for Journals by Title or ISSN
for Articles by Keywords
help
  Subjects -> CHEMISTRY (Total: 841 journals)
    - ANALYTICAL CHEMISTRY (50 journals)
    - CHEMISTRY (593 journals)
    - CRYSTALLOGRAPHY (21 journals)
    - ELECTROCHEMISTRY (25 journals)
    - INORGANIC CHEMISTRY (41 journals)
    - ORGANIC CHEMISTRY (44 journals)
    - PHYSICAL CHEMISTRY (67 journals)

CHEMISTRY (593 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: 34)
ACS Chemical Neuroscience     Full-text available via subscription   (Followers: 18)
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: 236)
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: 55)
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 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: 15)
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: 68)
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: 14)
American Mineralogist     Hybrid Journal   (Followers: 14)
Analyst     Full-text available via subscription   (Followers: 40)
Angewandte Chemie     Hybrid Journal   (Followers: 224)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 213)
Annales UMCS, Chemia     Open Access   (Followers: 1)
Annals of Clinical Chemistry and Laboratory Medicine     Open Access   (Followers: 3)
Annual Reports in Computational Chemistry     Full-text available via subscription   (Followers: 3)
Annual Reports Section A (Inorganic Chemistry)     Full-text available via subscription   (Followers: 4)
Annual Reports Section B (Organic Chemistry)     Full-text available via subscription   (Followers: 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: 15)
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: 4)
Australian Journal of Chemistry     Hybrid Journal   (Followers: 7)
Autophagy     Hybrid Journal   (Followers: 2)
Avances en Quimica     Open Access   (Followers: 1)
Biochemical Pharmacology     Hybrid Journal   (Followers: 10)
Biochemistry     Full-text available via subscription   (Followers: 295)
Biochemistry Insights     Open Access   (Followers: 6)
Biochemistry Research International     Open Access   (Followers: 6)
BioChip Journal     Hybrid Journal  
Bioinorganic Chemistry and Applications     Open Access   (Followers: 9)
Bioinspired Materials     Open Access   (Followers: 5)
Biointerface Research in Applied Chemistry     Open Access   (Followers: 2)
Biointerphases     Open Access   (Followers: 1)
Biology, Medicine, & Natural Product Chemistry     Open Access   (Followers: 1)
Biomacromolecules     Full-text available via subscription   (Followers: 19)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 10)
Biomedical Chromatography     Hybrid Journal   (Followers: 6)
Biomolecular NMR Assignments     Hybrid Journal   (Followers: 3)
BioNanoScience     Partially Free   (Followers: 5)
Bioorganic & Medicinal Chemistry     Hybrid Journal   (Followers: 120)
Bioorganic & Medicinal Chemistry Letters     Hybrid Journal   (Followers: 97)
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: 3)
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: 66)
Catalysis for Sustainable Energy     Open Access   (Followers: 7)
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: 8)
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: 13)
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: 177)
Chemical Science     Open Access   (Followers: 22)
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: 57)
Chemie-Ingenieur-Technik (Cit)     Hybrid Journal   (Followers: 26)
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: 142)
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: 44)
Chemistry of Materials     Full-text available via subscription   (Followers: 260)
Chemistry of Natural Compounds     Hybrid Journal   (Followers: 9)
Chemistry World     Full-text available via subscription   (Followers: 22)
Chemistry-Didactics-Ecology-Metrology     Open Access   (Followers: 1)
ChemistryOpen     Open Access   (Followers: 2)
Chemkon - Chemie Konkret, Forum Fuer Unterricht Und Didaktik     Hybrid Journal  
Chemoecology     Hybrid Journal   (Followers: 3)
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)
Clay Minerals     Full-text available via subscription   (Followers: 10)
Cogent Chemistry     Open Access  
Colloid and Interface Science Communications     Open Access  
Colloid and Polymer Science     Hybrid Journal   (Followers: 10)
Colloids and Surfaces B: Biointerfaces     Hybrid Journal   (Followers: 7)
Combinatorial Chemistry & High Throughput Screening     Hybrid Journal   (Followers: 4)
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   (Followers: 1)
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: 12)
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: 58)
Dalton Transactions     Full-text available via subscription   (Followers: 22)
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: 8)
Environmental Chemistry Letters     Hybrid Journal   (Followers: 4)
Environmental Science & Technology Letters     Full-text available via subscription   (Followers: 5)
Environmental Science : Nano     Partially Free   (Followers: 1)
Environmental Toxicology & Chemistry     Hybrid Journal   (Followers: 17)

        1 2 3 | Last

Journal Cover Angewandte Chemie
  [224 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0044-8249 - ISSN (Online) 1521-3757
   Published by John Wiley and Sons Homepage  [1577 journals]
  • An av-RGD integrin inhibitor toolbox: drug discovery insight, challenges
           and opportunities
    • Authors: Richard Hatley; Simon Macdonald, Robert Slack, Joelle Le, Steve Ludbrook, Pauline Lukey
      Abstract: There is a requirement for efficacious and safe medicines to treat diseases with high unmet need. The resurgence in av RGD integrin inhibitor drug discovery is poised to contribute to this requirement. However, drug discovery in the av integrin space is notoriously difficult due to the receptors being structurally very similar as well as the polar zwitterionic nature of the pharmacophore. This review aims to guide drug discovery research in this field through an av inhibitor toolbox, consisting of small molecules and antibodies. Small molecule av tool compounds with extended profiles in avb1, 3, 5, 6 and 8 cell adhesion assays, with key physicochemical properties, have been collated to assist in the selection of the right tool for the right experiment. This should also facilitate an understanding of partial selectivity profiles of compounds generated in different assays across research institutions. Prospects for further av integrin research and the critical importance of target validation are discussed, where increased knowledge of the selectivity for individual RGD v integrins is key. Insights into the design of small molecule RGD chemotypes for topical or oral administration are provided and clinical findings on advanced molecules are examined.
      PubDate: 2017-09-25T03:21:33.857824-05:
      DOI: 10.1002/ange.201707948
       
  • α-Carbonylkationen in Sulfoxid-vermittelten oxidativen Cyclisierungen
    • Authors: Tobias Stopka; Meike Niggemann, Nuno Maulide
      Abstract: Ausgehend von einfachen disubstituierten Alkinen gelang die selektive metallfreie Erzeugung von α-Carbonylkationen durch Addition eines Sulfoxids an ein Vinylkation. Die hohe Reaktivität dieser α-Carbonylkationen konnte genutzt werden, um Hydrid- und Kohlenstoff-Verschiebungen mit ungewöhnlicher Selektivität zu ermöglichen. Hierdurch konnten, basierend auf einfachen Vorläuferverbindungen, in einem Schritt komplexe und sterisch gehinderte tertiäre und vollständig substituierte, quartäre Kohlenstoffzentren aufgebaut werden. Mechanistische Untersuchungen stützen das Auftreten des Schlüsselintermediats und erlauben einfache Vorhersagen über die Wanderungstendenz unterschiedlicher Substituenten.Vereinte Kräfte ermöglichen die säurekatalysierte Umwandlung von Vinylkationen in α-Carbonylkationen, deren hohe Reaktivität zu Hydrid- und Kohlenstoffverschiebungen mit ungewöhnlichen Selektivitäten führt. Mechanistische Analysen bestätigen das Auftreten der beschriebenen Intermediate und erlauben eine allgemeine Aussage über die Wanderungstendenz unterschiedlicher Substituenten.
      PubDate: 2017-09-25T01:51:20.188386-05:
      DOI: 10.1002/ange.201705964
       
  • Black Phosphorus Quantum Dots Used for Boosting Light Harvesting in
           Organic Photovoltaics
    • Authors: Shenghua Liu; Shenghuang Lin, Peng You, Charles Surya, Daniel Lau, Feng Yan
      Abstract: Although organic photovoltaic devices (OPVs) have been investigated for more than two decades, the power conversion efficiencies of OPVs are much lower than those of inorganic or perovskite solar cells. One effective approach to improve the efficiency of OPVs is to introduce additives to enhance light harvesting as well as charge transportation in the devices. Here, black phosphorus quantum dots (BPQDs) are introduced in OPVs as an additive. By adding 0.055 wt % BPQDs relative to the polymer donors in the OPVs, the device efficiencies can be dramatically improved for more than 10 %. The weight percentage is much lower than that of any other additive used in OPVs before, which is mainly due to the two-dimentional structure as well as the strong broadband light absorption and scattering of the BPQDs. This work paves a way for using two-dimentional quantum dots in OPVs as a cost-effective approach to enhance device efficiencies.Starke Lichtabsorption: Die Wirkungsgrade organischer Photovoltaikeinheiten wurden durch Einführung von Quantenpunkten aus schwarzem Phosphor (BPQDs; 0.055 Gew.-% relativ zu den Donorpolymeren) verbessert. Der Effekt wird der starken Lichtabsorption und der zweidimensionalen Struktur der BPQDs zugeschrieben. Ein ausgeprägter Größeneffekt der BPQDs auf die Leistungssteigerung wird beobachtet.
      PubDate: 2017-09-25T01:51:02.27211-05:0
      DOI: 10.1002/ange.201707510
       
  • Practical Chemical Synthesis of Atypical Ubiquitin Chains by Using an
           Isopeptide-linked Ub Isomer
    • Authors: Shan Tang; Lu-Jun Liang, Yan-Yan Si, Shuai Gao, Jia-Xing Wang, Jun Liang, Ziqing Mei, Ji-Shen Zheng, Lei Liu
      Abstract: Chemical ubiquitination is an effective approach for accessing structurally defined, atypical ubiquitin (Ub) chains that are difficult to prepare by other techniques. Herein, we describe a strategy that uses a readily accessible premade isopeptide-linked 76-mer (isoUb), which has an N-terminal Cys and a C-terminal hydrazide, as the key building block to assemble atypical Ub chains in a modular fashion. This method avoids the use of auxiliary-modified Lys and instead employs the canonical and therefore more robust Cys-based native chemical ligation technique. The efficiency and capacity of this isoUb-based strategy is exemplified by the cost-effective synthesis of several linkage- and length-defined atypical Ub chains, including K27-linked tetra-Ub and K11/K48-branched tri-, tetra-, penta-, and hexa-Ubs.Verkettung ungewöhnlicher Ubiquitine: Durch chemische Proteinsynthese wurden ungewöhnliche homogene Ubiquitin(Ub)-Ketten erzeugt, die auf anderem Weg schwer zugänglich sind. Ein vorgebildetes Isopeptid-verknüpftes 76-mer (isoUb) mit N-terminalem Cys und C-terminaler Hydrazidfunktion ist der entscheidende Baustein dieser Ligationsmethode.
      PubDate: 2017-09-25T01:50:50.477646-05:
      DOI: 10.1002/ange.201708067
       
  • A Zwitterionic, 10 pi Aromatic Hemisphere
    • Authors: Nema Hafezi; Wondimagegn T Shewa, James C Fettinger, Mark Mascal
      Abstract: A new concept in anionic 10 pi aromaticity is described by the embedding of a compensating charge within an aromatic cyclononatetraenide ring by the symmetric interposition of a methylammonium bridge. This is accomplished by the alkylation of azatriquinacene to give a quaternary ammonium salt, followed by oxidation to the tetraene and final deprotonation. The resulting zwitterion is a stable [9]annulene with strong aromaticity as shown by its degree of C-C bond equalization and a nucleus independent chemical shift value lower than that of benzene. The solid-state structure shows an eclipsed stacking motif with the electron poor ammonium methyl groups occupying the electron rich cavity of the aromatic bowl.
      PubDate: 2017-09-24T21:20:57.224261-05:
      DOI: 10.1002/ange.201708521
       
  • Photoluminescence Lifetime Imaging of Newly Synthesized Proteins in Living
           Cells with Iridium-alkyne Probe
    • Authors: Xinrong Zhang; Jinyu Wang, Jie Xue, Zihe Yan, Sichun Zhang, Juan Qiao
      Abstract: Designing probes for real-time imaging of dynamic processes in living cells is a continual challenge. Herein, a novel near-infrared photoluminescence probe with long lifetime was exploited for photoluminescence lifetime imaging (PLIM) based on an Iridium-alkyne complex. This probe offers benefits of desirable deep-red to NIR emission, long stokes shift, excellent cell penetration, low cytotoxicity and good resistance to photobleaching. To the best of our knowledge this is the first PLIM probe applicable to click reaction of Cu(I)-catalysed azide-alkyne cycloaddition with remarkable lifetime shifts of 414 ns before and after click reaction. The approach fully eliminates the background interference and well distinguishes the reacted probes from the unreacted probes, thus enabling the wash-free imaging of the newly synthesized proteins in single living cells. Based on the unique properties of the Iridium complexes, it is anticipated to be applied in more important issues in living cells.
      PubDate: 2017-09-23T06:21:04.652052-05:
      DOI: 10.1002/ange.201708566
       
  • Switchable Hydrolase Based on Reversible Formation of Supramolecular
           Catalytic Site Using a Self-Assembling Peptide
    • Authors: Rein V Ulijn; Chunqiu Zhang, Ramim Shafi, Ayala Lampel, Douglas MacPherson, Charalampas Pappas, Vishal Narang, Tong Wang, Charles Madarelli
      Abstract: The reversible regulation of catalytic activity is a feature found in natural enzymes which is not commonly observed in artificial catalytic systems. Here, we fabricate an artificial hydrolase with pH-switchable activity, achieved by introducing a catalytic histidine residue at the terminus of a pH-responsive peptide. The peptide exhibits a conformational transition from random coil to β-sheet by changing the pH from acidic to alkaline. The β-sheet self-assembles to form long fibrils with the hydrophobic edge and histidine residues extending in an ordered array as the catalytic microenvironment, which shows significant esterase activity. Catalytic activity can be reversible switched by pH-induced assembly/ disassembles of the fibrils into random coils. At higher concentrations, the peptide forms a hydrogel which is also catalytically active and maintains its reversible (de-)activation.
      PubDate: 2017-09-22T23:25:50.281099-05:
      DOI: 10.1002/ange.201708036
       
  • Allosteric Tuning of Caspase-7: a Fragment-Based Drug Discovery Approach
    • Authors: Nicholas Robert Vance; Michael Ashley Spies, Lokesh Gakhar
      Abstract: The caspase family of cysteine proteases are highly sought after drug targets due to their essential roles in apoptosis, proliferation and inflammation pathways. High throughput screening efforts to discover inhibitors have gained little traction. Fragment-based screening has emerged as a powerful tool for the discovery of innovative drug leads. This methodology has become a central facet of drug discovery campaigns in the pharmaceutical industry and academia. A fragment-based drug discovery campaign against human caspase-7 resulted in the discovery of a novel series of allosteric inhibitors. An X-ray crystal structure of caspase-7 bound to a fragment hit, and a thorough kinetic characterization of a zymogenic form of the enzyme are used to investigate the allosteric mechanism of inhibition. This work further advances our understanding of the mechanisms of allosteric control of this class of pharmaceutically relevant enzymes, and provides a new path forward for drug discovery efforts.
      PubDate: 2017-09-22T23:25:25.37387-05:0
      DOI: 10.1002/ange.201706959
       
  • Adenylation Activity of Carboxylic Acid Reductases Enables the Synthesis
           of Amides
    • Authors: Sabine Flitsch; Alexander Wood, Nicholas Weise, Joseph Frampton, Mark Dunstan, Michael Hollas, Sasha Derrington, Richard LLoyd, Daniela Quaglia, Fabio Parmeggiani, David Leys, Nicholas Turner
      Abstract: Carboxylic acid reductases (CARs) catalyze the reduction of a broad range of carboxylic acids to aldehydes using the co-factors ATP and NADPH, and have become attractive biocatalysts for organic synthesis. Here we exploit our mechanistic understanding of CARs to expand their reaction scope, generating biocatalysts for amide bond formation from carboxylic acid and amine. After reaction engineering, CARs were found to have amidation activity for various acids and amines. Optimization of reaction conditions with respect to pH and temperature allowed for the synthesis of the anticonvulsant ilepcimide with up to 96% conversion. Mechanistic studies using site-directed mutagenesis suggest that following initial enzymatic adenylation of substrates, amidation of the carboxylic acid proceeds via direct reaction of the acyl adenylate with amine nucleophiles.
      PubDate: 2017-09-22T15:25:52.837202-05:
      DOI: 10.1002/ange.201707918
       
  • [SnBi3]5- − a carbonate analogue formed in solution and comprising
           exclusively metal atoms
    • Authors: Thomas Friedrich Fässler; Kerstin Mayer, Jasmin Dums, Wilhelm Klein
      Abstract: The new [SnBi3]5- polyanion is obtained by the reaction of K3Bi2 with K4Sn9 or K12Sn17 in liquid ammonia. The anion is iso(valence)electronic with and structurally analogous to the carbonate ion. Despite the high negative charge of the anion, the Sn-Bi bond lengths range between single and double bonds. Quantum-chemical calculations at a DFT-PBE0/def2-TZVPP/COSMO level of theory reveal that the partial double bond character between the heavy main group atoms Bi and Sn originates from a delocalized π-electronic system. The structure of the anion is determined by single crystal X-ray diffraction analyses of the compounds K5[SnBi3](NH3)9 (1) and K9[K(18-crown-6)][SnBi3]2(NH3)15 (2). The [SnBi3]5- unit is the first example of a carbonate-like anion obtained from solution, and it consists exclusively of metal atoms.
      PubDate: 2017-09-22T14:20:22.759405-05:
      DOI: 10.1002/ange.201709700
       
  • Electronic delocalization in two and three dimensions: differential
           aggregation in indium 'metalloid' clusters
    • Authors: Simon Aldridge; Andrey Protchenko, Juan Urbano, Joseph Abdalla, Jesus Campos, Dragoslav Vidovic, Andrew Schwarz, Matthew Blake, Philip Mountford, Cameron Jones
      Abstract: Reduction of indium boryl precursors to give two- and three-dimensional M-M bonded networks is influenced by the choice of supporting ligand. While the unprecedented nanoscale cluster [In68(boryl)12]- (with an In12@In44@In12(boryl)12 concentric structure), can be isolated from the potassium reduction of a bis(boryl)indium(III) chloride precursor, analogous reduction of the corresponding (benzamidinate)InIIIBr(boryl) system gives a near-planar (and weakly aromatic) tetranuclear [In4(boryl)4]2- system.
      PubDate: 2017-09-22T13:20:59.391672-05:
      DOI: 10.1002/ange.201708496
       
  • Visible Light-Induced Room Temperature Heck Reaction of Functionalized
           Alkyl Halides with Vinyl Arenes/Heteroarenes
    • Authors: Vladimir Gevorgyan; Daria Kurandina, Marvin Parasram
      Abstract: The first visible light-induced Pd-catalyzed Heck reaction of α-heteroatom substituted alkyl iodides and -bromides with vinyl arenes/heteroarenes has been developed. This transformation efficiently proceeds at room temperature and enables synthesis of valuable functionalized allylic systems, such as allylic silanes, -boronates, -germanes, -stannanes, -pivalates, -phosphonates, -phthalimides, and -tosylates from the corresponding α-substituted methyl iodides. Notably, synthesis of the latter substrates failed under existing thermally induced Pd-catalyzed conditions, which highlights the importance of visible light for this transformation.
      PubDate: 2017-09-22T13:20:29.431314-05:
      DOI: 10.1002/ange.201706554
       
  • Anti-freezing, conductive self-healing organohydrogels with stable
           strain-sensitivity at subzero temperatures
    • Authors: Qinfeng Rong; Wenwei Lei, Lie Chen, Yongai Yin, Jiajia Zhou, Mingjie Liu
      Abstract: Conductive hydrogels emerge as a fascinating class of stretchable conductive materials that are important for various applications. However, water-based conductive hydrogels inevitably lose elasticity and conductivity at subzero temperatures, which severely limits their practical applications at low temperatures. Here we report anti-freezing conductive organohydrogels by using an H2O/ethylene glycol binary solvent as dispersion medium. Owing to the freezing tolerance of the binary solvent, our organohydrogels exhibit stable flexibility and strain-sensitivity in the temperature range from -55.0 to 44.6 °C. Meanwhile, the solvent molecules could form hydrogen bonds with polyvinyl alcohol (PVA) chains and induce the crystallization of PVA, greatly improve the mechanical strength of the organohydrogels. Furthermore, the non-covalent crosslinks endow the conductive organohydrogels with intriguing remoldability and self-healing capability, which are important for practical applications.
      PubDate: 2017-09-22T11:28:10.285241-05:
      DOI: 10.1002/ange.201708614
       
