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  Subjects -> CHEMISTRY (Total: 849 journals)
    - ANALYTICAL CHEMISTRY (47 journals)
    - CHEMISTRY (603 journals)
    - CRYSTALLOGRAPHY (22 journals)
    - ELECTROCHEMISTRY (26 journals)
    - INORGANIC CHEMISTRY (41 journals)
    - ORGANIC CHEMISTRY (45 journals)
    - PHYSICAL CHEMISTRY (65 journals)

CHEMISTRY (603 journals)                  1 2 3 4 | Last

Showing 1 - 200 of 735 Journals sorted alphabetically
2D Materials     Hybrid Journal   (Followers: 5)
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: 28)
ACS Chemical Neuroscience     Full-text available via subscription   (Followers: 15)
ACS Combinatorial Science     Full-text available via subscription   (Followers: 23)
ACS Macro Letters     Full-text available via subscription   (Followers: 21)
ACS Medicinal Chemistry Letters     Full-text available via subscription   (Followers: 36)
ACS Nano     Full-text available via subscription   (Followers: 178)
ACS Photonics     Full-text available via subscription   (Followers: 7)
ACS Synthetic Biology     Full-text available via subscription   (Followers: 19)
Acta Chemica Iasi     Open Access   (Followers: 1)
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: 1)
adhäsion KLEBEN & DICHTEN     Hybrid Journal   (Followers: 5)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 6)
Adsorption Science & Technology     Full-text available via subscription   (Followers: 4)
Advanced Functional Materials     Hybrid Journal   (Followers: 44)
Advanced Science Focus     Free   (Followers: 3)
Advances in Chemical Engineering and Science     Open Access   (Followers: 52)
Advances in Chemical Science     Open Access   (Followers: 11)
Advances in Chemistry     Open Access   (Followers: 10)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 15)
Advances in Drug Research     Full-text available via subscription   (Followers: 21)
Advances in Enzyme Research     Open Access   (Followers: 5)
Advances in Fluorine Science     Full-text available via subscription   (Followers: 8)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 12)
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: 14)
Advances in Polymer Science     Hybrid Journal   (Followers: 39)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 16)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 16)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 5)
Advances in Science and Technology     Full-text available via subscription   (Followers: 6)
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)
Alchemy : Jurnal Penelitian Kimia     Open Access  
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 3)
AMB Express     Open Access   (Followers: 1)
Ambix     Hybrid Journal   (Followers: 3)
American Journal of Biochemistry and Biotechnology     Open Access   (Followers: 63)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 13)
American Journal of Chemistry     Open Access   (Followers: 23)
American Journal of Plant Physiology     Open Access   (Followers: 12)
American Mineralogist     Full-text available via subscription   (Followers: 8)
Anadolu University Journal of Science and Technology     Open Access  
Analyst     Full-text available via subscription   (Followers: 41)
Angewandte Chemie     Hybrid Journal   (Followers: 136)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 182)
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: 10)
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     Full-text available via subscription  
Applied Organometallic Chemistry     Hybrid Journal   (Followers: 5)
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: 8)
Biochemistry     Full-text available via subscription   (Followers: 241)
Biochemistry Insights     Open Access   (Followers: 4)
Biochemistry Research International     Open Access   (Followers: 5)
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: 17)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 11)
Biomedical Chromatography     Hybrid Journal   (Followers: 7)
Biomolecular NMR Assignments     Hybrid Journal   (Followers: 2)
BioNanoScience     Partially Free   (Followers: 4)
Bioorganic & Medicinal Chemistry     Hybrid Journal   (Followers: 110)
Bioorganic & Medicinal Chemistry Letters     Hybrid Journal   (Followers: 88)
Bioorganic Chemistry     Hybrid Journal   (Followers: 9)
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: 26)
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: 27)
Carbon     Hybrid Journal   (Followers: 68)
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: 6)
Cellulose     Hybrid Journal   (Followers: 5)
Cereal Chemistry     Full-text available via subscription   (Followers: 4)
ChemBioEng Reviews     Full-text available via subscription  
ChemCatChem     Hybrid Journal   (Followers: 7)
Chemical and Engineering News     Free   (Followers: 10)
Chemical Bulletin of Kazakh National University     Open Access  
Chemical Communications     Full-text available via subscription   (Followers: 64)
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: 141)
Chemical Science     Open Access   (Followers: 18)
Chemical Technology     Open Access   (Followers: 12)
Chemical Vapor Deposition     Hybrid Journal   (Followers: 4)
Chemical Week     Full-text available via subscription   (Followers: 7)
Chemie in Unserer Zeit     Hybrid Journal   (Followers: 53)
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: 29)
Chemistry & Industry     Hybrid Journal   (Followers: 4)
Chemistry - A European Journal     Hybrid Journal   (Followers: 127)
Chemistry - An Asian Journal     Hybrid Journal   (Followers: 14)
Chemistry and Materials Research     Open Access   (Followers: 15)
Chemistry Central Journal     Open Access   (Followers: 4)
Chemistry Education Research and Practice     Free   (Followers: 4)
Chemistry in Education     Open Access   (Followers: 2)
Chemistry International     Hybrid Journal   (Followers: 1)
Chemistry Letters     Full-text available via subscription   (Followers: 45)
Chemistry of Materials     Full-text available via subscription   (Followers: 159)
Chemistry of Natural Compounds     Hybrid Journal   (Followers: 8)
Chemistry-Didactics-Ecology-Metrology     Open Access  
ChemistryOpen     Open Access   (Followers: 1)
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: 6)
ChemPlusChem     Hybrid Journal  
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: 5)
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: 9)
Colloids and Surfaces B: Biointerfaces     Hybrid Journal   (Followers: 7)
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: 4)
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: 10)
Computational Chemistry     Open Access   (Followers: 2)
Computers & Chemical Engineering     Hybrid Journal   (Followers: 10)
Coordination Chemistry Reviews     Full-text available via subscription  
Copernican Letters     Open Access  
Critical Reviews in Biochemistry and Molecular Biology     Hybrid Journal   (Followers: 5)
Crystal Structure Theory and Applications     Open Access   (Followers: 2)
CrystEngComm     Full-text available via subscription   (Followers: 9)
Current Catalysis     Hybrid Journal   (Followers: 1)
Current Metabolomics     Hybrid Journal   (Followers: 3)
Current Opinion in Colloid & Interface Science     Hybrid Journal   (Followers: 7)
Current Opinion in Molecular Therapeutics     Full-text available via subscription   (Followers: 14)
Current Research in Chemistry     Open Access   (Followers: 7)
Current Science     Open Access   (Followers: 44)
Dalton Transactions     Full-text available via subscription   (Followers: 17)
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: 2)
Ecotoxicology and Environmental Contamination     Open Access  
Educación Química     Open Access   (Followers: 1)
Education for Chemical Engineers     Hybrid Journal   (Followers: 4)
EDUSAINS     Open Access  
Elements     Full-text available via subscription   (Followers: 1)
Environmental Chemistry     Hybrid Journal   (Followers: 5)
Environmental Chemistry Letters     Hybrid Journal   (Followers: 2)

        1 2 3 4 | Last

Journal Cover Angewandte Chemie
  [136 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  [1612 journals]
  • Small Molecule Microarray Based Discovery of PARP14 Inhibitors
    • Authors: Bo Peng; Ann-Gerd Thorsell, Tobias Karlberg, Herwig Schüler, Shao Q. Yao
      Abstract: Poly(ADP-ribose) polymerases (PARPs) are key enzymes in a variety of cellular processes. Most small-molecule PARP inhibitors developed to date have been against PARP1, and suffer from poor selectivity. PARP14 has recently emerged as a potential therapeutic target, but its inhibitor development has trailed behind. Herein, we describe a small molecule microarray-based strategy for high-throughput synthesis, screening of >1000 potential bidentate inhibitors of PARPs, and the successful discovery of a potent PARP14 inhibitor H10 with >20-fold selectivity over PARP1. Co-crystallization of the PARP14/H10 complex indicated H10 bound to both the nicotinamide and the adenine subsites. Further structure–activity relationship studies identified important binding elements in the adenine subsite. In tumor cells, H10 was able to chemically knockdown endogenous PARP14 activities.Auf dem Punkt genau: Ein Mikroarray ermöglicht die miniaturisierte Synthese und Screening von über 1000 niedermolekularen Verbindungen als potenzielle zweizähnige Inhibitoren von Poly(ADP-Ribose)-Polymerasen (PARPs) auf einem Chip. So wurde ein wirksamer PARP14-Inhibitor (IC50=0.49 μm) mit >20-facher Selektivität gegenüber PARP1 entdeckt.
      PubDate: 2016-12-05T09:46:13.420856-05:
      DOI: 10.1002/ange.201609655
       
  • Nickel-Catalyzed CO2 Rearrangement of Enol Metal Carbonates for the
           Efficient Synthesis of β-Ketocarboxylic Acids
    • Authors: Ryo Ninokata; Tatsuya Yamahira, Gen Onodera, Masanari Kimura
      Abstract: 4-Methylene-1,3-dioxolan-2-ones underwent oxidative addition of a Ni0 catalyst in the presence of Me2Al(OMe), followed by a coupling reaction with alkynes, to form δ,ϵ-unsaturated β-ketocarboxylic acids with high regio- and stereoselectivity. The reaction proceeds by [1,3] rearrangement of an enol metal carbonate intermediate and the formal reinsertion of CO2.Ausschneiden und einfügen: Die oxidative Addition eines 4-Methylen-1,3-dioxolan-2-ons an einen Ni0-Katalysator in Gegenwart von Me2Al(OMe) und die anschließende Kupplungsreaktion mit Alkinen liefert δ,ϵ-ungesättigte β-Ketocarbonsäuren mit hoher Regio- und Stereoselektivität (siehe Schema). Die Reaktion verläuft über eine [1,3]-Umlagerung eines Enolmetallcarbonats und die formale Reinsertion von CO2.
      PubDate: 2016-12-05T08:45:34.795562-05:
      DOI: 10.1002/ange.201609338
       
  • Frontispiz: Zuordnung der Rückgrat- und Seitenketten-Protonen in
           vollständig protonierten Proteinen durch Festkörper-NMR-Spektroskopie:
           Mikrokristalle, Sedimente und Amyloidfibrillen
    • Authors: Jan Stanek; Loren B. Andreas, Kristaps Jaudzems, Diane Cala, Daniela Lalli, Andrea Bertarello, Tobias Schubeis, Inara Akopjana, Svetlana Kotelovica, Kaspars Tars, Andrea Pica, Serena Leone, Delia Picone, Zhi-Qiang Xu, Nicholas E. Dixon, Denis Martinez, Mélanie Berbon, Nadia El Mammeri, Abdelmajid Noubhani, Sven Saupe, Birgit Habenstein, Antoine Loquet, Guido Pintacuda
      Abstract: Festkörper-NMR-Spektroskopie Neue MAS-Sonden ermöglichen die hochauflösende NMR-Spektroskopie von unlöslichen, kristallinen oder selbstorganisierten Proteinaggregaten ohne Deuterierung. G. Pintacuda et al. beschreiben die Methode in der Zuschrift auf S. 15730 ff.
      PubDate: 2016-12-05T07:50:10.261459-05:
      DOI: 10.1002/ange.201685061
       
  • Development of Cell-Permeable, Non-Helical Constrained Peptides to Target
           a Key Protein–Protein Interaction in Ovarian Cancer
    • Authors: Mareike M. Wiedmann; Yaw Sing Tan, Yuteng Wu, Shintaro Aibara, Wenshu Xu, Hannah F. Sore, Chandra S. Verma, Laura Itzhaki, Murray Stewart, James D. Brenton, David R. Spring
      Abstract: There is a lack of current treatment options for ovarian clear cell carcinoma (CCC) and the cancer is often resistant to platinum-based chemotherapy. Hence there is an urgent need for novel therapeutics. The transcription factor hepatocyte nuclear factor 1β (HNF1β) is ubiquitously overexpressed in CCC and is seen as an attractive therapeutic target. This was validated through shRNA-mediated knockdown of the target protein, HNF1β, in five high- and low-HNF1β-expressing CCC lines. To inhibit the protein function, cell-permeable, non-helical constrained proteomimetics to target the HNF1β–importin α protein–protein interaction were designed, guided by X-ray crystallographic data and molecular dynamics simulations. In this way, we developed the first reported series of constrained peptide nuclear import inhibitors. Importantly, this general approach may be extended to other transcription factors.Einfuhrstopp: Der Transkriptionsfaktor HNF1β wird in bestimmten Eierstock-Karzinomzellen überexprimiert. Röntgen-kristallographische Daten und Moleküldynamiksimulationen führten zu zellgängigen nichthelikalen Proteomimetika (orange), welche die Protein-Protein-Wechselwirkung zwischen HNF1β und Importin α stören und dadurch den Transport von HNF1β in den Zellkern verhindern. Dieser allgemeine Ansatz ließ sich auf andere Transkriptionsfaktoren übertragen.
      PubDate: 2016-12-05T05:37:49.212525-05:
      DOI: 10.1002/ange.201609427
       
  • Star PolyMOCs with Diverse Structures, Dynamics, and Functions by
           Three-Component Assembly
    • Authors: Yufeng Wang; Yuwei Gu, Eric G. Keeler, Jiwon V. Park, Robert G. Griffin, Jeremiah A. Johnson
      Abstract: We report star polymer metal–organic cage (polyMOC) materials whose structures, mechanical properties, functionalities, and dynamics can all be precisely tailored through a simple three-component assembly strategy. The star polyMOC network is composed of tetra-arm star polymers functionalized with ligands on the chain ends, small molecule ligands, and palladium ions; polyMOCs are formed via metal–ligand coordination and thermal annealing. The ratio of small molecule ligands to polymer-bound ligands determines the connectivity of the MOC junctions and the network structure. The use of large M12L24 MOCs enables great flexibility in tuning this ratio, which provides access to a rich spectrum of material properties including tunable moduli and relaxation dynamics.Netzworking: Eine Dreikomponentensynthese wird beschrieben, welche die Herstellung einer vielseitigen Klasse von polymeren Metall-organischen Käfigen (PolyMOCs) mit maßgeschneiderten Mikrostrukturen, mechanischen Eigenschaften, Funktionalitäten und Netzwerkdynamiken ermöglicht (siehe Bild; SML=niedermolekularer Ligand, PL=polymergebundener Ligand).
      PubDate: 2016-12-05T05:37:46.983801-05:
      DOI: 10.1002/ange.201609261
       
  • Luminescent Tungsten(VI) Complexes: Photophysics and Applicability to
           Organic Light-Emitting Diodes and Photocatalysis
    • Authors: Kwan-Ting Yeung; Wai-Pong To, Chenyue Sun, Gang Cheng, Chensheng Ma, Glenna So Ming Tong, Chen Yang, Chi-Ming Che
      Abstract: The synthesis, excited-state dynamics, and applications of two series of air-stable luminescent tungsten(VI) complexes are described. These tungsten(VI) complexes show phosphorescence in the solid state and in solutions with emission quantum yields up to 22 % in thin film (5 % in mCP) at room temperature. Complex 2 c, containing a 5,7-diphenyl-8-hydroxyquinolinate ligand, displays prompt fluorescence (blue–green) and phosphorescence (red) of comparable intensity, which could be used for ratiometric luminescent sensing. Solution-processed organic light-emitting diodes (OLEDs) based on 1 d showed a stable yellow emission with an external quantum efficiency (EQE) and luminance up to 4.79 % and 1400 cd m−2 respectively. These tungsten(VI) complexes were also applied in light-induced aerobic oxidation reactions.Lumineszierende Wolframkomplexe mit mehrzähnigen Liganden verfügen über interessante photophysikalische und photokatalytische Eigenschaften wie intensive Phosphoreszenz bei Raumtemperatur und duale Fluoreszenz-Phosphoreszenz über das gesamte Spektrum. Die Komplexe eignen sich als phosphoreszierende Dotierstoffe für organische Leuchtdioden.
      PubDate: 2016-12-05T05:37:44.440441-05:
      DOI: 10.1002/ange.201608240
       
  • Untersuchung von intrinsisch unstrukturierten Proteinen mithilfe des
           Austausches mit hyperpolarisiertem Wasser
    • Authors: Dennis Kurzbach; Estel Canet, Andrea G. Flamm, Aditya Jhajharia, Emmanuelle M. M. Weber, Robert Konrat, Geoffrey Bodenhausen
      Abstract: Hyperpolarisiertes Wasser kann NMR-Signale schnell austauschender Protonen des intrinsisch unstrukturierten Proteins Osteopontin (OPN), welches eine Rolle bei Metastasenbildung spielt, bei annähernd physiologischem pH-Wert und Temperatur verstärken. Der Transfer der Magnetisierung des hyperpolarisierten Wassers beschränkt sich auf lösungsmittelexponierte Aminosäuren und verstärkt deshalb nur selektiv bestimmte Signale in (1H,15N-)Korrelationsspektren. Die Bindung des Polysaccharids Heparin induziert die Entfaltung vorgeformter Strukturelemente von OPN.Geliehene Protonen: Die Untersuchung intrinsisch unstrukturierter Proteine unter physiologischen Bedingungen wird häufig durch schwache und überlappende NMR-Signale erschwert. Hier wird anhand des selektiven Austausches von hyperpolarisiertem Wasser mit exponierten Aminosäuren in Osteopontin und seinem Heparinkomplex demonstriert, wie dieses Problem mithilfe von dynamischer Kernpolarisation überwunden werden kann.
      PubDate: 2016-12-05T05:37:38.773038-05:
      DOI: 10.1002/ange.201608903
       
  • Versatile Trityl Spin Labels for Nanometer Distance Measurements on
           Biomolecules In Vitro and within Cells
    • Authors: J. Jacques Jassoy; Andreas Berndhäuser, Fraser Duthie, Sebastian P. Kühn, Gregor Hagelueken, Olav Schiemann
      Abstract: Structure determination of biomacromolecules under in-cell conditions is a relevant yet challenging task. Electron paramagnetic resonance (EPR) distance measurements in combination with site-directed spin labeling (SDSL) are a valuable tool in this endeavor but the usually used nitroxide spin labels are not well-suited for in-cell measurements. In contrast, triarylmethyl (trityl) radicals are highly persistent, exhibit a long relaxation time and a narrow spectral width. Here, the synthesis of a versatile collection of trityl spin labels and their application in in vitro and in-cell trityl–iron distance measurements on a cytochrome P450 protein are described. The trityl labels show similar labeling efficiencies and better signal-to-noise ratios (SNR) as compared to the popular methanethiosulfonate spin label (MTSSL) and enabled a successful in-cell measurement.Abstandsmessungen: Vier neue Triarylmethyl(Trityl)-Sonden für die ortsspezifische Spinmarkierung von Proteinen und Oligonukleotiden wurden synthetisiert. Ihre Anwendung in EPR-Abstandsmessungen wird für das CYP101-Protein unter In-vivo-Bedingungen gezeigt.
      PubDate: 2016-12-05T05:37:34.857157-05:
      DOI: 10.1002/ange.201609085
       
  • A Redox-Induced Spin-State Cascade in a Mixed-Valent Fe3(μ3-O)
           Triangle
    • Authors: Evgen V. Govor; Karrar Al-Ameed, Indranil Chakraborty, Carla S. Coste, Olena Govor, Yiannis Sanakis, John E. McGrady, Raphael G. Raptis
      Abstract: One-electron reduction of a pyrazolate-bridged triangular Fe3(μ3-O) core induces a cascade wherein all three metal centers switch from high-spin Fe3+ to low-spin Fe2.66+. This hypothesis is supported by spectroscopic data (1H-NMR, UV-vis-NIR, infra-red, 57Fe-Mössbauer, EPR), X-ray crystallographic characterization of the cluster in both oxidation states and also density functional theory. The reduction induces substantial contraction in all bond lengths around the metal centers, along with diagnostic shifts in the spectroscopic parameters. This is, to the best of our knowledge, the first example of a one-electron redox event causing concerted change in multiple iron centers.Ein-Elektronen-Reduktion wandelt alle drei High-Spin-Eisenzentren in einem dreikernigen Fe3+-Komplex in Low-Spin-Fe2.66+ um. Dies ist das erste Beispiel für einen Ein-Elektronen-Prozess, der eine konzertierte Spinänderung in mehreren Eisenzentren verursacht.
      PubDate: 2016-12-05T05:33:35.300481-05:
      DOI: 10.1002/ange.201610534
       
  • Conductance Switch of a Bromoplumbate Bistable Semiconductor by
           Electron-Transfer Thermochromism
    • Authors: Cai Sun; Ming-Sheng Wang, Pei-Xin Li, Guo-Cong Guo
      Abstract: Electron-transfer (redox) thermochromism was successfully used for switching the conductance of semiconductors, by introducing a thermally active organic component into an inorganic semiconducting framework. A moisture-resistant semiconductor {(MV)2[Pb7Br18]}n (MV2+=methyl viologen cation) has been prepared through an in situ synthetic method for MV2+. It features a rare 3D haloplumbate open framework and unprecedented electron-transfer thermochromic behavior in haloplumbates. The electrical conductivity of this compound dropped significantly after coloration and restored after decoloration, which was satisfactorily explained by valence band XPS and theoretical data. This work not only offers a new approach to modify electrical properties of semiconductors without altering components or structures, but may lead to the development of over-temperature color indicators, circuit overload protectors or photovoltaic materials.Leitwertschalter: Elektronentransfer(Redox)-Thermochromie wurde erfolgreich eingesetzt, um den Leitwert von Halbleitern zu schalten (siehe Bild). Der Effekt könnte zur Entwicklung von Übertemperatur-Farbindikatoren oder zum Überlastschutz für Stromkreise genutzt werden.
      PubDate: 2016-12-05T05:33:32.558327-05:
      DOI: 10.1002/ange.201610180
       
