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  Subjects -> CHEMISTRY (Total: 846 journals)
    - ANALYTICAL CHEMISTRY (48 journals)
    - CHEMISTRY (599 journals)
    - CRYSTALLOGRAPHY (22 journals)
    - ELECTROCHEMISTRY (25 journals)
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CHEMISTRY (599 journals)                  1 2 3 | Last

Showing 1 - 200 of 735 Journals sorted alphabetically
2D Materials     Hybrid Journal   (Followers: 6)
Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement     Hybrid Journal   (Followers: 25)
ACS Catalysis     Full-text available via subscription   (Followers: 30)
ACS Chemical Neuroscience     Full-text available via subscription   (Followers: 16)
ACS Combinatorial Science     Full-text available via subscription   (Followers: 24)
ACS Macro Letters     Full-text available via subscription   (Followers: 22)
ACS Medicinal Chemistry Letters     Full-text available via subscription   (Followers: 36)
ACS Nano     Full-text available via subscription   (Followers: 206)
ACS Photonics     Full-text available via subscription   (Followers: 9)
ACS Synthetic Biology     Full-text available via subscription   (Followers: 20)
Acta Chemica Iasi     Open Access   (Followers: 2)
Acta Chimica Sinica     Full-text available via subscription  
Acta Chimica Slovaca     Open Access   (Followers: 1)
Acta Chromatographica     Full-text available via subscription   (Followers: 8)
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: 7)
Adsorption Science & Technology     Full-text available via subscription   (Followers: 4)
Advanced Functional Materials     Hybrid Journal   (Followers: 45)
Advanced Science Focus     Free   (Followers: 3)
Advances in Chemical Engineering and Science     Open Access   (Followers: 53)
Advances in Chemical Science     Open Access   (Followers: 12)
Advances in Chemistry     Open Access   (Followers: 11)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 18)
Advances in Drug Research     Full-text available via subscription   (Followers: 22)
Advances in Enzyme Research     Open Access   (Followers: 10)
Advances in Fluorine Science     Full-text available via subscription   (Followers: 8)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 14)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 8)
Advances in Materials Physics and Chemistry     Open Access   (Followers: 16)
Advances in Nanoparticles     Open Access   (Followers: 12)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 15)
Advances in Polymer Science     Hybrid Journal   (Followers: 40)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 18)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 17)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 5)
Advances in Science and Technology     Full-text available via subscription   (Followers: 10)
African Journal of Bacteriology Research     Open Access  
African Journal of Chemical Education     Open Access   (Followers: 2)
African Journal of Pure and Applied Chemistry     Open Access   (Followers: 7)
Agrokémia és Talajtan     Full-text available via subscription   (Followers: 2)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 3)
AMB Express     Open Access   (Followers: 1)
Ambix     Hybrid Journal   (Followers: 3)
American Journal of Biochemistry and Biotechnology     Open Access   (Followers: 65)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 14)
American Journal of Chemistry     Open Access   (Followers: 24)
American Journal of Plant Physiology     Open Access   (Followers: 12)
American Mineralogist     Full-text available via subscription   (Followers: 12)
Analyst     Full-text available via subscription   (Followers: 44)
Angewandte Chemie     Hybrid Journal   (Followers: 145)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 202)
Annales UMCS, Chemia     Open Access   (Followers: 1)
Annals of Clinical Chemistry and Laboratory Medicine     Open Access   (Followers: 1)
Annual Reports in Computational Chemistry     Full-text available via subscription   (Followers: 3)
Annual Reports Section A (Inorganic Chemistry)     Full-text available via subscription   (Followers: 3)
Annual Reports Section B (Organic Chemistry)     Full-text available via subscription   (Followers: 7)
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: 14)
Anti-Infective Agents     Hybrid Journal   (Followers: 3)
Antiviral Chemistry and Chemotherapy     Hybrid Journal  
Applied Organometallic Chemistry     Hybrid Journal   (Followers: 6)
Applied Spectroscopy     Full-text available via subscription   (Followers: 23)
Applied Surface Science     Hybrid Journal   (Followers: 23)
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: 3)
Australian Journal of Chemistry     Hybrid Journal   (Followers: 6)
Autophagy     Hybrid Journal   (Followers: 2)
Avances en Quimica     Open Access   (Followers: 1)
Biochemical Pharmacology     Hybrid Journal   (Followers: 9)
Biochemistry     Full-text available via subscription   (Followers: 262)
Biochemistry Insights     Open Access   (Followers: 5)
Biochemistry Research International     Open Access   (Followers: 6)
BioChip Journal     Hybrid Journal  
Bioinorganic Chemistry and Applications     Open Access   (Followers: 9)
Bioinspired Materials     Open Access   (Followers: 3)
Biointerface Research in Applied Chemistry     Open Access   (Followers: 2)
Biointerphases     Open Access   (Followers: 1)
Biology, Medicine, & Natural Product Chemistry     Open Access  
Biomacromolecules     Full-text available via subscription   (Followers: 18)
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: 4)
Bioorganic & Medicinal Chemistry     Hybrid Journal   (Followers: 113)
Bioorganic & Medicinal Chemistry Letters     Hybrid Journal   (Followers: 103)
Bioorganic Chemistry     Hybrid Journal   (Followers: 10)
Biopolymers     Hybrid Journal   (Followers: 17)
Biosensors     Open Access   (Followers: 1)
Biotechnic and Histochemistry     Hybrid Journal   (Followers: 2)
Bitácora Digital     Open Access  
Boletin de la Sociedad Chilena de Quimica     Open Access  
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 3)
Bulletin of the Chemical Society of Japan     Full-text available via subscription   (Followers: 25)
Bulletin of the Korean Chemical Society     Hybrid Journal   (Followers: 1)
C - Journal of Carbon Research     Open Access   (Followers: 2)
Canadian Association of Radiologists Journal     Full-text available via subscription   (Followers: 2)
Canadian Journal of Chemistry     Full-text available via subscription   (Followers: 8)
Canadian Mineralogist     Full-text available via subscription   (Followers: 3)
Carbohydrate Research     Hybrid Journal   (Followers: 26)
Carbon     Hybrid Journal   (Followers: 65)
Catalysis for Sustainable Energy     Open Access   (Followers: 5)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 7)
Catalysis Science and Technology     Free   (Followers: 6)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 3)
Catalysts     Open Access   (Followers: 7)
Cellulose     Hybrid Journal   (Followers: 5)
Cereal Chemistry     Full-text available via subscription   (Followers: 4)
ChemBioEng Reviews     Full-text available via subscription   (Followers: 1)
ChemCatChem     Hybrid Journal   (Followers: 7)
Chemical and Engineering News     Free   (Followers: 12)
Chemical Bulletin of Kazakh National University     Open Access  
Chemical Communications     Full-text available via subscription   (Followers: 70)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 21)
Chemical Research in Chinese Universities     Hybrid Journal   (Followers: 3)
Chemical Research in Toxicology     Full-text available via subscription   (Followers: 18)
Chemical Reviews     Full-text available via subscription   (Followers: 161)
Chemical Science     Open Access   (Followers: 20)
Chemical Technology     Open Access   (Followers: 15)
Chemical Vapor Deposition     Hybrid Journal   (Followers: 4)
Chemical Week     Full-text available via subscription   (Followers: 7)
Chemie in Unserer Zeit     Hybrid Journal   (Followers: 55)
Chemie-Ingenieur-Technik (Cit)     Hybrid Journal   (Followers: 25)
ChemInform     Hybrid Journal   (Followers: 7)
Chemistry & Biodiversity     Hybrid Journal   (Followers: 5)
Chemistry & Biology     Full-text available via subscription   (Followers: 30)
Chemistry & Industry     Hybrid Journal   (Followers: 4)
Chemistry - A European Journal     Hybrid Journal   (Followers: 129)
Chemistry - An Asian Journal     Hybrid Journal   (Followers: 15)
Chemistry and Materials Research     Open Access   (Followers: 16)
Chemistry Central Journal     Open Access   (Followers: 4)
Chemistry Education Research and Practice     Free   (Followers: 5)
Chemistry in Education     Open Access   (Followers: 8)
Chemistry International     Hybrid Journal   (Followers: 1)
Chemistry Letters     Full-text available via subscription   (Followers: 43)
Chemistry of Materials     Full-text available via subscription   (Followers: 174)
Chemistry of Natural Compounds     Hybrid Journal   (Followers: 9)
Chemistry-Didactics-Ecology-Metrology     Open Access  
ChemistryOpen     Open Access   (Followers: 2)
Chemkon - Chemie Konkret, Forum Fuer Unterricht Und Didaktik     Hybrid Journal  
Chemoecology     Hybrid Journal   (Followers: 2)
Chemometrics and Intelligent Laboratory Systems     Hybrid Journal   (Followers: 15)
Chemosensors     Open Access  
ChemPhysChem     Hybrid Journal   (Followers: 8)
ChemPlusChem     Hybrid Journal   (Followers: 1)
ChemTexts     Hybrid Journal  
CHIMIA International Journal for Chemistry     Full-text available via subscription   (Followers: 3)
Chinese Journal of Chemistry     Hybrid Journal   (Followers: 6)
Chinese Journal of Polymer Science     Hybrid Journal   (Followers: 10)
Chromatographia     Hybrid Journal   (Followers: 24)
Chromatography Research International     Open Access   (Followers: 7)
Clay Minerals     Full-text available via subscription   (Followers: 8)
Cogent Chemistry     Open Access  
Colloid and Interface Science Communications     Open Access  
Colloid and Polymer Science     Hybrid Journal   (Followers: 10)
Colloids and Surfaces B: Biointerfaces     Hybrid Journal   (Followers: 8)
Combinatorial Chemistry & High Throughput Screening     Hybrid Journal   (Followers: 3)
Combustion Science and Technology     Hybrid Journal   (Followers: 18)
Comments on Inorganic Chemistry: A Journal of Critical Discussion of the Current Literature     Hybrid Journal   (Followers: 1)
Composite Interfaces     Hybrid Journal   (Followers: 5)
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: 1)
Copernican Letters     Open Access  
Critical Reviews in Biochemistry and Molecular Biology     Hybrid Journal   (Followers: 5)
Crystal Structure Theory and Applications     Open Access   (Followers: 3)
CrystEngComm     Full-text available via subscription   (Followers: 10)
Current Catalysis     Hybrid Journal   (Followers: 1)
Current Metabolomics     Hybrid Journal   (Followers: 3)
Current Opinion in Colloid & Interface Science     Hybrid Journal   (Followers: 8)
Current Opinion in Molecular Therapeutics     Full-text available via subscription   (Followers: 15)
Current Research in Chemistry     Open Access   (Followers: 8)
Current Science     Open Access   (Followers: 47)
Dalton Transactions     Full-text available via subscription   (Followers: 18)
Detection     Open Access   (Followers: 2)
Developments in Geochemistry     Full-text available via subscription   (Followers: 2)
Diamond and Related Materials     Hybrid Journal   (Followers: 11)
Dislocations in Solids     Full-text available via subscription  
Doklady Chemistry     Hybrid Journal  
Drying Technology: An International Journal     Hybrid Journal   (Followers: 3)
Eclética Química     Open Access   (Followers: 1)
Ecological Chemistry and Engineering S     Open Access   (Followers: 3)
Ecotoxicology and Environmental Contamination     Open Access  
Educación Química     Open Access   (Followers: 1)
Education for Chemical Engineers     Hybrid Journal   (Followers: 5)
Elements     Full-text available via subscription   (Followers: 2)
Environmental Chemistry     Hybrid Journal   (Followers: 6)
Environmental Chemistry Letters     Hybrid Journal   (Followers: 3)
Environmental Science & Technology Letters     Full-text available via subscription   (Followers: 4)
Environmental Science : Nano     Partially Free   (Followers: 1)
Environmental Toxicology & Chemistry     Hybrid Journal   (Followers: 18)

        1 2 3 | Last

Journal Cover Angewandte Chemie
  [145 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  [1616 journals]
  • Large-Area Elemental Imaging Reveals Van Eyck's Original Paint Layers on
           the Ghent Altarpiece (1432), Rescoping Its Conservation Treatment
    • Authors: Geert Van der Snickt; Hélène Dubois, Jana Sanyova, Stijn Legrand, Alexia Coudray, Cécile Glaude, Marie Postec, Piet Van Espen, Koen Janssens
      Abstract: A combination of large-scale and micro-scale elemental imaging, yielding elemental distribution maps obtained by, respectively non-invasive macroscopic X-ray fluorescence (MA-XRF) and by secondary electron microscopy/energy dispersive X-ray analysis (SEM-EDX) and synchrotron radiation-based micro-XRF (SR μ-XRF) imaging was employed to reorient and optimize the conservation strategy of van Eyck's renowned Ghent Altarpiece. By exploiting the penetrative properties of X-rays together with the elemental specificity offered by XRF, it was possible to visualize the original paint layers by van Eyck hidden below the overpainted surface and to simultaneously assess their condition. The distribution of the high-energy Pb-L and Hg-L emission lines revealed the exact location of hidden paint losses, while Fe-K maps demonstrated how and where these lacunae were filled-up using an iron-containing material. The chemical maps nourished the scholarly debate on the overpaint removal with objective, chemical arguments, leading to the decision to remove all skillfully applied overpaints, hitherto interpreted as work by van Eyck. MA-XRF was also employed for monitoring the removal of the overpaint during the treatment phase. To gather complementary information on the in-depth layer build-up, SEM-EDX and SR μ-XRF imaging was used on paint cross sections to record micro-scale elemental maps.In altem Glanz: Die Zusammensetzung der gesamten Farboberfläche der Flügelrückseiten des Genter Altars von van Eyck wurde durch chemische und Elementbildgebung im Groß- und Mikromaßstab analysiert. MA-XRF-Scans machten die übermalten originalen Farbschichten wieder sichtbar. Diese Elementanalyse lieferte objektive Argumente für die vollständige Entfernung der oberen Farbschichten.
      PubDate: 2017-03-22T09:40:57.432382-05:
      DOI: 10.1002/ange.201700707
       
  • HACA's Heritage: A Free-Radical Pathway to Phenanthrene in Circumstellar
           Envelopes of Asymptotic Giant Branch Stars
    • Authors: Tao Yang; Ralf I. Kaiser, Tyler P. Troy, Bo Xu, Oleg Kostko, Musahid Ahmed, Alexander M. Mebel, Marsel V. Zagidullin, Valeriy N. Azyazov
      Abstract: The hydrogen-abstraction/acetylene-addition (HACA) mechanism has been central for the last decades in attempting to rationalize the formation of polycyclic aromatic hydrocarbons (PAHs) as detected in carbonaceous meteorites such as in Murchison. Nevertheless, the basic reaction mechanisms leading to the formation of even the simplest tricyclic PAHs like anthracene and phenanthrene are still elusive. Here, by exploring the previously unknown chemistry of the ortho-biphenylyl radical with acetylene, we deliver compelling evidence on the efficient synthesis of phenanthrene in carbon-rich circumstellar environments. However, the lack of formation of the anthracene isomer implies that HACA alone cannot be responsible for the formation of PAHs in extreme environments. Considering the overall picture, alternative pathways such as vinylacetylene-mediated reactions are required to play a crucial role in the synthesis of complex PAHs in circumstellar envelopes of dying carbon-rich stars.Quo vadis HACA? Der HACA-Mechanismus (Wasserstoffabstraktion/Acetylenaddition) gilt als eines der wichtigsten Szenarien für die Bildung der polycyclischen aromatischen Kohlenwasserstoffe (PAHs). Der Nachweis von Phenanthren in der Reaktion von ortho-Biphenylylradikalen mit Acetylen unter verbrennungsartigen Bedingungen bestätigt die Bildung von PAHs jenseits des Naphthalins und rechtfertigt alternative Szenarien, z. B. Vinylacetylen-vermittelte Mechanismen.
      PubDate: 2017-03-22T09:39:48.573758-05:
      DOI: 10.1002/ange.201701259
       
  • The WSPC Reference on Organic Electronics: Organic Semiconductors.
           Materials and Energy Series. Band 1: Basic Concepts, Band 2: Fundamental
           Aspects of Materials and Applications. Herausgegeben von Jean-Luc Brédas
           und Seth R. Marder.
    • Authors: Enrico Da Como; Elizabeth von Hauff
      Abstract: World Scientific Publishing, Singapur 2016. 896 S., geb., 452.00 £.—ISBN 978-9814699228
      PubDate: 2017-03-22T09:37:30.151729-05:
      DOI: 10.1002/ange.201701913
       
  • Use of a Traceless Activating and Directing Group for the Construction of
           Trifluoromethylpyrazoles: One-Pot Transformation of Nitroolefins and
           Trifluorodiazoethane
    • Authors: Zhen Chen; Yan Zheng, Jun-An Ma
      Abstract: We disclose an efficient one-pot transformation of trifluorodiazoethane and higher perfluorinated homologues with various nitroolefins. This method takes advantage of the nitro group as a traceless activating and directing group (TADG) that is released in the aromatization step to produce 4-substituted 3-perfluoroalkyl pyrazoles with complete regioselectivity. The potential of this method is further demonstrated by the synthesis of penthiopyrad.Ohne Spuren zu hinterlassen: Eine Eintopfreaktion von Trifluordiazoethan und höheren perfluorierten Homologen mit verschiedenen Nitroolefinen nutzt die Nitrogruppen als eine spurlose aktivierende und dirigierende Gruppe, die im Aromatisierungsschritt freigesetzt wird, um 4-substituierte 3-Perfluoralkylpyrazole mit vollständiger Regioselektivität herzustellen (siehe Schema). Die Methode wurde für die Synthese des Fungizids Penthiopyrad genutzt.
      PubDate: 2017-03-22T09:22:33.255279-05:
      DOI: 10.1002/ange.201700955
       
  • Synthesis of C3-Fluorinated Oxindoles Through Reagent-Free
           Cross-Dehydrogenative Coupling
    • Authors: Zheng-Jian Wu; Hai-Chao Xu
      Abstract: Elektrizität wurde verwendet, um Ferrocen (Cp2Fe) zu laden und damit die Kreuzkupplung von C-H-Zentren zu katalysieren. In ihrer Zuschrift (
      DOI : 10.1002/ange.201701329) beschreiben H.-C. Xu und Z.-J. Wu eine effiziente und skalierbare Cp2Fe-katalysierte elektrochemische Synthese von funktionalisierten C3-fluorierten Oxindolen aus leicht zugänglichen Molanatamiden durch dehydrierende Kreuzkupplung von C(sp3)-H- und C(sp2)-H-Bindungen.
      PubDate: 2017-03-22T09:12:58.661542-05:
       
  • Zinc Regulates Chemical-Transmitter Storage in Nanometer Vesicles and
           Exocytosis Dynamics as Measured by Amperometry
    • Authors: Lin Ren; Masoumeh Dowlatshahi Pour, Soodabeh Majdi, Xianchan Li, Per Malmberg, Andrew G. Ewing
      Abstract: Die Wirkung von Zink, einem wichtigen Element für Lern- und Erinnerungsprozesse, auf die Neurotransmission in einem Einzelzellmodell für die Botenstoff-Freisetzung wurde mit amperometrischen Methoden untersucht. In ihrer Zuschrift (
      DOI : 10.1002/ange.201700095) belegen A. G. Ewing et al., dass Zink nicht nur den Vesikelgehalt von PC12-Zellen ändert, sondern auch die Dynamik einzelner Exozytoseprozesse, eine längere und stabile Fusion bewirkt. Diese Beobachtung gibt Aufschluss darüber, wie Zink diesen zellulären Schlüsselprozess beeinflusst und so die Zell-Zell-Kommunikation modifiziert.
      PubDate: 2017-03-22T09:12:57.539221-05:
       
  • Reagens- und metallfreie anodische C-C-Kreuzkupplung von Anilinderivaten
    • Authors: Lara Schulz; Mathias Enders, Bernd Elsler, Dieter Schollmeyer, Katrin M. Dyballa, Robert Franke, Siegfried R. Waldvogel
      Abstract: Die Bildung von Polyanilinen lässt sich durch anodische Kupplung von Anilinen mit einfachen carbonylbasierten und leicht entfernbaren Schutzgruppen vermeiden. In ihrer Zuschrift (
      DOI : 10.1002/ange.201612613) präsentieren S. R. Waldvogel und Mitarbeiter eine leicht durchführbare elektrolytische Synthese geschützter 2,2′-Diaminobiaryl-Derivate in hohen Ausbeuten und mit exzellenter Selektivität über oxidative Kreuzkupplung. Mit 1,1,1,3,3,3-Hexafluor-2-propanol als Lösungsmittel gelingt eine saubere elektrochemische Umsetzung.
      PubDate: 2017-03-22T09:12:53.726048-05:
       
  • A Symmetric Co(N5)2(H2O)4⋅4 H2O High-Nitrogen Compound Formed by
           Cobalt(II) Cation Trapping of a Cyclo-N5− Anion
    • Authors: Chong Zhang; Chen Yang, Bingcheng Hu, Chuanming Yu, Zhansheng Zheng, Chengguo Sun
      Abstract: The reactions of (N5)6(H3O)3(NH4)4Cl with Co(NO3)2⋅6 H2O at room temperature yielded Co(N5)2(H2O)4⋅4 H2O as an air-stable orange metal complex. The structure, as determined by single-crystal X-ray diffraction, has two planar cyclo-N5− rings and four bound water molecules symmetrically positioned around the central metal ion. Thermal analysis demonstrated the explosive properties of the material.Feuer frei: Die Umsetzung von (N5)6(H3O)3(NH4)4Cl mit Co(NO3)2⋅6 H2O in Methanol/Wasser bei Raumtemperatur liefert den Metall-Pentazolat-Komplex Co(N5)2(H2O)4⋅4 H2O. Die physikalischen Eigenschaften dieser brandfördernden Verbindung wurden untersucht, und eine Röntgen-Strukturanalyse wird vorgestellt.
      PubDate: 2017-03-22T09:12:52.874998-05:
      DOI: 10.1002/ange.201701070
       
  • One-Pot Multicomponent Synthesis of β-Amino Amides
    • Authors: Bo Huang; Linwei Zeng, Yangyong Shen, Sunliang Cui
      Abstract: Multicomponent reactions are excellent tools for rapid generation of small molecules with broad chemical diversity and molecular complexity. Herein, a novel one-pot multicomponent synthesis of β-amino amides from aldehydes, anilines, carboxylic acids and ynamides has been successfully developed. This process is practical and efficient to unravel synthetic utility and scalability. Moreover, an isotope labeling reaction was conducted to elucidate a plausible reaction mechanism.Vier gewinnt: Eine neuartige Vierkomponentensynthese von β-Aminoamiden wurde entwickelt (siehe Schema). Die Synthese ist praktisch, effizient und skalierbar. Eine Isotopenmarkierungsstudie wurde durchgeführt, um einen plausiblen Reaktionsmechanismus zu ermitteln.
      PubDate: 2017-03-22T09:12:48.873481-05:
      DOI: 10.1002/ange.201700840
       
  • Kontrolle der Freisetzungskinetik von Nanopartikeln aus 3D-gedruckten
           Hydrogelgerüsten
    • Authors: Bernhard Baumann; Tomasz Jungst, Simone Stichler, Susanne Feineis, Oliver Wiltschka, Matthias Kuhlmann, Mika Lindén, Jürgen Groll
      Abstract: Die bisher größtenteils unerforschte Kombination aus Biofabrikation und Nanotechnologie ermöglicht eine örtlich und zeitlich aufgelöste Freisetzung von Wirkstoffen aus hierarchischen, zellbeladenen Biomaterialien. Als ein erster Schritt in Richtung der Verknüpfung dieser beiden Forschungsgebiete wird hier gezeigt, dass die Einstellung der elektrostatischen Nanopartikel-Polymer- und Nanopartikel-Nanopartikel-Wechselwirkungen verwendet werden kann, um die Freisetzungskinetik von Nanopartikeln aus gedruckten 3D Hydrogelgerüsten zu steuern. Diese grundlegende Strategie kann für die räumliche und zeitliche Kontrolle der Freisetzungskinetik von nanopartikulären Wirkstoffträgern in biofabrizierten Konstrukten verwendet werden.Formulierungen von positiv und negativ geladenen Silika-Nanopartikeln oder sphärischen Gold-Nanopartikeln mit einer Hydrogel-Biotinte wurden für die Biofabrikation verwendet. Die schnelle Freisetzung der negativ geladenen Partikel sowie das gegensätzliche Verhalten der positiv geladenen Partikel werden demonstriert. Dieses allgemeine Prinzip könnte als Strategie für die Implementierung von Nanopartikeln in die Biofabrikation für die örtliche und zeitliche Kontrolle der Wirkstofffreisetzung dienen.
      PubDate: 2017-03-22T09:02:03.146894-05:
      DOI: 10.1002/ange.201700153
       
  • Coordination Polymerization of Renewable 3-Methylenecyclopentene with
           Rare-Earth Metal Precursors
    • Authors: Bo Liu; Shihui Li, Meiyan Wang, Dongmei Cui
      Abstract: Coordination polymerization of renewable 3-methylenecyclopentene has been investigated for the first time using rare-earth metal-based precursors bearing various bulky ligands. All the prepared complexes catalyze controllable polymerization of 3-methylenecyclopentene into high molecular weight polymers, of which the NPN- and NSN-tridentate non-Cp ligated lutetium-based catalytic systems exhibited extremely high activities up to 11 520 kg/(molLu⋅h) in a dilute toluene solution (3.2 g/100 mL) at room temperature. The resultant polymers have pure 1,4-regioregularity (>99 %) and tailorable number average molecular weights (1–20×104) with narrow molecular weight distributions (polydispersity index (PDI)=1.45–1.79). DFT simulations were employed to study the polymerization mechanism and stereoregularity control.1,4-Polymerisation: Seltenerdmetallvorstufen mit mäßig sperrigen Liganden vermitteln die Polymerisation des erneuerbaren Monomers 3-Methylencyclopenten (MCP). Bei Reaktionen in einem breiten Temperaturbereich liefern die hoch aktiven Katalysatoren regioisomerenreines 1,4-Poly(MCP) mit gewünschten Molekulargewichten.
      PubDate: 2017-03-22T09:01:32.437925-05:
      DOI: 10.1002/ange.201700546
       