  • Programmable Glycan-Presentation of Glycodendrimersomes and Cells React
           with Engineered Human Lectins to Unveil Cell-Surface Sugar Functionality
    • Authors: Jürgen Kopitz; Qi Xiao, Anna-Kristin Ludwig, Antonio Romero, Malwina Michalak, Samuel E Sherman, Xuhao Zhou, Cody Dazen, Sabine Vértesy, Herbert Kaltner, Michael L Klein, Hans-Joachim Gabius, Virgil Percec
      Abstract: Chemical and biological tools are harnessed to investigate the impact of spatial factors for functional pairing of human lectins with counterreceptors. The homodimeric adhesion/growth-regulatory galectin-1 and a set of covalently linked homo-oligomers from di- to tetramers serve as proof-of-principle test cases. Glycodendrimersomes provide a versatile and sensitive diagnostic platform to reveal thresholds for ligand density and protein concentration in aggregation assays (trans-activity), irrespective of linker length between lectin domains. Monitoring the affinity of cell binding and ensuing tumor growth inhibition reveal the linker length to be a bidirectional switch for cis-activity. The discovery that two aspects of lectin functionality (trans- versus cis- activity) respond non-uniformly to a structural change underscores the power of combining synthetic and biological tools to advance understanding of cell-surface sugar functionality.
      PubDate: 2017-09-22T10:21:35.245314-05:
      DOI: 10.1002/ange.201708237
       
  • The Surface of Ice is Like Supercooled Liquid Water
    • Authors: Wilbert J. Smit; Huib J. Bakker
      Abstract: The surface of ice has been reported to be disordered at temperatures well below the bulk melting point. However, the precise nature of this disorder has been a topic of intense debate. Here, we study the molecular properties of the surface of ice as a function of temperatures using heterodyne-detected sum-frequency generation spectroscopy. We observe that, down to 245 K, the spectral response of the surface of ice contains a component that is indistinguishable from supercooled liquid water.
      PubDate: 2017-09-22T08:20:37.140242-05:
      DOI: 10.1002/ange.201707530
       
  • Lanthanide-Coordinated Semiconducting Polymer Dots that Function for both
           Flow Cytometry and Mass Cytometry
    • Authors: Daniel T. Chiu; Xu Wu, Quinn Degottardi, I-Che Wu, Jiangbo Yu, Li Wu, Fangmao Ye, Chun-Ting Kuo, William W Kwok
      Abstract: Simultaneous monitoring of biomarkers as well as single-cell analyses based on flow cytometry and mass cytometry are important for investigations of disease mechanisms, drug discovery, and signaling-network studies. Flow cytometry and mass cytometry are complementary to each other; however, probes that can satisfy all the requirements for these two advanced technologies are limited. In this study, we report a probe of lanthanide-coordinated semiconducting polymer dots (Pdots), which possess fluorescence and mass signals. We demonstrated the usage of this dual-functionality probe for both flow cytometry and mass cytometry in a mimetic cell mixture and human peripheral blood mononuclear cells as model systems. The probes not only offer high fluorescence signal for use in flow cytometry, but also show better performance in mass cytometry than the commercially available counterparts.
      PubDate: 2017-09-22T08:20:27.841838-05:
      DOI: 10.1002/ange.201708463
       
  • Mesoporous Semimetallic Conductors: Structural and Electronic Properties
           of Cobalt Phosphide Systems
    • Authors: Malay Pramanik; Satoshi Tominaka, Zhong-Li Wang, Toshiaki Takei, Yusuke Yamauchi
      Abstract: Mesoporous cobalt phosphide (meso-CoP) was prepared by the phosphorization of ordered mesoporous cobalt oxide (meso-Co3O4). The electrical conductivity of meso-CoP is 37 times higher than that of nonporous CoP, and it displays semimetallic behavior with a negligibly small activation energy of 26 meV at temperatures below 296 K. Above this temperature, only materials with mesopores underwent a change in conductivity from semimetallic to semiconducting behavior. These properties were attributed to the coexistence of nanocrystalline Co2P phases. The poor crystallinity of mesoporous materials has often been considered to be a problem but this example clearly shows its positive aspects. The concept introduced here should thus lead to new routes for the synthesis of materials with high electronic conductivity.Durch das Phosphoridieren von geordnetem mesoporösem Cobaltoxid wurde mesoporöses Cobaltphosphid erhalten. Seine elektrische Leitfähigkeit ist 37-mal höher als die von nicht porösem CoP, und es zeigt halbmetallisches Verhalten mit einer sehr geringen Aktivierungsenergie von 26 meV unterhalb von 296 K. Diese Eigenschaften wurden auf die Koexistenz nanokristalliner Co2P-Phasen zurückgeführt.
      PubDate: 2017-09-22T06:31:11.635982-05:
      DOI: 10.1002/ange.201707878
       
  • Spin Changes Accompany Ultrafast Structural Interconversion in the Ground
           State of a Cobalt Nitrosyl Complex
    • Authors: Hugo J. B. Marroux; Basile F. E. Curchod, Charly A. Faradji, Timothy A. Shuttleworth, Hazel A. Sparkes, Paul G. Pringle, Andrew J. Orr-Ewing
      Abstract: Ultrafast, reversible intersystem crossing (ISC) is reported under ambient conditions for the electronic ground state of the pentacoordinate cobalt nitrosyl complexes, [CoX2(NO)(PMePh2)2] (X=Cl, Br), in solution. ISCs on such short timescales are more typically observed in electronically excited states reached by absorption of ultraviolet or visible light. Singlet and triplet electron spin states of the complex, corresponding to two different isomers, are populated at room temperature, and the two isomers exchange on a timescale of a few picoseconds. Ultrafast two-dimensional infrared spectroscopy observes the change in wavenumber of the NO ligand band accompanying the isomerization and associated ISC on the (spin) adiabatic ground potential energy surface. Comparison of the dynamics of the chloro- and bromo-complexes shows that inertial effects of the ligand motion have a greater effect than spin–orbit coupling on determining the forward and reverse isomerization and ISC rates.Intersystem-Crossing im Grundzustand wird für einen Cobalt-Nitrosylkomplex auf ultraschneller Zeitskala nachgewiesen. Die Dynamik des Elektronenspinübergangs wird mit 2DIR-Spektroskopie der mit den Elektronenzuständen assoziierten Kernschwingungsfrequenzen verfolgt. Vergleiche der Spinaustauschraten in zwei Halido-substituierten Komplexen belegen, dass Trägheitseffekte Spin-Bahn-Kopplungseffekte des Liganden überwiegen.
      PubDate: 2017-09-22T06:31:02.644499-05:
      DOI: 10.1002/ange.201707508
       
  • H2S-Activable MOF Nanoparticle Photosensitizer for Effective Photodynamic
           Therapy against Cancer with Controllable Singlet-Oxygen Release
    • Authors: Yu Ma; Xiangyuan Li, Aijie Li, Peng Yang, Caiyun Zhang, Bo Tang
      Abstract: Photodynamic therapy (PDT) has emerged as an important minimally invasive tumor treatment technology. The search for an effective photosensitizer to realize selective cancer treatment has become one of the major foci in recent developments of PDT technology. Controllable singlet-oxygen release based on specific cancer-associated events, as another major layer of selectivity mode, has attracted great attention in recent years. Here, for the first time, we demonstrated that a novel mixed-metal metal–organic framework nanoparticle (MOF NP) photosensitizer can be activated by a hydrogen sulfide (H2S) signaling molecule in a specific tumor microenvironment for PDT against cancer with controllable singlet-oxygen release in living cells. The effective removal of tumors in vivo further confirmed the satisfactory treatment effect of the MOF NP photosensitizer.Selektive Krebsbehandlung: Ein gemischtmetallischer MOF-Nanopartikelphotosensibilisator wird durch ein H2S-Signalmolekül in einer spezifischen Tumormikroumgebung durch steuerbare Freisetzung von Singulett-Sauerstoff für die photodynamische Therapie aktiviert. Die effektive Tumorbeseitigung in vivo bestätigt den zufriedenstellenden Behandlungseffekt des Photosensibilisators.
      PubDate: 2017-09-22T06:26:02.002853-05:
      DOI: 10.1002/ange.201708005
       
  • Preise der Royal Australian Chemical Institute Divisions/
    • PubDate: 2017-09-22T06:25:39.561988-05:
      DOI: 10.1002/ange.201709209
       
  • Valence Interconversion of Octahedral Nickel(II/III/IV) Centers
    • Authors: Masahiro Kouno; Nobuto Yoshinari, Naoto Kuwamura, Kohei Yamagami, Akira Sekiyama, Mitsutaka Okumura, Takumi Konno
      Abstract: Three oxidation states (+2, +3, +4) of an octahedral nickel center were stabilized in a newly prepared RhNiRh trinuclear complex, [Ni{Rh(apt)3}2]n+ (apt=3- aminopropanethiolate), in which the nickel center was bound by six thiolato donors sourced from two redox-inert fac-[RhIII(apt)3] octahedral units. The three oxidation states of the octahedral nickel center were fully characterized by single-crystal X-ray crystallography, as well as spectroscopic, electrochemical, and magnetic measurements; all three were interconvertible, and the conversion was accompanied by changes in color, magnetism, and Jahn–Teller distortion.Farbige Nickelchemie: Eine Reihe S-verbrückter RhNiRh-Dreikernkomplexe mit oktaedrisch umgebenem Nickelzentrum in drei verschiedenen Oxidationsstufen (+2, +3, +4) wurde isoliert. Wechsel der Oxidationsstufe gehen mit Änderungen von Farbe, magnetischen Eigenschaften und geometrischen Jahn-Teller-Verzerrungen einher, die dreikernige Gesamtstruktur bleibt aber erhalten.
      PubDate: 2017-09-22T06:25:32.259731-05:
      DOI: 10.1002/ange.201708169
       
  • Evaporation-Directed Crack-Patterning of Metal-Organic Framework Colloidal
           Films and their Application as Photonic Sensors
    • Authors: Olivier Dalstein; Effrosyni Gkaniatsou, Clemence Sicard, Ozlem Sel, Hubert Perrot, Christian Serre, Cedric Boissiere, Marco Faustini
      Abstract: Herein, a straightforward crack-patterning method is reported allowing the direct formation of periodic cracks in Metal-Organic Framework nanoparticles films during dip-coating deposition. The crack propagation and periodicity can be easily tailored by controlling the evaporation front and the withdrawal speed. Several MOF patterned films can be fabricated on large surfaces and on several substrates (flat, curved or flexible) including the inner surface of a tube, not achievable by other lithographic techniques. We demonstrate that the periodic cracked arrays diffract light and, thanks to the MOF sorption properties, photonic vapor sensors are fabricated. A new concept of "in-tube", MOF-based diffraction grating sensors is proposed with outstanding sensitivity that can be easily tuned "on-demand" as function of the desired detection range.
      PubDate: 2017-09-22T06:21:07.892252-05:
      DOI: 10.1002/ange.201706745
       
  • Silver Makes Better Electrical Contacts to Thiol-terminated Silanes than
           Gold
    • Authors: Haixing Li; Timothy Su, María Camarasa-Gómez, Daniel Hernangómez-Pérez, Simon Henn, Vladislav Pokorný, Caravaggio Dante Caniglia, Michael Inkpen, Richard Korytár, Michael Steigerwald, Colin Nuckolls, Ferdinand Evers, Latha Venkataraman
      Abstract: We report that the single molecule junction conductance of thiol-terminated silanes with Ag electrodes are higher than the conductance of those formed with Au electrodes. These results are in contrast to the trends in the metal work function Φ(Ag) < Φ(Au). As such, one would expect a better alignment of the Au Fermi level to the molecular orbital of silane that mediates charge transport. Additionally, this conductance trend is reversed when we replace the thiols with amines, highlighting the impact of metal—S covalent and metal—NH2 dative bonds in controlling the molecular conductance. Density functional theory calculations elucidate the crucial role of the chemical linkers in determining the level alignment when molecules are attached to different metal contacts. We also demonstrate that conductance of thiol terminated silanes with Pt electrodes is lower than the ones formed with Au and Ag electrodes again in contrast to what one would expect from trends in the metal work-functions.
      PubDate: 2017-09-22T06:20:20.329067-05:
      DOI: 10.1002/ange.201708524
       
  • Formation of Stable Tin Perovskites Co-crystallized with Three Halides for
           Carbon-Based Mesoscopic Lead-Free Perovskite Solar Cells
    • Authors: Cheng-Min Tsai; Nayantara Mohanta, Chi-Yung Wang, Yu-Pei Lin, Yaw-Wen Yang, Chien-Lung Wang, Chen-Hsiung Hung, Eric Wei-Guang Diau
      Abstract: We synthesized and characterized methylammonium (MA) mixed tri-halide tin perovskites (MASnIBr2−xClx) for carbon-based mesoscopic solar cells free of lead and hole-transporting layers. Varied SnCl2/SnBr2 ratios yielded tin perovskites with three halides (I, Br, and Cl) co-crystallized inside the tin-perovskite. When the SnCl2 proportion was ≥50 % (x≥1), phase separation occurred to give MASnI3−yBry and MASnCl3−zBrz in the stoichiometric proportions of their precursors, confirmed by XRD. A device with MASnIBr1.8Cl0.2 (SnCl2=10 %) showed the best photovoltaic performance: JSC=14.0 mA cm−2, VOC=380 mV, FF=0.573, and PCE=3.1 %, and long-term stability. Electrochemical impedance spectra (EIS) show superior charge recombination and dielectric relaxation properties for the MASnIBr1.8Cl0.2 cell. Transient PL decays showed the intrinsic problem of tin-based perovskites with average lifetimes less than 100 ps.Da ist Zinn drin: Stabile Zinn-Perowskite, die drei verschiedene Halogenide enthalten (I, Br und Cl), wurden durch Umsetzung von Methylammonium(MA)-Iodid mit SnCl2/SnBr2-Mischungen in Verhältnissen ≤25:75 synthetisiert. Die beste Solarzelle mit kohlenstoffbasierter mesoskopischer Elektrode und MASnIBr1.8Cl0.2 erzielte eine Wirkungsgrad von 3.1 %.
      PubDate: 2017-09-22T06:11:18.782606-05:
      DOI: 10.1002/ange.201707037
       
  • Electro-kinetic Separation of Rare Earth Elements Using a Redox-Active
           Ligand
    • Authors: Huayi Fang; Bren E. Cole, Yusen Qiao, Justin A. Bogart, Thibault Cheisson, Brian C. Manor, Patrick J. Carroll, Eric J. Schelter
      Abstract: Purification of rare earth elements is challenging due to their chemical similarities. All of the deployed separation methods rely on thermodynamic properties, such as distribution equilibria in solvent extraction. Rare-earth-metal separations based on kinetic differences have not been examined. Herein, we demonstrate a new approach for rare-earth-element separations by exploiting differences in the oxidation rates within a series of rare earth compounds containing the redox-active ligand [{2-(tBuN(O))C6H4CH2}3N]3−. Using this method, a single-step separation factor up to 261 was obtained for the separation of a 50:50 yttrium–lutetium mixture.Machen wir es kinetisch: Die Trennung von Seltenerdelementen nicht mithilfe thermodynamischer, sondern mithilfe kinetischer Methoden gelingt durch Nutzen der Unterschiede in den Reaktionsgeschwindigkeiten bei der Oxidation von [RE(TriNOx)thf]/[RE(TriNOx)] mit [Cp2Fe][BArF]. TriNOx3−=[{2-(tBuN(O))C6H4CH2}3N]3−, BArF=Tetra[3,5-bis(trifluormethyl)phenyl]borat.
      PubDate: 2017-09-22T06:11:13.591365-05:
      DOI: 10.1002/ange.201706894
       
  • Gas-Phase Synthesis of the Elusive Cyclooctatetraenyl Radical (C8H7) via
           Triplet Aromatic Cyclooctatetraene (C8H8) and Non-Aromatic Cyclooctatriene
           (C8H8) Intermediates
    • Authors: Michael Lucas; Aaron M. Thomas, Long Zhao, Ralf I. Kaiser, Gap-Sue Kim, Alexander M. Mebel
      Abstract: The 1,2,4,7-cyclooctatetraenyl radical (C8H7) has been synthesized for the very first time via the bimolecular gas-phase reaction of ground-state carbon atoms with 1,3,5-cycloheptatriene (C7H8) on the triplet surface under single-collision conditions. The barrier-less route to the cyclic 1,2,4,7-cyclooctatetraenyl radical accesses exotic reaction intermediates on the triplet surface, which cannot be synthesized via classical organic chemistry methods: the triplet non-aromatic 2,4,6-cyclooctatriene (C8H8) and the triplet aromatic 1,3,5,7-cyclooctatetraene (C8H8). Our approach provides a clean gas-phase synthesis of this hitherto elusive cyclic radical species 1,2,4,7-cyclooctatetraenyl via a single-collision event and opens up a versatile, unconventional path to access this previously largely obscure class of cyclooctatetraenyl radicals, which have been impossible to access through classical synthetic methods.Kohlenstoffatome im Grundzustand reagieren mit Cycloheptatrien (C7H8) unter Einzelstoßbedingungen in der Gasphase zum 1,2,4,7-Cyclooctatetraenyl-Radikal (C8H7). Ab-initio-Berechnungen der elektronischen Struktur zufolge verläuft die Reaktion über ungewöhnliche Triplett-C8H8-Zwischenstufen: nichtaromatisches 2,4,6-Cyclooctatrien und aromatisches 1,3,5,7-Cyclooctatetraen. Abgebildet ist die Flusskonturkarte der Reaktion.
      PubDate: 2017-09-22T06:11:04.671525-05:
      DOI: 10.1002/ange.201706861
       
  • Peristome-Mimetic Curved Surface for Spontaneous and Directional
           Separation of Micro Water-in-Oil Drop
    • Authors: Chuxin Li; Lei Wu, Cunlong Yu, Zhichao Dong, Lei Jiang
      Abstract: Separation of micro-scaled water-in-oil droplets is important in environmental protection, bioassays, and saving functional inks. So far, bulk oil–water separation has been achieved by membrane separation and sponge absorption, but micro-drop separation still remains a challenge. Herein we report that instead of the “plug-and-go” separation model, tiny water-in-oil droplets can be separated into pure water and oil droplets through “go-in-opposite ways” on curved peristome-mimetic surfaces, in milliseconds, without energy input. More importantly, this overflow controlled method can be applied to handle oil-in-oil droplets with surface tension differences as low as 14.7 mN m−1 and viscous liquids with viscosities as high as hundreds centipoises, which markedly increases the range of applicable liquids for micro-scaled separation. Furthermore, the curved peristome-mimetic surface guides the separated drops in different directions with high efficiency.Wasser links, Öl rechts: Eine künstliche gekrümmte Oberfläche ähnlich dem Peristom (der Saum um die Öffnung der Fallen tropischer Kannenpflanzen) scheidet ohne Energiezufuhr Wasser und Öl aus Wasser-in-Öl-Mikrotropfen. Der Vorgang dauert nur Millisekunden, und die getrennten Flüssigkeiten werden spontan in verschiedene Richtungen abgeführt.
      PubDate: 2017-09-22T06:10:58.687406-05:
      DOI: 10.1002/ange.201706665
       
  • An Extensive Family of Heterometallic Titanium(IV)–Metal(III) Rings with
           Structure Control through Templates
    • Authors: Grigore A. Timco; Antonio Fernandez, Andreas K. Kostopoulos, Christopher A. Muryn, Robin G. Pritchard, Ilya Strashnov, Inigo J. Vitorica-Yrezebal, George F. S. Whitehead, Richard E. P. Winpenny
      Abstract: A family of heterometallic [Cat][TixMO(x+1)(O2CtBu)2x+2] rings is reported where Cat=a secondary or tertiary alkyl ammonium ion, x=7, 8 or 9, and M=FeIII, GaIII, CrIII, InIII and AlIII. The structures are regular polygons with eight, nine or ten vertices with each edge bridged by an oxide and two pivalates. The size of the ring formed is controlled by the alkylammonium cation present. In each case a homometallic by-product is found [Cat][TixO(x+1)(O2CtBu)2x−1].Größenkontrolle: Eine Familie von [Kat][TixMO(x+1)(O2CtBu)2x+2]-Heterometallringen wird vorgestellt (Kat=ein sekundäres oder tertiäres Alkylammoniumion; x=7, 8 oder 9; M=Fe, Ga, Cr, In, Al). Die Strukturen sind regelmäßige Acht-, Neun- oder Zehnecke, in denen jede Kante von einem Oxid und zwei Pivalaten überbrückt wird. Die Ringgröße hängt vom vorliegenden Alkylammoniumkation ab.
      PubDate: 2017-09-22T06:10:37.88494-05:0
      DOI: 10.1002/ange.201706679
       