  • Anodized Aluminum Oxide-Templated Synthesis of Metal–Organic Frameworks
           Used as Membrane Reactors
    • Authors: Yifu Yu; Xue-Jun Wu, Meiting Zhao, Qinglang Ma, Junze Chen, Bo Chen, Melinda Sindoro, Jian Yang, Shikui Han, Qipeng Lu, Hua Zhang
      Abstract: The incorporation of metal–organic frameworks (MOFs) into membrane-shaped architectures is of great importance for practical applications. The currently synthesized MOF-based membranes show many disadvantages, such as poor compatibility, low dispersity, and instability, which severely limit their utility. Herein, we present a general, facile, and robust approach for the synthesis of MOF-based composite membranes through the in situ growth of MOF plates in the channels of anodized aluminum oxide (AAO) membranes. After being used as catalysis reactors, they exhibit high catalytic performance and stability in the Knoevenagel condensation reaction. The high catalytic performance might be attributed to the intrinsic structure of MOF-based composite membranes, which can remove the products from the reaction zone quickly, and prevent the aggregation and loss of catalysts during reaction and recycling process.Ein MOF-Reaktor: Ein allgemeiner, einfacher und robuster Ansatz zur Herstellung von MOF-basierten Kompositmembranen wird vorgestellt, der die In-situ-Bildung von MOF-Plättchen in den Kanälen anodisierter Aluminiumoxidmembranen einschließt. Die Membranen wurden als Membrankatalysereaktoren eingesetzt und zeigten exzellente katalytische Eigenschaften und Stabilität in der Knoevenagel-Kondensation.
      PubDate: 2016-12-05T05:33:29.58905-05:0
      DOI: 10.1002/ange.201610291
       
  • Iron-Catalyzed Oxidative C−C and N−N Coupling of Diarylamines and
           Synthesis of Spiroacridines
    • Authors: Raphael F. Fritsche; Gabriele Theumer, Olga Kataeva, Hans-Joachim Knölker
      Abstract: We describe iron-catalyzed intermolecular oxidative coupling reactions of diarylamines to form substituted 2,2′-bis(arylamino)biaryl compounds, tetraarylhydrazines, and 5,6-dihydrobenzo[c]cinnolines with the same hexadecafluorinated iron–phthalocyanine catalyst. The mild formation of C−C or N−N bonds was controlled by the use of acidic or basic additives. In contrast to most iron-catalyzed dehydrogenative coupling reactions, ambient air could be used as the sole oxidant. Moreover, iron(III) chloride hexahydrate promoted a one-pot coupling and subsequent intramolecular dearomative coupling to give 10H-spiro[acridine-9,1′-cyclohexa-2′,5′-dien-4′-ones].Wohin die Wege führen: Katalyse durch Eisenhexadecafluorphthalocyanin ermöglichte die aerobe Kupplung von Diarylaminen zur Bildung von entweder 2,2′-Bis(arylamino)biarylen, Tetraarylhydrazinen oder 5,6-Dihydrobenzo[c]cinnolinen. Die Chemoselektivität dieser Umwandlungen wurde durch Säure- oder Baseadditive gesteuert (siehe Bild).
      PubDate: 2016-12-05T05:33:20.920265-05:
      DOI: 10.1002/ange.201610168
       
  • Untersuchung der Struktur und Dynamik des B13+ mithilfe der
           Infrarot-Photodissoziationsspektroskopie
    • Authors: Matias R. Fagiani; Xiaowei Song, Petko Petkov, Sreekanta Debnath, Sandy Gewinner, Wieland Schöllkopf, Thomas Heine, André Fielicke, Knut R. Asmis
      Abstract: Die Struktur und Dynamik des “magischen” Borclusters B13+ wurde mithilfe der Gasphasen-Schwingungsspektroskopie an kryogenen Ionen untersucht. Das Infrarot-Photodissoziationspektrum (IRPD) des D2-komplexierten Monoisotopologs 11B13+ wurde im Bereich von 435 cm−1 bis 1790 cm−1 gemessen und durch Vergleich mit simulierten IR-Spektren energetisch tiefliegender Isomere aus Dichtefunktionaltheorie-Rechnungen eindeutig einer planaren Bor-Doppelradspezies zugeordnet. Born-Oppenheimer-Molekulardynamik(BOMD)-Simulationen sagen bereits unter 100 K eine interne Quasirotation voraus. Die berechneten BOMD-Schwingungsspektren ermöglichen, zusammen mit den experimentellen IRPD-Spektren, erstmals den spektroskopischen Nachweis dieser außergewöhnlichen Dynamik des B13+.Molekulares Kugellager: Der erste spektroskopische Nachweis der außergewöhnlichen Fluxionalität des „magischen” Borclusters B13+ wird vorgelegt. Anhand des gemessenen Schwingungsspektrums des D2-komplexierten 11B13+ wird, basierend auf einem Vergleich mit Ergebnissen aus DFT-Rechnungen, eine planare Doppelrad-Struktur zugeordnet. Darauf aufbauend erlauben Molekulardynamik-Simulationen, den spektralen Fingerabdruck der Quasirotation des internen B3-Rings zu charakterisieren.
      PubDate: 2016-12-05T05:33:17.387523-05:
      DOI: 10.1002/ange.201609766
       
  • Azidoperfluoroalkanes: Synthesis and Application in Copper(I)-Catalyzed
           Azide–Alkyne Cycloaddition
    • Authors: Zsófia E. Blastik; Svatava Voltrová, Václav Matoušek, Bronislav Jurásek, David W. Manley, Blanka Klepetářová, Petr Beier
      Abstract: We report an efficient and scalable synthesis of azidotrifluoromethane (CF3N3) and longer perfluorocarbon-chain analogues (RFN3; RF=C2F5, nC3F7, nC8F17), which enables the direct insertion of CF3 and perfluoroalkyl groups into triazole ring systems. The azidoperfluoroalkanes show good reactivity with terminal alkynes in copper(I)-catalyzed azide–alkyne cycloaddition (CuAAC), giving access to rare and stable N-perfluoroalkyl triazoles. Azidoperfluoroalkanes are thermally stable and the efficiency of their preparation should be attractive for discovery programs.Nicht länger Kuriositäten: Azidoperfluoralkane wurden auf einfache Weise aus Perfluoralkylcarbanionen und elektrophilen Azidreagentien hergestellt. Die Azidoperfluoralkane reagieren bereitwillig mit terminalen Alkinen in der Kupfer(I)-katalysierten Azid-Alkin-Cycloaddition (CuAAC) und bieten damit Zugang zu seltenen und stabilen N-Perfluoralkyltriazolen.
      PubDate: 2016-12-05T05:33:11.621277-05:
      DOI: 10.1002/ange.201609715
       
  • Photo-Modulated Therapeutic Protein Release from a Hydrogel Depot Using
           Visible Light
    • Authors: Johan S. Basuki; Fengxiang Qie, Xavier Mulet, Randy Suryadinata, Aditya V. Vashi, Yong Y. Peng, Lingli Li, Xiaojuan Hao, Tianwei Tan, Timothy C. Hughes
      Abstract: The use of biomacromolecular therapeutics has revolutionized disease treatment, but frequent injections are required owing to their short half-life in vivo. Thus there is a need for a drug delivery system that acts as a reservoir and releases the drug remotely “on demand”. Here we demonstrate a simple light-triggered local drug delivery system through photo-thermal interactions of polymer-coated gold nanoparticles (AuNPs) inside an agarose hydrogel as therapeutic depot. Localized temperature increase induced by the visible light exposure caused reversible softening of the hydrogel matrix to release the pre-loaded therapeutics. The release profile can be adjusted by AuNPs and agarose concentrations, light intensity and exposure time. Importantly, the biological activity of the released bevacizumab was highly retained. In this study we demonstrate the potential application of this facile AuNPs/hydrogel system for ocular therapeutics delivery through its versatility to release multiple biologics, compatibility to ocular cells and spatiotemporal control using visible light.Ein lichtgesteuertes Wirkstofftransportsystem wurde entwickelt, das auf der photothermischen Wechselwirkung von polymerbeschichteten Gold-Nanopartikeln (AuNPs) in einem Agarose-Hydrogel basiert. Ein durch sichtbares Licht bewirkter, lokalisierter Temperaturanstieg führt zur reversiblen Erweichung der Hydrogelmatrix und Freisetzung des Therapeutikums.Die biologische Aktivität des freigesetzten biomolekularen Wirkstoffs blieb weitgehend erhalten.
      PubDate: 2016-12-05T05:26:22.143217-05:
      DOI: 10.1002/ange.201610618
       
  • Synthesis of Chiral Vicinal Diamines by Silver(I)-Catalyzed
           Enantioselective Aminolysis of N-Tosylaziridines
    • Authors: Zhuo Chai; Pei-Jun Yang, Hu Zhang, Shaowu Wang, Gaosheng Yang
      Abstract: The kinetic resolution of 2-aryl-N-tosylaziridines and the asymmetric desymmetrization of meso-N-tosylaziridines by ring openings with various primary and secondary anilines, and aliphatic amines as nucleophile have been realized by using a single silver(I)/chiral diphosphine complex as catalyst for the first time. The simple starting materials, broad scope, and easy scalability render this protocol a practical way to chiral vicinal diamine derivatives.Die nukleophile Ringöffnung von N-Tosylaziridinen durch verschiedene primäre und sekundäre aromatische und aliphatische Amine unter kinetischer Racematspaltung gelingt mit dem Silber(I)-Komplex eines chiralen Diphosphans. Die Methode liefert eine Vielzahl nützlicher chiraler vicinaler Diamine.
      PubDate: 2016-12-05T05:26:16.305421-05:
      DOI: 10.1002/ange.201610693
       
  • Total Syntheses of Sarcandrolide J and Shizukaol D: Lindenane
           Sesquiterpenoid [4+2] Dimers
    • Authors: Changchun Yuan; Biao Du, Heping Deng, Yi Man, Bo Liu
      Abstract: The syntheses of members of a family of lindenane sesquiterpenoid [4+2] dimers led to the total syntheses of sarcandrolide J and shizukaol D. Inspired by a modified biosynthetic pathway, a cascade featuring furan formation/alkene isomerization/Diels–Alder cycloaddition was devised to construct the congested polycyclic architecture of the target molecules with the correct stereochemistry. This study presents a pioneering synthetic entry to this family of natural products and paves the way for fully exploring their biological functions.Nach dem Vorbild der Natur: Die Titelverbindungen wurden mithilfe eines modifizierten Biosynthesepfads über ein in situ erzeugtes konjugiertes Furanyldien hergestellt. Eine Kaskade aus Furanbildung, Doppelbindungsisomerisierung und Diels-Alder-Cycloaddition ermöglichte den Aufbau des polycyclischen Naturstoffgerüsts.
      PubDate: 2016-12-02T05:46:12.982935-05:
      DOI: 10.1002/ange.201610484
       
  • A Large π-Extended Carbon Nanoring Based on Nanographene Units: Bottom-Up
           Synthesis, Photophysical Properties, and Selective Complexation with
           Fullerene C70
    • Authors: Dapeng Lu; Guilin Zhuang, Haotian Wu, Song Wang, Shangfeng Yang, Pingwu Du
      Abstract: Herein we report the organoplatinum-mediated bottom-up synthesis, characterization, and properties of a novel large π-extended carbon nanoring based on a nanographene hexa-peri-hexabenzocoronene (HBC) building unit. This tubular structure can be considered as an example of the longitudinal extension of the cycloparaphenylene scaffold to form a large π-extended carbon nanotube (CNT) segment. The cyclic tetramer of a tetramesityl HBC ([4]CHBC) was synthesized by the reaction of a 2,11-diborylated hexa-peri-hexabenzocoronene with a platinum complex, followed by reductive elimination. The structure of this tubular molecule was further confirmed by physical characterization. Theoretical calculations indicate that the strain energy of this nanoring is as high as 49.18 kcal mol−1. The selective supramolecular host–guest interaction between [4]CHBC and C70 was also investigated.Ein ordentliches Stück einer Kohlenstoffnanoröhre wurde in Form eines großen Kohlenstoffnanorings aus Hexa-peri-hexabenzocoronen-Bausteinen synthetisiert (siehe Bild). Die photophysikalischen Eigenschaften des Nanorings wurden durch Steady-State- und zeitauflösende Fluoreszenzspektroskopie untersucht, und eine selektive supramolekulare Wirt-Gast-Wechselwirkung mit C70 wurde identifiziert.
      PubDate: 2016-12-02T03:41:33.753567-05:
      DOI: 10.1002/ange.201608963
       
  • Diverse Activation Modes in the Hydroboration of Aldehydes and Ketones
           with Germanium, Tin, and Lead Lewis Pairs
    • Authors: Julia Schneider; Christian P. Sindlinger, Sarah M. Freitag, Hartmut Schubert, Lars Wesemann
      Abstract: Intramolecular germylene, stannylene, and plumbylene Lewis pairs were reacted with hexanal and yielded the cyclic addition products only with the germanium and tin reagents. In further reactivity studies, the hydroboration of aldehydes and ketones catalyzed by intramolecular germylene, stannylene, and plumbylene Lewis pairs was studied. In the case of the cyclic germylene Lewis pair, the product of the oxidative addition of pinacolborane at the germylene moiety was observed. According to stoichiometric as well as catalytic experiments, the intramolecular germylene Lewis pair acts as a catalyst in the hydroboration of aldehydes and ketones. The homologous stannylene Lewis pair forms a reactive tin hydride during the catalysis, which can also act as a catalyst in this transformation.Unterschiedliche Reaktivität: Intramolekulare Germylen-, Stannylen- und Plumbylen-Lewis-Paare wurden mit Hexanal umgesetzt, aber nur die Germanium- und Zinn-Reagentien lieferten die cyclischen Additionsprodukte. Zudem wurde die katalytische Aktivität dieser intramolekularen Lewis-Paare in der Hydroborierung von Aldehyden und Ketonen untersucht.
      PubDate: 2016-12-02T03:41:13.77454-05:0
      DOI: 10.1002/ange.201609155
       
  • Catalyst-Free Polyhydroboration of Dodecaborate Yields Highly
           Photoluminescent Ionic Polyarylated Clusters
    • Authors: Mark W. Lee
      Abstract: The incorporation of polyhedral boranes into novel photoluminescent materials is an area with increasing interest. While the neutral carboranes have been widely investigated for this purpose, the dodecaborate ion has received much less attention. Herein we report a significant expansion to the scope of substitution reactions for the dodecaborate ion, whereby this cluster was observed to react directly with a wide range of arenes in a step-wise and controlled manner. In the products of these reactions, the dodecaborate ion serves as a core upon which up to nine mono- or polycyclic aromatic hydrocarbon ligands are exohedrally bonded. Spectroscopic evidence suggests the presence of conjugation between the π systems of the aryl ligands and the dodecaborate core, resulting in materials which exhibit high solution-phase photoluminescence, as well as molar absorptivities and Stokes shifts that are significantly larger than those of the free arenes from which they were derived. We propose that this broad reactivity is a valuable synthetic tool for the incorporation of polyhedral boron into novel organic structures.Lumineszierende Dodecaborat-Ionen: Bei nur leicht erhöhten Temperaturen und in Abwesenheit eines Katalysators reagiert das Dodecaborat-Ion in Lösung quantitativ mit einer großen Anzahl mono- und polycyclischer aromatischer Kohlenwasserstoffe. Die Polyarylboranprodukte sind in Lösung stark lumineszierend.
      PubDate: 2016-12-02T03:40:42.680984-05:
      DOI: 10.1002/ange.201608249
       
  • Isopropanol Dehydration on Amorphous Silica–Alumina: Synergy of
           Brønsted and Lewis Acidities at Pseudo-Bridging Silanols
    • Authors: Kim Larmier; Céline Chizallet, Sylvie Maury, Nicolas Cadran, Johnny Abboud, Anne-Félicie Lamic-Humblot, Eric Marceau, Hélène Lauron-Pernot
      Abstract: The mechanism of isopropanol dehydration on amorphous silica–alumina (ASA) was unraveled by a combination of experimental kinetic measurements and periodic density functional theory (DFT) calculations. We show that pseudo-bridging silanols (PBS-Al) are the most likely active sites owing to the synergy between the Brønsted and Lewis acidic properties of these sites, which facilitates the activation of alcohol hydroxy groups as leaving groups. Isopropanol dehydration was used to specifically investigate these PBS-Al sites, whose density was estimated to be about 10−1 site nm−2 on the silica-doped alumina surface under investigation, by combining information from experiments and theoretical calculations.Zusammenspiel zweier Arten von Säure: Periodische Ab-initio-Rechnungen und kinetische Messungen wurden kombiniert, um die katalytisch aktiven Zentren bei der Dehydratisierung von Isopropylalkohol über amorphem SiO2/Al2O3 zu bestimmen. Pseudo-verbrückende Silanole, die Lewis- und Brønsted-acide sind, spielen in dieser Reaktion eine entscheidende Rolle.
      PubDate: 2016-12-02T03:38:22.746899-05:
      DOI: 10.1002/ange.201609494
       
  • Stereocontrolled Total Syntheses of (−)-Rotenone and (−)-Dalpanol by
           1,2-Rearrangement and SNAr Oxycyclizations
    • Authors: Kayo Nakamura; Ken Ohmori, Keisuke Suzuki
      Abstract: The total syntheses of (−)-rotenone and (−)-dalpanol have been achieved by a group-selective, stereospecific 1,2-shift of an epoxy alcohol and SNAr cyclizations. Three oxacycles are constructed, thus illustrating a versatile synthetic route to various rotenoids.Oxacyclen im Dreierpack: Ein Ansatz zur Synthese von Rotenoiden wurde entwickelt, der auf der stereospezifischen 1,2-Verschiebung eines Epoxyalkohols und anschließenden SNAr-Oxycyclisierungen basiert. Die Methode wurde zur Synthese der natürlichen Rotenoide (−)-Rotenon und (−)-Dalpanol genutzt.
      PubDate: 2016-12-02T03:38:21.046925-05:
      DOI: 10.1002/ange.201609253
       
  • Cloaked Caged Compounds: Chemical Probes for Two-Photon Optoneurobiology
    • Authors: Matthew T. Richers; Joseph M. Amatrudo, Jeremy P. Olson, Graham C. R. Ellis-Davies
      Abstract: Caged neurotransmitters, in combination with focused light beams, enable precise interrogation of neuronal function, even at the level of single synapses. However, most caged transmitters are, surprisingly, severe antagonists of ionotropic gamma-aminobutyric acid (GABA) receptors. By conjugation of a large, neutral dendrimer to a caged GABA probe we introduce a “cloaking” technology that effectively reduces such antagonism to very low levels. Such cloaked caged compounds will enable the study of the signaling of the inhibitory neurotransmitter GABA in its natural state using two-photon uncaging microscopy for the first time.Maskierte Neurotransmitter wirken antagonistisch gegen den GABA-A-Rezeptor. Die Konjugation von photoaktivierbarem DEAC450-GABA an ein Polyester-Dendrimer senkt dessen antagonistische Wirkung deutlich. Die chemische Sonde war in den Konzentrationen für effektive Zwei-Photonen-Photolyse in lebenden Zellen ohne biologische Wirkung.
      PubDate: 2016-12-02T03:38:12.47283-05:0
      DOI: 10.1002/ange.201609269
       
  • Regioselective Hydrohydroxyalkylation of Styrene with Primary Alcohols or
           Aldehydes via Ruthenium-Catalyzed C−C Bond Forming Transfer
           Hydrogenation
    • Authors: Hongde Xiao; Gang Wang, Michael J. Krische
      Abstract: Transfer hydrogenative coupling of styrene with primary alcohols using the precatalyst HClRu(CO)(PCy3)2 modified by AgOTf or HBF4 delivers branched or linear adducts from benzylic or aliphatic alcohols, respectively. Related 2-propanol mediated reductive couplings also are described.Von Rohstoffen zu Bausteinen: Die hydrierende Transferkupplung von Styrol mit primären Alkoholen mit dem durch AgOTf oder HBF4 modifizierten Präkatalysator HClRu(CO)(PCy3)2 liefert verzweigte oder lineare Addukte ausgehend von benzylischen bzw. aliphatischen Alkoholen. Verwandte, durch 2-Propanol vermittelte reduktive Kupplungen werden ebenfalls beschrieben.
      PubDate: 2016-12-02T03:38:10.619495-05:
      DOI: 10.1002/ange.201609056
       
  • Stereospecific Construction of Contiguous Quaternary All-Carbon Centers by
           Oxidative Ring Contraction
    • Authors: Xin Yu; Jiadong Hu, Zhigao Shen, Hui Zhang, Jin-Ming Gao, Weiqing Xie
      Abstract: Oxidative ring contraction of cyclic α-formyl ketones was facilitated by the action of H2O2 under operationally simple and environmentally benign reaction conditions. The process was highly regioselective and enables stereospecific construction of contiguous quaternary all-carbon centers from stereodefined all-substituted all-cyclic ketones. The asymmetric syntheses of (+)-cuparene and (+)-tochuinyl acetate were also successively achieved by taking advantage of this novel protocol.Zusammenrücken: Durch H2O2-vermittelte Ringverengung cyclischer α-Formylketone gelingt die stereospezifische Einführung benachbarter ausschließlich kohlenstoffsubstituierter quartärer Zentren. Asymmetrische Synthesen von (+)-Cuparen und (+)-Tochuinylacetat demonstrieren die Anwendung des neuartigen Verfahrens.
      PubDate: 2016-12-02T03:31:24.853263-05:
      DOI: 10.1002/ange.201609975
       
  • C-H-Sulfinylierung von Heteroaromaten beschleunigt durch sichtbares Licht
    • Authors: Andreas Uwe Meyer; Alexander Wimmer, Burkhard König
      Abstract: Heteroaromatische Sulfoxide sind häufig in Naturstoffen, Pharmazeutika, Katalysatoren und Werkstoffen zu finden. Wir beschreiben eine metallfreie, durch sichtbares Licht beschleunigte Synthese von heteroaromatischen Sulfoxiden aus Sulfinamiden und Peroxodisulfat. Die Reaktion verläuft bei Raumtemperatur unter Bestrahlung mit blauem Licht und ermöglicht die C-H-Sulfinylierung von elektronenreichen Heteroaromaten wie Pyrrol und Indol. Basierend auf der Substratbreite, der Substitutionsselektivität und Konkurrenzexperimenten mit verschiedenen Nukleophilen schlagen wir als Mechanismus eine elektrophile aromatische Substitution vor.Sulfoxide sehen das Licht und werden mittels einer elektrophilen aromatischen Substitution von Sulfinamiden, elektronenreichen Heteroaromaten und Peroxodisulfat hergestellt.
      PubDate: 2016-12-02T03:31:22.286918-05:
      DOI: 10.1002/ange.201610210
       
