 10.1002/ange.201709946
       
  • A Gold-Catalyzed Domino Cyclization Enabling Rapid Construction of Diverse
           Polyheterocyclic Frameworks
    • Authors: Erik Van der Eycken; Yi He, Zhenghua Li, Koen Robeyns, Luc Van Meervelt
      Abstract: We report herein an efficient gold(I)-catalyzed post-Ugi domino dearomatization/ipso-cyclization/Michael sequence that enables access to libraries of diverse (hetero)arene-annulated tricyclic heterocycles. This process affords novel complex polycyclic scaffolds in moderate to good yields from readily available acyclic precursors with excellent chemo-, regio-, and diastereo-selectivity. The power of this strategy has been demonstrated by the rapid synthesis of 40 highly functionalized polyheterocycles bearing indole, pyrrole, (benzo)furan, (benzo)thiophene, pyrazole and electron-rich arenes in two-operational steps.
      PubDate: 2017-11-16T07:58:40.035033-05:
      DOI: 10.1002/ange.201710592
       
  • A Copper(II)-Phenanthroline Metallopeptide that Targets and Disrupts
           Mitochondrial Function in Breast Cancer Stem Cells
    • Authors: Kristine Laws Laws; Ganka Bineva-Todd, Arvin Eskandari, Chunxin Lu, Nicola O'Reilly, Kogularamanan Suntharalingam
      Abstract: The breast cancer stem cell (CSC) and bulk breast cancer cell potency of a series of metallopeptides, 1-4 containing dichloro(1,10-phenanthroline) copper(II) and various organelle-targeting peptide sequences, is reported. The mitochondrial-targeting metallopeptide, 1 exploits the higher mitochondrial load in breast CSCs over corresponding non-CSCs, and the vulnerability of breast CSCs to mitochondrial damage, to potently and selectivity kill breast CSCs. Strikingly, 1 reduces the formation and size of mammospheres to a better extent than salinomycin, an established CSC-potent agent. Mechanistic studies show that 1 enters CSC mitochondria, induces mitochondrial dysfunction, generates reactive oxygen species (ROS), activates JNK and p38 pathways, and prompts apoptosis. To the best of our knowledge, 1 is the first metallopeptide to selectivity kill breast CSC in vitro.
      PubDate: 2017-11-16T07:25:29.981922-05:
      DOI: 10.1002/ange.201710910
       
  • A Strontium- and Chlorine-Free Pyrotechnic Illuminant of High Color Purity
    • Authors: Thomas M. Klapötke; Magdalena Rusan, Joerg Stierstorfer, Jesse Sabatini, Johann Glueck
      Abstract: The need to develop a red-light-emitting pyrotechnic illuminant has garnered interest from the pyrotechnics community due to potential Environmental Protection Agency (EPA) regulations of strontium and chlorinated organic materials. To address these environmental regulatory concerns, the development of lithium-based red-light-emitting pyrotechnic compositions of high purity and color is described. These formulations do not contain strontium or chlorinated organic materials. Rather, the disclosed formulations are based on a non-hygroscopic dilithium high-nitrogen salt which serves as both the oxidizer and red colorant. These formulations are likely to draw interest from the civilian fireworks and military pyrotechnics communities for further development; both of whom have a vested interest in the development of environmentally conscious formulations.
      PubDate: 2017-11-16T06:25:22.467004-05:
      DOI: 10.1002/ange.201710746
       
  • Systemic Delivery of Bc12-Targeting siRNA by DNA Nanoparticles Suppresses
           Cancer Cell Growth
    • Authors: Mohammad Aminur Rahman; Pengfei Wang, Zhixiang Zhao, Dongsheng Wang, Sreenivas Nannapaneni, Chao Zhang, Zhengjia Chen, Christopher C. Griffith, Selwyn J. Hurwitz, Zhuo G. Chen, Yonggang Ke, Dong M. Shin
      Abstract: Short interfering RNA (siRNA) is a promising molecular tool for cancer therapy, but its clinical success is limited by the lack of robust in vivo delivery systems. Rationally designed DNA nanoparticles (DNPs) have emerged as facile delivery vehicles because their physicochemical properties can be precisely controlled. Nonetheless, few studies have used DNPs to deliver siRNAs in vivo, and none has demonstrated therapeutic efficacy. Herein, we constructed a number of DNPs of rectangular and tubular shapes with varied dimensions using the modular DNA brick method for the systemic delivery of siRNA that targets anti-apoptotic protein Bcl2. The siRNA delivered by the DNPs inhibited cell growth both in vitro and in vivo, which suppressed tumor growth in a xenograft model that specifically correlated with Bcl2 depletion. This study suggests that DNPs are effective tools for the systemic delivery of therapeutic siRNA and have great potential for further clinical translation.DNA-Nanopartikel unterdrücken durch systemische Transporter von siRNA das Tumorwachstum, indem sie ein antiapoptotisches Protein Bcl2 spezifisch inaktivieren.
      PubDate: 2017-11-16T04:50:59.566117-05:
      DOI: 10.1002/ange.201709485
       
  • Atropoenantioselective Redox-Neutral Amination of Biaryls Via Borrowing
           Hydrogen and Dynamic Kinetic Resolution
    • Authors: Jian Wang; Jianwei Zhang
      Abstract: We report here a novel atropoenantioselective redox-neutral amination of biaryls triggered by a cascade of borrowing hydrogen and DKR strategy under the co-catalysis of chiral Ir-complex and achiral Brønsted acid. This protocol features broad substrate scope and good functional group tolerance, and allows the rapid assembly of axially chiral biaryls in good to high yields and with high to excellent enantioselectivities.
      PubDate: 2017-11-16T04:26:36.016372-05:
      DOI: 10.1002/ange.201711126
       
  • Reaction of thiocarbonyl fluoride formed from difluorocarbene with amines
    • Authors: Ji-Chang Xiao; Jiao Yu, Jinhong Lin
      Abstract: The reaction of thiocarbonyl fluoride generated from difluorocarbene with various amines under mild conditions is described. Secondary amines, primary amines, and o-phenylenediamines are converted to thiocarbamoyl fluorides, isothiocyanates, and difluoromethylthiolated heterocycles, respectively. Thiocarbamoyl fluorides were further transformed into trifluoromethylated amines using a one-pot process. As thiocarbonyl fluoride is generated in situ and is rapidly fully converted in one pot under mild conditions, no special safety precautions are needed.
      PubDate: 2017-11-16T03:55:46.911446-05:
      DOI: 10.1002/ange.201710186
       
  • Restoration of ribozyme tertiary contact and function using a molecular
           glue for RNA
    • Authors: Chikara Dohno; Maki Kimura, Kazuhiko Nakatani
      Abstract: Some RNA classes require folding into the proper higher-order structures to exert their functions. Hammerhead ribozyme (HHR) requires a folding conformation stabilized by tertiary interaction for full activity. Here, we developed a rationally engineered HHR that was inactive, but could be activated by a synthetic RNA-binding ligand, naphthyridine carbamate tetramer with Z-stilbene linker (Z-NCTS). Binding of Z-NCTS could induce the formation of an active folding structure and thereby restore ribozyme activity, where Z-NCTS acts as a molecular glue to bring two isolated RNA loops into contact with each other. Next, we designed a Z-NCTS-responsive genetic switch using the HHR sequence inserted into the 3 untranslated region as a cis-acting element. We demonstrated that the rationally designed ribozyme switch enabled regulation of gene expression by Z-NCTS and was functional in mammalian cells.
      PubDate: 2017-11-16T00:26:29.275096-05:
      DOI: 10.1002/ange.201709041
       
  • Bioinspired Chemical Communication between Synthetic Nanomotors
    • Authors: Chuanrui Chen; Xiaocong Chang, Hazhir Teymourian, Doris E Ramírez Herrera, Berta Esteban Fernández de Ávila, Xiaolong Lu, Jinxing Li, Sha He, Chengcheng Fang, Yuyan Liang, Fangzhi Mou, Jianguo Guan, Joseph Wang
      Abstract: While chemical communication plays a key role in diverse natural processes, the intelligent chemical communication between synthetic nanomotors remains unexplored. Here we demonstrate the design and operation of bio-inspired synthetic nanomotors capable of chemical communication among themselves that influences their propulsion behavior. The chemical message is sent from a moving 'activator' motor to a nearby 'activated' (receiver) one, and involves release of silver ions from a Janus PS/Ni/Au/Ag 'activator' motor to the 'activated' Janus SiO2/Pt nanomotor. The transmitted silver signal is translated rapidly into a dramatic speed change associated with the enhanced catalytic activity of 'activated' motors. The concept of establishing chemical communication between different synthetic nanomotors paves the way to intelligent nanoscale robotic systems that are capable of cooperating with each other.
      PubDate: 2017-11-15T21:55:41.124841-05:
      DOI: 10.1002/ange.201710376
       
  • Distal Weak Coordination of Acetamides in Ruthenium(II)-Catalyzed C-H
           Activation Processes
    • Authors: Qingqing Bu; Torben Rogge, Vladislav Kotek, Lutz Ackermann
      Abstract: C-H activations with challenging arylacetamides were accomplished by versatile ruthenium(II) biscarboxylate catalysis. The distal C-H functionalization was characterized by ample scope, including twofold oxidative C-H functionalizations and alkyne hydroarylations, through facile base-assisted internal electrophilic-type substitution (BIES) C-H ruthenation by weak O coordination.
      PubDate: 2017-11-15T15:25:43.378394-05:
      DOI: 10.1002/ange.201711108
       
  • Highly Selective Manganese(I)/Lewis Acid Cocatalyzed Direct C−H
           Propargylation using Bromoallenes
    • Authors: Can Zhu; Luca Jonas Schwarz, Sara Cembellin, Steffen Greßies, Frank Glorius
      Abstract: A manganese(I)/Lewis acid cocatalyzed direct C−H propargylation with high selectivity has been developed. BPh3 was discovered to not only promote the reactivity, but also enhance the selectivity to afford the propargylation products rather than allene derivatives. Secondary, tertiary or even quaternary carbon centers at the propargylic position could be directly constructed. Both internal and terminal alkynes are easily accessible. The chirality was successfully transferred from an axially chiral allene to the central chirality. The reactivity of the manganese catalyst in this chemistry was found to be unique comparing other transition metal catalysts.
      PubDate: 2017-11-15T15:25:38.786766-05:
      DOI: 10.1002/ange.201710835
       
  • Fluorine in a C-F Bond as the Key to Cage Formation
    • Authors: Maxwell Gargiulo Holl; Cody Ross Pitts, Thomas Lectka
      Abstract: Cage molecules have long been employed to trap reactive or fleeting species, as their rigid nature allows them to enforce situations that otherwise would not persist. In this minireview, we discuss our use of rigid cage structures to investigate the close noncovalent interactions of fluorine with other functional groups and determine how mutual proximity affects both physical properties and reactivity. Unusual covalent interactions of fluorine are also explored: the cage can close to form the first solution-phase C-F-C fluoronium ion.
      PubDate: 2017-11-15T15:25:22.698228-05:
      DOI: 10.1002/ange.201710423
       
  • PbS/CdS core/shell QDs suppress charge transfer and enhance triplet
           transfer
    • Authors: Zhiyuan Huang; Zihao Xu, Melika Mahboub, Xin Li, Jordan Taylor, Hill Harman, Tianquan Lian, MingLee Tang
      Abstract: Here, we observe that a sub-monolayer CdS shell on PbS quantum dots (QDs) enhances triplet energy transfer (TET) by suppressing competitive charge transfer from QDs to molecules. The CdS shell increases the linear photon upconversion quantum yield (QY) from 3.5% for PbS QDs to 5.0% for PbS/CdS QDs when functionalized with a tetracene acceptor, 5-CT. While transient absorption spectroscopy reveals that both PbS and PbS/CdS QDs show the formation of the 5-CT triplet (with rate constants of 5.91 ±0.60 ns-1 and 1.03 ±0.09 ns-1 respectively), ultrafast hole transfer occurs only from PbS QDs to 5-CT. Although the CdS shell decreases the TET rate, it enhances TET efficiency from 60.3± 6.1% to 71.8 ±6.2% by suppressing the hole transfer process. In addition, the CdS shell prolongs the lifetime of the 5-CT triplet and thus enhances TET from 5-CT to the rubrene emitter, further bolstering the upconverison QY.
      PubDate: 2017-11-15T12:55:39.708654-05:
      DOI: 10.1002/ange.201710224
       
  • Multi-Step Crystallization of Barium Carbonate: Rapid Interconversion of
           Amorphous and Crystalline Precursors
    • Authors: Michael L. Whittaker; Paul J. M. Smeets, Hasti Asayesh-Ardakani, Reza Shahbazian-Yassar, Derk Joester
      Abstract: The direct observation of amorphous barium carbonate (ABC), which transforms into a previously unknown barium carbonate hydrate (herewith named gortatowskite) within a few hundred milliseconds of formation, is described. In situ X-ray scattering, cryo-, and low-dose electron microscopy were used to capture the transformation of nanoparticulate ABC into gortatowskite crystals, highly anisotropic sheets that are up to 1 μm in width, yet only about 10 nm in thickness. Recrystallization of gortatowskite to witherite starts within 30 seconds. We describe a bulk synthesis and report a first assessment of the composition, vibrational spectra, and structure of gortatowskite. Our findings indicate that transient amorphous and crystalline precursors can play a role in aqueous precipitation pathways that may often be overlooked owing to their extremely short lifetimes and small dimensions. However, such transient precursors may be integral to the formation of more stable phases.Die Präzipitation von Witherit (BaCO3) aus wässriger Lösung erfolgt unter Beteiligung von nicht nur einer, sondern zwei Vorstufen: amorphem Bariumcarbonat (ABC) und kristallinem Bariumcarbonat-Monohydrat (Gortatowskit), das mit quasi-zweidimensionalem Habitus kristallisiert. Beide Intermediate sind sehr kurzlebig, und ihre Charakterisierung erfordert In-situ-Techniken mit hoher Zeitauflösung, niedriger Strahlendosis und/oder Kryo-Elektronenmikroskopie.
      PubDate: 2017-11-15T12:27:21.256841-05:
      DOI: 10.1002/ange.201709526
       
  • The Metal–Support Interaction Concerning the Particle Size Effect of
           Pd/Al2O3 on Methane Combustion
    • Authors: Kazumasa Murata; Yuji Mahara, Junya Ohyama, Yuta Yamamoto, Shigeo Arai, Atsushi Satsuma
      Abstract: The particle size effect of Pd nanoparticles supported on alumina with various crystalline phases on methane combustion was investigated. Pd/θ, α-Al2O3 with weak metal-support interaction showed a volcano-shaped dependence of the catalytic activity on the size of Pd particles, and the catalytic activity of the strongly interacted Pd/γ-Al2O3 increased with the particle size. Based on a structural analysis of Pd nanoparticles using CO adsorption IR spectroscopy and spherical aberration-corrected scanning/transmission electron microscopy, the dependence of catalytic activity on Pd particle size and the alumina crystalline phase was due to the fraction of step sites on Pd particle surface. The difference in fraction of the step site is derived from the particle shape, which varies not only with Pd particle size but also with the strength of metal–support interaction. Therefore, this interaction perturbs the particle size effect of Pd/Al2O3 for methane combustion.Größe und Phase: Pd/θ-Al2O3 und Pd/ α-Al2O3 zeigen einen anderen Größeneffekt als Pd/γ-Al2O3. Einer spektroskopischen und mikroskopischen Strukturanalyse zufolge beruht die Größen- und Phasenabhängigkeit der katalytischen Aktivität auf dem Anteil an Stufenpositionen im Pd-Partikel. Unterschiedliche Anteile ergeben sich aus der Partikelform, die von der Größe der Pd-Partikel und der Stärke der Metall-Träger-Wechselwirkungen bestimmt wird.
      PubDate: 2017-11-15T12:26:33.419572-05:
      DOI: 10.1002/ange.201709124
       
  • Activation and Deactivation of Gold/Ceria–Zirconia in the
           Low-Temperature Water–Gas Shift Reaction
    • Authors: James H. Carter; Xi Liu, Qian He, Sultan Althahban, Ewa Nowicka, Simon J. Freakley, Liwei Niu, David J. Morgan, Yongwang Li, J. W. (Hans) Niemantsverdriet, Stanislaw Golunski, Christopher J. Kiely, Graham J. Hutchings
      Abstract: Gold (Au) on ceria–zirconia is one of the most active catalysts for the low-temperature water–gas shift reaction (LTS), a key stage of upgrading H2 reformate streams for fuel cells. However, this catalyst rapidly deactivates on-stream and the deactivation mechanism remains unclear. Using stop–start scanning transmission electron microscopy to follow the exact same area of the sample at different stages of the LTS reaction, as well as complementary X-ray photoelectron spectroscopy, we observed the activation and deactivation of the catalyst at various stages. During the heating of the catalyst to reaction temperature, we observed the formation of small Au nanoparticles (NPs; 1–2 nm) from subnanometer Au species. These NPs were then seen to agglomerate further over 48 h on-stream, and most rapidly in the first 5 h when the highest rate of deactivation was observed. These findings suggest that the primary deactivation process consists of the loss of active sites through the agglomeration and possible dewetting of Au NPs.Nach dem Goldrausch: Stopp-Start-Raster-TEM wurde genutzt, um während der Niedertemperatur-Wassergasreaktion über Au/CeZrO4 gebildete Au-Spezies zu detektieren. Au-Nanopartikel, die beim Aufheizen des Katalysators auf Reaktionstemperatur gebildet werden, agglomerieren unter den Reaktionsbedingungen. Röntgen-PES offenbart, dass die Katalysatordeaktivierung aus der Partikelagglomeration resultiert.
      PubDate: 2017-11-15T12:09:41.483644-05:
      DOI: 10.1002/ange.201709708
       
  • Intermolecular Pummerer Coupling with Carbon Nucleophiles in
           Non-Electrophilic Media
    • Authors: Kilian Colas; Raúl Martín-Montero, Abraham Mendoza
      Abstract: A new Pummerer-type C−C coupling protocol is introduced based on turbo-organomagnesium amides, which unlike traditional Pummerer reactions, does not require strong electrophilic activators, engages a broad range of C(sp3)-, C(sp2)-, and C(sp)-nucleophiles, and seamlessly integrates with C−H and C−X magnesiation. Given the central character of sulfur compounds in organic chemistry, this protocol allows access to unrelated carbonyls, olefins, organometallics, halides, and boronic esters through a single strategy.C-C-Verknüpfungen durch Pummerer-Kupplung gelingen in einem einzigen Arbeitsschritt, zur Aktivierung werden jedoch Elektrophile benötigt. Eine effiziente orthogonale Vorgehensweise für elektrophilfreie Pummerer-C-C-Kupplungen unter Verwendung von DIPAMgCl⋅ LiCl wird vorgestellt, die Einschränkungen des etablierten Protokolls überwindet.
      PubDate: 2017-11-15T12:09:27.708147-05:
      DOI: 10.1002/ange.201709715
       
  • Lead- and Iodide-Deficient (CH3NH3)PbI3 (d-MAPI): The Bridge between 2D
           and 3D Hybrid Perovskites
    • Authors: Antonin Leblanc; Nicolas Mercier, Magali Allain, Jens Dittmer, Vincent Fernandez, Thierry Pauporté
      Abstract: 3D and 2D hybrid perovskites, which have been known for more than 20 years, have emerged recently as promising materials for optoelectronic applications, particularly the 3D compound (CH3NH3)PbI3 (MAPI). The discovery of a new family of hybrid perovskites called d-MAPI is reported: the association of PbI2 with both methyl ammonium (MA+) and hydroxyethyl ammonium (HEA+) cations leads to a series of five compounds with general formulation (MA)1−2.48x(HEA)3.48x[Pb1−xI3−x]. These materials, which are lead- and iodide-deficient compared to MAPI while retaining 3D architecture, can be considered as a bridge between the 2D and 3D materials. Moreover, they can be prepared as crystallized thin films by spin-coating. These new 3D materials appear very promising for optoelectronic applications, not only because of their reduced lead content, but also in account of the large flexibility of their chemical composition through potential substitutions of MA+, HEA+, Pb2+ and I− ions.Die Assoziation von PbI2 mit Methylammonium (MA+) und Hydroxyethylammonium (HEA+) führt zu fünf Verbindungen der allgemeinen Summenformel (MA)1−2.48x(HEA)3.48x[Pb1−xI3−x]. Diese d-MAPI-Materialien, die gegenüber der Stammverbindung (CH3NH3)PbI3 (MAPI) einen Blei- und Iodidunterschuss aufweisen, können in Form dünner Filme hergestellt werden. Durch Beibehaltung ihrer 3D-Architektur bilden sie eine Brücke zwischen 2D-Hybridperowskiten und MAPI.
      PubDate: 2017-11-15T12:09:08.625175-05:
      DOI: 10.1002/ange.201710021
       
  • Olefin-Bildung durch eliminierende Dimerisierung und eliminierende
           Kreuzkupplung von Carbenoiden: eine stereochemische Herausforderung
    • Authors: Paul R. Blakemore; Reinhard W. Hoffmann
      Abstract: Bei der Dimerisierung von Carbenoiden entstehen Olefine, und zwar über die Bildung eines At-Komplexes, eine nachfolgende 1,2-Metallat-Umlagerung und eine abschließende β-Eliminierung. Da jeder dieser Schritte stereospezifisch ist, kann man das stereochemische Endergebnis nachvollziehen und – im Prinzip – auch steuern, vorausgesetzt, die absolute Konfiguration der reagierenden Carbenoide ist festgelegt. Eine eliminierende Kreuzkupplung zweier unterschiedlicher Carbenoide ermöglicht eine Aufbaureaktion, bei der im Unterschied zu bekannten Olefin-Synthesen die Geometrie der Doppelbindung unabhängig von der Art der Reste an der Doppelbindung festgelegt werden kann. Die Bildung von Olefinen durch eliminierende Dimerisierung/Kreuzkupplung von Carbenoiden wird an einer Reihe von typischen Beispielen illustriert, etwa an Reaktionen von α-lithiierten Halogenalkanen, Epoxiden und Carbamaten. Dabei gilt das Augenmerk auch der Erzeugung von sp3-hybridisierten Carbenoiden mit definierter Konfiguration und deren stereochemischer Zuordnung.Die wechselseitige Eliminierung einer elektrofugen (M) und einer nukleofugen (X) Abgangsgruppe aus einem Paar miteinander reagierender Carbenoide führt zur Bildung einer C-C-Doppelbindung. Diese elementare Aufbaureaktion ist inhärent regio- und stereospezifisch. In diesem Aufsatz werden Homo- und Kreuzkupplungen von Carbenoiden beschrieben und weitere Entwicklungsmöglichkeiten skizziert.
      PubDate: 2017-11-15T12:09:01.024201-05:
      DOI: 10.1002/ange.201707026
       
  • Creation of “Rose Petal” and “Lotus Leaf” Effects on Alumina by
           Surface Functionalization and Metal-Ion Coordination
    • Authors: Rahul Dev Mukhopadhyay; Balaraman Vedhanarayanan, Ayyappanpillai Ajayaghosh
      Abstract: Functional differences between superhydrophobic surfaces, such as lotus leaf and rose petals, are due to the subtle architectural features created by nature. Mimicry of these surfaces with synthetic molecules continues to be fascinating as well as challenging. Herein, we demonstrate how inherently hydrophilic alumina surface can be modified to give two distinct superhydrophobic behaviors. Functionalization of alumina with an organic ligand resulted in a rose-petal-like surface (water pinning) with a contact angle of 145° and a high contact angle hysteresis (±69°). Subsequent interaction of the ligand with Zn2+ resulted in a lotus-leaf-like surface with water rolling behavior owing to high contact angle (165°) and low-contact-angle-hysteresis (±2°). In both cases, coating of an aromatic bis-aldehyde with alkoxy chain substituents was necessary to emulate the nanowaxy cuticular feature of natural superhydrophobic materials.Ein neues Blatt: Oberflächenfunktionalisierung und Koordinationspolymerchemie werden genutzt, um MOF-basierte Nanoarchitekturen auf einer Aluminiumoxidoberfläche zu erzeugen. Die inhärente Superhydrophilie der Oberfläche wird derart modifiziert, dass sie das superhydrophobe Verhalten von Rosenblüten und Lotusblättern annimmt.
      PubDate: 2017-11-15T12:08:53.0811-05:00
      DOI: 10.1002/ange.201709463
       
  • Atomically Dispersed Copper–Platinum Dual Sites Alloyed with Palladium
           Nanorings Catalyze the Hydrogen Evolution Reaction
    • Authors: Tingting Chao; Xuan Luo, Wenxing Chen, Bin Jiang, Jingjie Ge, Yue Lin, Geng Wu, Xiaoqian Wang, Yanmin Hu, Zhongbin Zhuang, Yuen Wu, Xun Hong, Yadong Li
      Abstract: Designing highly active catalysts at an atomic scale is required to drive the hydrogen evolution reaction (HER). Copper–platinum (Cu-Pt) dual sites were alloyed with palladium nanorings (Pd NRs) containing 1.5 atom % Pt, using atomically dispersed Cu on ultrathin Pd NRs as seeds. The ultrafine structure of atomically dispersed Cu-Pt dual sites was confirmed with X-ray absorption fine structure (XAFS) measurements. The Pd/Cu-Pt NRs exhibit excellent HER properties in acidic solution with an overpotential of only 22.8 mV at a current density of 10 mA cm−2 and a high mass current density of 3002 A g−1(Pd+Pt) at a −0.05 V potential.Atomar dispergierte duale Kupfer-Platin(Cu-Pt)-Zentren legiert mit Palladium(Pd)-Nanoringen zeigen exzellente Eigenschaften in der Wasserstoffentwicklung. Die elektrokatalytische Aktivität übertrifft diejenige kommerzieller Platin-Kohlenstoff(Pt/C)-Katalysatoren.
      PubDate: 2017-11-15T12:08:28.623015-05:
      DOI: 10.1002/ange.201709803
       
  • Atom-Specific Mutagenesis Reveals Structural and Catalytic Roles for an
           Active-Site Adenosine and Hydrated Mg2+ in Pistol Ribozymes
    • Authors: Sandro Neuner; Christoph Falschlunger, Elisabeth Fuchs, Maximilian Himmelstoss, Aiming Ren, Dinshaw J. Patel, Ronald Micura
      Abstract: The pistol RNA motif represents a new class of self-cleaving ribozymes of yet unknown biological function. Our recent crystal structure of a pre-catalytic state of this RNA shows guanosine G40 and adenosine A32 close to the G53–U54 cleavage site. While the N1 of G40 is within 3.4 Å of the modeled G53 2′-OH group that attacks the scissile phosphate, thus suggesting a direct role in general acid–base catalysis, the function of A32 is less clear. We present evidence from atom-specific mutagenesis that neither the N1 nor N3 base positions of A32 are involved in catalysis. By contrast, the ribose 2′-OH of A32 seems crucial for the proper positioning of G40 through a H-bond network that involves G42 as a bridging unit between A32 and G40. We also found that disruption of the inner-sphere coordination of the active-site Mg2+ cation to N7 of G33 makes the ribozyme drastically slower. A mechanistic proposal is suggested, with A32 playing a structural role and hydrated Mg2+ playing a catalytic role in cleavage.Feuer frei: Atomspezifische Mutagenese zeigt, dass die Ribose-Einheit des konservierten Adenosins A32 und ein hydratisiertes Mg2+-Ion im aktiven Zentrum des Pistolen-Ribozyms zur Spaltungsaktivität beitragen. Im vorgeschlagenen Mechanismus nimmt A32 einen strukturellen Einfluss, und das hydratisierte Mg2+ katalysiert den Spaltungsprozess.
      PubDate: 2017-11-15T12:08:21.27875-05:0
      DOI: 10.1002/ange.201708679
       
  • Access to Chiral Hydropyrimidines through Palladium-Catalyzed Asymmetric
           Allylic C−H Amination
    • Authors: Pu-Sheng Wang; Meng-Lan Shen, Tian-Ci Wang, Hua-Chen Lin, Liu-Zhu Gong
      Abstract: A palladium-catalyzed asymmetric intramolecular allylic C−H amination controlled by a chiral phosphoramidite ligand was established for the preparation of various substituted chiral hydropyrimidinones, the precursors of hydropyrimidines, in high yields with high enantioselectivities. In particular, dienyl sodium N-sulfonyl amides bearing an arylethene-1-sulfonyl group underwent a sequential allylic C−H amination and intramolecular Diels–Alder (IMDA) reaction to produce chiral fused tricyclic tetrahydropyrimidinone frameworks in high yields and with high levels of stereoselectivity. Significantly, this method was used as the key step in an asymmetric synthesis of letermovir.Der Kern der Sache: Eine asymmetrische Palladium-katalysierte intramolekulare allylische C-H-Aminierung, die von einem chiralen Phosphoramiditliganden dirigiert wird, wurde zur effizienten Synthese unterschiedlich substituierter chiraler Hydropyrimidine genutzt. Diese Methode wurde zur asymmetrischen Synthese von Letermovir verwendet (siehe Schema; IMDA=intramolekulare Diels-Alder-Reaktion).
      PubDate: 2017-11-15T12:08:12.832036-05:
      DOI: 10.1002/ange.201709681
       