  • Selective C−H Bond Cleavage in Methane by Small Gold Clusters
    • Authors: Sandra M. Lang; Thorsten M. Bernhardt, Valeriy Chernyy, Joost M. Bakker, Robert N. Barnett, Uzi Landman
      Abstract: Methane represents the major constituent of natural gas. It is primarily used only as a source of energy by means of combustion, but could also serve as an abundant hydrocarbon feedstock for high quality chemicals. One of the major challenges in catalysis research nowadays is therefore the development of materials that selectively cleave one of the four C−H bonds of methane and thus make it amenable for further chemical conversion into valuable compounds. By employing infrared spectroscopy and first-principles calculations it is uncovered herein that the interaction of methane with small gold cluster cations leads to selective C−H bond dissociation and the formation of hydrido methyl complexes, H-Aux+-CH3. The distinctive selectivity offered by these gold clusters originates from a fine interplay between the closed-shell nature of the d states and relativistic effects in gold. Such fine balance in fundamental interactions could prove to be a tunable feature in the rational design of a catalyst.C-H-Spalterei: Schwingungsspektroskopie in Verbindung mit First-Principles-Rechnungen zeigt, dass kleine Goldcluster die selektive Dissoziation einer der vier C-H-Bindungen von Methan vermitteln können – der erste Schritt der CH4-Umwandlung in höherwertige Chemikalien. Die besondere Selektivität der Goldcluster resultiert aus ihrer fein abgestimmten elektronischen Struktur. Au: gelb, C: grau, H: weiß.
      PubDate: 2017-09-22T06:10:31.202708-05:
      DOI: 10.1002/ange.201706009
       
  • Selective Utilization of the Methoxy Group in Lignin to Produce Acetic
           Acid
    • Authors: Qingqing Mei; Huizhen Liu, Xiaojun Shen, Qinglei Meng, Hangyu Liu, Junfeng Xiang, Buxing Han
      Abstract: Selective transformation of lignin into a valuable chemical is of great importance and challenge owing to its complex structure. Herein, we propose a strategy for the transformation of methoxy group (-OCH3) which is abundant in lignin into pure highly valuable chemicals. As an example to apply this strategy, a route to produce acetic acid with high selectivity by conversion of methoxy group of lignin was developed. It was demonstrated that the methoxy group in lignin could react with CO and water to generate acetic acid over RhCl3 in the presence of a promoter. The conversions of methoxy group in the kraft lignin and organosolv lignin reached 87.5 % and 80.4 %, respectively, and no by-product was generated. This work opens the way to produce pure chemicals using lignin as the feedstock.Die (Bio)Masse macht's: Die Umwandlung von Methoxygruppen aus Lignin in Essigsäure gelingt durch selektive Umsetzung mit CO und Wasser über RhCl3. Bei 100 %iger Selektivität für Essigsäure sind Umsätze bis 87.5 % möglich.
      PubDate: 2017-09-22T06:10:26.753002-05:
      DOI: 10.1002/ange.201706846
       
  • Black Pigment Gallstone-Inspired Platinum-Chelated Bilirubin Nanoparticles
           for Combined Photoacoustic Imaging and Photothermal Therapy of Cancers
    • Authors: Dong Yun Lee; Jin Yong Kim, Yonghyun Lee, Soyoung Lee, Wenjun Miao, Hyeon Sik Kim, Jung-Joon Min, Sangyong Jon
      Abstract: Bilirubin (BR), a bile pigment that exerts potent antioxidant and anti-inflammatory effects, is also a major constituent of black pigment gallstones found in bile ducts under certain pathological conditions. Inspired by the intrinsic metal-chelating power of BR found in gallstones, herein we report a cisplatin-chelated BR-based nanoparticle (cisPt@BRNP) for use as a new photonic nanomedicine for combined photoacoustic imaging and photothermal therapy of cancers. The cisPt@BRNPs were prepared by simply mixing cisplatin with BRNPs, yielding ca. 150-nm-size NPs. Upon near-IR laser irradiation at 808 nm, cisPt@BRNPs generated considerable heat and induced clear death of cancer cells in vitro. Following intravenous injection into human colon cancer-bearing mice, cisPt@BRNPs allowed effective tumor visualization by photoacoustic imaging and remarkable antitumor efficacy by photothermal therapy, suggesting their potential for use as a new photonic nanomedicine for cancer therapy.Gallig gegen Krebs: Biologisch verträgliche und abbaubare, auf Nahinfrarotlicht reagierende photonische Nanomaterialien auf Basis des metallchelatisierenden Gallenfarbstoffs Bilirubin wurden entwickelt. Bilirubin-Nanopartikel mit chelatisiertem Cisplatin (cisPt@BRNPs) sind vielversprechend für eine kombinierte Krebsbehandlungen mit photoakustischer Bildgebung (PAI) und Photothermaltherapie (PTT).
      PubDate: 2017-09-22T06:05:32.000786-05:
      DOI: 10.1002/ange.201707137
       
  • Luciferases with tunable emission wavelengths
    • Authors: Kai Johnsson; Julien Hiblot, Qiluiyang Yu, Marina Sabbadini, Luc Reymond, Lin Xue, Olivier Sallin, Alberto Schena, Rudolf Griss, Nicholas Hill
      Abstract: We introduce luciferases whose emission maxima can be tuned to different wavelengths by chemical labeling. These tunable luciferases are generated by inserting the small luciferase NanoLuc into the structures of the self-labeling proteins SNAP-tag or HaloTag7 near their active sites. Labeling of the tags with a fluorophore shifts the emission maximum of NanoLuc to that of the fluorophore. Luciferases with tunable colors have applications as reporter genes, for the construction of biosensors and in bioimaging.
      PubDate: 2017-09-22T05:20:36.843492-05:
      DOI: 10.1002/ange.201708277
       
  • A bottom-up proteomic approach to identify substrate specificity of outer
           membrane protease OmpT
    • Authors: Sarah E. Wood; Gaurav Sinsinbar, Sushanth Gudlur, Madhavan Nallani, Che-Fan Huang, Bo Liedberg, Milan Mrksich
      Abstract: Identifying peptide substrates that are efficiently cleaved by proteases can give insights into the substrate recognition and specificity, guide the development of inhibitors and improve the sensitivity of assays. Peptide arrays and SAMDI mass spectrometry were used to identify a tetrapeptide substrate exhibiting high activity for the bacterial outer membrane protease (OmpT). Analysis of protease activity for the preferred residues at the cleavage site (P1, P1') and nearest neighbor positions (P2, P2') and their positional interdependence revealed FRRV as the optimal peptide with the highest OmpT activity. Substituting FRRV into a fragment of LL37, a natural substrate of OmpT, led to a>400 fold improvement in OmpT's catalytic efficiency with a kcat/Km value of 6.1 x 106 M-1 s-1. Interestingly, wild-type and mutant OmpT displayed significant differences in their substrate specificities, demonstrating that even modest mutants may not be suitable substitutes for the native enzyme.
      PubDate: 2017-09-22T03:22:12.397002-05:
      DOI: 10.1002/ange.201707535
       
  • Cooperative Effects between Chiral CpxIrIII Catalysts and Chiral
           Carboxylic Acids in Enantioselective C-H Amidations of Phosphine Oxides
    • Authors: Nicolai Cramer; Yun-Suk Jang, Michael Dieckmann
      Abstract: An enantioselective C-H amidation of phosphine oxides by using an iridium(III) catalyst bearing an atropchiral cyclopentadienyl (Cpx) ligand is reported. A very strong cooperative effect between the chiral Cpx ligand and a phthaloyl tert-leucine enabled the transformation. Matched-mismatched cases of the different acid enantiomers are shown. The amidated P-chiral arylphosphine oxides are formed in yields of up to 95 % and with excellent enantioselectivities of up to 99:1 er. Enantiospecific reduction provides access to valuable P-chiral phosphorus(III) compounds.
      PubDate: 2017-09-22T03:21:49.953647-05:
      DOI: 10.1002/ange.201708440
       
  • Pd-PEPPSI-IPent-SiO2: A Supported Catalyst for Challenging Negishi
           Coupling Reactions in Flow
    • Authors: Gregory A. Price; Abbas Hassan, Nalin Chandrasoma, Andrew R. Bogdan, Stevan W. Djuric, Michael G. Organ
      Abstract: A silica-supported precatalyst, Pd-PEPPSI-IPent-SiO2, has been prepared and evaluated for its proficiency in the Negishi cross-coupling of hindered and electronically deactivated coupling partners. The precatalyst Pd-PEPPSI-IPent loaded onto packed bed columns shows high catalytic activity for the room-temperature coupling of deactivated/hindered biaryl partners. Also for the first time, the flowed Csp3–Csp2 coupling of secondary alkylzinc reagents to (hetero)aromatics has been achieved with high selectivity with Pd-PEPPSI-IPent-SiO2. These couplings required residence times as short as 3 minutes to effect completion of these challenging transformations with excellent selectivity for the nonrearranged product.An der Oberfläche: Pd-PEPPSI-IPent wurde als Präkatalysator auf der Oberfläche von SiO2 verankert und in Festbettsäulen abgefüllt. Das resultierende hoch reaktive Katalysatorsystem vermittelt die Kupplung zwischen sekundären Alkylzinkreagentien und Heterocyclen bei Raumtemperatur binnen kurzer Verweilzeiten (ca. 3 bis 20 min.) mit hohem Umsatz und ausgezeichneter Selektivität. Die Produkte werden medizinalchemisch evaluiert.
      PubDate: 2017-09-22T02:51:20.097601-05:
      DOI: 10.1002/ange.201708598
       
  • Modern Heterogeneous Catalysis. An Introduction Von Rutger
           van Santen.
    • Authors: Evgenii V. Kondratenko
      Abstract: Wiley-VCH, Weinheim 2017. 564 S., Broschur, 89.00 €.—ISBN 978-3527339617
      PubDate: 2017-09-22T02:51:12.74804-05:0
      DOI: 10.1002/ange.201709088
       
  • Photoredox Imino Functionalizations of Olefins
    • Authors: Jacob Davies; Nadeem S. Sheikh, Daniele Leonori
      Abstract: Shown herein is that polyfunctionalized nitrogen heterocycles can be easily prepared by a visible-light-mediated radical cascade process. This divergent strategy features the oxidative generation of iminyl radicals and subsequent cyclization/radical trapping, which allows the effective construction of highly functionalized heterocycles. The reactions proceed efficiently at room temperature, utilize an organic photocatalyst, use simple and readily available materials, and generate, in a single step, valuable building blocks that would be difficult to prepare by other methods.Polyfunktionalisierte N-Heterocyclen sind leicht über einen durch sichtbares Licht vermittelten radikalischen Kaskadenprozess herstellbar. Die divergente Strategie beruht auf der oxidativen Bildung von Iminylradikalen und nachfolgende Cyclisierung/Radikalabfang.
      PubDate: 2017-09-22T02:51:11.35805-05:0
      DOI: 10.1002/ange.201708497
       
  • Copper-Catalyzed C(sp3)−H/C(sp3)−H Cross-Dehydrogenative Coupling with
           Internal Oxidants: Synthesis of 2-Trifluoromethyl-Substituted
           Dihydropyrrol-2-ols
    • Authors: Chuanle Zhu; Rui Zhu, Hao Zeng, Fulin Chen, Chi Liu, Wanqing Wu, Huanfeng Jiang
      Abstract: The first oxidative C(sp3)−H/C(sp3)−H cross-dehydrogenative coupling (CDC) reaction promoted by an internal oxidant is reported. This copper-catalyzed CDC reaction of oxime acetates and trifluoromethyl ketones provides a simple and efficient approach towards 2-trifluoromethyldihydropyrrol-2-ol derivatives in a highly diastereoselective manner by cascade C(sp3)−C(sp3) bond formation and cyclization. These products were further transformed into various significant and useful trifluoromethylated heterocyclic compounds, such as trifluoromethylated furan, thiophene, pyrrole, dihydropyridazine, and pyridazine derivatives. A trifluoromethylated analogue of an Aβ42 lowering agent was also synthesized smoothly. Preliminary mechanistic studies indicated that this reaction involves a copper(I)/copper(III) catalytic cycle with the oxime acetate acting as an internal oxidant.Interne Lösung: Eine Kupfer-katalysierte dehydrierende C(sp3)-H/C(sp3)-H-Kreuzkupplung mit internem Oxidationsmittel ermöglicht die hoch diastereoselektive Synthese von 2-Trifluormethyldihydropyrrol-2-olen in guten Ausbeuten. Die Produkte wurden zudem in verschiedene nützliche trifluormethylierte Heterocyclen überführt.
      PubDate: 2017-09-22T02:50:45.70461-05:0
      DOI: 10.1002/ange.201707719
       
  • Tree-Bark-Shaped N-Doped Porous Carbon Anode for Hydrazine Fuel Cells
    • Authors: Jaehoon Jeong; Myounghoon Choun, Jaeyoung Lee
      Abstract: Metal-free N-doped porous carbon has great potential as a catalyst for hydrazine oxidation in direct hydrazine fuel cells (DHFCs). However, previous studies have reported only half-cell characterization, and the effect of the pore size distribution has not been intensively investigated. Herein, we report the synthesis of highly active, metal-free N-doped carbon (NDC) by controlling the pore size distribution, and for the first time, the effect of the pore size distribution on the anode performance in a DHFC is investigated. As a result, tree-bark-shaped NDC with meso/macroporous (>10 nm) structures exhibit a remarkable power density of 127.5 mW cm−2 in a DHFC.Nano und Natur: N-dotierte poröse Nanofasern mit Baumrinden-artiger Maserung sind hoch aktive metallfreie Katalysatoren für die Hydrazinoxidation in Hydrazin-Brennstoffzellen.
      PubDate: 2017-09-22T02:47:14.148049-05:
      DOI: 10.1002/ange.201707880
       
  • Platinum Nanoparticle Impacts at a Liquid Liquid Interface
    • Authors: T. Jane Stockmann; Léo Angelé, Vitor Brasiliense, Catherine Combellas, Frédéric Kanoufi
      Abstract: Single nanoparticle (NP) electrochemistry detection at a micro liquid liquid interface (LLI) is exploited using the catalyzed oxygen reduction reaction (ORR). In this way, current spikes reminiscent of nanoimpacts were recorded, which corresponded to electrocatalytic enhancement of the ORR by Pt NPs. The nature of the LLI allows exploration of new phenomena in single NP electrochemistry. The recorded impacts result from a bipolar reaction occurring at the Pt NP straddling the LLI. O2 reduction takes place in the aqueous phase, while ferrocene hydride (Fc-H+; a complex generated upon facilitated interfacial proton transfer by Fc) is oxidized in the organic phase. Ultimately, the role of reactant partitioning, NP bouncing, or the ability of NPs to induce Marangoni effects, is demonstrated.Platin-Nanopartikel (Pt-NPs) wurden im Zuge der platinkatalysierten Sauerstoffreduktion anhand von Zufallsstößen an einer Flüssig/Flüssig-Mikrogrenzfläche elektrochemisch detektiert. Diese Beobachtung zeigt, dass einzelne Metall-NPs auch an weichen Grenzflächen nachgewiesen werden können. Außerdem gibt sie Einblicke in NP-Wechselwirkungen und mechanistische/physikochemische Prozesse an Flüssig/Flüssig-Grenzflächen.
      PubDate: 2017-09-22T02:47:08.715286-05:
      DOI: 10.1002/ange.201707589
       
  • Anionische Palladium(0)- und Palladium(II)-At-Komplexe
    • Authors: Marlene Kolter; Katharina Böck, Konstantin Karaghiosoff, Konrad Koszinowski
      Abstract: Palladium-At-Komplexe gelten als wichtige Zwischenstufen in Heck- und Kreuzkupplungsreaktionen, haben sich aber bisher einer Charakterisierung auf molekularer Ebene weitgehend entzogen. Mithilfe der Elektrosprayionisierungs-Massenspektrometrie, Messungen der elektrischen Leitfähigkeit und NMR-Spektroskopie wird hier gezeigt, dass der elektronenarme Katalysator [L3Pd] (L=Tris[3,5-bis(trifluormethyl)phenyl]phosphan) bereitwillig mit Br− zum anionischen, nullwertigen At-Komplex [L3PdBr]− reagiert. Elektronenreichere Pd-Katalysatoren weisen dagegen eine geringere Tendenz zur Bildung von At-Komplexen auf. Die Kombination von [L3Pd] mit LiI und einem Aryliodid ArI führt zur Entstehung des PdII-At-Komplexes [L2Pd(Ar)I2]−.At-Anionen analysiert: Palladium-At-Komplexe werden als wichtige Zwischenstufen in Heck- und Kreuzkupplungsreaktionen vorgeschlagen, sind aber bisher einer genauen Charakterisierung unzugänglich geblieben. Sie lassen sich durch Koordination mit einem elektronenarmen Phosphan stabilisieren, was ihre Analyse durch eine Kombination aus ESI-Massenspektrometrie, Messungen der elektrischen Leitfähigkeit und Multikern-NMR-Spektroskopie ermöglicht.
      PubDate: 2017-09-22T02:46:53.83162-05:0
      DOI: 10.1002/ange.201707362
       
  • Molecular Design of Bisphosphonates To Adjust Their Reactivity toward
           Metal Sources for the Surfactant-Assisted Synthesis of Mesoporous Films
    • Authors: Tatsuo Kimura
      Abstract: The precise control of primary reactions in solutions is one of the most significant steps for the nanoscale design of inorganic solids in multidisciplinary fields. However, further growth of the inorganic species to give bulkier species disturbs such designs. The surfactant-assisted synthesis of mesoporous materials is a good strategy for addressing such concerns because pores formed by supramolecularly mediated processes are surrounded by nanometer-sized continuous frameworks. Many experiments are generally conducted to optimize the reaction conditions for the synthesis of highly ordered mesostructures. Herein, to minimize such trial-and-error efforts, a new and practical concept is proposed for the precise design of porous materials. By adjusting the reactivity between bisphosphonates and metal sources through molecular design of the starting bisphosphonate compound, it was possible to synthesize mesoporous films with unique compositions by a surfactant-assisted approach.Schluss mit Versuch und Irrtum: Normalerweise erfordert die Optimierung der Reaktionsbedingungen zur Synthese hoch geordneter Mesostrukturen viele Experimente. Durch Abstimmung der Reaktivität zwischen Bisphosphonaten und einer Metallquelle mithilfe von molekularem Design des Bisphosphonats war es nun möglich, präzise entworfene mesoporöse Filme mit einzigartiger Zusammensetzung durch einen oberflächenunterstützten Ansatz zu synthetisieren.
      PubDate: 2017-09-22T02:46:39.127599-05:
      DOI: 10.1002/ange.201707225
       
  • Stereoselective Synthesis of Z Fluoroalkenes through Copper-Catalyzed
           Hydrodefluorination of gem-Difluoroalkenes with Water
    • Authors: Jiefeng Hu; Xiaowei Han, Yu Yuan, Zhuangzhi Shi
      Abstract: A copper catalytic system was established for the stereoselective hydrodefluorination of gem-difluoroalkenes through C−F activation to synthesize various Z fluoroalkenes. H2O is used as the hydrogen source for the fluorine acceptor moiety. This mild catalytic system shows good-functional group compatibility, accepting a range of carbonyls as precursors to the gem-difluoroalkenes, including aliphatic, aromatic, and α,β-unsaturated aldehydes and even ketones. It serves as a powerful synthetic method for the late-stage modification of complex compounds.Z für alle Fälle: Die gem-Difluoralkene für die Titelreaktion können aus leicht zugänglichen Aldehyden oder Ketonen erhalten werden. Der Ansatz nutzt billige Fluor- und Wasserstoffquellen und einen Kupferkatalysator und liefert Z-Fluoralkene unabhängig von der Z/E-Konfiguration der Substrate oder Zwischenstufen.
      PubDate: 2017-09-22T02:40:39.83125-05:0
      DOI: 10.1002/ange.201708224
       
