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  Subjects -> CHEMISTRY (Total: 860 journals)
    - ANALYTICAL CHEMISTRY (53 journals)
    - CHEMISTRY (603 journals)
    - CRYSTALLOGRAPHY (21 journals)
    - ELECTROCHEMISTRY (25 journals)
    - INORGANIC CHEMISTRY (42 journals)
    - ORGANIC CHEMISTRY (48 journals)
    - PHYSICAL CHEMISTRY (68 journals)

CHEMISTRY (603 journals)                  1 2 3 4 | Last

Showing 1 - 200 of 735 Journals sorted alphabetically
2D Materials     Hybrid Journal   (Followers: 12)
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: 40)
ACS Chemical Neuroscience     Full-text available via subscription   (Followers: 20)
ACS Combinatorial Science     Full-text available via subscription   (Followers: 23)
ACS Macro Letters     Full-text available via subscription   (Followers: 25)
ACS Medicinal Chemistry Letters     Full-text available via subscription   (Followers: 41)
ACS Nano     Full-text available via subscription   (Followers: 259)
ACS Photonics     Full-text available via subscription   (Followers: 12)
ACS Synthetic Biology     Full-text available via subscription   (Followers: 23)
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 Chimica Slovenica     Open Access  
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: 59)
Advances in Chemical Science     Open Access   (Followers: 14)
Advances in Chemistry     Open Access   (Followers: 16)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 18)
Advances in Drug Research     Full-text available via subscription   (Followers: 23)
Advances in Enzyme Research     Open Access   (Followers: 9)
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: 24)
Advances in Nanoparticles     Open Access   (Followers: 14)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 16)
Advances in Polymer Science     Hybrid Journal   (Followers: 41)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 18)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 20)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 6)
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)
Al-Kimia : Jurnal Penelitian Sains Kimia     Open Access  
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: 68)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 15)
American Journal of Chemistry     Open Access   (Followers: 28)
American Journal of Plant Physiology     Open Access   (Followers: 14)
American Mineralogist     Hybrid Journal   (Followers: 15)
Analyst     Full-text available via subscription   (Followers: 40)
Angewandte Chemie     Hybrid Journal   (Followers: 166)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 237)
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: 9)
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: 16)
Anti-Infective Agents     Hybrid Journal   (Followers: 3)
Antiviral Chemistry and Chemotherapy     Hybrid Journal   (Followers: 1)
Applied Organometallic Chemistry     Hybrid Journal   (Followers: 7)
Applied Spectroscopy     Full-text available via subscription   (Followers: 22)
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: 337)
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: 7)
Biomolecular NMR Assignments     Hybrid Journal   (Followers: 3)
BioNanoScience     Partially Free   (Followers: 5)
Bioorganic & Medicinal Chemistry     Hybrid Journal   (Followers: 120)
Bioorganic & Medicinal Chemistry Letters     Hybrid Journal   (Followers: 85)
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: 2)
Canadian Journal of Chemistry     Hybrid Journal   (Followers: 10)
Canadian Mineralogist     Full-text available via subscription   (Followers: 6)
Carbohydrate Research     Hybrid Journal   (Followers: 26)
Carbon     Hybrid Journal   (Followers: 69)
Catalysis for Sustainable Energy     Open Access   (Followers: 7)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 8)
Catalysis Science and Technology     Free   (Followers: 8)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 3)
Catalysts     Open Access   (Followers: 9)
Cellulose     Hybrid Journal   (Followers: 7)
Cereal Chemistry     Full-text available via subscription   (Followers: 5)
ChemBioEng Reviews     Full-text available via subscription   (Followers: 1)
ChemCatChem     Hybrid Journal   (Followers: 8)
Chemical and Engineering News     Free   (Followers: 16)
Chemical Bulletin of Kazakh National University     Open Access  
Chemical Communications     Full-text available via subscription   (Followers: 71)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 25)
Chemical Research in Chinese Universities     Hybrid Journal   (Followers: 3)
Chemical Research in Toxicology     Full-text available via subscription   (Followers: 22)
Chemical Reviews     Full-text available via subscription   (Followers: 188)
Chemical Science     Open Access   (Followers: 23)
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: 56)
Chemie-Ingenieur-Technik (Cit)     Hybrid Journal   (Followers: 24)
ChemInform     Hybrid Journal   (Followers: 8)
Chemistry & Biodiversity     Hybrid Journal   (Followers: 7)
Chemistry & Biology     Full-text available via subscription   (Followers: 31)
Chemistry & Industry     Hybrid Journal   (Followers: 5)
Chemistry - A European Journal     Hybrid Journal   (Followers: 152)
Chemistry - An Asian Journal     Hybrid Journal   (Followers: 16)
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: 43)
Chemistry of Materials     Full-text available via subscription   (Followers: 243)
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: 14)
Chemosensors     Open Access  
ChemPhysChem     Hybrid Journal   (Followers: 11)
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)
Chromatography     Open Access   (Followers: 2)
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 Interfaces     Open Access  
Colloids and Surfaces B: Biointerfaces     Hybrid Journal   (Followers: 6)
Combinatorial Chemistry & High Throughput Screening     Hybrid Journal   (Followers: 4)
Combustion Science and Technology     Hybrid Journal   (Followers: 22)
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: 11)
Computational Chemistry     Open Access   (Followers: 2)
Computers & Chemical Engineering     Hybrid Journal   (Followers: 10)
Coordination Chemistry Reviews     Full-text available via subscription   (Followers: 3)
Copernican Letters     Open Access   (Followers: 1)
Corrosion Series     Full-text available via subscription   (Followers: 6)
Critical Reviews in Biochemistry and Molecular Biology     Hybrid Journal   (Followers: 5)
Croatica Chemica Acta     Open Access  
Crystal Structure Theory and Applications     Open Access   (Followers: 4)
CrystEngComm     Full-text available via subscription   (Followers: 13)
Current Catalysis     Hybrid Journal   (Followers: 2)
Current Chromatography     Hybrid Journal  
Current Green Chemistry     Hybrid Journal  
Current Metabolomics     Hybrid Journal   (Followers: 5)
Current Microwave Chemistry     Hybrid Journal  
Current Opinion in Colloid & Interface Science     Hybrid Journal   (Followers: 9)
Current Opinion in Molecular Therapeutics     Full-text available via subscription   (Followers: 18)
Current Research in Chemistry     Open Access   (Followers: 9)
Current Science     Open Access   (Followers: 64)
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)

        1 2 3 4 | Last

Journal Cover Angewandte Chemie
  [166 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  [1592 journals]
  • Solvation-Induced Changes in the Mechanism of Alcohol Oxidation at
           Gold/Titania Nanocatalysts in the Aqueous Phase versus Gas Phase
    • Authors: Daniel Muñoz-Santiburcio; Matteo Farnesi Camellone, Dominik Marx
      Abstract: Lösungsmittel können heterogenkatalysierte Prozesse stark beeinflussen. In ihrer Zuschrift (
      DOI : 10.1002/ange.201710791) studieren D. Muñoz-Santiburcio et al. mithilfe von Ab-initio-Simulationen die Auswirkungen von Wasser auf die Methanol-Oxidation an Gold-Nanopartikeln auf einem Titandioxid-Träger. Die Mechanismen der Reaktionen in Gas- und Flüssigphase unterscheiden sich deutlich, da Wassermoleküle aktiv an der Oxidation teilnehmen und die Ladungstransferschritte ändern.
      PubDate: 2018-02-23T05:21:47.031381-05:
       
  • ACS National Awards 2018/
    • PubDate: 2018-02-23T05:21:29.983989-05:
      DOI: 10.1002/ange.201801904
       
  • Total Synthesis and Conformational Study of Callyaerin A:
           Anti-Tubercular Cyclic Peptide Bearing a Rare Rigidifying
           (Z)-2,3-Diaminoacrylamide Moiety
    • Authors: Shengping Zhang; Luis M. De Leon Rodriguez, Ivanhoe K. H. Leung, Gregory M. Cook, Paul W. R. Harris, Margaret A. Brimble
      Abstract: Callyaerin A ist ein natürliches cyclisches Peptid mit dem seltenen (Z)-2,3-Diaminoacrylamid(DAA)-Motiv. Es wirkt stark inhibierend gegen M. tuberculosis, ist aber nicht toxisch in menschlichen Zellen. In ihrer Zuschrift (
      DOI : 10.1002/ange.201712792) beschreiben M. Brimble et al. die Totalsynthese von Callyaerin A, und sie zeigen, dass dem Peptid durch die DAA-Einheit eine starre Konformation aufgezwungen wird. Diese Ergebnisse weisen den Weg für weitere Untersuchungen zum potenziellen therapeutischen Nutzen des Peptids.
      PubDate: 2018-02-23T05:21:27.072386-05:
       
  • A Chiral Ligand Assembly That Confers One-Electron O2 Reduction Activity
           for a Cu2+-Selective Metallohydrogel
    • Authors: Xiaojuan Wang; Chuanwan Wei, Ji-Hu Su, Bo He, Ge-Bo Wen, Ying-Wu Lin, Yi Zhang
      Abstract: The design of functional metallohydrogels is attractive but challenging. A rational approach is introduced for designing functional metallohydrogels using chiral ligands, a phenylalanine derivative with a pyridyl group (l/d-PF). Intriguingly, the as-prepared metallohydrogel exhibits excellent O2 binding and activating properties. Insights into the O2 binding pathway reveals the presence of a novel [(l+d)-PF-Cu3+-O2−] species, which can efficiently reduce ferric cytochrome c with the reactive O2− by receiving an electron from reductant ascorbic acid. This study provides helpful instructions for developing new artificial systems with specific functions through the effective combination of chiral ligands with metal ions.Mit beiden Händen: Die Kombination chiraler Liganden – wie am Beispiel eines Phenylalaninderivats mit einer Pyridylgruppe (l/d-PF) vorgeführt – ergibt ein Cu2+-selektives Metallohydrogel mit Ein-Elektronen-Reaktivität in der O2-Reduktion.
      PubDate: 2018-02-23T05:21:25.188363-05:
      DOI: 10.1002/ange.201801290
       
  • Selective Anion Extraction and Recovery Using a FeII4L4 Cage
    • Authors: Dawei Zhang; Tanya K. Ronson, Jesús Mosquera, Alexandre Martinez, Jonathan R. Nitschke
      Abstract: Selective anion extraction is useful for the recovery and purification of valuable chemicals, and in the removal of pollutants from the environment. Here we report that FeII4L4 cage 1 is able to extract an equimolar amount of ReO4−, a high-value anion and a nonradioactive surrogate of TcO4−, from water into nitromethane. Importantly, the extraction was efficiently performed even in the presence of 10 other common anions in water, highlighting the high selectivity of 1 for ReO4−. The extracted guest could be released into water as the cage disassembled in ethyl acetate, and then 1 could be recycled by switching the solvent to acetonitrile. The versatile solubility of the cage also enabled complete extraction of ReO4− (as the tetrabutylammonium salt) from an organic phase into water by using the sulfate salt of 1 as the extractant.Ein FeII4L4-Koordinationskäfig ermöglichte die vollständige Extraktion von ReO4−, einem nicht-radioaktiven Surrogat von TcO4−, aus Wasser in eine organische Phase. In Anwesenheit von 10 anderen Anionen wurden 97 % ReO4− selektiv entfernt. Das extrahierte ReO4− konnte freigesetzt werden, und der Käfig wurde durch einen Wechsel des Lösungsmittels zurückgewonnen. Indem der Käfig wasserlöslich gemacht wurde, konnte ReO4− auch aus einer organischen Phasen in Wasser überführt werden.
      PubDate: 2018-02-23T05:21:16.312816-05:
      DOI: 10.1002/ange.201800459
       
  • From Symmetry Breaking to Unraveling the Origin of the Chirality of
           Ligated Au13Cu2 Nanoclusters
    • Authors: Guocheng Deng; Sami Malola, Juanzhu Yan, Yingzi Han, Peng Yuan, Chaowei Zhao, Xiting Yuan, Shuichao Lin, Zichao Tang, Boon K. Teo, Hannu Häkkinen, Nanfeng Zheng
      Abstract: A general method, using mixed ligands (here diphosphines and thiolates) is devised to turn an achiral metal cluster, Au13Cu2, into an enantiomeric pair by breaking (lowering) the overall molecular symmetry with the ligands. Using an achiral diphosphine, a racemic [Au13Cu2(DPPP)3(SPy)6]+ was prepared which crystallizes in centrosymmetric space groups. Using chiral diphosphines, enantioselective synthesis of an optically pure, enantiomeric pair of [Au13Cu2((2r,4r)/(2s,4s)-BDPP)3(SPy)6]+ was achieved in one pot. Their circular dichroism (CD) spectra give perfect mirror images in the range of 250–500 nm with maximum anisotropy factors of 1.2×10−3. DFT calculations provided good correlations with the observed CD spectra of the enantiomers and, more importantly, revealed the origin of the chirality. Racemization studies show high stability (no racemization at 70 °C) of these chiral nanoclusters, which hold great promise in applications such as asymmetry catalysis.Eines oder das Andere: Eine Mischung aus Diphosphan- und Pyridinthiol-Liganden kann einen achiralen Au13Cu2-Cluster durch Bruch von Spiegel- und Punktsymmetrie in ein Enantiomerenpaar umwandeln. Chirale Diphosphane liefern optisch reine Enantiomere in einem Eintopfverfahren. In Racemisierungsstudien durch Erhitzen war die Chiralität bis 70 °C stabil. Dichtefunktionalrechnungen erklären, wie die Chiralität entsteht.
      PubDate: 2018-02-23T05:16:33.197337-05:
      DOI: 10.1002/ange.201800327
       
  • Halogen Bond Catalyzed Bromocarbocyclization
    • Authors: Yuk-Cheung Chan; Ying-Yeung Yeung
      Abstract: A halogen bond catalyzed bromo-carbocyclization of N-cinnamyl sulfonamides and O-cinnamyl phenyl ethers has been developed. N-methyl 4-iodopyridinium triflate is used as the halogen-bonding organocatalyst and the reaction is highly chemoselective. This report represents the first proof-of-concept for halogen-bonding organocatalyst-promoted electrophilic halogenation. Mechanistic study suggests the autocatalytic nature of this reaction.Eine bromierende Carbocyclisierung von N-Cinnamylsulfonamiden oder O-Cinnamylphenylethern unter Halogenbrücken-Katalyse liefert gute Ausbeuten bei hoher Chemoselektivität. Unter milden Bedingungen wird ein breites Spektrum an Substraten umgesetzt, und der Katalysator N-Methyl-4-iodpyridinium-Triflat ist luft- und feuchtigkeitsbeständig.
      PubDate: 2018-02-23T05:16:26.987964-05:
      DOI: 10.1002/ange.201800261
       
  • Transient-Ligand-Enabled ortho-Arylation of Five-Membered Heterocycles:
           Facile Access to Mechanochromic Materials
    • Authors: Bijin Li; Kapileswar Seth, Ben Niu, Lei Pan, Huiwen Yang, Haibo Ge
      Abstract: Reported herein is the first example of a direct arylation of heteroarenes by a transient-ligand-directed strategy without the need to construct and deconstruct the directing group. A wide range of heteroarenes undergoes the coupling with diverse aryl iodides to assemble a large library of highly selective and functionalized 3-arylthiophene-2-carbaldehydes. This route provides an opportunity to rapidly access new mechanofluorochromic materials. Moreover, a novel strategy for mechanochromic luminogens with chromism trends of red- and blue-shifts has been disclosed for the first time by facile functional-group modifications to a common structural core.Farbwandler: Die direkte Arylierung von Heteroarenen mithilfe transienter Liganden umgeht die Einführung und Abspaltung einer dirigierenden Gruppe. Der Ansatz öffnet einen schnellen Zugang zu neuarigen mechanofluorochromen Materialien.
      PubDate: 2018-02-23T05:16:03.772695-05:
      DOI: 10.1002/ange.201713357
       
  • Size-Selective Exclusion Effects of Liquid Crystalline Tactoids on
           Nanoparticles: A Separation Method
    • Authors: Pei-Xi Wang; Wadood Y. Hamad, Mark J. MacLachlan
      Abstract: Liquid crystalline tactoids are anisotropic microdroplets existing in isotropic phases. We studied the structure and evolution of tactoids in the presence of doping nanoparticles by electron microscopy at the resolution of individual mesogens and observed size-selective exclusion effects of liquid crystalline tactoids on foreign nanoparticles. We applied this principle to the separation of polymer nanospheres, gold nanoparticles, and magnetic nanoparticles by size. These results indicate a new way to size-selectively separate nanoparticles using lyotropic liquid crystals, in which nanoparticles smaller than a threshold size will be selectively transferred from the disordered phase into the ordered phase by tactoids during the phase separation process.Tic-Tac-Toide: Flüssigkristalline Tactoide haben einen größenselektiven Ausschluss-Effekt auf dotierende Nanopartikel, der bewirkt, dass Partikel unterhalb einer bestimmten Größe durch Tactoide selektiv gesammelt und in die flüssigkristalline Phase tranferiert werden. Dieses Prinzip wurde auf die größenbasierte Trennung von Polymer-, Gold- und magnetischen Nanopartikeln angewendet.
      PubDate: 2018-02-23T05:08:34.777273-05:
      DOI: 10.1002/ange.201712158
       
  • Highly Stable Aqueous Zinc-Ion Storage Using Layered Calcium Vanadium
           Oxide Bronze Cathode
    • Authors: Chuan Xia; Jing Guo, Peng Li, Xixiang Zhang, Husam N. Alshareef
      Abstract: Cost-effective aqueous rechargeable batteries are attractive alternatives to non-aqueous cells for stationary grid energy storage. Among different aqueous cells, zinc-ion batteries (ZIBs), based on Zn2+ intercalation chemistry, stand out as they can employ high-capacity Zn metal as the anode material. Herein, we report a layered calcium vanadium oxide bronze as the cathode material for aqueous Zn batteries. For the storage of the Zn2+ ions in the aqueous electrolyte, we demonstrate that the calcium-based bronze structure can deliver a high capacity of 340 mA h g−1 at 0.2 C, good rate capability, and very long cycling life (96 % retention after 3000 cycles at 80 C). Further, we investigate the Zn2+ storage mechanism, and the corresponding electrochemical kinetics in this bronze cathode. Finally, we show that our Zn cell delivers an energy density of 267 W h kg−1 at a power density of 53.4 W kg−1.Schichtförmige Calciumvanadiumoxid-Bronze, die Zn2+-Ionen aus dem Elektrolyt speichert, wurde als Kathodenmaterial in einer wasserbasierten Zinkionenbatterie verwendet. Die Zn-Zelle liefert eine Energiedichte von 267 W h kg−1 und eine Leistungsdichte von 53.4 W kg−1.
      PubDate: 2018-02-23T05:07:05.576204-05:
      DOI: 10.1002/ange.201713291
       
  • Interrupted Baeyer–Villiger Rearrangement: Building A Stereoelectronic
           Trap for the Criegee Intermediate
    • Authors: Vera A. Vil'; Gabriel dos Passos Gomes, Oleg V. Bityukov, Konstantin A. Lyssenko, Gennady I. Nikishin, Igor V. Alabugin, Alexander O. Terent'ev
      Abstract: The instability of hydroxy peroxyesters, the elusive Criegee intermediates of the Baeyer–Villiger rearrangement, can be alleviated by selective deactivation of the stereoelectronic effects that promote the 1,2-alkyl shift. Stable cyclic Criegee intermediates constrained within a five-membered ring can be prepared by mild reduction of the respective hydroperoxy peroxyesters (β-hydroperoxy-β-peroxylactones) which were formed in high yields in reaction of β-ketoesters with BF3⋅Et2O/H2O2.Abhilfe gegen die Unbeständigkeit von Hydroxyperoxyestern, den Criegee-Intermediaten der Baeyer-Villiger-Umlagerung, kann durch selektive Deaktivierung primärer und sekundärer stereoelektronischer Effekte geschaffen werden, die 1,2-Alkyl-Verschiebungen begünstigen. Stabile cyclische Criegee-Intermediate mit Fünfringstruktur sind durch milde Reduktion der entsprechenden Hydro peroxy-Peroxyester zugänglich.
      PubDate: 2018-02-23T05:06:56.704321-05:
      DOI: 10.1002/ange.201712651
       
  • Elucidation of the Oxygen Reduction Volcano in Alkaline Media using a
           Copper–Platinum(111) Alloy
    • Authors: Kim D. Jensen; Jakub Tymoczko, Jan Rossmeisl, Aliaksandr S. Bandarenka, Ib Chorkendorff, María Escudero-Escribano, Ifan E. L. Stephens
      Abstract: The relationship between the binding of the reaction intermediates and oxygen reduction activity in alkaline media was experimentally explored. By introducing Cu into the 2nd surface layer of a Pt(111) single crystal, the surface reactivity was tuned. In both 0.1 m NaOH and 0.1 m KOH, the optimal catalyst should exhibit OH binding circa 0.1 eV weaker than Pt(111), via a Sabatier volcano; this observation suggests that the reaction is mediated via the same surface bound intermediates as in acid, in contrast to previous reports. In 0.1 m KOH, the alloy catalyst at the peak of the volcano exhibits a maximum activity of 101±8 mA cm−2 at 0.9 V vs. a reversible hydrogen electrode (RHE). This activity constitutes a circa 60-fold increase over Pt(111) in 0.1 m HClO4.Durch Einlegieren von Cu in die zweite Oberflächenlage von Pt(111) kann die Sauerstoffreduktionsaktivität in basischen Elektrolyten gezielt eingestellt werden. Ähnlich wie in sauren Medien ist der Schlüsselfaktor für die Reaktionskontrolle die Oberflächenbindung der Intermediate.
      PubDate: 2018-02-23T05:06:30.717704-05:
      DOI: 10.1002/ange.201711858
       
  • Water-Assisted Size and Shape Control of CsPbBr3 Perovskite Nanocrystals
    • Authors: Xiaoyu Zhang; Xue Bai, Hua Wu, Xiangtong Zhang, Chun Sun, Yu Zhang, Wei Zhang, Weitao Zheng, William W. Yu, Andrey L. Rogach
      Abstract: Lead-halide perovskites are well known to decompose rapidly when exposed to polar solvents, such as water. Contrary to this common-place observation, we have found that through introducing a suitable minor amount of water into the reaction mixture, we can synthesize stable CsPbBr3 nanocrystals. The size and the crystallinity, and as a result the band gap tunability of the strongly emitting CsPbBr3 nanocrystals correlate with the water content. Suitable amounts of water change the crystallization environment, inducing the formation of differently shaped perovskites, namely spherical NCs, rectangular nanoplatelets, or nanowires. Bright CsPbBr3 nanocrystals with the photoluminescence quantum yield reaching 90 % were employed for fabrication of inverted hybrid inorganic/organic light-emitting devices, with the peak luminance of 4428 cd m−2 and external quantum yield of 1.7 %.Bleihalogenid-Perowskite sind normalerweise zersetzlich in polaren Lösungsmitteln. Dagegen konnten stabile CsPbBr3-Nanokristalle durch die Einbringung einer geringen Menge Wasser in die Reaktionsmischung synthetisiert werden. Die Größe, Kristallinität und Bandlücke der stark emittierenden CsPbBr3-Nanokristalle können über den Wassergehalt eingestellt werden.
      PubDate: 2018-02-23T05:05:59.53271-05:0
      DOI: 10.1002/ange.201710869
       
  • Li2B12 and Li3B12: Prediction of the smallest tubular and cage-like boron
           structures
    • Authors: Zhonghua Cui; Xue Dong, Said Jalife, Alejandro Vasquez-Espinal, Estefanía Ravell, Sudip Pan, José Luis Cabello, Wei-yan Liang, Gabriel Merino
      Abstract: We report an intriguing structural transition from the quasi-planar form of B12 cluster upon the interaction with lithium atoms. High-level computations show that the lowest energy structures of LiB12, Li2B12, and Li3B12 have quasi-planar (Cs), tubular (D6d), and cage-like (Cs) geometries, respectively. The energetic cost of distorting the B12 quasi-planar fragment is overcompensated by an enhanced electrostatic interaction between the Li cations and the tubular or cage-like B12 fragments, which is the main reason of such drastic structural changes, resulting in the smallest tubular (Li2B12) and cage-like (Li3B12) boron structures reported until now.
      PubDate: 2018-02-23T04:55:28.745367-05:
      DOI: 10.1002/ange.201800976
       
  • Vom Design der Moleküle des Lebens zum Design von Leben: Zukünftige
           Anwendungen von DNA-Technologien
    • Authors: Richie E. Kohman; Aditya M. Kunjapur, Eriona Hysolli, Yu Wang, George M. Church
      Abstract: Seit der Aufklärung ihrer Struktur steht die DNA im Zentrum der biologischen Forschung. In den letzten 50 Jahren ist die Entwicklung von DNA-Technologien rasant vorangeschritten, insbesondere im Bereich der DNA-Sequenzierung. Parallel dazu wurden auch gewaltige Fortschritte in der DNA-Synthese und DNA-Editierung erzielt, die sich von der Oligonukleotid- bis zur Genom-Ebene erstrecken. In diesem Aufsatz erörtern wir vier verschiedene Teilbereiche von DNA-Technologien und folgen dabei diesem Verlauf von kleinerem zu größerem Maßstab. Wir beginnen mit dem Aufbau von Materialien aus DNA, die wiederum als Transportsysteme in vivo dienen können. Anschließend diskutieren wir, wie die Modifizierung mikrobieller Genome zu neuartigen Methoden für die Produktion industrieller Biologika führen kann. Als nächstes reden wir über die Zukunft der Genomsynthese als eine Methode für die Evolutionsforschung. Schließlich erläutern wir, wie das Barcoding biologischer Systeme deren dreidimensionale Analyse in hoch parallelisierter Weise ermöglicht.Im Zentrum von allem: DNA-basierte Technologien entwickeln sich derzeit mit rasantem Tempo. Insbesondere Fortschritte in der DNA-Synthese und -Editierung bereiten den Weg für eine Vielzahl zukünftiger Anwendungen, vom Design neuer Nanomaterialien bis hin zum Design neuer Organismen.
      PubDate: 2018-02-23T04:42:13.207434-05:
      DOI: 10.1002/ange.201707976
       
  • Der Immuncheckpoint PD-1/PD-L1: Gibt es Therapieoptionen jenseits der
           Antikörper'
    • Authors: Markella Konstantinidou; Tryfon Zarganes-Tzitzikas, Katarzyna Magiera-Mularz, Tad A. Holak, Alexander Dömling
      Abstract: Die PD-1/PD-L1-Wechselwirkung hat sich als ein wichtiger Angriffspunkt für die Krebs-Immuntherapie erwiesen. Aktuelle Medikationen unter Einbeziehung monoklonaler Antikörper zeigen eindrucksvolle klinische Wirkungen beim Einsatz gegen verschiedene Tumortypen. Von der Cokristallstruktur von humanem PD-1 mit PD-L1 erwartet man – zusammen mit den aktuellen Kristallstrukturen mit monoklonalen Antikörpern, niedermolekularen Substanzen und Makrocyclen – einen wertvollen Ausgangspunkt für den Entwurf neuer Inhibitoren.Völlig klar: Von der FDA zugelassene monoklonale Antikörper (mAbs) gegen die PD-1/PD-L1-Wechselwirkung haben die Krebs-Immuntherapie revolutioniert. Die in letzter Zeit zunehmend verfügbaren Röntgenkristallographiedaten von Antikörpern, niedermolekularen Substanzen und Makrocyclen, die gegen PD-1 oder PD-L1 wirken, liefern wichtige Einblicke für den rationalen Entwurf neuer Wirkstoffe zur Hemmung dieser Protein-Protein-Wechselwirkung.
      PubDate: 2018-02-23T04:35:38.842369-05:
      DOI: 10.1002/ange.201710407
       
  • Metal-Free Dehydrogenation of N-Heterocycles by Ternary h-BCN Nanosheets
           with Visible Light
    • Authors: Meifang Zheng; Jiale Shi, Tao Yuan, Xinchen Wang
      Abstract: An efficient metal-free catalytic system has been developed using hexagon boron carbon nitride (h-BCN) nanosheets for the dehydrogenations of N-heterocycles with visible light, while releasing hydrogen gas (H2), and thus no proton acceptor is needed. This acceptorless dehydrogenation of hydroquinolines, hydroisoquinolines or indolines to the corresponding aromatic N-heterocycles has been achieved with excellent yield by visible light irradiation under the ambient temperature. With h-BCN as the photocatalyst and water as the solvent, this protocol shows broad substitution tolerance, environment benign and high efficiency. This metal-free photoredox catalytic system for organic synthesis expands our knowledge of chemical reactivity and enables new environmentally friendly synthetic protocols.
      PubDate: 2018-02-23T03:55:36.87569-05:0
      DOI: 10.1002/ange.201800319
       
  • Fluoride-Catalyzed Deblocking as a New Route to Polymeric Urethanes
    • Authors: Madhu Sheri; Umesh Choudhary, Sunitha Grandhee, Todd Shannon Emrick
      Abstract: We report a fluoride-catalyzed deblocking of urethanes as "blocked" isocyanates. Organic and inorganic sources of fluoride ion proved effective for deblocking urethanes and for converting polyurethanes to small molecules. Distinct from conventional deblocking chemistry involving organometallic compounds and high temperatures, the method we describe is metal-free and operates at or slightly above room temperature. The use of fluorescent blocking agents enabled visual and spectroscopic monitoring of blocking/deblocking reactions, and the selected conditions proved applicable to urethanes containing a variety of blocking groups. The method additionally enabled a one pot deblocking and polymerization with diols. Overall, this deblocking/polymerization strategy offers a convenient and efficient solution to problems that have limited the breadth of applications of polyurethane chemistry.
      PubDate: 2018-02-22T23:55:21.247611-05:
      DOI: 10.1002/ange.201800795
       
