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  Subjects -> CHEMISTRY (Total: 849 journals)
    - ANALYTICAL CHEMISTRY (50 journals)
    - CHEMISTRY (598 journals)
    - CRYSTALLOGRAPHY (22 journals)
    - ELECTROCHEMISTRY (25 journals)
    - INORGANIC CHEMISTRY (42 journals)
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    - PHYSICAL CHEMISTRY (67 journals)

CHEMISTRY (598 journals)                  1 2 3 | Last

Showing 1 - 200 of 735 Journals sorted alphabetically
2D Materials     Hybrid Journal   (Followers: 8)
Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement     Hybrid Journal   (Followers: 26)
ACS Catalysis     Full-text available via subscription   (Followers: 32)
ACS Chemical Neuroscience     Full-text available via subscription   (Followers: 17)
ACS Combinatorial Science     Full-text available via subscription   (Followers: 23)
ACS Macro Letters     Full-text available via subscription   (Followers: 23)
ACS Medicinal Chemistry Letters     Full-text available via subscription   (Followers: 39)
ACS Nano     Full-text available via subscription   (Followers: 227)
ACS Photonics     Full-text available via subscription   (Followers: 11)
ACS Synthetic Biology     Full-text available via subscription   (Followers: 21)
Acta Chemica Iasi     Open Access   (Followers: 2)
Acta Chimica Sinica     Full-text available via subscription   (Followers: 1)
Acta Chimica Slovaca     Open Access   (Followers: 1)
Acta Chromatographica     Full-text available via subscription   (Followers: 9)
Acta Facultatis Medicae Naissensis     Open Access  
Acta Metallurgica Sinica (English Letters)     Hybrid Journal   (Followers: 5)
Acta Scientifica Naturalis     Open Access   (Followers: 2)
adhäsion KLEBEN & DICHTEN     Hybrid Journal   (Followers: 5)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 7)
Adsorption Science & Technology     Full-text available via subscription   (Followers: 5)
Advanced Functional Materials     Hybrid Journal   (Followers: 50)
Advanced Science Focus     Free   (Followers: 3)
Advances in Chemical Engineering and Science     Open Access   (Followers: 53)
Advances in Chemical Science     Open Access   (Followers: 13)
Advances in Chemistry     Open Access   (Followers: 14)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 18)
Advances in Drug Research     Full-text available via subscription   (Followers: 22)
Advances in Enzyme Research     Open Access   (Followers: 9)
Advances in Fluorine Science     Full-text available via subscription   (Followers: 8)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 15)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 8)
Advances in Materials Physics and Chemistry     Open Access   (Followers: 19)
Advances in Nanoparticles     Open Access   (Followers: 14)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 15)
Advances in Polymer Science     Hybrid Journal   (Followers: 41)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 18)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 19)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 5)
Advances in Science and Technology     Full-text available via subscription   (Followers: 12)
African Journal of Bacteriology Research     Open Access  
African Journal of Chemical Education     Open Access   (Followers: 2)
African Journal of Pure and Applied Chemistry     Open Access   (Followers: 7)
Agrokémia és Talajtan     Full-text available via subscription   (Followers: 2)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 3)
AMB Express     Open Access   (Followers: 1)
Ambix     Hybrid Journal   (Followers: 3)
American Journal of Biochemistry and Biotechnology     Open Access   (Followers: 67)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 14)
American Journal of Chemistry     Open Access   (Followers: 26)
American Journal of Plant Physiology     Open Access   (Followers: 13)
American Mineralogist     Hybrid Journal   (Followers: 13)
Analyst     Full-text available via subscription   (Followers: 38)
Angewandte Chemie     Hybrid Journal   (Followers: 158)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 208)
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: 8)
Annual Review of Chemical and Biomolecular Engineering     Full-text available via subscription   (Followers: 12)
Annual Review of Food Science and Technology     Full-text available via subscription   (Followers: 14)
Anti-Infective Agents     Hybrid Journal   (Followers: 3)
Antiviral Chemistry and Chemotherapy     Hybrid Journal  
Applied Organometallic Chemistry     Hybrid Journal   (Followers: 7)
Applied Spectroscopy     Full-text available via subscription   (Followers: 23)
Applied Surface Science     Hybrid Journal   (Followers: 28)
Arabian Journal of Chemistry     Open Access   (Followers: 6)
ARKIVOC     Open Access   (Followers: 2)
Asian Journal of Biochemistry     Open Access   (Followers: 1)
Atomization and Sprays     Full-text available via subscription   (Followers: 3)
Australian Journal of Chemistry     Hybrid Journal   (Followers: 7)
Autophagy     Hybrid Journal   (Followers: 2)
Avances en Quimica     Open Access   (Followers: 1)
Biochemical Pharmacology     Hybrid Journal   (Followers: 10)
Biochemistry     Full-text available via subscription   (Followers: 283)
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: 5)
Biointerface Research in Applied Chemistry     Open Access   (Followers: 2)
Biointerphases     Open Access   (Followers: 1)
Biology, Medicine, & Natural Product Chemistry     Open Access   (Followers: 1)
Biomacromolecules     Full-text available via subscription   (Followers: 19)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 10)
Biomedical Chromatography     Hybrid Journal   (Followers: 6)
Biomolecular NMR Assignments     Hybrid Journal   (Followers: 3)
BioNanoScience     Partially Free   (Followers: 4)
Bioorganic & Medicinal Chemistry     Hybrid Journal   (Followers: 108)
Bioorganic & Medicinal Chemistry Letters     Hybrid Journal   (Followers: 93)
Bioorganic Chemistry     Hybrid Journal   (Followers: 10)
Biopolymers     Hybrid Journal   (Followers: 18)
Biosensors     Open Access   (Followers: 2)
Biotechnic and Histochemistry     Hybrid Journal   (Followers: 1)
Bitácora Digital     Open Access  
Boletin de la Sociedad Chilena de Quimica     Open Access  
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 2)
Bulletin of the Chemical Society of Japan     Full-text available via subscription   (Followers: 24)
Bulletin of the Korean Chemical Society     Hybrid Journal   (Followers: 1)
C - Journal of Carbon Research     Open Access   (Followers: 3)
Cakra Kimia (Indonesian E-Journal of Applied Chemistry)     Open Access  
Canadian Association of Radiologists Journal     Full-text available via subscription   (Followers: 2)
Canadian Journal of Chemistry     Hybrid Journal   (Followers: 10)
Canadian Mineralogist     Full-text available via subscription   (Followers: 3)
Carbohydrate Research     Hybrid Journal   (Followers: 26)
Carbon     Hybrid Journal   (Followers: 67)
Catalysis for Sustainable Energy     Open Access   (Followers: 6)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 8)
Catalysis Science and Technology     Free   (Followers: 6)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 3)
Catalysts     Open Access   (Followers: 7)
Cellulose     Hybrid Journal   (Followers: 7)
Cereal Chemistry     Full-text available via subscription   (Followers: 4)
ChemBioEng Reviews     Full-text available via subscription   (Followers: 1)
ChemCatChem     Hybrid Journal   (Followers: 8)
Chemical and Engineering News     Free   (Followers: 12)
Chemical Bulletin of Kazakh National University     Open Access  
Chemical Communications     Full-text available via subscription   (Followers: 70)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 23)
Chemical Research in Chinese Universities     Hybrid Journal   (Followers: 3)
Chemical Research in Toxicology     Full-text available via subscription   (Followers: 19)
Chemical Reviews     Full-text available via subscription   (Followers: 170)
Chemical Science     Open Access   (Followers: 21)
Chemical Technology     Open Access   (Followers: 16)
Chemical Vapor Deposition     Hybrid Journal   (Followers: 5)
Chemical Week     Full-text available via subscription   (Followers: 8)
Chemie in Unserer Zeit     Hybrid Journal   (Followers: 55)
Chemie-Ingenieur-Technik (Cit)     Hybrid Journal   (Followers: 25)
ChemInform     Hybrid Journal   (Followers: 8)
Chemistry & Biodiversity     Hybrid Journal   (Followers: 6)
Chemistry & Biology     Full-text available via subscription   (Followers: 30)
Chemistry & Industry     Hybrid Journal   (Followers: 5)
Chemistry - A European Journal     Hybrid Journal   (Followers: 144)
Chemistry - An Asian Journal     Hybrid Journal   (Followers: 15)
Chemistry and Materials Research     Open Access   (Followers: 18)
Chemistry Central Journal     Open Access   (Followers: 4)
Chemistry Education Research and Practice     Free   (Followers: 5)
Chemistry in Education     Open Access   (Followers: 9)
Chemistry International     Hybrid Journal   (Followers: 2)
Chemistry Letters     Full-text available via subscription   (Followers: 45)
Chemistry of Materials     Full-text available via subscription   (Followers: 226)
Chemistry of Natural Compounds     Hybrid Journal   (Followers: 9)
Chemistry World     Full-text available via subscription   (Followers: 22)
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: 9)
ChemPlusChem     Hybrid Journal   (Followers: 2)
ChemTexts     Hybrid Journal  
CHIMIA International Journal for Chemistry     Full-text available via subscription   (Followers: 2)
Chinese Journal of Chemistry     Hybrid Journal   (Followers: 6)
Chinese Journal of Polymer Science     Hybrid Journal   (Followers: 10)
Chromatographia     Hybrid Journal   (Followers: 24)
Chromatography Research International     Open Access   (Followers: 7)
Clay Minerals     Full-text available via subscription   (Followers: 9)
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: 2)
Composite Interfaces     Hybrid Journal   (Followers: 6)
Comprehensive Chemical Kinetics     Full-text available via subscription   (Followers: 2)
Comptes Rendus Chimie     Full-text available via subscription  
Comptes Rendus Physique     Full-text available via subscription   (Followers: 1)
Computational and Theoretical Chemistry     Hybrid Journal   (Followers: 9)
Computational Biology and Chemistry     Hybrid Journal   (Followers: 12)
Computational Chemistry     Open Access   (Followers: 2)
Computers & Chemical Engineering     Hybrid Journal   (Followers: 9)
Coordination Chemistry Reviews     Full-text available via subscription   (Followers: 2)
Copernican Letters     Open Access  
Critical Reviews in Biochemistry and Molecular Biology     Hybrid Journal   (Followers: 5)
Crystal Structure Theory and Applications     Open Access   (Followers: 3)
CrystEngComm     Full-text available via subscription   (Followers: 11)
Current Catalysis     Hybrid Journal   (Followers: 2)
Current Metabolomics     Hybrid Journal   (Followers: 5)
Current Opinion in Colloid & Interface Science     Hybrid Journal   (Followers: 9)
Current Research in Chemistry     Open Access   (Followers: 8)
Current Science     Open Access   (Followers: 56)
Dalton Transactions     Full-text available via subscription   (Followers: 20)
Detection     Open Access   (Followers: 2)
Developments in Geochemistry     Full-text available via subscription   (Followers: 2)
Diamond and Related Materials     Hybrid Journal   (Followers: 12)
Dislocations in Solids     Full-text available via subscription  
Doklady Chemistry     Hybrid Journal  
Drying Technology: An International Journal     Hybrid Journal   (Followers: 4)
Eclética Química     Open Access   (Followers: 1)
Ecological Chemistry and Engineering S     Open Access   (Followers: 4)
Ecotoxicology and Environmental Contamination     Open Access  
Educación Química     Open Access   (Followers: 1)
Education for Chemical Engineers     Hybrid Journal   (Followers: 5)
EJNMMI Radiopharmacy and Chemistry     Open Access  
Elements     Full-text available via subscription   (Followers: 2)
Environmental Chemistry     Hybrid Journal   (Followers: 9)
Environmental Chemistry Letters     Hybrid Journal   (Followers: 4)
Environmental Science & Technology Letters     Full-text available via subscription   (Followers: 5)

        1 2 3 | Last

Journal Cover Angewandte Chemie International Edition
  [SJR: 6.229]   [H-I: 397]   [208 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1433-7851 - ISSN (Online) 1521-3773
   Published by John Wiley and Sons Homepage  [1576 journals]
  • The Art of Building Small: From Molecular Switches to Motors (Nobel
           Lecture)
    • Authors: Ben L. Feringa
      Abstract: A journey into the nano-world: The ability to design, use and control motor-like functions at the molecular level sets the stage for numerous dynamic molecular systems. In his Nobel lecture, B. L. Feringa describes the evolution of the field of molecular motors and explains how to program and control molecules by incorporating responsive and adaptive properties.
      PubDate: 2017-07-27T04:57:30.640469-05:
      DOI: 10.1002/anie.201702979
       
  • Frontispiece: Single-Site Active Cobalt-Based Photocatalyst with a Long
           Carrier Lifetime for Spontaneous Overall Water Splitting
    • Authors: Wei Liu; Linlin Cao, Weiren Cheng, Yuanjie Cao, Xiaokang Liu, Wei Zhang, Xiaoli Mou, Lili Jin, Xusheng Zheng, Wei Che, Qinghua Liu, Tao Yao, Shiqiang Wei
      Abstract: Water Splitting In their Communication on page 9311 ff., T. Yao, S. Q. Wei et al. show that Co-P4 single sites confined on polymeric g-C3N4 give rise to a single-site photocatalyst for spontaneous overall water splitting.
      PubDate: 2017-07-27T03:50:38.786481-05:
      DOI: 10.1002/anie.201783261
       
  • Reversible Interconversion between 2,5-Dimethylpyrazine and
           2,5-Dimethylpiperazine by Iridium-Catalyzed Hydrogenation/Dehydrogenation
           for Efficient Hydrogen Storage
    • Authors: Ken-ichi Fujita; Tomokatsu Wada, Takumi Shiraishi
      Abstract: A new hydrogen storage system based on the hydrogenation and dehydrogenation of nitrogen heterocyclic compounds, employing a single iridium catalyst, has been developed. Efficient hydrogen storage using relatively small amounts of solvent compared with previous systems was achieved by this new system. Reversible transformations between 2,5-dimethylpyrazine and 2,5-dimethylpiperazine, accompanied by the uptake and release of three equivalents of hydrogen, could be repeated almost quantitatively at least four times without any loss of efficiency. Furthermore, hydrogen storage under solvent-free conditions was also accomplished.Storage wars: A new system for efficient storage of hydrogen based on the reversible interconversion between 2,5-dimethylpyrazine and 2,5-dimethylpiperazine by hydrogenation and dehydrogenation catalyzed by a single iridium complex has been developed. Reversible and repetitive transformations, accompanied by the uptake and release of three equivalents of hydrogen, could be repeated almost quantitatively at least four times without any loss of efficiency.
      PubDate: 2017-07-27T01:30:25.889397-05:
      DOI: 10.1002/anie.201705452
       
  • A Concise Enantioselective Total Synthesis of (−)-Virosaine A
    • Authors: Jonathan M. E. Hughes; James L. Gleason
      Abstract: The total synthesis of (−)-virosaine A (1) was achieved in ten steps starting from furan and 2-bromoacrolein. A one-pot Diels–Alder cycloaddition/organolithium addition initiated an efficient sequence to access a key oxime/epoxide intermediate. Heating this intermediate in acetic acid resulted in an intramolecular epoxide opening/nitrone [3+2] cycloaddition cascade to construct the caged core of 1 in a single step. Several methods of C−H functionalization were assessed on the cascade product, and ultimately, a directed lithiation/bromination effected selective C14 functionalization, enabling the synthesis of 1.Not too late: The core of virosaine A was prepared in five short steps by a cycloaddition/organolithium addition and a nitrone formation/cycloaddition cascade. Late-stage selective functionalization of an unactivated C−H group by directed lithiation enabled conversion of the shown key intermediate into the natural product.
      PubDate: 2017-07-27T01:26:26.446526-05:
      DOI: 10.1002/anie.201706273
       
  • Copper-catalyzed Amination of Congested and Functionalized
           α-Bromocarboxamides with Amines or Ammonia at Room Temperature
    • Authors: Takashi Nishikata; Syo Ishida, Kentaro Takeuchi, Nobuhiro Taniyama, Yusuke Sunada
      Abstract: There are several reports on the synthesis of alkylamines, but most of the reported methods are not suitable for the synthesis of hindered amines. In this research, we found that a copper catalyst is effective for the formation of congested C-N bonds at room temperature. Control experiments revealed that a copper amide is a key intermediate. Moreover, when a chiral amine was used, a quaternary carbon stereogenic center was created with good selectivity.
      PubDate: 2017-07-26T21:26:24.550208-05:
      DOI: 10.1002/anie.201706293
       
  • Forging Quaternary Fluorine Stereocenters by a Light-driven
           Organocatalytic Aldol Desymmetrization Process
    • Authors: Sara Cuadros; Luca Dell'Amico, Paolo Melchiorre
      Abstract: Reported herein is a light-triggered organocatalytic strategy for the desymmetrization of achiral 2-fluoro substituted cyclopentane-1,3-diketones. The chemistry is based on an intermolecular aldol reaction of photochemically generated hydroxy-o-quinodimethanes that simultaneously forges two adjacent fully substituted carbon stereocenters, one bearing a carbon-fluorine stereogenic unit. The method uses readily available substrates, a simple chiral organocatalyst, and mild reaction conditions to afford an array of highly functionalized chiral 2-fluoro-3-hydroxycyclopentanones
      PubDate: 2017-07-26T12:25:41.078159-05:
      DOI: 10.1002/anie.201706763
       
  • Enzyme responsive LipoCEST agents: assessment of MMP-2 activity by
           measuring the intra-liposomal water 1H-NMR resonance shift
    • Authors: Giuseppe Ferrauto; Enza Di Gregorio, Marta Ruzza, Valeria Catanzaro, Sergio Padovan, Silvio Aime
      Abstract: Mobile proton containing solutes can be detected by MRI via Chemical Exchange Saturation Transfer(CEST)method. The CEST sensitivity is dramatically enhanced by using, as exchanging protons, the water molecules confined inside liposomes, properly shifted by a paramagnetic Shift Reagent. The chemical shift of the intraliposomal water resonance(δIL) is affected by the overall shape of the supramolecular system. Herein, it is shown that δIL of a spherical LipoCEST acts as a sensitive reporter of the distribution of Streptavidin proteins anchored at the Liposomes'surface by biotinylated phospholipids.These observations prompted the design of a MMP-2 responsive LipoCEST agent as the Streptavidin moieties can be released from the Liposomes' surfaces when a properly tailored enzyme-cleavable peptide is inserted on the phospholipids before the terminal biotin residues. δIL reports on the overall changes in the supramolecular architecture associated to the cleavage carried out by MMP-2.
      PubDate: 2017-07-26T11:46:53.234304-05:
      DOI: 10.1002/anie.201706271
       
  • Enantioselective Tandem Cyclization of Alkyne-Tethered Indoles Using
           Cooperative Silver(I) and Chiral Phosphoric Acid Catalysis
    • Authors: Yugen Zhu; Wei He, Wei Wang, Chloe Pitsch, Xiaotai Wang, Xiang Wang
      Abstract: We report the enantioselective synthesis of tetracyclic indolines using cooperative silver(I) and chiral phosphoric acid catalysis. A variety of alkyne-tethered indoles are suitable for this process. Mechanistic studies suggest that the in situ-generated silver(I) chiral phosphate activates both the alkyne and the indole nucleophile in the initial cyclization step through an intermolecular hydrogen bond and the phosphate anion promotes proton transfer. In addition, further modifications of the cyclization products enabled stereochemistry-function studies of a series of bioactive indolines.
      PubDate: 2017-07-26T11:40:18.935506-05:
      DOI: 10.1002/anie.201706694
       
  • Synthesis of Chlorine-Substituted Graphdiyne and Applications for
           Lithium-Ion Storage
    • Authors: Ning Wang; Jianjiang He, Zeyi Tu, Ze Yang, Fuhua Zhao, Xiaodong Li, Changshui Huang, Kun Wang, Tonggang Jiu, Yuanping Yi, Yuliang Li
      Abstract: Chlorine-substituted graphdiyne (Cl-GDY) is prepared through a Glaser–Hay coupling reaction on the copper foil. Cl-GDY is endowed with a unique π-conjugated carbon skeleton with expanded pore size in two dimensions, having graphdiyne-like sp- and sp2- hybridized carbon atoms. As a result, the transfer tunnels for lithium (Li) ions in the perpendicular direction of the molecular plane are enlarged. Moreover, benefiting from the bottom-to-up fabrication procedure of graphdiyne and the strong chemical tailorability of the alkinyl-contained monomer, the amount of substitutional chlorine atoms with appropriate electronegativity and atom size is high and evenly distributed on the as-prepared carbon framework, which will synergistically stabilize the Li intercalated in the Cl-GDY framework, and thus generate more Li storage sites. Profiting from the above unique structure, Cl-GDY shows remarkable electrochemical properties in lithium ion half-cells.Lithium fishing net: Chlorine-substituted graphdiyne (Cl-GDY) is prepared through a bottom-up chemical strategy. Cl-GDY has a unique structure with expanded pore size and even distribution of chlorine in the π-conjugated carbon skeleton, which will synergistically stabilize the lithium atom intercalated in the Cl-GDY framework. Cl-GDY shows remarkable electrochemical performance in lithium ion half-cells.
      PubDate: 2017-07-26T08:00:53.025446-05:
      DOI: 10.1002/anie.201704779
       
  • Isolation, Detection, and Antigen-Based Profiling of Circulating Tumor
           Cells Using a Size-Dictated Immunocapture Chip
    • Authors: Metages Gashaw Ahmed; Mahlet Fasil Abate, Yanling Song, Zhi Zhu, Feng Yan, Yao Xu, Xiaomin Wang, Qingbiao Li, Chaoyong Yang
      Abstract: Even though the diagnostic and prognostic value of circulating tumor cells (CTCs) has been demonstrated, their clinical utility and widespread adoption have been limited. Herein, we describe a new device, size-dictated immunocapture chip (SDI-Chip), for efficient, sensitive, and spatially resolved capture and detection of CTCs. SDI-Chip enables selective, frequent, and extended interaction of CTCs with hydrodynamically optimized immunocoated micropillar surfaces. CTCs with different antigen expression levels can be efficiently captured and spatially resolved around the micropillars. Capture efficiency greater than 92 % with a purity of 82 % was achieved with blood samples. CTCs were detected in non-metastasis colorectal (CRC) patients, while none was detected from healthy volunteers. We believe that SDI-Chip will facilitate the transition of tumor diagnosis from anatomical pathology to molecular pathology in localized CRC patients.A size-dictated immunocapture chip (SDI-Chip) was designed through the rigorous computational analysis of various parameters. Frequent contact with and prolonged retention time on the immunocoated surface, as well as optimum hydrodynamic forces provided by the device, enables the efficient capture of CTCs from cancer patient samples as well as spatial profiling based on antigen expression levels.
      PubDate: 2017-07-26T07:57:07.512627-05:
      DOI: 10.1002/anie.201702675
       
  • Low-Voltage Gaseous HCl Electrolysis with an Iron Redox-Mediated Cathode
           for Chlorine Regeneration
    • Authors: Yun Zhao; Shuang Gu, Ke Gong, Jie Zheng, Junhua Wang, Yushan Yan
      Abstract: Gaseous HCl as a by-product is often produced from chlorination processes using Cl2 gas. Onsite Cl2 regeneration from HCl is highly desirable as it eliminates the need to buy new Cl2 and dispose HCl waste. A gaseous HCl electrolysis with Fe3+/Fe2+ redox-mediated cathode is demonstrated for Cl2 regeneration. HCl is oxidized to generate Cl2 and protons in the anode while Fe3+ is reduced to Fe2+ in the cathode. Simultaneously Fe3+ is regenerated by chemical oxidation of Fe2+ by oxygen (air) that also produces water. A low operational voltage and high coulombic efficiency are achieved by using a novel composite porous membrane and hydrophobic anode. Specifically, a cell voltage of only 0.64 V is needed at the typical current density of 4 kA m−2, leading to a low energy consumption of 483 kWh per ton of Cl2 (124 kJ molCl2−1) which is about 50–55 % of state-of-the-art HCl electrolysis processes.Gaseous HCl electrolysis with an Fe3+/Fe2+ redox-mediated cathode is demonstrated for Cl2 regeneration. A low operational voltage of 0.64 V at a typical current density of 4 kA m−2 are achieved by using a novel composite porous membrane and hydrophobic anode. This leads to a low energy consumption of 483 kWh per ton of Cl2, which is about 50–55 % of alternative HCl electrolysis processes.
      PubDate: 2017-07-26T07:56:11.266245-05:
      DOI: 10.1002/anie.201704749
       
  • Analyzing Reaction Rates with the Distortion/Interaction-Activation Strain
           Model
    • Authors: F. Matthias Bickelhaupt; Kendall N. Houk
      Abstract: A model for analyzing and predicting reaction rates is presented by F. M. Bickelhaupt and K. N. Houk in their Review (
      DOI : 10.1002/anie.201701486). This model is based on dissecting reaction profiles and energy barrier heights in terms of reactant properties, in particular, the strain associated with distorting the reactants and the interaction between the distorted reactants. The model is illustrated with examples from organic and inorganic chemistry.
      PubDate: 2017-07-26T07:55:44.23654-05:0
       
  • Carbon–Halogen Bond Activation by Selenium-Based Chalcogen Bonding
    • Authors: Patrick Wonner; Lukas Vogel, Maximilian Düser, Luís Gomes, Florian Kniep, Bert Mallick, Daniel B. Werz, Stefan M. Huber
      Abstract: Selenium compounds may form noncovalent interactions, so-called chalcogen bonds, with Lewis bases under certain conditions. In their Communication (
      DOI : 10.1002/anie.201704816), S. M. Huber and co-workers show that such chalcogen bond donors activate a benchmark reaction. Control experiments with non-selenated reference compounds confirmed the crucial role of the selenium substituent. The corresponding brominated halogen bond donor was somewhat less active.
      PubDate: 2017-07-26T07:55:21.810609-05:
       
  • Enantioselective Hydroazidation of Trisubstituted Non-Activated Alkenes
    • Authors: Daniel Meyer; Philippe Renaud
      Abstract: A one-pot procedure for the enantioselective hydroazidation of non-activated trisubstituted alkenes is described. Hydroboration with monoisopinocampheylborane (IpcBH2) provides dialkylboranes that are in situ selectively converted into monoalkyl-substituted catecholboranes; these undergo radical azidation upon treatment with benzenesulfonyl azide and a radical initiator. Enantiomerically enriched azides were thus obtained in yields of 59–81 % and enantioselectivities of up to 94:6 e.r. (98:2 e.r. if the intermediate dialkylborane is purified by crystallization). A rapid access to enantiomerically pure (+)-rodocaine is also described. The use of other arenesulfonyl radical traps enables enantioselective hydroallylation, hydrosulfanylation, and hydrobromination reactions with yields of 71–86 %.A one-pot process for the enantioselective hydroazidation of trisubstituted alkenes entails hydroboration with monoisopinocampheylborane (IpcBH2) to provide dialkylboranes. These intermediates are converted in situ into monoalkyl-substituted catecholboranes, which undergo radical azidation upon treatment with benzenesulfonyl azide and a radical initiator.
      PubDate: 2017-07-26T07:51:35.833263-05:
      DOI: 10.1002/anie.201703340
       
  • Stereoretentive Olefin Metathesis: An Avenue to Kinetic Selectivity
    • Authors: T. Patrick Montgomery; Tonia S. Ahmed, Robert H. Grubbs
      Abstract: Olefin metathesis is an incredibly valuable transformation that has gained widespread use in both academic and industrial settings. Lately, stereoretentive olefin metathesis has garnered much attention as a method for the selective generation of both E- and Z-olefins. Early studies employing ill-defined catalysts showed evidence for retention of the stereochemistry of the starting olefins at low conversion. However, thermodynamic ratios E/Z were reached as the reaction proceeded to equilibrium. Recent studies in olefin metathesis have focused on the synthesis of catalysts that can overcome the inherent thermodynamic preference of an olefin, providing synthetically useful quantities of a kinetically favored olefin isomer. These reports have led to the development of stereoretentive catalysts that not only generate Z-olefins selectively, but also kinetically produce E-olefins, a previously unmet challenge in olefin metathesis. Advancements in stereoretentive olefin metathesis using tungsten, ruthenium, and molybdenum catalysts are presented.Make your choice: The idea of stereoretentive olefin metathesis to kinetically generate both E- or Z-olefins has shown great promise of late and has encouraged the synthesis of new metathesis catalysts. Recent advancements using tungsten, ruthenium, and molybdenum catalysts are presented in this Minireview.
      PubDate: 2017-07-26T07:51:02.635616-05:
      DOI: 10.1002/anie.201704686
       
  • Hybrid TiO2–Ruthenium Nano-photosensitizer Synergistically Produces
           Reactive Oxygen Species in both Hypoxic and Normoxic Conditions
    • Authors: Rebecca C. Gilson; Kvar C. L. Black, Daniel D. Lane, Samuel Achilefu
      Abstract: Photodynamic therapy (PDT) is widely used to treat diverse diseases, but its dependence on oxygen to produce cytotoxic reactive oxygen species (ROS) diminishes the therapeutic effect in a hypoxic environment, such as solid tumors. Herein, we developed a ROS-producing hybrid nanoparticle-based photosensitizer capable of maintaining high levels of ROS under both normoxic and hypoxic conditions. Conjugation of a ruthenium complex (N3) to a TiO2 nanoparticle afforded TiO2-N3. Upon exposure of TiO2-N3 to light, the N3 injected electrons into TiO2 to produce three- and four-fold more hydroxyl radicals and hydrogen peroxide, respectively, than TiO2 at 160 mmHg. TiO2-N3 maintained three-fold higher hydroxyl radicals than TiO2 under hypoxic conditions via N3-facilitated electron–hole reduction of adsorbed water molecules. The incorporation of N3 transformed TiO2 from a dual type I and II PDT agent to a predominantly type I photosensitizer, irrespective of the oxygen content.Working through the oxygen debt: A dual type I and type II photodynamic therapy agent, titanium dioxide–ruthenium nano-photosensitizer (TiO2-N3) synergistically produced hydroxyl radicals under both normoxic and hypoxic conditions.
      PubDate: 2017-07-26T07:50:23.043615-05:
      DOI: 10.1002/anie.201704458
       
  • Catalytic Reductive Pinacol-Type Rearrangement of Unactivated 1,2-diols
           through a Concerted, Stereoinvertive Mechanism
    • Authors: Nikolaos Drosos; Gui-Juan Cheng, Erhan Ozkal, Bastien Cacherat, Walter Thiel, Bill Morandi
      Abstract: A catalytic pinacol-type, reductive rearrangement reaction of 1,2-internal diols is reported herein. Several scaffolds not usually amenable to pinacol-type reactions, such as aliphatic secondary-secondary diols, work well without the need for prefunctionalization. The reaction uses a simple boron catalyst and two silanes and proceeds through a concerted, stereoinvertive mechanism that enables the preparation of highly enantioenriched products. Computational studies have been used to rationalize the preference for migration over direct deoxygenation.
      PubDate: 2017-07-26T06:26:07.795402-05:
      DOI: 10.1002/anie.201704936
       
  • Switchable Stereoselectivity in Bromoaminocyclization of Olefins Catalyzed
           by Brønsted Acids of Anionic Chiral CoIII Complexes
    • Authors: Liuzhu Gong; Hua-Jie Jiang, kun Liu, Jie Yu, Ling Zhang
      Abstract: Brønsted acids of anionic chiral CoIII complexes have been first found to act as bifunctional phase-transfer catalysts to shuttle the substrates across interface and control stereoselectivity. The diastereomeric chiral CoIII-templated Brønsted acids with the same chiral ligands enabled a switchably enantioselective bromoamino-cyclization of olefins to afford two opposite enantiomers of 2-substituted pyrrolidines with high enantioselectivities (up to 99:1 e.r.), respectively.
      PubDate: 2017-07-26T06:25:42.71364-05:0
      DOI: 10.1002/anie.201705066
       