  • Asymmetric Synthesis of Spiropyrazolones by Rhodium-Catalyzed C(sp2)−H
           Functionalization/Annulation Reactions
    • Authors: Jun Zheng; Shao-Bo Wang, Chao Zheng, Shu-Li You
      Abstract: Rhodium-catalyzed C(sp2)−H functionalization reactions of 4-aryl-5-pyrazolones followed by [3+2] annulation reactions with alkynes provide rapid access to highly enantioenriched five-membered-ring 4-spiro-5-pyrazolones. The use of a chiral SCpRh catalyst enabled the synthesis of a large range of spiropyrazolones with all-carbon quaternary stereogenic centers in up to 99 % yield and 98 % ee from readily available substrates.Enantiomerenangereicherte 4-Spiro-5-pyrazolone mit einem fünfgliedrigen Spirocyclus wurden durch eine Rhodium-katalysierte C-(sp2)-H-Funktionalisierung von 4-Aryl-5-pyrazolonen und [3+2]-Anellierung mit Alkinen synthetisiert. Die Verwendung eines chiralen SCpRh-Katalysators führte zu exzellenter Enantioselektivität, Reaktivität und Regioselektivität in dieser Reaktionskaskade.
      PubDate: 2017-03-22T08:57:42.634972-05:
      DOI: 10.1002/ange.201700021
       
  • An Isolable Potassium Salt of a Borasilene–Chloride Adduct
    • Authors: Yuko Suzuki; Shintaro Ishida, Sota Sato, Hiroyuki Isobe, Takeaki Iwamoto
      Abstract: Among the variety of isolable compounds with multiple bonds involving silicon, examples of compounds that contain silicon–boron double bonds (borasilenes) still remain relatively rare. Herein, we report the synthesis of the potassium salt of a chloride adduct of borasilene 1 ([2]−), which was obtained as an orange crystalline solid. Single-crystal X-ray diffraction analysis and reactivity studies on [2]− confirmed the double-bond character of the Si=B bond as well as the reduced Lewis acidity, which is due to the coordination of Cl− to the boron center. A thermal reaction of [2]− afforded a bicyclic product by formal intramolecular C−H insertion across the Si=B bond of 1, which was corroborated by a theoretical study.Das Kaliumsalz eines Borasilen-Chlorid-Addukts wurde synthetisiert und isoliert. Der Doppelbindungscharakter der Si=B-Bindung und die reduzierte Lewis-Acidität wurden durch seine Reaktivität und Röntgenbeugungsanalyse am Einkristall belegt. Das Addukt wurde durch formale intramolekulare C-H-Insertion über die Si=B-Bindung in ein cyclisches Produkt überführt, und zwar möglicherweise über das entsprechende basenfreie Borasilen.
      PubDate: 2017-03-22T08:57:39.506061-05:
      DOI: 10.1002/ange.201612545
       
  • Ausnutzung oktaedrischer Stereozentren: von Enzymhemmung bis hin zu
           asymmetrischer Photoredoxkatalyse
    • Authors: Eric Meggers
      Abstract: Ein einfaches Konzept, nämlich die Ausnutzung der strukturellen und stereochemischen Komplexität der oktaedrischen Koordinationsgeometrie von Metallkomplexen, kann Anwendungen in ganz verschiedenen Forschungsgebieten, von Medizinalchemie und chemischen Biologie bis hin zu asymmetrischer Katalyse und Photoredoxchemie, ermöglichen.
      PubDate: 2017-03-22T08:57:28.595888-05:
      DOI: 10.1002/ange.201612516
       
  • Cell Fixation by Light-Triggered Release of Glutaraldehyde
    • Authors: Korwin M. Schelkle; Christopher Schmid, Klaus Yserentant, Markus Bender, Irene Wacker, Martin Petzoldt, Manuel Hamburger, Dirk-Peter Herten, Richard Wombacher, Rasmus R. Schröder, Uwe H. F. Bunz
      Abstract: Chemical fixation of living cells for microscopy is commonly achieved by crosslinking of intracellular proteins with dialdehydes prior to examination. We herein report a photocleavable protecting group for glutaraldehyde that results in a light-triggered and membrane-permeable fixative, which is nontoxic prior to photocleavage. Lipophilic ester groups allow for diffusion across the cell membrane and intracellular accumulation after enzymatic hydrolysis. Irradiation with UV light releases glutaraldehyde. The in situ generated fixative crosslinks intracellular proteins and preserves and stabilizes the cell so that it is ready for microscopy. In contrast to conventional glutaraldehyde fixation, tissue autofluorescence does not increase after fixation. Caged glutaraldehyde may in future enable functional experiments on living cells under a light microscope in which events of interest can be stopped in spatially confined volumes at defined time points. Samples with individually stopped events could then later be analyzed in ultrastructural studies.Cellfi-Flash: Ein Fixiermittel für die Lichtmikroskopie lebender Zellen wurde durch die Funktionalisierung von Glutaraldehyd mit photospaltbaren Schutzgruppen erhalten. Estersubstituenten stellen sicher, dass die Verbindung in maskierter Form in die Zelle eindringen kann, wo sie sich nach Esterase-vermittelter Hydrolyse ansammelt. Inkubierte Zellen werden bei Bestrahlung sofort fixiert, während gewöhnliche Fixierungen mit Aldehyden diffusionskontrolliert ablaufen.
      PubDate: 2017-03-22T08:43:15.367575-05:
      DOI: 10.1002/ange.201612112
       
  • Surfactant-Assisted Stabilization of Au Colloids on Solids for
           Heterogeneous Catalysis
    • Authors: Wangcheng Zhan; Yuan Shu, Yujie Sheng, Huiyuan Zhu, Yanglong Guo, Li Wang, Yun Guo, Jinshui Zhang, Guanzhong Lu, Sheng Dai
      Abstract: The stabilization of surfactant-assisted synthesized colloidal noble metal nanoparticles (NPs, such as Au NPs) on solids is a promising strategy for preparing supported nanocatalysts for heterogeneous catalysis because of their uniform particle sizes, controllable shapes, and tunable compositions. However, surfactant removal to obtain clean surfaces for catalysis through traditional approaches (such as solvent extraction and thermal decomposition) can easily induce the sintering of NPs, greatly hampering their use in synthesis of novel catalysts. Such unwanted surfactants have now been utilized to stabilize NPs on solids by a simple yet efficient thermal annealing strategy. After being annealed in N2 flow, the surface-bound surfactants are carbonized in situ as sacrificial architectures that form a conformal coating on NPs and assist in creating an enhanced metal-support interaction between NPs and substrate, thus slowing down the Ostwald ripening process during post-oxidative calcination to remove surface covers.Zum Vorteil gewendet: Durch eine einfache Wärmebehandlung können oberflächengebundene Tenside genutzt werden, um Au-Kolloide auf Trägern zu stabilisieren – statt ihre Oberfläche zu blockieren und die Partikelsinterung zu erschweren.
      PubDate: 2017-03-22T06:02:31.031254-05:
      DOI: 10.1002/ange.201701191
       
  • Frontispiz: Mechanical Trap Surface-Enhanced Raman Spectroscopy for
           Three-Dimensional Surface Molecular Imaging of Single Live Cells
    • Authors: Qianru Jin; Ming Li, Beril Polat, Santosh K. Paidi, Aimee Dai, Amy Zhang, Jayson V. Pagaduan, Ishan Barman, David H. Gracias
      Abstract: Einzelzell-Bildgebung I. Barman, D. H. Gracias et al. beschreiben in ihrer Zuschrift auf S. 3880 ff. einen mikromechanischen SERS-Sensor, der den Einfang und die Visualisierung der chemischen Zusammensetzung einzelner Zelloberflächen ermöglicht.
      PubDate: 2017-03-22T04:02:46.431402-05:
      DOI: 10.1002/ange.201781461
       
  • Ring Shuttling Controls Macroscopic Motion in a Three-Dimensional Printed
           Polyrotaxane Monolith
    • Authors: Qianming Lin; Xisen Hou, Chenfeng Ke
      Abstract: Amplification of molecular motions into the macroscopic world has great potential in the development of smart materials. Demonstrated here is an approach that integrates mechanically interlocked molecules into complex three-dimensional (3D) architectures by direct-write 3D printing. The design and synthesis of polypseudorotaxane hydrogels, which are composed of α-cyclodextrins and poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymers, and their subsequent fabrication into polyrotaxane-based lattice cubes by 3D printing followed by post-printing polymerization are reported. By switching the motion of the α-cyclodextrin rings between random shuttling and stationary states through solvent exchange, the polyrotaxane monolith not only exhibits macroscopic shape-memory properties but is also capable of converting the chemical energy input into mechanical work by lifting objects against gravity.Innere Ordnung: Durch 3D-Druck erzeugte Polyrotaxan-Monolithe (oben links) können reversibel ihre Form wechseln. Der Regenerationsprozess beruht auf der Bewegung der Cyclodextrinringe auf den Achsen des Polyrotaxans. DMSO=Dimethylsulfoxid.
      PubDate: 2017-03-22T03:15:59.234987-05:
      DOI: 10.1002/ange.201612440
       
  • Strings of Porous Carbon Polyhedrons as Self-Standing Cathode Host for
           High-Energy-Density Lithium–Sulfur Batteries
    • Authors: Yazhi Liu; Gaoran Li, Jing Fu, Zhongwei Chen, Xinsheng Peng
      Abstract: Rational design of cathode hosts with high electrical conductivity and strong sulfur confinement is a great need for high-performance lithium–sulfur batteries. Herein, we report a self-standing, hybrid-nanostructured cathode host comprised of metal–organic framework (MOF)-derived porous carbon polyhedrons and carbon nanotubes (CNTs) for the significant improvement of both the electrode cyclability and energy density. The strong coupling of the intertwined CNTs and strung porous carbon polyhedrons as a binder-free thin film significantly enhances the long-range electronic conductivity and provides abundant active interfaces as well as robust electrode integrity for sulfur electrochemistry. Attributed to the synergistic combination of the CNTs and carbon polyhedrons, the obtained sulfur electrodes exhibit outstanding cyclability, an excellent high-rate response up to 10 C, and an ultra-high volumetric capacity of 960 Ah L−1.Verwobene Kohlenstoffnanoröhren und aufgereihte poröse Kohlenstoffpolyeder wurden als freistehendes Kathodengerüst für Lithium-Schwefel-Batterien entwickelt. Die resultierende Schwefelelektrode ist hoch zyklierbar und verfügt über eine hohe Energiedichte.
      PubDate: 2017-03-22T03:15:56.320964-05:
      DOI: 10.1002/ange.201700686
       
  • From Millimeter to Subnanometer: Vapor–Solid Deposition of Carbon
           Nitride Hierarchical Nanostructures Directed by Supramolecular Assembly
    • Authors: Jingsan Xu; Hong Wang, Chao Zhang, Xiaofei Yang, Shaowen Cao, Jiaguo Yu, Menny Shalom
      Abstract: Shape and nanostructure control has great potential to enable graphitic carbon nitride (C3N4) structures with new properties and functionalities. In this work, a new type of hierarchically structured nanoporous C3N4 is introduced. The C3N4 exhibits unique, edelweiss-like morphology, with components ranging from millimeter-sized bunches to subnanometer-thick layers. A one-step vapor–solid deposition approach using supramolecular aggregates as the precursor is carried out to accomplish the growth. Supramolecular pre-association plays a crucial role in achieving this nanostructure by directing the vaporization and deposition processes. Furthermore, very small C3N4 quantum dots can be readily acquired by bath sonication of the thin layers in water. The supramolecular preorganization growth strategy developed herein may provide a general methodology in the design of advanced photoelectric materials with broad applications in energy conversion and storage.Edelweiß aus Melamin und Cyanursäure: Eine neue Art von hierarchisch strukturiertem nanoporösem C3N4 wird eingeführt, das Bestandteile von millimetergroßen Bündeln bis zu subnanometerdünnen Schichten aufweist. Das Wachstum erfolgt über einen Dampf-Feststoff-Ansatz unter Ausnutzung des dirigierenden Effekts der Assemblierungsvorstufen. Außerdem können C3N4-Quantenpunkte durch Ultraschallbehandlung der dünnen Schichten in Wasser leicht hergestellt werden.
      PubDate: 2017-03-22T03:10:39.099519-05:
      DOI: 10.1002/ange.201611946
       
  • Grand Prix de la Fondation de la Maison de Chimie für Vincenzo
           Balzani / Kurz gemeldet
    • PubDate: 2017-03-22T03:05:40.053336-05:
      DOI: 10.1002/ange.201702259
       
  • Wissenschaftliche Integrität
    • Authors: Joseph S. Francisco; Ulrike Hahn, Helmut Schwarz
      Abstract: „… Wissenschaftliche Integrität ist nicht nur die Grundlage wissenschaftlicher Untersuchungen, sondern zugleich die Voraussetzung für ein positives Image von Forschung … Für Einzelpersonen ist die Integrität ein Aspekt moralischer Natur und Erfahrung. Für Institutionen geht es um die Schaffung einer Umgebung, die verantwortungsbewusstes Handeln fördert … In erster Linie sind die Forschungseinrichtungen gefordert, Leitlinien und Verhaltenskodexe zur wissenschaftlichen Integrität bereitzustellen …” Lesen Sie mehr im Editorial von J. S. Francisco, U. Hahn und H. Schwarz.
      PubDate: 2017-03-22T03:05:25.114232-05:
      DOI: 10.1002/ange.201700613
       
  • Enantioselective Formal α-Methylation and α-Benzylation of Aldehydes by
           Means of Photo-Organocatalysis
    • Authors: Giacomo Filippini; Mattia Silvi, Paolo Melchiorre
      Abstract: Detailed herein is the photochemical organocatalytic enantioselective α-alkylation of aldehydes with (phenylsulfonyl)alkyl iodides. The chemistry relies on the direct photoexcitation of enamines to trigger the formation of reactive carbon-centered radicals from iodosulfones, while the ground-state chiral enamines provide effective stereochemical control over the radical trapping process. The phenylsulfonyl moiety, acting as a redox auxiliary group, facilitates the generation of radicals. In addition, it can eventually be removed under mild reducing conditions to reveal methyl and benzyl groups.Anregen und abfangen: Enantiomerenangereicherte α-alkylierte Aldehyde (2) wurden synthetisiert. Dazu wurden mithilfe von chiralen Enaminen (A) aus (Phenylsulfonyl)alkyliodiden (1) Radikale erzeugt und stereoselektiv abgefangen. Nach Desulfonylierung von 2 entstehen Produkte, in denen eine Methyl- oder Benzylgruppe hoch stereoselektiv eingeführt wurde. SET=Einelektrontransfer.
      PubDate: 2017-03-21T09:37:42.313313-05:
      DOI: 10.1002/ange.201612045
       
  • B(C6F5)3-Catalyzed Selective Chlorination of Hydrosilanes
    • Authors: Karina Chulsky; Roman Dobrovetsky
      Abstract: The chlorination of Si−H bonds often requires stoichiometric amounts of metal salts in conjunction with hazardous reagents, such as tin chlorides, Cl2, and CCl4. The catalytic chlorination of silanes often involves the use of expensive transition-metal catalysts. By a new simple, selective, and highly efficient catalytic metal-free method for the chlorination of Si−H bonds, mono-, di-, and trihydrosilanes were selectively chlorinated in the presence of a catalytic amount of B(C6F5)3 or Et2O⋅B(C6F5)3 and HCl with the release of H2 as a by-product. The hydrides in di- and trihydrosilanes could be selectively chlorinated by HCl in a stepwise manner when Et2O⋅B(C6F5)3 was used as the catalyst. A mechanism is proposed for these catalytic chlorination reactions on the basis of competition experiments and density functional theory (DFT) calculations.Eine gewinnbringende Kombination: Hydrosilane gehen bei Behandlung mit HCl in Gegenwart einer katalytischen Menge B(C6F5)3 eine selektive Chlorierung unter Freisetzung von H2 ein (siehe Schema). Für die Chlorierung von Di- und Trihydrosilanen erwies sich das Addukt Et2O⋅B(C6F5)3 als der selektivere Katalysator.
      PubDate: 2017-03-21T09:37:39.062593-05:
      DOI: 10.1002/ange.201700324
       
  • Photochemical Generation of Strained Cycloalkynes from
           Methylenecyclopropanes
    • Authors: Daniel P. Maurer; Rui Fan, Dasan M. Thamattoor
      Abstract: The hydrocarbons 1-cyclopentylidene-1a,9b-dihydro-1H-cyclopropa[l]phenanthrene and 1-cyclobutylidene-1a,9b-dihydro-1H-cyclopropa[l]phenanthrene undergo photolysis in solution at ambient temperature to produce cyclohexyne and cyclopentyne, respectively. These strained cycloalkynes, formed via the putative cycloalkylidenecarbenes, were intercepted as Diels–Alder adducts. Calculations at the CCSD(T)/cc-pVTZ//B3LYP/6-31+G* level of theory show that singlet cyclopentylidenecarbene has to overcome a barrier of 9.1 kcal mol−1 to rearrange into cyclohexyne (with ΔE for ring expansion=−15.1 kcal mol−1). By contrast, cyclobutylidenecarbene only needs to surmount a barrier of 1.6 kcal mol−1 to rearrange into cyclopentyne (with ΔE for ring expansion=−6.2 kcal mol−1).Zunehmende Spannungen: Die Photolyse der Kohlenwasserstoffe 1-Cyclopentyliden- und 1-Cyclobutyliden-1a,9b-dihydro-1H-cyclopropa[l]phenanthren in Lösung bei Raumtemperatur setzt Cyclohexin bzw. Cyclopentin frei (siehe Schema). Diese gespannten Cycloalkine, die vermutlich über Cycloalkylidencarbene entstehen, wurden in Form von Diels-Alder-Addukten abgefangen.
      PubDate: 2017-03-21T09:37:27.831323-05:
      DOI: 10.1002/ange.201701275
       
  • Synthesis and Optoelectronic Properties of
           Hexa-peri-hexabenzoborazinocoronene
    • Authors: Jacopo Dosso; Jonathan Tasseroul, Francesco Fasano, Davide Marinelli, Nicolas Biot, Andrea Fermi, Davide Bonifazi
      Abstract: The first rational synthesis of a BN-doped coronene derivative in which the central benzene ring has been replaced by a borazine core is described. This includes six C−C ring-closure steps that, through intramolecular Friedel–Crafts-type reactions, allow the stepwise planarization of the hexaarylborazine precursor. UV/Vis absorption, emission, and electrochemical investigations show that the introduction of the central BN core induces a dramatic widening of the HOMO–LUMO gap and an enhancement of the blue-shifted emissive properties with respect to its all-carbon congener.Ein BN-dotiertes Coronen-Derivat mit einem Borazin- anstelle des Benzolkerns wird beschrieben. UV/Vis-Absorptions- und Emissionsstudien sowie elektrochemische Untersuchungen zeigen, dass die Einführung des BN-Kerns den HOMO-LUMO-Abstand stark vergrößert und die blauverschobene Emission gegenüber dem Kohlenstoffanalogon deutlich erhöht.
      PubDate: 2017-03-21T09:37:19.533559-05:
      DOI: 10.1002/ange.201700907
       
  • Hydrophobic Water Probed Experimentally at the Gold Electrode/Aqueous
           Interface
    • Authors: Yujin Tong; François Lapointe, Martin Thämer, Martin Wolf, R. Kramer Campen
      Abstract: Hydrophobe Wassermoleküle wurden an der Grenzfläche zwischen einer Goldelektrode und dem wässrigen Elektrolyten mit Schwingungs-Summenfrequenz-Spektroskopie nachgewiesen. R. K. Campen et al. erklären in ihrer Zuschrift (
      DOI : 10.1002/ange.201612183), dass die Populations- und Strukturmerkmale dieses Wassertyps von der Vorspannung abhängen. Sun Wukong, eine Gestalt der chinesischen Mythologie, schwingt seine goldbebänderte Keule und richtet so die OH-Gruppen im Wasser in Richtung der Goldoberfläche aus.
      PubDate: 2017-03-21T09:32:25.899751-05:
       
  • Highly Active GaN-Stabilized Ta3N5 Thin-Film Photoanode for Solar Water
           Oxidation
    • Authors: Miao Zhong; Takashi Hisatomi, Yutaka Sasaki, Sayaka Suzuki, Katsuya Teshima, Mamiko Nakabayashi, Naoya Shibata, Hiroshi Nishiyama, Masao Katayama, Taro Yamada, Kazunari Domen
      Abstract: Ta3N5 is a very promising photocatalyst for solar water splitting because of its wide spectrum solar energy utilization up to 600 nm and suitable energy band position straddling the water splitting redox reactions. However, its development has long been impeded by poor compatibility with electrolytes. Herein, we demonstrate a simple sputtering-nitridation process to fabricate high-performance Ta3N5 film photoanodes owing to successful synthesis of the vital TaOδ precursors. An effective GaN coating strategy is developed to remarkably stabilize Ta3N5 by forming a crystalline nitride-on-nitride structure with an improved nitride/electrolyte interface. A stable, high photocurrent density of 8 mA cm−2 was obtained with a CoPi/GaN/Ta3N5 photoanode at 1.2 VRHE under simulated sunlight, with O2 and H2 generated at a Faraday efficiency of unity over 12 h. Our vapor-phase deposition method can be used to fabricate high-performance (oxy)nitrides for practical photoelectrochemical applications.Solarenergieumwandlung: Eine einfache Gasphasenabscheidungstechnik wurde entwickelt, um dünne GaN/Ta3N5-Filme mit konkurrenzfähiger Aktivität und Stabilität in der solaren Wasserspaltung herzustellen. Die GaN-Überschichtungsstrategie lässt sich leicht anwenden, um verschiedene (Oxy)nitride für praktische photoelektrochemische Anwendungen zu stabilisieren.
      PubDate: 2017-03-21T09:19:44.100603-05:
      DOI: 10.1002/ange.201700117
       
  • A Molecular Circuit Regenerator to Implement Iterative Strand Displacement
           Operations
    • Authors: Nicole V. DelRosso; Sarah Hews, Lee Spector, Nathan D. Derr
      Abstract: The predictable chemistry of Watson–Crick base-pairing imparts a unique structural programmability to DNA, enabling the facile design of molecular reactions that perform computations. However, many of the current architectures limit devices to a single operational cycle. Herein, we introduce the design of the “regenerator”, a device based on coupled enthalpic and entropic reactions that permits the regeneration of molecular circuit components.Wiederverwendbare DNA: Watson-Crick-Basenpaarung verleiht DNA eine einzigartige strukturelle Programmierbarkeit, sodass molekulare Reaktionen mit Rechenfunktionen entworfen werden können. Aktuelle Architekturen vollführen allerdings nur einen einzigen Zyklus. Ein System mit gekoppelten enthalpischen und entropischen Reaktionen ermöglicht nun die Regenerierung molekularer Komponenten.
      PubDate: 2017-03-21T05:28:58.197956-05:
      DOI: 10.1002/ange.201610890
       
  • Polyketidsynthase-Module: eine Neudefinition
    • Authors: Adrian T. Keatinge-Clay
      Abstract: Modulierte Definition: Eine lange gültige Lehrmeinung in der Enzymologie der modularen Polyketidsynthase – die Definition eines Moduls – wurde in einer aktuellen Arbeit von Abe et al. widerlegt. Mit diesen neuen Kenntnissen steigt die Hoffnung, künstliche Varianten enzymatischer Biosynthesemaschinerien herstellen zu können, um neue Materialien und Wirkstoffe zu produzieren.
      PubDate: 2017-03-21T04:16:26.253947-05:
      DOI: 10.1002/ange.201701281
       
  • A Polyoxoniobate–Polyoxovanadate Double-Anion Catalyst for Simultaneous
           Oxidative and Hydrolytic Decontamination of Chemical Warfare Agent
           Simulants
    • Authors: Jing Dong; Jufang Hu, Yingnan Chi, Zhengguo Lin, Bo Zou, Song Yang, Craig L. Hill, Changwen Hu
      Abstract: A novel double-anion complex, H13[(CH3)4N]12[PNb12O40(VVO)2⋅(VIV4O12)2]⋅22 H2O (1), based on bicapped polyoxoniobate and tetranuclear polyoxovanadate was synthesized, characterized by routine techniques and used in the catalytic decontamination of chemical warfare agents. Under mild conditions, 1 catalyzes both hydrolysis of the nerve agent simulant, diethyl cyanophosphonate (DECP) and selective oxidation of the sulfur mustard simulant, 2-chloroethyl ethyl sulfide (CEES). In the oxidative decontamination system 100 % CEES was transformed selectively to nontoxic 2-chloroethyl ethyl sulfoxide and vinyl ethyl sulfoxide using nearly stoichiometric 3 % aqueous H2O2 with a turnover frequency (TOF) of 16 000 h−1. Importantly, the catalytic activity is maintained even after ten recycles and CEES is completely decontaminated in 3 mins without formation of the highly toxic sulfone by-product. A three-step oxidative mechanism is proposed.Dekontamination mit POMs: H13[(CH3)4N]12[PNb12O40(VVO)2⋅(VIV4O12)2]⋅ 22 H2, ein ungewöhnlicher Komplex, katalysiert sowohl die Hydrolyse eines Nervengiftsimulans als auch die schnelle, selektive Oxidation eines Senfgassimulans.
      PubDate: 2017-03-21T04:01:51.840909-05:
      DOI: 10.1002/ange.201700159
       