  • Chaotropic Monovalent Anion Induced Rectification Inversion at
           Polyimidazolium Brushes Modified Nanopipettes
    • Authors: Ping Yu
      Abstract: Here we report a nonintuitive observation of monovalent anion-induced ion current rectification inversion at polyimidazolium brush (PimB) modified nanopipettes. The rectification inversion degree is found to be strongly dependent on the concentration and species of monovalent anions. For chaotropic anions , the rectification inversion is easily observed at a low concentration (5 mM), while there is no rectification inversion observed for kosmotropic anions (e.g., Cl-) even at a high concentration (1 M). Moreover, at the specific concentration (e.g., 10 mM), the variation of rectification ratio on the type of anions is ranged by Hofmeister series. Estimation of the electrokinetic charge density demonstrates that rectification inversion is originated from the charge inversion due to the over-adsorption of chaotropic monovalent anion. To qualitatively understand this phenomenon, the concentration-dependent adsorption mechanism is proposed and discussed.
      PubDate: 2018-02-22T21:56:54.362572-05:
      DOI: 10.1002/ange.201800335
       
  • Design, Synthesis and Application of Novel Chiral C2-symmetric
           Spiroketal-containing Ligands in Transition Metal Catalysis
    • Authors: Alonso J Argüelles; Siyuan Sun, Brenna Budaitis, Pavel Nagorny
      Abstract: We present an expedient and economical route to a new spiroketal-based C2-symmetric chiral scaffold termed SPIROL. Based on this spirocyclic scaffold, several chiral ligands were generated and successfully employed in an array of stereoselective transformations including Ir-catalyzed hydroarylation (up to 95% ee), Pd-catalyzed allylic alkylation (up to 97% ee), intermolecular Pd-catalyzed Heck reaction (up to 95% ee), and Rh-catalyzed hydrogenations of dehydroalanine (up to 93% ee).
      PubDate: 2018-02-22T21:56:17.150902-05:
      DOI: 10.1002/ange.201713304
       
  • Spectroscopic and computational characterization of DTPA-transplutonium
           chelates: evidencing heterogeneity in the heavy actinide(III) series
    • Authors: Gauthier Deblonde; Morgan Kelley, Jing Su, Enrique Batista, Ping Yang, Corwin Booth, Rebecca J Abergel
      Abstract: The chemistry of trivalent transplutonium ions (Am3+, Cm3+, Bk3+, Cf3+, Es3+) is usually perceived as monotonic and parallel to that of the trivalent lanthanide series. Herein, we present the first extended X-ray absorption fine structure (EXAFS) study performed on a series of aqueous heavy actinide chelates, extending past Cm. The results obtained on diethylenetriaminepentaacetic acid (DTPA) complexes of trivalent Am, Cm, Bk, and Cf show a break to a much shorter metal-oxygen nearest-neighbor bond lengths in the case of Cf3+. Corroborating those results, density functional theory calculations, extended to Es3+, suggest that the shorter Cf-O and Es-O bonds could arise from the departure of the coordinated water molecule and contraction of the ligand around the metal relative to the other [MIIIDTPA(H2O)]2- (M = Am, Cm, Bk) complexes. Taken together, these results demonstrate inhomogeneity within the trivalent transplutonium series that has been insinuated and debated in recent years.
      PubDate: 2018-02-22T21:55:42.152999-05:
      DOI: 10.1002/ange.201709183
       
  • Gene Expression on DNA Biochips Patterned with Strand Displacement
           Lithography
    • Authors: Günther Pardatscher; Matthaeus Schwarz-Schilling, Shirley S Daube, Roy H Bar-Ziv, Friedrich Christian Simmel
      Abstract: Lithographic patterning of DNA molecules enables spatial organization of cell-free genetic circuits under well-controlled experimental conditions. Here, we present a biocompatible, DNA-based resist termed "Bephore" based on commercially available components, which can be patterned by both photo- and electron beam lithography. The patterning mechanism is based on cleavage of a chemically modified DNA hairpin by ultraviolet light or electrons, and a subsequent strand displacement reaction. All steps are performed in aqueous solution and do not require chemical development of the resist, which makes the lithographic process robust and biocompatible. Bephore is well suited for multi-step lithographic processes, enabling immobilization of different types of DNA molecules with micrometer precision. As an application, we demonstrate compartmentalized, on-chip gene expression from three sequentially immobilized DNA templates, leading to three spatially resolved protein expression gradients.
      PubDate: 2018-02-22T11:25:44.872895-05:
      DOI: 10.1002/ange.201800281
       
  • Nanobody-enabled reverse pharmacology on GPCRs
    • Authors: Els Pardon; Cecilia Betti, Toon Laeremans, Florent Chevillard, Karel Guillemyn, Peter Kolb, Steven Ballet, jan Steyaert
      Abstract: The conformational complexity of G protein-coupled receptor (GPCR) transmembrane signaling is a central hurdle for the design of screens for receptor agonists. In their basal states, GPCRs have lower affinities for agonists compared to their G protein-bound active state conformations. Moreover, different agonists can stabilize distinct active receptor conformations and do not uniformly activate all cellular signaling pathways linked to a given receptor (agonist bias). Herein, comparative fragment screens were performed on a β2 adrenoreceptor-Nanobody fusion locked in its active state conformation by a G protein mimicking Nanobody, and the same receptor in its basal state conformation. This simple biophysical assay allowed the identification and ranking of multiple novel agonists and permitted to classify the efficacy of each hit in agonist, antagonist, or inverse agonist categories, opening doors to Nanobody-enabled reverse pharmacology.
      PubDate: 2018-02-22T09:57:18.374419-05:
      DOI: 10.1002/ange.201712581
       
  • Covalent Functionalization of Black Phosphorus with Conjugated Polymer for
           Information Storage
    • Authors: Yu Chen; Yaming Cao, Xiangyu Tian, Bo Liu, Sannian Song, Fei Fan, Bin Zhang, Junwei Gu
      Abstract: Major disadvantages of black phosphorus (BP) are its poor air-stability and poor solubility in common organic solvents. The best way to solve this problem is to incorporate BP into a polymer backbone or a polymer matrix to form novel functional materials that can provide both challenges and opportunities for new innovation in e.g., optoelectronic and photonic applications. As a proof-of concept application, we synthesized in situ the first highly soluble conjugated polymer-covalently functionalized BP derivative (PDDF-g-BP) which was used to fabricate a resistive random access memory (RRAM) device with a configuration of Au/PDDF-g-BP/ITO. In contrast to PDDF without memory effect, PDDF-g-BP-based device exhibits a nonvolatile rewritable memory performance, with a turn-on and turn-off voltages of +1.95V and -2.34V, and an ON/OFF current ratio of 10000. The current through the device in both the ON and OFF states is still kept unchanged even at 200th switching cycle. The PDDF/BP blends show a very unstable memory performance with a very small ON/OFF current ratio.
      PubDate: 2018-02-22T07:55:48.52573-05:0
      DOI: 10.1002/ange.201712675
       
  • Zirconium–Porphyrin-Based Metal–Organic Framework Hollow Nanotubes for
           Immobilization of Noble-Metal Single Atoms
    • Authors: Ting He; Shuangming Chen, Bing Ni, Yue Gong, Zhao Wu, Li Song, Lin Gu, Wenping Hu, Xun Wang
      Abstract: Single atoms immobilized on metal–organic frameworks (MOFs) with unique nanostructures have drawn tremendous attention in the application of catalysis but remain a great challenge. Various single noble-metal atoms have now been successfully anchored on the well-defined anchoring sites of the zirconium porphyrin MOF hollow nanotubes, which are probed by aberration-corrected scanning transmission electron microscopy and synchrotron-radiation-based X-ray absorption fine-structure spectroscopy. Owing to the hollow structure and excellent photoelectrochemical performance, the HNTM-Ir/Pt exhibits outstanding catalytic activity in the visible-light photocatalytic H2 evolution via water splitting. The single atom immobilized on MOFs with hollow structures are expected to pave the way to expand the potential applications of MOFs.Einzelne Edelmetallatome können an den wohldefinierten Ankerzentren von hohlen Zirconiumporphyrin-MOF-Nanoröhren immobilisiert werden. Dank der hohlen Struktur und exzellenten photoelektrochemischen Eigenschaften zeigt HNTM-Ir/Pt eine herausragende Aktivität in der photokatalytischen Wasserspaltung und H2-Entwicklung unter sichtbarem Licht.
      PubDate: 2018-02-22T07:37:20.43514-05:0
      DOI: 10.1002/ange.201800817
       
  • Small Molecules Targeting Mycobacterium tuberculosis Type II NADH
           Dehydrogenase Exhibit Antimycobacterial Activity
    • Authors: Michael B. Harbut; Baiyuan Yang, Renhe Liu, Takahiro Yano, Catherine Vilchèze, Bo Cheng, Jonathan Lockner, Hui Guo, Chenguang Yu, Scott G Franzblau, H. Mike Petrassi, William R. Jacobs, Harvey Rubin, Arnab K. Chatterjee, Feng Wang
      Abstract: The generation of ATP through oxidative phosphorylation is an essential metabolic function for Mycobaterium tuberculosis (Mtb), regardless of the growth environment. The type II NADH dehydrogenase (Ndh-2) is the conduit for electrons into the pathway, and is absent in the mammalian genome, thus making it a potential drug target. Herein, we report the identification of two types of small molecules as selective inhibitors for Ndh-2 through a multicomponent high-throughput screen. Both compounds block ATP synthesis, lead to effects consistent with loss of NADH turnover, and importantly, exert bactericidal activity against Mtb. Extensive medicinal chemistry optimization afforded the best analogue with an MIC of 90 nm against Mtb. Moreover, the two scaffolds have differential inhibitory activities against the two homologous Ndh-2 enzymes in Mtb, which will allow precise control over Ndh-2 function in Mtb to facilitate the assessment of this anti-TB drug target.Einfach mal abschalten: Ein Hochdurchsatz-Screening gegen den oxidativen Phosphorylierungsweg von M. tuberculosis führte zur Identifizierung zweier Inhibitoren der Typ-II-Dehydrogenase Ndh-2. Sie zeigen unterschiedliche Hemmaktivitäten gegen eines oder beide Ndh-2-Isozyme. Durch die Behandlung von Mtb mit diesen Verbindungen wird die ATP-Synthese abgeschaltet und das Bakterium getötet.
      PubDate: 2018-02-22T07:36:22.675296-05:
      DOI: 10.1002/ange.201800260
       
  • Titanium Phosphonate Based Metal–Organic Frameworks with Hierarchical
           Porosity for Enhanced Photocatalytic Hydrogen Evolution
    • Authors: Hui Li; Ying Sun, Zhong-Yong Yuan, Yun-Pei Zhu, Tian-Yi Ma
      Abstract: Photocatalytic hydrogen production is crucial for solar-to-chemical conversion process, wherein high-efficiency photocatalysts lie in the heart of this area. A photocatalyst of hierarchically mesoporous titanium phosphonate based metal–organic frameworks, featuring well-structured spheres, a periodic mesostructure, and large secondary mesoporosity, are rationally designed with the complex of polyelectrolyte and cathodic surfactant serving as the template. The well-structured hierarchical porosity and homogeneously incorporated phosphonate groups can favor the mass transfer and strong optical absorption during the photocatalytic reactions. Correspondingly, the titanium phosphonates exhibit significantly improved photocatalytic hydrogen evolution rate along with impressive stability. This work can provide more insights into designing advanced photocatalysts for energy conversion and render a tunable platform in photoelectrochemistry.Katalytische Golfbälle: Ein Metall-organisches Gerüst wurde unter Einwirkung eines Tensids zu einer Nanostruktur aufgebaut, die einen stabilen Titanphosphat-Rahmen, definierte Kugelform und hierarchische Nanoporen aufweist. Diese Eigenschaften verleihen eine konkurrenzfähige Aktivität und Beständigkeit in der photochemischen Wasserstoffentwicklung bei Bestrahlung mit sichtbarem Licht oder mit einem simulierten Gesamtspektrum.
      PubDate: 2018-02-22T07:36:12.543042-05:
      DOI: 10.1002/ange.201712925
       
  • Herausforderungen bei der Synthese siliciumbasierter dielektrischer
           Metamaterialien
    • Authors: Maria Letizia De Marco; Sanaa Semlali, Brian A. Korgel, Philippe Barois, Glenna L. Drisko, Cyril Aymonier
      Abstract: Metamaterialien haben optische Eigenschaften, die in der Natur beispiellos sind. Mit ihrer Fähigkeit, eine einfallende Wellenfront zu beugen, zu fokussieren, vollständig zu reflektieren, durchzulassen oder zu absorbieren, haben sie bei der Lichtmanipulation neue Horizonte eröffnet. Optisch aktive Metamaterialien sind einsetzbar für Anwendungen, die von der 3D-Informationsspeicherung bis zu photovoltaischen Zellen reichen. Siliciumpartikel gehören zu den vielversprechendsten Synthesebausteinen für optisch aktive Metamaterialien, bislang können sie aber nicht im großen Maßstab hergestellt werden. Besonders wünschenswert sind einheitliche kristalline Si-Synthesebausteine mit 75–200 nm Durchmesser und wenigen Verunreinigungen und Poren. Hier werden die theoretischen Hintergründe der optischen Eigenschaften von Si für Metamaterialien besprochen, außerdem werden aktuelle Synthesemethoden und die aussichtsreichsten Wege zu Si-Partikeln für Metamaterialienwerden vorgestellt.Volldielektrische Metamaterialien werden die Optiktechnologie verändern, sofern Chemiker einige Herausforderungen überwinden können. Siliciumnanopartikel sind aussichtsreiche Kandidaten zur Herstellung volldielektrischer Metamaterialien, die über das gesamte sichtbare Spektrum aktiv sind. Der Stand der Technik zu Siliciumpartikeln für optische Metamaterialien wird vorgestellt, und Anforderungen und Möglichkeiten werden diskutiert.
      PubDate: 2018-02-22T07:21:50.828695-05:
      DOI: 10.1002/ange.201709044
       
  • Catalytic and Atom-Economic Csp3 −Csp3 Bond Formation: Alkyl Tantalum
           Ureates for Hydroaminoalkylation
    • Authors: Rebecca C. DiPucchio; Sorin-Claudiu Roşca, Laurel L. Schafer
      Abstract: Atom-economic and regioselective Csp3−Csp3 bond formation has been achieved by rapid C−H alkylation of unprotected secondary arylamines with unactivated alkenes. The combination of Ta(CH2SiMe3)3Cl2, and a ureate N,O-chelating-ligand salt gives catalytic systems prepared in situ that can realize high yields of β-alkylated aniline derivatives from either terminal or internal alkene substrates. These new catalyst systems realize C−H alkylation in as little as one hour and for the first time a 1:1 stoichiometry of alkene and amine substrates results in high yielding syntheses of isolated amine products by simple filtration and concentration.Auf Geschwindigkeit ausgelegt: Die Titelreaktion beruht auf der schnellen C-H-Alkylierung ungeschützter sekundärer Arylamine mit nichtaktivierten Alkenen. Die Kombination von Ta(CH2SiMe3)3Cl2 mit einem N,O-chelatisierenden Harnstoffanion sorgt dabei für hohe Ausbeuten an β-alkylierten Anilinderivaten.
      PubDate: 2018-02-22T07:16:44.502023-05:
      DOI: 10.1002/ange.201712668
       
  • Electrochemical Dynamics of a Single Platinum Nanoparticle Collision Event
           for the Hydrogen Evolution Reaction
    • Authors: Zhi-peng Xiang; Hai-qiang Deng, Pekka Peljo, Zhi-yong Fu, Su-li Wang, Daniel Mandler, Gong-quan Sun, Zhen-xing Liang
      Abstract: Chronoamperometry was used to study the dynamics of Pt nanoparticle (NP) collision with an inert ultramicroelectrode via electrocatalytic amplification (ECA) in the hydrogen evolution reaction. ECA and dynamic light scattering (DLS) results reveal that the NP colloid remains stable only at low proton concentrations (1.0 mm) under a helium (He) atmosphere, ensuring that the collision events occur at genuinely single NP level. Amperometry of single NP collisions under a He atmosphere shows that each discrete current profile of the collision event evolves from spike to staircase at more negative potentials, while a staircase response is observed at all of the applied potentials under hydrogen-containing atmospheres. The particle size distribution estimated from the diffusion-controlled current in He agrees well with electron microscopy and DLS observations. These results shed light on the interfacial dynamics of the single nanoparticle collision electrochemistry.Das Stromprofil der elektrokatalytischen Wasserstoffentwicklung an einem einzelnen Platinnanopartikel (Pt NP) unter einer Heliumatmosphäre verändert sich von Spitzenform zu Stufenform, wenn das Potential der als Substrat dienenden inerten Ultramikroelektrode (UME) gesenkt wird. Unter Wasserstoffatmosphäre stabilisiert sich die Stufenform des Stromprofils bei allen Polarisierungspotentialen, und es ist mindestens 5-mal kleiner als unter Helium.
      PubDate: 2018-02-22T07:16:16.667275-05:
      DOI: 10.1002/ange.201712454
       
  • Die [2+2]-Cycloadditions-Retroelektrocyclisierungs(CA-RE)-Klick-Reaktion:
           ein einfacher Zugang zu molekularen und polymeren Push-pull-Chromophoren
    • Authors: Tsuyoshi Michinobu; François Diederich
      Abstract: Die [2+2]-Cycloadditions-Retroelektrocyclisierungs(CA-RE)-Reaktion von elektronenreichen Alkinen mit elektronenarmen Alkenen ist ein effizientes Verfahren zur Bildung nichtplanarer Donor-Akzeptor-Chromophore sowohl in molekularen als auch in polymeren Plattformen. Diese Chromophore zeigen ansprechende Eigenschaften, wie intramolekulare Charge-Transfer(ICT)-Banden, nichtlineare optische Eigenschaften und Redox-Eigenschaften zur Verwendung in elektronischen und optoelektronischen Funktionseinheiten der nächsten Generation. Dieser Aufsatz fasst die Entwicklung der CA-RE-Reaktion zusammen, beginnend mit den anfänglichen Berichten über Organometallverbindungen bis hin zu rein organischen Systemen. Die strukturellen Voraussetzungen für schnelle Umsetzungen in hohen Ausbeuten, Merkmale echter Klick-Chemie, werden anhand von Beispielen dargelegt, die die breiten möglichen Alkin- und Alkensubstitutionsmuster belegen. Die CA-RE-Klick-Reaktion wurde erfolgreich in der Polymerchemie eingesetzt. Die gebildeten polymeren Push-pull-Chromophore finden dabei zahlreiche interessante Anwendungen.Nur einen Klick entfernt sind nichtplanare Donor-Akzeptor-Chromophore, die durch Klick-Synthese mittels einer [2+2]-Cycloaddition-Retroelektrocyclisierung (CA-RE) erhalten werden. Dies ist eine leistungsfähige Methode zur Herstellung funktioneller molekularer und polymerer Systeme für den Einsatz in elektronischen und optoelektronischen Vorrichtungen der nächsten Generation.
      PubDate: 2018-02-22T07:16:07.638759-05:
      DOI: 10.1002/ange.201711605
       
  • Fire-retardant and thermally insulating phenolic-silica aerogels
    • Authors: Zhi-Long Yu; Ning Yang, Varvara Apostolopoulou-Kalkavoura, Bing Qin, Zhi-Yuan Ma, Wei-Yi Xing, Chan Qiao, Lennart Bergström, Markus Antonietta, Shu-Hong Yu
      Abstract: Energy efficient buildings require materials with a low thermal conductivity and a high fire resistance. Traditional organic insulation materials are limited by a poor fire resistance and inorganic insulation materials display a high thermal conductivity. Here we report a mechanically resilient organic/inorganic composite aerogel with a thermal conductivity significantly lower than expanded polystyrene and excellent fire resistance. Co-polymerization and nanoscale phase separation of the phenol-formaldehyde-resin (PFR) and silica generate a binary network with domain sizes below 20 nm. The PFR/SiO2 aerogel can resist high-temperature flame without disintegration and prevents the temperature on the non-exposed side to increase above temperature critical for collapse of reinforced concrete structures. Integration of the fire resistant organic/inorganic composite aerogels with architectural materials could be of interest to improve the appearance and energy efficiency of older building.
      PubDate: 2018-02-22T06:57:06.264775-05:
      DOI: 10.1002/ange.201711717
       
  • Total Synthesis of (−)-Enigmazole A
    • Authors: Keisuke Sakurai; Makoto Sasaki, Haruhiko Fuwa
      Abstract: Total synthesis of (−)-enigmazole A, a marine macrolide natural product with cytotoxic activity, has been accomplished. The tetrahydropyran moiety was constructed by means of a domino olefin cross-metathesis/intramolecular oxa-Michael addition of a δ-hydroxy olefin. After coupling of advanced intermediates, the macrocycle was forged via a gold-catalyzed rearrangement of a propargylic benzoate, followed by a ring-closing metathesis of the resultant α,β-unsaturated ketone.
      PubDate: 2018-02-22T06:26:08.052729-05:
      DOI: 10.1002/ange.201801561
       
  • Molecular recognition by a short partial peptide of adrenergic receptor -
           Bottom-up approach
    • Authors: Tsubasa Sekiguchi; Masato Tamura, Hikari Oba, Pierre Çarçarbal, Rolando Rafael Lozada-Garcia, Anne Zehnacker-Rentien, Gilles Grégoire, Shun-ichi Ishiuchi, Masaaki Fujii
      Abstract: Receptor-neurotransmitter molecular recognition is key of neurotransmission. Although crystal structures of the receptors are known, the mechanism for recognition is not clear. At present, the trial-and-error approach is the only sure method to identify ligands (e.g. drugs) that trigger the receptor. Here, we report the ultraviolet and infrared spectra of complexes between a partial peptide SIVSF, the binding motif of a catechol ring in the adrenergic receptor, and various ligands. The ultraviolet spectra show that two isomers coexist in the complex of SIVSF with properly recognized ligands, such as protonated adrenaline (adrenalineH+). From infrared spectra, they are assigned to catechol-bound and ammonium-bound structures. The catechol-bound structure is not observed when the ligand is replaced by non-proper molecules, such as noradrenalineH+. The results suggest that SIVSF not only recognizes the catechol ring but can distinguish differences in the amine side-chain. This suggests a new possibility for screening molecules as potential therapeutics that activate the receptor.
      PubDate: 2018-02-22T05:56:45.415797-05:
      DOI: 10.1002/ange.201712976
       
  • Selective Reductive Elimination at Alkyl Palladium(IV) by Dissociative
           Ligand Ionization: Catalytic C(sp3)−H Amination to Azetidines
    • Authors: Manuel Nappi; Chuan He, William G. Whitehurst, Ben G. N. Chappell, Matthew J. Gaunt
      Abstract: A palladium(II)-catalyzed γ-C−H amination of cyclic alkyl amines to deliver highly substituted azetidines is reported. The use of a benziodoxole tosylate oxidant in combination with AgOAc was found to be crucial for controlling a selective reductive elimination pathway to the azetidines. The process is tolerant of a range of functional groups, including structural features derived from chiral α-amino alcohols, and leads to the diastereoselective formation of enantiopure azetidines.Eine PdII-katalysierte γ-C-H-Aminierung von cyclischen Alkylaminen ergibt hoch substituierte Azetidine. Die Kombination aus Benziodoxoltosylat mit AgOAc ermöglichte die selektive reduktive Eliminierung unter Bildung der Azetidine. Der Prozess ist mit einigen funktionellen Gruppen kompatibel, darunter auch chirale α-Aminoalkohol-Motive, und führt in diastereoselektiver Weise zu enantiomerenreinen Azetidinen.
      PubDate: 2018-02-22T05:38:56.470426-05:
      DOI: 10.1002/ange.201800519
       
  • Direkte Umwandlung von Methan zu protoniertem Formaldehyd bei
           Raumtemperatur in der Gasphase: Zur Rolle von Quecksilber unter den
           Oxidkationen der Zinktriade
    • Authors: Lei Yue; Shaodong Zhou, Xiaoyan Sun, Maria Schlangen, Helmut Schwarz
      Abstract: In den thermischen Reaktionen der zweiatomigen Metalloxide [MO].+ der Zinktriade (M=Zn, Cd, Hg) entsteht protonierter Formaldehyd, und zwar als Hauptprodukt, ausschließlich für das [HgO].+/CH4-Paar. Durch quantenchemische Rechnungen konnten mechanistische Einblicke in diese Reaktion erhalten werden; die unerwartete Bildung von [CH2OH]+ aus [HgO].+/CH4 beruht vermutlich auf relativistischen Effekten.Starke relativistische Effekte des Quecksilberatoms führen zu einer sehr hohen Ionisierungsenergie IE [Hg] sowie zu geringen Bindungsenergien BDE [Hg-O]+ und BDE [Hg-H].. Die Kombination dieser thermodynamischen Daten erleichtert die durch [HgO].+ vermittelte thermische Umwandlung von Methan zu protoniertem Formaldehyd.
      PubDate: 2018-02-22T05:30:51.802394-05:
      DOI: 10.1002/ange.201712405
       
  • Sensortechnologien durch neuartige Materialien und Moleküle
    • Authors: Timothy M. Swager
      Abstract: Viele moderne Technologien und insbesondere die molekulare Sensorik beruhen auf Innovationen im Design neuer Moleküle. Das Design neuartiger, molekularer Sensoren ist erforderlich, um chemische und biologische Signale zu erfassen und somit kostengünstige, allgegenwärtige Chemosensoren zu entwickeln. Wir sind für viele neue Innovationen bereit, um neue Generationen von Sensortechnologien zu realisieren. Heutige Hardware zu erweitern, deren Kosten zu senken und eine breite Implementierung molekularer Sensorik sicherzustellen, ist nur mithilfe dieser neuartigen Materialien und Moleküle möglich.Sinn für Sensoren: Das Design neuartiger, molekularer Sensoren ist erforderlich, um chemische und biologische Signale zu erfassen und somit kostengünstige, allgegenwärtige Chemosensoren zu entwickeln. Nur mithilfe dieser neuartigen Materialien und Moleküle ist es möglich, heutige Hardware zu erweitern, deren Kosten zu senken und eine breite Implementierung molekularer Sensorik sicherzustellen.
      PubDate: 2018-02-22T05:30:45.353563-05:
      DOI: 10.1002/ange.201711611
       
  • Kleine Moleküle, ganz groß: niedermolekulare immunonkologische
           Kombinationstherapien
    • Authors: Bayard R. Huck; Lisa Kötzner, Klaus Urbahns
      Abstract: Immunonkologische Therapien haben das Potenzial, das Arsenal klinisch verfügbarer Tumortherapien nachhaltig zu verändern. Um die bisher erzielten klinischen Erfolge weiter zu verbessern, suchen Forscher nach neuen Wirkstoffkombinationen, bei denen die Blockade von Checkpoint-Proteinen das Rückgrat der Behandlung darstellt. In diesem Aufsatz wird die Bedeutung niedermolekularer Substanzen beleuchtet, die vielversprechend für die Entwicklung verbesserter Krebstherapien sind.Ein Todeskuss: Es gibt viele Möglichkeiten, eine Tumorzelle abzutöten. Mit dem Fokus auf klinisch relevante Verbindungen wird hier über niedermolekulare Wirkstoffe berichtet, die T-Zellen bei ihrem Kampf gegen Krebs unterstützen können.
      PubDate: 2018-02-22T05:10:38.765369-05:
      DOI: 10.1002/ange.201707816
       
  • RNA Cloaking by Reversible Acylation
    • Authors: Anastasia Kadina; Anna M. Kietrys, Eric T. Kool
      Abstract: We describe a selective and mild chemical approach for controlling RNA hybridization, folding, and enzyme interactions. Reaction of RNAs in aqueous buffer with an azide-substituted acylating agent (100–200 mm) yields several 2′-OH acylations per RNA strand in as little as 10 min. This poly-acylated (“cloaked”) RNA is strongly blocked from hybridization with complementary nucleic acids, from cleavage by RNA-processing enzymes, and from folding into active aptamer structures. Importantly, treatment with a water-soluble phosphine triggers a Staudinger reduction of the azide groups, resulting in spontaneous loss of acyl groups (“uncloaking”). This fully restores RNA folding and biochemical activity.Chemische Schaltung von RNA: Ein einfacher und selektiver chemischer Ansatz zur Kontrolle der RNA-Funktion beruht auf der Polyacylierung von 2′-OH-Gruppen mit einem tarnenden Nicotinyl-Imidazol-Reagens, das molekulare Erkennungsprozesse verhindert. Die RNA-Funktion wird wieder aktiviert, wenn die Acylgruppen durch Staudinger-Reduktion entfernt werden.
      PubDate: 2018-02-22T05:05:35.297064-05:
      DOI: 10.1002/ange.201708696
       