  • Atomically Dispersed Iron–Nitrogen Species as Electrocatalysts for
           Bifunctional Oxygen Evolution and Reduction Reactions
    • Authors: Pengzuo Chen; Tianpei Zhou, Lili Xing, Kun Xu, Yun Tong, Hui Xie, Lidong Zhang, Wensheng Yan, Wangsheng Chu, Changzheng Wu, Yi Xie
      Abstract: Rational design of non-noble materials as highly efficient, economical, and durable bifunctional catalysts for oxygen evolution and reduction reactions (OER/ORR) is currently a critical obstacle for rechargeable metal-air batteries. A new route involving S was developed to achieve atomic dispersion of Fe-Nx species on N and S co-decorated hierarchical carbon layers, resulting in single-atom bifunctional OER/ORR catalysts for the first time. The abundant atomically dispersed Fe-Nx species are highly catalytically active, the hierarchical structure offers more opportunities for active sites, and the electrical conductivity is greatly improved. The obtained electrocatalyst exhibits higher limiting current density and a more positive half-wave potential for ORR, as well as a lower overpotential for OER under alkaline conditions. Moreover, a rechargeable Zn–air battery device comprising this hybrid catalyst shows superior performance compared to Pt/C catalyst. This work will open a new avenue to design advanced bifunctional catalysts for reversible energy storage and conversion devices.Isoliert effizient: Isolierte Eisen-Stickstoff-Zentren auf hierarchischen, stickstoff- und schwefeldotierten Kohlenstoffnanoröhren vermitteln sehr effektiv die elektrokatalytische Sauerstoffentwicklung und -reduktion. Das Hybridmaterial ist in alkalischen Lösungen stabil und daher als Luft-Kathode in einer wiederaufladbaren Zink-Luft-Batterie einsetzbar.
      PubDate: 2016-12-02T03:31:18.65412-05:0
      DOI: 10.1002/ange.201610119
       
  • A Genetically Encoded Allysine for the Synthesis of Proteins with
           Site-Specific Lysine Dimethylation
    • Authors: Zhipeng A. Wang; Yu Zeng, Yadagiri Kurra, Xin Wang, Jeffery M. Tharp, Erol C. Vatansever, Willie W. Hsu, Susie Dai, Xinqiang Fang, Wenshe R. Liu
      Abstract: Using the amber suppression approach, Nϵ-(4-azidobenzoxycarbonyl)-δ,ϵ-dehydrolysine, an allysine precursor is genetically encoded in E. coli. Its genetic incorporation followed by two sequential biocompatible reactions allows convenient synthesis of proteins with site-specific lysine dimethylation. Using this approach, dimethyl-histone H3 and p53 proteins have been synthesized and used to probe functions of epigenetic enzymes including histone demethylase LSD1 and histone acetyltransferase Tip60. We confirmed that LSD1 is catalytically active toward H3K4me2 and H3K9me2 but inert toward H3K36me2, and methylation at p53 K372 directly activates Tip60 for its catalyzed acetylation at p53 K120.Zielführende Proteinsynthese: Eine Allysinvorstufe, Nϵ-(4-Azidobenzoxycarbonyl)-δ,ϵ-dehydrolysin, wurde in E. coli genetisch eincodiert. Ihre Proteinkonjugation, anschließende Staudinger-Reduktion und reduktive Aminierung ermöglichten die Synthese von Proteinen mit ortsspezifischer Lysin-Dimethylierung.
      PubDate: 2016-12-02T03:31:15.705921-05:
      DOI: 10.1002/ange.201609452
       
  • A Stable Manganese Pincer Catalyst for the Selective Dehydrogenation of
           Methanol
    • Authors: María Andérez-Fernández; Lydia K. Vogt, Steffen Fischer, Wei Zhou, Haijun Jiao, Marcel Garbe, Saravanakumar Elangovan, Kathrin Junge, Henrik Junge, Ralf Ludwig, Matthias Beller
      Abstract: For the first time, structurally defined manganese pincer complexes catalyze the dehydrogenation of aqueous methanol to hydrogen and carbon dioxide, which is a transformation of interest with regard to the implementation of a hydrogen and methanol economy. Excellent long-term stability was demonstrated for the Mn-PNPiPr catalyst, as a turnover of more than 20 000 was reached. In addition to methanol, other important hydrogen carriers were also successfully dehydrogenated.In die Zange genommen: Ein bemerkenswert stabiler molekularer Komplex des nichttoxischen Elements Mangan mit einem PNP-Liganden dehydriert Methanol selektiv unter Bildung von Wasserstoff und Kohlendioxid. Bei niedrigen Temperaturen werden hervorragende Umsatzzahlen (TON) über 20 000 erzielt, und der Katalysator war auch nach einem Monat noch aktiv.
      PubDate: 2016-12-02T03:30:51.272936-05:
      DOI: 10.1002/ange.201610182
       
  • Ursachen der unterschiedlichen Reaktivität von [AlCeOx]+ (x=2–4)
           gegenüber Methan in Abhängigkeit vom Sauerstoffgehalt
    • Authors: Shaodong Zhou; Jilai Li, Maria Schlangen, Helmut Schwarz
      Abstract: Die thermischen Gasphasenreaktionen der geschlossenschaligen heteronuklearen Metalloxidcluster [AlCeOx]+ (x=2–4) mit Methan wurden mittels FT-ICR-Massenspektrometrie und quantenchemischer Rechnungen untersucht. Während [AlCeO2]+ und [AlCeO4]+ unter thermischen Bedingungen gegenüber Methan inert sind, reagiert [AlCeO3]+ spontan unter Wasserstoffatomabstraktion. Unter Berücksichtigung mechanistischer Aspekte konnten die Ursachen dieser deutlich unterschiedlichen Eigenschaften der [AlCeOx]+/CH4-Paare aufgedeckt werden; die elektronische Grundlage der beispiellosen, einfachen Wasserstoffatomabstraktion von Methan durch den geschlossenschaligen Cluster [AlCeO3]+ wird diskutiert.Bei der thermischen Reaktion der geschlossenschaligen heteronuklearen Cluster [AlCeOx]+ (x=2–4) mit Methan ist nur [AlCeO3]+ reaktiv und bildet [AlCeO3H].+ und CH3. (siehe Schema). Die Ursachen hierfür wurden mit FT-ICR-Massenspektrometrie und quantenchemischen Rechnungen untersucht.
      PubDate: 2016-12-02T03:27:53.092028-05:
      DOI: 10.1002/ange.201610424
       
  • Modern Synthetic Avenues for the Preparation of Functional Fluorophores
    • Authors: Fabio De Moliner; Nicola Kielland, Rodolfo Lavilla, Marc Vendrell
      Abstract: Biomedical research relies on the fast and accurate profiling of specific biomolecules and cells in a non-invasive manner. Functional fluorophores have consolidated as powerful tools for such studies. Since these sophisticated structures are often difficult to access through conventional synthetic strategies, novel chemical processes have been developed in the last years. In this Minireview we describe the most recent advances in the design, preparation and fine-tuning of fluorophores by means of multicomponent reactions, C-H activation processes, cycloadditions and biomolecule-based chemical transformations.
      PubDate: 2016-12-01T15:50:42.740152-05:
      DOI: 10.1002/ange.201609394
       
  • Superacid-Catalyzed Trifluoromethylthiolation of Aromatic Amines
    • Authors: Longin Justin Clair Bonazaba Milandou; Hélène Carreyre, Sébastien Alazet, Gino Greco, Agnès Martin-Mingot, Célestine Nkounkou Loumpangou, Jean-Maurille Ouamba, Fodil Bouazza, Thierry Billard, Sébastien Thibaudeau
      Abstract: Supersäuren aktivieren N-SCF3-Sulfenamide unter Bildung superelektrophiler diprotonierter Spezies für die Trifluormethylthiolierung aromatischer Amine. In ihrer Zuschrift (
      DOI : 10.1002/ange.201609574) zeigen T. Billard, S. Thibaudeau et al., wie diese Methode für die Funktionalisierung komplexer Biomoleküle, wie z. B. Alkaloide und Steroide, verwendet werden kann.
      PubDate: 2016-12-01T09:17:53.873473-05:
       
  • Achiral Inorganic Gypsum Acts as an Origin of Chirality through Its
           Enantiotopic Surface in Conjunction with Asymmetric Autocatalysis
    • Authors: Arimasa Matsumoto; Yoshiyasu Kaimori, Mizuki Uchida, Haruna Omori, Tsuneomi Kawasaki, Kenso Soai
      Abstract: Achiral inorganic gypsum (CaSO4⋅2 H2O) triggers the asymmetric autocatalysis of pyrimidyl alkanol on its two-dimensional enantiotopic faces to give highly enantioenriched alkanol products with absolute configurations corresponding to the respective enantiotopic surfaces. This is the first example of highly enantioselective synthesis on the enantiotopic surface of an achiral mineral.Gips (CaSO4⋅2 H2O) löst auf seinen zweidimensionalen Oberflächen eine asymmetrische Autokatalyse mit einem Pyrimidylalkanol aus, welche die hoch enantiomerenangereicherten Alkanole ergibt, deren Absolutkonfigurationen denen der enantiotopen Oberfläche entsprechen. Somit gelang erstmals eine hoch enantioselektive Synthese an den enantiotopen Oberflächen eines achiralen Minerals.
      PubDate: 2016-12-01T09:17:48.985253-05:
      DOI: 10.1002/ange.201610099
       
  • Initial Carbon–Carbon Bond Formation during the Early Stages of the
           Methanol-to-Olefin Process Proven by Zeolite-Trapped Acetate and Methyl
           Acetate
    • Authors: Abhishek Dutta Chowdhury; Klaartje Houben, Gareth T. Whiting, Mohamed Mokhtar, Abdullah M. Asiri, Shaeel A. Al-Thabaiti, Suliman N. Basahel, Marc Baldus, Bert M. Weckhuysen
      Abstract: Der Reaktionsmechanismus der industriell wichtigen Methanol-zu-Olefin-Reaktion über Zeolithkatalysatoren wurde durch kombinierte Festkörper-NMR-Spektroskopie und Operando-UV/Vis-Spektroskopie untersucht. In ihrer Zuschrift (
      DOI : 10.1002/ange.201608643) beschreiben M. Baldus, B. M. Weckhuysen et al., wie mithilfe dieser Methode Hinweise für einen direkten Mechanismus bei der Bildung der ersten Kohlenstoff-Kohlenstoff-Bindung in der Anfangsphase der Reaktion gefunden wurden.
      PubDate: 2016-12-01T09:17:47.080258-05:
       
  • Solid-State Emission of the Anthracene-o-Carborane Dyad from the
           Twisted-Intramolecular Charge Transfer in the Crystalline State
    • Authors: Hirofumi Naito; Kenta Nishino, Yasuhiro Morisaki, Kazuo Tanaka, Yoshiki Chujo
      Abstract: The emission process of the o-carborane dyad with anthracene originating from the twisted intramolecular charge transfer (TICT) state in the crystalline state is described. The anthracene-o-carborane dyad was synthesized and its optical properties were investigated. Initially, the dyad had aggregation- and crystallization-induced emission enhancement (AIEE and CIEE) properties via the intramolecular charge transfer (ICT) state. Interestingly, the dyad presented the dual-emissions assigned to both locally excited (LE) and ICT states in solution. From the mechanistic studies and computer calculations, it was indicated that the emission band from the ICT should be attributable to the TICT emission. Surprisingly, even in the crystalline state, the TICT emission was observed. It was proposed from that the compact sphere shape of o-carborane would allow for rotation even in the condensed state.Der Emissionsprozess der o-Carboran-Anthracen-Dyade, der sich aus dem gewundenen intramolekularen Ladungstransferzustand (TICT) im kristallinen Zustand entwickelt, wird beschrieben. Die Dyade zeigt aggregations- und kristallisationsinduzierte Emissionsverstärkung, die über den TICT zustande kommt. Interessanterweise kann sogar im kondensierten Zustand Rotation auftreten.
      PubDate: 2016-12-01T09:07:55.299462-05:
      DOI: 10.1002/ange.201609656
       
  • Das Tris(pentafluorethyl)silanid-Anion
    • Authors: Nico Schwarze; Simon Steinhauer, Beate Neumann, Hans-Georg Stammler, Berthold Hoge
      Abstract: Während Tris(trifluormethyl)silane bei Raumtemperatur zur explosionsartigen Zersetzung neigen, erweisen sich entsprechende Pentafluorethyl-Derivate als thermisch äußerst robust. Durch den präparativen Zugang zu Li[Si(C2F5)3] ist es nun möglich, die elektronenziehende Si(C2F5)3-Einheit nukleophil auf Hauptgruppen- und Übergangsmetall-Verbindungen sowie auf organische Gerüste zu übertragen, wie B. Hoge et al. in zwei Zuschriften (
      DOI s: 10.1002/ange.201609096 und 10.1002/ange.201609575) zeigen.
      PubDate: 2016-12-01T09:03:13.074003-05:
       
  • A New Domain of Reactivity for High-Valent Dinuclear [M(μ-O)2M′]
           Complexes in Oxidation Reactions
    • Authors: Xenia Engelmann; Shenglai Yao, Erik R. Farquhar, Tibor Szilvási, Uwe Kuhlmann, Peter Hildebrandt, Matthias Driess, Kallol Ray
      Abstract: The strikingly different reactivity of a series of homo- and heterodinuclear [(MIII)(μ-O)2(MIII)′]2+ (M=Ni; M′=Fe, Co, Ni and M=M′=Co) complexes with β-diketiminate ligands in electrophilic and nucleophilic oxidation reactions is reported, and can be correlated to the spectroscopic features of the [(MIII)(μ-O)2(MIII)′]2+ core. In particular, the unprecedented nucleophilic reactivity of the symmetric [NiIII(μ-O)2NiIII]2+ complex and the decay of the asymmetric [NiIII(μ-O)2CoIII]2+ core through aromatic hydroxylation reactions represent a new domain for high-valent bis(μ-oxido)dimetal reactivity.Vereint im Unterschied: Der entscheidende Einfluss des zweiten Metallions (M) auf die elektronische Struktur und Reaktivität (von nukleophil zu elektrophil) einer Serie von [Ni(μ-O)2M]2+-Komplexen in Oxidationsreaktionen wird beschrieben. Die Beobachtungen unterstreichen die Bedeutung feiner elektronischer Unterschiede in der Reaktivität biologisch relevanter Metall-Sauerstoff-Zwischenstufen.
      PubDate: 2016-12-01T08:59:50.919525-05:
      DOI: 10.1002/ange.201607611
       
  • Verbesserte Erweiterung des eukaryotischen genetischen Codes für
           seitenspezifische, hochauflösende Click-PAINT-Mikroskopie
    • Authors: Ivana Nikić; Gemma Estrada Girona, Jun Hee Kang, Giulia Paci, Sofya Mikhaleva, Christine Koehler, Nataliia V. Shymanska, Camilla Ventura Santos, Daniel Spitz, Edward A. Lemke
      Abstract: Eine zytoplasmische Modifizierung der Pyrrolysin-basierten Maschinerie zur Erweiterung des genetischen Codes mithilfe eines Kernexportsignals (NES) erhöht den positionsspezifischen Einbau von zu Klick-Reaktionen befähigten Aminosäuren (grün) in Proteine von Säugerzellen, wie E. A. Lemke und Mitarbeiter in ihrer Zuschrift (
      DOI : 10.1002/ange.201608284) zeigen. Für die Untersuchung mit kontraststarker Click-PAINT-Superauflösungsmikroskopie lassen sich die Aminosäuren anschließend mit Bindesequenzen für kleine DNA-Stränge (rot) versehen.
      PubDate: 2016-12-01T08:52:18.490592-05:
       
  • Von Chlorophyll abstammende gelbe Phyllobiline höherer Pflanzen als
           umgebungsgesteuerte, chirale Photoschalter
    • Authors: Chengjie Li; Klaus Wurst, Steffen Jockusch, Karl Gruber, Maren Podewitz, Klaus R. Liedl, Bernhard Kräutler
      Abstract: Die schönen Herbstfarben entstehen, wenn Chlorophyll abgebaut wird, wodurch zumeist farblose Phyllobiline erzeugt werden. In ihrer Zuschrift (
      DOI : 10.1002/ange.201609481) berichten B. Kräutler et al. über gelbe Phyllobiline, die „rechtshändig” strukturiert natürlich in Herbstblättern vorkommen und außergewöhnliche vierstufige Photoschalter sind. Ihre ungewöhnlichen photochemischen Eigenschaften legen noch unbekannte Rollen solcher Phyllobiline in den Blättern nahe, womöglich im Zusammenhang mit der Photoregulation.
      PubDate: 2016-12-01T08:52:15.625297-05:
       
  • Sustainable Catalysis. Without Metals or Other Endangered Elements, Part 1
           and 2 Herausgegeben von Michael North.
    • Authors: Olga García Mancheño
      Abstract: RSC Publishing, 2016. 480+284 S., geb., 300.00 £.—ISBN 978-1782620570
      PubDate: 2016-12-01T08:52:07.170098-05:
      DOI: 10.1002/ange.201611225
       
  • 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
       
  • Nukleophile Übertragungsreaktionen der [Si(C2F5)3]−-Einheit
    • Authors: Nico Schwarze; Simon Steinhauer, Beate Neumann, Hans-Georg Stammler, Berthold Hoge
      Abstract: Das Tris(pentafluorethyl)silanid-Anion ist über die Deprotonierung von Si(C2F5)3H bei tiefen Temperaturen zugänglich. Anschließendes Abfangen der resultierenden salzartigen Verbindungen mit geeigneten Elektrophilen wie Übergangsmetallkomplexen oder Gruppe-14-Elementhalogeniden führt zu einer Fülle an neuen Tris(pentafluorethyl)silanderivaten. Hierdurch wird die Vielseitigkeit von Li[Si(C2F5)3] als potentes, nukleophiles Übertragungsreagens unterstrichen.Leicht übertragbar: Das Tris(pentafluorethyl)silanid-Anion ist ist durch Deprotonierung von Si(C2F5)3H bei tiefen Temperaturen zugänglich. Anschließendes Abfangen mit geeigneten Elektrophilen führt zu einer Fülle an Tris(pentafluorethyl)silan-Derivaten und unterstreicht die Vielseitigkeit von Li[Si(C2F5)3] als potentes nukleophiles Übertragungsreagens der [Si(C2F5)3]−-Einheit.
      PubDate: 2016-11-30T09:25:58.717314-05:
      DOI: 10.1002/ange.201609575
       
  • Die Entdeckung der elektrokinetischen Phänomene: Was ist wirklich
           geschehen?
    • Authors: Christian J. C. Biscombe
      Abstract: Elektroosmose und Elektrophorese wurden 1807 von F. F. Reuss in Moskau entdeckt – so oder ähnlich lautet die Geschichte. Dieser Essay beleuchtet die Beiträge von drei Wissenschaftlern bei der Entdeckung der elektrokinetischen Phänomene. Ziemlich sicher ist, dass Reuss tatsächlich die Elektroosmose entdeckt hat, wobei deren Name (indirekt) aus den Arbeiten von Porrett stammt. Entgegen dem derzeitigen Konsens stammt die früheste Beobachtung der Elektrophorese von Gautherot.
      PubDate: 2016-11-30T09:25:55.55398-05:0
      DOI: 10.1002/ange.201608536
       
  • Das Tris(pentafluorethyl)silanid-Anion
    • Authors: Nico Schwarze; Simon Steinhauer, Beate Neumann, Hans-Georg Stammler, Berthold Hoge
      Abstract: Tris(pentafluorethyl)silan, das durch die simple Umsetzung von Si(C2F5)3X (X=Cl, Br) mit Bu3SnH zugänglich ist, wird in Hydrosilylierungsreaktionen eingesetzt. In Gegenwart eines Palladiumkatalysators liefert die Hydrosilylierung von Phenylacetylen mit Si(C2F5)3H das α-Additionsprodukt, wohingegen die Hydrosilylierung von Trimethylsilylacetylen zur Bildung des β-trans-Produktes führt. Sterisch anspruchsvolle Basen wie Lithiumdiisopropylamid ermöglichen die Deprotonierung des Tris(pentafluorethyl)silans bei tiefen Temperaturen, was die Bildung des entsprechenden Silanid-Anions zur Folge hat. Die Zugabe von Kronenethern oder Kryptanden zu dieser hochreaktiven Spezies erlaubt die Isolierung und Charakterisierung des salzartigen Tris(pentafluorethyl)silanids bei Raumtemperatur.Tris(pentafluorethyl)silan wurde für Hydrosilylierungen eingesetzt. Sperrige Basen wie Lithiumdiisopropylamid ermöglichen die Deprotonierung von Si(C2F5)3H bei niedriger Temperatur unter Bildung des Silanid-Ions. Dessen Versetzen mit Kronenethern oder Kryptanden erlaubt die Isolierung und Charakterisierung des salzartigen Tris(pentafluorethyl)silanids bei Raumtemperatur, und sein Abfangen mit PtIICl2 liefert einen Silylplatinkomplex (siehe Struktur).
      PubDate: 2016-11-30T09:21:31.626448-05:
      DOI: 10.1002/ange.201609096
       
