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  Subjects -> CHEMISTRY (Total: 848 journals)
    - ANALYTICAL CHEMISTRY (47 journals)
    - CHEMISTRY (602 journals)
    - CRYSTALLOGRAPHY (22 journals)
    - ELECTROCHEMISTRY (26 journals)
    - INORGANIC CHEMISTRY (41 journals)
    - ORGANIC CHEMISTRY (45 journals)
    - PHYSICAL CHEMISTRY (65 journals)

CHEMISTRY (602 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: 29)
ACS Chemical Neuroscience     Full-text available via subscription   (Followers: 16)
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: 37)
ACS Nano     Full-text available via subscription   (Followers: 187)
ACS Photonics     Full-text available via subscription   (Followers: 7)
ACS Synthetic Biology     Full-text available via subscription   (Followers: 20)
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: 45)
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: 11)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 17)
Advances in Drug Research     Full-text available via subscription   (Followers: 22)
Advances in Enzyme Research     Open Access   (Followers: 6)
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: 17)
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: 64)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 14)
American Journal of Chemistry     Open Access   (Followers: 24)
American Journal of Plant Physiology     Open Access   (Followers: 12)
American Mineralogist     Full-text available via subscription   (Followers: 8)
Anadolu University Journal of Science and Technology     Open Access  
Analyst     Full-text available via subscription   (Followers: 42)
Angewandte Chemie     Hybrid Journal   (Followers: 138)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 188)
Annales UMCS, Chemia     Open Access   (Followers: 1)
Annals of Clinical Chemistry and Laboratory Medicine     Open Access   (Followers: 1)
Annual Reports in Computational Chemistry     Full-text available via subscription   (Followers: 3)
Annual Reports Section A (Inorganic Chemistry)     Full-text available via subscription   (Followers: 3)
Annual Reports Section B (Organic Chemistry)     Full-text available via subscription   (Followers: 7)
Annual Review of Chemical and Biomolecular Engineering     Full-text available via subscription   (Followers: 12)
Annual Review of Food Science and Technology     Full-text available via subscription   (Followers: 14)
Anti-Infective Agents     Hybrid Journal   (Followers: 3)
Antiviral Chemistry and Chemotherapy     Hybrid Journal  
Applied Organometallic Chemistry     Hybrid Journal   (Followers: 6)
Applied Spectroscopy     Full-text available via subscription   (Followers: 23)
Applied Surface Science     Hybrid Journal   (Followers: 23)
Arabian Journal of Chemistry     Open Access   (Followers: 6)
ARKIVOC     Open Access   (Followers: 2)
Asian Journal of Biochemistry     Open Access   (Followers: 1)
Atomization and Sprays     Full-text available via subscription   (Followers: 3)
Australian Journal of Chemistry     Hybrid Journal   (Followers: 6)
Autophagy     Hybrid Journal   (Followers: 2)
Avances en Quimica     Open Access   (Followers: 1)
Biochemical Pharmacology     Hybrid Journal   (Followers: 9)
Biochemistry     Full-text available via subscription   (Followers: 243)
Biochemistry Insights     Open Access   (Followers: 5)
Biochemistry Research International     Open Access   (Followers: 6)
BioChip Journal     Hybrid Journal  
Bioinorganic Chemistry and Applications     Open Access   (Followers: 9)
Bioinspired Materials     Open Access   (Followers: 3)
Biointerface Research in Applied Chemistry     Open Access   (Followers: 2)
Biointerphases     Open Access   (Followers: 1)
Biology, Medicine, & Natural Product Chemistry     Open Access  
Biomacromolecules     Full-text available via subscription   (Followers: 17)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 10)
Biomedical Chromatography     Hybrid Journal   (Followers: 7)
Biomolecular NMR Assignments     Hybrid Journal   (Followers: 3)
BioNanoScience     Partially Free   (Followers: 4)
Bioorganic & Medicinal Chemistry     Hybrid Journal   (Followers: 110)
Bioorganic & Medicinal Chemistry Letters     Hybrid Journal   (Followers: 98)
Bioorganic Chemistry     Hybrid Journal   (Followers: 10)
Biopolymers     Hybrid Journal   (Followers: 17)
Biosensors     Open Access   (Followers: 1)
Biotechnic and Histochemistry     Hybrid Journal   (Followers: 2)
Bitácora Digital     Open Access  
Boletin de la Sociedad Chilena de Quimica     Open Access  
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 3)
Bulletin of the Chemical Society of Japan     Full-text available via subscription   (Followers: 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: 26)
Carbon     Hybrid Journal   (Followers: 65)
Catalysis for Sustainable Energy     Open Access   (Followers: 5)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 7)
Catalysis Science and Technology     Free   (Followers: 6)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 3)
Catalysts     Open Access   (Followers: 6)
Cellulose     Hybrid Journal   (Followers: 5)
Cereal Chemistry     Full-text available via subscription   (Followers: 4)
ChemBioEng Reviews     Full-text available via subscription   (Followers: 1)
ChemCatChem     Hybrid Journal   (Followers: 7)
Chemical and Engineering News     Free   (Followers: 10)
Chemical Bulletin of Kazakh National University     Open Access  
Chemical Communications     Full-text available via subscription   (Followers: 70)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 22)
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: 146)
Chemical Science     Open Access   (Followers: 19)
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: 30)
Chemistry & Industry     Hybrid Journal   (Followers: 4)
Chemistry - A European Journal     Hybrid Journal   (Followers: 124)
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: 3)
Chemistry International     Hybrid Journal   (Followers: 1)
Chemistry Letters     Full-text available via subscription   (Followers: 45)
Chemistry of Materials     Full-text available via subscription   (Followers: 158)
Chemistry of Natural Compounds     Hybrid Journal   (Followers: 9)
Chemistry-Didactics-Ecology-Metrology     Open Access  
ChemistryOpen     Open Access   (Followers: 2)
Chemkon - Chemie Konkret, Forum Fuer Unterricht Und Didaktik     Hybrid Journal  
Chemoecology     Hybrid Journal   (Followers: 2)
Chemometrics and Intelligent Laboratory Systems     Hybrid Journal   (Followers: 15)
Chemosensors     Open Access  
ChemPhysChem     Hybrid Journal   (Followers: 8)
ChemPlusChem     Hybrid Journal   (Followers: 1)
ChemTexts     Hybrid Journal  
CHIMIA International Journal for Chemistry     Full-text available via subscription   (Followers: 3)
Chinese Journal of Chemistry     Hybrid Journal   (Followers: 6)
Chinese Journal of Polymer Science     Hybrid Journal   (Followers: 10)
Chromatographia     Hybrid Journal   (Followers: 24)
Chromatography Research International     Open Access   (Followers: 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: 10)
Colloids and Surfaces B: Biointerfaces     Hybrid Journal   (Followers: 8)
Combinatorial Chemistry & High Throughput Screening     Hybrid Journal   (Followers: 3)
Combustion Science and Technology     Hybrid Journal   (Followers: 18)
Comments on Inorganic Chemistry: A Journal of Critical Discussion of the Current Literature     Hybrid Journal   (Followers: 1)
Composite Interfaces     Hybrid Journal   (Followers: 5)
Comprehensive Chemical Kinetics     Full-text available via subscription   (Followers: 2)
Comptes Rendus Chimie     Full-text available via subscription  
Comptes Rendus Physique     Full-text available via subscription   (Followers: 1)
Computational and Theoretical Chemistry     Hybrid Journal   (Followers: 9)
Computational Biology and Chemistry     Hybrid Journal   (Followers: 11)
Computational Chemistry     Open Access   (Followers: 2)
Computers & Chemical Engineering     Hybrid Journal   (Followers: 10)
Coordination Chemistry Reviews     Full-text available via subscription  
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: 10)
Current Catalysis     Hybrid Journal   (Followers: 1)
Current Metabolomics     Hybrid Journal   (Followers: 3)
Current Opinion in Colloid & Interface Science     Hybrid Journal   (Followers: 8)
Current Opinion in Molecular Therapeutics     Full-text available via subscription   (Followers: 15)
Current Research in Chemistry     Open Access   (Followers: 8)
Current Science     Open Access   (Followers: 45)
Dalton Transactions     Full-text available via subscription   (Followers: 18)
Detection     Open Access   (Followers: 2)
Developments in Geochemistry     Full-text available via subscription   (Followers: 2)
Diamond and Related Materials     Hybrid Journal   (Followers: 11)
Dislocations in Solids     Full-text available via subscription  
Doklady Chemistry     Hybrid Journal  
Drying Technology: An International Journal     Hybrid Journal   (Followers: 3)
Eclética Química     Open Access   (Followers: 1)
Ecological Chemistry and Engineering S     Open Access   (Followers: 2)
Ecotoxicology and Environmental Contamination     Open Access  
Educación Química     Open Access   (Followers: 1)
Education for Chemical Engineers     Hybrid Journal   (Followers: 5)
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
  [138 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  [1605 journals]
  • Frontispiz: 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: Wirkstofftransportsysteme In der Zuschrift auf S. 986 ff. stellen T. W. Tan, T. C. Hughes et al. ein lichtgesteuertes Wirkstofftransportsystem aus Au-Nanopartikeln in einem Agarose-Hydrogel vor. Sichtbares Licht bewirkt die Erweichung der Hydrogelmatrix und Freisetzung des Therapeutikums.
      PubDate: 2017-01-13T04:10:35.148851-05:
      DOI: 10.1002/ange.201780461
       
  • Carbon-Carbon Bond Formation in a Weak Ligand Field: Leveraging Open Shell
           First Row Transition Metal Catalysts
    • Authors: Paul James Chirik
      Abstract: Unique features of Earth abundant transition metal catalysts are reviewed in the context of catalytic carbon-carbon bond forming reactions. Aryl-substituted bis(imino)pyridine iron and cobalt dihalide compounds, when activated with alkyl aluminum reagents, form highly active catalysts for the polymerization of ethylene. Open shell iron and cobalt alkyl complexes have been synthesized that serve as single component olefin polymerization catalysts. Reduced bis(imino)pyridine iron- and cobalt dinitrogen compounds have also been discovered that promote the unique [2+2] cycloaddition of unactivated terminal alkenes. Electronic structure studies support open shell intermediates, a deviation from traditional strong field organometallic compounds that promote catalytic C-C bond formation.
      PubDate: 2017-01-12T14:45:24.350363-05:
      DOI: 10.1002/ange.201611959
       
  • Highly Porous Thermoelectric Nanocomposites with Low Thermal Conductivity
           and High Figure of Merit from Large-Scale Solution-Synthesized
           Bi2Te2.5Se0.5 Hollow Nanostructures
    • Authors: Biao Xu; Tianli Feng, Matthias T. Agne, Lin Zhou, Xiulin Ruan, G. Jeffery Snyder, Yue Wu
      Abstract: To enhance the performance of thermoelectric materials and enable access to their widespread applications, it is beneficial yet challenging to synthesize hollow nanostructures in large quantities, with high porosity, low thermal conductivity (κ) and excellent figure of merit (z T). Herein we report a scalable (ca. 11.0 g per batch) and low-temperature colloidal processing route for Bi2Te2.5Se0.5 hollow nanostructures. They are sintered into porous, bulk nanocomposites (phi 10 mm×h 10 mm) with low κ (0.48 W m−1 K−1) and the highest z T (1.18) among state-of-the-art Bi2Te3−xSex materilas. Additional benefits of the unprecedented low relative density (68–77 %) are the large demand reduction of raw materials and the improved portability. This method can be adopted to fabricate other porous phase-transition and thermoelectric chalcogenide materials and will pave the way for the implementation of hollow nanostructures in other fields.Poröse thermoelektrische Komposite mit einer extrem niedrigen thermischen Leitfähigkeit und hoher Leistungszahl wurden in großen Mengen aus in Lösung synthetisierten hohlen Bi2Te2.5Se0.5-Nanostrukturen hergestellt. Die leichtgewichtigen Materialien erfordern weniger Rohmaterial und verbessern die Tragbarkeit thermoelektrischer Komponenten.
      PubDate: 2017-01-12T09:15:51.933313-05:
      DOI: 10.1002/ange.201612041
       
  • Au/La2Ti2O7 Nanostructures Sensitized with Black Phosphorous for
           Plasmon-Enhanced Photocatalytic Hydrogen Production in Visible and
           Near-Infrared Light
    • Authors: Mingshan Zhu; Xiaoyan Cai, Mamoru Fujitsuka, Junying Zhang, Tetsuro Majima
      Abstract: Efficient utilization of solar energy is a high-priority target and the search for suitable materials as photocatalysts that not only can harvest the broad wavelength of solar light, from UV to near-infrared (NIR) region, but also can achieve high and efficient solar-to-hydrogen conversion is one of the most challenging missions. Herein, using Au/La2Ti2O7 (BP-Au/LTO) sensitized with black phosphorus (BP), a broadband solar response photocatalyst was designed and used as efficient photocatalyst for H2 production. The optimum H2 production rates of BP-Au/LTO were about 0.74 and 0.30 mmol g−1 h−1 at wavelengths longer than 420 nm and 780 nm, respectively. The broad absorption of BP and plasmonic Au contribute to the enhanced photocatalytic activity in the visible and NIR light regions. Time-resolved diffuse reflectance spectroscopy revealed efficient interfacial electron transfer from excited BP and Au to LTO which is in accordance with the observed high photoactivities.Solare Energieumwandlung: Der durch sichtbares und nahinfrarotes (NIR) Licht aktivierte Au/La2Ti2O7-Photokatalysator wurde mit schwarzen Phosphor (BP) sensibilisiert und zur photokatalytischen Wasserstofferzeugung genutzt. Die breiten Absorptionen von BP und plasmonischem Au tragen zur verbesserten katalytischen Aktivität des Katalysators im sichtbaren und NIR-Bereich bei.
      PubDate: 2017-01-12T09:15:48.562882-05:
      DOI: 10.1002/ange.201612315
       
  • Water Catalysis of the Reaction between Methanol and OH at 294 K and the
           Atmospheric Implications
    • Authors: Rafael A. Jara-Toro; Federico J. Hernández, Raúl A. Taccone, Silvia I. Lane, Gustavo A. Pino
      Abstract: The rate coefficient for the reaction CH3OH+OH was determined by means of a relative method in a simulation chamber under quasi-real atmospheric conditions (294 K, 1 atm of air) and variable humidity or water concentration. Under these conditions, a quadratic dependence of the rate coefficient for the reaction CH3OH+OH on the water concentration was found. Thus the catalytic effect of water is not only important at low temperatures, but also at room temperature. The detailed mechanism responsible of the reaction acceleration is still unknown. However, this dependence should be included in the atmospheric global models since it is expected to be important in humid regions as in the tropics. Additionally, it could explain several differences regarding the global and local atmospheric concentration of methanol in tropical areas, for which many speculations about the sinks and sources of methanol have been reported.Der Geschwindigkeitskoeffizient für die Oxidation von CH3OH durch das OH-Radikal hängt vom Quadrat der Luftfeuchte ab. Dieser Zusammenhang bestimmt die Lebensdauer von CH3OH in der Troposphäre, die in trockenen Regionen wie Wüsten 14 Tage, in feuchten Regionen wie den Tropen aber nur 4 Tage beträgt.
      PubDate: 2017-01-12T09:15:41.705374-05:
      DOI: 10.1002/ange.201612151
       
  • Palladium-Catalyzed Remote Aryldifluoroalkylation of Alkenyl Aldehydes
    • Authors: Xingliang Nie; Cungui Cheng, Gangguo Zhu
      Abstract: A palladium-catalyzed three-component reaction between fluoroalkyl bromides, arylboronic acids, and alkenyl aldehydes has been developed and provides facile access to 5-, 6-, or 7-difluoroalkylated ketones under very mild reaction conditions. The resultant products can be smoothly converted into CF2-containing tetrahydronaphthalenes by a novel silver-catalyzed intramolecular decarboxylative cyclization of 5-aryl-2,2-difluoropentanoic acids.5-, 6- oder 7-difluoralkylierte Ketone sind über die Titelreaktion unter milden Bedingungen zugänglich. Die Produkte können mithilfe einer silberkatalysierten intramolekularen decarboxylierenden Cyclisierung für 5-Aryl-2,2-difluorpentansäuren glatt in CF2-Gruppen enthaltende Tetrahydronaphthaline umgewandelt werden.
      PubDate: 2017-01-12T09:15:37.988156-05:
      DOI: 10.1002/ange.201611697
       
  • A Stereoconvergent Cyclopropanation Reaction of Styrenes
    • Authors: Ana M. del Hoyo; Ana G. Herraiz, Marcos G. Suero
      Abstract: Seit römischer Zeit ist Tarragona eine Heimstätte für neue Entwicklungen und Entdeckungen. In dieser guten Tradition präsentieren M. G. Suero et al. vom Institute of Chemical Research of Catalonia in ihrer Zuschrift (10.1002/ange.201610924) nun ein neues Reaktivitätskonzept. Beim Studium einer Photoredoxreaktion für die stereokonvergente Cyclopropanierung von Alkenen fanden sie als Schlüsselintermediat ein Iodmethylradikal, bezeichnet als ein radikalisches Carbenoid. Obwohl es ein Radikal ist, ist seine Reaktivität ähnlich bzw. komplementär zu der von Singulett- und Triplett-Carbenen, was neue Möglichkeiten in der Carbenchemie eröffnet.
      PubDate: 2017-01-12T09:15:35.739587-05:
      DOI: 10.1002/ange.201700067
       
  • A 11-Steps Total Synthesis of Magellanine through a Gold(I)-Catalyzed
           Dehydro Diels–Alder Reaction
    • Authors: Philippe McGee; Geneviève Bétournay, Francis Barabé, Louis Barriault
      Abstract: We have developed an innovative strategy for the formation of angular carbocycles via a gold(I)-catalyzed dehydro Diels–Alder reaction. This transformation provides rapid access to a variety of complex angular cores in excellent diastereoselectivities and high yields. The usefulness of this AuI-catalyzed cycloaddition was further demonstrated by accomplishing a 11-steps total synthesis of (±)-magellanine.Aufbau von Komplexität: Eine effiziente und einfach anzuwendende Methode ermöglicht die Synthese von angularen Carbocyclen durch eine Gold(I)-katalysierte Dehydro-Diels-Alder-Reaktion. Diese Umwandlung bietet einen schnellen Zugang zu komplexen angularen Kernmotiven mit exzellenten Diastereoselektivitäten und wurde für die 11-stufige Totalsynthese von (±)-Magellanin genutzt.
      PubDate: 2017-01-12T09:11:27.357085-05:
      DOI: 10.1002/ange.201611606
       
  • An Exonuclease III-Powered, On-Particle Stochastic DNA Walker
    • Authors: Xiangmeng Qu; Dan Zhu, Guangbao Yao, Shao Su, Jie Chao, Huajie Liu, Xiaolei Zuo, Lihua Wang, Jiye Shi, Lianhui Wang, Wei Huang, Hao Pei, Chunhai Fan
      Abstract: DNA-based machines have attracted rapidly growing interest owing to their potential in drug delivery, biocomputing, and diagnostic applications. Herein, we report a type of exonuclease III (Exo III)-powered stochastic DNA walker that can autonomously move on a spherical nucleic acid (SNA)-based 3D track. The motion is propelled by unidirectional Exo III digestion of hybridized DNA tracks in a burnt-bridge mechanism. The operation of this Exo III-propelled DNA walker was monitored in real time and at the single-particle resolution using total internal reflection fluorescence microscopy (TIRF). We further interrogated the morphological effect of the 3D track on the nuclease activity, which suggested that the performance of the DNA walker was critically dependent upon the DNA density and the track conformation. Finally, we demonstrated potential bioanalytical applications of this SNA-based stochastic DNA walker by exploiting movement-triggered cascade signal amplification.Exonuklease III treibt einen stochastischen DNA-Schreiter an, der sich auf der Oberfläche einer sphärischen Nukleinsäure bewegt. Der Schreiter spricht empfindlich auf die Nukleinsäuredichte an, und diese Ansprechempfindlichkeit kann für mögliche bioanalytische Anwendungen an Amplifizierungsreaktionen gekoppelt werden.
      PubDate: 2017-01-12T09:11:21.168977-05:
      DOI: 10.1002/ange.201611777
       
  • Determining Electrochemical Surface Stress of Single Nanowires
    • Authors: Hui Wang; Xiaonan Shan, Hui Yu, Yan Wang, Wolfgang Schmickler, Hong-Yuan Chen, Nongjian Tao
      Abstract: Electrochemical surface stress is important in nanomaterials because of their large surface-to-volume ratios, which lead to unique mechanical and electrocatalytic properties, but directly measuring this quantity has been challenging. Here we report on experimental determination of the surface stress, and associated electrochemical processes of a single gold nanowire with an optical imaging technique. We show that surface stress changes linearly and reversibly with the potential between 0 and 0.8 V versus Ag/AgCl, but abruptly with large hysteresis, associated with the oxidation and reduction of the nanowire, between 0.8 and 1.5 V. The potential derivative of the surface stress closely resembles the cyclic voltammograms. We described the observations in terms of anion adsorption and surface oxidation/reduction. This work demonstrates a new approach to study electrochemical processes and the associated surface stress changes of nanomaterials.Goldnanodrähte im Stress: Die elektrische Spannung in individuellen Goldnanodrähten wurde als Funktion der elektrochemisch kontrollierten ladungsinduzierten Oberflächenbelastung gemessen. Die Längenänderung eines einzelnen Nanodrahts konnte in situ beobachtet werden, während das Potential des Nanodrahts verändert wurde (siehe Bild).
      PubDate: 2017-01-12T09:11:16.853914-05:
      DOI: 10.1002/ange.201611297
       