  • Dye-incorporated Polynaphthalenediimide Acceptor for Additive-free
           High-performance All-polymer Solar Cells
    • Authors: Dong Chen; Jia Yao, Jingping Yin, Ruizhi Lv, Bin Huang, Siqi Liu, Chunhe Yang, Zhiguo Zhang, Lie Chen, Yiwang Chen, Yongfang Li
      Abstract: All-polymer solar cells (all-PSCs) can offer unique advantages for applications in flexible devices, and naphthalene diimide (NDI)-based polymer acceptors are the widely used polymer acceptors. However, their power conversion efficiency (PCE) still lags behind that of state-of-the-art polymer solar cells, due to low light absorption, suboptimal energy levels and the strong aggregation of the NDI-based polymer acceptor. In this work, by means of simple random copolymerization, a rhodanine-based dye molecule was introduced into the NDI-based polymer acceptor and showed an improved light absorption coefficient, an up-shifted lowest unoccupied molecular orbital level and reduced crystallization. Consequently, additive-free all-PSCs demonstrated a high PCE of 8.13%, which is one of the highest performance characteristics reported for all-PSCs to date. These results indicate that incorporating dye into the n-type polymer yields insights into the precise design of high-performance polymer acceptors for all-PSCs.
      PubDate: 2018-02-22T04:50:25.975586-05:
      DOI: 10.1002/ange.201800035
       
  • Universality of the Sodium Ion Binding Mechanism in Class A
           G-Protein-Coupled Receptors
    • Authors: Balaji Selvam; Zahra Shamsi, Diwakar Shukla
      Abstract: The allosteric modulation of G-protein-coupled receptors (GPCRs) by sodium ions has received significant attention as crystal structures of several receptors show Na+ ions bound to the inactive conformations at the conserved Asp2.50. To date, structures from 24 families of GPCRs have been determined, though mechanistic insights into Na+ binding to the allosteric site are limited. We performed hundreds-of-microsecond long simulations of 18 GPCRs and elucidated their Na+ binding mechanism. In class A GPCRs, the Na+ ion binds to the conserved residue 2.50 whereas in class B receptors, it binds at 3.43b, 6.53b, and 7.49b. Using Markov state models, we obtained the free energy profiles and kinetics of Na+ binding to the allosteric site, which reveal a conserved mechanism of Na+ binding for GPCRs and show the residues that act as major barriers for ion diffusion. Furthermore, we also show that the Na+ ion can bind to GPCRs from the intracellular side when the allosteric site is inaccessible from the extracellular side.Die Freie-Energie-Barrieren für die Bindung eines Na+-Ions an das allosterische Zentrum von 18 G-Protein-gekoppelten Rezeptoren wurden mit Markow-Modellen berechnet. Rezeptoren aus unterschiedlichen Klassen und Familien folgen dem gleichen Bindungsmechanismus, allerdings variiert die Kinetik der Ionenbindung deutlich. In PAR1 und P2Y12 bindet das Na+-Ion von der interzellulären Seite.
      PubDate: 2018-02-22T04:46:32.942611-05:
      DOI: 10.1002/ange.201708889
       
  • Efficient CO2 Removal for Ultra-Pure CO Production by Two Hybrid
           Ultramicroporous Materials
    • Authors: Kai-Jie Chen; Qing-Yuan Yang, Susan Sen, David G. Madden, Amrit Kumar, Tony Pham, Katherine A. Forrest, Nobuhiko Hosono, Brian Space, Susumu Kitagawa, Michael J. Zaworotko
      Abstract: Removal of CO2 from CO gas mixtures is a necessary but challenging step during production of ultra-pure CO as processed from either steam reforming of hydrocarbons or CO2 reduction. Herein, two hybrid ultramicroporous materials (HUMs), SIFSIX-3-Ni and TIFSIX-2-Cu-i, which are known to exhibit strong affinity for CO2, were examined with respect to their performance for this separation. The single-gas CO sorption isotherms of these HUMs were measured for the first time and are indicative of weak affinity for CO and benchmark CO2/CO selectivity (>4000 for SIFSIX-3-Ni). This prompted us to conduct dynamic breakthrough experiments and compare performance with other porous materials. Ultra-pure CO (99.99 %) was thereby obtained from CO gas mixtures containing both trace (1 %) and bulk (50 %) levels of CO2 in a one-step physisorption-based separation process.Ein Referenzwert für die CO2/CO-Selektivität unter Umgebungsbedingungen zeichnet zwei mikroporöse Hybridmaterialien aus, die deutlich schwächer mit CO wechselwirken als mit CO2. Ausgehend von CO2-haltigen Gasmischungen (1 % und 50 % CO2) wird hoch reines CO (>99.99 %) effizient in einer einstufigen Trennung an einer Festbettsäule des Adsorptionsmittels erzeugt.
      PubDate: 2018-02-22T04:45:43.277465-05:
      DOI: 10.1002/ange.201706090
       
  • A Crosslinked Nucleic Acid Nanogel for Effective siRNA Delivery and
           Antitumor Therapy
    • Authors: Fei Ding; Quanbing Mou, Yuan Ma, Gaifang Pan, Yuanyuan Guo, Gangsheng Tong, Chung Hang Jonathan Choi, Xinyuan Zhu, Chuan Zhang
      Abstract: Functional siRNAs are employed as cross-linkers to direct the self-assembly of DNA-grafted polycaprolactone (DNA-g-PCL) brushes to form spherical and nanosized hydrogels via nucleic acid hybridization in which small interfering RNAs (siRNAs) are fully embedded and protected for systemic delivery. Owing to the existence of multivalent mutual crosslinking events inside, the crosslinked nanogels with tunable size exhibit not only good thermostability, but also remarkable physiological stability that can resist the enzymatic degradation. As a novel siRNA delivery system with spherical nucleic acid (SNA) architecture, the crosslinked nanogels can assist the delivery of siRNAs into different cells without any transfection agents and achieve the gene silencing effectively both in vitro and in vivo, through which a significant inhibition of tumor growth is realized in the anticancer treatment.Funktionelle siRNA wird als Vernetzer eingesetzt, um durch Nukleinsäurehybridisierung die Selbstorganisation von DNA-gebundenen Polycaprolacton(DNA-g-PCL)-Bürsten zu einem sphärischen und nanoskopischen Hydrogel zu lenken. Dabei schließt das Nanogel die siRNA vollständig ein und ermöglicht ihren systemischen Transport in Zellen ohne Transfektionsagentien für die wirksame Genstummschaltung.
      PubDate: 2018-02-22T04:41:32.081142-05:
      DOI: 10.1002/ange.201711242
       
  • Van der Waals Heterostructures Comprised of Ultrathin Polymer Nanosheets
           for Efficient Z-Scheme Overall Water Splitting
    • Authors: Lei Wang; Xusheng Zheng, Liang Chen, Yujie Xiong, Hangxun Xu
      Abstract: Inspired by natural photosynthesis, Z-scheme photocatalytic systems are very appealing for achieving efficient overall water splitting. Developing metal-free Z-scheme photocatalysts for overall water splitting, however, still remains challenging. The construction of polymer-based van der Waals heterostructures as metal-free Z-scheme photocatalytic systems for overall water splitting is described using aza-fused microporous polymers (CMP) and C2N ultrathin nanosheets as O2- and H2-evolving catalysts, respectively. Although neither polymer is able to split pure water using visible light, a 2:1 stoichiometric ratio of H2 and O2 was observed when aza-CMP/C2N heterostructures were used. A solar-to-hydrogen conversion efficiency of 0.23 % was determined, which could be further enhanced to 0.40 % by using graphene as the solid electron mediator to promote the interfacial charge-transfer process. This study highlights the potential of polymer photocatalysts for overall water splitting.Ein photokatalytisches System, das auf dem Z-Schema beruht und auf Metalle verzichtet, vermittelt effizient die gesamte Wasserspaltung. 2D-van-der-Waals-Heterostrukturen aus Polymernanoschichten erleichtern die Ladungstrennung mit der Folge verlängerter Lebensdauern und einer erhöhten Dichte an photogenerierten Exzitonen.
      PubDate: 2018-02-22T04:41:15.605308-05:
      DOI: 10.1002/ange.201710557
       
  • Palladium-Catalyzed Regioselective Aromatic Extension of Internal Alkynes
           through a Norbornene-Controlled Reaction Sequence
    • Authors: Qingyang Zhao; Wai Chung Fu, Fuk Yee Kwong
      Abstract: A regioselective aromatic π-extension reaction of internal alkynes is reported. The proposed method employs three easily available components, namely aryl halides, 2-haloarylcarboxylic acids, and disubstituted acetylenes. The transformation is driven by a controlled reaction sequence of C−H activation, decarboxylation, and annulation to give poly(hetero)aromatic compounds in a site-selective fashion. Unlike in previously reported palladium-catalyzed three-component annulations, alkyne carbopalladation is the last step of this tandem reaction.In eine Richtung: Eine regioselektive Mehrkomponentenreaktion von Arylhalogeniden, 2-Halogenarylcarbonsäuren und disubstituierten Alkinen liefert nach C-H-Aktivierung, Decarboxylierung und Anellierung durch aromatische Erweiterung poly(hetero)aromatische Verbindungen. Alkin-Carbopalladierung ist der letzte Schritt dieser Tandemreaktion.
      PubDate: 2018-02-22T04:36:38.808455-05:
      DOI: 10.1002/ange.201713207
       
  • Cytochrome-P450-Induced Ordering of Microsomal Membranes Modulates
           Affinity for Drugs
    • Authors: Carlo Barnaba; Bikash Ranjan Sahoo, Thirupathi Ravula, Ilce G. Medina-Meza, Sang-Choul Im, G. M. Anantharamaiah, Lucy Waskell, Ayyalusamy Ramamoorthy
      Abstract: Although membrane environment is known to boost drug metabolism by mammalian cytochrome P450s, the factors that stabilize the structural folding and enhance protein function are unclear. In this study, we use peptide-based lipid nanodiscs to “trap” the lipid boundaries of microsomal cytochrome P450 2B4. We report the first evidence that CYP2B4 is able to induce the formation of raft domains in a biomimetic compound of the endoplasmic reticulum. NMR experiments were used to identify and quantitatively determine the lipids present in nanodiscs. A combination of biophysical experiments and molecular dynamics simulations revealed a sphingomyelin binding region in CYP2B4. The protein-induced lipid raft formation increased the thermal stability of P450 and dramatically altered ligand binding kinetics of the hydrophilic ligand BHT. These results unveil membrane/protein dynamics that contribute to the delicate mechanism of redox catalysis in lipid membrane.Redoxkatalyse in der Lipidmembran: Eine neue Anwendung von Peptidnanoscheiben zeigt, dass Cytochrom P450 2B4 die Bildung von Lipid-Raft-Domänen in einer biomimetischen Verbindung des endoplasmatischen Retikulums (ER) induzieren kann. Die proteininduzierten Lipidflöße steigern die thermische Stabilität von Cytochrom P450 und modulieren die Ligandenbindungskinetik des hydrophilen BHT-Liganden.
      PubDate: 2018-02-22T04:36:08.329267-05:
      DOI: 10.1002/ange.201713167
       
  • Isolation of a Cationic Platinum(II) σ-Silane Complex
    • Authors: Pablo Ríos; Hugo Fouilloux, Pietro Vidossich, Josefina Díez, Agustí Lledós, Salvador Conejero
      Abstract: The platinum complex [Pt(ItBuiPr′)(ItBuiPr)][BArF] interacts with tertiary silanes to form stable (
      PubDate: 2018-02-22T04:35:50.956519-05:
      DOI: 10.1002/ange.201712791
       
  • Glass and Alchemy in Early Modern Europe: An Analytical Study of Glassware
           from the Oberstockstall Laboratory in Austria
    • Authors: Umberto Veronesi; Marcos Martinón-Torres
      Abstract: Glass distillation equipment from an early modern alchemical laboratory was analyzed for its technology of manufacture and potential origin. Chemical data show that the assemblage can be divided into sodium-rich, colorless distillation vessels made with glass from Venice or its European imitation, and potassium-rich dark-brown non-specialized forms produced within the technological tradition of forest glass typical for central and north-western Europe. These results complete our understanding of the supply of technical apparatus at one of the best-preserved alchemical laboratories and highlight an early awareness of the need for high-quality instruments to guarantee the successful outcome of specialized chemical operations. This study demonstrates the potential of archaeological science to inform historical research around the practice of early chemistry and the development of modern science.Welche Verfahren benutzten Alchemisten in ihren Laboratorien' Welche Werkzeuge' Kann uns die Beantwortung solcher Fragen helfen, die Entwicklung von Technologie und Wissenschaft in der Renaissance besser zu verstehen' Die archäometrische Analyse von Artefakten aus Laboratorien gibt Hinweise darauf, wie Alchemie im frühneuzeitlichen Europa praktiziert wurde.
      PubDate: 2018-02-22T04:35:43.780961-05:
      DOI: 10.1002/ange.201712523
       
  • Supramolecular Nanostructures of Structurally Defined Graphene Nanoribbons
           in the Aqueous Phase
    • Authors: Yinjuan Huang; Wei-Tao Dou, Fugui Xu, Hong-Bo Ru, Qiuyu Gong, Dongqing Wu, Deyue Yan, He Tian, Xiao-Peng He, Yiyong Mai, Xinliang Feng
      Abstract: Structurally well-defined graphene nanoribbons (GNRs) have attracted great interest because of their unique optical, electronic, and magnetic properties. However, strong π–π interactions within GNRs result in poor liquid-phase dispersibility, which impedes further investigation of these materials in numerous research areas, including supramolecular self-assembly. Structurally defined GNRs were synthesized by a bottom-up strategy, involving grafting of hydrophilic poly(ethylene oxide) (PEO) chains of different lengths (GNR-PEO). PEO grafting of 42–51 % percent produces GNR-PEO materials with excellent dispersibility in water with high GNR concentrations of up to 0.5 mg mL−1. The “rod–coil” brush-like architecture of GNR-PEO resulted in 1D hierarchical self-assembly behavior in the aqueous phase, leading to the formation of ultralong nanobelts, or spring-like helices, with tunable mean diameters and pitches. In aqueous dispersions the superstructures absorbed in the near-infrared range, which enabled highly efficient conversion of photon energy into thermal energy.Supramolekulare Nanostrukturen aus wohldefinierten Graphen-Nanobändern mit aufgepfropften hydrophilen Poly(ethylenoxid)-Ketten sind hervorragend in wässrigen Phasen dispergierbar. Solche Dispersionen absorbieren Nahinfrarotstrahlung und wandeln die Energie der Photonen in thermische Energie um.
      PubDate: 2018-02-22T04:35:36.029517-05:
      DOI: 10.1002/ange.201712637
       
  • Kohlendioxidabtrennung mithilfe von Kondensatoren
    • Authors: Kai Landskron
      Abstract: Schrottverwertung: Eine nachhaltige, kapazitive Methode zur Kohlendioxidabtrennung und -sequestrierung wandelt Schrottmetalle und CO2 energiegünstig in Metallcarbonate um.
      PubDate: 2018-02-22T04:31:14.766793-05:
      DOI: 10.1002/ange.201800941
       
  • Iron-Catalyzed Reductive Ethylation of Imines with Ethanol
    • Authors: Marie Vayer; Sara P. Morcillo, Jennifer Dupont, Vincent Gandon, Christophe Bour
      Abstract: The borrowing hydrogen strategy has been applied to the ethylation of imines with an air-stable iron complex as precatalyst. This approach opens new perspectives in this area as it enables the synthesis of unsymmetric tertiary amines from readily available substrates and ethanol as a C2 building block. A variety of imines bearing electron-rich aryl or alkyl groups at the nitrogen atom could be efficiently reductively alkylated without the need for molecular hydrogen. The mechanism of this reaction, which shows complete selectivity for ethanol over other alcohols, has been studied experimentally and by means of DFT computations.Die Ethylierung von Aminen in Gegenwart eines luftstabilen Eisenkomplexes gelang durch eine „Borrowing-Hydrogen”-Strategie. Aus leicht zugänglichen Substraten und Ethanol als C2-Baustein wurden unsymmetrische tertiäre Amine erhalten. Die reduktive Alkylierung von Iminen mit elektronenreichen Aryl- oder Alkyl-Substituenten am N-Atom kann so in Abwesenheit von molekularem Sauerstoff durchgeführt werden.
      PubDate: 2018-02-22T04:31:03.369766-05:
      DOI: 10.1002/ange.201800328
       
  • Discovery of a Fungal Multicopper Oxidase That Catalyzes the
           Regioselective Coupling of a Tricyclic Naphthopyranone To Produce
           Atropisomers.
    • Authors: Mio Kawaguchi; Taichi Ohshiro, Masayuki Toyoda, Satoshi Ohte, Junji Inokoshi, Isao Fujii, Hiroshi Tomoda
      Abstract: Atropisomer dinapinones (DP) A1 and A2 were isolated from a culture of Talaromyces pinophilus FKI-3864. Monapinone coupling enzyme (MCE), which dimerizes naphthopyranone monapinone (MP) A, was purified from a cell-free extract of T. pinophilus FKI-3864. MCE uses MPA as a substrate and regioselectively dimerizes it at the 8,8' positions to synthesize the atropisomers DPA1 and DPA2 at a ratio of approximately 1:2.5 without a cofactor. The optimal pH and temperature for MCE were 4.0 and 50°C, and the apparent Km and Vmax values for MPA were 72.7±23.2 μM and 1.21±0.170 μmol/min/mg protein, respectively. The MCE polypeptide is significantly homologous with multicopper oxidases. Heterologous expression of MCE and functional analysis confirmed that MCE catalyzes the regioselective coupling reaction of MPA to produce DPA. This is the first report that a fungal multicopper oxidase can catalyze the regioselective intermolecular oxidative phenol coupling to produce naphthopyranone atropisomers.
      PubDate: 2018-02-22T03:25:51.088058-05:
      DOI: 10.1002/ange.201800415
       
  • The Cyclic Hydrogen-Bonded 6-Azaindole Trimer and Its Prominent
           Excited-State Triple Proton Transfer Reaction
    • Authors: Pi-Tai Chou; Ting-Hsun Tu, Yi-Ting Chen, Yi-An Chen, Yu-Chen Wei, You-Hua Chen, Chi-Lin Chen, Jiun-Yi Shen, Yi-Han Chen, Ssu-Yu Ho, Kum-Yi Cheng, Shern-Long Lee, Chun-hsien Chen
      Abstract: We report a previously unrecognized feature in that 6-azaindole undergoes self-assembling via N(1)-H...N(6) hydrogen bond (H-bond) formation, forming a cyclic, triply H-bonded trimer. The 6-azaindole trimer formation is visualized by the scanning tunnelling microscopy. Remarkably, this H-bonded trimer undergoes excited-state triple proton transfer (ESTPT), resulting in a proton-transfer tautomer emission maximized at 435 nm (cf. 325 nm of the normal emission) in cyclohexane. Computational approaches further affirm the thermodynamically favourable H-bonded trimer formation and the associated ESTPT reaction. Thus, nearly half century after Michael Kasha discovered the double H-bonded dimer of 7-azaindole and its associated excited-state double proton transfer reaction[3], we demonstrate the triply H-bonded trimer formation of 6-azaindole and its ESTPT reaction.
      PubDate: 2018-02-22T00:50:34.009499-05:
      DOI: 10.1002/ange.201800944
       
  • The Fourth Alloying Mode by Way of Anti-Galvanic Reaction
    • Authors: Zhikun Wu
      Abstract: Anti-galvanic reaction (AGR) not only defies classic galvanic theory but also is a promising method for tuning noble metal nanoparticles' compositions, structures and properties. In particular, employing AGR for the preparation of alloy nanoparticles has recently received extensive interest. Herein, we report on a unprecedented alloying mode by way of AGR, in which the foreign atoms induce the structural transformation of the mother nanoparticles and enter the novel nanoparticles in a non-replacement fashion. A novel, active metal-doped, gold nanoparticle was facilely synthesized by this novel alloying mode, and its structure was resolved by single-crystal X-ray crystallography. Surprisingly, one CdSH motif was found in the protecting staples of the novel bimetal nanoparticle for the first time. The density functional theory (DFT) calculations revealed that the Au20Cd4(SH)(SR)19 is a 8e superatom cluster. Furthermore, although the Cd-doping does not essentially alter the absorption of the mother nanocluster, it distinctly enhances the stability and catalytic selectivity of the mother nanoclusters.
      PubDate: 2018-02-21T23:20:30.921109-05:
      DOI: 10.1002/ange.201800877
       
  • Readily production of flow reactor cartridges by 3D printing of
           thermostable enzymes
    • Authors: Manfred Maier; Carsten P. Radtke, Jürgen Hubbuch, Christof M. Niemeyer, Kersten S. Rabe
      Abstract: Compartmentalization of chemical reactions is an essential principle of life that provides a major source of innovation for the development of novel approaches in biocatalysis. To implement spatially controlled biotransformations, rapid manufacturing methods are needed for the production of biocatalysts applicable in flow systems. While three-dimensional (3D) printing techniques offer high throughput manufacturing capability, they are not usually compatible with the delicate nature of enzymes, which call for physiological processing parameters. We here demonstrate the utility of thermostable enzymes to realize biocatalytic agarose-based inks for a simple temperature-controlled 3D printing process. As examples we utilized an esterase and an alcohol dehydrogenase from thermophilic organisms as well as a decarboxylase, which has been thermostabilized by directed protein evolution. We applied the resulting 3D printed parts for a continuous, two-step sequential biotransformation in a fluidic setup.
      PubDate: 2018-02-21T13:20:27.104978-05:
      DOI: 10.1002/ange.201711072
       
  • Revealing Transient Concentration of CO2 in a Mixed Matrix Membrane by IR
           Microimaging and Molecular Modeling
    • Authors: Seungtaik Hwang; Rocio Semino, Beatriz Seoane, Marufa Zahan, Christian Chmelik, Rustem Valiullin, Marko Bertmer, Jürgen Haase, Freek Kapteijn, Jorge Gascon, Guillaume Maurin, Jörg Kärger
      Abstract: Through IR microimaging the spatially and temporally resolved development of the CO2 concentration in a ZIF-8@6FDA-DAM mixed matrix membrane was visualized during transient adsorption. By recording the evolution of the CO2 concentration, it is observed that the CO2 molecules propagate from the ZIF-8 filler, which acts as a transport "highway", towards the surrounding polymer. A high-CO2-concentration layer is formed at the MOF/polymer interface, which becomes more pronounced at higher CO2 gas pressures. A microscopic explanation of the origins of this phenomenon is suggested by means of molecular modeling. By applying a computational methodology combining quantum and force-field based calculations, the formation of microvoids at the MOF/polymer interface is predicted. Grand Canonical Monte Carlo simulations further demonstrate that CO2 tends to preferentially reside in these microvoids, which is expected to facilitate CO2 accumulation at the interface.
      PubDate: 2018-02-21T09:50:32.648631-05:
      DOI: 10.1002/ange.201713160
       
  • Classical N-Heterocyclic Carbenes Derived Crystalline Radicals
    • Authors: Rajendra Ghadwal; Dennis Rottschäfer, Beate Neumann, Hans-Georg Stammler, Maurice van Gastel, Diego Andrada
      Abstract: One electron reduction of C2-arylated 1,3-imidazoli(ni)um salts (IPrAr)Br (Ar = Ph, 3a; 4-DMP, 3b; 4-DMP = 4-Me2NC6H4) and (SIPrAr)I (Ar = Ph, 4a; 4-Tol, 4b) derived from classical NHCs (IPr = :C{N(2,6-iPr2C6H3)}2CHCH, 1; SIPr = :C{N(2,6- iPr2C6H3)}2CH2CH2, 2) gives radicals [(IPrAr)]* (Ar = Ph, 5a; 4-DMP, 5b) and [(SIPrAr)]* (Ar = Ph, 6a; 4-Tol, 6b). Each of 5a,b and 6a,b exhibits a doublet EPR signal, a characteristic of monoradical species. The first solid-state characterization of NHC-derived carbon-centered radicals 6a,b by single crystal X-ray diffraction is reported. DFT calculations indicate that the unpaired electron is mainly located at the original carbene carbon atom and stabilized by partial delocalization over the adjacent aryl group.
      PubDate: 2018-02-21T06:50:59.895305-05:
      DOI: 10.1002/ange.201801596
       
  • Literally green chemical synthesis of artemisinin from plant extracts
    • Authors: Susann Triemer; Kerry Gilmore, Giang T Vu, Peter H Seeberger, Andreas Seidel-Morgenstern
      Abstract: Active pharmaceutical ingredients are either extracted from biological sources - where they are synthesized in complex, dynamic environments - or prepared via step-wise chemical syntheses by reacting pure reagents and catalysts under controlled conditions. A combination of these two approaches, where plant extracts containing reagents and catalysts are utilized in intensified chemical syntheses, creates expedient and sustainable processes. We illustrate the principle by reacting crude plant extract, oxygen, acid, and light to produce artemisinin, a key active pharmaceutical ingredient of the most powerful anti-malaria drugs. The traditionally discarded extract of Artemisia annua plants contains dihydroartemisinic acid - the final biosynthetic precursor - as well as chlorophyll, which acts as a photosensitizer. Efficient illumination with visible light in a continuous flow setup produces artemisinin in high yield, and the artificial biosynthetic process outperforms syntheses using pure reagents.
      PubDate: 2018-02-21T06:50:25.160737-05:
      DOI: 10.1002/ange.201801424
       
  • Epoxy-functionalized Porous Organic Polymers via the Diels–Alder
           Cycloaddition Reaction for Atmospheric Water Capture
    • Authors: Yearin Byun; Ali Coskun
      Abstract: The synthesis of highly microporous, epoxy-functionalized porous organic polymers (ep-POPs) by a one-pot, catalyst-free Diels–Alder cycloaddition polymerization is reported. The high oxygen content of ep-POPs offer efficient hydrogen-bonding sites for water molecules, thus leading to high water-uptake capacities up to 39.2–42.4 wt % under a wide temperature range of 5–45 °C, which covers the span of climatic conditions and manufacturing applications in which such materials might be used. Importantly, ep-POPs demonstrated regeneration temperatures as low as 55 °C, as well as excellent water stability, recyclability, and high specific surface areas up to 852 m2 g−1.Durstige Polymere: Poröse organische Polymere mit Epoxygruppen wurden durch Diels-Alder-Cycloadditionspolymerisation in einem Eintopfverfahren ohne Katalysator synthetisiert. Wasserstoffbrücken zwischen den Epoxygruppen und Wassermolekülen optimieren die Bindungsaffinität, sodass eine Balance zwischen hoher Wasseraufnahme und niedriger Regenerationstemperatur erreicht wird.
      PubDate: 2018-02-21T06:25:02.812435-05:
      DOI: 10.1002/ange.201800380
       
  • Reversible Clustering of Gold Nanoparticles under Confinement
    • Authors: Ana Sánchez-Iglesias; Nathalie Claes, Diego M. Solís, Jose M. Taboada, Sara Bals, Luis M. Liz-Marzán, Marek Grzelczak
      Abstract: A limiting factor of solvent-induced nanoparticle self-assembly is the need for constant sample dilution in assembly/disassembly cycles. Changes in the nanoparticle concentration alter the kinetics of the subsequent assembly process, limiting optical signal recovery. Herein, we show that upon confining hydrophobic nanoparticles in permeable silica nanocapsules, the number of nanoparticles participating in cyclic aggregation remains constant despite bulk changes in solution, leading to highly reproducible plasmon band shifts at different solvent compositions.Veränderungen in der Nanopartikelkonzentration während der lösungsmittelinduzierten Nanopartikelaggregation beeinflussen die Kinetik dieses Prozesses. Werden hydrophobe Nanopartikel in durchlässigen Nanokapseln aus Kieselsäure eingeschlossen, bleibt die Anzahl an aggregierenden Nanopartikeln auch bei Änderungen der Lösungszusammensetzung gleich. Dies führt zu reproduzierbaren Verschiebungen der Plasmonenresonanz.
      PubDate: 2018-02-21T06:24:37.448959-05:
      DOI: 10.1002/ange.201800736
       
  • Zwei Diterpensynthasen für Spiroalbaten und Cembren A aus
           Allokutzneria albata
    • Authors: Jan Rinkel; Lukas Lauterbach, Patrick Rabe, Jeroen S. Dickschat
      Abstract: Zwei bakterielle Diterpensynthasen aus dem Actinomyceten Allokutzneria albata wurden untersucht. Dies führte zur Identifizierung des strukturell neuartigen Produkts Spiroalbaten des ersten und Cembren A des zweiten Enzyms. Beide Enzyme wurden durch Isotopenmarkierungsexperimente, ortsgerichtete Mutagenese, Variation des Metallcofaktors und des pH-Wertes auf ihre Mechanismen untersucht. Für die Spiroalbaten-Synthase wurde eine pH- und Mn2+-abhängige Bildung des Nebenproduktes Thunbergol beobachtet, das biosynthetisch mit Spiroalbaten verwandt ist.Zwei Diterpensynthasen aus Allokutzneria albata wurden auf ihre Produkte untersucht, was zur Identifizierung der strukturell komplexen Verbindung Spiroalbaten und von Cembren A führte. Die Enzymmechanismen wurden durch Isotopenmarkierungsexperimente, Mutationen und Variation von Inkubationsbedingungen studiert. Für die Spiroalbaten-Synthase führten veränderte Bedingungen zur Bildung von Thunbergol.
      PubDate: 2018-02-21T06:22:12.777707-05:
      DOI: 10.1002/ange.201800385
       