  • Picomolar traces of AmIII introduce drastic changes in the structural
           chemistry of TbIII: a break in the "gadolinium break"
    • Authors: Jan Welch; Danny Müller, Christian Knoll, Martin Wilkovitsch, Gerald Giester, Johannes Ofner, Bernhard Lendl, Peter Weinberger, Georg Steinhauser
      Abstract: Crystallization of terbium 5,5'-azobis[1H-tetrazol-1-ide] (ZT) in the presence of trace amounts (~1 pmol) of americium results in 1) the concentration of Am tracer in the crystalline solids and 2) material that adopts a different crystal structure than that formed in the absence of Am. The structure found for Am-doped Tb(Am)2ZT3·24 H2O is isostructural to those found for the light Ln (La-Gd) ZT compounds, rather than that of the heavy Ln (Tb-Lu) ZT compounds. Traces of Am seem to force the Tb compound into a structure normally preferred by the lighter Ln, despite a 1E8-fold Tb excess. The resulting Am-doped material was investigated by single crystal X-ray diffraction, vibrational spectroscopy, radiochemical neutron activation analysis and scanning electron microcopy to confirm the structure and composition of the resulting material. In addition, the carrying behavior of Tb2ZT3 for Am was quantified and a model for the crystallization process is proposed based on these investigations.
      PubDate: 2017-07-26T05:26:38.427148-05:
      DOI: 10.1002/anie.201703971
       
  • Copper-Catalyzed Three-Component Carboazidation of Alkenes with
           Acetonitrile and Sodium Azide
    • Authors: Ala Bunescu; Tu M. Ha, Qian Wang, Jieping Zhu
      Abstract: A copper-catalyzed three-component reaction of alkenes, acetonitrile, and sodium azide afforded γ-azido alkyl nitriles by formation of one C(sp3)−C(sp3) bond and one C(sp3)−N bond. The transformation allows concomitant introduction of two highly versatile groups (CN and N3) across the double bond. A sequence involving the copper-mediated generation of a cyanomethyl radical and its subsequent addition to an alkene, and a C(sp3)−N bond formation accounted for the reaction outcome. The resulting γ-azido alkyl nitrile can be easily converted into 1,4-diamines, γ-amino nitriles, γ-azido esters, and γ-lactams of significant synthetic value.Be disciplined: Regioselective azidocyanomethylation of alkenes takes place smoothly in the presence of di-tert-butyl peroxide (DTBP), a catalytic amount of Cu(OAc)2, and MnF3 to afford γ-azido alkylnitriles, which are highly valued synthetic building blocks. The reaction involves the copper-mediated generation of a cyanomethyl radical and its subsequent addition to an alkene, and a C(sp3)−N bond formation.
      PubDate: 2017-07-26T03:03:31.227307-05:
      DOI: 10.1002/anie.201705353
       
  • Enantioselective Oxidative (4+3) Cycloadditions between Allenamides and
           Furans through Bifunctional Hydrogen-Bonding/Ion-Pairing Interactions
    • Authors: Laura Villar; Uxue Uria, Jose I. Martínez, Liher Prieto, Efraim Reyes, Luisa Carrillo, Jose L. Vicario
      Abstract: BINOL-based N-trifluoromethanesulfonyl phosphoramides catalyze the enantioselective (4+3) cycloaddition between furans and oxyallyl cations, the latter being generated in situ by oxidation of allenamides. The chiral organic phosphoramide counteranion is proposed to engage in the activation of the oxyallyl cation intermediate through cooperative hydrogen-bonding and ion-pairing interactions, enabling an efficient chirality transfer that provide the final adducts with high diastereo- and enantioselectivities. Remarkably, the reaction shows a wide substrate scope that includes a variety of substituted allenamides and furans.Opposite charges attract: In situ generated oxyallyl cations react with a variety of furans in the presence of a BINOL-based N-sulfonyl phosphoramide catalyst, furnishing (4+3) cycloaddition products in excellent yields and with high stereocontrol. The reaction is enabled by bifunctional activation of the oxyallyl cation by hydrogen bonding in combination with the formation of a tightly bound ion pair.
      PubDate: 2017-07-26T03:03:23.038746-05:
      DOI: 10.1002/anie.201704804
       
  • Nanostructured Materials for Heterogeneous Electrocatalytic CO2 Reduction
           and their Related Reaction Mechanisms
    • Authors: Lei Zhang; Zhi-Jian Zhao, Jinlong Gong
      Abstract: The gradually increased concentration of carbon dioxide (CO2) in the atmosphere has been recognized as the primary culprit for the rise of the global mean temperature. In recent years, development of routes for highly efficient conversion of CO2 has received much attention. This Review describes recent progress on the design and synthesis of solid-state catalysts for the electrochemical reduction of CO2. The significance of this catalytic conversion is presented, followed by the general parameters for CO2 electroreduction and a summary of the reaction apparatus. We also discuss various types of solid catalysts based on their CO2 conversion mechanisms. We summarize the crucial factors (particle size, surface structure, composition, etc.) determining the performance for electroreduction.CO2 can do: Electroreduction of CO2 is an important CO2 conversion route because of its high environmental compatibility and good combination with other renewable energy sources. Nanostructured materials exhibit outstanding performances for heterogeneous electrocatalytic CO2 reduction. This Review describes recent advances for these nanostructured heterogeneous catalysts.
      PubDate: 2017-07-26T03:03:11.01156-05:0
      DOI: 10.1002/anie.201612214
       
  • E-Mobility and the Energy Transition
    • Authors: Robert Schlögl
      Abstract: Since the reduction of greenhouse gases is the top priority of the Energy Transition, primary electricity should be converted to material energy carriers. In this way electricity can be “stored” and made accessible for other applications. This Essay focuses on the integration of mobility in the Energy Transition and the development of sustainable alternatives to electricity-based transportation.
      PubDate: 2017-07-26T03:01:38.516195-05:
      DOI: 10.1002/anie.201701633
       
  • Unprecedented Nucleophilic Additions of Highly Polar Organometallic
           Compounds to Imines and Nitriles Using Water as a Non-Innocent Reaction
           Medium
    • Authors: Giuseppe Dilauro; Marzia Dell'Aera, Paola Vitale, Vito Capriati, Filippo Maria Perna
      Abstract: In contrast to classic methods carried out under inert atmospheres with dry volatile organic solvents and often low temperatures, the addition of highly polar organometallic compounds to non-activated imines and nitriles proceeds quickly, efficiently, and chemoselectively with a broad range of substrates at room temperature and under air with water as the only reaction medium. Secondary amines and tertiary carbinamines are furnished in yields of up to and over 99 %. The significant solvent D/H isotope effect observed for the on-water nucleophilic additions of organolithium compounds to imines suggests that the on-water catalysis arises from proton transfer across the organic–water interface. The strong intermolecular hydrogen bonds between water molecules may play a key role in disfavoring protonolysis, which occurs extensively in other protic media such as methanol. This work lays the foundation for reshaping many fundamental s-block metal-mediated organic transformations in water.Symphony between RLi and water: Unprecedented access to secondary amines and tertiary carbinamines from imines and nitriles using highly polar organometallic compounds and with water as the only reaction medium was achieved in very good yields. These reactions proceed quickly, smoothly, and chemoselectively at room temperature and under air.
      PubDate: 2017-07-26T02:56:17.560887-05:
      DOI: 10.1002/anie.201705412
       
  • Ta(CNDipp)6: An Isocyanide Analogue of Hexacarbonyltantalum(0)
    • Authors: Khetpakorn Chakarawet; Zachary W. Davis-Gilbert, Stephanie R. Harstad, Victor G. Young, Jeffrey R. Long, John E. Ellis
      Abstract: Hexakis(2,6-diisopropylphenylisocyanide)tantalum is the first isocyanide analogue of the highly unstable Ta(CO)6 and represents the only well-defined zerovalent tantalum complex to be prepared by conventional laboratory methods. Two prior examples of homoleptic Ta0 complexes are known, Ta(benzene)2 and Ta(dmpe)3, dmpe=1,2-bis(dimethylphosphano)ethane, but these have only been accessed via ligand co-condensation with tantalum vapor in a sophisticated metal-atom reactor. Consistent with its 17-electron nature, Ta(CNDipp)6 undergoes facile one-electron oxidation, reduction, or disproportionation reactions. In this sense, it qualitatively resembles V(CO)6, the only paramagnetic homoleptic metal carbonyl isolable under ambient conditions.Ta tantalizing: The first paramagnetic homoleptic metal isocyanide of a 5d-transition metal is hexakis(2,6-diisopropylphenylisocyanide)tantalum. It is an analogue of the highly unstable hexacarbonyltantalum(0) and is the only structurally authenticated zerovalent tantalum complex to be prepared by conventional laboratory methods. It has properties consistent with a 17-electron metalloradical.
      PubDate: 2017-07-26T02:51:19.723215-05:
      DOI: 10.1002/anie.201706323
       
  • Delineating the Mechanism of Ionic Liquids in the Synthesis of
           Quinazoline-2,4(1H,3H)-dione from 2-Aminobenzonitrile and CO2
    • Authors: Martin Hulla; Sami M. A. Chamam, Gabor Laurenczy, Shoubhik Das, Paul J. Dyson
      Abstract: Ionic liquids (ILs) are versatile solvents and catalysts for the synthesis of quinazoline-2,4-dione from 2-aminobenzonitrile and CO2. However, the role of the IL in this reaction is poorly understood. Consequently, we investigated this reaction and showed that the IL cation does not play a significant role in the activation of the substrates, and instead plays a secondary role in controlling the physical properties of the IL. A linear relationship between the pKa of the IL anion (conjugate acid) and the reaction rate was identified with maximum catalyst efficiency observed at a pKa of>14.7 in DMSO. The base-catalyzed reaction is limited by the acidity of the quinazoline-2,4-dione product, which is deprotonated by more basic catalysts, leading to the formation of the quinazolide anion (conjugate acid pKa 14.7). Neutralization of the original catalyst and formation of the quinazolide anion catalyst leads to the observed reaction limit.The ionic liquid (IL) cation does not play a significant role in the activation of the substrates in the synthesis of quinazoline-2,4-dione from 2-aminobenzonitrile and CO2. Instead, it plays a secondary role in controlling the physical properties of the IL. A linear relationship between the pKa of the IL anion (conjugate acid) and the reaction rate was identified, with maximum catalyst efficiency observed at a pKa of>14.7 in DMSO.
      PubDate: 2017-07-26T02:50:32.304993-05:
      DOI: 10.1002/anie.201705438
       
  • meso-meso β-β β-β Triply Linked Subporphyrin Dimer
    • Authors: Atsuhiro Osuka; Yasuhiro Okuda, Norihito Fukui, Jinseok Kim, Taeyeon Kim, Hua-Wei Jiang, Graeme Copley, Masaaki Kitano, Dongho Kim
      Abstract: meso-meso β-β β-β Triply linked subporphyrin dimer 6 was synthesized via stepwise reductive elimination of β-to-β doubly PtII-bridged subporphyrin dimer 9. Dimer 6 was characterized by spectroscopic and electrochemical measurements, theoretical caluculations, and picosecond time-resolved transient absorption spectroscopy. The X-ray diffraction analysis revealed that 6 took a bowl-shaped structure with a positive Gaussian curvature. Despite the curved structure, 6 exhibited a remarkably red-shifted absorption band at 942 nm and a small electrochemical HOMO-LUMO gap (1.35 eV), indicating the effectively conjugated π-electronic network.
      PubDate: 2017-07-26T00:26:00.792355-05:
      DOI: 10.1002/anie.201707123
       
  • Efficient photoelectrochemical reduction of CO2 to formic acid with
           functionalized ionic liquid as absorbent and electrolyte
    • Authors: Weiwei Lu; Bo Jia, Beilei Cui, Yuan Zhang, Kaisheng Yao, Yuling Zhao, Jian Ji Wang
      Abstract: Photoelectrochemical (PEC) reduction of CO2 is a potential way to produce fuels and chemicals by using C1-feedstock accumulated in the atmosphere. However, low solubility of CO2 in water and complicated processes of capture and conversion make the conversion efficiency quite low. In this study, a new conception of "ionic liquid assisted capture and conversion of CO2 in PEC system" is proposed and demonstrated by using 1-aminopropyl-3-methylimidazolium bromide aqueous solution as both the absorbent and electrolyte at ambient temperature and pressure. It is found that in this PEC reduction strategy, ionic liquid plays a critical role in promoting the conversion of CO2 to formic acid and suppressing the reduction of H2O to H2. Faradaic efficiency of formic acid is as high as 94.1% and the electro-to-chemical efficiency is 86.2% at the applied voltage of 1.7 V.
      PubDate: 2017-07-25T12:25:45.249523-05:
      DOI: 10.1002/anie.201703977
       
  • Dendritic Hematite Nanoarray Photoanode Modified by Conformal Titanium
           Dioxide Interlayer for Effective Charge Collection
    • Authors: Jinlong Gong; Zhibin Luo, Tuo Wang, Jijie Zhang, Chengcheng Li, Huimin Li
      Abstract: This paper describes the introduction of a thin titanium dioxide interlayer that serves as passivation layer and dopant source for hematite (α-Fe2O3) nanoarray photoanode. This interlayer is demonstrated to boost the photocurrent by suppressing the substrate/hematite interfacial charge recombination, and increase the electrical conductivity by enabling Ti4+ incorporation. A dendritic nanostructure of this photoanode with enhanced solid-liquid junction area further improves to the surface charge collection efficiency, generating a photocurrent of ~2.5 mA cm-2 at 1.23 V versus reversible hydrogen electrode (vs. RHE) under air mass 1.5G illumination. A photocurrent of ~3.1 mA cm-2 at 1.23 V vs. RHE could be achieved by loading hydroxyl-ferric oxide cocatalyst.
      PubDate: 2017-07-25T12:25:39.350277-05:
      DOI: 10.1002/anie.201705772
       
  • Ni-Catalyzed Enantioselective Conjunctive Cross-Coupling of 9-BBN Borates
    • Authors: James Patrick Morken; Matteo Chierchia, Chunyin Law
      Abstract: Catalytic enantioselective conjunctive cross-coupling be-tween 9-BBN boronate complexes and aryl electrophiles can be accomplished with Ni salts in the presence of a chiral diamine ligand. The reactions furnish chiral 9-BBN derivatives in an enantioselective fashion and these are converted to chiral alcohols and amines, or engaged in other stereospecific C-C bond forming reactions.
      PubDate: 2017-07-25T11:26:59.995242-05:
      DOI: 10.1002/anie.201706719
       
  • Solid-state transformation of amorphous calcium carbonate to aragonite
           captured by cryoTEM
    • Authors: Jessica Mary Walker; Bartosz Marzec, Fabio Nudelman
      Abstract: Early stage reaction mechanisms for aragonite promoting systems are relatively unknown, compared to the more thermodynamically stable calcium carbonate polymorph, calcite. Using cryoTEM and SEM, we identified the early reaction stages taking place during aragonite formation in a highly supersaturated solution using an alcohol-water solvent, and described an overall particle attachment growth mechanism for the system. We provide the first evidence for the solid-state transformation of amorphous calcium carbonate to aragonite, demonstrating the co-existence of both amorphous and crystalline material within the same aragonite needle. This supports non-classical formation of aragonite within both a synthetic and biological context.
      PubDate: 2017-07-25T11:25:27.393706-05:
      DOI: 10.1002/anie.201703158
       
  • Controlled supramolecular self-assembly of "supercharged β-lactoglobulin
           A - PEG conjugates" into nanocapsules.
    • Authors: Amit Kumar Khan; Sushanth Gudlur, Hans-Peter de Hoog, Winna Siti, Bo Liedberg, Madhavan Nallani
      Abstract: We describe the synthesis and characterization of a new protein-polymer conjugate composed of β lactoglobulin A (βLG A) and poly(ethylene glycol) PEG. βLG A was selectively modified to self-assemble by supercharging via amidation or succinylation followed by conjugation with PEG. An equimolar mixture of the oppositely charged protein-polymer conjugates self-assemble into spherical capsules of 80-100 nm in diameter. The self-assembly proceeds by taking simultaneous advantage of the protein-polymer conjugate's amphiphilicity and polyelectrolyte nature. These protein-polymer capsules or proteinosomes are reminiscent of protein capsids, and are capable of encapsulating solutes in their interior. We envisage this approach to be applicable to other globular proteins.
      PubDate: 2017-07-25T10:26:00.602531-05:
      DOI: 10.1002/anie.201704298
       
  • Asymmetric Synthesis of alfa,alfa-Disubstituted Allylic Amines via
           Pd-Catalyzed Allylic Substitution
    • Authors: Arjan Willem Kleij; Wusheng Guo, Aijie Cai, Jaining Xie
      Abstract: The first asymmetric synthesis of important alfa,alfa-disubstituted N-alkyl allyl amine scaffolds via allylic substitution is reported. This approach is based on palladium catalysis and features ample scope in both allylic precursor and amine reagent, and high asymmetric induction with the enantiomeric ratio (er) up to 98.5:1.5.The use of less reactive anilines is also feasible providingenantioenriched alfa,alfa-disubstituted N-aryl allylic amines.
      PubDate: 2017-07-25T10:25:52.917423-05:
      DOI: 10.1002/anie.201705825
       
  • Structural Revision and Biomimetic Synthesis of Goupiolone B
    • Authors: Yosuke Matsuo; Ayane Yoshida, Yoshinori Saito, Takashi Tanaka
      Abstract: Goupiolones A and B are unique phenolic compounds with significant DNA-damaging activity. In this study, the structure of goupiolone B was revised on the basis of DFT calculations of the ¹³C NMR chemical shifts and biosynthetic considerations. The dibenzobicyclo[3.2.2]nonane skeleton of the revised structure suggested that goupiolone B was produced by oxidative coupling between catechol and goupiolone A, which was strongly supported by this biomimetic synthesis. Furthermore, the racemization of goupiolone B was observed during the examination for the chiral separation of its racemic mixture. A plausible racemization mechanism involving α-ketol rearrangement was also proposed.
      PubDate: 2017-07-25T09:26:03.691115-05:
      DOI: 10.1002/anie.201706532
       
  • Copper-Catalyzed Decarboxylative Radical Silylation of Redox-Active
           Aliphatic Carboxylic Acid Derivatives
    • Authors: Weichao Xue; Martin Oestreich
      Abstract: A decarboxylative silylation of aliphatic N-hydroxyphthalimide (NHPI) esters using Si-B reagents as silicon pronucleophiles is reported. This C(sp3)-Si cross-coupling is catalyzed by copper(I) and follows a radical mechanism, even with exclusion of light. Both primary and secondary alkyl groups couple effectively whereas tertiary groups are probably too sterically hindered. The functional-group tolerance is generally excellent, and alpha-heteroatom-substituted substrates also participate well. This enables, for example, the synthesis of alpha-silylated amines starting from NHPI esters derived from alpha-amino acids. The new method complements the still limited number of C(sp3)-Si cross-couplings of unactivated alkyl electrophiles.
      PubDate: 2017-07-25T08:25:28.177833-05:
      DOI: 10.1002/anie.201706611
       
  • Conversion of a Dehalogenase into a Nitroreductase by Swapping its Flavin
           Cofactor with a 5-Deazaflavin Analogue
    • Authors: Qi Su; Petrina A. Boucher, Steven E. Rokita
      Abstract: Natural and engineered nitroreductases have rarely supported full reduction of nitroaromatics to their amine products, and more typically, transformations are limited to formation of the hydroxylamine intermediates. Efficient use of these enzymes also requires a regenerating system for NAD(P)H to avoid the costs associated with this natural reductant. Iodotyrosine deiodinase is a member of the same structural superfamily as many nitroreductases but does not directly consume reducing equivalents from NAD(P)H, nor demonstrate nitroreductase activity. However, exchange of its flavin cofactor with a 5-deazaflavin analogue dramatically suppresses its native deiodinase activity and leads to significant nitroreductase activity that supports full reduction to an amine product in the presence of the convenient and inexpensive NaBH4.Old enzyme, new tricks: The dehalogenase IYD was converted into a nitroreductase by exchanging its native flavin cofactor for a 5-deazaflavin analogue (5dFMN). The resulting enzyme catalyzes full reduction of nitrotyrosine to aminotyrosine in the presence of NaBH4.
      PubDate: 2017-07-25T07:01:11.977893-05:
      DOI: 10.1002/anie.201703628
       
  • Semihydrogenation of Acetylene on Indium Oxide: Proposed Single-Ensemble
           Catalysis
    • Authors: Davide Albani; Marçal Capdevila-Cortada, Gianvito Vilé, Sharon Mitchell, Oliver Martin, Núria López, Javier Pérez-Ramírez
      Abstract: Indium oxide catalyzes acetylene hydrogenation with high selectivity to ethylene (>85 %); even with a large excess of the alkene. In situ characterization reveals the formation of oxygen vacancies under reaction conditions, while an in depth theoretical analysis links the surface reduction with the creation of well-defined vacancies and surrounding In3O5 ensembles, which are considered responsible for this outstanding catalytic function. This behavior, which differs from that of other common reducible oxides, originates from the presence of four crystallographically inequivalent oxygen sites in the indium oxide surface. These resulting ensembles are 1) stable against deactivation, 2) homogeneously and densely distributed, and 3) spatially isolated and confined against transport; thereby broadening the scope of oxides in hydrogenation catalysis.In dium we trust: Indium oxide selectively catalyzes the partial hydrogenation of acetylene in the presence of excess ethylene. Theoretical analysis links the observed surface reduction with the creation of robust and well-defined oxygen vacancies and surrounding In3O5 ensembles, which are considered responsible for this outstanding catalytic function.
      PubDate: 2017-07-25T07:01:03.780948-05:
      DOI: 10.1002/anie.201704999
       
  • γ-Functionalizations of Amines through Visible-Light-Mediated,
           Redox-Neutral C−C Bond Cleavage
    • Authors: Wei Shu; Alexandre Genoux, Zhaodong Li, Cristina Nevado
      Abstract: Cleavage of unstrained C−C bonds under mild, redox-neutral conditions represents a challenging endeavor which is accomplished here in the context of a flexible, visible-light-mediated, γ-functionalization of amines. In situ generated C-centered radicals are harvested in the presence of Michael acceptors, thiols and alkyl halides to efficiently form new C(sp3)−C(sp3), C(sp3)−H and C(sp3)−Br bonds, respectively.Visible light enables the facile cleavage of unstrained C−C bonds and the subsequent remote functionalization of in situ generated C-centered radicals in γ-position to amino groups. In the presence of Michael acceptors, thiols, or alkyl halides new C(sp3)−C(sp3), C(sp3)−H and C(sp3)−Br bonds are efficiently formed.
      PubDate: 2017-07-25T06:55:32.454719-05:
      DOI: 10.1002/anie.201704068
       
  • Directing the Activation of Donor-Acceptor Cyclopropanes To-wards
           Stereoselective 1,3-Dipolar Cycloaddition Reactions by Brønsted Base
           Catalysis
    • Authors: Karl Anker Jørgensen; Jakob Blom, Andreu Vidal-Albalat, Julie Jørgensen, Casper L. Barløse, Kamilla S. Jessen, Marc V. Iversen
      Abstract: The first organocatalyzed stereoselective [3+2] cycloaddition reaction of donor-acceptor cyclopropanes is presented. It is demonstrated that applying an optically active bifunctional Brønsted base catalyst, racemic bis-cyano cyclopropylketones can be activated to undergo a stereoselective 1,3-dipolar reac-tion with mono- and polysubstituted nitroolefins. The reaction affords highly functionalized cyclopentanes with three con-secutive stereocenters, formed in high yield and stereoselec-tivity. Based on the stereochemical outcome a possible mech-anism in which the organocatalyst activates both the donor-acceptor cyclopropane and nitroolefin is proposed. Finally, chemoselective transformations of the cycloaddition products are demonstrated.
      PubDate: 2017-07-25T06:21:02.639278-05:
      DOI: 10.1002/anie.201706150
       
  • Peptide-Directed Binding for the Discovery of Modulators of
           α-Helix-Mediated Protein–Protein Interactions: Proof-of-Concept Studies
           with the Apoptosis Regulator Mcl-1
    • Authors: Andrew Michael Beekman; Maria Anne O'Connell, Lesley Ann Howell
      Abstract: Targeting PPIs with small molecules can be challenging owing to large, hydrophobic binding surfaces. Herein, we describe a strategy that exploits selective α-helical PPIs, transferring these characteristics to small molecules. The proof of concept is demonstrated with the apoptosis regulator Mcl-1, commonly exploited by cancers to avoid cell death. Peptide-directed binding uses few synthetic transformations, requires the production of a small number of compounds, and generates a high percentage of hits. In this example, about 50 % of the small molecules prepared showed an IC50 value of less than 100 μm, and approximately 25 % had IC50 values below 1 μm to Mcl-1. Compounds show selectivity for Mcl-1 over other anti-apoptotic proteins, possess cytotoxicity to cancer cell lines, and induce hallmarks of apoptosis. This approach represents a novel and economic process for the rapid discovery of new α-helical PPI modulators.Selective α-helical protein–protein interactions were exploited to develop small-molecule inhibitors of these interactions. Proof-of-concept studies were conducted with the apoptosis regulator Mcl-1, and compounds that show selectivity for Mcl-1 over other anti-apoptotic proteins, are cytotoxic to cancer cell lines, and induce hallmarks of apoptosis were thus identified.
      PubDate: 2017-07-25T06:14:13.512217-05:
      DOI: 10.1002/anie.201705008
       
  • The Narrow Road to the Deep Past: in Search of the Chemistry of the Origin
           of Life
    • Authors: Jack W. Szostak
      Abstract: The sequence of events that gave rise to the first life on our planet took place in the Earth's deep past, seemingly forever beyond our reach. Perhaps for that very reason the idea of reconstructing our ancient story is tantalizing, almost irresistible. Understanding the processes that led to synthesis of the chemical building blocks of biology and the ways in which these molecules self-assembled into cells that could grow, divide and evolve, nurtured by a rich and complex environment, seems at times insurmountably difficult. And yet, to my own surprise, simple experiments have revealed robust processes that could have driven the growth and division of primitive cell membranes. The nonenzymatic replication of RNA is more complicated and less well understood, but here too significant progress has come from surprising developments. Even our efforts to combine replicating compartments and genetic materials into a full protocell model have moved forward in unexpected ways. Fortunately, many challenges remain before we will be close to a full understanding of the origin of life, so the future of research in this field is brighter than ever!Life from chemistry: How did the first living cells reproduce before the evolution of enzymes' Primitive cell membranes can grow and divide in response to a variety of environmental fluctuations or competitive situations. Recent progress brings us closer to understanding the nonenzymatic replication of the primordial genetic material, but many puzzles remain.
      PubDate: 2017-07-25T06:11:24.832403-05:
      DOI: 10.1002/anie.201704048
       
  • Boronic Acid Functionalized Photosensitizers: A Strategy to Target the
           Surface of Bacteria and Implement Active Agents in Polymer Coatings
    • Authors: Anzhela Galstyan; Roswitha Schiller, Ulrich Dobrindt
      Abstract: Advanced methods for preventing and controlling hospital-acquired infections via eradication of free-floating bacteria and bacterial biofilms are of great interest. In this regard, the attractiveness of unconventional treatment modalities such as antimicrobial photodynamic therapy (aPDT) continues to grow. This study investigated a new and innovative strategy for targeting polysaccharides found on the bacterial cell envelope and the biofilm matrix using the boronic acid functionalized and highly effective photosensitizer (PS) silicon(IV) phthalocyanine. This strategy has been found to be successful in treating planktonic cultures and biofilms of Gram-negative E. coli. An additional advantage of boronic acid functionality is a possibility to anchor the tailor made PS to poly(vinyl alcohol) and to fabricate a self-disinfecting coating.Making and breaking barriers: The boronic acid–diol interaction was used to anchor a photosensitizer into the bacterial cell surface and biofilm matrix and break the barrier by photodynamic action. The same functional group enables implementation of the active agent in a poly(vinyl alcohol) coating, providing a photo-bactericidal barrier against microbial adhesion.
      PubDate: 2017-07-25T06:11:14.880049-05:
      DOI: 10.1002/anie.201703398
       
  • Intrinsic Photoprotective Mechanisms in Chlorophylls
    • Authors: Michał Kotkowiak; Alina Dudkowiak, Leszek Fiedor
      Abstract: Photosynthetic energy conversion competes with the formation of chlorophyll triplet states and the generation of reactive oxygen species. These may, especially under high light stress, damage the photosynthetic apparatus. Many sophisticated photoprotective mechanisms have evolved to secure a harmless flow of excitation energy through the photosynthetic complexes. Time-resolved laser-induced optoacoustic spectroscopy was used to compare the properties of the T1 states of pheophytin a and its metallocomplexes. The lowest quantum yield of the T1 state is always observed in the Mg complex, which also shows the least efficient energy transfer to O2. Axial coordination to the central Mg further lowers the yield of both T1 and singlet oxygen. These results reveal the existence of intrinsic photoprotective mechanisms in chlorophylls, embedded in their molecular design, which substantially suppress the formation of triplet states and the efficiency of energy transfer to O2, each by 20–25 %. Such intrinsic photoprotective effects must have created a large evolutionary advantage for the Mg complexes during their evolution as the principal photoactive cofactors of photosynthetic proteins.Time-resolved laser-induced optoacoustic spectroscopy was used to compare the properties of the T1 states of pheophytin a and its metallocomplexes. The lowest quantum yield of the T1 state is always observed in the Mg complex, which also shows the least efficient energy transfer to O2. Axial coordination to the central Mg further lowers the yield of both T1 and singlet oxygen. This justifies why chlorophyll a is the principal photosynthetic pigment on Earth.
      PubDate: 2017-07-25T06:05:33.326475-05:
      DOI: 10.1002/anie.201705357
       
  • A Doubly Boron-Doped Perylene by N-Heterocylic Carbene-Borenium
           Hydroboration—C-H Borylation—Dehydrogenation
    • Authors: Jeffrey M Farrell; David Schmidt, Vincenzo Grande, Frank Würthner
      Abstract: Reaction of an N-heterocyclic carbene (NHC)-borenium ion with 9,10-distyrylanthracene forms four B-C bonds through two selective, tandem hydroboration—electrophilic C-H borylations to yield an isolable, crystallographically characterizable polycyclic diborenium ion as its [NTf2]- salt (1). Dehydrogenation of 1 with TEMPO radical followed by acidic workup yields a 3,9-diboraperylene as its corresponding borinic acid (2). This sequence can be performed in one pot to allow the facile, metal-free conversion of an alkene to a small molecule containing a boron-doped graphene substructure. Doubly boron-doped perylene 2 exhibits visible range absorbance and fluorescence in chloroform solution (Φ = 0.63) and undergoes two reversible one electron reductions at moderate potentials of -1.30 and -1.64 eV vs. ferrocenium/ferrocene in DMSO. Despite sterically accessible boron centers and facile electrochemical reductions, compound 2 is air-, moisture- and silica gel-stable.
      PubDate: 2017-07-25T05:27:03.182225-05:
      DOI: 10.1002/anie.201706346
       
  • Old dog new tricks in the antibiotic toolbox: -lactam synthesis through
           diodomethane addition onto amide dianions.
    • Authors: laurent El Kaim; Alaa Zidan, Julian Garrec, marie Cordier, Ali Khalil Ali, Abeer El-Naggar, Nour Eldein Abdel-Sattar, Mohamed Ali Hassan
      Abstract: We propose a novel route for the quick and easy synthesis of a broad range of -lactams. The synthesis involves a [3+1] cyclization of amide dianions with diiodomethane. In opposition to the seminal work of Hirai et al, the reaction proved to be a general and efficient approach towards azetidinones. The easiness of the process was confirmed by DFT calculations and its power demonstrated by a diversity oriented synthesis of -lactams with 4 point of diversity brought by the choice of Ugi adducts as starting materials.
      PubDate: 2017-07-25T05:26:52.71697-05:0
      DOI: 10.1002/anie.201706315
       