  • Living Supramolecular Polymerization of a Perylene Bisimide Dye into
           Fluorescent J-Aggregates
    • Authors: Wolfgang Wagner; Marius Wehner, Vladimir Stepanenko, Soichiro Ogi, Frank Würthner
      Abstract: The self-assembly of a new perylene bisimide (PBI) organogelator with 1,7-dimethoxy substituents in the bay position affords non-fluorescent H-aggregates at high cooling rates and fluorescent J-aggregates at low cooling rates. Under properly adjusted conditions, the kinetically trapped “off-pathway” H-aggregates are transformed into the thermodynamically favored J-aggregates, a process that can be accelerated by the addition of J-aggregate seeds. Spectroscopic studies revealed a subtle interplay of π–π interactions and intra- and intermolecular hydrogen bonding for monomeric, H-, and J-aggregated PBIs. Multiple polymerization cycles initiated from the seed termini demonstrate the living character of this chain-growth supramolecular polymerization process.Lebende supramolekulare Polymerisation: Erstmals konnte ein Perylenbisimid (PBI) durch lebende Keimpolymerisation in mehreren Wachstumszyklen verlängert werden. Der PBI-Organogelator bildet „off-pathway”-H-Aggregate, die in die thermodynamisch begünstigten fluoreszierenden J-Aggregate überführt werden.
      PubDate: 2017-11-15T12:08:02.314245-05:
      DOI: 10.1002/ange.201709307
       
  • Double Catalytic Kinetic Resolution (DoCKR) of Acyclic anti-1,3-Diols: The
           Additive Horeau Amplification
    • Authors: Jérémy Merad; Prashant Borkar, Frédéric Caijo, Jean-Marc Pons, Jean-Luc Parrain, Olivier Chuzel, Cyril Bressy
      Abstract: The concept of a synergistic double catalytic kinetic resolution (DoCKR) as described in this article was successfully applied to racemic acyclic anti-1,3-diols, a common motif in natural products. This process takes advantage of an additive Horeau amplification involving two successive enantioselective organocatalytic acylation reactions, and leads to diesters and recovered diols with high enantiopurities. It was first developed with C2-symmetrical diols and then further extended to non-C2-symmetrical anti diols to prepare useful chiral building blocks. The protocol is highly practical as it only requires 1 mol % of a commercially available organocatalyst and leads to easily separable products. This procedure was applied to the shortest reported total synthesis of (+)-cryptocaryalactone, a natural product with anti-germinative activity.Dem Katalysator eine zweite Chance: Eine synergistische doppelte katalytische kinetische Racematspaltung (DoCKR) wurde auf racemische acyclische anti-1,3-Diole, ein häufiges Strukturmotiv von Naturstoffen, angewendet. Die organokatalytische doppelte Acylierung liefert Diester und nichtumgesetzte Diole in hohen Enantiomerenreinheiten. Nach C2-symmetrischen Diolen bewährten sich auch nicht-C2-symmetrische anti-Diole beim Aufbau chiraler Synthesebausteine.
      PubDate: 2017-11-15T12:07:32.1201-05:00
      DOI: 10.1002/ange.201709844
       
  • Modulation of Quorum Sensing in a Gram Positive Pathogen by Linear
           Imprinted Copolymers with anti-Infective Properties
    • Authors: Anfal Motib; Antonio Guerreiro, Firas Al-Bayati, Elena Piletska, Irfan Manzoor, Sulman Shafeeq, Anagha Kadam, Oscar Kuipers, Luisa Hiller, Todd Cowen, Sergey Piletsky, Peter Andrew, Hasan Yesilkaya
      Abstract: Here we describe the development, characterization and biological testing of a new type of linear molecularly imprinted polymer (LMIP) designed to act as anti-infective by blocking the quorum sensing (QS) mechanism and so preventing virulence of the pathogen Streptococcus pneumoniae. The LMIP is prepared (polymerized) in presence of a template molecule, but unlike in traditional molecular imprinting approaches no cross-linker is used. This results in soluble low molecular weight polymer that can act as drug agent in vitro and in vivo. The LMIP was characterized by mass spectrometry to determine its monomer composition. Fragments identified were then aligned along the peptide template by computer modeling, predicting the possible monomer sequence of the LMIP. These findings provide proof of principle that LMIP can be used to block QS, setting the stage for studies on a novel drug-discovery platform and class of materials to target Gram positive pathogens.
      PubDate: 2017-11-15T10:39:15.645608-05:
      DOI: 10.1002/ange.201709313
       
  • Simple Access to the Heaviest Alkaline-Earth Metal Hydride: A Strongly
           Reducing Hydrocarbon-Soluble Barium Hydride Cluster
    • Authors: Sjoerd Harder; Brant Maitland, Michael Wiesinger, Christian Färber, Gerd Ballmann, Holger Elsen, Christian Fischer
      Abstract: Reaction of Ba[N(SiMe3)2]2 with PhSiH3 in toluene gave simple access to the unique Ba hydride cluster Ba7H7[N(SiMe3)2]7 that can be described as a square pyramide spanned by five Ba2+ ions with two flanking BaH[N(SiMe3)2] units. This heptanuclear cluster is well soluble in aromatic solvents and the hydride 1H NMR signals and coupling pattern suggests that the structure is stable in solution. At 95 °C, no coalescence of hydride signals is observed but the cluster slowly decomposes to undefined Ba hydride species. Complex Ba7H7[N(SiMe3)2]7 is a very strong reducing agent that already at room temperature reacts with Me3SiCH=CH2, norbornadiene and ethylene. The highly reactive alkylbarium intermediates cannot be observed and deprotonate the (Me3Si)2Nˉ ion, as confirmed by the crystal structure of Ba14H12[N(SiMe3)2]12[(Me3Si)(Me2SiCH2)N]4.
      PubDate: 2017-11-15T09:25:40.142057-05:
      DOI: 10.1002/ange.201709771
       
  • Frontispiz: Mechanism-Based Inhibitors of the Human Sirtuin 5 Deacylase:
           Structure–Activity Relationship, Biostructural, and Kinetic Insight
    • Authors: Nima Rajabi; Marina Auth, Kathrin R. Troelsen, Martin Pannek, Dhaval P. Bhatt, Martin Fontenas, Matthew D. Hirschey, Clemens Steegborn, Andreas S. Madsen, Christian A. Olsen
      Abstract: Medizinische Chemie C. A. Olsen et al. beschreiben in der Zuschrift auf S. 15032 die Identifizierung wirkungsvoller Inhibitoren der Hydrolase Sirtuin-5 durch ausführliche Struktur-Wirkungs-Studien.
      PubDate: 2017-11-15T08:06:07.79754-05:0
      DOI: 10.1002/ange.201784761
       
  • Durch sichtbares Licht und Nahinfrarotstrahlung abbaubare supramolekulare
           Metallo-Gele
    • Authors: Sabrina Theis; Aitziber Iturmendi, Christian Gorsche, Marco Orthofer, Markus Lunzer, Stefan Baudis, Aleksandr Ovsianikov, Robert Liska, Uwe Monkowius, Ian Teasdale
      Abstract: Der lichtempfindliche Rutheniumkomplex [Ru(bpy)2(4AMP)2](PF6)2 (4AMP=4-(Aminomethyl)pyridin) wurde über die reaktiven Aminogruppen der durch Licht abspaltbaren 4AMP-Liganden in Polyharnstoff-Organo- oder -Hydrogele eingebaut. Im Dunkeln sind diese Gele sehr stabil. Durch Bestrahlen mit sichtbarem Licht oder NIR-Strahlung (letzteres mittels Zweiphotonenabsorption) werden die Ruthenium-Pyridin-Bindungen gespalten, was zum Abbau des supramolekularen Gels führt. Dies ermöglicht eine räumlich und zeitlich aufgelöste Mikrostrukturierung des Gels mithilfe einer Photomaske oder eines gepulsten NIR-Lasers.Ein Hydrogel auf Basis eines supramolekularen, Ruthenium-haltigen Metallopolymers ist im Dunkeln oder bei Abwesenheit von Lösungsmitteln stabil, zeigt aber bei Belichtung mit sichtbarem Licht oder NIR-Strahlung Abbau und schnelle Degelierung.
      PubDate: 2017-11-15T05:32:57.857035-05:
      DOI: 10.1002/ange.201707321
       
  • Crossover between Tilt Families and Zero Area Thermal Expansion in Hybrid
           Prussian Blue Analogues
    • Authors: Anthony E. Phillips; A. Dominic Fortes
      Abstract: Materials in the family of Prussian blue analogues (C3H5N2)2K[M(CN)6], where C3H5N2 is the imidazolium ion and M=Fe, Co, undergo two phase transitions with temperature; at low temperatures the imidazolium cations have an ordered configuration (C2/c), while in the intermediate- and high-temperature phases (both previously reported as R3‾m) they are dynamically disordered. We show from high-resolution powder neutron diffraction data that the high-temperature phase has zero area thermal expansion in the ab-plane. Supported by Landau theory and single-crystal X-ray diffraction data, we re-evaluate the space group symmetry of the intermediate-temperature phase to R3‾. This reveals that the low-to-intermediate temperature transition is due to competition between two different tilt patterns of the [M(CN)6]3− ions. Controlling the relative stabilities of these tilt patterns offers a potential means to tune the exploitable electric behaviour that arises from motion of the imidazolium guest.Zerrbilder und Kippschalter: Eine erneute Untersuchung der Symmetrie zweier cyanidverbrückter Perowskit-Analoga zeigt, dass die Phasenübergänge in diesen Materialien auf zwei konkurrierende Verkippungsmuster zurückzuführen sind. Eine Beeinflussung der Verkippung dieser Hybridmaterialien führt zu Kombinationen von Verzerrungen, die für anorganische Perowskite selten, wenn nicht unmöglich sind.
      PubDate: 2017-11-15T05:32:09.404786-05:
      DOI: 10.1002/ange.201708514
       
  • Enantioselektive Totalsynthese von 3β-Hydroxy-7β-kemp-8(9)-en-6-on, ein
           aus höheren Termiten isoliertes Diterpen
    • Authors: Yuzhou Wang; Anne Jäger, Margit Gruner, Tilo Lübken, Peter Metz
      Abstract: Die erste Totalsynthese des Titelditerpens wurde ausgehend vom Wieland-Miescher-Keton erreicht. Eine diastereoselektive Sulfa-Michael-Addition ermöglichte die Erzeugung der empfindlichen β,γ-ungesättigten Ketoneinheit, während das tetracyclische Kempan-Gerüst problemlos durch Dominometathese aufgebaut wurde.Schwefel hilft! Die erste Totalsynthese des Titelditerpens wurde ausgehend vom Wieland-Miescher-Keton erreicht. Eine diastereoselektive Sulfa-Michael-Addition ermöglichte die Erzeugung der empfindlichen β,γ-ungesättigten Ketoneinheit, während das tetracyclische Kempan-Gerüst problemlos durch Dominometathese aufgebaut wurde.
      PubDate: 2017-11-15T05:32:03.778848-05:
      DOI: 10.1002/ange.201708561
       
  • High-Pressure Band-Gap Engineering in Lead-Free Cs2AgBiBr6 Double
           Perovskite
    • Authors: Qian Li; Yonggang Wang, Weicheng Pan, Wenge Yang, Bo Zou, Jiang Tang, Zewei Quan
      Abstract: Novel inorganic lead-free double perovskites with improved stability are regarded as alternatives to state-of-art hybrid lead halide perovskites in photovoltaic devices. The recently discovered Cs2AgBiBr6 double perovskite exhibits attractive optical and electronic features, making it promising for various optoelectronic applications. However, its practical performance is hampered by the large band gap. In this work, remarkable band gap narrowing of Cs2AgBiBr6 is, for the first time, achieved on inorganic photovoltaic double perovskites through high pressure treatments. Moreover, the narrowed band gap is partially retainable after releasing pressure, promoting its optoelectronic applications. This work not only provides novel insights into the structure–property relationship in lead-free double perovskites, but also offers new strategies for further development of advanced perovskite devices.Hochdruck wurde verwendet, um die Kristallstruktur des Cs2AgBiBr6-Doppelperovskits zu modulieren und seine Bandlücke zu manipulieren. Eine um 22.3 % verengte Bandlücke wurde für den anorganischen, photovoltaischen Doppelperovskit erzielt. Die verengte Bandlücke bleibt nach Druckentlastung teilweise bestehen, was Anwendungen des Perovskits in der Optoelektronik eröffnet.
      PubDate: 2017-11-15T05:31:58.706988-05:
      DOI: 10.1002/ange.201708684
       
  • Scandium-Catalyzed Self-Assisted Polar Co-monomer Enchainment in Ethylene
           Polymerization
    • Authors: Jiazhen Chen; Yanshan Gao, Binghao Wang, Tracy L. Lohr, Tobin J. Marks
      Abstract: Direct coordinative copolymerization of ethylene with functionalized co-monomers is a long-sought-after approach to introducing polyolefin functionality. However, functional-group Lewis basicity typically depresses catalytic activity and co-monomer incorporation. Finding alternatives to intensively studied group 4 d0 and late-transition-metal catalysts is crucial to addressing this long-standing challenge. Shown herein is that mono- and binuclear organoscandium complexes with a borate cocatalyst are active for ethylene + amino olefin [AO; H2C=CH(CH2)nNR2] copolymerizations in the absence of a Lewis-acidic masking reagent. Both activity (up to 4.2×102 kg mol−1⋅h−1> atm−1>) and AO incorporation (up to 12 % at 0.2 m [AO]) are appreciable. Linker-length-dependent (n) AO incorporation and mechanistic probes support an unusual functional-group-assisted enchainment mechanism. Furthermore, the binuclear catalysts exhibit enhanced AO tolerance and enhanced long chain AO incorporation.Selbstunterstützt: Scandium-katalysierte Copolymerisationen von Ethylen mit Aminoolefin (AO) gelingen ohne Zugabe von Lewis-sauren Maskierungsreagentien. Von der Linkerlänge abhängige AO-Verkettungsmuster verweisen auf einen ungewöhnlichen Aminogruppen-unterstützten Verkettungsmechanismus. Die Polymerisationsraten mit zweikernigen Katalysatoren hängen weniger von der AO-Konzentration ab, und die Einbaumuster bei größeren Linkerlängen sprechen für eine bimetallische kooperative Verkettung.
      PubDate: 2017-11-15T05:31:51.361308-05:
      DOI: 10.1002/ange.201708797
       
  • Localized Supramolecular Peptide Self-Assembly Directed by Enzyme-Induced
           Proton Gradients
    • Authors: Jennifer Rodon Fores; Miguel Leonardo Martinez Mendez, Xiyu Mao, Déborah Wagner, Marc Schmutz, Morgane Rabineau, Philippe Lavalle, Pierre Schaaf, Fouzia Boulmedais, Loïc Jierry
      Abstract: Electrodes are ideal substrates for surface localized self-assembly processes. Spatiotemporal control over such processes is generally directed through the release of ions generated by redox reactions occurring specifically at the electrode. The so-used gradients of ions proved their effectiveness over the last decade but are in essence limited to material-based electrodes, considerably reducing the scope of applications. Herein is described a strategy to enzymatically generate proton gradients from non-conductive surfaces. In the presence of oxygen, immobilization of glucose oxidase (GOx) on a multilayer film provides a flow of protons through enzymatic oxidation of glucose by GOx. The confined acidic environment located at the solid–liquid interface allows the self-assembly of Fmoc-AA-OH (Fmoc=fluorenylmethyloxycarbonyl and A=alanine) dipeptides into β-sheet nanofibers exclusively from and near the surface. In the absence of oxygen, a multilayer nanoreactor containing GOx and horseradish peroxidase (HRP) similarly induces Fmoc-AA-OH self-assembly.Die Kraft der Enzyme: In einem mehrschichtigen Film mit Protonengradient und einem Reaktionssystem aus zwei Enzymen wird lokalisiert ein supramolekulares Hydrogel gebildet. Dieser Ansatz bildet eine Alternative zur pH-responsiven Selbstorganisation an Elektrodenoberflächen.
      PubDate: 2017-11-15T05:31:44.58671-05:0
      DOI: 10.1002/ange.201709029
       
  • Oxidative P-P-Bindungsaddition an Cobalt(−I): Bildung eines
           Low-spin-Cobalt(III)-Phosphanidokomplexes
    • Authors: Peter Coburger; Serhiy Demeshko, Christian Rödl, Evamarie Hey-Hawkins, Robert Wolf
      Abstract: Die oxidative P-P-Bindungsaddition eines ortho-Carboran-substituierten 1,2-Diphosphetans an Cobalt(−I) in [K(thf)0.2][Co(η4-cod)2)] (cod=1,5-Cycloctadien) ermöglichte die Darstellung des ersten homoleptischen Cobalt(III)-Phosphanidokomplexes [K(thf)4][Co{1,2-(PtBu)2C2B10H12}2] (1). Diese Verbindung ist ein seltenes Beispiel eines verzerrt tetraedrisch koordinierten 3d6-Komplexes mit einem Low-spin-Grundzustand. Magnetische Messungen ergaben, dass 1 zwischen 2 und 270 K im Festkörper und bei 298 K in einer [D8]THF-Lösung diamagnetisch ist. Dichtefunktionalrechnungen zeigten, dass der diamagnetische Grundzustand durch die starken σ-Donor- und die moderaten π-Donoreigenschaften der Bisphosphanidoliganden verursacht wird.Ein homoleptischer Cobaltphosphanidokomplex wird durch die Reaktion eines Carboran-1,2-diphosphetans mit einer Cobalt(−I)-Quelle gebildet. Die resultierende Cobalt(III)-Verbindung ist der erste Vertreter einer neuen Klasse tetraedrischer Low-spin-Phosphanidokomplexe.
      PubDate: 2017-11-15T05:31:37.643735-05:
      DOI: 10.1002/ange.201709140
       
  • Quantitative Prediction of Rate Constants for Aqueous Racemization To
           Avoid Pointless Stereoselective Syntheses
    • Authors: Andrew Ballard; Hiwa O. Ahmad, Stefania Narduolo, Lucy Rosa, Nikki Chand, David A. Cosgrove, Peter Varkonyi, Nabil Asaad, Simone Tomasi, Niklaas J. Buurma, Andrew G. Leach
      Abstract: Racemization has a large impact upon the biological properties of molecules but the chemical scope of compounds with known rate constants for racemization in aqueous conditions was hitherto limited. To address this remarkable blind spot, we have measured the kinetics for racemization of 28 compounds using circular dichroism and 1H NMR spectroscopy. We show that rate constants for racemization (measured by ourselves and others) correlate well with deprotonation energies from quantum mechanical (QM) and group contribution calculations. Such calculations thus provide predictions of the second-order rate constants for general-base-catalyzed racemization that are usefully accurate. When applied to recent publications describing the stereoselective synthesis of compounds of purported biological value, the calculations reveal that racemization would be sufficiently fast to render these expensive syntheses pointless.Das Racemisierungspotential komplexer organischer Moleküle wurde mithilfe einfacher quantenmechanischer Rechnungen und einem Gruppenadditivitätsschema vorhergesagt. Organochemiker können damit erst überprüfen, ob vorgegebene Syntheseziele strukturell stabil sind, bevor sie eine potentiell langwierige und kostenintensive chirale Synthese beginnen.
      PubDate: 2017-11-15T05:31:30.7103-05:00
      DOI: 10.1002/ange.201709163
       
  • Layer-by-Layer Assembled Conductive Metal–Organic Framework Nanofilms
           for Room-Temperature Chemiresistive Sensing
    • Authors: Ming-Shui Yao; Xiao-Jing Lv, Zhi-Hua Fu, Wen-Hua Li, Wei-Hua Deng, Guo-Dong Wu, Gang Xu
      Abstract: The utility of electronically conductive metal–organic frameworks (EC-MOFs) in high-performance devices has been limited to date by a lack of high-quality thin film. The controllable thin-film fabrication of an EC-MOF, Cu3(HHTP)2, (HHTP=2,3,6,7,10,11-hexahydroxytriphenylene), by a spray layer-by-layer liquid-phase epitaxial method is reported. The Cu3(HHTP)2 thin film can not only be precisely prepared with thickness increment of about 2 nm per growing cycle, but also shows a smooth surface, good crystallinity, and high orientation. The chemiresistor gas sensor based on this high-quality thin film is one of the best room-temperature sensors for NH3 among all reported sensors based on various materials.Hauchdünne Sensoren: Auf der Grundlage hochorientierter kristalliner Filme aus einem elektronenleitenden Metall-organischen Gerüst mit genau einstellbarer Dicke wurden langlebige chemoresistive Sensoren für den schnellen und selektiven Nachweis von NH3 bei Raumtemperatur hergestellt.
      PubDate: 2017-11-15T05:31:25.950125-05:
      DOI: 10.1002/ange.201709558
       
  • Antibacterial Narrow-Band-Gap Conjugated Oligoelectrolytes with High
           Photothermal Conversion Efficiency
    • Authors: Bing Wang; Guangxue Feng, Martin Seifrid, Ming Wang, Bin Liu, Guillermo C. Bazan
      Abstract: Two conjugated oligoelectrolytes (COEs), WMG1 and WMG2, were designed with the goal of achieving near infrared absorption and high photothermal conversion efficiency. Specifically, electron-rich thiophene and electron-poor benzo[1,2-c:4,5-c′]bis[1,2,5]thiadiazole subunits were introduced into the conjugated core to modulate the optical gap and to reduce the fluorescence emission efficiency. WMG1 and WMG2 show absorption maxima at around 800 nm, which favors tissue penetration. Although relatively small in size, WMG1 and WMG2 exhibit photothermal conversion efficiencies of circa 60 % and 54 %, respectively. WMG1 shows dark toxicity to the Gram positive bacterium B. subtilis and good photothermal killing efficiency toward both B. subtilis and Gram negative E. coli, features that demonstrate the promising potential of the COE molecular design for photothermal applications.Zwei konjugierte Oligoelektrolyte (COEs), WMG1 und MWG2, zeigen NIR-Absorption und hohe photothermische Wirkungsgrade. WMG1 zeichnet sich durch eine effiziente photothermische Abtötung von Pathogenen aus und wirkt im Dunkeln toxisch gegen Gram-positive Bakterien.
      PubDate: 2017-11-15T05:31:17.784482-05:
      DOI: 10.1002/ange.201709887
       
  • Rational Design of Single Molybdenum Atoms Anchored on N-Doped Carbon for
           Effective Hydrogen Evolution Reaction
    • Authors: Wenxing Chen; Jiajing Pei, Chun-Ting He, Jiawei Wan, Hanlin Ren, Youqi Zhu, Yu Wang, Juncai Dong, Shubo Tian, Weng-Chon Cheong, Siqi Lu, Lirong Zheng, Xusheng Zheng, Wensheng Yan, Zhongbin Zhuang, Chen Chen, Qing Peng, Dingsheng Wang, Yadong Li
      Abstract: The highly efficient electrochemical hydrogen evolution reaction (HER) provides a promising pathway to resolve energy and environment problems. An electrocatalyst was designed with single Mo atoms (Mo-SAs) supported on N-doped carbon having outstanding HER performance. The structure of the catalyst was probed by aberration-corrected scanning transmission electron microscopy (AC-STEM) and X-ray absorption fine structure (XAFS) spectroscopy, indicating the formation of Mo-SAs anchored with one nitrogen atom and two carbon atoms (Mo1N1C2). Importantly, the Mo1N1C2 catalyst displayed much more excellent activity compared with Mo2C and MoN, and better stability than commercial Pt/C. Density functional theory (DFT) calculation revealed that the unique structure of Mo1N1C2 moiety played a crucial effect to improve the HER performance. This work opens up new opportunities for the preparation and application of highly active and stable Mo-based HER catalysts.Einzelne Mo-Atome dispergiert auf N-dotiertem Kohlenstoff zeigen hohe katalytische Aktivität und Stabilität in der Wasserstoffentwicklung (HER). Die Katalysatorstruktur wurde durch Elektronenmikroskopie und XAFS charakterisiert, und die einzigartigen katalytischen Eigenschaften wurden in DFT-Rechnungen untersucht.
      PubDate: 2017-11-15T05:31:08.15851-05:0
      DOI: 10.1002/ange.201710599
       
  • Biomimic Peptide-Gated Nanoporous Membrane for On-Demand Molecule
           Transport
    • Authors: Kai Xiao; Kai Wu, Lu Chen, Xiang-Yu Kong, Yuqi Zhang, Liping Wen, Lei Jiang
      Abstract: The controllable molecule transport is crucial to realize many highly valuable applications both in vivo and in vitro. Nanoporous membrane, with nanoscopic pores, high porosity, uniform pore dimension, and controllable surface chemical properties, hold tremendous potential to achieve this function. Here, we report a nano-gating system for on-demand molecule transport based on peptide-gated nanoporous membrane. Acting as gatekeeper, the peptides introduced to the nanoporous membrane provide an opportunity to realize on-demand on-off-states transport profiles via reversible conformational switch of peptides. This nano-gating system with sustained release performance provides a more sophisticated molecule transport platform, which anticipates applications in localized drug delivery with feedback function.
      PubDate: 2017-11-15T04:59:27.773024-05:
      DOI: 10.1002/ange.201708695
       
  • Photo-induced Pedalo-type Motion in an Azodicarboxamide-based Molecular
           Switch
    • Authors: Saeed Amirjalayer; Alberto Martinez-Cuezva, Jose Berná, Sander Woutersen, Wybren Jan Buma
      Abstract: Well-defined structural changes of molecular units that can be triggered by light are crucial for the development of photoactive functional materials. Here we report on a novel switch that has azodicarboxamide as its photo triggerable element. Time-resolved UV-pump/IR probe spectroscopy in combination with quantum chemical calculations shows that the azodicarboxamide functionality -in contrast to other azo-based chromophores- does not undergo trans-cis photoisomerization. Instead, a photo-induced pedalo-type motion occurs, which due to its volume-conserving properties enables to design functional molecular systems with controllable motion in a confined space.
      PubDate: 2017-11-15T04:59:24.786154-05:
      DOI: 10.1002/ange.201709666
       
  • Deep Level Defect-Enhanced Photothermal Performance of Bismuth
           Sulfide-Gold Heterojunction Nanorods for CT Imaging-Guided Photothermal
           Therapy of Cancer
    • Authors: Yan Cheng; Yun Chang, Yanlin Feng, Hui Jian, Zhaohui Tang, Haiyuan Zhang
      Abstract: Bismuth sulfide (Bi2S3) nanomaterials are emerging as a promising theranostic platform for CT imaging and photothermal therapy of cancer. Herein, the photothermal property of Bi2S3 nanorods (NRs) was unveiled to intensely correlate to their intrinsic deep level defects (DLDs) that potentially could work as electron-hole nonradiative recombination centers to promote phonon production, ultimately leading to photothermal performance. Bi2S3-Au heterojunction NRs were designed to hold more significant DLD property, exhibiting more potent photothermal performance than Bi2S3 NRs. Under 808 nm laser irradiation, Bi2S3-Au NRs could trigger higher cellular heat shock protein 70 expression and more apoptotic cells than Bi2S3 NRs, and caused severe cell death and tumor growth inhibition, showing great potential for CT imaging-guided photothermal therapy of cancer.
      PubDate: 2017-11-15T02:50:31.183409-05:
      DOI: 10.1002/ange.201710399
       
  • Subporpholactone, Subporpholactam, Imidazolosubporphyrin, and Iridium
           Complexes of Imidazolosubporphyrin: Formation of Iridium Carbene Complexes
           
    • Authors: Atsuhiro Osuka; Kota Yoshida
      Abstract: Pyrrole-modified subporphyrins bearing a non-pyrrolic cyclic unit, subporpholactone, subporpholactam, and imidazolosubporphyrin were newly synthesized. They show subporphyrin-like absorption and fluorescence spectra that are red-shifted in the order of subporpholactam < subporpholactone < imidazolosubporphyrin. Metalation of the imidazolosubporphyrin with (pentamethylcyclopentadienyl)iridium(III) dichloride dimer gave a complex, in which the Ir(III) atom was attached at the peripheral nitrogen atom of the imidazole moiety and the ortho-position of the meso-phenyl group. Reaction of this complex with diphenylacetylene gave different products depending on an additive; a phenyl-rearranged product in the presence of NaBArF4 (ArF = 3,5-bis(trifluoromethyl)phenyl) and two isomeric carbene complexes in the presence of KPF6.
      PubDate: 2017-11-15T00:50:45.490897-05:
      DOI: 10.1002/ange.201711166
       
  • Achieving Strong Positive Cooperativity through Activating Weak
           Non-Covalent Interactions
    • Authors: Yan-Long Ma; Hua Ke, Arto Valkonen, Kari Rissanen, Wei Jiang
      Abstract: Positive cooperativity achieved through activating weak non-covalent interactions is common in biological assemblies but is rarely observed in synthetic complexes. Two new naphthotubes have been synthesized and the syn isomer binds DABCO-based organic cations with high orientational selectivity. Surprisingly, the ternary complex with two hosts and one guest shows a high cooperativity factor (α=580), which is the highest reported for synthetic systems without involving ion-pairing interactions. The X-ray single-crystal structure revealed that the strong positive cooperativity likely originates from eight C-H⋅⋅⋅O hydrogen bonds between the two head-to-head-arranged syn tube molecules. These relatively weak hydrogen bonds were not observed in the free hosts and only emerged in the complex. Furthermore, this complex was used as a basic motif to construct a robust [2+2] cyclic assembly, thus demonstrating its potential in molecular self-assembly.
      PubDate: 2017-11-14T21:55:42.050967-05:
      DOI: 10.1002/ange.201711077
       
  • Preise der Real Sociedad Española de Química 2017
    • PubDate: 2017-11-14T12:51:23.549755-05:
      DOI: 10.1002/ange.201710990
       