  • Supramolecular Nanofibrillar Thermoreversible Hydrogel for Growth and
           Release of Cancer Spheroids
    • Authors: Yunfeng Li; Nancy Khuu, Albert Gevorkian, Sharon Sarjinsky, Heloise Therien-Aubin, Yihe Wang, Sangho Cho, Eugenia Kumacheva
      Abstract: Growth of three-dimensional cancer spheroids (CSs) in man-made hydrogels mimicking natural extracellular matrix is an important and challenging task. Herein, we report on a supramolecular temperature-responsive hydrogel designed for the growth and subsequent release of CSs. A filamentous hydrogel was formed at 37 °C from an aqueous suspension of cellulose nanocrystals surface-functionalized with temperature-responsive polymer molecules. The encapsulation of cells in the hydrogel enabled effective growth of CSs with dimensions determined by the concentration of cellulose nanocrystals in the hydrogel. On demand release of CSs without loss of cell viability and spheroid integrity was achieved upon hydrogel cooling. The tumorigenic properties of the released CSs were examined by encapsulating and re-growing them in fibrin hydrogel. The results in this work can be used in fundamental cancer research and in cancer drug screening.Zellulose-Nanokristalle wurden mit Poly(N-isopropylacrylamid) modifiziert, um ein supramolekulares nanofibrilläres thermoreversibles Hydrogel zu bilden. Das Hydrogel unterstützt das dreidimensionale Wachstum von Tumorsphäroiden und bewirkt deren Freisetzung beim Abkühlen.
      PubDate: 2016-11-30T05:46:16.328384-05:
      DOI: 10.1002/ange.201610353
       
  • Regio- and Enantioselective Cobalt-Catalyzed Sequential
           Hydrosilylation/Hydrogenation of Terminal Alkynes
    • Authors: Jun Guo; Xuzhong Shen, Zhan Lu
      Abstract: A highly regio- and enantioselective cobalt-catalyzed sequential hydrosilylation/hydrogenation of alkynes was developed to afford chiral silanes. This one-pot method is operationally simple and atom economic. It makes use of relatively simple and readily available starting materials, namely alkynes, silanes, and hydrogen gas, to construct more valuable chiral silanes. Primary mechanistic studies demonstrated that highly regioselective hydrosilylation of alkynes with silanes occurred as a first step, and the subsequent cobalt-catalyzed asymmetric hydrogenation of the resulting vinylsilanes showed good enantioselectivity.Als atomökonomischer Eintopfprozess überführt die Titelreaktion leicht zugängliche Ausgangsmaterialien in chirale Silane. Durch Funktionalisierung der Produkte sind diverse siliciumhaltige chirale Verbindungen erreichbar.
      PubDate: 2016-11-30T05:22:01.404623-05:
      DOI: 10.1002/ange.201610121
       
  • Biomimicry Promotes the Efficiency of a 10-Step Sequential Enzymatic
           Reaction on Nanoparticles, Converting Glucose to Lactate
    • Authors: Chinatsu Mukai; Lizeng Gao, Jacquelyn L. Nelson, James P. Lata, Roy Cohen, Lauren Wu, Meleana M. Hinchman, Magnus Bergkvist, Robert W. Sherwood, Sheng Zhang, Alexander J. Travis
      Abstract: For nanobiotechnology to achieve its potential, complex organic–inorganic systems must grow to utilize the sequential functions of multiple biological components. Critical challenges exist: immobilizing enzymes can block substrate-binding sites or prohibit conformational changes, substrate composition can interfere with activity, and multistep reactions risk diffusion of intermediates. As a result, the most complex tethered reaction reported involves only 3 enzymes. Inspired by the oriented immobilization of glycolytic enzymes on the fibrous sheath of mammalian sperm, here we show a complex reaction of 10 enzymes tethered to nanoparticles. Although individual enzyme efficiency was higher in solution, the efficacy of the 10-step pathway measured by conversion of glucose to lactate was significantly higher when tethered. To our knowledge, this is the most complex organic–inorganic system described, and it shows that tethered, multi-step biological pathways can be reconstituted in hybrid systems to carry out functions such as energy production or delivery of molecular cargo.Nach dem Vorbild eines Spermiums wurden 10 glykolytische Enzyme über Linkermoleküle in orientierter Weise an Nanopartikel immobilisiert. Sequenzielle Reaktionen zur Umsetzung von Glukose zu Lactat waren an den immobilisierten Enzymen deutlich effizienter als mit Enzymen in Lösung. Die Ergebnisse sind ein prinzipieller Beleg, dass komplexe biologische Reaktionswege in hybriden organisch-anorganischen Systemen reproduziert werden können.
      PubDate: 2016-11-30T05:21:56.36095-05:0
      DOI: 10.1002/ange.201609495
       
  • Spontaneous Emergence of S-Adenosylmethionine and the Evolution of
           Methylation
    • Authors: Paola Laurino; Dan S. Tawfik
      Abstract: S-Adenosylmethionine (SAM) is an essential methylation cofactor. The origins of SAM methylation are complex, seemingly demanding the simultaneous emergence of an enzyme that makes SAM and enzyme(s) that utilize it. We report that both ATP and adenosine spontaneously react with methionine to yield SAM, thus suggesting that SAM could have emerged by chance. SAM methylation thus exemplifies how metabolites and pathways can co-emerge through the gradual recruitment of individual enzymes in reverse order.Aus so einfachem Anfang: S-Adenosylmethionin (SAM), ein essenzieller Enzymkofaktor, und die Enzyme, die ihn nutzen, sind seit 3.7 Milliarden Jahren bekannt. Die spontane Erzeugung von SAM aus seinen heute üblichen Vorstufen – Methionin und ATP – sowie aus Methionin und Adenosin wird beschrieben. Dabei zeigt sich, wie Stoffwechselwege ursprünglich zufällig entstanden sein könnten, sodass das erste Enzym im Ablauf (SAM-Synthase) in Wirklichkeit als letztes evolvierte.
      PubDate: 2016-11-30T05:21:53.101661-05:
      DOI: 10.1002/ange.201609615
       
  • Bottom-up trifft auf Top-down: Patch-artig strukturierte Hybridfasermatten
           als effiziente Katalyseplattform
    • Authors: Judith Schöbel; Matthias Burgard, Christian Hils, Roland Dersch, Martin Dulle, Kirsten Volk, Matthias Karg, Andreas Greiner, Holger Schmalz
      Abstract: Die heterogene Katalyse an trägerfixierten Nanopartikeln (NP) ist ein überaus attraktives Forschungsfeld. Eine der größten Herausforderungen ist jedoch weiterhin die effiziente Stabilisierung der NP ohne Einschränkung ihrer katalytischen Aktivität. Durch eine Kombination bekannter Top-down- (koaxiales Elektrospinnen) und Bottom-up-Methoden (kristallisationsinduzierte Selbstassemblierung) ist es uns gelungen, Fasermatten mit funktionellen, nanometergroßen Kompartimenten (Patches) auf der Oberfläche herzustellen. Diese Patches sind in der Lage, Gold-Nanopartikel (AuNP) selektiv zu binden und zu stabilisieren. Die mit AuNP beladenen Hybridfasermatten zeigten in der Alkoholyse von Dimethylphenylsilan bereits nach vergleichsweise kurzen Reaktionszeiten sowie unter milden Bedingungen quantitativen Umsatz. Die exzellente Wiederverwendbarkeit zeigt sich darin, dass selbst nach 10 aufeinanderfolgenden Zyklen keine Reduktion der katalytischen Aktivität oder ein “Ausbluten” von Gold beobachtet werden konnte. Die Flexibilität der vorgestellten Methode erlaubt eine einfache Übertragung auf andere Trägerfasern und unterschiedliche katalytisch aktive NP, wodurch sich ein breites Anwendungsspektrum in der heterogenen Katalyse eröffnet.Patch-artige Träger: Durch Kombination von Top-down- (Elektrospinnen) und Bottom-up-Methoden (kristallisationsinduzierte Selbstassemblierung) wurden Fasermatten mit einer Patch-artig nanostrukturierten Oberfläche hergestellt, die eine effiziente Anbindung und Stabilisierung von katalytisch aktiven Nanopartikeln ermöglichen. Die Hybridfasermatten erweisen sich als überaus effiziente und wiederverwendbare Katalyseplattform in der Alkoholyse von Dimethylphenylsilan.
      PubDate: 2016-11-30T03:40:55.143496-05:
      DOI: 10.1002/ange.201609819
       
  • Low-Frequency CH Stretch Vibrations of Free Alkoxide Ions
    • Authors: Jos Oomens; Giel Berden, Thomas Hellman Morton
      Abstract: CH stretches in hydrocarbon cations often shift to lower frequencies relative to neutral molecules, because they do not have sufficient electrons to give every bond an electron pair. A parallel effect in negatively charged species has not been previously observed. Here we show that CH bond weakening occurs in alkoxide anions as a consequence of hyperconjugation. The reasoning differs somewhat from the case of positively charged ions, but the net effect is the same: to lower CH stretching frequencies by hundreds of wavenumbers.Alkoxide hyperkonjugieren: Die α-CH-Streckschwingung isolierter Alkoxidionen in der Gasphase ist im Vergleich zu derjenigen der entsprechenden Alkohole um mehrere hundert Wellenzahlen rotverschoben. Dieses Ergebnis belegt, dass Wasserstoff in hyperkonjugierten Anionen als Elektronensenke wirken kann.
      PubDate: 2016-11-30T03:40:43.395028-05:
      DOI: 10.1002/ange.201609437
       
  • Lithium-Ion-Transfer Kinetics of Single LiMn2O4 Particles
    • Authors: Giorgia Zampardi; Christopher Batchelor-McAuley, Enno Kätelhön, Richard G. Compton
      Abstract: A stochastic investigation of lithium deinsertion from individual 200-nm-sized particles of LiMn2O4 reveals the rate-determining step at high overpotentials to be the transfer of the cation across the particle–electrolyte interface. Measurement of the (electro)chemical behavior of the spinel is undertaken without forming a conductive composite electrode. The kinetics of the interfacial ion transfer defines a theoretical upper limit for the discharge rates of batteries using LiMn2O4 in an aqueous environment.Transfer durch die Grenzfläche: Die intrinsische Antwort des aktiven Materials in Lithiumionenbatterien lässt sich mit gängigen Verbundelektroden, die Bindemittel und leitende Additive enthalten, kaum ermitteln. Dagegen ermöglicht die Nanoimpact-Methode, angewendet auf individuelle LiMn2O4-Nanopartikel, Einblicke in den intrinsischen Prozess der Li+-(De)Insertion, bei dem sich der Transfer durch die Grenzfläche als geschwindigkeitsbestimmend erwies.
      PubDate: 2016-11-30T03:40:32.280083-05:
      DOI: 10.1002/ange.201610485
       
  • Stapled Peptides by Late-Stage C(sp3)−H Activation
    • Authors: Anaïs F. M. Noisier; Jesús García, Ioana A. Ionuţ, Fernando Albericio
      Abstract: Despite the importance of stapled peptides for drug discovery, only few practical processes to prepare cross-linked peptides have been described; thus the structural diversity of available staple motifs is currently limited. At the same time, C−H activation has emerged as an efficient approach to functionalize complex molecules. Although there are many reports on the C−H functionalization of amino acids, examples of post-synthetic peptide C−H modification are rare and comprise almost only C(sp2)−H activation. Herein, we report the development of a palladium-catalyzed late-stage C(sp3)−H activation method for peptide stapling, affording an unprecedented hydrocarbon cross-link. This method was first employed to prepare a library of stapled peptides in solution. The compatibility with various amino acids as well as the influence of the size (i,i+3 and i,i+4) and length of the staple were investigated. Finally, a simple solid-phase procedure was also established.„Heftklammer”-Modifikationen von Peptiden durch Palladium-katalysierte C(sp3)-H-Aktivierung ermöglichen die Synthese von Peptiden mit einer strukturell neuartigen Kohlenwasserstoff-Querverbindung zwischen einem Ala- und einem Phe-Rest. Eine Reihe von (i,i+3)- und (i,i+4)-geklammerten Peptiden wurde durch Flüssig- und Festphasensynthese erhalten.
      PubDate: 2016-11-30T03:33:28.952092-05:
      DOI: 10.1002/ange.201608648
       
  • Enyne [4+4] Cycloaddition/Oxidation: Ring Contraction via Cyclopropanones
           and Their Anionic Ring-Opening Reactions
    • Authors: Svitlana Kulyk; Buddha B. Khatri, Scott McN. Sieburth
      Abstract: Irradiation of a 1,3-enyne tethered to a 2-pyridone, in the presence of oxygen, leads to formation of a seven-membered ring product, an overall [4+4−1] reaction. This transformation involves two unstable intermediates and a sequence of unusual reactions. An initial [4+4] photocycloaddition of the enyne with the pyridone yields a 1,2,5-cyclooctatriene. Photooxidation of this triene forms a cyclopropanone and subsequent photoextrusion of carbon monoxide gives the observed 1,4-cycloheptadiene product. The first-formed cyclooctatriene and the cyclopropanone could be observed and characterized spectroscopically. The cyclopropanone underwent CO extrusion both photochemically and thermally to give the cycloheptadiene product. Addition of fluoride or acetylide to the most stable cyclopropanone occurred chemoselectively at the two different silicon groups rather than the carbonyl group. The resulting cyclopropanone ring openings gave unsaturated aldehydes.Addieren, Subtrahieren, Modifizieren: Eine Photocycloaddition höherer Ordnung zwischen einem Enin und einem Dien (in Form eines Pyridons) liefert einen achtgliedrigen Ring mit Alleneinheit. In Gegenwart von Luft verläuft die Reaktion über Photooxidation und Extrusion von CO insgesamt als [4+4−1]-Prozess. Nucleophile addieren an die Siliciumatome neben der Ketogruppe und lösen dadurch eine Ringöffnung des Cyclopropanons zum Enal aus.
      PubDate: 2016-11-30T03:33:26.530851-05:
      DOI: 10.1002/ange.201608684
       
  • Rhodium-Complex-Catalyzed Hydroformylation of Olefins with CO2 and
           Hydrosilane
    • Authors: Xinyi Ren; Zhiyao Zheng, Lei Zhang, Zheng Wang, Chungu Xia, Kuiling Ding
      Abstract: A rhodium-catalyzed one-pot hydroformylation of olefins with CO2 , hydrosilane, and H2 has been developed that affords the aldehydes in good chemoselectivities at low catalyst loading. Mechanistic studies indicate that the transformation is likely to proceed through a tandem sequence of poly(methylhydrosiloxane) (PMHS) mediated CO2 reduction to CO and a conventional rhodium-catalyzed hydroformylation with CO/H2. The hydrosilylane-mediated reduction of CO2 in preference to aldehydes was found to be crucial for the selective formation of aldehydes under the reaction conditions.Abfallprodukte für Hydroformylierungen: Ein Rhodium-Phosphoramidit-Katalysator ermöglicht die Hydroformylierung von Olefinen zu Aldehyden in Gegenwart von CO2, Hydrosilan und H2. Diese Umsetzung verläuft wahrscheinlich über Polymethylhydrosiloxan(PMHS)-vermittelte CO2-Reduktion zu CO und eine gewöhnliche Rhodium-katalysierte Hydroformylierung mit CO/H2.
      PubDate: 2016-11-30T03:31:10.846413-05:
      DOI: 10.1002/ange.201608628
       
  • Large-Area, Freestanding MOF Films of Planar, Curvilinear, or
           Micropatterned Topographies
    • Authors: Seok Min Yoon; Jun Heuk Park, Bartosz A. Grzybowski
      Abstract: Freestanding MOF films up to six-inches across and replicating various surface (micro)patterns are prepared via a templated growth method. When grown on copper supports, these films have preferred orientation of the constituent crystallites, translating into markedly different wetting properties of the film's two surfaces (water-pinning vs. water repellant). In addition, the films exhibit differential sorption of various organic solvents, can recover oil spills from seawater, and can also act as active layers of chemical sensors.Nano wird erwachsen: Bis 15 cm dicke robuste MOF-Filme wurden auf verschiedene Trägermaterialien aufgebracht. Insbesondere Kupfer- oder verkupferte Substrate vermitteln das Wachstum von Mikrokristalliten mit einer bevorzugten Orientierung in den MOF-Filmen. Diese Aufbaumerkmale auf der Mikrometerebene beeinflussen die makroskopischen Eigenschaften.
      PubDate: 2016-11-30T03:31:05.322183-05:
      DOI: 10.1002/ange.201607927
       
  • Effect of Preorganized Charge-Display on the Cell-Penetrating Properties
           of Cationic Peptides
    • Authors: Yvonne A. Nagel; Philipp S. Raschle, Helma Wennemers
      Abstract: The effect of preorganized versus undefined charge display on the cellular uptake of cationic cell-penetrating peptides (CPPs) was investigated by comparing conformationally well-defined guanidinylated oligoprolines with flexible oligoarginines. Flow cytometry and confocal microscopy studies with different cancer cell lines (HeLa, MCF-7, and HT-29) showed that preorganization of cationic charges in lateral distances of ≈9 Å enhanced the cellular uptake of CPPs. Binding affinity measurements revealed tighter binding of analogues of cell-surface glycans to the guanidinylated octaproline with localized charges compared to flexible octaarginine, a finding that was further correlated to the cellular uptake by studies with CHO cells deficient in glycans on the outer plasma membrane.Passende Ladungen: Kationische Oligoproline mit Ladungen im lateralen Abstand von 9 Å dringen bei submikromolaren Konzentrationen in Krebszellen ein. Die zelluläre Aufnahme korreliert mit Bindungsaffinitäten an das Zelloberflächenglycan-Analogon Heparin mit vergleichbaren Abständen zwischen den anionischen Sulfatgruppen.
      PubDate: 2016-11-30T03:30:54.044672-05:
      DOI: 10.1002/ange.201607649
       
  • Spontaner Aufbau einer organisch-anorganischen
           Nukleinsäure-Z-DNA-Doppelhelix-Struktur
    • Authors: Vladislav Kulikov; Naomi A. B. Johnson, Andrew Surman, Marie Hutin, Sharon M. Kelly, Mohammed Hezwani, De-Liang Long, Gerd Meyer, Leroy Cronin
      Abstract: Wir berichten hier über ein hybrides organisch-anorganisches Polyoxometallat, Na2[(HGMP)2Mo5O15]⋅7 H2O (1) (mit GMP=Guanosinmonophosphat), das sich spontan zu einer Struktur zusammenfügt, deren Dimensionen jenen der natürlich vorkommenden linkshändigen Z-Form der DNA verblüffend ähnlich sind. Die Helixparameter in der Kristallstruktur dieser neuen Verbindung, wie Anstieg pro Windung und helikale Verdrillung pro Dimer, sind nahezu identisch zur DNA, was einen eingehenden Vergleich von beiden Strukturen erlaubt. Zirkulardichroismus (CD) in Lösung zeigt, dass Verbindung 1 auch in Lösung ausgedehnte Sekundärstrukturen aufweist. Gelelektrophorese-Untersuchungen weisen die Bildung nichtkovalenter Addukte mit natürlichen Plasmiden nach. Damit können wir einen Weg aufzeigen, auf dem einfache, hybride organisch-anorganische Monomere, wie in Verbindung 1, sich spontan zu einer Doppelhelix zusammenlagern können, ohne dass dazu eine kovalent gebundene lineare Sequenz von Nuklein-Säure-Base-Paaren nötig wäre.Halb und halb: Ein einfaches organisch-anorganisches Hybrid aus einem Polyoxometallat (POM) und Guanosinmonophosphat (links) fügt sich spontan zu einer Struktur zusammen, deren Dimensionen jenen der natürlichen linkshändigen Z-Form der DNA (rechts) verblüffend ähnlich sind. Eine komplexe biochemische Maschinerie ist zur Bildung einer Doppelhelix mit einem hohen Grad an Ähnlichkeit zur Z-DNA also nicht erforderlich.
      PubDate: 2016-11-30T03:30:47.601527-05:
      DOI: 10.1002/ange.201606658
       
  • Highly ortho-Selective Chlorination of Anilines Using a Secondary Ammonium
           Salt Organocatalyst
    • Authors: Xiaodong Xiong; Ying-Yeung Yeung
      Abstract: An organocatalytic, highly facile, efficient, and regioselective ortho-chlorination of anilines is described. A secondary ammonium chloride salt has been employed as the catalyst and the reaction can be conducted at room temperature without protection from air and moisture. In addition, the reaction is readily scalable and the catalyst can be recycled and reused. This catalytic protocol has been applied to the efficient synthesis of a highly potent c-Met kinase inhibitor. Mechanistic studies revealed that unique structural features of the secondary ammonium chloride salt are important for both the catalysis and regioselectivity of the electrophilic ortho-chlorination.Das Salz in der Suppe: Eine effiziente regioselektive ortho-Chlorierung von Anilinen beruht auf einem sekundären Ammoniumchlorid als Organokatalysator. Unter Umgebungsatmosphäre und bei Raumtemperatur wird ein breites Spektrum an Substraten, auch im größeren Maßstab, umgesetzt. Als Anwendungsbeispiel dient die Synthese eines potenten c-Met-Kinase-Inhibitors. DCDMH=1,3-Dichlor-5,5-dimethylhydantoin.
      PubDate: 2016-11-30T03:30:40.852671-05:
      DOI: 10.1002/ange.201607388
       
  • Selective [3+1] Fragmentations of P4 by “P” Transfer from a Lewis Acid
           Stabilized [RP4]− Butterfly Anion
    • Authors: Jaap E. Borger; Andreas W. Ehlers, Martin Lutz, J. Chris Slootweg, Koop Lammertsma
      Abstract: Two [3+1] fragmentations of the Lewis acid stabilized bicyclo[1.1.0]tetraphosphabutanide Li[Mes*P4⋅ BPh3] (Mes*=2,4,6-tBu3C6H2) are reported. The reactions proceed by extrusion of a P1 fragment, induced by either an imidazolium salt or phenylisocyanate, with release of the transient triphosphirene Mes*P3, which was isolated as a dimer and trapped by 1,3-cyclohexadiene as a Diels–Alder adduct. DFT quantum chemical computations were used to delineate the reaction mechanisms. These unprecedented pathways grant access to both P1- and P3-containing organophosphorus compounds in two simple steps from white phosphorus.P4 wird geknackt: Zwei [3+1]-Fragmentierungen des Lewis-Säure-stabilisierten Bicyclo[1.1.0]tetraphosphabutanids Li[Mes*P4⋅BPh3] (Mes*=2,4,6-tBu3C6H2) werden durch ein Imidazoliumsalz oder Phenylisocyanat induziert (siehe Schema). Diese ungewöhnlichen Reaktionswege führen in zwei Stufen ausgehend von weißem Phosphor zu P1- und P3-haltigen Organophosphorverbindungen.
      PubDate: 2016-11-30T03:30:35.660791-05:
      DOI: 10.1002/ange.201607234
       