  • Trimetallic Oxyhydroxide Coralloids for Efficient Oxygen Evolution
           Electrocatalysis
    • Authors: Yecan Pi; Qi Shao, Pengtang Wang, Fan Lv, Shaojun Guo, Jun Guo, Xiaoqing Huang
      Abstract: Trimetallic oxyhydroxides are one of the most effective materials for oxygen evolution reaction (OER) catalysis, a key process for water splitting. Herein, we describe a facile wet-chemical method to directly grow a series of coralloid trimetallic oxyhydroxides on arbitrary substrates such as nickel foam (NF) and carbon nanotubes (CNTs). The amount of iron in these oxyhydroxide sponges on NF and CNTs was precisely controlled, revealing that the electrocatalytic activity of the WCoFe trimetallic oxyhydroxides depends on the Fe amount in a volcano-like fashion. The optimized W0.5Co0.4Fe0.1/NF catalyst exhibited an overpotential of only 310 mV to deliver a large current density of 100 mA cm−2 and a very low Tafel slope of 32 mV dec−1. It also showed superior stability with negligible activity decay after use in the OER for 21 days (>500 h). X-ray photoelectron spectroscopy revealed that the addition of Fe leads to an on average lower Co oxidation state, which contributes to the enhanced OER performance.Korallenförmige W0.5Co0.5−xFex-Oxyhydroxide mit genau einstellbarer Fe-Beladung wurden durch ein nasschemisches Verfahren direkt auf einem leitenden Substrat abgeschieden. Die Aktivität dieses Materials in der Sauerstoffentwicklung (OER) ist vulkanartig von der Fe-Beladung abhängig. Das optimierte Material, W0.5Co0.4Fe0.1, ist in der OER-Katalyse besonders aktiv und stabil.
      PubDate: 2017-03-21T03:55:36.799683-05:
      DOI: 10.1002/ange.201701533
       
  • Authors Profile
    • PubDate: 2017-03-21T03:55:26.690681-05:
      DOI: 10.1002/ange.201702167
       
  • Synthesis of Indoles and Pyrroles Utilizing Iridium Carbenes Generated
           from Sulfoxonium Ylides
    • Authors: Janakiram Vaitla; Annette Bayer, Kathrin H. Hopmann
      Abstract: Metal carbenes can undergo a myriad of synthetic transformations. Sulfur ylides are potential safe precursors of metal carbenes. Herein, we report cascade reactions that involve carbenoids derived from sulfoxonium ylides for the efficient and regioselective synthesis of indoles and pyrroles. The tandem action of iridium and Brønsted acid catalysts enables rapid assembly of the heterocycles from unmodified anilines or readily accessible enamines under microwave irradiation. The key mechanistic steps are the catalytic transformation of the sulfoxonium ylide into an iridium–carbene complex, followed by N−H or C−H functionalization of an aniline or enamine, respectively, and a final acid-catalyzed cyclization. The present method was successfully applied to the synthesis of the densely functionalized pyrrole subunit of atorvastatin.Die Abkürzung nehmen: Substituierte Indole und Pyrrole, darunter die dicht funktionalisierte Pyrrol-Untereinheit von Atorvastatin, wurden in einem Schritt aus Sulfoxoniumyliden und nichtmodifizierten Anilinen oder einfachen Enaminen durch Tandemkatalyse mit [{Ir(cod)Cl}2] und einer Brønsted-Säure unter Mikrowellenbestrahlung aufgebaut (siehe Schema). Die Transformation umfasst die Bildung eines Iridium-Carben-Komplexes und einen beispiellosen C-H-Funktionalisierungsschritt.
      PubDate: 2017-03-20T10:15:35.641398-05:
      DOI: 10.1002/ange.201610520
       
  • Zinc Regulates Chemical-Transmitter Storage in Nanometer Vesicles and
           Exocytosis Dynamics as Measured by Amperometry
    • Authors: Lin Ren; Masoumeh Dowlatshahi Pour, Soodabeh Majdi, Xianchan Li, Per Malmberg, Andrew G. Ewing
      Abstract: We applied electrochemical techniques with nano-tip electrodes to show that micromolar concentrations of zinc not only trigger changes in the dynamics of exocytosis, but also vesicle content in a model cell line. The vesicle catecholamine content in PC12 cells is significantly decreased after 100 μm zinc treatment, but, catecholamine release during exocytosis remains nearly the same. This contrasts with the number of molecules stored in the exocytosis vesicles, which decreases, and we find that the amount of catecholamine released from zinc-treated cells reaches nearly 100 % content expelled. Further investigation shows that zinc slows down exocytotic release. Our results provide the missing link between zinc and the regulation of neurotransmitter release processes, which might be important in memory formation and storage.Zinkronisiert: Einzelzellamperometrie und intrazelluläre elektrochemische Vesikelstoßzytometrie belegen die Auswirkungen von Zink auf Exozytose und Vesikelgehalt von PC12-Zellen. Zink verändert nicht nur die Speicherung von Botenstoffen, sondern auch die Dynamik der Exozytose, indem es den Öffnungs- und Schließprozess von Fusionsporen stabilisiert.
      PubDate: 2017-03-20T10:10:51.169596-05:
      DOI: 10.1002/ange.201700095
       
  • Activation of SF6 at Platinum Complexes: Formation of SF3 Derivatives and
           their Application in Deoxyfluorination Reactions
    • Authors: Claudia Berg; Thomas Braun, Mike Ahrens, Philipp Wittwer, Roy Herrmann
      Abstract: The activation of SF6 at [Pt(PR3)2] R=Cy, iPr complexes in the presence of PR3 led selectively and in an unprecedented reaction route to the generation of the SF3 complexes trans-[Pt(F)(SF3)(PR3)2]. These can also be synthesized from SF4 and the SF2 derivative trans-[Pt(F)(SF2)(PCy3)2][BF4] was characterized by X-ray crystallography. trans-[Pt(F)(SF3)(PR3)2] complexes are useful tools for deoxyfluorination reactions and novel fluorido complexes bearing a SOF ligand are formed. Based on these studies a process for the deoxyfluorination of ketones was developed with SF6 as fluorinating agent.SpezialeFFekte: Die Aktivierung von SF6 an Pt-Komplexen ergibt SF3-Fluorido-Komplexe, die Ketone fluorieren können.
      PubDate: 2017-03-20T10:00:51.28047-05:0
      DOI: 10.1002/ange.201612417
       
  • Bis-Gadolinium Complexes for Solid Effect and Cross Effect Dynamic Nuclear
           Polarization
    • Authors: Monu Kaushik; Mian Qi, Adelheid Godt, Björn Corzilius
      Abstract: High-spin complexes act as polarizing agents (PAs) for dynamic nuclear polarization (DNP) in solid-state NMR spectroscopy and feature promising aspects towards biomolecular DNP. We present a study on bis(Gd-chelate)s which enable cross effect (CE) DNP owing to spatial confinement of two dipolar-coupled electron spins. Their well-defined Gd⋅⋅⋅Gd distances in the range of 1.2–3.4 nm allowed us to elucidate the Gd⋅⋅⋅Gd distance dependence of the DNP mechanism and NMR signal enhancement. We found that Gd⋅⋅⋅Gd distances above 2.1 nm result in solid effect DNP while distances between 1.2 and 2.1 nm enable CE for 1H, 13C, and 15N nuclear spins. We compare 263 GHz electron paramagnetic resonance (EPR) spectra with the obtained DNP field profiles and discuss possible CE matching conditions within the high-spin system and the influence of dipolar broadening of the EPR signal. Our findings foster the understanding of the CE mechanism and the design of high-spin PAs for specific applications of DNP.Bis-Gd-Komplexe wurden als Polarisationsmittel für die dynamische Kernpolarisation (DNP) untersucht. Bei Verkleinerung des Abstandes zwischen den beiden GdIII-Ionen wird ein Übergang vom „Solid-Effect”- zum „Cross-Effect”-DNP-Mechanismus beobachtet. Die Analyse der NMR-Signalverstärkungen für 1H, 13C und 15N gibt Aufschluss über die Abstandsabhängigkeit zwischen zwei Elektronenspins für den Kreuzeffekt.
      PubDate: 2017-03-20T10:00:49.738476-05:
      DOI: 10.1002/ange.201612388
       
  • Composition-Dependent Hot Carrier Relaxation Dynamics in Cesium Lead
           Halide (CsPbX3, X=Br and I) Perovskite Nanocrystals
    • Authors: Heejae Chung; Seok Il Jung, Hyo Jin Kim, Wonhee Cha, Eunji Sim, Dongho Kim, Weon-Kyu Koh, Jiwon Kim
      Abstract: Cesium-based perovskite nanocrystals (NCs) have outstanding photophysical properties improving the performances of lighting devices. Fundamental studies on excitonic properties and hot-carrier dynamics in perovskite NCs further suggest that these materials show higher efficiencies compared to the bulk form of perovskites. However, the relaxation rates and pathways of hot-carriers are still being elucidated. By using ultrafast transient spectroscopy and calculating electronic band structures, we investigated the dependence of halide in Cs-based perovskite (CsPbX3 with X=Br, I, or their mixtures) NCs on the hot-carrier relaxation processes. All samples exhibit ultrafast (CsPbBr1.5I1.5 (380 fs)>CsPbI3 NC (580 fs). These result accounts for a reduced light emission efficiency of CsPbI3 NC compared to CsPbBr3 NC.Heiße Träger: Die signifikante Abhängigkeit der Relaxationsrate heißer Träger vom Halogen (X=Br, I oder Mischung) wird hauptsächlich der Zustandsdichte der Löcher im Valenzband von CsPbX3-Nanokristallen zugeordnet. Die Relaxationsrate verringert sich beim Übergang von CsPbBr3- zu CsPbI3-Nanokristallen. VB=Valenzband, CB=Leitungsband.
      PubDate: 2017-03-20T10:00:44.000778-05:
      DOI: 10.1002/ange.201611916
       
  • Chemoselective Alteration of Fluorophore Scaffolds as a Strategy for the
           Development of Ratiometric Chemodosimeters
    • Authors: Xinqi Zhou; Lauren Lesiak, Rui Lai, Jon R. Beck, Jia Zhao, Christian G. Elowsky, Hui Li, Cliff I. Stains
      Abstract: Ratiometric sensors generally couple binding events or chemical reactions at a distal site to changes in the fluorescence of a core fluorophore scaffold. However, such approaches are often hindered by spectral overlap of the product and reactant species. We provide a strategy to design ratiometric sensors that display dramatic spectral shifts by leveraging the chemoselective reactivity of novel functional groups inserted within fluorophore scaffolds. As a proof-of-principle, fluorophores containing a borinate (RF620) or silanediol (SiOH2R) functionality at the bridging position of the xanthene ring system are developed as endogenous H2O2 sensors. Both these fluorophores display far-red to near-infrared excitation and emission prior to reaction. Upon oxidation by H2O2 both sensors are chemically converted to tetramethylrhodamine, producing significant (≥66 nm) blue-shifts in excitation and emission maxima. This work provides a new concept for the development of ratiometric probes.Ratiometrische Sensoren: Eine neuartige Methode für die gezielte Entwicklung ratiometrischer Sensoren, bezeichnet als chemoselektive Veränderung von Fluorophorgerüsten (CAFS), wird vorgestellt. Das Konzept wird am Beispiel zweier Wasserstoffperoxidsensoren mit großen Anregungs- und Emissionsverschiebungen (≥66 nm) demonstriert.
      PubDate: 2017-03-20T10:00:41.26387-05:0
      DOI: 10.1002/ange.201612628
       
  • Asymmetric Grignard Synthesis of Tertiary Alcohols through Rational Ligand
           Design
    • Authors: Bartosz Bieszczad; Declan G. Gilheany
      Abstract: A simple, general and practical method is reported for highly enantioselective construction of tertiary alcohols through the direct addition of organomagnesium reagents to ketones. Discovered by rational ligand design based on a mechanistic hypothesis, it has an unprecedented broad scope. It utilizes a new type of chiral tridentate diamine/phenol ligand that is easily removed from the reaction mixture. It is exemplified by application to a formal asymmetric synthesis (>95:5 d.r.) of vitamin E.Drei Plätze frei: Eine einfache und allgemeine Route für die direkte asymmetrische Grignard-Synthese tertiärer Alkohole nutzt die Koordination dreizähniger Liganden an Magnesium. Die rational entwickelte Methode wurde in einer formalen asymmetrischen Synthese von Vitamin E eingesetzt.
      PubDate: 2017-03-20T10:00:38.002489-05:
      DOI: 10.1002/ange.201610462
       
  • Merging Distal Alkynyl Migration and Photoredox Catalysis for Radical
           Trifluoromethylative Alkynylation of Unactivated Olefins
    • Authors: Yan Xu; Zhen Wu, Jingxing Jiang, Zhuofeng Ke, Chen Zhu
      Abstract: Disclosed herein is a novel, redox-neutral protocol for the visible-light-induced radical alkynylation of unactivated olefins. The intramolecular migration of an alkynyl group, by cleaving an inert C−C σ bond, is realized for the first time. A wide range of synthetically useful trifluoroethylated linear alkynes are readily obtained under mild reaction conditions.1+1>2: Ein redoxneutraler Ansatz zur katalytischen radikalischen Alkinylierung nichtaktivierter Olefine unter Bestrahlung mit sichtbarem Licht wird vorgestellt. Dabei gelingt die intramolekulare Verschiebung einer Alkinylgruppe unter Spaltung einer inerten C-C-σ-Bindung. Viele nützliche trifluorethylierte lineare Alkine sind unter milden Bedingungen effizient zugänglich.
      PubDate: 2017-03-20T09:55:52.918836-05:
      DOI: 10.1002/ange.201700413
       
  • Polarisation auf der Mesoskala durch geometrische Frustration in
           kolumnaren supramolekularen Kristallen
    • Authors: Christoph S. Zehe; Joshua A. Hill, Nicholas P. Funnell, Klaus Kreger, Kasper P. van der Zwan, Andrew L. Goodwin, Hans-Werner Schmidt, Jürgen Senker
      Abstract: Kolumnare supramolekulare Phasen, die eine Polarisation entlang der Kolumnenachse aufweisen, haben das Potential zur Entwicklung von Datenspeichern mit ultrahoher Dichte, da jede einzelne Kolumne als Speicherelement fungieren kann. Wir zeigen anhand von Untersuchungen der Struktur und Unordnung von vier kolumnaren 1,3,5-Benzoltrisamiden mittels totaler Röntgenstreuung und DFT-Rechnungen, dass die Kolumnenorientierung und damit das kolumnare Dipolmoment empfindlich auf geometrische Frustration ist, sofern die Kolumnen in hexagonalen Stabpackungen aggregieren. Die Frustration unterdrückt die konventionelle antiferroelektrische Ordnung und erhöht die Sensitivität für kollektive interkolumnare Packungseffekte. Dieser Befund erlaubt es, Domänen auf der Mesoskala zu erzeugen, die eine spontane Polarisation aufweisen. Unsere Ergebnisse zeigen auf, wie das komplexe Zusammenspiel von sterischen und elektrostatischen Wechselwirkungen durch ein einfaches Design der molekularen Synthone beeinflusst wird, um spontane Polarisation zu erzeugen und die Größe der mesoskopischen Domänen einzustellen.Supramolekulare Chemie trifft geometrische Frustration in axial polaren Volumenphasen von 1,3,5-Benzoltrisamiden. Diese bilden supramolekulare Kolumnen aus, und die so entstehenden Makrodipole frustrieren, wenn sich die Kolumnen zu hexagonalen Stabpackungen zusammenlagern. Mittels totaler Röntgenstreuung wird gezeigt, dass die Frustration genutzt werden kann, um spontane Polarisation auf der Mesoskala zu erzeugen.
      PubDate: 2017-03-20T09:50:32.095778-05:
      DOI: 10.1002/ange.201612122
       
  • Diversity in Gold Finger Structure Elucidated by Traveling-Wave Ion
           Mobility Mass Spectrometry
    • Authors: Zhifeng Du; Raphael E. F. de Paiva, Kristina Nelson, Nicholas P. Farrell
      Abstract: Traveling wave ion mobility (TWIM) mass spectrometry (MS) is a powerful method for the structural and conformational analysis of proteins and peptides, enabling the differentiation of isomeric peptides (or proteins) that have the same sequence but are modified at different residues. In this study, the TWIM-MS technique was used to separate isomeric AuI metallopeptide ions that were formed by ZnII displacement from the parent zinc fingers (ZFs). The synthetic gold finger peptides were derived from the C-terminus of the HIV nucleocapsid p7 protein (NCp7-F2) and finger 3 of the Sp1 transcription factor (Sp1-F3). TWIM-MS enabled the acquisition of distinct product ion spectra for each isomer, clearly indicating the binding sites for the major conformers in the presence of multiple coordination possibilities. Collision cross-section measurements showed that the aurated peptide has a slightly more compact structure than the parent zinc compound NCp7-F2, which showed only one conformation.Goldrichtige Methode: Wanderwellen-Ionenmobilitätsmassenspektrometrie wurde verwendet, um die Isomere von Gold(I)-metallierten Peptidionen zu trennen, und ermöglichte so die Aufnahme unterschiedlicher Produktionenspektren für jedes Isomer (blau und rot). Die gemessenen Stoßquerschnitte zeigen, dass das Gold-substituierte Peptid etwas kompakter als der ursprüngliche Zinkfinger ist.
      PubDate: 2017-03-20T09:50:25.353773-05:
      DOI: 10.1002/ange.201612494
       
  • Grünlicht-induzierte Rezeptorinaktivierung durch Cobalamin-bindende
           Domänen
    • Authors: Stephanie Kainrath; Manuela Stadler, Eva Reichhart, Martin Distel, Harald Janovjak
      Abstract: Optogenetik und Photopharmakologie ermöglichen präzise räumliche und zeitliche Kontrolle von Proteinwechselwirkung und -funktion in Zellen und Tieren. Optogenetische Methoden, die auf grünes Licht ansprechen und zum Trennen von Proteinkomplexen geeignet sind, sind nicht weitläufig verfügbar, würden jedoch mehrfarbige Experimente zur Beantwortung von biologischen Fragestellungen ermöglichen. Hier demonstrieren wir die Verwendung von Cobalamin(Vitamin B12)-bindenden Domänen von bakteriellen CarH-Transkriptionsfaktoren zur Grünlicht-induzierten Dissoziation von Rezeptoren. Fusioniert mit dem Fibroblasten-Wachstumsfaktor-Rezeptor 1 führten diese im Dunkeln in kultivierten Zellen zu Signalaktivität durch Oligomerisierung, welche durch Beleuchten umgehend aufgehoben wurde. In Zebrafischembryonen, die einen derartigen Rezeptor exprimieren, ermöglichte grünes Licht die Kontrolle über abnormale Signalaktivität während der Embryonalentwicklung.Normale Entwicklung im grünen Bereich: Die Fusion einer bakteriellen Cobalamin(Vitamin B12)-bindenden Domäne (CBD) mit einer Kinasedomäne (KD) aus Säugern resultiert in einer konstitutiv aktiven Signalgabe im Dunkeln. Die Signale führen zu Fehlentwicklungen in Zebrafischen. Grüne Bestrahlung verhindert diese Prozesse und ermöglicht eine normale Entwicklung (MYR: Myristoylierungs-Membrananker, AdoCbl: 5′-Desoxyadenosylcobalamin).
      PubDate: 2017-03-20T09:45:29.132306-05:
      DOI: 10.1002/ange.201611998
       
  • Precisely Regulated and Efficient Locking of Linear Peptides into Stable
           Multicyclic Topologies through a One-Pot Reaction
    • Authors: Weidong Liu; Yiwu Zheng, Xudong Kong, Christian Heinis, Yibing Zhao, Chuanliu Wu
      Abstract: Lineare Peptide lassen sich präzise und effizient in einer Eintopfreaktion (PROP-Locking) in multicyclischen Topologien fixieren. C. Wu et al. beschreiben in ihrer Zuschrift (
      DOI : 10.1002/ange.201610942) die Entwicklung eines kleinen Phenylmoleküls mit vier isosteren Thiolat-reaktiven Gruppen, das zum PROP-Locking linearer Peptide eingesetzt wurde. Das Prinzip der Methode erinnert an das chinesische Kongming-Lock-Denkspiel.
      PubDate: 2017-03-20T09:40:22.734243-05:
       
  • Brønsted-Säure-Katalyse der [2+2]-Photocycloaddition von Enondithianen
           bei Bestrahlung mit sichtbarem Licht
    • Authors: Christoph Brenninger; Alexander Pöthig, Thorsten Bach
      Abstract: Die intramolekulare [2+2]-Photocycloaddition von Enonen, deren Carbonylgruppe als 1,3-Dithian geschützt ist (Enondithiane), gelang unter Verwendung einer Brønsted-Säure (7.5–10 Mol-%) mit sichtbarem Licht (λ=405 nm). Entscheidend für den Erfolg der Reaktion ist vermutlich die Bildung von farbigen Thioniumionen, die Intermediate des Katalysezyklus sind. Als Produkte werden in sehr guten Ausbeuten (78–90 %) Cyclobutane erhalten. Es wird gezeigt, dass die Dithianeinheit reduktiv oder oxidativ entfernt werden kann, ohne das photochemisch aufgebaute Ringgerüst zu beeinträchtigen.Saure Verwandlung: Die photochemisch inerten Enondithiane 1 werden durch die Brønsted-Säure 3 zu gelb gefärbten Thioniumionen und lassen sich daher unter Säurekatalyse mit sichtbarem Licht in sehr guten Ausbeuten (78–90 %) zu den [2+2]-Photocycloadditionsprodukten 2 umsetzen.
      PubDate: 2017-03-20T09:21:07.114294-05:
      DOI: 10.1002/ange.201700837
       
  • Successive Charge Transitions of Unusually High-Valence Fe3.5+: Charge
           Disproportionation and Intermetallic Charge Transfer
    • Authors: Yoshiteru Hosaka; Fabio Denis Romero, Noriya Ichikawa, Takashi Saito, Yuichi Shimakawa
      Abstract: A perovskite-structure oxide containing unusually high-valence Fe3.5+ was obtained by high-pressure synthesis. Instability of the Fe3.5+ in Ca0.5Bi0.5FeO3 is relieved first by charge disproportionation at 250 K and then by intermetallic charge transfer between A-site Bi and B-site Fe at 200 K. These previously unobserved successive charge transitions are due to competing intermetallic and disproportionation charge instabilities. Both transitions change magnetic and structural properties significantly, indicating strong coupling of charge, spin, and lattice in the present system.Druckvolles Spiel: Ein Oxid mit Perowskitstruktur, das ungewöhnlich hochvalentes Fe3.5+ enthält, wurde durch Hochdrucksynthese erhalten. Die Instabilität des Fe3.5+ in Ca0.5Bi0.5FeO3 wird zuerst durch Fe-Ladungsdisproportionierung bei 250 K und dann durch Ladungstransfer von Bi auf Fe bei 200 K abgebaut.
      PubDate: 2017-03-20T09:20:57.442372-05:
      DOI: 10.1002/ange.201700881
       
  • Rhodium-Catalyzed Enantioselective Isomerization of
           meso-Oxabenzonorbornadienes to 1,2-Naphthalene Oxides
    • Authors: Andy Yen; Ken-Loon Choo, Shabnam K. Yazdi, Patrick T. Franke, Robert Webster, Ivan Franzoni, Charles C. J. Loh, Amalia I. Poblador-Bahamonde, Mark Lautens
      Abstract: Herein we describe a rhodium-catalyzed enantioselective isomerization of meso-oxabicyclic alkenes to 1,2-naphthalene oxides. These potentially useful building blocks can be accessed in moderate to excellent yields with impressive enantioselectivities. Additionally, experimental findings supported by preliminary computations suggest that ring-opening reactions of bridgehead disubstituted oxabicyclic alkenes proceed through the intermediacy of these epoxides and may point to a kinetically and thermodynamically favored reductive elimination as the origin for the observed enantioselectivities.Eine enantioselektive Isomerisierung von disubstituierten meso-oxabicyclischen Alkenen in Gegenwart eines [Rh(cod)2]OTf/(R)-(S)-PPF-PtBu2-Katalysatorsystems wird beschrieben. Die erhaltenen 1,2-Naphthalinoxide könnten als nützliche Bausteine für die asymmetrische Synthese dienen. Die Beteiligung dieser Epoxide als Zwischenstufen in asymmetrischen Ringöffnungsreaktionen von oxabicyclischen Alkenen wird ebenfalls erforscht.
      PubDate: 2017-03-20T09:20:54.404594-05:
      DOI: 10.1002/ange.201700632
       
  • Tandem Coupling of Azide with Isonitrile and Boronic Acid: Facile Access
           to Functionalized Amidines
    • Authors: Zhen Zhang; Baoliang Huang, Guanyu Qiao, Liu Zhu, Fan Xiao, Feng Chen, Bin Fu, Zhenhua Zhang
      Abstract: Amidine is a notable nitrogen-containing structural motif found in bioactive natural products and pharmaceuticals. Herein, a novel rhodium(I)-catalyzed tandem reaction of readily accessible azides with isonitriles and boronic acids via a carbodiimide intermediate is achieved. This protocol offers an alternative approach toward N-sulfonyl-, N-acyl-, and N- phosphoryl-functionalized, as well as general N-aryl and N-alkyl amidines with broad substrate scope. In addition, functionalized guanidines can also been synthesized when amines are used instead. The accomplishment of estrone-derived amidine and glibenclamide bioisosteres further reveals the practical utility of this strategy.Im Tandem: Eine Rhodium(I)-katalysierte Tandemreaktion von leicht verfügbaren Aziden mit Isocyaniden und Boronsäuren über eine Carbodiimid-Zwischenstufe wird als alternativer Weg zu N-Sulfonyl-, N-Acyl- und N-Phosphoryl- sowie allgemein zu N-Aryl- und N-Alkylamidinen vorgestellt. Die Synthese von Östron-Amidinen und Glibenclamid-Bioisosteren belegt den praktischen Nutzen der Strategie.
      PubDate: 2017-03-20T09:20:47.867013-05:
      DOI: 10.1002/ange.201700539
       