  • A Manganese Pre-Catalyst: Mild Reduction of Amides, Ketones, Aldehydes,
           and Esters
    • Authors: Colin M. Kelly; Robert McDonald, Orson L. Sydora, Mark Stradiotto, Laura Turculet
      Abstract: A new (N-phosphinoamidinate)manganese complex is shown to be a useful pre-catalyst for the hydrosilative reduction of carbonyl compounds, and in most cases at room temperature. The Mn-catalyzed reduction of tertiary amides to tertiary amines, with a useful scope, is demonstrated for the first time by use of this catalyst, and is competitive with the most effective transition-metal catalysts known for such transformations. Ketones, aldehydes, and esters were also successfully reduced under mild conditions by using this new Mn catalyst.Man(gan) kann: Ein neuer (N-Phosphinoamidinat)mangan-Präkatalysator vermittelt die Reduktion verschiedener Carbonylverbindungen durch Hydrosilylierung unter vergleichbaren Reaktionsbedingungen wie bekannte effektive Übergangsmetallkatalysatoren. Das Ergebnis ist eine Klasse präparativ nützlicher Mn-katalysierter Umsetzungen.
      PubDate: 2017-11-14T12:51:12.123332-05:
      DOI: 10.1002/ange.201709441
       
  • Enantioselective Copper-Catalyzed Alkylation of Quinoline N-Oxides with
           Vinylarenes
    • Authors: Songjie Yu; Hui Leng Sang, Shaozhong Ge
      Abstract: An asymmetric copper-catalyzed alkylation of quinoline N-oxides with chiral Cu–alkyl species, generated by migratory insertion of a vinylarene into a chiral Cu−H complex, is reported. A variety of quinoline N-oxides and vinylarenes underwent this Cu-catalyzed enantioselective alkylation reaction, affording the corresponding chiral alkylated N-heteroarenes in high yield with high-to-excellent enantioselectivity. This enantioselective protocol represents the first general and practical approach to access a wide range of chiral alkylated quinolines.Ein breites Spektrum an Chinolin-N-oxiden und Vinylarenen kann in der Titelreaktion zu den entsprechenden chiralen alkylierten Chinolinen umgesetzt werden. Die Produkte werden hoch enantioselektiv und in hohen Ausbeuten erhalten.
      PubDate: 2017-11-14T12:51:08.61571-05:0
      DOI: 10.1002/ange.201709411
       
  • Kationische stickstoffdotierte helikale Nanographene
    • Authors: Kun Xu; Yubin Fu, Youjia Zhou, Felix Hennersdorf, Peter Machata, Ilka Vincon, Jan J. Weigand, Alexey A. Popov, Reinhard Berger, Xinliang Feng
      Abstract: Wir berichten über Design und Synthese einer Serie von neuen kationischen stickstoffdotierten Nanographenen (CNDN) mit einer nichtplanaren Geometrie und axialer Chiralität. Einkristall-Röntgendiffraktometrie beweist deren helikale und teils “Cove”-terminierte Struktur. Verglichen mit den reinen Kohlenstoffanalogen liegen die Grenzorbitale der CNDN energetisch tiefer, was zu einer verringerten optischen Energielücke und einer erhöhten Elektronenaffinität führt. Alle Derivate zeigen in cyclovoltammetrischen Untersuchungen quasireversibles Reduktionsverhalten. Abhängig von der Zahl an Stickstoffdotanden ist es möglich, neutrale Radikale (bei einem Stickstoffdotanden) oder Radikalkationen (bei zwei Stickstoffdotanden) während des Reduktionsprozesses über In-situ-Spektroelektrochemie zu analysieren. Kationische Stickstoffdotierung kombiniert mit Helizität erschließt neue Wege für das Design und die Synthese von ausgedehnten Nanographenen und Nanographenstreifen.Stickstoff Plus: Ein „Bottom-up”-Ansatz ermöglicht einen einfachen Zugang zu kationischen stickstoffdotierten helikalen Nanographenen. Die neuen Nanographene haben vielversprechende Eigenschaften für optische und elektronische Anwendungen.
      PubDate: 2017-11-14T12:50:54.490552-05:
      DOI: 10.1002/ange.201707714
       
  • Ausgewählte Kupfer-katalysierte Reaktionen für die Bildung von C-N-,
           C-O-, C-S- und C-C-Bindungen
    • Authors: Subhajit Bhunia; Govind Goroba Pawar, S. Vijay Kumar, Yongwen Jiang, Dawei Ma
      Abstract: Die metallkatalysierte Kreuzkupplung ist eine der wichtigsten Umwandlungen der organischen Synthese. Aufgrund der geringen Toxizität und des günstigen Preises von Kupfer hat die Kupferkatalyse viel Interesse geweckt. Die traditionelle Ullmann-Kupplung hat jedoch eine geringe Substratbreite und erfordert harsche Reaktionsbedingungen. In den vergangenen zwei Jahrzehnten wurden zweizähnige Liganden, z. B. Aminosäuren, Diamine, 1,3-Diketone und Oxalsäurediamide, eingeführt, die Cu-katalysierte Kupplungen von Arylhalogeniden und Nucleophilen sowohl bei niedrigen Temperaturen als auch in katalytischer Weise ermöglichen. Dadurch ist die Cu-vermittelte Kreuzkupplung zu einer attraktiven Reaktion für die akademische Forschung und die Industrie geworden. Dieser Aufsatz fasst Fortschritte bei Kupplungen von (Hetero)Arylhalogeniden mit verschiedenen Nucleophilen zusammen und stellt Entwicklungen bei Cu-katalysierten Kupplungen mit Arylboronaten und Cu-vermittelten Trifluormethylierungen von aromatischen Elektrophilen vor.Aktuelle Fortschritte bei Cu/Ligand-katalysierten Kupplungen von (Hetero)Arylhalogeniden und Nucleophilen, Cu-katalysierten Kupplungen mit Arylboronaten und Cu-vermittelten Trifluormethylierungen von aromatischen Elektrophilen werden in diesem Aufsatz zusammengefasst.
      PubDate: 2017-11-14T12:50:46.206255-05:
      DOI: 10.1002/ange.201701690
       
  • Time-Resolved Interception of Multiple-Charge Accumulation in a
           Sensitizer–Acceptor Dyad
    • Authors: Stéphanie Mendes Marinho; Minh-Huong Ha-Thi, Van-Thai Pham, Annamaria Quaranta, Thomas Pino, Christophe Lefumeux, Thierry Chamaillé, Winfried Leibl, Ally Aukauloo
      Abstract: Biomimetic models that contain elements of photosynthesis are fundamental in the development of synthetic systems that can use sunlight to produce fuel. The critical task consists of running several rounds of light-induced charge separation, which is required to accumulate enough redox equivalents at the catalytic sites for the target chemistry to occur. Long-lived first charge-separated state and distinct electronic signatures for the sequential charge accumulated species are essential features to be able to track these events on a spectroscopic ground. Herein, we use a double-excitation nanosecond pump–pump–probe experiment to interrogate two successive rounds of photo-induced electron transfer on a molecular dyad containing a naphthalene diimide (NDI) linked to a [Ru(bpy)3]2+ (bpy=bipyridine) chromophore by using a reversible electron donor. We report an unprecedented long-lived two-electron charge accumulation (t=200 μs).Eine molekulare Dyade aus einer Naphthalendiimid(NDI)-Einheit und einem [Ru(bpy)3]2+-Chromophor (bpy=Bipyridin) wurde in einem Nanosekunden-Pump-Probe-Experiment mit Doppelblitzanregung hinsichtlich zweier aufeinanderfolgender lichtinduzierter Elektronentransfers untersucht. Dabei tritt eine beispiellos langlebige Zwei-Elektronen-Ladungsakkumulation auf. CSS=ladungsgetrennter Zustand.
      PubDate: 2017-11-14T12:50:36.970807-05:
      DOI: 10.1002/ange.201706564
       
  • 3D-Laser-Mikro-Nanodruck: Herausforderungen für die Chemie
    • Authors: Christopher Barner-Kowollik; Martin Bastmeyer, Eva Blasco, Guillaume Delaittre, Patrick Müller, Benjamin Richter, Martin Wegener
      Abstract: 3D-Druck ist eine leistungsfähige Technik für die maßgeschneiderte Herstellung funktionaler Materialien. Dieser Aufsatz fasst den Stand der Technik im Hinblick auf 3D-Laser-Mikro- und -Nanodruck zusammen und erkundet die chemischen Herausforderungen, die derzeit die volle Etablierung dieser Technologie limitieren: von der Entwicklung fortgeschrittener Materialien für Anwendungen in der Zellbiologie und der Elektronik bis hin zu den bestehenden chemischen Grenzen des schnellen Schreibens mit Auflösungen unterhalb der Beugungsgrenze. Des Weiteren untersuchen wir Möglichkeiten zur Realisierung des direkten Laserschreibens mehrerer Materialien aus einem Photolack heraus, basierend auf wellenlängenselektiven photochemischen Prozessen (λ-Orthogonalität). Schließlich betrachten wir chemische Prozesse, mit deren Hilfe adaptive 3D-Strukturen geschrieben werden können, die auf externe Stimuli wie Licht, Wärme, pH-Wert oder spezifische Moleküle reagieren, sowie fortgeschrittene Konzepte für abbaubare Stützstrukturen.Alles ist gedruckt: Fortschritte im Mikro- und Nanodruck durch 3D-Laserlithographie werden vorgestellt, und verbleibende chemischen Herausforderungen der Technologie werden identifiziert – z. B. das Design funktionaler Photolacke für die Erzeugung multifunktionaler Nanostrukturen sowie die Fähigkeit, unterschiedliche Materialeigenschaften aus einem Lack heraus mit unterschiedlichen Lichtfarben zu schreiben, und die Fähigkeit, 3D-Lithographie unterhalb der Beugungsgrenze zu betreiben.
      PubDate: 2017-11-14T12:50:32.003217-05:
      DOI: 10.1002/ange.201704695
       
  • N-Heterocyclic Carbene Catalysis via Azolium Dienolates: An Efficient
           Strategy for Enantioselective Remote Functionalizations
    • Authors: Dieter Enders; Xiang-Yu Chen, Qiang Liu, Pankaj Chauhan
      Abstract: N-heterocyclic carbene (NHC) catalysis has emerged as a powerful strategy in organic synthesis. In recent years a number of reviews have been published on NHC-catalyzed transformations involving Breslow intermediates, acyl azoliums, α,β-unsaturated acyl azoliums, homoenolate equivalents and azolium enolates. However, the azolium dienolate intermediates generated by NHCs have been employed in asymmetric synthesis only very recently, especially in cycloadditions dealing with remote functionalization. This Minireview highlights all the developments and the new advances in the NHC-catalyzed asymmetric cycloaddition resections involving azolium dienolate intermediates.
      PubDate: 2017-11-14T10:21:46.574416-05:
      DOI: 10.1002/ange.201709684
       
  • In Situ Scatheless Cell Detachment Reveals Connections Between Adhesion
           Strength and Viability at Single-Cell Resolution
    • Authors: Sifeng Mao; Wanling Zhang, Qiushi Huang, Masqooh Khan, Haifang Li, Katsumi Uchiyama, Jin-Ming Lin
      Abstract: Single-cell biology provides insights to some of the most fundamental processes in biology and promotes the understanding of life's mysteries. And as the technologies to study single-cells expand, they will require sophisticated analytical tools to make sense of various behaviors and components of single-cells as well as their relations in adherent tissue culture. In this paper, we revealed cell heterogeneity and uncovered the connections between cell adhesion strength and cell viability at single-cell resolution by extracting single adherent cells of interest from standard tissue culture via a microfluidic chip based Live Single-Cell Extractor (LSCE). We not only uncovered cell heterogeneity and the connections between cell adhesion strength and cell viability, but also provided a new methodology for single-cell biology.
      PubDate: 2017-11-14T10:20:43.385235-05:
      DOI: 10.1002/ange.201710273
       
  • Oxime Ether Radical Cations Stabilized by N-Heterocyclic Carbene
    • Authors: Youngsuk Kim; Kimoon Kim, Eunsung Lee
      Abstract: N-heterocyclic carbene nitric oxide (NHCNO) radicals, which can be regarded as iminoxyl radicals stabilized by NHCs, were found to react with a series of silyl and alkyl triflates to generate the corresponding oxime ether radical cations. The structures of the resulting oxime ether radical cations were determined by X-ray crystallography, along with EPR and computational analysis. In contrast, lutidinium triflate produced a 1:1 mixture of [NHCNO+][OTf-] and [NHCNHOH+][OTf-] upon the reaction with NHCNO. This study adds an important example of stable singlet carbenes stabilizing main group radicals due to their π-conjugating effect, the synthesis and structures of which have never been elucidated previously.
      PubDate: 2017-11-14T08:27:18.810563-05:
      DOI: 10.1002/ange.201710530
       
  • A Simple Pre-lithiation Strategy to Build High-Rate and Long-life
           Lithium-ion Battery with Improved Low-temperature Performance
    • Authors: Yonggang Wang; Yao Liu, Bingchang Yang, Xiaoli Dong, Yongyao Xia
      Abstract: Lithium-ion batteries (LIBs) are being used to power the commercial electric vehicles (EVs). However, the charge/discharge rate and life of current LIBs still cannot satisfy the further development of EVs. Furthermore, the poor low temperature performance of LIBs limits their application in cold climates and high altitude areas. Herein, a simple pre-lithiation method is developed to fabricate a new LIB. In this strategy, a Li3V2(PO4)3 cathode and a pristine hard carbon anode are used to form a primary cell, and the initial Li+ extraction from Li3V2(PO4)3 is used to pre-lithiate the hard carbon. Then, the self-formed Li2V2(PO4)3 cathode and pre-lithiated hard carbon anode are used to form a 4 V LIB. It is demonstrated that the LIB exhibits a maximum energy density of 208.3 Wh kg-1, a maximum power density of 8291 W kg-1 and a long-life of 2000 cycles. When operated at -40 oC, the LIB can keep 67 % capacity of room temperature, which is much better than conventional LIBs.
      PubDate: 2017-11-14T08:27:08.723545-05:
      DOI: 10.1002/ange.201710555
       
  • Internal Peptide Late-Stage Diversification: Peptide Isosteric Triazoles
           for Primary and Secondary C(sp3)‒H Activation
    • Authors: Michaela Bauer; Wei Wang, Mélanie L. Lorion, Chuan Dong, Lutz Ackermann
      Abstract: Secondary C(sp3)-H arylations were accomplished by peptide bond isosteric triazoles in palladium catalysis. The unique power of this approach was reflected by enabling secondary C(sp3)-H functionalizations on terminal peptides as well as the unprecedented positional-selective C(sp3)-H functionalization of internal peptides, setting the stage for modular peptide late-stage diversification.
      PubDate: 2017-11-14T08:26:38.861505-05:
      DOI: 10.1002/ange.201710136
       
  • Organocatalyzed photo-controlled radical polymerization of
           semi-fluorinated (meth)acrylates driven by visible light
    • Authors: Mao Chen; Honghong Gong, Yucheng Zhao, Xianwang Shen, Jun Lin
      Abstract: Fluorinated polymers are important materials that are widely used in many areas. Herein, we report the development of a metal-free photo-controlled radical polymerization of semi-fluorinated (meth)acrylates with a new visible light absorbing organocatalyst. This method allows the production of a variety of semi-fluorinated polymers with narrow molar weight distributions from semi-fluorinated trithiocarbonates or perfluoroalkyl iodide. The high performance of "ON/OFF" control and chain extension experiments further demonstrate the utility and reliability of this method. Furthermore, to streamline the preparation of semi-fluorinated polymers, a scalable continuous-flow approach has been developed. Given the broad interest in fluorinated materials and photopolymerization, we expect this method will facilitate the development of advanced materials with unique property.
      PubDate: 2017-11-14T07:50:27.6974-05:00
      DOI: 10.1002/ange.201711053
       
  • Conductive Microporous Covalent Triazine-Based Framework for
           High-Performance Electrochemical Capacitive Energy Storage
    • Authors: Weiqiao Deng; Yajuan Li, Shuanghao Zheng, Xue Liu, Pan Li, Lei Sun, Ruixia Yang, Sen Wang, Zhongshuai Wu, Xinhe Bao
      Abstract: Nitrogen enriched porous nanocarbon, graphene and conductive polymers attracted increasing attention in the application of supercapacitors. However, the electrode material possessing large specific surface area (SSA) and high nitrogen doping concentration simultaneously, which is needed for excellent supercapacitors, has not been achieved thus far. Herein, we developed a class of tetracyanoquinodimethane-derived conductive microporous covalent triazine-based frameworks (marked as TCNQ-CTFs) with high nitrogen content (> 8%) and large SSA (> 3600 m²/g) at the same time. These CTFs exhibited excellent specific capacitances with the highest value exceeding 380 F/g, considerable energy density of 42.8 Wh/kg and remarkable cycling stability without any capacitance degradation after 10000 cycles. This class of CTFs should hold a great potential as high-performance electrode material for electrochemical energy storage system.
      PubDate: 2017-11-14T07:20:50.82118-05:0
      DOI: 10.1002/ange.201711169
       
  • Cobalt-catalyzed Suzuki biaryl coupling of aryl halides
    • Authors: Robin Bedford; Soneela Asghar, Sanita Tailor, Elorriaga David
      Abstract: Readily accessed cobalt pre-catalysts with N-heterocyclic carbene ligands catalyze the Suzuki cross-coupling of aryl chlorides and bromides with alkyllithium-activated arylboronic pinacolate esters. Preliminary mechanistic studies indicate that the cobalt is reduced to Co(0) during catalysis.
      PubDate: 2017-11-14T05:51:52.277173-05:
      DOI: 10.1002/ange.201710053
       
  • Transition Metal pi-Ligation of a Tetrahalodiborane
    • Authors: Holger Braunschweig; Rian D. Dewhurst, J. Oscar C. Jimenez-Halla, Eduard Matito, Jonas Muessig
      Abstract: The reaction of tetraiododiborane (B2I4) with trans- [Pt(BI2)I(PCy3)2] led to isolation of the diplatinum(II) complex [{(Cy3P)(I2B)Pt}2(μ2:h3:h3-B2I4)], supported by the bridging diboranyl dianion ligand [B2I4]2-. The complex is the first transition metal complex of a diboranyl dianion, as well as the first example of intact coordination of a B2X4 (X = halide) unit of any type to a metal center.
      PubDate: 2017-11-14T03:50:37.787397-05:
      DOI: 10.1002/ange.201709515
       
  • Crochelins, siderophores with a novel iron-chelating moiety from the
           nitrogen-fixing bacterium Azotobacter chroococcum
    • Authors: Oliver Baars; Xinning Zhang, Marcus I. Gibson, Alan T. Stone, Francois M. M. Morel, Mohammad R. Seyedsayamdost
      Abstract: Microbes utilize siderophores to access essential iron resources. Over 500 siderophores are known, but they utilize a small set of common moieties to bind iron. Azotobacter chroococcum expresses iron-rich nitrogenases with which it reduces N2. Though an important agricultural inoculant, the structures of its iron-binding molecules remain unknown. Herein, we examine the 'chelome' of A. chroococcum using a small molecule discovery and bioinformatics approach. We find that it produces vibrioferrin and amphibactins as well as a novel family of siderophores, the crochelins. Detailed characterization shows that the most abundant member, crochelin A, binds iron in a hexadentate fashion using a new iron-chelating γ-amino acid. Insights into the biosynthesis of crochelins and the mechanism by which iron may be removed upon import of the holo-siderophore are presented. Our work expands the repertoire of iron-chelating moieties in microbial siderophores.
      PubDate: 2017-11-14T03:20:40.677983-05:
      DOI: 10.1002/ange.201709720
       
  • Unraveling the Mechanism for the Sharp-Tip Enhanced Electrocatalytic
           Carbon Dioxide Reduction: The Kinetics Decide
    • Authors: Huijun Jiang; Zhonghuai Hou, Yi Luo
      Abstract: The electrocatalytic reduction reaction of carbon dioxide can be significantly enhanced by the use of a sharp-tip electrode. However, the experimentally observed rate enhancement is many orders of magnitudes smaller than what would be expected from an energetic point of view. The kinetics of this tip-enhanced reaction are shown to play a decisive role, and a novel reaction-diffusion kinetic model is proposed. The experimentally observed sharp-tip enhanced reaction and the maximal producing rate of carbon monoxide under different electrode potentials are well-reproduced. Moreover, the optimal performance shows a strong dependence on the interaction between CO2 and the local electric field, on the adsorption rate of CO2, but not on the reaction barrier. Two new strategies to further enhance the reaction rate have also been proposed. The findings highlight the importance of kinetics in modeling electrocatalytic reactions.Auf die Spitze getrieben: Der Mechanismus der spitzenverstärkten elektrokatalytischen Kohlendioxidreduktion wurde mithilfe eines Modells aufgeklärt, das sowohl Thermodynamik als auch Kinetik berücksichtigt. Es werden Vorhersagen zur weiteren Optimierung der Reaktion getroffen.
      PubDate: 2017-11-14T02:41:20.541896-05:
      DOI: 10.1002/ange.201708825
       
  • Revealing Conformational Variants of Solution-Phase Intrinsically
           Disordered Tau Protein at the Single-Molecule Level
    • Authors: Lydia H. Manger; Alexander K. Foote, Sharla L. Wood, Michael R. Holden, Kevin D. Heylman, Martin Margittai, Randall H. Goldsmith
      Abstract: Intrinsically disordered proteins, such as tau protein, adopt a variety of conformations in solution, complicating solution-phase structural studies. We employed an anti-Brownian electrokinetic (ABEL) trap to prolong measurements of single tau proteins in solution. Once trapped, we recorded the fluorescence anisotropy to investigate the diversity of conformations sampled by the single molecules. A distribution of anisotropy values obtained from trapped tau protein is conspicuously bimodal while those obtained by trapping a globular protein or individual fluorophores are not. Time-resolved fluorescence anisotropy measurements were used to provide an explanation of the bimodal distribution as originating from a shift in the compaction of the two different families of conformations.Eine Anti-Brownsche elektrokinetische Falle wurde verwendet, um Messungen einzelner Tau-Proteine in Lösung zu verlängern. Die unterschiedlichen Konformationen der einzelnen Moleküle wurden durch Fluoreszenzanisotropie bestimmt. Die Verteilung der Anisotropiewerte von gefangenem Tau-Protein ist im Gegensatz zu denen von globularen Proteinen und einzelnen Fluorophoren auffällig bimodal.
      PubDate: 2017-11-14T02:41:15.435831-05:
      DOI: 10.1002/ange.201708242
       
  • Metallfreie Bor-haltige Heterogenkatalysatoren
    • Authors: Yuanxing Fang; Xinchen Wang
      Abstract: Metallfreie Katalysatoren haben spezifische Vorteile gegenüber Metall- und Metalloxidkatalysatoren, z. B. sind sie kostengünstiger, zuverlässiger und nachhaltiger. Unter den Nichtmetallverbindungen für die Katalyse wurden Bor-haltige Verbindungen mit einigen einzigartigen Eigenschaften entwickelt. In diesem Kurzaufsatz werden die aktuellen Entwicklungen auf dem Gebiet Bor-haltiger, metallfreier Katalysatoren vorgestellt, darunter binäre und ternäre Bor-haltige Katalysatormaterialien. Außerdem werden die drei Hauptanwendungen in der Katalyse angesprochen, nämlich die Elektrokatalyse, Thermokatalyse und Photokatalyse. Hierbei wird die jeweilige Rolle von Bor für die spezifische Katalyseanwendung vertieft diskutiert. Bor-haltige Verbindungen könnten das Gebiet der metallfreien Katalyse zukünftig wesentlich beeinflussen.Bor geht vor! Metallfreie Katalysatoren haben Vorteile gegenüber Metall(oxid)katalysatoren, wie geringere Kosten sowie höhere Zuverlässigkeit und Nachhaltigkeit. Unter den Nichtmetallkatalysatoren haben Bor-haltige Verbindungen einige besondere Eigenschaften. Der Kurzaufsatz präsentiert Fortschritte auf dem Gebiet der metallfreien Bor-haltigen Katalysatoren und stellt die drei Hauptanwendungen vor: Elektrokatalyse, Thermokatalyse und Photokatalyse.
      PubDate: 2017-11-14T02:41:09.253213-05:
      DOI: 10.1002/ange.201707824
       
  • A De Novo Heterodimeric Due Ferri Protein Minimizes the Release of
           Reactive Intermediates in Dioxygen-Dependent Oxidation
    • Authors: Marco Chino; Linda Leone, Ornella Maglio, Daniele D'Alonzo, Fabio Pirro, Vincenzo Pavone, Flavia Nastri, Angela Lombardi
      Abstract: Metalloproteins utilize O2 as an oxidant, and they often achieve a 4-electron reduction without H2O2 or oxygen radical release. Several proteins have been designed to catalyze one or two-electron oxidative chemistry, but the de novo design of a protein that catalyzes the net 4-electron reduction of O2 has not been reported yet. We report the construction of a diiron-binding four-helix bundle, made up of two different covalently linked α2 monomers, through click chemistry. Surprisingly, the prototype protein, DF-C1, showed a large divergence in its reactivity from earlier DFs (DF: due ferri, two iron). DFs release the quinone imine and free H2O2 in the oxidation of 4-aminophenol in the presence of O2, whereas FeIII-DF-C1 sequesters the quinone imine into the active site, and catalyzes inside the scaffold an oxidative coupling between oxidized and reduced 4-aminophenol. The asymmetry of the scaffold allowed a fine-engineering of the substrate binding pocket, that ensures selectivity.Peroxid unerwünscht: Ein Dieisen-bindendes Vier-Helix-Bündel mit einem asymmetrischen aktiven Zentrum bewirkt eine Erhöhung der Selektivität in der Eisen-katalysierten oxidativen Kupplung von Phenolen. Die Stabilisierung der oxidierten Zwischenstufe in der Bindungstasche ermöglicht die Vier-Elektronen-Reduktion von O2 ohne nachweisbare Freisetzung von H2O2.
      PubDate: 2017-11-14T02:40:35.168567-05:
      DOI: 10.1002/ange.201707637
       
  • Synthesis of Pyrrole-Fused Corannulenes: 1,3-Dipolar Cycloaddition of
           Azomethine Ylides to Corannulene
    • Authors: Yuki Tokimaru; Shingo Ito, Kyoko Nozaki
      Abstract: In the long history of corannulene chemistry, the 1,3-dipolar cycloaddition to corannulene is unprecedented. Reported herein is the 1,3-dipolar cycloaddition of a polycyclic aromatic azomethine ylide to corannulene, a reaction which occurs exclusively at the rim bond of corannulene, from the convex side in an exo fashion. The cycloadducts were successfully converted, by successive oxidative dehydrogenation, into pyrrole-fused corannulenes, which exhibited pronounced solvatofluorochromism.Randbedingungen: Die 1,3-dipolare Cycloaddition eines polycyclischen aromatischen Azomethin-Ylids an Corannulen erfolgt ausschließlich am äußeren Rand des Corannulens auf endo-Weise von der konvexen Seite aus. Die Cycloaddukte wurden durch oxidative Dehydrierung in Pyrrol-anellierte Corannulene mit ausgeprägter Solvatofluorochromie überführt.
      PubDate: 2017-11-14T02:40:29.841435-05:
      DOI: 10.1002/ange.201707087
       
  • Unprecedented Sensitivity in a Probe for Monitoring Cathepsin B:
           Chemiluminescence Microscopy Cell-Imaging of a Natively Expressed Enzyme
    • Authors: Michal E. Roth-Konforti; Christoph R. Bauer, Doron Shabat
      Abstract: Until recently, chemiluminescence cell images could only be obtained using luciferase-activated probes. Moreover, chemiluminescence microscopy cell-imaging has not been demonstrated for natively expressed enzymes like cathepsin B. Herein, we describe the design, synthesis, and evaluation of the first chemiluminescence probe for the detection and imaging of cathepsin B. The probe activation mechanism relies on the release of a dioxetane intermediate, which undergoes chemiexcitation to emit green light with high efficiency under physiological conditions. Using the probe, we obtained clear images of cancerous leukemia and colon cells. This is the first demonstration of chemiluminescence cell images obtained by a probe for a natively expressed endogenous enzyme. We anticipate that the concept presented in this study will be broadly used to develop analogous probes for other important proteases relevant to biomolecular processes.Eine Chemilumineszenzsonde zum Nachweis von Cathepsin B wird vorgestellt. Die Sonde ist viel empfindlicher als eine klassische Fluoreszenzsonde für Cathepsin B und lieferte erstmals Chemilumineszenzmikroskopiebilder eines nativ in Zellen exprimierten Enzyms, anhand derer Krebszellen von normalem Gewebe unterschieden werden können.
      PubDate: 2017-11-14T02:36:52.064065-05:
      DOI: 10.1002/ange.201709347
       