  • Enantioselective Direct Mannich-Type Reactions Catalyzed by Frustrated
           Lewis Acid/Brønsted Base Complexes
    • Authors: Ming Shang; Min Cao, Qifan Wang, Masayuki Wasa
      Abstract: An enantioselective direct Mannich-type reaction catalyzed by a sterically frustrated Lewis acid/Brønsted base complex is disclosed. Cooperative functioning of the chiral Lewis acid and achiral Brønsted base components gives rise to in situ enolate generation from monocarbonyl compounds. Subsequent reaction with hydrogen-bond-activated aldimines delivers β-aminocarbonyl compounds with high enantiomeric purity.Ein sterisch frustriertes Paar aus chiralem Organoboran und achiralem Amin bildet einen wirksamen kooperativen Säure-Base-Katalysator für direkte diastereo- und enantioselektive Mannich-Reaktionen. Keton-, Ester- und Thioester-Pronukleophile konnten enolisiert und mit Aldiminen zu β-Aminocarbonyl-Verbindungen umgesetzt werden.
      PubDate: 2017-09-22T02:40:25.436503-05:
      DOI: 10.1002/ange.201708103
       
  • Reversible S0/MgSx Redox Chemistry in a MgTFSI2/MgCl2/DME Electrolyte for
           Rechargeable Mg/S Batteries
    • Authors: Tao Gao; Singyuk Hou, Fei Wang, Zhaohui Ma, Xiaogang Li, Kang Xu, Chunsheng Wang
      Abstract: The redox chemistry of magnesium and its application in rechargeable Mg batteries has received increasing attention owing to the unique benefits of Mg metal electrodes, namely high reversibility without dendrite formation, low reduction potentials, and high specific capacities. The Mg/S couple is of particular interest owing to its high energy density and low cost. Previous reports have confirmed the feasibility of a rechargeable Mg/S battery; however, only limited cycling stability was achieved, and the complicated procedure for the preparation of the electrolytes has significantly compromised the benefits of Mg/S chemistry and hindered the development of Mg/S batteries. Herein, we report the development of the first rechargeable Mg/S battery with a MgTFSI2/MgCl2/DME electrolyte (DME=1,2-dimethoxyethane, TFSI=bis(trifluoromethanesulfonyl)imide) and realize the best cycling stability among all reported Mg/S batteries by suppressing polysulfide dissolution. Mechanistic studies show that the battery works via S0/MgSx redox processes and that the large voltage hysteresis is mainly due to the Mg anode overpotential.Die Mischung macht's: Eine MgTFSI2/MgCl2/DME-Mischung (DME=1,2-Dimethoxyethan, TFSI=Bis(trifluormethansulfonyl)imid) wurde als Silylamid-freies, leicht herzustellendes Elektrolyt in Untersuchungen zur S0/MgSx-Redoxchemie eingesetzt. Seine Verwendung in einer Mg/S-Batterie führte zur besten Zyklenstabilität, die bislang für solche Systeme beobachtet wurde, da sich Polysulfide im konzentrierten Elektrolyt (1 m) nicht auflösen.
      PubDate: 2017-09-22T02:35:29.920512-05:
      DOI: 10.1002/ange.201708241
       
  • A Rewritable, Reprogrammable, Dual Light-Responsive Polymer Actuator
    • Authors: Anne Helene Gelebart; Dirk J. Mulder, Ghislaine Vantomme, Albertus P. H. J. Schenning, Dirk J. Broer
      Abstract: We report on the fabrication of a rewritable and reprogrammable dual-photoresponsive liquid crystalline-based actuator containing an azomerocyanine dye that can be locally converted into the hydroxyazopyridinium form by acid treatment. Each dye absorbs at a different wavelength giving access to programmable actuators, the folding of which can be controlled by using different colors of light. The acidic patterning is reversible and allows the erasing and rewriting of patterns in the polymer film, giving access to reusable, adjustable soft actuators.Muster und Form: Wiederbeschreibbbare und -programmierbare Aktuatoren werden durch lokale Aktivierung eines chemisch zunächst homogenen Films erhalten. Das lokal aktivierte Material wird UV-Strahlung ausgesetzt, die den Aktuator präzise faltet. Durch Wechsel der Wellenlänge sind verschiedene Formen erhältlich. Das Muster kann schließlich gelöscht und durch ein neues ersetzt werden, sodass der Aktuator zahlreiche Formen einnehmen kann.
      PubDate: 2017-09-22T02:17:00.549984-05:
      DOI: 10.1002/ange.201706793
       
  • Assessing the Stability of Fluorescently Encoded Nanoparticles in
           Lysosomes by using Complementary Methods
    • Authors: Ana M. Milosevic; Laura Rodriguez-Lorenzo, Sandor Balog, Christophe A. Monnier, Alke Petri-Fink, Barbara Rothen-Rutishauser
      Abstract: Nanoparticles (NPs) are promising tools in biomedical research. In vitro testing is still the first method for initial evaluation; however, NP colloidal behavior and integrity, in particular inside cells (that is, in lysosomes), are largely unknown and difficult to evaluate because of the complexity of the environment. Furthermore, while the majority of NPs are usually labeled with fluorescent dyes for tracking purposes, the effect of the lysosomal environment on the fluorophore properties, as well as the ensuing effects on data interpretation, is often only sparsely addressed. In this work, we have employed several complementary analytical methods to better understand the fate of fluorescently encoded NPs and identify potential pitfalls that may arise from focusing primary analysis on a single attribute, for example, fluorophore detection. Our study shows that in a lysosomal environment NPs can undergo significant changes resulting in dye quenching and distorted fluorescence signals.Instabile Nanopartikel: Verhalten und Stabilität fluoreszenzmarkierter Goldnanopartikel nach Zellaufnahme wurden mit verschiedenen analytischen Methoden untersucht. Die lysosomale Umgebung – ein begrenzter und azider Raum – kann die Fluoreszenz polymerbeschichteter NPs mit integrierten Fluorophoren zum Erlöschen bringen.
      PubDate: 2017-09-22T02:16:56.453634-05:
      DOI: 10.1002/ange.201705422
       
  • Moderne Anorganische Aerogele
    • Authors: Christoph Ziegler; André Wolf, Wei Liu, Anne-Kristin Herrmann, Nikolai Gaponik, Alexander Eychmüller
      Abstract: Der Begriff Aerogel beschreibt im Wesentlichen eine besondere geometrische Struktur der Materie, die materialunabhängig ist und keinem speziellen Syntheseverfahren unterliegt. Grundsätzlich können daher Aerogele aus unzähligen Materialien bestehen, wodurch die Anwendungsmöglichkeiten nahezu unbegrenzt sind. Dasselbe trifft auf Nanopartikel zu. Diese werden ebenso durch ihre geometrischen Eigenschaften definiert. In den letzten Jahrzehnten standen daher nanoskalige Materialien im Fokus der Forschung, und es entwickelten sich mögliche Anwendungen in vielen naturwissenschaftlichen Bereichen. Heute ist eine Vielzahl an Metall-, Halbleiter-, Oxid- und anderen Nanopartikeln durch kolloidale Synthesen zugänglich. Dennoch ist es für eine Anwendung oft notwendig, dass diese Materialien zuvor in makroskopische Strukturen angeordnet werden. Dieser Aufsatz gibt eine ausführliche Übersicht über die Entwicklung, die die Welt der kolloidalen Nanopartikel und der Aerogele miteinander vereint. Ermöglicht wurde dies durch die kontrollierte Destabilisierung der vorab gebildeten Nanopartikel, die zu einer Anordnung der Nanopartikel zu einem dreidimensionalen, makroskopischen Netzwerk führt. Dieses revolutionäre Konzept verleiht die Möglichkeit, präzise kontrollierte Nanopartikel als Grundbausteine für makroskopische, poröse Strukturen mit einstellbaren Eigenschaften zu nutzen.Erschaffe etwas Großes! Die kontrollierte Destabilisierung kolloidaler Nanopartikel und die resultierende Anordnung in makroskopische 3D-Strukturen ermöglicht die Fusion der Nano- und der Makrowelt. Nanopartikel können verwendet werden, um Materialien mit neuartigen und einstellbaren Eigenschaften zu erschaffen. Der Aufsatz fasst diesen interessanten Teil der modernen Nanotechnologie zusammen.
      PubDate: 2017-09-22T02:16:44.938921-05:
      DOI: 10.1002/ange.201611552
       
  • Fluoreszenzsonden mit mehreren Bindungsstellen unterscheiden zwischen Cys,
           Hcy und GSH
    • Authors: Cai-Xia Yin; Kang-Ming Xiong, Fang-Jun Huo, James C. Salamanca, Robert M. Strongin
      Abstract: Thiole wie Cystein (Cys), Homocystein (Hcy) und Glutathion (GSH) spielen für das Redoxgleichgewicht in biologischen Systemen eine entscheidende Rolle. Dieser Kurzaufsatz fasst aktuelle Aspekte aus dem Bereich der reaktiven Thiolsonden für die biomedizinische Forschung und Diagnostik zusammen und betont die verbleibenden Herausforderungen für Chemiker im Bereich der selektiven Sonden und Sensoren. Der Fortschritt bei Sonden mit mehreren Bindungsstellen stellt eine kreative neue Richtung des Feldes dar, die gleichzeitige und akkurate ratiometrische Messungen ermöglichen kann. Neue Strategien zur Entwicklung von Sonden können helfen, aktuelle Aufgaben anzugehen. Dazu zählt das Monitoring von Krankheiten, die durch abweichende GSH-, Cys- und Hcy-Spiegel gekennzeichnet sind, wie etwa Autismus und chronische Erkrankungen, die auf oxidativem Stress beruhen.Cystein, Homocystein und Glutathion (Cys, Hcy und GSH) spielen für die menschliche Gesundheit eine große Rolle. Es gibt sehr wenige molekulare Sonden und abiotische Sensoren, die zwischen diesen biologischen Thiolen unterscheiden können. Fortschritte bei Sonden, die mehrere Bindungsstellen aufweisen und dadurch Cys, Hcy und GSH unterscheiden können, sowie die verbleibenden Herausforderungen für Chemiker im Bereich der Thiolsonden werden hier zusammengefasst.
      PubDate: 2017-09-22T02:15:31.488391-05:
      DOI: 10.1002/ange.201704084
       
  • Buchwald–Hartwig Amination of Nitroarenes
    • Authors: Fumiyoshi Inoue; Myuto Kashihara, M. Ramu Yadav, Yoshiaki Nakao
      Abstract: The Buchwald–Hartwig amination of nitroarenes was achieved for the first time by using palladium catalysts bearing dialkyl(biaryl)phosphine ligands. These cross-coupling reactions of nitroarenes with diarylamines, arylamines, and alkylamines afforded the corresponding substituted arylamines. A catalytic cycle involving the oxidative addition of the Ar−NO2 bond to palladium(0) followed by nitrite/amine exchange is proposed based on a stoichiometric reaction.Von Amin zu Amin: Die Buchwald-Hartwig-Aminierung von Nitroarenen wird von einem Palladiumkomplex mit einem Dialkyl(biaryl)phosphin-Liganden katalysiert. So gelang die Kreuzkupplung von Nitroarenen mit Diarylaminen, Arylaminen und Alkylaminen zu den entsprechenden Arylaminen.
      PubDate: 2017-09-22T02:10:33.73923-05:0
      DOI: 10.1002/ange.201706982
       
  • On the Role of Chirality in Guiding the Self-Assembly of Peptides
    • Authors: Shibaji Basak; Ishwar Singh, Annaleizle Ferranco, Jebreil Syed, Heinz-Bernhard Kraatz
      Abstract: Homochirality in peptides is crucial in sustaining “like–like” intermolecular interactions that allow the formation of assemblies and aggregates and is ultimately responsible for the resulting material properties. With the help of a series of stereoisomers of the tripeptide F–F–L, we demonstrate the critical role that peptide stereochemistry plays in the self-assembly of peptides, guided by molecular recognition, and for self-sorting. Homochiral self-assemblies are thermally and mechanically more robust compared to heterochiral self-assemblies. Morphological studies of the multicomponent peptide systems showed that aggregates formed from homochiral peptides possessed a uniform nano-fibrous structure, whereas heterochiral systems resulted in self-sorted systems with a heterogeneous morphology. In essence, homochiral peptides form the stronger aggregates, which may be one of reasons why homochirality is preferred in living systems.Reich' mir die Händigkeit, mein Leben: Stereochemie ist ein wichtiger Faktor in der Peptid-Selbstorganisation unter dem steuernden Einfluss von molekularer Erkennung und Selbstsortierung. Homochirale Peptide bilden die stärkeren Aggregate, was ein Grund für die bevorzugte Homochiralität in lebenden Systemen ist.
      PubDate: 2017-09-22T01:07:06.714104-05:
      DOI: 10.1002/ange.201706162
       
  • Columnar Lithium Metal Anodes
    • Authors: Xue-Qiang Zhang; Xiang Chen, Rui Xu, Xin-Bing Cheng, Hong-Jie Peng, Rui Zhang, Jia-Qi Huang, Qiang Zhang
      Abstract: The rechargeable lithium metal anode is of utmost importance for high-energy-density batteries. Regulating the deposition/dissolution characteristics of Li metal is critical in both fundamental researches and practical applications. In contrast to gray Li deposits featured with dendritic and mossy morphologies, columnar and uniform Li is herein plated on lithium-fluoride (LiF)-protected copper (Cu) current collectors. The electrochemical properties strongly depended on the microscale morphologies of deposited Li, which were further embodied as macroscale colors. The as-obtained ultrathin and columnar Li anodes contributed to stable cycling in working batteries with a dendrite-free feature. This work deepens the fundamental understanding of the role of LiF in the nucleation/growth of Li and provides emerging approaches to stabilize rechargeable Li metal anodes.Li-Säulen können auf einheitlichen und dichten Keimstellen abgeschieden werden, die gesteuert durch LiF gebildet wurden. Die Beziehung zwischen Mikrostruktur und makroskopischer Farbe liefert einen Deskriptor, mit dem die Gleichförmigkeit des abgeschiedenen Li beurteilt werden kann. Überdies wurden ultradünne und stabile Li-Anoden für Batterien mit hoher Energiedichte entwickelt.
      PubDate: 2017-09-22T01:06:20.794067-05:
      DOI: 10.1002/ange.201707093
       
  • Diols as Dienophiles: Bridged Carbocycles via Ruthenium(0) Catalyzed
           Transfer Hydrogenative Cycloadditions of Cyclohexadiene or Norbornadiene
    • Authors: Michael Joseph Krische; Hiroki Sato, Keisuke Fukaya, Binit Sharma Poudel
      Abstract: Highly exo-selective ruthenium(0) catalyzed transfer hydrogenative cycloadditions of 1,2-diols with cyclohexadiene or norbornadiene are described. Novel bridged bicyclic ring systems are accessible from the diol, α-ketol or 1,2-dione oxidation levels with complete control of diastereoselectivity.
      PubDate: 2017-09-21T15:20:27.467262-05:
      DOI: 10.1002/ange.201708189
       
  • The full pressure-temperature phase envelope of a mixture in 1000
           microfluidic chambers
    • Authors: Yi Xu; Jason Riordon, Xiang Cheng, Bo Bao, David Sinton
      Abstract: Knowing the thermodynamic state of complex mixtures - liquid, gas, supercritical or two-phase - is essential to industrial chemical processes. Traditionally, phase diagrams are compiled piecemeal from individual measurements in a pressure-volume-temperature cell performed in series, where each point is subject to a long fluid equilibrium time. Herein, 1,000 microfluidic chambers, each isolated by a liquid piston and set to a different pressure and temperature combination, provide the complete pressure-temperature phase diagram of a hydrocarbon mixture at once, including the thermodynamic phase envelope. Measurements closely match modelled values, with a standard deviation of 0.13 MPa between measurement and model for the dew and bubble point lines, and a difference of 0.04 MPa and 0.25 ºC between measurement and model for the critical point.
      PubDate: 2017-09-21T12:21:00.704781-05:
      DOI: 10.1002/ange.201708238
       
  • Non-canonical bases in the genome: The regulatory information layer in DNA
    • Authors: Thomas Carell; Matthias Q Kurz, Markus Müller, Martin Rossa, Fabio Spada
      Abstract: The sequence of the four canonical bases dA, dC, dG and dT forming two defined Watson-Crick base pairs (dT:dA, dG:dC), held together by H-bonding, establish the sequence information in the DNA double strand. The faithful replication of the sequence information during cell division, the transcription of the DNA information into RNA and the final translation of the sequence information into proteins is the basis for life on earth. Multicellular organisms developed the concept of specialized cells that perform specific functions. Examples are neurons and fibroblast to name just two out of more than 200. These cellular differences are established based on the same sequence information stored in the cell nucleus of all cells of an organism. The sequence information needs consequently different interpretations by the different cell types. During cellular development, when a zygote develops finally into a complex organism with its multitude of specialized cells, this interpretation of the genetic code has to be tightly regulated in space and time. Interpretation of the sequence information involves the controlled activation and silencing of specific genes so that certain proteins are made in one cell type but not in others. This involves an additional regulatory information layer beyond the pure base sequence. One aspect of this regulatory information layer relies on functional groups that are attached to the C(5) position of the canonical base dC. Currently four regulatory, non-canonical bases with a methyl (CH3)-, a hydroxymethyl (CH2OH)-, a formyl (CHO)- and a carboxyl (COOH)- group are known. While 5-methyl-cytidine is long recognized to be a regulatory base in the genome, the other three bases and the enzymes responsible for generating them, were just recently discovered. This review summarizes the discovery of the new bases and focusses at the chemical biology aspects associated with the regulatory DNA bases beyond Watson and Crick.
      PubDate: 2017-09-21T11:20:44.353473-05:
      DOI: 10.1002/ange.201708228
       
  • Synthesis and Characterization of an Eclipsed Digermylene as a Building
           Block to Construct a Cyclic Octagermylene
    • Authors: Yu-Te Wey; Fan-Shan Yang, Hsien-Chen Yu, Ting-Shen Kuo, Yi-Chou Tsai
      Abstract: Here we report the preparation of an unprecedented Ge(I)-Ge(I) bonded digermylene [K2{Ge2(μ-κ2:η2:η4-2,6-(2,6-iPr2C6H3-N)2-4-CH3C5H2N)2}] (3) in an eclipsed conformation stabilized by two bridging diamidopyridyl ligands. Although 3 exhibits an eclipsed conformation, the Ge-Ge bond length is 2.5168(6) Å, shorter than those in the trans-bent and gauche digermylenes. In combination with two pendant amido groups, the GeI2 motif of 3 is employed as a building block to assemble the first example of octagermylene [Ge4(μ-κ2:κ1-2,6-(2,6-iPr2C6H3-N)2-4-CH3C5H2N)2]2 (5) showing a cyclic configuration and containing three distinct types of Ge(I)-Ge(I) bonds.
      PubDate: 2017-09-21T09:21:12.838391-05:
      DOI: 10.1002/ange.201708551
       
  • Tuning Crystallization Pathways through the Mesoscale Assembly of
           Biomacromolecular Nanocrystals
    • Authors: Fei Tao; Qian Han, Kaiqiang Liu, Peng Yang
      Abstract: Macromolecular crystallization has many implications in biological and materials science. Similar to the crystallization of other molecules, macromolecular crystallization conventionally considers a critical nucleus, followed by crystallographic packing of macromolecules to drive further crystal growth. Herein, we discover a distinctive macromolecular crystallization pathway by developing the concept of a macromolecular mesocrystal. This nonclassical polymer crystallization occurs through the mesoscale self-assembly of (bio)macromolecular nanocrystals. The new concept for macromolecular crystallization presented herein is fundamental and relevant to many fields, including materials science, chemistry, biomimetics, nanoscience, and structural biology.Design makromolekularer Kristalle: Makromolekulare Mesokristalle wurden entworfen und über einen besonderen Kristallisationspfad hergestellt. Durch programmierte Anordnung auf der Mesoebene und Verschmelzen von Kern-Schale-Architekturen sind flexible kristalline makromolekulare Materialien mit komplexen Formen und hierarchischen Strukturen leicht manipulierbar.
      PubDate: 2017-09-21T08:52:47.050321-05:
      DOI: 10.1002/ange.201706843
       