  • Manganese-Catalyzed N-Formylation of Amines by Methanol Liberating H2: A
           Catalytic and Mechanistic Study
    • Authors: Subrata Chakraborty; Urs Gellrich, Yael Diskin-Posner, Gregory Leitus, Liat Avram, David Milstein
      Abstract: The first example of a base metal (manganese) catalyzed acceptorless dehydrogenative coupling of methanol and amines to form formamides is reported herein. The novel pincer complex (iPr-PNHP)Mn(H)(CO)2 catalyzes the reaction under mild conditions in the absence of any additives, bases, or hydrogen acceptors. Mechanistic insight based on the observation of an intermediate and DFT calculations is also provided.Formamide wurden durch eine akzeptorfreie dehydrierende Kupplung von Methanol und Aminen synthetisiert, die durch einen Mangan-Pinzettenkomplex katalysiert wird (siehe Schema). Die Beobachtung eines Intermediats und Dichtefunktionalrechnungen geben mechanistische Einblicke.
      PubDate: 2017-03-20T09:20:32.522197-05:
      DOI: 10.1002/ange.201700681
       
  • Twisted Aromatic Frameworks: Readily Exfoliable and Solution-Processable
           Two-Dimensional Conjugated Microporous Polymers
    • Authors: A. Belen Marco; Diego Cortizo-Lacalle, Iñigo Perez-Miqueo, Giovanni Valenti, Alessandro Boni, Jan Plas, Karol Strutyński, Steven De Feyter, Francesco Paolucci, Mario Montes, Andrei N. Khlobystov, Manuel Melle-Franco, Aurelio Mateo-Alonso
      Abstract: Twisted two-dimensional aromatic frameworks have been prepared by overcrowding the nodes with bulky and rigid substituents. The highly distorted aromatic framework with alternating out-of-plane substituents results in diminished interlayer interactions that favor the exfoliation and dispersion of individual layers in organic media.Schicksalhafte Wendung: Eine verdrehte zweidimensionale aromatische Gerüstverbindung wurde durch sterische Überfrachtung der Knotenstellen mit sperrigen und starren Substituenten hergestellt (siehe Struktur). Das Gerüst weist verringerte Wechselwirkungen zwischen den Ebenen auf, was das Abblättern und Dispergieren einzelner Schichten in organischen Medien erleichtert.
      PubDate: 2017-03-20T07:25:37.211191-05:
      DOI: 10.1002/ange.201700271
       
  • 3-Aminodeoxypyranoses in Glycosylation: Diversity-Oriented Synthesis and
           Assembly in Oligosaccharides
    • Authors: Jing Zeng; Guangfei Sun, Wang Yao, Yangbin Zhu, Ruobin Wang, Lei Cai, Ke Liu, Qian Zhang, Xue-Wei Liu, Qian Wan
      Abstract: A concise, diversity-oriented approach for the synthesis of naturally occurring 3-amino- and 3-nitro-2,3,6-trideoxypyranose derivatives and analogues thereof from simple sugars has been developed. In addition, we investigated the synthesis of various 3-aminoglycosyl donors and their application in glycosylation reactions. These studies led to the successful synthesis of a tetrasaccharide containing four different 3-aminosugar components using ortho-alkynylbenzoate donors.Ein diversitätsorientierter Ansatz für die Synthese natürlich vorkommender 3-Amino- und 3-Nitro-2,3,6-trideoxypyranosen aus einfachen Zuckern wurde entwickelt. Dieser ermöglichte die Synthese eines Tetrasaccharids aus vier unterschiedlichen 3-Aminozuckern durch die stereoselektive Glycosylierung von ortho-Alkinylbenzoat-Donoren.
      PubDate: 2017-03-20T07:25:30.101363-05:
      DOI: 10.1002/ange.201700178
       
  • Catalytic Direct-type 1,4-Addition Reactions of Alkylazaarenes
    • Authors: Hirotsugu Suzuki; Ryo Igarashi, Yasuhiro Yamashita, Shū Kobayashi
      Abstract: 1,4-addition reactions of alkylazaarenes catalyzed by strong Brønsted bases have been developed for the first time. The desired reactions with α,β-unsaturated amides proceeded under mild reaction conditions to give the 1,4-adducts in high yields. Both ortho- and para-substituted azaarenes afforded the desired adducts in high yields. Regioselective reactions of di- or trimethylpyridine were found to be possible depending on the acidity of the α-hydrogen atoms. Furthermore, a candidate of allosteric protein kinase modulators was synthesized in two steps. An asymmetric variant of this reaction was also found to be feasible.Starker Stoff: Eine starke Brønsted-Base katalysiert 1,4-Additionen von Alkylazaarenen. Reaktionen mit α,β-ungesättigten Amiden führen unter milden Bedingungen in hohen Ausbeuten zu den 1,4-Addukten. KHMDS=Kaliumhexamethyldisilazid, THF=Tetrahydrofuran.
      PubDate: 2017-03-20T07:25:26.046615-05:
      DOI: 10.1002/ange.201611374
       
  • Authors Profile
    • PubDate: 2017-03-20T07:25:21.891504-05:
      DOI: 10.1002/ange.201701949
       
  • Cr(0), Mo(0) and W(0) isocyanide complexes as luminophores and
           photosensitizers with long-lived excited states
    • Authors: Laura A. Büldt; Oliver S. Wenger
      Abstract: Group 6 d6 metal complexes with arylisocyanide ligands are earth-abundant alternatives to photoactive complexes made from precious metals such as Ru(II), Re(I), Os(II), or Ir(III). Some of them have long-lived 3MLCT excited states that exhibit luminescence with good quantum yields combined with nano- to microsecond lifetimes, and they are very strongly reducing. Recent studies have demonstrated that Cr(0), Mo(0), and W(0) arylisocyanides have great potential for application in luminescent devices, photoredox catalysis, and dye-sensitized solar cells.
      PubDate: 2017-03-20T02:16:22.373626-05:
      DOI: 10.1002/ange.201701210
       
  • Application of Methyl Bisphosphine-Ligated Palladium Complexes for Low
           Pressure N-11C-Acetylation of Peptides
    • Authors: Thomas L. Andersen; Patrik Nordeman, Heidi F. Christoffersen, Hélène Audrain, Gunnar Antoni, Troels Skrydstrup
      Abstract: A mild and effective method is described for 11C-labeling of peptides selectively at the N-terminal nitrogen or at internal lysine positions. The presented method relies on the use of specific biphosphine palladium–methyl complexes and their high reactivity towards amino-carbonylation of amine groups in the presence [11C]carbon monoxide. The protocol facilitates the production of native N-11C-acetylated peptides, without any structural modifications and has been applied to a selection of bioactive peptides.PET-Tracer aus 11CO: Die 11C-Markierung von Peptiden durch selektive N-Acetylierung am endständigen Stickstoff oder einer internen Lysinposition gelingt mit Methyl- und Biphosphan-ligierten Palladiumkomplexen in Gegenwart von [11C]Kohlenmonoxid.
      PubDate: 2017-03-16T08:55:43.95189-05:0
      DOI: 10.1002/ange.201700446
       
  • Jerome A. Berson (1924–2017)
    • Authors: Robert G. Bergman
      Abstract: Jerome A. Berson, emeritierter Sterling Professor der Yale University, ist am 13. Januar 2017 verstorben. Berson spielte eine herausragende Rolle in der physikalisch-organischen Chemie und in der Untersuchung der Mechanismen organischer Reaktionen, und er publizierte zwei großartige Bücher zur Geschichte der Chemie.
      PubDate: 2017-03-16T08:55:32.211514-05:
      DOI: 10.1002/ange.201701770
       
  • Next-Generation Polymer Shells for Inorganic Nanoparticles are Highly
           Compact, Ultra-Dense, and Long-Lasting Cyclic Brushes
    • Authors: Giulia Morgese; Behzad Shirmardi Shaghasemi, Valerio Causin, Marcy Zenobi-Wong, Shivaprakash N. Ramakrishna, Erik Reimhult, Edmondo M. Benetti
      Abstract: Polymere Schutzhüllen für anorganische Nanopartikel (NPs) wurden gezielt auf Haltbarkeit und Stabilität hin entworfen. E. M. Benetti et al. demonstrieren in ihrer Zuschrift (
      DOI : 10.1002/ange.201700196), dass cyclische Polymerliganden auf anorganischen NPs ultradichte und hoch kompakte Hüllen aus Polymerbürsten bilden. Diese NPs mit cyclischen Polymerhüllen sind deutlich stabiler als solche mit linearen Liganden und erweisen sich als vollständig biologisch inert gegenüber Serumproteinen.
      PubDate: 2017-03-16T08:50:53.975934-05:
       
  • A Stable, Soluble, and Crystalline Supramolecular System with a Triplet
           Ground State
    • Authors: Tsukasa Futagoishi; Tomoko Aharen, Tatsuhisa Kato, Azusa Kato, Toshiyuki Ihara, Tomofumi Tada, Michihisa Murata, Atsushi Wakamiya, Hiroshi Kageyama, Yoshihiko Kanemitsu, Yasujiro Murata
      Abstract: A supramolecular complex was constructed by encapsulation of a 3O2 molecule inside an open-cage C60 derivative. Its single-crystal X-ray diffraction analysis revealed the presence of the 3O2 at the center of the fullerene cage. The CV measurements suggested that unprecedented dehydrogenation was promoted by the encapsulated 3O2 after two-electron reduction. The ESR measurements displayed the triplet character as well as the anisotropy of the 3O2. Additionally, the SQUID measurements also demonstrated the paramagnetic behavior above 3 K without an antiferromagnetic transition. Upon photoirradiation with visible light, three phosphorescent bands at the NIR region were observed, arising from the exited 1O2 generated by self-sensitization with the outer cage, whose lifetimes were not affected by the environments. These studies confirmed that the complex is a crystalline triplet system with incompatible “high spin density” but “small interspin interaction” properties.Triplett-Charakter: Durch Einschluss eines 3O2-Moleküls in ein offenes C60-Derivat wurde ein supramolekularer Komplex synthetisiert. Elektronische, magnetische und photophysikalische Untersuchungen charakterisieren den Komplex als stabiles, lösliches und kristallines Triplett-System mit inkompatibler High-spin-Dichte bei kleiner Wechselwirkung zwischen den Spins.
      PubDate: 2017-03-16T05:56:30.400627-05:
      DOI: 10.1002/ange.201701212
       
  • The Catalytic Mechanism of the Class C radical S-Adenosylmethionine
           Methyltransferase NosN
    • Authors: Wei Ding; Yongzhen Li, Junfeng Zhao, Xinjian Ji, Tianlu Mo, Haocheng Qianzhu, Tao Tu, Zixin Deng, Yi Yu, Fener Chen, Qi Zhang
      Abstract: Im Unterschied zu allen anderen bekannten S-Adenosylmethionin(SAM)-abhängigen Methyltransferasen produziert das Enzym NosN nicht S-Adenosylhomocystein (SAH) als Beiprodukt, wie Q. Zhang und Mitarbeiter in ihrer Zuschrift (
      DOI : 10.1002/ange.201609948) nachweisen. Stattdessen wandelt NosN als direkter Methyldonor SAM über einen radikalischen Methylierungsmechanismus in 5′-Methylthioadenosin um, wobei 5′-Thioadenosin als Beiprodukt freigesetzt wird.
      PubDate: 2017-03-15T03:06:32.505943-05:
       
  • Fervent Hype behind Magnesium Batteries: An Open Call to Synthetic
           Chemists - Electrolytes and Cathodes Needed
    • Authors: John Muldoon; Claudiu B Bucur, Thomas Gregory
      Abstract: Magnesium metal is an ideal anode which has double the volumetric capacity of lithium metal and has a negative reduction potential of -2.37V vs. the standard hydrogen electrode. The major advantage of magnesium is the apparent lack of dendritic formation during charging which is one of the major concerns of using a lithium metal anode. In this review, we highlight the major research in the development of electrolytes and cathodes and discuss some of the major challenges which must be overcome in realizing a practical magnesium battery.
      PubDate: 2017-03-10T12:43:08.347148-05:
      DOI: 10.1002/ange.201700673
       
  • Cationic Polymerization: From Photoinitiation to Photocontrol
    • Authors: Quentin Michaudel; Veronika Kottisch, Brett P. Fors
      Abstract: During the last 40 years, researchers investigating photoinitiated cationic polymerizations have delivered tremendous success in both industrial and academic settings. A myriad of photoinitiating systems have been developed, allowing for the polymerization of a broad array of monomers (e.g., epoxides, vinyl ethers, alkenes, cyclic ethers, and lactones) under practical, inexpensive, and environmentally benign conditions. More recently, owing to progress in photoredox catalysis, photocontrolled cationic polymerization has emerged as a means to precisely regulate polymer chain growth. This review provides a concise historical perspective on cationic polymerization induced by light and discusses the latest advances in both photoinitiated and photocontrolled processes. The latter are exciting new directions for the field that will likely impact industries ranging from micropatterning to the synthesis of complex biomaterials and sequence-controlled polymers.
      PubDate: 2017-03-09T09:35:25.66218-05:0
      DOI: 10.1002/ange.201701425
       
  • Measuring Spin⋅⋅⋅Spin Interactions between Heterospins
           in a Hybrid [2]Rotaxane
    • Authors: Marie-Emmanuelle Boulon; Antonio Fernandez, Eufemio Moreno Pineda, Nicholas F. Chilton, Grigore Timco, Alistair J. Fielding, Richard E. P. Winpenny
      Abstract: Use of molecular electron spins as qubits for quantum computing will depend on the ability to produce molecules with weak but measurable interactions between the qubits. Here we demonstrate use of pulsed EPR spectroscopy to measure the interaction between two inequivalent spins in a hybrid rotaxane molecule.Um molekulare Elektronenspins als Qubits für Quantenrechner nutzen zu können, müssen Systeme mit kohärenten Quantenzuständen und geeigneten Wechselwirkungen zwischen diesen Spins erzeugt werden. Mithilfe einer Puls-EPR-spektroskopischen RIDME-Sequenz wurde eine sehr schwache Wechselwirkung zwischen zwei nichtäquivalenten Spins in einem Hybrid-Rotaxan gemessen.
      PubDate: 2017-03-09T08:05:26.56245-05:0
      DOI: 10.1002/ange.201612249
       
  • Copper(I)-Catalyzed Chemoselective Coupling of Cyclopropanols with
           Diazoesters: Ring-Opening C−C Bond Formations
    • Authors: Hang Zhang; Guojiao Wu, Heng Yi, Tong Sun, Bo Wang, Yan Zhang, Guangbin Dong, Jianbo Wang
      Abstract: Reported herein is an exceptional chemoselective ring-opening/C(sp3)−C(sp3) bond formation in the copper(I)-catalyzed reaction of cyclopropanols with diazo esters. The conventional O−H insertion product is essentially suppressed by judicious choice of reaction conditions. DFT calculations provide insights into the reaction mechanism and the rationale for this unusual chemoselectivity.Neue Wege finden: In Gegenwart eines Kupfer(I)-Katalysators reagieren Cyclopropanole mit Diazoestern zu Ringöffnungs- und C(sp3)-C(sp3)-Kupplungsprodukten anstatt den üblichen O-H-Insertionsprodukten. Die Ursache dieser ungewöhnlichen Chemoselektivität wird durch DFT-Studien ermittelt.
      PubDate: 2017-03-09T08:00:35.842317-05:
      DOI: 10.1002/ange.201612138
       
  • Catalytic Enantioselective Protonation/Nucleophilic Addition of
           Diazoesters with Chiral Oxazaborolidinium Ion Activated Carboxylic Acids
    • Authors: Ki-Tae Kang; Seung Tae Kim, Geum-Sook Hwang, Do Hyun Ryu
      Abstract: A new chiral Brønsted acid derived from carboxylic acid and a chiral oxazaborolidinium ion (COBI), as an activator, is introduced. This acid was successfully applied as a catalyst for the highly enantioselective protonation/nucleophilic addition of diazoesters with carboxylic acids.Vorübergehend chiral: Ein chirales Oxazaborolidinium-Ion (COBI) katalysiert eine hoch enantioselektive Protonierung/nukleophile Addition zwischen Diazoestern und Carbonsäuren, indem es die Carbonsäure in eine chirale Brønsted-Säure umwandelt. Tf=Trifluormethansulfonyl.
      PubDate: 2017-03-09T08:00:30.119192-05:
      DOI: 10.1002/ange.201612655
       
  • Silica-Encapsulated Pt-Sn Intermetallic Nanoparticles: A Robust Catalytic
           Platform for Parahydrogen-Induced Polarization of Gases and Liquids
    • Authors: Evan W. Zhao; Raghu Maligal-Ganesh, Chaoxian Xiao, Tian-Wei Goh, Zhiyuan Qi, Yuchen Pei, Helena E. Hagelin-Weaver, Wenyu Huang, Clifford R. Bowers
      Abstract: Recently, a facile method for the synthesis of size-monodisperse Pt, Pt3Sn, and PtSn intermetallic nanoparticles (iNPs) that are confined within a thermally robust mesoporous silica (mSiO2) shell was introduced. These nanomaterials offer improved selectivity, activity, and stability for large-scale catalytic applications. Here we present the first study of parahydrogen-induced polarization NMR on these Pt-Sn catalysts. A 3000-fold increase in the pairwise selectivity, relative to the monometallic Pt, was observed using the PtSn@mSiO2 catalyst. The results are explained by the elimination of the three-fold Pt sites on the Pt(111) surface. Furthermore, Pt-Sn iNPs are shown to be a robust catalytic platform for parahydrogen-induced polarization for in vivo magnetic resonance imaging.Parawasserstoff-induzierte Polarisierung mit intermetallischen Pt-Sn-Nanopartikeln (iNPs) resultiert in einer>3000-fach erhöhten Signalverstärkung. Die Pt-Sn-iNPs sind eine robuste katalytische Plattform für die Parawasserstoff-induzierte Polarisierung von Flüssigkeiten mit Anwendungsmöglichkeiten in der In-vivo-Bildgebung.
      PubDate: 2017-03-09T07:55:52.842683-05:
      DOI: 10.1002/ange.201701314
       
  • Fritz Vögtle (1939–2017)
    • Authors: Frank-Gerrit Klärner
      Abstract: Am 3. Januar 2017 starb Fritz Vögtle, Professor Emeritus für Organische Chemie, ehemaliger Direktor des Kekulé-Instituts für Organische Chemie und Biochemie der Universität Bonn. Er war maßgeblich an der Entwicklung der supramolekularen Chemie als neuem zukunftsträchtigem Forschungsgebiet beteiligt und hat mit seinen herausragenden Arbeiten, darunter die Synthese von Dendrimeren, Catenanen, Rotaxanen und Knoten, dafür gesorgt, dass dieses Gebiet sowohl weltweit als auch in Deutschland große Aufmerksamkeit erlangt hat.
      PubDate: 2017-03-09T07:55:32.271537-05:
      DOI: 10.1002/ange.201701484
       
  • Transition Metal-Catalyzed Utilization of Methanol as C1 Source in Organic
           Synthesis
    • Authors: Jagadeesh Rajenahally; Kishore Natte, Helfried Neumann, Matthias Beller
      Abstract: Methanol represents one of the privileged and widespread platform chemicals, which is used in many science sectors such as chemistry, biology, medicine and energy. This essential alcohol serves as common solvent, cost-effective reagent and sustainable feedstock for value-added chemicals, pharmaceuticals and materials. Among different applications, the utilization of methanol as C1 source for the formation of carbon-carbon, carbon-nitrogen and carbon-oxygen bonds continues to be important in organic synthesis and drug discovery. Particularly, the synthesis of C-methylated, N-methylated and O-methylated products is of central interest because these motifs are found in a large number of life science molecules as well as fine and bulk chemicals. In this Minireview, we summarize the utilization of methanol as C1 source in C-methylation, N-methylation, C-methoxylation, N-formylation, methoxycarbonylation and oxidative methyl esterification reactions for the synthesis of C-methylated products, N-methylamines, formamides, urea derivatives, ethers, esters and heterocycles.
      PubDate: 2017-03-09T06:36:03.049864-05:
      DOI: 10.1002/ange.201612520
       
  • Preise der ACS 2017
    • PubDate: 2017-03-08T07:40:50.881425-05:
      DOI: 10.1002/ange.201702032
       
  • Water as a Hydride Source in Palladium-Catalyzed Enantioselective
           Reductive Heck Reactions
    • Authors: Wangqing Kong; Qian Wang, Jieping Zhu
      Abstract: Pd-catalyzed intramolecular asymmetric carbopalladation of N-aryl acrylamides followed by reduction of C(sp3)-Pd intermediate using diboron–water as a hydride source afforded enantioenriched 3,3-disubstituted oxindoles in high yields and enantioselectivities. When heavy water was used as a deuterium donor in combination with bis(catecholato)diboron (Cat2B2), deuterium was incorporated into the products with high synthetic efficiency. The ligand determined both the enantioselectivity of the reaction and the reaction pathways, thereby affording either hydroarylation (reductive Heck) or carboborylation products.Reduzieren mit Wasser' Durch intramolekulare asymmetrische Carbopalladierung von N-Arylacrylamiden, gefolgt von der Reduktion des C(sp3)-Pd-Intermediats mit Hydrid, das aus Wasser stammt, sind 3,3-disubstituierte Oxindole in hohe Ausbeuten und Enantioselektivitäten zugänglich. Mit D2O als Reduktionsmittel wurden enantiomerenangereicherte Oxindole mit einem CH2D-Substituenten erhalten.
      PubDate: 2017-03-08T05:15:58.858125-05:
      DOI: 10.1002/ange.201700195
       
  • Regiocontrolled Direct C−H Arylation of Indoles at the C4 and C5
           Positions
    • Authors: Youqing Yang; Pan Gao, Yue Zhao, Zhuangzhi Shi
      Abstract: An effective and practical strategy has been established for the direct and site-selective arylation of indoles at the C4 and C5 positions with the aid of a readily accessible, cheap, and removable pivaloyl directing group at the C3 position. This transformation shows good functional-group tolerance and could serve as a powerful synthetic tool for the synthesis of medicinally relevant compounds. This method and those developed in previous research together enable the regiocontrolled direct arylation of indole at each C−H bond without prefunctionalization of the reactive sites.Grand Slam: Eine effektive und praktische Strategie für die regioselektive Arylierung von Indolen in C4- oder C5-Stellung nutzt ein leicht abspaltbares Pivaloyl als dirigierende Gruppe (DG) an C3. Damit steht nun ein vollständiger Satz komplementärer Methoden für die regioselektive Arylierung von Indolen an jeder beliebigen C-H-Bindung zur Verfügung.
      PubDate: 2017-03-08T03:25:44.516607-05:
      DOI: 10.1002/ange.201612599
       
  • Dynamic Macromolecular Material Design - The Versatility of Cyclodextrin
           Based Host/Guest Chemistry
    • Authors: Bernhard Schmidt; Christopher Barner-Kowollik
      Abstract: Dynamic and adaptive materials are powerful constructs in macromolecular and polymer chemistry with a wide array of applications in drug-delivery, bioactive systems or self-healing materials. Very frequently dynamic materials featuring non-covalent interactions driven by supramolecular chemistry are based on carefully tailored cyclodextrin (CD) host/guest interactions. The precise incorporation of these host and guest moieties into macromolecular building blocks allows for the formation of complex macromolecular structures that can be utilized to form higher level assemblies executing specific pre-defined functions. Thus, dynamic materials with extraordinary adaptive property profiles - responsive to thermal, chemical and photonic fields - become accessible. In the current critical review the hierarchical formation of dynamic materials and complex macromolecular structures is explored from the molecular to the macromolecular on to the colloidal and macroscopic level, with a specific emphasis on the functionality and outer field responsiveness of the assemblies, specifically in biological contexts.
      PubDate: 2017-02-28T08:45:49.050061-05:
      DOI: 10.1002/ange.201612150
       
  • Applications of the Wittig-Still rearrangement in organic synthesis
    • Authors: Lukas Rycek; Tomas Hudlicky
      Abstract: This review traces the discovery of the Wittig-Still rearrangement and its applications in organic synthesis. Its relationship to Wittig rearrangements is discussed along with detailed analysis of E/Z- and diastereoselectivity. Modifications of the products arising from the Wittig-Still rearrangement are reviewed in the context of increased complexity in intermediates potentially useful in target oriented synthesis. Early applications of the Wittig-Still rearrangement to modifications of steroids are reviewed as are applications to various terpene and alkaloid natural product targets and miscellaneous compounds. To the best of our knowledge, the literature is covered through December 2016.
      PubDate: 2017-02-16T22:00:28.05727-05:0
      DOI: 10.1002/ange.201611329
       
  • A Tale of Two Elements: The Lewis Acidity/Basicity Umpolung of Boron and
           Phosphorus
    • Authors: Douglas Wade Stephan
      Abstract: This mini-review focuses on the Lewis acidity/basicity "umpolung" of B-based nucleophiles and P-based electrophiles.
      PubDate: 2017-02-13T06:15:30.294519-05:
      DOI: 10.1002/ange.201700721
       
  • New Modalities for Challenging Targets in Drug Discovery
    • Authors: Herbert Waldmann; Eric Valeur, Stéphanie M. Guéret, Hélène Adihou, Ranganath Gopalakrishnan, Malin Lemurell, Tom N. Grossmann, Alleyn T. Plowright
      Abstract: An ever increasing understanding of biological systems is providing a range of exciting novel biological targets whose modulation may enable novel therapeutic options in many diseases. These targets include protein-protein and protein-nucleic acid interactions, which are, however, often refractory to classical small molecule approaches. Other types of molecules, or modalities, are therefore required to address these targets, which has led several academic research groups and pharmaceutical companies to increasingly use the concept of so-called 'New Modalities'. This review defines for the first time the scope of this term, which includes novel peptidic scaffolds, oligonucleotides, hybrids, molecular conjugates as well as new uses of classical small molecules. We provide herein a journey through the most representative examples of these modalities to target large binding surface areas such as those found in protein-protein interactions and for biological processes at the center of cell regulation.
      PubDate: 2017-02-10T07:10:33.631609-05:
      DOI: 10.1002/ange.201611914
       