  • Ein pH-abhängiger, mechanisch verzahnter Schalter: organometallisches
           [2]Rotaxan und organisches [3]Rotaxan
    • Authors: Philipp J. Altmann; Alexander Pöthig
      Abstract: Wir stellen das erste [2]Rotaxan mit einer funktionellen organometallischen Ringkomponente vor. Im Unterschied zu etablierten organischen Systemen zeigt diese molekulare Architektur eine hohe postsynthetische Modifizierbarkeit. Die Reaktivität der Ag8-Pillarplex-Ringkomponente bleibt vollständig erhalten, was anhand der ersten Transmetallierung an einem Rotaxangerüst zum Au8-Analogon verdeutlicht wird. Zusätzlich kann im sauren Milieu ein ausschließlich organisches [3]Rotaxan erhalten werden; diese Reaktion ist durch Zugabe einer geeigneten Base umkehrbar und kann somit als pH-abhängiger Schalter genutzt werden. Dabei wird gezeigt, dass die mechanisch verzahnte Natur des Moleküls die kinetische Stabilität des NHC-Wirtkomplexes um einen Faktor>1000 erhöht, was die erste Beobachtung eines stabilisierenden “Rotaxand-Effektes” darstellt.Ein [2]Rotaxan mit einem funktionalen organometallischen Ag8-Wirt, dessen Transmetallierung zum entsprechenden Au8-Analogon und die reversibel schaltbare, säureunterstützte Umwandlung zu einem organischen [3]Rotaxan werden vorgestellt. Die verzahnte Anordnung erhöht die kinetische Stabilität des NHC-Wirtes um einen Faktor>1000, was der ersten Beobachtung eines stabilisierenden „Rotaxand-Effekts” entspricht.
      PubDate: 2017-11-14T02:36:32.614238-05:
      DOI: 10.1002/ange.201709921
       
  • A General Strategy for Development of Near-Infrared Fluorescent Probes for
           Bioimaging
    • Authors: Ming Xian; Wei Chen, Shi Xu, Jacob J Day, Difei Wang
      Abstract: Near-infrared (NIR) fluorescent dyes with favorable photophysical properties are highly useful for bioimaging, but such dyes are still rare. Here, we describe the development of a unique class of NIR dyes via modifying the rhodol-scaffold with fused tetrahydroquinoxaline rings. These new dyes showed large Stokes shifts (>110 nm). Among them, WR3, WR4, WR5 and WR6 displayed high fluorescence quantum yields and excellent photostability in aqueous solutions. Moreover, their fluorescence properties were tunable by easy modifications on the phenolic hydroxyl group. Based on WR6, two NIR fluorescent turn-on probes, WSP-NIR and SeSP-NIR, were devised for the detection of H2S. The probe SeSP-NIR was applied in visualizing intracellular H2S. The dyes presented herein are expected to be useful fluorophore scaffolds in the development of new NIR probes for bioimaging.
      PubDate: 2017-11-14T02:10:32.565105-05:
      DOI: 10.1002/ange.201710688
       
  • One-pot synthesis of contracted and expanded porphyrins with meso-CF3
           groups, from affordable precursors
    • Authors: Zeev Gross; Qiu-cheng Chen, Matan Soll, Amir Mizrahi, Irena Saltsman, Natalia Fridman, magal Saphier
      Abstract: Corrole and sapphyrin with the smallest meso-substituents reported so far were prepared in a one-pot synthesis that relies on a non-aldehydic precursor for introducing CF3 groups. The substantial amounts of products obtained by this facile pathway allowed for the full characterization of 5,10-15-tris(trifluoromethyl)corrole, the access to a variety of stable chelates thereof and investigations that disclose the unique structural and chemical properties induced by the CF3 substituents. The novel 5,10,15,20-tetra(trifluoromethyl)sapphyrin does undergo only single protonation, which according to its crystal structure is stabilized by favorable non-bonding F/H interaction between the meso-CF3 and the inverted pyrrolic NH.
      PubDate: 2017-11-13T23:51:00.395561-05:
      DOI: 10.1002/ange.201710106
       
  • Total Syntheses of the Monoterpenoid Indole Alkaloids
           (±)-Alstoscholarisine B and C
    • Authors: Steven M. Weinreb; Jeremy D Mason
      Abstract: Total syntheses of the monoterpenoid indole alkaloids (±)-alstoscholarisine B (2) and C (3) have been accomplished starting from readily available indole-2-acetic ester 6 and unsaturated N-sulfonyllactam 7.
      PubDate: 2017-11-13T08:15:30.070419-05:
      DOI: 10.1002/ange.201710943
       
  • Adsorption von hydrierten Protonen an der Luft-Wasser-Grenzfläche
           durch Orientierung
    • Authors: Shavkat I. Mamatkulov; Christoph Allolio, Roland R. Netz, Douwe Jan Bonthuis
      Abstract: Die Oberflächenspannung der Wasser-Luft-Grenzfläche steigt bei Zugabe von anorganischen Salzen, entsprechend einer Verarmung von Ionen. Hingegen verursachen die meisten Säuren eine Verringerung der Oberflächenspannung, was einen Überschuss von hydrierten Protonen an der Oberfläche anzeigt. Zusammen mit der scheinbar negativen Ladung der Grenzfläche zwischen Luft und reinem Wasser, die aus elektrokinetischen Experimenten folgt, führte diese experimentelle Beobachtung zu heftigen Diskussionen seit der Mitte des 19. Jahrhunderts. Hier bestimmen wir die Oberflächenspannung und Affinität der Ionen zur Oberfläche aus klassischen, thermodynamisch konsistenten Molekulardynamiksimulationen. Die Oberflächenspannungen der Lösungen mit NaOH, HCl und NaCl stimmen quantitativ bemerkenswert gut mit experimentell gemessenen Werten überein. Von den untersuchten Ionen wird nur H3O+ an der Luft-Wasser-Grenzfläche adsorbiert. Die Adsorption lässt sich durch den tiefen Potentialtopf erklären, der durch die Ausrichtung des H3O+-Dipols im elektrischen Feld der Grenzfläche entsteht, was wir mit Ab-initio-Simulationen bestätigen.Oberflächenspannungen und Ionenaffinitäten zur Luft-Wasser-Oberfläche wurden mithilfe von Molekulardynamiksimulationen bestimmt. Die Oberflächenspannungen von NaOH-, HCl- und NaCl-Lösungen stimmen bemerkenswert gut mit Experimenten überein, und von den untersuchten Ionen wird nur H3O+ an der Luft-Wasser-Grenzfläche adsorbiert. Die Adsorption lässt sich durch den tiefen Potentialtopf erklären, der durch die Ausrichtung des H3O+-Dipols im elektrischen Feld der Grenzfläche entsteht.
      PubDate: 2017-11-13T06:30:37.759822-05:
      DOI: 10.1002/ange.201707391
       
  • Catalytic Hydroalkylation of Allenes
    • Authors: Mitchell Lee; Mary Nguyen, Chance Brandt, Werner Kaminsky, Gojko Lalic
      Abstract: We have developed a catalytic method for the hydroalkylation of allenes using alkyl triflates as electrophiles and silane as a hydride source. The reaction has an excellent substrate scope and is compatible with a wide range of functional groups, including esters, aryl halides, aryl boronic esters, sulfonamides, alkyl tosylates, and alkyl bromides. We found evidence for a reaction mechanism that involves unusual dinuclear copper ally complexes as catalytic intermediates. The unusual structure of these complexes provides a rationale for their unexpected reactivity.Ein katalytisches Verfahren zur Hydroalkylierung von Allenen nutzt Alkyltriflate als Elektrophile und ein Silan als Hydridquelle. Die Reaktion hat eine große Substratbreite und toleriert Ester-, Arylhalogenid-, Arylboronsäureester-, Sulfonamid-, Alkyltosylat- und Alkylbromidfunktionen. Im Katalysezyklus scheint ein ungewöhnlicher Dikupfer-Allylkomplexe als Zwischenstufe beteiligt zu sein.
      PubDate: 2017-11-13T06:17:30.673229-05:
      DOI: 10.1002/ange.201709144
       
  • Direct Aryl C−H Amination with Primary Amines using Organic
           Photoredox Catalysis
    • Authors: Kaila A. Margrey; Alison Levens, David A. Nicewicz
      Abstract: The direct catalytic C−H amination of arenes is a powerful synthetic strategy with useful applications in pharmaceuticals, agrochemicals, and materials chemistry. Despite the advances in catalytic C−H functionalization, the use of aliphatic amine coupling partners is limited. Described herein is the construction of C−N bonds, using primary amines, by direct C−H functionalization with an acridinium photoredox catalyst under an aerobic atmosphere. A wide variety of primary amines, including amino acids and more complex amines are competent coupling partners. Various electron-rich aromatics and heteroaromatics are useful scaffolds in this reaction, as are complex, biologically active arenes. We also describe the ability to functionalize arenes that are not oxidized by an acridinium catalyst, such as benzene and toluene, thus supporting a reactive amine cation radical intermediate.Mit Licht und Luft: C-N-Bindungen wurden mithilfe primärer Amine durch direkte C-H-Funktionalisierung mit einem Acridinium-Photoredoxkatalysator unter aeroben Bedingungen aufgebaut. Die Methode toleriert vielfältige primäre Amine, z. B. Aminosäuren, und die Regiochemie wird durch das Arensubstitutionsmuster beeinflusst. Auch eine kontinuierliche Prozessführung ist möglich.
      PubDate: 2017-11-13T06:16:22.798277-05:
      DOI: 10.1002/ange.201709523
       
  • EU-40 Materials Prize für Bettina V. Lotsch / Ehrenmitgliedschaft in
           der polnischen chemischen Gesellschaft für Hans-Ulrich Reißig / Welch
           Award für John B. Goodenough
    • PubDate: 2017-11-13T06:15:31.919291-05:
      DOI: 10.1002/ange.201710408
       
  • Singulett-Sauerstoff in der aprotischen Natrium-O2-Batterie
    • Authors: Lukas Schafzahl; Nika Mahne, Bettina Schafzahl, Martin Wilkening, Christian Slugovc, Sergey M. Borisov, Stefan A. Freunberger
      Abstract: Nebenreaktionen sind die größte Hürde für die Entwicklung von Na-O2-Batterien. In ihrer Zuschrift (
      DOI : 10.1002/ange.201709351) zeigen S. A. Freunberger et al., dass sich der hochreaktive Singulett-Sauerstoff in allen Phasen des Zellbetriebes bildet, besonders bei hohen Ladespannungen, und dass er die Hauptursache für die Nebenreaktionen ist. Wasserspuren ermöglichen hohe Kapazitäten, beschleunigen aber auch Nebenreaktionen. Daher müssen Wege gefunden werden, um die Bildung von Singulett-Sauerstoff zu verhindern oder diesen unschädlich zu machen.
      PubDate: 2017-11-13T06:15:29.952455-05:
       
  • Oxidative Dissolution of Resoles: A Versatile Approach to Intricate
           Nanostructures
    • Authors: Min Zhang; Hao Song, Yannan Yang, Xiaodan Huang, Yang Liu, Chao Liu, Chengzhong Yu
      Abstract: Resoles are base-catalyzed phenol-formaldehyde resins with a 3-dimensional cross-linked framework. The chemistry of resoles is generally considered as highly chemical resistant, thus calcination is always used in the treatment of resole-type resin, which significantly limit the diversity of nanostructured materials derived from resole-type resins. Here we report that selected metal nitrate solutions can be applied to dissolve various types of nanostructured resoles through an oxidative dissolution mechanism. This strategy not only allows for controlled dissolution of resoles, but more importantly provides a new approach to selectively etch resole based nanocomposites, giving rise to a variety of nanostructured materials with unprecedented architectures and great potential in bio-applications.
      PubDate: 2017-11-13T05:51:39.988695-05:
      DOI: 10.1002/ange.201709591
       
  • Mesoporous Carbon@Titanium Nitride Hollow Spheres as an Efficient SeS2
           Host for Advanced Li–SeS2 Batteries
    • Authors: Zhen Li; Jintao Zhang, Bu Yuan Guan, Xiong Wen (David) Lou
      Abstract: The introduction of a certain proportion of selenium into sulfur-based cathodes is an effective strategy for enhancing the integrated battery performance. However, similar to sulfur, selenium sulfide cathodes suffer from poor cycling stability owing to the dissolution of reaction intermediate products. In this study, to exploit the advantages of SeS2 to the full and avoid its shortcomings, we designed and synthesized a hollow mesoporous carbon@titanium nitride (HMC@TiN) host for loading 70 wt % of SeS2 as a cathode material for Li–SeS2 batteries. Benefiting from both physical and chemical entrapment by hollow mesoporous carbon and TiN, the HMC@TiN/SeS2 cathode manifests high utilization of the active material and excellent cycling stability. Moreover, it exhibits promising areal capacity (up to 4 mAh cm−2) with stable cell performance in the high-mass-loading electrode.Eine Doppelfalle: Hohles mesoporöses Kohlenstoff@Titannitrid (HMC@TiN) mit 70 Gew.-% SeS2 wurde als Kathodenmaterial für Li-SeS2-Batterien entwickelt (siehe Bild). Resultierend aus dem physikalischen und chemischen Einschluss in dem hohlen mesoporösen Kohlenstoff und TiN zeigt die HMC@TiN/SeS2-Kathode einen hohen Nutzungsgrad des aktiven Materials und exzellente Zyklenstabilität.
      PubDate: 2017-11-13T04:47:56.545167-05:
      DOI: 10.1002/ange.201709176
       
  • A Magneto-optical Molecular Device: Interplay of Spin Crossover,
           Luminescence, Photomagnetism, and Photochromism
    • Authors: Marta Estrader; Jorge Salinas Uber, Leoní A. Barrios, Jordi Garcia, Paul Lloyd-Williams, Olivier Roubeau, Simon J. Teat, Guillem Aromí
      Abstract: A bis(pyrazolylpyridyl) ligand, L, containing a central photochromic dithienylethene spacer predictably forms a ferrous [Fe2L3]4+ helicate exhibiting spin crossover (SCO). In solution, the compound [Fe2L3](ClO4)4 (1) preserves the magnetic properties and is fluorescent. The structure of 1 is photo-switchable following the reversible ring closure/opening of the central dithienylethene via irradiation with UV/visible light. This photoisomerization switches on and off some emission bands of 1 and provides a means of externally manipulating the magnetic properties of the assembly.Ein eisenhaltiges Spin-Crossover-Molekül mit einer photoschaltbaren Einheit wurde hergestellt. Durch diese Einheit lassen sich seine magnetischen Eigenschaften und seine Fluoreszenzantwort mithilfe von Licht reversibel schalten.
      PubDate: 2017-11-13T04:47:31.027125-05:
      DOI: 10.1002/ange.201709136
       
  • A Multivalent Structure-Specific RNA Binder with Extremely Stable Target
           Binding but Reduced Interaction to Nonspecific RNAs
    • Authors: Jeong Min Lee; Ahreum Hwang, Hyeongjoo Choi, Yongsang Jo, Bongsoo Kim, Taejoon Kang, Yongwon Jung
      Abstract: By greatly enhancing binding affinities against target biomolecules, multivalent interactions provide an attractive strategy for biosensing. However, there is also a major concern for increased binding to nonspecific targets by multivalent binding. A range of charge-engineered probes of a structure-specific RNA binding protein PAZ as well as multivalent forms of these PAZ probes were constructed by using diverse multivalent avidin proteins (2-mer, 4-mer, and 24-mer). Increased valency vastly enhanced the binding stability of PAZ to structured target RNA. Surprisingly, nonspecific RNA binding of multivalent PAZ can be reduced even below that of the PAZ monomer by controlling negative charges on both PAZ and multivalent avidin scaffolds. The optimized 24-meric PAZ showed nearly irreversible binding to target RNA with negligible binding to nonspecific RNA, and this ultra-specific 24-meric PAZ probe allowed SERS detection of intact microRNAs at an attomolar level.Ein RNA-bindendes Monomer und multivalente Gerüstproteine wurden optimiert, um eine multivalente Sonde zu erzeugen, die praktisch irreversibel an die Ziel-RNA und vernachlässigbar an nichtspezifische RNA bindet. Der resultierende hochspezifische 24-mere RNA-Binder ermöglicht den SERS-Nachweis von intakten miRNAs auf attomolarem Niveau.
      PubDate: 2017-11-13T04:47:22.043943-05:
      DOI: 10.1002/ange.201709153
       
  • Valence-Engineering of Quantum Dots Using Programmable DNA Scaffolds
    • Authors: Jianlei Shen; Qian Tang, Li Li, Jiang Li, Xiaolei Zuo, Xiangmeng Qu, Hao Pei, Lihua Wang, Chunhai Fan
      Abstract: Precise control over the valency of quantum dots (QDs) is critical and fundamental for quantitative imaging in living cells. However, prior approaches on valence control of QDs remain restricted to single types of valences. A DNA-programmed general strategy is presented for valence engineering of QDs with high modularity and high yield. By employing a series of programmable DNA scaffolds, QDs were generated with tunable valences in a single step with near-quantitative yield (>95 %). The use of these valence-engineered QDs was further demonstrated to develop 12 types of topologically organized QDs-QDs and QDs-AuNPs and 4 types of fluorescent resonance energy transfer (FRET) nanostructures. Quantitative analysis of the FRET nanostructures and live-cell imaging reveal the high potential of these nanoprobes in bioimaging and nanophotonic applications.Eine DNA-programmierte, allgemeingültige Strategie ermöglicht die gezielte Einstellung der Valenz von Quantenpunkten (QDs). Unter Verwendung einer Reihe von programmierbaren DNA-Gerüsten wurden QDs mit einstellbaren Valenzen in einem einzigen Schritt fast quantitativ (>95 %) erhalten. Die QDs wurden verwendet, um zwölf Typen topologisch organisierter QDs-QDs und QDs-AuNPs sowie vier Typen von FRET-Nanostrukturen zu entwickeln.
      PubDate: 2017-11-13T04:46:58.569341-05:
      DOI: 10.1002/ange.201710309
       
  • Fluorinated Vinylsilanes from the Copper-Catalyzed Defluorosilylation of
           Fluoroalkene Feedstocks
    • Authors: Hironobu Sakaguchi; Masato Ohashi, Sensuke Ogoshi
      Abstract: Herein, a copper-catalyzed C-F bond defluorosilylation reaction of tetrafluoroethylene and other polyfluoroalkenes is described. Mechanistic studies, based on a series of stoichiometric reactions with copper complexes, revealed that the key steps of this defluorosilylation reaction are: i) the 1,2-addition of a silylcopper intermediate to the polyfluoroalkene, and ii) a subsequent selective β-fluorine elimination, which generates a Cu-F species. The β-fluorine elimination is facilitated by the Lewis acidic F-Bpin, which is generated in situ during the defluorosilylation.
      PubDate: 2017-11-12T21:56:51.113513-05:
      DOI: 10.1002/ange.201710866
       
  • Magnetic actuation of discrete liquid entities with a deformable
           paramagnetic liquid substrate
    • Authors: Damien Baigl; Jacopo Vialetto, Masayuki Hayakawa, Nikita Kavokine, Masahiro Takinoue, Subramanyan Namboodiri Varanakkottu, Sergii Rudiuk, Manos Anyfantakis, Mathieu Morel
      Abstract: Magnetic actuation of drops has mainly relied on volume forces exerted on the liquid to be transported, which is poorly efficient with conventional diamagnetic liquids such as water or oil, unless magnetosensitive particles are added. Here, we describe a new way to magnetically control the motion of discrete liquid entities, in an additive-free and surface tension-independent manner. Our strategy consists of using a paramagnetic liquid as a deformable substrate to direct, using a magnet, the motion of various floating liquid entities, ranging from naked drops to liquid marbles. We show that a broad variety of liquids, including diamagnetic (water, oil) and nonmagnetic ones can be efficiently transported using the moderate magnetic field (≈ 50 mT) produced by a cost-effective, cm-sized permanent magnet. Complex trajectories can be achieved in a reliable manner and multiplexing potential is demonstrated through on-demand drop fusion.
      PubDate: 2017-11-12T21:56:43.557818-05:
      DOI: 10.1002/ange.201710668
       
  • Columnar Liquid-Crystal from a Giant Macrocycle Mesogen
    • Authors: Shin-ichiro Kawano; Masahiro Kato, Shinya Soumiya, Masato Nakaya, Jun Onoe, Kentaro Tanaka
      Abstract: Columnar liquid crystals composed of a giant macrocyclic mesogen were prepared. The giant macrocyclic mesogen has a square hollow with a 2.5 nm diagonal, which was bounded by diindolo[3,2-b:2',3'-h]carbazole (diindolocarbazole) moieties as the edges and bis(salicylidene)-o-phenylenediamine (salphen) moieties as the corners. The shape and size of the macrocycle were directly observed by scanning tunneling microscopy (STM). Each side of the bright square in the STM image corresponds to a diindolocarbazole moiety, and the length of the sides was consistent with the result of the single crystal analysis of diindolocarbazole. Finally, we successfully obtained a giant macrocycle with long and branched side chains, which exhibited a rectangular columnar LC phase over a wide temperature range. To the best of our knowledge, it contained the largest discrete inner space of any thermotropic columnar liquid crystal composed of macrocyclic mesogens.
      PubDate: 2017-11-12T21:56:18.421221-05:
      DOI: 10.1002/ange.201709542
       
  • Supramolecular Radical Anions Triggered by Bacteria in situ for Selective
           Photothermal Therapy
    • Authors: Yuchong Yang; Ping He, Yunxia Wang, Haotian Bai, Shu Wang, Jiang-Fei Xu, Xi Zhang
      Abstract: In this work, we explored a supramolecular complex that can be selectively reduced to radical anions in situ by facultative anaerobic bacteria. To this end, a water-soluble bifunctional monomer bearing perylene diimide was synthesized, and its supramolecular complex with cucurbit[7]uril was fabricated on the basis of host-guest complexation, which could be reduced to forming radical anions in the presence of E. coli. It was interestingly found that this supramolecular complex could display different ability of generating radical anions by facultative anaerobic and aerobic bacteria in terms of their various reductive abilities. The selective antibacterial activity of the supramolecular complex could be realized by photothermal performance of radical anions under near-infrared irradiation. It is anticipated that this method may lead to a novel bacteria-responsive photothermal therapy to regulate balance of bacterial flora.
      PubDate: 2017-11-11T07:36:04.363939-05:
      DOI: 10.1002/ange.201708971
       
  • Molecular Magnesium Hydrides
    • Authors: Jun Okuda; Debabrata Mukherjee
      Abstract: Solid magnesium hydride [MgH2]∞ has been continuously pursued as a potential hydrogen storage material. Organic chemists were rather interested in soluble magnesium hydride reagents from mid-20th century. But it was only in the last two decades that molecular magnesium hydride chemistry received a major boost from organometallic chemists with a series of structurally well-characterized examples that continues to build a whole new class of compounds. Nearly 40 such species have been isolated, ranging from mononuclear terminal hydrides to large hydride clusters with more than 10 magnesium atoms. They provide not only insights into the structure and bonding of MgH motifs, but also serve as models for hydrogen storage materials. Some of them are also recognized to participate in useful catalytic transformations. An overview of these molecular magnesium hydrides is given here, focusing on their synthesis and structural characterization.
      PubDate: 2017-11-11T07:21:07.521629-05:
      DOI: 10.1002/ange.201708592
       
  • Three-Dimensional Graphene Networks with Abundant Sharp Edge Sites for
           Efficient Electrocatalytic Hydrogen Evolution
    • Authors: Gui Yu; Huping Wang, Xu-Bing Li, Lei Gao, Hao-Lin Wu, Jie Yang, Le Cai, Tian-Bao Ma, Chen-Ho Tung, Li-Zhu Wu
      Abstract: To achieve sustainable production of hydrogen (H2) through water splitting, establishing efficient and earth-abundant electrocatalysts is of great necessity. Here, we firstly reveal that morphology engineering of graphene can modulate the electronic structure of carbon skeleton and in turn endow it with excellent ability of proton reduction. Three-dimensional (3D) graphene networks with the high density of sharp edge sites are synthesized. Electrocatalytic measurements indicate that the obtained 3D graphene networks can electrocatalyze H2 evolution with an extremely low onset potential of ~18 mV in 0.5 M H2SO4 solution, together with good stability. A combination of control experiments and density functional theory (DFT) investigations indicates that the exceptional H2 evolution performance is attributed to the abundant sharp-edge sites of the advanced frameworks, which are responsible for promoting the adsorption and reduction of protons.
      PubDate: 2017-11-11T07:20:42.213504-05:
      DOI: 10.1002/ange.201709901
       
  • An in-situ Dynamic Continuum of Supramolecular Phosphoglycopeptides
           Enables Formation of 3D Cell Spheroids
    • Authors: Huaimin Wang; Junfeng Shi, Zhaoqianqi Feng, Rong Zhou, Shiyu Wang, Avital A. Rodal, Bing Xu
      Abstract: Higher-order assemblies of proteins, with a structural and dynamic continuum, is a new paradigm in biology, but these insights have yet to be applied in designing biomaterials. Dynamic assemblies of supramolecular phosphoglycopeptides (sPGPs) transform a 2D cell sheet to 3D cell spheroids. A ligand-receptor interaction between a glycopeptide and a phosphopeptide produces sPGPs that form nanoparticles, which transform to nanofibrils upon partially enzymatic dephosphorylation. The assemblies form dynamically and hierarchically in situ on the cell surface, and interact with extracellular matrix molecules and effectively abolish contact inhibition of locomotion (CIL) of the cells. Integrating molecular recognition, catalysis, and assembly, these active assemblies act as a dynamic continuum to disrupt CIL, thus illustrating a new kind of biomaterials for regulating cell behavior.
      PubDate: 2017-11-10T15:04:53.897633-05:
      DOI: 10.1002/ange.201710269
       
  • Direct Dehydroxytrifluoromethoxylation of Alcohols
    • Authors: Xiaohuan Jiang; Zhijie Deng, pingping tang
      Abstract: The first example of a direct dehydroxytrifluoromethoxylation of alcohols has been developed. This method generated an alkyl fluoroformate in situ from alcohols and followed nucleophilic trifluoromethoxylation with trifluoromethyl arylsulfonate (TFMS) as the trifluoromethoxylation reagent. This reaction is operationally simple, scalable and proceeds under mild reaction conditions, and provides access to a wide range of trifluoromethyl ethers from alcohols. In addition, this method is suitable for the late-stage trifluoromethoxylation of complex small molecules
      PubDate: 2017-11-10T10:55:25.870348-05:
      DOI: 10.1002/ange.201711050
       
  • Biocatalytic Oxidative Cascade for the Conversion of Fatty Acids to
           alpha-Ketoacids via Internal H2O2 Recycling
    • Authors: Somayyeh Gandomkar; Alexander Dennig, Andela Dordic, Lucas Hammerer, Mathias Pickl, Thomas Haas, Mélanie Hall, Kurt Faber
      Abstract: The functionalization of bio-based chemicals is essential to allow valorization of natural carbon sources. An atom-efficient biocatalytic oxidative cascade was developed for the conversion of saturated fatty acids to alpha-ketoacids. Employment of P450 monooxygenase in the peroxygenase mode for regioselective alpha-hydroxylation of fatty acids combined with enantioselective oxidation by alpha-hydroxyacid oxidase(s) resulted in internal recycling of the oxidant H2O2, thus minimizing degradation of ketoacid product and maximizing biocatalyst lifetime. The O2-dependent cascade relies on catalytic amounts of H2O2 and releases water as sole by-product. Octanoic acid was converted under mild conditions in aqueous buffer to 2-oxooctanoic acid in a simultaneous one-pot two-step cascade in up to>99% without accumulation of hydroxyacid intermediate. Scale-up allowed isolation of final product in 91% isolated yield and the cascade was applied to fatty acids of various chain lengths (C6:0-C10:0).
      PubDate: 2017-11-10T10:05:46.453588-05:
      DOI: 10.1002/ange.201710227
       
  • Simultaneous application of photothermal therapy and anti-inflammatory
           prodrug using pyrene-aspirin loaded gold nanorod-graphitic-nanocapsules
    • Authors: Qian Dong; Xuewei Wang, Xiaoxiao Hu, Langqiu Xiao, Liang Zhang, Lijuan Song, Minglu Xu, Yuxiu Zou, Long Chen, Zhuo Chen, Weihong Tan
      Abstract: Photothermal therapy (PTT) has been extensively developed as an effective approach against cancer. In some cases, however, PTT can trigger inflammatory responses, in turn simulating tumor regeneration and hindering subsequent therapy. We herein developed a therapeutic strategy able to deliver enhanced PTT and simultaneously inhibite PTT-induced inflammatory response. 1-Pyrene methanol was utilize to synthesize anti-inflammatory prodrug pyrene-aspirin (P-aspirin) with cleavable ester bond, and also facilitate loading the prodrug on gold nanorod (AuNR)-encapsulated graphitic nanocapsule (AuNR@G), a photothermal agent, through π-π interaction. Such AuNR@G-P-aspirin complexes were used for near-infrared laser-triggered photothermal ablation of solid tumor and simultaneous inhibition of PTT-induced inflammation through the release of aspirin in tumor milieu. This strategy showed excellent effects in vitro and in vivo, thus having profound significance for the extended development of PTT.
      PubDate: 2017-11-10T10:05:40.910443-05:
      DOI: 10.1002/ange.201709648
       
  • Spata-13,17-diene Synthase, an Enzyme with Sesqui-, Di- and Sesterterpene
           Synthase Activity from Streptomyces xinghaiensis
    • Authors: Jan Rinkel; Lukas Lauterbach, Jeroen Sidney Dickschat
      Abstract: A terpene synthase from the marine bacterium Streptomyces xinghaiensis was characterised, including a full structure elucidation of its products from various substrates and an in-depth investigation of the enzyme mechanism by isotopic labelling experiments, substrate and metal cofactor variations, and mutation experiments. The results revealed an interesting dependency of Mn2+ catalysis on the presence of Asp-217, a residue that is occupied by a highly conserved Glu in most other bacterial terpene synthases.
      PubDate: 2017-11-10T10:05:36.979793-05:
      DOI: 10.1002/ange.201711142
       