  • Enantioselective and Regiodivergent Addition of Purines to Terminal
           Allenes: Synthesis of Abacavir
    • Authors: Niels Thieme; Bernhard Breit
      Abstract: The rhodium-catalyzed atom-economic asymmetric N-selective intermolecular addition of purine derivatives to terminal allenes is reported. Branched allylic purines were obtained in high yields, regioselectivity and outstanding enantioselectivity utilizing a Rh/Josiphos catalyst. Conversely, linear selective allylation of purines could be realized in good to excellent regio- and E/Z-selectivity with a Pd/dppf catalyst system. Furthermore, the new methodology was applied to a straightforward asymmetric synthesis of carbocyclic nucleoside abacavir.Eine atomökonomische und regiodivergente Rh- und Pd-katalysierte Kupplung von Purinderivaten und terminalen Allenen wurde entwickelt. Vielfältig funktionalisierte Substrate konnten mit hoher Regioselektivität und exzellentem Enantiomerenüberschuss umgesetzt werden. Die Methode wurde für eine einfache Synthese des carbocyclischen Nukleosids Abacavir genutzt.
      PubDate: 2017-01-12T09:11:13.553283-05:
      DOI: 10.1002/ange.201610876
       
  • Conformational SERS Classification of K-Ras Point Mutations for Cancer
           Diagnostics
    • Authors: Judit Morla-Folch; Patricia Gisbert-Quilis, Matteo Masetti, Eduardo Garcia-Rico, Ramon A. Alvarez-Puebla, Luca Guerrini
      Abstract: Point mutations in Ras oncogenes are routinely screened for diagnostics and treatment of tumors (especially in colorectal cancer). Here, we develop an optical approach based on direct SERS coupled with chemometrics for the study of the specific conformations that single-point mutations impose on a relatively large fragment of the K-Ras gene (141 nucleobases). Results obtained offer the unambiguous classification of different mutations providing a potentially useful insight for diagnostics and treatment of cancer in a sensitive, fast, direct and inexpensive manner.Klassifizierung von Mutationen: Ein optischer Ansatz basierend auf direkter oberflächenverstärkter Raman-Streuung (SERS) gekoppelt mit chemometrischen Methoden wurde entwickelt, mit dem sich Einzelpunktmutationen in relativ großen Fragmenten des K-Ras-Gens unterscheiden lassen. Die Methode nutzt die spezifischen Konformationen aus, die durch Basensubstitutionen der DNA-Stränge entstehen.
      PubDate: 2017-01-12T09:11:08.5293-05:00
      DOI: 10.1002/ange.201611243
       
  • Entfernung von organischen, anorganischen und mikrobiellen Schadstoffen
           aus Wasser durch immobilisierte Polyoxometallat-ionische Flüssigkeiten
           (POM-SILPs)
    • Authors: Sven Herrmann; Laura De Matteis, Jesús M. de la Fuente, Scott G. Mitchell, Carsten Streb
      Abstract: Die gleichzeitige Entfernung organischer, anorganischer und mikrobieller Schadstoffe aus Wasser durch ein einziges Material bietet deutliche Vorteile, insbesondere für den dezentralen Einsatz in entlegenen Regionen. Dieser Beitrag beschreibt ein Komposit, welches diese Aufgabe erfüllt. Es besteht aus Polyoxometallat-ionischen Flüssigkeiten (POM-ILs) die auf porösem Silika immobilisiert sind (POM-SILP; supported ionic liquid phase) Dazu wurde eine wasserunlösliche POM-IL bestehend aus antimikrobiellen Alkylammonium-Kationen und Polyoxometallat-Anionen mit einer Metallbindungsstelle auf porösem Silika abgeschieden. Mit dem Komposit lassen sich in einem einfachen Filtrationsprozess Schwermetallkationen, Radionuklide, organische und mikrobielle Verunreinigungen aus Wasser entfernen. Die neue Materialklasse zeigt, wie molekulares Design und Materialentwicklung zu innovativen Kompositen für die Wasseraufbereitung führen.Multifunktionelle immobilisierte Polyoxometallat-ionische Flüssigkeiten (POM-SILPs) wurden für die Entferung organischer, anorganischer und mikrobieller Verunreinigungen aus Wasser entwickelt. Jede Komponente zielt selektiv auf eine Verunreinigung ab, sodass gifitige Schwermetalle, Radionuklide, aromatische Farbstoffe und Bakterien aus Wasser zielgerichtet entfernt werden können.
      PubDate: 2017-01-12T09:11:05.862353-05:
      DOI: 10.1002/ange.201611072
       
  • Olefin Insertion into a Pd–F Bond: Catalyst Reactivation Following β-F
           Elimination in Ethylene/Vinyl Fluoride Copolymerization
    • Authors: Shinji Wada; Richard F. Jordan
      Abstract: The discrete (phosphinoarenesulfonate)Pd fluoride complex (POBp,OMe)PdF(lutidine), where POBp,OMe=(2-MeOC6H4)(2-{2,6-(MeO)2C6H3}C6H4)(2-SO3-5-MeC6H3)P, inserts vinyl fluoride (VF) to form (POBp,OMe)PdCH2CHF2(lutidine) and inserts multiple ethylene (E) units to generate polyethylene that contains −CH2F chain ends. These results provide strong evidence that the −CHF2 and −CH2F chain ends in E/VF copolymer generated by (phosphinoarenesulfonate)PdR catalysts form by β-F elimination of Pd(β-F-alkyl) species, VF or E insertion of the resulting (PO)PdF species, and subsequent chain growth. These results also imply that β-F elimination is not an important catalyst deactivation reaction in this system.Lieber aktiv bleiben: Ein (Phosphinoarensulfonat)Pd-Fluoridkomplex wurde synthetisiert, der ungewöhnliche Insertionen von Vinylfluorid und Ethylen eingeht und Pd-CH2CHF2- und Pd-CH2CH2F-Spezies bildet. Eine wichtige Folge davon ist, dass in (Phosphinoarensulfonat)PdR-katalysierten Copolymerisationen unter Ethylen/Vinylfluorid-Insertion die β-F-Eliminierung zu einem Kettentransfer führt, statt zur Katalysatordeaktivierung.
      PubDate: 2017-01-12T09:11:04.457772-05:
      DOI: 10.1002/ange.201611198
       
  • Ein S-oxygenierter [NiFe]-Komplex als Modell für Sulfenat- intermediate
           einer O2-toleranten Hydrogenase
    • Authors: Nils J. Lindenmaier; Stefan Wahlefeld, Eckhard Bill, Tibor Szilvási, Christopher Eberle, Shenglai Yao, Peter Hildebrandt, Marius Horch, Ingo Zebger, Matthias Driess
      Abstract: Um das Wissen über die aerobe Umsetzung von Diwasserstoff durch eine lösliche, NAD+-reduzierende [NiFe]-Hydrogenase auf molekularer Ebene zu vertiefen, wird hier der erste bioinspirierte, heterobimetallische S-oxygenierte [NiFe]-Komplex als strukturelles und schwingungsspektroskopisches Modell des sauerstoffinhibierten aktiven Zentrums vorgestellt. Dieser S-oxygenierte Komplex und seine nicht-S-oxygenierte Variante wurden vollständig charakterisiert. Die elektronischen Strukturen beider Verbindungen wurden experimentell sowie durch theoretische Untersuchungen aufgeklärt, wobei ein besonderes Augenmerk auf der verbrückenden Sulfenatogruppe lag. Aufbauend auf den schwingungsspektroskopischen Eigenschaften dieser Verbindungen können außerdem neue Strategien zur Untersuchung von S-oxygenierten Intermediaten in Hydrogenasen und verwandten Enzymen vorgeschlagen werden.Beschwingende Einblicke: Der erste S-oxygenierte [NiFe]-Komplex stellt ein strukturelles und schwingungsspektroskopisches Modell des S-oxygenierten aktiven Zentrums der NAD+-reduzierenden [NiFe]-H2ase aus Ralstonia eutropha dar. Seine spektroskopische und theoretische Untersuchung lässt auf eine stark polare SO-Einheit schließen, die einen Ansatz für zukünftige Untersuchungen des Enzyms bietet.
      PubDate: 2017-01-12T09:11:02.823355-05:
      DOI: 10.1002/ange.201611069
       
  • An Unusually Delocalized Mixed-Valence State of a Cyanidometal-Bridged
           Compound Induced by Thermal Electron Transfer
    • Authors: Xiao Ma; Chen-Sheng Lin, Xiao-Quan Zhu, Sheng-Min Hu, Tian-Lu Sheng, Xin-Tao Wu
      Abstract: The heterometallic complexes trans-[Cp(dppe)FeNCRu(o-bpy)CNFe(dppe)Cp][PF6]n (1[PF6]n, n=2, 3, 4; o-bpy=1,2-bis(2,2′-bipyridyl-6-yl)ethane, dppe=1,2-bis(diphenylphosphino)ethane, Cp=1,3-cyclopentadiene) in three distinct states have been synthesized and fully characterized. 13+[PF6]3 and 14+[PF6]4 are the one- and two-electron oxidation products of 12+[PF6]2, respectively. The investigated results suggest that 1[PF6]3 is a Class II mixed valence compound. 1[PF6]4 after a thermal treatment at 400 K shows an unusually delocalized mixed valence state of [FeIII-NC-RuIII-CN-FeII], which is induced by electron transfer from the central RuII to the terminal FeIII in 1[PF6]4, which was confirmed by IR spectroscopy, magnetic data, and EPR and Mössbauer spectroscopy.Heiße Delokalisierung: Bei thermischer Aktivierung auf 400 K geht ein mehrkerniger Eisen-Ruthenium-Cyanidkomplex [FeIII-NC-RuII-CN-FeIII] von einem lokalisierten diamagnetischen Zustand in einen ungewöhnlichen delokalisierten gemischtvalenten Zustand [FeIII-NC-RuIII-CN-FeII] über.
      PubDate: 2017-01-12T09:11:01.451337-05:
      DOI: 10.1002/ange.201610855
       
  • Solubilisierung von Membranproteinen in funktionelle
           Lipiddoppelschicht-Nanodiscs mithilfe eines Diisobutylen/
           Maleinsäure-Copolymers
    • Authors: Abraham Olusegun Oluwole; Bartholomäus Danielczak, Annette Meister, Jonathan Oyebamiji Babalola, Carolyn Vargas, Sandro Keller
      Abstract: Nach Entfernung aus ihrer natürlichen Umgebung sind Membranproteine auf membranmimetische Systeme angewiesen, um ihre nativen Strukturen und Funktionen beizubehalten. Als Alternativen zu Detergensmizellen und Liposomen wurden für die In-vitro-Membranproteinforschung Lipiddoppelschicht-Nanodiscs eingeführt, die von Gerüstproteinen oder amphiphilen Polymeren wie Styrol/Maleinsäure(SMA)-Copolymeren umgrenzt sind. Hier zeigen wir, dass ein alternierendes Diisobutylen/Maleinsäure(DIBMA)-Copolymer bei der Solubilisierung von Phospholipiden SMA ebenbürtig ist, ein integrales Membranenzym in funktionellen Doppelschicht-Nanodiscs stabilisiert und Proteine unterschiedlicher Größen direkt aus zellulären Membranen extrahiert. Im Gegensatz zu aromatischem SMA hat aliphatisches DIBMA nur einen milden Effekt auf die Lipid-Acylkettenordnung, interferiert nicht mit optischer Spektroskopie im fernen UV-Bereich und präzipitiert nicht in Gegenwart von niedrigen millimolaren Konzentrationen zweiwertiger Kationen.Kleine Scheiben ganz groß: Ein Diisobutylen/Maleinsäure(DIBMA)-Copolymer extrahiert Proteine direkt aus biologischen Membranen und bildet dabei Nanodiscs, in denen das Polymer Lipiddoppelschichtfragmente umschließt, in die Membranproteine eingebettet sind. Die Ordnung der Lipid-Acylketten sowie die Enzymaktivität eines Modellproteins werden in den Nanodiscs erhalten, die einer großen Bandbreite an In-vitro-Methoden zugänglich sind.
      PubDate: 2017-01-12T09:10:59.949749-05:
      DOI: 10.1002/ange.201610778
       
  • BAB-random-C Monomer Sequence via Radical Terpolymerization of
           Limonene (A), Maleimide (B), and Methacrylate (C): Terpene Polymers
           with Randomly Distributed Periodic Sequences
    • Authors: Masataka Ojika; Kotaro Satoh, Masami Kamigaito
      Abstract: A naturally abundant terpene, limonene (A), was radically polymerized with a maleimide derivative (B) and methacrylate (C) in a fluorinated alcohol to give terpolymers with unprecedented BAB-random-C sequences in which the BAB monomer sequence was randomly copolymerized with a C unit. In each binary system, limonene was hardly copolymerized with methacrylate while it was efficiently copolymerized with maleimide to result in a 1:2-alternating BAB periodic sequence, in part due to the penultimate effects and hydrogen-bonding interactions with fluoroalcohol. Methacrylate and maleimide were randomly copolymerized to give copolymers rich in methacrylate units with minimal amounts of maleimide–maleimide sequences. Their terpolymerization resulted in a BAB-r-C sequence as a consequence of the selective BAB polymerization between limonene and maleimide, the random copolymerization between methacrylate and maleimide, and the lack of copolymerization between limonene and methacrylate.Eines der häufigsten Terpene in der Natur, Limonen (A), wurde radikalisch mit Phenylmaleimid (B) und Methylmethacrylat (C) in einem Fluoralkohol copolymerisiert, wobei Terpolymere mit neuartigen BAB-random-C-Sequenzen entstanden. Diese Sequenz resultiert aus einer selektiven BAB-Polymerisation zwischen A und B, einer statistischen Copolymerisation zwischen B und C sowie praktisch keiner Copolymerisation zwischen A und C.
      PubDate: 2017-01-12T09:10:53.749236-05:
      DOI: 10.1002/ange.201610768
       
  • Glucose-Responsive Sequential Generation of Hydrogen Peroxide and Nitric
           Oxide for Synergistic Cancer Starving-Like/Gas Therapy
    • Authors: Wenpei Fan; Nan Lu, Peng Huang, Yi Liu, Zhen Yang, Sheng Wang, Guocan Yu, Yijing Liu, Junkai Hu, Qianjun He, Junle Qu, Tianfu Wang, Xiaoyuan Chen
      Abstract: Eine endogene synergetische Krebstherapie für die effiziente Eradikation von Tumoren wurde durch Kombination von NO-Gastherapie und dem Aushungern der Tumorzellen entwickelt. In ihrer Zuschrift (
      DOI : 10.1002/ange.201610682) beschreiben P. Huang, T. Wang, X. Chen et al. biokompatible, poröse Nanokapseln aus Organosilikaten, die Glukoseoxidase und l-Arginin gleichzeitig in Tumorzellen transportieren. Das auf Glukose reagierende Nanotransportsystem zeigt die sequentielle Bildung von H2O2 und NO.
      PubDate: 2017-01-12T09:10:28.725906-05:
       
  • Reversible Photoactivated Phosphorescence of Gold(I) Arylethynyl Complexes
           in Aerated DMSO Solutions and Gels
    • Authors: Shigang Wan; Wei Lu
      Abstract: Phosphorescence in fluid solutions at ambient temperature is usually quenched by molecular oxygen via energy transfer, and singlet oxygen is concomitantly sensitized. The long-lived phosphorescence of a series of AuI arylethynyl complexes with tunable emission energies in aerated dimethyl sulfoxide (DMSO) solutions can be completely and repeatedly switched on by controlled photoirradiation. A trace amount of DMSO oxidation by the sensitized singlet oxygen is proposed to lead to a depletion of molecular oxygen in the local microenvironment of the AuI phosphor in the photoactivation processes. Harnessing the photoactivated phosphorescence and using UV light as a non-contact pen, a writing–erasing–rewriting prototype has been demonstrated with a DMSO gel containing AuI arylethynyl complexes.Die langlebige Phosphoreszenz einer Reihe von AuI-Arylethinyl-Komplexen mit einstellbaren Emissionsenergien in belüfteten Dimethylsulfoxid(DMSO)-Lösungen kann vollständig und wiederholt durch gezielte Bestrahlung mit Licht angeschaltet werden.
      PubDate: 2017-01-12T07:55:27.400066-05:
      DOI: 10.1002/ange.201610762
       
  • An Isolable Silicon Dicarbonate Complex from Carbon Dioxide Activation
           with a Silylone
    • Authors: Alexander Burchert; Shenglai Yao, Robert Müller, Caspar Schattenberg, Yun Xiong, Martin Kaupp, Matthias Driess
      Abstract: The first isolable molecular silicon dicarbonate complex (bis-NHC)Si(CO3)2 2 (bis-NHC=H2C[{NC(H)=C(H)N(Dipp)}C:]2, Dipp=2,6-iPr2C6H3) was synthesized by facile reaction of the bis-N-heterocyclic carbene stabilized silylone (bis-NHC)Si 1, bearing a zero-valent silicon atom, with carbon dioxide. The monomeric silicon dioxide complex (bis-NHC)SiO2 3 supported by the bis-NHC ligand was proposed as a key intermediate resulting from double oxygenation of the zero-valent silicon atom in 1 by two molar equivalents of CO2 under liberation of CO; its subsequent Lewis acid–base reaction with CO2 leads to 2 which has been fully characterized including an single-crystal X-ray diffraction analysis. Its electronic structure, spectroscopic data and the thermochemistry of the formation have been studied quantum-chemically.Silicium trifft Kohlendioxid: Das nullwertige Siliciumatom im (Bis-NHC)-stabilisierten Silylon 1 kann mit vier Äquivalenten Kohlendioxid reagieren und ergibt den ersten molekularen Silicium-Dicarbonat-Komplex, (Bis-NHC)Si(CO3)2 4 (siehe Schema, Dipp=2,6-iPr2C6H3). Die Umsetzung verläuft über die Bildung der Siliciummonoxid- und -dioxid-Komplexe 2 und 3, wie aus quantenchemischen Rechnungen hervorgeht.
      PubDate: 2017-01-12T07:51:05.658579-05:
      DOI: 10.1002/ange.201610498
       
  • Molecular Polygons Probe the Role of Intramolecular Strain in the
           Photophysics of π-Conjugated Chromophores
    • Authors: Philipp Wilhelm; Jan Vogelsang, Georgiy Poluektov, Nina Schönfelder, Tristan J. Keller, Stefan-Sven Jester, Sigurd Höger, John M. Lupton
      Abstract: π-Conjugated segments, chromophores, are the electronically active units of polymer materials used in organic electronics. To elucidate the effect of the bending of these linear moieties on elementary electronic properties, such as luminescence color and radiative rate, we introduce a series of molecular polygons. The π-system in these molecules becomes so distorted in bichromophores (digons) that these absorb and emit light of arbitrary polarization: any part of the chain absorbs and emits radiation with equal probability. Bending leads to a cancellation of transition dipole moment (TDM), increasing excited-state lifetime. Simultaneously, fluorescence shifts to the red as radiative transitions require mixing of the excited state with vibrational modes. However, strain can become so large that excited-state localization on shorter units of the chain occurs, compensating TDM cancellation. The underlying correlations between shape and photophysics can only be resolved in single molecules.Gebogene π-Systeme: Das π-System konjugierter Makromoleküle kann durch den Einbau von Chromophoren in molekulare Polygontemplate auf eine kontrollierte Art gebogen werden. Die Verbiegung führt zur einer isotropen Polarisation von Absorption und Fluoreszenz und beeinflusst außerdem die Eigenschaften des angeregten Zustands. Auf Einzelmolekülebene zeigt sich eine Korrelation zwischen Lumineszenzspektrum und Lebensdauer, die geringfügigen Variationen des Biegeradius entstammt.
      PubDate: 2017-01-12T07:50:28.22804-05:0
      DOI: 10.1002/ange.201610723
       
  • Coordination of KrF2 to a Naked Metal Cation, Mg2+
    • Authors: Matic Lozinšek; Hélène P. A. Mercier, David S. Brock, Boris Žemva, Gary J. Schrobilgen
      Abstract: Examples of coordination compounds in which KrF2 functions as a ligand are very rare. In contrast, XeF2 provides a rich coordination chemistry with a variety of main-group and transition metal cations. The reactions of Mg(AsF6)2 and KrF2 in HF or BrF5 solvent have afforded [Mg(KrF2)4(AsF6)2] and [Mg(KrF2)4(AsF6)2]⋅2 BrF5, respectively, the first examples of a metal cation ligated by KrF2. Their X-ray crystal structures and Raman spectra show that the KrF2 ligands and [AsF6]− anions are F-coordinated to a naked Mg2+ cation. Quantum-chemical calculations are consistent with essentially non-covalent ligand-metal bonding. These compounds significantly extend the XeF2–KrF2 analogy and the limited chemistry of krypton by introducing a new class of coordination compound in which KrF2 functions as a ligand towards a naked metal cation.Kryptondifluorid, ein thermodynamisch instabiles, stark oxidatives fluorierendes Molekül, koordiniert an Mg2+ unter Bildung der Koordinationskomplexe [Mg(KrF2)4(AsF6)2] und [Mg(KrF2)4(AsF6)2]⋅2 BrF5. Die Komplexe wurden durch Röntgenkristallographie und Raman-Spektroskopie bei tiefen Temperaturen charakterisiert. Computerstudien zeigen, dass die Mg-F-Bindungen praktisch nichtkovalente, schwach elektrostatische Wechselwirkungen sind.
      PubDate: 2017-01-12T04:45:32.573629-05:
      DOI: 10.1002/ange.201611534
       