  • Advanced Biofuels and Beyond: Chemistry Solutions for Propulsion and
           Production
    • Authors: Walter Leitner; Jürgen Klankermayer, Stefan Pischinger, Heinz Pitsch, Katharina Kohse-Höinghaus
      Abstract: Sustainably produced biofuels are being discussed intensively as one possible component in the energy scenarios for future ground transportation, especially when they are derived from lignocellulosic biomass. Traditionally, research activities on their production focus on the synthesis process, while leaving their combustion properties to subsequent evaluation by a different community. The present article adopts an integrative view of engine combustion and fuel synthesis, focusing on the chemical aspects as the common denominator. We wish to demonstrate that fundamental understanding of the combustion process can be instrumental to derive design criteria for the molecular structure of fuel candidates that can then be targets for the analysis of synthetic pathways and the development of catalytic production routes. With such an integrative approach to fuel design, it will be possible to improve systematically the entire system, spanning biomass feedstock, conversion process, fuel, engine, and pollutants with a perspective to improve the carbon footprint, increase efficiency, and reduce emissions of the transportation sector along the whole value chain.
      PubDate: 2017-02-10T03:25:57.689265-05:
      DOI: 10.1002/ange.201607257
       
  • Nanostructured Materials for Heterogeneous Electrocatalytic CO2 Reduction
           and Related Reaction Mechanisms
    • Authors: Jinlong Gong; Lei Zhang, Zhi-Jian Zhao
      Abstract: The gradually increased concentration of carbon dioxide (CO2) in the atmosphere has been recognized as the primary culprit for the raise of the global mean temperature, thus resulting in the aggravated desert formation and extinction of species. In recent years, development of the routes for highly efficient conversion of CO2 has received numerous attentions. Among them, the reduction of CO2 with electric power is an important transformation route with high application prospect, due to its high environmental compatibility and good combination with other renewable energy sources such as solar and wind energy. This review describes recent progress on the design and synthesis of solid state catalysts (i.e., heterogeneous catalysts) and their emerging catalytic performances in the CO2 reduction. The significance for catalytic conversion of CO2 and the advantages of CO2 electroreduction will be presented in the introduction section, followed by the general parameters for CO2 electroreduction and the summary of reaction apparatus. We also discuss various types of solid catalysts according to CO2 conversion mechanisms. Furthermore, we summarize the crucial factors (particle size, surface structure, composition and etc.) determining the performance for electroreduction. These studies in improvement of solid state catalysts for CO2 reduction offer numerous experiences for developing potential industrialized CO2 electroreduction catalysts in the future. Additionally, the abundant experience for controllable synthesis of solid state catalysts could effectively guide the rational design of catalysts for other electrocatalytic reactions.
      PubDate: 2017-02-06T22:20:26.596093-05:
      DOI: 10.1002/ange.201612214
       
  • Catalytic Dearomatization of N-Heteroarenes with Silicon and Boron
           Compounds
    • Authors: Sukbok Chang; Sehoon Park
      Abstract: Dearomatized N-heterocycles provide a class of structural motifs important in the fields of synthetic organic chemistry and chemical biology. The catalytic dearomative reduction of unactivated N-heteroarenes using silicon and/or boron-containing compounds as a reductant is one of the most straightforward alternatives to hydrogenation. However, scattered precedents on the catalytic reduction of N-heteroaromatics with silane or borane reducing agents have been reported thus far, and a handful of elegant catalytic procedures for the reduction of N-aromatics have emerged only recently as a viable tool in organic synthesis. This review presents recent advances in the catalytic reduction of unactivated N-heteroarenes using hydrosilanes, hydroboranes, silaboranes, and diboranes. The focus presents the general chemical behavior and selectivity of transition-metal or metal-free organocatalyst systems for the dearomative homogeneous reduction of N-heteroarenes. In addition, the working modes of these catalysis will be described particularly on the basis of the experimental mechanistic insights.
      PubDate: 2017-02-05T22:21:02.01778-05:0
      DOI: 10.1002/ange.201612140
       
  • Modern Inorganic Aerogels
    • Authors: Alexander Eychmüller; Christoph Ziegler, André Wolf, Wei Liu, Anne-Kristin Herrmann, Nikolai Gaponik
      Abstract: Essentially, the term aerogel describes a special geometric structure of matter. It is neither limited to any material nor to any synthesis procedure. Hence, the possible variety of materials and therefore the multitude of their applications are almost unbounded. In fact, the same applies for nanoparticles. These are also just defined by their geometrical properties. In the past decades nano-sized materials were intensively studied and possible applications appeared in nearly all areas of natural sciences. To date a large variety of metal, semiconductor, oxide and other nanoparticles are available from colloidal synthesis. However, for many applications of these materials an assembly into macroscopic structures is needed. Here we present a comprehensive picture of the developments that enabled the fusion of the colloidal nanoparticle and the aerogel world. This became possible by the controlled destabilization of pre-formed nanoparticles, which leads to their assembly into three-dimensional macroscopic networks. This revolutionary approach makes it possible to use precisely controlled nanoparticles as building blocks for macroscopic porous structures with programmable properties.
      PubDate: 2017-02-03T12:11:09.703588-05:
      DOI: 10.1002/ange.201611552
       
  • Uniform Supersonic Chemical Reactors: 30 Years of Astrochemical History
           and Future Challenges
    • Authors: Alexey Potapov; André Canosa, Elena Jiménez, Bertrand Rowe
      Abstract: The interstellar medium attracts our great attention, as the place where stars and planets are born and from where, probably, the molecular precursors of life have come to Earth. To understand the chemical pathways to the formation of stars, planets, and biological molecules, astronomical observations, astrochemical modelling, and laboratory astrochemistry should go hand in hand. In this paper we review the laboratory experiments devoted to investigations of the reaction dynamics of species of astrochemical interest at the temperatures of the interstellar medium and performed by using one of the most popular techniques in the field, CRESU. We discuss new technical developments and scientific ideas for CRESU, which, if realized, will bring us one more step closer to an understanding of the astrochemical history and future of our Universe.
      PubDate: 2017-02-03T04:06:24.845538-05:
      DOI: 10.1002/ange.201611240
       
  • Luminescence, Plasmonic and Magnetic Properties of Doped Semiconductor
           Nanocrystals: Current Developments and Future Prospects
    • Authors: Narayan Pradhan; Samrat Das Adhikari, Angshuman Nag, D D Sarma
      Abstract: Introducing few atoms of impurities or dopants in semiconductor nanocrystals can drastically alter the existing or even introduce new properties. For example, mid-gap states created by doping tremendously affect photocatalytic activities and surface controlled redox reactions, generate new emission centres, show thermometric optical switching, make suitable FRET donors by enhancing the excited state lifetime and also create localized surface plasmon resonance induced low energy absorption. In addition, researchers have more recently started focusing their attention on doped nanocrystals as an important and alternative material for solar energy conversion in order to meet the current demand for renewable energy. Moreover, electrical as well as magnetic properties of the host are also strongly altered on doping. These dopant-induced beneficial changes in material properties suggest that doped nanocrystals with proper selections of dopant-host pairs may be helpful for generating designer materials for a wide range of current technological needs. Such exciting properties related to various aspects of doping a variety of semiconductor nanocrystals are summarized and reported in this mini review.
      PubDate: 2017-02-02T05:31:07.03112-05:0
      DOI: 10.1002/ange.201611526
       
  • Protein-templated fragment ligations - from molecular recognition to drug
           discovery
    • Authors: Mike Jaegle; Ee Lin Wong, Carolin Tauber, Eric Nawrotzky, Christoph Arkona, Jörg Rademann
      Abstract: The understanding and manipulation of molecular recognition events is the key to modern approaches in drug discovery. Protein-templated fragment ligation is a novel concept to support drug discovery and can help to improve the efficacy of already existing protein ligands. Protein-templated fragment ligations are chemical reactions between small molecules ("fragments") that utilize a protein´s surface as a template to combine and to form a protein ligand with increased binding affinity. The approach exploits the molecular recognition of reactive small molecule fragments by proteins both for ligand assembly and for the identification of bioactive fragment combinations. Chemical synthesis and bioassay are thus integrated in one single step. In this article we portrait the biophysical basis of reversible and irreversible fragment ligations and the available methods to detect protein-templated ligation products. The scope of known chemical reactions providing templated ligation products is reviewed and the possibilities to extend the reaction portfolio are discussed. Selected recent applications of the method in protein ligand discovery are reported. Finally, the strengths and limitations of the concept are discussed and an outlook on the future impact of templated fragment ligations on the drug discovery process is given.
      PubDate: 2017-01-24T08:45:33.189727-05:
      DOI: 10.1002/ange.201610372
       
  • Black Phosphorus Rediscovered: From Bulk to Monolayer
    • Authors: Rui Gusmao; Zdenek Sofer, Martin Pumera
      Abstract: Phosphorus is a non-metal with several allotropes, from the highly reactive white phosphorus to the thermodynamically stable black phosphorus (BP) with a puckered orthorhombic layered structure. The bulk form of BP was synthesized for the first time more than a century ago, in 1914, not receiving much attention until very recently rediscovered, in 2014, joining the new wave of 2D layered nanomaterials. BP can be exfoliated to a single sheet structure with tunable direct band, semiconducting, high carrier mobility at room temperature and in-plane anisotropic layered structure. Surface chemistry degradation can still be a holdback for the advancement of BP applications, thus compelling efforts to achieve effective BP passivation are ongoing, such as its integration in van der Waals heterostructures. Currently, BP has been tested as a novel nanomaterial in batteries, transistors, sensors and photonics related fields. In this review we take a look back at BP origin story, taking the path from bulk to nowadays few/single layer. Physical and chemical properties are summarized, highlighting the state-of-the-art in BP applications.
      PubDate: 2017-01-23T02:35:58.618983-05:
      DOI: 10.1002/ange.201610512
       
  • Xenobiology meets enzymology: Exploring the potential of unnatural
           building blocks in biocatalysis
    • Authors: Nediljko Budisa; Jan-Stefan Völler, Beate Koksch, Carlos G. Acevedo-Rocha, Vladimir Kubyshkin, Federica Agostini
      Abstract: Xenobiology (XB) aims to design biological systems endowed with unusual biochemistries, while enzymology concerns the study of enzymes, the workhorses of biocatalysis. Biocatalysis employs enzymes and organisms to perform useful biotransformations in synthetic chemistry and biotechnology. During the past years, the effects of incorporating noncanonical amino acids (ncAAs) into enzymes with potential applications in biocatalysis have been increasingly investigated. Here we provide an overview of the effects of new chemical functionalities that have been introduced into proteins to improve various facets of enzymatic catalysis. We also discuss future research avenues that will complement unnatural mutagenesis with the standard protein-engineering toolbox for producing novel and versatile biocatalysts with applications in synthetic organic chemistry and biotechnology.
      PubDate: 2017-01-13T14:20:35.017578-05:
      DOI: 10.1002/ange.201610129
       
  • Carbon-Carbon Bond Formation in a Weak Ligand Field: Leveraging Open Shell
           First Row Transition Metal Catalysts
    • Authors: Paul James Chirik
      Abstract: Unique features of Earth abundant transition metal catalysts are reviewed in the context of catalytic carbon-carbon bond forming reactions. Aryl-substituted bis(imino)pyridine iron and cobalt dihalide compounds, when activated with alkyl aluminum reagents, form highly active catalysts for the polymerization of ethylene. Open shell iron and cobalt alkyl complexes have been synthesized that serve as single component olefin polymerization catalysts. Reduced bis(imino)pyridine iron- and cobalt dinitrogen compounds have also been discovered that promote the unique [2+2] cycloaddition of unactivated terminal alkenes. Electronic structure studies support open shell intermediates, a deviation from traditional strong field organometallic compounds that promote catalytic C-C bond formation.
      PubDate: 2017-01-12T14:45:24.350363-05:
      DOI: 10.1002/ange.201611959
       
  • Fullerenes in space
    • Authors: John Paul Maier; Ewen Kyle Campbell
      Abstract: In 1985 the football structure of $\textrm{C}_{60}$, buckminsterfullerene was proposed and subsequently confirmed following its macroscopic synthesis in 1990. From the very beginning the role of $\textrm{C}_{60}$ and $\textrm{C}_{60}^{+}$ in space was considered, particularly in the context of the enigmatic diffuse interstellar bands. These are absorption features found in the spectra of reddened star light. The first astronomical observations were made around one hundred years ago and despite significant efforts none of the interstellar molecules responsible have been identified. The absorption spectrum of $\textrm{C}_{60}^{+}$ was measured in a $5\,\textrm{K}$ neon matrix in 1993 and two prominent bands near $9583\,\textrm{\AA}$ and $9645\,\textrm{\AA}$ were observed. On the basis of this data the likely wavelength range in which the gas phase $\textrm{C}_{60}^{+}$ absorptions should lie was predicted. In 1994 two diffuse interstellar bands were found in this spectral region and proposed to be due to $\textrm{C}_{60}^{+}$. It took over 20 years to measure the absorption spectrum of $\textrm{C}_{60}^{+}$ under conditions similar to those prevailing in diffuse clouds. In 2015, sophisticated laboratory experiments led to the confirmation that these two interstellar bands are indeed caused by $\textrm{C}_{60}^{+}$, providing the first answer to this century old puzzle. Here, we describe the experiments, concepts and astronomical observations that led to the detection of $\textrm{C}_{60}^{+}$ in interstellar space.
      PubDate: 2017-01-10T04:20:29.09953-05:0
      DOI: 10.1002/ange.201612117
       
  • Titelbild: Photoelectrochemical Reduction of Carbon Dioxide to Methanol
           through a Highly Efficient Enzyme Cascade (Angew. Chem. 14/2017)
    • Authors: Su Keun Kuk; Raushan K Singh, Dong Heon Nam, Ranjitha Singh, Jung-Kul Lee, Chan Beum Park
      Pages: 3779 - 3779
      Abstract: Ein künstliches Photosynthesesystem … … wurde durch Kombination einer photoelektrochemischen Zelle mit einer Multienzymkaskade konstruiert. J. K. Lee, C. B. Park und Mitarbeiter nutzen in ihrer Zuschrift auf S. 3885 ff. Wasser als Elektronendonor, eine Hämatit-Photoanode und eine Bismutferrit-Photokathode zur Regenerierung von NADH mit sichtbarem Licht sowie eine Kaskade aus drei Dehydrogenasen für die hoch selektive und schnelle Umwandlung von Kohlendioxid in Methanol.
      PubDate: 2017-02-17T02:50:48.967835-05:
      DOI: 10.1002/ange.201701353
       
  • Graphisches Inhaltsverzeichnis: Angew. Chem. 14/2017
    • Pages: 3783 - 3797
      PubDate: 2017-03-22T04:02:46.482996-05:
      DOI: 10.1002/ange.201781411
       
  • Top-Beiträge aus unseren Schwesterzeitschriften: Angew. Chem. 14/2017
    • Pages: 3798 - 3801
      PubDate: 2017-03-22T04:02:52.43751-05:0
      DOI: 10.1002/ange.201781413
       
  • Neil K. Garg
    • Pages: 3802 - 3802
      Abstract: „Etwas, dem ich nie widerstehen kann, sind Jelly Beans. Was ich gerne entdeckt hätte, ist das Rad. ...“ Dies und mehr von und über Neil K. Garg finden Sie auf Seite 3802.
      PubDate: 2017-01-31T03:25:52.186845-05:
      DOI: 10.1002/ange.201700568
       
  • NHC-Katalyse kombiniert mit Ein-Elektronen-Transfer: eine neue Strategie
           für asymmetrische Transformationen
    • Authors: Kun Zhao; Dieter Enders
      Pages: 3808 - 3810
      Abstract: Radikalchemie mit NHCs: NHC-Katalyse und Ein-Elektronen-Oxidationsmittel wurden kombiniert, um die stereoselektive Synthese von wertvollen β-Hydroxyestern, Cyclopentanonen und spirocyclischen γ-Lactonen zu ermöglichen. Der Schlüsselschritt ist die Oxidation des NHC-Homoenolat-Äquivalents zu einer Radikalspezies unter Ein-Elektronen-Transfer (siehe Schema).
      PubDate: 2017-03-06T08:15:27.847382-05:
      DOI: 10.1002/ange.201700370
       
  • Moderne Strategien zur Synthese funktioneller Fluorophore
    • Authors: Fabio de Moliner; Nicola Kielland, Rodolfo Lavilla, Marc Vendrell
      Pages: 3812 - 3823
      Abstract: Die biomedizinische Forschung ist auf die schnelle, akkurate und nicht-invasive Charakterisierung spezifischer Biomoleküle und Zellen angewiesen. Funktionelle Fluorophore sind für derartige Studien von enormem Nutzen. Da diese komplexen Strukturen oftmals mit konventionellen Mitteln der Synthese nur schwer zugänglich sind, wurden in den letzten Jahren neuartige chemische Prozesse entwickelt. Dieser Kurzaufsatz beschreibt die jüngsten Entwicklungen im Bezug auf Design, Herstellung und Feinregulierung von Fluorophoren mittels Mehrkomponentenreaktionen, C-H-Aktivierungsprozessen, Cycloadditionen und Biomolekül-basierten chemischen Transformationen.Funktionelle Fluorophore ermöglichen die schnelle und akkurate Charakterisierung von Biomolekülen. Oft ist jedoch der Zugang zu diesen komplexen Strukturen mithilfe konventioneller Synthesestrategien schwierig. Dieser Aufsatz präsentiert jüngste Fortschritte bei Design, Herstellung und Feinregulierung von Fluorophoren mittels Mehrkomponentenreaktionen (MCRs), C-H-Aktivierung, Cycloadditionen und Biomolekül-basierten chemischen Umwandlungen.
      PubDate: 2017-02-16T10:20:40.386669-05:
      DOI: 10.1002/ange.201609394
       
  • Nicht-ribosomale Peptidsynthese – Prinzipien und Perspektiven
    • Authors: Roderich D. Süssmuth; Andi Mainz
      Pages: 3824 - 3878
      Abstract: Nicht-ribosomale Peptidsynthetasen (NRPSs) sind große Multienzymmaschinerien, die zahlreiche Peptide mit enormer struktureller und funktionaler Diversität erzeugen. Unter diesen Produkten befinden sich mehr als 20 auf dem Markt befindliche Wirkstoffe, darunter Antibiotika (Penicillin, Vancomycin), antitumorale Medikamente (Bleomycin) und Immunsuppressiva (Cyclosporin). In den vergangenen Jahrzehnten haben biochemische sowie strukturbiologische Studien mechanistische Einblicke in die hochkomplexen NRPSs gewährt. Dieser Aufsatz fasst den aktuellen Kenntnisstand über die zugrundeliegenden Mechanismen von NRPSs zusammen und gibt einen Überblick über die Vielfalt ihrer Produkte. Ebenso behandelt werden die Probleme und Herausforderungen, die mit der Umprogrammierung von NRPS-Systemen einhergehen. Das Potenzial einer solchen Umprogrammierung liegt begründet in einer nachhaltigen Generierung von Wirkstoffanaloga und neuen Substanzbibliotheken, die anderenfalls kaum zugänglich sind.Die Größe allein zählt nicht: Nicht-ribosomale Peptide (NRPs) werden durch große Multienzymmaschinerien zusammengefügt und repräsentieren eine strukturell sehr vielfältige Klasse von Naturstoffen mit diversen Bioaktivitäten. Dieser Aufsatz liefert einen umfassenden Überblick über NRPs hinsichtlich ihrer Bioaktivitäten und ihrer Biosynthese sowie der Generierung neuartiger NRPs durch biokombinatorische Ansätze.
      PubDate: 2017-03-21T07:28:22.542797-05:
      DOI: 10.1002/ange.201609079
       
  • Mechanical Trap Surface-Enhanced Raman Spectroscopy for Three-Dimensional
           Surface Molecular Imaging of Single Live Cells
    • Authors: Qianru Jin; Ming Li, Beril Polat, Santosh K. Paidi, Aimee Dai, Amy Zhang, Jayson V. Pagaduan, Ishan Barman, David H. Gracias
      Pages: 3880 - 3884
      Abstract: Reported is a new shell-based spectroscopic platform, named mechanical trap surface-enhanced Raman spectroscopy (MTSERS), for simultaneous capture, profiling, and 3D microscopic mapping of the intrinsic molecular signatures on the membrane of single live cells. By leveraging the functionalization of the inner surfaces of the MTs with plasmonic gold nanostars, and conformal contact of the cell membrane, MTSERS permits excellent signal enhancement, reliably detects molecular signatures, and allows non-perturbative, multiplex 3D surface imaging of analytes, such as lipids and proteins on the surface of single cells. The demonstrated ability underscores the potential of MTSERS to perform 3D spectroscopic microimaging and to furnish biologically interpretable, quantitative, and dynamic molecular maps in live cell populations.Einzelne Zellen werden durch mit Au-Nanosternen beschichtete mikromechanische Fallen eingefangen, die die Zelle greifen und zugleich als Sensor für die oberflächenverstärkte Raman-Spektroskopie dienen. Diese nichtinvasive markierungsfreie Methode ermöglicht die Identifizierung von Proteinen und Lipiden auf der Zelloberfläche, und die Spektren können zur Rekonstruktion eines 3D-Bildes der chemischen Zusammensetzung der Zelloberfläche genutzt werden.
      PubDate: 2017-02-15T15:21:00.437065-05:
      DOI: 10.1002/ange.201700695
       
  • Photoelectrochemical Reduction of Carbon Dioxide to Methanol through a
           Highly Efficient Enzyme Cascade
    • Authors: Su Keun Kuk; Raushan K Singh, Dong Heon Nam, Ranjitha Singh, Jung-Kul Lee, Chan Beum Park
      Pages: 3885 - 3890
      Abstract: Natural photosynthesis is an effective route for the clean and sustainable conversion of CO2 into high-energy chemicals. Inspired by the natural process, a tandem photoelectrochemical (PEC) cell with an integrated enzyme-cascade (TPIEC) system was designed, which transfers photogenerated electrons to a multienzyme cascade for the biocatalyzed reduction of CO2 to methanol. A hematite photoanode and a bismuth ferrite photocathode were applied to fabricate the iron oxide based tandem PEC cell for visible-light-assisted regeneration of the nicotinamide cofactor (NADH). The cell utilized water as an electron donor and spontaneously regenerated NADH. To complete the TPIEC system, a superior three-dehydrogenase cascade system was employed in the cathodic part of the PEC cell. Under applied bias, the TPIEC system achieved a high methanol conversion output of 220 μm h−1, 1280 μmol g−1 h−1 using readily available solar energy and water.Auf gute Zusammenarbeit! In einer photoelektrochemischen Tandemzelle werden photochemisch erzeugte Elektronen auf eine Multienzymkaskade übertragen, um CO2 mit hoher Ausbeute zu Methanol zu reduzieren. Der Ansatz nutzt Wasser als Elektronendonor, eine Hämatit-Photoanode und eine Bismutferrit-Photokathode zur Regenerierung von NADH mithilfe von sichtbarem Licht sowie eine Kaskade aus drei Dehydrogenasen.
      PubDate: 2017-01-25T03:10:30.977867-05:
      DOI: 10.1002/ange.201611379
       
  • Water-Restructuring Mutations Can Reverse the Thermodynamic Signature of
           Ligand Binding to Human Carbonic Anhydrase
    • Authors: Jerome M. Fox; Kyungtae Kang, Madhavi Sastry, Woody Sherman, Banumathi Sankaran, Peter H. Zwart, George M. Whitesides
      Pages: 3891 - 3895
      Abstract: This study uses mutants of human carbonic anhydrase (HCAII) to examine how changes in the organization of water within a binding pocket can alter the thermodynamics of protein–ligand association. Results from calorimetric, crystallographic, and theoretical analyses suggest that most mutations strengthen networks of water-mediated hydrogen bonds and reduce binding affinity by increasing the enthalpic cost and, to a lesser extent, the entropic benefit of rearranging those networks during binding. The organization of water within a binding pocket can thus determine whether the hydrophobic interactions in which it engages are enthalpy-driven or entropy-driven. Our findings highlight a possible asymmetry in protein–ligand association by suggesting that, within the confines of the binding pocket of HCAII, binding events associated with enthalpically favorable rearrangements of water are stronger than those associated with entropically favorable ones.Wasser in der Tasche: Zur Wasser-Restrukturierung führende Mutationen beeinflussen die Thermodynamik der Protein-Ligand-Assoziation. Empirische und theoretische Resultate sprechen dafür, dass Mutationen über die Modulierung der thermodynamischen Eigenschaften von Wasser in der Bindetasche von humaner Carboanhydrase II die thermodynamische Signatur umkehren und die Stärke der Ligandenbindung deutlich verändern können.
      PubDate: 2017-03-02T10:26:00.40637-05:0
      DOI: 10.1002/ange.201609409
       
  • Optomechanical Control of Quantum Yield in Trans–Cis Ultrafast
           Photoisomerization of a Retinal Chromophore Model
    • Authors: Alessio Valentini; Daniel Rivero, Felipe Zapata, Cristina García-Iriepa, Marco Marazzi, Raúl Palmeiro, Ignacio Fdez. Galván, Diego Sampedro, Massimo Olivucci, Luis Manuel Frutos
      Pages: 3900 - 3904
      Abstract: The quantum yield of a photochemical reaction is one of the most fundamental quantities in photochemistry, as it measures the efficiency of the transduction of light energy into chemical energy. Nature has evolved photoreceptors in which the reactivity of a chromophore is enhanced by its molecular environment to achieve high quantum yields. The retinal chromophore sterically constrained inside rhodopsin proteins represents an outstanding example of such a control. In a more general framework, mechanical forces acting on a molecular system can strongly modify its reactivity. Herein, we show that the exertion of tensile forces on a simplified retinal chromophore model provokes a substantial and regular increase in the trans-to-cis photoisomerization quantum yield in a counterintuitive way, as these extension forces facilitate the formation of the more compressed cis photoisomer. A rationale for the mechanochemical effect on this photoisomerization mechanism is also proposed.Mechanische Effekte in der Photochemie: Die Quantenausbeute einer Photoisomerisierung kann mechanochemisch kontrolliert werden. Die Einwirkung von Zugkräften auf einen Retinal-Modellchromophor erhöht die Quantenausbeute der trans-cis-Photoisomerisierung erheblich.
      PubDate: 2017-03-02T02:50:26.415321-05:
      DOI: 10.1002/ange.201611265
       