  • Trichalcogenasumanene ortho-Quinones: Synthesis, Properties, and
           Transformation into Various Heteropolycycles
    • Authors: Yantao Sun; Xuexiang Li, Chunlin Sun, Hongguang Shen, Xueqing Hou, Dongxu Lin, Hao-Li Zhang, Chong-an Di, Daoben Zhu, Xiangfeng Shao
      Abstract: The regioselective transformation of heterobuckybowl trichalcogenasumanenes 1 a,b at peripheral butoxy groups afforded trichalcogenasumanene ortho-quinones 2 a,b. Compounds 2 a,b are distinct from 1 a,b in terms of their molecular geometry and electronic state; that is, they have a shallower bowl depth and show absorbance in the NIR region. The reaction of 2 a,b with diamines resulted in a variety of heteropolycycles, including molecular spoon 3 a–6 a, planar π-systems 3 b–6 b, and highly twisted [7-6-6]-fused systems 7 a,b. These new heteropolycycles had different optical/electrical properties: 4 a,b showed hole mobility of approximately 0.002 cm2 V−1 s−1, 6 a displayed red emission in both solution and the solid state, and 7 a,b formed tight stacks of the curved π-surface.Schalen und Löffel: Regioselektiv synthetisierte Trichalkogenasumanen-ortho-chinone zeigen NIR-Absorption und an/aus-schaltbare Fluoreszenz als Reaktion auf elektrochemische Stimuli. Modifizierung dieser Verbindungen führte zu verschiedenen Heteropolycyclen, z. B. zu molekularen Löffeln mit Halbleiterverhalten und/oder Festkörperemission (siehe Schema) und zu einem [7-6-6]-kondensierten gekrümmten π-System.
      PubDate: 2017-09-21T08:51:48.292644-05:
      DOI: 10.1002/ange.201707397
       
  • Regio- and Stereoselective Chlorocyanation of Alkynes
    • Authors: Alejandro G. Barrado; Adam Zieliński, Richard Goddard, Manuel Alcarazo
      Abstract: A variety of terminal and internal alkynes were converted regio- and stereoselectively into (Z)-3-chloroacrylonitriles by treatment with BCl3 in the presence of stoichiometric amounts of imidazolium thiocyanates. These products could be readily functionalized to provide useful building blocks, thus demonstrating the synthetic value of the method. Preliminary mechanistic studies suggest initial activation of the cationic thiocyanate by the Lewis acid, followed by electrophilic attack of the alkyne. The syn addition of a chloride to the vinyl cation intermediate and final elimination of the thiourea unit afford the desired chloroacrylonitriles.Bereits, willens und in der Lage: Alkine wurden mit Imidazoliumthiocyanaten als elektrophilen Cyanierungsreagentien in (Z)-3-Chloracrylnitrile überführt. Die Umwandlung ist effizient (schnell bei Raumtemperatur), vielseitig (24 Beispiele, interne und terminale Alkine) und selektiv (exzellente Regio- und Stereoselektivität; siehe Schema), und die Produkte können leicht funktionalisiert werden.
      PubDate: 2017-09-21T08:50:38.66157-05:0
      DOI: 10.1002/ange.201705851
       
  • CIT-9: A Fault-Free Gmelinite Zeolite
    • Authors: Michiel Dusselier; Jong Hun Kang, Dan Xie, Mark E. Davis
      Abstract: A synthetic, fault-free gmelinite (GME) zeolite is prepared using a specific organic structure-directing agent (OSDA), cis-3,5-dimethylpiperidinium. The cis-isomers align in the main 12-membered ring (MR) channel of GME. Trans-isomer OSDA leads to the small-pore zeolite SSZ-39 with the OSDA in its cages. Data from N2-physisorption and rotation electron diffraction provide evidence for the openness of the 12 MR channel in the GME 12×8×8 pore architecture and the absence of stacking faults, respectively. CIT-9 is hydrothermally stable when K+-exchanged, while in the absence of exchange, the material transforms into an aluminous AFI-zeolite. The process of this phase-change was followed by in situ variable temperature powder X-ray diffraction. CIT-9 has the highest Si/Al ratio reported for GME, and along with its good porosity, opens the possibility of using GME in a variety of applications including catalysis.Eine 40-jährige Suche nach einem wirklich porösen Gmelinit-Zeolith (GME) ist mit der Entdeckung von CIT-9 beendet, und GME kann nun in wichtigen Kohlenwasserstoffreaktionen getestet werden. Die Synthese hängt stark von der Konzentration des organischen strukturdirigierenden Agens und dessen cis/trans-Isomerie ab, wie durch molekulare Modellierung bestätigt wurde.
      PubDate: 2017-09-21T08:50:29.482157-05:
      DOI: 10.1002/ange.201707452
       
  • Graphene Oxide Membranes with Heterogeneous Nanodomains for Efficient CO2
           Separations
    • Authors: Shaofei Wang; Yu Xie, Guangwei He, Qingping Xin, Jinhui Zhang, Leixin Yang, Yifan Li, Hong Wu, Yuzhong Zhang, Michael D. Guiver, Zhongyi Jiang
      Abstract: Achieving high membrane performance in terms of gas permeance and carbon dioxide selectivity is an important target in carbon capture. Aiming to manipulate the channel affinity towards CO2 to implement efficient separations, we report gas separation membranes containing CO2-philic and non-CO2-philic nanodomains in the interlayer channels of graphene oxide (GO), by intercalating poly(ethylene glycol) diamines (PEGDA). PEGDA reacts with epoxy groups on the GO surface, constructing CO2-philic nanodomains and rendering a high sorption capacity, whereas unreacted GO surfaces give non-CO2-philic nanodomains, rendering low-friction diffusion. Owing to the orderly stacking of nanochannels through cross-linking and the heterogeneous nanodomains with moderate CO2 affinity, a GO-PEGDA500 membrane exhibits a high CO2 permeance of 175.5 GPU and a CO2/CH4 selectivity of 69.5, which is the highest performance reported for dry-state GO-stacking membranes.
      PubDate: 2017-09-21T08:30:18.86255-05:0
      DOI: 10.1002/ange.201708048
       
  • Controlling the coordination sphere of alkyllithiums results in selective
           reactions with allylic amines
    • Authors: Ulrike Kroesen; Christian Unkelbach, Daniel Schildbach, Carsten Strohmann
      Abstract: In this communication, a selective way and a better understanding to control the reaction of allylic amines with metalorganic bases depending on the amine handle as well as the metalorganic base is presented. Depending on the number of coordinating groups within the amine handle either a selective carbometalation or deprotonation reaction can be performed. By changing the alkali metal within the base from lithium to sodium or potassium, a change of chemoselectivity takes place and the reaction of piperidinoallylamine can be controlled.
      PubDate: 2017-09-21T06:26:00.706198-05:
      DOI: 10.1002/ange.201708620
       
  • Interlayer bond formation in black Phosphorus at high pressure
    • Authors: Matteo Ceppatelli; Demetrio Scelta, Roberto Bini, Maurizio Peruzzini, Kamil Dziubek, Adhara Baldassarre, Manuel Serrano-Ruiz, Andrew Cairns
      Abstract: Black Phosphorus was compressed at room T across the A17, A7 and simple-cubic phases up to 30 GPa, using a diamond anvil cell and He as pressure transmitting medium. Synchrotron X-ray diffraction showed the persistence of two previously unreported peaks related to the A7 structure in the pressure range of the simple-cubic one. The Rietveld refinement of the data demonstrates the occurrence of a two-step mechanism for the A7 to simple-cubic phase transition, indicating the existence of an intermediate pseudo simple-cubic structure. From a chemical point of view this study represents a deep insight on the mechanism of interlayer bond formation during the transformation from the layered A7 to the non-layered simple-cubic phase of Phosphorus, opening new perspectives for the design, synthesis and stabilization of Phosphorene based systems. As superconductivity is concerned, a new experimental evidence to explain the anomalous pressure behavior of Tc in Phosphorus below 30 GPa is provided.
      PubDate: 2017-09-21T06:20:29.774416-05:
      DOI: 10.1002/ange.201708368
       
  • An ultra-flexible silicon-oxygen battery fiber with high energy density
    • Authors: Ye Zhang; Yiding Jiao, Lijun Lu, Lie Wang, Taiqiang Chen, Huisheng Peng
      Abstract: To satisfy the rapid development of portable and wearable electronics, it is highly desired to make batteries with both high energy densities and flexibility. Although some progresses have been made in recent decades, the available batteries share critical problems of poor energy storage capacity and low flexibility. Herein, we have developed a silicon-oxygen battery fiber with high energy density and ultra-flexibility by designing a coaxial architecture with lithiated silicon/carbon nanotube hybrid fiber as inner anode, polymer gel as middle electrolyte and bare carbon nanotube sheet as outer cathode. It exhibited a high energy density of 512 Wh/kg and could effectively work after bending for 20,000 cycles. These battery fibers had been further woven into flexible textiles for a large-scale application.
      PubDate: 2017-09-21T05:21:03.720435-05:
      DOI: 10.1002/ange.201707840
       
  • Orientation induces adsorption of the hydrated proton at the air-water
           interface
    • Authors: Shavkat Mamatkulov; Christoph Allolio, Roland Netz, Douwe Jan Bonthuis
      Abstract: The surface tension of the air-water interface increases upon the addition of inorganic salts, implying a negative surface excess of ionic species. Most acids, however, induce a decrease in surface tension, indicating a positive surface excess of hydrated protons. In combination with the apparent negative charge at pure air-water interfaces derived from electrokinetic experiments, this experimental fact has presented a source of intense debate since the mid 19th century. Here, we calculate surface tensions and ionic surface propensities at air-water interfaces from classical thermodynamically consistent molecular dynamics simulations. The surface tensions of NaOH, HCl and NaCl solutions show outstanding quantitative agreement with experiment. Of the studied ions, only H3O+ adsorbs to the air-water interface. The adsorption is explained by the deep potential well caused by the orientation of the H3O+ dipole in the interfacial electric field, which we comfirm using ab initio simulations.
      PubDate: 2017-09-21T01:21:31.28945-05:0
      DOI: 10.1002/ange.201707391
       
  • Quantitative and Comparative Profiling of Protease Substrates through a
           Genetically Encoded Multifunctional Photocrosslinker
    • Authors: Dan HE; Xiao Xie, Fan Yang, Heng Zhang, Haomiao Su, Yun Ge, Haiping Song, Peng Chen
      Abstract: We developed a genetically encoded, multifunctional photocrosslinker for quantitative and comparative proteomics. By bearing a bioorthogonal handle and a releasable linker in addition to its photo-affinity warhead, this probe enables the enrichment of transient and low-abundance prey proteins after intracellular photocrosslinking and prey-bait separation, which can be subject to stable isotope dimethyl labeling and mass spectrometry analysis. This quantitative strategy (termed isoCAPP) allowed us to adopt a comparative proteomic approach to identify the proteolytic substrates of an E. coli protease-chaperone dual machinery DegP. Two newly identified substrates were subsequently confirmed by proteolysis experiments.
      PubDate: 2017-09-20T23:15:27.46602-05:0
      DOI: 10.1002/ange.201708151
       
  • Metallo-Supramolecular Photocleavable Gels Sensitive to Visible and Near
           Infrared Irradiation
    • Authors: Sabrina Theis; Aitziber Iturmendi, Christian Gorsche, Marco Orthofer, Markus Lunzer, Stefan Baudis, Aleksandr Ovsianikov, Robert Liska, Uwe Monkowius, Ian Teasdale
      Abstract: A photolabile ruthenium-based complex [Ru(bpy)₂(4AMP)₂](PF₆)₂ is presented. The metal centre was incorporated into polyurea organo and hydrogels via the reactive amine moieties on the photocleavable 4-(aminomethyl)pyridine (4AMP) ligands. While showing long-term stability in the dark, cleavage of the pyridine-ruthenium bond upon irradiation with visible and near infrared irradiation (in a two-photon process) leads to rapid degelation of the supramolecular gels, thus enabling spatiotemporal micropatterning by photomasking or pulsed NIR-laser irradiation.
      PubDate: 2017-09-20T21:21:35.957596-05:
      DOI: 10.1002/ange.201707321
       
  • Trapping White Phosphorus within a Purely Organic Molecular Container
           Produced via Imine Condensation
    • Authors: Hao Li; Tianyu Jiao, Liang Chen, Dong Yang, Xin Li, Guangcheng Wu, Pingmei Zeng, Ankun Zhou, Qi Yin, Yuanjiang Pan, Biao Wu, Xin Hong, Xueqian Kong, Vincent M Lynch, Jonathan L Sessler
      Abstract: Three tetrahedral organic cages have been obtained by condensing a triamino linker with a set of three ostensibly analogous triformyl precursors. In spite of the large number of imine bonds formed, the corresponding cages were obtained in exceptionally high yields. Both theory and experimental results demonstrate that, the presence of intramolecular CH***π interactions within all of the cage frameworks plays an important role in abeting the condensations and contributes to the near-quantitative synthetic yields. The three cages of this study exhibit high stability, both thermodynamically and kinetically. A variety of small neutral guest molecules with complementary sizes and geometries may be used as templates in the cage forming reactions. Among the guests that may be used in this way is white phosphorus (P4), whose inherent reactivity towards oxygen is almost fully attenuated when bound within one of the cages of this study.
      PubDate: 2017-09-20T12:21:26.777919-05:
      DOI: 10.1002/ange.201708246
       
  • Gold(I)-Catalyzed Synthesis of Indenes and Cyclopentadienes: Access to
           (±)-Laurokamurene B and the Skeletons of Cycloaurenones and Dysiherbols
    • Authors: Antonio M. Echavarren; Xiang Yin, Mauro Mato
      Abstract: The formal (3 + 2) cycloaddition between terminal allenes with aryl or styryl gold(I) carbenes generated by retro-Buchner reaction of 7-substituted 1,3,5-cycloheptatrienes leads to indenes and cyclopentadienes, respectively. These cycloadditions have been applied to the construction of the carbon skeleton of the cycloaurenones and the dysiherbols as well as to the total synthesis of ()-laurokamurene B.
      PubDate: 2017-09-20T12:21:17.189288-05:
      DOI: 10.1002/ange.201708947
       
  • Radical heterocyclization and heterocyclization cascades triggered by
           electron transfer to amide-type carbonyls
    • Authors: Huan-Ming Huang; David John Procter
      Abstract: Radical heterocyclizations triggered by electron transfer to amide-type carbonyls using SmI2-H2O provides straightforward access to bicyclic heterocyclic scaffolds containing bridgehead nitrogens. Furthermore, the first radical heterocyclization cascades triggered by reduction of amide-type carbonyls deliver novel, complex tetracyclic architectures containing five contiguous stereocenters with excellent diastereocontrol.
      PubDate: 2017-09-20T09:20:38.40327-05:0
      DOI: 10.1002/ange.201708354
       
  • Time-resolved in situ MAS NMR monitoring of the nucleation and growth of
           zeolite BEA catalysts under hydrothermal conditions
    • Authors: Irina I. Ivanova; Yury G. Kolyagin, Ivan A. Kasyanov, Alexander V. Yakimov, Tatiana O. Bok, Dmitry N. Zarubin
      Abstract: Time-resolved 13C, 23Na, 27Al and 29Si MAS NMR has been applied in situ for monitoring the hydrothermal synthesis of zeolite BEA. Isotopic labelling with 29Si and 13C isotopes has been used to follow the fate of silicious species and structure directing agent ((13CH3-CH2)4NOH). Two mechanistic pathways, namely, solution mediated and solid-solid hydrogel rearrangement have been distinguished for two synthesis procedures studied. The mechanisms of structure directing behavior of TEA+ cations in two reaction pathways have been elucidated. The results show that multinuclear MAS NMR can serve as a superior tool for monitoring hydrothermal synthesis of various solids including zeolites, zeotypes, mesoporous materials, metal organic frameworks and etc. and for the design of novel outstanding materials for different applications.
      PubDate: 2017-09-20T07:21:48.282769-05:
      DOI: 10.1002/ange.201709039
       
  • Therapeutic Vesicular Nanoreactors with Tumor-Specific Activation and
           Self-Destruction for Synergistic Tumor Ablation
    • Authors: Junjie Li; Anjaneyulu Dirisala, Zhishen Ge, Yuheng Wang, Wei Yin, Wendong Ke, Kazuko Toh, Jinbing Xie, Yu Matsumoto, Yasutaka Anraku, Kensuke Osada, Kazunori Kataoka
      Abstract: Polymeric nanoreactors (NRs) have distinct advantages to improve chemical reaction efficiency, but the in vivo applications were limited by lack of tissue-specificity. Herein, novel glucose oxidase (GOD)-loaded therapeutic vesicular NRs (theraNR) are constructed based on the diblock copolymer containing poly(ethylene glycol) (PEG) and copolymerized phenylboronic ester or piperidine-functionalized methacrylate (P(PBEM-co-PEM)). Upon systemic injection, theraNR keep inactive in normal tissues. At tumor site, theraNR are specifically activated by tumor acidity via improved permeability of the membranes. Hydrogen peroxide (H2O2) production by the catalysis of GOD in theraNR increases tumor oxidative stress significantly. Meanwhile, high level of H2O2 induces self-destruction of theraNR releasing quinone methide (QM) to deplete glutathione and suppress antioxidant ability of cancer cells. Finally, theraNR efficiently kill cancer cells and ablate tumor via the synergistic effect.
      PubDate: 2017-09-20T07:21:34.279048-05:
      DOI: 10.1002/ange.201706964
       
  • Rapid Assembly of Diversely Functionalized Spiroindenes by a
           Three-Component Palladium-Catalyzed C-H Amination/Phenol Dearomatization
           Domino Reaction
    • Authors: Liangxin Fan; Jingjing Liu, Lu Bai, Yaoyu Wang, Xinjun Luan
      Abstract: A novel palladium-catalyzed three-component reaction of phenol-derived biaryls with N-benzoyloxyamines and norbornadiene (NBD) has been developed for the assembly of highly functionalized spiroindenes. This domino process was realized through NBD-assisted C-H amination and phenol dearomatization by forming one C-N bond and two C-C bonds in a single step. Preliminary studies indicated that asymmetric control of this transformation was feasible with chiral ligands. Moreover, the potential synthetic utility of this methodology was highlighted by a series of further transformations.
      PubDate: 2017-09-20T04:15:26.323673-05:
      DOI: 10.1002/ange.201708310
       
  • High-Temperature Formed Protective Film at Cathode/Electrolyte Interface:
           A Functional Layer in Lithium-Sulfur Batteries
    • Authors: Shuang-Yan Lang; Yang Shi, Yu-Guo Guo, Rui Wen, Li-Jun Wan
      Abstract: Lithium-sulfur (Li-S) batteries have been attracting wide attention due to their promising high specific capacity. Deep understanding of Li-S interfacial mechanism including the temperature (T) effect is increasingly required to meet the burgeoning demands for battery modification and systematic researches. Herein, interfacial behavior during discharge/charge is investigated at high temperature (HT) of 60 ̊C in electrolyte based on lithium bis(fluorosulfonyl) imide (LiFSI). By in situ atomic force microscopy (AFM), dynamic evolution of insoluble Li2S2 and Li2S is studied at the nanoscale. An in situ formed protective film can be directly monitored at 60 ̊C after Li2S nucleation, retarding side reactions and facilitating interfacial redox. The deep insight into the interfacial processes at HT discovers a direct evidence of the existence of the protective film and reveals its dynamic behaviors, providing a new avenue for electrolyte design and performance enhancement with a long span.
      PubDate: 2017-09-20T03:16:32.133522-05:
      DOI: 10.1002/ange.201706979
       
  • Stable Oxindolyl-based Chichibabin's Hydrocarbon and Müller's
           Hydrocarbon Analogues
    • Authors: Jishan Wu; Jian Wang, Xingdong Xu, Hoa Phan, Tun Seng Herng, Tullimilli Y. Gopalakrishna, Guangwu Li, Jun Ding
      Abstract: Chichibabin's hydrocarbon and Müller's hydrocarbon are classical open-shell singlet diradicaloids but they are highly reactive. Herein we report the successful synthesis of their respective stable analogues, OxR-2 and OxR-3, based on the newly developed oxindolyl radical. X-ray crystallographic analysis on OxR-2 reveals a planar quinoidal backbone similar to Chichibabin's hydrocarbon, in accordance with its small diradical character (y0 = 11.1%) and large singlet-triplet gap (ΔES-T = -10.8 kcal/mol). Variable-temperature NMR studies on OxR-2 disclose a slow cis-/trans- isomerization process in solution through a diradical transition state, with a moderate energy barrier (ΔGǂ298K = 15~16 kcal/mol). OxR-3 exhibits a much larger diradical character (y0 = 80.6%) and a smaller singlet-triple gap (ΔES-T = -3.5 kcal/mol), and thus can be easily populated to paramagnetic triplet diradical. Our studies provide a new type of stable carbon-centered monoradical and diradicaloid.
      PubDate: 2017-09-20T02:21:07.85299-05:0
      DOI: 10.1002/ange.201708612
       