  • Self-Templating Synthesis of Hollow Co3O4 Microtube Arrays for Highly
           Efficient Water Electrolysis
    • Authors: Yun Pei Zhu; Tian Yi Ma, Mietek Jaroniec, Shi Zhang Qiao
      Abstract: In spite of recent advances in the synthesis of hollow micro/nanostructures, the fabrication of three-dimensional electrodes on the basis of these structures remains a major challenge. Herein, we develop an electrochemical sacrificial-template strategy to fabricate hollow Co3O4 microtube arrays with hierarchical porosity. The resultant unique structures and integrated electrode configurations impart enhanced mass transfer and electron mobility, ensuring high activity and stability in catalyzing oxygen and hydrogen evolution reactions. Impressively, the apparent performance can rival that of state-of-the-art noble-metal and transition-metal electrocatalysts. Furthermore, this bifunctional electrode can be used for highly efficient overall water splitting, even competing with the integrated performance of Pt/C and IrO2/C.Hohl und hierarchisch: Eine elektrochemische Templatstrategie wurde entwickelt, um hohle Co3O4-Mikroröhren mit hierarchischer Porosität herzustellen. Diese Strukturen zeichnen sich durch exzellente elektrokatalytische Aktivität und Haltbarkeit in der Sauerstoff- und Wasserstoffentwicklung aus und können daher die Wasserspaltung katalysieren.
      PubDate: 2016-11-30T03:26:24.813071-05:
      DOI: 10.1002/ange.201610413
       
  • Cooperation of Three Chromophores Generates the Water-Resistant Nitrate
           Nonlinear Optical Material Bi3TeO6OH(NO3)2
    • Authors: Sangen Zhao; Yi Yang, Yaoguo Shen, Bingqing Zhao, Lina Li, Chengmin Ji, Zhenyue Wu, Daqiang Yuan, Zheshuai Lin, Maochun Hong, Junhua Luo
      Abstract: Nitrates have long been ignored for practical uses as nonlinear optical (NLO) materials because they are usually very easy to dissolve in water; despite this, the π-conjugated [NO3]− is among the most desirable NLO-active structural units. The cooperation of three structural chromophores, namely, Bi3O6OH short chains with 6s2 lone pair electrons, distorted TeO6 octahedra with d10 electrons, and π-conjugated [NO3]− triangles, generates a new nitrate NLO material, Bi3TeO6OH(NO3)2, which exhibits an enhanced phase-matchable NLO response of three times that of KH2PO4 (3×KH2PO4), exceeding those of most nitrate NLO materials. Remarkably, the new material did not show obvious weight loss and degeneration of NLO response after being dipped in de-ionized water for 24 h, indicating that it is highly resistant to water. Theoretical calculations reveal that foreign water molecules cannot stably stay in the crystal lattice of Bi3TeO6OH(NO3)2. These findings highlight the introduction of diverse chromophores into the nitrate systems as an effective approach for developing practical nitrate NLO materials that are of high water-resistance and good optical performance.Gute Zusammenarbeit: Die Kooperation dreier Strukturchromophore in einem neuen nichtlinear-optischen Nitrat, Bi3TeO6OH(NO3)2, resultiert in einer starken Obertonbildung (dreimal so stark wie die von KH2PO4). Bemerkenswerterweise ist das Material stabil in Wasser.
      PubDate: 2016-11-30T03:26:15.950585-05:
      DOI: 10.1002/ange.201609876
       
  • Periodic Oscillatory Motion of a Self-Propelled Motor Driven by
           Decomposition of H2O2 by Catalase
    • Authors: Satoshi Nakata; Mio Nomura, Hiroya Yamamoto, Shunsuke Izumi, Nobuhiko J. Suematsu, Yumihiko Ikura, Takashi Amemiya
      Abstract: A self-propelled motor driven by the enzymatic reaction of catalase adsorbed onto a filter paper floating on an aqueous solution of H2O2 was used to study nonlinear behavior in the motor's motion. An increase in the concentration of H2O2 resulted in a change from no motion to irregular oscillatory motion, periodic oscillatory motion, and continuous motion. The mechanisms underlying oscillation and mode bifurcation are discussed based on experimental results on O2 bubble formation and growth on the underside of the motor.Aus eigenem Antrieb, auf der Grundlage der Katalase-Reaktion, schwimmt ein Papierfilter auf einer wässrigen H2O2-Lösung. Der nichtlineare Fortbewegungsmodus wurde untersucht. Je nach H2O2-Konzentration wurden drei Bewegungsarten – irregulär oszillatorisch, periodisch oszillatorisch und kontinuierlich – beobachtet. Die Mechanismen von Oszillation und Modusselektion werden diskutiert.
      PubDate: 2016-11-30T03:26:06.545956-05:
      DOI: 10.1002/ange.201609971
       
  • Cerium-Catalyzed Hydrosilylation of Acrylates to Give α-Silyl Esters
    • Authors: Aradhana Pindwal; Smita Patnaik, William C. Everett, Arkady Ellern, Theresa L. Windus, Aaron D. Sadow
      Abstract: The homoleptic organocerium complex Ce{C(SiHMe2)3}3 (1) reacts with B(C6F5)3 to produce the zwitterionic bis(alkyl) hydridoborato Ce{C(SiHMe2)3}2HB(C6F5)3 (2). NMR and IR spectroscopy and X-ray crystallography indicate that each alkyl ligand contains two bridging Ce↼H-Si interactions in both 1 and 2. Compound 2 serves as a precatalyst for the hydrosilylation of acrylates to give α-silyl esters at room temperature with a turnover number of 2200.Ein zwitterionischer Organocer-Hydridoborat-Komplex ist ein hoch aktiver Katalysator für die Addition von sekundären Silanen an Acrylate zur Bildung von α-Silylestern. Trotz der Oxophilie des Cer-Katalysators wird die Esterfunktion unter den Reaktionsbedingungen nicht reduziert. NMR- und IR-Spektroskopie sowie Röntgen-Kristallographie deuten darauf hin, dass jeder Alkylligand zwei verbrückende Ce↼H-Si-Motive bildet. TOF=Umsatzfrequenz, TON=Umsatzzahl.
      PubDate: 2016-11-30T03:26:01.498236-05:
      DOI: 10.1002/ange.201610263
       
  • 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
       
  • Quinoidal/Aromatic Transformation in π-conjugated oligomers: Vibrational
           Raman studies on the limit of rupture of π-bonds
    • Authors: Juan Casado; Paula Mayorga Burrezo, José L. Zafra, Juan T. López Navarrete
      Abstract: The vibrational Raman spectra of several series of aromatic and quinoidal compounds have been analyzed considering the down-shifts and up-shifts of the frequencies of the relevant Raman bands as a function of the number of repeating units. Oligothiophenes, oligophenylene-vinylenes, oligoperylenes (oligophenyls) derivatives are studied in a common context. These shifts are taken as spectroscopic fingerprints of the changes in π-conjugation. For a given family, aromatic and quinoidal oligomers have been studied together and according with their Raman frequency shifts located in the two-well BLA-energy curve of their ground electronic state as a function of the bond-length-alternation pattern (BLA). The connection among BLA, π-conjugation and Raman frequencies is taken here as the basis of our study. These Raman shifts/BLA changes have been related to important electronic properties of these one-dimension linear π-electron delocalized systems such as quinoidal (polyene) and aromatic characters.
      PubDate: 2016-11-11T04:40:28.692813-05:
      DOI: 10.1002/ange.201605893
       
  • Formation and Reactivity of Electron-Precise B-B Single and Multiple Bonds
    • Authors: Merle Arrowsmith; Holger Braunschweig, Tom Stennett
      Abstract: Recent years have seen rapid advances in the chemistry of small molecules containing electron-precise boron-boron bonds. This review provides an overview of the latest methods for the controlled synthesis of B-B single and multiple bonds as well as the ever-expanding range of reactivity displayed by the latter.
      PubDate: 2016-11-10T02:01:45.672947-05:
      DOI: 10.1002/ange.201610072
       
  • Cryo-EM as a tool for structure-based drug development
    • Authors: Felipe Merino; Stefan Raunser
      Abstract: For decades, X-ray crystallography and NMR have been the major techniques to study the atomic structure of macromolecules. However, because of size, instability, low yield, and other factors, many macromolecules are recalcitrant to crystallization or NMR studies. Electron cryo microscopy (cryo-EM) does not depend on crystals and has therefore been the method of choice for many macromolecular complexes that could not be crystallized, but atomic resolution was mostly beyond its reach. Capable of sensing directly the incident electrons, a new generation of detectors has recently revolutionized the field, with structures of macromolecules being now solved routinely to near-atomic resolution. In this review, we summarize some of the most recent examples of high-resolution cryo-EM. We put particular emphasis on proteins with pharmacological relevance that have been traditionally inaccessible to crystallography. Furthermore, we discuss examples where the interaction with small molecules was fully characterized at atomic resolution. Finally, we stress the current limits of cryo-EM, and methodological issues related to its usage as drug development tool.
      PubDate: 2016-11-10T01:01:53.510647-05:
      DOI: 10.1002/ange.201608432
       
  • 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
       
  • Indenylmetal Catalysis in Organic Synthesis
    • Authors: Barry M. Trost; Michael C. Ryan
      Abstract: Synthetic organic chemists have a long-standing appreciation for transition metal cyclopentadienyl complexes, of which many have been used as catalysts for organic transformations. Much less well known are the contributions of the benzo-fuzed relative of the cyclopentadienyl ligand, the indenyl ligand, whose unique properties have in many cases imparted differential reactivity in catalytic processes toward the synthesis of small molecules. In this review, we will present examples of indenylmetal complexes in catalysis and compare their reactivity to their cyclopentadienyl analogues, wherever possible.
      PubDate: 2016-11-02T16:42:06.811623-05:
      DOI: 10.1002/ange.201609054
       
  • 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
       
  • Controlled polymerization of multivinyl monomers: toward single chain
           cyclized/knotted polymer architecture
    • Authors: Yongsheng Gao; Ben Newland, Dezhong Zhou, Krzysztof Matyjaszewski, Wenxin Wang
      Abstract: Seventy years ago, Flory and Stockmayer predicted that the polymerization of multivinyl monomers (MVM) would inevitably lead to insoluble crosslinked gel networks. MVMs have since been largely limited to use as crosslinking agents. More recently, however, polymerization strategies such as reversible deactivation radical polymerization (RDRP) have paved the way for the exploration of new possibilities both in polymer architectures and functional capabilities. This mini review firstly provides historical context to the problem of polymerizing MVMs before highlighting how RDRP has led to the formation of new cyclized/knotted polymer structures. Whilst the potential of such polymer architectures is far from being fulfilled, some emerging applications of cyclized/knot polymers are also discussed.
      PubDate: 2016-10-27T09:20:54.975553-05:
      DOI: 10.1002/ange.201608786
       
  • Vesicles and their multiple facets: underpinning biological and synthetic
           progress
    • Authors: Paula M. Mendes; Francisco Fernandez-Trillo, Liam Grover, Alex Stephenson-Brown, Paul Harrison
      Abstract: The important role of vesicles in many aspects of cell function is well recognised but only recently have sophisticated imaging techniques begun to reveal their ubiquity in nature. While we further our understanding of the biological properties of vesicles and their physiological functions, increasingly elegantly designed artificial vesicles are being reported for a wide range of technological applications and basic studies. Herein, we bring together both the biological and synthetic state-of-the-art on vesicles and place their biological features in the context of recent synthetic developments, providing a unique view of these complex and rapidly developing fields. The perspectives on the challenges and opportunities for future biological and synthetic progress on vesicles are also presented.
      PubDate: 2016-10-12T13:26:03.249846-05:
      DOI: 10.1002/ange.201607825
       
  • 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
       
  • Multidimensional Mass Spectrometry of Synthetic Polymers and Advanced
           Materials
    • Authors: Chrys Wesdemiotis
      Abstract: Multidimensional mass spectrometry interfaces a suitable ionization technique and mass analysis (MS) with tandem mass spectrometry (MS²) fragmentation and an orthogonal online separation method. Separation choices include liquid chromatography (LC) and ion mobility spectrometry (IMS), which disperse pre-ionization in the solution state or post-ionization in the gas phase, respectively. The MS step provides elemental composition information, while MS² exploits differences in the bond stabilities of a polymer, yielding connectivity and sequence information. LC conditions can be tuned to separate by polarity, end group functionality or hydrodynamic volume, whereas IMS adds selectivity by macromolecular shape and architecture. This minireview discusses how select combinations of the MS, MS², LC and IMS dimensions can be applied, together with the appropriate ionization method, to determine the constituents, structures, end groups, sequences and architectures of a wide variety of homo- and copolymeric materials, including multicomponent blends, supramolecular assemblies, novel hybrid materials and large cross-linked or non-ionizable polymers.
      PubDate: 2016-10-06T10:45:47.56021-05:0
      DOI: 10.1002/ange.201607003
       
  • Cyclometalated AuIII complexes: Synthesis, Reactivity and Physicochemical
           Properties
    • Authors: Cristina Nevado; Roopender Kumar
      Abstract: In this review, we aim to give the non-gold expert reader an overview of the key design principles behind the different existing ligand templates and the representative methods to access the corresponding stabilized AuIII complexes. In addition, we have aimed at providing a basic understanding on the reactivity of these motifs as a guiding principle to generate derivatives on which to further acquire the desirable both chemical and photophysical properties. Finally, the role of some of these species as probes to unravel mechanistic insights of relevant catalytic transformations has also been discussed.
      PubDate: 2016-09-29T14:20:30.577715-05:
      DOI: 10.1002/ange.201607225
       
  • Electrophilic Activation of Silicon‐Hydrogen Bonds in Catalytic
           Hydrosilations
    • Authors: Mark C. Lipke; Allegra L. Liberman-Martin, T. Don Tilley
      Abstract: Hydrosilation reactions represent an important class of chemical transformations and there has been considerable recent interest in expanding the scope of these reactions by developing new catalysts. A major theme to emerge from these investigations is the development of catalysts with electrophilic character that transfer electrophilicity to silicon via Si—H activation. This type of mechanism has been proposed for catalysts ranging from Group 4 transition metals to Group 15 main group species. Additionally, other electrophilic silicon species, such as silylene complexes and η3‐H2SiRR' complexes, have been identified as intermediates in hydrosilation reactions. In this Review, different types of catalysts are compared to highlight the range of hydrosilation mechanisms that feature electrophilic silicon centers, and the importance of these catalysts to the development of new hydrosilation reactions is discussed.
      PubDate: 2016-09-19T04:25:02.766756-05:
      DOI: 10.1002/ange.201605198
       
  • Microplastic in Aquatic Ecosystems
    • Authors: Natalia P. Ivleva; Alexandra C. Wiesheu, Reinhard Niessner
      Abstract: The contamination of marine and freshwater ecosystems with plastic, and especially with microplastic (MP), is a global ecological problem of increasing scientific concern. This has stimulated a great deal of studies on the occurrence of MP, interaction of MP with chemical pollutants, the uptake of MP by aquatic organisms, and the resulting (negative) impact of MP, etc.Here we review the major issues of MP in aquatic environments, with the principal aims i) to characterize the methods applied for MP analysis (including sampling, processing, identification and quantification), indicate the most reliable techniques and discuss the required further improvements; ii) to estimate the abundance of MP in marine / freshwater ecosystems and clarify the problems that hamper the comparability of such results; iii) to summarize the reports on the uptake of MP by the biota. Finally, we identify knowledge gaps, suggest possible strategies to assess environmental risks arising from MP, and discuss prospects to minimize the MP abundance in aquatic ecosystems.
      PubDate: 2016-09-12T14:20:33.701286-05:
      DOI: 10.1002/ange.201606957
       
  • 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
       
  • Carbocatalysts in Liquid Phase
    • Authors: Dangsheng Su; Guodong Wen, Shuchang Wu, Feng Peng, Robert Schloegl
      Abstract: Metal‐free catalysis has gained broad interest for sustainable chemistry. Carbocatalysis is one green option for catalytic transformation in the gas phase as well as in the liquid phase. This is documented by the numerous reports on gas phase dehydrogenation and selective oxidation where carbon can be successful alternatives to metal oxide systems. Carbocatalysis for liquid phase reactions, especially for organic synthesis, is an emerging research discipline and has been under rapid development in recent years. This review provides a critical analysis on the state‐of‐the‐art carbocatalysts for liquid phase reactions, with the focus on the underlying mechanisms, the advantages and limitations when only carbon, without any intentional metal species (supported systems), is used to catalyze some traditional liquid phase reactions.
      PubDate: 2016-08-12T02:56:32.815512-05:
      DOI: 10.1002/ange.201600906
       
  • Wertmetalle ‐ Gewinnungsverfahren, aktuelle Trends und
           Recyclingstrategien
    • Authors: Martin Bertau; Peter Froehlich, Beate Brett, Tom Lorenz, Gunther Martin
      Abstract: Dieser Aufsatz gibt einen Überblick über Wertmetalle, deren Versorgungslage für Europa als kritisch eingestuft wird. Aufbauend auf einer Darstellung des Stands der Technik werden neue Ansätze, vornehmlich seit 2005, zur Gewinnung aus Primärrohstoffen vorgestellt und die Recyclingverfahren diskutiert. Ausgehend von den jeweiligen Lagerstätten bzw. der Mineralchemie wird aufgezeigt, welche Strategien zur Gewinnung der Metalle verfolgt werden. Außerdem wird auf die wirtschaftliche Bedeutung und Verwendung der Metalle eingegangen.
      PubDate: 2016-08-11T01:08:53.925659-05:
      DOI: 10.1002/ange.201605417
       
  • Promotion of Organic Reactions by Non‐Benzenoid Carbocylic Aromatic
           Ions
    • Authors: Demelza J. M. Lyons; Reece D. Crocker, Marcus Blümel, Thanh Vinh Nguyen
      Abstract: The first three primary members of the non‐benzenoid carbocyclic aromatic ion family, namely cyclopropenium, cyclopentadienide and cycloheptatrienium (tropylium) ions, are well‐known chemical entities. All of them have planar cyclic structures with (4n+2) electrons in fully conjugated systems, allowing the charge to delocalise across the rings. They fulfill Hückel's rule for aromaticity and hence possess extraordinary stability for charged cyclopolyenes. Since the historic discovery of tropylium bromide in the late 19th century, these non‐benzenoid aromatic ions have always attracted a lot of attention from chemists due to their unique combination of stability and reactivity. Bearing a charge, aromatic ions are more prone to nucleophilic/electrophilic reactions than the neutral benzenoid counterparts. This feature enables aromatic ions to participate in a variety of chemical transformations. Within the last seven years, there has been an incredible number of important investigations in utilising aromatic ions to mediate organic reactions. In this review, we aim to highlight these recent developments and discuss the prospective of aromatic ions in promoting synthetically useful organic transformations.
      PubDate: 2016-08-10T03:26:49.336762-05:
      DOI: 10.1002/ange.201605979
       
  • Name Reactions in Biological Chemistry
    • Authors: Hung-wen Liu; Chia-I Lin, Reid M. McCarty
      Abstract: Chemical reactions that are named in honor of their true or at least perceived discoverers are known as "name reactions". This review is a collection of biological representatives of named chemical reactions. Emphasis is placed on reaction types and catalytic mechanisms that showcase both the chemical diversity in natural product biosynthesis as well as the parallels with synthetic organic chemistry. An attempt has been made to describe the enzymatic mechanisms of catalysis within the context of their synthetic counterparts whenever possible and to discuss the mechanistic hypotheses for those reactions that are presently active areas of investigation. This review has been categorized by reaction type, e.g., condensation, reduction and oxidation, substitution, carboxylation, radical‐mediated, and rearrangements, which are subdivided by named reactions.
      PubDate: 2016-08-09T07:30:46.620315-05:
      DOI: 10.1002/ange.201603291
       
  • Phage‐Enabled Nanomedicine: From Probes to Therapeutics in Precision
           Medicine
    • Authors: Kegan Sunderland; Mingying Yang, Chuanbin Mao
      Abstract: Nanomedicine is the application of nanotechnology in medicine. This review is focused on the use of both lytic and temperate bacteriophages (phages) nanoparticles in nanomedicine, in particular, in the context of developing nano‐probes for precise disease diagnosis and nano‐therapeutics for targeted disease treatment. Phages as bacteria‐specific viruses do not naturally infect eukaryotic cells and are not toxic to them. They not only can be genetically engineered to bear the capability of targeting nanoparticles, cells, tissues, and organs, but also can be integrated with functional abiotic nanomaterials to gain physical properties that enable disease diagnosis and treatment. Therefore, they are ideal for many applications in precision nanomedicine. This review will summarize the current use of the great diversity of phage structures in many aspects of precision nanomedicine including ultrasensitive biomarker detection, enhanced bioimaging for disease diagnosis, targeted drug and gene delivery, directed stem cell differentiation, accelerated tissue formation, effective vaccination, and nano‐therapeutics for targeted disease treatment. It will also propose future directions in the area of phage‐based nanomedicines as well as the state of phage‐based clinical trials.
      PubDate: 2016-08-05T04:25:39.419807-05:
      DOI: 10.1002/ange.201606181
       