  • Rapid Room-Temperature Gelation of Crude Oils by a Wetted Powder Gelator
    • Authors: Changliang Ren; Jie Shen, Feng Chen, Huaqiang Zeng
      Pages: 3905 - 3909
      Abstract: Phase-selective organogelators (PSOGs) not only exhibit ability to phase-selectively congeal oil from oily water but also allow easy separation of gelled oil from the body of water. However, all hitherto reported PSOGs either necessitate carrier solvents for their dissolution or suffer from an extremely slow action in gelling oil in the powder form. A previously unexplored generally applicable wetting strategy is now described to dramatically enhance, by up to two orders of magnitude, gelling speed of the resultant wet but non-sticky gelator in the powder form in crude oils of widely ranging viscosities. Such unprecedented rapid gelling speeds enable rapid gelation of six types of (un)weathered crude oils within minutes at room temperature, making PSOGs one step closer to their eventual practical uses as one of important oil spill control technologies.Schnell gebunden: Befeuchten unter Aufnahme einer geringen Menge an polaren Acetonitrilmoleküle beschleunigt das Gelieren eines im trockenen Zustand langsam wirkenden Gelbildner-Pulvers um bis zu zwei Größenordnungen. Das schnelle phasenselektive Gelieren von Rohölen sehr verschiedener Viskosität in Gegenwart von Meerwasser gelingt binnen Minuten bei Raumtemperatur mit dem befeuchteten, aber nicht klebrigen Gelbildner-Pulver.
      PubDate: 2017-03-06T03:31:35.331781-05:
      DOI: 10.1002/ange.201611852
       
  • Regio- and Enantioselective Photodimerization within the Confined Space of
           a Homochiral Ruthenium/Palladium Heterometallic Coordination Cage
    • Authors: Jing Guo; Yao-Wei Xu, Kang Li, Li-Min Xiao, Sha Chen, Kai Wu, Xu-Dong Chen, Yan-Zhong Fan, Jun-Min Liu, Cheng-Yong Su
      Pages: 3910 - 3914
      Abstract: The photoinduced regio- and enantioselective coupling of naphthols and derivatives thereof is achieved in the confined chiral coordination space of a RuII metalloligand based cage. The racemic or enantiopure cages encapsulate naphthol guests, which then undergo a regiospecific 1,4-coupling, rather than the normal 1,1-coupling, to form 4-(2-hydroxy-1-naphthyl)-1,2-napthoquinones; moderate stereochemical control is achieved with homochiral cages. The photoreactions proceed under both aerobic and anaerobic conditions but through distinct pathways that nevertheless involve the same radical intermediates. This unusual dimerization constitutes a very rare example of asymmetric induction in biaryl coupling by making use of coordination cages with dual functionality—photoredox reactivity and stereoselectivity.Beengte Koordinationsräume in redoxaktiven Ruthenium(II)-Käfigen ermöglichen die regio- und enantioselektive photoinduzierte Kupplung von Naphtholen. Die Photoreaktionen laufen sowohl unter aeroben als auch unter anaeroben Bedingungen ab, basieren dann aber auf unterschiedlichen Reaktionsmechanismen, die dennoch die gleichen radikalischen Intermediate involvieren.
      PubDate: 2017-03-01T02:10:37.938339-05:
      DOI: 10.1002/ange.201611875
       
  • The Catalytic Mechanism of the Class C Radical S-Adenosylmethionine
           Methyltransferase NosN
    • Authors: Wei Ding; Yongzhen Li, Junfeng Zhao, Xinjian Ji, Tianlu Mo, Haocheng Qianzhu, Tao Tu, Zixin Deng, Yi Yu, Fener Chen, Qi Zhang
      Pages: 3915 - 3919
      Abstract: S-Adenosylmethionine (SAM) is one of the most common co-substrates in enzyme-catalyzed methylation reactions. Most SAM-dependent reactions proceed through an SN2 mechanism, whereas a subset of them involves radical intermediates for methylating non-nucleophilic substrates. Herein, we report the characterization and mechanistic investigation of NosN, a class C radical SAM methyltransferase involved in the biosynthesis of the thiopeptide antibiotic nosiheptide. We show that, in contrast to all known SAM-dependent methyltransferases, NosN does not produce S-adenosylhomocysteine (SAH) as a co-product. Instead, NosN converts SAM into 5′-methylthioadenosine as a direct methyl donor, employing a radical-based mechanism for methylation and releasing 5′-thioadenosine as a co-product. A series of biochemical and computational studies allowed us to propose a comprehensive mechanism for NosN catalysis, which represents a new paradigm for enzyme-catalyzed methylation reactions.Eine mechanistische Studie zu der Klasse-C-Radikal-S-Adenosylmethionin(SAM)-Methyltransferase NosN zeigt, dass NosN im Unterschied zu allen bekannten SAM-abhängigen Methyltransferasen nicht S-Adenosylhomocystein als Koppelprodukt erzeugt. NosN wandelt SAM stattdessen in 5′-Methylthioadenosin als direkten Methyldonor um, und es nutzt einen radikalischen Mechanismus für die Methylierung und Freisetzung von 5′-Thioadenosin als Koppelprodukt.
      PubDate: 2017-01-23T08:00:30.828914-05:
      DOI: 10.1002/ange.201609948
       
  • 19F-NMR Reveals the Role of Mobile Loops in Product and Inhibitor Binding
           by the São Paulo Metallo-β-Lactamase
    • Authors: Martine I. Abboud; Philip Hinchliffe, Jürgen Brem, Robert Macsics, Inga Pfeffer, Anne Makena, Klaus-Daniel Umland, Anna M. Rydzik, Guo-Bo Li, James Spencer, Timothy D. W. Claridge, Christopher J. Schofield
      Pages: 3920 - 3924
      Abstract: Resistance to β-lactam antibiotics mediated by metallo-β-lactamases (MBLs) is a growing problem. We describe the use of protein-observe 19F-NMR (PrOF NMR) to study the dynamics of the São Paulo MBL (SPM-1) from β-lactam-resistant Pseudomonas aeruginosa. Cysteinyl variants on the α3 and L3 regions, which flank the di-ZnII active site, were selectively 19F-labeled using 3-bromo-1,1,1-trifluoroacetone. The PrOF NMR results reveal roles for the mobile α3 and L3 regions in the binding of both inhibitors and hydrolyzed β-lactam products to SPM-1. These results have implications for the mechanisms and inhibition of MBLs by β-lactams and non-β-lactams and illustrate the utility of PrOF NMR for efficiently analyzing metal chelation, identifying new binding modes, and studying protein binding from a mixture of equilibrating isomers.Widerstand zwecklos: Die durch Metallo-β-lactamase (MBL) vermittelte Resistenz gegen β-Lactam-Antibiotika ist ein zunehmendes Problem. Für eine 19F-NMR-spektroskopische Untersuchung der Dynamik der São-Paulo-MBL aus β-Lactam-resistenten Pseudomonas aeruginosa wurden Cysteinylvarianten der α3- und L3-Regionen mit 3-Brom-1,1,1-trifluoraceton 19F-markiert. Die Ergebnisse geben Einblick in die Rolle der beweglichen α3- und L3-Regionen bei der Bindung von Inhibitoren und hydrolysierten β-Lactam-Produkten.
      PubDate: 2017-03-02T07:10:38.463543-05:
      DOI: 10.1002/ange.201612185
       
  • An Efficient Iron(III)-Catalyzed Aerobic Oxidation of Aldehydes in Water
           for the Green Preparation of Carboxylic Acids
    • Authors: Han Yu; Shi Ru, Guoyong Dai, Yongyan Zhai, Hualin Lin, Sheng Han, Yongge Wei
      Pages: 3925 - 3929
      Abstract: The first example of a heterogeneous iron(III)-catalyzed aerobic oxidation of aldehydes in water was developed. This method utilizes 1 atmosphere of oxygen as the sole oxidant, proceeds under extremely mild aqueous conditions, and covers a wide range of various functionalized aldehydes. Chromatography is generally not necessary for product purification. Its operational simplicity, gram-scale oxidation, and the ability to successively reuse the catalyst, make this new methodology environmentally benign and cost effective. The generality of this methodology gives it the potential to be used on an industrial scale.Eine heterogene aerobe Oxidation von Aldehyden in Wasser mit einem Polyoxometallat-Eisen-Katalysator nutzt Sauerstoff (1 atm) als alleiniges Oxidationsmittel unter sehr milden Bedingungen und eignet sich für verschiedenartig funktionalisierte Aldehyde.
      PubDate: 2017-03-02T07:10:36.856872-05:
      DOI: 10.1002/ange.201612225
       
  • The Borderline between Reactivity and Pre-reactivity of Binary Mixtures of
           Gaseous Carboxylic Acids and Alcohols
    • Authors: Luca Evangelisti; Lorenzo Spada, Weixing Li, Fanny Vazart, Vincenzo Barone, Walther Caminati
      Pages: 3930 - 3933
      Abstract: By mixing primary and secondary alcohols with carboxylic acids just before the supersonic expansion within pulsed Fourier transform microwave experiments, only the rotational spectrum of the ester was observed. However, when formic acid was mixed with tertiary alcohols, adducts were formed and their rotational spectra could be easily measured. Quantum mechanical calculations were performed to interpret the experimental evidence.Rotationsstudien an 1:1-Mischungen aus Carbonsäuren und primären oder sekundären Alkoholen bei Überschallentspannung in der Gasphase zeigen ca. 100-prozentige Veresterung an, mit tertiären Alkoholen entstehen hingegen Addukte. Um diesen experimentellen Befund zu interpretieren, wurden quantenmechanische Rechnungen durchgeführt.
      PubDate: 2017-03-02T10:30:44.347308-05:
      DOI: 10.1002/ange.201612231
       
  • Efficient Construction of Well-Defined Multicompartment Porous Systems in
           a Modular and Chemically Orthogonal Fashion
    • Authors: Ning Gao; Tian Tian, Jiecheng Cui, Wanlin Zhang, Xianpeng Yin, Shiqiang Wang, Jingwei Ji, Guangtao Li
      Pages: 3938 - 3943
      Abstract: A microfluidic assembly approach was developed for efficiently producing hydrogel spheres with reactive multidomains that can be employed as an advantageous platform to create spherical porous networks in a facile manner with well-defined multicompartments and spatiotemporally controlled functions. This strategy allows for not only large scale fabrication of various robust hydrogel microspheres with controlled size and porosity, but also the domains embedded in hydrogel network could be introduced in a modular manner. Additionally, the number of different domains and their ratio could be widely variable on demand. More importantly, the reactive groups distributed in individual domains could be used as anchor sites to further incorporate functional units in an orthogonal fashion, leading to well-defined multicompartment systems. The strategy provides a new and efficient route to construct well-defined functional multicompartment systems with great flexibility and extendibility.Ein mikrofluidischer Aggregationsansatz verknüpft Kompositdomänen, die orthogonal reagierende Ankergruppen tragen, (links) in modularer Weise zu Hydrogelkügelchen mit integrierten Multidomänen (Mitte). Ausgehend von diesen mikrostrukturierten Kügelchen lassen sich funktionale Mehrkompartimentsysteme im Inneren der Kügelchen aufbauen (rechts).
      PubDate: 2017-03-06T03:31:27.327853-05:
      DOI: 10.1002/ange.201612280
       
  • “114”-Type Nitrides LnAl(Si4−xAlx)N7Oδ with Unusual [AlN6]
           Octahedral Coordination
    • Authors: Saifang Huang; Zhaohui Huang, Peng Cao, Zoran Zujovic, Jason R. Price, Maxim Avdeev, Meidan Que, Furitsu Suzuki, Tsuyoshi Kido, Xin Ouyang, Hironori Kaji, Minghao Fang, Yan-gai Liu, Wei Gao, Tilo Söhnel
      Pages: 3944 - 3949
      Abstract: Aluminum–nitrogen six-fold octahedral coordination, [AlN6], is unusual and has only been seen in the high-pressure rocksalt-type aluminum nitride or some complex compounds. Herein we report novel nitrides LnAl(Si4−xAlx)N7Oδ (Ln=La, Sm), the first inorganic compounds with [AlN6] coordination prepared via non-high-pressure synthesis. Structure refinements of neutron powder diffraction and single-crystal X-ray diffraction data show that these compounds crystallize in the hexagonal Swedenborgite structure type with P63mc symmetry where Ln and Al atoms locate in anticuboctahedral and octahedral interstitials, respectively, between the triangular and Kagomé layers of [SiN4] tetrahedra. Solid-state NMR data of high-purity La-114 powders confirm the unusual [AlN6] coordination. These compounds are the first examples of the “33-114” sub-type in the “114” family. The additional site for over-stoichiometric oxygen in the structure of 114-type compounds was also identified.6 × N, 1 × Al: Das unübliche [AlN6]-Koordinationsmuster findet sich bei der bei Normaldruck hergestellten La-114-Verbindung LnAl(Si4−xAlx)N7Oδ (Ln=La, Sm). Eine Kristallstrukturanalyse bestätigt diese Oktaederkoordination, ebenso wie die chemische Verschiebung von δ=3.5 ppm in 27Al-NMR-Spektren von La-114-Pulvern. Die zusätzlichen Sauerstoffatome umgeben die [AlN6]-Oktaeder in ungeordneter Weise.
      PubDate: 2017-02-28T05:00:41.201975-05:
      DOI: 10.1002/ange.201612488
       
  • Cyclometalated Gold(III) Complexes Containing N-Heterocyclic Carbene
           Ligands Engage Multiple Anti-Cancer Molecular Targets
    • Authors: Sin Ki Fung; Taotao Zou, Bei Cao, Pui-Yan Lee, Yi Man Eva Fung, Di Hu, Chun-Nam Lok, Chi-Ming Che
      Pages: 3950 - 3954
      Abstract: Metal N-heterocyclic carbene (NHC) complexes are a promising class of anti-cancer agents displaying potent in vitro and in vivo activities. Taking a multi-faceted approach employing two clickable photoaffinity probes, herein we report the identification of multiple molecular targets for anti-cancer active pincer gold(III) NHC complexes. These complexes display potent and selective cytotoxicity against cultured cancer cells and in vivo anti-tumor activities in mice bearing xenografts of human cervical and lung cancers. Our experiments revealed the specific engagement of the gold(III) complexes with multiple cellular targets, including HSP60, vimentin, nucleophosmin, and YB-1, accompanied by expected downstream mechanisms of action. Additionally, PtII and PdII analogues can also bind the cellular proteins targeted by the gold(III) complexes, uncovering a distinct pincer cyclometalated metal–NHC scaffold in the design of anti-cancer metal medicines with multiple molecular targets.Die Waffe der Wahl: Cyclometallierte Gold(III)-Komplexe mit N-heterocyclischen Carbenliganden bekämpfen Krebs nach einem kombinierten Ansatz aus Photoaffinitätsmarkierung und Klick-Chemie durch Angriff auf multiple Zielstrukturen. Ihre PdII- und PtII-Analoga binden kompetitiv an dieselben zellulären Strukturen.
      PubDate: 2017-03-01T02:10:44.950318-05:
      DOI: 10.1002/ange.201612583
       
  • Carbon-Incorporated Nickel–Cobalt Mixed Metal Phosphide Nanoboxes with
           Enhanced Electrocatalytic Activity for Oxygen Evolution
    • Authors: Peilei He; Xin-Yao Yu, Xiong Wen (David) Lou
      Pages: 3955 - 3958
      Abstract: Hollow nanostructures have attracted increasing research interest in electrochemical energy storage and conversion owing to their unique structural features. However, the synthesis of hollow nanostructured metal phosphides, especially nonspherical hollow nanostructures, is rarely reported. Herein, we develop a metal–organic framework (MOF)-based strategy to synthesize carbon incorporated Ni–Co mixed metal phosphide nanoboxes (denoted as NiCoP/C). The oxygen evolution reaction (OER) is selected as a demonstration to investigate the electrochemical performance of the NiCoP/C nanoboxes. For comparison, Ni–Co layered double hydroxide (Ni–Co LDH) and Ni–Co mixed metal phosphide (denoted as NiCoP) nanoboxes have also been synthesized. Benefiting from their structural and compositional merits, the as-synthesized NiCoP/C nanoboxes exhibit excellent electrocatalytic activity and long-term stability for OER.Auf Äußerlichkeiten ist zu achten: Hohle ZIF-67@LDH-Nanowürfel (LDH=schichtförmiges Doppelhydroxid) werden durch die Umsetzung einheitlicher ZIF-67-Nanowürfel mit Ni(NO3)2 bei Raumtemperatur erhalten. Phosphidierung mit NaH2PO2 überführt die ZIF-67@LDH-Strukturen in hohle NiCoP/C-Nanowürfel, die leistungsfähigere Elektrokatalysatoren der Sauerstoffentwicklung sind.
      PubDate: 2017-02-28T07:25:29.566218-05:
      DOI: 10.1002/ange.201612635
       
  • Nanomechanical Infrared Spectroscopy with Vibrating Filters for
           Pharmaceutical Analysis
    • Authors: Maksymilian Kurek; Matthias Carnoy, Peter E. Larsen, Line H. Nielsen, Ole Hansen, Thomas Rades, Silvan Schmid, Anja Boisen
      Pages: 3959 - 3963
      Abstract: Standard infrared spectroscopy techniques are well-developed and widely used. However, they typically require milligrams of sample and can involve time-consuming sample preparation. A promising alternative is represented by nanomechanical infrared spectroscopy (NAM-IR) based on the photothermal response of a nanomechanical resonator, which enables the chemical analysis of picograms of analyte directly from a liquid solution in only a few minutes. Herein, we present NAM-IR using perforated membranes (filters). The method was tested with the pharmaceutical compound indomethacin to successfully perform a chemical and morphological analysis on roughly 100 pg of sample. With an absolute estimated sensitivity of 109±15 fg, the presented method is suitable for ultrasensitive vibrational spectroscopy.Nanomechanische Resonatoren für die IR-Spektroskopie: Perforierte Siliciumnitrid-Membranen eignen sich als poröse Filter für die Analyse von Pikogramm-Mengen eines aus Dispersion vernebelten Analyten. Messungen der Resonanzfrequenz solcher Strukturen unter IR-Bestrahlung liefern IR-Spektren der jeweiligen Verbindung. Das Prinzip wurde beispielhaft für Indomethacin illustriert.
      PubDate: 2017-03-07T02:35:33.703694-05:
      DOI: 10.1002/ange.201700052
       
  • Facile Two-Step Synthesis of 1,10-Phenanthroline-Derived
           Polyaza[7]helicenes with High Fluorescence and CPL Efficiency
    • Authors: Takashi Otani; Ami Tsuyuki, Taiki Iwachi, Satoshi Someya, Kotaro Tateno, Hidetoshi Kawai, Takao Saito, Kyalo Stephen Kanyiva, Takanori Shibata
      Pages: 3964 - 3968
      Abstract: A facile two-step synthesis of aza[7]helicenes possessing a 6-5-6-6-6-5-6 skeleton from commercially available 2,9-dichloro-1,10-phenanthroline via double amination with aniline derivatives followed by hypervalent iodine reagent-mediated intramolecular double-NH/CH couplings was developed. Single-crystal X-ray analyses of the helicenes revealed unique structures, including both a significantly twisted center and planar terminals of the skeleton. The azahelicenes show high fluorescent quantum yields (Φs) under both neutral (Φ: 0.25–0.55) and acidic conditions (Φ: up to 0.80). An enantiomerically pure aza[7]helicene showed high circularly polarized luminescence (CPL) activity under both neutral and acidic conditions (glum: up to 0.009).In zwei Stufen zu Polyaza[7]helicenen führt eine durch ein hypervalentes Iodreagens vermittelte doppelte NH/CH-Kupplung kommerziell erhältlicher Vorstufen. Die Azahelicene zeichnen sich durch hohe Fluoreszenzquantenausbeuten (Φ bis 0.80) aus, und ein enantiomerenreines Tetraazahelicen zeigt unter neutralen wie sauren Bedingungen eine starke zirkular polarisierte Lumineszenz (CPL) mit hohen glum-Werten (bis 0.009).
      PubDate: 2017-03-07T09:00:54.120649-05:
      DOI: 10.1002/ange.201700507
       
  • HPCO—A Phosphorus-Containing Analogue of Isocyanic Acid
    • Authors: Alexander Hinz; René Labbow, Chris Rennick, Axel Schulz, Jose M. Goicoechea
      Pages: 3969 - 3973
      Abstract: We describe the isolation and spectroscopic characterization of the heavier phosphorus-containing analogue of isocyanic acid (HPCO), and its isotopologue (DPCO). This fundamental small molecule, which has been postulated to exist in interstellar space, has thus far only been observed at low gas phase concentrations or in inert gas matrices. In this report we describe its synthesis, spectroscopic properties, and reactivity in solution.Puzzlespiel mit vier Atomen: Die Protonierung des 2-Phosphaethinolat-Anions führt ausschließlich zu HPCO. Metastabile Lösungen der freien Säure konnten in Toluol und Dichlormethan erhalten werden, wohingegen in THF Oligomerisierung erfolgte.
      PubDate: 2017-03-02T07:10:53.600977-05:
      DOI: 10.1002/ange.201700368
       
  • Fluorooxoborates: Beryllium-Free Deep-Ultraviolet Nonlinear Optical
           Materials without Layered Growth
    • Authors: Bingbing Zhang; Guoqiang Shi, Zhihua Yang, Fangfang Zhang, Shilie Pan
      Pages: 3974 - 3977
      Abstract: Deep-ultraviolet nonlinear optical (DUV NLO) crystals are the key materials to extend the output range of solid-state lasers to below 200 nm. The only practical material KBe2BO3F2 suffers high toxicity through beryllium and strong layered growth. Herein, we propose a beryllium-free material design and synthesis strategy for DUV NLO materials. Introducing the (BO3F)4−, (BO2F2)3−, and (BOF3)2− groups in borates could break through the fixed 3D B–O network that would produce a larger birefringence without layering and simultaneously keep a short cutoff edge down to DUV. The theoretical and experimental studies on a series of fluorooxoborates confirm this strategy. Li2B6O9F2 is identified as a DUV NLO material with a large second harmonic generation efficiency (0.9×KDP) and a large predicted birefringence (0.07) without layering. This study provides a feasible way to break down the DUV wall for NLO materials.Ohne Be tief ins UV: Ein Beryllium-freies Material, das keine Schichtstruktur aufweist, wurde in Hinblick auf nichtlinear-optische (NLO) Materialien für den Tief-UV-Bereich entworfen und hergestellt. Durch Einführung von (BO3F)4−-, (BO2F2)3−- und (BOF3)2−-Gruppen in Borate lassen sich die Kriterien für Tief-UV-NLO-Materialien erfüllen.
      PubDate: 2017-03-02T03:01:20.148957-05:
      DOI: 10.1002/ange.201700540
       
  • Coordination Polymer Framework Based On-Chip Micro-Supercapacitors with AC
           Line-Filtering Performance
    • Authors: Chongqing Yang; Karl Sebastian Schellhammer, Frank Ortmann, Sai Sun, Renhao Dong, Melike Karakus, Zoltán Mics, Markus Löffler, Fan Zhang, Xiaodong Zhuang, Enrique Cánovas, Gianaurelio Cuniberti, Mischa Bonn, Xinliang Feng
      Pages: 3978 - 3982
      Abstract: On-chip micro-supercapacitors (MSCs) are important Si-compatible power-source backups for miniaturized electronics. Despite their tremendous advantages, current on-chip MSCs require harsh processing conditions and typically perform like resistors when filtering ripples from alternating current (AC). Herein, we demonstrated a facile layer-by-layer method towards on-chip MSCs based on an azulene-bridged coordination polymer framework (PiCBA). Owing to the good carrier mobility (5×10−3 cm2 V−1 s−1) of PiCBA, the permanent dipole moment of azulene skeleton, and ultralow band gap of PiCBA, the fabricated MSCs delivered high specific capacitances of up to 34.1 F cm−3 at 50 mV s−1 and a high volumetric power density of 1323 W cm−3. Most importantly, such MCSs exhibited AC line-filtering performance (−73° at 120 Hz) with a short resistance–capacitance constant of circa 0.83 ms.Mikrosuperkondensatoren auf Basis eines Azulen-verbrückten Koordinationspolymers wurden schichtweise auf einem Chip aufgebaut. Die Strukturen zeichnen sich durch hohe spezifische Kapazitäten, volumenspezifische Leistungen und Energiedichten aus. Außerdem sind sie vielversprechende Wechselstrom-Netzfilter mit sehr kurzer RC-Zeit.
      PubDate: 2017-03-07T09:01:00.17697-05:0
      DOI: 10.1002/ange.201700679
       