  • Morphology Dependent Cell Imaging by a Self-assembled Diacetylene Peptide
           Amphiphile
    • Authors: Carsten Schmuck; Hao Jiang, Xiao-Yu Hu, Stefanie Schlesiger, Mao Li, Elio Zellermann, Shirley Knauer
      Abstract: Herein, a novel cationic peptide gemini amphiphile containing diacetylene motifs (DA2P) is presented which self-assembles into novel tadpole- and bola-shaped nanostructures at low concentration and nanofibers at higher concentration, respectively. Interestingly, the DA2P assemblies can be polymerized to a fluorescent red phase but only during incubation with HeLa cells, most likely owing to the reorganization of the diacetylene chains of DA2P upon interaction with the cell membrane. The red-fluorescent polymerized DA2P assemblies can serve as a novel cell imaging probe. However, only vesicles, tadpole- and bola-shaped DA2P assemblies can be translocated into HeLa cells, while the nanofiber-like DA2P assemblies are trapped by the cell membranes and do not enter the cells. Hence, morphology dependent cell imaging is observed.
      PubDate: 2017-09-20T02:20:54.342761-05:
      DOI: 10.1002/ange.201708168
       
  • Frontispiz: Facile One-Pot Synthesis of Functional Giant Polymeric
           Vesicles Controlled by Oscillatory Chemistry
    • Authors: Bishnu Prasad Bastakoti; Juan Perez-Mercader
      Abstract: Polymervesikel B. P. Bastakoti und J. Perez-Mercader zeigen in ihrer Zuschrift auf S. 12254, wie die oszillierende Belousov-Zhabotinsky-Reaktion zur Eintopfsynthese selbstorganisierender riesiger Polymervesikel genutzt werden kann.
      PubDate: 2017-09-20T01:55:22.454331-05:
      DOI: 10.1002/ange.201784061
       
  • High thermoelectric performance of new rhombohedral phase of GeSe
           stabilized via alloying with AgSbSe2
    • Authors: Zhiwei Huang; Samuel Miller, Binghui Ge, Mingtao Yan, Shashwat Anand, Tianmin Wu, Pengfei Nan, Yuanhu Zhu, Wei Zhuang, Jeffrey Snyder, Peng Jiang, Xinhe Bao
      Abstract: GeSe is a IV-VI semiconductor, like the excellent thermoelectric materials PbTe and SnSe. Orthorhombic GeSe has been predicted theoretically to have good thermoelectric performance but is difficult to dope experimentally. Like PbTe, rhombohedral GeTe has a multivalley band structure, which is ideal for thermoelectrics and also promotes the formation of Ge vacancies to provide enough carriers for electrical transport. Herein, we investigate the thermoelectric properties of GeSe alloyed with AgSbSe2, which stabilizes a new rhombohedral structure with higher symmetry that leads to a multivalley Fermi surface and a dramatic increase in carrier concentration. The zT of GeAg0.2Sb0.2Se1.4 reaches 0.86 at 710 K, which is 18 times higher than that of pristine GeSe and over four times higher than doped orthorhombic GeSe. Our results open a new avenue towards developing novel thermoelectric materials via crystal phase engineering using a strategy of entropy stabilization of high symmetry alloys.
      PubDate: 2017-09-20T01:15:58.037789-05:
      DOI: 10.1002/ange.201708134
       
  • (4+3)-Cycloaddition Reactions of N-Alkyl Oxidopyridinium Ions
    • Authors: Chencheng Fu; Nestor Lora, Patrick L. Kirchhoefer, Dong Reyoul Lee, Erich Altenhoefer, Natasha L. Hungerford, Elizabeth H. Krenske, Michael Harmata
      Abstract: N-Methylation of methyl 5-hydroxynicotinate followed by reaction with a diene in the presence of triethylamine afforded (4+3)-cycloadducts in good to excellent yields. High regioselectivity was exhibited with 1-substituted and 1,2-disubstituted butadienes. Density functional theory calculations indicate that the cycloaddition involves concerted addition of the diene onto the oxidopyridinium ion. The process provides rapid access to bicyclic nitrogenous structures resembling natural alkaloids.
      PubDate: 2017-09-19T20:46:34.139298-05:
      DOI: 10.1002/ange.201708320
       
  • Olefin-Supported Rhenium(III) Terminal Oxo Complexes Generated by
           Nucleophilic Addition to a Cyclopentadienyl Ligand
    • Authors: Trevor Lohrey; Robert Bergman, John Arnold
      Abstract: The reactivity of the oxo Re(V) β-diketiminate, OReCl2(BDI), with various cyclopentadienide (Cp) sources has been investigated. As a result, we have developed a route to a new class of terminal oxo complexes of Re(III) supported by olefin moieties of substituted cyclopentadienes. The success of this pathway is due to the electrophilic nature of the Cp ligand in the cation, [ORe(η5-Cp)(BDI)]+ (3+), which allows for nucleophilic attack by a variety of reagents under mild conditions. In contrast, tBuNC was found to attack at the oxo moiety to produce isocyanate by oxygen atom transfer.
      PubDate: 2017-09-19T20:46:28.478537-05:
      DOI: 10.1002/ange.201707957
       
  • Synthesis and Utilization of Nitroalkyne Equivalents in Batch and
           Continuous Flow
    • Authors: Peter D Morse; Timothy F Jamison
      Abstract: We report a method for overcoming the low stability of nitroalkynes through the development of nitrated vinyl silyltriflate equivalents. Because of their instability, nitroalkynes have only rarely been utilized in synthesis. The reactivity of these silyltriflates, which are prepared in situ, is exemplified by dipolar cycloaddition reactions with nitrones to give highly substituted 4-nitro-4-isoxazolines in high yields. This approach has proven general for several different alkyl and aryl substituted alkynes. In order to minimize the accumulation of potentially hazardous reaction intermediates, we have also developed a continuous flow variant of this method that is capable of carrying out the entire reaction sequence in a good yield and a short residence time.
      PubDate: 2017-09-19T20:46:19.846433-05:
      DOI: 10.1002/ange.201706157
       
  • Alkynylation of sp2 C(O)−H Bonds Enabled by Photoredox-Mediated
           Hydrogen Atom Transfer
    • Authors: Satobhisha Mukherjee; Aleyda Garza-Sanchez, Adrian Tlahuext Aca, Frank Glorius
      Abstract: The development of new Hydrogen Atom Transfer (HAT) strategies within the framework of photoredox catalysis is highly appealing for its power to activate a desired C−H bond in the substrate leading to its selective functionalization. Reported here, is the first photoredox mediated Hydrogen Atom Transfer protocol for the efficient synthesis of ynones, ynamides and ynoates with high regio- and chemoselectivity by direct functionalization of sp2 C(O)-H bonds. The broad synthetic application of this method has been demonstrated by the selective functionalization of C(O)-H bonds within complex molecular scaffolds.
      PubDate: 2017-09-19T20:46:10.082784-05:
      DOI: 10.1002/ange.201708037
       
  • Total Synthesis of (+)-Gracilamine Based on Oxidative Phenolic Coupling
           Reaction and Determination of its Absolute Configuration
    • Authors: Kazuo Nagasawa; Minami Odagi, Yoshiharu Yamamoto
      Abstract: The Amaryllidaceae alkaloid (+)-gracilamine (1), isolated from Galanthus gracilis, contains a characteristic pentacyclic ring system with seven consecutive stereogenic centers, including an all-carbon quaternary stereocenter. Herein, we report the first enantioselective total synthesis of (+)-gracilamine (1), featuring a diastereoselective phenolic coupling reaction followed by a regioselective intramolecular aza-Michael reaction to construct the ABCE ring system. The stereochemistry at C3a in 1 is controlled by the stereocenter at C9a, which was selectively generated (91% ee) by utilizing an organocatalytic enantioselective aza-Friedel-Crafts reaction developed by our group. This synthesis reveals that the absolute configuration of (+)-gracilamine (1) is (3aR, 4S, 5S, 6R, 7aS, 8R, 9aS).
      PubDate: 2017-09-19T20:45:58.081963-05:
      DOI: 10.1002/ange.201708575
       
  • One-pot, Three-Component Sulfonimidamide Synthesis exploiting the
           Sulfinylamine Reagent N-Sulfinyltritylamine, TrNSO
    • Authors: Thomas Q Davies; Adrian Hall, Michael C. Willis
      Abstract: Sulfonimidamides are increasingly important molecules in medicinal chemistry and agrochemistry, but their preparation requires lengthy synthetic sequences, which has likely limited their use. We describe a one-pot de novo synthesis of sulfonimidamides from widely available organometallic reagents and amines. This convenient and efficient process uses a stable sulfinylamine reagent, N-sulfinyltritylamine (TrNSO), available in one step on 10 gram scale, as a linchpin. In contrast to classical approaches starting from thiols or their derivatives, our TrNSO-based approach facilitates the rapid assembly of the three reaction components into a variety of differentially substituted sulfonimidamides containing medicinally relevant moieties, including pyridines and indoles. Analogues of the sulfonamide-containing COX-2 inhibitor Celecoxib were prepared and evaluated.
      PubDate: 2017-09-19T20:45:46.142873-05:
      DOI: 10.1002/ange.201708590
       
  • Covalent Triazine Frameworks via a Low Temperature Polycondensation
           Approach
    • Authors: kewei Wang; Liming Yang, Xi wang, Liping Guo, Guang Cheng, Chun Zhang, Shangbin Jin, Bien Tan, Andrew Cooper
      Abstract: Covalent triazine frameworks (CTFs) are normally synthesized by ionothermal methods. The harsh synthetic conditions and associated limited structural diversity do not benefit for further development and practical large-scale synthesis of CTFs. Herein we report a new strategy to construct CTFs (CTF-HUSTs) via a polycondensation approach, which allows the synthesis of CTFs under mild conditions from a wide array of building blocks. Interestingly, these CTFs display a layered structure. The CTFs synthesized were also readily scaled up to gram quantities. The CTFs are potential candidates for separations, photocatalysis and for energy storage applications. In particular, CTF-HUSTs are found to be promising photocatalysts for sacrificial photocatalytic hydrogen evolution with a maximum rate of 2647 µmol h-1 g-1 under visible light. We also applied a pyrolyzed form of CTF-HUST-4 as an anode material in a sodium-ion battery achieving an excellent discharge capacity of 467 mAh g-1.
      PubDate: 2017-09-19T11:41:22.916554-05:
      DOI: 10.1002/ange.201708548
       
  • Synthesis of a Metallo-Iminosilane via a Silanone-Metal π-Complex
    • Authors: Matthias Driess; Terrance J Hadlington, Tibor Szilvási
      Abstract: Facile oxygenation of the acyclic amido chlorosilylene-bis(N-heterocyclic carbene) Ni0 complex 1, [{N(Dipp)(SiMe3)ClSi:Ni(NHC)2] (Dipp = 2,6-Pri2C6H4; N-heterocyclic carbene = C[(Pri)NC(Me)]2) with N2O furnishes the first Si-metallo-iminosilane complex, [DippN=Si(OSiMe3)Ni(Cl)(NHC)2] 3, in a cascade of rearrangement reactions. Markedly, the formation of 3 ensues via a silanone (Si=O)-Ni pi-complex 2 as the initial product, which has been predicted by DFT calculations and could be observed spectroscopically. Both the Si=O and Si=N moieties in 2 and 3, respectively, undergo hydroboration, a reaction which typically requires a catalyst for the C=O and C=N analogues.
      PubDate: 2017-09-19T10:46:37.388949-05:
      DOI: 10.1002/ange.201708923
       
  • Hydrogen Transfer-Mediated a-Functionalization of 1,8-Naphthyridines by a
           Strategy Overcoming the Over-Hydrogenation Barrier
    • Authors: Xiuwen Chen; He Zhao, Chunlian Chen, Huanfeng Jiang, Min Zhang
      Abstract: By a hydrogen transfer-mediated activation mode for non-activated pyridyl nucleus, a general catalytic hydrogen transfer-mediated -functionalization of 1,8-naphthyridines is reported for the first time. Its -site selectively couples with the C8-site of various tetrahydroquinolines (THQs) to afford novel -functionalized tetrahydro 1,8-naphthyridines, a class of synthetically useful building blocks and potential candidates for the discovery of therapeutic and bio-active products. The utilization of THQs as inactive hydrogen donors (HDs) appears to be a key strategy to overcome the over-hydrogenation barrier and address the chemo-selectivity issue. The developed chemistry features operational simplicity, readily available catalyst and good functional tolerance, and offers a significant basis for further development of new protocols to directly transform or functionalize inert N-heterocycles.
      PubDate: 2017-09-19T10:46:19.888127-05:
      DOI: 10.1002/ange.201707702
       
  • Asymmetric Total Syntheses of Communesin F and a Putative Member of the
           Communesin Family
    • Authors: David Yu-Kai Chen
      Abstract: Here we report asymmetric total syntheses of communesin F and a putative member of the communesin family of bis-aminal alkaloid natural products. The successful strategy featured the invention of an asymmetric organocatalytic reaction to unify two oxindole subunits, a Ti(OiPr)4-mediated dehydrative skeletal rearrangement, and a late-stage Pd(OAc)2-catalyzed directed CH-alkenylation reaction. Collectively, the synthetic technologies disclosed herein enabled the preparation of a late-stage polycyclic intermediate catered for the synthesis of both naturally occurring and designed communesins. More importantly, speculated and yet to be discovered member(s) of the communesin family can now be accessed to facilitate a better understanding of the communesin biosynthetic network.
      PubDate: 2017-09-19T10:45:52.466198-05:
      DOI: 10.1002/ange.201707806
       
  • Cobalt versus osmium: control of both trans and cis selectivity in
           construction of the EFG rings of pectenotoxin 4
    • Authors: Ahria Roushanbakhti; Yifan Liu, Paul Winship, Michael Tucker, Wasim Akhtar, Daryl Walter, Gail Wrigley, Timothy James Donohoe
      Abstract: Catalytic oxidative cyclisation reactions have been employed for the synthesis of the E and F rings of the complex natural product target pectenotoxin 4. The choice of metal catalyst (cobalt or osmium based) allowed for the formation of THF rings with either trans or cis stereoselectivity. Fragment union using a modified Julia reaction then enabled the synthesis of an advanced synthetic intermediate containing the EF and G rings of the target.
      PubDate: 2017-09-19T10:45:38.510384-05:
      DOI: 10.1002/ange.201708278
       
  • One-Step Reforming of CO2 and CH4 into High-Value Liquid Chemicals and
           Fuels at Room Temperature by Plasma-Driven Catalysis
    • Authors: Li Wang; Yanhui Yi, Chunfei Wu, Hongchen Guo, Xin Tu
      Abstract: The conversion of CO2 with CH4 into liquid fuels and chemicals in a single-step catalytic process that bypasses the production of syngas remains a challenge. In this study, liquid fuels and chemicals (e.g., acetic acid, methanol, ethanol, and formaldehyde) were synthesized in a one-step process from CO2 and CH4 at room temperature (30 °C) and atmospheric pressure for the first time by using a novel plasma reactor with a water electrode. The total selectivity to oxygenates was approximately 50–60 %, with acetic acid being the major component at 40.2 % selectivity, the highest value reported for acetic acid thus far. Interestingly, the direct plasma synthesis of acetic acid from CH4 and CO2 is an ideal reaction with 100 % atom economy, but it is almost impossible by thermal catalysis owing to the significant thermodynamic barrier. The combination of plasma and catalyst in this process shows great potential for manipulating the distribution of liquid chemical products in a given process.Elegante Abkürzung: Die Synthese von flüssigen Brennstoffen und Chemikalien (z. B. Essigsäure, Methanol, Ethanol und Formaldehyd) aus CO2 und CH4 gelang durch die Verwendung eines neuen Plasmareaktors mit einer Wasserelektrode erstmals in einem einstufigen Prozess bei Raumtemperatur (30 °C) und Atmosphärendruck. Die Selektivität für sauerstoffhaltige Verbindungen beträgt 50–60 %, mit Essigsäure als Hauptkomponente.
      PubDate: 2017-09-19T08:06:10.578202-05:
      DOI: 10.1002/ange.201707131
       
  • Intramolekulare π-π-Wechselwirkungen in flexibel verbrückten, teilweise
           fluorierten Bisarenen in der Gasphase
    • Authors: Sebastian Blomeyer; Marvin Linnemannstöns, Jan Hendrick Nissen, Jannik Paulus, Beate Neumann, Hans-Georg Stammler, Norbert W. Mitzel
      Abstract: Mittels Hydrosilylierungs- und C-C-Kupplungsreaktionen wurden drei mit (CH2)3- und (CH2)2SiMe2-Einheiten verbrückte Verbindungen mit Phenyl- und Pentafluorphenylringen synthetisiert. Im Festkörper bilden sie primär dimere oder kettenartige, von intermolekularen π-π-Wechselwirkungen dominierte Aggregate. Die Struktur des häufigsten Konformers der freien Moleküle zeigt jeweils, bestimmt mittels Gas-Elektronen-Diffraktion, eine signifikante intramolekulare Stabilisierung durch π-π-Wechselwirkungen. Die nächstenergiereicheren Konformere für die Siliciumverbindungen zeigen σ-π-Wechselwirkungen zwischen Methyl- und (Pentafluor-)Phenylgruppen und können im GED-Experiment nicht vollständig ausgeschlossen werden. Im Unterschied dazu besteht C6H5(CH2)3C6F5 nur aus einem einzigen Konformer. Die Gasphasenstrukturen dienen als Referenz für die Evaluation einer Reihe (dispersionskorrigierter) quantenchemischer Methoden.Ungestörte Strukturen von Verbindungen mit C6H5- und C6F5-Gruppen, verbrückt durch (CH2)3- und (CH2)2SiMe2-Einheiten, in der Gasphase zeigen Faltung durch intramolekulare Dispersionskräfte, während im Festkörper die gestreckten Formen vorliegen und intermolekular wechselwirken. Die experimentellen Daten dienen als Qualitätsreferenz für quantenchemische Rechnungen.
      PubDate: 2017-09-19T08:05:46.424638-05:
      DOI: 10.1002/ange.201707716
       
  • Alkynyl Thioethers in Gold-Catalyzed Annulations to form Oxazoles
    • Authors: Raju Jannapu Reddy; Matthew P. Ball-Jones, Paul W. Davies
      Abstract: Non-oxidative, regioselective, and convergent access to densely functionalized oxazoles is realized in a functional-group tolerant manner using alkynyl thioethers. Sulfur-terminated alkynes provide access to reactivity previously requiring strong donor-substituted alkynes such as ynamides. Sulfur does not act in an analogous donor fashion in this gold-catalyzed reaction, thus leading to complementary regioselective outcomes and addressing the limitations of using ynamides.Auf anderem Wege: Goldkatalysierte Ringschlüsse von Alkinylthioethern führen glatt und konvergent zu hochfunktionalisierten 1,3-Oxazolen. Der Schwefelsubstituent ist entscheidend für die gewünschte Reaktivität und bietet außerdem einen Ansatzpunkt für die spätere Funktionalisierung. Anders als früher beschrieben, verläuft die Reaktion nicht über einen Ketenthionium-Pfad.
      PubDate: 2017-09-19T08:01:23.571932-05:
      DOI: 10.1002/ange.201706850
       