  • Titelbild: Topological Polymer Chemistry Enters Surface Science: Linear
           versus Cyclic Polymer Brushes (Angew. Chem. 50/2016)
    • Authors: Giulia Morgese; Lucca Trachsel, Matteo Romio, Mohammad Divandari, Shivaprakash N. Ramakrishna, Edmondo M. Benetti
      Pages: 15671 - 15671
      Abstract: Topologische Effekte durch cyclische Polymere … … werden in oberflächengebundener Form verstärkt. E. M. Benetti et al. zeigen in der Zuschrift auf S. 15812 ff., dass cyclische Polyoxazolin-Bürsten sterisch stabiler sind als ihre linearen Analoga und ein exzellentes Schmierverhalten in Wasser aufweisen. Topologische Polymerchemie und Oberflächenchemie finden zusammen und decken Ergebnisse auf, die das Zitat Wolfgang Paulis zu bestätigen scheinen: “Gott erschuf die Materie, aber der Teufel die Oberflächen.”
      PubDate: 2016-10-28T06:35:48.076037-05:
      DOI: 10.1002/ange.201610385
       
  • Innentitelbild: A Conformationally Stable Contorted Hexabenzoovalene
           (Angew. Chem. 50/2016)
    • Authors: Kevin Baumgärtner; Ana Lucia Meza Chincha, Andreas Dreuw, Frank Rominger, Michael Mastalerz
      Pages: 15672 - 15672
      Abstract: Unter Arrest Zwei tert-Butyl-Gruppen beeinflussen die konformative Flexibilität und die Lichtemission eines Hexabenzoovalens. In ihrer Zuschrift auf S. 15823 ff. beschreiben M. Mastalerz et al., wie sich eine flexible Vorläuferverbindung durch oxidative Cyclodehydrierung zu einem orange emittierenden Hexabenzoovalen konformativ einfangen lässt. Eine selektive Dealkylierung gibt dem System seine Bewegungsfreiheit zurück – es emittiert grün.
      PubDate: 2016-11-15T02:30:58.611385-05:
      DOI: 10.1002/ange.201610633
       
  • Graphisches Inhaltsverzeichnis: Angew. Chem. 50/2016
    • Pages: 15675 - 15686
      PubDate: 2016-12-05T07:50:10.353578-05:
      DOI: 10.1002/ange.201685011
       
  • Top-Beiträge aus unseren Schwesterzeitschriften: Angew. Chem. 50/2016
    • Pages: 15690 - 15693
      PubDate: 2016-12-05T07:50:07.223763-05:
      DOI: 10.1002/ange.201685013
       
  • Xiaogang Liu
    • Pages: 15694 - 15694
      Abstract: „Etwas, dem ich nie widerstehen kann, sind Meeresfrüchte und frisches Obst. Mein Lieblingszitat ist: ,Nothing is impossible, the word itself says ‘I'm possible’!‘ (Audrey Hepburn) ...“ Dies und mehr von und über Xiaogang Liu finden Sie auf Seite 15694.
      PubDate: 2016-06-23T11:20:47.303916-05:
      DOI: 10.1002/ange.201605390
       
  • Malcolm-McIntosh-Preis: R. J. Payne / Heinrich-Wieland-Preis: P. G.
           Schultz / FCI-Dozentenpreis: T. Magauer / Bohlmann-Vorlesung: F. H.
           Arnold
    • Pages: 15695 - 15695
      PubDate: 2016-11-10T08:17:21.402214-05:
      DOI: 10.1002/ange.201610316
       
  • Maßgeschneiderte funktionelle Graphen-Nanokomposite durch einfaches
           Stapeln, Schneiden und Falten
    • Authors: Xiaoyan Zhang; Paolo Samorì
      Pages: 15698 - 15700
      Abstract: Molekulare Bastelstunde: Stapeln, Schneiden und Falten ist ein geeigneter Weg für die Herstellung robuster Nanokomposite aus großflächigen Graphenfilmen und Polymeren. Die Methode öffnet neue Wege zu starken, langlebigen und multifunktionellen Nanomaterialien mit faszinierenden Eigenschaften.
      PubDate: 2016-10-14T06:34:00.103018-05:
      DOI: 10.1002/ange.201608964
       
  • Photoinduzierte Mehrkomponentenreaktionen
    • Authors: Silvia Garbarino; Davide Ravelli, Stefano Protti, Andrea Basso
      Pages: 15702 - 15711
      Abstract: Die Kombination von Mehrkomponentenansätzen mit lichtgetriebenen Prozessen erschließt neue Bereiche auf dem Gebiet der organischen Synthesechemie, deren Bedarf an nachhaltigen und atom- sowie energieeffizienten Reaktionen immer dringlicher wird. Photoinduzierte Mehrkomponentenreaktionen befinden sich noch immer in einem frühen Stadium, für die nahe Zukunft ist jedoch mit deutlichen Fortschritten zu rechnen.MCRs in neuem Licht: In der letzten Zeit sind Mehrkomponentenprozesse auf lichtgetriebene Reaktionen angewendet worden, um nachhaltige und atom- sowie energieeffiziente Reaktionen zu entwickeln. In diesem Kurzaufsatz ist eine umfassende Sammlung photoinduzierter Mehrkomponentenreaktionen (MCRs) zusammengestellt.
      PubDate: 2016-10-12T01:12:02.1856-05:00
      DOI: 10.1002/ange.201605288
       
  • Schwefel in der modernen Materialwissenschaft
    • Authors: Darryl A. Boyd
      Pages: 15712 - 15729
      Abstract: Schwefel ist eines der häufigsten Elemente im Universum, fällt als Hauptnebenprodukt bei der Erdölraffination an und stellt ein häufiges Reaktionszentrum in biologischen Systemen dar. Die Forschung über Schwefel ist daher breit gefächert und hat große Relevanz und Auswirkungen auf unser tägliches Leben. So hat das Interesse an schwefelbasierten Reaktionen in den letzten zehn Jahren eine deutliche Wiederbelebung erfahren. Weitere relevante Themengebiete sind Forschungen zur Verbesserung von Energieeffizienzen, umweltfreundliche Anwendungen für Abfallprodukte der Erdölraffination, Polymere mit besonderen optischen und mechanischen Eigenschaften sowie Materialien für biologische Anwendungen. Dieser Aufsatz stellt einige der neuesten Anwendungen von Schwefel und schwefelbasierten Reaktionen für die Herstellung von Materialien für den Energiebereich, Umweltschutz und andere praktische Anwendungen vor.Ein Schmelztiegel an Möglichkeiten: Schwefel und Schwefelverbindungen werden seit Jahrtausenden vielfach genutzt und sind Bestandteil des täglichen Lebens. Aktuelle Forschungsthemen rund um den Schwefel sind dessen Einsatz in verbesserten Vulkanisationsverfahren, Li- und Na-Schwefelbatterien und Anwendungen der Thiol-Kupplung in der Materialsynthese.
      PubDate: 2016-11-08T08:26:03.015572-05:
      DOI: 10.1002/ange.201604615
       
  • Zuordnung der Rückgrat- und Seitenketten-Protonen in vollständig
           protonierten Proteinen durch Festkörper-NMR-Spektroskopie:
           Mikrokristalle, Sedimente und Amyloidfibrillen
    • Authors: Jan Stanek; Loren B. Andreas, Kristaps Jaudzems, Diane Cala, Daniela Lalli, Andrea Bertarello, Tobias Schubeis, Inara Akopjana, Svetlana Kotelovica, Kaspars Tars, Andrea Pica, Serena Leone, Delia Picone, Zhi-Qiang Xu, Nicholas E. Dixon, Denis Martinez, Mélanie Berbon, Nadia El Mammeri, Abdelmajid Noubhani, Sven Saupe, Birgit Habenstein, Antoine Loquet, Guido Pintacuda
      Pages: 15730 - 15735
      Abstract: Wir beschreiben die empfindliche Messung von α-Protonen in vollständig protonierten Proteinen durch Festkörper-NMR-Spektroskopie mit Rotation um den magischen Winkel (MAS) von 100–111 kHz. Die exzellente Auflösung in der Cα-Hα-Ebene wird für fünf Proteine gezeigt, darunter Mikrokristalle, ein sedimentierter Komplex, ein Kapsid und Amyloidfibrillen. Ausgehend davon wurde ein Satz 3D-Spektren für die sequenzspezifische Zuordnung der Rückgrat- und der aliphatischen Seitenketten-Resonanzen entwickelt. Dabei wurden nur 500 μg Probe verwendet. Diese Entwicklungen beschleunigen strukturelle Untersuchungen von biomolekularen Komplexen, die nur in Submilligramm-Mengen verfügbar sind, ohne die Notwendigkeit einer Deuterierung.Keine Deuterierung nötig: Mithilfe neuer 111-kHz-MAS-Sonden gelingt die hochauflösende 1H-NMR-Spektroskopie von unlöslichen, kristallinen oder selbstorganisierten Proteinaggregaten ohne den Austausch von Seitenkettenprotonen durch Deuterium. α-Protonen werden zu empfindlichen und spektral aufgelösten NMR-Sonden, die für Proteine von ca. 20 kDa die Zuordnung der Rückgrat- und Seitenkettenresonanzen in ungefähr einer Woche Messzeit erlauben.
      PubDate: 2016-11-16T09:36:59.951731-05:
      DOI: 10.1002/ange.201607084
       
  • Eintopfsynthese ungeschützter anomerer Glykosylthiole in Wasser für
           Glykan-Ligationen mit hochfunktionalisierten Zuckern
    • Authors: Sebastian Köhling; Matthias P. Exner, Saba Nojoumi, Jürgen Schiller, Nediljko Budisa, Jörg Rademann
      Pages: 15736 - 15740
      Abstract: Die chemische Synthese von Oligosaccharid-Konjugaten ist essenziell für ein tieferes Verständnis der Funktionen von Kohlenhydraten. Sie könnte durch effektive Methoden der anomeren Ligation von ungeschützten Zuckern in Wasser deutlich erleichtert werden. Hier stellen wir ein leistungsfähiges Protokoll zur Herstellung anomerer Glykosylthiole von komplexen Mono-, Di-, und Oligosacchariden vor. Unter Ausnutzung der Nachbargruppenbeteiligung von 2-Acetamidozuckern erzeugte 1,2-Oxazoline wurden durch Zugabe von 1-Thiosäuren in die entsprechenden Gykosylthioester überführt. Die in situ erzeugten Glykosylthiolate wurden dann mit Michael-Akzeptoren, aliphatischen Halogeniden und Aziridinen zu vielseitig einsetzbaren Glykokonjugaten umgesetzt. Durch Thiol-En-Reaktionen wurden auch Konjugate mit Aminosäuren und Proteinen erhalten. Somit wurde ein effizienter Zugang zu anomeren Glykosylthiolen und Thiolaten geschaffen, der eine anomere Funktionalisierung von komplexen ungeschützten Glykanen in Wasser ermöglicht.Zuckerthiole: Ein direkter Zugang zu anomeren Thiolen von ungeschützten Mono- und Oligosacchariden wird vorgestellt. Dazu wurden Zucker-Oxazoline durch Thiosäuren geöffnet, wobei geruchlose, lagerfähige Glykosylthioester entstanden, die als Vorstufen für 1-Thiolzucker, Thiolate und weitere funktionalisierte Glykoside mit Amin- und Thiolspacern, S-glykosylierte Aminosäuren und S-verknüpfte Glykoproteine dienen.
      PubDate: 2016-11-11T07:15:41.517275-05:
      DOI: 10.1002/ange.201607228
       
  • Eine monoanionische Arsenid-Quelle: Decarbonylierung des
           2-Arsaethinolat-Anions bei der Reaktion mit Stannylenen
    • Authors: Alexander Hinz; Jose M. Goicoechea
      Pages: 15741 - 15746
      Abstract: Wir berichten über eine fundamentale Studie zur Reaktivität des 2-Arsaethinolat-Anions (AsCO−), einer Spezies, die erst kürzlich synthetisch zugänglich wurde. Die Reaktion von AsCO− gegenüber dem Stannylen Ter2Sn (Ter=Bis-2,6-(2,4,6-trimethylphenyl)phenyl), die zur unerwarteten Bildung eines [Ter3Sn2As2]−-Clusters führt, ist beschrieben. Auf dem Reaktionspfad zu diesem Cluster wurden verschiedene Intermediate identifiziert und charakterisiert. Nach der anfänglichen Assoziierung von AsCO− an Ter2Sn tritt Decarbonylierung ein, wodurch ein Anion mit einfach koordiniertem Arsen, [Ter2SnAs]−, gebildet wird. Diese beiden Spezies sind bei Raumtemperatur nicht stabil, und [Ter2SnAs]− durchläuft eine Umlagerung zu [TerSnAsTer]−, einem präzedenzlosen anionischen gemischten Gruppe-14/15-Alkenanalogon.Schwere Doppelbindungen: Die Reaktion von AsCO− mit Ter2Sn (Ter=Bis-2,6-(2,4,6-trimethylphenyl)phenyl) führt zur unerwarteten Bildung von [Ter3Sn2As2]−. Nach der Assoziierung von AsCO− an Ter2Sn wird durch Decarbonylierung ein Anion mit einfach koordiniertem Arsen, [Ter2SnAs]−, gebildet. Beide Spezies sind nicht bei Raumtemperatur stabil, und [Ter2SnAs]− lagert sich zu [TerSnAsTer]−, einem präzedenzlosen anionischen Alkenanalogon, um.
      PubDate: 2016-11-15T05:58:46.464526-05:
      DOI: 10.1002/ange.201609309
       
  • Ein zweikerniges Quecksilber(II)-vermitteltes Basenpaar in DNA
    • Authors: Soham Mandal; Marian Hebenbrock, Jens Müller
      Pages: 15747 - 15750
      Abstract: Erstmals konnte ein zweikerniges metallvermitteltes Basenpaar mit zweiwertigen Metallionen erzeugt werden. Dies gelang durch Kombination des neutralen Purinderivats 1,N6-Ethenoadenin (ϵA), das als doppelt einzähniger Ligand bevorzugt zwei Metallionen über parallel ausgerichtete N-M-Bindungen bindet, mit der kanonischen Nucleobase Thymin (T), die in Gegenwart von HgII deprotoniert wird und so die angehäufte positive Ladung der in geringem Abstand zueinander lokalisierten zweiwertigen Metallionen teilweise kompensiert, so dass das zweikernige T-HgII2-ϵA-Basenpaar gebildet wird. Das metallvermittelte Basenpaar erhöht die Schmelztemperatur des untersuchten DNA-Oligonucleotidduplexes um 8 °C. Die Bildung des Basenpaars wurde durch temperaturabhängige UV-Spektroskopie sowie in Titrationsexperimenten mittels UV- und CD-Spektroskopie gezeigt.Doppelt hält besser: Das erste zweikernige metallvermittelte Basenpaar mit zweiwertigen Metallionen wurde durch Kombination von Thymin mit einer geeigneten künstlichen Nucleobase erhalten, die durch doppelt einzähnige Koordination die Bindung zweier HgII-Ionen in direkter Nachbarschaft ermöglicht.
      PubDate: 2016-11-15T02:45:28.629367-05:
      DOI: 10.1002/ange.201608354
       
  • CpPEt2As4 – eine organosubstituierte As4-Butterfly-Verbindung
    • Authors: Sebastian Heinl; Gábor Balázs, Andreas Stauber, Manfred Scheer
      Pages: 15751 - 15755
      Abstract: CpPEt2As4 (CpPEt=C5(4-EtC6H4)5) (1) wird durch die Reaktion von CpPEt.-Radikalen mit gelbem Arsen (As4) synthetisiert. Dabei lässt sich ein Gleichgewicht der Ausgangsstoffe mit dem Produkt in Lösung beobachten. Jedoch kann 1 isoliert und als Feststoff ohne Zersetzung gelagert werden. As4 wird aus 1 unter thermischen oder photochemischen Bedingungen leicht abgegeben. Aus pulvrigen Proben von CpPEt2As4 kann gelbes Arsen unter relativ milden Bedingungen (T=125 °C) sublimiert werden. Ein ähnliches Verhalten wurde auch bei der verwandten Phosphorverbindung CpBIG2P4 (2; CpBIG=C5(4-nBuC6H4)5) als P4-abgebendes Reagenz festgestellt. Dichtefunktionalrechnungen zeigen, wie wichtig Dispersionskräfte für die Stabilität der Produkte sind.As4-Verbindungen mit Schmetterlings-Struktur sind selten, mit organischen Substituenten waren sie bisher sogar unbekannt. Die Synthese des ersten Organoderivates CpPEt2As4 (siehe Strukturbild, CpPEt=C5(4-EtC6H4)5) wird vorgestellt, ebenso wie die Freisetzung von gelbem Arsen durch dieses in Lösung und im festen Zustand. Ähnliche Ergebnisse wurden für das verwandte P4- Molekül CpBIG2P4 erzielt (CpBIG=C5(4-nBuC6H4)5).
      PubDate: 2016-11-15T02:45:22.185773-05:
      DOI: 10.1002/ange.201608478
       
  • Pentafluorethylkieselsäuren
    • Authors: Nico Schwarze; Simon Steinhauer, Beate Neumann, Hans-Georg Stammler, Berthold Hoge
      Pages: 15756 - 15759
      Abstract: Reine, wasserfreie Hexafluorkieselsäure, H2[SiF6], ist immer noch schwer fassbar, obwohl ihre Existenz in wässriger Lösung ausführlich dokumentiert wurde. Beim Einengen entsprechender Lösungen tritt unausweichlich Zersetzung unter Bildung von Tetrafluorsilan und Fluorwasserstoff ein. Auch Oxoniumhexafluorosilicat ist bei Raumtemperatur nicht stabil. Partielle Substitution von Fluoratomen im [SiF6]2−-Ion durch stark elektronenziehende Perfluoralkylgruppen führt zu einer erheblichen Stabilisierung der entsprechenden Fluorkieselsäure-Derivate. So wurden mono- und bis(pentafluorethyl)substituierte Fluorkieselsäuren durch Umsetzung der zugehörigen Halogensilane (Si(C2F5)nX4−n, mit X=Cl, Br) mit Flusssäure (wässrige HF) synthetisiert und in Form ihrer Oxonium-Salze als farblose Feststoffe isoliert. Die Präparate sind bei Raumtemperatur mehrere Monate ohne Zersetzung beständig und repräsentieren die ersten stabilen Hydrate von Fluorkieselsäuren.Wasserfreie Hexafluorkieselsäure, H2[SiF6], ist eine schwer zu fassende Spezies, obwohl ihre Existenz in wässrigen Lösung ausführlich dokumentiert wurde. Substitution von Fluoratomen durch Pentafluorethylgruppen führt zu einer erheblichen Stabilisierung der entsprechenden Fluorkieselsäuren. Mono- und Bis(pentafluorethyl)-Fluorkieselsäuren wurden durch Umsetzung der jeweiligen Halogensilane mit wässriger Flusssäure erhalten.
      PubDate: 2016-11-09T15:51:44.201382-05:
      DOI: 10.1002/ange.201609097
       
  • Biocatalytic Properties and Structural Analysis of Phloroglucinol
           Reductases
    • Authors: David Conradt; Bianca Hermann, Stefan Gerhardt, Oliver Einsle, Michael Müller
      Pages: 15760 - 15763
      Abstract: Phloroglucinol reductases (PGRs) are involved in anaerobic degradation in bacteria, in which they catalyze the dearomatization of phloroglucinol into dihydrophloroglucinol. We identified three PGRs, from different bacterial species, that are members of the family of NAD(P)H-dependent short-chain dehydrogenases/reductases (SDRs). In addition to catalyzing the reduction of the physiological substrate, the three enzymes exhibit activity towards 2,4,6-trihydroxybenzaldehyde, 2,4,6-trihydroxyacetophenone, and methyl 2,4,6-trihydroxybenzoate. Structural elucidation of PGRcl and comparison to known SDRs revealed a high degree of conservation. Several amino acid positions were identified as being conserved within the PGR subfamily and might be involved in substrate differentiation. The results enable the enzymatic dearomatization of monoaromatic phenol derivatives and provide insight into the functional diversity that may be found in families of enzymes displaying a high degree of structural homology.Gebündelte Vielfalt: Drei Phloroglucin-Reduktasen wurden entdeckt, die im Vergleich zu anderen, strukturell stark homologen SDRs jeweils eine enge, genau begrenzte Substratspezifität aufweisen, wobei eine 1,3,5-Anordnung der Hydroxygruppen essenziell war. Sie ermöglichen die enzymatische Desaromatisierung von monoaromatischen Phenolderivaten und geben Einblick in die funktionelle Diversität innerhalb von Enzymfamilien mit stark homologen Strukturen.
      PubDate: 2016-11-22T07:40:24.852969-05:
      DOI: 10.1002/ange.201607494
       
  • Efficient Coupling Reaction of Quinone Monoacetal with Phenols Leading to
           Phenol Biaryls
    • Authors: Tohru Kamitanaka; Koji Morimoto, Kohei Tsuboshima, Daichi Koseki, Hitoho Takamuro, Toshifumi Dohi, Yasuyuki Kita
      Pages: 15764 - 15767
      Abstract: A simple and efficient synthesis of phenol biaryls by the cross-couplings of quinone monoacetals (QMAs) and phenols is reported. The Brønsted acid catalytic system in 1,1,1,3,3,3-hexafluoro-2-propanol was found to be particularly efficient for this transformation. This reaction can be extended to the synthesis of various phenol biaryls, including sterically hindered biaryls, with yields ranging from 58 to 90 % under mild reaction conditions and in a highly regiospecific manner.Unsymmetrische Phenol-Biaryle entstehen als Hauptprodukte der MeSO3H-katalysierten Kupplung von Chinonmonoacetalen (QMAs) mit Phenolen. In diesem Reaktionssystem ist die Wahl der Säure entscheidend für die Produktbildung. Die Methode nutzt preisgünstige Reagentien, ist gut mit Luft verträglich und vermeidet den Einsatz teurer Katalysatoren.
      PubDate: 2016-11-15T05:53:12.924218-05:
      DOI: 10.1002/ange.201608013
       