  • Elasticity in Macrophage-Synthesized Biocrystals
    • Authors: Elizabeth M. Horstman; Rahul K. Keswani, Benjamin A. Frey, Phillip M. Rzeczycki, Vernon LaLone, Jeffery A. Bertke, Paul J. A. Kenis, Gus R. Rosania
      Abstract: Supramolecular crystalline assembly constitutes a rational approach to bioengineer intracellular structures. Here, biocrystals of clofazimine (CFZ) that form in vivo within macrophages were measured to have marked curvature. Isolated crystals, however, showed reduced curvature suggesting that intracellular forces bend these drug crystals. Consistent with the ability of biocrystals to elastically deform, the inherent crystal structure of the principal molecular component of the biocrystals—the hydrochloride salt of CFZ (CFZ-HCl)—has a corrugated packing along the (001) face and weak dispersive bonding in multiple directions. These characteristics were previously found to be linked to the elasticity of other organic crystals. Internal stress in bent CFZ-HCl led to photoelastic effects on the azimuthal orientation of polarized light transmittance. We propose that elastic, intracellular crystals can serve as templates to construct functional microdevices with different applications.Clofazimin-Hydrochlorid-Kristalle (CFZ-HCl), der hauptsächliche Bestandteil von CFZ-assoziierten Biokristallen, die intrazellulär in Makrophagen kristallisieren, zeigen elastisches Verhalten. Maßgeblich für die Elastizität sind die multidirektionalen Wechselwirkungen, die durch das Chlorid und die gewellte Kristallpackung verursacht werden.
      PubDate: 2017-01-12T04:30:59.174146-05:
      DOI: 10.1002/ange.201611195
       
  • Mononuclear Clusterfullerene Single-Molecule Magnet Containing Strained
           Fused-Pentagons Stabilized by a Nearly Linear Metal Cyanide Cluster
    • Authors: Fupin Liu; Song Wang, Cong-Li Gao, Qingming Deng, Xianjun Zhu, Aram Kostanyan, Rasmus Westerström, Fei Jin, Su-Yuan Xie, Alexey A. Popov, Thomas Greber, Shangfeng Yang
      Abstract: Fused-pentagons results in an increase of local steric strain according to the isolated pentagon rule (IPR), and for all reported non-IPR clusterfullerenes multiple (two or three) metals are required to stabilize the strained fused-pentagons, making it difficult to access the single-atom properties. Herein, we report the syntheses and isolations of novel non-IPR mononuclear clusterfullerenes MNC@C76 (M=Tb, Y), in which one pair of strained fused-pentagon is stabilized by a mononuclear cluster. The molecular structures of MNC@C76 (M=Tb, Y) were determined unambiguously by single-crystal X-ray diffraction, featuring a non-IPR C2v(19138)-C76 cage entrapping a nearly linear MNC cluster, which is remarkably different from the triangular MNC cluster within the reported analogous clusterfullerenes based on IPR-obeying C82 cages. The TbNC@C76 molecule is found to be a field-induced single-molecule magnet (SMM).In Fullerenen der Zusammensetzung MNC@C76 (M=Tb, Y), die nicht der Regel isolierter Fünfecke (IPR) entsprechen, ist ein Paar benachbarter Fünfecke durch einen annähernd linearen einkernigen Cyanidcluster stabilisiert. Diese Situation unterscheidet sich von dreieckigen MNC-Clustern in den analogen Clusterfullerenen mit IPR-konformen C82-Käfigen. TbNC@C76 ist ein feldinduzierter Einzelmolekülmagnet.
      PubDate: 2017-01-12T04:30:53.59238-05:0
      DOI: 10.1002/ange.201611345
       
  • Surface-Enhanced Raman Spectra Promoted by a Finger Press in an
           All-Solid-State Flexible Energy Conversion and Storage Film
    • Authors: Haitao Li; Han Dai, Yihe Zhang, Wangshu Tong, Hua Gao, Qi An
      Abstract: Electrochemically up-regulated surface-enhanced Raman spectroscopy (E-SERS) effectively increases Raman signal intensities. However, the instrumental requirements and the conventional measurement conditions in an electrolyte cell have hampered its application in fast and on-site detection. To circumvent the inconveniences of E-SERS, we propose a self-energizing substrate that provides electrical potential by converting film deformation from a finger press into stored electrical energy. The substrate combines an energy conversion film and a SERS-active Ag nanowire layer. A composite film prepared from a piezoelectric polymer matrix and surface-engineered rGO that simultaneously presents high permittivity and low dielectric loss is the key component herein. Using our substrate, increased E-SERS signals up to 10 times from a variety of molecules were obtained in the open air. Various tests on real-life sample surfaces demonstrated the potentials of the substrate in fast on-site detection.Energie per Fingerdruck: Ein selbstverstärkendes SERS-aktives Trägermaterial wurde durch Kombination eines piezoelektrischen Kompositfilms hoher Permittivität mit Silbernanodrahtschichten erhalten (SERS=oberflächenverstärkte Raman-Streuung). Der polymere Kompositfilm speichert Druck mit dem Finger als elektrische Energie und steigert die SERS-Intensität um eine Größenordnung.
      PubDate: 2017-01-12T04:25:47.729503-05:
      DOI: 10.1002/ange.201610737
       
  • Clamped Hybridization Chain Reactions for the Self-Assembly of Patterned
           DNA Hydrogels
    • Authors: Jianbang Wang; Jie Chao, Huajie Liu, Shao Su, Lianhui Wang, Wei Huang, Itamar Willner, Chunhai Fan
      Abstract: DNA hydrogels hold great potential for biological and biomedical applications owing to their programmable nature and macroscopic sizes. However, most previous studies involve spontaneous and homogenous gelation procedures in solution, which often lack precise control. A clamped hybridization chain reaction (C-HCR)-based strategy has been developed to guide DNA self-assembly to form macroscopic hydrogels. Analogous to catalysts in chemical synthesis or seeds in crystal growth, we introduced DNA initiators to induce the gelation process, including crosslinked self-assembly and clamped hybridization in three dimensions with spatial and temporal control. The formed hydrogels show superior mechanical properties. The use of printed, surface-confined DNA initiators was also demonstrated for fabricating 2D hydrogel patterns without relying on external confinements. This simple method can be used to construct DNA hydrogels with defined geometry, composition, and order for various bioapplications.Die Selbstorganisation von DNA zu makroskopischen Gelen gelingt mithilfe einer Clamp-Hybridisierungskettenreaktion (C-HCR). Die Gelbildung lässt sich in alle drei Richtungen räumlich und zeitlich präzise steuern. H1, H2=DNA-Haarnadelstränge, I=Initiatorstrang.
      PubDate: 2017-01-12T04:11:04.74702-05:0
      DOI: 10.1002/ange.201610125
       
  • Controlling the Helix Handedness of ααβ-Peptide Foldamers
           through Sequence Shifting
    • Authors: Monika Szefczyk; Ewelina Węglarz-Tomczak, Paulina Fortuna, Agnieszka Krzysztoń, Ewa Rudzińska-Szostak, Łukasz Berlicki
      Abstract: Peptide foldamers containing both cis-β-aminocyclopentanecarboxylic acid and α-amino acid residues combined in various sequence patterns (ααβ, αααβ, αβααβ, and ααβαααβ) were screened using CD and NMR spectroscopy for the tendency to form helices. ααβ-Peptides were found to fold into an unprecedented and well-defined 16/17/15/18/14/17-helix. By extending the length of the sequence or shifting a fragment of the sequence from one terminus to another in ααβ-peptides, the balance between left-handed and right-handed helix populations present in the solution can be controlled. Engineering of the peptide sequence could lead to compounds with either a strong propensity for the selected helix sense or a mixture of helical conformations of opposite senses.Links-rechts-Kombination: Die Modifizierung der Peptidtermini durch Extension oder Sequenzverschiebung ermöglicht die Steuerung des Gleichgewichts zwischen rechts- und linksgängigen Helices für ααβ-Peptidfoldamere, die cis-2-Aminocyclopentancarbonsäure (rot im Bild) als Baustein enthalten.
      PubDate: 2017-01-12T04:10:59.672443-05:
      DOI: 10.1002/ange.201610154
       
  • Mangan-katalysierte Mehrkomponentensynthese von Pyrimidinen aus Alkoholen
           und Amidinen
    • Authors: Nicklas Deibl; Rhett Kempe
      Abstract: Die Entwicklung von neuartigen, vorzugsweise katalytischen Reaktionen, um Verbindungsklassen ausgehend von Alkoholen herzustellen, ist von hoher Bedeutung, da sie zur Erhaltung der fossilen Kohlenstoffressourcen und zur Reduktion von CO2-Emissionen beiträgt. Um die extrem seltenen Edelmetallressourcen zu schonen, ist der Ersatz von seltenen Metallen wie Ir, Rh oder Pt durch breit verfügbare 3d-Metalle in Schlüsseltechnologien wie der Katalyse ebenso wichtig. Wir berichten hier über eine durch einen Mangankomplex katalysierte Version der Mehrkomponentensynthese von Pyrimidinen aus Amidinen und drei (unterschiedlichen) Alkoholen. Die Reaktion verläuft über Kondensations- und Dehydrierungsschritte, was selektive C-C-und C-N-Bindungsknüpfungen erlaubt. Wir nutzen selektive β-Alkylierungen, um sekundäre Alkohole mehrfach mit unterschiedlichen primären Alkoholen zu alkylieren, um vollständig substituierte Pyrimidine in einem Eintopfprozess zu synthetisieren. PN5P-Mn-Pincer-Komplexe, die in unserem Labor entwickelt wurden, katalysieren diesen nachhaltigen Mehrkomponentenprozess am effizientesten. Ein Vergleich unserer Mangankomplexe mit verwandten Cobaltkomplexen zeigt, dass Mangan der katalytischen Reaktivität von Iridium nahekommt, Cobalt jedoch nicht. Wir erwarten, dass diese Analogie dazu genutzt werden kann, weitere katalytische Anwendungen von Mangankomplexen zu entwickeln, bei denen Hydrierungs- oder Dehydrierungsschritte involviert sind.Ressourcenschonend: Ein PN5P-Mangankomplex katalysiert die Mehrkomponentensynthese von Pyrimidinen aus Amidinen und bis zu drei (unterschiedlichen) Alkoholen. Die konsekutive 4-Komponentenreaktion kombiniert das Konzept des Borrowing-Hydrogen oder Hydrogen-Autotransfers mit der dehydrierenden Kondensation und erlaubt so selektive C-N- und C-C- Kupplungen.
      PubDate: 2017-01-12T04:10:56.650124-05:
      DOI: 10.1002/ange.201611318
       
  • Ligand-Enabled Alkynylation of C(sp3)−H Bonds with Palladium(II)
           Catalysts
    • Authors: Haiyan Fu; Peng-Xiang Shen, Jian He, Fanglin Zhang, Suhua Li, Peng Wang, Tao Liu, Jin-Quan Yu
      Abstract: The palladium(II)-catalyzed β- and γ-alkynylation of amide C(sp3)−H bonds is enabled by pyridine-based ligands. This alkynylation reaction is compatible with substrates containing α-tertiary or α-quaternary carbon centers. The β-methylene C(sp3)−H bonds of various carbocyclic rings were also successfully alkynylated.Pyridin macht's möglich: Die Palladium(II)-katalysierte β- und γ-Alkinylierung von amidischen C(sp3)-H-Bindungen gelang mithilfe von Pyridin-Liganden. Diese Alkinylierungsmethode kann für Substrate mit α-tertiären oder α-quartären Kohlenstoffzentren verwendet werden. Die β-Methylen-C(sp3)-H-Bindungen verschiedener Carbocyclen wurden ebenfalls alkinyliert.
      PubDate: 2017-01-12T04:10:54.008906-05:
      DOI: 10.1002/ange.201610426
       
  • Carbon-Nanotube-Supported Bio-Inspired Nickel Catalyst and Its Integration
           in Hybrid Hydrogen/Air Fuel Cells
    • Authors: Solène Gentil; Noémie Lalaoui, Arnab Dutta, Yannig Nedellec, Serge Cosnier, Wendy J. Shaw, Vincent Artero, Alan Le Goff
      Abstract: A biomimetic nickel bis-diphosphine complex incorporating the amino acid arginine in the outer coordination sphere was immobilized on modified carbon nanotubes (CNTs) through electrostatic interactions. The functionalized redox nanomaterial exhibits reversible electrocatalytic activity for the H2/2 H+ interconversion from pH 0 to 9, with catalytic preference for H2 oxidation at all pH values. The high activity of the complex over a wide pH range allows us to integrate this bio-inspired nanomaterial either in an enzymatic fuel cell together with a multicopper oxidase at the cathode, or in a proton exchange membrane fuel cell (PEMFC) using Pt/C at the cathode. The Ni-based PEMFC reaches 14 mW cm−2, only six-times-less as compared to full-Pt conventional PEMFC. The Pt-free enzyme-based fuel cell delivers ≈2 mW cm−2, a new efficiency record for a hydrogen biofuel cell with base metal catalysts.Zweifach verwendbar: Ein biomimetischer Nickelkatalysator auf Kohlenstoffnanoröhren wurde für die effiziente Platin-freie H2-Oxidation entwickelt. Die hohe Aktivität des Komplexes über einen großen pH-Bereich ermöglicht seine Verwendung in einer enzymatischen Brennstoffzelle zusammen mit einer Multikupferoxidase an der Kathode oder in einer PEMFC mit Pt/C an der Kathode.
      PubDate: 2017-01-12T04:10:47.877695-05:
      DOI: 10.1002/ange.201611532
       
  • Der cyclo-P4-Sandwichkomplex des Cobalts und seine Rolle bei der Bildung
           von Polyphosphorverbindungen
    • Authors: Fabian Dielmann; Alexey Timoshkin, Martin Piesch, Gábor Balázs, Manfred Scheer
      Abstract: Es wurde ein Syntheseweg zum Sandwichkomplex [Cp′′′Co(η4-P4)] (2), der einen cyclo-P4-Liganden als Enddeck enthält, gefunden. Der Komplex 2 ist das noch fehlende Homologe in der Serie der cyclo-Pn-Sandwich-Komplexe der 3d-Elemente und zeigt eine einzigartige Neigung zur Dimerisierung in Lösung unter Bildung zweier isomerer P8-Komplexe [(Cp′′′Co)2(μ,η4:η2:η1-P8)] (3 und 4). Reaktivitätsstudien belegen, dass 2 und 3 mit weiteren [Cp′′′Co]-Fragmenten reagieren und dabei [(Cp′′′Co)2(μ,η2:η2-P2)2] (5) bzw. [(Cp′′′Co)3P8] (6) ergeben. Darüber hinaus zersetzen sich die Komplexe 2, 3 und 4 thermisch unter Bildung von 5, 6 und dem P12-Komplex [(Cp′′′Co)3P12] (7). DFT-Berechnungen des P4-Aktivierungsprozesses lassen auf einen η3-P4-Co-Komplex als Schlüsselzwischenstufe sowohl bei der Synthese von 2 als auch bei der Bildung größerer Polyphosphorkomplexe über einen einzigartigen Oligomerisierungsweg schließen.[Cp′′′Co(η4-P4)], der erste Carbonyl-freie Sandwichkomplex mit einem cyclo-P4-Liganden als Enddeck, wird in der Reaktion von [(Cp′′′Co)2(η4:η4-C7H8)] mit P4 erhalten. Während [Cp′′′Co(η4-P4)] im Festzustand stabil ist, hat er eine starke Neigung, in Lösung zu dimerisieren, und bildet Komplexe, die größere Pn-Liganden enthalten. Der Reaktionsmechanismus wird mittels spektroskopischer Methoden und DFT-Rechnungen beleuchtet.
      PubDate: 2017-01-12T02:27:07.79793-05:0
      DOI: 10.1002/ange.201610967
       
  • Silver-Catalyzed Chemoselective [4+2] Annulation of Two Isocyanides: A
           General Route to Pyridone-Fused Carbo- and Heterocycles
    • Authors: Zhongyan Hu; Jinhuan Dong, Yang Men, Zhichen Lin, Jinxiong Cai, Xianxiu Xu
      Abstract: A silver-catalyzed chemoselective [4+2] annulation of aryl and heteroaryl isocyanides with α-substituted isocyanoacetamides was developed for the facile and efficient synthesis of 2-aminoquinolones, naphthyridines, and phenanthrolines. A mechanism for this multistep domino reaction is proposed on the basis of a 13C-labeling experiment, according to which an unprecedented chemoselective heterodimerization of two different isocyanides generates an α-amidoketenimine intermediate, which undergoes 1,3-amino migration to form an α-imidoylketene, followed by 6 π electrocyclization.Dominoeffekt: Eine ungewöhnliche [4+2]-Anellierung von (Hetero)Arylisocyaniden mit α-substituierten Isocyanoacetamiden wurde entwickelt und zur Synthese von Aminochinolonen, Naphthyridinen und Phenanthrolinen genutzt. Beide Isocyanidtypen zeigen ein neuartiges Reaktivitätsprofil in dieser Dominoreaktion, die über ihre Heterodimerisierung und anschließende 1,3-Aminowanderung und 6π-Elektrocyclisierung verläuft (siehe Schema).
      PubDate: 2017-01-12T02:26:35.299774-05:
      DOI: 10.1002/ange.201611024
       
  • Stable and Rapid Thiol Bioconjugation by Light-Triggered Thiomaleimide
           Ring Hydrolysis
    • Authors: Dimpy Kalia; Sharad P. Pawar, Jyoti S. Thopate
      Abstract: Maleimide-mediated thiol-specific derivatization of biomolecules is one of the most efficacious bioconjugation approaches currently available. Alarmingly, however, recent work demonstrates that the resulting thiomaleimide conjugates are susceptible to breakdown via thiol exchange reactions. Herein, we report a new class of maleimides, namely o-CH2NHiPr phenyl maleimides, that undergo unprecedentedly rapid ring hydrolysis after thiol conjugation to form stable thiol exchange-resistant conjugates. Furthermore, we overcome the problem of low shelf lives of maleimide reagents owing to their propensity to undergo ring hydrolysis prior to bioconjugation by developing a photocaged version of this scaffold that resists ring hydrolysis. UV irradiation of thiol bioconjugates formed with this photocaged maleimide unleashes rapid thiomaleimide ring hydrolysis to yield the desired stable conjugates within 1 h under gentle, ice-cold conditions.Mit Licht und Wasser: Ein photoaktivierbares Reagens für eine stabile Thiol-Biokonjugation unter Eiskühlung wurde entwickelt. Zunächst bildet das Reagens ein kovalentes Addukt mit dem gewünschten Biomolekül, unter UV-Bestrahlung folgt dann eine schnelle Ringhydrolyse über intramolekulare Katalyse durch eine protonierte Aminogruppe, die das stabile Biokonjugat liefert.
      PubDate: 2017-01-12T02:26:17.8149-05:00
      DOI: 10.1002/ange.201609733
       
  • Low-Temperature Hydrogenation of Carbon Dioxide to Methanol with a
           Homogeneous Cobalt Catalyst
    • Authors: Jacob Schneidewind; Rosa Adam, Wolfgang Baumann, Ralf Jackstell, Matthias Beller
      Abstract: Herein we describe the first homogeneous non-noble metal catalyst for the hydrogenation of CO2 to methanol. The catalyst is formed in situ from [Co(acac)3], Triphos, and HNTf2 and enables the reaction to be performed at 100 °C without a decrease in activity. Kinetic studies suggest an inner-sphere mechanism, and in situ NMR and MS experiments reveal the formation of the active catalyst through slow removal of the acetylacetonate ligands.Ein Nicht-Edelmetall-Katalysator für die effiziente Hydrierung von CO2 zu Methanol wurde entwickelt. Der Katalysator entsteht in situ aus [Co(acac)3], 1,1,1-Tris(diphenylphosphinomethyl)ethan (Triphos) und HNTf2 und produziert Methanol aus CO2 bei nur 100 °C (siehe Schema).
      PubDate: 2017-01-12T02:26:04.47173-05:0
      DOI: 10.1002/ange.201609077
       