  • Highly Syndiotactic or Isotactic Polyhydroxyalkanoates by
           Ligand-Controlled Yttrium-Catalyzed Stereoselective Ring-Opening
           Polymerization of Functional Racemic β-Lactones
    • Authors: Romain Ligny; Mikko M. Hänninen, Sophie M. Guillaume, Jean-François Carpentier
      Abstract: Reported herein is the first stereoselective controlled ROP of a specific family of racemic functional β-lactones, namely 4-alkoxymethylene-β-propiolactones (BPLORs). This process is catalyzed by an yttrium complex stabilized by a nonchiral tetradentate amino alkoxy bisphenolate ligand {ONOOR′2}2−, which features both a good activity and a high degree of control over the molar masses of the resulting functional poly(3-hydroxyalkanoate)s. A simple modification of the R′ substituents in ortho and para position on the ligand platform allows for a complete reversal from virtually pure syndioselectivity (Ps up to 0.91 with R′=cumyl) to very high isoselectivity (Pi up to 0.93 with R′=Cl), as supported by DFT insights. This is the first example of a highly isoselective ROP of a racemic chiral β-lactone.Make your choice: Highly syndiotactic or isotactic polyhydroxyalkanoates were obtained from racemic mixtures of functional alkoxymethylene-β-lactones in an yttrium-catalyzed ring-opening polymerization. The selectivity can be completely switched by a simple modification of substituents on the catalyst ligand.
      PubDate: 2017-07-25T03:52:01.396669-05:
      DOI: 10.1002/anie.201704283
       
  • Catalytic Stereoselective 1,4-Addition Reactions Using CsF on Alumina as a
           Solid Base: Continuous-Flow Synthesis of Glutamic Acid Derivatives
    • Authors: Parijat Borah; Yasuhiro Yamashita, Shū Kobayashi
      Abstract: A novel methodology using CsF⋅Al2O3 as a highly efficient, environmentally benign, and reusable solid-base catalyst was developed to synthesize glutamic acid derivatives by stereoselective 1,4-addition of glycine derivatives to α,β-unsaturated esters. CsF⋅Al2O3 showed not only great selectivity toward 1,4-addtion reactions by suppressing the undesired formation of pyrrolidine derivations by [3+2] cycloadditions, but also offered high yields for the 1,4-adduct with excellent anti diastereoselectivities. The catalyst was well characterized by using XRD, 19F MAS-NMR and 19F NMR spectroscopy, FT-IR, CO2-TPD, and XPS. And highly basic F from Cs3AlF6 was identified as the most probable active basic site for the 1,4-addition reactions. Continuous-flow synthesis of 3-methyl glutamic acid derivative was successfully demonstrated by using this solid-base catalysis.A solid base: A method to synthesize glutamic acid derivatives by the highly stereoselective 1,4-addition of glycine derivatives to α,β-unsaturated esters, using CsF⋅Al2O3 as a reusable solid-base catalyst, was developed for both batch and continuous-flow systems. Cs3AlF6 was identified as the active basic site for the addition reaction.
      PubDate: 2017-07-25T03:47:54.10833-05:0
      DOI: 10.1002/anie.201701789
       
  • Exclusive formation of formic acid from CO2 electroreduction by tunable
           Pd-Sn alloy
    • Authors: Xiaofang Bai; Wei Chen, Chengcheng Zhao, Shenggang Li, Yanfang Song, Ruipeng Ge, Wei Wei, Yuhan Sun
      Abstract: Conversion of carbon dioxide (CO2) into fuels and chemicals via electroreduction has attracted significant interest derived from renewable energy storage and environmental sustainability, although it suffered from large overpotential and low selectivity. Here, we report a Pd-Sn alloy electrocatalyst for the exclusive conversion of CO2 into formic acid in an aqueous solution. This catalyst showed a nearly perfect faradaic efficiency toward formic acid formation at the very low overpotential of -0.26 V, where both CO formation and hydrogen evolution were completely suppressed. Density functional theory (DFT) calculations suggested that the formation of the key reaction intermediate HCOO* as well as the product formic acid was the most favourable over the Pd-Sn alloy catalyst surface with an atomic composition of PdSnO2, consistent with our experiments. This indicates the great potential of the tunable Pd-Sn alloy catalyst for the efficient conversion of CO2 into valuable products.
      PubDate: 2017-07-25T03:37:19.56161-05:0
      DOI: 10.1002/anie.201707098
       
  • A Cu/Pd Synergistic Dual Catalysis for Enantioselective Allylic Alkylation
           of Aldimine Esters: A Facile Access to alpha,alpha-Disubstituted
           alpha-Amino Acids
    • Authors: Chun-Jiang Wang; Liang Wei, Shi-Ming Xu, Qiao Zhu, Chao Che
      Abstract: An unprecedented enantioselective allylic alkylation of readily-available aldimine esters has been developed, which was efficiently catalyzed by a Cu/Pd synergistic dual catalyst. This strategy provides a facile access to nonproteinogenic alpha,alpha-disubstituted alpha-amino acids (alpha-AAs) in high yield with excellent enantioselectivity. The more challenging double allylic allylation of glycinate derived imine esters could also be realized. Furthermore, this methodology was applied for the construction of the key intermediate of PLG peptidomimetics.
      PubDate: 2017-07-25T03:20:48.717044-05:
      DOI: 10.1002/anie.201707019
       
  • Preparation of Polyfunctional Diorgano-Magnesium and -Zinc Reagents Using
           In Situ Trapping Halogen-Lithium Exchange of Highly Functionalized
           (Hetero)aryl Halides in Continuous Flow
    • Authors: Marthe Ketels; Maximilian Andreas Ganiek, Niels Weidmann, Paul Knochel
      Abstract: We report a halogen-lithium exchange performed in the presence of various metal salts (ZnCl2, MgCl2·LiCl) on a broad range of sensitive bromo- or iodo-(hetero)arenes using BuLi or PhLi as exchange reagent and a commercially available continuous flow setup. The resulting diarylmagnesium or diarylzinc species were trapped with various electrophiles resulting in the formation of polyfunctional (hetero)arenes in high yields. This methodology enabled the functionalization of (hetero)arenes containing highly sensitive groups such as an isothiocyanate, nitro, azide or ester. A straightforward scale-up was possible without further optimization.
      PubDate: 2017-07-25T03:20:37.403024-05:
      DOI: 10.1002/anie.201706609
       
  • Nucleophilic Amination of Methoxy Arenes by a Sodium Hydride-Iodide
           Composite
    • Authors: Atsushi Kaga; Hirohito Hayashi, Hiroyuki Hakamata, Miku Oi, Masanobu Uchiyama, Ryo Takita, Shunsuke Chiba
      Abstract: A new protocol for nucleophilic amination of methoxy arenes was established using sodium hydride (NaH) in the presence of lithium iodide (LiI), offering an efficient route to supply benzannulated nitrogen-heterocycles. Mechanistic studies showed that unusual concerted nucleophilic aromatic substitution operates in the present process.
      PubDate: 2017-07-25T02:20:47.624598-05:
      DOI: 10.1002/anie.201705916
       
  • Homoleptic Alkynyl-Protected Gold Nanoclusters: Au44(PhCC)28 and
           Au36(PhCC)24
    • Authors: Xian-Kai Wan; Zong-Jie Guan, Quan-Ming Wang
      Abstract: For the first time total structure determination of homoleptic alkynyl-protected gold nanoclusters are reported. The nanoclusters are synthesized by direct reduction of PhCCAu, and their compositions are determined to be Au44(PhCC)28 and Au36(PhCC)24. The Au44 and Au36 nanoclusters have fcc-type Au36 and Au28 kernels, respectively, as well as surrounding PhCºC-Au-C2(Ph)Au-CºCPh dimeric "staples" and simple PhCºC bridges. The structures of Au44(PhCºC)28 and Au36(PhCC)24 are similar to Au44(SR)28 and Au36(SR)24, respectively, but the UV-Vis spectra are distinctly different between alkynyl and thiolate protected nanoclusters. The protecting ligands influence the electronic structures of nanoclusters significantly. This work indicates that a series of gold nanoclusters in the general formula Aux(RCC)y as counterparts of Aux(SR)y can be expected. More importantly, the structural similarity between Aux(RCC)y and Aux(SR)y offers great opportunities to study ligand effects of nanoclusters.
      PubDate: 2017-07-24T15:41:38.994808-05:
      DOI: 10.1002/anie.201706021
       
  • Redox-Driven Migration of Copper Ions in the Cu-CHA Zeolite as Shown by
           the In Situ PXRD/XANES Technique
    • Authors: Casper Welzel Andersen; Elisa Borfecchia, Martin Bremholm, Mads Ry Vogel Jørgensen, Peter Nicolai Ravnborg Vennestrøm, Carlo Lamberti, Lars Fahl Lundegaard, Bo Brummerstedt Iversen
      Abstract: Using quasi-simultaneous in situ PXRD and XANES, the direct correlation between the oxidation state of Cu ions in the commercially relevant deNOx NH3-SCR zeolite catalyst Cu-CHA and the Cu ion migration in the zeolitic pores was revealed during catalytic activation experiments. A comparison with recent reports further reveals the high sensitivity of the redox-active centers concerning heating rates, temperature, and gas environment during catalytic activation. Previously, Cu+ was confirmed present only in the 6R. Results verify a novel 8R monovalent Cu site, an eventually large Cu+ presence upon heating to high temperatures in oxidative conditions, and demonstrate the unique potential in combining in situ PXRD and XANES techniques, with which both oxidation state and structural location of the redox-active centers in the zeolite framework could be tracked.Quasi-simultaneous in situ PXRD/XANES was used to show the direct correlation between oxidation state and Cu ion migration in the commercially relevant deNOx zeolite catalyst Cu-CHA. Results reveal a surprisingly severe auto-reduction of Cu in oxidative conditions above 400 °C, verify a possible 8R site for Cu+ from heating in inert conditions, and demonstrate the potential of quasi-simultaneous PXRD and XANES techniques.
      PubDate: 2017-07-24T15:20:40.478202-05:
      DOI: 10.1002/anie.201703808
       
  • New 1.2 GHz NMR Spectrometers— New Horizons'
    • Authors: Harald Schwalbe
      Abstract: The latest ultrahigh-field NMR spectrometers are a huge technological challenge that require large financial investments. In his Guest Editorial, Harald Schwalbe justifies the need for spectrometers with higher magnetic field strengths. The important results from previous generations of high-field NMR spectrometers are discussed, and research areas are identified that will benefit from the latest spectrometers.
      PubDate: 2017-07-24T15:16:49.798114-05:
      DOI: 10.1002/anie.201705936
       
  • Mechanistic Insight Leads to a Ligand Which Facilitates the
           Palladium-Catalyzed Formation of 2-(Hetero)Arylaminooxazoles and
           4-(Hetero)Arylaminothiazoles
    • Authors: Esben P. K. Olsen; Pedro L. Arrechea, Stephen L. Buchwald
      Abstract: By using mechanistic insight, a new ligand (EPhos) for the palladium-catalyzed C−N cross-coupling between primary amines and aryl halides has been developed. Employing an isopropoxy group at the C3-position favors the C-bound isomer of the ligand-supported palladium(II) complexes and leads to significantly improved reactivity. The use of a catalyst system based on EPhos with NaOPh as a mild homogeneous base proved to be very effective in the formation of 4-arylaminothiazoles and highly functionalized 2-arylaminooxazoles. Previously, these were not readily accessible using palladium catalysis.Cross-examination: A new ligand, EPhos, for palladium-catalyzed C−N cross-couplings has been developed based on a structure–activity relationship of BrettPhos-related ligands. EPhos was successfully applied in the Pd-catalyzed formation of 2-(hetero)arylaminooxazoles and 4-(hetero)arylaminothiazoles, the synthesis of which had previously proven problematic in transition-metal catalysis.
      PubDate: 2017-07-24T15:16:35.521256-05:
      DOI: 10.1002/anie.201705525
       
  • Trifluoroacetic Anhydride Promoted Copper(I)-Catalyzed Interrupted Click
           Reaction: From 1,2,3-Triazoles to 3-Trifluoromethyl-Substituted
           1,2,4-Triazinones
    • Authors: Wei Wu; Junwen Wang, Yukang Wang, Yangjie Huang, Yingfei Tan, Zhiqiang Weng
      Abstract: A copper(I)-catalyzed interrupted click reaction in the presence of trifluoroacetic anhydride has been developed, wherein an N-trifluoroacetyl group is used to accelerate the ring-opening of the putative 5-copper(I) triazolide intermediate. Under the optimized reaction conditions, a broad range of azides and alkynes were found to participate in this transformation, thus affording 3-trifluoromethyl-substituted 1,2,4-triazinones in moderate to excellent yields. The reaction has proven to be compatible with a variety of electron-withdrawing and electron–donating groups, halogens, and nitrogen- and sulfur-containing heterocycles, as well as pharmaceutically relevant molecules.Quick, not dirty: 3-Trifluoromethyl-substituted 1,2,4-triazinones are obtained from copper(I)-catalyzed interrupted click reaction of azides, alkynes, and trifluoroacetic anhydride. This cycloaddition reaction proceeds under mild reaction conditions, exhibits good tolerance of a broad range of functional groups, and provides a direct approach for the synthesis of valuable trifluoromethyl-substituted triazinones from inexpensive starting materials.
      PubDate: 2017-07-24T15:15:25.049741-05:
      DOI: 10.1002/anie.201705620
       
  • The Effect of Pressure on Organic Reactions in Fluids—a New
           Theoretical Perspective
    • Authors: Bo Chen; Roald Hoffmann, Roberto Cammi
      Abstract: This Review brings a new perspective to the study of chemical reactions in compressed fluid media. We begin by reviewing the substantial insight gained from more than 50 years of experimental studies on organic reactions in solution under pressure. These led to a proper estimation of the critical roles of volume of activation (Δ≠V) and reaction volume (ΔV) in understanding pressure effect on rates and equilibria of organic reactions. A recently developed computational method, the XP-PCM (extreme pressure polarizable continuum model) method, capable of carrying out quantum mechanical calculations of reaction pathways of molecules under pressure, is introduced. A case study of the Diels–Alder cycloaddition of cyclopentadiene with ethylene serves, in pedagogical detail, to describe the methodology. We then apply the XP-PCM method to a selection of other pericyclic reactions, including the parent Diels–Alder cycloaddition of butadiene with ethylene, electrocyclic ring-opening of cyclobutene, electrocyclic ring-closing of Z-hexatriene, the [1,5]-H shift in Z-pentadiene, and the Cope rearrangement. These serve as examples of some of the most common combinations of Δ≠V and ΔV. Interesting phenomena such as a shift in a transition state along a reaction coordinate, a switch of rate-determining step, and the possible turning of a transition state into a stable minimum are revealed by the calculations. A reaction volume profile, the change in the volume of the reacting molecules as the reaction proceeds, emerges as being useful.Squeeze me: A general method for analyzing chemical reactions run under compression in fluids is introduced, calibrated and tested on pericyclic reactions. As we knew, volumes of reaction and activation matter. In some cases transition states could turn into intermediates, and conformational pre- or post-equilibria become rate-determining.
      PubDate: 2017-07-24T15:15:09.891855-05:
      DOI: 10.1002/anie.201705427
       
  • Electrochemical Exfoliation of Layered Black Phosphorus into Phosphorene
    • Authors: Adriano Ambrosi; Zdeněk Sofer, Martin Pumera
      Abstract: Among 2D materials that recently have attracted enormous interest, black phosphorus (BP) is gaining a rising popularity due to its tunable band-gap structure, which is strongly correlated to the thickness and can enable its use in optoelectronic and electronic applications. It is therefore important to provide a facile and scalable methodology to prepare single or few-layer BP nanosheets. We propose herein a simple and fast top-down method to exfoliate a BP crystal into nanosheets of reduced thickness by using electrochemistry. The application of an anodic potential to the crystal in an acidic aqueous solution allows control over the exfoliation efficiency and quality of the nanosheets produced. X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and scanning transmission electron microscopy (STEM) have been applied to fully characterize the exfoliated material, which presented significantly reduced layer thickness compared to the starting bulk material.A layered approach: A simple and fast top-down electrochemical method for exfoliating a BP crystal into nanosheets of reduced thickness is proposed. The application of an anodic potential to the crystal in an acidic solution allows control over the exfoliation efficiency and quality of the nanosheets produced.
      PubDate: 2017-07-24T15:12:53.143799-05:
      DOI: 10.1002/anie.201705071
       
  • Diazirines as Potential Molecular Imaging Tags: Probing the Requirements
           for Efficient and Long-Lived SABRE-Induced Hyperpolarization
    • Authors: Kun Shen; Angus W. J. Logan, Johannes F. P. Colell, Junu Bae, Gerardo X. Ortiz, Thomas Theis, Warren S. Warren, Steven J. Malcolmson, Qiu Wang
      Abstract: Diazirines are an attractive class of potential molecular tags for magnetic resonance imaging owing to their biocompatibility and ease of incorporation into a large variety of molecules. As recently reported, 15N2-diazirine can be hyperpolarized by the SABRE-SHEATH method, sustaining both singlet and magnetization states, thus offering a path to long-lived polarization storage. Herein, we show the generality of this approach by illustrating that the diazirine tag alone is sufficient for achieving excellent signal enhancements with long-lasting polarization. Our investigations reveal the critical role of Lewis basic additives, including water, on achieving SABRE-promoted hyperpolarization. The application of this strategy to a 15N2-diazirine-containing choline derivative demonstrates the potential of 15N2-diazirines as molecular imaging tags for biomedical applications.Tag team: 15N2-diazirine motifs are demonstrated to be capable of supporting long-lasting polarization by the experimentally simple and cost-effective hyperpolarization method of SABRE-SHEATH, presenting promising potential as molecular tags for NMR/MRI imaging.
      PubDate: 2017-07-24T14:52:22.371211-05:
      DOI: 10.1002/anie.201704970
       
  • Long-Term Live-Cell STED Nanoscopy of Primary and Cultured Cells with the
           Plasma Membrane HIDE Probe DiI-SiR
    • Authors: Alexander D. Thompson; Mitchell H. Omar, Felix Rivera-Molina, Zhiqun Xi, Anthony J. Koleske, Derek K. Toomre, Alanna Schepartz
      Abstract: Super-resolution imaging of live cells over extended time periods with high temporal resolution requires high-density labeling and extraordinary fluorophore photostability. Herein, we achieve this goal by combining the attributes of the high-density plasma membrane probe DiI-TCO and the photostable STED dye SiR-Tz. These components undergo rapid tetrazine ligation within the plasma membrane to generate the HIDE probe DiI-SiR. Using DiI-SiR, we visualized filopodia dynamics in HeLa cells over 25 min at 0.5 s temporal resolution, and visualized dynamic contact-mediated repulsion events in primary mouse hippocampal neurons over 9 min at 2 s temporal resolution. HIDE probes such as DiI-SiR are non-toxic and do not require transfection, and their apparent photostability significantly improves the ability to monitor dynamic processes in live cells at super-resolution over biologically relevant timescales.Hiding Out: Live cells were imaged with super-resolution over extended time periods by combining the high-density plasma membrane probe DiI-TCO and the photostable STED dye SiR-Tz. These components undergo rapid tetrazine ligation within the plasma membrane to generate the high-density environment-sensitive (HIDE) probe DiI-SiR, which was used to visualize the filopodia dynamics in HeLa cells over 25 min at 0.5 s temporal resolution.
      PubDate: 2017-07-24T14:51:31.174875-05:
      DOI: 10.1002/anie.201704783
       
  • Towards a Comprehensive Understanding of the Reaction Mechanisms Between
           Defective MoS2 and Thiol Molecules
    • Authors: Qiang Li; Yinghe Zhao, Chongyi Ling, Shijun Yuan, Qian Chen, Jinlan Wang
      Abstract: Sulfur vacancies (SVs) inherent in MoS2 are generally detrimental for carrier mobility and optical properties. Thiol chemistry has been explored for SV repair and surface functionalization. However, the resultant products and reaction mechanisms are still controversial. Herein, a comprehensive understanding on the reactions is provided by tracking potential energy surfaces and kinetic studies. The reactions are dominated by two competitive mechanisms that lead to either functionalization products or repair SVs, and the polarization effect from decorating thiol molecules and thermal effect are two determining factors. Electron-donating groups are conducive to the repairing reaction whereas electron-withdrawing groups facilitate the functionalization process. Moreover, the predominant reaction mechanism can be switched by increasing the temperature. This study fosters a way of precisely tailoring the electronic and optical properties of MoS2 by means of thiol chemistry approaches.Sulfur vacancies (SVs) inherent in MoS2 are generally detrimental for carrier mobility and optical properties. Thiols have been investigated for SV repair and surface functionalization. Electron-donating groups on thiols support repair whereas electron-withdrawing groups facilitate functionalization. The predominant reaction can also be switched by increasing the temperature.
      PubDate: 2017-07-24T14:44:30.710837-05:
      DOI: 10.1002/anie.201706038
       
  • A Fairly Stable Crystalline Silanone
    • Authors: Isabel Alvarado-Beltran; Alfredo Rosas-Sánchez, Antoine Baceiredo, Nathalie Saffon-Merceron, Vicenç Branchadell, Tsuyoshi Kato
      Abstract: Silanones 2 substituted by bulky amino- and phosphonium ylide substituents have been synthesized and isolated in crystalline form. Thanks to the steric protection and the strong electron-donating ability of the substituents, silanones 2 are persistent and only slowly dimerizes at room temperature (t1/2=0.5 or 5 h). Structural and theoretical analysis of 2 indicate a short Si=O bond (1.533 Å) and an enhanced polarization toward the O atom compared to Me2Si=O owing to the strong π-electron donation from the phosphonium ylide substituent.Stabilizers for silanones: Silanones substituted by bulky amino and (phosphonium)ylide substituents have been synthesized and isolated in crystalline form. Thanks to the steric protection and the strong electron-donating ability of substituents, these silanones are persistent and only slowly dimerize at room temperature (t1/2=0.5 or 5 h).
      PubDate: 2017-07-24T14:44:22.23984-05:0
      DOI: 10.1002/anie.201705644
       
  • Self-healable Organogel Nanocomposite with Angle-Independent Structural
           Colors
    • Authors: Jinming Zhou; Peng Han, Meijin Liu, Haiyan Zhou, Yingxue Zhang, Jieke Jiang, Peng Liu, Yu Wei, Yanlin Song, Xi Yao
      Abstract: Structural colors have profound implications in the fields of pigments, displays and sensors, but none of the current non-iridescent photonic materials can restore their functions after mechanical damage. Herein, we report the first self-healable organogel nanocomposites with angle-independent structural colors. The organogel nanocomposites were prepared through the co-assembly of oleophilic silica nanoparticles, silicone-based supramolecular gels, and carbon black. The organogel system enables amorphous aggregation of silica nanoparticles and the angle-independent structural colors in the nanocomposites. Moreover, the hydrogen bonding in the supramolecular gel provides self-healing ability to the system, and the structural colored films obtained could heal themselves in tens of seconds to restore storage modulus, structural color, and surface slipperiness from mechanical cuts or shear failure repeatedly.Colors, the director′s cut: Organogel nanocomposites capable of fast self-healing and are prepared. The gels can form films that have angle-independent structural colors and are water repellant, properties that are restored on self-healing.
      PubDate: 2017-07-24T14:43:12.516022-05:
      DOI: 10.1002/anie.201705462
       
  • Asymmetric Synthesis of Tertiary Alcohols and Thiols via Non-Stabilized
           Tertiary α-Oxy- and α-Thio-Organolithiums
    • Authors: Varinder Kumar Aggarwal; Alex Pulis, Ana Verela, Cinzia Citti, Pradip Songara, Daniele Leonori
      Abstract: Non-stabilised α-O-tertiary organolithiums are difficult to generate and the α-S analogues are configurationally unstable. We now report that they can both be generated easily and trapped with a range of electrophiles with high enantioselectivity providing ready access to a range of enantioenriched tertiary alcohols and thiols. Enhanced configurational stability of the -S-organolithiums was achieved by using a less coordinating solvent and short reaction times.
      PubDate: 2017-07-24T14:15:31.950272-05:
      DOI: 10.1002/anie.201706722
       
  • Diketopyrrolopyrrole Columnar Liquid-Crystalline Assembly Directed by
           Quadruple Hydrogen Bonds
    • Authors: Bartolome Soberats; Markus Hecht, Frank Würthner
      Abstract: A diketopyrrolopyrrole (DPP) dye self-assembles via a unique hydrogen-bonding motif into an unprecedented columnar liquid-crystalline (LC) structure. X-ray and polarized FTIR experiments reveal that the DPPs organize into a one-dimensional assembly with the chromophores oriented parallel to the columnar axis. This columnar structure is composed of two π–π-stacked DPP dimers with mirror-image configurations that stack alternately through quadruple hydrogen bonding by 90° rotation. This exotic packing is dictated by the complementarity between H-bonds and the steric demands of the wedge-shaped groups attached at the core. This novel LC supramolecular material opens a new avenue of research on DPP dye assemblies with photofunctional properties tailored by H-bonding networks.A carefully designed diketopyrrolopyrrole dye self-assembles via quadruple hydrogen bonds into columnar liquid-crystalline phases. The 1D assembly is formed by the stack of two enantiomerically related dimers (A and B) with complementary hydrogen-bonding topology. As a result of this stacking mode, the dyes are oriented parallel to the columnar axis.
      PubDate: 2017-07-24T07:56:33.166954-05:
      DOI: 10.1002/anie.201705137
       
  • Enantioselective Organocatalytic Intramolecular Aza-Diels–Alder
           Reaction
    • Authors: Lucie Jarrige; Florent Blanchard, Géraldine Masson
      Abstract: A highly efficient catalytic enantioselective intramolecular Povarov reaction was developed with primary anilines as 2-azadiene precursors. A wide variety of angularly fused azacycles were obtained without column chromatography in high to excellent yields and with excellent diastereo- and enantioselectivity (d.r.>99:1 and up to e.r. 99:1). Furthermore, the catalyst loading could be lowered to 1 mol %, and the obtained azacycles could be used as key intermediates for further transformations to generate additional molecular diversity.A match made in heaven: A matching effect between a chiral phosphoric acid and cycloadduct precursors enabled the development of an enantioselective intramolecular Povarov reaction (see scheme). The efficient reaction is broad in scope and proceeded with high diastereo- and enantioselectivity. Simple precipitation was sufficient for the isolation of each product in excellent purity and without the need for chromatographic separation.
      PubDate: 2017-07-24T07:56:04.641609-05:
      DOI: 10.1002/anie.201705746
       
  • A Stimuli-Responsive Zirconium Metal–Organic Framework Based on
           Supermolecular Design
    • Authors: Simon Krause; Volodymyr Bon, Ulrich Stoeck, Irena Senkovska, Daniel M. Többens, Dirk Wallacher, Stefan Kaskel
      Abstract: A flexible, yet very stable metal–organic framework (DUT-98, Zr6O4(OH)4(CPCDC)4(H2O)4, CPCDC=9-(4-carboxyphenyl)-9H-carbazole-3,6-dicarboxylate) was synthesized using a rational supermolecular building block approach based on molecular modelling of metal–organic chains and subsequent virtual interlinking into a 3D MOF. Structural characterization via synchrotron single-crystal X-ray diffraction (SCXRD) revealed the one-dimensional pore architecture of DUT-98, envisioned in silico. After supercritical solvent extraction, distinctive responses towards various gases stimulated reversible structural transformations, as detected using coupled synchrotron diffraction and physisorption techniques. DUT-98 shows a surprisingly low water uptake but a high selectivity for pore opening towards specific gases and vapors (N2, CO2, n-butane, alcohols) at characteristic pressure resulting in multiple steps in the adsorption isotherm and hysteretic behavior upon desorption.Switchability meets stability: A flexible, yet very stable metal–organic framework (DUT-98, Zr6O4(OH)4(CPCDC)4(H2O)4, CPCDC=9-(4-carboxyphenyl)-9H-carbazole-3,6-dicarboxylate) was synthesized using a rational supermolecular building block approach based on molecular modelling. DUT-98 shows a surprisingly low water uptake but a high selectivity for pore opening towards specific gases and vapors.
      PubDate: 2017-07-24T07:55:42.560489-05:
      DOI: 10.1002/anie.201702357
       
  • Opto-electrochemical In Situ Monitoring of the Cathodic Formation of
           Single Cobalt Nanoparticles
    • Authors: Vitor Brasiliense; Jan Clausmeyer, Alice L. Dauphin, Jean-Marc Noël, Pascal Berto, Gilles Tessier, Wolfgang Schuhmann, Fréderic Kanoufi
      Abstract: Single-particle electrochemistry at a nanoelectrode is explored by dark-field optical microscopy. The analysis of the scattered light allows in situ dynamic monitoring of the electrodeposition of single cobalt nanoparticles down to a radius of 65 nm. Larger sub-micrometer particles are directly sized optically by super-localization of the edges and the scattered light contains complementary information concerning the particle redox chemistry. This opto-electrochemical approach is used to derive mechanistic insights about electrocatalysis that are not accessible from single-particle electrochemistry.Single-particle electrochemistry at a nanoelectrode can be explored by dark-field optical microscopy. The analysis of the scattered light makes it possible to monitor the electrodeposition of single cobalt nanoparticles in situ down to a radius of 65 nm. The scattered light also contains information used to derive mechanistic insights not accessible from single-particle electrochemistry.
      PubDate: 2017-07-24T07:34:48.523962-05:
      DOI: 10.1002/anie.201704394
       
  • Full Selectivity Control in Cobalt(III)-Catalyzed C−H Alkylations by
           Switching of the C−H Activation Mechanism
    • Authors: Daniel Zell; Markus Bursch, Valentin Müller, Stefan Grimme, Lutz Ackermann
      Abstract: Selectivity control in hydroarylation-based C−H alkylation has been dominated by steric interactions. A conceptually distinct strategy that exploits the programmed switch in the C−H activation mechanism by means of cobalt catalysis is presented, which sets the stage for convenient C−H alkylations with unactivated alkenes. Detailed mechanistic studies provide compelling evidence for a programmable switch in the C−H activation mechanism from a linear-selective ligand-to-ligand hydrogen transfer to a branched-selective base-assisted internal electrophilic-type substitution.Sterically hindered carboxylate additives promote cobalt-catalyzed C−H alkylation (alkyl=Alk) of unactivated alkenes. Bulky additives switch on a base-assisted internal electrophilic-type substitution (BIES) C−H activation mechanism, thereby favoring congested Markovnikov products. Without additive, a linear-selective ligand-to-ligand hydrogen transfer (LLHT) mechanism occurs.
      PubDate: 2017-07-24T07:34:20.281119-05:
      DOI: 10.1002/anie.201704196
       
  • Coaxial Triple-Layered versus Helical Be6B11− Clusters: Dual Structural
           Fluxionality and Multifold Aromaticity
    • Authors: Jin-Chang Guo; Lin-Yan Feng, Ying-Jin Wang, Said Jalife, Alejandro Vásquez-Espinal, José Luis Cabellos, Sudip Pan, Gabriel Merino, Hua-Jin Zhai
      Abstract: Two low-lying structures are unveiled for the Be6B11− nanocluster system that are virtually isoenergetic. The first, triple-layered cluster has a peripheral B11 ring as central layer, being sandwiched by two Be3 rings in a coaxial fashion, albeit with no discernible interlayer Be−Be bonding. The B11 ring revolves like a flexible chain even at room temperature, gliding freely around the Be6 prism. At elevated temperatures (1000 K), the Be6 core itself also rotates; that is, two Be3 rings undergo relative rotation or twisting with respect to each other. Bonding analyses suggest four-fold (π and σ) aromaticity, offering a dilute and fluxional electron cloud that lubricates the dynamics. The second, helix-type cluster contains a B11 helical skeleton encompassing a distorted Be6 prism. It is chiral and is the first nanosystem with a boron helix. Molecular dynamics also shows that at high temperature the helix cluster readily converts into the triple-layered one.Fluxional or helical: The Be6B11− cluster is calculated to adopt two competitive conformations. The coaxial triple-layered cluster mimics the earth–moon system, featuring three-dimensional structural fluxionality and dual dynamic modes (revolution versus rotation). The helix-type cluster is the first boron helix; the highly charged boron core presumably governs the helical arrangement.
      PubDate: 2017-07-24T07:33:39.333095-05:
      DOI: 10.1002/anie.201703979
       