  • Copper-Catalyzed Highly Stereoselective Trifluoromethylation and
           Difluoroalkylation of Secondary Propargyl Sulfonates
    • Authors: Xing Gao; Yu-Lan Xiao, Xiaolong Wan, Xingang Zhang
      Abstract: It is challenging to stereoselectively introduce a trifluoromethyl group (CF3) into organic molecules. To date, only limited strategies involving direct asymmetric trifluoromethylation have been reported. Herein, we describe a new strategy for direct asymmetric trifluoromethylation through the copper-catalyzed stereospecific trifluoromethylation of optically active secondary propargyl sulfonates. The reaction enables propargylic trifluoromethylation with high regioselectivity and stereoselectivity. The reaction could also be extended to stereospecific propargylic difluoroalkylation. Transformations of the resulting enantiomerically enriched fluoroalkylated alkynes led to a variety of chiral fluoroalkylated compounds, thus providing a useful protocol for applications in the synthesis of fluorinated complexes.Erst der Anfang: Die Titelreaktion ermöglicht hoch regio- und stereoselektive propargylische Trifluormethylierungen und Difluoralkylierungen zur Herstellung von vielseitigen Synthesebausteinen. Für den Kupfer-katalysierten Prozess wurde Konfigurationsumkehr beobachtet, sodass offenbar eine oxidative SN2-Addition von Kupfer an das sekundäre Propargylsulfonat stattfindet.
      PubDate: 2018-02-21T06:10:51.071599-05:
      DOI: 10.1002/ange.201711463
       
  • Ultrathin Palladium Nanomesh for Electrocatalysis
    • Authors: Jingjie Ge; Pei Wei, Geng Wu, Yudan Liu, Tongwei Yuan, Zhijun Li, Yunteng Qu, Yuen Wu, Hai Li, Zhongbin Zhuang, Xun Hong, Yadong Li
      Abstract: An ordered mesh of palladium with a thickness of about 3 nm was synthesized by a solution-based oxidative etching. The ultrathin palladium nanomeshes have an interconnected two-dimensional network of densely arrayed, ultrathin quasi-nanoribbons that form ordered open holes. The unique mesoporous structure and high specific surface area make these ultrathin Pd nanomeshes display superior catalytic performance for ethanol electrooxidation (mass activity of 5.40 Am g−1 and specific activity of 7.09 mA cm−2 at 0.8 V vs. RHE). Furthermore, the regular mesh structure can be applied to support other noble metals, such as platinum, which exhibits extremely high hydrogen evolution reaction (HER) activity and durability.Gitter „top-down”: Ein ultradünnes Pd-Nanogitter mit dicht angeordneten Quasi-Nanobändern und regelmäßigen Löchern wurde durch lösungsmittelbasierte freie Korrosion aus einer Pd-Nanoschicht erhalten. Das Nanogitter zeigt eine außergewöhnliche elektrokatalytische Leistung.
      PubDate: 2018-02-21T06:08:40.925278-05:
      DOI: 10.1002/ange.201800552
       
  • Mono-allyloxylated Cucurbit[7]uril Acts as an Unconventional Amphiphile to
           Form Light-Responsive Vesicles
    • Authors: Kyeng Min Park; Kangkyun Baek, Young Ho Ko, Annadka Shrinidhi, James Murray, Won Hyuk Jang, Ki Hean Kim, Jun-Seok Lee, Jejoong Yoo, Sungwan Kim, Kimoon Kim
      Abstract: Serendipitously, mono-allyloxylated cucurbit[7]uril (AO1CB[7]) was discovered to act as an unconventional amphiphile which self-assembles into light-responsive vesicles (AO1CB[7]VC) in water. Although the mono-allyloxy group, directly tethered on the periphery of CB[7], is much shorter (C4) than the hydrophobic tails of conventional amphiphiles, it played an important role in vesicle formation. Light-activated transformation of the allyloxy group by conjugation with glutathione was exploited as a remote tool to disrupt the vesicle. The vesicle showed on-demand release of cargo upon irradiation by a laser, after they were internalized into cancer cells. This result demonstrated the potential of AO1CB[7]VC as a new type of light-responsive intracellular delivery vehicle for the release of therapeutic cargo, within cells, on demand.Zufällig amphiphil: Monoallyloxyliertes Cucurbit[7]uril bildet in Wasser photoresponsive Vesikel, obwohl dieses ungewöhnliche Amphiphil nur eine kurze hydrophobe Kette trägt. Die Vesikel eignen sich für den Transport von Wirkstoffen in Krebszellen. Die Freisetzung der Fracht kann gezielt durch Zwei-Photonen-Absorption ausgelöst werden.
      PubDate: 2018-02-21T06:08:30.452582-05:
      DOI: 10.1002/ange.201713059
       
  • Incorporation of Non-canonical Amino Acids into 2,5-Diketopiperazines by
           Cyclodipeptide Synthases
    • Authors: Nicolas Canu; Pascal Belin, Robert Thai, Isabelle Correia, Olivier Lequin, Jérôme Seguin, Mireille Moutiez, Muriel Gondry
      Abstract: The manipulation of natural product biosynthetic pathways is a powerful means of expanding the chemical diversity of bioactive molecules. 2,5-diketopiperazines (2,5-DKPs) have been widely developed by medicinal chemists, but their biological production is yet to be exploited. We introduce an in vivo method for incorporating non-canonical amino acids (ncAAs) into 2,5-DKPs using cyclodipeptide synthases (CDPSs), the enzymes responsible for scaffold assembly in many 2,5-DKP biosynthetic pathways. CDPSs use aminoacyl-tRNAs as substrates. We exploited the natural ability of aminoacyl-tRNA synthetases to load ncAAs onto tRNAs. We found 26 ncAAs to be usable as substrates by CDPSs, leading to the enzymatic production of approximately 200 non-canonical cyclodipeptides. CDPSs constitute an efficient enzymatic tool for the synthesis of highly diverse 2,5-DKPs. Such diversity could be further expanded, for example, by using various cyclodipeptide-tailoring enzymes found in 2,5-DKP biosynthetic pathways.Nichtnatürlich und doch natürlich: Cyclodipeptid-Synthasen (CDPSs) sind Enzyme, die Aminoacyl-tRNAs aus der Translationsmaschinerie abzweigen, um Cyclodipeptide herzustellen. Die natürliche Promiskuität von Aminoacyl-tRNA-Synthetasen wurde genutzt, um zu zeigen, dass CDPSs ein breites Spektrum nichtkanonischer Aminosäuren als Substrate tolerieren. So gelang die Biosynthese von ca. 200 Cyclodipeptiden mit nichtkanonischen Aminosäuren.
      PubDate: 2018-02-21T06:08:19.545537-05:
      DOI: 10.1002/ange.201712536
       
  • Synthesis and Electronic Structure of Boron-Graphdiyne with an
           sp-Hybridized Carbon Skeleton and Its Application in Sodium Storage
    • Authors: Ning Wang; Xiaodong Li, Zeyi Tu, Fuhua Zhao, Jianjiang He, Zhaoyong Guan, Changshui Huang, Yuanping Yi, Yuliang Li
      Abstract: Boron-graphdiyne (BGDY), which has a unique π-conjugated structure comprising an sp-hybridized carbon skeleton and evenlydistributed boron heteroatoms in a well-organized 2D molecular plane, is prepared through a bottom-up synthetic strategy. Excellent conductivity, a relatively low band gap and a packing mode of the planar BGDY are observed. Notably, the unusual bonding environment of the all sp-carbon framework and the electron-deficient boron centers generates affinity to metal atoms, and thus provides extra binding sites. Furthermore, the expanded molecule pores of the BGDY molecular plane can also facilitate the transfer of metal ions in the perpendicular direction. The practical effect of the all sp-carbon structure and boron heteroatoms on the properties of BGDY are demonstrated in its performance as the anode in sodium-ion batteries.Nach einer Bottom-up-Strategie aufgebautes Bor-Graphdiin (BGDY) hat eine beispiellose Struktur, die Boratome an den Rändern von molekularen Poren aufweist. Das Gerüst aus sp-hybridisierten Kohlenstoffatomen und die Boratome stabilisieren interkalierte Metallatome. BGDY zeigt eine bemerkenswerte elektrochemische Leistungsfähigkeit in Natriumionen-Halbzellen.
      PubDate: 2018-02-21T06:08:11.020451-05:
      DOI: 10.1002/ange.201800453
       
  • Contra-Thermodynamic, Photocatalytic EZ Isomerization of Styrenyl Boron
           Species: Vectors to Facilitate Exploration of Two-Dimensional Chemical
           Space
    • Authors: John J. Molloy; Jan B. Metternich, Constantin G. Daniliuc, Allan J. B. Watson, Ryan Gilmour
      Abstract: Designing strategies to access stereodefined olefinic organoboron species is an important synthetic challenge. Despite significant advances, there is a striking paucity of routes to Z-α-substituted styrenyl organoborons. Herein, this strategic imbalance is redressed by exploiting the polarity of the C(sp2)−B bond to activate the neighboring π system, thus enabling a mild, traceless photocatalytic isomerization of readily accessible E-α-substituted styrenyl BPins to generate the corresponding Z-isomers with high fidelity. Preliminary validation of this contra-thermodynamic EZ isomerization is demonstrated in a series of stereoretentive transformations to generate Z-configured trisubstituted alkenes, as well as in a concise synthesis of the anti-tumor agent Combretastatin A4.Die Polarität der C(sp2)-B-Bindung wurde genutzt, um ein benachbartes π-System zu aktivieren und die photokatalytische Isomerisierung leicht erhältlicher E-α-substituierter Styrenyl-BPin-Ester in die entsprechenden Z-Isomere auszulösen. Die Methode ermöglicht eine Reihe stereoretentiver Umwandlungen zur Bildung Z-konfigurierter trisubstituierter Alkene sowie eine kurze Synthese des Antitumorwirkstoffs Combretastatin A4.
      PubDate: 2018-02-21T06:07:59.097295-05:
      DOI: 10.1002/ange.201800286
       
  • Highly Efficient Artificial Light-Harvesting Systems Constructed in
           Aqueous Solution Based on Supramolecular Self-Assembly
    • Authors: Shuwen Guo; Yongshang Song, Yuling He, Xiao-Yu Hu, Leyong Wang
      Abstract: Highly efficient light-harvesting systems were successfully fabricated in aqueous solution based on the supramolecular self-assembly of a water-soluble pillar[6]arene (WP6), a salicylaldehyde azine derivative (G), and two different fluorescence dyes, Nile Red (NiR) or Eosin Y (ESY). The WP6-G supramolecular assembly exhibits remarkably improved aggregation-induced emission enhancement and acts as a donor for the artificial light-harvesting system, and NiR or ESY, which are loaded within the WP6-G assembly, act as acceptors. An efficient energy-transfer process takes place from the WP6-G assembly not only to NiR but also to ESY for these two different systems. Furthermore, both of the WP6-G-NiR and WP6-G-ESY systems show an ultrahigh antenna effect at a high donor/acceptor ratio.Lichtsammelsysteme entstehen aus dem löslichen Pillar[6]aren (WP6), einem Salicylaldehyd-Azin-Derivat (G) und zwei verschiedenen Fluoreszenzfarbstoffen, Nilrot oder Eosin Y, durch Selbstorganisation in wässriger Lösung. Die supramolekularen Einheiten zeigen aggregationsinduziert verstärkte Emission und wirken als Donor in einem künstlichen Lichtsammelsystem. Der Farbstoff im WP6-G-Gerüst übernimmt die Rolle des Akzeptors.
      PubDate: 2018-02-21T06:07:46.108139-05:
      DOI: 10.1002/ange.201800175
       
  • Isolation of an Eleven-Atom Polydentate Carbon-Chain Chelate Obtained by
           Cycloaddition of a Cyclic Osmium Carbyne with an Alkyne
    • Authors: Congqing Zhu; Jun Zhu, Xiaoxi Zhou, Qin Zhu, Yuhui Yang, Ting Bin Wen, Haiping Xia
      Abstract: Carbon ligands have long played an important role in organometallic chemistry. However, previous examples of all-carbon chelating ligands are limited. Herein, we present a novel complex with an eleven-atom carbon chain as a polydentate chelating ligand. This species was formed by the [2+2+2] cycloaddition reaction of two equivalents of an alkyne with an osmapentalyne that contains the smallest carbyne bond angle (127.9°) ever observed. Density functional calculations revealed that electron-donating groups play a key role in the stabilization of this polydentate carbon-chain chelate. This process is also the first [2+2+2] cycloaddition reaction of an alkyne with a late-transition-metal carbyne complex. This study not only enriches the chemistry of polydentate carbon-chain chelates, but also deepens our understanding of the chelating ability of carbon ligands.Mehrzähnige Kohlenstoff-Liganden: Die erste organometallische Verbindung mit einer elfgliedrigen Kohlenstoffkette als mehrzähnigem Chelatliganden wurde durch die [2+2+2]-Cycloaddition eines Alkins mit dem Carbin-Komplex eines späten Übergangmetalls erhalten. So wurden neue Erkenntnisse zur Koordinationsfähigkeit von Kohlenstoff-Liganden gewonnen.
      PubDate: 2018-02-21T06:07:37.14408-05:0
      DOI: 10.1002/ange.201713391
       
  • Potassium-Zincate-Catalyzed Benzylic C−H Bond Addition of
           Diarylmethanes to Styrenes
    • Authors: Yu-Feng Liu; Dan-Dan Zhai, Xiang-Yu Zhang, Bing-Tao Guan
      Abstract: Direct functionalization of the benzylic C−H bond of diarylmethanes is an important strategy for the synthesis of diarylmethine-containing compounds. However, the methods developed to date for this purpose require a stoichiometric amount (usually more) of either a strong base or an oxidant. Reported here is the first catalytic benzylic C−H bond addition of diarylmethanes to styrenes and conjugated dienes. A potassium zincate complex, generated from potassium benzyl and zinc amide, acts as a catalyst and displays good activity and chemoselectivity. Considering the atom economy of the reaction and the ready availability of the catalyst, this reaction constitutes a practical, efficient method for diarylalkane synthesis.Gut gezinkt: Diarylmethane addieren in Gegenwart eines Kaliumzincat-Katalysators über ihr benzylisches Kohlenstoffzentrum an Styrole und konjugierte Diene. Die Reaktion eignet sich für eine große Auswahl an Substraten und ergibt die Produkte in hohen Ausbeuten.
      PubDate: 2018-02-21T06:07:30.778127-05:
      DOI: 10.1002/ange.201713165
       
  • Nitrogen-Based Lewis Acids: Synthesis and Reactivity of a Cyclic
           (Alkyl)(Amino)Nitrenium Cation
    • Authors: Jiliang Zhou; Liu Leo Liu, Levy L. Cao, Douglas W. Stephan
      Abstract: A room-temperature-stable crystalline cyclic (alkyl)(amino)nitrenium cation 2 features cationic nitrogen atom with a smaller HOMO–LUMO gap compared to that of a 1,2,3-triazolium 5 (an N-heterocyclic nitrenium cation). The low-lying LUMO of 2 results in an enhanced electrophilicity, which allowed for the formation of Lewis adducts with neutral Lewis bases, such as Me3P, nBu3P, and IiPr. The N-based Lewis acid 2 also forms an FLP with tBu3P but subsequently reacts with (PrS)2 to cleave the S−S bond. Both experimental and theoretical results suggest that the Lewis acidity of 2 is stronger than its N3 analogues.Das bei Raumtemperatur stabile kristalline, cyclische Alkylaminonitrenium weist ein kationisches Stickstoffatom auf und zeigt erhöhte Elektrophilie, wobei Lewis-Addukte mit Me3P, nBu3P und IiPr und ein frustriertes Lewis-Paar mit tBu3P erhalten werden.
      PubDate: 2018-02-21T06:07:23.754708-05:
      DOI: 10.1002/ange.201713118
       
  • Dikationische E4-Ketten (E=P, As, Sb, Bi) eingebettet in der
           Koordinationssphäre von Übergangsmetallen
    • Authors: Luis Dütsch; Martin Fleischmann, Stefan Welsch, Gábor Balázs, Werner Kremer, Manfred Scheer
      Abstract: Es wird ein Vergleich der Oxidationschemie der Komplexe [{CpMo(CO)2}2(μ,η2:η2-E2)] (E=P (A), As (B), Sb (C), Bi (D)) präsentiert. Die Oxidation von A–D mit [Thia]+ (=[C12H8S2]+) führt zur selektiven Bildung der dikationischen E4-Komplexe [{CpMo(CO)2}4(μ4,η2:η2:η2:η2-E4)]2+ (E=P (1), As (2), Sb (3), Bi (4)), die von vier [CpMo(CO)2]-Fragmenten stabilisiert werden. Die Bildung der entsprechenden Monokationen [A]+, [C]+ und [D]+ konnte weder durch Cyclovoltammetrie noch durch EPR- oder NMR-Spektroskopie nachgewiesen werden. Dies deutet auf eine schnelle Dimerisierung und keine Dissoziation in Lösung hin, was auch durch DFT-Rechnungen prognostiziert wurde. Allerdings belegen EPR-Messungen von 2 die Existenz geringer Mengen des Radikalkations [B]+ in Lösung. Die Einkristall-Röntgenstrukturanalysen zeigen, dass die Produkte 1 und 2 im Festzustand eine Zickzack-E4-Kette aufweisen, wohingegen 3 und 4 über einen zentralen E4-Käfig mit einer verzerrten, Butterfly-artigen Geometrie verfügen. Darüber hinaus kann 1 einfach und reversibel in eine symmetrische und eine asymmetrische Form umgewandelt werden.Präzedenzlose dikationische E4-Ketten und -Käfige (E=Pnicogen, außer N) werden mittels Oxidation der Komplexe [{CpMo(CO)2}2(μ,η2:η2-E2)] unter Bildung von E-E-Bindungen erhalten. Die dikationischen Gerüste enthalten keine organischen Substituenten und werden in der Koordinationssphäre von Molybdänkomplexen stabilisiert.
      PubDate: 2018-02-21T06:07:16.819285-05:
      DOI: 10.1002/ange.201712884
       
  • N-Carboxyanhydride Polymerization of Glycopolypeptides that Activate
           Antigen-Presenting Cells through Dectin-1 and Dectin-2
    • Authors: Matthew N. Zhou; Corleone S. Delaveris, Jessica R. Kramer, Justin A. Kenkel, Edgar G. Engleman, Carolyn R. Bertozzi
      Abstract: The C-type lectins dectin-1 and dectin-2 contribute to innate immunity against microbial pathogens by recognizing their foreign glycan structures. These receptors are promising targets for vaccine development and cancer immunotherapy. However, currently available agonists are heterogeneous glycoconjugates and polysaccharides from natural sources. Herein, we designed and synthesized the first chemically defined ligands for dectin-1 and dectin-2. They comprised glycopolypeptides bearing mono-, di-, and trisaccharides and were built through polymerization of glycosylated N-carboxyanhydrides. Through this approach, we achieved glycopolypeptides with high molecular weights and low dispersities. We identified structures that elicit a pro-inflammatory response through dectin-1 or dectin-2 in antigen-presenting cells. With their native proteinaceous backbones and natural glycosidic linkages, these agonists are attractive for translational applications.Liganden für Dectine: Die ersten chemisch definierten Liganden für Dectin-1 und -2 wurden entwickelt. Sie bestehen aus Glykopolypeptiden, die durch Polymerisation glykosylierter N-Carboxyanhydride aufgebaut wurden. Strukturen wurden identifiziert, die eine proinflammatorische Reaktion über Dectin-1 und -2 in Antigen-präsentierenden Zellen auslösen.
      PubDate: 2018-02-21T06:07:05.66065-05:0
      DOI: 10.1002/ange.201713075
       
  • Direct Observation of an Imidoylnitrene: Photochemical Formation of
           PhC(=NMe)−N and Me−N from 1-Methyl-5-phenyltetrazole
    • Authors: Manabu Abe; Didier Bégué, Hugo Santos-Silva, Alain Dargelos, Curt Wentrup
      Abstract: The imidoylnitrene 8, N-methyl-C-phenylimidoylnitrene, has been generated by laser photolysis of 1-methyl-5-phenyltetrazole 6 at 5 K and characterized by its ESR spectrum ( D/hc =0.9602, E/hc =0.0144 cm−1). In addition, the triplet excited states of 6 and of 2-methyl-5-phenyltetrazole 11 were also observed by ESR spectroscopy in the 5 K matrices (6: D/hc =0.123 cm−1, E/hc=0.0065 cm−1, 11: D/hc =0.126 cm−1, E/hc =0.0056 cm−1). The imidoylnitrene 8 is unstable both thermally (disappearing at 80 K) and photochemically (disappearing on continued irradiation at 266 nm). Methyl(phenyl)carbodiimide is the end product of photolysis.Gefangen in den Kälte: N-Methyl-C-phenylimidoylnitren (3) wurde zusammen mit Methylnitren (1) hergestellt und in seinem Triplett-Grundzustand mittels ESR-Spektroskopie bei 5 K charakterisiert ( D/hc =0.9602, E/hc =0.0144 cm−1). Die ESR-Spektren der angeregten Triplett-Zustände der Vorläufer, 1-Methyl-5-phenyltetrazol (2) und 2-Methyl-5-phenyltetrazol, wurden ebenfalls beobachtet.
      PubDate: 2018-02-21T06:06:56.009072-05:
      DOI: 10.1002/ange.201712689
       
  • Catalytic CO Oxidation by O2 Mediated by Noble-Metal-Free Cluster Anions
           Cu2VO3–5−
    • Authors: Li-Na Wang; Xiao-Na Li, Li-Xue Jiang, Bin Yang, Qing-Yu Liu, Hong-Guang Xu, Wei-Jun Zheng, Sheng-Gui He
      Abstract: Catalytic CO oxidation by molecular O2 is an important model reaction in both the condensed phase and gas-phase studies. Available gas-phase studies indicate that noble metal is indispensable in catalytic CO oxidation by O2 under thermal collision conditions. Herein, we identified the first example of noble-metal-free heteronuclear oxide cluster catalysts, the copper–vanadium bimetallic oxide clusters Cu2VO3–5− for CO oxidation by O2. The reactions were characterized by mass spectrometry, photoelectron spectroscopy, and density functional calculations. The dynamic nature of the Cu−Cu unit in terms of the electron storage and release is the driving force to promote CO oxidation and O2 activation during the catalysis.Edelmetallfreie Mischoxidcluster-Katalysatoren der Zusammensetzung Cu2VO3–5− für die CO-Oxidation durch O2 wurden experimentell identifiziert. Die Katalyse wird durch den Redoxzyklus innerhalb der Cu-Cu-Einheit der Cu2VO3–5−-Cluster angetrieben.
      PubDate: 2018-02-21T06:06:46.930565-05:
      DOI: 10.1002/ange.201712129
       
  • An Intracellular H2O2-Responsive AIEgen for the Peroxidase-Mediated
           Selective Imaging and Inhibition of Inflammatory Cells
    • Authors: Yong Cheng; Jun Dai, Chunli Sun, Rui Liu, Tianyou Zhai, Xiaoding Lou, Fan Xia
      Abstract: Inflammatory cells have gained widespread attention because inflammatory diseases increase the risk for many types of cancer. Therefore, it is urgent and important to implement detection and treatment methods for inflammatory cells. Herein, we constructed a theranostic probe with aggregation-induced emission (AIE) characteristics, in which tetraphenylethene (TPE) was modified with two tyrosine (Tyr) moieties. Owing to the H2O2-dependent, enzyme-catalyzed dityrosine formation, Tyr-containing TPE (TT) molecules crosslink through dityrosine linkages to induce the formation of hydrophobic aggregates, activating the AIE process in inflammatory cells that contain H2O2 and overexpress myeloperoxidase. The emission turn-on resulting from the crosslinking of TT molecules could be used to distinguish between inflammatory and normal cells. Moreover, the massive TT aggregates induced mitochondria damage and cell apoptosis. This study demonstrates that the H2O2-responsive peroxidase-activated AIEgen holds great promise for inflammatory-cell selective imaging and inhibition.Gruppentherapie: Ein Therapieansatz auf der Basis von aggregationsinduzierter Emission, kombiniert mit intrazellulärer H2O2- und Peroxidase-Antwort, wurde entwickelt. Das theranostische Verfahren erfasst inflammatorische Zellen durch selektive Bildgebung und ermöglicht deren Inhibition im Sinne einer gezielten Behandlung.
      PubDate: 2018-02-21T06:06:40.449267-05:
      DOI: 10.1002/ange.201712803
       
  • Supramolecular Nested Microbeads as Building Blocks for Macroscopic
           Self-Healing Scaffolds
    • Authors: Ziyi Yu; Ji Liu, Cindy Soo Yun Tan, Oren A. Scherman, Chris Abell
      Abstract: The ability to construct self-healing scaffolds that are injectable and capable of forming a designed morphology offers the possibility to engineer sustainable materials. Herein, we introduce supramolecular nested microbeads that can be used as building blocks to construct macroscopic self-healing scaffolds. The core–shell microbeads remain in an “inert” state owing to the isolation of a pair of complementary polymers in a form that can be stored as an aqueous suspension. An annealing process after injection effectively induces the re-construction of the microbead units, leading to supramolecular gelation in a preconfigured shape. The resulting macroscopic scaffold is dynamically stable, displaying self-recovery in a self-healing electronic conductor. This strategy of using the supramolecular assembled nested microbeads as building blocks represents an alternative to injectable hydrogel systems, and shows promise in the field of structural biomaterials and flexible electronics.Selbstheilende Struktur: Supramolekulare Mikroperlen, die ein Paar von komplementären Polymere isolieren können, wurden für den Aufbau makroskopischer selbstheilender Systeme verwendet. So bleiben die Polymere flüssig genug, um injizierbar zu sein, während die dynamischen molekularen Wechselwirkungen Selbstheilung ermöglichen.
      PubDate: 2018-02-21T06:06:28.235558-05:
      DOI: 10.1002/ange.201711522
       
  • Metal-Free and Alkali-Metal-Catalyzed Synthesis of Isoureas from Alcohols
           and Carbodiimides
    • Authors: Arnaud Imberdis; Guillaume Lefèvre, Pierre Thuéry, Thibault Cantat
      Abstract: The first addition of alcohols to carbodiimides catalyzed by transition-metal-free compounds employs 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) and its alkali metal salts. Isoureas are obtained in short reaction times and high yields when TBDK is used as the catalyst. Control of the coordination sphere of potassium with exogenous chelating ligands, in combination with mechanistic DFT calculations, demonstrated the role and positive influence of the alkali-metal cation on the kinetics.Die Addition von Alkoholen an Carbodiimide wird von übergangsmetallfreien Verbindungen, wie 1,5,7-Triazabicyclo[4.4.0]dec-5-en (TBD) und dessen Alkalimetallsalzen, katalysiert. Mit TBDK als Katalysator wurden Isoharnstoffe nach kurzer Reaktionszeit in guten Ausbeuten erhalten.
      PubDate: 2018-02-21T06:06:18.298963-05:
      DOI: 10.1002/ange.201711737
       
  • Conformation-Enabled Total Syntheses of Ohmyungsamycins A and B and
           Structural Revision of Ohmyungsamycin B
    • Authors: Joonseong Hur; Jaebong Jang, Jaehoon Sim, Woo Sung Son, Hee-Chul Ahn, Tae Sung Kim, Yern-Hyerk Shin, Changjin Lim, Seungbeom Lee, Hongchan An, Seok-Ho Kim, Dong-Chan Oh, Eun-Kyeong Jo, Jichan Jang, Jeeyeon Lee, Young-Ger Suh
      Abstract: The first total syntheses of the bioactive cyclodepsipeptides ohmyungsamycin A and B are described. Key features of our synthesis include the concise preparation of a linear cyclization precursor that consists of N-methyl amides and non-proteinogenic amino acids, and its macrolactamization from a bent conformation. The proposed structure of ohmyungsamycin B was revised based on its synthesis. The cyclic core of the ohmyungsamycins was shown to be responsible for the excellent antituberculosis activity, and ohmyungsamycin variants with truncated chains were evaluated for their biological activity.Schleifeninduziert: Die ersten Totalsynthesen des bioaktiven Cyclodepsipeptids Ohmyungsamycin A und der vorgeschlagenen Struktur von Ohmyungsamycin B basieren auf der effizienten Herstellung einer linearen Cyclisierungsvorstufe und Makrocyclisierung. Zudem wurde die vorgeschlagene Struktur von Ohmyungsamycin B revidiert und die korrekte Position der zusätzlichen Methyl-Gruppe aufgeklärt.
      PubDate: 2018-02-21T06:00:56.803843-05:
      DOI: 10.1002/ange.201711286
       
  • Site-Specific Studies of Nucleosome Interactions by Solid-State NMR
    • Authors: ShengQi Xiang; Ulric B. le Paige, Velten Horn, Klaartje Houben, Marc Baldus, Hugo van Ingen
      Abstract: Chromatin function depends on a dense network of interactions between nucleosomes and wide range of proteins. A detailed description of these protein-nucleosome interactions is required to reach a full molecular understanding of chromatin function in both genetics and epigenetics. Here, we show that the structure, dynamics and interactions of nucleosomes can be interrogated in a residue-specific manner using state-of-the-art solid-state NMR. Using sedimented nucleosomes, high-resolution spectra are obtained for both flexible histone tails and the non-mobile histone core. Through co-sedimentation of a nucleosome-binding peptide, we demonstrate that protein binding sites on the nucleosome surface can be determined. We believe that this approach holds great promise as it is generally applicable, extendable to include the structure and dynamics of the bound proteins, and scalable to interactions of proteins with higher-order chromatin structures, including isolated or cellular chromatin.
      PubDate: 2018-02-21T05:20:32.776829-05:
      DOI: 10.1002/ange.201713158
       