  • Experimental and Computational Studies of the Copper Borate Complexes
           [(NHC)Cu(HBEt3)] and [(NHC)Cu(HB(C6F5)3)]
    • Authors: Lee R. Collins; Nasir A. Rajabi, Stuart A. Macgregor, Mary F. Mahon, Michael K. Whittlesey
      Pages: 15768 - 15772
      Abstract: The synthesis of the Cu-borate complexes [(6Mes)Cu(HBR3)] featuring the unusual [HBEt3]− (5) and [HB(C6F5)3]− (6) ligands is described. Experimental and computational studies show both compounds feature a direct Cu–H interaction, but that while 5 is two-coordinate, 6 displays an additional, stabilizing Cu–Cipso(C6F5) interaction.Ungewöhnliche Cu-Boratkomplexe [(6Mes)Cu(HBR3)] (R=Et (I), C6F5 (II)) werden beschrieben. Experimentelle und theoretische Studien belegen für beide Spezies eine direkte Cu-H-Wechselwirkung, wobei I ein zweifach koordiniertes Cu enthält und II eine zusätzliche Cu-Cipso-Wechselwirkung zu einem C6F5-Substituenten aufweist.
      PubDate: 2016-11-15T05:58:58.207537-05:
      DOI: 10.1002/ange.201608081
       
  • Preparation of Vinyl Arenes by Nickel-Catalyzed Reductive Coupling of Aryl
           Halides with Vinyl Bromides
    • Authors: Jiandong Liu; Qinghua Ren, Xinghua Zhang, Hegui Gong
      Pages: 15773 - 15777
      Abstract: This work emphasizes the synthesis of substituted vinyl arenes by reductive coupling of aryl halides with vinyl bromides under mild and easy-to-operate nickel-catalyzed reaction conditions. A broad range of aryl halides, including heteroaromatics, and vinyl bromides were employed to yielding products in moderate to excellent yields with high functional-group tolerance. The nickel-catalytic system displays good chemoselectivity between the two C(sp2)-halide coupling partners, thus demonstrating a mechanistic pathway distinct from other stepwise protocols.Ähnlich, doch nicht gleich: Eine nickelkatalysierte reduktive Kreuzkupplung von Elektrophilen verknüpft Arylhalogenide und Vinylbromide zu Vinylarenen. Da das Katalysatorsystem zwischen den beiden C(sp2)-Halogeniden als Kupplungspartner unterscheidet, muss ein anderer Reaktionsmechanismus vorliegen als bei stufenweisen Umsetzungen.
      PubDate: 2016-11-11T07:15:28.176217-05:
      DOI: 10.1002/ange.201607959
       
  • Practical Photocatalytic Trifluoromethylation and
           Hydrotrifluoromethylation of Styrenes in Batch and Flow
    • Authors: Natan J. W. Straathof; Sten E. Cramer, Volker Hessel, Timothy Noël
      Pages: 15778 - 15782
      Abstract: Styrenes represent a challenging class of substrates for current radical trifluoromethylation and hydrotrifluoromethylation methods due to a myriad of potential side reactions. Herein, we describe the development of mild, selective and broadly applicable photocatalytic trifluoromethylation and hydrotrifluoromethylation protocols for these challenging substrates. The methods use fac-Ir(ppy)3, visible light and inexpensive CF3I and can be applied to a diverse set of vinylarene substrates. The use of continuous-flow photochemical reaction conditions allowed to reduce the reaction time and increase the reaction selectivity.Eine robuste photokatalytische Methode für die radikalische Trifluormethylierung und Hydrotrifluormethylierung von Styrolen wurde entwickelt. Die milden Reaktionsbedingungen ermöglichten die Umsetzung einer Vielzahl von Vinylarenen. Photochemie unter kontinuierlichem Fluss erlaubt die Verringerung der Reaktionszeiten und eine Steigerung der Selektivität.
      PubDate: 2016-11-15T05:52:57.505207-05:
      DOI: 10.1002/ange.201608297
       
  • A Two-Coordinate Cyclic (Alkyl)(amino)silylene: Balancing Thermal
           Stability and Reactivity
    • Authors: Tomoyuki Kosai; Shintaro Ishida, Takeaki Iwamoto
      Pages: 15783 - 15787
      Abstract: A crystalline two-coordinate cyclic (alkyl)(amino)silylene (1) was successfully synthesized and isolated. Its 29Si NMR and UV/Vis spectra indicate that the electronic properties of 1 fall between those of cyclic dialkylsilylenes and diaminosilylenes. At very low temperature, the color of a solution of 1 turned from colorless to yellow, which was monitored by UV/Vis spectroscopy. DFT calculations supported the hypothesis that head-to-head dimers (disilenes) with a very long Si–Si distance are formed at such low temperatures. Although 1 is thermally stable, it readily undergoes cycloadditions, Si−H insertions, and photochemical reactions with benzene similar to dialkylsilylenes. At higher temperatures, 1 is also susceptible to intermolecular benzylic C−H insertion reactions, as well as unprecedented dehydrogenation reactions with cyclohexa-1,4-diene and 9,10-dihydroanthracene to afford benzene and anthracene, respectively.Etwas von beidem: Ein zweifach koordiniertes cyclisches (Alkyl)(amino)silylen wurde synthetisiert und in Form farbloser Kristalle isoliert. Spektroskopische Daten weisen für die elektronischen Eigenschaften von 1 eine Mittelstellung zwischen cyclischen Dialkylsilylenen und Diaminosilylenen aus. Silylen 1 ist thermisch stabil, dimerisiert aber reversibel bei tiefer Temperatur. Mit Cyclohexa-1,4-dien und 9,10-Dihydroanthracen reagiert 1 zu Benzol bzw. Anthracen.
      PubDate: 2016-11-15T05:53:44.25069-05:0
      DOI: 10.1002/ange.201608736
       
  • Palladium-Catalyzed Fluorination of Cyclic Vinyl Triflates: Effect of
           TESCF3 as an Additive
    • Authors: Yuxuan Ye; Takashi Takada, Stephen L. Buchwald
      Pages: 15788 - 15792
      Abstract: A method for the palladium-catalyzed fluorination of cyclic vinyl triflates has been developed. As with several previous palladium-catalyzed fluorination reactions using fluoride salts, controlling the regioselectivity presented a challenge in developing a practical synthetic procedure. The addition of triethyl(trifluoromethyl)silane (TESCF3) was found to effectively address this problem and resulted in drastically improved regioselectivities in this palladium-catalyzed fluorination reaction. This discovery, along with the use of a new biarylphosphine ligand, allowed for the development of an efficient and highly regioselective protocol for the fluorination of vinyl triflates. This method is compatible with a range of sensitive functional groups and provides access to five-, six-, and seven-membered cyclic vinyl fluorides.Regioselektives Additiv: Ein Verfahren zur palladiumkatalysierten Fluorierung cyclischer Vinyltriflate wurde entwickelt. Fünf-, sechs- und siebengliedrige Vinyltriflate sowie einige acyclische Substrate reagierten effizient bei guter Verträglichkeit mit funktionellen Gruppen. Der Zusatz von Triethyl(trifluormethyl)silan (TESCF3) verbesserte die Regioselektivität der Methode in drastischer Weise.
      PubDate: 2016-11-15T02:45:25.254987-05:
      DOI: 10.1002/ange.201608927
       
  • A Platinum(IV) Anticancer Prodrug Targeting Nucleotide Excision Repair To
           Overcome Cisplatin Resistance
    • Authors: Zhigang Wang; Zoufeng Xu, Guangyu Zhu
      Pages: 15793 - 15797
      Abstract: DNA damage response plays a key role not only in maintaining genome integrity but also in mediating the antitumor efficacy of DNA-damaging antineoplastic drugs. Herein, we report the rational design and evaluation of a PtIV anticancer prodrug inhibiting nucleotide excision repair (NER), one of the most pivotal processes after the formation of cisplatin-induced DNA damage that deactivates the drug and leads to drug resistance in the clinic. This dual-action prodrug enters cells efficiently and causes DNA damage while simultaneously inhibiting NER to promote apoptotic response. The prodrug is strongly active against the proliferation of cisplatin-resistant human cancer cells with an up to 88-fold increase in growth inhibition compared with cisplatin, and the prodrug is much more active than a mixture of cisplatin and an NER inhibitor. Our study highlights the importance of targeting downstream pathways after the formation of Pt-induced DNA damage as a novel strategy to conquer cisplatin resistance.Keine DNA-Reparatur: Ein Platin(IV)-basiertes Antikrebs-Prodrug, das die Nukleotidexzisionsreparatur inhibiert, wurde entwickelt, um Cisplatin-Resistenzen zu überwinden. Die Zytotoxizität dieses Wirkstoffs war bis zu 88-mal höher als die von Cisplatin in Cisplatin-resistenten humanen Krebszellen.
      PubDate: 2016-10-13T08:10:31.043338-05:
      DOI: 10.1002/ange.201608936
       
  • Rhodium-Catalyzed Diastereoselective Cyclization of
           Allenyl-Sulfonylcarbamates: A Stereodivergent Approach to 1,3-Aminoalcohol
           Derivatives
    • Authors: Pierre A. Spreider; Alexander M. Haydl, Marc Heinrich, Bernhard Breit
      Pages: 15798 - 15802
      Abstract: A diastereoselective and stereodivergent rhodium-catalyzed intramolecular coupling of sulfonylcarbamates with terminal allenes is described and it provides selective access to 1,3-aminoalcohol derivatives, scaffolds found in bioactive compounds. The reaction is compatible with a large range of different functional groups, thus furnishing products with high diastereoselectivities and yields. Moreover, multigram scale reactions, as well as the application of suitable product transformations were demonstrated.Syn oder anti: Die diastereoselektive und stereodivergente rhodiumkatalysierte intramolekulare Kupplung von Sulfonylcarbamaten mit terminalen Allenen ermöglicht die selektive Synthese von N-allylischen 1,3-Aminoalkohol-Derivaten. Die Reaktion ist mit zahlreichen funktionellen Gruppen kompatibel und ergibt die Produkte in hohen Diastereoselektivitäten und Ausbeuten.
      PubDate: 2016-11-15T05:53:24.553574-05:
      DOI: 10.1002/ange.201609366
       
  • Macroscopic Hexagonal Tubes of 3 d–4 f Metallocycles
    • Authors: Jianfeng Wu; Lang Zhao, Li Zhang, Xiao-Lei Li, Mei Guo, Annie K. Powell, Jinkui Tang
      Pages: 15803 - 15807
      Abstract: The self-assembly of three giant hexagonal 3d–4f metallocycles with inner diameters of 16.4, 16.5, and 16.4 Å, is described. Hexagonal metallocycles were stacked along the crystallographic c axis, producing unique hexagonal macroscopic tubular single crystals. The assembly mechanism of the tubular crystals was investigated. Remarkably, all three hexagonal metallocycles show typical single-molecule magnet behavior, benefiting from the ferromagnetic couplings between the 3d and 4f ions.Riesige hexagonale Heterometallocyclen mit einem Innendurchmesser von 16.4 Å wurden entworfen. Durch kombinierte Auflösungsprozesse und Transformation aggregieren sie zu makroskopisch röhrenartigen hohlen Kristallen.
      PubDate: 2016-11-11T07:35:28.321262-05:
      DOI: 10.1002/ange.201609539
       
  • Ultrahigh-Resolution Diffusion-Ordered Spectroscopy
    • Authors: Mohammadali Foroozandeh; Laura Castañar, Lucas G. Martins, Davy Sinnaeve, Guilherme Dal Poggetto, Claudio F. Tormena, Ralph W. Adams, Gareth A. Morris, Mathias Nilsson
      Pages: 15808 - 15811
      Abstract: Diffusion-ordered spectroscopy (DOSY) is an effective method for the analysis of intact mixtures, but the quality of results is critically limited by resolution in the NMR dimension. A new experiment integrating diffusion weighting into the PSYCHE method for pure shift NMR spectroscopy allows DOSY spectra to be measured with ultrahigh NMR resolution at improved sensitivity.Diffusionsgeordnete Spektroskopie (DOSY) ist eine effektive Methode für die Analyse intakter Mischungen, aber die Qualität der Ergebnisse wird durch die Auflösung in der NMR-Dimension entscheidend begrenzt. Die Aufnahme von pure-shift-DOSY-Spektren mit besonders hoher NMR-Auflösung bei verbesserter Sensitivität wurde hier durch die Kombination von Diffusionsgewichtung mit der PSYCHE-Methode ermöglicht.
      PubDate: 2016-11-10T08:17:01.991211-05:
      DOI: 10.1002/ange.201609676
       
  • Topological Polymer Chemistry Enters Surface Science: Linear versus Cyclic
           Polymer Brushes
    • Authors: Giulia Morgese; Lucca Trachsel, Matteo Romio, Mohammad Divandari, Shivaprakash N. Ramakrishna, Edmondo M. Benetti
      Pages: 15812 - 15817
      Abstract: The cyclic polymer topology strongly alters the interfacial, physico-chemical properties of polymer brushes, when compared to the linear counterparts. In this study, we especially concentrated on poly-2-ethyl-2-oxazoline (PEOXA) cyclic and linear grafts assembled on titanium oxide surfaces by the “grafting-to” technique. The smaller hydrodynamic radius of ring PEOXAs favors the formation of denser brushes with respect to linear analogs. Denser and more compact cyclic brushes generate a steric barrier that surpasses the typical entropic shield by a linear brush. This phenomenon, translates into an improved resistance towards biological contamination from different protein mixtures. Moreover, the enhancement of steric stabilization coupled to the intrinsic absence of chain ends by cyclic brushes, produce surfaces displaying a super-lubricating character when they are sheared against each other. All these topological effects pave the way for the application of cyclic brushes for surface functionalization, enabling the modulation of physico-chemical properties that could be just marginally tuned by applying linear grafts.Cyclische Polymerbürsten: Die Topologie der cyclischen Polymere verändert stark die Grenzflächeneigenschaften von Polymerbürsten. Das kleine hydrodynamische Volumen gekoppelt mit der ausgeprägt cyclischen Architektur erzeugt Oberflächenassemblate mit höherer Pfropfdichte, besserer sterischer Stabilisierung sowie verbesserten Antifouling- und Schmiereigenschaften im Vergleich zu entsprechenden linearen Bürsten.
      PubDate: 2016-10-24T03:30:47.324975-05:
      DOI: 10.1002/ange.201607309
       
  • Induction of Strong Long-Lived Room-Temperature Phosphorescence of
           N-Phenyl-2-naphthylamine Molecules by Confinement in a Crystalline
           Dibromobiphenyl Matrix
    • Authors: Jinbei Wei; Baoyan Liang, Ruihong Duan, Zong Cheng, Chenglong Li, Tianlei Zhou, Yuanping Yi, Yue Wang
      Pages: 15818 - 15822
      Abstract: The design and preparation of metal-free organic materials that exhibit room-temperature phosphorescence (RTP) is a very attractive topic owing to potential applications in organic optoelectronic devices. Herein, we present a facile approach to efficient and long-lived organic RTP involving the doping of N-phenylnaphthalen-2-amine (PNA) or its derivatives into a crystalline 4,4′-dibromobiphenyl (DBBP) matrix. The resulting materials showed strong and persistent RTP emission with a quantum efficiency of approximately 20 % and a lifetime of a few to more than 100 milliseconds. Bright white dual emission containing blue fluorescence and yellowish-green RTP from the PNA-doped DBBP crystals was also confirmed by Commission Internationale de l'Eclairage (CIE) coordinates of (x=0.29–0.31, y=0.38–0.41).Dotierung verstärkt Emission: Eine starke Raumtemperaturphosphoreszenz (RTP) bei rein organischen Verbindungen wurde durch Dotieren von PNA und PNA-Derivaten in eine DBBP-Kristallmatrix induziert. Das PNA/DBBP-Kristallsystem emittierte eine stabile und langlebige RTP unter Umgebungsbedingungen (siehe Bild).
      PubDate: 2016-11-15T05:58:10.075433-05:
      DOI: 10.1002/ange.201607653
       
  • A Conformationally Stable Contorted Hexabenzoovalene
    • Authors: Kevin Baumgärtner; Ana Lucia Meza Chincha, Andreas Dreuw, Frank Rominger, Michael Mastalerz
      Pages: 15823 - 15827
      Abstract: Contorted two-dimensional aromatic molecules are fascinating synthetic targets because they are molecular “cutouts” of nonplanar graphene structures, fullerenes, or carbon nanotubes. In most cases, the curvature is introduced by the implementation of either five-, seven-, or eight-membered rings into the fused aromatic plane. Curvature can also be generated for two-dimensional systems consisting of six-membered rings exclusively, by the introduction of cove or fjord regions. The synthesis of a polycyclic aromatic hydrocarbon (PAH) that contains two peripheral triptycene units and six tert-butyl substituents is described. As a result of steric repulsion, the structure is highly contorted with two phenylene blades of the peripheral triptycene units oriented almost coplanar with respect to each other at a distance of 16 Å, as has been verified by single crystal X-ray diffraction. The conformation is stable in solution even at a temperature of 150 °C. Additionally, internal tert-butyl groups could be selectively removed, allowing a UV/Vis-spectroscopic comparison of two structures with the same π-system, but different degrees of contortion.Gleich und doch anders: Zwei Hexabenzoovalene mit demselben π-Gerüst unterscheiden sich deutlich in ihrer konformativen Stabilität und Emission. Der entscheidende Faktor ist das Vorliegen oder Fehlen zweier tert-Butyl-Gruppen.
      PubDate: 2016-09-21T06:20:36.102171-05:
      DOI: 10.1002/ange.201607740
       
  • Chirality-Assisted Synthesis of a Very Large Octameric Hydrogen-Bonded
           Capsule
    • Authors: Daniel Beaudoin; Frank Rominger, Michael Mastalerz
      Pages: 15828 - 15832
      Abstract: The strategy of chirality-assisted synthesis, which makes use of enantiomerically pure building blocks that are designed to associate in a single geometric orientation, was applied to synthesize an octameric hydrogen-bonded capsule with a cavity volume of 2300 Å3. This cube-shaped capsule forms even host–guest complexes with tetraalkylammonium ions, and accommodates the large tetrahexadecylammonium cation in its cavity. The use of an enantiopure building block was shown to be highly beneficial for capsule formation, whereas its racemate also generates a large amount of ill-defined aggregates in solution and crystallizes as a hydrogen-bonded network.Der Erfolg kommt mit der enantiomerenreinen Verbindung: Eine octamere molekulare Kapsel, die durch Wasserstoffbrücken zusammengehalten wird, war mithilfe der Chiralitäts-gestützten Synthese zugänglich. In ihren 2300 Å3 großen Hohlraum können ionische wie neutrale Gäste eingeschlossen werden. Das racemische Ausgangsmaterial führte zu einer Mischung, die auch oligomere und polymere Spezies enthielt.
      PubDate: 2016-11-10T08:14:01.69104-05:0
      DOI: 10.1002/ange.201609073
       
  • Chemically Delaminated Free-Standing Ultrathin Covalent Organic Nanosheets
    • Authors: M. Abdul Khayum; Sharath Kandambeth, Shouvik Mitra, Sanoop B. Nair, Anuja Das, Samadhan S. Nagane, Rabibrata Mukherjee, Rahul Banerjee
      Pages: 15833 - 15837
      Abstract: Covalent organic nanosheets (CONs) are a new class of porous thin two-dimensional (2D) nanostructures that can be easily designed and functionalized and could be useful for separation applications. Poor dispersion, layer restacking, and difficult postsynthetic modifications are the major hurdles that need to be overcome to fabricate scalable CON thin films. Herein, we present a unique approach for the chemical exfoliation of an anthracene-based covalent organic framework (COF) to N-hexylmaleimide-functionalized CONs, to yield centimeter-sized free-standing thin films through layer-by-layer CON assembly at the air–water interface. The thin-layer fabrication technique presented here is simple, scalable, and does not require any surfactants or stabilizing agents.Die chemische Exfoliation von Anthracen-basierten kovalenten organischen Gerüste (COFs) zu kovalenten organischen Nanoschichten (CONs) wurde durch eine [4+2]-Diels-Alder-Cycloaddition mit N-Hexylmaleimid ermöglicht. Zentimetergroße freistehende CON-Filme wurden dann durch schichtweise Abscheidung an der Luft-Wasser-Grenzfläche erhalten.
      PubDate: 2016-11-10T08:00:34.05662-05:0
      DOI: 10.1002/ange.201607812
       
  • Rhodium(III)-Catalyzed Alkenylation–Annulation of closo-Dodecaborate
           Anions through Double B−H Activation at Room Temperature
    • Authors: Yuanbin Zhang; Yuji Sun, Furong Lin, Jiyong Liu, Simon Duttwyler
      Pages: 15838 - 15843
      Abstract: 1,2,3-Trisubstituted closo-dodecaborates with B−O, B−N, and B−C bonds as well as a fused borane oxazole ring have been synthesized by rhodium-catalyzed direct cage B−H alkenylation and annulation of ureido boranes in the first reported example of regioselective B−H bond functionalization of the [B12H12]2− cage by transition-metal catalysis. This reaction proceeded at room temperature under ambient conditions and exhibited excellent selectivity for efficient monoalkenylation with good functional-group tolerance. The urea moiety enabled B−H activation by acting as a directing group, was incorporated in the oxazole ring in situ, and also avoided multiple alkenylation. A possible mechanism is proposed on the basis of the isolation of a rhodium agostic intermediate and control experiments.Regioselektive Funktionalisierung: 1,2,3-Trisubstituierte closo-Dodecaborate mit B-O-, B-N- und B-C-Bindungen wurden durch Rhodium(III)-katalysierte doppelte B-H-Aktivierung von Ureidoboranen synthetisiert (siehe Schema). Ein möglicher Mechanismus für diese regioselektive B-H-Bindungsfunktionalisierung des [B12H12]2−-Käfigs wird anhand von Kontrollexperimenten und einer isolierbaren Rhodium-Zwischenstufe vorgeschlagen.
      PubDate: 2016-11-15T05:53:18.511368-05:
      DOI: 10.1002/ange.201607867
       