  • New Modalities for Challenging Targets in Drug Discovery
    • Authors: Eric Valeur; Stéphanie M. Guéret, Hélène Adihou, Ranganath Gopalakrishnan, Malin Lemurell, Herbert Waldmann, Tom N. Grossmann, Alleyn T. Plowright
      Abstract: Our ever-increasing understanding of biological systems is providing a range of exciting novel biological targets, whose modulation may enable novel therapeutic options for many diseases. These targets include protein–protein and protein–nucleic acid interactions, which are, however, often refractory to classical small-molecule approaches. Other types of molecules, or modalities, are therefore required to address these targets, which has led several academic research groups and pharmaceutical companies to increasingly use the concept of so-called “new modalities”. This Review defines for the first time the scope of this term, which includes novel peptidic scaffolds, oligonucleotides, hybrids, molecular conjugates, as well as new uses of classical small molecules. We provide the most representative examples of these modalities to target large binding surface areas such as those found in protein–protein interactions and for biological processes at the center of cell regulation.Out of the box: A new generation of molecules, including novel peptides, oligonucleotides, hybrids, and molecular conjugates, is enabling novel strategies to address challenging targets and biological processes at the center of cell regulation. This Review defines these “new modalities”, and highlights how progress in this area is now leading to a range of novel drug candidates.
      PubDate: 2017-07-24T07:32:59.158822-05:
      DOI: 10.1002/anie.201611914
       
  • An Electrochemical Biosensor with Dual Signal Outputs: Toward Simultaneous
           Quantification of pH and O2 in the Brain upon Ischemia and in a Tumor
           during Cancer Starvation Therapy
    • Authors: Li Liu; Fan Zhao, Wei Liu, Tong Zhu, John Z. H. Zhang, Chen Chen, Zhihui Dai, Huisheng Peng, Jun-Long Huang, Qin Hu, Wenbo Bu, Yang Tian
      Abstract: Herein, we develop a novel method for designing electrochemical biosensors with both current and potential signal outputs for the simultaneous determination of two species in a living system. Oxygen (O2) and pH, simple and very important species, are employed as model molecules. By designing and synthesizing a new molecule, Hemin-aminoferrocene (Hemin-Fc), we create a single electrochemical biosensor for simultaneous detection and ratiometric quantification of O2 and pH in the brain. The reduction peak current of the hemin group increases with the concentration of O2 from 1.3 to 200.6 μm. Meanwhile, the peak potential positively shifts with decreasing pH from 8.0 to 5.5, resulting in the simultaneous determination of O2 and pH. The Fc group can serve as an internal reference for ratiometric biosensing because its current and potential signals remain almost constant with variations of O2 and pH. The developed biosensor has high temporal and spatial resolutions, as well as remarkable selectivity and accuracy, and is successfully applied in the real-time quantification of O2 and pH in the brain upon ischemia, as well as in tumor during cancer therapy.Two birds with one stone: A novel method for designing electrochemical biosensors by monitoring both current and potential signal outputs is presented. The molecule Hemin-Fc was designed for the simultaneous detection and ratiometric quantification of O2 and pH and was successfully applied to the real-time quantification in the rat brain upon ischemia and in tumor during cancer starvation therapy.
      PubDate: 2017-07-24T06:20:54.755235-05:
      DOI: 10.1002/anie.201705615
       
  • Synthesis of WOn-WX2 (n=2.7, 2.9; X=S, Se) Heterostructures for Highly
           Efficient Green Quantum Dot Light-Emitting Diodes
    • Authors: Shikui Han; Xuyong Yang, Yihan Zhu, Chaoliang Tan, Xiao Zhang, Junze Chen, Ying Huang, Bo Chen, Zhimin Luo, Qinglang Ma, Melinda Sindoro, Hao Zhang, Xiaoying Qi, Hai Li, Xiao Huang, Wei Huang, Xiao Wei Sun, Yu Han, Hua Zhang
      Abstract: Preparation of two-dimensional (2D) heterostructures is important not only fundamentally, but also technologically for applications in electronics and optoelectronics. Herein, we report a facile colloidal method for the synthesis of WOn-WX2 (n=2.7, 2.9; X=S, Se) heterostructures by sulfurization or selenization of WOn nanomaterials. The WOn-WX2 heterostructures are composed of WO2.9 nanoparticles (NPs) or WO2.7 nanowires (NWs) grown together with single- or few-layer WX2 nanosheets (NSs). As a proof-of-concept application, the WOn-WX2 heterostructures are used as the anode interfacial buffer layer for green quantum dot light-emitting diodes (QLEDs). The QLED prepared with WO2.9 NP-WSe2 NS heterostructures achieves external quantum efficiency (EQE) of 8.53 %. To our knowledge, this is the highest efficiency in the reported green QLEDs using inorganic materials as the hole injection layer.Sulfur green: Sulfurization or selenization of WOn nanomaterials gives WOn-WX2 (n=2.7, 2.9; X=S, Se) heterostructures. Highly efficient green quantum dot light-emitting diodes (QLEDs) have been prepared by using the as-prepared WOn-WX2 heterostructures as the hole-injection layer.
      PubDate: 2017-07-24T06:18:29.483665-05:
      DOI: 10.1002/anie.201705617
       
  • Lateral Organization of Host Heterogeneous Raft-Like Membranes Altered by
           the Myristoyl Modification of Tyrosine Kinase c-Src
    • Authors: Mridula Dwivedi; Tom Mejuch, Herbert Waldmann, Roland Winter
      Abstract: Membrane-bound c-Src non-receptor tyrosine kinase, unlike other acyl-modified lipid-anchored proteins, anchors to the membrane by a myristoyl chain along with a polybasic residue stretch, which is shorter in chain length than its host membrane. The packing defect arising from this mismatched chain length of the host and the lipid anchor significantly affects the lateral organization of heterogeneous membranes. We reveal the mixing of phase domains and formation of novel nanoscale-clusters upon membrane binding of the Myr-Src (2–9) peptide. Fluorescence cross correlation spectroscopy was used to explore the nature of these clusters. We show that Myr-Src (2–9) is able to oligomerize, and the peptide clusters are embedded in a lipid platform generated by lipid sorting. Further, using confocal fluorescence microscopy and FRET assays we show that localized charge enrichment and membrane curvature are able to shift the partition coefficient towards the more ordered lipid phase.Lipid–protein nanoclusters: Tyrosine kinase c-Src attaches to the plasma membrane using a myristoyl (Myr) anchor that is shorter than the surrounding lipid matrix. Insertion of lipidated anchor of Myr-Src into various model biomembranes alters the nanoscale organization of the peptide upon membrane binding and leads to an altered lateral structure of the host membrane.
      PubDate: 2017-07-24T06:18:13.435611-05:
      DOI: 10.1002/anie.201706233
       
  • Jean-François Lutz
    • PubDate: 2017-07-24T06:17:56.50249-05:0
      DOI: 10.1002/anie.201706838
       
  • Crystalline Diuranium Phosphinidiide and μ-Phosphido Complexes with
           Symmetric and Asymmetric UPU Cores
    • Authors: Thomas M. Rookes; Benedict M. Gardner, Gábor Balázs, Matthew Gregson, Floriana Tuna, Ashley J. Wooles, Manfred Scheer, Stephen T. Liddle
      Abstract: Reaction of [U(TrenTIPS)(PH2)] (1, TrenTIPS=N(CH2CH2NSiPri3)3) with C6H5CH2K and [U(TrenTIPS)(THF)][BPh4] (2) afforded a rare diuranium parent phosphinidiide complex [{U(TrenTIPS)}2(μ-PH)] (3). Treatment of 3 with C6H5CH2K and two equivalents of benzo-15-crown-5 ether (B15C5) gave the diuranium μ-phosphido complex [{U(TrenTIPS)}2(μ-P)][K(B15C5)2] (4). Alternatively, reaction of [U(TrenTIPS)(PH)][Na(12C4)2] (5, 12C4=12-crown-4 ether) with [U{N(CH2CH2NSiMe2But)2CH2CH2NSi(Me)(CH2)(But)}] (6) produced the diuranium μ-phosphido complex [{U(TrenTIPS)}(μ-P){U(TrenDMBS)}][Na(12C4)2] [7, TrenDMBS=N(CH2CH2NSiMe2But)3]. Compounds 4 and 7 are unprecedented examples of uranium phosphido complexes outside of matrix isolation studies, and they rapidly decompose in solution underscoring the paucity of uranium phosphido complexes. Interestingly, 4 and 7 feature symmetric and asymmetric UPU cores, respectively, reflecting their differing steric profiles.Outside the matrix: Prepared by two different routes, the first examples of uranium phosphido complexes outside of cryogenic matrix isolation conditions are reported, revealing symmetric and asymmetric (shown; U green, P purple, N blue, Si yellow) UPU cores in the solid-state crystal structures.
      PubDate: 2017-07-24T06:17:54.942753-05:
      DOI: 10.1002/anie.201706002
       
  • Covalently Interlocked Cyclohexa-m-phenylenes and Their Assembly: En Route
           to Supramolecular 3D Carbon Nanostructures
    • Authors: Bastian Dumslaff; Anna N. Reuss, Manfred Wagner, Xinliang Feng, Akimitsu Narita, George Fytas, Klaus Müllen
      Abstract: In our search to cluster as many phenylene units as possible in a given space, we have proceeded to the three-dimensional world of benzene-based molecules by employing covalently interlocked cyclohexa-m-phenylenes, as present in the unique paddlewheel-shaped polyphenylene 10. A precursor was conceived, in which freely rotating m-chlorophenylene units provide sufficient solubility along with the necessary proximity for the final ring closure to give 10. Monitoring the assembly of solubilized tert-butyl derivatives of 10 into supramolecular carbon nanostructures by dynamic light scattering (DLS) and Brillouin light scattering (BLS) revealed the dimensions of the initially formed aggregates as well as the amorphous character of the solid state.Essentially strain-free and thermally stable paddlewheel polyphenylenes consisting of two covalently interlocked cyclohexa-m-phenylenes have been synthesized. Tuning of the solubility allowed the hierarchical formation of three-dimensional carbon nanostructures to be monitored.
      PubDate: 2017-07-24T06:17:43.528504-05:
      DOI: 10.1002/anie.201705403
       
  • Hydroformylation of Alkenes in a Planetary Ball Mill: from
           Additive-Controlled Reactivity to Supramolecular Control of
           Regioselectivity
    • Authors: Kévin Cousin; Stéphane Menuel, Eric Monflier, Frédéric Hapiot
      Abstract: The Rh-catalyzed hydroformylation of aromatic-substituted alkenes is performed in a planetary ball mill under CO/H2 pressure. The dispersion of the substrate molecules and the Rh-catalyst into the grinding jar is ensured by saccharides: methyl-α-d-glucopyranoside, acyclic dextrins, or cyclodextrins (CDs, cyclic oligosaccharides). The reaction affords the exclusive formation of aldehydes whatever the saccharide. Acyclic saccharides disperse the components within the solid mixture leading to high conversions of alkenes. However, they showed typical selectivity for α-aldehyde products. If CDs are the dispersing additive, the steric hindrance exerted by the CDs on the primary coordination sphere of the metal modifies the selectivity so that the β-aldehydes were also formed in non-negligible proportions. Such through-space control via hydrophobic effects over reactivity and regioselectivity reveals the potential of such solventless process for catalysis in solid state.Ground sugar: The rhodium-catalyzed hydroformylation of aromatic-substituted alkenes is efficiently performed in a planetary ball mill under CO/H2 pressure. It gives aldehydes in high chemoselectivity and with modification of the regioselectivity to the less-preferred β-aldehydes.
      PubDate: 2017-07-24T06:17:34.446295-05:
      DOI: 10.1002/anie.201705467
       
  • Reentrant Structural Transitions and Collapse of Charge and Orbital Orders
           in Quadruple Perovskites
    • Authors: Alexei A. Belik; Yoshitaka Matsushita, Dmitry D. Khalyavin
      Abstract: Charge and orbital degrees of freedom determine properties of many materials, and are central to many important phenomena. At high temperatures, thermal fluctuations overcome them, and high-symmetry structures are realized. On decreasing temperature, different charge- and orbital-order transitions take place accompanied by symmetry lowering. Remarkable exceptions to this general tendency, realized in Cu-doped BiMn7O12 quadruple perovskites, are presented. Introduction of Cu2+ produces mixtures of Mn3+ and Mn4+ and charge degree of freedom. BiCuMn6O12 (and compositions in the vicinity) exhibits well-defined 1:3 charge order of Mn4+ and Mn3+ and orbital order of Mn3+ near room temperature, but both charge and orbital orders collapse below about 115 K with the reentrance of the high-temperature cubic Im3‾ phase. What is interesting the collapse can be controlled by a magnetic field even without long-range magnetic order, and the collapsed phase shows nearly zero thermal expansion.Total collapse: Effects of the introduction of the charge degree of freedom into the B site of BiMn7O12 through BiCuxMn7−xO12 solid solutions are explored. BiCuMn6O12 exhibits well-defined 1:3 charge order of Mn4+ and Mn3+ and orbital order of Mn3+ near room temperature, but both charge and orbital orders collapse below about 115 K with the reentrance of the high-temperature cubic Im3‾ phase.
      PubDate: 2017-07-24T06:17:30.387277-05:
      DOI: 10.1002/anie.201704798
       
  • Integrated In Situ Characterization of a Molten Salt Catalyst Surface:
           Evidence of Sodium Peroxide and Hydroxyl Radical Formation
    • Authors: Kazuhiro Takanabe; Abdulaziz M. Khan, Yu Tang, Luan Nguyen, Ahmed Ziani, Benjamin W. Jacobs, Ayman M. Elbaz, S. Mani Sarathy, Franklin (Feng) Tao
      Abstract: Sodium-based catalysts (such as Na2WO4) were proposed to selectively catalyze OH radical formation from H2O and O2 at high temperatures. This reaction may proceed on molten salt state surfaces owing to the lower melting point of the used Na salts compared to the reaction temperature. This study provides direct evidence of the molten salt state of Na2WO4, which can form OH radicals, using in situ techniques including X-ray diffraction (XRD), scanning transmission electron microscopy (STEM), laser induced fluorescence (LIF) spectrometry, and ambient-pressure X-ray photoelectron spectroscopy (AP-XPS). As a result, Na2O2 species, which were hypothesized to be responsible for the formation of OH radicals, have been identified on the outer surfaces at temperatures of ≥800 °C, and these species are useful for various gas-phase hydrocarbon reactions, including the selective transformation of methane to ethane.In situ characterizations at high temperature revealed that the molten state of Na2WO4 on the oxide surface produces a Na2O2-rich outer surface that catalyzes OH radical formation from an O2/H2O mixture. This process is useful for H abstraction from hydrocarbons in the gas phase.
      PubDate: 2017-07-24T06:17:24.338384-05:
      DOI: 10.1002/anie.201704758
       
  • CO2-Sourced α-Alkylidene Cyclic Carbonates: A Step Forward in the Quest
           for Functional Regioregular Poly(urethane)s and Poly(carbonate)s
    • Authors: Sandro Gennen; Bruno Grignard, Thierry Tassaing, Christine Jérôme, Christophe Detrembleur
      Abstract: Described is a robust platform for the synthesis of a large diversity of novel functional CO2-sourced polymers by exploiting the regiocontrolled ring-opening of α-alkylidene carbonates by various nucleophiles. The reactivity of α-alkylidene carbonates is dictated by the exocyclic olefinic group. The polyaddition of CO2-sourced bis(α-alkylidene carbonate)s (bis-αCCs) with primary and secondary diamines provides novel regioregular functional poly(urethane)s. The reactivity of bis-αCCs is also exploited for producing new poly(β-oxo-carbonate)s by organocatalyzed polyaddition with a diol. This synthesis platform provides new functional variants of world-class leading polymer families (polyurethanes, polycarbonates) and valorizes CO2 as a chemical feedstock.Opening up: The regioselective ring-opening of bis(α-alkylidene carbonate)s with diamines and diols is exploited to provide a broad scope of functional regioregular polymers under ambient conditions. This robust synthesis platform provides new functional variants of world-class leading polymer families (polyurethanes and polycarbonates) and valorizes CO2 as a chemical feedstock.
      PubDate: 2017-07-24T06:16:18.593516-05:
      DOI: 10.1002/anie.201704467
       
  • Gold(Core)–Lead(Shell) Nanoparticle-Loaded Titanium(IV) Oxide Prepared
           by Underpotential Photodeposition: Plasmonic Water Oxidation
    • Authors: Ryo Negishi; Shin-ichi Naya, Hisayoshi Kobayashi, Hiroaki Tada
      Abstract: Underpotential photodeposition of Pb yields an ultrathin shell layer on the Au(111) surface of Au nanoparticle(NP)-loaded TiO2 (Au/TiO2) with heteroepitaxial nanojunctions. The localized surface plasmon resonance of Au/TiO2 undergoes no damping with the Pb-shell formation, and the Pb shell offers resistance to aerobic oxidation. Mesoporous films comprising the Au(core)–Pb(shell) NP-loaded TiO2 and unmodified Au/TiO2 were formed on fluorine-doped tin oxide (FTO) electrode. Using them as the photoanode, photoelectrochemical cells were fabricated, and the photocurrent was measured under illumination of simulated sunlight. The photocurrent for water splitting is dramatically enhanced by the Pb-shell formation. The photoelectrochemical measurements of the hot-electron lifetime and density functional theory calculations for model clusters indicate that the Pb-shell effect originates from the charge separation enhancement.Lead on: Underpotential photodeposition of Pb yields an ultrathin shell layer on the Au(111) surface of Au nanoparticle-loaded TiO2 (Au/TiO2). By incorporating this system in a photoanode, the photocurrent for water splitting is dramatically enhanced as a result of the Pb-shell formation.
      PubDate: 2017-07-24T06:16:10.500821-05:
      DOI: 10.1002/anie.201703093
       
  • Insulin—From its Discovery to the Industrial Synthesis of Modern
           Insulin Analogues
    • Authors: Luis Moroder; Hans-Jürgen Musiol
      Abstract: After the discovery of insulin as a drug for diabetes, the pharmaceutical companies were faced with the challenge to meet the demand for insulin with the highest possible degree of purity in the required quantities from animal sources. The observation of an immune reaction of patients to insulin from animal pancreatic extracts made the availability of human insulin of highest priority. Only the enzyme-catalyzed semisynthesis at the C-terminus of the insulin B-chain led to a commercial process, but it depended on porcine insulin and was aggravated by supply concerns. The advent of rDNA technology allowed the commercial preparation of human insulin by biosynthesis in virtually unlimited quantities. An increased chemical diversity was only envisaged through chemical synthesis, which was simplified by advances in solid-phase peptide synthesis and chemical ligation. Single-chain insulin precursors are now being synthesized that should enable fast screening of insulin analogues for improved biophysical, biological, and thus promising new therapeutic properties, as well as for the industrial manufacture of insulin analogues not accessible by biosynthesis.Building bridges: After a short historical overview of the discovery of insulin to its production from animal sources, and later by semi- and biosynthesis, this Review focuses on the most recent advances of chemical synthesis that progressively surmounted all the technical obstacles of assembling disulfide-bridged structures via biomimetic insulin precursors in the search for analogues of improved therapeutic properties.
      PubDate: 2017-07-24T06:15:46.975297-05:
      DOI: 10.1002/anie.201702493
       
  • Unexpected Chiro-Thermoresponsive Behavior of Helical
           Poly(phenylacetylene)s Bearing Elastin-Based Side-Chains
    • Authors: Sandra Arias; Felix Freire, Marcelo Calderon, Julian Bergueiro
      Abstract: The thermoresponsive behavior of an elastin based polymer can be altered by the polymeric macromolecular conformation. Thus, when the elastin basic amino-acid sequence VPGVG is used as a pendant group of a poly(phenylacetylene) (PPA) its thermoresponsivity in water can be remotely detected due to conformational changes on the formed helix. Circular dichroism at different temperatures show an inversion of the first Cotton effect (450 nm) at 25.8 ºC that matches with the cloud point temperature. Interestingly, this elastin-based side-chain PPA shows an upper critical solution temperature with low pH and concentration dependency, not expected in elastin based polymers. All these results indicate that the macromolecular structure like a helical one has a strong influence on its thermoresponsive response and tunes its native behavior. Finally, it was found that the polymer self-assembles in water into spherical nanoparticles with hydrodynamic diameters of 140 nm at the hydrophobic state.
      PubDate: 2017-07-24T05:20:34.495573-05:
      DOI: 10.1002/anie.201704821
       
  • Facile One-Pot Synthesis of Functional Giant Polymeric Vesicles Controlled
           by Oscillatory Chemistry
    • Authors: Bishnu Prasad Bastakoti; Juan Perez-Mercader
      Abstract: We introduce a novel application of an oscillatory chemical reaction to the synthesis of block copolymers. The Belousov–Zhabotinsky (B-Z) reaction is coupled with the polymerization of an amphiphilic block copolymer. Radicals generated in the B-Z reaction initiate the polymerization between a polyethylene glycol (PEG) macroreversible addition-fragmentation chain-transfer agent and butyl acrylate monomers. The attachment of a hydrophobic block on PEG leads to self-assembly and formation of spherical micelles. The nanoscale micelles transform into submicrometer vesicles and grow to giant vesicles as a consequence of the oscillatory behavior of the B-Z reaction. The one-pot synthesis of an amphiphilic di-block copolymer and retention of oscillatory behavior for the B-Z reaction with the formation of giant vesicles bring a new insight into possible pathways for the synthesis of active functional microreactors in the range from hundreds of nanometers to tens of micrometers.Get into the swing of things: An oscillatory chemical reaction is used to synthesize self-assembling active giant polymeric vesicles in one pot. The hydrophobic block on polyethylene glycol (PEG) undergoes self-assembly to form vesicles. In the scheme, the green squiggly line represents the PEG, the red star is the chain transfer agent (CTA), the yellow diamonds are components of the B-Z reaction, and the purple spheres are monomer units.
      PubDate: 2017-07-24T03:36:58.027883-05:
      DOI: 10.1002/anie.201703816
       
  • Homogenous Alloys of Formamidinium Lead Triiodide and Cesium Tin Triiodide
           for Efficient Ideal-Bandgap Perovskite Solar Cells
    • Authors: Yingxia Zong; Ning Wang, Lin Zhang, Ming-Gang Ju, Xiao Cheng Zeng, Xiao Wei Sun, Yuanyuan Zhou, Nitin P. Padture
      Abstract: The alloying behavior between FAPbI3 and CsSnI3 perovskites is studied carefully for the first time, which has led to the realization of single-phase hybrid perovskites of (FAPbI3)1−x(CsSnI3)x (0
      PubDate: 2017-07-24T03:35:48.098522-05:
      DOI: 10.1002/anie.201705965
       
  • Practical Alkoxythiocarbonyl Auxiliaries for Iridium(I)-Catalyzed
           C−H Alkylation of Azacycles
    • Authors: Anh T. Tran; Jin-Quan Yu
      Abstract: The development of new and practical 3-pentoxythiocarbonyl auxiliaries for IrI-catalyzed C−H alkylation of azacycles is described. This method allows for the α-C−H alkylation of a variety of substituted pyrrolidines, piperidines, and tetrahydroisoquinolines through alkylation with alkenes. While the practicality of these simple carbamate-type auxiliaries is underscored by the ease of installation and removal, the method's utility is demonstrated in its ability to functionalize biologically relevant l-proline and l-trans-hydroxyproline, delivering unique 2,5-dialkylated amino acid analogues that are not accessible by other C−H functionalization methods.Fine-tuning: A carbamate-type 3-pentoxythiocarbonyl auxiliary has been developed for the α-C−H alkylation of a variety of substituted N-heterocycles through reaction with alkenes (see scheme). Application to biologically relevant l-proline and l-trans-hydroxyproline delivered unique 2,5-dialkylated amino acid analogues.
      PubDate: 2017-07-24T03:31:14.363507-05:
      DOI: 10.1002/anie.201704755
       
  • Fast Adsorption of Soft Hydrogel Microspheres on Solid Surfaces in Aqueous
           Solution
    • Authors: Shusuke Matsui; Takuma Kureha, Seina Hiroshige, Mikihiro Shibata, Takayuki Uchihashi, Daisuke Suzuki
      Abstract: The real-time adsorption behavior of polymeric colloidal microspheres onto solid surfaces in aqueous solution was visualized for the first time using high-speed atomic force microscopy (HS-AFM) in order to reveal how the softness of the microspheres affects their dynamic adsorption. Studies that focus on the deformability of microspheres upon dynamic adsorption have not yet been reported, most likely on account of a lack of techniques that appropriately depict the dynamic adsorption and deformation behavior of individual microspheres at the nanoscale in real time. In this study, we revealed that the deformability of microspheres plays a crucial role on the adsorption kinetics, i.e., soft hydrogel microspheres adsorb faster than harder elastomeric or rigid microspheres. The results of this study should provide insight towards development of new colloidal nanomaterials that exhibit effective adsorption on specific sites in aqueous solution.
      PubDate: 2017-07-23T21:26:52.300049-05:
      DOI: 10.1002/anie.201705808
       
  • Photon-induced near-field electron microscopy (PINEM) of eukaryotic cells
    • Authors: Mohammed Kaplan; Byung-Kuk Yoo, Jau Tang, Tony Karam, Bolin Liao, Devdoot Majumdar, david Baltimore, Grant Jensen, Ahmed Zewail
      Abstract: Photon-induced near-field electron microscopy (PINEM) is a technique to produce and then image evanescent electromagnetic fields on the surfaces of nanostructures. Most previous applications of PINEM have imaged surface plasmon-polariton waves on conducting nanomaterials. Here, the application of PINEM on whole human cancer cells and membrane vesicles isolated from them is reported. We show that photons induce time-, orientation-, and polarization-dependent evanescent fields on the surfaces of A431 cancer cells and isolated membrane vesicles. Furthermore, the addition of a ligand to the major surface receptor on these cells and vesicles (Epidermal Growth Factor Receptor, EGFR) reduces the intensity of these fields in both preparations. In the absence of plasmon waves in biological samples, we propose these evanescent fields reflect the changes of EGFR kinase domain polarization upon ligand binding.
      PubDate: 2017-07-23T21:25:38.099545-05:
      DOI: 10.1002/anie.201706120
       
  • Biomimetic Synthesis of Complex Flavonoids Isolated From Daemonorops
           "Dragon's Blood"
    • Authors: Dirk Trauner; Matthias Schmid
      Abstract: The dragonbloodins are a pair of complex flavonoid trimers isolated from the palm tree Daemonorops draco, one of the sources of the ancient resin known as "Dragon's Blood". We present a short synthesis that clarifies their relative configuration and sheds light on their origin in Nature. It features biomimetic cascade reactions that involve both ionic and radical intermediates. The biogenetic relationships between dracorhodin, the dracoflavans C, and the dragonbloodins A1 and A2 is discussed.
      PubDate: 2017-07-23T21:25:31.995946-05:
      DOI: 10.1002/anie.201705390
       
  • Oxygenation of Simple Olefins via Selective Allylic C-C Bond Cleavage: A
           Direct Approach to Cinnamyl Aldehydes
    • Authors: Ning Jiao; Jianzhong Liu, Xiaojin Wen, Chong Qin, Xiao Luo, Ao Sun, Bencong Zhu, Song Song, Xinyao Li
      Abstract: A novel metal-free allylic C-C σ-bond cleavage of simple olefins leading to valuable cinnamyl aldehydes is reported. 1,2-Aryl or alkyl migration through allylic C-C bond cleavage occurs in this transformation assisted by an alkyl azide reagent. This protocol enables the O-atom incorporation into simple unfunctionalized olefins to construct cinnamyl aldehydes. The chemistry features simple hydrocarbon substrates, metal-free conditions, and high regio- and stereo-selectivities.
      PubDate: 2017-07-22T08:15:29.932695-05:
      DOI: 10.1002/anie.201705671
       
  • Highly Selective and Efficient Ring Hydroxylation of Alkylbenzenes with
           H2O2 based on an Osmium(VI) Nitrido Catalyst
    • Authors: Tai-Chu Lau; Hoi Ki Kwong, Po Kam Lo, Shek Man Yiu, Hajime Hirao, Kai Chung Lau
      Abstract: The osmium(VI) nitrido complex, OsVI(N)(quin)2(OTs) (1, quin = 2-quinaldinate, OTs = tosylate), is a highly selective and efficient catalyst for the ring hydroxylation of alkylbenzenes with H2O2 under ambient conditions. Oxidation of various alkylbenzenes occurs with ring/chain oxidation ratios ranging from 96.7/3.3 to 99.9/0.1, and total product yields from 93% to 98%. Moreover, turnover numbers (TONs) up to 6360, 5670 and 3880 can be achieved for the oxidation of p-xylene, ethylbenzene and mesitylene respectively. DFT calculations suggest that the active intermediate is an OsVIII nitrido oxo species.
      PubDate: 2017-07-22T04:10:28.280265-05:
      DOI: 10.1002/anie.201705986
       
  • Total Syntheses of Cystobactamids and Structural Confirmation of
           Cystobactamid 919-2
    • Authors: Dirk Trauner; Bichu Cheng, Rolf Müller
      Abstract: The cystobactamids are a family of antibacterial natural products with unprecedented chemical scaffolds that are active against both Gram positive and negative pathogens. Herein, we describe the first total synthesis of cystobactamid 919-2 from three fragments. Our convergent synthesis both confirmed the correct structure and determined the absolute configuration of cystobactamid 919-2.
      PubDate: 2017-07-21T10:10:58.201801-05:
      DOI: 10.1002/anie.201705387
       
  • Stereoselective Synthesis of Piperidines via Iridium-Catalyzed
           Cyclocondensation
    • Authors: Erick Moran Carreira; Tobias Sandmeier, Simon Krautwald
      Abstract: Iridium-catalyzed cyclocondensation of amino alcohols and aldehydes is reported. Intramolecular allylic substitution by an enamine intermediate and subsequent in situ reduction furnishes 3,4-disubstituted piperidines with high enantiospecificity and good diastereoselectivity. The modular approach and the broad functional group tolerance give access to diverse piperidine derivatives, which are further functionalized to give a versatile set of products.
      PubDate: 2017-07-21T09:11:00.592862-05:
      DOI: 10.1002/anie.201706374
       
  • Enzymatic Synthesis of Homogenous Chondroitin Sulfate oligosaccharides
    • Authors: Jian Liu; Jine Li, Guowei Su
      Abstract: Chondroitin sulfate (CS) is a sulfated polysaccharide that plays essential physiological roles. Here, we report to utilize an enzyme-based method to synthesize a library of CS oligosaccharides consisting of 15 different CS oligosaccharides. The library covers 4-O-sulfated and 6-O-sulfated oligosaccharides with the size ranging from trisaccharide to nonasaccharide. We also demonstrate the synthesis of unnatural 6-O-sulfated CS pentasaccharides containing either a 6-O-sulfo 2-azido galactosamine or a 6-O-sulfo galactosamine residue. The availability of structurally defined CS oligosaccharides offers a novel approach to investigate the biological functions of CS.
      PubDate: 2017-07-21T09:10:34.975173-05:
      DOI: 10.1002/anie.201705638
       