  • Iron-Catalyzed anti-Selective Carbosilylation of Internal Alkynes
    • Authors: Takahiro Iwamoto; Tatsushi Nishikori, Naohisa Nakagawa, Hikaru Takaya, Masaharu Nakamura
      Abstract: Reported is the anti-selective carbosilylation of internal alkynes with silylborane and alkyl halides using a FeBr2/DPPE catalyst system. The iron catalyst allows simultaneous introduction of a carbon electrophile and a silicon nucleophile to simple internal alkynes, including diaryl-, dialkyl-, and aryl/alkyl-substituted alkynes, in a highly stereoselective manner. Alkyl halides are applicable as the electrophiles, thereby enabling the synthesis of a variety of tetrasubstituted alkenylsilanes. In addition, syn-selective carbosilylation was achieved through stereoswitching, by using a silylborane having oxygen functionality on the silyl group. This novel iron-catalyzed carbosilylation is a useful tool for expedient synthesis of stereodefined multisubstituted olefins, a fundamental structural motif in organic chemistry.Wahlweise syn oder anti: Die Carbosilylierung interner Alkine mit PhMe2SiBpin und Alkylhalogeniden gelingt unter FeBr2/dppe-Katalyse unabhängig von der Struktur des Alkins und Elektrophils mit hoher anti-Selektivität. Durch Verwendung von Ph2(MeO)SiBpin ist auch eine syn-selektive Carbosilylierung möglich. Die Sauerstoff-Funktionalität ist entscheidend für die syn-Selektivität.
      PubDate: 2017-09-19T08:01:09.783923-05:
      DOI: 10.1002/ange.201706333
       
  • Radikalische Hydrodehalogenierung von Arylbromiden und -chloriden mit
           Natriumhydrid und 1,4-Dioxan
    • Authors: Tobias Hokamp; Abhishek Dewanji, Maximilian Lübbesmeyer, Christian Mück-Lichtenfeld, Ernst-Ulrich Würthwein, Armido Studer
      Abstract: Eine praktische Methode zur radikalischen Kettenreduktion von diversen Arylbromiden und -chloriden wird vorgestellt. In dem thermischen Prozess werden NaH und 1,4-Dioxan als Reagenzien sowie 1,10-Phenanthrolin als Initiator eingesetzt. Die Hydrodehalogenierungen können mit typischen radikalischen Cyclisierungsreaktionen kombiniert werden, was ihren radikalischen Charakter belegt. DFT-Berechnungen und experimentelle Studien stützen den vorgeschlagenen Mechanismus über Elektronenkatalyse.Die Kombination macht's! NaH dient in Kombination mit 1,4-Dioxan als Reagenz für die radikalische Kettenreduktion diverser Arylhalogenide. Die Hydrodehalogenierung wird durch Phenanthrolin (Phen) bei erhöhten Temperaturen initiiert und kann mit typischen radikalischen Cyclisierungen kombiniert werden. Die Reaktionen verlaufen über Elektronenkatalyse.
      PubDate: 2017-09-19T08:00:23.365906-05:
      DOI: 10.1002/ange.201706534
       
  • Protonation of Ferrocene: A Low-Temperature X-ray Diffraction Study of
           [Cp2FeH](PF6) Reveals an Iron-Bound Hydrido Ligand
    • Authors: Moritz Malischewski; Konrad Seppelt, Jörg Sutter, Frank W. Heinemann, Birger Dittrich, Karsten Meyer
      Abstract: Ferrocene, Cp2Fe, is quantitatively protonated in a mixture of liquid HF/PF5 to yield [Cp2FeH](PF6), which was characterized by 1H/13C NMR and 57Fe Mössbauer spectroscopy as well as single-crystal X-ray diffraction analysis. X-ray diffraction analysis at 100 K revealed a disordered, iron-coordinated hydrido ligand, which was unambiguously located by aspherical atom refinement at 100 K, and by analyzing the non-disordered crystal structure at 30 K, revealing a non-agostic structure.Nach mehr als 50 Jahren wurde der Mechanismus elektrophiler Substitutionen an Ferrocen mit dem einfachsten Elektrophil, H+, erneut untersucht, und das potenzielle Intermediat [Cp2FeH]+ konnte isoliert werden. [Cp2FeH](PF6)-Einkristalle wurden aus einer wasserfreien HF/PF5-Mischung erhalten. Die Röntgenstrukturanalyse erbrachte den Nachweis für eine nicht-agostische Struktur mit einem an das Eisenzentrum gebundenen Hydrido-Liganden.
      PubDate: 2017-09-19T07:41:24.256524-05:
      DOI: 10.1002/ange.201704854
       
  • Meta-Selective C−H Borylation of Benzylamine, Phenethylamine and
           Phenylpropylamine-Derived Amides Enabled by a Single Anionic Ligand
    • Authors: Holly J. Davis; Georgi R. Genov, Robert J. Phipps
      Abstract: Selective functionalization at the meta position of arenes remains a significant challenge. In this work, we demonstrate that a single anionic bipyridine ligand bearing a remote sulfonate group enables selective iridium-catalyzed borylation of a range of common amine-containing aromatic molecules at the arene meta position. We propose that this selectivity is the result of a key hydrogen bonding interaction between the substrate and catalyst. The scope of this meta-selective borylation is demonstrated on amides derived from benzylamines, phenethylamines and phenylpropylamines; amine-containing building blocks of great utility in many applications.Geschickte Positionierung: Ein Bipyridinligand, der eine entfernt stehende anionische Sulfonatgruppe trägt, dirigiert bei einer Reihe von amidischen Arenen die Iridium-katalysierte Borylierung an die meta-Position. Eine Wasserstoffbrückenwechselwirkung sorgt für die richtige Positionierung des Iridiumzentrums in der entscheidenden C-H-Aktivierung.
      PubDate: 2017-09-19T07:35:45.115058-05:
      DOI: 10.1002/ange.201708967
       
  • Preorganization and Cooperation for Highly Efficient and Reversible
           Capture of Low-Concentration CO2 by Ionic Liquids
    • Authors: Yanjie Huang; Guokai Cui, Yuling Zhao, Huiyong Wang, Zhiyong Li, Sheng Dai, Jianji Wang
      Abstract: A novel strategy based on the concept of preorganization and cooperation has been designed for a superior capacity to capture low-concentration CO2 by imide-based ionic liquids. By using this strategy, for the first time, an extremely high gravimetric CO2 capacity of up to 22 wt % (1.65 mol mol−1) and excellent reversibility (16 cycles) have been achieved from 10 vol. % of CO2 in N2 when using an ionic liquid having a preorganized anion. Through a combination of quantum-chemical calculations and spectroscopic investigations, it is suggested that cooperative interactions between CO2 and multiple active sites in the preorganized anion are the driving force for the superior CO2 capacity and excellent reversibility.Eine neuartige Strategie der Vororganisation und Kooperation ergab eine höhere Kapazität (22 Gew.-%, 1.65 mol mol−1) für den Einfang von niedrig konzentriertem CO2 (10 Vol.-% CO2 in N2) durch imidbasierte ionische Flüssigkeiten und eine exzellente Reversibilität (16 Zyklen). Kooperative Wechselwirkungen zwischen CO2 und mehreren aktiven Zentren im vororganisierten Anion sind beteiligt.
      PubDate: 2017-09-19T07:35:25.521194-05:
      DOI: 10.1002/ange.201706280
       
  • Solution Structure of AlMe2F and its Reactivity with Metallocenes:
           Mimicking Cation-Anion Interactions in Metallocenium-MAO Inner-Sphere Ion
           Pairs
    • Authors: Leone Oliva; Patrizia Oliva, Nunzia Galdi, Claudio Pellecchia, Leonardo Sian, Alceo Macchioni, Cristiano Zuccaccia
      Abstract: The solution structure of AlMe2F and its reactivity with a prototypical ansa-metallocene have been investigated by advanced NMR techniques, in an attempt to indirectly shed some light on the "structure and working principles" of methylalumoxane (MAO) mixtures in olefin polymerization. In solution, AlMe2F leads to a complex equilibrium of oligomeric species, including a heterocubane [(Me2Al)4F4] tetramer, resembling the behavior of MAO. Such a complex mixture reacts with the prototypical ansa-zirconocene (ETH)ZrMe2 affording [(ETH)ZrMeδ+(μ-F)(AlMe2F)nAlMe3δ-] inner-sphere ion pairs through the successive insertions/deinsertion of AlMe2F units into the Zr…(μ-F) bond.
      PubDate: 2017-09-19T06:45:26.658313-05:
      DOI: 10.1002/ange.201707194
       
  • Highly 2,3-Selective Polymerization of Phenylallene and Derivatives with
           Rare-Earth Metal Catalyst: from Amorphous to Crystalline Products
    • Authors: Fei Lin; Zhaohe Liu, Tiantian Wang, Dongmei Cui
      Abstract: Rare-earth metal complexes (Flu-CH2-Py)Ln(CH2SiMe3)2(THF)n (Ln = Sc(1), Lu(2), Tm(3), Y(4) and Gd(5)), upon the activation of [Ph3C][B(C6F5)4] and AliBu3, were firstly employed to catalyze the polymerization of allene derivatives under mild conditions. The Gd, Y, Tm, Lu metal based precursors exhibited distinguished 2,3-selectivity (>99.9%) for phenylallene (PA) polymerization, whereas the smallest Sc metal based precursor showed a moderate 2,3-selectivity. The activity increased with the central metal size following the trend of Gd(5)>Tm(4)>Y(3)>Lu(2)>Sc(1). Moreover, Gd(5) also realized unprecedentedly the purely 2,3-selective polymerizations of polar or nonpolar allene derivatives, para-methylphenylallene, para-flourophenylallene and para-methoxyphenylallene, regardless of the electron donating or withdrawing substituents. Owing to the highly regular backbones, these polymers except PPA were crystalline, which represent the first crystalline allene derivatives based polymers.
      PubDate: 2017-09-19T04:40:37.19321-05:0
      DOI: 10.1002/ange.201707601
       
  • Stereospecific Reaction of Donor-Acceptor Cyclopropanes with Thioketones:
           A Novel Access to Highly Substituted Tetrahydrothiophenes
    • Authors: Daniel B. Werz; André Augustin, Peter G. Jones, Maximilian Sensse
      Abstract: Lewis-acid-catalyzed reactions of 2-substituted cyclopropane 1,1-dicarboxylates with thioketones are described. Highly substituted tetrahydrothiophenes with two adjacent quaternary carbon atoms were obtained in a stereospecific manner under mild conditions and in high yield using AlCl3 as Lewis acid. Moreover, an intramolecular approach was successfully implemented to gain access to sulfur-bridged [n.2.1] bicyclic ring systems. Conversion of selenoketones, the heavier analogs, under similar conditions resulted in the formation of various tetrahydroselenophenes.
      PubDate: 2017-09-19T04:40:26.798022-05:
      DOI: 10.1002/ange.201708346
       
  • Organocatalytic Enantioselective Protonation for Photoreduction of
           Activated Ketones and Ketimines Induced by Visible Light
    • Authors: Lu Lin; Xiangbin Bai, Xinyi Ye, Xiaowei Zhao, Choon-Hong Tan, Zhiyong Jiang
      Abstract: The first catalytic asymmetric photoreduction of 1,2-diketones and α-keto ketimines under visible light irradiation is reported. A transition-metal-free synergistic catalysis platform harnessing dicyanopyrazine-derived chromophore (DPZ) as the photoredox catalyst and a non-covalent chiral organocatalyst is effective for these transformations. With the flexible use of a chiral Brønsted acid or base in H+ transfer interchange to control the elusive enantioselective protonation, a variety of chiral α-hydroxy ketones and α-amino ketones were obtained with high yields and enantioselectivities.
      PubDate: 2017-09-19T03:40:46.840216-05:
      DOI: 10.1002/ange.201707899
       
  • A Simple and Broadly Applicable C-N Bond Forming Dearomatization Protocol
           Enabled by Bifunctional Amino-Reagents
    • Authors: Xiaofeng Ma; Joshua Farndon, Tom Young, Natalie Fey, John Bower
      Abstract: A C-N bond forming dearomatization protocol with broad scope is outlined. Specifically, bifunctional amino-reagents are used for sequential nucleophilic and electrophilic C-N bond formations, with the latter effecting the key dearomatization step. Using this approach, γ-arylated alcohols are converted to a wide range of differentially protected spirocyclic pyrrolidines in just two or three steps.
      PubDate: 2017-09-19T02:40:47.193008-05:
      DOI: 10.1002/ange.201708176
       
  • Constructing a Strongly Absorbing Low-Bandgap Polymer Acceptor for
           High-Performance All-Polymer Solar Cells
    • Authors: Zhi-Guo Zhang; Yankang Yang, Jia Yao, Lingwei Xue, Shanshan Chen, Xiaojun Li, William Morrison, Changduk Yang, Yongfang Li
      Abstract: All-polymer solar cells (all-PSCs) offer unique morphology stability for the application as flexible devices, but the lack of high-performance polymer acceptors limits their power conversion efficiency (PCE) to a value lower than those of the PSCs based on fullerene derivative or organic small molecule acceptors. We herein demonstrate a strategy to synthesize a high-performance polymer acceptor PZ1 by embedding an acceptor–donor–acceptor building block into the polymer main chain. PZ1 possesses broad absorption with a low band gap of 1.55 eV and high absorption coefficient (1.3×105 cm−1). The all-PSCs with the wide-band-gap polymer PBDB-T as donor and PZ1 as acceptor showed a record-high PCE of 9.19 % for the all-PSCs. The success of our polymerization strategy can provide a new way to develop efficient polymer acceptors for all-PSCs.Energieumwandlung: Durch Einbau eines organischen Halbleiterbausteins mit Akzeptor-Donor-Akzeptor-Struktur in eine Polymerhauptkette wird ein ungewöhnlicher Polymerakzeptor mit niedriger Bandlücke, rotverschobener Absorption und großem Absorptionskoeffizienten erhalten. Der Polymerakzeptor liefert einen rekordhohen Wirkungsgrad von 9.19 % in Polymersolarzellen.
      PubDate: 2017-09-19T00:35:32.571487-05:
      DOI: 10.1002/ange.201707678
       
  • Conjugated Polymer with Intrinsic Alkyne Units for Synergistically
           Enhanced Raman Imaging in Living Cells
    • Authors: Shengliang Li; Tao Chen, Yunxia Wang, Libing Liu, Fengting Lv, Zhiliang Li, Yanyi Huang, Kirk S. Schanze, Shu Wang
      Abstract: Development of Raman-active materials with enhanced and distinctive Raman vibrations in the Raman-silent region (1800–2800 cm−1) is highly required for specific molecular imaging of living cells with high spatial resolution. Herein, water-soluble cationic conjugated polymers (CCPs), poly(phenylene ethynylene) (PPE) derivatives, are explored for use as alkyne-state-dependent Raman probes for living cell imaging due to synergetic enhancement effect of alkyne vibrations in Raman-silent region compared to alkyne-containing small molecules. The enhanced alkyne signals result from the integration of alkyne groups into the rigid backbone and the delocalized π-conjugated structure. PPE-based conjugated polymer nanoparticles (CPNs) were also prepared as Raman-responsive nanomaterials for distinct imaging application. This work opens a new way into the development of conjugated polymer materials for enhanced Raman imaging.Zellbeobachtung: Kationische Poly(phenylenethinylen)(PPE)-Derivate wurden als Raman-Sonden für die Lebendzell-Bildgebung entwickelt. Das Funktionsprinzip beruht auf synergistischer Verstärkung der Alkinschwingungen in Raman-stummen Regionen durch Einbau von Alkingruppen in das Polymergerüst. Außerdem wurden PPE-basierte konjugierte Polymernanopartikel als Raman-responsive Nanomaterialien für spezifische Bildgebungsanwendungen hergestellt.
      PubDate: 2017-09-19T00:31:09.540269-05:
      DOI: 10.1002/ange.201707042
       
  • Polyamine-Mediated Stoichiometric Assembly of Ribonucleoproteins for
           Enhanced mRNA Delivery
    • Authors: Jiahe Li; Yanpu He, Wade Wang, Connie Wu, Celestine Hong, Paula T. Hammond
      Abstract: Messenger RNA (mRNA) represents a promising class of nucleic acid drugs. Although numerous carriers have been developed for mRNA delivery, the inefficient mRNA expression inside cells remains a major challenge. Inspired by the dependence of mRNA on 3′-terminal polyadenosine nucleotides (poly A) and poly A binding proteins (PABPs) for optimal expression, we complexed synthetic mRNA containing a poly A tail with PABPs in a stoichiometric manner and stabilized the ribonucleoproteins (RNPs) with a family of polypeptides bearing different arrangements of cationic side groups. We found that the molecular structure of these polypeptides modulates the degree of PABP-mediated enhancement of mRNA expression. This strategy elicits an up to 20-fold increase in mRNA expression in vitro and an approximately fourfold increase in mice. These findings suggest a set of new design principles for gene delivery by the synergistic co-assembly of mRNA with helper proteins.Obwohl bereits mehrere Träger für den mRNA-Transport entwickelt worden sind, stellt die ineffiziente mRNA-Expression in Zellen weiterhin ein großes Hindernis dar. Weil zur optimalen Expression von mRNA 3′-terminale Polyadenosin-Nucleotide (poly A) und poly-A-bindende Proteine (PABPs) notwendig sind, wurde synthetische mRNA mit einem poly-A-Rest stöchiometrisch mit PABPs komplexiert.
      PubDate: 2017-09-19T00:30:52.144065-05:
      DOI: 10.1002/ange.201707466
       
  • Fluorine Pseudocontact Shifts Used for Characterizing the Protein–Ligand
           Interaction Mode in the Limit of NMR Intermediate Exchange
    • Authors: Jia Gao; E Liang, Rongsheng Ma, Fudong Li, Yixiang Liu, Jiuyang Liu, Ling Jiang, Conggang Li, Haiming Dai, Jihui Wu, Xuncheng Su, Wei He, Ke Ruan
      Abstract: The characterization of protein–ligand interaction modes becomes recalcitrant in the NMR intermediate exchange regime as the interface resonances are broadened beyond detection. Here, we determined the 19F low-populated bound-state pseudocontact shifts (PCSs) of mono- and di-fluorinated inhibitors of the BRM bromodomain using a highly skewed protein/ligand ratio. The bound-state 19F PCSs were retrieved from 19F chemical exchange saturation transfer (CEST) in the presence of the lanthanide-labeled protein, which was termed the 19F PCS-CEST approach. These PCSs enriched in spatial information enabled the identification of best-fitting poses, which agree well with the crystal structure of a more soluble analog in complex with the BRM bromodomain. This approach fills the gap of the NMR structural characterization of lead-like inhibitors with moderate affinities to target proteins, which are essential for structure-guided hit-to-lead evolution.Starke Linienverbreiterung durch intermediären Austausch limitiert die Anwendung der NMR-Spektroskopie für Untersuchungen der Interaktionsweise Leitsubstanz-ähnlicher Inhibitoren mit moderater Affinität für Targetproteine. Durch 19F-Austauschsättigungstransfer werden im gebundene Zustand schwach populierte 19F-Pseudokontaktverschiebungen erhalten, die die Identifizierung der besten Konformation des BRM-Bromodomäneninhibitors ermöglichen.
      PubDate: 2017-09-19T00:30:25.243966-05:
      DOI: 10.1002/ange.201707114
       
  • Peroxidyme-Amplified Radical Chain Reaction (PARCR): Visible Detection of
           a Catalytic Reporter
    • Authors: John P. Goertz; Ian M. White
      Abstract: Peroxidyme Amplified Radical Chain Reaction (PARCR), a novel enzyme-free system that achieves exponential amplification of a visible signal, is presented. Typical enzyme-free amplification systems that produce a visible readout suffer from long reaction times, low sensitivity, and narrow dynamic range. PARCR employs photocatalyzed nonlinear signal generation, enabling unprecedented one-pot, naked-eye detection of a catalytic reporter from 1 μm down to 100 pm. In this reaction, hemin-binding peroxidase-mimicking DNAzymes (“peroxidymes”) mediate the NADH-driven oxidation of a colorless, nonfluorescent phenoxazine dye (Amplex Red) to a brightly colored, strongly fluorescent product (resorufin); illumination with green light initiates multiple radical-forming positive-feedback loops, rapidly producing visible levels of resorufin. Collectively, these results demonstrate the potential of PARCR as an easy-to-use readout for a range of detection schemes, including aptamer labels, hybridization assays, and nucleic acid amplification.Vom Nachteil zum Vorteil: Die Oxidationswirkung katalytischer Nucleinsäuren und die viel geschmähte Lichtempfindlichkeit des Phenoxazinfarbstoffs Amplex Red ermöglichten zusammen die Entwicklung einer exponentiell fortschreitenden Reaktion, die optisch verfolgt werden kann. Mit diesem Assay lässt sich der katalytische Reporter im Konzentrationsbereich 1 μm–100 pm einfach erkennen.
      PubDate: 2017-09-19T00:26:05.041404-05:
      DOI: 10.1002/ange.201706163
       