  • Highly Stable Lithium Metal Batteries Enabled by Regulating the Li+
           Solvation in Nonaqueous Electrolyte
    • Authors: Xue-Qiang Zhang; Xiang Chen, Xin-Bing Cheng, Bo-Quan Li, Xin Shen, Chong Yan, Jia-Qi Huang, Qiang Zhang
      Abstract: Safe and rechargeable lithium (Li) metal batteries have been hindered by the uncontrollable Li dendrites, where nonaqueous electrolyte always plays a significant role in practical batteries. Herein an emerging electrolyte based on a simple solvation strategy was proposed for highly stable Li metal anodes in both coin and pouch cells. Fluoroethylene carbonate (FEC) and lithium nitrate (LiNO3) were concurrently introduced into electrolyte, altering the solvation sheath of Li ions and then forming uniform solid electrolyte interphase (SEI) with abundant LiF and LiNxOy on a working Li metal anode that contributes to dendrite-free Li deposition. Ultrahigh Coulombic efficiency (99.96%) and long lifespans (1000 cycles) were achieved when FEC/LiNO3 electrolyte was applied in working batteries. The solvation chemistry of electrolyte was further explored by molecular dynamics simulations and first-principles calculations. This work provides a fruitful insight on understanding the critical role of the solvation of Li ions in forming SEI and delivers an effective route to optimize electrolytes for safe Li metal batteries.
      PubDate: 2018-02-21T05:20:23.158767-05:
      DOI: 10.1002/ange.201801513
       
  • Ein Instrumentarium von αv-RGD-Integrin-Inhibitoren: Wirkstoffsuche,
           Herausforderungen und Möglichkeiten
    • Authors: Richard J. D. Hatley; Simon J. F. Macdonald, Robert J. Slack, Joelle Le, Steven B. Ludbrook, Pauline T. Lukey
      Abstract: Es gibt einen Bedarf an wirksamen und sicheren Pharmazeutika für die Behandlung vernachlässigter Krankheiten, und aktuelle Bestrebungen bei der Suche von Inhibitoren des αv-RGD-Integrins zielen in diese Richtung. Allerdings erweist sich die Entwicklung von Wirkstoffen im Bereich der αv-Integrine aufgrund der sehr ähnlichen Strukturen dieser Rezeptoren und der polaren, zwitterionischen Natur des Pharmakophors als notorisch schwierig. Ziel dieses Aufsatzes ist es, einen Leitfaden für die Wirkstoffsuche in diesem Gebiet anzubieten. Wir tun dies, indem wir hier ein Instrumentarium von αv-Inhibitoren bestehend aus niedermolekularen Verbindungen (“kleinen Molekülen”) und Antikörpern vorstellen. Niedermolekulare αv-Verbindungen mit erweiterten Profilen in αvβ1-, αvβ3-, αvβ5-, αvβ6- und αvβ8-Zelladhäsionsassays wurden zusammengetragen, um die Auswahl der richtigen Verbindung für das richtige Experiment zu unterstützen. Dies sollte außerdem helfen, die partiellen Selektivitätsprofile von Verbindungen besser zu verstehen, die in unterschiedlichen Assays unterschiedlicher Forschungsinstitute generiert wurden. Die Perspektiven der zukünftigen Forschung an αv-Integrinen und die zentral wichtige Targetvalidierung werden diskutiert; fundierte Kenntnisse der Selektivität individueller RGD-αv-Integrine sind hier ganz entscheidend. Einblicke in das Design niedermolekularer RGD-Chemotypen für die topische oder orale Verabreichung werden vorgestellt und klinische Befunde zu fortgeschrittenen Molekülen betrachtet.Integrine sind Transmembranproteine, die die extrazelluläre Matrix mit dem Cytoskelett von Zellen verknüpfen und als Rezeptoren für die Signaltransduktion wirken. Dieser Aufsatz stellt ein Instrumentarium von αv-Inhibitoren bestehend aus kleinen Molekülen und Antikörpern vor und soll als Leitfaden für die Wirkstoffentwicklung im Bereich der αv-Integrine dienen.
      PubDate: 2018-02-21T05:15:38.667776-05:
      DOI: 10.1002/ange.201707948
       
  • Revealing active species for aerobic alcohol oxidation using
           stoichiometrically uniform supported Pd catalysts
    • Authors: Dingsheng Wang; Pingyu Xin, Jia Li, Yu Xiong, Xi Wu, Juncai Dong, Wenxing Chen, Yu Wang, Lin Gu, Jun Luo, Hongpan Rong, Chen Chen, Qing Peng, Yadong Li
      Abstract: Supported metal catalysts are one of the foundations of modern chemical industry. The active species in such catalysts are always elusive to identify, and in the meanwhile large quantities of inert species can cause significant waste. Herein, using a stoichiometrically precise synthetic method, we prepare atomically dispersed palladium-cerium oxide (Pd1/CeO2) and hexapalladium cluster-cerium oxide (Pd6/CeO2), as confirmed by spherical-aberration-corrected transmission electron microscopy and X-ray absorption fine structure spectroscopy. We discover that, for aerobic alcohol oxidation, Pd1/CeO2 shows extremely high catalytic activity with a TOF of 6739 h-1 and satisfactory selectivity (almost 100% for benzaldehyde), while Pd6/CeO2 is inactive, indicating that the true active species are single Pd atoms. Theoretical simulations reveal that the bulkier Pd6 clusters hinder the interactions between hydroxyl groups and the CeO2 surface, thus suppressing synergy of Pd-Ce perimeter. This work provides a new way to maximize material utilization and reduce waste in supported metal catalysts.
      PubDate: 2018-02-21T04:23:48.747037-05:
      DOI: 10.1002/ange.201801103
       
  • Super-chelators for advanced protein labeling in living cells
    • Authors: Karl Gatterdam; Eike F. Joest, Marina S. Dietz, Mike Heilemann, Robert Tampé
      Abstract: Live-cell labeling, super-resolution microscopy, single-molecule applications, protein localization or chemically induced assembly are emerging approaches, which require specific and very small interaction pairs. The minimal disturbance of protein function is essential to derive unbiased insights into cellular processes. Here, we define a new class of hexavalent N-nitrilotriacetic acid (hexaNTA) chelators, displaying the highest affinity and stability of all NTA-based small interaction pairs described so far. Coupled to bright organic fluorophores with fine-tuned photo-physical properties, these super-chelator probes were delivered into human cells by chemically gated nanopores. These super-chelators permit kinetic profiling, multiplexed labeling of His6 and His12-tagged proteins as well as single-molecule based super-resolution imaging.
      PubDate: 2018-02-20T21:51:00.275728-05:
      DOI: 10.1002/ange.201800827
       
  • Odorant receptor 7D4 activation dynamics
    • Authors: Jerome Golebiowski; claire de march, jeremie topin, hiroaki matsunami, gleb novikov, kentaro ikegami, elise bruguera
      Abstract: Deciphering how an odorant activates an odorant receptor (OR) and how changes in specific OR residues affect its responsiveness are central to understanding how we smell. A joint approach combining site-directed mutagenesis and functional assays with computational modeling has been used to explore the signaling mechanics of OR7D4. In this OR, a genetic polymorphism affects our perception of androstenone. A total of 0.12 ms molecular simulations predicted that, similarly to observations from other G protein-coupled receptors with known experimental structures, an activation pathway connects the ligand and G protein binding site. The 3D model activation mechanism correlates with in vitro data and notably predicts that the OR7D4 WM variant does not activate. Upon activation, an OR-specific sequence motif is the convergence point of the mechanism. Our study suggests that robust homology modeling can serve as a powerful tool to capture OR dynamics related to smell perception.
      PubDate: 2018-02-20T13:50:37.06314-05:0
      DOI: 10.1002/ange.201713065
       
  • Customizing the Electrochemical Properties of Carbon Nanodots with
           Quinones in Bottom-Up Syntheses
    • Authors: Maurizio Prato; Francesco Rigodanza, Francesca Arcudi, Luka Dordevich
      Abstract: We show how the redox potentials of Carbon Nanodots (CNDs) can be modulated by employing quinones as electroactive precursors during the microwave-assisted synthetic step. We prepared and characterized a redox library of CNDs, demonstrating that this approach can promote the use of carbon nanodots for ad-hoc applications, including photocatalysis.
      PubDate: 2018-02-20T12:50:42.164768-05:
      DOI: 10.1002/ange.201801707
       
  • O2 sensitivity of [Fe]-hydrogenase in the Presence of Reducing Substrates
    • Authors: Gangfeng Huang; Tristan Wagner, Ulrich Ermler, Eckhard Bill, Kenichi Ataka, Seigo Shima
      Abstract: [Fe]-hydrogenase reversibly catalyzes the transfer of a hydride ion from H2 to methenyl-tetrahydromethanopterin (methenyl-H4MPT+) to form methylene-H4MPT. Its iron-guanylylpyridinol (FeGP) cofactor plays a key role in H2 activation. Here, we show that [Fe]-hydrogenase becomes O2-sensitive under turnover conditions in the presence of the reducing-substrates, methylene-H4MPT or methenyl-H4MPT+/H2. Only then, H2O2 is generated and decomposes the FeGP cofactor as demonstrated by spectroscopic analyses and the crystal structure of the inactivated enzyme. O2 reduction to H2O2 requires a reductant, which can be a catalytic intermediate transiently formed during the [Fe]-hydrogenase reaction. The most probable candidate is an iron-hydride species; its presence has already been predicted by theoretical studies of the catalytic reaction. Our finding supported the prediction because the same type of reduction reaction is described for ruthenium hydride complexes that hydrogenate polar compounds.
      PubDate: 2018-02-20T12:50:30.294839-05:
      DOI: 10.1002/ange.201712293
       
  • Enzymatic or in vivo installation of propargyl groups in combination with
           click chemistry enables enrichment and detection of methyltransferase
           target sites in RNA
    • Authors: Katja Hartstock; Benedikt Nilges, Anna Ovcharenko, Nicolas Cornelissen, Nikolai Puellen, Sebastian Leidel, Andrea Rentmeister
      Abstract: m6A is the most abundant internal modification in eukaryotic mRNA. It is introduced by METTL3-METTL14 and tunes mRNA metabolism, impacting cell differentiation and development. Precise transcriptome-wide assignment of m6A sites is of utmost importance. However, m6A does not interfere with Watson-Crick base pairing making polymerase-based detection challenging. We developed a chemical-biology approach for the precise mapping of methyltransferase (MTase) target sites based on the introduction of a bioorthogonal propargyl group in vitro and in cells. We show that propargyl can be introduced enzymatically by wild-type METTL3-METTL14. Reverse transcription terminated up to 65 % at m6A sites after bioconjugation and purification, hence enabling detection of METTL3-METTL14 target sites by next generation sequencing. Importantly, we implemented metabolic propargyl labeling of RNA MTase target sites in vivo based on propargyl-L-selenohomocysteine and validated different types of known rRNA methylation sites.
      PubDate: 2018-02-20T11:50:47.864445-05:
      DOI: 10.1002/ange.201800188
       
  • Chiral 1,3,2-Diazaphospholenes as Catalytic Molecular Hydrides for
           Enantioselective Conjugate Reductions
    • Authors: Nicolai Cramer; Solène Miaskiewicz, John H. Reed, Pavel A. Donets, Caio C. Oliveira
      Abstract: Secondary 1,3,2-diazaphospholenes have a polarized P‒H bond and are emerging as molecular hydrides. A class of chiral conformationally restricted methoxy-1,3,2-diazaphospholene catalysts is reported. We demonstrate their catalytic potential in enantioselective 1,4-reduction of α,β-unsaturated carbonyl derivatives comprising enones, acyl pyrroles and amides in enantioselectivities of up to 95.5:4.5 er.
      PubDate: 2018-02-20T11:50:36.265316-05:
      DOI: 10.1002/ange.201801300
       
  • Unprecedented Dearomatized Spirocyclopropane in a Sequential
           Rh(III)-catalyzed C-H Activation and Rearrangement Reaction
    • Authors: Xiaoming Wang; Yingzi Li, Tobias Knecht, Constantin Daniliuc, Ken Houk, Frank Glorius
      Abstract: An unprecedented dearomatized spirocyclopropane intermediate was discovered in a sequential Cp*Rh(III)-catalyzed C-H activation and Wagner-Meerwein-type rearrangement reaction. How the oxidative O-N bond is cleaved and the role of HOAc were uncovered in this study. Furthermore, a Cp*Rh(III)-catalyzed dearomatization reaction of N-(naphthalen-1-yloxy)acetamide with strained olefins was developed, affording a variety of spirocyclopropanes.
      PubDate: 2018-02-20T10:50:36.851959-05:
      DOI: 10.1002/ange.201800803
       
  • One-Pot Tandem Photoredox and Cross-Coupling Catalysis with a Single
           Pd-Carbodicarbene Complex
    • Authors: Tiow-Gan Ong; Yu-Chen Hsu, Vincent C.-C. Wang, Ka-Chun Au-Yeung, Chung-Yu Tsai, Chun-Chi Chang, Bo-Chao Lin, Yi-Tsu Chan, Chao-Ping Hsu, Glenn P. A. Yap, Titel Jurca
      Abstract: The combination of conventional transition metal-catalyzed coupling (2e- process) and photoredox catalysis (1e- process) has emerged as a powerful approach to catalyze difficult cross-coupling reactions under mild conditions. We report a Pd-carbodicarbene (CDC) complex that mediates both Suzuki-Miyaura coupling and photoredox catalysis for C-N bond formation upon visible-light irradiation. These two catalytic pathways can be further merged to promote both conventional transition-metal-catalyzed coupling and photoredox catalysis to mediate C-H arylation under ambient conditions with a single component catalyst in an efficient one-pot process.
      PubDate: 2018-02-20T10:21:15.155389-05:
      DOI: 10.1002/ange.201800951
       
  • Lewis Acid Catalyzed Enantioselective Desymmetrization of Donor-Acceptor
           Meso-Diaminocyclopropanes
    • Authors: Daniele Perrotta; Ming-Ming Wang, Jerome Waser
      Abstract: The first example of Lewis acid catalyzed enantioselective ring-opening desymmetrization of donor-acceptor meso-diaminocyclopropanes is reported herein. A copper(II)-catalyzed Friedel-Crafts alkylation of indoles and a pyrrole with an unprecedented meso-diaminocyclopropane delivered enantioenriched diastereomerically pure urea products, which are structurally related to natural and synthetic bioactive compounds. The development of a new ligand through the investigation of an underexplored subclass of BOX ligands was essential for obtaining high enantiomeric ratios.
      PubDate: 2018-02-20T10:20:36.378481-05:
      DOI: 10.1002/ange.201800494
       
  • Direct formation of C-C triple bonded structural motifs by on-surface
           dehalogenative homocoupling of tribromomethyl molecules
    • Authors: Qiang Sun; Xin Yu, Meiling Bao, Mengxi Liu, Jinliang Pan, Zeqi Zha, Liangliang Cai, Honghong Ma, Chunxue Yuan, Xiaohui Qiu, Wei Xu
      Abstract: On-surface synthesis shows significant potential in constructing novel nanostructures/nanomaterials, which has been intensely studied over the recent years. The formation of acetylenic scaffoldings provides an important route to the fabrication of emerging carbon nanostructures including carbyne, graphyne and graphdiyne, which involve the chemically vulnerable sp-hybridized carbons. Herein, we designed and synthesized a tribromomethyl group, by using the combination of high-resolution scanning tunneling microscopy and non-contact atomic force microscopy imaging and density functional theory calculations, we demonstrated that it is feasible to achieve the direct formation of C-C triple bonded structural motifs via on-surface dehalogenative homocoupling reactions. Correspondingly, we are able to convert the sp3 hybridized state to sp hybridized state of carbon atoms, i.e., from an alkyl group to an alkynyl one. Moreover, we successfully achieved the formation of dimer structures, one-dimensionalmolecular wires and two-dimensional molecular networks on Au(111) surface,which would inspire further studies towards the two-dimensional graphyne structures.
      PubDate: 2018-02-20T05:21:05.689209-05:
      DOI: 10.1002/ange.201801056
       
  • Iron-Catalyzed Cross-Coupling in the Synthesis of Pharmaceuticals: In
           Pursuit of Sustainability
    • Authors: Aleksandra Piontek; Elwira Bisz, Michal Szostak
      Abstract: The scarcity of precious metals has given raise to the development of sustainable strategies for metal-catalyzed cross-coupling reactions. The establishment of new catalytic methods using iron is attractive due to low cost, abundance, ready availability and very low toxicity of iron. In the last few years sustainable methods for iron-catalyzed cross-couplings have entered the critical area of pharmaceutical research. Most notably, iron is one of the very few metals that have been successfully field tested as highly effective base-metal catalysts in practical, kilogram-scale industrial cross-couplings, thus validating the potential and promise of iron-catalysis to address the challenge of sustainability for chemical synthesis. In this minireview, we critically discuss the strategic benefits of using iron catalysis as a green and sustainable alternative to precious metals in cross-coupling applications for the synthesis of pharmaceuticals. The minireview provides an essential introduction to the fundamental aspect of practical iron catalysis, highlights areas for improvement and identifies new fields to explore.
      PubDate: 2018-02-19T22:51:11.451123-05:
      DOI: 10.1002/ange.201800364
       
  • NiH-Catalyzed Reductive Relay Hydroalkylation: A Strategy for Remote sp3
           C-H Alkylation of Alkenes
    • Authors: Fang Zhou; Jin Zhu, Yao Zhang, Shaolin Zhu
      Abstract: The terminal-selective, remote sp3 C-H alkylation of alkenes was achieved by a NiH-catalyzed reductive, chainwalking and sequential alkylation relay process. This method allows the construction of unfunctionalized C(sp3)-C(sp3) bonds, under mild conditions from two simple feedstock chemicals, olefins and alkyl halides. The practical value of this transformation is further demonstrated by the large-scale and regioconvergent alkylation of isomeric mixtures of olefins with low catalyst loading.
      PubDate: 2018-02-19T22:50:49.919967-05:
      DOI: 10.1002/ange.201712731
       
  • Counting the Clicks in Fluorescent Polymer Networks
    • Authors: Diego Estupiñán; Christopher Barner-Kowollik, Leonie Barner
      Abstract: We introduce a fluorescence-based methodology enabling the quantification of ligation points in photochemically prepared polymer networks, addressing the vexed question of quantifying the number of linkages within networks. Well-defined α,ω-tetrazole-capped polymer strands prepared via RAFT polymerization are crosslinked under UV irradiation by a trimaleimide via nitrile imine-mediated tetrazole-ene cycloaddition. Thus, for each linkage point a fluorescent pyrazoline ring is formed, resulting fluorescent networks, which are degradable by aminolysis of the trithiocarbonate functionalities, resulting in soluble fragments. The fluorescence emission of the soluble network fragments correlates directly with the number of pyrazoline moieties originally present in the network, thus providing a direct measure of the elusive number of ligation points constituting the network. The herein introduced strategy based on a fluorescence readout is a powerful yet simple approach to quantify network formation processes applicable to a wide class of polymers accessible via RAFT.
      PubDate: 2018-02-19T21:51:17.702495-05:
      DOI: 10.1002/ange.201713388
       
  • Atomically dispersed metal sites in MOF-based materials for
           electrocatalytic and photocatalytic energy conversion
    • Authors: Zibin Liang; Chong Qu, Dingguo Xia, Ruqiang Zou, Qiang Xu
      Abstract: Metal sites play an essential role for both electrocatalytic and photocatalytic energy conversion applications. The highly ordered arrangements of the organic linkers and metal nodes and the well-defined pore structures of metal-organic frameworks (MOFs) make them ideal substrates to support atomically dispersed metal sites (ADMSs) located in their metal nodes, linkers, and pores. Besides, porous carbon materials doped with ADMSs can be derived from these ADMS-incorporated MOF precursors through controlled treatments. These ADMSs incorporated in pristine MOFs and MOF-derived carbon materials possess unique merits over the molecular or the bulk metal-based catalysts, bridging the gap between homogeneous and heterogeneous catalysts for energy conversion applications. In this review, recent progress and perspective of design and incorporation of ADMSs in pristine MOFs and MOF-derived materials for energy conversion applications are highlighted, which will hopefully promote further developments of advanced MOF-based catalysts in foreseeable future.
      PubDate: 2018-02-19T21:51:07.535036-05:
      DOI: 10.1002/ange.201800269
       
  • Phosphoric Acid Catalyzed Asymmetric [2+2]
           Cyclization/Penicillin-penillonic Acid Rearrangement
    • Authors: Ming Zhang; Changjun Yu, Junqiu Xie, Xudong Xun, Wangsheng Sun, Liang Hong, Rui Wang
      Abstract: The first example of asymmetric penicillin-penillonic acid (PPA) rearrangement was reported that is based on the first [2+2] cyclization followed by acid-catalyzed asymmetric rearrangement. In the presence of a phosphoric acid catalyst, the reaction of azlactones with β-carbolines generates α-amino-β-lactams, which undergo PPA rearrangement with high selectivities. This process represents the first [2+2] cyclization of azlactones with imines and the first PPA rearrangement, which are linked together by the phosphoric acid catalyst.
      PubDate: 2018-02-19T21:50:52.291924-05:
      DOI: 10.1002/ange.201712571
       
  • Visible-Light Photocatalysis: Does it make a difference in Organic
           Synthesis'
    • Authors: Leyre Marzo; Santhosh K. Pagire, Oliver Reiser, Burkhard König
      Abstract: Visible light photocatalysis has evolved over the last decade into a widely used method in organic synthesis. For many important transformations, such as cross-coupling reactions, alpha-amino functionalizations, cycloadditions, ATRA reactions, or fluorinations, photocatalytic variants have been reported. In this review, we try to compare classical and photocatalytic procedures for selected classes of reactions and highlight their advantages and limitations. In many cases, the photocatalytic reactions proceed at milder reaction conditions, typically at room temperature, and stoichiometric reagents are replaced by simple oxidants or reductants, like air oxygen or amines. This way, besides providing alternative protocols for established transformations that allow a broadening of the substrate scope, also new transformations become possible, especially by merging photocatalysis with organo- or metal catalysis. Does visible light photocatalysis make a difference in organic synthesis' The prospect to shuttle electrons back and forth to substrates and intermediates or to selectively transfer energy through a visible light absorbing photocatalyst holds the promise to improve current protocols in radical chemistry and to open up new avenues by accessing reactive species hitherto unknown.
      PubDate: 2018-02-19T14:50:27.887048-05:
      DOI: 10.1002/ange.201709766
       
  • A Stable Metal-Organic Framework Featuring Local Buffer Environment for
           Carbon Dioxide Fixation
    • Authors: Hongming He; Qi Sun, Wenyang Gao, Jason A. Perman, Fuxing Sun, Guangshan Zhu, Briana Aguila, Katherine Forrest, Brian Space, Shengqian Ma
      Abstract: A majority of metal-organic frameworks (MOFs) fail to preserve their physical and chemical properties after exposure to acidic, neutral, or alkaline aqueous solutions, therefore limiting their practical applications in many areas. The strategy demonstrated herein is the design and synthesis of an organic ligand that behaves as a buffer to drastically boost the aqueous stability of a porous MOF (JUC-1000), which maintains its structural integrity at low and high pH values. The local buffer environment resulting from the weak acid-base pairs of the custom-designed organic ligand also greatly facilitates the performance of JUC-1000 in the chemical fixation of carbon dioxide under ambient conditions, outperforming a series of benchmark catalysts.
      PubDate: 2018-02-19T12:50:30.084846-05:
      DOI: 10.1002/ange.201801122
       
  • Promoted Fixation of Molecular Nitrogen with Surface Oxygen Vacancies on
           Plasmon-Enhanced TiO2 Photoelectrodes
    • Authors: Chengcheng Li; Tuo Wang, Zhi-Jian Zhao, Weimin Yang, Jianfeng Li, Ang Li, Zhilin Yang, Geoffrey A. Ozin, Jinlong Gong
      Abstract: A hundred years on energy-intensive Haber-Bosch process continuously turn the nitrogen in air into fertilizer, nourishing billions of people while causing pollution and greenhouse gas emissions. The urgency of mitigating climate change motivates people to progress towards a more sustainable way in fixing nitrogen based on clean energy. Surface oxygen vacancies (surface Ovac) hold great potential for N2 adsorption and activation, but introducing Ovac on the very surface without affecting bulk properties remains a great challenge. This communication describes the promotional role of surface OVac in outer layers of amorphous TiO2 thin films in the adsorption and activation of nitrogen. This facilitates nitrogen reduction to ammonia by excited electrons from ultraviolet-light-driven rutile TiO2 nanorod arrays and visible-light-driven Au surface plasmons. This demonstration contributes to the ongoing efforts of developing new approaches for nitrogen fixation under ambient conditions. (i.e., room temperature, atmospheric pressure).
      PubDate: 2018-02-19T11:20:51.844349-05:
      DOI: 10.1002/ange.201713229
       
  • Postsynthetic Functionalization of Three-Dimensional Covalent Organic
           Framework for Selective Extraction of Lanthanide Ions
    • Authors: Qianrong Fang; Qiuyu Lu, Yunchao Ma, Hui Li, Xinyu Guan, Yusran Yusran, Ming Xue, Yushan Yan, Shilun Qiu, Valentin Valtchev
      Abstract: Chemical Functionalization of covalent organic frameworks (COFs) is critical to tune their properties and broaden their potential applications. However, the introduction of functional groups especially in three-dimensional (3D) COFs still remains largely unexplored. Here we report a general strategy for generating a 3D carboxyl-functionalized COF through postsynthetic modification of a hydroxyl COF, and for the first time explore the carboxyl COF for selective extraction of lanthanide ions. The obtained COF shows high crystalllinity, good chemical stability, and large specific surface area. Furthermore, the carboxyl COF displays high metal loading capacities together with excellent adsorption selectivity for Nd3+ over Sr2+ and Fe3+ confirmed by the Langmuir adsorption isotherms and ideal adsorbed solution theory (IAST) calculations. This study not only provides a strategy for versatile functionalization of 3D COFs, but also opens the route to their environmental related applications.
      PubDate: 2018-02-19T10:15:29.509145-05:
      DOI: 10.1002/ange.201712246
       
  • Towards structural studies of self-assembled subviral particles: combining
           cell-free expression with 100 kHz MAS NMR
    • Authors: Guillaume David; Marie-Laure Fogeron, Maarten Schledorn, Roland Montserret, Uta Haselmann, Susanne Penzel, Aurelie Badillo, Lauriane Lecoq, Patrice André, Michael Nassal, Ralf Bartenschlager, Beat H Meier, Anja Böckmann
      Abstract: Viral membrane proteins are prime targets in the combat against infection. Still, their structure determination remains a challenge, both with respect to sample preparation, and the need for structural methods allowing analysis in a native-like lipid environment. Cell-free protein synthesis and solid-state NMR are promising approaches in this context, one with respect to its high potential of native expression of complex proteins, and the other for its ability to analyze membrane proteins in lipids. We here show that milligram amounts of the small envelope protein of the duck hepatitis B virus (DHBV) can be produced using cell-free expression, and that the protein self-assembles into subviral particles. 2D proton-detected NMR spectra recorded at 110 kHz magic angle spinning on < 500 μg protein show a number of isolated peaks with linewidths comparable to model membrane proteins, paving the way for structural studies this homologous protein to a potential drug target in HBV infection.
      PubDate: 2018-02-19T09:27:51.055835-05:
      DOI: 10.1002/ange.201712091
       
  • Dual input regulation and positional control in hybrid
           oligonucleotide-discotic supramolecular wires
    • Authors: Miguel Ángel Alemán García; Eva Magdalena Estirado, Lech-Gustav Milroy, Luc Brunsveld
      Abstract: The combination of oligonucleotides and synthetic supramolecular systems allows for novel and long needed modes of regulation of the self-assembly of both molecular elements. Discotic molecules were conjugated with short oligonucleotides and their assembly into responsive supramolecular wires studied. The self-assembly of the discotics provides additional stability for DNA-duplex formation due to a cooperative effect. Reversely, the appended oligonucleotides allow for positional control of the discotic elements within the supramolecular wire. The programmed assembly of these hybrid architecture can be modulated via the DNA, e.g. by changing the number of base pairs or salt concentration, and via the discotic platform by the addition of discotics without oligonucleotide handles. These hybrid supramolecular-DNA structures allow for advanced levels of control over 1-D dynamic platforms with responsive regulatory elements at the interface with biological systems.
      PubDate: 2018-02-19T09:21:55.211079-05:
      DOI: 10.1002/ange.201800148
       