  • Macroscopic Polarization Enhancement Promoting Photo- and
           Piezoelectric-Induced Charge Separation and Molecular Oxygen Activation
    • Authors: Hongwei Huang; Shuchen Tu, Chao Zeng, Tierui Zhang, A. H. Reshak, Yihe Zhang
      Abstract: We report that both efficient photo- and piezoelectric- induced molecular oxygen activation are achieved via macroscopic polarization enhancement on a noncentrosymmetric piezoelectric semiconductor BiOIO3. The replacement of V5+ ions for I5+ in IO3 polyhedra gives rise to strengthened macroscopic polarization of BiOIO3, which facilitates the charge separation in the photocatalytic and piezoelectric-catalytic process, and renders largely promoted photo- and piezoelectric induced reactive oxygen species (ROS) evolution, such as superoxide radicals (*O2−) and hydroxyl radicals (*OH). The present work advances piezoelectricity as a new route to efficient ROS generation, and also discloses macroscopic polarization engineering on improvement of multi-responsive catalysis.
      PubDate: 2017-07-21T06:10:33.903709-05:
      DOI: 10.1002/anie.201706549
       
  • Manganese(I)-catalyzed Enantioselective Hydrogenation of Ketones using a
           Defined Chiral PNP Pincer Ligand
    • Authors: Marcel Garbe; Kathrin Junge, Svenja Walker, Zhihong Wei, Haijun Jiao, Anke Spannenberg, Stephan Bachmann, Michelangelo Scalone, Matthias Beller
      Abstract: A new chiral manganese PNP pincer complex is described. Asymmetric hydrogenation of several prochiral ketones with molecular hydrogen in the presence of this complex proceeds under mild conditions (40 °C, 4 h, 30 bar H₂). Besides high catalytic activity for aromatic substrates, aliphatic ketones are hydrogenated with remarkable selectivities (er up to 92:8). DFT calculations support an outer sphere hydrogenation mechanism as well as the experimentally determined stereochemistry.
      PubDate: 2017-07-21T03:11:01.8154-05:00
      DOI: 10.1002/anie.201705471
       
  • Discovery and total synthesis of natural cystobactamid derivatives with
           superior activity against Gram-negative pathogens
    • Authors: Rolf Müller; Stephan Hüttel, Giambattista Testolin, Jennifer Herrmann, Therese Planke, Franziska Gille, Maria Moreno, Marc Stadler, Mark Brönstrup, Andreas Kirschning
      Abstract: Antibiotic discovery and development is challenging as chemical scaffolds of synthetic origin often lack the required pharmaceutical properties, and the discovery of novel ones from natural sources is tedious. Herein we report the discovery of new cystobactamids with a significantly improved antibacterial profile through detailed screening of myxobacterial producer strains. Some of these new derivatives display antibacterial activities in the sub µgmL-1 range against Gram-negative pathogens, including clinical isolates of Klebsiella oxytoca, Pseudomonas aeruginosa, and fluoroquinolone-resistant Enterobacteriaceae, which were not observed for previously reported cystobactamids. Our findings provide structure-activity relationships and show how pathogen resistance can be overcome by natural scaffold diversity. The most promising derivative 861-2 was prepared by total synthesis, enabling further chemical optimization of this privileged scaffold.
      PubDate: 2017-07-20T21:16:44.421809-05:
      DOI: 10.1002/anie.201705913
       
  • Novel Modulated Structure of Superconducting Hydrogen Sulfide
    • Authors: John S Tse; Yansun Yao, Arnab Majumdar
      Abstract: Compression of hydrogen sulfide using first principles metadynamics and molecular dynamics calculations revealed a modulated structure with high proton mobility which exhibits a diffraction pattern matching well with experiment. The structure consists of a sublattice of rectangular meandering SH- chains and molecular-like H3S+ stacked alternately in tetragonal and cubic slabs forming a long-period modulation. The novel structure offers a new perspective on the possible origin of the superconductivity at very high temperatures in which the conducting electrons in the SH chains are perturbed by the fluxional motions of the H3S resulting in strong electron-phonon coupling.
      PubDate: 2017-07-20T21:16:03.532483-05:
      DOI: 10.1002/anie.201704364
       
  • Electrophilic Amination with Nitroarenes
    • Authors: Marian Rauser; Christoph Ascheberg, Meike Niggemann
      Abstract: An exceptionally general electrophilic amination, which directly transforms commercially available nitroarenes with zinc organyls to alkylated aromatic aminoboranes was developed. The reaction starts with a two-step partial reduction of the nitro group to a nitrenoid, which is used in-situ as the electrophilic amination reagent. To facilitate isolation, the resulting air and moisture sensitive aminoboranes were reacted with a range of electrophiles. The protocol not only represents a direct transformation of nitro compounds into an electrophilic amination reagent but also provides an elegant alternative to dehydrocoupling methods for the generation of aminoboranes.
      PubDate: 2017-07-20T13:10:32.071582-05:
      DOI: 10.1002/anie.201705356
       
  • Mechanochemistry induced with a robust functionalized tip
    • Authors: Yajie Zhang; Yongfeng Wang, Jing-Tao Lü, Mads Brandbyge, Richard Berndt
      Abstract: Atomic-scale mechanochemistry is realized from force exerted by a C₆₀-functionalized scanning tunneling microscope (STM) tip. Two conformers of tin phthalocyanine (SnPc) can be prepared on coinage metal surfaces. A transition between these conformers is induced on Cu(111) and Ag(100). Density functional theory (DFT) calculations reveal details of this reaction. Because of the large energy barrier of the reaction and the strong interaction of SnPc with Cu(111), the process can not be achieved by electrical means.
      PubDate: 2017-07-20T11:10:44.725017-05:
      DOI: 10.1002/anie.201704940
       
  • Enzymatic and chemoenzymatic 3-step cascades for the synthesis of
           stereochemically complementary trisubstituted tetrahydroisoquinolines
    • Authors: Vanessa Erdmann; Benjamin R. Lichmann, Jianxiong Zhao, Robert C. Simon, Wolfgang Kroutil, John M. Ward, Helen C. Hailes, Dörte Rother
      Abstract: The work described demonstrates the ability of chemo-enzymatic and enzymatic cascades to form complex stereocomplementary 1,3,4-trisubstituted tetrahydroisoquinolines (THIQ) with three chiral centres in a step-efficient and selective manner, without requiring the purification of intermediates. The cascade starting from cheap substrates (3-hydroxybenzaldehyde and pyruvate) involves a carboligation step, a subsequent transamination and finally, together with a carbonyl co-substrate, a Pictet-Spengler-reaction. Appropriate selection of the carboligase and transaminase enzymes enabled the biocatalytic formation of (1R,2S)-metaraminol. Subsequent cyclisation catalysed either enzymatically by a norcoclaurine synthase or chemically by phosphate resulted in opposite stereoselectivities in the products at C-1, thus enabling access to both orientations of the THIQ 1-substituent.
      PubDate: 2017-07-20T11:10:30.374729-05:
      DOI: 10.1002/anie.201705855
       
  • Recognition and Extraction of Cesium Hydroxide and Carbonate using a
           Neutral Multitopic Ion-Pair Receptor
    • Authors: Qing He; Gretchen Marie Peters, Vincent M. Lynch, Jonathan L. Sessler
      Abstract: Current approaches to lowering the pH of basic media rely on the addition of a proton source. An alternative approach is described here that involves the liquid-liquid extraction-based removal of cesium salts, specifically CsOH and Cs2CO3, from highly basic media. A multitopic ion-pair receptor (2) is used that can recognize and extract the hydroxide and carbonate anions as their cesium salts, as confirmed by 1H NMR spectroscopic titrations, ICP-MS, single-crystal structural analyses and theoretical calculations. A sharp increase in the pH and cesium concentrations in the receiving phase is observed when receptor 2 is employed as a carrier in U-tube experiments involving the transport of CsOH through an intervening chloroform layer. The pH of the source phase likewise decreases.
      PubDate: 2017-07-20T08:11:44.004653-05:
      DOI: 10.1002/anie.201705788
       
  • Structural and Electronic Flexibility in Hydrides of Zintl Phases with
           Tetrel-Hydrogen and Tetrel-Tetrel Bonds
    • Authors: Henry Auer; Holger Kohlmann
      Abstract: The hydrogenation of Zintl phases enables the formation of new structural entities with main group element-hydrogen bonds in the solid state. The hydrogenation of SrSi, BaSi and BaGe yields the hydrides SrSiH5/3-x, BaSiH5/3-x and BaGeH5/3-x, whose crystal structures were solved by a combination of X-ray, neutron and electron diffraction. Layers of connected HSr4 (HBa4) tetrahedra containing hydride ions alternate with layers of infinite single- and double-chain polyanions, where hydrogen atoms are covalently bound to silicon and germanium. The idealized formulae AeTtH5/3 (Ae = alkaline earth, Tt = tetrel) can be rationalized with the Zintl-Klemm concept according to (Ae2+)3(TtH-)(Tt2H2-)(H-)3, where all Tt atoms are three-binding. The non-stoichiometry (SrSiH5/3-x, x = 0.174(12); BaGeH5/3-x, x = 0.10(3)) can be explained by additional π-bonding of the Tt chains. DFT calculations suggest BaGeH5/3 to be a narrow-bandgap semiconductor and SrSiH5/3 to exhibit poor metallic conductivity.
      PubDate: 2017-07-20T07:11:28.873469-05:
      DOI: 10.1002/anie.201706523
       
  • Stereospecific Decarboxylative Nazarov Cyclization Mediated by Carbon
           Dioxide for Preparation of Highly-Substituted 2-Cyclopentenones
    • Authors: Keiichi Komatsuki; Yuta Sadamitsu, Kohei Sekine, Kodai Saito, Tohru Yamada
      Abstract: Highly-substituted 2-cyclopentenones were stereospecifically and regioselectively constructed with a high catalytic efficiency through the Lewis-acid catalyzed decarboxylative Nazarov cyclization of the cyclic carbonate derivative, prepared by the reaction of the propargyl alcohol with carbon dioxide in the presence of a silver catalyst. The stereochemistry of the 2-cyclopentenone could be strictly controlled by the geometry of the alkene in the starting material. This method was applicable for various substrates.
      PubDate: 2017-07-20T07:11:11.428394-05:
      DOI: 10.1002/anie.201705909
       
  • Unified Total Synthesis of Polyoxin J, L, and Their Fluorinated Analogues
           Based on Decarbonylative Radical Coupling Reactions
    • Authors: Masayuki Inoue; Haruka Fujino, Masanori Nagatomo, Atmika Paudel, Suresh Panthee, Hiroshi Hamamoto, Kazuhisa Sekimizu
      Abstract: Polyoxins J (1a) and L (1b) are important members of nucleoside antibiotics. The complex and densely functionalized dipeptide structures of 1a and 1b possess thymine and uracil nucleobases, respectively. Here we report the unified total synthesis of 1a, 1b, and their artificial analogues 1c and 1d, with trifluorothymine and fluorouracil structures. Decarbonylative radical coupling reactions between a-alkoxyacyl tellurides and a chiral glyoxylic oxime ether led to chemo- and stereoselective construction of the ribonucleoside a-amino acid structures of 1a-d without damaging the preinstalled nucleobases. The high applicability of the radical-based methodology was further demonstrated by preparation of the trihydroxynorvaline moiety of 1a-d. The two amino acid fragments were connected and elaborated into 1a-d (longest linear sequence: 11 steps). The thus-assembled 1a and 1b exhibited potent activities against true fungi, while only 1d was active against Gram-positive bacteria.
      PubDate: 2017-07-20T05:12:23.207014-05:
      DOI: 10.1002/anie.201706671
       
  • Fractal Crystals: Hunting the Hidden Dimension in Nanoporous Materials
    • Authors: Lei Wang; Shengcai Zhu, Meikun Shen, Haiwen Tian, Songhai Xie, Hongbin Zhang, Yahong Zhang, Yi Tang
      Abstract: Screw dislocation structure in crystal are origin of symmetry breaking in a wide range of dense phase crystals. Preparation of such analogous structure in framework phase crystals is of great importance in zeolites but still a challenge. On the basis of crystal structure-solving and model building, we found that the two specific intergrowths in MTW zeolite produce this complex fractal and spiral structure. With the structure determined parameters (spiral pitch h, screw angle θ and spatial angle ψ) of Burgers circuit, the screw dislocation structure can be constructed by two different dimensional intergrowth sections. Thus the reported complexity of various dimensions in diverse crystals can be unified.
      PubDate: 2017-07-20T05:12:18.377554-05:
      DOI: 10.1002/anie.201704499
       
  • Asymmetric Synthesis of Chiral Cyclopentanes Bearing an All-Carbon
           Quaternary Stereocenter via Zr-catalyzed Doubled Carboalumination
    • Authors: Shiqing Xu; Chuan Wang, Masato Komiyama, Yasuhiko Tomonari, Ei-ichi Negishi
      Abstract: Herein we report a Zr-catalyzed enantio- and diastereoselective inter-intramolecular doubled carboalumination of unactivated 2-substituted-1,5-dienes which provides an efficient and direct access to chiral cyclopentanes with generation of two stereocenters including an all-carbon quaternary stereocenter generally in excellent diastereomeric ratios and high enantiomeric excesses. This tandem carboalumination process creates two new C-C bonds as well as a C-Al bond which can be in-situ oxidized with O2 or hydrolyzed. Furthermore, the obtained chiral cyclopentanes can be readily functionalized to provide various chiral compounds.
      PubDate: 2017-07-20T00:34:37.800208-05:
      DOI: 10.1002/anie.201706198
       
  • Enantioselective Construction of Trifluoromethoxylated Stereogenic Centers
           by Nickel-Catalyzed Asymmetric Suzuki-Miyaura Coupling of Secondary Benzyl
           Bromides
    • Authors: Weichen Huang; Xiaolong Wan, Qilong Shen
      Abstract: A method for the construction of trifluoromethoxy-containing stereogenic centers with high enantiometric excess via nickel-catalyzed Suzuki-Miyaura coupling of easily available -bromobenzyl trifluoromethylethers 1a-g with a variety of aryl pinacol boronates was described. The reaction conditions were mild and a variety of common functional groups such as fluoride, chloride, bromide, ester, enolizable ketone, nitro, cyano, amino and vinyl group were well tolerated. Furthermore, the reaction can be easily scaled up to gram quantities without erosion of the enantioselectivity.
      PubDate: 2017-07-20T00:13:38.100557-05:
      DOI: 10.1002/anie.201706868
       
  • Colossal Stability of Gas Phase Tri-anions: The Concept of
           Super-pnictogens
    • Authors: Tianshan Zhao; Jian Zhou, Qian Wang, Puru Jena
      Abstract: Multiply charged negative ions are ubiquitous in nature. In crystals, they are stable due to charge compensating cations while in solutions, solvent molecules protect them; but they are rarely stable in the gas phase due to strong electrostatic repulsion between the extra electrons. Understanding their stability without the influence of the environment, therefore, has been of great interest to scientists for decades. While much of the past work has focused on the di-anions, work on triply charged negative ions is sparse and the search for the smallest stable tri-anion against spontaneous electron emission or fragmentation continues. We show here that BeB₁₁(X)₁₂³- (X=CN, SCN, BO) tri-anions are all stable in the gas phase, with BeB₁₁(CN)₁₂³- exhibiting colossal stability against electron emission by 2.65 eV and against its neutral by 15.85 eV! The unusual stability of these tri-anions opens the door to a new class of super-pnictogens with potential applications in Al-ion batteries.
      PubDate: 2017-07-20T00:10:38.513808-05:
      DOI: 10.1002/anie.201706764
       
  • Crystalline π-Stack Containing Five Stereoisomers: Insights into
           Conformational Isomorphism, Chirality Inversion and Disorder
    • Authors: Agnieszka Nowak-Krol; Merle Röhr, David Schmidt, Frank Würthner
      Abstract: An unprecedented crystal packing arrangement of a tetramethoxy-bay-substituted perylene bisimide (PBI) consists of three crystallographically independent molecules, i.e. an achiral (AC) PBI of saddle-shaped geometry along with two pairs of propeller-like twisted (P) and (M)enantiomeric PBI frameworks. All these five conformations are observed within a single π-stack revealing an intriguing packing sequence with an inversion of chirality from P to M via AC. Nudged elastic band calculations for the isolated molecule show that AC is a local minimum of the P to M interconversion path. In addition, two minor conformations were observed in the crystal, one of which resembles a transition state molecule. Theoretical studies of dimeric and trimeric stacks reveal that the coexistence of all these structures in the crystal lattice is facilitated by the strong dispersion interactions between PBI cores and perfectly interdigitated dodecyl chains which stabilize energetically higher conformations.
      PubDate: 2017-07-19T09:10:50.327128-05:
      DOI: 10.1002/anie.201705445
       
  • Fluorinative Rearrangements of Substituted Phenylallenes Mediated by
           (Difluoroiodo)toluene: Synthesis of a-(Difluoromethyl)styrenes
    • Authors: Zhensheng Zhao; Léanne Racicot, Graham K. Murphy
      Abstract: Phenylallenes undergo a fluorinative rearrangement by the action of (difluoroiodo)toluene, in the presence of 20 mol% BF3*OEt2, to yield a-difluoromethyl styrenes. This unprecedented reaction was entirely chemoselective for the internal allene pi-bond, and showed remarkable regioselectivity during the fluorination event. Substituted phenylallenes, phenylallenes possessing both phenyl- and a-allenyl substituents, and diphenylallenes were investigated, and good functional group compatibility was observed throughout. The ease with which allenes can be prepared on large scale, and the operational simplicity of this reaction have allowed us to rapidly access fluorine-containing building blocks that have not been accessed by conventional deoxyfluorination strategies.
      PubDate: 2017-07-19T08:12:13.238753-05:
      DOI: 10.1002/anie.201706798
       
  • Efficient Access to All-Carbon Quaternary and Tertiary α-Functionalized
           Homoallyl Aldehydes from Ketones
    • Authors: VITTORIO PACE; Laura Castoldi, Eugenia Mazzeo, Marta Rui, Thierry Langer, Wolfgang Holzer
      Abstract: Widely substituted all-carbon quaternary and tertiary α-homoallyl aldehydes are rapidly assembled through a unique synthetic operation from ketones consisting in: 1) C1-homologation; 2) epoxide-aldehyde Lewis acid mediated isomerization and, 3) electrophilic trapping. The synthetic equivalence between a vinyl oxirane and a β,γ-unsaturated aldehyde is the key concept for introducing such a previously undisclosed tactic. Mechanistic studies and labeled experiments suggest the intervention of an aldehyde enolate as the crucial intermediate. Significantly, the homologating carbenoid formation event (carbenoid precursor and organolithium) plays a critical role in determining the chemoselectivity.
      PubDate: 2017-07-19T07:11:58.706663-05:
      DOI: 10.1002/anie.201706236
       
  • RadH a Versatile Halogenase for Integration into Synthetic Pathways.
    • Authors: Binuraj Menon; Eileen Brandenburger, Humera Sharif, Ulrike Klemstein, Sarah Shepherd, Michael Greaney, Jason Micklefield
      Abstract: Flavin-dependent halogenases are useful enzymes providing halogenated molecules with improved biological activity or intermediates for synthetic derivatization. Here we demonstrate how the fungal halogenase RadH can be used to regioselectively halogenate a range of bioactive aromatic scaffolds. Site-directed mutagenesis of RadH was used to identify catalytic residues and provide insights into the mechanism of fungal halogenases. A high throughput fluorescence screen was also developed enabling a RadH mutant to be evolved with improved properties. Finally we demonstrate how biosynthetic genes from fungi, bacteria and plants can be combined, to encode a new pathway generating a novel chlorinated coumarin 'non-natural' product in E. coli.
      PubDate: 2017-07-19T05:11:10.164429-05:
      DOI: 10.1002/anie.201706342
       
  • Control of Redox Events by Dye Encapsulation Applied to Light-driven
           Splitting of Hydrogen Sulfide
    • Authors: Xu Jing; Yang Yang, Cheng He, Zhiduo Chang, Joost N. H. Reek, Chunying Duan
      Abstract: Inspired by the pocket feature of enzymes, a synthetic platform to combine photocatalytic hydrogen evolution with sulfide oxidation in a one-pot process via control over the location of electron transfer steps is reported in this paper. The redox-active coordination vessel Ni-TFT, which exhibits an octahedral pocket, encapsulates an organic dye to pre-organize for photocatalytic proton reduction via an oxidative quenching pathway using the nickel corners as catalysts, generating molecular hydrogen and the oxidized dye. The oxidized dye is displaced by a neutral dye and oxidizes sulfide once outside the pocket to give element sulfur. The overall reaction constitutes hydrogen sulfide splitting, forming molecular hydrogen and elemental sulfur, which is analogous to the water-splitting reaction. The high efficiency, simple separation of hydrogen gas and sulfur solid from the reaction mixture, represent major advantages for potential applications.
      PubDate: 2017-07-19T04:16:45.313225-05:
      DOI: 10.1002/anie.201704327
       
  • Enantioselective Synthesis of Acyclic α-Quaternary Carboxylic Acid
           Derivatives via Iridium-Catalyzed Allylic Alkylation
    • Authors: Samantha Shockley; John Caleb Hethcox, Brian Stoltz
      Abstract: : The first highly enantioselective iridium-catalyzed allylic alkylation providing access to products bearing an allylic all-carbon quaternary stereogenic center has been developed. The reaction utilizes a masked acyl cyanide (MAC) reagent, which enables the one-pot preparation of α-quaternary carboxylic acids, esters, and amides with a high degree of enantioselectivity. The utility of these products is further explored via a series of diverse product transformations.
      PubDate: 2017-07-19T04:16:42.31666-05:0
      DOI: 10.1002/anie.201707015
       
  • Understanding the Role of Additive Leads to an Improved Synthetic Protocol
           Obviating Additive: Organocatalytic Synthesis of Chiral Diarylmethyl
           Alkynes
    • Authors: Min Chen; Jianwei Sun
      Abstract: The use of additives for organic synthesis has become a common tactic to improve organic reaction outcomes. In this report, using an organocatalytic process for the synthesis of chiral diarylmethyl alkynes as a platform, we describe how an additive is involved in the improvement of the process. The evolution of an excellent synthetic protocol has been achieved via three stages, from (1) initially no catalyst turnover to (2) good conversion and enantioselectivity with a superior additive, and eventually (3) even better efficiency and selectivity without using additive. It is an important and rare demonstration that understanding the role of additive can be so beneficial as to obviate using the additive.
      PubDate: 2017-07-19T04:16:36.653107-05:
      DOI: 10.1002/anie.201706579
       
  • Anti-Markovnikov Hydrofunctionalization of Alkenes - Use of a Benzyl Group
           as a Traceless Redox-active Hydrogen Donor
    • Authors: Geoffroy Hervé Lonca; Derek Yiren Ong, Thi Mai Huong Tran, Ciputra Tejo, Shunsuke Chiba, Fabien Gagosz
      Abstract: A protocol for the anti-Markovnikov hydrofunctionalization of alkenes, that utilizes a benzyl group as a traceless redox-active hydrogen donor, has been developed. Under copper catalysis and in the presence of CF3- or N3-containing hypervalent iodine reagents, a series of homoallylic alcohol derivatives could be regioselectivity hydrofunctionalized. A similar principle was also applied to the hydrofunctionalization of alkenols.
      PubDate: 2017-07-19T04:16:23.709968-05:
      DOI: 10.1002/anie.201705368
       
  • Metal-Free Nitrile Diboration through Activation by an Electron-Rich
           Diborane
    • Authors: Markus Frick; Elisabeth Kaifer, Hans-Jörg Himmel
      Abstract: Diboration of unsaturated organic compounds is an extremely useful reaction in synthetic chemistry. Herein we report the first diboration of a nitrile by an electron-rich diborane, mediated by an electrophilic borane. The reaction is metal-free, and all reagents are readily available.
      PubDate: 2017-07-19T03:05:38.951006-05:
      DOI: 10.1002/anie.201706001
       
  • Stereospecific 1,3-Aminobromination of Donor-Acceptor Cyclopropanes
    • Authors: Saikat Das; Constantin Gabriel Daniliuc, Armido Studer
      Abstract: Sn(OTf)2-catalyzed 1,3-aminobromination of donor-acceptor cyclopropanes with various sulfonyl amides or electron poor anilines and N-bromosuccinimide is reported. Reactions which are experimentally easy to conduct, occur with complete regio- and stereospecificity (for anilines) resulting in γ-aminated α-brominated malonic diesters which are obtained in good to excellent yields (up to 98%). These compounds are valuable substrates for follow-up chemistry to provide substituted azetidines and γ-lactams in high yields.
      PubDate: 2017-07-19T02:30:32.718751-05:
      DOI: 10.1002/anie.201704092
       
  • Mineralized State of the Avian Influenza Virus in the Environment
    • Authors: Hangyu Zhou; Guangchuan Wang, Xiaoyu Wang, Zhiyong Song, Ruikang Tang
      Abstract: Although the circulation of avian influenza in humans is limited, they can be transmitted from Aves to humans, representing a great challenge. Herein, we suggest that influenza viruses from Aves might exist in a mineralized state due to the high calcium concentrations in the avian intestine. Using two typical influenza viruses as examples, we demonstrate these viruses can self-mineralize in simulated avian intestinal fluid, resulting in egg-like virus-mineral structured composites. The mineralized viruses are more robust, with enhanced infectivity and thermostability. More importantly, the mineral exterior of mineralized viruses can alter their cell internalization, expanding the possible tropisms. The discovery of a mineralized state of influenza highlights the integration of nanomaterials and viruses in the environment, which provides a new understanding of avian influenza infection and its control.
      PubDate: 2017-07-18T23:30:34.27042-05:0
      DOI: 10.1002/anie.201705769
       
  • Cover Picture: Tetranitromethane: A Nightmare of Molecular Flexibility in
           the Gaseous and Solid States (Angew. Chem. Int. Ed. 32/2017)
    • Authors: Yury V. Vishnevskiy; Denis S. Tikhonov, Jan Schwabedissen, Hans-Georg Stammler, Richard Moll, Burkhard Krumm, Thomas M. Klapötke, Norbert W. Mitzel
      Pages: 9243 - 9243
      Abstract: After 70 years of numerous attempts to determine the structure of the high-energy molecule tetranitromethane, it has become possible to describe the electron and X-ray scattering data of the gas and two solid phases, respectively. In their Communication on page 9619 ff., N. W. Mitzel et al. report a structural analysis of this nightmare of molecular flexibility. The cover picture shows Johann Heinrich Füssli′s “The Nightmare” from 1790, a model of the solid high-temperature phase, and an ignition experiment.
      PubDate: 2017-07-06T07:14:00.782585-05:
      DOI: 10.1002/anie.201706569
       
  • Inside Cover: Tricyanomethane and Its Ketenimine Tautomer: Generation from
           Different Precursors and Analysis in Solution, Argon Matrix, and as a
           Single Crystal (Angew. Chem. Int. Ed. 32/2017)
    • Authors: Klaus Banert; Madhu Chityala, Manfred Hagedorn, Helmut Beckers, Tony Stüker, Sebastian Riedel, Tobias Rüffer, Heinrich Lang
      Pages: 9244 - 9244
      Abstract: Tricyanomethane and its ketenimine tautomer were not simultaneously observed in the studies described by K. Banert, H. Beckers, and co-workers in their Communication on page 9582 ff. Whereas the latter species was detected after irradiation of an appropriate vinyl azide in argon matrix, photolysis or thermolysis of the same precursor in solution led to cyanoform with a pyramidal structure, which can also be generated from tricyanomethanide. Single crystals of pure tricyanomethane were found to be surprisingly stable.
      PubDate: 2017-07-04T06:37:10.126779-05:
      DOI: 10.1002/anie.201706518
       
  • Graphical Abstract: Angew. Chem. Int. Ed. 32/2017
    • Pages: 9247 - 9266
      PubDate: 2017-07-27T03:50:34.197137-05:
      DOI: 10.1002/anie.201783211
       
  • Corrigendum: A Highly Active Manganese Catalyst for Enantioselective
           Ketone and Ester Hydrogenation
    • Authors: Magnus B. Widegren; Gavin J. Harkness, Alexandra M. Z. Slawin, David B. Cordes, Matthew L. Clarke
      Pages: 9265 - 9265
      PubDate: 2017-07-27T03:50:46.441588-05:
      DOI: 10.1002/anie.201706466
       
  • Corrigendum: The Interstitial Carbon of the Nitrogenase FeMo Cofactor is
           Far Better Stabilized than Previously Assumed
    • Authors: Jörg Grunenberg
      Pages: 9265 - 9265
      PubDate: 2017-07-27T03:50:37.881308-05:
      DOI: 10.1002/anie.201706050
       
  • Corrigendum: Pyridylidene-Mediated Dihydrogen Activation Coupled with
           Catalytic Imine Reduction
    • Authors: Johanna Auth; Jaroslav Padevet, Pablo Mauleón, Andreas Pfaltz
      Pages: 9266 - 9266
      PubDate: 2017-07-27T03:50:47.130455-05:
      DOI: 10.1002/anie.201706608
       
  • Corrigendum: Localized Chemical Remodeling for Live Cell Imaging of
           Protein-Specific Glycoform
    • Authors: Jingjing Hui; Lei Bao, Siqiao Li, Yi Zhang, Yimei Feng, Lin Ding, Huangxian Ju
      Pages: 9266 - 9266
      PubDate: 2017-07-27T03:50:37.183107-05:
      DOI: 10.1002/anie.201706520
       
  • Spotlights on our sister journals: Angew. Chem. Int. Ed. 32/2017
    • Pages: 9268 - 9271
      PubDate: 2017-07-27T03:50:38.65771-05:0
      DOI: 10.1002/anie.201783213
       
  • Erwin Reisner
    • Pages: 9272 - 9272
      Abstract: “My favorite place on earth is Europe (including the UK). I can never resist a good board game ...” This and more about Erwin Reisner can be found on page 9272.
      PubDate: 2017-03-27T06:53:59.141308-05:
      DOI: 10.1002/anie.201702474
       
  • Officer of the Order of the British Empire: P. L. Arnold / Robert T.
           Koch Gold Medal: C. T. Walsh / Inhoffen Medal: H. Wennemers / OMCOS
           Award: Rubén Martín
    • Pages: 9273 - 9273
      PubDate: 2017-07-13T08:00:23.284418-05:
      DOI: 10.1002/anie.201706735
       
  • Stopping Aerobic Oxidation in Its Tracks: Chemoselective Synthesis of
           Benzaldehydes from Methylarenes
    • Authors: Jean-Philip Lumb
      Pages: 9276 - 9277
      Abstract: A practical and elegant solution to the long-standing challenge of methylarene partial oxidation has recently been provided by Pappo and co-workers who devised a catalytic aerobic route to benzaldehydes. The solution hinges on the unique hydrogen-bonding capacity of hexafluoroisopropanol, which prevents overoxidation of the aldehyde to the carboxylic acid.
      PubDate: 2017-06-12T14:15:20.594121-05:
      DOI: 10.1002/anie.201704160
       