  • Diversity of Dimerization Behaviors of N-Substituted Dicyanomethyl
           Radicals: Boundary between Dynamically Stabilized Radicals and a Stable
           Radical
    • Authors: Kohei Okino; Daisuke Sakamaki, Shota Hira, Yuki Inoue, Shu Seki
      Abstract: Herein we demonstrate the characteristic switching of the dimerization behaviors of amine-substituted dicyanomethyl radicals, from - to -dimerization, simply by varying the electron-donating substituents. Dicyanomethyl radicals with 4,4'-ditolylamine (DT·) and with phenothiazine (PT·) are in equilibrium between the monomeric radical form and the corresponding dimer connected by a reversible C-C bond (-dimer) in solutions. On the other hand, a radical with julolidine skeleton (JD·) do not undergo -dimerization and is isolated as stable radical in spite of the absence of bulky protecting groups. X-ray single crystal analysis reveals that JD· forms the -dimer in the crystalline state, and the variable temperature spectroscopic measurements reveals that JD· is in equilibrium with the -dimer in toluene solution. DFT calculations suggests the importance of the electrostatic interaction in the driving force of the -dimerization of JD· due to its polarized structure.
      PubDate: 2017-11-10T10:03:03.479679-05:
      DOI: 10.1002/ange.201710354
       
  • Site-Selective O-Arylation of Glycosides
    • Authors: Dawen Niu; Weidong Shang, Ze-Dong Mou, Hua Tang, Xia Zhang, Jie Liu, Zhengyan Fu
      Abstract: Direct and site-selective O-arylation of carbohydrates has been a challenge in synthesis. Here we report a method that is based on the copper-catalyzed O-arylation reaction to address this challenge. Proper choice of the ancillary ligand to copper is critical for the efficiency and site-selectivity of this transformation. This method features mild conditions, tolerates various functional groups, and demonstrates broad substrate scope.
      PubDate: 2017-11-10T08:26:00.522291-05:
      DOI: 10.1002/ange.201710310
       
  • Molecular Barium Hydrido Complex Stabilized by a Super Bulky
           Hydrotris(pyrazolyl)borate Ligand
    • Authors: Xianghui Shi; Cuiping Hou, Chulu Zhou, Yanyao Song, Jianhua Cheng
      Abstract: Hydrogenolysis of the scorpionate-supported barium alkyl complex (Tp^Ad,iPr)Ba[CH(SiMe3)2](THF) (Tp^Ad,iPr = hydrotris(3-adamantyl-5-isopropyl-pyrazolyl)borate) afforded the dinuclear barium hydrido complex [(Tp^Ad,iPr)Ba(µ-H)]2 (2), which was characterized by NMR spectroscopy and single crystal X-ray analysis. Exposure of 2 with 1 atm of CO resulted in a reductive coupling process to form the cis-ethendiolate dianion (3). Reaction of 2 with one equivalent of PhCC-CCPh gave barium 1,4-diphenyl-2-butyne-1,4-diyl complex {[(Tp^Ad,iPr)Ba]2(PhCH-CC-CHPh) (4).
      PubDate: 2017-11-10T05:55:36.641117-05:
      DOI: 10.1002/ange.201709344
       
  • Offenzellige Schwämme mit niedrigen Dichten als Funktionsmaterialien
    • Authors: Shaohua Jiang; Seema Agarwal, Andreas Greiner
      Abstract: Makroporöse Schwämme sind eine Chance und Herausforderung für die Chemie und Materialwissenschaften. Die Herausforderung liegt in der Herstellung der Schwämme, die bestimmte Eigenschaftskombinationen aufweisen und zu neuen Anwendungen führen. Kennzeichnend für derartige Schwämme sind geringes Gewicht, Atmungsaktivität, spezielle Benetzungseigenschaften, großer Massentransfer, mechanische Stabilität und große Porenvolumina. Bottom-up- und Top-down-Methoden zur Herstellung von Schwämmen aus Kohlenstoff und Polymeren sowie ausgewählte Eigenschaften und mögliche Anwendungen werden in diesem Aufsatz diskutiert.Weniger ist mehr: Makroporöse Schwämme geringer Dichte aus Kohlenstoff oder Polymermaterialien sind eine Chance für Chemie und Materialwissenschaften. Geringes Gewicht, Nachhaltigkeit, Atmungsaktivität, spezielle Benetzungseigenschaften, hoher Massentransfer, mechanische Stabilität und großes Porenvolumen dieser Materialien führen zu „perfekten” Schwämmen. Dieser Aufsatz stellt den aktuellen Stand dieser Forschung zusammen mit ihren Anwendungen und Perspektiven vor.
      PubDate: 2017-11-10T04:31:27.859069-05:
      DOI: 10.1002/ange.201700684
       
  • Living ab initio Emulsion Polymerization of Methyl Methacrylate in Water
           Using a Water-Soluble Organotellurium Chain Transfer Agent under Thermal
           and Photochemical Conditions
    • Authors: Weijia Fan; Masatoshi Tosaka, Shigeru Yamago, Michael F. Cunningham
      Abstract: Ab initio emulsion polymerization of methyl methacrylate (MMA) using a water-soluble organotellurium chain transfer agent in the presence of the surfactant Brij 98 in water is reported. Polymerization proceeded under both thermal and visible light-irradiation conditions giving poly(methyl methacrylate) (PMMA) with controlled molecular weight and low dispersity (Đ
      PubDate: 2017-11-10T02:25:22.218297-05:
      DOI: 10.1002/ange.201710754
       
  • Porous polyelectrolytes: charge pores for more functionalities
    • Authors: Weiyi Zhang; Qiang Zhao, Jiayin Yuan
      Abstract: The past decade has witnessed rapid advances in porous polyelectrolytes and there is tremendous ongoing interest in their synthesis and applications in environment, energy, biomedicine and catalysis. The porous polyelectrolytes research is motivated by the synergy of, apart from the flexible choice of functional organic groups and processing technologies, the charge and pores spanning length scales from individual polyelectrolyte backbones to their nano/micro superstructures. This review surveys recent progresses on porous polyelectrolytes including membranes, particles, scaffolds, high surface area powders/resins, and their derivatives. Our focus is the interplay between surface chemistry, Columbic interaction and poreconfinement that defines new chemistry and physics in such materials for implications including energy conversion, molecular separation, water purification, sensing/actuation, catalysis, tissue engineering, and nanomedicine.
      PubDate: 2017-11-09T21:55:46.970362-05:
      DOI: 10.1002/ange.201710272
       
  • Titelbild: Selective Utilization of the Methoxy Group in Lignin to Produce
           Acetic Acid (Angew. Chem. 47/2017)
    • Authors: Qingqing Mei; Huizhen Liu, Xiaojun Shen, Qinglei Meng, Hangyu Liu, Junfeng Xiang, Buxing Han
      Pages: 14967 - 14967
      Abstract: Die selektive Umwandlung von Lignin in Essigsäure ist das Thema der Zuschrift von B. Han, H. Liu et al. auf S. 15064. Mit einer von ihnen entwickelten Strategie überführen sie in Lignin zahlreich vorhandene Methoxygruppen in reine Essigsäure, wobei Umsätze von 87.3% und 80.4% für Kraft- bzw. Organosolv-Lignin erreicht werden und keine Nebenprodukte entstehen.
      PubDate: 2017-10-27T05:02:08.774278-05:
      DOI: 10.1002/ange.201710736
       
  • Innentitelbild: Organoiridium Photosensitizers Induce Specific Oxidative
           Attack on Proteins within Cancer Cells (Angew. Chem. 47/2017)
    • Authors: Pingyu Zhang; Cookson K. C. Chiu, Huaiyi Huang, Yuko P. Y. Lam, Abraha Habtemariam, Thomas Malcomson, Martin J. Paterson, Guy J. Clarkson, Peter B. O'Connor, Hui Chao, Peter J. Sadler
      Pages: 14968 - 14968
      Abstract: Photodynamische Therapien bieten neue Möglichkeiten, um Krebszellen unschädlich zu machen und Resistenzen zu überwinden. In ihrer Zuschrift auf S. 15094 berichten P. B. O'Connor, H. Chao, P. J. Sadler et al. über lumineszierende Organoiridiumkomplexe mit langlebigen angeregten Zuständen, die Krebszellen nach Zwei-Photonen-Aktivierung mit rotem Licht selektiv schädigen. Die Komplexe erzeugen Sauerstoff, der wichtige zelluläre Proteine angreift. (Bildgestaltung: Juanjuan Huang)
      PubDate: 2017-11-06T08:06:04.346344-05:
      DOI: 10.1002/ange.201710973
       
  • Graphisches Inhaltsverzeichnis: Angew. Chem. 47/2017
    • Pages: 14971 - 14989
      PubDate: 2017-11-15T08:06:00.104937-05:
      DOI: 10.1002/ange.201784711
       
  • Top-Beiträge aus unseren Schwesterzeitschriften: Angew. Chem. 47/2017
    • Pages: 14990 - 14993
      PubDate: 2017-11-15T08:06:04.287075-05:
      DOI: 10.1002/ange.201784713
       
  • Tomoya Miura
    • Pages: 14994 - 14994
      Abstract: „Meine liebsten Moleküle sind Alkine mit endständigen Dreifachbindungen. Wenn ich ein Laborgerät sein könnte, wäre ich eine Pinzette ...“ Dies und mehr von und über Tomoya Miura finden Sie auf Seite 14994.
      PubDate: 2017-08-17T07:50:46.655973-05:
      DOI: 10.1002/ange.201707581
       
  • Schlenk-Vorlesung: S. Harder / Kabiller-Preis: R. S. Langer /
           Kabiller-Preis für Nachwuchsforscher: L. Zhang /
           Wilhelm-Manchot-Professur: P. S. Baran
    • Pages: 14995 - 14995
      PubDate: 2017-10-25T10:02:11.99501-05:0
      DOI: 10.1002/ange.201710438
       
  • Gérard Férey (1941–2017)
    • Authors: Christian Serre
      Pages: 14996 - 14996
      Abstract: Gérard Férey, ein führender Festkörperchemiker und Pionier auf dem Gebiet der Metall-organischen Gerüstverbindungen (MOFs), ist am 19. August 2017 in Paris gestorben. Er hat sowohl Metallfluorophosphate (die ULM-n-Reihen) als auch topische poröse MOFs (die MIL-n-Reihen) entwickelt. Außerdem geht auf ihn die Vorhersage der Struktur neuer poröser Feststoffe mithilfe der Methode der automatisierten Assoziation sekundärer Baueinheiten zurück.
      PubDate: 2017-10-19T02:00:29.297032-05:
      DOI: 10.1002/ange.201709508
       
  • Aktive Cokatalysatoren mit molekularen Nickel- und Cobaltkomplexen für
           die photokatalytische Wasserstoffentwicklung
    • Authors: Yi Huang; Bin Zhang
      Pages: 14998 - 15000
      Abstract: Eine preiswerte und robuste Strategie für die Verankerung von molekularen Cokatalysatoren für die Wasserstoffentwicklung auf Halbleitern wurde kürzlich vorgestellt. Die Hybridmaterialien sind hoch effizient und stabil in der photokatalytischen H2-Entwicklung, und die Ergebnisse liefern Anhaltspunkte für das Design und die Synthese von hoch aktiven heterogenen Photokatalysatoren.
      PubDate: 2017-10-11T07:25:37.22154-05:0
      DOI: 10.1002/ange.201708844
       
  • Flash-Vakuumpyrolyse – Techniken und Reaktionen
    • Authors: Curt Wentrup
      Pages: 15002 - 15031
      Abstract: Die Anfänge der Flash-Vakuumpyrolyse (FVP) ergaben sich in den 1940er und 1950er Jahren hauptsächlich aus dem massenspektrometrischen Nachweis pyrolytisch entstandener freier Radikale. In den 1960er Jahren begannen Organiker mit der Durchführung von FVP-Experimenten zum Zweck der Isolierung neuer und interessanter Verbindungen und zum Verständnis pyrolytischer Prozesse. Seitdem wurden viele unterschiedliche Typen von Apparaten und Techniken entwickelt. Zielsetzung dieses Aufsatzes ist es, die wichtigsten Methoden vorzustellen wie auch eine Übersicht über typische Reaktionen und Beobachtungen zu geben, die mit den verschiedenen Techniken erreicht werden können. Dies umfasst unter anderem präparative FVP, chemische Abfangreaktionen, Matrixisolierung sowie Tieftemperatur-Spektroskopie reaktiver Intermediate und instabiler Moleküle. Darüber hinaus ist die Kombination von FVP mit Matrixisolierung und Photochemie ein wirkungsvolles Instrument für Untersuchungen von Reaktionsmechanismen.Blitzschnell erhitzt: Dieser Aufsatz beschreibt Flash-Pyrolysemethoden zur Synthese ungewöhnlicher Moleküle und zur Charakterisierung reaktiver Zwischenstufen. Dabei stellt er die wichtigsten Methoden vor und gibt eine Übersicht über typische Reaktionen und Beobachtungen, die mit den verschiedenen Techniken möglich sind.
      PubDate: 2017-10-26T03:56:44.382647-05:
      DOI: 10.1002/ange.201705118
       
  • Mechanism-Based Inhibitors of the Human Sirtuin 5 Deacylase:
           Structure–Activity Relationship, Biostructural, and Kinetic Insight
    • Authors: Nima Rajabi; Marina Auth, Kathrin R. Troelsen, Martin Pannek, Dhaval P. Bhatt, Martin Fontenas, Matthew D. Hirschey, Clemens Steegborn, Andreas S. Madsen, Christian A. Olsen
      Pages: 15032 - 15037
      Abstract: The sirtuin enzymes are important regulatory deacylases in a variety of biochemical contexts and may therefore be potential therapeutic targets through either activation or inhibition by small molecules. Here, we describe the discovery of the most potent inhibitor of sirtuin 5 (SIRT5) reported to date. We provide rationalization of the mode of binding by solving co-crystal structures of selected inhibitors in complex with both human and zebrafish SIRT5, which provide insight for future optimization of inhibitors with more “drug-like” properties. Importantly, enzyme kinetic evaluation revealed a slow, tight-binding mechanism of inhibition, which is unprecedented for SIRT5. This is important information when applying inhibitors to probe mechanisms in biology.Struktur-Wirkungs-Studien für mechanismusbasierte Inhibitoren zusammen mit Informationen aus Röntgen-Kokristallstrukturen führen zu wirkungsvollen Inhibitoren der Hydrolase Sirtuin-5. Außerdem decken kinetische Messungen für einige SIRT5-Inhibitoren ein bisher unbekanntes, langsames, schwach bindendes Verhalten auf.
      PubDate: 2017-11-02T04:36:17.540555-05:
      DOI: 10.1002/ange.201709050
       
  • Analysis of Molecular Orientation in Organic Semiconducting Thin Films
           Using Static Dynamic Nuclear Polarization Enhanced Solid-State NMR
           Spectroscopy
    • Authors: Katsuaki Suzuki; Shosei Kubo, Fabien Aussenac, Frank Engelke, Tatsuya Fukushima, Hironori Kaji
      Pages: 15038 - 15042
      Abstract: Molecular orientation in amorphous organic semiconducting thin-film devices is an important issue affecting device performance. However, to date it has not been possible to analyze the “distribution” of the orientations. Although solid-state NMR (ssNMR) spectroscopy can provide information on the “distribution” of molecular orientations, the technique is limited because of the small amount of sample in the device and the low sensitivity of ssNMR. Here, we report the first application of dynamic nuclear polarization enhanced ssNMR (DNP-ssNMR) spectroscopy for the orientational analysis of amorphous phenyldi(pyren-1-yl)phosphine oxide (POPy2). The 31P DNP-ssNMR spectra exhibited a sufficient signal-to-noise ratio to quantify the distribution of molecular orientations in amorphous films: the P=O axis of the vacuum-deposited and drop-cast POPy2 shows anisotropic and isotropic distribution, respectively. The different molecular orientations reflect the molecular origin of the different charge transport behaviors.Die Ausrichtung organischer Halbleitermoleküle in einem amorphen dünnen Film wurde durch Festkörper-NMR-Spektroskopie mit statischer dynamischer Kernpolarisation untersucht. In einem im Vakuum abgeschiedenen Film des Elektronentransportmaterials POPy2 richtet sich die P=O-Achse bevorzugt senkrecht zum Substrat aus. Es gibt einen engen Zusammenhang zwischen der Orientierungsverteilung und dem Ladungstransportverhalten.
      PubDate: 2017-10-25T02:45:24.359622-05:
      DOI: 10.1002/ange.201707208
       
  • Reducing the Charge Carrier Transport Barrier in Functionally Layer-Graded
           Electrodes
    • Authors: Yanyan Zhang; Oleksandr I. Malyi, Yuxin Tang, Jiaqi Wei, Zhiqiang Zhu, Huarong Xia, Wenlong Li, Jia Guo, Xinran Zhou, Zhong Chen, Clas Persson, Xiaodong Chen
      Pages: 15043 - 15048
      Abstract: Lithium-ion batteries (LIBs) are primary energy storage devices to power consumer electronics and electric vehicles, but their capacity is dramatically decreased at ultrahigh charging/discharging rates. This mainly originates from a high Li-ion/electron transport barrier within a traditional electrode, resulting in reaction polarization issues. To address this limitation, a functionally layer-graded electrode was designed and fabricated to decrease the charge carrier transport barrier within the electrode. As a proof-of-concept, functionally layer-graded electrodes composing of TiO2(B) and reduced graphene oxide (RGO) exhibit a remarkable capacity of 128 mAh g−1 at a high charging/discharging rate of 20 C (6.7 A g−1), which is much higher than that of a traditionally homogeneous electrode (74 mAh g−1) with the same composition. This is evidenced by the improvement of effective Li ion diffusivity as well as electronic conductivity in the functionally layer-graded electrodes.Eine Elektrode mit Gradient schwächt die Reaktionspolarisation in Lithiumionenbatterien ab, indem die effektive Diffusionsfähigkeit der Lithiumionen und die elektronische Leitfähigkeit erhöht werden. Eine solche Elektrode aus TiO2(B) und reduziertem Graphenoxid ergibt eine deutlich höhere Kapazität (128 mAh g−1) als eine herkömmliche homogene Elektrode (74 mAh g−1) bei einer höheren Ladestromdichte von 6.7 A g−1.
      PubDate: 2017-10-20T04:40:56.163161-05:
      DOI: 10.1002/ange.201707883
       
  • Structural Snapshots of α-1,3-Galactosyltransferase with Native
           Substrates: Insight into the Catalytic Mechanism of Retaining
           Glycosyltransferases
    • Authors: David Albesa-Jové; M. Ángela Sainz-Polo, Alberto Marina, Marcelo E. Guerin
      Pages: 15049 - 15053
      Abstract: Glycosyltransferases (GTs) are a key family of enzymes that catalyze the synthesis of glycosidic bonds in all living organisms. The reaction involves the transfer of a glycosyl moiety and can proceed with retention or inversion of the anomeric configuration. To date, the catalytic mechanism of retaining GTs is a topic of great controversy, particularly for those enzymes containing a putative nucleophilic residue in the active site, for which the occurrence of a double-displacement mechanism has been suggested. We report native ternary complexes of the retaining glycosyltransferase α-1,3-galactosyltransferase (α3GalT) from Bos taurus, which contains such a nucleophile in the active site, in a productive mode for catalysis in the presence of its sugar donor UDP-Gal, the acceptor substrate lactose, and the divalent cation cofactor. This new experimental evidence supports the occurrence of a front-side substrate-assisted SNi-type reaction for α3GalT, and suggests a conserved common catalytic mechanism among retaining GTs.Kristallklar: Für den nativen ternären Komplex der α-1,3-Galactosyl-Transferase (α3GalT) aus der GT6-Familie der Glykosyltransferasen wurde die Kristallstruktur mit einem vermuteten Nukleophil in einer katalytisch produktiven Anordnung im aktiven Zentrum gelöst. Die Konfiguration des aktiven Zentrums spricht für einen substratunterstützten Vorderseitenangriff (SNi) und deutet auf einen konservierten Mechanismus in konfigurationserhaltenden Glykosyltransferasen hin.
      PubDate: 2017-10-20T01:35:53.477738-05:
      DOI: 10.1002/ange.201707922
       
  • Induction of Single-Handed Helicity of Polyacetylenes Using Mechanically
           Chiral Rotaxanes as Chiral Sources
    • Authors: Fumitaka Ishiwari; Kazuko Nakazono, Yasuhito Koyama, Toshikazu Takata
      Pages: 15054 - 15058
      Abstract: Effective induction of preferred-handed helicity of polyacetylenes by pendant mechanically chiral rotaxanes is discussed. Polyacetylenes possessing optically active mechanically chiral rotaxanes in the side chains were synthesized by the polymerization of the corresponding enantiopure [2]rotaxane-type ethynyl monomers prepared by the chiral-phase HPLC separations. The CD Cotton effects revealed that the polyacetylenes took preferred-handed helical conformations depending on the rotaxane chirality. The preferred-handed helix was not disturbed by an additional chiral substituent on the rotaxane side chain. These results demonstrate the significance and utility of mechanically chiral rotaxanes for the effective construction of asymmetric fields.Mechanisch chirale Verbindungen dienen als Quelle für Chiralität. Polyacetylene mit optisch aktiven, mechanisch chiralen Rotaxanen als Seitenketten ergeben einen starken Zirkulardichroismus in den Absorptionsbereichen der Hauptketten, woraus sich eine effiziente Helizitätsinduktion durch die Rotaxane ableiten lässt. Die Ergebnisse belegen die Erzeugung asymmetrischer Felder durch mechanisch chirale Rotaxane.
      PubDate: 2017-10-18T03:35:25.696285-05:
      DOI: 10.1002/ange.201707926
       
  • Experimental and Computational Study of an Unexpected Iron-Catalyzed
           Carboetherification by Cooperative Metal and Ligand Substrate Interaction
           and Proton Shuttling
    • Authors: Osama El-Sepelgy; Aleksandra Brzozowska, Luis Miguel Azofra, Yoon Kyung Jang, Luigi Cavallo, Magnus Rueping
      Pages: 15059 - 15063
      Abstract: An iron-catalyzed cycloisomerization of allenols to deoxygenated pyranose glycals has been developed. Combined experimental and computational studies show that the iron complex exhibits a dual catalytic role in that the non-innocent cyclopentadienone ligand acts as proton shuttle by initial hydrogen abstraction from the alcohol and by facilitating protonation and deprotonation events in the isomerization and demetalation steps. Molecular orbital analysis provides insight into the unexpected and selective formation of the 3,4-dihydro-2H-pyran.Nicht so unschuldig wie es scheint: Allenole cycloisomerisieren zu deoxygenierten Pyranose-Glykalen in Gegenwart eines Eisenkomplexes, dessen Cyclopentadienon-Ligand als Protonen-Shuttle die Protonierungs- und Deprotonierungsereignisse in den Isomerisierungs- und Demetallierungsschritten fördert. Eine Molekülorbitalanalyse gibt Einblick in die unerwartete und selektive Bildung der 3,4-Dihydro-2H-pyran-Produkte.
      PubDate: 2017-10-24T06:22:17.268452-05:
      DOI: 10.1002/ange.201708240
       
  • Selective Utilization of the Methoxy Group in Lignin to Produce Acetic
           Acid
    • Authors: Qingqing Mei; Huizhen Liu, Xiaojun Shen, Qinglei Meng, Hangyu Liu, Junfeng Xiang, Buxing Han
      Pages: 15064 - 15068
      Abstract: Selective transformation of lignin into a valuable chemical is of great importance and challenge owing to its complex structure. Herein, we propose a strategy for the transformation of methoxy group (-OCH3) which is abundant in lignin into pure highly valuable chemicals. As an example to apply this strategy, a route to produce acetic acid with high selectivity by conversion of methoxy group of lignin was developed. It was demonstrated that the methoxy group in lignin could react with CO and water to generate acetic acid over RhCl3 in the presence of a promoter. The conversions of methoxy group in the kraft lignin and organosolv lignin reached 87.5 % and 80.4 %, respectively, and no by-product was generated. This work opens the way to produce pure chemicals using lignin as the feedstock.Die (Bio)Masse macht's: Die Umwandlung von Methoxygruppen aus Lignin in Essigsäure gelingt durch selektive Umsetzung mit CO und Wasser über RhCl3. Bei 100 %iger Selektivität für Essigsäure sind Umsätze bis 87.5 % möglich.
      PubDate: 2017-09-22T06:10:26.753002-05:
      DOI: 10.1002/ange.201706846
       
  • Carbene Footprinting Reveals Binding Interfaces of a Multimeric
           Membrane-Spanning Protein
    • Authors: Lucio Manzi; Andrew S. Barrow, Jonathan T. S. Hopper, Renata Kaminska, Colin Kleanthous, Carol V. Robinson, John E. Moses, Neil J. Oldham
      Pages: 15069 - 15073
      Abstract: Mapping the interaction sites between membrane-spanning proteins is a key challenge in structural biology. In this study a carbene-footprinting approach was developed and applied to identify the interfacial sites of a trimeric, integral membrane protein, OmpF, solubilised in micelles. The diazirine-based footprinting probe is effectively sequestered by, and incorporated into, the micelles, thus leading to efficient labelling of the membrane-spanning regions of the protein upon irradiation at 349 nm. Areas associated with protein–protein interactions between the trimer subunits remained unlabelled, thus revealing their location.Carbenmarkierungen wurden genutzt, um die Wechselwirkungsstellen eines in Micellen solubilisierten trimeren integralen Membranproteins zu identifizieren. Die Diazirin-Sonde wird in die Micellen eingeführt, und nach Bestrahlung bei 349 nm sind die membrandurchspannenden Regionen des Proteins markiert. Bereiche mit Protein-Protein-Wechselwirkungen zwischen den Trimer-Untereinheiten bleiben unmarkiert, was ihre Lokalisierung offenlegt.
      PubDate: 2017-10-20T01:30:43.767954-05:
      DOI: 10.1002/ange.201708254
       
  • A Radiolabeling-Free, qPCR-Based Method for Locus-Specific Pseudouridine
           Detection
    • Authors: Zhixin Lei; Chengqi Yi
      Pages: 15074 - 15078
      Abstract: Pseudouridine (Ψ) is the most abundant post-transcriptional RNA modification. Methods have been developed for locus-specific Ψ detection; however, they often involve radiolabeling of RNA, require advanced experimental skills, and can be time-consuming. Herein we report a radiolabeling-free, qPCR-based method to rapidly detect locus-specific Ψ. Pseudouridine residues were labeled chemically, and the resulting adducts induced mutation/deletion during reverse transcription (RT) to generate qPCR products with different melting temperatures and hence altered melting curves. We validated our method on known Ψ sites in rRNA and then used it to sensitively detect Ψ residues in lncRNA and mRNA of low abundance. Finally, we applied our method to pseudouridine synthase identification and showed that Ψ616 in PSME2 mRNA is dependent on PUS7. Our facile and cost-effective method takes only 1.5 days to complete, and with slight adjustment it can be applied to the detection of other epitranscriptomic marks.Auf Spurensuche: Eine schnelle und kostengünstige Methode für den Nachweis der verbreiteten posttranskriptionalen RNA-Modifikation Pseudouridin im humanen Transkriptom wurde entwickelt. Pseudouridin wird chemisch markiert, und die resultierenden Addukte induzieren Mutationen/Deletionen bei der reversen Transkription (RT), um qPCR-Produkte mit unterschiedlichen Schmelztemperaturen und somit veränderten Schmelzkurven zu generieren.
      PubDate: 2017-10-19T07:05:33.066894-05:
      DOI: 10.1002/ange.201708276
       
  • Cobalt versus Osmium: Control of Both trans and cis Selectivity in
           Construction of the EFG Rings of Pectenotoxin 4
    • Authors: Ahria Roushanbakhti; Yifan Liu, Paul C. M. Winship, Michael J. Tucker, Wasim M. Akhtar, Daryl S. Walter, Gail Wrigley, Timothy J. Donohoe
      Pages: 15079 - 15083
      Abstract: Catalytic oxidative cyclisation reactions have been employed for the synthesis of the E and F rings of the complex natural product target pectenotoxin 4. The choice of metal catalyst (cobalt- or osmium-based) allowed for the formation of THF rings with either trans or cis stereoselectivity. Fragment union using a modified Julia reaction then enabled the synthesis of an advanced synthetic intermediate containing the EF and G rings of the target.Zwei Arten oxidativer Cyclisierungen, die entweder Osmium- oder Cobalt-Katalyse verwenden, ermöglichen die vollständige Kontrolle der relativen Stereochemie der THF-Ringe in dem komplexen Ringsystem von Pectenotoxin-4. Auf diese Weise gelingt der rasche Zugang zu den trans- (Co) oder cis-2,5-disubstituierten (Os) THF-Ringen des Naturstoffs.
      PubDate: 2017-10-19T06:41:49.236247-05:
      DOI: 10.1002/ange.201708278
       