  • Photoisomerisierung eines Schalters auf Basis eines chiralen Imins:
           Verfolgung durch Matrixisolations-VCD-Spektroskopie
    • Authors: Corina H. Pollok; Tim Riesebeck, Christian Merten
      Abstract: Die Charakterisierung der Stereochemie kurzlebiger Photoisomerisierungsprodukte ist eine anspruchsvolle Aufgabe bei der Entwicklung molekularer Maschinen, beispielsweise unidirektionaler molekularer Motoren. Diese Zustände sind oft nicht genügend lange stabil, um eine detaillierte Charakterisierung mithilfe konventioneller spektroskopischer Methoden zu ermöglichen. Anhand des strukturell sehr einfachen Campherchinonimins 1 wird gezeigt, wie die Kombination der Matrixisolationstechnik mit der VCD-Spektroskopie zur Untersuchung der Photoisomerisierung von chiralen Molekülen genutzt werden kann. Es wird gezeigt, dass die Isomere (E)-1 und (Z)-1 photochemisch unter kryogenen Bedingungen in einer Argonmatrix erzeugt und anschließend auch die Stereochemie beider Schaltzustände verlässlich charakterisiert werden kann.Schalten und walten: Die chiroptischen Eigenschaften des E- und des Z-Isomers eines Campherchinonimin-Derivats wurden mithilfe der Matrixisolations-VCD-Spektroskopie untersucht (VCD=Schwingungscirculardichroismus). Diese Technik erweist sich als sehr nützlich für die Charakterisierung der Schaltzustände chiraler molekularer Motoren.
      PubDate: 2017-01-12T02:25:52.629713-05:
      DOI: 10.1002/ange.201610918
       
  • Iron-Catalyzed Mild and Selective Hydrogenative Cross-Coupling of Nitriles
           and Amines to Form Secondary Aldimines
    • Authors: Subrata Chakraborty; Gregory Leitus, David Milstein
      Abstract: The first example of a base-metal-catalyzed homogeneous hydrogenative coupling of nitriles and amines to selectively form secondary cross-imines is reported. The reaction is catalyzed under mild conditions by a well-defined (iPr-PNP)Fe(H)Br(CO) pincer pre-catalyst and catalytic tBuOK.Ein leicht verfügbares Metall bildet die Grundlage für eine katalytische hydrierende Kreuzkupplung von Nitrilen und Aminen zu sekundären Aldiminen. Die Reaktion läuft unter milden Bedingungen in Gegenwart des definierten Komplexes (iPr-PNP)Fe(H)Br(CO) als Präkatalysator mit tBuOK ab.
      PubDate: 2017-01-12T02:20:57.116657-05:
      DOI: 10.1002/ange.201608537
       
  • Rapid Asymmetric Synthesis of Disubstituted Allenes by Coupling of
           Flow-Generated Diazo Compounds and Propargylated Amines
    • Authors: Jian-Siang Poh; Szabolcs Makai, Timo von Keutz, Duc N. Tran, Claudio Battilocchio, Patrick Pasau, Steven V. Ley
      Abstract: We report herein the asymmetric coupling of flow-generated unstabilized diazo compounds and propargylated amine derivatives, using a new pyridinebis(imidazoline) ligand, a copper catalyst and base. The reaction proceeds rapidly, generating chiral allenes in 10–20 minutes with high enantioselectivity (89–98 % de/ee), moderate yields and a wide functional group tolerance.Kupfer-Katalyse: Eine asymmetrische kupferkatalysierte Reaktion zwischen nichtstabilisierten Diazoverbindungen, die im kontinuierlichen Durchflussprozess erzeugt wurden, und terminalen Propargylaminen wird beschrieben. Die Diazo-Alkin-Kupplung verläuft schnell, enantioselektiv und ist zur späten Funktionalisierung von komplexen Verbindungen anwendbar.
      PubDate: 2017-01-11T08:31:05.903848-05:
      DOI: 10.1002/ange.201611067
       
  • Characterization of Giant Modular PKSs Provides Insight into Genetic
           Mechanism for Structural Diversification of Aminopolyol Polyketides
    • Authors: Lihan Zhang; Takuya Hashimoto, Bin Qin, Junko Hashimoto, Ikuko Kozone, Teppei Kawahara, Masahiro Okada, Takayoshi Awakawa, Takuya Ito, Yoshinori Asakawa, Masashi Ueki, Shunji Takahashi, Hiroyuki Osada, Toshiyuki Wakimoto, Haruo Ikeda, Kazuo Shin-ya, Ikuro Abe
      Abstract: Polyketides form many clinically valuable compounds. However, manipulation of their biosynthesis remains highly challenging. An understanding of gene cluster evolution provides a rationale for reprogramming of the biosynthetic machinery. Herein, we report characterization of giant modular polyketide synthases (PKSs) responsible for the production of aminopolyol polyketides. Heterologous expression of over 150 kbp polyketide gene clusters successfully afforded their products, whose stereochemistry was established by taking advantage of bioinformatic analysis. Furthermore, phylogenetic analysis of highly homologous but functionally diverse domains from the giant PKSs demonstrated the evolutionary mechanism for structural diversification of polyketides. The gene clusters characterized herein, together with their evolutionary insights, are promising genetic building blocks for de novo production of unnatural polyketides.Modultausch: Aminopolyole sind eine Klasse von bioaktiven Polyketiden, die durch große modulare Polyketidsynthasen (PKSs) aufgebaut werden. Die heterologe Expression von PKS-Genclustern mit über 150 kbp führte zu neuartigen Aminopolyolen, und ein phylogenetischer Vergleich von vier Aminopolyol-PKS-Genclustern veranschaulicht den präzisen Mechanismus der PKS-Umprogrammierung in der Natur.
      PubDate: 2017-01-11T08:25:58.236174-05:
      DOI: 10.1002/ange.201611371
       
  • Authors Profile
    • PubDate: 2017-01-11T08:25:39.901931-05:
      DOI: 10.1002/ange.201611954
       
  • Regio- and Enantioselective Rhodium-Catalyzed Addition of 1,3-Diketones to
           Allenes: Construction of Asymmetric Tertiary and Quaternary All Carbon
           Centers
    • Authors: Thorsten M. Beck; Bernhard Breit
      Abstract: An unprecedented highly regio- and enantioselective rhodium-catalyzed addition of 1,3-diketones to terminal and 1,1-disubstituted allenes furnishing asymmetric tertiary and quaternary all-carbon centers is reported. By applying a RhI/phosphoramidite/TFA catalytic system under mild conditions, the desired chiral branched α-allylated 1,3-diketones could be obtained in good to excellent yields, with perfect regioselectivity and in high enantioselectivity. The reaction shows a broad functional-group tolerance on both reaction partners highlighting its synthetic potential.Rh-Katalyse: Eine regio- und enantioselektive atomökonomische katalytische Addition von 1,3-Diketonen an Allene wird beschrieben, die tertiäre und quartäre Kohlenstoffstereozentren unter milden Reaktionsbedingungen erzeugt. Die Reaktion toleriert zahlreiche funktionelle Gruppen, und das breite Substratspektrum unterstreicht ihren präparativen Nutzen.
      PubDate: 2017-01-11T08:15:41.218076-05:
      DOI: 10.1002/ange.201610577
       
  • Assembly of Ring-Shaped Phosphorus within Carbon Nanotube Nanoreactors
    • Authors: Jinying Zhang; Dan Zhao, Dingbin Xiao, Chuansheng Ma, Hongchu Du, Xin Li, Lihui Zhang, Jialiang Huang, Hongyang Huang, Chun-Lin Jia, David Tománek, Chunming Niu
      Abstract: A phosphorus allotrope that has not been observed so far, ring-shaped phosphorus consisting of alternate P8 and P2 structural units, has been assembled inside multi-walled carbon nanotube nanoreactors with inner diameters of 5–8 nm by a chemical vapor transport and reaction of red phosphorus at 500 °C. The ring-shaped nanostructures with surrounding graphene walls are stable under ambient conditions. The nanostructures were characterized by high-resolution transmission electron microscopy, scanning transmission electron microscopy, energy-dispersive X-ray spectroscopy, Raman scattering, attenuated total reflectance Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy.Ringförmiger Phosphor: Ein neues Phosphorallotrop, ringförmiger Phosphor, wurde durch eine Dampfphasenreaktion in Kohlenstoffnanoröhren synthetisiert. Die selbstorganisierten ringförmigen Phosphornanostrukturen bestehen aus P8- und P2-Struktureinheiten und sind innerhalb der Nanoröhren (Innendurchmesser 5–8 nm) unter Umgebungsbedingungen stabil.
      PubDate: 2017-01-11T03:26:17.302998-05:
      DOI: 10.1002/ange.201611740
       
  • Isolation and Characterization of Radical Anions Derived from a
           Boryl-Substituted Diphosphene
    • Authors: Shun-suke Asami; Shintaro Ishida, Takeaki Iwamoto, Katsunori Suzuki, Makoto Yamashita
      Abstract: Radical anions of a diphosphene with two boryl substituents were isolated and characterized by single-crystal X-ray diffraction, electron spin resonance (ESR), and UV/Vis absorption spectroscopy as well as DFT calculations. Structural analysis of the radical anions revealed an elongation of the P=P bond and a contraction of the B−P bonds relative to the neutral diphosphene. The UV/Vis spectra of these radical anions showed a strong absorption in the visible region, which was assigned to SOMO-related transitions on the basis of DFT calculations. The ESR spectra revealed that the hyperfine coupling constant with the phosphorus nuclei is the smallest that has been reported thus far. The results of the DFT calculations furthermore suggest that this should be attributed to a soaking of electron spin to the vacant p orbitals of the boryl substituents.Die Radikalanionen eines Diphosphens mit zwei Boryl-Substituenten wurden isoliert und durch DFT-Rechnungen, Röntgenbeugung, ESR- und UV/Vis-Spektroskopie charakterisiert. Alle strukturellen Parameter weisen darauf hin, dass der Elektronenspin in die vakanten p-Orbitale der Boryl-Substituenten einfließt.
      PubDate: 2017-01-11T03:26:14.044235-05:
      DOI: 10.1002/ange.201611762
       
  • A World From Dust. How the Periodic Table Shaped Life Von Ben McFarland.
    • Authors: Uwe J. Meierhenrich
      Abstract: Oxford University Press 2016. 333 S., geb., 22.99 £.—ISBN 978-0190275013
      PubDate: 2017-01-11T03:26:10.759045-05:
      DOI: 10.1002/ange.201612218
       
  • Heterocumulene Sulfinyl Radical OCNSO
    • Authors: Zhuang Wu; Qifan Liu, Jian Xu, Hailong Sun, Dingqing Li, Chao Song, Diego M. Andrada, Gernot Frenking, Tarek Trabelsi, Joseph S. Francisco, Xiaoqing Zeng
      Abstract: Neutral five-atomic cumulenes formally consisting of two pseudohalogens (e.g., NCO, NNN, NSO) by sharing the central nitrogen atom are exotic species that have been barely studied. Through flash vacuum pyrolysis of CF3S(O)NCO at ca. 1200 K, sulfinyl isocyanate, bearing resonance structures of O=C−N=S=O and O=C=N−S=O, has been generated in the gas phase and subsequently characterized in cryogenic matrices (Ar and N2). Its reversible conformational (syn and anti) interconversion and photodecomposition were observed.Heterocumulen OCNSO, das durch das gemeinsame zentrale Stickstoffatom zum Interpseudohalogen wird, wurde durch Blitzvakuumpyrolyse von CF3S(O)NCO bei 1200 K in der Gasphase erzeugt. Zwei Konformere von OCNSO und ihre reversible gegenseitige Umwandlung in kryogenen Matrices (2.8–15 K) wurden beobachtet.
      PubDate: 2017-01-11T03:26:09.998418-05:
      DOI: 10.1002/ange.201611576
       
  • Total Synthesis of (−)-Tetrodotoxin and 11-norTTX-6(R)-ol
    • Authors: Tomoaki Maehara; Keisuke Motoyama, Tatsuya Toma, Satoshi Yokoshima, Tohru Fukuyama
      Abstract: The enantioselective total synthesis of (−)-tetrodotoxin [(−)-TTX] and 4,9-anhydrotetrodotoxin, which are selective blockers of voltage-gated sodium channels, was accomplished from the commercially available p-benzoquinone. This synthesis was based on efficient stereocontrol of the six contiguous stereogenic centers on the core cyclohexane ring through Ogasawara's method, [3,3]-sigmatropic rearrangement of an allylic cyanate, and intramolecular 1,3-dipolar cycloaddition of a nitrile oxide. Our synthetic route was applied to the synthesis of the tetrodotoxin congeners 11-norTTX-6(R)-ol and 4,9-anhydro-11-norTTX-6(R)-ol through late-stage modification of the common intermediate. Neutral deprotection at the final step enabled easy purification of tetrodotoxin and 11-norTTX-6(R)-ol without competing dehydration to their 4,9-anhydro forms.Wähle Dein Gift: Die Totalsynthese das spannungsgesteuerten Natriumkanalblockers (−)-Tetrodotoxin (TTX) gelang ausgehend von p-Benzochinon in 31 Stufen. Die Synthese, die auch für TTX-Derivate wie 11-norTTX-6(R)-ol verwendet werden kann, beinhaltet eine stereoselektive Oxygenierung des tricyclischen Grundgerüsts, eine diastereoselektive [3,3]-sigmatrope Umlagerung eines Allylcyanats und eine intramolekulare 1,3-dipolare Cycloaddition eines Nitriloxids.
      PubDate: 2017-01-11T03:26:06.535728-05:
      DOI: 10.1002/ange.201611574
       
  • The Chemistry of Metal–Organic Frameworks. Synthesis, Characterization,
           and Applications, 2 Bände. Herausgegeben von Stefan Kaskel.
    • Authors: Andrew D. Burrows
      Abstract: Wiley-VCH, Weinheim 2016. 904 S., geb., 299.00 €.—ISBN 978-3527338740
      PubDate: 2017-01-11T03:20:53.422866-05:
      DOI: 10.1002/ange.201611669
       
  • Colloidal Synthesis of CH3NH3PbBr3 Nanoplatelets with Polarized Emission
           through Self-Organization
    • Authors: Lige Liu; Sheng Huang, Longfei Pan, Li-Jie Shi, Bingsuo Zou, Luogen Deng, Haizheng Zhong
      Abstract: We report a combined experimental and theoretical study of the synthesis of CH3NH3PbBr3 nanoplatelets through self-organization. Shape transformation from spherical nanodots to square or rectangular nanoplatelets can be achieved by keeping the preformed colloidal nanocrystals at a high concentration (3.5 mg mL−1) for 3 days, or combining the synthesis of nanodots with self-organization. The average thickness of the resulting CH3NH3PbBr3 nanoplatelets is similar to the size of the original nanoparticles, and we also noticed several nanoplatelets with circular or square holes, suggesting that the shape transformation experienced a self-organization process through dipole–dipole interactions along with a realignment of dipolar vectors. Additionally, the CH3NH3PbBr3 nanoplatelets exhibit excellent polarized emissions for stretched CH3NH3PbBr3 nanoplatelets embedded in a polymer composite film, showing advantageous photoluminescence properties for display backlights.Ein Selbstorganisationsprozess wurde genutzt, um CH3NH3PbBr3-Nanoplättchen durch Umwandlung sphärischer Nanopunkte herzustellen. Die Formumwandlung wurde durch Materialcharakterisierung und theoretische Simulationen untermauert, und die erhaltenen Nanoplättchen zeigten polarisierte Photolumineszenzeigenschaften.
      PubDate: 2017-01-11T03:20:51.819706-05:
      DOI: 10.1002/ange.201610619
       
  • Iridium-Catalyzed Intramolecular Asymmetric Allylic Dearomatization
           Reaction of Benzoxazoles, Benzothiazoles, and Benzimidazoles
    • Authors: Ze-Peng Yang; Chao Zheng, Lin Huang, Chao Qian, Shu-Li You
      Abstract: An iridium-catalyzed intramolecular asymmetric allylic dearomatization reaction of benzoxazoles, benzothiazoles, and benzimidazoles was developed. The reaction was found to be compatible with a wide range of five-membered-ring electron-deficient heteroaromatic compounds and furnished the corresponding dearomatized heterocycles in high yield with excellent enantioselectivity.Weniger ist mehr: Eine große Auswahl von elektronenarmen Stickstoff-haltigen Arenen mit Allylcarbonat-Seitenkette geht eine intramolekulare asymmetrische allylische Dearomatisierung in Gegenwart eines Iridium-Katalysators mit dem chiralen Liganden Me-THQphos ein (siehe Schema). Die dearomatisierten Heterocyclen wurden in hohen Ausbeuten und mit exzellenter Enantioselektivität erhalten.
      PubDate: 2017-01-11T03:20:49.604873-05:
      DOI: 10.1002/ange.201611056
       
  • Bioorthogonal Diversification of Peptides through Selective
           Ruthenium(II)-Catalyzed C–H Activation
    • Authors: Alexandra Schischko; Hongjun Ren, Nikolaos Kaplaneris, Lutz Ackermann
      Abstract: Methods for the chemoselective modification of amino acids and peptides are powerful techniques in biomolecular chemistry. Among other applications, they enable the total synthesis of artificial peptides. In recent years, significant momentum has been gained by exploiting palladium-catalyzed cross-coupling for peptide modification. Despite major advances, the prefunctionalization elements on the coupling partners translate into undesired byproduct formation and lengthy synthetic operations. In sharp contrast, we herein illustrate the unprecedented use of versatile ruthenium(II)carboxylate catalysis for the step-economical late-stage diversification of α- and β-amino acids, as well as peptides, through chemo-selective C−H arylation under racemization-free reaction conditions. The ligand-accelerated C−H activation strategy proved water-tolerant and set the stage for direct fluorescence labelling as well as various modes of peptide ligation with excellent levels of positional selectivity in a bioorthogonal fashion. The synthetic utility of our approach is further demonstrated by twofold C−H arylations for the complexity-increasing assembly of artificial peptides within a multicatalytic C−H activation manifold.Eine vielseitige Katalysestrategie mit einem Ruthenium(II)-carboxylat wurde entwickelt, die die stufenökonomische späte Diversifizierung von α- und β-Aminosäuren und Peptiden durch bioorthogonale C-H-Arylierung unter racemisierungsfreien Reaktionsbedingungen ermöglicht. Die ligandbeschleunigte C-H-Aktivierung ist wasserverträglich und schafft die Voraussetzung für direkte Fluoreszenzmarkierung und verschiedene Arten der Peptidligation.
      PubDate: 2017-01-11T03:20:44.071765-05:
      DOI: 10.1002/ange.201609631
       
  • A Biosurfactant-Inspired Heptapeptide with Improved Specificity to Kill
           MRSA
    • Authors: Yuan Liu; Shuangyang Ding, Richard Dietrich, Erwin Märtlbauer, Kui Zhu
      Abstract: The emergence and rapid spread of methicillin-resistant Staphylococcus aureus (MRSA) poses a serious threat to public health. New antibiotics and strategies are urgently needed to combat S. aureus associated infections. Bacaucin, a novel cyclic lipopeptide from Bacillus subtilis CAU21, is reported. Bacaucin shows broad antibacterial activity against Gram-positive bacteria, but is also hemolytic and cytotoxic. However, bacaucin-1, a bacaucin-inspired ring-opened heptapeptide, shows specific antibacterial activity against MRSA by a membrane-disruptive mechanism without detectable toxicity to mammalian cells or induction of bacterial resistance. Bacaucin-1 was efficient in preventing infections in both in vitro and in vivo models and is a valuable prototype antibiotic with high potential against S. aureus infections.Der zytotoxische antibiotische Naturstoff Bacaucin (rot) ist ein cyclisches Lipopeptid von Bacillus subtilis. Das sichere synthetische Bacaucin-Derivat Bacaucin-1 (blau) wirkt spezifisch antibakteriell gegen Methicillin-resistenten Staphylococcus aureus (MRSA) und verhindert Infektionen in vitro wie in vivo.
      PubDate: 2017-01-11T03:20:38.779516-05:
      DOI: 10.1002/ange.201609277
       
  • A Vesicle-to-Worm Transition Provides a New High-Temperature Oil
           Thickening Mechanism
    • Authors: Matthew J. Derry; Oleksandr O. Mykhaylyk, Steven P. Armes
      Abstract: Diblock copolymer vesicles are prepared via RAFT dispersion polymerization directly in mineral oil. Such vesicles undergo a vesicle-to-worm transition on heating to 150 °C, as judged by TEM and SAXS. Variable-temperature 1H NMR spectroscopy indicates that this transition is the result of surface plasticization of the membrane-forming block by hot solvent, effectively increasing the volume fraction of the stabilizer block and so reducing the packing parameter for the copolymer chains. The rheological behavior of a 10 % w/w copolymer dispersion in mineral oil is strongly temperature-dependent: the storage modulus increases by five orders of magnitude on heating above the critical gelation temperature of 135 °C, as the non-interacting vesicles are converted into weakly interacting worms. SAXS studies indicate that, on average, three worms are formed per vesicle. Such vesicle-to-worm transitions offer an interesting new mechanism for the high-temperature thickening of oils.Ein morphologischer Übergang in eine wurmartige Form wird beim Erhitzen vesikulärer Poly(stearylmethacrylat)13-Poly(benzylmethacrylat)96-Blockcopolymere in Erdöl beobachtet. Der Prozess beschreibt einen neuartigen Hochtemperatur-Ölverdickungsmechanismus.
      PubDate: 2017-01-10T08:21:00.357846-05:
      DOI: 10.1002/ange.201609365
       