  • Direct Asymmetric Alkylation of Ketones: Still Unconquered
    • Authors: Rafael Cano; Armen Zakarian, Gerard P. McGlacken
      Pages: 9278 - 9290
      Abstract: The alkylation of ketones is taught at basic undergraduate level. In many cases this transformation leads to the formation of a new stereogenic center. However, the apparent simplicity of the transformation is belied by a number of problems. So much so, that a general method for the direct asymmetric alkylation of ketones remains an unmet target. Despite the advancement of organocatalysis and transition-metal catalysis, neither field has provided an adequate solution. Indeed, even use of an efficient and general stoichiometric chiral reagent has yet to be reported. Herein we describe the state-of-the-art in terms of direct alkylation reactions of some carbonyl groups. We outline the limited progress that has been made with ketones, and potential routes towards ultimately achieving a widely applicable methodology for the asymmetric alkylation of ketones.Still some way to go: Despite various advancements a general method for the direct asymmetric alkylation of ketones remains an unmet target. This Minireview summarizes the state-of-the-art in terms of direct alkylation reactions of some carbonyl groups with a focus on potential routes towards ultimately achieving a widely applicable methodology for the asymmetric alkylation of ketones.
      PubDate: 2017-06-27T07:48:20.796513-05:
      DOI: 10.1002/anie.201703079
       
  • Mixed-Matrix Membranes
    • Authors: Janina Dechnik; Jorge Gascon, Christian J. Doonan, Christoph Janiak, Christopher J. Sumby
      Pages: 9292 - 9310
      Abstract: Research into extended porous materials such as metal-organic frameworks (MOFs) and porous organic frameworks (POFs), as well as the analogous metal-organic polyhedra (MOPs) and porous organic cages (POCs), has blossomed over the last decade. Given their chemical and structural variability and notable porosity, MOFs have been proposed as adsorbents for industrial gas separations and also as promising filler components for high-performance mixed-matrix membranes (MMMs). Research in this area has focused on enhancing the chemical compatibility of the MOF and polymer phases by judiciously functionalizing the organic linkers of the MOF, modifying the MOF surface chemistry, and, more recently, exploring how particle size, morphology, and distribution enhance separation performance. Other filler materials, including POFs, MOPs, and POCs, are also being explored as additives for MMMs and have shown remarkable anti-aging performance and excellent chemical compatibility with commercially available polymers. This Review briefly outlines the state-of-the-art in MOF-MMM fabrication, and the more recent use of POFs and molecular additives.Challenging separations: The need for greater energy efficiency and the maximum use of limited resources has focused attention on improved separation technologies. For gas separations, mixed-matrix membranes can provide enhanced separation performance and lead to more energy-efficient, sustainable, and cost-effective commercial applications.
      PubDate: 2017-07-07T03:11:50.706089-05:
      DOI: 10.1002/anie.201701109
       
  • Single-Site Active Cobalt-Based Photocatalyst with a Long Carrier Lifetime
           for Spontaneous Overall Water Splitting
    • Authors: Wei Liu; Linlin Cao, Weiren Cheng, Yuanjie Cao, Xiaokang Liu, Wei Zhang, Xiaoli Mou, Lili Jin, Xusheng Zheng, Wei Che, Qinghua Liu, Tao Yao, Shiqiang Wei
      Pages: 9312 - 9317
      Abstract: An active and stable photocatalyst to directly split water is desirable for solar-energy conversion. However, it is difficult to accomplish overall water splitting without sacrificial electron donors. Herein, we demonstrate a strategy via constructing a single site to simultaneously promote charge separation and catalytic activity for robust overall water splitting. A single Co1-P4 site confined on g-C3N4 nanosheets was prepared by a facile phosphidation method, and identified by electron microscopy and X-ray absorption spectroscopy. This coordinatively unsaturated Co site can effectively suppress charge recombination and prolong carrier lifetime by about 20 times relative to pristine g-C3N4, and boost water molecular adsorption and activation for oxygen evolution. This single-site photocatalyst exhibits steady and high water splitting activity with H2 evolution rate up to 410.3 μmol h−1 g−1, and quantum efficiency as high as 2.2 % at 500 nm.A good CoP: Highly active and stable Co1-P4 single-sites confined on polymeric g-C3N4 are prepared. The resulting single-site photocatalyst performs spontaneous overall water splitting with high H2 evolution rates under solar irradiation without the need for a sacrificial donor.
      PubDate: 2017-06-13T08:55:24.930676-05:
      DOI: 10.1002/anie.201704358
       
  • Topological Transformation of π-Conjugated Molecules Reduces
           Resistance to Crystallization
    • Authors: Cheng Zhou; Qiuhong Cui, Caitlin McDowell, Martin Seifrid, Xiankai Chen, Jean-Luc Brédas, Ming Wang, Fei Huang, Guillermo C. Bazan
      Pages: 9318 - 9321
      Abstract: Two electronically delocalized molecules were designed as models to understand how molecular shape impacts the tradeoff between solubility and crystallization tendencies in molecular semiconductors. The more soluble compound TT contains a non-planar bithiophene central fragment, whereas CT has a planar cyclopentadithiophene unit. Calorimetry studies show that CT can crystallize more easily than TT. However, absorption spectroscopy shows that the initially amorphous TT film can eventually form crystals in which the molecular shape is significantly more planar. Two thermally reversible polymorphs for TT were observed by XRD and grazing-incidence wide-angle X-ray scattering (GIWAXS) measurements. These findings are relevant within the context of designing soft semiconductors that exhibit high solubility and a tendency to provide stable organized structures with desirable electronic properties.Molecular topological transformation: A molecule was designed that adopts a twisted, and therefore more soluble, conformation in solution. The molecule rearranges into a planar shape in the solid state and is able to form highly crystalline films. These transformations are fully reversible and encourage their applications as a new design element for producing organic semiconductors that are highly ordered and simple to process.
      PubDate: 2017-07-04T07:40:29.624422-05:
      DOI: 10.1002/anie.201702646
       
  • Segmental, Domain-Selective Perdeuteration and Small-Angle Neutron
           Scattering for Structural Analysis of Multi-Domain Proteins
    • Authors: Miriam Sonntag; Pravin Kumar Ankush Jagtap, Bernd Simon, Marie-Sousai Appavou, Arie Geerlof, Ralf Stehle, Frank Gabel, Janosch Hennig, Michael Sattler
      Pages: 9322 - 9325
      Abstract: Multi-domain proteins play critical roles in fine-tuning essential processes in cellular signaling and gene regulation. Typically, multiple globular domains that are connected by flexible linkers undergo dynamic rearrangements upon binding to protein, DNA or RNA ligands. RNA binding proteins (RBPs) represent an important class of multi-domain proteins, which regulate gene expression by recognizing linear or structured RNA sequence motifs. Here, we employ segmental perdeuteration of the three RNA recognition motif (RRM) domains in the RBP TIA-1 using Sortase A mediated protein ligation. We show that domain-selective perdeuteration combined with contrast-matched small-angle neutron scattering (SANS), SAXS and computational modeling provides valuable information to precisely define relative domain arrangements. The approach is generally applicable to study conformational arrangements of individual domains in multi-domain proteins and changes induced by ligand binding.Segmentally perdeuterated multi-domain proteins are obtained by Sortase A mediated ligation. Using contrast-matched small-angle neutron scattering (SANS) experiments on different samples with selectively perdeuterated domains of the same multi-domain protein gives insight into domain arrangements and changes induced by ligand binding, thus providing unique information for structural analysis.
      PubDate: 2017-07-05T12:26:02.135085-05:
      DOI: 10.1002/anie.201702904
       
  • Optically Triggered Melting of DNA on Individual Semiconducting Carbon
           Nanotubes
    • Authors: Chunyan Wang; Brendan Meany, YuHuang Wang
      Pages: 9326 - 9330
      Abstract: Optical excitation of nanostructures is known to induce local heating, a phenomenon that has been intensely exploited for drug release, gene delivery, cancer thermotherapy, and energy harvesting. However, the effect is typically small requiring collective heating of a large concentration or aggregates of particles. Herein, we show that optical excitation of individual semiconducting single-walled carbon nanotubes triggers strongly localized heating adequate to melt non-covalently attached double-stranded oligonucleotides in solution. In contrast to conventional thermal dehybridization, this optically triggered DNA melting occurs at a solution temperature that is 22 °C lower than the DNA melting temperature. This unexpectedly large localized optical heating effect provides important new insights to design selective optical nanoheaters at the single particle level.Stop the world and melt with ν: A laser beam with frequency tuned to resonate with a single semiconducting carbon nanotube heats the nanotube–DNA complex locally, leading to the melting of the DNA complex and release of the short DNA strand in aqueous solution.
      PubDate: 2017-07-07T06:15:51.432334-05:
      DOI: 10.1002/anie.201703332
       
  • Environmentally Benign, Rapid, and Selective Extraction of Gold from Ores
           and Waste Electronic Materials
    • Authors: Chunlin Yue; Huaming Sun, Wen-Jing Liu, Binbin Guan, Xudong Deng, Xu Zhang, Peng Yang
      Pages: 9331 - 9335
      Abstract: The extraction of gold from ores and electronic waste is an important topic worldwide, as this precious metal has immense value in a variety of fields. However, serious environmental pollution and high energy consumption due to the use of toxic oxidation reagents and harsh reaction conditions is a well-known problem in the gold industry. Herein, we report a new chemical method based on the combined use of N-bromosuccinimide (NBS) and pyridine (Py), which has a greatly decreased environmental impact and reagent cost, as well as mild reaction requirements. This method can directly leach Au0 from gold ore and electronic waste to form AuIII in water. The process is achieved in a yield of approximately 90 % at room temperature and a nearly neutral pH. The minimum dose of NBS/Py is as low as 10 mm, which exhibits low toxicity towards mammalian cells and animals as well as aquatic creatures. The high leaching selectivity of Au over other metals during gold leaching is demonstrated, showing that this method has great potential for practical industrial application towards the sustainable refining of gold from ores and electronic waste.Mild gold leaching: A chemical method based on the use of an aqueous solution of N-bromosuccinimide (NBS) and pyridine (Py) is applied to selectively leach Au0 from gold ore and electronic waste to form Au3+ in aqueous solution. A yield of approximately 90 % at room temperature and a nearly neutral pH is achieved.
      PubDate: 2017-06-30T06:06:44.547591-05:
      DOI: 10.1002/anie.201703412
       
  • Visible-Light-Irradiated Graphitic Carbon Nitride Photocatalyzed
           Diels–Alder Reactions with Dioxygen as Sustainable Mediator for
           Photoinduced Electrons
    • Authors: Yubao Zhao; Markus Antonietti
      Pages: 9336 - 9340
      Abstract: Photocatalytic Diels–Alder (D–A) reactions with electron rich olefins are realized by graphitic carbon nitride (g-C3N4) under visible-light irradiation and aerobic conditions. This heterogeneous photoredox reaction system is highly efficient, and the apparent quantum yield reaches a remarkable value of 47 % for the model reaction. Dioxygen plays a critical role as electron mediator, which is distinct from the previous reports in the homogeneous RuII complex photoredox system. Moreover, the reaction intermediate vinylcyclobutane is captured and monitored during the reaction, serving as a direct evidence for the proposed reaction mechanism. The cycloaddition process is thereby determined to be the combination of direct [4+2] cycloaddition and [2+2] cycloaddition followed by photocatalytic rearrangement of the vinylcyclobutane intermediate.Photocatalytic Diels–Alder reactions with electron-rich olefins are realized by graphitic carbon nitride (g-C3N4) under visible-light irradiation, with an apparent quantum yield of 47 % for the model reaction. O2 plays a critical role as the electron mediator. The cycloaddition process is the combination of direct [4+2] cycloaddition and [2+2] cycloaddition followed by photocatalytic rearrangement of the vinylcyclobutane intermediate.
      PubDate: 2017-07-06T07:08:32.324599-05:
      DOI: 10.1002/anie.201703438
       
  • Quantum Mechanics/Molecular Mechanics Study on the Photoreactions of Dark-
           and Light-Adapted States of a Blue-Light YtvA LOV Photoreceptor
    • Authors: Xue-Ping Chang; Yuan-Jun Gao, Wei-Hai Fang, Ganglong Cui, Walter Thiel
      Pages: 9341 - 9345
      Abstract: The dark- and light-adapted states of YtvA LOV domains exhibit distinct excited-state behavior. We have employed high-level QM(MS-CASPT2)/MM calculations to study the photochemical reactions of the dark- and light-adapted states. The photoreaction from the dark-adapted state starts with an S1T1 intersystem crossing followed by a triplet-state hydrogen transfer from the thiol to the flavin moiety that produces a diradical intermediate, and a subsequent internal conversion that triggers a barrierless C−S bond formation in the S0 state. The energy profiles for these transformations are different for the four conformers of the dark-adapted state considered. The photochemistry of the light-adapted state does not involve the triplet state: photoexcitation to the S1 state triggers C−S bond cleavage followed by recombination in the S0 state; both these processes are essentially barrierless and thus ultrafast. The present work offers new mechanistic insights into the photoresponse of flavin-containing blue-light photoreceptors.Electronic structure calculations (QM(MS-CASPT2)/MM) on YtvA LOV domains reveal the detailed mechanism of the excited-state relaxation processes for the dark- (via T1 hydrogen transfer and S0 C−S bond formation) and light-adapted states (S1 C−S bond fission and S0 recombination). The photochemistry of the dark-adapted state is found to be conformer-dependent (IC=internal conversion, ISC=intersystem crossing, FMN=flavin mononucleotide).
      PubDate: 2017-07-10T10:52:36.608382-05:
      DOI: 10.1002/anie.201703487
       
  • Modular Assembly of Reversible Multivalent Cancer-Cell-Targeting Drug
           Conjugates
    • Authors: Fábio M. F. Santos; Ana I. Matos, Ana E. Ventura, João Gonçalves, Luís F. Veiros, Helena F. Florindo, Pedro M. P. Gois
      Pages: 9346 - 9350
      Abstract: Herein is described a new modular platform for the construction of cancer-cell-targeting drug conjugates. Tripodal boronate complexes featuring reversible covalent bonds were designed to accommodate a cytotoxic drug (bortezomib), poly(ethylene glycol) (Peg) chains, and folate targeting units. The B-complex core was assembled in one step, proved stable under biocompatible conditions, namely, in human plasma (half-life up to 60 h), and underwent disassembly in the presence of glutathione (GSH). Stimulus-responsive intracellular cargo delivery was confirmed by confocal fluorescence microscopy, and a mechanism for GSH-induced B-complex hydrolysis was proposed on the basis of mass spectrometry and DFT calculations. This platform enabled the modular construction of multivalent conjugates with high selectivity for folate-positive MDA-MB-231 cancer cells and IC50 values in the nanomolar range.Getting together for group therapy: Tripodal boronate complexes accommodating the cytotoxic drug bortezomib (Btz), poly(ethylene glycol) (PEG) chains, and folate targeting units showed high selectivity for folate-positive MDA-MB-231 cancer cells and stimulus-responsive intracellular cargo delivery (see picture). The core structure was assembled in one step and was stable in human plasma but underwent disassembly in the presence of glutathione (GSH).
      PubDate: 2017-07-10T10:40:45.427216-05:
      DOI: 10.1002/anie.201703492
       
  • Probing the Role of a Non-Thermal Plasma (NTP) in the Hybrid NTP Catalytic
           Oxidation of Methane
    • Authors: Emma K Gibson; Cristina E Stere, Bronagh Curran-McAteer, Wilm Jones, Giannantonio Cibin, Diego Gianolio, Alexandre Goguet, Peter P. Wells, C. Richard A. Catlow, Paul Collier, Peter Hinde, Christopher Hardacre
      Pages: 9351 - 9355
      Abstract: Three recurring hypotheses are often used to explain the effect of non-thermal plasmas (NTPs) on NTP catalytic hybrid reactions; namely, modification or heating of the catalyst or creation of new reaction pathways by plasma-produced species. NTP-assisted methane (CH4) oxidation over Pd/Al2O3 was investigated by direct monitoring of the X-ray absorption fine structure of the catalyst, coupled with end-of-pipe mass spectrometry. This in situ study revealed that the catalyst did not undergo any significant structural changes under NTP conditions. However, the NTP did lead to an increase in the temperature of the Pd nanoparticles; although this temperature rise was insufficient to activate the thermal CH4 oxidation reaction. The contribution of a lower activation barrier alternative reaction pathway involving the formation of CH3(g) from electron impact reactions is proposed.Methane combustion was undertaken using a hybrid non-thermal plasma palladium-based catalyst system without heating of the catalyst bed. No significant structural changes were found in the catalyst by in situ X-ray absorption spectroscopy. Plasma heating of the palladium nanoparticles did not introduce sufficient energy to activate methane oxidation, thus an alternative reaction pathway is proposed.
      PubDate: 2017-07-06T05:35:54.75848-05:0
      DOI: 10.1002/anie.201703550
       
  • Tuning the Inter-nanofibril Interaction To Regulate the Morphology and
           Function of Peptide/DNA Co-assembled Viral Mimics
    • Authors: Rong Ni; Ying Chau
      Pages: 9356 - 9360
      Abstract: The ability to tune the inter-subunit interaction within the virus capsid may be critical to assembly and biological function. This process was extended here with peptide/DNA co-assembled viral mimics. The resulting co-assemblies, formed and stabilized by both peptide nanofibril–DNA and peptide nanofibril–nanofibril interactions, were tuned through hydrophobic packing interactions of the peptide sequences. By strengthening peptide side-chain complementarity and/or elongating the peptide chain (from 4 to 8 residues), we report strengthening the inter-nanofibril interaction to create stable nanococoons that give high gene-transfection efficacy.We go together: DNA/peptide co-assembly to give viral capsid mimics can be optimized through tuning the hydrophobic packing of the peptide side chains (blue). By strengthening the peptide side-chain complementarity and/or elongating the peptide chain (from 4 to 8 residues), the inter-nanofibril interactions were strengthened to create stable nanococoons that give high gene-transfection efficacy.
      PubDate: 2017-07-10T10:40:54.96363-05:0
      DOI: 10.1002/anie.201703596
       
  • Nanoscale Chemical Imaging of Interfacial Monolayers by Tip-Enhanced Raman
           Spectroscopy
    • Authors: Feng Shao; Vivian Müller, Yao Zhang, A. Dieter Schlüter, Renato Zenobi
      Pages: 9361 - 9366
      Abstract: We report an investigation of interfacial fluorinated hydrocarbon (carboxylic-fantrip) monolayers by nanoscale imaging using tip-enhanced Raman spectroscopy (TERS) and density functional theory (DFT) calculations. By comparing TERS images of a sub-monolayer prepared by spin-coating and a π–π-stacked monolayer on Au(111) in which the molecular orientation is confined, specific Raman peaks shift and line widths narrow in the transferred LB monolayer. Based on DFT calculations that take into account dispersion corrections and surface selection rules, these specific effects are proposed to originate from π–π stacking and molecular orientation restriction. TERS shows the possibility to distinguish between a random and locked orientation with a spatial resolution of less than 10 nm. This work combines experimental TERS imaging with theoretical DFT calculations and opens up the possibility of studying molecular orientations and intermolecular interaction at the nanoscale and molecular level.A small tip for studying monolayers: An experimental and theoretical investigation of interfacial monolayers at the molecular level by using DFT calculations and nanoscale TERS imaging is presented. Based on DFT calculations that take into account dispersion corrections and surface selection rules, differences of TERS spectra in the LB monolayer are proposed to originate from π–π stacking and molecular orientation flexibility.
      PubDate: 2017-07-04T04:57:21.198827-05:
      DOI: 10.1002/anie.201703800
       
  • Coupling of Magnetic and Elastic Domains in the Organic–Inorganic
           Layered Perovskite-Like (C6H5C2H4NH3)2FeIICl4 Crystal
    • Authors: Yuki Nakayama; Sadafumi Nishihara, Katsuya Inoue, Takashi Suzuki, Mohamedally Kurmoo
      Pages: 9367 - 9370
      Abstract: Multiferroic materials coupling ferroelasticity and ferromagnetism show strong magnetoelastic effects as magnetization is induced by mechanical stress or alternately strain induced by applying a magnetic field. These effects were reported for inorganic multiferroics such as LaCoxSr1−xO3. (C6H5C2H4NH3)2FeIICl4 is the first example of an organic–inorganic perovskite to exhibit such effects below the canted antiferromagnetism at TC=98 K and ferroelasticity at TC=433 K. This is shown by switching the magnetic hysteresis on and off by uniaxial pressure through the strong coupling of the magnetic and elastic domains. The spin-canting direction was controlled by mechanical stress in the heating and cooling cycles. This unique observation gives additional impetus in the search for coupled hysteretic effect in organic–inorganic multiferroics.Molecule-based multiferroics: An air-stable crystal of (C6H5C2H4NH3)2FeIICl4 shows a magnetoelastic effect below the canted antiferromagnetism (TC=98 K) and ferroelasticity (TC=433 K). Uniaxial stress along the b axis leads to an exchange of the a and b axes and consequently switches off the magnetic hysteresis. This on/off switch uses the strong coupling between magnetic and elastic domains.
      PubDate: 2017-07-07T06:31:28.019585-05:
      DOI: 10.1002/anie.201703898
       
  • Operando 3D Visualization of Migration and Degradation of a Platinum
           Cathode Catalyst in a Polymer Electrolyte Fuel Cell
    • Authors: Hirosuke Matsui; Nozomu Ishiguro, Tomoya Uruga, Oki Sekizawa, Kotaro Higashi, Naoyuki Maejima, Mizuki Tada
      Pages: 9371 - 9375
      Abstract: The three-dimensional (3D) distribution and oxidation state of a Pt cathode catalyst in a practical membrane electrode assembly (MEA) were visualized in a practical polymer electrolyte fuel cell (PEFC) under fuel-cell operating conditions. Operando 3D computed-tomography imaging with X-ray absorption near edge structure (XANES) spectroscopy (CT-XANES) clearly revealed the heterogeneous migration and degradation of Pt cathode catalyst in an MEA during accelerated degradation test (ADT) of PEFC. The degradative Pt migration proceeded over the entire cathode catalyst layer and spread to MEA depth direction into the Nafion membrane.3D visualization of catalyst degradation: The 3D distribution and oxidation state of a Pt cathode catalyst in a practical membrane electrode assembly (MEA) were visualized under polymer electrolyte fuel cell operating conditions. Operando 3D CT-XANES techniques clearly revealed the heterogeneous migration and degradation of the Pt cathode catalyst during accelerated degradation test cycles.
      PubDate: 2017-07-06T10:57:54.684245-05:
      DOI: 10.1002/anie.201703940
       
  • Mg2+-Dependent High Mechanical Anisotropy of Three-Way-Junction pRNA as
           Revealed by Single-Molecule Force Spectroscopy
    • Authors: Yang Sun; Weishuai Di, Yiran Li, Wenmao Huang, Xin Wang, Meng Qin, Wei Wang, Yi Cao
      Pages: 9376 - 9380
      Abstract: Mechanical anisotropy is ubiquitous in biological tissues but is hard to reproduce in synthetic biomaterials. Developing molecular building blocks with anisotropic mechanical response is the key towards engineering anisotropic biomaterials. The three-way-junction (3WJ) pRNA, derived from ϕ29 DNA packaging motor, shows strong mechanical anisotropy upon Mg2+ binding. In the absence of Mg2+, 3WJ-pRNA is mechanically weak without noticeable mechanical anisotropy. In the presence of Mg2+, the unfolding forces can differ by more than 4-fold along different pulling directions, ranging from about 47 pN to about 219 pN. Mechanical anisotropy of 3WJ-pRNA stems from pulling direction dependent cooperativity for the rupture of two Mg2+ binding sites, which is a novel mechanism for the mechanical anisotropy of biomacromolecules. It is anticipated that 3WJ-pRNA can be used as a key element for the construction of biomaterials with controllable mechanical anisotropy.A three-way RNA junction (3WJ-pRNA) shows diverse unfolding forces ranging from 47 pN to 219 pN depending on the force direction. Such a mechanical anisotropy originates from different cooperativity for the rupture of two Mg2+ binding sites. It is anticipated that 3WJ-pRNA can be used in the construction of biomaterials with controllable mechanical anisotropy.
      PubDate: 2017-07-04T06:35:25.319035-05:
      DOI: 10.1002/anie.201704113
       
  • Mild Hydrogenation of Amides to Amines over a Platinum-Vanadium Bimetallic
           Catalyst
    • Authors: Takato Mitsudome; Kazuya Miyagawa, Zen Maeno, Tomoo Mizugaki, Koichiro Jitsukawa, Jun Yamasaki, Yasutaka Kitagawa, Kiyotomi Kaneda
      Pages: 9381 - 9385
      Abstract: Hydrogenation of amides to amines is an important reaction, but the need for high temperatures and H2 pressures is a problem. Catalysts that are effective under mild reaction conditions, that is, lower than 30 bar H2 and 70 °C, have not yet been reported. Here, the mild hydrogenation of amides was achieved for the first time by using a Pt-V bimetallic catalyst. Amide hydrogenation, at either 1 bar H2 at 70 °C or 5 bar H2 at room temperature was achieved using the bimetallic catalyst. The mild reaction conditions enable highly selective hydrogenation of various amides to the corresponding amines, while inhibiting arene hydrogenation. Catalyst characterization showed that the origin of the catalytic activity for the bimetallic catalyst is the oxophilic V-decorated Pt nanoparticles, which are 2 nm in diameter.Two metals: Hydrogenation of amides to amines under mild reaction conditions, that is, lower than 30 bar H2 and 70 °C, with a reusable Pt-V bimetallic catalyst is reported. The reaction proceeds with high selectivity, and the Pt-V bimetal is the first example of a catalyst which works at either ambient temperature or 1 bar of H2. NP=nanoparticle.
      PubDate: 2017-07-06T10:58:35.470049-05:
      DOI: 10.1002/anie.201704199
       
  • Reaction Acceleration in Thin Films with Continuous Product Deposition for
           Organic Synthesis
    • Authors: Zhenwei Wei; Michael Wleklinski, Christina Ferreira, R. Graham Cooks
      Pages: 9386 - 9390
      Abstract: Thin film formats are used to study the Claisen–Schmidt base-catalyzed condensation of 6-hydroxy-1-indanone with substituted benzaldehydes and to compare the reaction acceleration relative to the bulk. Relative acceleration factors initially exceeded 103 and were on the order of 102 at steady state, although the confined volume reaction was not electrostatically driven. Substituent effects were muted compared to those in the corresponding bulk and microdroplet reactions and it is concluded that the rate-limiting step at steady state is reagent transport to the interface. Conditions were found that allowed product deposition from the thin film to occur continuously as the reaction mixture was added and as the solvent evaporated. Yields of 74 % and production rates of 98 mg h−1 were reached in a very simple experimental system that could be multiplexed to greater scales.Scaling up thin films: Thin films with continuous reactant deposition and product precipitation are used for accelerated, scaled-up organic synthesis. Mechanistic studies show two stages of thin film reaction. A constant acceleration factor of 102 and conversion ratios of 70–98 % in the diffusion controlled stage 2 enable a rate of circa 100 mg h−1 of Claisen–Schmidt product synthesis.
      PubDate: 2017-07-05T12:33:08.441714-05:
      DOI: 10.1002/anie.201704520
       
  • Oriented Two-Dimensional Porous Organic Cage Crystals
    • Authors: Shan Jiang; Qilei Song, Alan Massey, Samantha Y. Chong, Linjiang Chen, Shijing Sun, Tom Hasell, Rasmita Raval, Easan Sivaniah, Anthony K. Cheetham, Andrew I. Cooper
      Pages: 9391 - 9395
      Abstract: The formation of two-dimensional (2D) oriented porous organic cage crystals (consisting of imine-based tetrahedral molecules) on various substrates (such as silicon wafers and glass) by solution-processing is reported. Insight into the crystallinity, preferred orientation, and cage crystal growth was obtained by experimental and computational techniques. For the first time, structural defects in porous molecular materials were observed directly and the defect concentration could be correlated with crystal growth rate. These oriented crystals suggest potential for future applications, such as solution-processable molecular crystalline 2D membranes for molecular separations.To the boundary for six: Oriented 2D porous organic cage crystals consisting of imine-based tetrahedral molecules have been fabricated on various substrates such as silicon wafers and glass with a new hexagonal-shaped morphology. The controlled cage crystal growth, alignment, and molecular defects were investigated.
      PubDate: 2017-07-06T11:00:42.938502-05:
      DOI: 10.1002/anie.201704579
       
  • Simulated Isotope Exchange Patterns Enable Protein Structure Determination
    • Authors: Antoni J. Borysik
      Pages: 9396 - 9399
      Abstract: Understanding the myriad protein–protein interactions required for cell function requires efficient leveraging of biophysical data to drive computational docking. The detailed insight into protein interfaces provided by isotope exchange endows this experimental technique with a unique importance for docking approaches. However, progress in coupling these methods is hindered by the inability to interpret the complex exchange patterns in relation to protein structure. A method to simulate protein isotope exchange patterns from docking outputs is described and its utility to guide the selection of native assemblies demonstrated. Unique signatures are generated for each docking pose, allowing high-throughput ranking of whole docking simulations by pairwise comparison to experimental outputs. Native assemblies are obtained using nothing but their simulated profiles as restraints and experimental difference data for individual proteins are sufficient to drive structure determination for the whole complex.HDX to the rescue: Protein structures can be determined by isotope exchange using hydrogen–deuterium exchange mass spectrometry (HDX-MS). Protein complexes are assembled by simulating their complex isotope patterns and comparing these outputs to those obtained by experiment.
      PubDate: 2017-07-05T07:41:19.274384-05:
      DOI: 10.1002/anie.201704604
       
  • Intramolecular Singlet Fission in an Antiaromatic Polycyclic Hydrocarbon
    • Authors: Yishi Wu; Yuancheng Wang, Jianwei Chen, Guanxin Zhang, Jiannian Yao, Deqing Zhang, Hongbing Fu
      Pages: 9400 - 9404
      Abstract: Singlet fission (SF), in which one singlet exciton (S1) splits into two triplets (T1) on adjacent molecules through a correlated triplet-pair 1(TT) state, requires precise but difficult tuning of exciton energetics and intermolecular electronic couplings in the solid state. Antiaromatic 4nπ dibenzopentalenes (DPs) are demonstrated as a new class of single-chromophore-based intramolecular SF materials that exhibit an optically allowed S2 state with E(S2)>2×E(T1) and an optically forbidden S1 state. Ultrafast population transfer from a high-lying S2 state to a 1(TT) state was observed in monomeric solution of styryl-substituted DP (SDP) on a sub-picosecond timescale. There is evidence of exciton diffusion (ED) of the 1(TT) state to yield two individual long-lived triplets in SDP thin film. The overall triplet yield via intramolecular SF and subsequent triplet-pair diffusion can be as high as 142±10 % in thin film.Exciton diffusion of 1(TT): Single-chromophore molecules based on the antiaromatic pentalene skeleton were developed that are singlet-fission-active. Ultrafast population transfer from a high-lying S2 state to a 1(TT) state via intramolecular singlet fission (iSF) was observed in solution. Efficient exciton diffusion of the 1(TT) state was observed to yield two long-lived triplets in film.
      PubDate: 2017-07-06T07:12:57.47851-05:0
      DOI: 10.1002/anie.201704668
       
  • Organogelator–Cellulose Composite for Practical and Eco-Friendly
           Marine Oil-Spill Recovery
    • Authors: Annamalai Prathap; Kana M. Sureshan
      Pages: 9405 - 9409
      Abstract: Marine oil spills pose serious threats to the ecosystem and economy. There is much interest in developing sorbents that can tackle such spills. We have developed a novel sorbent by impregnating cellulose pulp with a sugar-derived oleogelator, 1,2:5,6-di-O-cyclohexylidene-mannitol. The gelator molecules mask the surface-exposed hydroxyl groups of cellulose fibrils by engaging them in H-bonding and expose their hydrophobic parts making the fibers temporarily hydrophobic (water contact angle 110°). This sorbent absorbs oil effectively, selectively and instantly from oil–water mixtures due to its hydrophobicity. Then the gelator molecules get released uniformly in the oil and later self-assemble to fibers, as evident from SEM analysis, congealing the oil within the matrix. This hierarchical entrapment of the oil by non-covalent polymeric fibers within a covalent polymer matrix makes the gel very strong (230-fold increase in the yield stress) and rigid, making it suitable for practical use.A sorbent for marine oil-spill recovery was developed by impregnating cellulose pulp with a sugar-derived gelator. This sorbent absorbs oil from crude oil–water biphasic mixtures and the gelator molecules congeal the oil within the matrix. The crude-oil-absorbed matrix can be collected and the oil is recovered by applying pressure or by distillation.
      PubDate: 2017-07-05T12:27:38.294981-05:
      DOI: 10.1002/anie.201704699
       