  • Peptide Logic Circuits Based on Chemoenzymatic Ligation for Programmable
           Cell Apoptosis
    • Authors: Yong Li; Sujuan Sun, Lin Fan, Shanfang Hu, Yan Huang, Ke Zhang, Zhou Nie, Shouzhou Yao
      Pages: 15084 - 15088
      Abstract: A novel and versatile peptide-based bio-logic system capable of regulating cell function is developed using sortase A (SrtA), a peptide ligation enzyme, as a generic processor. By modular peptide design, we demonstrate that mammalian cells apoptosis can be programmed by peptide-based logic operations, including binary and combination gates (AND, INHIBIT, OR, and AND-INHIBIT), and a complex sequential logic circuit (multi-input keypad lock). Moreover, a proof-of-concept peptide regulatory circuit was developed to analyze the expression profile of cell-secreted protein biomarkers and trigger cancer-cell-specific apoptosis.Nur bio-logisch: Ein vielseitiges Logiksystem auf Peptidbasis nutzt das Peptidligationsenzym Sortase A (SrtA) als generischen Prozessor. Die Verwendung modularer Eingabe-Peptide ermöglicht die Programmierung einer Krebszellapoptose über das Peptid-Logiksystem.
      PubDate: 2017-10-24T06:22:08.614378-05:
      DOI: 10.1002/ange.201708327
       
  • Generalized Self-Doping Engineering towards Ultrathin and Large-Sized
           Two-Dimensional Homologous Perovskites
    • Authors: Junnian Chen; Yaguang Wang, Lin Gan, Yunbin He, Huiqiao Li, Tianyou Zhai
      Pages: 15089 - 15093
      Abstract: Two-dimensional (2D) homologous perovskites are arousing intense interest in photovoltaics and light-emitting fields, attributing to significantly improved stability and increasing optoelectronic performance. However, investigations on 2D homologous perovskites with ultrathin thickness and large lateral dimension have been seldom reported, being mainly hindered by challenges in synthesis. A generalized self-doping directed synthesis of ultrathin 2D homologous (BA)2(MA)n−1PbnBr3n+1 (1
      PubDate: 2017-10-20T01:35:41.276918-05:
      DOI: 10.1002/ange.201708434
       
  • Organoiridium Photosensitizers Induce Specific Oxidative Attack on
           Proteins within Cancer Cells
    • Authors: Pingyu Zhang; Cookson K. C. Chiu, Huaiyi Huang, Yuko P. Y. Lam, Abraha Habtemariam, Thomas Malcomson, Martin J. Paterson, Guy J. Clarkson, Peter B. O'Connor, Hui Chao, Peter J. Sadler
      Pages: 15094 - 15098
      Abstract: Strongly luminescent iridium(III) complexes, [Ir(C,N)2(S,S)]+ (1) and [Ir(C,N)2(O,O)] (2), containing C,N (phenylquinoline), O,O (diketonate), or S,S (dithione) chelating ligands, have been characterized by X-ray crystallography and DFT calculations. Their long phosphorescence lifetimes in living cancer cells give rise to high quantum yields for the generation of 1O2, with large 2-photon absorption cross-sections. 2 is nontoxic to cells, but potently cytotoxic to cancer cells upon brief irradiation with low doses of visible light, and potent at sub-micromolar doses towards 3D multicellular tumor spheroids with 2-photon red light. Photoactivation causes oxidative damage to specific histidine residues in the key proteins in aldose reductase and heat-shock protein-70 within living cancer cells. The oxidative stress induced by iridium photosensitizers during photoactivation can increase the levels of enzymes involved in the glycolytic pathway.Produktiver Stress: Ein stark lumineszierender Organoiridium-Komplex erzeugt effizient 1O2 und oxidiert spezifische Reste im Hitzeschockprotein-70 und in Aldose-Reduktase in Krebszellen. Der oxidative Stress, der durch Iridium- Photosensibilisatoren während der Photoaktivierung induziert wird, kann die Konzentration der am Glykolysestoffwechselweg beteiligten Enzyme erhöhen.
      PubDate: 2017-10-19T01:45:55.717662-05:
      DOI: 10.1002/ange.201709082
       
  • Experimental and Computational Exploration of para-Selective Silylation
           with a Hydrogen-Bonded Template
    • Authors: Arun Maji; Srimanta Guin, Sheng Feng, Amit Dahiya, Vikas Kumar Singh, Peng Liu, Debabrata Maiti
      Pages: 15099 - 15103
      Abstract: The regioselective conversion of C−H bonds into C−Si bonds is extremely important owing to the natural abundance and non-toxicity of silicon. Classical silylation reactions often suffer from poor functional group compatibility, low atom economy, and insufficient regioselectivity. Herein, we disclose a template-assisted method for the regioselective para silylation of toluene derivatives. A new template was designed, and the origin of selectivity was analyzed experimentally and computationally. An interesting substrate–solvent hydrogen-bonding interaction was observed. Kinetic, spectroscopic, and computational studies shed light on the reaction mechanism. The synthetic significance of this strategy was highlighted by the generation of a precursor of a potential lipophilic bioisostere of γ-aminobutyric acid (GABA), various late-stage diversifications, and by mimicking enzymatic transformations.Ein neues Templat ermöglicht die regioselektive para-Silylierung von Toluol- Derivaten. Der Ursprung der Selektivität wurde sowohl experimentell als auch rechnerisch untersucht, und eine wichtige Wasserstoffbrücke zwischen Substrat und Lösungsmittel wurde entdeckt.
      PubDate: 2017-10-25T02:45:48.375618-05:
      DOI: 10.1002/ange.201708449
       
  • Lanthanide-Coordinated Semiconducting Polymer Dots Used for Flow Cytometry
           and Mass Cytometry
    • Authors: Xu Wu; Quinn DeGottardi, I-Che Wu, Jiangbo Yu, Li Wu, Fangmao Ye, Chun-Ting Kuo, William W. Kwok, Daniel T. Chiu
      Pages: 15104 - 15108
      Abstract: Simultaneous monitoring of biomarkers as well as single-cell analyses based on flow cytometry and mass cytometry are important for investigations of disease mechanisms, drug discovery, and signaling-network studies. Flow cytometry and mass cytometry are complementary to each other; however, probes that can satisfy all the requirements for these two advanced technologies are limited. In this study, we report a probe of lanthanide-coordinated semiconducting polymer dots (Pdots), which possess fluorescence and mass signals. We demonstrated the usage of this dual-functionality probe for both flow cytometry and mass cytometry in a mimetic cell mixture and human peripheral blood mononuclear cells as model systems. The probes not only offer high fluorescence signal for use in flow cytometry, but also show better performance in mass cytometry than the commercially available counterparts.Lanthanoid-koordinierte, halbleitende Polymernanopartikel mit starker Fluoreszenz zeigen hervorragende Leistungen in der Durchfluss- und Massenzytometrie bei Zellanalysen.
      PubDate: 2017-10-12T06:20:35.314438-05:
      DOI: 10.1002/ange.201708463
       
  • Structure and Mechanism of the Monoterpene Cyclolavandulyl Diphosphate
           Synthase that Catalyzes Consecutive Condensation and Cyclization
    • Authors: Takeo Tomita; Masaya Kobayashi, Yuma Karita, Yoko Yasuno, Tetsuro Shinada, Makoto Nishiyama, Tomohisa Kuzuyama
      Pages: 15109 - 15113
      Abstract: We report the three-dimensional structure of cyclolavandulyl diphosphate (CLPP) synthase (CLDS), which consecutively catalyzes the condensation of two molecules of dimethylallyl diphosphate (DMAPP) followed by cyclization to form a cyclic monoterpene, CLPP. The structures of apo-CLDS and CLDS in complex with Tris, pyrophosphate, and Mg2+ ion were refined at 2.00 Å resolution and 1.73 Å resolution, respectively. CLDS adopts a typical fold for cis-prenyl synthases and forms a homo-dimeric structure. An in vitro reaction using a regiospecifically 2H-substituted DMAPP substrate revealed the intramolecular proton transfer mechanism of the CLDS reaction. The CLDS structure and structure-based mutagenesis provide mechanistic insights into this unprecedented terpene synthase. The combination of structural and mechanistic insights advances the knowledge of intricate terpene synthase-catalyzed reactions.Eine Synthase, die beides kann: Cyclolavandulyldiphosphat(CLPP)-Synthase (CLDS) katalysiert die „Kopf-zu-Mitte”-Kondensation von zwei Molekülen Dimethylallyldiphosphat (DMAPP) und die anschließende Cyclisierung zu CLPP. Die Kristallstruktur von CLDS im Komplex mit Tris, Pyrophosphat und Mg2+ wurde mit 1.73 Å Auflösung bestimmt. Eine In-vitro-Reaktion mit regiospezifisch deuteriertem DMAPP, die CLDS-Struktur und Mutagenese liefern Einblicke in den Mechanismus dieser einzigartigen Terpensynthase.
      PubDate: 2017-10-11T04:40:45.026624-05:
      DOI: 10.1002/ange.201708474
       
  • Fluorine Effects on Group Migration via a Rhodium(V) Nitrenoid
           Intermediate
    • Authors: Cheng-Qiang Wang; Yu Zhang, Chao Feng
      Pages: 15114 - 15118
      Abstract: An unprecedented rhodium(III)-catalyzed hydroarylation of α,α-difluoromethylene alkynes with N-pivaloxyl aroylamides through sequential C−H activation and aryl migration is detailed herein. A large array of α,α-difluoromethylene alkynes and N-pivaloxyl aryl amides were amenable to this transformation, thus providing a novel synthetic protocol for the construction of difluorinated 2-alkenyl aniline derivatives in high yields and with excellent regioselectivity. Notably, unique fluorine effects were found to underlie the thus unconventional reaction manifold.Neue Wege erkunden: Die Rhodium(III)-katalysierte Hydroarylierung von α,α-Difluormethylenalkinen mit N-Pivaloyloxyarylamiden ermöglicht die effiziente regiospezifische Synthese von difluorierten 2-Alkenylanilinen (siehe Schema). Die Fluorsubstituenten in den Alkinsubstraten lenken den Reaktionsverlauf vom konventionellen Anellierungsweg hin zu einem Hydroarylierungsprozess, der eine Lossen-Umlagerung einschließt.
      PubDate: 2017-10-09T04:56:43.451717-05:
      DOI: 10.1002/ange.201708505
       
  • Compartmentalizing Supramolecular Hydrogels Using Aqueous Multi-phase
           Systems
    • Authors: Serhii Mytnyk; Alexandre G. L. Olive, Frank Versluis, Jos M. Poolman, Eduardo Mendes, Rienk Eelkema, Jan H. van Esch
      Pages: 15119 - 15123
      Abstract: A generic method is used for compartmentalization of supramolecular hydrogels by using water-in-water emulsions based on aqueous multi-phase systems (AMPS). By forming the low-molecular-weight hydrogel throughout all phases of all-aqueous emulsions, distinct, micro-compartmentalized materials were created. This structuring approach offers control over the composition of each type of the compartments by directing the partitioning of objects to be encapsulated. Moreover, this method allows for barrier-less, dynamic exchange of even large hydrophilic solutes (MW≈60 kDa) between separate aqueous compartments. These features are expected to find use in the fields of, for instance, micro-structured catalysts, templating, and tissue engineering.Hydrogel-Kompartimente: Ein vielseitiger Ansatz wird genutzt, um mittels Polymerphasentrennung wässrige Mikrokompartimente in niedermolekularen Hydrogelen zu erzeugen. Man erhält spezifische mikrometergroße Domänen mit kontrollierter Zusammensetzung, die selbst große polare Solute austauschen können. Die Methode hat Potenzial für die Templatsynthese von porösen weichen Materialien oder die Herstellung künstlicher Gewebe.
      PubDate: 2017-09-12T01:40:49.868122-05:
      DOI: 10.1002/ange.201706272
       
  • Photoluminescence Lifetime Imaging of Synthesized Proteins in Living Cells
           Using an Iridium–Alkyne Probe
    • Authors: Jinyu Wang; Jie Xue, Zihe Yan, Sichun Zhang, Juan Qiao, Xinrong Zhang
      Pages: 15124 - 15128
      Abstract: Designing probes for real-time imaging of dynamic processes in living cells is a continuous challenge. Herein, a novel near-infrared (NIR) photoluminescence probe having a long lifetime was exploited for photoluminescence lifetime imaging (PLIM) using an iridium-alkyne complex. This probe offers the benefits of deep-red to NIR emission, a long Stokes shift, excellent cell penetration, low cytotoxicity, and good resistance to photobleaching. This example is the first PLIM probe applicable to the click reaction of copper(I)-catalyzed azide–alkyne cycloaddition (CuAAC) with remarkable lifetime shifts of 414 ns, before and after click reaction. The approach fully eliminates the background interference and distinguishes the reacted probes from the unreacted probes, thus enabling the wash-free imaging of the newly synthesized proteins within single living cells. Based on the unique properties of the iridium complexes, it is anticipated to have applications for imaging other processes within living cells.Pflegeleichte Bildgebung: Eine neuartige bioorthogonale Sonde, ein Ir-Alkin-Komplex, zeigt eine Emission vom tiefroten bis in den Nah-IR-Bereich und eine unerwartet große Lebensdauerdifferenz von 414 ns vor und nach der Klick-Reaktion. Die Sonde ermöglichte die aufreinigungsfreie Bildgebung neu synthetisierter Proteine in lebenden Zellen. NP=Nanopartikel.
      PubDate: 2017-10-13T06:16:29.144874-05:
      DOI: 10.1002/ange.201708566
       
  • Enzyme Encapsulation by a Ferritin Cage
    • Authors: Stephan Tetter; Donald Hilvert
      Pages: 15129 - 15132
      Abstract: Ferritins, conserved across all kingdoms of life, are protein nanocages that evolved to mineralize iron. The last several decades have shown that these cages have considerable technological and medical potential owing to their stability and tolerance to modification, as well as their ability to template nanoparticle synthesis and incorporate small molecules. Here we show that it is possible to encapsulate proteins in a ferritin cage by exploiting electrostatic interactions with its negatively charged interior. Positively supercharged green fluorescent protein is efficiently taken up by Archaeoglobus fulgidus ferritin in a tunable fashion. Moreover, several enzymes were readily incorporated when genetically tethered to this fluorescent protein. These fusion proteins retained high catalytic activity and showed increased tolerance to proteolysis and heat. Equipping ferritins with enzymatic activity paves the way for many new nanotechnological and pharmacological applications.Aktives Innenleben: Der natürliche Nanokäfig Ferritin aus Archaeoglobus fulgidus verkapselt positiv geladene Proteine (grün) mithilfe elektrostatischer Wechselwirkungen. Enzyme (grau), die an solche geladenen Gastspezies gebunden sind, behalten ihre Aktivität bei [Substrat (S)Produkt (P)] und verleihen dem Ferritin dadurch neue katalytische Funktionen, die nanotechnologisch oder pharmakologisch nutzbar sein könnten.
      PubDate: 2017-10-12T08:15:38.305466-05:
      DOI: 10.1002/ange.201708530
       
  • One-Pot, Three-Component Sulfonimidamide Synthesis Exploiting the
           Sulfinylamine Reagent N-Sulfinyltritylamine, TrNSO
    • Authors: Thomas Q. Davies; Adrian Hall, Michael C. Willis
      Pages: 15133 - 15137
      Abstract: Sulfonimidamides are increasingly important molecules in medicinal chemistry and agrochemistry, but their preparation requires lengthy synthetic sequences, which has likely limited their use. We describe a one-pot de novo synthesis of sulfonimidamides from widely available organometallic reagents and amines. This convenient and efficient process uses a stable sulfinylamine reagent, N-sulfinyltritylamine (TrNSO), available in one step on 10 gram scale, as a linchpin. In contrast to classical approaches starting from thiols or their derivatives, our TrNSO-based approach facilitates the rapid assembly of the three reaction components into a variety of differentially substituted sulfonimidamides containing medicinally relevant moieties, including pyridines and indoles. Analogues of the sulfonamide-containing COX-2 inhibitor Celecoxib were prepared and evaluated.Komm zu uns! Das stabile, einfach herzustellende Sulfinylamin-Reagens TrNSO wird als Verbindungsstück für die Verknüpfung von metallorganischen Reagentien und Aminen zu Sulfonimidamiden in einem Ein-Topf-Prozess genutzt. Beide Reaktionspartner können breit variiert werden.
      PubDate: 2017-10-10T06:51:59.188705-05:
      DOI: 10.1002/ange.201708590
       
  • Transient Behavior of the Metal Interface in Lithium Metal–Garnet
           Batteries
    • Authors: Kun (Kelvin) Fu; Yunhui Gong, Zhezhen Fu, Hua Xie, Yonggang Yao, Boyang Liu, Marcus Carter, Eric Wachsman, Liangbing Hu
      Pages: 15138 - 15143
      Abstract: The interface between solid electrolytes and Li metal is a primary issue for solid-state batteries. Introducing a metal interlayer to conformally coat solid electrolytes can improve the interface wettability of Li metal and reduce the interfacial resistance, but the mechanism of the metal interlayer is unknown. In this work, we used magnesium (Mg) as a model to investigate the effect of a metal coating on the interfacial resistance of a solid electrolyte and Li metal anode. The Li–Mg alloy has low overpotential, leading to a lower interfacial resistance. Our motivation is to understand how the metal interlayer behaves at the interface to promote increased Li-metal wettability of the solid electrolyte surface and reduce interfacial resistance. Surprisingly, we found that the metal coating dissolved in the molten piece of Li and diffused into the bulk Li metal, leading to a small and stable interfacial resistance between the garnet solid electrolyte and the Li metal. We also found that the interfacial resistance did not change with increase in the thickness of the metal coating (5, 10, and 100 nm), due to the transient behavior of the metal interface layer.Widerstand zwecklos: Magnesium wurde als Modellmaterial verwendet, um den Einfluss einer Metallbeschichtung auf den Grenzflächenwiderstand zwischen dem Granat-Festkörperelektrolyten (Li7La3Zr2O12) und der Li-Metallanode in einer Li-Granat-Batterie zu untersuchen. Überraschenderweise löst sich die Metallschicht auf und diffundiert in das Li-Metall, sodass ein kleiner und stabiler Grenzflächenwiderstand resultiert.
      PubDate: 2017-10-19T07:25:33.454221-05:
      DOI: 10.1002/ange.201708637
       
  • Synthesis of Arylamines via Aminium Radicals
    • Authors: Thomas D. Svejstrup; Alessandro Ruffoni, Fabio Juliá, Valentin M. Aubert, Daniele Leonori
      Pages: 15144 - 15148
      Abstract: Arylamines constitute the core structure of many therapeutic agents, agrochemicals, and organic materials. The development of methods for the efficient and selective construction of these structural motifs from simple building blocks is desirable but still challenging. We demonstrate that protonated electron-poor O-aryl hydroxylamines give aminium radicals in the presence of Ru(bpy)3Cl2. These highly electrophilic species undergo polarized radical addition to aromatic compounds in high yield and selectivity. We successfully applied this method to the late-stage modification of chiral catalyst templates, therapeutic agents, and natural products.Radikale als Lösung: Protonierte elektronenarme O-Arylhydroxylamine setzen in Gegenwart von Ru(bpy)3Cl2 hoch elektrophile Aminium-Radikale frei, deren polare radikalische Additionen an aromatische Verbindungen hoch selektiv und in hohen Ausbeuten zu Arylaminen führen. Die Methode ist breit anwendbar, auch zur späten Modifizierung von chiralen Katalysatorgerüsten, Wirk- und Naturstoffen.
      PubDate: 2017-10-24T11:31:25.839775-05:
      DOI: 10.1002/ange.201708693
       
  • A Low-Cost Neutral Zinc–Iron Flow Battery with High Energy Density for
           Stationary Energy Storage
    • Authors: Congxin Xie; Yinqi Duan, Wenbin Xu, Huamin Zhang, Xianfeng Li
      Pages: 15149 - 15153
      Abstract: Flow batteries (FBs) are one of the most promising stationary energy-storage devices for storing renewable energy. However, commercial progress of FBs is limited by their high cost and low energy density. A neutral zinc–iron FB with very low cost and high energy density is presented. By using highly soluble FeCl2/ZnBr2 species, a charge energy density of 56.30 Wh L−1 can be achieved. DFT calculations demonstrated that glycine can combine with iron to suppress hydrolysis and crossover of Fe3+/Fe2+. The results indicated that an energy efficiency of 86.66 % can be obtained at 40 mA cm−2 and the battery can run stably for more than 100 cycles. Furthermore, a low-cost porous membrane was employed to lower the capital cost to less than $ 50 per kWh, which was the lowest value that has ever been reported. Combining the features of low cost, high energy density and high energy efficiency, the neutral zinc–iron FB is a promising candidate for stationary energy-storage applications.Eine neutrale Zn-Fe-Flussbatterie mit niedrigen Kosten und hoher Energiedichte wird vorgestellt. Hoch lösliche FeCl2/ZnBr2-Spezies ermöglichen eine Ladungsenergiedichte von 56.30 Wh L−1. DFT-Rechnungen zeigen, dass Glycin Eisen komplexiert, um Hydrolyse und Crossover von Fe3+/Fe2+ zu unterdrücken. Eine Energieeffizienz von 86.66 % mit 40 mA cm−2 wird erreicht, und die Batterie kann über mindestens 100 Zyklen stabil betrieben werden.
      PubDate: 2017-10-20T01:31:04.235956-05:
      DOI: 10.1002/ange.201708664
       
  • Electrostatic-Assisted Liquefaction of Porous Carbons
    • Authors: Peipei Li; Jennifer A. Schott, Jinshui Zhang, Shannon M. Mahurin, Yujie Sheng, Zhen-An Qiao, Xunxiang Hu, Guokai Cui, Dongdong Yao, Suree Brown, Yaping Zheng, Sheng Dai
      Pages: 15154 - 15158
      Abstract: Porous liquids are a newly developed porous material that combine unique fluidity with permanent porosity, which exhibit promising functionalities for a variety of applications. However, the apparent incompatibility between fluidity and permanent porosity makes the stabilization of porous nanoparticle with still empty pores in the dense liquid phase a significant challenging. Herein, by exploiting the electrostatic interaction between carbon networks and polymerized ionic liquids, we demonstrate that carbon-based porous nanoarchitectures can be well stabilized in liquids to afford permanent porosity, and thus opens up a new approach to prepare porous carbon liquids. Furthermore, we hope this facile synthesis strategy can be widely applicated to fabricate other types of porous liquids, such as those (e.g., carbon nitride, boron nitride, metal–organic frameworks, covalent organic frameworks etc.) also having the electrostatic interaction with polymerized ionic liquids, evidently advancing the development and understanding of porous liquids.Poröse Kohlenstoff-Flüssigkeiten: Die elektrostatische Wechselwirkung zwischen Kohlenstoffnetzwerken und polymerisierten ionischen Flüssigkeiten wurde genutzt, um hohle sphärische Kohlenstoffpartikel in Flüssigkeiten zu stabilisieren und damit permanente Porosität zu erzeugen. Poröse Kohlenstoff-Flüssigkeiten (HCS-liquid) haben zahlreiche Anwendungsmöglichkeiten, z. B. in der Abtrennung und Speicherung von CO2.
      PubDate: 2017-10-23T01:22:01.540817-05:
      DOI: 10.1002/ange.201708843
       
  • Oxetane Grafts Installed Site-Selectively on Native Disulfides to Enhance
           Protein Stability and Activity In Vivo
    • Authors: Nuria Martínez-Sáez; Shuang Sun, Davide Oldrini, Pietro Sormanni, Omar Boutureira, Filippo Carboni, Ismael Compañón, Michael J. Deery, Michele Vendruscolo, Francisco Corzana, Roberto Adamo, Gonçalo J. L. Bernardes
      Pages: 15159 - 15163
      Abstract: A four-membered oxygen ring (oxetane) can be readily grafted into native peptides and proteins through site-selective bis-alkylation of cysteine residues present as disulfides under mild and biocompatible conditions. The selective installation of the oxetane graft enhances stability and activity, as demonstrated for a range of biologically relevant cyclic peptides, including somatostatin, proteins, and antibodies, such as a Fab arm of the antibody Herceptin and a designed antibody DesAb-Aβ against the human Amyloid-β peptide. Oxetane grafting of the genetically detoxified diphtheria toxin CRM197 improves significantly the immunogenicity of this protein in mice, which illustrates the general utility of this strategy to modulate the stability and biological activity of therapeutic proteins containing disulfides in their structures.Stabiler Zusammenhalt: Eine effiziente Ein-Topf-Methode führt unter biokompatiblen wässrigen Bedingungen Oxetan-Oberflächengruppen an nativen Disulfiden von Peptiden und Proteinen ein. Die Methode ermöglicht die Stabilisierung von gefalteten Strukturen (vier Beispiele sind gezeigt) und die Verstärkung ihrer biologischen Aktivität in vitro und in vivo.
      PubDate: 2017-10-20T01:50:44.240813-05:
      DOI: 10.1002/ange.201708847
       
  • Oxidative Rearrangement Coupling Reaction for the Functionalization of
           Tetrahydro-β-carbolines with Aromatic Amines
    • Authors: Jinxiang Ye; Jianlei Wu, Tingting Lv, Guolin Wu, Yu Gao, Haijun Chen
      Pages: 15164 - 15168
      Abstract: The observation of an unexpected oxidative rearrangement coupling reaction led to the development of a novel method for the efficient functionalization of tetrahydro-β-carbolines (THβCs). The treatment of THβCs with photogenerated singlet oxygen (1O2) afforded unstable dioxetanes, which underwent further transformation to form new bonds in the presence of trifluoroacetic acid. This operationally simple protocol exhibits broad functional-group tolerance and is suitable for the late-stage functionalization of complex druglike molecules.Alle umgruppieren bitte: Die Behandlung von Tetrahydro-β-carbolinen mit photogeneriertem Singulett-Sauerstoff ergibt instabile Dioxetane, die unter Ringöffnung neungliedrige Intermediate bilden, die mit Aminen in Gegenwart einer Säure zu aminosubstituierten Dihydropyrrolochinolinen umgesetzt werden können (siehe Schema). Die einfache Methode eignet sich für die späte Funktionalisierung von komplexen wirkstoffartigen Molekülen.
      PubDate: 2017-10-19T02:01:41.94985-05:0
      DOI: 10.1002/ange.201708893
       
  • Conotoxin Φ-MiXXVIIA from the Superfamily G2 Employs a Novel Cysteine
           Framework that Mimics Granulin and Displays Anti-Apoptotic Activity
    • Authors: Ai-Hua Jin; Zoltan Dekan, Michael J. Smout, David Wilson, Sébastien Dutertre, Irina Vetter, Richard J. Lewis, Alex Loukas, Norelle L. Daly, Paul F. Alewood
      Pages: 15169 - 15172
      Abstract: Conotoxins are a large family of disulfide-rich peptides that contain unique cysteine frameworks that target a broad range of ion channels and receptors. We recently discovered the 33-residue conotoxin Φ-MiXXVIIA from Conus miles with a novel cysteine framework comprising three consecutive cysteine residues and four disulfide bonds. Regioselective chemical synthesis helped decipher the disulfide bond connectivity and the structure of Φ-MiXXVIIA was determined by NMR spectroscopy. The 3D structure displays a unique topology containing two β-hairpins that resemble the N-terminal domain of granulin. Similar to granulin, Φ-MiXXVIIA promotes cell proliferation (EC50 17.85 μm) while inhibiting apoptosis (EC50 2.2 μm). Additional framework XXVII sequences were discovered with homologous signal peptides that define the new conotoxin superfamily G2. The novel structure and biological activity of Φ-MiXXVIIA expands the repertoire of disulfide-rich conotoxins that recognize mammalian receptors.Das Schneckentoxin Conotoxin Φ-MiXXVIIA enthält ein Molekülgerüst aus drei aufeinanderfolgenden Cysteinen und vier Disulfidbrücken, deren Konnektivität durch NMR-Spektroskopie und regioselektive chemische Synthese ermittelt wurde. Φ-MiXXVIIA zeigt eine einzigartige Struktur sowie proliferative und antiapoptotische Aktivität.
      PubDate: 2017-10-24T06:21:37.302296-05:
      DOI: 10.1002/ange.201708927
       
  • Mass-Production of Mesoporous MnCo2O4 Spinels with Manganese(IV)- and
           Cobalt(II)-Rich Surfaces for Superior Bifunctional Oxygen Electrocatalysis
           
    • Authors: Wenhai Wang; Long Kuai, Wei Cao, Marko Huttula, Sami Ollikkala, Taru Ahopelto, Ari-Pekka Honkanen, Simo Huotari, Mengkang Yu, Baoyou Geng
      Pages: 15173 - 15177
      Abstract: A mesoporous MnCo2O4 electrode material is made for bifunctional oxygen electrocatalysis. The MnCo2O4 exhibits both Co3O4-like activity for oxygen evolution reaction (OER) and Mn2O3-like performance for oxygen reduction reaction (ORR). The potential difference between the ORR and OER of MnCo2O4 is as low as 0.83 V. By XANES and XPS investigation, the notable activity results from the preferred MnIV- and CoII-rich surface. The electrode material can be obtained on large-scale with the precise chemical control of the components at relatively low temperature. The surface state engineering may open a new avenue to optimize the electrocatalysis performance of electrode materials. The prominent bifunctional activity shows that MnCo2O4 could be used in metal–air batteries and/or other energy devices.ORR und OER: Mesoporöses Spinell-MnCo2O4 mit hervorragenden Eigenschaften in der elektrokatalytischen Sauerstoffreduktion (ORR) und Sauerstoffentwicklung (OER) kann in großem Maßstab hergestellt werden. Das Material verfügt über eine MnIV- und CoII-reiche Oberfläche für die ausgezeichnete difunktionelle Elektrokatalyse.
      PubDate: 2017-10-23T01:22:10.285705-05:
      DOI: 10.1002/ange.201708765
       