  • Activation of the B−F Bond by Diphenylcarbene: A Reversible 1,2-Fluorine
           Migration between Boron and Carbon
    • Authors: Paolo Costa; Joel Mieres Perez, Nesli Özkan, Wolfram Sander
      Abstract: Experiments in low-temperature matrices reveal that triplet diphenylcarbene inserts into the very strong B−F bond of BF3 in a two-step reaction. The first step is the formation of a strongly bound Lewis acid–base complex between the singlet state of diphenylcarbene and BF3. This step involves an inversion of the spin state of the carbene from triplet to singlet. The second step requires visible-light photochemical activation to induce a 1,2-F migration from boron to the adjacent carbon atom under formation of the formal insertion product of the carbene center into BF3. The 1,2-F migration is reversible under short-wavelength UV irradiation, thus leading back to the Lewis acid–base adduct.Kurze Wanderung: Triplett-Diphenylcarben insertiert unter reversibler Fluormigration in die B-F-Bindung des BF3-Moleküls – und das trotz einer Bindungsdissoziationsenergie von 170 kcal mol−1. Die 1,2-F-Migration ist durch kurzwellige UV-Strahlung umkehrbar.
      PubDate: 2017-01-10T08:20:56.504938-05:
      DOI: 10.1002/ange.201610179
       
  • Hydrodehalogenation of Haloarenes by a Sodium Hydride–Iodide
           Composite
    • Authors: Derek Yiren Ong; Ciputra Tejo, Kai Xu, Hajime Hirao, Shunsuke Chiba
      Abstract: A simple protocol for hydrodebromination and -deiodination of halo(hetero)arenes was enabled by sodium hydride (NaH) in the presence of lithium iodide (LiI). Mechanistic studies showed that an unusual concerted nucleophilic aromatic substitution operates in the present process.Ein einfaches Protokoll für die Hydrodebromierung und -deiodierung von Halogen(hetero)arenen wurde entwickelt, das Natriumhydrid (NaH) in Gegenwart von Lithiumiodid (LiI) verwendet. Mechanistische Studien zeigen, dass eine ungewöhnliche konzertierte nukleophile aromatische Substitution stattfindet.
      PubDate: 2017-01-10T08:20:51.752188-05:
      DOI: 10.1002/ange.201611495
       
  • Trapping Rare and Elusive Phosphinidene Chalcogenides
    • Authors: Cameron M. E. Graham; Taylor E. Pritchard, Paul D. Boyle, Juuso Valjus, Heikki M. Tuononen, Paul J. Ragogna
      Abstract: Four-membered rings with a P2Ch2 core (Ch=S, Se) and phosphorus in the +3 oxidation state have been synthesized. The utility of these rings as a source of monomeric phosphinidene chalcogenides was probed by the addition of an N-heterocyclic carbene, resulting in a base-stabilized phosphinidene sulfide. Similarly, persistence of the phosphinidene selenide in solution was shown through cycloaddition chemistry with 2,3-dimethylbutadiene at elevated temperatures. The observed reactivity was explained by detailed computational work that established the conditions upon which the P2Ch2 rings can liberate phosphinidene chalcogenides.Viergliedrige Ringe mit einem P2Ch2-Kern (Ch=S, Se) wurden durch die Cyclokondensation von Ar*PCl2 und Ch(TMS)2 synthetisiert, wobei der Phosphor in der Oxidationsstufe +III verbleibt (Ar*=2,6-Mes2C6H3, Mes=2,4,6-(CH3)3C6H2). Die Nützlichkeit dieser Ringe als Quelle für monomere Phosphinidenchalkogenide wurde durch die Addition eines N-heterocyclischen Carbens und von 2,3-Dimethylbutadien demonstriert.
      PubDate: 2017-01-10T08:20:44.045813-05:
      DOI: 10.1002/ange.201611196
       
  • Berichtigung: Benign-by-Design Solventless Mechanochemical Synthesis of
           Three-, Two-, and One-Dimensional Hybrid Perovskites
    • Authors: Alexander D. Jodlowski; Alfonso Yépez, Rafael Luque, Luis Camacho, Gustavo de Miguel
      PubDate: 2017-01-10T08:20:38.100562-05:
      DOI: 10.1002/ange.201612188
       
  • Preprogramming Complex Hydrogel Responses using Enzymatic Reaction
           Networks
    • Authors: Sjoerd G. J. Postma; Ilia N. Vialshin, Casper Y. Gerritsen, Min Bao, Wilhelm T. S. Huck
      Abstract: The creation of adaptive matter is heavily inspired by biological systems. However, it remains challenging to design complex material responses that are governed by reaction networks, which lie at the heart of cellular complexity. The main reason for this slow progress is the lack of a general strategy to integrate reaction networks with materials. Herein we use a systematic approach to preprogram the response of a hydrogel to a trigger, in this case the enzyme trypsin, which activates a reaction network embedded within the hydrogel. A full characterization of all the kinetic rate constants in the system enabled the construction of a computational model, which predicted different hydrogel responses depending on the input concentration of the trigger. The results of the simulation are in good agreement with experimental findings. Our methodology can be used to design new, adaptive materials of which the properties are governed by reaction networks of arbitrary complexity.Frage-und-Antwort-Spiel: Ein systematischer Ansatz für die Integration von Reaktionsnetzwerken in responsive Hydrogele wird vorgestellt. Basierend auf Kenntnissen der Systemkinetik wurden in Abhängigkeit von der Anfangskonzentration des Netzwerktriggers unterschiedliche Gelantworten erhalten.
      PubDate: 2017-01-10T08:20:35.685127-05:
      DOI: 10.1002/ange.201610875
       
  • Macromolecular Design Strategies for Preventing Active-Material Crossover
           in Non-Aqueous All-Organic Redox-Flow Batteries
    • Authors: Sean E. Doris; Ashleigh L. Ward, Artem Baskin, Peter D. Frischmann, Nagarjuna Gavvalapalli, Etienne Chénard, Christo S. Sevov, David Prendergast, Jeffrey S. Moore, Brett A. Helms
      Abstract: Intermittent energy sources, including solar and wind, require scalable, low-cost, multi-hour energy storage solutions in order to be effectively incorporated into the grid. All-Organic non-aqueous redox-flow batteries offer a solution, but suffer from rapid capacity fade and low Coulombic efficiency due to the high permeability of redox-active species across the battery's membrane. Here we show that active-species crossover is arrested by scaling the membrane's pore size to molecular dimensions and in turn increasing the size of the active material above the membrane's pore-size exclusion limit. When oligomeric redox-active organics (RAOs) were paired with microporous polymer membranes, the rate of active-material crossover was reduced more than 9000-fold compared to traditional separators at minimal cost to ionic conductivity. This corresponds to an absolute rate of RAO crossover of less than 3 μmol cm−2 day−1 (for a 1.0 m concentration gradient), which exceeds performance targets recently set forth by the battery industry. This strategy was generalizable to both high and low-potential RAOs in a variety of non-aqueous electrolytes, highlighting the versatility of macromolecular design in implementing next-generation redox-flow batteries.Besseres Sieben durch Chemie: Makromolekulare Chemie bietet einen allgemeinen Ansatz, um bei nur minimalem Verlust an Ionenleitfähigkeit den Durchtritt redoxaktiver organischer Moleküle durch Batteriemembranen zu blockieren. Dieses Resultat löst ein zentrales Problem für die Entwicklung von Redox-Flow-Batterien der nächsten Generation und bereitet den Weg für eine effiziente und preisgünstige Energiespeicherung.
      PubDate: 2017-01-10T08:20:34.150313-05:
      DOI: 10.1002/ange.201610582
       
  • GXXXG-Mediated Parallel and Antiparallel Dimerization of Transmembrane
           Helices and Its Inhibition by Cholesterol: Single-Pair FRET and 2D IR
           Studies
    • Authors: Yoshiaki Yano; Kotaro Kondo, Yuta Watanabe, Tianqi O. Zhang, Jia-Jung Ho, Shinya Oishi, Nobutaka Fujii, Martin T. Zanni, Katsumi Matsuzaki
      Abstract: Small-residue-mediated interhelical packings are ubiquitously found in helical membrane proteins, although their interaction dynamics and lipid dependence remain mostly uncharacterized. We used a single-pair FRET technique to examine the effect of a GXXXG motif on the association of de novo designed (AALALAA)3 helices in liposomes. Dimerization occurred with sub-second lifetimes, which was abolished by cholesterol. Utilizing the nearly instantaneous time-resolution of 2D IR spectroscopy, parallel and antiparallel helix associations were identified by vibrational couplings across helices at their interface. Taken together, the data illustrate that the GXXXG motif controls helix packing but still allows for a dynamic and lipid-regulated oligomeric state.Das Motiv ist wichtig: Transmembranäre Helixmodelle mit GXXXG-Motiv wurden hergestellt, um die Effekte dieses Motivs sowie der Lipidzusammensetzung auf die Helixassoziation zu untersuchen. Einzelpaar-FRET- und 2D-IR-Experimente offenbarten die dynamische Natur, spezifische Grenzflächen und eine hohe Cholesterol-Sensitivität der GXXXG-vermittelten Wechselwirkungen, wodurch die Funktion des Membranproteins aktiv reguliert werden kann.
      PubDate: 2017-01-10T08:15:45.142537-05:
      DOI: 10.1002/ange.201609708
       
  • Tip-Enhanced Raman Spectroscopy to Distinguish Toxic Oligomers from
           Aβ1–42 Fibrils at the Nanometer Scale
    • Authors: Sébastien Bonhommeau; David Talaga, Julien Hunel, Christophe Cullin, Sophie Lecomte
      Abstract: For the first time, natural Aβ1–42 fibrils (WT) implicated in Alzheimer's disease, as well as two synthetic mutants forming less toxic amyloid fibrils (L34T) and highly toxic oligomers (oG37C), are chemically characterized at the scale of a single structure using tip-enhanced Raman spectroscopy (TERS). While the proportion of TERS features associated with amino acid residues is similar for the three peptides, a careful examination of amide I and amide III bands allows us to clearly distinguish WT and L34T fibers organized in parallel β-sheets from the small and more toxic oG37C oligomers organized in anti-parallel β-sheets.Parallel oder antiparallel: Alzheimer-relevante Amyloid-Aβ1–42-Fibrillen sowie zwei Mutanten mit niedrigerer und höherer Zytotoxizität wurden mithilfe spitzenverstärkter Raman-Spektroskopie auf dem Niveau einzelner Fibrillen/Oligomere charakterisiert. Anhand von Amid-Raman-Markerbanden lassen sich zu parallelen β-Faltblättern organisierte Aβ1–42-Fibrillen von den zu antiparallelen β-Faltblättern organisierten Oligomeren unterscheiden.
      PubDate: 2017-01-10T08:15:36.769335-05:
      DOI: 10.1002/ange.201610399
       
  • Electron Solvation and the Unique Liquid Structure of a Mixed-Amine
           Expanded Metal: The Saturated Li–NH3–MeNH2 System
    • Authors: Andrew G. Seel; Helen Swan, Daniel T. Bowron, Jonathan C. Wasse, Thomas Weller, Peter P. Edwards, Christopher A. Howard, Neal T. Skipper
      Abstract: Metal–amine solutions provide a unique arena in which to study electrons in solution, and to tune the electron density from the extremes of electrolytic through to true metallic behavior. The existence and structure of a new class of concentrated metal-amine liquid, Li–NH3–MeNH2, is presented in which the mixed solvent produces a novel type of electron solvation and delocalization that is fundamentally different from either of the constituent systems. NMR, ESR, and neutron diffraction allow the environment of the solvated electron and liquid structure to be precisely interrogated. Unexpectedly it was found that the solution is truly homogeneous and metallic. Equally surprising was the observation of strong longer-range order in this mixed solvent system. This is despite the heterogeneity of the cation solvation, and it is concluded that the solvated electron itself acts as a structural template. This is a quite remarkable observation, given that the liquid is metallic.Gelöste Elektronen: Eine neue Klasse konzentrierter gemischter Metall-Amin-Flüssigkeiten – Li-NH3-MeNH2 – ergibt eine homogene metallische Lösung, in der die delokalisierten solvatisierten Elektronen als Strukturtemplat wirken. Multielement-Isotopensubstitution in Kombination mit NMR- und EPR-Spektroskopie sowie Neutronenstreuung ermöglicht die genaue Untersuchung der Umgebung des solvatisierten Elektrons und der Flüssigkeitsstruktur.
      PubDate: 2017-01-10T08:05:32.831144-05:
      DOI: 10.1002/ange.201609192
       
  • Fullerenes in space
    • Authors: John Paul Maier; Ewen Kyle Campbell
      Abstract: In 1985 the football structure of $\textrm{C}_{60}$, buckminsterfullerene was proposed and subsequently confirmed following its macroscopic synthesis in 1990. From the very beginning the role of $\textrm{C}_{60}$ and $\textrm{C}_{60}^{+}$ in space was considered, particularly in the context of the enigmatic diffuse interstellar bands. These are absorption features found in the spectra of reddened star light. The first astronomical observations were made around one hundred years ago and despite significant efforts none of the interstellar molecules responsible have been identified. The absorption spectrum of $\textrm{C}_{60}^{+}$ was measured in a $5\,\textrm{K}$ neon matrix in 1993 and two prominent bands near $9583\,\textrm{\AA}$ and $9645\,\textrm{\AA}$ were observed. On the basis of this data the likely wavelength range in which the gas phase $\textrm{C}_{60}^{+}$ absorptions should lie was predicted. In 1994 two diffuse interstellar bands were found in this spectral region and proposed to be due to $\textrm{C}_{60}^{+}$. It took over 20 years to measure the absorption spectrum of $\textrm{C}_{60}^{+}$ under conditions similar to those prevailing in diffuse clouds. In 2015, sophisticated laboratory experiments led to the confirmation that these two interstellar bands are indeed caused by $\textrm{C}_{60}^{+}$, providing the first answer to this century old puzzle. Here, we describe the experiments, concepts and astronomical observations that led to the detection of $\textrm{C}_{60}^{+}$ in interstellar space.
      PubDate: 2017-01-10T04:20:29.09953-05:0
      DOI: 10.1002/ange.201612117
       
  • Bis(Cyclic Alkyl Amino Carbene) Ruthenium Complexes: A Versatile, Highly
           Efficient Tool for Olefin Metathesis
    • Authors: Rafał Gawin; Anna Kozakiewicz, Piotr A. Guńka, Paweł Dąbrowski, Krzysztof Skowerski
      Abstract: Ein Bis(CAAC)-Ruthenium-Komplex (CAAC=cyclisches Alkyl(amino)carben) weist eine unerwartet hohe Reaktivität auf und ermöglicht damit die Bildung terminaler und interner C=C-Bindungen bei sehr niedriger Katalysatorkonzentration. K. Skowerski et al. berichten in ihrer Zuschrift (10.1002/ange.201609009) über Wechselzahlen >3×106 für die Selbstmetathese von 1-Decen. Klassische Grubbs- und Hoveyda-Grubbs-Komplexe waren weniger selektiv und wesentlich weniger effizient bei dieser Umwandlung.
      PubDate: 2017-01-04T07:46:01.390093-05:
      DOI: 10.1002/ange.201612373
       
  • Graphisches Inhaltsverzeichnis: Angew. Chem. 4/2017
    • Pages: 933 - 944
      PubDate: 2017-01-13T04:10:29.586314-05:
      DOI: 10.1002/ange.201780411
       
  • Top-Beiträge aus unseren Schwesterzeitschriften: Angew. Chem. 4/2017
    • Pages: 948 - 951
      PubDate: 2017-01-13T04:10:33.692384-05:
      DOI: 10.1002/ange.201780413
       
  • Rücktitelbild: From Palladium to Brønsted Acid Catalysis: Highly
           Enantioselective Regiodivergent Addition of Alkoxyallenes to Pyrazolones
           (Angew. Chem. 4/2017)
    • Authors: Hui Zhou; Zhao Wei, Jinlong Zhang, Huameng Yang, Chungu Xia, Gaoxi Jiang
      Pages: 1180 - 1180
      Abstract: Zwei katalytische Prozesse …… , nämlich Palladium-Katalyse und Brønsted-Säure-Katalyse, liefern unterschiedliche Produkte bei der Addition von Alkoxyallenen an Pyrazolone. Wie G. Jiang et al. in ihrer Zuschrift auf S. 1097 zeigen, führt Pd-Katalyse zu verzweigten allylischen Pyrazol-5-onen unter extrem milden Bedingungen, während eine chirale Brønsted-Säure lineare Additionsprodukte ergibt.
      PubDate: 2017-01-09T07:56:20.26659-05:0
      DOI: 10.1002/ange.201612284
       
  • From Palladium to Brønsted Acid Catalysis: Highly Enantioselective
           Regiodivergent Addition of Alkoxyallenes to Pyrazolones
    • Authors: Hui Zhou; Zhao Wei, Jinlong Zhang, Huameng Yang, Chungu Xia, Gaoxi Jiang
      Abstract: A highly enantioselective regiodivergent addition of alkoxyallenes to pyrazolones was developed to afford multiply functionalized alkylated products bearing a quaternary carbon stereocenter in high yields with excellent stereoselectivities. One approach is enabled by palladium catalysis, thus leading to branched allylic pyrazol-5-ones under mild reaction conditions. The other is catalyzed by a chiral Brønsted acid to give linear products exclusively. Moreover, the usefulness of this new method was highlighted by converting the allylic products into other interesting multifunctionalized pyrazolone derivatives which would be of great potential for the exploitation of pharmaceutically important molecules.Pd gegen Brønsted: Die Titelreaktion liefert mehrfach funktionalisierte alkylierte Produkte in hohen Ausbeuten und mit exzellenten Stereoselektivitäten. Im einen Fall werden unter Palladiumkatalyse verzweigte allylische Pyrazol-5-one unter extrem milden Reaktionsbedingungen erhalten. Die zweite Reaktion wird durch eine chirale Brønsted-Säure katalysiert und liefert ausschließlich lineare Produkte.
      PubDate: 2016-12-30T05:20:47.066695-05:
      DOI: 10.1002/ange.201610473
       
  • Authors Profile
    • PubDate: 2016-12-29T05:40:54.536259-05:
      DOI: 10.1002/ange.201611663
       
  • From composition to cure: A systems engineering approach to anti-cancer
           drug carriers
    • Authors: Sarah Reagan MacEwan; Ashutosh Chilkoti
      Abstract: The molecular complexity and heterogeneity of cancer has led to a persistent, and as yet unsolved, challenge of developing cures for this disease. Although the pharmaceutical industry focuses the bulk of its efforts on the development of new drugs, an alternative —and in many ways complementary— approach is the improvement of the delivery of existing drugs with drug carriers that can manipulate when, where, and how a drug exerts its therapeutic effect. For the treatment of solid tumors, systemically delivered drug carriers face significant challenges that are imposed by the pathophysiological barriers that lie between their site of administration and their site of therapeutic action in the tumor. Furthermore, drug carriers face additional challenges in their translation from pre-clinical validation to clinical approval and adoption. Addressing this diverse network of challenges requires a systems engineering approach to anti-cancer drug delivery. Such a perspective is needed to better enable the rational design of optimized vehicles that navigate the trade-offs of this complex system to create next generation anti-cancer drug carriers that have a realistic prospect for translation from the lab to the patient.
      PubDate: 2016-12-27T22:20:32.206682-05:
      DOI: 10.1002/ange.201610819
       
  • Halogenverbrückte supramolekulare Kapseln im Festkörper, in Lösung und
           in der Gasphase.
    • Authors: Oliver Dumele; Benedikt Schreib, Ulrike Warzok, Nils Trapp, Christoph A. Schalley, François Diederich
      Abstract: Halogen-verbrückte supramolekulare Kapseln wurden im Festkörper, in Lösung und in der Gasphase studiert. F. Diederich et al. beschreiben in ihrer Zuschrift (10.1002/ange.201610884) die erste Röntgenkristallstruktur einer diskreten, neutralen, dimeren Kapsel, die allein über Halogenbrücken aufgebaut wurde. Das Abstimmen des Halogenbrückendonors mit Iodethinyl führte zur höchsten berichteten Assoziationskonstante für neutrale Halogenbrücken-Wechselwirkungen in Lösung.
      PubDate: 2016-12-27T08:31:01.136966-05:
      DOI: 10.1002/ange.201611992
       
  • A Leaf-Inspired Luminescent Solar Concentrator for Energy-Efficient
           Continuous-Flow Photochemistry
    • Authors: Dario Cambié; Fang Zhao, Volker Hessel, Michael G. Debije, Timothy Noël
      Abstract: Solarbetriebene Durchflussreaktionen wurden mit einer innovativen, einem Laubblatt nachempfundenen Funktionseinheit basierend auf dem Konzept des lumineszierenden Solarkonzentrators (LSC) realisiert. In ihrer Zuschrift (
      DOI : 10.1002/ange.201611101) zeigen T. Noël et al. die Fähigkeiten dieser Funktionseinheit, Photonen zu sammeln und spektral umzuwandeln. Diese erste Anwendung eines LSC in der organischen Synthese bietet eine einfache und preiswerte Lösung für die solarbetriebene Photochemie.
      PubDate: 2016-12-23T01:20:22.646575-05:
       