  • Carbon Atom Hybridization Matters: Ultrafast Humidity Response of
           Graphdiyne Oxides
    • Authors: Lanqun Mao; Hailong Yan, Shuyue Guo, Fei Wu, Ping Yu, Huibiao Liu, Yuliang Li
      Abstract: Graphdiyne (GDY), a new kind of 2D carbon allotrope consisting of sp- and sp2-hybridized carbon atoms, has been envisaged to be promising in fundamental studies and various applications due to their unique atomic arrangement and electronic structure as well as surface chemistry. We herein for the first time find that graphdiyne oxide (GDO) exhibits an ultrafast humidity response with an unprecedented response speed (~ 7 ms), which is considered to benefit from the unique carbon hybridization of GDO that contains acetylenic bonds with stronger electron-withdrawing property than ethylenic bonds in GO. The GDO-based humidity sensor shows an ultrafast response speed, good selectivity and high sensitivity. These properties well validate the sensor to monitor the respiration rate change of human and hypoxic rats. This study not only demonstrates the unprecedented humidity-sensing capability of GDO but also provides new insight into the structure-property relationship of 2D carbon materials.
      PubDate: 2018-02-19T07:15:24.626187-05:
      DOI: 10.1002/ange.201709417
       
  • Features of protonation of the simplest weakly basic molecules, SO2, CO,
           N2O, CO2, and others, by solid carborane superacids
    • Authors: Evgenii Stoyanov; Irina S Stoyanova
      Abstract: Experimental study on protonation of simple weakly basic molecules (L) by the strongest solid superacid, H(CHB11F11), showed that basicity of SO2 is high enough (during attachment to the acidic H atoms at partial pressure of 1 atm) to break the bridged H-bonds of the polymeric acid and to form a mixture of solid mono- and disolvates, LH+‧‧‧An˗ and L-H+-L. With a decrease in the basicity of L = CO (via C), N2O, and CO (via O), only proton monosolvates are formed, which approach L-H+-An species with convergence of the strengths of bridged H-bonds. The molecules with the weakest basicity, such as CO2 and weaker, when attached to the proton, cannot break the bridged H-bond of the polymeric superacid, and the interaction stops at stage of physical adsorption. It is shown here that under the conditions of acid monomerization, it is possible to protonate such weak bases as CO2, N2, and Xe.
      PubDate: 2018-02-19T06:21:07.808554-05:
      DOI: 10.1002/ange.201704645
       
  • Tailored microstructured hyperpolarizing matrices for optimal magnetic
           resonance imaging
    • Authors: Matthieu Cavaillès; Aurélien bornet, Xavier Jaurand, Basile Vuichoud, David Baudouin, Mathieu Baudin, Laurent Veyre, Geoffrey Baudenhausen, Jean-Nicolas Dumez, Sami Jannin, Christophe Copéret, Chloé Thieuleux
      Abstract: Tailoring the physical features and the porous network architecture of silica-based hyperpolarizing solids containing TEMPO radicals, known as HYPSO (HYbrid Polarizing SOlids), enable unprecedented performance of dissolution Dynamic Nuclear Polarization (d-DNP). High polarization values up to P(1H) = 99 % were reached for samples impregnated with a mixture of H2O:D2O and loaded in a 6.7 T polarizer at temperatures around 1.2 K. These HYPSO materials combine the best performance of homogeneous DNP formulations with the advantages of solid polarizing matrices which provide hyperpolarized solutions free of any - potentially toxic - additives (radicals and glass-forming agents). The hyperpolarized solutions can be expelled from the porous solids, filtered and rapidly transferred either to a Nuclear Magnetic Resonance (NMR) spectrometer or to a Magnetic Resonance Imaging (MRI) system.
      PubDate: 2018-02-19T05:22:46.761196-05:
      DOI: 10.1002/ange.201801009
       
  • The Dewar isomer of 1,2-dihydro-1,2-azaborinines: Isolation,
           fragmentation, and energy storage
    • Authors: Holger Bettinger; Klara Edel, Xinyu Xinyu, Jacob Ishibashi, Ashley Lamm, Cäcilia Maichle-Mössmer, Zachary Giustra, Shih-Yuan Liu
      Abstract: The photochemistry of 1,2-dihydro-1,2-azaborinine derivatives was studied under matrix isolation conditions and in solution. Photoisomerization occurs exclusively to the Dewar valence isomers upon irradiation with UV light (> 280 nm) with high quantum yield (46 %). Further photolysis with UV light (254 nm) results in the formation of cyclobutadiene and iminoborane. The thermal electrocyclic ring opening reaction of the Dewar valence isomer back to the 1,2-dihydro-1-tert-butyldimethylsilyl-2-mesityl-1,2-azaborinine has an activation barrier of 27.0 ± 1.2 kcal·mol-1. In the presence of Wilkinson's catalyst, the ring opening occurs rapidly and exothermically (H = -48 ± 1 kcal·mol-1) at room temperature.
      PubDate: 2018-02-19T05:21:44.147391-05:
      DOI: 10.1002/ange.201712683
       
  • Frontispiz: Enantio- and Diastereoselective Cyclopropanation of
           1-Alkenylboronates: Synthesis of 1-Boryl-2,3-Disubstituted Cyclopropanes
    • Authors: Javier Carreras; Ana Caballero, Pedro J. Pérez
      Abstract: Asymmetrische Cyclopropanierung A. Caballero, P. Pérez et al. stellen in ihrer Zuschrift auf S. 2358 eine Methode für die hoch selektive Umwandlung von endständigen Alkinen in 2,3-disubstituierte 1-Borylcyclopropane vor.
      PubDate: 2018-02-19T05:11:32.102675-05:
      DOI: 10.1002/ange.201880961
       
  • From Linear to Angular Isomers: Achieving Tunable Charge Transport in
           Single Crystal Indolocarbazoles via Delicate Synergetic CH/NH···Pi
           Interactions
    • Authors: Hui Jiang; Peng Hu, Jun Ye, Apoorva Chaturvedi, Keke K. Zhang, Yongxin Li, Yi Long, Denis Fichou, Christian Kloc, Wenping Hu
      Abstract: Four five fused-ring isomers were rationally designed and synthesized to investigate the isomeric influence of linear and angular shapes in affecting their molecular packing and resultant electronic properties. Single-crystal field-effect transistors showed mobility order of 5,7-ICZ (3.61 cm2 V-1 s-1)> 5,11-ICZ (0.55 cm2 V-1 s-1)> 5,12-ICZ (~10-5 cm2 V-1 s-1) and 11,12-ICZ (~10-6 cm2 V-1 s-1). Theoretical calculations based on density functional theory (DFT) and polaron transport model revealed that 5, 7-ICZ can reach higher mobilities than the others thanks to relatively higher hole transfer integral that links to stronger intermolecular interaction due to the presence of multiple NH···pi and CH···pi(py) interactions with energy close to common NH···N hydrogen bonds, as well as overall lower hole-vibrational coupling owing to the absence of coupling of holes to low frequency modes due to better pi conjugation.
      PubDate: 2018-02-18T23:47:12.032536-05:
      DOI: 10.1002/ange.201713288
       
  • Electrochemical Exfoliation of Pillared-layer Metal-Organic Framework for
           Boosting the Oxygen Evolution Reaction
    • Authors: Jin Huang; Yu Li, Rui-Kang Huang, Chun-Ting He, Li Gong, Qiong Hu, Lishi Wang, Yan-Tong Xu, Xiao-Yun Tian, Si-Yang Liu, Zi-Ming Ye, Fuxin Wang, Dong-Dong Zhou, Wei-Xiong Zhang, Jie-Peng Zhang
      Abstract: Having high surface areas and fully exposed active sites, two-dimensional (2D) materials and ultrathin nanosheets are advantageous for elevating the catalysis performance and elucidating the catalysis mechanism. 2D materials are mostly restricted to inorganic or organic materials based on covalent bonds, because strong bonding within two dimensions and weak interactions in the third dimension are beneficial to stabilize the 2D structure. Here, we report an electrochemical exfoliation strategy for synthesizing metal-organic 2D materials based on coordination bonds. A catechol functionalized ligand is used as the redox active pillar to construct a pillared-layer framework. As an electrocatalyst for water oxidation, the pillar ligand can be in-situ oxidized and removed to yield ultrathin (2 nm) nanosheets, giving extraordinary catalytic activity at pH = 13 with overpotential as low as 211 mV at 10 mA cm^-2 and turnover frequency as high as 34 s^-1 at an overpotential of 300 mV.
      PubDate: 2018-02-18T21:50:35.630931-05:
      DOI: 10.1002/ange.201801029
       
  • Tracking the Dynamic Folding and Unfolding of RNA G-Quadruplexes in Live
           Cells
    • Authors: Xiu-Cai Chen; Shuo-Bin Chen, Jing Dai, Jia-Hao Yuan, Tian-Miao Ou, Zhi-Shu Huang, Jia-Heng Tan
      Abstract: Due to the absence of methods for tracking RNA G-quadruplex dynamics, especially the folding and unfolding of this attractive structure in live cells, understanding of the biological roles of RNA G-quadruplexes is so far limited. Here we reported a new red-emitting fluorescent probe, QUMA-1, for a selective, continuous and real-time visualization of RNA G-quadruplexes in live cells. The applications of QUMA-1 in several previously intractable applications, including live-cell imaging of the dynamic folding, unfolding and movement of RNA G-quadruplexes and visualizing the unwinding of RNA G-quadruplexes by RNA helicase have been demonstrated. Notably, our real-time results revealed the complexity of the dynamics of RNA G-quadruplexes in live cells. We anticipate that the further application of QUMA-1 in combination with appropriate biological and imaging methods to explore the dynamics of RNA G-quadruplexes will uncover more information about the biological roles of RNA G-quadruplexes.
      PubDate: 2018-02-17T10:40:28.654417-05:
      DOI: 10.1002/ange.201801999
       
  • Lewis Acid Catalyzed Stereoselective Dearomative Coupling of Indolylboron
           Ate Complexes with D-A Cyclopropanes and Alkyl Halides
    • Authors: Saikat Das; Constantin Gabriel Daniliuc, Armido Studer
      Abstract: Indolylboron ate complexes readily generated from 2-lithio indoles and boronic esters undergo multicomponent dearomative coupling with D-A cyclopropanes and alkyl halides in the presence of Sc(OTf)3 as a catalyst. Reactions proceed with complete diastereoselectivity and excellent stereospecificity to provide indolines bearing three contiguous stereocenters. The valuable boronic ester moiety remains in the product and allows for subsequent functionalization.
      PubDate: 2018-02-17T04:40:34.367473-05:
      DOI: 10.1002/ange.201711923
       
  • N-Heterocyclic Carbene-Treated Gold Surfaces in Pentacene Organic
           
    • Authors: Aifeng Lv; Matthias Freitag, Kathryn M. Chepiga, Andreas H. Schäfer, Frank Glorius, Lifeng Chi
      Abstract: N-Heterocyclic carbene (NHC) molecules, which reacted with the surface of Au electrodes, have been successfully applied in the pentacene transistors. With the application of NHCs, the charge carrier mobility of pentacene transistors increased by five times, while the contact resistance at the pentacene-Au interface reduced down to 85%. Even after annealing the NHC-Au electrodes at 200 oC for two hours before pentacene deposition, the charge carrier mobility of the pentacene transistors did not decrease. The distinguished performance renders the NHCs as excellent alternatives to thiols as metal modifiers for the application in organic field-effect transistors (OFETs).
      PubDate: 2018-02-16T21:40:26.077642-05:
      DOI: 10.1002/ange.201713415
       
  • Nucleopeptide Assemblies Selectively Sequester ATP in Cells
    • Authors: Huaimin Wang; Zhaoqianqi Feng, Yanan Qin, Jiaqing Wang, Bing Xu
      Abstract: Here we report that assemblies of nucleopeptides selectively sequestrate ATP in complex conditions (e.g., serum and cytosol). We develop assemblies of nucleopeptides that selectively sequester ATP over ADP. Counteracting enzymes interconvert ATP and ADP to modulate the nanostructures formed by the nucleopeptides and the nucleotides. The nucleopeptides, sequestering ATP effectively in cells, slow down efflux pumps in multidrug resistance cancer cells, thus boosting the efficacy of an anticancer drug. Examining additional 11 nucleopeptides (including D- and L-enantiomers) yields five more nucleopeptides that differentiate ATP and ADP via either precipitation or gelation. As the first example of using assemblies of nucleopeptides for interacting with ATP and disrupting intracellular ATP dynamics, this work illustrates the use of supramolecular assemblies to interact with small and essential biological molecules for controlling cell behaviors
      PubDate: 2018-02-16T15:40:28.700099-05:
      DOI: 10.1002/ange.201712834
       
  • One-Step Synthesis of Hybrid Core-Shell Metal-Organic Frameworks
    • Authors: Xinyu Yang; Shuai Yuan, Lanfang Zou, Hannah Drake, Yingmu Zhang, Junsheng Qin, Ali Alsalme, Hongcai Zhou
      Abstract: Epitaxial growth of MOF-on-MOF composite is an evolving research topic. In current methods, the core-shell MOFs are synthesized via a stepwise strategy which involves growing the shell-MOFs on top of the preformed core-MOFs with matched lattice parameters. However, the inconvenient stepwise synthesis and the strict lattice-matching requirement have limited the development of core-shell MOFs. Herein, we demonstrate that hybrid core-shell MOFs with mismatching lattices can be synthesized under the guidance of nucleation kinetics. A series of MOF composites with mesoporous core and microporous shell were constructed and characterized by optical microscopy, powder X-ray diffraction, gas sorption measurement, and scanning electron microscopy. Isoreticular expansion of microporous shells and orthogonal modification of the core was realized to produce multifunctional MOF composites, which acted as size selective catalysts for olefin epoxidation with high activity and selectivity.
      PubDate: 2018-02-16T15:10:24.744237-05:
      DOI: 10.1002/ange.201710019
       
  • Rational tuning of fluorobenzene probes for cysteine-selective protein
           modification
    • Authors: Ahmed M. Embaby; Sanne Schoffelen, Christian Kofoed, Meldal Morten, Frederik Diness
      Abstract: Fluorobenzene probes for protein profiling through selective cysteine labeling have been developed by rational reactivity tuning. Tuning was achieved by selecting an electron-withdrawing para-substituent combined with variation of the number of fluorine substituents. Optimized probes chemo-selectively arylated cysteine residues in proteins under aqueous conditions. Probes linked to azide, biotin or a fluorophore were applicable to labeling of eGFP and albumin. Selective inhibition of cysteine proteases was also demonstrated with the probes. Additionally, probes were tuned for site selective labeling among cysteine residues and for activity based protein profiling in cell lysates.
      PubDate: 2018-02-16T13:40:48.628007-05:
      DOI: 10.1002/ange.201712589
       
  • Direct Measurement of Charge Regulation in Metalloprotein Electron
           Transfer
    • Authors: Collin T. Zahler; Hongyu Zhou, Alireza Abdolvahabi, Rebecca L. Holden, Sanaz Rasouli, Peng Tao, Bryan Shaw
      Abstract: Quantifying how a protein regulates its net electrostatic charge during electron transfer (ET) is a means of directly measuring factors that contribute to either redox potential and/or reorganization energy. Charge regulation by proteins during ET has never been measured because few tools exist to measure the net charge of a folded protein in solution at different oxidation states. Here, by using protein charge ladders and capillary electrophoresis, we determined that the net charge of myoglobin, cytochrome c, and azurin changed by 0.62 ± 0.06, 1.19 ± 0.02, and 0.51 ± 0.04 units upon single ET. Computational analysis predicts that these fluctuations in charge arise from changes in the pKa of multiple non-coordinating residues (predominantly histidine) and require between 0.42-0.90 eV. These results suggest that ionizable residues can tune the reactivity of redox centers via charge regulation.
      PubDate: 2018-02-16T13:40:30.435301-05:
      DOI: 10.1002/ange.201712306
       
  • Enhanced Photodynamic Therapy by Reduced Intracellular Glutathione Levels
           Employing Nano-MOF with Cu (II) as Active Center
    • Authors: Wei Zhang; Jun Lu, Xiaonan Gao, Ping Li, Wen Zhang, Yu Ma, Hui Wang, Bo Tang
      Abstract: In photodynamic therapy (PDT), the level of reactive oxygen species (ROS) produced in the cell directly determines therapeutic effect. Therefore, the development of photosensitizers combining the ability of reducing GSH levels through synergisticallyimproving ROS concentration to strengthen the efficacy of PDT for tumor is important. We report a nano-metal-organic framework based on Cu (II) as active center for PDT. This MOF-2 is readily uptaken by breast cancer cells, and high-level ROS is generated under light irradiation. Meanwhile, intracellular GSH is considerably decreased owing to absorption on MOF-2, synergistically increasing ROS concentration and accelerating apoptosis, thereby enhancing the effect of PDT. Notably, through the direct adsorption of GSH, MOF-2 showed comparable effect with commercial antitumor drug camptothecin in mouse breast cancer treatment. This work provides strong evidence for MOF-2 as a promising new PDT candidate and anti-cancer drug.
      PubDate: 2018-02-16T10:40:27.005198-05:
      DOI: 10.1002/ange.201710800
       
  • Selective sp3 C-H Aerobic Oxidation enabled by Deca-tungstate
           Photocatalysis in Flow
    • Authors: Gabriele Laudadio; Sebastian Govaerts, Ying Wang, Davide Ravelli, Hannes Koolman, Maurizio Fagnoni, Stevan Djuric, Timothy Noel
      Abstract: A mild and selective sp3 C-H aerobic oxidation enabled by deca-tungstate photocatalysis has been developed. The reaction can be significantly improved in a microflow reactor enabling the safe use of oxygen and the enhanced irradiation of the reaction mixture. Our method allows for the oxidation of both activated and unactivated C-H bonds (30 examples). The ability to selectively oxidize natural scaffolds, such as (-)-ambroxide, pregnenolone acetate, (+)-sclareolide and artemisinin exemplifies the utility of this new method.
      PubDate: 2018-02-16T10:05:41.409409-05:
      DOI: 10.1002/ange.201800818
       
  • Phosphinic Acid Based Linkers: New Building Block in MOF Chemistry
    • Authors: Jan Hynek; Petr Brázda, Jan Rohlíček, Michael G.S. Londesborough, Jan Demel
      Abstract: Metal-organic frameworks (MOFs) are a chemically and topologically diverse family of materials composed of inorganic nodes and organic linkers bound together by coordination bonds. In this contribution we present two significant innovations in this field. The first is the use of a new coordination group in phenylene-1,4-bis(methylphosphinic acid) (PBPA), a phosphinic acid analogue of commonly-used terephtalic acid. We show that the use of this new linker group leads to the formation of a hydrothermally stable permanently porous MOF structure. The second innovation is the application of electron diffraction tomography (EDT), coupled with dynamical refinement of the EDT data, to the elucidation of the structure of the new material including the localization of hydrogen atoms.
      PubDate: 2018-02-16T09:10:25.351856-05:
      DOI: 10.1002/ange.201800884
       
  • ADUC-Preise / Carl-Duisberg-Gedächtnispreis für Bill Morandi / Neue
           Mitglieder der Académie des Sciences / Max-Delbrück-Nachwuchspreis für
           Sabrina Disch / Novartis Early Career Award
    • PubDate: 2018-02-16T04:03:08.905872-05:
      DOI: 10.1002/ange.201801006
       
  • Die enantioselektive Totalsynthese von Bischinolizidin-Alkaloiden: Ein
           modularer “Inside-Out”-Zugang
    • Authors: Dagmar Scharnagel; Jessica Goller, Nicklas Deibl, Wolfgang Milius, Matthias Breuning
      Abstract: Charakteristisch für Bischinolizidin-Alkaloide ist ein chirales Bispidin-Kerngerüst (3,7-Diazabicylo[3.3.1]nonan), an das Kombinationen aus einem α,N-anellierten 2-Pyridon, endo- oder exo-α,N-anellierten Piperidin(on)en und einem exo-Allylsubstituenten angebracht sind. Wir entwickelten eine modulare “Inside-Out”-Strategie, die einen Zugang zu den meisten Vertretern dieser Naturstoffklasse erlaubt. Ihr Anwendungspotential wurde anhand der asymmetrischen Synthese von 21 Bischinolizidin-Naturstoffen demonstriert, darunter mehr als zehn enantioselektive Erstsynthesen. Schlüsselschritte sind die erste erfolgreiche Herstellung beider Enantiomere von C2-symmetrischem 2,6-Dioxobispidin durch Desymmetrisierung einer 2,4,6,8-Tetraoxo-Vorstufe, der Aufbau des α,N-anellierten 2-Pyridons über eine Enamin-Bromacrylsäure-Strategie und die Einführung von endo- oder, wahlweise, exo-anellierten Piperidin(on)en.Alle auf einen Streich: Ein diversitätsorientierter, modularer „Inside-Out”-Zugang zu Bischinolizidin-Naturstoffen wurde entwickelt und seine Flexibilität anhand der enantioselektiven Totalsynthese von 21 Alkaloiden demonstriert. Schlüsselschritte sind eine Desymmetrisierung, die Zugang zu beiden Enantiomeren eines C2-symmetrischen 2,6-Dioxobispidins erlaubt, und die Anellierung eines 2-Pyridons und von endo- oder exo-Piperidin(on)en an diesen chiralen Kernbaustein.
      PubDate: 2018-02-12T03:11:32.743185-05:
      DOI: 10.1002/ange.201712852
       
  • Kohlenhydratresponsive Oberflächenhaftung basierend auf dynamisch
           
    • Authors: Sebastian Lamping; Tobias Otremba, Bart Jan Ravoo
      Abstract: Ein Kleber, dessen starke Haftfähigkeit (2.38 kg) auf dynamisch kovalenter Chemie beruht, welche zudem wasserbeständig und durch Kohlenhydrateinfluss schaltbar ist, wird vorgestellt. Zu diesem Zweck wurden Glas- und Siliciumoberflächen mithilfe der oberflächeninitiierten radikalischen Atomtransferpolymerisation (surface-induced atom transfer radical polymerization, SI-ATRP) mit Copolymeren, die zum einen Phenylboronsäuren und zum anderen Catechole enthielten, funktionalisiert. Nach Strukturierung mit Mikrokontaktdruck (microcontact printing, μCP) wird aus den Polymerbürsten ein kohlenhydratresponsiver supramolekularer “Klettverschluss” erhalten.Verklebt und gelöst: Die Kombination von oberflächeninitiierter radikalischer Atomtransferpolymerisation und dynamischer kovalenter Chemie von Phenylboronsäuren und Catecholen führt zu einer supramolekularen Oberflächenhaftung. Die Oberflächenhaftung ist robust (2.38 kg cm−2), wasserbeständig und wiederverwendbar, aber löst sich nach Zugabe eines Kohlenhydrates.
      PubDate: 2018-02-09T02:28:07.975157-05:
      DOI: 10.1002/ange.201711529
       
  • Titelbild: Die enantioselektive Totalsynthese von
           Bischinolizidin-Alkaloiden: Ein modularer “Inside-Out”-Zugang (Angew.
           Chem. 9/2018)
    • Authors: Dagmar Scharnagel; Jessica Goller, Nicklas Deibl, Wolfgang Milius, Matthias Breuning
      Pages: 2283 - 2283
      Abstract: 21 natürliche Bischinolizidin-Alkaloide wurden nach einem modularen “Inside-out”-Ansatz hergestellt, den M. Breuning et al. in ihrer Zuschrift auf S. 2456 vorstellen. Unter den Beispielen sind mehr als zehn erste enantioselektive Totalsynthesen. Entscheidend waren die erfolgreiche Herstellung beider Enantiomere von C2-symmetrischem 2,6-Dioxobispidin durch Desymmetrisierung und die sukzessive α,N-Anellierung eines 2-Pyridons und endo- oder exo-kondensierter Piperidine an den chiralen Kernbaustein.
      PubDate: 2018-02-05T10:12:34.364326-05:
      DOI: 10.1002/ange.201800930
       
  • Innentitelbild: Durch zwei Liganden ermöglichte nicht-dirigierte
           C-H-Olefinierung von Arenen (Angew. Chem. 9/2018)
    • Authors: Hao Chen; Philipp Wedi, Tim Meyer, Ghazal Tavakoli, Manuel van Gemmeren
      Pages: 2284 - 2284
      Abstract: Wie viele Liganden braucht man, um eine Bindung zu wechseln' Die oxidative C-H-Arylierung von Olefinen (die Fujiwara-Moritani-Reaktion) litt bisher unter einer geringen Effizienz und der Notwendigkeit, die wertvollen Arene im Überschuss einsetzen zu müssen. M. van Gemmeren und Mitarbeiter berichten in ihrer Zuschrift auf S. 2523 über die Verwendung von zwei Liganden als Strategie zur Optimierung des in dieser Reaktion eingesetzten Palladiumkatalysators.
      PubDate: 2018-02-02T02:53:05.508958-05:
      DOI: 10.1002/ange.201800928
       
  • Graphisches Inhaltsverzeichnis: Angew. Chem. 9/2018
    • Pages: 2289 - 2300
      PubDate: 2018-02-19T05:11:36.46636-05:0
      DOI: 10.1002/ange.201880911
       
  • Top-Beiträge aus unseren Schwesterzeitschriften: Angew. Chem. 9/2018
    • Pages: 2302 - 2305
      PubDate: 2018-02-19T05:11:34.911741-05:
      DOI: 10.1002/ange.201880913
       
  • Keiji Morokuma (1934–2017)
    • Authors: Qiang Cui; Stephan Irle, Jamal Musaev
      Pages: 2310 - 2311
      Abstract: Keiji Morokuma, emeritierter William Henry Emerson Professor der Emory University und Forschungsgruppenleiter am Fukui Institute for Fundamental Chemistry, Kyoto University, ist am 27. November 2017 im Alter von 83 Jahren verstorben. Morokumas Beiträge bereicherten die theoretischen Methoden zur Bestimmung von Reaktionsmechanismen und den zugehörigen intermolekularen Wechselwirkungen.
      PubDate: 2018-02-02T02:52:52.014649-05:
      DOI: 10.1002/ange.201800390
       
  • Heißes Wasser ermöglicht Kristallinität in organischen
           Materialien
    • Authors: Miriam M. Unterlass
      Pages: 2314 - 2316
      Abstract: Hydrothermale Kristallisation wurde kürzlich angewendet, um amorphe Polymernetzwerke in Amid-verknüpfte, kovalent gebundene organische Gerüststrukturen zu überführen. Diese Arbeit wird im Kontext der Synthese und Kristallisation organischer Materialien mithilfe von Wasser bei hohen Temperaturen diskutiert.
      PubDate: 2018-01-30T08:21:18.824748-05:
      DOI: 10.1002/ange.201713359
       
  • Steigerung der Katalysatoreffizienz in der C-H-Aktivierungskatalyse
    • Authors: Tobias Gensch; Michael J. James, Toryn Dalton, Frank Glorius
      Pages: 2318 - 2328
      Abstract: Nur wenige Katalysatoren erreichen hohe Umsatzzahlen in Reaktionen zur Aktivierung von C-H-Bindungen. Stattdessen werden üblicherweise 10 Mol-% eines Katalysators in solchen Reaktionen eingesetzt. Wir geben eine repräsentative Übersicht über effiziente Katalysatornutzung in der C-H-Aktivierung, um diesem vernachlässigten Aspekt der Katalyseforschung mehr Aufmerksamkeit zukommen zu lassen und zukünftige Entwicklungen noch effizienterer C-H-Aktivierungen zu inspirieren. Wir zeigen Beispiele aus der Palladiumkatalyse, Cp*RhIII- und Cp*CoIII-katalysierter Reaktionen, der Borylierung und Silylierung von C-H-Bindungen sowie der C-H-Aktivierung von Methan. In diesen Reaktionen wurden bis zu zehntausende Katalysatorumsätze beobachtet.Los, Katalysator! C-H-Aktivierungsreaktionen mit hohen Katalysatorumsätzen sind immer noch sehr selten in der Literatur, und 10 Mol-% ist eine gängige Katalysatorbeladung in diesem Gebiet. Ein repräsentativer Überblick über effiziente katalytische C-H-Aktivierungen wird gegeben, um diesen vernachlässigten Aspekt der Katalysatorentwicklung hervorzuheben und zukünftige Arbeiten an noch effizienteren C-H-Aktivierungen zu inspirieren.
      PubDate: 2018-01-29T08:35:37.354996-05:
      DOI: 10.1002/ange.201710377
       
  • Lektion gelernt' Die molekularen Grundlagen von Kinase-gerichteten
           Therapien und Wirkstoffresistenz im nicht-kleinzelligen Lungenkrebs
    • Authors: Jonas Lategahn; Marina Keul, Daniel Rauh
      Pages: 2329 - 2335
      Abstract: Die Behandlung des nicht-kleinzelligen Lungenkrebs (NSCLC) erfährt derzeit eine Revolution. Innerhalb der letzten Dekade führten die gewonnenen Erkenntnisse über die biologische Bedeutung von Biomarkern und deren prädiktiver Charakter zur Entwicklung von Tyrosinkinase-Inhibitoren, die eine Alternative zur Chemotherapie darstellen. Die Verwendung dieser innovativen Therapeutika verbessert die Lebensqualität und erhöht das Überleben betroffener Patienten. Das detaillierte Verständnis der Biologie der Zielproteine gepaart mit innovativen chemischen Ansätzen zu deren Modulation, ermutigten weitere Forschungen auf diesem Gebiet. Vor diesem Hintergrund präsentieren wir einen Rückblick auf ausgewählte molekulare Aspekte der Zielproteine und geben einen Überblick über aktuelle Fragestellungen und Herausforderungen bei der rationalen Wirkstoffentwicklung zur Behandlung von NSCLC.Alternative zur Chemotherapie: Das über die letzte Dekade gewonnene Verständnis von Biomarkern und deren prädiktiven Eigenschaften führte zur Entwicklung einer Präzisionsmedizin, die die Lebensqualität und das Überleben von Patienten deutlich verbesserte. Dieser Kurzaufsatz beleuchtet ausgewählte Aspekte der Zielstrukturen und gibt einen Überblick über aktuelle Themen und Herausforderungen bei der Behandlung von Lungenkrebs (NSCLC).
      PubDate: 2018-01-12T03:06:23.527708-05:
      DOI: 10.1002/ange.201710398
       