  • Guest-Switchable Multi-Step Spin Transitions in an Amine-Functionalized
           Metal–Organic Framework
    • Authors: Wei Liu; Yuan-Yuan Peng, Si-Guo Wu, Yan-Cong Chen, Md. Najbul Hoque, Zhao-Ping Ni, Xiao-Ming Chen, Ming-Liang Tong
      Pages: 15178 - 15182
      Abstract: Materials with hysteretic multi-step spin-crossover (SCO) have potential application in high-order data storage. Here, an unprecedented hysteretic four-step SCO behavior with the sequence of LSHS0.25LS0.75HS0.5LS0.5 HS0.75LS0.25HS is found in a three-dimensional (3D) Hofmann-type metal–organic framework (MOF), which is evidenced by magnetic, differential scanning calorimetry, and crystal data. Further experiments involving guest exchange leads to the first reversible modulation of four-, two-, and one-stepped SCO behaviors, which provides a new strategy for developing multi-step SCO materials.Hysteretischer vierstufiger Spin-Crossover gemäß LS HS0.25LS0.75 HS0.5LS0.5 HS0.75LS0.25 HS wurde anhand von magnetischen Messungen, Differenzkalorimetrie und Kristalldaten bestätigt. Eine reversible Modulation von vier-, zwei- und einstufigem Spin-Crossover ist durch Austausch einer Gastspezies möglich.
      PubDate: 2017-10-24T06:21:31.144751-05:
      DOI: 10.1002/ange.201708973
       
  • Breaking the Limits in Analyzing Carbohydrate Recognition by NMR
           Spectroscopy: Resolving Branch-Selective Interaction of a Tetra-Antennary
           N-Glycan with Lectins
    • Authors: Angeles Canales; Irene Boos, Lukas Perkams, Lukas Karst, Thomas Luber, Theodoros Karagiannis, Gemma Domínguez, F. Javier Cañada, Javier Pérez-Castells, Daniel Häussinger, Carlo Unverzagt, Jesus Jiménez-Barbero
      Pages: 15183 - 15187
      Abstract: The biological recognition of complex-type N-glycans is part of many key physiological and pathological events. Despite their importance, the structural characterization of these events remains unsolved. The inherent flexibility of N-glycans hampers crystallization and the chemical equivalence of individual branches precludes their NMR characterization. By using a chemoenzymatically synthesized tetra-antennary N-glycan conjugated to a lanthanide binding tag, the NMR signals under paramagnetic conditions discriminated all four N-acetyl lactosamine antennae with unprecedented resolution. The NMR data revealed the conformation of the N-glycan and permitted for the first time the direct identification of individual branches involved in the recognition by two N-acetyllactosamine-binding lectins, Datura stramonium seed lectin (DSL) and Ricinus Communis agglutinin (RCA120).Alle vier Äste eines komplexen Vier-Antennen-N-Glykans konnten mithilfe von paramagnetischer NMR-Spektroskopie direkt identifiziert werden. Dank einer beispiellosen Auflösung war eine detaillierte Charakterisierung der Konformationen und Molekülerkennungsmuster des komplexen Oligosaccharids möglich.
      PubDate: 2017-10-24T06:21:23.102844-05:
      DOI: 10.1002/ange.201709130
       
  • Direct Synthesis of Amides by Dehydrogenative Coupling of Amines with
           either Alcohols or Esters: Manganese Pincer Complex as Catalyst
    • Authors: Amit Kumar; Noel Angel Espinosa-Jalapa, Gregory Leitus, Yael Diskin-Posner, Liat Avram, David Milstein
      Pages: 15188 - 15192
      Abstract: The first example of base-metal-catalysed synthesis of amides from the coupling of primary amines with either alcohols or esters is reported. The reactions are catalysed by a new manganese pincer complex and generate hydrogen gas as the sole byproduct, thus making the overall process atom-economical and sustainable.Mangan in der Pinzette: Ein Mangan-Pinzettenkomplex mit günstigem Zentralmetall katalysiert die Synthese von Amiden durch Kupplung primärer Amine mit Alkoholen oder Estern. In diesem atomökonomischen und nachhaltigen Prozess entsteht Wasserstoffgas als einziges Koppelprodukt.
      PubDate: 2017-10-20T01:45:27.927077-05:
      DOI: 10.1002/ange.201709180
       
  • Characterization of the Conjugation Pattern in Large
           Polysaccharide–Protein Conjugates by NMR Spectroscopy
    • Authors: Stefano Giuntini; Evita Balducci, Linda Cerofolini, Enrico Ravera, Marco Fragai, Francesco Berti, Claudio Luchinat
      Pages: 15193 - 15197
      Abstract: Carbohydrate-based vaccines are among the safest and most effective vaccines and represent potent tools for prevention of life-threatening bacterial infectious diseases, like meningitis and pneumonia. The chemical conjugation of a weak antigen to protein as a source of T-cell epitopes generates a glycoconjugate vaccine that results more immunogenic. Several methods have been used so far to characterize the resulting polysaccharide–protein conjugates. However, a reduced number of methodologies has been proposed for measuring the degree of saccharide conjugation at the possible protein sites. Here we show that detailed information on large proteins conjugated with large polysaccharides can be achieved by a combination of solution and solid-state NMR spectroscopy. As a test case, a large protein assembly, l-asparaginase II, has been conjugated with Neisseria meningitidis serogroup C capsular polysaccharide and the pattern and degree of conjugation were determined.Festkörper-NMR-Spektren von bemerkenswerter Qualität konnten von stark glykosylierten Proteinen (l-Asparaginase-II aus E. coli) aufgenommen werden. Basierend auf dieser Beobachtung wurde ein kombiniertes Flüssig- und Festkörper-NMR-Verfahren entwickelt, mit dem eine semiquantitative Evaluierung des Konjugationsgrades und -musters von Glykokonjugat-Impfstoffen möglich ist.
      PubDate: 2017-10-19T01:46:15.918163-05:
      DOI: 10.1002/ange.201709274
       
  • Changing the Mechanism for CO2 Hydrogenation Using Solvent-Dependent
           Thermodynamics
    • Authors: Samantha A. Burgess; Aaron M. Appel, John C. Linehan, Eric S. Wiedner
      Pages: 15198 - 15201
      Abstract: A critical scientific challenge for utilization of CO2 is the development of catalyst systems that function in water and use inexpensive and environmentally friendly reagents. We have used thermodynamic insights to predict and demonstrate that the HCoI(dmpe)2 catalyst system, previously described for use in organic solvents, can hydrogenate CO2 to formate in water with bicarbonate as the only added reagent. Replacing tetrahydrofuran as the solvent with water changes the mechanism for catalysis by altering the thermodynamics for hydride transfer to CO2 from a key dihydride intermediate. The need for a strong organic base was eliminated by performing catalysis in water owing to the change in mechanism. These studies demonstrate that the solvent plays a pivotal role in determining the reaction thermodynamics and thereby catalytic mechanism and activity.Der Wechsel von einem organischen Lösungsmittel zu Wasser ändert den Mechanismus der katalytischen CO2-Hydrierung durch einen Cobalt-Phosphankomplex. Der Mechanismuswechsel wird auf den günstigen Einfluss von Wasser auf die Hydriddonorfähigkeit eines katalytischen Schlüsselintermediats zurückgeführt. Kinetische Studien zeigen, dass dieser Katalysator zu den aktivsten unedlen Metallkatalysatoren für die CO2-Hydrierung in Wasser zählt.
      PubDate: 2017-10-23T06:50:31.974533-05:
      DOI: 10.1002/ange.201709319
       
  • Combining Charge-Transfer Pathways to Achieve Unique Thermally Activated
           Delayed Fluorescence Emitters for High-Performance Solution-Processed,
           Non-doped Blue OLEDs
    • Authors: Xu-Lin Chen; Ji-Hui Jia, Rongmin Yu, Jian-Zhen Liao, Ming-Xue Yang, Can-Zhong Lu
      Pages: 15202 - 15205
      Abstract: Two efficient blue thermally activated delayed fluorescence compounds, B-oCz and B-oTC, composed of ortho-donor (D)–acceptor (A) arrangement were designed and synthesized. The significant intramolecular D–A interactions induce a combined charge transfer pathway and thus achieve small ΔEST and high efficiencies. The concentration quenching can be effectively inhibited in films of these compounds. The blue non-doped organic light emitting diodes (OLEDs) based on B-oTC prepared from solution processes shows record-high external quantum efficiency (EQE) of 19.1 %.Blau gemacht: Materialien mit hoch effizienter thermisch aktivierter verzögerter blauer Fluoreszenz wurden entwickelt. Nach Lösungsverfahren hergestellte, nichtdotierte, organische blaue Leuchtdioden mit diesen Emittern erreichten eine externe Quantenausbeute von 19.1 %.
      PubDate: 2017-10-24T11:30:33.970723-05:
      DOI: 10.1002/ange.201709125
       
  • Synthesis of Octaaryl Naphthalenes and Anthracenes with Different
           Substituents
    • Authors: Shin Suzuki; Kenichiro Itami, Junichiro Yamaguchi
      Pages: 15206 - 15209
      Abstract: A synthesis of multiply arylated naphthalenes and anthracenes with eight different substituents has been accomplished. The key intermediates are tetraarylthiophene S-oxides, which are synthesized through a method involving sequential C−H arylation and cross-coupling from 3-methoxythiophene, followed by oxidation of the sulfur atom. The resulting tetraarylthiophene S-oxides can be converted into a tetraaryl benzynes or naphthalynes and then merged through [4+2] cycloaddition reaction with another tetraarylthiophene S-oxide, thereby resulting in the programmed synthesis of octaarylnaphthalenes and octaarylanthracenes.Acht Individualisten: Die Synthese von Oktaarylnaphthalinen (OANs) und Oktaarylanthracenen (OAAs) mit acht verschiedenen Arylsubstituenten verläuft über [4+2]-Cycloadditionen von Tetraarylthiophen-S-oxiden mit mehrfach arylierten Arinen.
      PubDate: 2017-10-19T02:00:49.220985-05:
      DOI: 10.1002/ange.201709332
       
  • Sequence-Mandated, Distinct Assembly of Giant Molecules
    • Authors: Wei Zhang; Xinlin Lu, Jialin Mao, Chih-Hao Hsu, Gaoyan Mu, Mingjun Huang, Qingyun Guo, Hao Liu, Chrys Wesdemiotis, Tao Li, Wen-Bin Zhang, Yiwen Li, Stephen Z. D. Cheng
      Pages: 15210 - 15215
      Abstract: Although controlling the primary structure of synthetic polymers is itself a great challenge, the potential of sequence control for tailoring hierarchical structures remains to be exploited, especially in the creation of new and unconventional phases. A series of model amphiphilic chain-like giant molecules was designed and synthesized by interconnecting both hydrophobic and hydrophilic molecular nanoparticles in precisely defined sequence and composition to investigate their sequence-dependent phase structures. Not only compositional variation changed the self-assembled supramolecular phases, but also specific sequences induce unconventional phase formation, including Frank–Kasper phases. The formation mechanism was attributed to the conformational change driven by the collective hydrogen bonding and the sequence-mandated topology of the molecules. These results show that sequence control in synthetic polymers can have a dramatic impact on polymer properties and self-assembly.Molekulare Nanopartikel (NPs) können präzise zu kettenartigen Makromolekülen mit vorbestimmter Sequenz aufgereiht werden. Über die Sequenz und Zusammensetzung der synthetischen Polymere lässt sich auch die Struktur ihrer supramolekularen Phase steuern. POSS=polyedrisches oligomeres Silsesquioxan; B hydrophob, D hydrophil.
      PubDate: 2017-10-24T06:21:00.119423-05:
      DOI: 10.1002/ange.201709354
       
  • Assembly, Thermodynamics, and Structure of a Two-Wheeled Composite of a
           Dumbbell-Shaped Molecule and Cylindrical Molecules with Different Edges
    • Authors: Taisuke Matsuno; Sho Kamata, Sota Sato, Atsutoshi Yokoyama, Parantap Sarkar, Hiroyuki Isobe
      Pages: 15216 - 15220
      Abstract: A carbonaceous dumbbell was able to spontaneously glue two tubular receptors to form a unique two-wheeled composite through van der Waals interactions, thus forcing the wheel components into contact with each other at the edges. In the present study, two tubular receptors with enantiomeric carbon networks were assembled on the dumbbell joint, and the handedness of the receptors was discriminated, thus leading to the self-sorting of homomeric receptors from a mixture of enantiomeric tubes. The crystal structures of the composites revealed the structural origins of the molecular recognition driven by van der Waals forces as well as the presence of a columnar array of C120 molecules in a 1:1 composite.Gut sortiertes Fullerensortiment: C120 agiert als hantelförmiges Verbindungsstück für die Anordnung zweier röhrenförmiger Rezeptoren (siehe Bild). Enantiomere Kohlenstoffnetzwerke der Rezeptoren können anhand der Strukturen der Kontaktkanten unterschieden werden, was die Selbstsortierung homomerer Rezeptoren aus einer Mischung enantiomerer Röhren ermöglicht.
      PubDate: 2017-10-23T06:50:45.582829-05:
      DOI: 10.1002/ange.201709442
       
  • Co-adsorption of Cations as the Cause of the Apparent pH Dependence of
           Hydrogen Adsorption on a Stepped Platinum Single-Crystal Electrode
    • Authors: Xiaoting Chen; Ian T. McCrum, Kathleen A. Schwarz, Michael J. Janik, Marc T. M. Koper
      Pages: 15221 - 15225
      Abstract: The successful deployment of advanced energy-conversion systems depends critically on our understanding of the fundamental interactions of the key adsorbed intermediates (hydrogen *H and hydroxyl *OH) at electrified metal–aqueous electrolyte interfaces. The effect of alkali metal cations (Li+, Na+, K+, Cs+) on the non-Nernstian pH shift of the step-related voltammetric peak of the Pt(553) electrode is investigated over a wide pH window (1 to 13) by means of experimental and computational methods. The co-adsorbed alkali cations along the step weaken the OH adsorption at the step sites, causing a positive shift of the potential of the step-related peak on Pt(553). Density functional calculations explain the observations on the identity and concentration of alkali cations on the non-Nernstian pH shift, and demonstrate that cation–hydroxyl co-adsorption causes the apparent pH dependence of “hydrogen” adsorption in the step sites of platinum electrodes.Zwei auf einer Stufe: Experimente und Rechnungen zeigen, dass die apparente pH-Abhängigkeit der Wasserstoffadsorption an Stufen und Defekten auf Platinelektroden aus einer Koadsorption von Kationen und Hydroxyl resultiert. Ein Modell beschreibt diesen Effekt, der entscheidend für die Interpretation der elektrokatalytischen Aktivität von Platin ist.
      PubDate: 2017-10-23T01:41:43.026085-05:
      DOI: 10.1002/ange.201709455
       
  • Diastereoselective Construction of Densely Functionalized
           1-Halocyclopentenes Using an Alkynyl Halo-Prins/Halo-Nazarov Cyclization
           Strategy
    • Authors: Georgios Alachouzos; Alison J. Frontier
      Pages: 15226 - 15230
      Abstract: A diastereoselective two-step strategy for the synthesis of densely functionalized 1-halocyclopentenes with several chiral centers has been developed. In the first step, a multicomponent alkynyl halo-Prins reaction joins an enyne, a carbonyl derivative, and either a chloride, bromide, or iodide to produce a cyclic ether intermediate. In the subsequent step, the intermediate is ionized to generate a halopentadienyl cation, which undergoes an interrupted halo-Nazarov cyclization. The products contain three new contiguous stereogenic centers, generated with a high level of stereocontrol, as well as a vinyl halide allowing for additional functionalization. The strategy creates two new carbon–carbon bonds, one carbon–halide bond, and one carbon–oxygen bond.Ein zweistufiger Prozess ermöglicht die diastereoselektive Synthese funktionalisierter 1-Halogencyclopentene. Zuerst werden in einer Alkinyl-Halo-Prins-Reaktion ein Enin, eine Carbonylverbindung und entweder Chlorid, Bromid oder Iodid zu einem cyclischen Ether-Intermediat verknüpft. Dessen Ionisierung generiert ein Halogenpentadienyl-Kation, das in einer unterbrochenen halo-Nazarov-Cyclisierung weiterreagiert.
      PubDate: 2017-10-24T06:34:00.221118-05:
      DOI: 10.1002/ange.201709482
       
  • Copper-Catalyzed Synthesis of γ-Amino Acids Featuring Quaternary
           Stereocenters
    • Authors: José Enrique Gómez; Wusheng Guo, Silvia Gaspa, Arjan W. Kleij
      Pages: 15231 - 15234
      Abstract: The first general asymmetric synthesis of γ,γ-disubstituted γ-amino acids by copper-catalyzed ring opening of nonstrained lactones with amines is reported. This approach features ample scope, operational simplicity, and wide functional-group diversity. The catalytic process allows access to a series of highly functionalized enantioenriched γ-amino acids featuring quaternary stereocenters with excellent enantiomeric ratios of up to 98:2 and excellent yields of up to 98 %.Sesam öffne dich: Die erste allgemeine asymmetrische Synthese von γ,γ-disubstituierten γ-Aminosäuren durch die kupferkatalysierte Ringöffnung nichtgespannter Lactone mit Aminen wird vorgestellt. Dieses Katalysatorsystem ermöglichte die Synthese einer Serie von hoch funktionalisierten γ-Aminosäuren mit quartären Stereozentren mit Enantiomerenverhältnissen bis 98:2 und Ausbeuten bis 98 %.
      PubDate: 2017-10-24T06:33:33.674716-05:
      DOI: 10.1002/ange.201709511
       
  • Radical-Based C−C Bond-Forming Processes Enabled by the Photoexcitation
           of 4-Alkyl-1,4-dihydropyridines
    • Authors: Luca Buzzetti; Alexis Prieto, Sudipta Raha Roy, Paolo Melchiorre
      Pages: 15235 - 15239
      Abstract: We report herein that 4-alkyl-1,4-dihydropyridines (alkyl-DHPs) can directly reach an electronically excited state upon light absorption and trigger the generation of C(sp3)-centered radicals without the need for an external photocatalyst. Selective excitation with a violet-light-emitting diode turns alkyl-DHPs into strong reducing agents that can activate reagents through single-electron transfer manifolds while undergoing homolytic cleavage to generate radicals. We used this photochemical dual-reactivity profile to trigger radical-based carbon–carbon bond-forming processes, including nickel-catalyzed cross-coupling reactions.In neuem Licht erstrahlen 4-Alkyl-1,4-dihydropyridine 1, die vor allem als Hydridquellen in ihrem Grundzustand bekannt sind. Durch Anregung mit einer violetten Leuchtdiode werden sie zu starken Reduktionsmitteln, die Reagentien über Einelektronentransfer aktivieren und Alkylradikale liefern können. Dieser Prozess wurde für radikalische C-C-Verknüpfungen genutzt, beispielsweise für nickelkatalysierte Kreuzkupplungen.
      PubDate: 2017-10-24T06:20:43.091284-05:
      DOI: 10.1002/ange.201709571
       
  • Tetrazole-Based Probes for Integrated Phenotypic Screening, Affinity-Based
           Proteome Profiling, and Sensitive Detection of a Cancer Biomarker
    • Authors: Ke Cheng; Jun-Seok Lee, Piliang Hao, Shao Q. Yao, Ke Ding, Zhengqiu Li
      Pages: 15240 - 15244
      Abstract: Target-identification phenotypic screening has been a powerful approach in drug discovery; however, it is hindered by difficulties in identifying the underlying cellular targets. To address this challenge, we have combined phenotypic screening of a fully functionalized small-molecule library with competitive affinity-based proteome profiling to map and functionally characterize the targets of screening hits. Using this approach, we identified ANXA2, PDIA3/4, FLAD1, and NOS2 as primary cellular targets of two bioactive molecules that inhibit cancer cell proliferation. We further demonstrated that a panel of probes can label and/or image annexin A2 (a cancer biomarker) from different cancer cell lines, thus providing opportunities for potential cancer diagnosis and therapy.Tetrazolbasierte Sonden mit Alkinfunktion eignen sich für Phänotyp-Screening und affinitätsbasierte Proteomprofilerstellung. Eine solche Sonde (Tz6) erkennt mit hoher Empfindlichkeit einen Krebsbiomarker über sowohl Proteinmarkierung als auch biologische Bildgebung.
      PubDate: 2017-11-15T08:06:10.15104-05:0
      DOI: 10.1002/ange.201709584
       
  • Total Synthesis of Lycoricidine and Narciclasine by Chemical
           Dearomatization of Bromobenzene
    • Authors: Emma H. Southgate; Daniel R. Holycross, David Sarlah
      Pages: 15245 - 15248
      Abstract: The total synthesis of lycoricidine and narciclasine is enabled by an arenophile-mediated dearomative dihydroxylation of bromobenzene. Subsequent transpositive Suzuki coupling and cycloreversion deliver a key biaryl dihydrodiol intermediate, which is rapidly converted into lycoricidine through site-selective syn-1,4-hydroxyamination and deprotection. The total synthesis of narciclasine is accomplished by the late-stage, amide-directed C−H hydroxylation of a lycoricidine intermediate. Moreover, the general applicability of this strategy to access dihydroxylated biphenyls is demonstrated with several examples.Die desaromatisierende Dihydroxylierung von Brombenzol ermöglicht in Kombination mit einer transpositiven Suzuki-Kupplung die effiziente Synthese der Naturstoffe Narciclasin und Lycoricidin. Die Anwendbarkeit dieser Synthesesequenz wurde durch die Synthese mehrerer cis-dihydroxylierter Biphenyle bestätigt.
      PubDate: 2017-10-23T01:47:36.02181-05:0
      DOI: 10.1002/ange.201709712
       
  • Enantioselective Light Harvesting with Perylenediimide Guests on
           Self-Assembled Chiral Naphthalenediimide Nanofibers
    • Authors: Ramarani Sethy; Jatish Kumar, Rémi Métivier, Marine Louis, Keitaro Nakatani, Nila Mohan Thazhe Mecheri, Akhila Subhakumari, K. George Thomas, Tsuyoshi Kawai, Takuya Nakashima
      Pages: 15249 - 15253
      Abstract: Self-assembling molecular systems often display amplified chirality compared to the monomeric state, which makes the molecular recognition more sensitive to chiral analytes. Herein, we report the almost absolute enantioselective recognition of a chiral perylenediimide (PDI) molecule by chiral supramolecular nanofibers of a bichromophoric naphthalenediimide (NDI) derivative. The chiral recognition was evaluated through the Förster resonance energy transfer (FRET) from the NDI-based host nanofibers to the guest PDI molecules. The excitation energy was successfully transferred to the guest molecule through efficient energy migration along the host nanofiber, thus demonstrating the light-harvesting capability of these hybrid systems. Furthermore, circularly polarized luminescence (CPL) was enantioselectively sensitized by the guest molecule as the wavelength band and sign of the CPL signal were switched in response to the chiral guest molecule.Die enantioselektive Erkennung eines chiralen Perylendiimids (PDI) durch chirale supramolekulare Nanofasern aus einem bichromophoren Naphthalindiimid(NDI)-Derivat wird beschrieben. Der Erkennungsprozess wurde durch den Förster-Energietransfer von den NDI-Nanofasern zu den PDI-Molekülen bestätigt. Zudem wurde so gezeigt, dass diese Hybridsysteme zur Lichtsammlung geeignet sind.
      PubDate: 2017-09-14T06:26:23.223385-05:
      DOI: 10.1002/ange.201707160
       
  • A Triple Salting-Out Effect is Required for the Formation of
           Ionic-Liquid-Based Aqueous Multiphase Systems
    • Authors: Helena Passos; Sara H. Costa, Ana M. Fernandes, Mara G. Freire, Robin D. Rogers, João A. P. Coutinho
      Pages: 15254 - 15258
      Abstract: Novel aqueous multiphase systems (MuPSs) formed by quaternary mixtures composed of cholinium-based ionic liquids (ILs), polymers, inorganic salts, and water are reported herein. The influence of several ILs, polymers, and salts was studied, demonstrating that a triple salting-out is a required phenomenon to prepare MuPSs. The respective phase diagrams and “tie-surfaces” were determined, followed by the evaluation of the effect of temperature. Finally, the remarkable ability of IL-based MuPSs to selectively separate mixtures of textile dyes is shown.Dreifaches Aussalzen ist erforderlich, um wässrige Dreiphasensysteme auf Basis ionischer Flüssigkeiten (ILs) zu erzeugen. Die wässrigen Mehrphasensysteme (MuPSs) bewiesen ihr Potenzial für industrielle und Umweltanwendungen in der selektiven Abtrennung von Textilfarbstoffen.
      PubDate: 2017-10-19T01:58:45.139753-05:
      DOI: 10.1002/ange.201705704
       
  • Synergistic Manganese(I) C−H Activation Catalysis in Continuous Flow:
           Chemoselective Hydroarylation
    • Authors: Hui Wang; Fabio Pesciaioli, João C. A. Oliveira, Svenja Warratz, Lutz Ackermann
      Pages: 15259 - 15263
      Abstract: Chemoselective hydroarylations were accomplished by a novel synergistic Brønsted acid/manganese(I)-catalyzed C−H activation manifold. Thus, alkynes bearing O-leaving groups could, for the first time, be employed for C−H alkenylations without concurrent β-O elimination, thereby setting the stage for versatile late-stage diversifications. Also described is the first manganese-catalyzed C−H activation in continuous flow, thus enabling efficient hydroarylations within only 20 minutes.Mangan-Katalyse im Fluss: Chemoselektive Hydroarylierungen im Durchflussverfahren unter synergistischer Brønsted-Säure/Mangan(I)-Katalyse sind binnen 1 bis 20 Minuten abgeschlossen. Das Verfahren nutzt ein ungiftiges Metall, um die C-H-Bindungsspaltung zu erleichtern, und es bietet sich für Modifizierungen in späten Synthesestadien an.
      PubDate: 2017-10-24T06:34:45.608284-05:
      DOI: 10.1002/ange.201708271
       
  • Catalytic Asymmetric [8+2] Annulation Reactions Promoted by a Recyclable
           Immobilized Isothiourea
    • Authors: Shoulei Wang; Carles Rodríguez-Escrich, Miquel A. Pericàs
      Pages: 15264 - 15268
      Abstract: Higher-order cycloaddition reactions constitute an efficient approach towards the construction of medium to large ring systems. However, enantioselective versions of these transformations remain scarce, which hampers their deployment in medicinal chemistry, or any other discipline in which homochirality is deemed crucial. Herein, we report a novel method for the production of enantiomerically enriched cycloheptatrienes fused to a pyrrolidone ring on the basis of an isothiourea-catalyzed periselective [8+2] cycloaddition reaction between chiral ammonium enolates (generated in situ from carboxylic acids) and azaheptafulvenes. The resulting bicyclic compounds can be hydrogenated, but, most remarkably, they can also undergo completely regioselective [4+2] cycloaddition with active dienophiles to give architecturally complex polycyclic compounds in a straightforward manner.Bereit für mehr: Eine periselektive [8+2]-Cycloaddition zwischen chiralen Ammoniumenolaten und Azaheptafulvenen mit einem rezyklierbaren Isothioharnstoff-Katalysator liefert enantiomerenangereicherte Cycloheptatriene, die mit einem Pyrrolidonring verkettet sind (siehe Schema). Derivatisierung dieser vielseitigen Cycloaddukte durch eine weitere regio- und diastereoselektive Cycloaddition führte zu komplexen polycyclischen Verbindungen.
      PubDate: 2017-10-23T06:51:35.135734-05:
      DOI: 10.1002/ange.201707341
       
  • Photoredox Generation of Carbon-Centered Radicals Enables the Construction
           of 1,1-Difluoroalkene Carbonyl Mimics
    • Authors: Simon B. Lang; Rebecca J. Wiles, Christopher B. Kelly, Gary A. Molander
      Pages: 15269 - 15273
      Abstract: Described is a facile, scalable route to access functional-group-rich gem-difluoroalkenes. Using visible-light-activated catalysts in conjunction with an arsenal of carbon-radical precursors, an array of trifluoromethyl-substituted alkenes undergoes radical defluorinative alkylation. Nonstabilized primary, secondary, and tertiary radicals can be used to install functional groups in a convergent manner, which would otherwise be challenging by two-electron pathways. The process readily extends to other perfluoroalkyl-substituted alkenes. In addition, we report the development of an organotrifluoroborate reagent to expedite the synthesis of the requisite trifluoromethyl-substituted alkene starting materials.CF3 wird CF2: Eine einfache, skalierbare Synthese von hoch funktionalisierten gem-Difluoalkenen wird beschrieben. Trifluormethyl-substituierte Alkene unterliegen bereitwillig einer radikalischen defluorierenden Alkylierung in Gegenwart von Photokatalysatoren und einer Bandbreite von C-Radikal-Vorstufen. Nichtstabilisierte primäre, sekundäre und tertiäre Radikale können eingesetzt werden, um diverse funktionelle Gruppen einzuführen.
      PubDate: 2017-10-23T01:48:14.435788-05:
      DOI: 10.1002/ange.201709487
       