  • Beryllium-Phosphan-Komplexe: Synthese, Eigenschaften und Reaktivität von
           (PMe3)2BeCl2 und (Ph2PC3H6PPh2)BeCl2
    • Authors: Magnus R. Buchner; Matthias Müller, Stefan S. Rudel
      Abstract: Es wird über die gezielte Synthese, die spektroskopischen Eigenschaften und die Reaktivität von Bis(trimethylphosphan)berylliumdichlorid (1) und Bisdiphenylphosphinopropanberylliumdichlorid (2), inklusive der Kristallstruktur von (PMe3)2BeCl2 (1) berichtet. Diese vierfach koordinierten Berylliumverbindungen können mit nButyllithium (nBuLi) zu dreifach koordiniertem (Ph2PC3H6PPh2)BenBu2 (3) und (PMe3)BenBu2 (4) alkyliert werden. PMe3 kann im Vakuum aus (PMe3)BenBu2 (4) entfernt werden, um [nBu2Be]2 (5) zu erhalten. Zum ersten Mal wurde die seit Dekaden postulierte Dimerisierung von [nBu2Be]2 in Lösung spektroskopisch beobachtet. Diese neuartige, etherfreie Syntheseroute ermöglicht den Zugang zu Berylliumdialkylen, unter völligem Ausschluss sauerstoffatomhaltiger Reagenzien und Lösungsmittel. Diese “Sauerstofffreiheit” ist entscheidend für Halbleiteranwendungen, bei denen Sauerstoff oft unerwünscht ist und um jeden Preis vermieden werden muss.Sauerstoffbefreit: Phosphankomplexe von Berylliumchlorid wurden synthetisiert und auf ihre Eigenschaften und Reaktivität untersucht. Die Phosphanliganden agieren als entfernbare Lösungsvermittler, um Reaktionen in unpolaren, sauerstoffatomfreien Lösungsmitteln zu ermöglichen. Dies führte zu einer neuartigen Syntheseroute für Berylliumalkyle und dem ersten spektroskopischen Nachweis für die Dimerisierung von nBu2Be.
      PubDate: 2016-12-22T03:55:36.691149-05:
      DOI: 10.1002/ange.201610956
       
  • Asymmetric Strecker Reaction Arising from the Molecular Orientation of an
           Achiral Imine at the Single-Crystal Face: Enantioenriched l- and d-Amino
           Acids
    • Authors: Shinobu Miyagawa; Koji Yoshimura, Yusuke Yamazaki, Naoya Takamatsu, Tetsuya Kuraishi, Shohei Aiba, Yuji Tokunaga, Tsuneomi Kawasaki
      Abstract: Strecker synthesis has long been considered one of the prebiotic reactions for the synthesis of α-amino acids. However, the correlation between the origin of chirality and highly enantioenriched α-amino acids through this method remains a puzzle. In the reaction, it may be conceivable that the handedness of amino acids has been determined at the formation stage of the chiral intermediate α-aminonitrile, that is, the enantioselective addition of hydrogen cyanide to an imine. Herein, an enantiotopic crystal surface of an achiral imine acted as an origin of chirality for the enantioselective formation of α-aminonitriles by the addition of HCN. In conjunction with the amplification of the enantiomeric excess and multiplication of enantioenriched aminonitrile, a large amount of near enantiopure α-amino acids, with the l- and d-handedness corresponding to the molecular orientation of the imine, is reported.Enantiotope Flächen: Ein hoch enantiomerenangereichertes Aminonitril wurde durch asymmetrische Addition von HCN an eine der Kristallflächen eines achiralen Imins gebildet, einhergehend mit der Verstärkung des ee-Wertes und der Multiplikation enantiomerenangereicherter Produkte. Damit wurde ein möglicher Einstieg in den Ursprung chiraler Aminosäuren im Rahmen der Strecker-Reaktion gefunden.
      PubDate: 2016-12-22T03:50:54.412769-05:
      DOI: 10.1002/ange.201611128
       
  • A Leaf-Inspired Luminescent Solar Concentrator for Energy-Efficient
           Continuous-Flow Photochemistry
    • Authors: Dario Cambié; Fang Zhao, Volker Hessel, Michael G. Debije, Timothy Noël
      Abstract: The use of solar light to promote chemical reactions holds significant potential with regard to sustainable energy solutions. While the number of visible light-induced transformations has increased significantly, the use of abundant solar light has been extremely limited. We report a leaf-inspired photomicroreactor that constitutes a merger between luminescent solar concentrators (LSCs) and flow photochemistry to enable green and efficient reactions powered by solar irradiation. This device based on fluorescent dye-doped polydimethylsiloxane collects sunlight, focuses the energy to a narrow wavelength region, and then transports that energy to embedded microchannels where the flowing reactants are converted.Ein künstliches Laubblatt: Eine Funktionseinheit, die das Konzept des lumineszierenden Solarkonzentrators mit einem Photomikroreaktor verbindet, ermöglicht die Lichtsammlung für photochemische Reaktionen. Der einem Laubblatt ähnelnde Photomikroreaktor sammelt Sonnenlicht, fokussiert die Energie auf einen schmalen Wellenlängenbereich und transportiert die Energie zu eingebetteten Mikrokanälen, in denen die strömenden Reaktanden umgewandelt werden.
      PubDate: 2016-12-22T01:38:46.547667-05:
      DOI: 10.1002/ange.201611101
       
  • Lithium Dihydropyridine Dehydrogenation Catalysis: A Group 1 Approach to
           the Cyclization of Diamine Boranes
    • Authors: Ross McLellan; Alan R. Kennedy, Samantha A. Orr, Stuart D. Robertson, Robert E. Mulvey
      Abstract: In reactions restricted previously to a ruthenium catalyst, a 1-lithium-2-alkyl-1,2-dihydropyridine complex is shown to be a competitive alternative dehydrogenation catalyst for the transformation of diamine boranes into cyclic 1,3,2-diazaborolidines, which can in turn be smoothly arylated in good yields. This study established the conditions and solvent dependence of the catalysis through NMR monitoring, with mechanistic insight provided by NMR (including DOSY) experiments and X-ray crystallographic studies of several model lithio intermediates.Copy-Kat: In Reaktionen, die zuvor auf Rutheniumkatalysatoren beschränkt waren, wirkt ein 1-Lithium-2-alkyl-1,2-dihydropyridin-Komplex als Dehydrierungskatalysator zur Umsetzung von Diaminboranen in cyclische 1,3,2-Diazaborolidine (siehe Schema). Der Mechanismus wurde durch NMR-Experimente und Röntgenkristallographie von Modellzwischenstufen untersucht.
      PubDate: 2016-12-21T08:25:54.172091-05:
      DOI: 10.1002/ange.201610905
       
  • CO2 Capture from Ambient Air by Crystallization with a Guanidine Sorbent
    • Authors: Charles A. Seipp; Neil J. Williams, Michelle K. Kidder, Radu Custelcean
      Abstract: Carbon capture and storage is an important strategy for stabilizing the increasing concentration of atmospheric CO2 and the global temperature. A possible approach toward reversing this trend and decreasing the atmospheric CO2 concentration is to remove the CO2 directly from air (direct air capture). Herein we report a simple aqueous guanidine sorbent that captures CO2 from ambient air and binds it as a crystalline carbonate salt by guanidinium hydrogen bonding. The resulting solid has very low aqueous solubility (Ksp=1.0(4)×10−8), which facilitates its separation from solution by filtration. The bound CO2 can be released by relatively mild heating of the crystals at 80–120 °C, which regenerates the guanidine sorbent quantitatively. Thus, this crystallization-based approach to CO2 separation from air requires minimal energy and chemical input, and offers the prospect for low-cost direct air capture technologies.Lufterfrischer: Ein einfacher wässriger Bisiminoguanidin-Ligand (PyBIG) fängt CO2 aus der Umgebungsluft ab und bindet es über Guanidinium-Wasserstoffbrücken in Form eines kristallinen Carbonatsalzes. CO2-Gas kann durch mildes Erwärmen der Carbonatkristalle freigesetzt werden, und der Guanidin-Ligand wird quantitativ zurückgewonnen.
      PubDate: 2016-12-21T08:25:50.99681-05:0
      DOI: 10.1002/ange.201610916
       
  • In-Cell Activation of Organo-Osmium(II) Anticancer Complexes
    • Authors: Russell J. Needham; Carlos Sanchez-Cano, Xin Zhang, Isolda Romero-Canelón, Abraha Habtemariam, Margaret S. Cooper, Levente Meszaros, Guy J. Clarkson, Philip J. Blower, Peter J. Sadler
      Abstract: The family of iodido OsII arene phenylazopyridine complexes [Os(η6-p-cym)(5-R1-pyridylazo-4-R2-phenyl))I]+ (where p-cym=para-cymene) exhibit potent sub-micromolar antiproliferative activity towards human cancer cells and are active in vivo. Their chemical behavior is distinct from that of cisplatin: they do not readily hydrolyze, nor bind to DNA bases. We report here a mechanism by which they are activated in cancer cells, involving release of the I− ligand in the presence of glutathione (GSH). The X-ray crystal structures of two active complexes are reported, 1-I (R1=OEt, R2=H) and 2-I (R1=H, R2=NMe2). They were labelled with the radionuclide 131I (β−/γ emitter, t1/2 8.02 d), and their activity in MCF-7 human breast cancer cells was studied. 1-[131I] and 2-[131I] exhibit good stability in both phosphate-buffered saline and blood serum. In contrast, once taken up by MCF-7 cells, the iodide ligand is rapidly pumped out. Intriguingly, GSH catalyzes their hydrolysis. The resulting hydroxido complexes can form thiolato and sulfenato adducts with GSH, and react with H2O2 generating hydroxyl radicals. These findings shed new light on the mechanism of action of these organo-osmium complexes.Os-I-Bindungsaktivierung: Iodid-OsII-Arenphenylazopyridin-Komplexe zeigen vielversprechende Antitumoreigenschaften in vitro und in vivo. Überraschenderweise können sie durch Hydrolyse der Os-I-Bindung in Gegenwart von Glutathion (GSH) in Zellen aktiviert werden. Die neu gebildeten Hydroxidokomplexe sind reaktiver und können Chlorid-, Thiolat- und Sulfenat-Addukte mit GSH bilden sowie mit H2O2 unter Bildung von Hydroxylradikalen reagieren.
      PubDate: 2016-12-21T08:25:49.073884-05:
      DOI: 10.1002/ange.201610290
       
  • Gaining Momentum: Sulfonimidamides in Medicinal- and Agrochemistry
    • Authors: Praveen K Chinthakindi; Tricia Naicker, Niranjan Thota, Thavendran Govender, Hendrik G Kruger, Per I. Arvidsson
      Abstract: Synthesis and evaluation of structural analogues and isosteres represent a cornerstone methodology among the practitioners of medicinal- and agrochemistry. The sulfonamide functional group represents one of the most important amide isosteres in contemporary drug design, with some 500 compounds that has overcome both the pharmacological and regulatory hurdles that precede studies in humans. We note that mono aza-analogues of sulfonamides, i.e. sulfonimidamides, are rapidly gaining popularity as a novel functional group among molecular architects involved in the design of biologically active compounds for both pharmaceutical- and agrochemical applications. Herein, we review these recent developments with the ambition to showcase the promise of this functional group to the wider chemical community.
      PubDate: 2016-12-13T06:05:24.30595-05:0
      DOI: 10.1002/ange.201610456
       
  • Methyltransferase directed labeling of biomolecules and its applications
    • Authors: Jochem Deen; Charlotte Vranken, Volker Leen, Robert K Neely, Kris Pieter Frans Janssen, Johan Hofkens
      Abstract: Methyltransferases (MTases) compose a large family of enzymes which have the ability to methylate a diverse set of targets, ranging from the three major biopolymers DNA, RNA and protein to small molecules. Most of these MTases use the cofactor S-Adenosyl-L-Methionine (AdoMet) as their methyl source. Given the important biological role of methylation, e.g. in epigenetic regulation of gene activity and the vast potential of targeted functionalization in biology, diagnostics and nanotechnology, it should come as no surprise that recent years have seen significant efforts in the development of AdoMet analogues with the aim of transferring moieties other than simple methyl groups. Two major classes of AdoMet analogues currently exist- the doubly-activated and aziridine based molecules- each of which employs a different approach for transalkylation, as opposed to transmethylation, of the target molecule. In this review, we discuss the various strategies for labelling and functionalizing biomolecules using AdoMet-dependent MTases and AdoMet analogues. We cover the synthetic routes to AdoMet analogues, their stability in biological environments and their application in transalkylation reactions. Finally, some perspectives are presented for the potential use of AdoMet analogues in biology research, (epi)genetics and nanotechnology.
      PubDate: 2016-12-12T04:16:28.246834-05:
      DOI: 10.1002/ange.201608625
       
  • Synthetic Biology - The Synthesis of Biology
    • Authors: Simon Ausländer; David Ausländer, Martin Fussenegger
      Abstract: Synthetic biology envisages the engineering of man-made living biomachines from standardized components that can perform pre-defined functions in a (self-)controlled manner. Different research strategies and interdisciplinary efforts are pursued to implement engineering principles to biology. The "top-down" strategy exploits nature's incredible diversity of existing, natural parts to construct synthetic compositions of genetic, metabolic or signalling networks with predictable and controllable properties. This mainly application-driven approach results in living factories that produce drugs, biofuels, biomaterials and fine chemicals and results in living pills that are based on engineered cells with the capacity to autonomously detect and treat disease states in vivo. In contrast, the "bottom-up" strategy seeks to be independent of existing living systems by designing biological systems from scratch and synthesizing artificial biological entities not found in nature. This more knowledge-driven approach investigates the reconstruction of minimal biological systems that are capable of performing basic biological phenomena, such as self-organization, self-replication and self-sustainability. Moreover, the syntheses of artificial biological units, such as synthetic nucleotides or amino acids, and their implementation into polymers inside living cells currently set the boundaries between natural and artificial biological systems. In particular, the in vitro design, synthesis and transfer of complete genomes into host cells and the application of efficient genome-wide intervention techniques point to the future of synthetic biology: the creation of living designer cells with tailored desirable properties for biomedicine and biotechnology.
      PubDate: 2016-12-11T23:24:13.846386-05:
      DOI: 10.1002/ange.201609229
       
  • 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
       
  • 50 (and more) Years of Propellane Chemistry - From a Chemical Curiosity to
           "Explosive" Applications in Material Sciences and Natural Product
           Chemistry
    • Authors: Alicia Merve Dilmac; Eduard Spuling, Armin de Meijere, Stefan Bräse
      Abstract: Propellanes are a unique class of compounds with well over 10000 members with an inverted tetrahedral configuration featuring a weak single bond between two carbon atoms linked by three additional bridge. Not only structurally interesting, these propella-type compounds exhibit unusual reactivities. In this review, we highlight their synthesis and applications in material sciences, natural product chemistry and medicinal chemistry. We feature the chemistry of [1.1.1]propellane like the synthesis of oligomeric and polymeric structures derived from it such as bicyclo[1.1.1]pentanes and staffanes. A selected number of natural products are discussed in detail. Heteropropellanes and inorganic propellanes are also addressed. The historical background is given in brief showing the pioneering work of David Ginsburg, Günther Snatzke, Günter Szeimies, Kenneth Wiberg and others.
      PubDate: 2016-11-30T12:15:40.668115-05:
      DOI: 10.1002/ange.201603951
       
  • Label-free molecular imaging of biological cells and tissues by linear and
           non-linear Raman spectroscopic approaches
    • Authors: Jürgen Popp; Christoph Krafft, Michael Schmitt, Iwan Schie, Dana Cialla-May, Christian Matthaeus, Thomas Bocklitz
      Abstract: Raman spectroscopy is an emerging technique in bioanalysis and imaging of biomaterials due to its unique spectroscopic fingerprint capabilities. Imaging of cells and tissues by Raman microspectroscopy represents a non-destructive and label-free approach. All components of cells or tissues contribute to the Raman signals giving complex spectral signatures. Long acquisitions times are often required due to the relatively small Raman scattering cross sections. To overcome these limitations, Raman signal enhancing methods like resonance Raman scattering and surface enhanced Raman scattering can be applied that also reduce the spectral complexity because the enhancement is often restricted to selected bands. Raman-active labels can be introduced to increase specificity and multimodality. In addition, non-linear coherent Raman scattering such as coherent anti-Stokes Raman scattering and stimulated Raman scattering offer higher sensitivities which enable rapid imaging of larger sampling areas. Finally, fiber based imaging techniques open the way towards in vivo applications of Raman spectroscopy. This critical review summarizes theory, instrumentation, data processing and progress of medical Raman imaging since 2012.
      PubDate: 2016-11-15T16:29:42.063815-05:
      DOI: 10.1002/ange.201607604
       
  • 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
       
  • 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
       
  • 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
       
  • 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
       
  • 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
       
  • 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
       
  • Perlmutt-Mimetika durch Ice-Templating
    • Authors: Qunfeng Cheng; Lei Jiang
      Pages: 954 - 955
      Abstract: Perlmutt aus dem Eis: Die bioinspirierte Methode des Ice-Templating bietet Zugang zu leistungsfähigen lamellaren Kompositstoffen. Permuttartige Materialien mit einstellbaren Nano- und Mikrostrukturen und exzellenten physikalischen Eigenschaften sind auf diese Weise zugänglich.
      PubDate: 2016-12-14T05:05:48.067115-05:
      DOI: 10.1002/ange.201610176
       
  • Carbokatalyse in Flüssigphasenreaktionen
    • Authors: Dang Sheng Su; Guodong Wen, Shuchang Wu, Feng Peng, Robert Schlögl
      Pages: 956 - 985
      Abstract: Die metallfreie Katalyse ist in Bezug auf nachhaltige Chemie auf ein breites Interesse gestoßen. Kohlenstoffkatalyse ist eine “grüne” Alternative für katalytische Prozesse in der Gas- und Flüssigphase. Insbesondere für Dehydrierungen in der Gasphase wurde dies anhand von zahlreichen Beispielen dokumentiert, wobei Kohlenstoff ein vielversprechender Ersatz für Metalloxidsysteme sein kann. Die Kohlenstoffkatalyse in der Flüssigphase, speziell in der organischen Synthese, ist eine aufstrebende Forschungsrichtung, die sich in den letzten Jahren sehr schnell entwickelt hat. Hier wird der aktuelle Entwicklungsstand von Kohlenstoffkatalysatoren für Flüssigphasenreaktionen kritisch analysiert, wobei ein Fokus auf die Reaktionsmechanismen sowie auf Vorteile und Einschränkungen von metallfreien Kohlenstoffkatalysatoren gelegt ist.Katalyse mit Kohlenstoff: Die Carbokatalyse von Flüssigphasenreaktionen, eine speziell für die organische Synthese neue Forschungsrichtung, hat in den vergangenen Jahren eine schnelle Entwicklung durchlaufen. Dieser Aufsatz analysiert den aktuellen Stand auf diesem Gebiet, wobei der Fokus auf den möglichen Reaktionsmechanismen sowie Vorteilen und Grenzen liegt.
      PubDate: 2016-12-07T07:40:00.189202-05:
      DOI: 10.1002/ange.201600906
       
  • 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
      Pages: 986 - 991
      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
       
  • Quasimolecules in Compressed Lithium
    • Authors: Mao-sheng Miao; Roald Hoffmann, Jorge Botana, Ivan I. Naumov, Russell J. Hemley
      Pages: 992 - 995
      Abstract: Under high pressure, some materials form electrides, with valence electrons separated from all atoms and occupying interstitial regions. This is often accompanied by semiconducting or insulating behavior. The interstitial quasiatoms (ISQ) that characterize some high pressure electrides have been postulated to show some of the chemical features of atoms, including the potential of forming covalent bonds. It is argued that in the observed high-pressure semiconducting Li phase (oC40, Aba2), an example of such quasimolecules is realized. The theoretical evaluation of electron density, electron localization function, Wannier orbitals, and bond indices forms the evidence for covalently bonded ISQ pairs in this material. The quasimolecule concept thus provides a simple chemical perspective on the unusual insulating behavior of such materials, complementing the physical picture previously presented where the global crystal symmetry of the system plays the major role.Die interstitiellen Quasiatome in der Hochdruckelektridphase von elementarem Lithium können kovalent gebundene Paare bilden. Die bindenden und antibindenden Zustände dieser Quasimoleküle öffnen eine Energielücke. Das Quasimolekülkonzept bietet einen einfachen chemischen Blick auf das ungewöhnliche isolierende Verhalten von Hochdrucklithium. Die Fähigkeit zur Bildung kovalenter Bindungen untermauert die Rolle interstitieller Quasiatome als fundamentale chemische Spezies.
      PubDate: 2016-12-21T02:05:39.300324-05:
      DOI: 10.1002/ange.201608490
       