  • In Situ Synthesis of a Supramolecular Hydrogelator at an Oil/Water
           Interface for Stabilization and Stimuli-Induced Fusion of Microdroplets
    • Authors: Yuki Nishida; Akiko Tanaka, Shota Yamamoto, Yudai Tominaga, Nobuaki Kunikata, Minoru Mizuhata, Tatsuo Maruyama
      Pages: 9410 - 9414
      Abstract: Supramolecular hydrogels are expected to have applications as novel soft materials in various fields owing to their designable functional properties. Herein, we developed an in situ synthesis of supramolecular hydrogelators, which can trigger gelation of an aqueous solution without the need for temperature change. This was achieved by mixing two precursors, which induced the synthesis of a supramolecular gelator and its instantaneous self-assembly into nanofibers. We then performed the in situ synthesis of this supramolecular gelator at an oil/water interface to produce nanofibers that covered the surfaces of the oil droplets (nanofiber-stabilized oil droplets). External stimuli induced fusion of the droplets owing to disassembly of the gelator molecules. Finally, we demonstrated that this stimuli-induced droplet fusion triggered a synthetic reaction within the droplets. This means that the confined nanofiber-stabilized droplets can be utilized as stimuli-responsive microreactors.Droplet reactor: A novel supramolecular hydrogelator is reported, which can trigger gelation of an aqueous solution. The in situ synthesis of the gelator at an oil/water interface allows the production of nanofibers that cover the surfaces of the oil droplets, resulting in a stabilized oil-in-water emulsion. The droplets are responsive to external stimuli to induce fusion, triggering a synthetic reaction within the droplets.
      PubDate: 2017-07-05T12:33:26.687401-05:
      DOI: 10.1002/anie.201704731
       
  • Methylenecyclopropane Annulation by Manganese(I)-Catalyzed Stereoselective
           C−H/C−C Activation
    • Authors: Yu-Feng Liang; Valentin Müller, Weiping Liu, Annika Münch, Dietmar Stalke, Lutz Ackermann
      Pages: 9415 - 9419
      Abstract: C−H/C−C functionalizations with methylenecyclopropanes (MCPs) were accomplished with a versatile base-metal catalyst. A robust manganese(I) complex enabled the expedient annulation of MCPs by synthetically meaningful ketimines to deliver, upon one-pot hydroarylation, densely substituted polycylic anilines in a step-economical fashion. Mechanistic studies provided strong support for a facile organometallic C−H manganation, while typical cobalt, ruthenium, rhodium, and palladium catalysts were found completely ineffective.One stone, two birds: C−H/C−C activations were realized by a versatile MnI catalysis regime, thus enabling the stereoselective construction of polycyclic anilines. Mechanistic studies provided strong support for a facile C−H manganation while typical Co, Ru, Rh, and Pd catalysts were completely ineffective.
      PubDate: 2017-07-13T01:36:29.866087-05:
      DOI: 10.1002/anie.201704767
       
  • Biologically Controlled Morphology and Twinning in Guanine Crystals
    • Authors: Anna Hirsch; Benjamin A. Palmer, Nadav Elad, Dvir Gur, Steve Weiner, Lia Addadi, Leeor Kronik, Leslie Leiserowitz
      Pages: 9420 - 9424
      Abstract: Guanine crystals are widely used in nature as components of multilayer reflectors. Guanine-based reflective systems found in the copepod cuticle and in the mirror of the scallop eye are unique in that the multilayered reflectors are tiled to form a contiguous packed array. In the copepod cuticle, hexagonal crystals are closely packed to produce brilliant colors. In the scallop eye, square crystals are tiled to obtain an image-forming reflecting mirror. The tiles are about 1 μm in size and 70 nm thick. According to analysis of their electron diffraction patterns, the hexagon and square tiles are not single crystals. Rather, each tile type is a composite of what appears to be three crystalline domains differently oriented and stacked onto one another, achieved through a twice-repeated twinning about their ⟨011⟩ and ⟨021⟩ crystal axes, respectively. By these means, the monoclinic guanine crystal mimics higher symmetry hexagonal and tetragonal structures to achieve unique morphologies.Guanignma: The brilliant colors of the copepod and the image-forming reflecting mirror in the eye of the scallop are both the result of guanine-based multilayer reflectors. Both systems form tessellated arrays composed of guanine monoclinic crystals biologically engineered into symmetrical hexagon and square tiles. Electron diffraction patterns reveal that their morphologies are achieved by crystal twinning, each forming a composite of three domains.
      PubDate: 2017-07-06T11:00:31.203677-05:
      DOI: 10.1002/anie.201704801
       
  • Flow Asymmetric Propargylation: Development of Continuous Processes for
           the Preparation of a Chiral β-Amino Alcohol
    • Authors: Hui Li; Jillian W. Sheeran, Andrew M. Clausen, Yuan-Qing Fang, Matthew M. Bio, Scott Bader
      Pages: 9425 - 9429
      Abstract: The development of a flow chemistry process for asymmetric propargylation using allene gas as a reagent is reported. The connected continuous process of allene dissolution, lithiation, Li-Zn transmetallation, and asymmetric propargylation provides homopropargyl β-amino alcohol 1 with high regio- and diastereoselectivity in high yield. This flow process enables practical use of an unstable allenyllithium intermediate. The process uses the commercially available and recyclable (1S,2R)-N-pyrrolidinyl norephedrine as a ligand to promote the highly diastereoselective (32:1) propargylation. Judicious selection of mixers based on the chemistry requirement and real-time monitoring of the process using process analytical technology (PAT) enabled stable and scalable flow chemistry runs.Go with the flow: Continuous flow is used for the practical preparation of highly reactive allenyllithium from allene gas under non-cryogenic conditions. On-line process analytical technologies such as FlowIR allowed real-time monitoring of the formation of reactive intermediates.
      PubDate: 2017-07-07T02:16:46.655705-05:
      DOI: 10.1002/anie.201704882
       
  • A DNA Structure Containing AgI-Mediated G:G and C:C Base Pairs
    • Authors: Hehua Liu; Fusheng Shen, Phensinee Haruehanroengra, Qingqing Yao, Yunshan Cheng, Yiqing Chen, Chun Yang, Jing Zhang, Baixing Wu, Qiang Luo, Ruixue Cui, Jixi Li, Jinbiao Ma, Jia Sheng, Jianhua Gan
      Pages: 9430 - 9434
      Abstract: Metal-mediated base pairs have been extensively utilized in many research fields, including genetic-code extension, novel therapeutics development, and nanodevice design. Compared to other cations, AgI is more flexible in pairing with natural base pairs. Herein, we present a DNA structure containing two C-AgI-C pairs and the first reported G-AgI-G pair in a short 8mer DNA strand. This structure not only provides detailed insight into these AgI-mediated base-pairing patterns in DNA, but also represents the first nonhelical DNA structure driven by heavy-metal ions, thus further contributing to the structural diversity of DNA. This unique complex structure is highly sequence-dependent, thus implying functional potentials as a new DNA aptamer that can bind and recognize silver ions. These results not only advance our understanding of the interactions between AgI and nucleobases, but also provide a unique structural component for the rational design of new DNA nanodevices.A pretty pair: In a novel DNA structure containing G-AgI-G and C-AgI-C pairs, the DNA adopts an unusual nonhelical fold with sharp turns in each strand. In the crystal, many DNA molecules are tightly bound together through metallophilic attraction and hydrogen-bonding interactions between the metallo base pairs. These results provided a useful structural basis for the rational design of new DNA nanodevices based on AgI-mediated base pairs.
      PubDate: 2017-07-07T05:54:52.587402-05:
      DOI: 10.1002/anie.201704891
       
  • The Viologen Cation Radical Pimer: A Case of Dispersion-Driven Bonding
    • Authors: Margarita R. Geraskina; Andrew S. Dutton, Mark J. Juetten, Samuel A. Wood, Arthur H. Winter
      Pages: 9435 - 9439
      Abstract: The π bonds between organic radicals have generated excitement as an orthogonal interaction for designing self-assembling architectures in water. A systematic investigation of the effect of the viologen cation radical structure on the strength and nature of the pimer bond is provided. A striking and unexpected feature of this π bond is that the bond strength is unchanged by substitution with electron-donating groups or withdrawing groups or with increased conjugation. Furthermore, the interaction is undiminished by sterically bulky N-alkyl groups. Theoretical modeling indicates that strong dispersion forces dominate the interaction between the radicals, rationalizing the insensitivity of the bonding interaction to substituents: The stacking of polarizable π radicals leads to attractive dispersion forces in excess of typical dispersion interactions of small molecules and helps overcome the Coulombic repulsion of bringing two cationic species into contact.A piece of pimer: Experimental and computational investigations of the pimer bond between viologen cation radicals show that the bonding interaction is dominated by exceptionally strong dispersion forces from ultra-polarizable π radicals. These forces overwhelm Coulombic repulsion.
      PubDate: 2017-07-07T06:26:38.606091-05:
      DOI: 10.1002/anie.201704959
       
  • Dual Catalytic Activity of a Cytochrome P450 Controls Bifurcation at a
           Metabolic Branch Point of Alkaloid Biosynthesis in Rauwolfia serpentina
    • Authors: Thu-Thuy T. Dang; Jakob Franke, Evangelos Tatsis, Sarah E. O'Connor
      Pages: 9440 - 9444
      Abstract: Plants create tremendous chemical diversity from a single biosynthetic intermediate. In plant-derived ajmalan alkaloid pathways, the biosynthetic intermediate vomilenine can be transformed into the anti-arrhythmic compound ajmaline, or alternatively, can isomerize to form perakine, an alkaloid with a structurally distinct scaffold. Here we report the discovery and characterization of vinorine hydroxylase, a cytochrome P450 enzyme that hydroxylates vinorine to form vomilenine, which was found to exist as a mixture of rapidly interconverting epimers. Surprisingly, this cytochrome P450 also catalyzes the non-oxidative isomerization of the ajmaline precursor vomilenine to perakine. This unusual dual catalytic activity of vinorine hydroxylase thereby provides a control mechanism for the bifurcation of these alkaloid pathway branches. This discovery highlights the unusual catalytic functionality that has evolved in plant pathways.Two roads diverged: A cytochrome P450 enzyme from plant Rauwolfia serpentina effects the bifurcation of alkaloid synthesis through an unusual dual catalytic function. Vinorine hydroxylase (VH) catalyzes hydroxylation followed by non-oxidative isomerization of the monoterpene indole alkaloid to form vomilenine and perakine, respectively. This dual activity provides additional chemical diversity, and highlights the versatility of cytochrome P450s in plant metabolism.
      PubDate: 2017-07-12T05:00:53.963482-05:
      DOI: 10.1002/anie.201705010
       
  • Formation of a Tunneling Product in the Photorearrangement of
           o-Nitrobenzaldehyde
    • Authors: Dennis Gerbig; Peter R. Schreiner
      Pages: 9445 - 9448
      Abstract: The photochemical rearrangement of o-nitrobenzaldehyde to o-nitrosobenzoic acid, first reported in 1901, has been shown to proceed via a distinct ketene intermediate. In the course of matrix isolation experiments in various host materials at temperatures as low as 3 K, the ketene was re-investigated in its electronic and vibrational ground states. It was shown that hitherto unreported H-tunneling dominates its reactivity, with half-lives of a few minutes. Unexpectedly, the tunneling product is different from o-nitrosobenzoic acid formed in the photoprocess: Once prepared by irradiation, the ketene spontaneously rearranges to an isoxazolone via an intriguing mechanism initiated by H-tunneling. CCSD(T)/cc-pVTZ computations reveal that this isoxazolone is neither thermodynamically nor kinetically favored under the experimental conditions, and that formation of this unique tunneling product constitutes a remarkable and new example of tunneling control.Triggered by tunneling: The ketene intermediate derived from photoexcited o-nitrobenzaldehyde rearranges to a hitherto unobserved tunneling-exclusive isoxazolone product under cryogenic conditions. This process constitutes a new reactivity paradigm in chemistry.
      PubDate: 2017-07-04T00:35:32.112126-05:
      DOI: 10.1002/anie.201705140
       
  • A Bifunctional Spin Label for Ligand Recognition on Surfaces
    • Authors: Michael A. Hollas; Simon J. Webb, Sabine L. Flitsch, Alistair J. Fielding
      Pages: 9449 - 9453
      Abstract: In situ monitoring of biomolecular recognition, especially at surfaces, still presents a significant technical challenge. Electron paramagnetic resonance (EPR) of biomolecules spin-labeled with nitroxides can offer uniquely sensitive and selective insights into these processes, but new spin-labeling strategies are needed. The synthesis and study of a bromoacrylaldehyde spin label (BASL), which features two attachment points with orthogonal reactivity is reported. The first examples of mannose and biotin ligands coupled to aqueous carboxy-functionalized gold nanoparticles through a spin label are presented. EPR spectra were obtained for the spin-labeled ligands both free in solution and attached to nanoparticles. The labels were recognized by the mannose-binding lectin, Con A, and the biotin-binding protein avidin-peroxidase. Binding gave quantifiable changes in the EPR spectra from which binding profiles could be obtained that reflect the strength of binding in each case.An easily accessible spin label has been developed as a valuable tool for the integration of an EPR-sensitive probe into linkers between bioligands and surfaces. Gold nanoparticles were linked through the spin label to bioligands, and CW-EPR spectroscopy was utilized to monitor recognition of surface-bound mannose and biotin ligands by concanavalin A and avidin-peroxidase, respectively.
      PubDate: 2017-07-06T08:15:43.99856-05:0
      DOI: 10.1002/anie.201703929
       
  • A Stretchable Electrochemical Sensor for Inducing and Monitoring Cell
           Mechanotransduction in Real Time
    • Authors: Yan-Ling Liu; Yu Qin, Zi-He Jin, Xue-Bo Hu, Miao-Miao Chen, Rong Liu, Christian Amatore, Wei-Hua Huang
      Pages: 9454 - 9458
      Abstract: Existing methods offer little direct and real-time information about stretch-triggered biochemical responses during cell mechanotransduction. A novel stretchable electrochemical sensor is reported that takes advantage of a hierarchical percolation network of carbon nanotubes and gold nanotubes (CNT-AuNT). This hybrid nanostructure provides the sensor with excellent time-reproducible mechanical and electrochemical performances while granting very good cellular compatibility, making it perfectly apt to induce and monitor simultaneously transient biochemical signals. This is validated by monitoring stretch-induced transient release of small signaling molecules by both endothelial and epithelial cells cultured on this sensor and submitted to stretching strains of different intensities. This work demonstrates that the hybrid CNT-AuNT platform offers a versatile and highly sensitive way to characterize and quantify short-time mechanotransduction responses.Cell stretching: A stretchable electrochemical sensor with excellent mechanical and electrochemical behavior and very good cellular compatibility has been developed. Transient biochemical signals during cell mechanotransduction can be induced and monitored in real time. This work offers a powerful platform to characterize and quantify mechanotransduction responses from mechanically sensitive cells.
      PubDate: 2017-07-06T07:13:48.636596-05:
      DOI: 10.1002/anie.201705215
       
  • Design of a Tunable Self-Oscillating Polymer with Ureido and Ru(bpy)3
           Moieties
    • Authors: Tsukuru Masuda; Naohiko Shimada, Taira Sasaki, Atsushi Maruyama, Aya Mizutani Akimoto, Ryo Yoshida
      Pages: 9459 - 9462
      Abstract: An upper critical solution temperature (UCST)-type self-oscillating polymer was designed that exhibited rhythmic soluble–insoluble changes induced by the Belousov–Zhabotinsky (BZ) reaction. The target polymers were prepared by conjugating Ru(bpy)3, a catalyst for the BZ reaction, to ureido-containing poly(allylamine-co-allylurea) (PAU) copolymers. The Ru(bpy)3-conjugated PAUs exhibited a UCST-type phase-transition behavior, and the solubility of the polymer changed in response to the alternation in the valency of Ru(bpy)3. The ureido content influences the temperature range of self-oscillation, and the oscillation occurred at higher temperatures than conventional LCST-type self-oscillating polymers. Furthermore, the self-oscillating behavior of the Ru-PAU could be regulated by addition of urea, which is a unique tuning strategy. We envision that novel self-oscillating polymers with widely tunable soluble-insoluble behaviors can be rationally designed based these UCST-type polymers.A tunable self-oscillating polymer was designed by introducing a metal catalyst for the Belousov–Zhabotinsky reaction to ureido-containing poly(allylamine-co-allylurea) copolymers. Oscillation occurred at a higher temperature range (22.5–42.5 °C) than for conventional self-oscillating polymers. The self-oscillation could be uniquely regulated by addition of urea.
      PubDate: 2017-07-07T05:55:15.915475-05:
      DOI: 10.1002/anie.201705277
       
  • Bending, Curling, Rolling, and Salient Behavior of Molecular Crystals
           Driven by [2+2] Cycloaddition of a Styrylbenzoxazole Derivative
    • Authors: Haoran Wang; Peng Chen, Zhu Wu, Jinyu Zhao, Jingbo Sun, Ran Lu
      Pages: 9463 - 9467
      Abstract: We report interesting photomechanical behaviors of the dynamic molecular crystals of (E)-2-(2,4-dichlorostyryl)benzo[d]oxazole (BOACl24). The photosalient effect of the rod-like crystal based on a metal-free olefin driven by photodimerization is observed. Moreover, the needle-like crystals of BOACl24 exhibit a reversible bending away from a UV light source. The nanofibers curl easily under UV irradiation in an organogel, in which the photo-induced rolling of a small slice occurs. This suggests that the rapid release of the accumulated strain during photodimerization may lead to a photosalient effect, and the bending or curling happens when the strain is released slowly. Notably, [2+2] cycloaddition takes place between two different conformational isomers of BOACl24 on account of the rotation of the benzoxazole ring around the C−C bond in an excited state before photodimerization. Such topo-photochemical reaction has not been reported elsewhere.Rollin' and tumblin': The dynamic molecular crystals of (dichlorostyryl)benzoxazole BOACl24 exhibit photomechanical motion induced by topo-photochemical dimerization. The reversible controllable bending of these needle-like crystals away from the light source driven by [2+2] cycloaddition resulted from the slow release of the strain accumulated by the movement of the atoms during photodimerization.
      PubDate: 2017-07-05T07:22:02.225103-05:
      DOI: 10.1002/anie.201705325
       
  • Visible Light Photocatalysis of 6π Heterocyclization
    • Authors: Niels Münster; Nicholas A. Parker, Lucy van Dijk, Robert S. Paton, Martin D. Smith
      Pages: 9468 - 9472
      Abstract: Photo-mediated 6π cyclization is a valuable method for the formation of fused heterocyclic systems. Here we demonstrate that irradiation of cyclic 2-aryloxyketones with blue LED light in the presence of an IrIII complex leads to efficient and high yielding arylation across a panoply of substrates by energy transfer. 2-Arylthioketones and 2-arylaminoketones also cyclize effectively under these conditions. Quantum calculation demonstrates that the reaction proceeds via conrotatory ring closure in the triplet excited state. Subsequent suprafacial 1,4-hydrogen shift and epimerization leads to the observed cis-fused products.Irradiation of cyclic 2-aryloxy-, 2-arylthio-, and 2-arylaminoketones with blue LED light in the presence of an IrIII complex leads to efficient intramolecular arylation of various substrates (see scheme). The reaction proceeds via conrotatory ring closure followed by a suprafacial 1,4-hydrogen shift and epimerization leading to the observed cis-fused products.
      PubDate: 2017-07-04T00:36:18.502267-05:
      DOI: 10.1002/anie.201705333
       
  • Janusarene: A Homoditopic Molecular Host
    • Authors: Tao Li; Luoyi Fan, Hao Gong, Zeming Xia, Yanpeng Zhu, Nianqiang Jiang, Long Jiang, Gaofeng Liu, Yang Li, Jiaobing Wang
      Pages: 9473 - 9477
      Abstract: A homoditopic molecular host, janusarene, is presented that has two back-to-back compactly arranged nanocavities for guest complexation. The unique two-face structural feature of janusarene allows it to bind and align various guest compounds concurrently, which include spherical pristine fullerene C60 and planar polycyclic aromatic hydrocarbons (PAHs), such as pyrene, perylene, and 9,10-dimethylanthracene. The host–guest interactions were characterized by single-crystal X-ray diffraction. A pairwise encapsulation of the PAH guests by janusarene enables PAH dimers to be obtained that deliver spectroscopic properties distinct from those of PAHs dissolved in solution, or in the bulk state. A monotopic control host was also synthesized and used to characterize the host–guest complexing behavior in solution.Two-faced host: A back-to-back arranged homoditopic host compound, janusarene, is presented. The unique two-face structural feature of janusarene allows it to bind and align guest compounds that vary greatly in size and shape, such as spherical pristine fullerene and planar polycyclic aromatic hydrocarbons.
      PubDate: 2017-07-13T07:50:37.612521-05:
      DOI: 10.1002/anie.201705451
       
  • Biosynthesis of Complex Indole Alkaloids: Elucidation of the Concise
           Pathway of Okaramines
    • Authors: Chen-Yu Lai; I-Wen Lo, Ranuka T. Hewage, Yi-Chen Chen, Chien-Ting Chen, Chi-Fang Lee, Steven Lin, Man-Cheng Tang, Hsiao-Ching Lin
      Pages: 9478 - 9482
      Abstract: The okaramines are a class of complex indole alkaloids isolated from Penicillium and Aspergillus species. Their potent insecticidal activity arises from selectively activating glutamate-gated chloride channels (GluCls) in invertebrates, not affecting human ligand-gated anion channels. Okaramines B (1) and D (2) contain a polycyclic skeleton, including an azocine ring and an unprecedented 2-dimethyl-3-methyl-azetidine ring. Owing to their complex scaffold, okaramines have inspired many total synthesis efforts, but the enzymology of the okaramine biosynthetic pathway remains unexplored. Here, we identified and characterized the biosynthetic gene cluster (oka) of 1 and 2, then elucidated the pathway with target gene inactivation, heterologous reconstitution, and biochemical characterization. Notably, we characterized an α-ketoglutarate-dependent non-heme FeII dioxygenase that forged the azetidine ring on the okaramine skeleton.Okaramines are a class of complex indole alkaloids and potential insecticidal agents that activate glutamate-gated chloride channels (GluCls) in invertebrates selectively over human ligand-gated anion channels. The biosynthesis pathway was mapped with genetic inactivation, pathway enzyme reconstitution in a yeast heterologous system, and biochemical characterization.
      PubDate: 2017-07-06T11:01:18.242471-05:
      DOI: 10.1002/anie.201705501
       
  • Total Synthesis of Ovafolinins A and B: Unique Polycyclic Benzoxepin
           Lignans through a Cascade Cyclization
    • Authors: Samuel J. Davidson; David Barker
      Pages: 9483 - 9486
      Abstract: Ovafolinins A and B, isolated from Lyonia ovalifolia var. elliptica, are lignans that contain a unique bridged structure containing a penta- and tetracyclic benzoxepin and an aryl tetralin. We report the first total synthesis of these natural products in which an acyl-Claisen rearrangement was initially utilized to construct the lignan backbone with correct relative stereochemistry. Judicious use of a bulky protecting group placed reactive moieties in the correct orientation, thereby resulting in a cascade reaction to form the bridged benzoxepin/aryl tetralin from a linear precursor in a single step. Modification of this route allowed the enantioselective synthesis of (+)-ovafolinins A and B, which confirmed the absolute stereochemistry, and comparison of optical rotation suggests that these compounds are found as scalemic mixtures in nature.Building bridges: Ovafolinins A and B from Lyonia ovalifolia are lignans with a unique bridged structure containing a penta- and tetracyclic benzoxepin and an aryl tetralin. These natural products were synthesized by utilizing an acyl-Claisen rearrangement and a cascade cyclization to form the bridged polycyclic structure, and a subsequent enantioselective synthesis of ovafolinins A and B allowed assignment of the absolute stereochemistry of these natural products.
      PubDate: 2017-07-07T05:55:34.407107-05:
      DOI: 10.1002/anie.201705575
       
  • Catalyst-Controlled, Enantioselective, and Diastereodivergent Conjugate
           Addition of Aldehydes to Electron-Deficient Olefins
    • Authors: S. B. Jennifer Kan; Hiroki Maruyama, Matsujiro Akakura, Taichi Kano, Keiji Maruoka
      Pages: 9487 - 9491
      Abstract: A chiral-amine-catalyzed enantioselective and diastereodivergent method for aldehyde addition to electron-deficient olefins is presented. Hydrogen bonding was used as a control element to achieve unusual anti selectivity, which was further elucidated through mechanistic and computational studies.Diastereoswitch: A chiral-amine-catalyzed enantioselective and diastereodivergent method for aldehyde addition to electron-deficient olefins is presented. Hydrogen bonding was used as a control element to achieve unusual anti selectivity, which was further elucidated through mechanistic and computational studies.
      PubDate: 2017-07-10T10:41:03.765098-05:
      DOI: 10.1002/anie.201705546
       
  • ABi2(IO3)2F5 (A=K, Rb, and Cs): A Combination of Halide and Oxide Anionic
           Units To Create a Large Second-Harmonic Generation Response with a Wide
           Bandgap
    • Authors: Hongming Liu; Qi Wu, Xingxing Jiang, Zheshuai Lin, Xianggao Meng, Xingguo Chen, Jingui Qin
      Pages: 9492 - 9496
      Abstract: A family of nonlinear optical materials that contain the halide, oxide, and oxyhalide polar units simultaneously in a single structure, namely ABi2(IO3)2F5 (A=K (1), Rb (2), and Cs (3)), have been designed and synthesized. They crystallize in the same polar space group (P21) with a two-dimensional double-layered framework constructed by [BiF5]2− and [BiO2F4]5− units connected to each other by four F atoms, in which two [IO3]− groups are linked to [BiO2F4]5− unit on the same side. A hanging Bi−F bond of [BiF5]2− unit is located on the other side via ionic interaction with the layer-inserted alkali metal ions to form three-dimensional structure. The well-ordered alignments of these polar units lead to a very strong second-harmonic generation response of 12 (1), 9.5 (2), and 7.5 (3) times larger than that of potassium dihydrogen phosphate under 1064 nm laser radiation. All of them exhibited a wide energy bandgap over 3.75 eV, suggesting that they will have a high laser damage threshold.Harmonic generator: A combination of polar halide and oxide anionic groups creates a family of promising mid-IR nonlinear optical crystals, ABi2(IO3)2F5 (A=K, Rb, and Cs). They have a strong second-harmonic generation response of 12 (K), 9.5 (Rb), and 7.5 (Cs) times larger than that of potassium dihydrogen phosphate and a wide energy bandgap of over 3.75 eV.
      PubDate: 2017-07-05T07:22:28.417825-05:
      DOI: 10.1002/anie.201705672
       
  • Bacteriophage Tail-Tube Assembly Studied by Proton-Detected 4D Solid-State
           NMR
    • Authors: Maximilian Zinke; Pascal Fricke, Camille Samson, Songhwan Hwang, Joseph S. Wall, Sascha Lange, Sophie Zinn-Justin, Adam Lange
      Pages: 9497 - 9501
      Abstract: Obtaining unambiguous resonance assignments remains a major bottleneck in solid-state NMR studies of protein structure and dynamics. Particularly for supramolecular assemblies with large subunits (>150 residues), the analysis of crowded spectral data presents a challenge, even if three-dimensional (3D) spectra are used. Here, we present a proton-detected 4D solid-state NMR assignment procedure that is tailored for large assemblies. The key to recording 4D spectra with three indirect carbon or nitrogen dimensions with their inherently large chemical shift dispersion lies in the use of sparse non-uniform sampling (as low as 2 %). As a proof of principle, we acquired 4D (H)COCANH, (H)CACONH, and (H)CBCANH spectra of the 20 kDa bacteriophage tail-tube protein gp17.1 in a total time of two and a half weeks. These spectra were sufficient to obtain complete resonance assignments in a straightforward manner without use of previous solution NMR data.Tube map revealed: Non-uniform sparse sampling as low as 2 % allowed the introduction of a four-dimensional assignment strategy for proton-detected solid-state NMR. A complex, large bacteriophage tail-tube assembly was successfully studied by using this new approach.
      PubDate: 2017-07-07T05:55:40.840797-05:
      DOI: 10.1002/anie.201706060
       
  • A T-Shaped Nickel(I) Metalloradical Species
    • Authors: Changho Yoo; Yunho Lee
      Pages: 9502 - 9506
      Abstract: A T-shaped NiI complex was synthesized using a rigid acridane-based pincer ligand to prepare a metalloradical center. Structural data displays a nickel ion is embedded in the plane of a PNP ligand. Having a sterically exposed half-filled dx2-y2 orbital, this three-coordinate NiI species reveals unique open-shell reactivity including the homolytic cleavage of various σ-bonds, such as H−H, N−N, and C−C.Tee off: A T-shaped metalloradical NiI species was synthesized using a rigid acridane-based pincer ligand to prepare a metalloradical center. Having a sterically exposed half-filled orbital, the T-shaped NiI species reveals unique open-shell reactivity including the homolytic cleavage of various σ-bonds, such as H−H, N−N, and C−C.
      PubDate: 2017-06-07T06:10:27.163877-05:
      DOI: 10.1002/anie.201704487
       
  • Polymerization of 1-Phosphaisoprene: Synthesis and Characterization of a
           Chemically Functional Phosphorus Version of Natural Rubber
    • Authors: Klaus Dück; Benjamin W. Rawe, Michael R. Scott, Derek P. Gates
      Pages: 9507 - 9511
      Abstract: Macromolecules derived from 1,3-dienes, such as polyisoprene (or natural rubber), are of considerable importance in polymer science. Given the parallels between P=C and C=C bonds, the prospect of polymerizing P-containing 1,3-dienes, such as 1-phosphaisoprene, is intriguing due to the unique chemical functionality imparted by the heavier element combined with their structural relationship to natural rubber. Herein, we report the synthesis, characterization and coordination chemistry of the first polymers derived from Mes*P=CR−CH=CH2 (Mes*=2,4,6-t-Bu3C6H2; R=H, Me). In the case of 1-phosphaisoprene (R=Me), the monomer is isolable and its anionic polymerization affords a polymer that retains P=C bonds in its microstructure. The chemical functionality of these novel materials is demonstrated by forming the macromolecular gold(I) complex where the P=C bond is retained for further chemical elaboration.Un-natural rubber: A phosphorus-containing polyisoprene is obtained by polymerization of 1-phosphaisoprene with anionic initiators to afford the first example of a P-polymer of isoprene, the monomer in natural rubber. The chemical functionality of poly(1-phosphaisoprene) is demonstrated by its binding of gold(I) to give novel metal-containing macromolecules.
      PubDate: 2017-07-06T08:16:19.850523-05:
      DOI: 10.1002/anie.201703590
       