  • Ruthenation of Non-stacked Guanines in DNA G-Quadruplex Structures:
           Enhancement of c-MYC Expression
    • Authors: Jéssica Rodríguez; Jesús Mosquera, José R. Couceiro, M. Eugenio Vázquez, José L. Mascareñas
      Pages: 15844 - 15847
      Abstract: Guanine quadruplexes (GQs) are compact four-stranded DNA structures that play a key role in the control of a variety of biological processes, including gene transcription. Bulky ruthenium complexes featuring a bipyridine, a terpyridine, and one exchangeable ligand ([Ru(terpy)(bpy)X]n+) are able to metalate exposed guanines present in the GQ of the c-MYC promoter region that are not involved in quadruplex base pairing. qRT-PCR and western-blot experiments indicated that the complexes promote a remarkable increase in the expression of this oncogene. We also show that exchangeable thioether ligands (X=RSR′, Met) allow regulation of the metalating activity of the complex with visible light.G-sucht, G-funden: Sperrige [Ru(terpy)(bpy)X]n+-Komplexe eignen sich für die spezifische Metallierung zugänglicher Guanineinheiten in der G-Quadruplex-Struktur der Promotorregion von c-MYC. Durch die Ruthenierung wird die Expression dieses Onkogens verstärkt. Austauschbare Thioetherliganden ermöglichen die Regulierung der Metallierungsaktivität mithilfe von sichtbarem Licht.
      PubDate: 2016-11-17T09:00:54.386379-05:
      DOI: 10.1002/ange.201607965
       
  • Selective Production of Carbon Monoxide via Methane Oxychlorination over
           Vanadyl Pyrophosphate
    • Authors: Vladimir Paunović; Guido Zichittella, Réne Verel, Amol P. Amrute, Javier Pérez-Ramírez
      Pages: 15848 - 15852
      Abstract: A catalytic process is demonstrated for the selective conversion of methane into carbon monoxide via oxychlorination chemistry. The process involves addition of HCl to a CH4–O2 feed to facilitate C−H bond activation under mild conditions, leading to the formation of chloromethanes, CH3Cl and CH2Cl2. The latter are oxidized in situ over the same catalyst, yielding CO and recycling HCl. A material exhibiting chlorine evolution by HCl oxidation, high activity to oxidize chloromethanes into CO, and no ability to oxidize CO, is therefore essential to accomplish this target. Following these design criteria, vanadyl pyrophosphate (VPO) was identified as an outstanding catalyst, exhibiting a CO yield up to approximately 35 % at 96 % selectivity and stable behavior. These findings constitute a basis for the development of a process enabling the on-site valorization of stranded natural-gas reserves using CO as a highly versatile platform molecule.Natürlich wertvoll: Durch die hoch selektive Kohlenmonoxiderzeugung aus Methan mittels Oxychlorierung über Vanadylpyrophosphat könnten isolierte Erdgasvorkommen nutzbar gemacht werden. Die Umwandlung in wertvolle Chemikalien und Brennstoffe vor Ort mit Kohlenmonoxid als Plattform erscheint möglich.
      PubDate: 2016-11-16T09:16:33.797269-05:
      DOI: 10.1002/ange.201608165
       
  • Symmetry-Breaking Charge Transfer and Hydrogen Bonding: Toward
           Asymmetrical Photochemistry
    • Authors: Bogdan Dereka; Arnulf Rosspeintner, Maciej Krzeszewski, Daniel T. Gryko, Eric Vauthey
      Pages: 15853 - 15857
      Abstract: Symmetry-breaking charge transfer upon photoexcitation of a linear A-π-D-π-A molecule (D and A being electron donating and accepting groups) could be visualized using ultrafast time-resolved infrared spectroscopy by monitoring the CN stretching modes on the A units. Whereas in apolar solvents, the S1 state remains symmetric and quadrupolar, symmetry breaking occurs within ca. 100 fs in polar solvents as shown by the presence of two CN bands, instead of one in apolar solvents, with a splitting that increases with polarity. In protic solvents, symmetry breaking is significantly amplified by H-bonding interactions, which are the strongest at the CN group with the highest basicity. In strongly protic solvents, the two CN bands transform in about 20 ps into new bands with a larger splitting, and the lifetime of the S1 state is substantially reduced. This is attributed to the formation of an excited asymmetric tight H-bond complex.Schlagseite: Der Symmetriebruch bei der Anregung eines quadrupolaren Moleküls mit Licht kann durch ultraschnelle transiente Infrarotspektroskopie visualisiert werden. Polare Solvatisierung bewirkt eine unsymmetrische Verteilung der elektronischen Anregung binnen 100 fs, und H-Brücken verstärken dies. In den meisten protischen Lösungsmitteln liegt daher ein komplett unsymmetrischer, eng über H-Brücken gebundener Anregungskomplex vor.
      PubDate: 2016-11-15T02:45:33.839241-05:
      DOI: 10.1002/ange.201608567
       
  • Microsecond Timescale Dynamics of GDP-Bound Ras Underlies the Formation of
           Novel Inhibitor-Binding Pockets
    • Authors: Yunyun Mao; Haijie Yao, Hui Wang, Peng Cheng, Dong Long
      Pages: 15858 - 15861
      Abstract: The recent discovery of inhibitory compounds binding to distinct pockets on GDP-bound Ras has renewed the view on the druggability of this crucial cancer driver. However, the origin of these pockets, which are not readily formed in the crystal structure in the absence of the compounds, is yet unclear. Herein, we explored the intrinsic flexibility of Ras⋅GDP on microsecond to millisecond timescales using relaxation-based NMR experiments, and identified substantial slow dynamics with τex of 34 μs at 5 °C, which maps to the regions showing a high level of correlation with those displaying conformational differences between the inhibitor-bound and free states. These findings, which have been demonstrated in both wild-type Ras and the oncogenic mutant (G12V), support the mechanism of extended conformational selection for Ras–inhibitor interactions where the small molecules redistribute the protein conformational ensemble favoring the final bound states.Relaxationsbasierte NMR-Spektroskopie wurde genutzt, um die intrinsische Dynamik von GDP-gebundenem Ras zu analysieren. Die Messungen ergeben eine langsame Austauschkorrelationszeit von 34 μs bei 5 °C und bestätigen einen hohen Grad an Korrelation mit den bei der Bindung niedermolekularer Inhibitoren umlagernden Regionen. Die Ergebnisse stützen den Mechanismus der Populationsumverteilung für die Bildung der neuartigen Bindungstaschen.
      PubDate: 2016-11-17T08:15:34.351362-05:
      DOI: 10.1002/ange.201608653
       
  • Structure and Reactivity of an Asymmetric Synthetic Mimic of Nitrogenase
           Cofactor
    • Authors: Kazuki Tanifuji; Nathaniel Sickerman, Chi Chung Lee, Takayuki Nagasawa, Kosuke Miyazaki, Yasuhiro Ohki, Kazuyuki Tatsumi, Yilin Hu, Markus W. Ribbe
      Pages: 15862 - 15865
      Abstract: The Mo nitrogenase catalyzes the ambient reduction of N2 to NH3 at its M-cluster site. A complex metallocofactor with a core composition of [MoFe7S9C], the M-cluster, can be extracted from the protein scaffold and used to facilitate the catalytic reduction of CN−, CO, and CO2 into hydrocarbons in the isolated state. Herein, we report the synthesis, structure, and reactivity of an asymmetric M-cluster analogue with a core composition of [MoFe5S9]. This analogue, referred to as the Mo-cluster, is the first synthetic example of an M-cluster mimic with Fe and Mo positioned at opposite ends of the cluster. Moreover, the ability of the Mo-cluster to reduce C1 substrates to hydrocarbons suggests the feasibility of developing nitrogenase-based biomimetic approaches to recycle C1 waste into fuel products.Ein synthetisches Analogon (Mo-Cluster) des Nitrogenase-Cofaktors (M-Cluster) mit einem [MoFe7S9C]-Kern katalysiert die Reduktion von C1-Substraten zu Kohlenwasserstoffen. Dieses Ergebnis lässt vermuten, dass die Entwicklung Nitrogenase-basierter biomimetischer Methoden zur Rückgewinnung nützlicher Kraftstoffe aus C1-Abfällen möglich sein sollte.
      PubDate: 2016-11-10T08:00:42.626924-05:
      DOI: 10.1002/ange.201608806
       
  • Light-Controlled Ion Transport through Biomimetic DNA-Based Channels
    • Authors: Pei Li; Ganhua Xie, Xiang-Yu Kong, Zhen Zhang, Kai Xiao, Liping Wen, Lei Jiang
      Pages: 15866 - 15870
      Abstract: Light-controlled nanochannels are fabricated through self-assembling azobenzene-incorporated DNA (Azo-DNA) strands to regulate ion transport. By switching between collapsed and relaxed states using visible and ultraviolet light alternately, the Azo-DNA channels can be opened and closed because the conformation of Azo-DNA changes, that is, Azo-DNA is used as switchable controlling unit. In addition to sharing short response time and reversibility with other photoresponsive apparatuses, the Azo-DNA-based nanochannel system has advantages in good biocompatibility and versatile design, which could potentially be applied in light-controlled drug release, optical information storage, and logic networks.Lichtgesteuerte Nanokanäle wurden durch Modifizieren von Polymerkanälen mit Azobenzol-derivatisierten DNA-Strängen (Azo-DNA) hergestellt. Durch Schalten zwischen sichtbarem und UV-Licht werden die Kanäle geöffnet und geschlossen, da sich die Konformation der Azo-DNA ändert.
      PubDate: 2016-11-17T09:01:01.011895-05:
      DOI: 10.1002/ange.201609161
       
  • A Hyperpolarizable 1H Magnetic Resonance Probe for Signal Detection
           15 Minutes after Spin Polarization Storage
    • Authors: Soumya S. Roy; Philip Norcott, Peter J. Rayner, Gary G. R. Green, Simon B. Duckett
      Pages: 15871 - 15874
      Abstract: Nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) are two extremely important techniques with applications ranging from molecular structure determination to human imaging. However, in many cases the applicability of NMR and MRI are limited by inherently poor sensitivity and insufficient nuclear spin lifetime. Here we demonstrate a cost-efficient and fast technique that tackles both issues simultaneously. We use the signal amplification by reversible exchange (SABRE) technique to hyperpolarize the target 1H nuclei and store this polarization in long-lived singlet (LLS) form after suitable radiofrequency (rf) pulses. Compared to the normal scenario, we achieve three orders of signal enhancement and one order of lifetime extension, leading to 1H NMR signal detection 15 minutes after the creation of the detected states. The creation of such hyperpolarized long-lived polarization reflects an important step forward in the pipeline to see such agents used as clinical probes of disease.Kernspinresonanz-Marker: Die Lebensdauer von 1H-hyperpolarisierten NMR-Signalen kann ausgehend vom Normalniveau um eine Größenordnung erhöht werden, was deren Detektion 15 Minuten nach Erzeugung des Anfangszustands ermöglicht (siehe Bild; RF=Radiofrequenz). Dieses Ergebnis wurde mit einem stark gekoppelten 1H-Spinpaar in einem Pyridazin-basierten Molekül erzielt.
      PubDate: 2016-11-15T05:58:06.860192-05:
      DOI: 10.1002/ange.201609186
       
  • Quantitative Method to Investigate the Balance between Metabolism and
           Proteome Biomass: Starting from Glycine
    • Authors: Haiwei Gu; Patrick A. Carroll, Jianhai Du, Jiangjiang Zhu, Fausto Carnevale Neto, Robert N. Eisenman, Daniel Raftery
      Pages: 15875 - 15879
      Abstract: The balance between metabolism and biomass is very important in biological systems; however, to date there has been no quantitative method to characterize the balance. In this methodological study, we propose to use the distribution of amino acids in different domains to investigate this balance. It is well known that endogenous or exogenous amino acids in a biological system are either metabolized or incorporated into free amino acids (FAAs) or proteome amino acids (PAAs). Using glycine (Gly) as an example, we demonstrate a novel method to accurately determine the amounts of amino acids in various domains using serum, urine, and cell samples. As expected, serum and urine had very different distributions of FAA- and PAA-Gly. Using Tet21N human neuroblastoma cells, we also found that Myc(oncogene)-induced metabolic reprogramming included a higher rate of metabolizing Gly, which provides additional evidence that the metabolism of proliferating cells is adapted to facilitate producing new cells. It is therefore anticipated that our method will be very valuable for further studies of the metabolism and biomass balance that will lead to a better understanding of human cancers.Die Balance zwischen Metabolismus und Biomasse ist sehr wichtig in biologischen Systemen, bisher gab es jedoch keine quantitative Methode zu ihrer Charakterisierung. Es wird vorgeschlagen, die relative Verteilung von Aminosäuren in unterschiedlichen Domänen zur Quantifizierung dieser Balance heranzuziehen. Am Beispiel von Glycin wird demonstriert, dass diese Verteilung ein universeller phänotypischer Parameter für routinemäßige Messungen sein könnte.
      PubDate: 2016-11-15T05:53:20.625798-05:
      DOI: 10.1002/ange.201609236
       
  • Ultrashort Beryllium−Beryllium Distances Rivalling Those of
           Metal−Metal Quintuple Bonds Between Transition Metals
    • Authors: Caixia Yuan; Xue-Feng Zhao, Yan-Bo Wu, Xiaotai Wang
      Pages: 15880 - 15884
      Abstract: Chemical bonding is at the heart of chemistry. Recent work on high bond orders between homonuclear transition metal atoms has led to ultrashort metal−metal (TM−TM) distances defined as dM−M
      PubDate: 2016-11-16T05:01:10.917462-05:
      DOI: 10.1002/ange.201609455
       
  • Explaining the Size Dependence in Platinum-Nanoparticle-Catalyzed
           Hydrogenation Reactions
    • Authors: Licheng Bai; Xin Wang, Qiang Chen, Yifan Ye, Haoquan Zheng, Jinghua Guo, Yadong Yin, Chuanbo Gao
      Pages: 15885 - 15890
      Abstract: Hydrogenation reactions are industrially important reactions that typically require unfavorably high H2 pressure and temperature for many functional groups. Herein we reveal surprisingly strong size-dependent activity of Pt nanoparticles (PtNPs) in catalyzing this reaction. Based on unambiguous spectral analyses, the size effect has been rationalized by the size-dependent d-band electron structure of the PtNPs. This understanding enables production of a catalyst with size of 1.2 nm, which shows a sixfold increase in turnover frequency and 28-fold increase in mass activity in the regioselective hydrogenation of quinoline, compared with PtNPs of 5.3 nm, allowing the reaction to proceed under ambient conditions with unprecedentedly high reaction rates. The size effect and the synthesis strategy developed herein may provide a general methodology in the design of metal-nanoparticle-based catalysts for a broad range of organic syntheses.Stark größenabhängig ist die Aktivität von Pt-Nanopartikeln (PtNPs) als Katalysatoren der regioselektiven Hydrierung von Chinolin (siehe Bild). Dieses Resultat wird mit der größenabhängigen d-Band-Elektronenstruktur der PtNPs erklärt, die sich auf die Wechselwirkungen mit Reaktanten und Produkten auswirkt.
      PubDate: 2016-11-11T07:35:39.700023-05:
      DOI: 10.1002/ange.201609663
       
  • Copper Catalysis in Living Systems and In Situ Drug Synthesis
    • Authors: Jessica Clavadetscher; Scott Hoffmann, Annamaria Lilienkampf, Logan Mackay, Rahimi M. Yusop, Sebastien A. Rider, John J. Mullins, Mark Bradley
      Pages: 15891 - 15895
      Abstract: The copper-catalyzed azide–alkyne cycloaddition (CuAAC) reaction has proven to be a pivotal advance in chemical ligation strategies with applications ranging from polymer fabrication to bioconjugation. However, application in vivo has been limited by the inherent toxicity of the copper catalyst. Herein, we report the application of heterogeneous copper catalysts in azide–alkyne cycloaddition processes in biological systems ranging from cells to zebrafish, with reactions spanning from fluorophore activation to the first reported in situ generation of a triazole-containing anticancer agent from two benign components, opening up many new avenues of exploration for CuAAC chemistry.Gezielte Wirkstoffsynthese: Biokompatible Kupfernanopartikel wurden synthetisiert und als Katalysatoren in der Aktivierung eines Profluorophors in lebenden Zellen und in Zebrafisch-Embryonen eingesetzt. Zusätzlich wurde ein Krebsmedikament in situ aus zwei unschädlichen Komponenten synthetisiert, das bei Ovarialkarzinomzellen zu Apoptose führte.
      PubDate: 2016-11-15T05:59:00.995071-05:
      DOI: 10.1002/ange.201609837
       
  • Synthesis of Atisine, Ajaconine, Denudatine, and Hetidine Diterpenoid
           Alkaloids by a Bioinspired Approach
    • Authors: Xiao-Huan Li; Min Zhu, Zhi-Xiu Wang, Xiao-Yu Liu, Hao Song, Dan Zhang, Feng-Peng Wang, Yong Qin
      Pages: 15896 - 15900
      Abstract: A unified approach to four different (atisine, ajaconine, denudatine, and hetidine) diterpenoid alkaloid skeletons was developed and applied to the total synthesis of the natural products dihydroajaconine (2, atisine type) and gymnandine (4, denudatine type). The synthesis features a biogenetically inspired strategy that relies on C−H oxidation, aza-pinacol coupling, and aza-Prins cyclization as key steps.Wertvolle Kerne: Ein vereinheitlichter Syntheseansatz für vier Arten von Diterpenoid-Alkaloiden mit käfigartigen Strukturen wurde entwickelt, der auf einer biogenetisch inspirierten C-H-Oxidation, einer Aza-Pinakolkupplung und einer Aza-Prins-Cyclisierung basiert (siehe Schema). Die vier Kernstrukturen dienten als Ausgangspunkt für weitere Verbindungen, darunter die Naturstoffe Dihydroajaconin und Gymnandin.
      PubDate: 2016-11-17T09:00:50.94952-05:0
      DOI: 10.1002/ange.201609882
       
  • Engineered Substrate-Specific Delta PKC Antagonists to Enhance Cardiac
           Therapeutics
    • Authors: Nir Qvit; Opher S. Kornfeld, Daria Mochly-Rosen
      Pages: 15901 - 15908
      Abstract: Most protein kinases phosphorylate multiple substrates, each of which induces different and sometimes opposing functions. Determining the role of phosphorylation of each substrate following a specific stimulus is challenging but is essential to elucidate the role of that substrate in the signaling event. Here we describe a rational approach to identify inhibitors of delta protein kinase C (δPKC), each inhibiting the phosphorylation of only one of δPKC′s substrates. δPKC regulates many signaling events and we hypothesized that a docking inhibitor of a given substrate to δPKC should selectively abrogate the phosphorylation of only that substrate, without affecting the phosphorylation of the other δPKC substrates. Here we report the development of selective inhibitors of three δPKC substrates (in vitro Kd≈3 nm); two greatly reduced ischemia-induced cardiac injury with an IC50 of ≈200 nm and the third had no effect, indicating that its respective substrate phosphorylation by δPKC has no role in the response to cardiac ischemia and reperfusion. The three inhibitors are highly specific; even at 1 μm, the phosphorylation of other δPKC protein substrates was unaffected. The rationale we describe is likely applicable for the development of other substrate-specific inhibitors as well.Rational entworfene Peptidinhibitoren der Delta-Proteinkinase C (δPKC) hemmen selektiv die Wechselwirkung des Enzyms mit nur einem seiner Substrate (siehe Bild; grün: δPKC, rot: Inhibitor). Die Ergebnisse geben Aufschluss über die Rolle des Substrats beim Schutz vor Durchblutungsstörungen des Herzens.
      PubDate: 2016-11-17T08:15:46.892486-05:
      DOI: 10.1002/ange.201605429
       
  • Innenrücktitelbild: Selective Production of Carbon Monoxide via Methane
           Oxychlorination over Vanadyl Pyrophosphate (Angew. Chem. 50/2016)
    • Authors: Vladimir Paunović; Guido Zichittella, Réne Verel, Amol P. Amrute, Javier Pérez-Ramírez
      Pages: 15909 - 15909
      Abstract: Riesige Erdgasvorkommen, die andernfalls abgefackelt würden, können potenziell zur Herstellung von Chemikalien und Treibstoffen dienen. In ihrer Zuschrift auf S. 15848 ff. stellen J. Pérez-Ramírez und Mitarbeiter einen katalytischen Oxychlorierungsprozess vor, der Methan in den vielseitigen chemischen Grundbaustein Kohlenmonoxid umwandelt. Vanadylpyrophosphat als Katalysator liefert eine stete Kohlenmonoxidausbeute um 35 % bei 96 % Selektivität.
      PubDate: 2016-11-16T05:01:06.128355-05:
      DOI: 10.1002/ange.201610858
       
  • Rücktitelbild: A Platinum(IV) Anticancer Prodrug Targeting Nucleotide
           Excision Repair To Overcome Cisplatin Resistance (Angew. Chem. 50/2016)
    • Authors: Zhigang Wang; Zoufeng Xu, Guangyu Zhu
      Pages: 15910 - 15910
      Abstract: DNA-Reparatur …… spielt nicht nur bei der Erhaltung der Genomintegrität eine wichtige Rolle, sondern reduziert auch die Wirksamkeit DNA-schädigender Antineoplastika. In der Zuschrift auf S. 15793 ff. beschreiben G. Zhu et al. ein PtIV-basiertes Antikrebs-Prodrug, das die Nukleotidexzisionsreparatur (NER) inhibiert, um Cisplatin-Resistenzen zu überwinden. Das Prodrug ist mit Cisplatin- und Inhibitor-Einheiten ausgerüstet und verursacht DNA-Schädigungen bei gleichzeitiger NER-Hemmung, was zu deutlich erhöhter Zytotoxizität in Cisplatin-resistenten humanen Krebszellen führt.
      PubDate: 2016-11-03T08:21:20.398195-05:
      DOI: 10.1002/ange.201610431
       
 
 
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