  • Widely Controllable Syngas Production by a Dye-Sensitized TiO2 Hybrid
           System with ReI and CoIII Catalysts under Visible-Light Irradiation
    • Authors: Jong-Su Lee; Dong-Il Won, Won-Jo Jung, Ho-Jin Son, Chyongjin Pac, Sang Ook Kang
      Pages: 996 - 1000
      Abstract: Visible-light irradiation of a ternary hybrid catalyst prepared by grafting a dye, an H2 evolving CoIII catalyst and a CO-producing ReI catalyst on TiO2 have been found to produce both H2 and CO (syngas) in CO2-saturated N,N-dimethyl formamide (DMF)/water solution containing a 0.1 m sacrificial electron donor. The H2/CO ratios are effectively controlled by changing either the water content of the solvent or the molar ratio of the ReI and CoIII catalysts ranging from 1:2 to 15:1. The controlled syngas formation is discussed in terms of competitive electron flow from TiO2 to each of the CO2-reduction and hydrogen-evolving sites depending on the efficiencies of the two catalytic reaction cycles under given reaction conditions.Synthesegasproduktion: Ein farbstoffsensibilisiertes TiO2-Hybridsystem aus TiO2-Partikeln, an deren Oberfläche ein Farbstoff, ein H2-entwickelnder CoIII-Katalysator und ein CO-produzierender ReI-Katalysator gebunden wurden, produziert H2 und CO (Synthesegas) in einer CO2-gesättigten Dimethylformamid/Wasser-Lösung. Das H2/CO-Verhältnis konnte über einen breiten Bereich kontrolliert werden.
      PubDate: 2016-12-14T05:10:52.725222-05:
      DOI: 10.1002/ange.201608593
       
  • Bis(Cyclic Alkyl Amino Carbene) Ruthenium Complexes: A Versatile, Highly
           Efficient Tool for Olefin Metathesis
    • Authors: Rafał Gawin; Anna Kozakiewicz, Piotr A. Guńka, Paweł Dąbrowski, Krzysztof Skowerski
      Pages: 1001 - 1006
      Abstract: The state-of-the-art in olefin metathesis is application of N-heterocyclic carbene (NHC)-containing ruthenium alkylidenes for the formation of internal C=C bonds and of cyclic alkyl amino carbene (CAAC)-containing ruthenium benzylidenes in the production of terminal olefins. A straightforward synthesis of bis(CAAC)Ru indenylidene complexes, which are highly effective in the formation of both terminal and internal C=C bonds at loadings as low as 1 ppm, is now reported.Einer für alle: Bis(CAAC)-Ru-Indenyliden-Komplexe (CAAC=cyclisches Alkyl(amino)carben) wurden für die Olefinmetathese hergestellt. Diese Katalysatoren fördern hoch effizient und selektiv die Bildung endständiger und innerer C-C-Doppelbindungen. CM=Kreuzmetathese, RCM=Ringschlussmetathese, ROMP=ringöffnende Metathesepolymerisation.
      PubDate: 2016-12-12T03:30:35.952903-05:
      DOI: 10.1002/ange.201609009
       
  • Copper(II)–Thymine Coordination Polymer Nanoribbons as Potential
           Oligonucleotide Nanocarriers
    • Authors: Verónica G. Vegas; Romina Lorca, Ana Latorre, Khaled Hassanein, Carlos J. Gómez-García, Oscar Castillo, Álvaro Somoza, Félix Zamora, Pilar Amo-Ochoa
      Pages: 1007 - 1011
      Abstract: The direct reaction between copper nitrate, thymine-1-acetic acid, and 4,4′-bipyridine in water leads to the formation of a blue colloid comprising uniform crystalline nanoribbons (length >1 μm; width ca. 150–185 nm; diameter ca. 15–60 nm) of a coordination polymer. The polymer displays a thymine-based structure freely available for supramolecular interactions. These nanostructures show significant selective interaction with single-stranded oligonucleotides based on adenine. Remarkably, they present low cell toxicity in three cell lines–despite the copper(II) content–and can be used as nanocarriers of oligonucleotides. These results suggest the potential of these types of nanostructures in several biological applications.Kristalline Nanobänder eines Kupfer-Thymin-Koordinationspolymers binden bevorzugt an Adenin-haltige Oligonukleotide und sind nur schwach zytotoxisch. Die Nanostrukturen eignen sich für den Transport von Oligonukleotiden in Zellen.
      PubDate: 2016-12-09T05:56:10.620243-05:
      DOI: 10.1002/ange.201609031
       
  • Coupling Sensitive Nucleic Acid Amplification with Commercial Pregnancy
           Test Strips
    • Authors: Yan Du; Arti Pothukuchy, Jimmy D. Gollihar, Armin Nourani, Bingling Li, Andrew D. Ellington
      Pages: 1012 - 1016
      Abstract: The detection of nucleic acid biomarkers for point-of-care (POC) diagnostics is currently limited by technical complexity, cost, and time constraints. To overcome these shortcomings, we have combined loop-mediated isothermal amplification (LAMP), programmable toehold-mediated strand-exchange signal transduction, and standard pregnancy test strips. The incorporation of an engineered hCG–SNAP fusion reporter protein (human chorionic gonadotropin-O6-alkylguanine-DNA alkyltransferase) led to LAMP-to-hCG signal transduction on low-cost, commercially available pregnancy test strips. Our assay reliably detected as few as 20 copies of Ebola virus templates in both human serum and saliva and could be adapted to distinguish a common melanoma-associated SNP allele (BRAF V600E) from the wild-type sequence. The methods described are completely generalizable to many nucleic acid biomarkers, and could be adapted to provide POC diagnostics for a range of pathogens.Alternative Verwendung für Schwangerschaftsteststreifen: Ein Reporter-Fusionsprotein aus humanem Choriongonadotropin (hCG) und dem SNAP-Protein ermöglichte die Synthese des hCG-DNA-Konjugats. Isotherme Amplifizierungsassays wurden mit Strangaustausch-Nucleinsäure-Transducern gekoppelt und auf diese Art hCG-Signale erzeugt, die direkt mithilfe käuflicher Schwangerschaftsteststreifen interpretiert werden können.
      PubDate: 2016-12-19T04:35:34.707995-05:
      DOI: 10.1002/ange.201609108
       
  • Graphene Oxide Restricts Growth and Recrystallization of Ice Crystals
    • Authors: Hongya Geng; Xing Liu, Guosheng Shi, Guoying Bai, Ji Ma, Jingbo Chen, Zhuangyuan Wu, Yanlin Song, Haiping Fang, Jianjun Wang
      Pages: 1017 - 1021
      Abstract: We show graphene oxide (GO) greatly suppresses the growth and recrystallization of ice crystals, and ice crystals display a hexagonal shape in the GO dispersion. Preferred adsorption of GO on the ice crystal surface in liquid water leads to curved ice crystal surface. Therefore, the growth of ice crystal is suppressed owing to the Gibbs–Thompson effect, that is, the curved surface lowers the freezing temperature. Molecular dynamics simulation analysis reveals that oxidized groups on the basal plane of GO form more hydrogen bonds with ice in comparison with liquid water because of the honeycomb hexagonal scaffold of graphene, giving a molecular-level mechanism for controlling ice formation. Application of GO for cryopreservation shows that addition of only 0.01 wt % of GO to a culture medium greatly increases the motility (from 24.3 % to 71.3 %) of horse sperms. This work reports the control of growth of ice with GO, and opens a new avenue for the application of 2D materials.Liquide bleiben: Graphenoxid (GO) hat einen starken Einfluss auf die Form von Eiskristallen und unterdrückt das Wachstum und die Umkristallisation von Eis. Der Effekt resultiert aus der bevorzugten Adsorption von GO an Eiskristalloberflächen in flüssigem Wasser und eröffnet Möglichkeiten für die Verwendung von GO als Gefrierschutz.
      PubDate: 2016-12-15T06:10:52.912736-05:
      DOI: 10.1002/ange.201609230
       
  • Protein Structural Ensembles Visualized by Solvent Paramagnetic Relaxation
           Enhancement
    • Authors: Zhou Gong; Xin-Hua Gu, Da-Chuan Guo, Jin Wang, Chun Tang
      Pages: 1022 - 1026
      Abstract: A protein can be in different conformations when fulfilling its function. Yet depiction of protein structural ensembles remains difficult. Here we show that the accurate measurement of solvent paramagnetic relaxation enhancement (sPRE) in the presence of an inert paramagnetic cosolute allows the assessment of protein dynamics. Demonstrated with two multi-domain proteins, we present a method to characterize protein microsecond–millisecond dynamics based on the analysis of the sPRE. Provided with the known structures of a protein, our method uncovers an ensemble of structures that fully accounts for the observed sPRE. In conjunction with molecular dynamics simulations, our method can identify protein alternative conformation that has only been theorized before. Together, our method expands the application of sPRE beyond structural characterization of rigid proteins and complements the established PRE NMR technique.Alternative Proteinkonformationen: Paramagnetische Relaxationsverstärkung (sPRE) wird ausgelöst, wenn ein inerter paramagnetischer gelöster Stoff mit einem Protein kollidiert. Ein Proteinnukleus kann ensemblegemittelte sPRE erfahren, wenn das Protein zwischen verschiedenen Konformationszuständen fluktuiert. Die Untersuchung der sPRE ermöglicht somit die Visualisierung des Proteinstrukturensembles.
      PubDate: 2016-12-19T04:35:41.49205-05:0
      DOI: 10.1002/ange.201609830
       
  • Structural Basis of Sirtuin 6 Activation by Synthetic Small Molecules
    • Authors: Weijie You; Dante Rotili, Tie-Mei Li, Christian Kambach, Marat Meleshin, Mike Schutkowski, Katrin F. Chua, Antonello Mai, Clemens Steegborn
      Pages: 1027 - 1031
      Abstract: Sirtuins are protein deacylases regulating metabolism and stress responses, and are implicated in aging-related diseases. Small molecule activators for the human sirtuins Sirt1-7 are sought as chemical tools and potential therapeutics, such as for cancer. Activators are available for Sirt1 and exploit its unique N-terminus, whereas drug-like activators for Sirt2–7 are lacking. We synthesized and screened pyrrolo[1,2-a]quinoxaline derivatives, yielding the first synthetic Sirt6 activators. Biochemical assays show direct, substrate-independent compound binding to the Sirt6 catalytic core and potent activation of Sirt6-dependent deacetylation of peptide substrates and complete nucleosomes. Crystal structures of Sirt6/activator complexes reveal that the compounds bind to a Sirt6-specific acyl channel pocket and identify key interactions. Our results establish potent Sirt6 activation with small molecules and provide a structural basis for further development of Sirt6 activators as tools and therapeutics.Sirt6-Aktivatoren: Sirtuine sind Proteindeacylasen, die an Stressantworten und altersbedingten Krankheiten beteiligt sind. Mehrere Pyrrolo[1,2-a]chinoxaline werden als die ersten potenten synthetischen Sirt6-Aktivatoren beschrieben. Die Kristallstrukturen von Sirtuin 6/Aktivator-Komplexen offenbaren eine isoformspezifische Bindungsstelle und schaffen die Grundlage für weitere Wirkstoffentwicklungen.
      PubDate: 2016-12-19T04:30:34.205172-05:
      DOI: 10.1002/ange.201610082
       
  • High-Throughput Screening of Catalytic H2 Production
    • Authors: Jamin Koo; Tim Schnabel, Sylvie Liong, Niklaus H. Evitt, James R. Swartz
      Pages: 1032 - 1036
      Abstract: Hydrogenases, ferredoxins, and ferredoxin-NADP+ reductases (FNR) are redox proteins that mediate electron metabolism in vivo, and are also potential components for biological H2 production technologies. A high-throughput H2 production assay device (H2PAD) is presented that enables simultaneous evaluation of 96 individual H2 production reactions to identify components that improve performance. Using a CCD camera and image analysis software, H2PAD senses the chemo-optical response of Pd/WO3 thin films to the H2 produced. H2PAD-enabled discovery of hydrogenase and FNR mutants that enhance biological H2 production is reported. From a library of 10 080 randomly mutated Clostridium pasteurianum [FeFe] hydrogenases, we found a mutant with nearly 3-fold higher H2 production specific activity. From a library of 400 semi-randomly mutated Oryza sativa FNR, the top hit enabled a 60 % increase in NADPH-driven H2 production rates. H2PAD can also facilitate elucidation of fundamental biochemical mechanisms within these systems.H2PAD: Eine Plattform für das quantitative Screening der H2-Produktionsraten enzymkatalysierter Elektronentransferpfade wurde entwickelt. Gegenüber dem gaschromatographischen Screening kann der Durchsatz um eine Größenordnung gesteigert werden. Zudem ist die Plattform mit der zellfreien Proteinsynthese auf 96er Titerplatten kompatibel.
      PubDate: 2016-12-15T06:10:54.212235-05:
      DOI: 10.1002/ange.201610260
       
  • Gold-Catalyzed Direct Oxidative Arylation with Boron Coupling Partners
    • Authors: Manuel Hofer; Alexandre Genoux, Roopender Kumar, Cristina Nevado
      Pages: 1041 - 1045
      Abstract: An efficient synthesis of biaryls through a gold-catalyzed oxidative cross-coupling of arenes with strong electron-deprived aryl boronates is presented herein. Regio- and chemocontrol are achieved by the selective activation of these coupling partners by gold at different oxidation states. Under reaction conditions devoid of basic additives or directing groups, the role of acetato ligand as an internal base has been revealed as a key parameter for expanding the reaction scope in these transformations.Eine goldkatalysierte Biarylsynthese ausgehend von Arenen und elektronenarmen Arylboranen benötigt weder dirigierende Gruppen noch basische Additive und bietet eine Ergänzung zu existierenden Methoden. Die hohe Regio- und Chemoselektivität ist das Ergebnis der spezifischen Reaktivität der Reaktionspartner mit Gold in verschiedenen Oxidationsstufen und der Rolle des Acetatoliganden als interne Base.
      PubDate: 2016-12-21T08:25:27.819425-05:
      DOI: 10.1002/ange.201610457
       
  • Development of Gold-catalyzed [4+1] and [2+2+1]/[4+2] Annulations between
           Propiolate Derivatives and Isoxazoles
    • Authors: Rajkumar Lalji Sahani; Rai-Shung Liu
      Pages: 1046 - 1050
      Abstract: Two new gold-catalyzed annulations of isoxazoles with propiolates have been developed. Most isoxazoles follow an initial O attack on the alkyne to afford a [4+1] annulation product. This process results in a remarkable alkyne cleavage of initial propiolates. Unsubstituted isoxazoles proceed through an N attack step to yield formal [2+2+1]/[4+2] annulation products. These two annulation products arise initially from two seven-membered heterocyclic intermediates, which then lead to products.Angriffsplan: Zwei neue goldkatalysierte Anellierungen von Isoxazolen mit Propiolaten wurden entwickelt, die als [4+1]-Anellierungen mit den meisten Isoxazolen und als formale [2+2+1]/[4+2]-Anellierungen mit unsubstituierten Isoxazolen verlaufen. Die Verschiedenartigkeit der Anellierungen resultiert aus unterschiedlichen Angriffen – N oder O – des Isoxazols am Propiolat.
      PubDate: 2016-12-16T04:45:30.533777-05:
      DOI: 10.1002/ange.201610665
       
  • Stable Di- and Tri-coordinated Carbon(II) Supported by an Electron-Rich
           β-Diketiminate Ligand
    • Authors: Vianney Regnier; Yoan Planet, Curtis E. Moore, Jacques Pecaut, Christian Philouze, David Martin
      Pages: 1051 - 1055
      Abstract: Complexes of the ubiquitous β-diketiminates (NacNac) ligands have been reported with most elements of the periodic table, including Group 14 Si, Ge, Sn, and Pb. The striking absence of carbon representatives has been attributed to the extreme electrophilicity of the putative C-NacNac adducts. An electron enriched 2,4-(dimethylamino)diketiminato backbone is described, which allowed for the synthesis and isolation of such stable pyrimidin-1,3-diium and pyrimidinium-2-ylidene salts. Structural and preliminary reactivity studies are reported, including an air-stable gold complex. An unforeseen original class of stable N-heterocyclic carbenes and, more generally, the potential of electron-rich NacNac patterns for taming highly electrophilic centers are showcased.Endlich auch Kohlenstoff: Nach den meisten Elementen des Periodensystems, einschließlich Silicium, Germanium, Zinn und Blei aus der Gruppe 14, wurden nun auch niedervalente Addukte von Kohlenstoff(II) – mit einem β-Diketiminat-Liganden – entworfen und isoliert.
      PubDate: 2016-12-20T02:21:33.582517-05:
      DOI: 10.1002/ange.201610798
       
  • Brute Force Orientation of Matrix-Isolated Molecules: Reversible
           
    • Authors: Youngwook Park; Hani Kang, Heon Kang
      Pages: 1066 - 1069
      Abstract: Brute force orientation by an electric field is a promising way of controlling the orientation of polar molecules in the gas phase, but its application to condensed-phase molecules has been very limited. We studied the reorientation of formaldehyde molecules in a solid Ar matrix under the influence of a strong electric field using reflection absorption infrared spectroscopy. Asymptotically perfect alignment of the formaldehyde molecules along the field was achieved at field strengths exceeding 1×108 V m−1. The vibrational bands of the aligned molecules exhibited a unidirectional Stark shift proportional to the field strength. The reorientation of the molecules was reversible despite the cryogenic solid environment of the system.Mit roher Gewalt: Starke elektrische Felder können die Orientierung von Formaldehyd-Molekülen in einer Argonmatrix reversibel ändern, und bei Feldstärken >1×108 V m−1 resultiert eine asymptotisch perfekte Ausrichtung der Moleküle. Die Schwingungsbanden der ausgerichteten Moleküle zeigen proportional zur Feldstärke eine unidirektionale Stark-Verschiebung.
      PubDate: 2016-12-20T05:55:39.559082-05:
      DOI: 10.1002/ange.201610948
       
  • Non-Viral CRISPR/Cas Gene Editing In Vitro and In Vivo Enabled by
           Synthetic Nanoparticle Co-Delivery of Cas9 mRNA and sgRNA
    • Authors: Jason B. Miller; Shuyuan Zhang, Petra Kos, Hu Xiong, Kejin Zhou, Sofya S. Perelman, Hao Zhu, Daniel J. Siegwart
      Pages: 1079 - 1083
      Abstract: CRISPR/Cas is a revolutionary gene editing technology with wide-ranging utility. The safe, non-viral delivery of CRISPR/Cas components would greatly improve future therapeutic utility. We report the synthesis and development of zwitterionic amino lipids (ZALs) that are uniquely able to (co)deliver long RNAs including Cas9 mRNA and sgRNAs. ZAL nanoparticle (ZNP) delivery of low sgRNA doses (15 nm) reduces protein expression by >90 % in cells. In contrast to transient therapies (such as RNAi), we show that ZNP delivery of sgRNA enables permanent DNA editing with an indefinitely sustained 95 % decrease in protein expression. ZNP delivery of mRNA results in high protein expression at low doses in vitro (
      PubDate: 2016-12-16T04:30:37.8453-05:00
      DOI: 10.1002/ange.201610209
       
  • High-Performance Electrolytic Oxygen Evolution in Neutral Media Catalyzed
           by a Cobalt Phosphate Nanoarray
    • Authors: Lisi Xie; Rong Zhang, Liang Cui, Danni Liu, Shuai Hao, Yongjun Ma, Gu Du, Abdullah M. Asiri, Xuping Sun
      Pages: 1084 - 1088
      Abstract: The topotactic conversion of cobalt phosphide nanoarray on Ti mesh into a cobalt phosphate nanoarray (Co-Pi NA) via oxidative polarization in phosphate-buffered water is presented. As a 3D oxygen evolution reaction (OER) catalyst electrode at neutral pH, the resulting Co-Pi NA/Ti shows exceptionally high catalytic activity and demands an overpotential of only 450 mV to drive a geometrical catalytic current density of 10 mA cm−2. Notably, this catalyst also shows superior long-term electrochemical stability. The excellent catalytic activity can be attributed to that such 3D nanoarray configuration allows for the exposure of more active sites and the easier diffusion of electrolytes and oxygen.Oxidative Polarisation einer Cobaltphosphid-Nanoanordnung (CoP-NA) in phosphatgepuffertem wässrigem Medium löst eine topotaktische Umwandlung einer Cobaltphosphat-Nanoanordnung aus (Co-Pi-NA), die als robuste katalytische 3D-Elektrode die Wasseroxidation hoch aktiv und mit Stromdichten von 10 mA cm−2 bei einem Überpotential von 450 mV in 0.1 m PBS vermittelt.
      PubDate: 2016-12-16T04:50:35.299384-05:
      DOI: 10.1002/ange.201610776
       
  • C−H and C−N Activation at Redox-Active Pyridine Complexes of
           Iron
    • Authors: K. Cory MacLeod; Richard A. Lewis, Daniel E. DeRosha, Brandon Q. Mercado, Patrick L. Holland
      Pages: 1089 - 1092
      Abstract: Pyridine activation by inexpensive iron catalysts has great utility, but the steps through which iron species can break the strong (105–111 kcal mol−1) C−H bonds of pyridine substrates are unknown. In this work, we report the rapid room-temperature cleavage of C−H bonds in pyridine, 4-tert-butylpyridine, and 2-phenylpyridine by an iron(I) species, to give well-characterized iron(II) products. In addition, 4-dimethylaminopyridine (DMAP) undergoes room-temperature C−N bond cleavage, which forms a dimethylamidoiron(II) complex and a pyridyl-bridged tetrairon(II) square. These facile bond-cleaving reactions are proposed to occur through intermediates having a two-electron reduced pyridine that bridges two iron centers. Thus, the redox non-innocence of the pyridine can play a key role in enabling high regioselectivity for difficult reactions.Ein Eisen(I)-Komplex aktiviert C-H- und C-N-Bindungen in Pyridinen über einen Mechanismus, der die Redoxaktivität des Pyridins ausnutzt. Die Bindungsspaltungen verlaufen über Zwischenstufen bestehend aus einem 2-Elektronen-reduzierten Pyridin, das zwei Eisenzentren verknüpft.
      PubDate: 2016-12-21T02:10:35.454195-05:
      DOI: 10.1002/ange.201610679
       