  • Selected Mutations Reveal New Intermediates in the Biosynthesis of
           Mupirocin and the Thiomarinol Antibiotics
    • Authors: Shu-Shan Gao; Luoyi Wang, Zhongshu Song, Joanne Hothersall, Elton R. Stevens, Jack Connolly, Peter J. Winn, Russell J. Cox, Matthew P. Crump, Paul R. Race, Christopher M. Thomas, Thomas J. Simpson, Christine L. Willis
      Pages: 3988 - 3992
      Abstract: Thiomarinol and mupirocin are assembled on similar polyketide/fatty acid backbones and exhibit potent antibiotic activity against methicillin-resistant Staphylococcus aureus (MRSA). They both contain a tetrasubstituted tetrahydropyran (THP) ring that is essential for biological activity. Mupirocin is a mixture of pseudomonic acids (PAs). Isolation of the novel compound mupirocin P, which contains a 7-hydroxy-6-keto-substituted THP, from a ΔmupP strain and chemical complementation experiments confirm that the first step in the conversion of PA-B into the major product PA-A is oxidation at the C6 position. In addition, nine novel thiomarinol (TM) derivatives with different oxidation patterns decorating the central THP core were isolated after gene deletion (tmlF). These metabolites are in accord with the THP ring formation and elaboration in thiomarinol following a similar order to that found in mupirocin biosynthesis, despite the lack of some of the equivalent genes. Novel mupirocin–thiomarinol hybrids were also synthesized by mutasynthesis.Ein langer, kurviger Weg: Neue Metaboliten von P. fluorescens-Mutanten und des marinen Bakteriums Pseudoalteromonas wurden isoliert und ihre Strukturen bestimmt. Dabei wurde gezeigt, dass die Bildung des Tetrahydropyranrings und die Funktionalisierung von Thiomarinol in einer ähnlichen Reihenfolge wie bei der Mupirocin-Biosynthese ablaufen, obwohl einige Gene fehlen.
      PubDate: 2017-02-09T02:30:30.971063-05:
      DOI: 10.1002/ange.201611590
       
  • A Stable Monomeric SiO2 Complex with Donor–Acceptor Ligands
    • Authors: Ricardo Rodriguez; David Gau, Jérémy Saouli, Antoine Baceiredo, Nathalie Saffon-Merceron, Vicenç Branchadell, Tsuyoshi Kato
      Pages: 3993 - 3997
      Abstract: Isolation of a monomeric SiO2 compound 3 as a stable donor–acceptor complex with two different ligands —a σ-donating ligand (pyridine, dimethylaminopyridine, N-heterocyclic carbene) and a donor–acceptor ligand (iminophosphorane)—is presented. The SiO2 complex 3 is soluble in ordinary organic solvents and is stable at room temperature in solution and in the solid state. Of particular interest, 3 remains reactive and can be used as a stable and soluble unimolecular SiO2 reagent.Ein stabiler Komplex von monomerem SiO2 mit σ-Donor- und Donor-Akzeptor-Liganden wurde isoliert. Der Komplex ist löslich in gängigen organischen Lösungsmitteln und bei Raumtemperatur in Lösung und im Festkörper beständig. Dadurch eignet er sich als molekulares Reagens.
      PubDate: 2017-03-01T02:10:26.551969-05:
      DOI: 10.1002/ange.201611851
       
  • The Discovery of 2-Aminobenzimidazoles That Sensitize Mycobacterium
           smegmatis and M. tuberculosis to β-Lactam Antibiotics in a Pattern
           Distinct from β-Lactamase Inhibitors
    • Authors: T. Vu Nguyen; Meghan S. Blackledge, Erick A. Lindsey, Bradley M. Minrovic, David F. Ackart, Albert B. Jeon, Andrés Obregón-Henao, Roberta J. Melander, Randall J. Basaraba, Christian Melander
      Pages: 3998 - 4002
      Abstract: A library of 2-aminobenzimidazole derivatives was screened for the ability to suppress β-lactam resistance in Mycobacterium smegmatis. Several non-bactericidal compounds were identified that reversed intrinsic resistance to β-lactam antibiotics in a manner distinct from β-lactamase inhibitors. Activity also translates to M. tuberculosis, with a lead compound from this study potently suppressing carbenicillin resistance in multiple M. tuberculosis strains (including multidrug-resistant strains). Preliminary mechanistic studies revealed that the lead compounds act through a mechanism distinct from that of traditional β-lactamase inhibitors.Ein 2-Aminobenzimidazol (2-ABI, siehe Bild) überwindet die intrinsische Resistenz von Mycobacterium smegmatis gegenüber β-Lactam-Antibiotika auf andere Weise als β-Lactamase-Inhibitoren. Zudem unterdrückt dieser Wirkstoff effektiv die Carbenicillin-Resistenz mehrerer M.-tuberculosis-Stämme.
      PubDate: 2017-03-01T07:10:22.977818-05:
      DOI: 10.1002/ange.201612006
       
  • Transition-Metal-Free C3 Arylation of Indoles with Aryl Halides
    • Authors: Ji Chen; Jimmy Wu
      Pages: 4009 - 4013
      Abstract: We report an unprecedented transition metal-free coupling of indoles with aryl halides. The reaction is promoted by KOtBu and is regioselective for C3 over N. The use of degassed solvents devoid of oxygen is necessary for the success of the transformation. Preliminary studies implicate a hybrid mechanism that involves both aryne intermediates and non-propagative radical processes. Electron transfer is also a distinct possibility. These conclusions were substantiated by EPR data, isotopic labeling studies, and the use of radical scavengers and electron transfer inhibitors.Metalle? Was für Metalle? Eine regioselektive übergangsmetallfreie Kreuzkupplung von Arylhalogeniden mit Indolen in der C3-Position wurde entwickelt. Die Reaktion verläuft über einen ungewöhnlichen Radikal-Arin-Hybridmechanismus.
      PubDate: 2017-03-03T06:10:41.914549-05:
      DOI: 10.1002/ange.201612311
       
  • 4,5-Dimethyl-2-Iodoxybenzenesulfonic Acid Catalyzed Site-Selective
           Oxidation of 2-Substituted Phenols to 1,2-Quinols
    • Authors: Muhammet Uyanik; Tatsuya Mutsuga, Kazuaki Ishihara
      Pages: 4014 - 4018
      Abstract: A site-selective hydroxylative dearomatization of 2-substituted phenols to either 1,2-benzoquinols or their cyclodimers, catalyzed by 4,5-dimethyl-2-iodoxybenzenesulfonic acid with Oxone, has been developed. Natural products such as biscarvacrol and lacinilene C methyl ether could be synthesized efficiently under mild reaction conditions. Furthermore, both the reaction rate and site selectivity could be further improved by the introduction of a trialkylsilylmethyl substituent at the 2-position of phenols. The corresponding 1,2-quinols could be transformed into various useful structural motifs by [4+2] cycloaddition cascade reactions.Oxidativer Cocktail: Eine hydroxylierende Dearomatisierung von Phenolen unter Katalyse durch 4,5-Me2IBS in Gegenwart von Oxon ergibt entweder 1,2-Chinole oder deren Dimere. Sowohl die Reaktionsgeschwindigkeit als auch die Regioselektivität steigen bei Einführung eines Trialkylsilylmethyl-Substituenten an der 2-Position des Phenols. Entsprechende 1,2-Benzochinole könnten durch [4+2]-Cycloadditionskaskaden in verschiedene nützliche Strukturmotive umgewandelt werden.
      PubDate: 2017-02-21T07:56:37.623977-05:
      DOI: 10.1002/ange.201612463
       
  • Isocyanide-Induced Activation of Copper Sulfate: Direct Access to
           Functionalized Heteroarene Sulfonic Esters
    • Authors: Xiaohu Hong; Qitao Tan, Bingxin Liu, Bin Xu
      Pages: 4019 - 4023
      Abstract: A novel and direct approach to alkyl/aryl heteroarene sulfonic esters using copper sulfate as the environmentally benign inorganic sulfonation reagent was first realized with the aid of isocyanide. A variety of heterocycles reacted to afford the corresponding sulfonic esters through C−H functionalization. In this transformation, the otherwise inert copper sulfate was unusually activated by an isocyanide and employed as the source of the sulfonic substituents in an unprecedented fashion. The findings suggest that an appropriate activator may liberate the chemical activities of some relatively inert inorganic salts for organic synthesis.Blaue Kristalle und ein kleiner Trick: Ein direkter Weg zu Alkyl/Arylestern von Heteroarensulfonsäuren mit Kupfersulfat als Sulfonierungsreagens beruht auf dem Einsatz eines Isocyanid-Additivs, welches das ansonsten inerte Kupfersulfat aktiviert und zu einer Quelle für Sulfonsäuregruppen macht.
      PubDate: 2017-03-07T09:00:47.731828-05:
      DOI: 10.1002/ange.201612565
       
  • Selective Reductive Removal of Ester and Amide Groups from Arenes and
           Heteroarenes through Nickel-Catalyzed C−O and C−N Bond Activation
    • Authors: Huifeng Yue; Lin Guo, Shao-Chi Lee, Xiangqian Liu, Magnus Rueping
      Pages: 4030 - 4034
      Abstract: An inexpensive nickel(II) catalyst and a hydrosilane were used for the efficient reductive defunctionalization of aryl and heteroaryl esters through a decarbonylative pathway. This versatile method could be used for the removal of ester and amide functional groups from various organic molecules. Moreover, a scale-up experiment and a synthetic application based on the use of a removable carboxylic acid directing group highlight the usefulness of this reaction.CO geht raus: Ein Nickel(II)-Katalysator und ein Hydrosilan wurden für die effiziente reduktive Defunktionalisierung von Aryl- und Heteroarylestern über einen Decarbonylierungsweg genutzt (siehe Schema). Diese vielseitige Methode ermöglicht die Entfernung von Ester- und Amidgruppen, einschließlich dirigierender Carbonylgruppen, aus einer Vielzahl von organischen Molekülen.
      PubDate: 2017-03-21T02:10:42.709118-05:
      DOI: 10.1002/ange.201612624
       
  • Möbius Aromatic [28]Hexaphyrin Germanium(IV) and Tin(IV) Complexes:
           Efficient Formation of Triplet Excited States
    • Authors: Mondo Izawa; Taeyeon Kim, Shin-ichiro Ishida, Takayuki Tanaka, Tadashi Mori, Dongho Kim, Atsuhiro Osuka
      Pages: 4040 - 4044
      Abstract: [28]Hexaphyrin GeIV and SnIV complexes were synthesized in high yields by reactions of [28]hexaphyrin with GeCl4 or SnCl4 in the presence of triethylamine. Both complexes display distinct 28π Möbius aromatic character and possess a trigonal bipyramidal geometry at the central GeIV or SnIV atom. The equatorial hydroxy group of the GeIV complex was smoothly exchanged with neutral nucleophiles, such as phenol derivatives and thiophenol, with retention of configuration. In the SnIV complex, intersystem crossing to the T1 state is remarkably enhanced owing to the effective heavy-atom effect, thus allowing the formation of the T1 state in high yield. The T1 states of the GeIV and SnVI complexes were found to be antiaromatic on the basis of the transient absorption features in line with the Baird rule.Schweratomeffekt: GeIV- und SnIV-Komplexe von [28]Hexaphyrin wurden synthetisiert und als Möbius-aromatische 28π-Moleküle identifiziert. Die Hydroxygruppe des GeIV-Komplexes kann unter Beibehaltung der Konfiguration durch Phenole und Thiophenol leicht substituiert werden. Im SnIV-Komplex ist das Intersystem-Crossing zum T1-Zustand wegen des Schweratomeffekts bemerkenswert erhöht, daher ist der T1-Zustand gemäß der Bairdschen Regel antiaromatisch.
      PubDate: 2017-02-28T05:21:00.169817-05:
      DOI: 10.1002/ange.201700063
       
  • A Facile Steam Reforming Strategy to Delaminate Layered Carbon Nitride
           Semiconductors for Photoredox Catalysis
    • Authors: Pengju Yang; Honghui Ou, Yuanxing Fang, Xinchen Wang
      Pages: 4050 - 4054
      Abstract: The delamination of layered crystals that produces single or few-layered nanosheets while enabling exotic physical and chemical properties, particularly for semiconductor functions in optoelectronic applications, remains a challenge. Here, we report a facile and green approach to prepare few-layered polymeric carbon nitride (PCN) semiconductors by a one-step carbon/nitrogen steam reforming reaction. Bulky PCN, obtained from typical precursors including urea, melamine, dicyandiamide, and thiourea, are exfoliated into few-layered nanosheets, while engineering its surface carbon vacancies. The unique sheet structures with strengthened surface properties endow PCNs with more active sites, and an increased charge separation efficiency with a prolonged charge lifetime, drastically promoting their photoredox performance. After an assay of a H2 evolution reaction, an apparent quantum yield of 11.3 % at 405 nm was recorded for the PCN nanosheets, which is much higher than those of PCN nanosheets. This delamination method is expandable to other carbon-based 2D materials for advanced applications.Lichtgetriebene Wasserstoffproduktion: Ein C/N-basierter Dampfreformierungsansatz wurde entwickelt, um mehrlagige polymere Kohlenstoffnitrid-Nanoschichten mit kontrollierten Kohlenstoff-Fehlstellen für die photokatalytische Wasserstoffproduktion herzustellen. Die einzigartige Schichtstruktur mit verstärkten Oberflächeneigenschaften stattet das Material mit mehr aktiven Zentren aus.
      PubDate: 2017-03-01T02:05:30.231275-05:
      DOI: 10.1002/ange.201700286
       
  • Fluorinated Sulfilimino Iminiums: Efficient and Versatile Sources of
           Perfluoroalkyl Radicals under Photoredox Catalysis
    • Authors: Marion Daniel; Guillaume Dagousset, Patrick Diter, Pierre-André Klein, Béatrice Tuccio, Anne-Marie Goncalves, Géraldine Masson, Emmanuel Magnier
      Pages: 4055 - 4059
      Abstract: Reported herein is the use of S-perfluoroalkyl sulfilimino iminiums as a new source of RF radicals under visible-light photoredox catalysis (RF=CF3, C4F9, CF2Br, CFCl2). These shelf-stable perfluoroalkyl reagents, readily prepared on gram scale from the corresponding sulfoxide using a one-pot procedure, allow the efficient photoredox-induced oxyperfluoroalkylation of various alkenes using fac-Ir(ppy)3 as the photocatalyst. Importantly, spin-trapping/electron paramagnetic resonance experiments were carried out to characterize all the radical intermediates involved in this radical/cationic process.Alternative Radikalquelle: S-Perfluoralkyl-Sulfilimino-Iminiumionen sind eine neue Quelle für Perfluoralkylradikale (RF=CF3, CF2Br, C4F9, CFCl2). Die Bildung dieser Radikale, und anderer wichtiger Zwischenstufen, wurde durch Spinabfang-Experimente und EPR-Spektroskopie bestätigt. Die Reagentien wurden in einer Drei-Komponenten-Oxyperfluoralkylierung von Alkenen unter Bestrahlung mit sichtbarem Licht genutzt. ppy=2-Phenylpyridin.
      PubDate: 2017-03-02T07:10:45.148465-05:
      DOI: 10.1002/ange.201700290
       
  • Enantioselective Iridium-Catalyzed Allylic Substitution with
           2-Methylpyridines
    • Authors: Xi-Jia Liu; Shu-Li You
      Pages: 4060 - 4063
      Abstract: An enantioselective iridium-catalyzed allylic substitution with a set of highly unstabilized nucleophiles generated in situ from 2-methylpyridines is described. Enantioenriched 2-substituted pyridines, which are frequently encountered in natural products and pharmaceuticals, could be easily constructed by this simple method in good yields and excellent enantioselectivity. The synthetic utility of the pyridine products is demonstrated through the synthesis of a key intermediate of a reported Na+/H+ exchanger inhibitor and the total synthesis of (−)-lycopladine A.Eine Reihe nicht stabilisierter Nukleophile wurde bei der Titelreaktion in situ erzeugt. Enantiomerenangereicherte 2-substituierte Pyridine, ein häufiges Strukturmotiv in Naturstoffen und pharmazeutischen Wirkstoffen, sind auf diesem einfachen Weg hoch enantioselektiv und in guten Ausbeuten zugänglich. Ein Anwendungsbeispiel für die Pyridin-Produkte bietet die Totalsynthese von (−)-Lycopladin A.
      PubDate: 2017-03-07T02:40:29.430863-05:
      DOI: 10.1002/ange.201700433
       
  • Regioselective α-Addition of Deconjugated Butenolides: Enantioselective
           Synthesis of Dihydrocoumarins
    • Authors: Bo Wu; Zhaoyuan Yu, Xiang Gao, Yu Lan, Yong-Gui Zhou
      Pages: 4064 - 4068
      Abstract: The enantioselective α-addition of deconjugated butenolides has rarely been exploited, in contrast to the well-studied γ-addition of deconjugated butenolides. In this study, an unprecedented asymmetric α-addition/transesterification of deconjugated butenolides with ortho-quinone methides generated in situ afforded a series of functionalized 3,4-dihydrocoumarins containing two contiguous stereogenic centers with excellent diastereo- and enantioselectivity. DFT calculations suggested that the rarely observed regioselectivity was due to the distortion energy that resulted from the interaction between the nucleophilic dienolate and the electrophilic ortho-quinone methide.Das Alpha… aber nicht das Gamma: Die α-Addition von dekonjugierten Butenoliden wurden bislang selten genutzt – ganz im Gegensatz zu der gut untersuchten γ-Addition. Eine beispiellose asymmetrische α-Addition/Umesterung von dekonjugierten Butenoliden mit in situ hergestellten ortho-Chinonmethiden wurde nun entwickelt und für die Synthese von funktionalisierten 3,4-Dihydrocumarinen mit zwei aufeinanderfolgenden stereogenen Zentren verwendet (siehe Schema).
      PubDate: 2017-03-01T03:10:38.58744-05:0
      DOI: 10.1002/ange.201700437
       
  • Synthesis of Azanucleosides by Anodic Oxidation in a Lithium
           Perchlorate–Nitroalkane Medium and Diversification at the 4′-Nitrogen
           Position
    • Authors: Takao Shoji; Shokaku Kim, Kazuhiro Chiba
      Pages: 4069 - 4072
      Abstract: Azanucleosides, in which the 4′-oxygen atom has been replaced with a nitrogen atom, have drawn much attention owing to their anticancer and antivirus activity, and tolerance towards nucleases. However, the traditional synthetic strategy requires multiple steps and harsh conditions, thereby limiting the structural and functional diversity of the products. Herein we describe the synthesis of azanucleosides by an electrochemical reaction in a lithium perchlorate–nitroethane medium, followed by postmodification at the 4′-N position. N-Acryloyl prolinol derivatives were converted into azanucleosides by anodic activation of the N-α-C−H bond. Moreover, the use of nitroethane instead of nitromethane lowered the oxidation potential of the N-acryloyl prolinols and increased the Faradic yield. The prepared azanucleosides were efficiently functionalized at the 4′-N-acryloyl group with a lipophilic alkanethiol and a fluorescent dye by conjugate addition and olefin cross-metathesis, respectively.Für mehr Vielfalt: Azanukleoside mit einer Acryloylgruppe am 4′-N-Atom wurden durch anodische Oxidation in einer Lithiumperchlorat/Nitroalkan-Lösung hergestellt, wobei die Verwendung von Nitroethan statt Nitromethan das Oxidationspotential des N-Acryloylprolinols deutlich absenkte. Die erhaltenen Azanukleoside konnten mit einem liphophilen Alkanthiol oder einem Fluoreszenzfarbstoff an der Acryloylgruppe funktionalisiert werden.
      PubDate: 2017-03-07T02:35:30.929394-05:
      DOI: 10.1002/ange.201700547
       
  • Yttrium-Catalyzed Intramolecular Hydroalkoxylation/Claisen Rearrangement
           Sequence: Efficient Synthesis of Medium-Sized Lactams
    • Authors: Bo Zhou; Long Li, Xin-Qi Zhu, Juan-Zhu Yan, Yi-Lin Guo, Long-Wu Ye
      Pages: 4073 - 4077
      Abstract: An efficient yttrium-catalyzed intramolecular hydroalkoxylation/Claisen rearrangement sequence has been achieved, thus enabling facile access to a diverse array of valuable medium-sized lactams. Furthermore, a mechanistic rationale for this novel cascade reaction is well supported by a variety of control experiments.Ringmacher: Eine Yttrium-katalysierte intramolekulare Hydroxyalkylierung/ Claisen-Umlagerung wurde entwickelt, die einen einfachen Zugang zu wertvollen Lactamen mittlerer Ringgröße eröffnet. Verschiedene Kontrollexperimente bieten Einblick in den Mechanismus dieser neuartigen Tandemsequenz.
      PubDate: 2017-03-07T09:00:55.808179-05:
      DOI: 10.1002/ange.201700596
       
  • One-Pot Transformation of Simple Furans into Octahydroindole Scaffolds
    • Authors: Dimitris Kalaitzakis; Myron Triantafyllakis, Georgios I. Ioannou, Georgios Vassilikogiannakis
      Pages: 4078 - 4081
      Abstract: A highly efficient and general singlet-oxygen-initiated one-pot transformation of readily accessible furans into octahydroindole scaffolds has been developed.Komplexitätsgenerator: Eine Vielfalt an wichtigen Hydroindol-Gerüsten wurde über eine Eintopf-Reaktionssequenz hergestellt, die mit der Photooxygenierung einfacher Furane beginnt (siehe Schema).
      PubDate: 2017-03-07T09:01:09.940363-05:
      DOI: 10.1002/ange.201700620
       
  • Spectroscopic Evidence for a Monomeric Copper(I) Hydride and
           Crystallographic Characterization of a Monomeric Silver(I) Hydride
    • Authors: Erik A. Romero; Pauline M. Olsen, Rodolphe Jazzar, Michele Soleilhavoup, Milan Gembicky, Guy Bertrand
      Pages: 4082 - 4085
      Abstract: (1,3-bis[2,6-bis[di(4-tert-butylphenyl)methyl]-4-methylphenyl]imidazol-2-ylidene)CuOPh [(IPr**)CuOPh] reacts with poly(methylhydrosiloxane) as the hydride donor to afford the monomeric (IPr**)CuH complex, which was spectroscopically characterized. The latter is in equilibrium in solution with [(IPr**)CuH]2, the dimer being exclusively present in the solid state. These results support the hypothesis that copper hydride aggregates dissociate in solution. In contrast, addition of pinacolborane to [(IPr**)AgOPh] at −40 °C allows the isolation of the monomeric (IPr**)AgH complex, which was crystallographically characterized.RCuH paarweise, RAgH alleine: Monomeres (IPr**)CuH liegt in Lösung im Gleichgewicht mit [(IPr**)CuH]2 vor. Während der Kupferkomplex im Festkörper nicht als Monomer vorliegt, konnte (IPr**)AgH kristallographisch charakterisiert werden.
      PubDate: 2017-03-02T03:01:11.376042-05:
      DOI: 10.1002/ange.201700858
       
  • B(C6F5)3-Catalyzed Ring Opening and Isomerization of Unactivated
           Cyclopropanes
    • Authors: Zi-Yu Zhang; Zhi-Yun Liu, Rui-Ting Guo, Yu-Quan Zhao, Xiang Li, Xiao-Chen Wang
      Pages: 4086 - 4090
      Abstract: Catalytic amounts of B(C6F5)3 promote the ring opening and subsequent isomerization of a series of unactivated cyclopropanes to afford terminal olefins in good yields when a hydrosilane and 2,6-dibromopyridine are employed as additives.Cyclopropan-Öffnung: B(C6F5)3-katalysierte Ringöffnungen und Isomerisierungen von Aryl-, Alkyl- und Vinyl-substituierten Cyclopropanen werden beschrieben. So entstehen durch C-C-Bindungsbruch, 1,2-Hydridwanderung und B(C6F5)3-Dissoziation terminale Olefine. Die Zugabe von 2,6-Dibrompyridin und Ph3SiH ist für die Reaktivität entscheidend.
      PubDate: 2017-03-07T02:30:30.141224-05:
      DOI: 10.1002/ange.201700864
       
  • Asymmetric C-Alkylation by the S-Adenosylmethionine-Dependent
           Methyltransferase SgvM
    • Authors: Christina Sommer-Kamann; Alexander Fries, Silja Mordhorst, Jennifer N. Andexer, Michael Müller
      Pages: 4091 - 4094
      Abstract: S-Adenosylmethionine-dependent methyltransferases (MTs) play a decisive role in the biosynthesis of natural products and in epigenetic processes. MTs catalyze the methylation of heteroatoms and even of carbon atoms, which, in many cases, is a challenging reaction in conventional synthesis. However, C-MTs are often highly substrate-specific. Herein, we show that SgvM from Streptomyces griseoviridis features an extended substrate scope with respect to the nucleophile as well as the electrophile. Aside from its physiological substrate 4-methyl-2-oxovalerate, SgvM catalyzes the (di)methylation of pyruvate, 2-oxobutyrate, 2-oxovalerate, and phenylpyruvate at the β-carbon atom. Chiral-phase HPLC analysis revealed that the methylation of 2-oxovalerate occurs with R selectivity while the ethylation of 2-oxobutyrate with S-adenosylethionine results in the S enantiomer of 3-methyl-2-oxovalerate. Thus SgvM could be a valuable tool for asymmetric biocatalytic C-alkylation reactions.Enzymatische Alkylierung: Die Methyltransferase SgvM aus Streptomyces griseoviridis zeichnet sich durch eine große Substratbreite hinsichtlich sowohl des nucleophilen als auch des elektrophilen Reaktionspartners aus. So kann sie die asymmetrische Methylierung und Ethylierung verschiedener α-Oxosäuren katalysieren.
      PubDate: 2017-03-01T02:15:36.866186-05:
      DOI: 10.1002/ange.201609375
       