  • Toward Cost-Effective Manufacturing of Silicon Solar Cells:
           Electrodeposition of High-Quality Si Films in a CaCl2-based Molten Salt
    • Authors: Xiao Yang; Li Ji, Xingli Zou, Taeho Lim, Ji Zhao, Edward T. Yu, Allen J. Bard
      Pages: 15274 - 15278
      Abstract: Electrodeposition of Si films from a Si-containing electrolyte is a cost-effective approach for the manufacturing of solar cells. Proposals relying on fluoride-based molten salts have suffered from low product quality due to difficulties in impurity control. Here we demonstrate the successful electrodeposition of high-quality Si films from a CaCl2-based molten salt. Soluble SiIV−O anions generated from solid SiO2 are electrodeposited onto a graphite substrate to form a dense film of crystalline Si. Impurities in the deposited Si film are controlled at low concentrations (both B and P are less than 1 ppm). In the photoelectrochemical measurements, the film shows p-type semiconductor character and large photocurrent. A p–n junction fabricated from the deposited Si film exhibits clear photovoltaic effects. This study represents the first step to the ultimate goal of developing a cost-effective manufacturing process for Si solar cells based on electrodeposition.Ein Schritt zu billigen Solarzellen: Hochwertige Si-Filme für die Photovoltaik werden durch elektrochemische Abscheidung aus CaCl2-CaO-SiO2-Schmelzen hergestellt. Dabei werden lösliche SiIVO-Anionen auf ein Graphitsubtrat abgeschieden, um einen dichten und dicken Film von p-Si mit kontrolliert niedrigen Verunreinigungen zu bilden. Der Film zeigt gute photoelektrochemische Eigenschaften und deutliche photovoltaische Effekte.
      PubDate: 2017-10-19T02:01:10.884641-05:
      DOI: 10.1002/ange.201707635
       
  • “On-Droplet” Chemistry: The Cycloaddition of Diethyl
           Azodicarboxylate and Quadricyclane
    • Authors: Ryan M. Bain; Shyam Sathyamoorthi, Richard N. Zare
      Pages: 15279 - 15283
      Abstract: Sharpless and co-workers previously studied the [2σ+2σ+2π] cycloaddition of diethyl azodicarboxylate (DEAD) and quadricyclane and reported that the addition of water to the neat reagents caused an acceleration in the reaction rate, giving birth to what has been called “on-water” chemistry. We have examined the same reaction in aqueous microdroplets (ca. 5 μm diameter) and find that the cycloaddition reaction is accelerated even further (by a factor of 102) compared to that of the “on-water” reaction reported previously. The trends of acceleration in solvents other than water demonstrated by Sharpless and colleagues were replicated in the corresponding microdroplet experiments. We also find that DEAD reacts with itself to form a variety of hydrazine carboxylates and intercept intermediates of this reaction in microdroplets to validate a mechanism proposed herein. We suggest that “on-droplet” chemistry, similar to “on-water” chemistry, may be a general process of synthetic interest.Beschleunigte Reaktionen: Die spezifische Reaktivität von [2σ+2σ+2π]-Cycloadditionen in wässrigen Suspensionen („on water”) wird in durch Elektrospray-Ionisation erzeugten Mikrotröpfchen („on droplet”) weiter erhöht. Diese Reaktionsbeschleunigung wurde für die Cycloaddition von Azodicarbonsäurediethylester mit Quadricyclan genutzt.
      PubDate: 2017-10-24T06:34:28.500656-05:
      DOI: 10.1002/ange.201708413
       
  • Cooperative Effects between Chiral Cpx–Iridium(III) Catalysts and Chiral
           
    • Authors: Yun-Suk Jang; Michael Dieckmann, Nicolai Cramer
      Pages: 15284 - 15288
      Abstract: An enantioselective C−H amidation of phosphine oxides by using an iridium(III) catalyst bearing an atropchiral cyclopentadienyl (Cpx) ligand is reported. A very strong cooperative effect between the chiral Cpx ligand and a phthaloyl tert-leucine enabled the transformation. Matched–mismatched cases of the different acid enantiomers are shown. The amidated P-chiral arylphosphine oxides are formed in yields of up to 95 % and with excellent enantioselectivities of up to 99:1 er. Enantiospecific reduction provides access to valuable P-chiral phosphorus(III) compounds.Katalytischer Handschlag: Ein kooperativer Effekt zwischen einem chiralen CpxIrIII-Komplex und einer chiralen Carbonsäure ermöglicht hoch enantioselektive C-H-Amidierungen von Phosphinoxiden mit bis zu 99:1 er. Matched-Mismatched-Paare haben einen starken Einfluss auf die Reaktivität und Selektivität.
      PubDate: 2017-10-06T05:47:54.753916-05:
      DOI: 10.1002/ange.201708440
       
  • Iridium-Catalyzed Asymmetric Allylic Dearomatization by a Desymmetrization
           Strategy
    • Authors: Ye Wang; Chao Zheng, Shu-Li You
      Pages: 15289 - 15293
      Abstract: A desymmetrization strategy was developed involving iridium-catalyzed allylic dearomatization of indoles. The six-membered-ring spiroindolenines contain three contiguous stereogenic centers, including an all-carbon quaternary center, and were obtained in up to 99 % yield with 99 % ee and>95:5 d.r. When treated with a catalytic amount of tosylic acid, six-membered spiroindolenine undergoes an unprecedented six-to-seven-membered ring expansion, affording the corresponding hexahydroazepino[4,5-b]indole.Erst sechs, dann sieben: Eine Iridium-katalysierte Desymmetrisierung unter Beteiligung einer allylischen Dearomatisierung von Indolen wurde entwickelt. Sechsgliedrige Spiroindolenine wurden in bis zu 99 % Ausbeute mit 99 % ee und>95:5 d.r. erhalten. Sie gehen bei Behandlung mit Toluolsulfonsäure eine Ringerweiterung unter Bildung von siebengliedrigen Hexahydroazepino[4,5-b]indolen ein.
      PubDate: 2017-10-24T06:34:22.207922-05:
      DOI: 10.1002/ange.201708419
       
  • Electronic Delocalization in Two and Three Dimensions: Differential
           Aggregation in Indium “Metalloid” Clusters
    • Authors: Andrey V. Protchenko; Juan Urbano, Joseph A. B. Abdalla, Jesús Campos, Dragoslav Vidovic, Andrew D. Schwarz, Matthew P. Blake, Philip Mountford, Cameron Jones, Simon Aldridge
      Pages: 15294 - 15298
      Abstract: Reduction of indium boryl precursors to give two- and three-dimensional M−M bonded networks is influenced by the choice of supporting ligand. While the unprecedented nanoscale cluster [In68(boryl)12]− (with an In12@In44@In12(boryl)12 concentric structure), can be isolated from the potassium reduction of a bis(boryl)indium(III) chloride precursor, analogous reduction of the corresponding (benzamidinate)InIIIBr(boryl) system gives a near-planar (and weakly aromatic) tetranuclear [In4(boryl)4]2− system.Cluster à la carte: Die Reduktion von Indiumboryl-Komplexen zu 2D- und 3D-Aggregaten kann durch die Wahl des Liganden gesteuert werden. Der ungewöhnliche Cluster In12@In44@In12(Boryl)12 (siehe Bild) wird aus der Reduktion eines Bis(boryls) mit Kalium isoliert, während die Reduktion von (Amidinat)InIIIBr(Boryl) ein (schwach aromatisches) planares vierkerniges [In4(Boryl)4]2−-System ergibt.
      PubDate: 2017-10-11T04:35:42.261073-05:
      DOI: 10.1002/ange.201708496
       
  • Synthesis and Characterization of an Eclipsed Digermylene as a Building
           Block to Construct a Cyclic Octagermylene
    • Authors: Yu-Te Wey; Fan-Shan Yang, Hsien-Cheng Yu, Ting-Shen Kuo, Yi-Chou Tsai
      Pages: 15304 - 15308
      Abstract: The preparation of an unprecedented GeI-GeI bonded digermylene [K2{Ge2(μ-κ2:η2:η4-2,6-(2,6-iPr2C6H3-N)2-4-CH3C5H2N)2}] in an eclipsed conformation stabilized by two bridging diamidopyridyl ligands is presented. Although it exhibits an eclipsed conformation, the Ge−Ge bond length is 2.5168(6) Å, which is shorter than those in the trans-bent and gauche digermylenes. In combination with two pendant amido groups, the GeI2 motif is employed as a building block to assemble the first example of octagermylene [Ge4(μ-κ2:κ1-2,6-(2,6-iPr2C6H3-N)2-4-CH3C5H2N)2]2 showing a cyclic configuration and containing three distinct types of GeI−GeI bonds.Ausnahmeerscheinung: Als Gegenstück zu vielen Beispielen trans-gebogener Digermylene mit gestaffelter Konfiguration wurde ein Digermylen mit ekliptischer Geometrie charakterisiert. Das ekliptische Digermylen diente als Baustein für ein cyclisches Octagermylen, das drei Arten von GeI-GeI-Bindungen aufweist (siehe Bild; Ge braun, N magenta).
      PubDate: 2017-10-06T05:47:32.126339-05:
      DOI: 10.1002/ange.201708551
       
  • Single-Step Reagentless Laser Scribing Fabrication of Electrochemical
           Paper-Based Analytical Devices
    • Authors: William R. de Araujo; Carolina M. R. Frasson, Wilson A. Ameku, José R. Silva, Lúcio Angnes, Thiago R. L. C. Paixão
      Pages: 15309 - 15313
      Abstract: A single-step laser scribing process is used to pattern nanostructured electrodes on paper-based devices. The facile and low-cost technique eliminates the need for chemical reagents or controlled conditions. This process involves the use of a CO2 laser to pyrolyze the surface of the paperboard, producing a conductive porous non-graphitizing carbon material composed of graphene sheets and composites with aluminosilicate nanoparticles. The new electrode material was extensively characterized, and it exhibits high conductivity and an enhanced active/geometric area ratio; it is thus well-suited for electrochemical purposes. As a proof-of-concept, the devices were successfully employed for different analytical applications in the clinical, pharmaceutical, food, and forensic fields. The scalable and green fabrication method associated with the features of the new material is highly promising for the development of portable electrochemical devices.Elektrochemie auf dem Pappkarton: Leicht und in großem Maßstab können nanostrukturierte elektrochemische Analysesysteme mithilfe eines CO2-Lasers auf Pappe geschrieben werden. Zusätzliche Reagentien sind für diese Herstellungsstrategie nicht erforderlich.
      PubDate: 2017-10-23T01:25:00.408318-05:
      DOI: 10.1002/ange.201708527
       
  • High Sulfur Content Material with Stable Cycling in Lithium-Sulfur
           Batteries
    • Authors: Molleigh B. Preefer; Bernd Oschmann, Craig J. Hawker, Ram Seshadri, Fred Wudl
      Pages: 15314 - 15318
      Abstract: We demonstrate a novel crosslinked disulfide system as a cathode material for Li-S cells that is designed with the two criteria of having only a single point of S−S scission and maximizing the ratio of S−S to the electrochemically inactive framework. The material therefore maximizes theoretical capacity while inhibiting the formation of polysulfide intermediates that lead to parasitic shuttle. The material we report contains a 1:1 ratio of S:C with a theoretical capacity of 609 mAh g−1. The cell gains capacity through 100 cycles and has 98 % capacity retention thereafter through 200 cycles, demonstrating stable, long-term cycling. Raman spectroscopy confirms the proposed mechanism of disulfide bonds breaking to form a S−Li thiolate species upon discharge and reforming upon charge. Coulombic efficiencies near 100 % for every cycle, suggesting the suppression of polysulfide shuttle through the molecular design.Maximaler S-Gehalt, minimaler Shuttle: Ein vernetztes Disulfidmaterial mit hohem Schwefelgehalt ermöglicht stabile Lade-Entlade-Zyklen in einer Lithium-Schwefel-Batterie ohne Anzeichen eines schädlichen Polysulfid-Shuttle.
      PubDate: 2017-10-19T02:01:23.296367-05:
      DOI: 10.1002/ange.201708746
       
  • Catalytic Reduction of Alkyl and Aryl Bromides Using Propan-2-ol
    • Authors: Michael C. Haibach; Brian M. Stoltz, Robert H. Grubbs
      Pages: 15319 - 15322
      Abstract: Milstein's complex, (PNN)RuHCl(CO), catalyzes the efficient reduction of aryl and alkyl halides under relatively mild conditions by using propan-2-ol and a base. Sterically hindered tertiary and neopentyl substrates are reduced efficiently, as well as more functionalized aryl and alkyl bromides. The reduction process is proposed to occur by radical abstraction/hydrodehalogenation steps at ruthenium. Our research represents a safer and more sustainable alternative to typical silane, lithium aluminium hydride, and tin-based conditions for these reductions.Einfach komplex: Der Milstein-Komplex (PNN)RuHCl(CO) katalysiert die effiziente Reduktion von Alkylbromiden und -chloriden durch Propan-2-ol unter Verwendung einer Base. Sterisch gehinderte tertiäre und Neopentylsubstrate werden ebenso umgesetzt wie funktionalisierte Aryl- und Alkylbromide. Die vermutlich radikalische Reaktion bildet eine Alternative zu Reduktionen mit Silanen, Lithiumaluminiumhydrid und Zinnreagentien.
      PubDate: 2017-10-24T11:31:03.283704-05:
      DOI: 10.1002/ange.201708800
       
  • Selective Reduction of CO2 to a Formate Equivalent with Heterobimetallic
           Gold- - -Copper Hydride Complexes
    • Authors: Alexandra Hicken; Andrew J. P. White, Mark R. Crimmin
      Pages: 15323 - 15326
      Abstract: A series of heterobimetallic complexes containing three-center, two-electron Au−H−Cu bonds have been prepared from addition of a parent gold hydride to a bent d10 copper(I) fragment. These highly unusual heterobimetallic complexes represent a missing link in the widely investigated series of neutral and cationic coinage metal hydride complexes containing Cu−H−Cu and M−H−M+ moieties (M=Cu, Ag). The well-defined heterobimetallic hydride complexes act as precatalysts for the conversion of CO2 into HCO2Bpin with HBpin as the reductant. The selectivity of the heterobimetallic complexes for the catalytic production of a formate equivalent surpasses that of the parent monomeric Group 11 complexes.Eine Serie von Heterobimetallkomplexen mit Au-H-Cu-Dreizentren-Zweielektronen-Bindungen wurde synthetisiert. Diese ungewöhnlichen Verbindungen fehlten bislang in der ausführlich untersuchten Reihe neutraler und kationischer Münzmetallhydridkomplexe mit Cu-H-Cu- oder M-H-M+-Einheiten (M=Cu, Ag), und sie katalysieren die selektive Reduktion von CO2 zu HCO2Bpin.
      PubDate: 2017-10-19T01:46:04.855312-05:
      DOI: 10.1002/ange.201709072
       
  • Ruthenium-Catalyzed para-Selective C−H Alkylation of Aniline
           Derivatives
    • Authors: Jamie A. Leitch; Claire L. McMullin, Andrew J. Paterson, Mary F. Mahon, Yunas Bhonoah, Christopher G. Frost
      Pages: 15327 - 15331
      Abstract: The para-selective C−H alkylation of aniline derivatives furnished with a pyrimidine auxiliary is herein reported. This reaction is proposed to take place via an N−H-activated cyclometalate formed in situ. Experimental and DFT mechanistic studies elucidate a dual role of the ruthenium catalyst. Here the ruthenium catalyst can undergo cyclometalation by N−H metalation (as opposed to C−H metalation in meta-selective processes) and form a redox active ruthenium species, to enable site-selective radical addition at the para position.Para-normale Aktivität: Eine para-selektive C-H-Alkylierung von Anilinderivaten wird vorgestellt. Der vorgeschlagene Mechanismus sieht für Ruthenium eine Doppelrolle vor: Cycloruthenierung an der N-H-Bindung und Radikalbildung über einen Redoxprozess. Die Strategie beruht auf dem Einsatz von Pyrimidin- und Chinazolin-Auxiliaren.
      PubDate: 2017-10-24T11:30:59.290459-05:
      DOI: 10.1002/ange.201708961
       
  • A Lewis Base Catalysis Approach for the Photoredox Activation of Boronic
           Acids and Esters
    • Authors: Fabio Lima; Upendra K. Sharma, Lars Grunenberg, Debasmita Saha, Sandra Johannsen, Joerg Sedelmeier, Erik V. Van der Eycken, Steven V. Ley
      Pages: 15332 - 15336
      Abstract: We report herein the use of a dual catalytic system comprising a Lewis base catalyst such as quinuclidin-3-ol or 4-dimethylaminopyridine and a photoredox catalyst to generate carbon radicals from either boronic acids or esters. This system enabled a wide range of alkyl boronic esters and aryl or alkyl boronic acids to react with electron-deficient olefins via radical addition to efficiently form C−C coupled products in a redox-neutral fashion. The Lewis base catalyst was shown to form a redox-active complex with either the boronic esters or the trimeric form of the boronic acids (boroxines) in solution.Ein duales Katalysatorsystem bestehend aus einer Lewis-Base (LB), z. B. Chinucludin-3-ol oder 4-Dimethylaminopyridin, und einem Photoredoxkatalysator ermöglicht die Erzeugung von Kohlenstoffradikalen aus Boronsäuren und -estern. Verschiedene Alkylboronsäureester sowie Aryl- und Alkylboronsäuren reagieren mit elektronenarmen Olefinen in einem redoxneutralen Prozess zu C-C-Kupplungsprodukten.
      PubDate: 2017-10-24T06:20:34.810788-05:
      DOI: 10.1002/ange.201709690
       
  • Eine wasserhaltige Organokaliumverbindung basierend auf
           Bis(4,6-tert-Butylbenzoxazol-2-yl)methanid und ihre unerwartete
           Hydrolysebeständigkeit
    • Authors: Ingo Koehne; Sebastian Bachmann, Regine Herbst-Irmer, Dietmar Stalke
      Pages: 15337 - 15342
      Abstract: Auf Grundlage des sterisch anspruchsvollen Ligandensystems Bis(4,6-tBu-benzoxazol-2-yl)methan konnte mit der wasserhaltigen Organokaliumverbindung [(18-Krone-6)K{(4,6-tBu-OCNC6H2)2CH}⋅H2O] (2) ein einzigartiges Beispiel einer reaktiven, wasserbeständigen Organokaliumverbindung synthetisiert werden. Darüber hinaus ist 2 ein seltener Vertreter eines Metallkomplexes, in dem ein Bis(benzoxazol-2-yl)methanid eine ausschließliche O-Koordination zu einem Metallion zeigt. Verbindung 2 wurde vollständig anhand ihrer Festkörperstruktur charakterisiert. Zusätzlich wurde sein Verhalten in Lösung durch DOSY-NMR- und durch NMR-Titrationsexperimente beschrieben. Letztere zeigten eine vollständige Protonierung des Komplexes erst nach der Zugabe von 114 Äquivalenten Wasser und einer Reaktionszeit von sieben Tagen.Feuer und Wasser vereinen sich nachhaltig in einem ausschließlich O-koordinierten Organokaliumkomplex auf Basis des ambidenten Bis(4,6-tBu-benzoxazol-2-yl)methanid-Liganden. Der Komplex erreicht erst nach sieben Tagen und der Zugabe von 114 Äquivalenten Wasser seine vollständige Protonierung und könnte sich als nachhaltiges Synthon für die Synthese in niedrig schmelzenden eutektischen Lösungsmitteln herausstellen.
      PubDate: 2017-10-23T01:30:10.917047-05:
      DOI: 10.1002/ange.201706316
       
  • Umgehung des Gas-flüssig-Stofftransports von Sauerstoff durch Kopplung
           der photosynthetischen Wasseroxidation an eine biokatalytische
           Oxyfunktionalisierung
    • Authors: Anna Hoschek; Bruno Bühler, Andreas Schmid
      Pages: 15343 - 15346
      Abstract: Der Gas-flüssig-Stofftransport gasförmiger Reaktanten limitiert die Raum-Zeit-Ausbeute O2-abhängiger (bio)katalytischer Reaktionen in wässrigen Lösungen. In dieser Studie wurde die oxygene Photosynthese für den homogenen Sauerstoffeintrag durch In-situ-Erzeugung von O2 in der Flüssigphase genutzt, um diese Limitierung zu umgehen. Hierfür produziert das phototrophe Cyanobakterium Synechocystis sp. PCC6803 als Ganzzellbiokatalysator heterolog die Alkanmonooxygenase AlkBGT aus Pseudomonas putida GPo1. Die chemo- und regioselektive Hydroxylierung von Pelargonsäuremethylester zu ω-Hydroxypelargonsäuremethylester kann so bei Belichtung, jedoch ohne externe Zugabe von molekularem Sauerstoff katalysiert werden. Der Sauerstoff stammt aus der photosynthetischen Wasseroxidation. Die Photosynthese liefert ebenfalls die nötigen Reduktionsäquivalente zur Regeneration von Fe2+ in AlkB für den Sauerstofftransfer zur terminalen Methylgruppe. Die In-situ-Kopplung der oxygenen Photosynthese an O2-übertragende Enzyme ermöglicht nun das Design schneller Oxyfunktionalisierungsreaktionen.Oxidationsreaktionen sind oftmals durch den Stofftransport von O2 zwischen der Gas- und Flüssigphase limitiert. Die Kopplung der oxygenen Photosynthese mit O2-nutzenden Enzymen zur selektiven Hydroxylierung von Kohlenwasserstoffen hat das Potential, diese Limitierung zu umgehen. Cyanobakterien als Ganzzellbiokatalysatoren erzeugen O2 homogen in Wasser und können so O2-abhängige oxidierende Enzyme direkt antreiben.
      PubDate: 2017-10-27T03:00:45.8155-05:00
      DOI: 10.1002/ange.201706886
       
  • Ether auf Si(001): Ein Paradebeispiel für die Gemeinsamkeiten zwischen
           Oberflächenwissenschaften und organischer Molekülchemie
    • Authors: Lisa Pecher; Slimane Laref, Marc Raupach, Ralf Tonner
      Pages: 15347 - 15351
      Abstract: Wir zeigen mit quantenchemischen Methoden, dass sich die Adsorption von Ether-Molekülen auf Si(001) im Ultrahochvakuum durch klassische Konzepte der organischen Molekülchemie verstehen lässt. Wie unsere detaillierte Analyse zeigt, spiegelt der zweistufige Mechanismus – 1) Ausbildung einer dativen Bindung zwischen dem Sauerstoffatom am Ether und einem Lewis-sauren Oberflächenatom, 2) nukleophiler Angriff eines nahegelegenen Lewis-basischen Oberflächenatoms – die säurekatalysierte Etherspaltung in Lösung wider. Zudem ist die dative O-Si-Bindung die stärkste ihrer Art und die Reaktivität in Schritt 2 verläuft entgegen dem Bell-Evans-Polanyi-Prinzip. Mithilfe einer neuartigen Methode der Bindungsanalyse wird außerdem die Umverteilung von Elektronendichte während des C-O-Bindungsbruchs visualisiert. Hierbei wird deutlich, dass der Mechanismus nukleophiler Substitutionen auf Halbleiteroberflächen identisch zu molekularen SN2-Reaktionen ist. Unsere Untersuchungen verdeutlichen, wie die Forschungsfelder der Oberflächenwissenschaften und Molekülchemie voneinander profitieren können und so unerwartete Einblicke ermöglichen.Ein gar nicht so seltsames Paar: Die Gemeinsamkeiten von Oberflächenwissenschaften und organischer Molekülchemie werden in dieser quantenchemischen Studie von Ethern auf Si(001) deutlich. Der quantitative Einblick in die Bindungssituation und Reaktivität zeigt, dass sich diese Systeme mit klassischen Konzepten der organischen Chemie verstehen lassen.
      PubDate: 2017-10-19T07:10:42.765594-05:
      DOI: 10.1002/ange.201707428
       
  • Dimethylamin als Substrat in Hydroaminoalkylierungsreaktionen
    • Authors: Jens Bielefeld; Sven Doye
      Pages: 15352 - 15355
      Abstract: Übergangsmetallkatalysierte Hydroaminoalkylierungen von Alkenen haben im vergangenen Jahrzehnt große Fortschritte gemacht und entwickeln sich zu einer greifbaren Alternative zur industriellen Synthese von Aminen durch Hydroformylierung von Alkenen und nachfolgende reduktive Aminierung. Ein großes Hindernis war in der Vergangenheit, dass Methylamin und Dimethylamin als industriell wichtigste Amine in diesen Reaktionen nicht zufriedenstellend umgesetzt werden konnten. Wir zeigen hier erstmals die erfolgreiche Umsetzung von Dimethylamin in katalytischen Hydroaminoalkylierungen von Alkenen mit guten Ausbeuten, sowie die Anwendbarkeit für eine Reihe verschiedener Alkene und die Toleranz gegenüber verschiedenen funktionellen Gruppen. Zusätzlich präsentieren wir die katalytische Dihydroaminoalkylierungsreaktion mit Dimethylamin, über die nie zuvor berichtet wurde.Die Größe zählt: Erstmals seit dem Beginn der katalytischen Hydroaminoalkylierungschemie vor 37 Jahren ist es möglich, Dimethylamin effizient an Alkene zu addieren, und zwar mit einem günstigen und einfach zugänglichen Ti-Katalysator. Die Größe des Reaktionsgefäßes bestimmt dabei den Verlauf der Reaktion – Monohydroaminoalkylierung oder Dihydroaminoalkylierung.
      PubDate: 2017-10-26T08:27:20.852898-05:
      DOI: 10.1002/ange.201708959
       
  • [SnBi3]5− – ein Carbonat-Analogon aus Metallatomen
    • Authors: Kerstin Mayer; Jasmin V. Dums, Wilhelm Klein, Thomas F. Fässler
      Pages: 15356 - 15361
      Abstract: Das neue Polyanion [SnBi3]5− wurde aus der Reaktion von K3Bi2 mit K4Sn9 oder K12Sn17 in flüssigem Ammoniak erhalten. Das Anion ist iso(valenz)elektronisch und strukturell analog zum Carbonation. Trotz der hohen negativen Ladung des Anions sind die Sn-Bi-Bindungslängen zwischen Einfach- und Zweifachbindung angesiedelt. Quantenchemische Rechnungen auf DFT-PBE0/def2-TZVPP/COSMO-Level zeigen einen partiellen Doppelbindungscharakter zwischen den Atomen der schweren Hauptgruppenelemente Bi und Sn, der von einem delokalisierten π-Elektronensystem herrührt. Die Struktur des Anions wurde durch Einkristallstrukturanalyse der Verbindungen K5[SnBi3]⋅9 NH3 (1) und K9[K(18-Krone-6)][SnBi3]2⋅15 NH3 (2) bestimmt. Die [SnBi3]5−-Einheit ist das erste Beispiel eines Carbonat-ähnlichen Anions, das aus Lösung erhalten wurde und ausschließlich aus Metallatomen aufgebaut ist. Damit führt es die Reihe der bekannten CO- und CO2-Analoga fort.Carbonat aus Metallatomen: Während Alkalimetallcarbonate meist unlöslich in flüssigem Ammoniak sind, bildet sich ein Carbonat-analoges Anion aus Bi- und Sn-Atomen über die Reaktion tiefgefärbter Lösungen von Bismutid- und Stannidpolyanionen in flüssigem Ammoniak. Im Gegensatz zum Carbonat zersetzt sich das hochgeladene [SnBi3]5−-Anion in Anwesenheit von Spuren von Wasser.
      PubDate: 2017-10-24T06:20:00.273883-05:
      DOI: 10.1002/ange.201709700
       
  • Innenrücktitelbild: Compartmentalizing Supramolecular Hydrogels Using
           Aqueous Multi-phase Systems (Angew. Chem. 47/2017)
    • Authors: Serhii Mytnyk; Alexandre G. L. Olive, Frank Versluis, Jos M. Poolman, Eduardo Mendes, Rienk Eelkema, Jan H. van Esch
      Pages: 15363 - 15363
      Abstract: Die Kompartmentierung von Hydrogelen die J. H. van Esch et al. in ihrer Zuschrift auf S. 15119 vorstellen, nutzt die Inkompatibilität wässriger Polymerlösungen zur Bildung wässriger Mikrodomänen im Gerüst eines supramolekularen Hydrogels. Die Strategie verzichtet auf hydrophobe Barrieren und ermöglicht es, die Domänenzusammensetzung vorzugeben, sodass neuartige strukturierte Materialien erzeugt werden können.
      PubDate: 2017-10-27T04:55:22.184826-05:
      DOI: 10.1002/ange.201710805
       
  • Rücktitelbild: Enantioselective Light Harvesting with Perylenediimide
           Guests on Self-Assembled Chiral Naphthalenediimide Nanofibers (Angew.
           Chem. 47/2017)
    • Authors: Ramarani Sethy; Jatish Kumar, Rémi Métivier, Marine Louis, Keitaro Nakatani, Nila Mohan Thazhe Mecheri, Akhila Subhakumari, K. George Thomas, Tsuyoshi Kawai, Takuya Nakashima
      Pages: 15364 - 15364
      Abstract: Die enantioselektive Erkennung …… eines chiralen Perylendiimids (PDI) durch chirale supramolekulare Nanofasern aus einem Naphthalindiimid(NDI)-Derivat wird von T. Kawai, T. Nakashima et al. in der Zuschrift auf S. 15249 beschrieben. NDI-Nanofasern mit rechtsgängiger Helizität erkennen selektiv bichromophore PDI-Derivate, die gegen den Uhrzeigersinn ausgerichtet sind.
      PubDate: 2017-10-05T03:42:02.207584-05:
      DOI: 10.1002/ange.201709986
       
 
 
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