  • Buttressing Salicylaldehydes: A Multipurpose Directing Group for
           C(sp3)−H Bond Activation
    • Authors: Akira Yada; Wenqing Liao, Yuta Sato, Masahiro Murakami
      Pages: 1093 - 1096
      Abstract: A palladium-catalyzed reaction of primary amines with iodoarenes produces γ-arylated primary amines. A bulky salicylaldehyde, which is marked as easily available, installable, removable, and recoverable, plays a key role in directing palladium to site-selectively activate the C−H bond located γ to the amino group.Zwangsmaßnahme: Eine Palladium-katalysierte Reaktion von primären Aminen mit Iodarenen liefert γ-arylierte primäre Amine. Ein sterisch anspruchsvoller Salicylaldehyd, der leicht installiert, entfernt und zurückgewonnen werden kann, dirigiert das Palladium zur positionsselektiven Aktivierung der C-H-Bindung in γ-Stellung zur Aminogruppe.
      PubDate: 2016-12-19T04:30:41.280273-05:
      DOI: 10.1002/ange.201610666
       
  • A Robust and Broadly Applicable Cobalt-Catalyzed Cross-Coupling of
           
    • Authors: Jeffrey M. Hammann; Ferdinand H. Lutter, Diana Haas, Paul Knochel
      Pages: 1102 - 1106
      Abstract: We report a robust and broadly applicable CoCl2-catalyzed cross-coupling between functionalized aryl and heteroaryl zinc pivalates and various electron-poor aryl and heteroaryl halides (X=Cl, Br, I). Couplings with (E)- or (Z)-bromo- or iodo-alkenes proceed with retention of configuration. Also, alkynyl bromides react with arylzinc pivalates providing arylated alkynes.Ein Pivalat für alle Kupplungen: Die Titelreaktion ermöglicht die Kreuzkupplung von funktionalisierten Aryl- und Heteroarylzinkpivalaten mit einer Vielzahl an elektronenarmen Aryl- und Heteroarylhalogeniden (X=Cl, Br, I). Auch Kreuzkupplungen von Arylzinkpivalaten mit Bromalkinen oder Alkenylbromiden und -iodiden laufen bereitwillig ab.
      PubDate: 2016-12-16T04:50:33.659195-05:
      DOI: 10.1002/ange.201610324
       
  • Total Synthesis of (−)-Histrionicotoxin through a Stereoselective
           Radical Translocation–Cyclization Reaction
    • Authors: Manabu Sato; Hiroki Azuma, Akihiro Daigaku, Sota Sato, Kiyosei Takasu, Kentaro Okano, Hidetoshi Tokuyama
      Pages: 1107 - 1111
      Abstract: Stereoselective total syntheses of (−)-histrionicotoxin and (−)-histrionicotoxin 235A are described. The 1-azaspiro[5.5]undecane skeleton was constructed diastereoselectively by a radical translocation–cyclization reaction involving a chiral cyclic acetal; the use of tris(trimethylsilyl)silane was crucial for the high diastereoselectivity. The cyclization product was converted into (−)-histrionicotoxin 235A through a one-pot partial-reduction–allylation reaction of a derivative containing an unprotected lactam. Finally, two terminal alkenes were transformed into enynes with the 1,3-amino alcohol protected as an oxathiazolidine oxide to complete the total synthesis of (−)-histrionicotoxin.Eine leistungsfähige Schutzgruppenstrategie führte effizient zu (−)-Histrionicotoxin. Der diastereoselektive Aufbau des 1-Azaspiro[5.5]undecan-Gerüsts durch radikalische Translokation/Cyclisierung gelang mithilfe eines chiralen cyclischen Acetals (siehe Schema), während das ungeschützte Lactam Reduktion und Allylierung einging. Nach abermaligem Schützen des 1,3-Aminoalkohols als Oxathiazolidinoxid wurden die Alken- in Eningruppen überführt.
      PubDate: 2016-12-19T04:30:25.368759-05:
      DOI: 10.1002/ange.201609941
       
  • A Chiral Nitrogen Ligand for Enantioselective, Iridium-Catalyzed
           Silylation of Aromatic C−H Bonds
    • Authors: Bo Su; Tai-Gang Zhou, Xian-Wei Li, Xiao-Ru Shao, Pei-Lin Xu, Wen-Lian Wu, John F. Hartwig, Zhang-Jie Shi
      Pages: 1112 - 1116
      Abstract: Iridium catalysts containing dative nitrogen ligands are highly active for the borylation and silylation of C−H bonds, but chiral analogs of these catalysts for enantioselective silylation reactions have not been developed. We report a new chiral pyridinyloxazoline ligand for enantioselective, intramolecular silylation of symmetrical diarylmethoxy diethylsilanes. Regioselective and enantioselective silylation of unsymmetrical substrates was also achieved in the presence of this newly developed system. Preliminary mechanistic studies imply that C−H bond cleavage is irreversible, but not the rate-determining step.Iridium funktioniert jetzt: Ein neuer chiraler Pyridinyloxazolin-Ligand wurde entwickelt, der die enantioselektive, intramolekulare Silylierung von symmetrischen Diarylmethoxydiethylsilanen ermöglicht. Auch die regioselektive und enantioselektive Silylierung unsymmetrischer Substrate wurde mit diesem neu entwickelten System erzielt.
      PubDate: 2016-12-15T06:10:55.869643-05:
      DOI: 10.1002/ange.201609939
       
  • Facile Reductive Silylation of UO22+ to Uranium(IV) Chloride
    • Authors: John J. Kiernicki; Matthias Zeller, Suzanne C. Bart
      Pages: 1117 - 1120
      Abstract: General reductive silylation of the UO22+ cation occurs readily in a one-pot, two-step stoichiometric reaction at room temperature to form uranium(IV) siloxides. Addition of two equivalents of an alkylating reagent to UO2X2(L)2 (X=Cl, Br, I, OTf; L=triphenylphosphine oxide, 2,2′-bipyridyl) followed by two equivalents of a silyl (pseudo)halide, R3Si-X (R=aryl, alkyl, H; X=Cl, Br, I, OTf, SPh), cleanly affords (R3SiO)2UX2(L)2 in high yields. Support is included for the key step in the process, reduction of UVI to UV. This procedure is applicable to a wide range of commercially available uranyl salts, silyl halides, and alkylating reagents. Under this protocol, one equivalent of SiCl4 or two equivalents of Me2SiCl2 results in direct conversion of the uranyl to uranium(IV) tetrachloride. Full spectroscopic and structural characterization of the siloxide products is reported.Die Beständigkeit von Uran(VI)-Spezies in der Natur ist problematisch, auch wegen ihrer hohen Löslichkeit in Wasser. Eine allgemeine Methode für die stöchiometrische reduktive Silylierung üblicher Uranylsalze unter milden Bedingungen ermöglicht die direkte Umwandlung von UO22+ in Uran(IV)-chlorid durch die Verwendung von SiCl4.
      PubDate: 2016-12-19T04:35:27.193557-05:
      DOI: 10.1002/ange.201609838
       
  • Hypervalent Iodine(III)-Mediated Oxidative Fluorination of Alkylsilanes by
           Fluoride Ions
    • Authors: Peng Xu; Feng Wang, Guilan Fan, Xiufang Xu, Pingping Tang
      Pages: 1121 - 1124
      Abstract: The first example of a hypervalent iodine(III)-mediated oxidative fluorination of alkylsilanes by fluoride ions without the use of transition metals is demonstrated. This reaction is operationally simple, scalable, and proceeds under mild reaction conditions. Mechanistic studies suggest the involvement of a single-electron transfer resulting from the interaction of an organopentafluorosilicate and aryliodonium difluoride, which were generated in situ from the corresponding alkylsilane and iodosobenzene, respectively, in the presence of fluoride ions.F ersetzt Si: Eine durch hypervalentes Iod(III) vermittelte Fluorierung von Alkylsilanen wurde entwickelt, die ohne Übergangsmetalle auskommt. Die Reaktion ist einfach durchzuführen und gut skalierbar. Mechanistische Studien und DFT-Rechnungen ergeben, dass die Reaktion über einen radikalischen Mechanismus verläuft.
      PubDate: 2016-12-14T05:05:34.913312-05:
      DOI: 10.1002/ange.201609741
       
  • Copper/P(tBu)3-Mediated Regiospecific Synthesis of Fused Furans and
           Naphthofurans
    • Authors: Togati Naveen; Arghya Deb, Debabrata Maiti
      Pages: 1131 - 1135
      Abstract: A novel [3+2] cycloaddition between a variety of cyclic ketones and diverse olefins or alkynes can be effectively promoted by copper in combination with the tri-tert-butylphosphine [P(tBu)3] ligand. This protocol exhibits excellent selectivity and provides an exemplary set of fused heterocycles in good to excellent yields. Present strategy also represents an extremely simple and atom-economic way to construct substituted fused furans and naphthofurans from readily available starting materials under mild reaction conditions. The utility of the method is further demonstrated by the synthesis of chiral furans from (R)-(−)-carvone and (S)-(+)-carvone. A plausible mechanism involving the oxidative radical cyclization has been suggested based on experimental observations.Fusionschemie: Eine [3+2]-Cycloaddition zwischen cyclischen Ketonen und Olefinen in Gegenwart von Cu/P(tBu)3 wurde entwickelt. Die Synthese liefert kondensierte Heterocyclen in guten Ausbeuten und bietet einen atomökonomischen Weg zu Furanen und Naphthofuranen aus einfachen Edukten unter milden Reaktionsbedingungen. Ein Mechanismus unter Beteiligung einer oxidativen radikalischen Cyclisierung wird vorgeschlagen.
      PubDate: 2016-12-20T07:20:27.625698-05:
      DOI: 10.1002/ange.201609401
       
  • Palladium-Catalyzed Asymmetric Allylic Allylation of Racemic
           Morita–Baylis–Hillman Adducts
    • Authors: Xubin Wang; Xiaoming Wang, Zhaobin Han, Zheng Wang, Kuiling Ding
      Pages: 1136 - 1139
      Abstract: A palladium-catalyzed asymmetric allyl–allyl cross-coupling of acetates of racemic Morita–Baylis–Hillman adducts and allylB(pin) has been developed using a spiroketal-based bis(phosphine) as the chiral ligand, thus affording a series of chiral 1,5-dienes bearing a vinylic ester functionality in good yields, high branched regioselectivities, and uniformly excellent enantioselectivities (95–99 % ee). Further synthetic manipulations of the allylation products provided novel ways for rapid access to a range of chiral polycyclic lactones and polycyclic lactams, as well as the antidepressant drug (−)-Paroxetine, in high optical purities.Optisch einwandfrei: Die asymmetrische Allyl-Allyl-Kreuzkupplung zwischen Morita-Baylis-Hillman-Addukten und Allylboronaten in Gegenwart eines SKP/Palladium-Komplexes bietet einen einfachen Zugang zu optisch aktiven 1,5-Dienen. Die Produkte wurden in hohen optischen Reinheiten in eine Reihe von chiralen polycyclischen Lactonen und Lactamen sowie das Antidepressivum (−)-Paroxetin überführt.
      PubDate: 2016-12-20T05:55:31.797873-05:
      DOI: 10.1002/ange.201609332
       
  • Photocatalytic Dehydrogenative Cross-Coupling of Alkenes with Alcohols or
           Azoles without External Oxidant
    • Authors: Hong Yi; Linbin Niu, Chunlan Song, Yiying Li, Bowen Dou, Atul K. Singh, Aiwen Lei
      Pages: 1140 - 1144
      Abstract: Direct cross-coupling between alkenes/R-H or alkenes/RXH is a dream reaction, especially without external oxidants. Inputting energy by photocatalysis and employing a cobalt catalyst as a two-electron acceptor, a direct C−H/X−H cross-coupling with H2 evolution has been achieved for C−O and C−N bond formation. A new radical alkenylation using alkene as the redox compound is presented. A wide range of aliphatic alcohols—even long chain alcohols—are tolerated well in this system, providing a new route to multi-substituted enol ether derivatives using simple alkenes. Additionally, this protocol can also be used for N-vinylazole synthesis. Mechanistic insights reveal that the cobalt catalyst oxidizes the photocatalyst to revive the photocatalytic cycle.Ein photokatalytischer Prozess mit einem Cobaltkomplex als Elektronenakzeptor vermittelt direkte C-H-/X-H-Kreuzkupplungen unter Freisetzung von H2 und C-O- oder C-N-Verknüpfung.
      PubDate: 2016-12-19T04:35:32.220907-05:
      DOI: 10.1002/ange.201609274
       
  • Construction of Chiral Tetraorganosilicons by Tandem Desymmetrization of
           Silacyclobutanes/Intermolecular Dehydrogenative Silylation
    • Authors: Qing-Wei Zhang; Kun An, Li-Chuan Liu, Qi Zhang, Huifang Guo, Wei He
      Pages: 1145 - 1149
      Abstract: We report a method to construct chiral tetraorganosilicons by tandem silacyclobutane (SCB) desymmetrization–dehydrogenative silylations. A wide array of dibenzosiloles with stereogenic quaternary silicon centers were obtained in good yields and enantioselectivities up to 93 % ee. Chiral TMS-segphos was found to be a superior ligand in terms of reactivity and enantioselectivity.Chiral am Silicium: Eine Rh-katalysierte Reaktion zwischen Silacyclobutan und (Hetero)arenen in der Gegenwart von (R)- oder (S)-TMS-segphos liefert eine breite Auswahl von chiralen Dibenzosilolen in guten Ausbeuten und Enantioselektivitäten (bis 93 % ee). Die Reaktion verläuft über eine selten beschriebene Desymmetrisierung von Silacyclobutan mit anschließenden intra- und intermolekularen dehydrierenden Silylierungsprozessen.
      PubDate: 2016-12-19T04:40:23.157729-05:
      DOI: 10.1002/ange.201609022
       
  • Durch N-heterocyclische Carbene stabilisierte Borylradikale
    • Authors: Miguel F. Silva Valverde; Peter Schweyen, Daria Gisinger, Thomas Bannenberg, Matthias Freytag, Christian Kleeberg, Matthias Tamm
      Pages: 1155 - 1160
      Abstract: Die Reaktion von 2-(Trimethylsilyl)imidazoliumtriflat 9 mit Diarylborhalogeniden (4-R-C6H4)2BX (R=H, X=Br; R=CH3, X=Cl; R=CF3, X=Cl) führte zu den NHC-stabilisierten Boreniumkationen 10 a–c. Cyclovoltammetrische Untersuchungen offenbarten eine lineare Korrelation zwischen den Hammett-Parametern σp der para-Substituenten und den Halbstufenpotentialen. Die chemische Reduktion mittels Decamethylcobaltocen, [(C5Me5)2Co], lieferte die entsprechenden Radikale 11 a–c; ihre Charakterisierung durch EPR-Spektroskopie bestätigte den paramagnetischen Charakter von 11 a–c und ergab große Hyperfeinkopplungskonstanten zu den Bor-Isotopen 11B und 10B, während die Delokalisierung des ungepaarten Elektrons in das NHC vernachlässigbar ist. DFT-Berechnungen der Anteile der Spindichteverteilung zwischen dem Carben (NHC) und dem Borylfragment (BR2) offenbarte für 11 a–c ein Spindichteverhältnis (BR2 /NHC) von ca. 9:1, wodurch ihr eindeutiger Borylcharakter unterstrichen wird. Die Molekülstruktur der stabilsten Spezies 11 c wurde durch Röntgenstrukturanalyse bestimmt.Lange haltbar: Die Reaktion eines frustrierten N-heterocyclisches Carben-Silylium-Lewis-Paares mit Diarylhalogenboranen ergab eine Serie von NHC-gestützten Boreniumkationen. Deren Ein-Elektronen-Reduktion lieferte persistente Borylradikale, die mittels EPR-Spektroskopie, Einkristall-Röntgendiffraktometrie und DFT-Methoden untersucht wurden. Die Radikale offenbaren eine nahezu ausschließliche Lokalisierung des ungepaarten Elektrons auf den Diarylboryl-Fragmenten.
      PubDate: 2016-12-20T05:50:23.656258-05:
      DOI: 10.1002/ange.201610903
       
  • 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
      Pages: 1161 - 1165
      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
       
  • Die Kristallstruktur von RosB: Einblicke in den Reaktionsmechanismus des
           ersten Mitglieds einer flavodoxinähnlichen Enzymfamilie
    • Authors: Valentino Konjik; Steffen Brünle, Ulrike Demmer, Amanda Vanselow, Roger Sandhoff, Ulrich Ermler, Matthias Mack
      Pages: 1166 - 1171
      Abstract: Die 8-Demethyl-8-aminoriboflavin-5′-phosphat(AFP)-Synthase RosB katalysiert die Schlüsselreaktion der Roseoflavinbiosynthese, die Bildung von AFP aus Riboflavin-5′-phosphat (RP) und Glutamat. Zwischenprodukte dieser enzymatischen Reaktion sind 8-Demethyl-8-formylriboflavin-5′-phosphat (OHC-RP) und 8-Demethyl-8-carboxylriboflavin-5′-phosphat (HO2C-RP). Um den schwierigen Austausch einer Methylgruppe am Aromaten gegen eine Aminogruppe zu verstehen, haben wir die Struktur von RosB im Komplex mit OHC-RP (2.0 Å) und im Komplex mit AFP (1.7 Å) gelöst. RosB ist als Homotetramer aktiv und wurde im Verlauf der Evolution mit spezifischen Domänen und einem einzigartigen C-terminalen Arm ausgestattet. Wir glauben, dass RosB dabei aus einem einfachen Elektronen- oder Hydrid-übertragenden Flavoprotein zu einem komplexen mehrstufigen Enzym “entwickelt” wurde. Im Gegensatz zu anderen Flavoenzymen nutzt RosB RP als Substrat und nicht als Kofaktor. Die strukturelle Analyse des aktiven Zentrums von RosB wurde durch Mutagenesestudien und isotopenbasierte massenspektrometrische Untersuchungen ergänzt. Auf Grundlage dieser Ergebnisse schlagen wir einen Reaktionsmechanismus auf atomarer Ebene vor.Teamwork: Die strukturelle Analyse des Tetramers RosB aus Streptomyces davawensis offenbart ein flavodoxinähnliches Protein, das mithilfe von speziellen Erweiterungen und unter Beteiligung von Aminosäuren aller Untereinheiten eine einzigartige, oxidative Kaskade katalysiert. Die Reaktionen führen zum Schlüsselintermediat AFP der Roseoflavinbiosynthese.
      PubDate: 2016-12-16T04:55:47.577399-05:
      DOI: 10.1002/ange.201610292
       
  • Halogenverbrückte supramolekulare Kapseln im Festkörper, in Lösung und
           in der Gasphase
    • Authors: Oliver Dumele; Benedikt Schreib, Ulrike Warzok, Nils Trapp, Christoph A. Schalley, François Diederich
      Pages: 1172 - 1177
      Abstract: Supramolekulare Kapseln wurden durch neutrale Halogenbrücken (XBs) aufgebaut und im Festkörper, in Lösung sowie in der Gasphase untersucht. Die Geometrie der hoch organisierten Kapseln wird durch eine Röntgenkristallstruktur belegt, die den Aufbau aus zwei XB-Hemisphären zeigt, die geometrisch durch H-Brücken zu acht MeOH-Molekülen verfestigt sind und zwei Benzol-Gäste einschließen. Aufgrund von Desolvatationseffekten in protischen Lösungsmitteln führen Änderungen des XB-Donors zu einer effektiveren Erhöhung der Assoziationskonstante als Änderungen des XB-Akzeptors. Dies wird am Beispiel einer Tetrachinuclidin-XB-Akzeptorhemisphäre gezeigt. Mit einem Tetra(iodethinyl)-XB-Donor und einem Tetralutidin-XB-Akzeptor wird eine Assoziationskonstante in deuteriertem Benzol/Aceton/Methanol 70:30:1 bei 283 K von Ka=(2.11±0.39)×105 m−1 (ΔG=(−6.9±0.1) kcal mol−1) erreicht. Die Stabilität der XB-Kapsel in der Gasphase wurde durch ESI-MS bestätigt. Innerhalb der verlängerten Iodethinyl-Kapsel wurde eine neue Gastbindungsstelle beobachtet.Drei auf einen Streich: Die Geometrie neutraler dimerer Halogenbrücken(XB)-Kapseln wurde durch Röntgenstrukturanalyse eines 12-Komponenten-Aufbaus erstmals bestätigt. Die XB-Donor- und XB-Akzeptorhemisphären wurden variiert und ergaben Solvatationseffekte, die zu einem neuen Konzept für die Erhöhung der Stabilität von XB-Strukturen in protischem Lösungsmittel führen. Die Stabilität der XB-Kapsel in der Gasphase wurde durch ESI-MS bestätigt.
      PubDate: 2016-12-21T02:15:37.210438-05:
      DOI: 10.1002/ange.201610884
       
 
 
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