  • Catalytic Alkylation Using a Cyclic S-Adenosylmethionine Regeneration
           System
    • Authors: Silja Mordhorst; Jutta Siegrist, Michael Müller, Michael Richter, Jennifer N. Andexer
      Pages: 4095 - 4099
      Abstract: S-Adenosylmethionine-dependent methyltransferases are versatile tools for the specific alkylation of many compounds, such as pharmaceuticals, but their biocatalytic application is severely limited owing to the lack of a cofactor regeneration system. We report a biomimetic, polyphosphate-based, cyclic cascade for methyltransferases. In addition to the substrate to be methylated, only methionine and polyphosphate have to be added in stoichiometric amounts. The system acts catalytically with respect to the cofactor precursor adenosine in methylation and ethylation reactions of selected substrates, as shown by HPLC analysis. Furthermore, 1H and 13C NMR measurements were performed to unequivocally identify methionine as the methyl donor and to gain insight into the selectivity of the reactions. This system constitutes a vital stage in the development of economical and environmentally friendly applications of methyltransferases.Spiel es noch einmal, SAM! Biokatalytische Alkylierungen sind ein aufstrebendes Gebiet der Biotechnologie. Voraussetzungen für ihre wirtschaftliche Anwendung sind die Verfügbarkeit hoch effizienter und selektiver Methyltransferasen sowie die Entwicklung eines effizienten Regenerationssystems für den Cofaktor S-Adenosylmethionin (SAM). Nun gelang der Aufbau eines biomimetischen In-vitro-SAM-Regenerationszyklus mit verschiedenen Methyltransferasen als Modellsystem.
      PubDate: 2017-02-07T08:20:30.2056-05:00
      DOI: 10.1002/ange.201611038
       
  • Ausrichtung amorpher Eisenoxid-Cluster: ein nichtklassischer Mechanismus
           für die Magnetitbildung
    • Authors: Shengtong Sun; Denis Gebauer, Helmut Cölfen
      Pages: 4100 - 4104
      Abstract: Obwohl schon viele Studien auf dem Gebiet der Nukleation und Kristallisation von Eisen(oxyhydr)oxiden durchgeführt wurden, ist die Rolle der Spezies, die sich in den frühen Stadien entwickeln, besonders primäre Cluster und amorphe Übergangspartikel, immer noch schlecht verstanden. Hier wurden sowohl ligandenfreie als auch ligandengeschützte amorphe Eisenoxid-Cluster (“amorphous iron oxide”, AIO,
      PubDate: 2017-03-02T07:11:01.300452-05:
      DOI: 10.1002/ange.201610275
       
  • Polymerbasierte Halogenbrückendonoren mit selbstheilenden
           Eigenschaften in Filmen
    • Authors: Ronny Tepper; Stefan Bode, Robert Geitner, Michael Jäger, Helmar Görls, Jürgen Vitz, Benjamin Dietzek, Michael Schmitt, Jürgen Popp, Martin D. Hager, Ulrich S. Schubert
      Pages: 4105 - 4110
      Abstract: Dieser Beitrag beschreibt die Synthese einer systematischen Reihe polymerbasierter Anionenrezeptoren und deren umfassende Charakterisierung sowohl in Lösung als auch im Polymerfilm. Erstmals wurden hierbei polymerbasierte Halogenbrückendonoren mittels isothermer kalorimetrischer Titration vermessen, um die Abhängigkeit der Anionenaffinität von verschiedenen Parametern (d. h. monomerbasiert gegenüber polymerbasiert, Halogenbrücken im Vergleich zu Wasserstoffbrücken sowie Ladungsassistenz) zu beurteilen. Durch die Kombination dieser Donorsysteme mit einem carboxylathaltigem Copolymer konnten supramolekulare Polymernetzwerke mit ausgezeichnetem intrinsischem Selbstheilungsverhalten hergestellt werden. FT-Raman-Spektroskopie und Nanoindentierungsmessungen der durch die Halogenbrücken vernetzten Polymerfilme dienten zur Aufklärung des thermisch induzierten Selbstheilungsmechanismus. Diese selbstheilenden Polymere basierend auf Halogenbrücken ebnen den Weg für neue Anwendungsgebiete der Halogenbrückendonoren.Polymerbasierte Halogenbrückendonoren wurden hinsichtlich ihres thermodynamischen Verhaltens in Lösung untersucht und anschließend zur Herstellung vernetzter Polymerfilme mit selbstheilenden Eigenschaften verwendet. Isotherme Titrationskalorimetrie, Nanoindentierung, Röntgenkristallstrukturanalyse, Dichtefunktionalrechnungen und FT-Raman-Spektroskopie wurden zur Charakterisierung der Halogenbrückensysteme verwendet.
      PubDate: 2017-03-07T02:30:26.713993-05:
      DOI: 10.1002/ange.201610406
       
  • Universelles Superauflösungs-Multiplexing durch DNA-Austausch
    • Authors: Florian Schueder; Maximilian T. Strauss, David Hoerl, Joerg Schnitzbauer, Thomas Schlichthaerle, Sebastian Strauss, Peng Yin, Hartmann Harz, Heinrich Leonhardt, Ralf Jungmann
      Pages: 4111 - 4114
      Abstract: Superauflösende Mikroskopie ermöglicht optische Bildgebung unterhalb der klassischen Beugungsgrenze von Licht mit bis zu 20-fach verbesserter räumlicher Auflösung. Jedoch ist derzeit das Beobachten mehrerer unterschiedlicher Zielmoleküle (“Multiplexing”) schwierig und zeitintensiv in der Durchführung. Hier stellen wir einen einfachen Ansatz für sequenzielles Multiplexing vor, der auf einem schnellen Austausch von DNA-Sonden basiert. Dies ermöglicht eine effiziente Detektion vieler Zielmoleküle mit Superauflösungsmethoden wie (d)STORM, STED und SIM. Wir evaluieren unseren Ansatz mit DNA-Origami-Nanostrukturen, um Markierung, Bildgebung und die Wascheffizienz quantitativ zu testen. Darüber hinaus demonstrieren wir die Anwendbarkeit unserer Methode zur Bildgebung mehrerer Proteine in fixierten Zellen.Mehr Runden, mehr Ziele: Ein geradliniger sequenzieller Multiplexing-Ansatz auf der Grundlage des schnellen Austausches von DNA-Sonden ermöglicht den effizienten Nachweis mehrerer Zielmoleküle mithilfe von gängigen superauflösenden Techniken wie (d)STORM, STED und SIM.
      PubDate: 2017-03-03T05:55:35.076391-05:
      DOI: 10.1002/ange.201611729
       
  • Ein Aluminium-Fluorid-Komplex mit gekoppelter Ammonium-Einheit als
           außergewöhnlich aktiver kooperativer Katalysator in der asymmetrischen
           Carboxycyanierung von Aldehyden
    • Authors: Daniel Brodbeck; Florian Broghammer, Jan Meisner, Julian Klepp, Delphine Garnier, Wolfgang Frey, Johannes Kästner, René Peters
      Pages: 4115 - 4119
      Abstract: Al-F-Bindungen gehören zu den stärksten bekannten σ-Bindungen und weisen sogar höhere Bindungsenergien als Si-F-Bindungen auf. Trotz eines Stabilitätsvorteils und einer potenziell hohen Lewis-Acidität von Al-F-Komplexen, wurden diese bisher nicht als strukturell definierte Katalysatoren für enantioselektive Reaktionen beschrieben. Hier zeigen wir, dass Al-F-Salen-Komplexe mit gekoppelten Ammonium-Einheiten eine außergewöhnlich hohe katalytische Aktivität in asymmetrischen Carboxycyanierungen aufweisen. Neben aromatischen Aldehyden wurden auch Enale und aliphatische Substrate effizient umgesetzt. Umsatzzahlen bis zu ca. 104 wurden erreicht, wohingegen sie mit vorherigen Katalysatoren üblicherweise im Bereich von 101–102 lagen. Anders als Al-Me- und Al-Cl-Salen-Komplexe sind die analogen Al-F-Spezies bemerkenswert stabil gegenüber Luft, Wasser und Hitze, und sie konnten nach der Katalyse unverändert zurückgewonnen werden. Sie zeichnen sich laut DFT-Rechnungen durch eine beträchtlich erhöhte Lewis-Acidität aus.AlF ist gelandet: Ein strukturell definierter {Al-F}-Komplex ist im Vergleich zu seinen {Al-Me}- und {Al-Cl}-Analoga auffällig stabil gegenüber Luft, Feuchtigkeit und Hitze, wahrscheinlich aufgrund der sehr starken Al-F-Bindung. In asymmetrischen Carboxycyanierungen wies der {Al-F}-Komplex eine herausragende katalytische Aktivität auf.
      PubDate: 2017-03-01T02:10:42.022812-05:
      DOI: 10.1002/ange.201612493
       
  • 16-Gliedriger Au8P8-Makrocyclus aus Gold(I) und Diphospha(III)-guanidin
    • Authors: Anup K. Adhikari; Menyhárt B. Sárosi, Toni Grell, Peter Lönnecke, Evamarie Hey-Hawkins
      Pages: 4120 - 4123
      Abstract: Die Reaktion von cyclo-P4Mes4C(NCy) (1) mit zwei Äquivalenten [AuCl(tht)] (tht=Tetrahydrothiophen) führte zur Bildung des ungewöhnlichen 16-gliedrigen Au-P-Makrocyclus 2. Der Makrocyclus weist Diphospha(III)-guanidinat-Liganden auf, die durch Spaltung der P-P-Bindungen in 1 gebildet werden. Die Charakterisierung von 2 erfolgte durch Multikern-NMR-Spektroskopie, Massenspektrometrie und Röntgenkristallstrukturanalyse.Eine Krone aus Gold – und Phosphor: Die Reaktion von cyclo-P4Mes4C(NCy) mit zwei Äquivalenten [AuCl(tht)] (tht= Tetrahydrothiophen) führt zur Bildung eines ungewöhnlichen 16-gliedrigen Au-P-Makrocyclus mit Diphospha(III)-guanidin als koordinierendem Liganden, das durch Spaltung der P-P-Bindungen in cyclo-P4Mes4C(NCy) entsteht. Der Makrocyclus wurde durch Multikern-NMR-Spektroskopie und Röntgenstrukturanalyse charakterisiert.
      PubDate: 2017-03-02T07:10:39.737795-05:
      DOI: 10.1002/ange.201700383
       
  • Innenrücktitelbild: “114”-Type Nitrides LnAl(Si4−xAlx)N7Oδ with
           Unusual [AlN6] Octahedral Coordination (Angew. Chem. 14/2017)
    • Authors: Saifang Huang; Zhaohui Huang, Peng Cao, Zoran Zujovic, Jason R. Price, Maxim Avdeev, Meidan Que, Furitsu Suzuki, Tsuyoshi Kido, Xin Ouyang, Hironori Kaji, Minghao Fang, Yan-gai Liu, Wei Gao, Tilo Söhnel
      Pages: 4125 - 4125
      Abstract: Oktaedrisch koordiniertes Aluminium in Form von [AlN6] (rot im Titelbild) wurde in einem Nitrid mit Swedenborgit-Struktur gefunden. In ihrer Zuschrift auf S. 3944 ff. lösen S. F. Huang, Z. H. Huang, T. Söhnel und Mitarbeiter die Kristallstruktur mithilfe von Synchrotron-, Röntgen- und Neutronenbeugung. Sie bestätigen den außergewöhnlichen Koordinationsmodus durch 27Al-NMR-Spektroskopie, und sie entschlüsseln die Anordnung der übrigen Atome (grün), die das [AlN6]-Oktaeder in ungeordneter Weise umgeben.
      PubDate: 2017-03-06T08:15:29.758582-05:
      DOI: 10.1002/ange.201702125
       
  • Rücktitelbild: Selected Mutations Reveal New Intermediates in the
           Biosynthesis of Mupirocin and the Thiomarinol Antibiotics (Angew. Chem.
           14/2017)
    • Authors: Shu-Shan Gao; Luoyi Wang, Zhongshu Song, Joanne Hothersall, Elton R. Stevens, Jack Connolly, Peter J. Winn, Russell J. Cox, Matthew P. Crump, Paul R. Race, Christopher M. Thomas, Thomas J. Simpson, Christine L. Willis
      Pages: 4126 - 4126
      Abstract: Die Umwandlung …… des biosynthetischen Intermediats Pseudomonsäure B in Pseudomonsäure A, die mit dem formalen Verlust einer Hydroxygruppe einhergeht, ist notwendig, um dessen antibiotisches Potential vollständig auszuschöpfen. In der Zuschrift auf S. 3988 ff. beschreiben T. J. Simpson, C. L. Willis et al. die komplette Sequenz der beteiligten Intermediate und die Identifizierung der assoziierten Gene durch Gen-Knockout und Komplementierungsexperimente.
      PubDate: 2017-03-06T03:25:38.95563-05:0
      DOI: 10.1002/ange.201702123
       
  • From composition to cure: A systems engineering approach to anti-cancer
           drug carriers
    • Authors: Sarah Reagan MacEwan; Ashutosh Chilkoti
      Abstract: The molecular complexity and heterogeneity of cancer has led to a persistent, and as yet unsolved, challenge of developing cures for this disease. Although the pharmaceutical industry focuses the bulk of its efforts on the development of new drugs, an alternative —and in many ways complementary— approach is the improvement of the delivery of existing drugs with drug carriers that can manipulate when, where, and how a drug exerts its therapeutic effect. For the treatment of solid tumors, systemically delivered drug carriers face significant challenges that are imposed by the pathophysiological barriers that lie between their site of administration and their site of therapeutic action in the tumor. Furthermore, drug carriers face additional challenges in their translation from pre-clinical validation to clinical approval and adoption. Addressing this diverse network of challenges requires a systems engineering approach to anti-cancer drug delivery. Such a perspective is needed to better enable the rational design of optimized vehicles that navigate the trade-offs of this complex system to create next generation anti-cancer drug carriers that have a realistic prospect for translation from the lab to the patient.
      PubDate: 2016-12-27T22:20:32.206682-05:
      DOI: 10.1002/ange.201610819
       
  • Methyltransferase directed labeling of biomolecules and its applications
    • Authors: Jochem Deen; Charlotte Vranken, Volker Leen, Robert K Neely, Kris Pieter Frans Janssen, Johan Hofkens
      Abstract: Methyltransferases (MTases) compose a large family of enzymes which have the ability to methylate a diverse set of targets, ranging from the three major biopolymers DNA, RNA and protein to small molecules. Most of these MTases use the cofactor S-Adenosyl-L-Methionine (AdoMet) as their methyl source. Given the important biological role of methylation, e.g. in epigenetic regulation of gene activity and the vast potential of targeted functionalization in biology, diagnostics and nanotechnology, it should come as no surprise that recent years have seen significant efforts in the development of AdoMet analogues with the aim of transferring moieties other than simple methyl groups. Two major classes of AdoMet analogues currently exist- the doubly-activated and aziridine based molecules- each of which employs a different approach for transalkylation, as opposed to transmethylation, of the target molecule. In this review, we discuss the various strategies for labelling and functionalizing biomolecules using AdoMet-dependent MTases and AdoMet analogues. We cover the synthetic routes to AdoMet analogues, their stability in biological environments and their application in transalkylation reactions. Finally, some perspectives are presented for the potential use of AdoMet analogues in biology research, (epi)genetics and nanotechnology.
      PubDate: 2016-12-12T04:16:28.246834-05:
      DOI: 10.1002/ange.201608625
       
  • Synthetic Biology - The Synthesis of Biology
    • Authors: Simon Ausländer; David Ausländer, Martin Fussenegger
      Abstract: Synthetic biology envisages the engineering of man-made living biomachines from standardized components that can perform pre-defined functions in a (self-)controlled manner. Different research strategies and interdisciplinary efforts are pursued to implement engineering principles to biology. The "top-down" strategy exploits nature's incredible diversity of existing, natural parts to construct synthetic compositions of genetic, metabolic or signalling networks with predictable and controllable properties. This mainly application-driven approach results in living factories that produce drugs, biofuels, biomaterials and fine chemicals and results in living pills that are based on engineered cells with the capacity to autonomously detect and treat disease states in vivo. In contrast, the "bottom-up" strategy seeks to be independent of existing living systems by designing biological systems from scratch and synthesizing artificial biological entities not found in nature. This more knowledge-driven approach investigates the reconstruction of minimal biological systems that are capable of performing basic biological phenomena, such as self-organization, self-replication and self-sustainability. Moreover, the syntheses of artificial biological units, such as synthetic nucleotides or amino acids, and their implementation into polymers inside living cells currently set the boundaries between natural and artificial biological systems. In particular, the in vitro design, synthesis and transfer of complete genomes into host cells and the application of efficient genome-wide intervention techniques point to the future of synthetic biology: the creation of living designer cells with tailored desirable properties for biomedicine and biotechnology.
      PubDate: 2016-12-11T23:24:13.846386-05:
      DOI: 10.1002/ange.201609229
       
  • 50 (and more) Years of Propellane Chemistry - From a Chemical Curiosity to
           "Explosive" Applications in Material Sciences and Natural Product
           Chemistry
    • Authors: Alicia Merve Dilmac; Eduard Spuling, Armin de Meijere, Stefan Bräse
      Abstract: Propellanes are a unique class of compounds with well over 10000 members with an inverted tetrahedral configuration featuring a weak single bond between two carbon atoms linked by three additional bridge. Not only structurally interesting, these propella-type compounds exhibit unusual reactivities. In this review, we highlight their synthesis and applications in material sciences, natural product chemistry and medicinal chemistry. We feature the chemistry of [1.1.1]propellane like the synthesis of oligomeric and polymeric structures derived from it such as bicyclo[1.1.1]pentanes and staffanes. A selected number of natural products are discussed in detail. Heteropropellanes and inorganic propellanes are also addressed. The historical background is given in brief showing the pioneering work of David Ginsburg, Günther Snatzke, Günter Szeimies, Kenneth Wiberg and others.
      PubDate: 2016-11-30T12:15:40.668115-05:
      DOI: 10.1002/ange.201603951
       
  • Label-free molecular imaging of biological cells and tissues by linear and
           non-linear Raman spectroscopic approaches
    • Authors: Jürgen Popp; Christoph Krafft, Michael Schmitt, Iwan Schie, Dana Cialla-May, Christian Matthaeus, Thomas Bocklitz
      Abstract: Raman spectroscopy is an emerging technique in bioanalysis and imaging of biomaterials due to its unique spectroscopic fingerprint capabilities. Imaging of cells and tissues by Raman microspectroscopy represents a non-destructive and label-free approach. All components of cells or tissues contribute to the Raman signals giving complex spectral signatures. Long acquisitions times are often required due to the relatively small Raman scattering cross sections. To overcome these limitations, Raman signal enhancing methods like resonance Raman scattering and surface enhanced Raman scattering can be applied that also reduce the spectral complexity because the enhancement is often restricted to selected bands. Raman-active labels can be introduced to increase specificity and multimodality. In addition, non-linear coherent Raman scattering such as coherent anti-Stokes Raman scattering and stimulated Raman scattering offer higher sensitivities which enable rapid imaging of larger sampling areas. Finally, fiber based imaging techniques open the way towards in vivo applications of Raman spectroscopy. This critical review summarizes theory, instrumentation, data processing and progress of medical Raman imaging since 2012.
      PubDate: 2016-11-15T16:29:42.063815-05:
      DOI: 10.1002/ange.201607604
       
  • Metal Fluorides as Analogs for Studies on Phosphoryl Transfer Enzymes
    • Authors: George Michael Blackburn; Yi Jin, Nigel G Richards, Jonathan P Waltho
      Abstract: The 1994 structure of a transition state analog with AlF4- and GDP complexed to G1, a small G protein, heralded a new field of research into structure and mechanism of enzymes that manipulate transfer of the phosphoryl (PO3-) group. The list of enzyme structures that embrace metal fluorides, MFx, as ligands that imitate either the phosphoryl group or a phosphate, is now growing at over 80 per triennium. They fall into three distinct geometrical classes: (i) Tetrahedral complexes, based on BeF3-, mimic ground state phosphates; (ii) Octahedral complexes, primarily based on AlF4-, mimic "in-line" anionic transition state for phosphoryl transfer; and (iii) Trigonal bipyramidal complexes, represented by MgF3- and putative AlF30 moieties, additionally mimic the tbp geometry of the transition state. The interpretation of these structures provides a deeper mechanistic understanding of the behavior and manipulation of phosphate monoesters in molecular biology. This review provides a comprehensive overview of these structures, their uses, and their computational development. It questions the identification of AlF30 and MgF4= as tbp species in protein complexes and discusses the relevance of physical organic chemistry and water-based model studies for understanding phosphoryl group transfer in enzymes. It describes two roles for amino acid side-chains that mediate proton transfers during phosphoryl transfer, based on the analysis of protein/MFx structures. First, they deploy hydrogen bonding to neutral oxygen nucleophiles so as to orientate them for correct orbital overlap with the electrophilic phosphorus center. Secondly, they behave as classical general acid/base catalysts.
      PubDate: 2016-11-08T11:02:56.779882-05:
      DOI: 10.1002/ange.201606474
       
  • The Stability Challenges of Oxygen Evolving Electrocatalysts: Towards a
           Common Fundamental Understanding and Mitigation of Catalyst Degradation
    • Authors: Camillo Spoeri; Jason Tai Hong Kwan, Arman Bonakdarpour, David Wilkinson, Peter Strasser
      Abstract: The electrochemical oxygen evolution reaction (OER) is an important reaction in the industrial production of numerous inorganic chemicals. However, over the last decade it has also received growing attention as scalable proton- and electron-providing process for use in the production of solar fuels, such as hydrogen, hydrocarbons, or alcohols carried out in water- and CO2-electrolyzers. To operate these devices efficiently and economically , active and stable electrocatalysts are required. While advances have been made in understanding and tuning OER efficiency and activity, the stability of OER catalysts and the reduction of their degradation continue to be major challenges. While most stability studies limit themselves to short-term testing in idealized three-electrode set ups, a much stronger focus on advancing our understanding of degradation of OER catalysts in realistic Membrane Electrode Assemblies (MEAs) with industrial current densities, is critically needed.This review addresses the technical challenges, their scientific basis, as well as recent progress and the road ahead regarding stability and degradation of OER catalysts operating at electrolyzer anodes in acidic MEA environments. First, we start clarifying the complexity associated with the term "catalyst stability", cover today's performance targets and outline major catalyst degradation mechanisms and their mitigation strategies. Then we evaluate suitable in-situ experimental methods to get insight into catalyst degradation and describe achievements in tuning OER catalyst stability. Finally, we highlight the importance of identifying universal figures of merit for stability and develop a comprehensive accelerated life test (ALT) that would yield comparable performance data across labs and catalyst types. As a whole, this review will help to disseminate and highlight the important relations between structure, composition and stability of OER catalysis under different operating conditions.
      PubDate: 2016-11-01T09:20:36.743545-05:
      DOI: 10.1002/ange.201608601
       
  • Power-to-Syngas - an enabling technology for the transition of the energy
           system' Production of tailored synfuels and chemicals using renewably
           generated electricity.
    • Authors: Severin Foit; Rüdiger-A. Eichel, Izaak C. Vinke, Lambertus G.J. de Haart
      Abstract: Power-to-X concepts promise a significant reduction of greenhouse gas emissions and simultaneously guaranteeing a safe energy supply even at high share of renewable power generation, thus becoming a cornerstone of a sustainable energy system. Power-to-Syngas, i.e. the electrochemical conversion of steam and carbon dioxide with the use of renewably generated electricity to syngas for the production of synfuels and high-value chemicals, offers an efficient technology to couple different energy-intense sectors, such as 'traffic and transportation' and 'chemical industry'. Consequently, co-electrolysis can be regarded as a key-enabling step for a transition of the energy system that offers additionally features of CO2-valorization and closed carbon cycles. In this Minireview, we outline and discuss advantages and current technical limitations of low- and high-temperature co-electrolysis. Advances in both, a fundamental understanding of the basic reaction schemes and in stable high-performance materials are essential to further promote co-electrolysis.
      PubDate: 2016-10-07T02:46:24.908026-05:
      DOI: 10.1002/ange.201607552
       
  • Surface Modification of Water Purification Membranes: a Review
    • Authors: Daniel Miller; Daniel Dreyer, Christopher Bielawski, Donald Paul, Benny Freeman
      Abstract: Polymer membranes are an energy-efficient means of purifying water, but they suffer from fouling during filtration. Membrane surface modification is one route to mitigate membrane fouling as it helps to maintain high levels of water productivity. Here, a series of common membrane surface modification techniques are reviewed, including surface coating, grafting, and various treatment techniques such as chemical treatment, UV irradiation, and plasma treatment, among others. Historical background on membrane development and surface modification is also provided. Finally, polydopamine, an emerging material that can be easily deposited onto a wide variety of substrates, is discussed in the context of membrane modification. The chemistry of polydopamine is also reviewed.
      PubDate: 2016-09-08T06:35:42.626644-05:
      DOI: 10.1002/ange.201601509
       
  • Mixed-Valence Nickel Bis(azamacrocycle) Compounds with Ghost-Leg-type
           Sheets
    • Authors: Ryota Hashiguchi; Kazuya Otsubo, Mitsuhiko Maesato, Kunihisa Sugimoto, Akihiko Fujiwara, Hiroshi Kitagawa
      Pages: 3896 - 3899
      Abstract: The fabrication of so-called ghost-leg sheets and their electronic properties is reported. This unique sheet structure is composed of one-dimensional mixed-valence nickel chains, which are linked with one another by bis(azamacrocycle) ligands. They are also topologically unique NiII/NiIII mixed-valence complexes, as confirmed by X-ray and optical measurements. Moreover, their magnetic susceptibilities indicated two-dimensional antiferromagnetic behavior following the Fisher 1D chain model with interchain interactions, where spins on NiIII sites mutually interact antiferromagnetically in the sheets.Geisterfuß-Schichten: Die ersten Beispiele einer gemischtvalenten NiII/NiIII-Schichtstruktur wurden in Form von zweikernigen Nickelbausteinen mit bisazamakrocyclischen Liganden hergestellt und auf ihre elektronischen Eigenschaften untersucht. Die Schichten sind magnetisch wechselwirkende Systeme, in denen die Spins auf den NiIII-Ionen antiferromagnetisch miteinander wechselwirken.
      PubDate: 2016-12-21T02:16:30.813006-05:
      DOI: 10.1002/ange.201610515
       
 
 
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