  • Nanobodys: Strategien zur chemischen Funktionalisierung und
           intrazelluläre Anwendungen
    • Authors: Dominik Schumacher; Jonas Helma, Anselm F. L. Schneider, Heinrich Leonhardt, Christian P. R. Hackenberger
      Pages: 2336 - 2357
      Abstract: Nanobodys sind ein modernes Mittel zur Erkennung und Modulation von Antigenen, die für herkömmliche Antikörper unzugänglich sind. Aufgrund ihrer kompakten Form und ihrer hohen Stabilität werden sie häufig in der Grundlagenforschung verwendet. In diesem Aufsatz werden zentrale Aspekte der Funktionalisierung von Nanobodys nebst ausgewählten Anwendungen in der Molekularbiologie dargestellt. Während ältere Konjugationsstrategien auf der zufälligen Modifikation natürlicher Aminosäuren beruhen, basieren neuere Methoden auf ortsspezifischer Modifikation mit funktionellen Einheiten. Solche Techniken umfassen chemoenzymatische Ansätze, Ligation exprimierter Proteine und die Unterdrückung des Amber-Codons in Kombination mit bioorthogonalen Modifikationsstrategien. Mit einer ständig wachsenden Auswahl an Methoden aus der Proteinsynthese und -konjugation sind auch die Anwendungen auf dem Vormarsch. Diese reichen von hochentwickelter Bildgebung und Massenspektrometrie bis hin zum Einschleusen von Nanobodys in lebende Zellen, um intrazelluläre Antigene zu visualisieren und zu manipulieren.Nano-Bodybuilding: Kleine antigenbindende Proteine (Nanobodys) sind leistungsfähige Hilfsmittel in den Lebenswissenschaften. Durch Anwendung chemischer Markierungsstrategien lassen sich intrazelluläre Zielstrukturen bildlich darstellen und manipulieren.
      PubDate: 2018-01-26T03:35:55.626838-05:
      DOI: 10.1002/ange.201708459
       
  • Enantio- and Diastereoselective Cyclopropanation of 1-Alkenylboronates:
           Synthesis of 1-Boryl-2,3-Disubstituted Cyclopropanes
    • Authors: Javier Carreras; Ana Caballero, Pedro J. Pérez
      Pages: 2358 - 2362
      Abstract: A novel, highly enantio- and diastereoselective synthesis of 1-boryl-2,3-disubstituted cyclopropanes has been developed by means of the cyclopropanation of alkenylboronates with ethyl diazoacetate in the presence of catalytic amounts of a chiral copper(I) complex. The products can also be directly accessed from alkynes through an operationally simple, sequential hydroboration–cyclopropanation protocol. The resulting enantioenriched 1-boryl-2,3-disubstituted cyclopropanes are versatile synthetic intermediates that undergo further transformations at the carbon–boron bond.Mehrfach funktionalisierte, 1-Boryl-2,3-disubstituierte Cyclopropane werden in hohen Ausbeuten, Diastereo- und Enantioselektivitäten aus Alkenylboronsäureestern durch Umsetzung mit Diazoessigsäureethylester in Gegenwart eines Kupfer(I)-Bisoxazolin-Katalysators erhalten. Die Produkte sind vielseitige Synthesebausteine und durch das Vorhandensein einer Kohlenstoff-Bor-Bindung leicht modifizierbar.
      PubDate: 2018-01-02T08:36:00.45144-05:0
      DOI: 10.1002/ange.201710415
       
  • Seeded Polymerization through the Interplay of Folding and Aggregation of
           an Amino-Acid-based Diamide
    • Authors: Soichiro Ogi; Kentaro Matsumoto, Shigehiro Yamaguchi
      Pages: 2363 - 2367
      Abstract: Amino acid based diamides are widely used as a substructure in supramolecular polymers and are also key components of polypeptides that help to understand protein folding. The interplay of folding and aggregation of a diamide was used to achieve seed-initiated supramolecular polymerization. For that purpose, a pyrene-substituted diamide was synthesized in which pyrene is used as a tracer to monitor the supramolecular polymerization. Thermodynamics and time-dependent studies revealed that the folding of the diamide moiety, via the formation of intramolecular hydrogen bonds, effectively prevents a spontaneous nucleation that leads to supramolecular polymerization. Under such out-of-equilibrium conditions, the addition of seeds successfully initiates the supramolecular polymerization. These results demonstrate the utility of such amino acid based diamides in programmable supramolecular polymerizations.Wasserstoffbrücken steuern die Faltung einer Diamidgruppe und vermeiden dadurch effektiv die spontane Keimbildung für eine supramolekulare Polymerisation. Die Polymerisation des Pyrenderivats, als Beispiel für ein lumineszierendes konjugiertes π-System, lief dagegen unter Ungleichgewichtsbedingungen ab.
      PubDate: 2018-02-02T02:51:40.392212-05:
      DOI: 10.1002/ange.201712119
       
  • The Ideal Ionic Liquid Salt Bridge for the Direct Determination of Gibbs
           Energies of Transfer of Single Ions, Part I: The Concept
    • Authors: Valentin Radtke; Andreas Ermantraut, Daniel Himmel, Thorsten Koslowski, Ivo Leito, Ingo Krossing
      Pages: 2368 - 2371
      Abstract: Described is a procedure for the thermodynamically rigorous, experimental determination of the Gibbs energy of transfer of single ions between solvents. The method is based on potential difference measurements between two electrochemical half cells with different solvents connected by an ideal ionic liquid salt bridge (ILSB). Discussed are the specific requirements for the IL with regard to the procedure, thus ensuring that the liquid junction potentials (LJP) at both ends of the ILSB are mostly canceled. The remaining parts of the LJPs can be determined by separate electromotive force measurements. No extra-thermodynamic assumptions are necessary for this procedure. The accuracy of the measurements depends, amongst others, on the ideality of the IL used, as shown in our companion paper Part II.Extralos! Können Gibbs-Transferenergien einzelner Ionen ohne außerthermodynamische Annahmen bestimmt werden' Bisher lautete die Antwort „Nein”. Um ein „Ja” daraus zu machen, wird eine Methode vorgeschlagen, die auf einfachen potentiometrischen Messungen beruht. Eine zweite Zuschrift liefert erste experimentelle Belege hierfür.
      PubDate: 2018-02-05T10:18:44.764101-05:
      DOI: 10.1002/ange.201707333
       
  • The Ideal Ionic Liquid Salt Bridge for Direct Determination of Gibbs
           Energies of Transfer of Single Ions, Part II: Evaluation of the Role of
           Ion Solvation and Ion Mobilities
    • Authors: Andreas Ermantraut; Valentin Radtke, Niklas Gebel, Daniel Himmel, Thorsten Koslowski, Ivo Leito, Ingo Krossing
      Pages: 2372 - 2376
      Abstract: An important intermediate goal to evaluate our concept for the assumption-free determination of single-ion Gibbs transfer energies ΔtrG°(i, S1S2) is presented. We executed the crucial steps a) and b) of the methodology, described in Part I of this treatise, exemplarily for Ag+ and Cl- with S1 being water and S2 being acetonitrile. The experiments showed that virtually all parts of the liquid junction potentials (LJPs) at both ends of a salt bridge cancel, if the bridge electrolyte is an “ideal” ionic liquid, that is, one with nearly identical diffusion of anion and cation. This ideality holds for [N2225]+[NTf2]- in the pure IL, but also in water and acetonitrile solution. Electromotive force measurements of solvation cells between S1 and S2 demonstrated Nernstian behavior for Ag+ concentration cells and constant like cell potentials for solutions with five tested Ag+ counterions.Ideal: Ein Schritt hin zur Messung von Gibbs-Transferenergien einzelner Ionen ohne außerthermodynamische Annahmen wurde aufgezeigt. Die Messung von Zellspannungen mithilfe einer ionischen Flüssigkeit als ideale Salzbrücke konnte zeigen, dass praktisch alle Teile des Flüssigkeitsgrenzpotentials zwischen verschiedenen Lösungsmitteln für Ag+-Systeme umgangen werden, da [N2225]+ und [NTf2]− sowohl in der Salzbrücke als auch im Medium fast identische Diffusionseigenschaften aufweisen.
      PubDate: 2018-02-07T02:20:27.927079-05:
      DOI: 10.1002/ange.201707334
       
  • All-in-One Cellulose Nanocrystals for 3D Printing of Nanocomposite
           Hydrogels
    • Authors: Jieping Wang; Annalisa Chiappone, Ignazio Roppolo, Feng Shao, Erika Fantino, Massimo Lorusso, Daniel Rentsch, Kurt Dietliker, Candido Fabrizio Pirri, Hansjörg Grützmacher
      Pages: 2377 - 2380
      Abstract: Cellulose nanocrystals (CNCs) with>2000 photoactive groups on each can act as highly efficient initiators for radical polymerizations, cross-linkers, as well as covalently embedded nanofillers for nanocomposite hydrogels. This is achieved by a simple and reliable method for surface modification of CNCs with a photoactive bis(acyl)phosphane oxide derivative. Shape-persistent and free-standing 3D structured objects were printed with a mono-functional methacrylate, showing a superior swelling capacity and improved mechanical properties.Alleskönner: Multifunktionelle Cellulose-Nanokristalle (CNCs) wurden durch einfache Oberflächenimmobilisierung photoaktiver Gruppen erhalten. Die modifizierten CNCs dienen als hoch effiziente Photoinitiatoren unter sichtbarem Licht, Vernetzungsagentien und kovalent eingelassene Nanofüllstoffe für den 3D-Druck von Nanokomposithydrogelen, wobei als Monomer ein monofunktionelles Methacrylat ohne jedes konventionelle Vernetzungsagens zum Einsatz kommt.
      PubDate: 2018-01-16T09:51:08.744647-05:
      DOI: 10.1002/ange.201710951
       
  • Rapid Capture and Release of Nucleic Acids through a Reversible
           Photo-Cycloaddition Reaction in a Psoralen-Functionalized Hydrogel
    • Authors: Yizhe Zhang; Peggy P. Y. Chan, Amy E. Herr
      Pages: 2381 - 2385
      Abstract: Reversible immobilization of DNA and RNA is of great interest to researchers who seek to manipulate DNA or RNA in applications such as microarrays, DNA hydrogels, and gene therapeutics. However, there is no existing system that can rapidly capture and release intact nucleic acids. To meet this unmet need, we developed a functional hydrogel for rapid DNA/RNA capture and release based on the reversible photo-cycloaddition of psoralen and pyrimidines. The functional hydrogel can be easily fabricated through copolymerization of acrylamide with the synthesized allylated psoralen. The psoralen-functionalized hydrogel exhibits effective capture and release of nucleic acids spanning a wide range of lengths in a rapid fashion; over 90 % of the capture process is completed within 1 min, and circa 100 % of the release process is completed within 2 min. We observe no deleterious effects on the hybridization to the captured targets.Reversibler DNA- und RNA-Einfang: Ein Polyacrylamid-Gel wurde durch Copolymerisation von Acrylamid mit allyliertem Psoralen dahingehend modifiziert, dass es DNA/RNA effizient einfangen kann. Die reversible Photocycloaddition zwischen Psoralen und Pyrimidin führt zu DNA/RNA-Einfang und -Freisetzung binnen Minuten unter UV-Bestrahlung. Vielfältige DNA- und RNA-Sequenzen unterschiedlicher Länge reagieren in dieser Weise, und der Prozess ist kompatibel mit Hybridisierung.
      PubDate: 2018-01-24T04:10:25.594217-05:
      DOI: 10.1002/ange.201711441
       
  • Optical Control of a Biological Reaction–Diffusion System
    • Authors: Philipp Glock; Johannes Broichhagen, Simon Kretschmer, Philipp Blumhardt, Jonas Mücksch, Dirk Trauner, Petra Schwille
      Pages: 2386 - 2390
      Abstract: Patterns formed by reaction and diffusion are the foundation for many phenomena in biology. However, the experimental study of reaction–diffusion (R–D) systems has so far been dominated by chemical oscillators, for which many tools are available. In this work, we developed a photoswitch for the Min system of Escherichia coli, a versatile biological in vitro R–D system consisting of the antagonistic proteins MinD and MinE. A MinE-derived peptide of 19 amino acids was covalently modified with a photoisomerizable crosslinker based on azobenzene to externally control peptide-mediated depletion of MinD from the membrane. In addition to providing an on–off switch for pattern formation, we achieve frequency-locked resonance with a precise 2D spatial memory, thus allowing new insights into Min protein action on the membrane. Taken together, we provide a tool to study phenomena in pattern formation using biological agents.Von Licht geleitet: Das Min-System, ein biologisches Reaktions-Diffusions-System vieler Bakterien, kann in vitro mithilfe eines Azobenzol-vernetzten, von MinE abgeleiteten Peptids optisch gesteuert werden. Dieses System öffnet neue Wege für die Untersuchung biologischer Musterbildungsprozesse.
      PubDate: 2018-01-26T03:36:37.877843-05:
      DOI: 10.1002/ange.201712002
       
  • Discovery and Enumeration of Organic-Chemical and Biomimetic Reaction
           Cycles within the Network of Chemistry
    • Authors: Michał D. Bajczyk; Piotr Dittwald, Agnieszka Wołos, Sara Szymkuć, Bartosz A. Grzybowski
      Pages: 2391 - 2395
      Abstract: Analysis of the chemical-organic knowledge represented as a giant network reveals that it contains millions of reaction sequences closing into cycles. Without realizing it, independent chemists working at different times have jointly created examples of cyclic sequences that allow for the recovery of useful reagents and for the autoamplification of synthetically important molecules, those that mimic biological cycles, and those that can be operated one-pot.Eine Big-Data-Analyse des Netzwerks der organischen Chemie (NOC) offenbart, dass Chemiker unwissentlich Millionen zyklischer Reaktionssequenzen erschaffen haben, z. B. solche, die wertvolle Substrate zurückbringen, nützliche Chemikalien vervielfältigen und biologische Zyklen nachahmen. Das Bild zeigt einen Zyklustyp (die „Clique”; Farben: Jahre der erstmaligen Beschreibung einer Reaktion), in dem jedes Mitglied aus einem anderen in einem Schritt hergestellt werden kann.
      PubDate: 2018-02-06T08:20:44.289786-05:
      DOI: 10.1002/ange.201712052
       
  • Palladium-Catalyzed Asymmetric Aminohydroxylation of 1,3-Dienes
    • Authors: Hong-Cheng Shen; Yu-Feng Wu, Ying Zhang, Lian-Feng Fan, Zhi-Yong Han, Liu-Zhu Gong
      Pages: 2396 - 2400
      Abstract: A PdII-catalyzed asymmetric aminohydroxylation of 1,3-dienes with N-tosyl-2-aminophenols was developed by making use of a chiral pyridinebis(oxazoline) ligand. The highly regioselective reaction provides direct and efficient access to chiral 3,4-dihydro-2H-1,4-benzoxazines in high yield and enantioselectivity (up to 96:4 e.r.). The reaction employs readily available N-tosyl-2-aminophenols as a unique aminohydroxylation reagent and is complementary to known asymmetric aminohydroxylation methods.Ein neuer Ring: Die Titelreaktion von 1,3-Dienen mit N-Tosyl-2-aminophenolen in Gegenwart eines chiralen Pyridinbis(oxazolin)-Liganden ergibt optisch aktive 3,4-Dihydro-2H-1,4-benzoxazine in hohen Ausbeuten und mit hoher Regio- und Stereoselektivität.
      PubDate: 2018-02-06T02:31:00.11353-05:0
      DOI: 10.1002/ange.201712350
       
  • Highly Fluorescent Chiral N-S-Doped Carbon Dots from Cysteine: Affecting
           Cellular Energy Metabolism
    • Authors: Feng Li; Yiye Li, Xiao Yang, Xuexiang Han, Yang Jiao, Taotao Wei, Dayong Yang, Huaping Xu, Guangjun Nie
      Pages: 2401 - 2406
      Abstract: Cysteine-based chiral optically active carbon dots (CDs) and their effects on cellular energy metabolism, which is vital for essential cellular functions, have been barely reported. A green and effective synthesis strategy for chiral N-S-doped CDs (fluorescence quantum yield ca. 41.26 %) based on hydrothermal treatment of l- or d-cysteine at as low as 60 °C has been developed. This suggested that cysteine was instable in aqueous solutions and acts as a warning for high-temperature synthesis of nanomaterials using cysteine as stabilizer. Human bladder cancer T24 cells treated with l-CDs showed up-regulated glycolysis, while d-CDs had no similar effects. In contrast, no disturbance to the basal mitochondrial aerobic respiration of T24 cells was caused by either chiral CD.Der grüne Punkt: Eine grüne und effiziente Synthese chiraler Kohlenstoffpunkte (CDs; Fluoreszenzquantenausbeute ca. 41 %) beruht auf der hydrothermalen Behandlung von l- oder d-Cystein bei nur 60 °C. Die l-CDs ergeben eine chiralitätsabhängige Erhöhung der zellulären Glykolyse, beeinflussen aber nicht die ATP-Spiegel von T24-Zellen.
      PubDate: 2018-02-08T02:56:55.265328-05:
      DOI: 10.1002/ange.201712453
       
  • Electrochemical C−H/N−H Activation by Water-Tolerant Cobalt Catalysis
           at Room Temperature
    • Authors: Cong Tian; Leonardo Massignan, Tjark H. Meyer, Lutz Ackermann
      Pages: 2407 - 2411
      Abstract: Electrochemistry enabled C−H/N−H functionalizations at room temperature by external oxidant-free cobalt catalysis. Thus, the sustainable cobalt electrocatalysis manifold proceeds with excellent levels of chemoselectivity and positional selectivity, and with ample scope, thus allowing electrochemical C−H activation under exceedingly mild reaction conditions at room temperature in water.Strom und Wasser: Cobaltkatalysierte C-H/N-H-Funktionalisierungen, die elektrochemisch in H2O bei 23 °C ablaufen, machen den Einsatz giftiger oxidierender Metallreagentien überflüssig. Die nachhaltigen Cobalt-Elektrokatalysen sind hoch chemo- und positionsselektiv für ein breites Substratspektrum.
      PubDate: 2018-01-17T09:21:14.42323-05:0
      DOI: 10.1002/ange.201712647
       
  • Cationic Metallo-Polyelectrolytes for Robust Alkaline Anion-Exchange
           Membranes
    • Authors: Tianyu Zhu; Shichao Xu, Anisur Rahman, Emir Dogdibegovic, Peng Yang, Parasmani Pageni, Mohammad Pabel Kabir, Xiao-dong Zhou, Chuanbing Tang
      Pages: 2412 - 2416
      Abstract: Chemically inert, mechanically tough, cationic metallo-polyelectrolytes were conceptualized and designed as durable anion-exchange membranes (AEMs). Ring-opening metathesis polymerization (ROMP) of cobaltocenium-containing cyclooctene with triazole as the only linker group, followed by backbone hydrogenation, led to a new class of AEMs with a polyethylene-like framework and alkaline-stable cobaltocenium cation for ion transport. These AEMs exhibited excellent thermal, chemical and mechanical stability, as well as high ion conductivity.ROMP (Ringöffnungsmetathesepolymerisation) von Cobaltocenium-haltigem Cycloocten mit Triazol als einzigem Linker mit nachfolgender Rückgrat-Hydrierung liefert eine neue Klasse von Anionenaustauschmembranen (AEMs) mit Polyethylen-Gerüst und alkalistabilen Cobaltocenium-Kationen für den Ionentransport. Die AEMs zeigen eine exzellente thermische, chemische und mechanische Stabilität sowie eine hohe Ionenleitfähigkeit.
      PubDate: 2018-01-16T03:35:30.291707-05:
      DOI: 10.1002/ange.201712387
       
  • Design of Metal-Free Polymer Carbon Dots: A New Class of Room-Temperature
           Phosphorescent Materials
    • Authors: Songyuan Tao; Siyu Lu, Yijia Geng, Shoujun Zhu, Simon A. T. Redfern, Yubin Song, Tanglue Feng, Weiqing Xu, Bai Yang
      Pages: 2417 - 2422
      Abstract: Polymer carbon dots (PCDs) are proposed as a new class of room-temperature phosphorescence (RTP) materials. The abundant energy levels in PCDs increase the probability of intersystem crossing (ISC) and their covalently crosslinked framework structures greatly suppress the nonradiative transitions. The efficient methods allow the manufacture of PCDs with unique RTP properties in air without additional metal complexation or complicated matrix composition. They thus provide a route towards the rational design of metal-free RTP materials that may be synthesized easily. Furthermore, we find that RTP is associated with a crosslink-enhanced emission (CEE) effect, which provides further routes to design improved PCDs with diverse RTP performance. Our results show the potential of PCDs as a universal route to achieve effective metal-free RTP.Raumtemperatur-Phosphoreszenz: Polymere Kohlenstoffpunkte (PCDs) mit Metall-freier Raumtemperatur-Phosphoreszenz (RTP) wurden mithilfe einer einfachen Synthesemethode hergestellt. Der Beitrag eines durch Quervernetzung verstärkten Emissionseffekts auf die RTP-Erzeugung wurde verifiziert und als Richtlinie zur Vorhersage und Synthese einer Reihe von PCDs mit unterschiedlichen RTP-Leistungen vorgeschlagen (ISC=Intersystem Crossing).
      PubDate: 2018-02-06T09:27:07.29292-05:0
      DOI: 10.1002/ange.201712662
       
  • Orientation Control of Molecularly Functionalized Surfaces Applied to the
           Simultaneous Alignment and Sorting of Carbon Nanotubes
    • Authors: Serxho Selmani; Derek J. Schipper
      Pages: 2423 - 2427
      Abstract: Self-assembly has been relied upon for molecular alignment in many advanced technological applications. However, although effective, it is inherently limited in its capability for optimization. Despite the potential benefits, the seemingly fundamental strategy of external orientation control has yet to be realized. Herein we demonstrate an approach that allows control of the orientation of small molecules covalently bound to a surface. The method exploits an alignment relay technique, passing alignment information through a liquid-crystal medium to small molecules to control surface functionalization events. The method is technically simple and can be carried out on a bench top without the need for specialized equipment. Moreover, we demonstrate the utility of the resulting surfaces to address two long-standing problems in nanoscience: the sorting and alignment of single-walled carbon nanotubes. This new method enabled significant alignment of the nanotubes as well as length and diameter sorting.Molekülartistik: Eine als ART („alignment relay technique”) bezeichnete Methode zur Anordnung von kovalent gebundenen organischen Molekülen auf einer Oberfläche wurde entwickelt. Die resultierende funktionalisierte Oberfläche wurde für die simultane Ausrichtung, Längen- und Durchmessersortierung von einwandigen Kohlenstoffnanoröhren genutzt (siehe Bild).
      PubDate: 2018-02-05T10:14:55.700007-05:
      DOI: 10.1002/ange.201712779
       
  • Enzymatic Electrosynthesis of Alkanes by Bioelectrocatalytic
           Decarbonylation of Fatty Aldehydes
    • Authors: Sofiene Abdellaoui; Florika C. Macazo, Rong Cai, Antonio L. De Lacey, Marcos Pita, Shelley D. Minteer
      Pages: 2428 - 2432
      Abstract: An enzymatic electrosynthesis system was created by combining an aldehyde deformylating oxygenase (ADO) from cyanobacteria that catalyzes the decarbonylation of fatty aldehydes to alkanes and formic acid with an electrochemical interface. This system is able to produce a range of alkanes (octane to propane) from aldehydes and alcohols. The combination of this bioelectrochemical system with a hydrogenase bioanode yields a H2/heptanal enzymatic fuel cell (EFC) able to simultaneously generate electrical energy with a maximum current density of 25 μA cm−2 at 0.6 V and produce hexane with a faradaic efficiency of 24 %.Eine Aldehyd-deformylierende Oxygenase für die Decarbonylierung von Lipidaldehyden zu Alkanen und Ameisensäure ergibt zusammen mit einer elektrochemischen Grenzfläche ein System, das Alkane aus Aldehyden und Alkoholen generiert. In Kombination mit einer Hydrogenase-Bioanode bildet dieses bioelektrochemische System eine enzymatische H2/Heptanal-Brennstoffzelle, die gleichzeitig elektrische Energie und Hexan erzeugt.
      PubDate: 2018-01-16T10:01:40.980354-05:
      DOI: 10.1002/ange.201712890
       
  • Fe2Si5N8: Access to Open-Shell Transition-Metal Nitridosilicates
    • Authors: Philipp Bielec; Oliver Janka, Theresa Block, Rainer Pöttgen, Wolfgang Schnick
      Pages: 2433 - 2436
      Abstract: Highly condensed nitridosilicates doped with Eu2+ or Ce3+ play an important role in saving energy by converting the blue light of (In,Ga)N-LEDs. Although nitridosilicates are known for great structural variety based on covalent anionic Si-N networks, elemental variety is restricted. Presenting a significant extension of the latter, this work describes a general access to open-shell transition-metal nitridosilicates. As a proof-of-principle, the first iron nitridosilicate, namely Fe2Si5N8, was prepared by exchanging Ca2+ in α-Ca2Si5N8 applying a FeCl2 melt (salt metathesis). The title compound was analyzed by powder X-ray diffraction, EDX, ICP-OES, combustion analysis, TG/DSC, Mössbauer spectroscopy and magnetic susceptibility measurements. Furthermore, the structure of α-Ca2Si5N8 was determined at 1073 and 1173 K confirming the anionic network of α-Ca2Si5N8 providing possible migration pathways for the ion-exchange reaction.Kationenaustausch ist machbar in Nitridosilicaten: Durch den Einsatz von Salzschmelzen wurde das erste Eisennitridosilicat, Fe2Si5N8, hergestellt und somit die Elementvielfalt der Nitridosilicate deutlich erweitert. Auf der Grundlage der experimentellen Resultate wurde der Mechanismus des Ionenaustauschs untersucht, und mögliche Kanäle für die Wanderung zweiwertiger Kationen in α-Ca2Si5N8 wurden ausfindig gemacht.
      PubDate: 2018-02-06T06:10:50.97414-05:0
      DOI: 10.1002/ange.201713006
       
  • Manipulating Band Structure through Reconstruction of Binary Metal Sulfide
           for High-Performance Thermoelectrics in Solution-Synthesized
           Nanostructured Bi13S18I2
    • Authors: Biao Xu; Tianli Feng, Matthias T. Agne, Qing Tan, Zhe Li, Kazuki Imasato, Lin Zhou, Je-Hyeong Bahk, Xiulin Ruan, G. Jeffery Snyder, Yue Wu
      Pages: 2437 - 2442
      Abstract: Reconstructing canonical binary compounds by inserting a third agent can significantly modify their electronic and phonon structures. Therefore, it has inspired the semiconductor communities in various fields. Introducing this paradigm will potentially revolutionize thermoelectrics as well. Using a solution synthesis, Bi2S3 was rebuilt by adding disordered Bi and weakly bonded I. These new structural motifs and the altered crystal symmetry induce prominent changes in electrical and thermal transport, resulting in a great enhancement of the figure of merit. The as-obtained nanostructured Bi13S18I2 is the first non-toxic, cost-efficient, and solution-processable n-type material with z T=1.0.Bi2S3 wurde rekonstruiert, indem fehlgeordnetes Bi und schwach gebundenes I durch eine Synthese in Lösung addiert wurden. Die neuen Strukturmotive und die veränderte Kristallsymmetrie induzieren ausgeprägte Veränderungen in Elektronen- und Wärmeleitung. Das nanostrukturierte Bi13S18I2 ist ein ungiftiges, kostengünstiges und in Lösung prozessierbares thermoelektrisches Material vom n-Typ mit z T=1.0.
      PubDate: 2018-02-05T10:13:03.436099-05:
      DOI: 10.1002/ange.201713223
       
  • Synthesis and Structure Revision of Dichrocephones A and B
    • Authors: Volker M. Schmiedel; Young J. Hong, Dieter Lentz, Dean J. Tantillo, Mathias Christmann
      Pages: 2443 - 2446
      Abstract: Herein, we report the first enantioselective synthesis of dichrocephones A and B, which are cytotoxic triquinane sesquiterpenes with a dense array of stereogenic centers within a strained polycyclic environment. Key features include the application of a catalytic asymmetric Wittig reaction, followed by stereoselective functionalization of the propellane core into a pentacyclic intermediate. Double reductive ring cleavage yielded the proposed structure of dichrocephone A. Mismatched spectroscopic data for our synthetic material compared to the natural isolate led us to revise the previously proposed configuration based on biosynthetic considerations and NMR calculations. Implementation of these findings culminated in the synthesis of dichrocephones A and B.Cyclisieren und revidieren: Die Schlüsselschritte einer Totalsynthese der Dichrocephone A und B sind eine katalytische asymmetrische Wittig-Reaktion mit anschließender stereoselektiver Funktionalisierung des Propellan-Strukturkerns zu einer pentacyclischen Zwischenstufe. Abweichende spektroskopische Daten für das ursprüngliche Syntheseprodukt und den isolierten Naturstoff führten zu einer Revision der zuvor vorgeschlagenen Konfiguration.
      PubDate: 2018-01-16T09:56:39.170077-05:
      DOI: 10.1002/ange.201711766
       