  • Expanding the Boundaries of Water-Tolerant Frustrated Lewis Pair
           Hydrogenation: Enhanced Back Strain in the Lewis Acid Enables the
           Reductive Amination of Carbonyls
    • Authors: Éva Dorkó; Márk Szabó, Bianka Kótai, Imre Pápai, Attila Domján, Tibor Soós
      Pages: 9512 - 9516
      Abstract: The development of a boron/nitrogen-centered frustrated Lewis pair (FLP) with remarkably high water tolerance is presented. As systematic steric tuning of the boron-based Lewis acid (LA) component revealed, the enhanced back-strain makes water binding increasingly reversible in the presence of relatively strong base. This advance allows the limits of FLP's hydrogenation to be expanded, as demonstrated by the FLP reductive amination of carbonyls. This metal-free catalytic variant displays a notably broad chemoselectivity and generality.No fear of water: A boron/nitrogen-centered frustrated Lewis pair (FLP) with remarkably high water tolerance is presented. Systematic steric tuning of the boron-based Lewis acid component revealed that enhanced back-strain makes water binding increasingly reversible in the presence of a relatively strong base. The limits of FLP hydrogenation are thus expanded, as demonstrated by the reductive amination of carbonyls.
      PubDate: 2017-07-05T07:36:50.317452-05:
      DOI: 10.1002/anie.201703591
       
  • Catalytic Oxidative Trifluoromethoxylation of Allylic C−H Bonds
           Using a Palladium Catalyst
    • Authors: Xiaoxu Qi; Pinhong Chen, Guosheng Liu
      Pages: 9517 - 9521
      Abstract: A catalytic intermolecular allylic C−H trifluoromethoxylation reaction of alkenes has been developed based on the use of a palladium catalyst, CsOCF3 as the trifluoromethoxide source, and benzoquinone as the oxidant. This reaction provides an efficient route for directly accessing allylic trifluoromethoxy derivatives with excellent regioselectivities from terminal alkenes via an allylic C−H bond activation process.A palladium catalyst enables the intermolecular allylic C−H trifluoromethoxylation of alkenes in the presence of CsOCF3 as the trifluoromethoxide source and benzoquinone as the oxidant. This reaction provides an efficient regioselective approach towards allylic trifluoromethyl ethers from terminal alkenes.
      PubDate: 2017-07-06T08:15:39.912465-05:
      DOI: 10.1002/anie.201703841
       
  • An Auto-Inductive Cascade for the Optical Sensing of Thiols in Aqueous
           Media: Application in the Detection of a VX Nerve Agent Mimic
    • Authors: Xiaolong Sun; Eric V. Anslyn
      Pages: 9522 - 9526
      Abstract: A new auto-inductive protocol employs a Meldrum's-acid-based conjugate acceptor (1) as a latent source of thiol for signal amplification, as well as optical detection of thiols. The auto-induction is initiated by a thiol-disulfide exchange that leads to the generation of β-mercaptoethanol, which in turn decouples the conjugate acceptor to release more thiols, resulting in a self-propagating cycle that continues until all the conjugate acceptor is consumed. Using 1 in a two-step integrated protocol yields a rapid, sensitive, and precise diagnostic assay for the ultratrace quantitation of a thiophosphate nerve agent surrogate.Thiol detection: Combining thiol-disulfide exchange with decoupling of a conjugate acceptor (1), a new thiol auto-inductive cascade was developed for signal amplification, as well as colorimetric and fluorometric detection of thiols. Using 1 in a two-step protocol yields a rapid assay for the ultratrace quantitation of a thiophosphate nerve agent surrogate at ppb levels.
      PubDate: 2017-07-03T07:16:34.319449-05:
      DOI: 10.1002/anie.201704472
       
  • Visible-Light-Driven Aza-ortho-quinone Methide Generation for the
           Synthesis of Indoles in a Multicomponent Reaction
    • Authors: Yi-Yin Liu; Xiao-Ye Yu, Jia-Rong Chen, Ming-Ming Qiao, Xiaotian Qi, De-Qing Shi, Wen-Jing Xiao
      Pages: 9527 - 9531
      Abstract: A visible-light-driven radical-mediated strategy for the in situ generation of aza-ortho-quinone methides from 2-vinyl-substituted anilines and alkyl radical precursors is described. This process enables an efficient multicomponent reaction of 2-vinylanilines, halides, and sulfur ylides, and has a wide substrate scope and good functional group tolerance. Treatment of the cycloaddition products with a base leads to densely functionalized indoles in a single-flask operation.Aza-ortho-quinone methides were generated in situ from 2-vinyl-substituted anilines and alkyl radical precursors in a visible-light-driven reaction. This process enables the multicomponent coupling of 2-vinylanilines, alkyl halides, and sulfur ylides, and ultimately generates densely functionalized indoles in a single-flask operation.
      PubDate: 2017-07-05T07:41:36.925349-05:
      DOI: 10.1002/anie.201704690
       
  • Dibenzothiophene Sulfoximine as an NH3 Surrogate in the Synthesis of
           Primary Amines by Copper-Catalyzed C−X and C−H Bond Amination
    • Authors: Zhen Li; Hao Yu, Carsten Bolm
      Pages: 9532 - 9535
      Abstract: Readily accessible dibenzothiophene sulfoximine is an NH3 surrogate allowing the preparation of free anilines by copper-catalyzed cross-coupling reactions with aryl iodides or amides followed by radical S−N bond cleavage. The one-pot/two-step reactions sequence leads to the aminated products in good yields.A useful substitute: Dibenzothiophene sulfoximine is an NH3 surrogate allowing halo arenes and amides to be converted into aminated analogues by copper-catalyzed Buchwald–Hartwig-type or dehydrogenative C−H/N−H cross-coupling reactions followed by radical sulfoxide cleavage.
      PubDate: 2017-07-05T12:27:47.432075-05:
      DOI: 10.1002/anie.201705025
       
  • Addition of a Cyclophosphine to Nitriles: An Inorganic Click Reaction
           Featuring Protio, Organo, and Main-Group Catalysis
    • Authors: Saurabh S. Chitnis; Hazel A. Sparkes, Vincent T. Annibale, Natalie E. Pridmore, Alex M. Oliver, Ian Manners
      Pages: 9536 - 9540
      Abstract: The addition of a cyclotriphosphine to a broad range of nitriles gives access to the first examples of free 1-aza-2,3,4-triphospholenes in a rapid, ambient temperature, one-pot, high-yield protocol. The reaction produces electron-rich heterocycles (four lone pairs) and features homoatomic σ-bond heterolysis, thereby combining the key features of the 1,3-dipolar cycloaddition chemistry of azides and cyclopropanes. Also reported is the first catalytic addition of P−P bonds to the C≡N bond. The coordination chemistry of the new heterocycles is explored.Click for P: The catalytic cycloaddition of nitriles to a cyclotriphosphine gives the first examples of free 1-aza-2,3,4-triphospholenes. This electrophile-mediated reaction is rapid (
      PubDate: 2017-07-07T05:55:03.559315-05:
      DOI: 10.1002/anie.201704991
       
  • Iridium(I)-Catalyzed Intramolecular Hydrocarbonation of Alkenes: Efficient
           Access to Cyclic Systems Bearing Quaternary Stereocenters
    • Authors: David F. Fernández; Moisés Gulías, José L. Mascareñas, Fernando López
      Pages: 9541 - 9545
      Abstract: A catalytic, versatile and atom-economical C−H functionalization process that provides a wide variety of cyclic systems featuring methyl-substituted quaternary stereocenters is described. The method relies on the use of a cationic IrI–bisphosphine catalyst, which promotes a carboxamide-assisted activation of an olefinic C(sp2)−H bond followed by exo-cyclization to a tethered 1,1-disubstituted alkene. The extension of the method to aromatic and heteroaromatic C−H bonds, as well as developments on an enantioselective variant, are also described.Versatile and atom-economical: The first IrI-catalyzed intramolecular hydroalkenylation that yields cyclic products bearing quaternary stereocenters is reported. The method is based on a carboxamide-directed activation of C(sp2)−H bonds followed by an exo-cyclization pathway. Not only alkenyl precursors, but also (hetero)aromatic systems are tolerated.
      PubDate: 2017-07-12T05:01:03.618524-05:
      DOI: 10.1002/anie.201705105
       
  • Chiral Side Groups Trigger Second Harmonic Generation Activity in 3D
           Octupolar Bipyrimidine-Based Organic Liquid Crystals
    • Authors: Stijn van Cleuvenbergen; Przemysław Kędziora, Jean-Luc Fillaut, Thierry Verbiest, Koen Clays, Huriye Akdas-Kilig, Franck Camerel
      Pages: 9546 - 9550
      Abstract: The design of efficient noncentrosymmetric materials remains the ultimate goal in the field of organic second-order nonlinear optics. Unlike inorganic crystals currently used in second-order nonlinear optical applications, organic materials are an attractive alternative owing to their fast electro-optical response and processability, but their alignment into noncentrosymmetric film remains challenging. Here, symmetry breaking by judicious functionalization of 3D organic octupoles allows the emergence of multifunctional liquid crystalline chromophores which can easily be processed into large, flexible, thin, and self-oriented films with second harmonic generation responses competitive to the prototypical inorganic KH2PO4 crystals. The liquid-crystalline nature of these chiral organic films also permits the modulation of the nonlinear optical properties owing to the sensitivity of the supramolecular organization to temperature, leading to the development of tunable macroscopic materials.The rational design of chiral 3D octupoles allows the formation of high-quality flexible organic liquid-crystalline thin films. These display strong second-harmonic generation that is competitive with the prototypical inorganic crystalline material KH2PO4 (KDP).
      PubDate: 2017-07-04T00:35:26.027852-05:
      DOI: 10.1002/anie.201705138
       
  • Bismuth–Boron Multiple Bonding in BiB2O− and Bi2B−
    • Authors: Tian Jian; Ling Fung Cheung, Teng-Teng Chen, Lai-Sheng Wang
      Pages: 9551 - 9555
      Abstract: Despite its electron deficiency, boron is versatile in forming multiple bonds. Transition-metal–boron double bonding is known, but boron–metal triple bonds have been elusive. Two bismuth boron cluster anions, BiB2O− and Bi2B−, containing triple and double B−Bi bonds are presented. The BiB2O− and Bi2B− clusters are produced by laser vaporization of a mixed B/Bi target and characterized by photoelectron spectroscopy and ab initio calculations. Well-resolved photoelectron spectra are obtained and interpreted with the help of ab initio calculations, which show that both species are linear. Chemical bonding analyses reveal that Bi forms triple and double bonds with boron in BiB2O− ([Bi≡B−B≡O]−) and Bi2B− ([Bi=B=Bi]−), respectively. The Bi−B double and triple bond strengths are calculated to be 3.21 and 4.70 eV, respectively. This is the first experimental observation of Bi−B double and triple bonds, opening the door to design main-group metal–boron complexes with multiple bonding.The more the merrier: Two bismuth–boron cluster anions, BiB2O− and Bi2B−, are shown to contain triple and double B−Bi bonds. The BiB2O− and Bi2B− clusters are produced by laser vaporization of a mixed B/Bi target. Well-resolved photoelectron spectra were obtained and interpreted using ab initio calculations, showing that both species are linear.
      PubDate: 2017-06-30T06:06:50.128249-05:
      DOI: 10.1002/anie.201705209
       
  • Reversible Product Release and Recapture by a Fungal Polyketide Synthase
           Using a Carnitine Acyltransferase Domain
    • Authors: Leibniz Hang; Man-Cheng Tang, Colin J. B. Harvey, Claire G. Page, Jian Li, Yiu-Sun Hung, Nicholas Liu, Maureen E. Hillenmeyer, Yi Tang
      Pages: 9556 - 9560
      Abstract: Fungal polyketides have significant biological activities, yet the biosynthesis by highly reducing polyketide synthases (HRPKSs) remains enigmatic. An uncharacterized group of HRPKSs was found to contain a C-terminal domain with significant homology to carnitine O-acyltransferase (cAT). Characterization of one such HRPKS (Tv6-931) from Trichoderma virens showed that the cAT domain is capable of esterifying the polyketide product with polyalcohol nucleophiles. This process is readily reversible, as confirmed through the holo ACP-dependent transesterification of the released product. The methyltransferase (MT) domain of Tv6-931 can perform two consecutive α-methylation steps on the last β-keto intermediate to yield an α,α-gem-dimethyl product, a new programing feature among HRPKSs. Recapturing of the released product by cAT domain is suggested to facilitate complete gem-dimethylation by the MT.An uncharacterized group of highly reducing polyketide synthases (HRPKSs) contains a C-terminal domain with significant homology to carnitine O-acyltransferase (cAT). Characterization of one such HRPKS (Tv6-931) from Trichoderma virens showed that the cAT domain is capable of esterifying the polyketide product with polyalcohol nucleophiles.
      PubDate: 2017-07-05T12:28:21.381886-05:
      DOI: 10.1002/anie.201705237
       
  • Heterogeneous Sodium-Manganese Oxide Catalyzed Aerobic Oxidative Cleavage
           of 1,2-Diols
    • Authors: Vincent Escande; Chun Ho Lam, Philip Coish, Paul T. Anastas
      Pages: 9561 - 9565
      Abstract: The aerobic oxidative cleavage of 1,2-diols using a heterogeneous catalyst only based on earth-abundant metals manganese and sodium is reported for the first time. This reusable catalyst cleaves a variety of substrates into aldehydes or ketones with high selectivity. The reaction requires small catalytic loadings and is performed under mild conditions using ambient pressure O2 or air as the oxidant while producing water as the only by-product. Mechanistic investigations reveal a monodentate, two-electron oxidative fragmentation process involving a MnIV species. The eco-friendly, innocuous catalyst is compatible with a wide range of functional groups and conditions, making it highly competitive with classical reagents, such as periodic acid or lead tetraacetate, as a preferred method for activated 1,2-diols.Catalytic scissors: A reusable heterogeneous catalyst, easily prepared from earth-abundant elements Na and Mn, cleaved 1,2-diols by using atmospheric O2 as the sole oxidant and forming water as the only by-product. Aldehydes or ketones are formed with high yield and selectivity, making this eco-friendly method a competitive alternative to classical reagents.
      PubDate: 2017-07-05T12:27:52.941926-05:
      DOI: 10.1002/anie.201705934
       
  • LiTMP Trans-Metal-Trapping of Fluorinated Aromatic Molecules: A
           Comparative Study of Aluminum and Gallium Carbanion Traps
    • Authors: Ross McLellan; Marina Uzelac, Alan R. Kennedy, Eva Hevia, Robert E. Mulvey
      Pages: 9566 - 9570
      Abstract: Fluoroaromatic scaffolds pose a challenge to lithiation due to low stability of lithiated intermediates. Here we apply trans-metal-trapping (TMT) to a series of key fluorinated aromatics. In TMT, LiTMP performs the metalation, while an organometallic trap intercepts the emergent carbanion. This study contrasts the trapping abilities of iBu2AlTMP and Ga(CH2SiMe3)3, structurally mapping their TMT reactions and probing relative stabilities of metalated fluoroaromatic intermediates by NMR studies. Results show the installed Al−C(aryl) bonds are more prone to decomposition by benzyne formation and Li-F liberation, than the Ga−C(aryl) species. The latter are thus better for onward reactivity as demonstrated in cross-coupling reactions with benzoyl chloride that produce ketones.Coping with the Flu: The highly sensitive intermediates produced via lithiation of synthetically important fluorinated aromatic molecules are best stabilized for onward reactions via the gallium tris-alkyl Ga(CH2SiMe3)3 carbanion trap rather than by the related aluminum trap iBu2AlTMP.
      PubDate: 2017-07-17T06:15:29.443198-05:
      DOI: 10.1002/anie.201706064
       
  • Top-Down Fabrication of Stable Methylammonium Lead Halide Perovskite
           Nanocrystals by Employing a Mixture of Ligands as Coordinating Solvents
    • Authors: He Huang; Qi Xue, Bingkun Chen, Yuan Xiong, Julian Schneider, Chunyi Zhi, Haizheng Zhong, Andrey L. Rogach
      Pages: 9571 - 9576
      Abstract: A top-down method is demonstrated for the fabrication of CH3NH3PbBr3 and CH3NH3PbI3 perovskite nanocrystals, employing a mixture of ligands oleic acid and oleylamine as coordinating solvents. This approach avoids the use of any polar solvents, skips multiple reaction steps by employing a simple ultrasonic treatment of the perovskite precursors, and yields rather monodisperse blue-, green-, and red-emitting methylammonium lead halide nanocrystals with a high photoluminescence quantum yield (up to 72 % for the green-emitting nanocrystals) and remarkably improved stability. After discussing all relevant reaction parameters, the green-emitting CH3NH3PbBr3 nanocrystals are employed as a component of down-conversion white-light-emitting devices.Top-down synthesis of CH3NH3PbBr3 and CH3NH3PbI3 perovskite nanocrystals was achieved by employing a mixture of oleic acid and oleylamine as coordinating solvents. The method avoids polar solvents, skips multiple reaction steps by employing a simple ultrasonic treatment of the perovskite precursors, and results in perovskite nanocrystals with strong emission and improved stability.
      PubDate: 2017-07-04T00:37:48.296531-05:
      DOI: 10.1002/anie.201705595
       
  • Palladium-Catalyzed Enantioselective Narasaka–Heck Reaction/Direct C−H
           Alkylation of Arenes: Iminoarylation of Alkenes
    • Authors: Xu Bao; Qian Wang, Jieping Zhu
      Pages: 9577 - 9581
      Abstract: A palladium-catalyzed reaction of γ,δ-unsaturated oxime esters with oxadiazoles afforded dihydropyrroles in good to excellent yields through an intramolecular iminopalladation/intermolecular direct heteroarene C−H alkylation cascade. This unprecedented iminoarylation of alkenes was subsequently realized in an enantioselective manner in the presence of a chiral bidentate phosphine ligand (Synphos).Not too radical: A palladium-catalyzed reaction of γ,δ-unsaturated oxime esters with oxadiazoles afforded enantioenriched dihydropyrroles in excellent yields through an asymmetric iminopalladation/direct arene C−H alkylation cascade.
      PubDate: 2017-07-04T00:40:53.52956-05:0
      DOI: 10.1002/anie.201705641
       
  • Tricyanomethane and Its Ketenimine Tautomer: Generation from Different
           Precursors and Analysis in Solution, Argon Matrix, and as a Single Crystal
           
    • Authors: Klaus Banert; Madhu Chityala, Manfred Hagedorn, Helmut Beckers, Tony Stüker, Sebastian Riedel, Tobias Rüffer, Heinrich Lang
      Pages: 9582 - 9586
      Abstract: Solutions of azidomethylidenemalononitrile were photolyzed at low temperatures to produce the corresponding 2H-azirine and tricyanomethane, which were analyzed by low-temperature NMR spectroscopy. The latter product was also observed after short thermolysis of the azide precursor in solution whereas irradiation of the azide isolated in an argon matrix did not lead to tricyanomethane, but to unequivocal detection of the tautomeric ketenimine by IR spectroscopy for the first time. When the long-known “aquoethereal” greenish phase generated from potassium tricyanomethanide, dilute sulfuric acid, and diethyl ether was rapidly evaporated and sublimed, a mixture of hydronium tricyanomethanide and tricyanomethane was formed instead of the previously claimed ketenimine tautomer. Under special conditions of sublimation, single crystals of tricyanomethane could be isolated, which enabled the analysis of the molecular structure by X-ray diffraction.Held incommunicado in an argon matrix, a long-sought ketenimine was detected after irradiation of an appropriate vinyl azide whereas photolysis or thermolysis of the same precursor in solution led to cyanoform, which is also available as single crystals from potassium tricyanomethanide.
      PubDate: 2017-06-22T01:52:11.573959-05:
      DOI: 10.1002/anie.201704561
       
  • Protonation of Nitramines: Where Does the Proton Go'
    • Authors: Thomas Saal; Martin Rahm, Karl O. Christe, Ralf Haiges
      Pages: 9587 - 9591
      Abstract: The reactions of nitramine, N-methyl nitramine, and N,N-dimethyl nitramine with anhydrous HF and the superacids HF/MF5 (M=As, Sb) were investigated at temperatures below −40 °C. In solution, exclusive O-protonation was observed by multinuclear NMR spectroscopy. Whereas no solid product could be isolated from the neat HF solutions even at −78 °C, in the HF/MF5 systems, protonated nitramine MF6− salts were isolated for the first time as moisture-sensitive solids that decompose at temperatures above −40 °C. In the solid state, depending on the counterion, O-protonated or N-protonated cations can be formed, in accord with theoretical calculations which show that the energy differences between O-protonation and N-protonation are very small. The salts [H2N-NO2H][AsF6], [H3N-NO2][SbF6], [MeHNNO2H][SbF6], and [Me2NNO2H][SbF6] were characterized by their X-ray crystal structures.The reaction of nitramines with HF/MF5 at low temperatures resulted in the first isolation of protonated nitramine species. The salts [H2N-O2H][AsF6], [H3N-NO2][SbF6], [MeHN-NO2H][SbF6], and [Me2N-NO2H][SbF6] were isolated and characterized by X-ray diffraction. Picture: protonated nitramine, [H2NNO2]H+; white H, blue N, red O.
      PubDate: 2017-07-11T05:57:01.227037-05:
      DOI: 10.1002/anie.201705397
       
  • Isomerization, Ring Expansion, and Ring Contraction of 1,3-Diphosphete
           Complexes
    • Authors: Eva-Maria Rummel; Gábor Balázs, Veronika Heinl, Manfred Scheer
      Pages: 9592 - 9596
      Abstract: Reactions between the 1,3-diphosphete complex [Cp′′′Co(η4-P2C2tBu2)] (1) and Ag[Al{OC(CF3)3}4] (Ag[pftb]) were carried out under different conditions. In CH2Cl2, the unprecedented 1,2-diphosphete isomerization product [Ag2{Cp′′′Co(μ,η4:η1:η1-1,2-P2C2tBu2)}2{Cp′′′Co(μ,η4:η1-1,2-P2C2tBu2)}2]⋅2[pftb] (2) could be isolated. In diffusion experiments of 1 in n-hexane with Ag[pftb] in CH2Cl2, the triphosphacobaltocenium complex [Cp′′′Co(η5-P3C2tBu2)][pftb] (4) and the phosphirenylium complex [Cp′′′Co(η3-PC2tBu2)][pftb] (5) were obtained, showing a ring expansion and a ring contraction, respectively, under mild conditions. Moreover, addition of pyridine to the Ag complex 2 led to the new 1,2-diphosphete complex [Cp′′′Co(η4-1,2-P2C2tBu2)] (3). Compound 3 is also formed by thermolysis of 1, making it a promising method for this type of isomerization. 1,2-Diphosphete complexes like 3 are thermodynamically more stable but also synthetically more elusive than their 1,3-isomer counterparts.The oxidative activation of the 1,3-diphosphete complex [Cp′′′Co(P2C2tBu2)] to Ag[Al{OC(CF3)3}4] leads to new isomerization products. Thermolysis of the 1,3-derivative provides a new route to 1,2-diphosphete complexes as well as an access to unprecedented C2Pn ligands (n=1, 2, 3).
      PubDate: 2017-07-06T08:16:34.112733-05:
      DOI: 10.1002/anie.201703633
       
  • Avoiding Self-Poisoning: A Key Feature for the High Activity of Au/Mg(OH)2
           Catalysts in Continuous Low-Temperature CO Oxidation
    • Authors: Yuchen Wang; Daniel Widmann, Felix Lehnert, Dong Gu, Ferdi Schüth, R. Jürgen Behm
      Pages: 9597 - 9602
      Abstract: Au/Mg(OH)2 catalysts have been reported to be far more active in the catalytic low-temperature CO oxidation (below 0 °C) than the thoroughly investigated Au/TiO2 catalysts. Based on kinetic and in situ infrared spectroscopy (DRIFTS) measurements, we demonstrate that the comparatively weak interaction of Au/Mg(OH)2 with CO2 formed during the low-temperature reaction is the main reason for the superior catalyst performance. This feature enables rapid product desorption and hence continuous CO oxidation at temperatures well below 0 °C. At these temperatures, Au/TiO2 also catalyzes CO2 formation, but does not allow for CO2 desorption, which results in self-poisoning. At higher temperatures (above 0 °C), however, CO2 formation is rate-limiting, which results in a much higher activity for Au/TiO2 under these reaction conditions.Kinetic and in situ IR measurements show that the interaction of the catalyst surface with the CO2 formed during low-temperature CO oxidation is the crucial support effect at low temperatures (
      PubDate: 2017-07-06T07:08:08.719228-05:
      DOI: 10.1002/anie.201702178
       
  • Reversible Stabilization of Vesicles: Redox-Responsive Polymer
           Nanocontainers for Intracellular Delivery
    • Authors: Wilke C. de Vries; David Grill, Matthias Tesch, Andrea Ricker, Harald Nüsse, Jürgen Klingauf, Armido Studer, Volker Gerke, Bart Jan Ravoo
      Pages: 9603 - 9607
      Abstract: We present the self-assembly of redox-responsive polymer nanocontainers comprising a cyclodextrin vesicle core and a thin reductively cleavable polymer shell anchored via host–guest recognition on the vesicle surface. The nanocontainers are of uniform size, show high stability, and selectively respond to a mild reductive trigger as revealed by dynamic light scattering, transmission electron microscopy, atomic force microscopy, a quantitative thiol assay, and fluorescence spectroscopy. Live cell imaging experiments demonstrate a specific redox-responsive release and cytoplasmic delivery of encapsulated hydrophilic payloads, such as the pH-probe pyranine, and the fungal toxin phalloidin. Our results show the high potential of these stimulus-responsive nanocontainers for cell biological applications requiring a controlled delivery.Inside and outside the box: A new concept for the self-assembly of redox-responsive polymer nanocontainers is based on the stabilization of a cyclodextrin vesicle core by a reductively cleavable polymer shell anchored via host–guest recognition. Controlled release of cargo from the container is possible by a redox trigger.
      PubDate: 2017-06-09T01:35:39.643675-05:
      DOI: 10.1002/anie.201702620
       
  • Secondary-Structure-Driven Self-Assembly of Reactive Polypept(o)ides:
           
    • Authors: Kristina Klinker; Olga Schäfer, David Huesmann, Tobias Bauer, Leon Capelôa, Lydia Braun, Natascha Stergiou, Meike Schinnerer, Anjaneyulu Dirisala, Kanjiro Miyata, Kensuke Osada, Horacio Cabral, Kazunori Kataoka, Matthias Barz
      Pages: 9608 - 9613
      Abstract: Achieving precise control over the morphology and function of polymeric nanostructures during self-assembly remains a challenge in materials as well as biomedical science, especially when independent control over particle properties is desired. Herein, we report on nanostructures derived from amphiphilic block copolypept(o)ides by secondary-structure-directed self-assembly, presenting a strategy to adjust core polarity and function separately from particle preparation in a bioreversible manner. The peptide-inherent process of secondary-structure formation allows for the synthesis of spherical and worm-like core-cross-linked architectures from the same block copolymer, introducing a simple yet powerful approach to versatile peptide-based core–shell nanostructures.Worms and spheres: Secondary-structure-driven self-assembly allows for the synthesis of spherical and worm-like architectures with cross-linked cores from the same amphiphilic block copolypept(o)ide. By utilizing bioreversible disulfide cross-linking, the core polarity and function are adjusted independently from particle preparation, providing a versatile biocompatible nanoparticle platform.
      PubDate: 2017-07-06T08:15:58.403883-05:
      DOI: 10.1002/anie.201702624
       
  • Pyxipyrrolones: Structure Elucidation and Biosynthesis of Cytotoxic
           Myxobacterial Metabolites
    • Authors: Louise Kjaerulff; Ritesh Raju, Fabian Panter, Ullrich Scheid, Ronald Garcia, Jennifer Herrmann, Rolf Müller
      Pages: 9614 - 9618
      Abstract: In the search for new secondary metabolites from myxobacteria, a strain from the genus Pyxidicoccus was investigated. This led to the identification of a new class of natural products showing structural novelty and interesting biological activity. Isolation and structure elucidation of two analogues led to the identification of pyxipyrrolone A and B, harboring the novel 3-methylene-2,3,4,5,6,7,8,9-octahydro-1H-benzo[e]isoindol-1-one scaffold. Mosher's ester analysis combined with NMR studies allowed the determination of all stereocenters but one. Genome sequencing of the producer strain led to the identification of a putative biosynthetic gene cluster for the pyxipyrrolones. The compounds showed activity against several cancer cell lines (μm range) with pyxipyrrolone B having 2- to 11-fold higher activity than A, although they differ only by one methylene group.Down-to-earth research: Pyxipyrrolones isolated from an underexplored myxobacterium (Pyxidicoccus sp.) are shown to have structural novelty and rather selective cytotoxic activity in the micromolar range. A trans-AT PKS-NRPS hybrid gene cluster is outlined along with a proposal for the biosynthesis of pyxipyrrolones.
      PubDate: 2017-07-05T12:25:37.118725-05:
      DOI: 10.1002/anie.201704790
       
  • Tetranitromethane: A Nightmare of Molecular Flexibility in the Gaseous and
           Solid States
    • Authors: Yury V. Vishnevskiy; Denis S. Tikhonov, Jan Schwabedissen, Hans-Georg Stammler, Richard Moll, Burkhard Krumm, Thomas M. Klapötke, Norbert W. Mitzel
      Pages: 9619 - 9623
      Abstract: After numerous attempts over the last seven decades to obtain a structure for the simple, highly symmetric molecule tetranitromethane (C(NO2)4, TNM) that is consistent with results from diffraction experiments and spectroscopic analysis, the structure has now been determined in the gas phase and the solid state. For the gas phase, a new approach based on a four-dimensional dynamic model for describing the correlated torsional dynamics of the four C−NO2 units was necessary to describe the experimental gas-phase electron diffraction intensities. A model describing a highly disordered high-temperature crystalline phase was also established, and the structure of an ordered low-temperature phase was determined by X-ray diffraction. TNM is a prime example of molecular flexibility, bringing structural methods to the limits of their applicability.Highly dynamic is the structural behavior of tetranitromethane, C(NO2)4. After more than half a century of investigations, its structure in the gas phase was solved through the development and application of a new approach for the dynamic modeling of electron diffraction data while the refinement of single-crystal X-ray diffraction data has now been successful for two phases.
      PubDate: 2017-06-19T02:40:47.479097-05:
      DOI: 10.1002/anie.201704396
       
  • Inside Back Cover: Reversible Stabilization of Vesicles: Redox-Responsive
           Polymer Nanocontainers for Intracellular Delivery (Angew. Chem. Int. Ed.
           32/2017)
    • Authors: Wilke C. de Vries; David Grill, Matthias Tesch, Andrea Ricker, Harald Nüsse, Jürgen Klingauf, Armido Studer, Volker Gerke, Bart Jan Ravoo
      Pages: 9625 - 9625
      Abstract: Redox-responsive nanocontainers are prepared by the supramolecular assembly of a responsive polymer shell around a cyclodextrin vesicle core. In their Communication on page 9603 ff., A. Studer, V. Gerke, B. J. Ravoo, and co-workers demonstrate that vesicles stabilized with a disulfide-crosslinked polymer shell can encapsulate functional payloads and release them on encountering a reductive trigger. Cell experiments visualize the release of the toxin phalloidin inside the reducing intracellular microenvironment and its binding to actin filaments.
      PubDate: 2017-06-16T03:15:57.835961-05:
      DOI: 10.1002/anie.201705754
       
  • Back Cover: A T-Shaped Nickel(I) Metalloradical Species (Angew. Chem. Int.
           Ed. 32/2017)
    • Authors: Changho Yoo; Yunho Lee
      Pages: 9626 - 9626
      Abstract: A T-shaped nickel(I) metalloradical species that is prepared by using a rigid acridane-based PNP pincer ligand displays novel open-shell reactivity. In their Communication on page 9502 ff., Y. Lee and C. Yoo show that because of its sterically exposed half-filled orbital, this d9 metalloradical species shows unique reactivity and can be used for the homolytic cleavage of various σ-bonds, such as H−H, N−N, and C−C bonds, in a binuclear two-electron process.
      PubDate: 2017-06-20T06:57:35.217542-05:
      DOI: 10.1002/anie.201705762
       
 
 
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