  • Mechanochemical Activation of Iron Cyano Complexes: A Prebiotic Impact
           Scenario for the Synthesis of α-Amino Acid Derivatives
    • Authors: Carsten Bolm; Rita Mocci, Christian Schumacher, Mathias Turberg, Francesco Puccetti, José G. Hernández
      Pages: 2447 - 2450
      Abstract: Mechanochemical activation of iron cyano complexes by ball milling results in the formation of HCN, which can be trapped and incorporated into α-aminonitriles. This prebiotic impact scenario can be extended by mechanochemically transforming the resulting α-aminonitriles into α-amino amides using a chemical route related to early Earth conditions.Präbiotischer (An)Stoß: Mithilfe von Mechanochemie wird ein präbiotisches Einschlagszenario zur Bildung von α-Aminosäure-Derivaten nachgestellt. Eisencyanokomplexe setzen bei der Behandlung in einer Kugelmühle HCN frei, das abgefangen und in α-Aminonitrile eingebaut werden kann.
      PubDate: 2018-02-05T09:59:52.962948-05:
      DOI: 10.1002/ange.201713109
       
  • MoP Nanoparticles Supported on Indium-Doped Porous Carbon: Outstanding
           Catalysts for Highly Efficient CO2 Electroreduction
    • Authors: Xiaofu Sun; Lu Lu, Qinggong Zhu, Congyi Wu, Dexin Yang, Chunjun Chen, Buxing Han
      Pages: 2451 - 2455
      Abstract: Electrochemical reduction of CO2 into value-added product is an interesting area. MoP nanoparticles supported on porous carbon were synthesized using metal–organic frameworks as the carbon precursor, and initial work on CO2 electroreduction using the MoP-based catalyst were carried out. It was discovered that MoP nanoparticles supported on In-doped porous carbon had outstanding performance for CO2 reduction to formic acid. The Faradaic efficiency and current density could reach 96.5 % and 43.8 mA cm−2, respectively, when using ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate as the supporting electrolyte. The current density is higher than those reported up to date with very high Faradaic efficiency. The MoP nanoparticles and the doped In2O3 cooperated very well in catalyzing the CO2 electroreduction.MoP-Nanopartikel auf In-dotiertem porösem Kohlenstoff sind hervorragend für die Reduktion von CO2 zu Formiat geeignet. Faraday-Wirkungsgrad und Stromdichte können 96.5 % bzw. 43.8 mA cm−2 erreichen, wenn eine ionische Flüssigkeit als Elektrolyt eingesetzt wird. MoP und der In-dotierte Kohlenstoffträger wirken bei dieser Reaktion ausgezeichnet zusammen.
      PubDate: 2018-02-02T02:51:45.893736-05:
      DOI: 10.1002/ange.201712221
       
  • Direkte Umwandlung von Estern in heterocyclische Fluorophore
    • Authors: Christian Fischer; Christof Sparr
      Pages: 2461 - 2465
      Abstract: Obwohl heterocyclische Fluorophore vielseitig eingesetzt werden, kann mit den derzeitigen Synthesemethoden nur ein Bruchteil der erwünschten Farbstoffdiversität zugänglich gemacht werden. Hier beschreiben wir eine modulare Methode, welche verschiedenste Carbonsäureester direkt in ein breites Spektrum an Heteroanthrylium-Fluorophore umwandelt. Die doppelte Addition von Heteroatom-verknüpften 1,5-difunktionellen Organomagnesium-Reagenzien an Ester führt nach dehydratisierender saurer Aufarbeitung zur Bildung von Acridinium-, Xanthylium- und SiR-Fluorophoren. Diese einstufige Synthesemethode liefert organische Photoredoxkatalysatoren für die duale Katalyse mit Nickel und Fluorophore, welche Fluoreszenzverstärkungsreaktionen zulassen.Ein Spektrum an Estern: Mit Heteroatom-verbrückten 1,5-difunktionellen Organomagnesium-Reagenzien wurden Carbonsäureester direkt in Acridinium-, Xanthylium- und SiR-Fluorophore umgesetzt. Durch die Vielfalt von Estern lassen sich die chemischen, photophysikalischen und elektrochemischen Eigenschaften der Fluorophore ideal modulieren und für die Photoredoxkatalyse oder Reaktionen zur Fluoreszenzverstärkung einsetzen.
      PubDate: 2018-01-29T05:00:34.542484-05:
      DOI: 10.1002/ange.201711296
       
  • Synthese α-chiraler Ketone und chiraler Alkane durch eine
           radikalisch/ionische Kreuzungsreaktion von Vinyl-Bor-At-Komplexen
    • Authors: Carolin Gerleve; Marvin Kischkewitz, Armido Studer
      Pages: 2466 - 2469
      Abstract: Vinyl-Bor-At-Komplexe, hergestellt aus Enantiomeren-angereicherten Alkylpinakolboronsäureestern, durchlaufen stereospezifische, radikalisch induzierte 1,2-Wanderungen in radikalisch/ionischen Kreuzungsreaktionen. In dieser Dreikomponentenreaktion können verschiedene kommerziell erhältliche Alkyliodide als Radikalvorstufen verwendet werden, und Licht fungiert als Ketteninitiator. Eine nachfolgende Oxidation oder Protodeborylierung führt zu wertvollen α-chiralen Ketonen und chiralen Alkanen mit exzellenten Enantiomerenreinheiten.Radikalisch und ionisch: Verschiedene Vinyl-Bor-At-Komplexe, einfach zugänglich aus dem entsprechenden Pinakolboronsäureester und Vinyllithium, reagieren in einer radikalisch/ionischen Kreuzungsreaktion zu sekundären Alkylboronsäureestern, die entweder zu wertvollen α-chiralen Ketonen oxidiert oder zu Alkanen protodeboryliert werden können. Die Produkte werden in guten Gesamtausbeuten mit exzellenter Stereospezifität isoliert. Pin=Pinakolat.
      PubDate: 2018-01-16T09:51:28.9508-05:00
      DOI: 10.1002/ange.201711390
       
  • Disilenylsilylen-Reaktivität eines Cyclotrisilens
    • Authors: Hui Zhao; Kinga Leszczyńska, Lukas Klemmer, Volker Huch, Michael Zimmer, David Scheschkewitz
      Pages: 2470 - 2474
      Abstract: Die hoch reaktiven Silicium-Kongenere des Cyclopropens, die Cyclotrisilene (c-Si3R4), reagieren typischerweise unter π-Addition an ihre Si=Si-Doppelbindung oder unter σ-Insertion in eine ihrer Si-Si-Einfachbindungen. Im Gegensatz dazu führt die Behandlung von c-Si3Tip4 (Tip=2,4,6-iPr3C6H2) mit Styrol und Benzil zur Ringöffnung des Dreirings zum formalen [1+2]- bzw. [1+4]-Cycloadditionsprodukt des isomeren Disilenysilylens mit der C=C-Bindung bzw. dem Diketon. Bei erhöhten Temperaturen setzt das [1+2]-Additionsprodukt Styrol frei, das in einer [2+2]-Cycloaddition mit c-Si3Tip4 zu der thermodynamisch stabileren Hausan-Spezies reagiert.Geschwindigkeit ist entscheidend, um den Ring des Peraryl-substituierten Cyclotrisilens (R=2,4,6-iPr3C6H2) zu öffnen und ihm die Disilenylsilylen-Reaktivität gegenüber Benzil und Styrol zu entlocken. Im Falle von Styrol wandelt sich das kinetische Produkt mit einem intakten R2Si=SiR-Substituenten bei erhöhten Temperaturen unter Loslösung von Styrol in das gesättigte thermodynamische Produkt um, was durch ein Kontrollexperiment im Vakuum bewiesen wird.
      PubDate: 2018-02-08T05:11:11.098145-05:
      DOI: 10.1002/ange.201711833
       
  • Aktive Anode auf Molybdänbasis für dehydrierende Kupplungen
    • Authors: Sebastian B. Beil; Timo Müller, Sydney B. Sillart, Peter Franzmann, Alexander Bomm, Michael Holtkamp, Uwe Karst, Wolfgang Schade, Siegfried R. Waldvogel
      Pages: 2475 - 2479
      Abstract: Es wurde ein leistungsfähiges aktives Anodensystem entwickelt, das in 1,1,1,3,3,3-Hexafluor-2-propanol (HFIP) eingesetzt werden kann. Die Molybdänanode bildet in HFIP eine kompakte, leitfähige und elektroaktive Schicht aus höhervalenten Molybdänspezies. Dieses System kann als Ersatz für leistungsfähige, aber stöchiometrisch notwendige MoV-Reagenzien in dehydrierenden Kupplungen von Arenen eingesetzt werden. Diese Elektrolyse ist nachhaltiger und ermöglicht die Umsetzung eines breiten Spektrums von aktivierten Arenen.Elektrochemisch betrieben und mit einer vergleichbaren Reaktivität wie in MoV-Reagenzien vermittelt ein neuartiges aktive System auf Basis einer Molybdänanode und 1,1,1,3,3,3-Hexafluor-2-propanol dehydrierenden Arenkupplungen.
      PubDate: 2018-02-05T10:16:12.918869-05:
      DOI: 10.1002/ange.201712718
       
  • RuBisCO-inspirierte CO2-Aktivierung und Umwandlung durch einen
           Iridium(I)-Komplex
    • Authors: Jens Langer; Andrea Hamza, Imre Pápai
      Pages: 2480 - 2483
      Abstract: Die Synthese eines neuen Iridium(I)-Komplexes mit dem Enamidophosphan-Anion dbuP− und seine einzigartige Reaktivität gegenüber CO2 werden vorgestellt. Der Komplex bindet zwei Äquivalente CO2 und initiiert dabei eine hoch selektive Reaktionskaskade, die reversibel zur Spaltung sowohl von CO2 als auch des Enamido-Liganden führt. Die computergestützte Analyse des Systems lässt auf die Bildung eines relativ stabilen CO2-Komplexes als Schlüsselintermediat der CO2-Spaltung schließen, was experimentell bestätigt werden konnte. Die untersuchte Umwandlung weist einige Parallelen zur enzymatischen CO2-Fixierung durch RuBisCO auf.CO2 peration: Die hochselektive Bindung und Transformation von CO2 durch einen Iridiumkomplex zeigt eindeutig kooperative Effekte zwischen den beiden involvierten CO2-Molekülen. Die reversible Transformation ähnelt in einigen Aspekten der CO2-Fixierung durch das Enzym RuBisCO.
      PubDate: 2018-01-29T08:51:00.563068-05:
      DOI: 10.1002/ange.201712893
       
  • Photokatalytische aerobe Phosphatierung von Alkenen
    • Authors: Christian Depken; Felix Krätzschmar, Rene Rieger, Katharina Rode, Alexander Breder
      Pages: 2484 - 2488
      Abstract: Es wurde ein katalytisches Verfahren für die direkte Phosphatierung einfacher unpolarisierter Alkene entwickelt, das erstmals die Nutzung von gewöhnlichen unaktivierten Phosphorsäurediestern als Phosphatquelle und O2 als terminales Oxidationmittel ermöglicht. Die Methode erlaubt einen direkten und höchst ökonomischen Aufbau von verschiedenen Allylphosphatestern. Im Vergleich zu herkömmlichen Verfahren zur Gewinnung von Phosphorsäureestern ist die aerobe Phosphatierung vollständig komplementär, da erstere zum Großteil auf der Verwendung von vorfunktionalisierten oder voraktivierten Reagenzien wie Alkoholen oder Phosphorylhalogeniden beruhen. Ermöglicht wird die Reaktion durch das katalytische Zusammenwirken eines Photokatalysators und einer Selen-π-Säure über eine Abfolge von Ein-Elektronen-Transferprozessen.Die aerobe dehydrierende Kupplung einfacher Hydrogenphosphate mit unaktivierten Alkenen gelang erstmals durch das katalytische Zusammenspiel eines Photokatalysators (PK) und einer Chalkogen-Lewis-Säure (Se) und bietet Zugang zu einem breiten Spektrum von Allylphosphaten. Neben der hohen Praxistauglichkeit und Chemoselektivität ermöglicht die Methode auch die einfache konsekutive Redoxalkylierung von Olefinen mit Organocupraten.
      PubDate: 2018-01-17T08:45:37.010288-05:
      DOI: 10.1002/ange.201711599
       
  • Die katalytische, asymmetrische Mukaiyama-Michael-Reaktion von
           Silylketenacetalen mit α,β-ungesättigten Methylestern
    • Authors: Tim Gatzenmeier; Philip S. J. Kaib, Julia B. Lingnau, Richard Goddard, Benjamin List
      Pages: 2489 - 2493
      Abstract: α,β-Ungesättigte Ester sind einfach zugängliche, aber schwierig zu aktivierende Substrate in der asymmetrischen Katalyse. Wir stellen hier eine effiziente, allgemeine und hochenantioselektive Mukaiyama-Michael-Reaktion von Silylketenacetalen mit α,β-ungesättigten Methylestern vor, die durch silylierte Imidodiphosphorimidat(IDPi)-Lewis-Säuren katalysiert wird.Über 35 Millionen Jahre Reaktionshalbwertzeit ohne Katalyse: Zimtsäureester gehören zu den am wenigsten elektrophilen Michael-Akzeptoren und reagieren selbst mit starken Nukleophilen wie Silylketenacetalen extrem langsam ohne Katalyse. Hochaktive silylierte Imidodiphosphorimidat(IDPi)-Lewis-Säuren ermöglichen nun effiziente Mukaiyama-Michael-Reaktionen mit niedrigen Katalysatorbeladungen und exzellenter Kontrolle der Diastereo- und Enantioselektivität.
      PubDate: 2018-01-26T07:35:57.825327-05:
      DOI: 10.1002/ange.201712088
       
  • Reduktive Aminierung durch Photoredoxkatalyse über polaritätsangepassten
           Wasserstoffatomtransfer
    • Authors: Xingwei Guo; Oliver S. Wenger
      Pages: 2494 - 2498
      Abstract: Die Anregung eines RuII-Photosensibilisators in Gegenwart von Ascorbinsäure führt zur Reduktion von Iminium-Ionen zu elektronenreichen α-Aminoalkylradikalen, die durch einen thiolvermittelten Wasserstoffatomtransfer (HAT) in Produkte der reduktiven Aminierung umgewandelt werden. Mit diesem Konzept erfolgt die photoredoxkatalytische reduktive Aminierung von Carbonylverbindungen mit Aminen in guten bis hervorragenden Ausbeuten, wobei viele funktionelle Gruppen toleriert werden. Die drei entscheidenden Besonderheiten dieser Arbeit sind: (i) Das schnelle Abfangen elektronenreicher α-Aminoalkylradikale durch polaritätsangepassten HAT, (ii) die eigentliche Methode der reduktiven Aminierung durch Photoredoxkatalyse und (iii) die Anwendung dieser neuen Methode für zeitlich und räumlich kontrollierte Reaktionen auf festen Trägermaterialen, wie durch das Anbringen eines Fluoreszenzfarbstoffs auf einem aktivierten Celluloseträger durch photoredoxkatalytische reduktive Aminierung veranschaulicht wird.Licht ersetzt Hydrid: Eine Methode für die photoredoxkatalytische reduktive Aminierung wird vorgestellt, wobei neben Untersuchungen zum Anwendungsbereich auch detaillierte mechanistische Studien präsentiert werden. Die neue Methode ermöglicht zeitliche und räumliche Reaktionskontrolle (z. B. auf festen Trägern).
      PubDate: 2018-01-18T07:55:30.489756-05:
      DOI: 10.1002/ange.201711467
       
  • Lichtgesteuerte Freisetzung von Chemikalien aus polymeren Nano- und
           Mikropartikelbehältern
    • Authors: Christoph Englert; Ivo Nischang, Cornelia Bader, Philipp Borchers, Julien Alex, Michael Pröhl, Martin Hentschel, Matthias Hartlieb, Anja Traeger, Georg Pohnert, Stephanie Schubert, Michael Gottschaldt, Ulrich S. Schubert
      Pages: 2504 - 2508
      Abstract: Ein Diol-Linker mit Benzoin-Grundkörper wurde synthetisiert und zur Herstellung biokompatibler Polyester verwendet, die bei Bedarf durch UV-Licht vollständig abgebaut werden können. Um eine definierte Einkapselung von strukturell unterschiedlichen organischen Verbindungen in den hergestellten polymeren Materialien und einen gut kontrollierbaren Polymerabbauprozess zu ermöglichen, wurde eine umfassende strukturelle Optimierung der Monomerlinkereinheit durchgeführt. Die Verfolgung der Freisetzungskinetik verkapselter Modellverbindungen aus den polymeren Nano- und Mikropartikelbehältern wurde durch konfokale Laser-Scanning-Mikroskopie als grundsätzlicher Nachweis für gewünschte Anwendungen ermöglicht. Die physikochemischen Eigenschaften der Modellverbindungen reichen dabei von vollständig hydrophil bis vollständig hydrophob. Die nachgewiesene Biokompatibilität der verwendeten Polyester und ihrer Abbauprodukte ermöglichen weitere Anwendungen, z. B. als intelligente Verpackung von UV-empfindlichen pharmazeutisch oder ernährungsrelevanten Substanzen oder auch für räumlich selektive Selbstheilungsprozesse.Chemikalien auf Wunsch: Biokompatible Polyester wurden synthetisiert, die durch UV-Licht vollständig abgebaut werden können. Die Herstellung von Nano- und Mikropartikeln ermöglicht die definierte Verkapselung von organischen Verbindungen und einen kontrollierten Abbauprozess. Entsprechende Partikel können für anspruchsvolle Anwendungen, z. B. für die smarte Verpackung von UV-sensitiven pharmazeutischen Komponenten oder für räumlich selektive Selbstheilungsprozesse eingesetzt werden.
      PubDate: 2018-01-16T09:55:53.530709-05:
      DOI: 10.1002/ange.201710756
       
  • Kontrollierte Polymermikrostruktur in anionischer Polymerisation durch
           Kompartimentierung
    • Authors: Elisabeth Rieger; Jan Blankenburg, Eduard Grune, Manfred Wagner, Katharina Landfester, Frederik R. Wurm
      Pages: 2509 - 2513
      Abstract: Eine ideale, statistische anionische Copolymerisation wird durch physikalische Trennung der beiden Monomere in Kompartimente einer Emulsion gezwungen, um so Gradientencopolymere zu bilden. Das eine Monomer (M) ist vorzugsweise in den Tröpfchen löslich, während das andere (D) die kontinuierliche Phase einer DMSO-in-Cyclohexan-Emulsion bevorzugt. Die lebende anionische Copolymerisation von zwei aktivierten Aziridinen ist auf die DMSO-Kompartimente beschränkt, da die Polymerisation selektiv in diesen Tröpfchen stattfindet. Über die Verdünnung der kontinuierlichen Phase wird die lokale Konzentration von Monomer D in den Tröpfchen bestimmt und folglich der Gradient des resultierenden Copolymers. Die Copolymerisationen in der Emulsion werden durch Echtzeit-1H-NMR-Kinetiken überwacht, was die Änderung der Copolymerisationsparameter beider Monomere bei Verdünnung der kontinuierlichen Phase von ideal statistischen Copolymeren zu Gradientencopolymeren zeigt.Die selektive Löslichkeit von zwei Monomeren in einer DMSO:Cyclohexan-Emulsion erzwingt die Bildung einstellbarer Gradientencopolymere.
      PubDate: 2018-01-18T07:50:36.417754-05:
      DOI: 10.1002/ange.201710417
       
  • Die gemeinsamen Zwischenprodukte von Sauerstoffentwicklung und Auflösung
           während der Wasserelektrolyse an Iridium
    • Authors: Olga Kasian; Jan-Philipp Grote, Simon Geiger, Serhiy Cherevko, Karl J. J. Mayrhofer
      Pages: 2514 - 2517
      Abstract: Dem Wissen über Reaktionsmechanismen beim Katalysatorabbau während der Sauerstoffentwicklung kommt eine Schlüsselrolle bei der Weiterentwicklung von effizienteren und stabileren Elektrolyseuren zu, da die korrosiven Bedingungen an der Anode selbst für vielversprechende Materialien auf Iridium-Basis problematisch sind. Der Auflösungsmechanismus ist von komplexer Natur, und Zusammenhänge mit der Sauerstoffentwicklung sind wenig erforscht. Die Kopplung einer Rasterflusszelle mit Massenspektrometrie ermöglicht es, Sauerstoffentwicklungs- und Abbauprodukte in situ zu detektieren. Demnach sind bei hohen anodischen Potentialen mehrere Auflösungswege möglich, welche auch die Bildung von gasförmigem IrO3 beinhalten. Auf der Basis der experimentellen Daten werden mögliche Reaktionswege der, durch Sauerstoffentwicklung bedingten, Auflösung von Iridium aufgezeigt und die Rolle von gemeinsamen Intermediaten dieser Reaktionen diskutiert.Mögliche Reaktionswege der Iridium-Auflösung werden auf Basis von gemeinsamen Zwischenprodukten mit der Sauerstoffentwicklung vorgeschlagen. Abhängig von der Art der Elektrode und des Potentials sind mindestens drei Auflösungswege möglich. Bei hohen Stromdichten durchlaufen beide Reaktionen die Bildung von flüchtigem IrO3. Die Hemmung seiner Hydrolyse kann eine Strategie zur Verbesserung der Elektrodenstabilität während der Sauerstoffentwicklung werden.
      PubDate: 2018-02-05T10:18:51.020247-05:
      DOI: 10.1002/ange.201709652
       
  • Lanthanoidkomplexe mit Trizink-Kronenether als Katalysatoren für die
           alternierende Copolymerisation von Epoxid und CO2: eine durch
           Carboxylat-Anionen kontrollierte Telomerisierung
    • Authors: Haruki Nagae; Ryota Aoki, Shin-nosuke Akutagawa, Julian Kleemann, Risa Tagawa, Tobias Schindler, Gyeongshin Choi, Thomas P. Spaniol, Hayato Tsurugi, Jun Okuda, Kazushi Mashima
      Pages: 2518 - 2522
      Abstract: Eine neue Familie von Heterometallkatalysatoren auf Basis von dreifach metallierten makrocyclischen Tris(salen)-Liganden und Seltenerdmetallen wurde hergestellt und strukturell charakterisiert. Das LaZn3-System mit seinen anionischen Liganden wie Acetat spielt eine zentrale Rolle bei der katalysierten alternierenden Copolymerisation von Cyclohexenoxid (CHO) und CO2 und liefert ein Produkt mit einem hohen Gehalt an Carbonatverknüpfungen. Bei den Lanthanoiden zeigt das CeZn3-System eine hohe katalytische Aktivität mit einer Wechselzahl (TOF) von über 370 h−1. Die NMR-spektroskopische Analyse des Komplexes und die Bestimmung der Endgruppen im Polymer weisen auf einen schnellen Austausch der Acetatliganden hin. Die koordinierten Acetate werden nicht nur untereinander, sondern auch gegen zugesetzte Carboxylat-Anionen ausgetauscht. Mit solch einzigartigen Eigenschaften ist dieses System das erste Beispiel für eine als Telomerisierung ablaufende Copolymerisation von CHO und CO2.Homogene Heterometallkomplexe auf Basis des Makrocyclus Trisaloph mit drei Zinkzentren und einem Seltenerdmetall zeigte eine hohe katalytische Aktivität in der alternierenden Copolymerisation von Cyclohexenoxid und CO2 mit einem hohen Anteil an Carbonat-Wiederholungseinheiten. Das Carboxylat-Anion in Ammoniumsalzen initiierte die fortschreitende Telomerisierung zu Polycarbonat mit entsprechenden Carboxylaten.
      PubDate: 2018-01-17T08:51:15.478885-05:
      DOI: 10.1002/ange.201709218
       
  • Durch zwei Liganden ermöglichte nicht-dirigierte C-H-Olefinierung von
           Arenen
    • Authors: Hao Chen; Philipp Wedi, Tim Meyer, Ghazal Tavakoli, Manuel van Gemmeren
      Pages: 2523 - 2527
      Abstract: Die klassische Pd-katalysierte oxidative C-H-Olefinierung von Arenen, auch bekannt als die Fujiwara-Moritani-Reaktion, ist durch die Notwendigkeit von dirigierenden Gruppen am Substrat oder des Einsatzes des Arens im großen Überschuss, typischerweise als (Ko-)Lösungsmittel, eingeschränkt. Hier beschreiben wir die Entwicklung eines Katalysatorsystems, das durch das Zusammenwirken von zwei komplementären Liganden erstmals die Nutzung von Arenen ohne dirigierende Gruppen als limitierendes Reagenz ermöglicht. Die Reaktionen verlaufen unter einer Kombination aus sterischer und elektronischer Kontrolle und ermöglichen die Anwendung auf wertvolle Arene, die nicht in Überschuss eingesetzt werden müssen.Wie viele Liganden braucht man, um eine Bindung zu wechseln' Die Pd-katalysierte C-H-Olefinierung von Arenen als limitierende Reagenzien wird beschrieben. Die kombinierte Wirkung zweier Liganden, N-Acetylglycin und ein Pyridin, ermöglicht es, dass diese Fujiwara-Moritani-Reaktion, die klassisch das Aren als (Ko-)Lösungsmittel oder dirigierende Gruppen am Substrat benötigte, ohne diese Anforderungen unter sterischer/elektronischer Kontrolle abläuft.
      PubDate: 2018-01-26T07:36:04.701218-05:
      DOI: 10.1002/ange.201712235
       
  • Innenrücktitelbild: Cationic Metallo-Polyelectrolytes for Robust Alkaline
           Anion-Exchange Membranes (Angew. Chem. 9/2018)
    • Authors: Tianyu Zhu; Shichao Xu, Anisur Rahman, Emir Dogdibegovic, Peng Yang, Parasmani Pageni, Mohammad Pabel Kabir, Xiao-dong Zhou, Chuanbing Tang
      Pages: 2529 - 2529
      Abstract: Kationische Polyelektrolyte werden in alkalischen Brennstoffzellen als Anionenaustauschmembranen (AEMs) verwendet, um Kraftstoff in Elektrizität umzuwandeln. C. Tang et al. berichten in ihrer Zuschrift auf S. 2412 über eine Klasse von Metallopolyelektrolyten, die für chemisch inerte AEMs unter stark basischen Bedingungen konzipiert wurden. Die AEMs zeigen exzellente thermische, chemische und mechanische Stabilität sowie eine hohe Ionenleitfähigkeit.
      PubDate: 2018-01-31T03:09:40.526209-05:
      DOI: 10.1002/ange.201800722
       
  • Rücktitelbild: Seeded Polymerization through the Interplay of Folding and
           Aggregation of an Amino-Acid-based Diamide (Angew. Chem. 9/2018)
    • Authors: Soichiro Ogi; Kentaro Matsumoto, Shigehiro Yamaguchi
      Pages: 2530 - 2530
      Abstract: Ein Aminosäure-Diamid …… ist der Schlüssel zu einem supramolekularen Polymerisationsprozess. S. Ogi, K. Matsumoto und S. Yamaguchi zeigen in ihrer Zuschrift auf S. 2363, dass die spontane Aggregation (rechter Weg) von Diamiden in der gestreckten Form durch die Faltung der Diamideinheit über intramolekulare Wasserstoffbrückenbildung effektiv erschwert wird. Unter derartigen Ungleichgewichtsbedingungen kann der zeitliche Verlauf der Selbstorganisation über einen Impfansatz (linker Weg) gesteuert werden.
      PubDate: 2018-02-02T02:53:12.384005-05:
      DOI: 10.1002/ange.201800993
       
  • Europa und die Chemie voranbringen
    • Authors: Gilberte Chambaud
      Pages: 2286 - 2287
      Abstract: Für die Wissenschaftlerwelt sind die Reisemöglichkeiten, die den persönlichen Austausch zwischen Forschern begünstigen, von großer Bedeutung. Wesentliche Erfolge waren die Verschmelzung nationaler Zeitschriften zu erfolgreichen europäischen Journalen und die Schaffung der EuCheMS-Kongresse …” Lesen Sie mehr im Gast-Editorial von Gilberte Chambaud.
      PubDate: 2017-12-14T04:40:25.016843-05:
      DOI: 10.1002/ange.201709947
       
  • Shunai Che
    • Pages: 2306 - 2306
      Abstract: „Das Geheimnis, ein erfolgreicher Wissenschaftler zu sein, ist, bekannte Ergebnisse und Folgerungen zu hinterfragen. Mein liebstes Molekül ist die DNA mit ihren wunderschönen Strukturen und erstaunlichen Funktionalitäten ...“ Dies und mehr von und über Shunai Che finden Sie auf Seite 2306.
      PubDate: 2017-11-17T05:16:07.771887-05:
      DOI: 10.1002/ange.201711485
       
  • Cristina Nevado
    • Pages: 2307 - 2307
      Abstract: „Meine liebste Art, Urlaub zu machen, ist, in warmen Gewässern zu tauchen. Auf meine Karriere zurückblickend würde ich sagen, ich stehe eigentlich noch am Anfang, und die letzten zehn Jahre sind viel zu schnell vergangen! ...“ Dies und mehr von und über Cristina Nevado finden Sie auf Seite 2307.
      PubDate: 2017-12-20T04:56:52.301844-05:
      DOI: 10.1002/ange.201712494
       
 
 
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