  • Enhanced Photoactivity from Single-crystalline SrTaO2N Nanoplates
           Synthesized by Topotactic Nitridation
    • Authors: Jie Fu; Sara Elizabeth Skrabalak
      Abstract: There are few methods yielding oxynitride crystals with defined shape, yet shape-controlled crystals often render enhanced photoactivity. Here, single-crystalline SrTaO2N nanoplates and polyhedra are achieved selectively. Central to these synthetic advances is the crystallization pathways used, where single-crystalline SrTaO2N nanoplates form by topotactic nitridation of aerosol-prepared Sr2Ta2O7 nanoplates and SrTaO2N polyhedra form by flux-assisted nitridation of the nanoplates. Evaluation of these materials for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) showed improved performance for the SrTaO2N nanoplates, with a record apparent quantum efficiency (AQE) of 6.1% for OER compared to the polyhedra (AQE: 1.6%) and SrTaO2N polycrystals (AQE: 0.6%). The enhanced performance from the nanoplates arises from their morphology and lower defect density. These results highlight the importance of developing new synthetic routes to high quality oxynitrides.
      PubDate: 2017-09-18T20:45:53.338735-05:
      DOI: 10.1002/ange.201708645
       
  • Biphasic Synergistic Gel Materials with Switchable Mechanics and
           Self-Healing Capacity
    • Authors: Ziguang Zhao; Yuxia Liu, Kangjun Zhang, Shuyun Zhuo, Ruochen Fang, Jianqi Zhang, Lei Jiang, Mingjie Liu
      Abstract: A fabrication strategy for biphasic gels is reported, which incorporates high-internal-phase emulsions. Closely packed micro-inclusions within the elastic hydrogel matrix greatly improve the mechanical properties of the materials. The materials exhibit excellent switchable mechanics and shape-memory performance because of the switchable micro- inclusions that are incorporated into the hydrogel matrix. The produced materials demonstrated a self-healing capacity that originates from the noncovalent effect of the biphasic heteronetwork. The aforementioned characteristics suggest that the biphasic gels may serve as ideal composite gel materials with validity in a variety of applications, such as soft actuators, flexible devices, and biological materials.Zeit für Veränderungen: Dicht gepackte schaltbare Mikroeinschlüsse in einer Hydrogelmatrix ergeben biphasige synergistische Gelmaterialien mit schaltbarer Mechanik, Selbstheilungs- und Formgedächtniseigenschaften.
      PubDate: 2017-09-18T11:33:22.402552-05:
      DOI: 10.1002/ange.201707239
       
  • Ein aktiver und widerstandsfähiger difunktioneller
           Sauerstoff-Elektrokatalysator durch kohlenstofffreie hierarchische
           Funktionalisierung
    • Authors: Kevin Huang
      Abstract: In einer hierarchisch funktionalisierten Hybridelektrode für Zn-Luft-Batterien, die keinen Kohlenstoff benötigt, dient ein bei der Sauerstoffentwicklung (OER) aktives, poröses, leitfähiges und korrosionsbeständiges Nitrid, Ni3FeN, als Trägermaterial für bei der Sauerstoffreduktion (ORR) wirksame geordnete Fe3Pt-NPs. Die Porosität des Ni3FeN-Substrats ist entscheidend für eine hohe OER-Aktivität.
      PubDate: 2017-09-18T11:32:43.89305-05:0
      DOI: 10.1002/ange.201707322
       
  • Copper-Catalyzed Borylacylation of Activated Alkenes with Acid Chlorides
    • Authors: Yuan Huang; Kevin B. Smith, M. Kevin Brown
      Abstract: A method for the copper-catalyzed borylacylation of activated alkenes is presented. The reaction involves borylcupration of the alkene, followed by capture of the generated alkyl–copper intermediate with an acid chloride. The reactions operated with low catalyst loading and generally occurre within 15 min at room temperature for a range of activated alkenes. In the case of vinyl arenes, enantioselective borylacylation was possible.Aktivierte Alkene gehen eine schnelle Kupfer-katalysierte Borylacylierung bei Raumtemperatur bei niedrigen Katalysatorbeladungen ein (siehe Schema). Die Reaktion umfasst die Borylcuprierung des Alkens und den Abfang der resultierenden Alkyl-Kupfer-Zwischenstufe mit einem Säurechlorid. Im Fall von Vinylarenen konnte die Umwandlung in einer enantioselektiven Weise durchgeführt werden.
      PubDate: 2017-09-18T11:32:37.854746-05:
      DOI: 10.1002/ange.201707323
       
  • Tuning the Structure of Platinum Particles on Ceria In Situ for
           Enhancing the Catalytic Performance of Exhaust Gas Catalysts
    • Authors: Andreas M. Gänzler; Maria Casapu, Philippe Vernoux, Stéphane Loridant, Francisco J. Cadete Santos Aires, Thierry Epicier, Benjamin Betz, Rüdiger Hoyer, Jan-Dierk Grunwaldt
      Abstract: A dynamic structural behavior of Pt nanoparticles on the ceria surface under reducing/oxidizing conditions was found at moderate temperatures (H2>C3H6). This dynamic nature of Pt on ceria at such low temperatures (250–500 °C) was additionally confirmed by in situ environmental transmission electron microscopy. A general concept is proposed to adjust the noble metal dispersion (size, structure), for example, during operation of an exhaust gas catalyst.Unter Kontrolle: Die katalytische Aktivität von Diesel-Oxidationskatalysatoren bei niedriger Temperatur wurde durch Aufklärung des dynamischen Strukturverhaltens von Pt-Nanopartikeln auf Ceroxid durch Operando-XAS und ETEM erhöht. Hieraus wurde ein allgemeines Konzept abgeleitet, um die Größe und Struktur von Edelmetallpartikeln auf stark wechselwirkenden Trägermaterialien während des Betriebs unter realen Bedingungen gezielt einzustellen.
      PubDate: 2017-09-18T11:32:14.113298-05:
      DOI: 10.1002/ange.201707842
       
  • Discovery of a Novel Inhibitor of the Hedgehog Signaling Pathway through
           Cell-based Compound Discovery and Target Prediction
    • Authors: Lea Kremer; Carsten Schultz-Fademrecht, Matthias Baumann, Peter Habenberger, Axel Choidas, Bert Klebl, Susanne Kordes, Hans R. Schöler, Jared Sterneckert, Slava Ziegler, Gisbert Schneider, Herbert Waldmann
      Abstract: Cell-based assays enable monitoring of small-molecule bioactivity in a target-agnostic manner and help uncover new biological mechanisms. Subsequent identification and validation of the small-molecule targets, typically employing proteomics techniques, is very challenging and limited, in particular if the targets are membrane proteins. Herein, we demonstrate that the combination of cell-based bioactive-compound discovery with cheminformatic target prediction may provide an efficient approach to accelerate the process and render target identification and validation more efficient. Using a cell-based assay, we identified the pyrazolo-imidazole smoothib as a new inhibitor of hedgehog (Hh) signaling and an antagonist of the protein smoothened (SMO) with a novel chemotype. Smoothib targets the heptahelical bundle of SMO, prevents its ciliary localization, reduces the expression of Hh target genes, and suppresses the growth of Ptch+/− medulloblastoma cells.Gemeinsam geht es besser: Die kombinierte Anwendung von chemischer Biologie und computerbasierter Targetvorhersage ermöglichte die Identifizierung des Pyrazolo-Imidazol-Derivats smoothib als neuartigen Inhibitor des Hedgehog-Signalwegs und des Membranproteins Smoothened als dessen Target.
      PubDate: 2017-09-18T11:31:31.327443-05:
      DOI: 10.1002/ange.201707394
       
  • Discovery of Key Physicochemical, Structural, and Spatial Properties of
           RNA-Targeted Bioactive Ligands
    • Authors: Brittany S. Morgan; Jordan E. Forte, Rebecca N. Culver, Yuqi Zhang, Amanda E. Hargrove
      Abstract: While a myriad non-coding RNAs are known to be essential in cellular processes and misregulated in diseases, the development of RNA-targeted small molecule probes has met with limited success. To elucidate the guiding principles for selective small molecule/RNA recognition, we analyzed cheminformatic and shape-based descriptors for 104 RNA-targeted ligands with demonstrated biological activity (RNA-targeted BIoactive ligaNd Database, R-BIND). We then compared R-BIND to both FDA-approved small molecule drugs and RNA ligands without reported bioactivity. Several striking trends emerged for bioactive RNA ligands, including: 1) Compliance to medicinal chemistry rules, 2) distinctive structural features, and 3) enrichment in rod-like shapes over others. This work provides unique insights that directly facilitate the selection and synthesis of RNA-targeted libraries with the goal of efficiently identifying selective small molecule ligands for therapeutically relevant RNAs.Im RNA-Raum: Sammlung und Analyse der „RNA-targeted BIoactive ligaNd Database” (R-BIND) offenbaren 2D- und 3D-Moleküleigenschaften, die für die Existenz eines privilegierten chemischen Raums in Bezug auf RNA sprechen. Diese Richtgrößen erleichtern den Entwurf selektiver Liganden für therapeutisch relevante RNA.
      PubDate: 2017-09-18T11:31:26.335688-05:
      DOI: 10.1002/ange.201707641
       
  • Sensuke Ogoshi
    • PubDate: 2017-09-18T11:31:19.737387-05:
      DOI: 10.1002/ange.201708270
       
  • Chan Beum Park
    • PubDate: 2017-09-18T11:31:05.768997-05:
      DOI: 10.1002/ange.201709297
       
  • Mass Production and Pore Size Control of Holey Carbon Microcages
    • Authors: Lei Zhang; Xiaoxiao Liu, Yuhai Dou, Binwei Zhang, Huiling Yang, Shixue Dou, Huakun Liu, Yunhui Huang, Xianluo Hu
      Abstract: Architectural control of porous solids, such as porous carbon cages, has received considerable attention for versatile applications because of their attractive ability to interact with liquids and gases not only at the surface, but throughout the bulk. Here we report a scalable, facile spray-pyrolysis route to synthesize holey carbon microcages with mosquito-net-like shells. Using the surfaces of water droplets as the growth templates, styrene-butadiene rubber macromolecules are controllably cross-linked, and size-tunable holes on the carbon shells are generated. The as-formed carbon microcages encapsulating Si nanoparticles exhibit enhanced lithium-storage performances for lithium-ion batteries. The scalable, inexpensive synthesis of porous carbon microcages with controlled porosity and the demonstration of outstanding electrochemical properties are expected to extend their uses in energy storage, molecular sieves, catalysis, adsorbents, water/air filters and biomedical engineering.
      PubDate: 2017-09-18T10:40:25.900488-05:
      DOI: 10.1002/ange.201708732
       
  • Structure and mechanism of the monoterpene cyclolavandulyl diphosphate
           synthase that catalyses consecutive condensation and cyclisation
    • Authors: Tomohisa Kuzuyama; Takeo Tomita, Masaya Kobayashi, Yuma Karita, Yoko Yasuno, Tetsuro Shinada, Makoto Nishiyama
      Abstract: Here, we report the three-dimensional structure of cyclolavandulyl diphosphate (CLPP) synthase (CLDS), which consecutively catalyses the condensation of two molecules of dimethylallyl diphosphate (DMAPP) followed by cyclisation to form a cyclic monoterpene, CLPP. The structures of apo-CLDS and CLDS in complex with Tris, pyrophosphate, and Mg2+ ion were refined at 2.00 Å resolution and 1.73 Å resolution, respectively. CLDS adopts a typical fold for cis-prenyl synthases and forms a homo-dimeric structure. An in vitro reaction using a regiospecifically 2H-substituted DMAPP substrate revealed the intramolecular proton transfer mechanism of the CLDS reaction. The CLDS structure and structure-based mutagenesis provide mechanistic insights into this unprecedented terpene synthase. The combination of structural and mechanistic insights advances the knowledge of intricate terpene synthase-catalysed reactions.
      PubDate: 2017-09-18T09:41:58.765244-05:
      DOI: 10.1002/ange.201708474
       
  • Asymmetric Iron-Catalyzed C−H Alkylation Enabled by Remote Ligand
           meta-Substitution
    • Authors: Joachim Loup; Daniel Zell, Joao Carlos Agostinho de Oliveira, Helena Keil, Dietmar Stalke, Lutz Ackermann
      Abstract: Highly enantioselective iron-catalyzed C−H alkylations by inner-sphere C−H activation were accomplished with ample scope. High levels of enantiocontrol proved viable through a novel ligand design that exploits a remote meta-substitution on N-heterocyclic carbenes within a facile LLHT C−H cleavage.
      PubDate: 2017-09-18T09:41:36.300084-05:
      DOI: 10.1002/ange.201709075
       
  • Ein ikosidodekaedrisches Supramolekül auf Basis von Pentaphosphaferrocen:
           von einer fehlgeordneten gemittelten Struktur zu einzelnen Isomeren
    • Authors: Claudia Heindl; Eugenia Peresypkina, Alexander V. Virovets, Ivan S. Bushmarinov, Michael G. Medvedev, Barbara Krämer, Birger Dittrich, Manfred Scheer
      Abstract: Die Pentaphosphaferrocene [CpRFe(η5-P5)] (1) und CuI-Halogenide sind exzellente Bausteine für die Bildung diskreter Supramoleküle. Hier wird das Potenzial von Cu(CF3SO3) für die Herstellung des neuartigen 2D-Polymers [{Cp*Fe(μ4,η5:1:1:1-P5)}{Cu(CF3SO3)}]n (2) und eines einzigartigen Nanoballs (CH2Cl2)1.4@[{CpBnFe(η5-P5)}12{Cu(CF3SO3)}19.6] (3) gezeigt. Das Supramolekül 3 hat ein außergewöhnliches Gerüst jenseits der Fulleren-Topologie, das aus 20 Cu-Atomen besteht, die statistisch auf 30 Eckpunkte eines Ikosidodekaeders verteilt sind. Erstmals wurde die Kombinatorik zur Interpretation einer gemittelten fehlgeordneten Struktur von Supramolekülen genutzt. Dabei zeigte sich, dass für die zweizähnige verbrückende Koordination von Triflatliganden im Gerüst nur zwei Paare enantiomerer Formen mit D5- und D2-Symmetrie möglich sind. DFT-Rechnungen zeigen, dass die Energieunterschiede der Isomere vernachlässigt werden können. Die Benzyl-Liganden von 3 ermöglichen NMR-spektroskopische und MS-Untersuchungen.Mit CF3SO3− als Abstandhalter wurde ausgehend von Pentaphosphaferrocen und Cu+ ein neuer Typ eines riesigen Supramoleküls erhalten. Mit 20 Kupferatomen, verteilt über 30 Ecken des riesigen Ikosidodekaeders, enthält sein beispielloses Gerüst intrinsische Fehlstellen und verfügt über vier isomere Formen.
      PubDate: 2017-09-18T09:01:46.503071-05:
      DOI: 10.1002/ange.201706756
       
  • Borane-Stabilized Isomeric Dimers of the Phosphaethynolate Anion
    • Authors: Kevin Szkop; Andrew Jupp, Riccardo Suter, Hansjorg Gruetzmacher, Douglas Wade Stephan
      Abstract: The reactions of the phosphaethynolate anion ([PCO]-) with a range of boranes were explored. BPh3 and [PCO]- form a dimeric anion featuring P-B bonds and is prone to dissociation at room temperature. The more Lewis acidic borane B(C6F5)3 yields a less symmetric dimer of [PCO]- with P-B and P-O bonds. Less sterically demanding HB(C6F5)2 and H2B(C6F5) boranes form a third isomer with [PCO]- with both boranes bound to the same phosphorus atom. Despite the unexpected thermodynamic preference for P-coordination, computational data illustrate that electronic and steric features impact the binding modes of the resulting dianionic dimers.
      PubDate: 2017-09-18T08:40:48.707893-05:
      DOI: 10.1002/ange.201708646
       
  • Titelbild: Diazirines as Potential Molecular Imaging Tags: Probing the
           Requirements for Efficient and Long-Lived SABRE-Induced Hyperpolarization
           (Angew. Chem. 40/2017)
    • 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
      Pages: 12179 - 12179
      Abstract: Diazirine sind dank ihrer Biokompatibilität und ihres leichten Einbaus in verschiedenartige Verbindungen aussichtsreiche molekulare Marker für Kernspintomographie und NMR-Spektroskopie. In ihrer Zuschrift auf S. 12280 zeigen W. S. Warren, S. J. Malcolmson, Q. Wang und Mitarbeiter anhand eines entsprechenden Cholinderivats, dass 15N2-Diazirin-Motive eine lang anhaltende Polarisation durch die einfache SABRE-SHEATH-Hyperpolarisationsmethode unterstützen.
      PubDate: 2017-08-01T08:36:42.081386-05:
      DOI: 10.1002/ange.201707296
       
  • Innentitelbild: Capturing Elusive Cobaltacycle Intermediates: A Real-Time
           Snapshot of the Cp*CoIII-Catalyzed Oxidative Alkyne Annulation (Angew.
           Chem. 40/2017)
    • Authors: Jesús Sanjosé-Orduna; Daniel Gallego, Alèria Garcia-Roca, Eddy Martin, Jordi Benet-Buchholz, Mónica H. Pérez-Temprano
      Pages: 12180 - 12180
      Abstract: Cp*CoIII-Komplexe haben Potenzial für katalytische C-H-Funktionalisierungen. Die Erforschung dieser Systeme hat in den vergangenen Jahren Fortschritte gemacht, es fehlen aber immer noch Informationen über die zugehörigen Reaktionsmechanismen. In ihrer Zuschrift auf S. 12305 ff. stellen M. H. Pérez-Temprano et al. bislang nicht zugängliche mechanistische Details der Cp*CoIII-katalysierten Alkin-Anellierung unter C-H-Oxidation vor. Es gelang ihnen, eine hoch reaktive Cobaltspezies mit MeCN abzufangen.
      PubDate: 2017-08-03T05:01:24.065053-05:
      DOI: 10.1002/ange.201707433
       
  • Graphisches Inhaltsverzeichnis: Angew. Chem. 40/2017
    • Pages: 12183 - 12199
      PubDate: 2017-09-20T01:55:08.251293-05:
      DOI: 10.1002/ange.201784011
       
  • Top-Beiträge aus unseren Schwesterzeitschriften: Angew. Chem. 40/2017
    • Pages: 12202 - 12205
      PubDate: 2017-09-20T01:55:25.334319-05:
      DOI: 10.1002/ange.201784013
       
  • Andrey P. Antonchick
    • Pages: 12208 - 12208
      Abstract: „Das Geheimnis, ein erfolgreicher Wissenschaftler zu sein, ist Geduld. Mein liebste Namensreaktion ist die Belousov-Zhabotinsky-Reaktion ...“ Dies und mehr von und über Andrey P. Antonchick finden Sie auf Seite 12208.
      PubDate: 2017-05-10T07:30:40.121293-05:
      DOI: 10.1002/ange.201704212
       
  • Preise der Royal Society of Chemistry für 2017
    • Pages: 12209 - 12210
      PubDate: 2017-08-28T12:42:29.476797-05:
      DOI: 10.1002/ange.201708393
       
  • Lewis Base Catalysis in Organic Synthesis. 3 Bände. Herausgegeben von
           Edwin Vedejs und Scott E. Denmark.
    • Authors: Marialuisa Aufiero; Ryan Gilmour
      Pages: 12211 - 12211
      Abstract: Wiley-VCH, Weinheim 2016. 1488 S., geb., € 449.00.—ISBN 978-3527336180
      PubDate: 2017-08-18T01:17:04.434191-05:
      DOI: 10.1002/ange.201707836
       
  • Die Hemmung von Protein-Protein-Wechselwirkungen: neue Ansätze zur
           Entwicklung von Wirkstoffen gegen Tropenkrankheiten
    • Authors: Thorsten Berg
      Pages: 12214 - 12216
      Abstract: Wacht auf! Die Schlafkrankheit und die Chagas-Krankheit werden durch Infektionen mit Trypanosomen verursacht. Die Entwicklung niedermolekularer Hemmstoffe der für die Parasiten essenziellen PEX14/PEX5-Wechselwirkung hat großes Potenzial für die Wirkstoffentwicklung.
      PubDate: 2017-08-11T05:57:44.828804-05:
      DOI: 10.1002/ange.201706479
       
  • Das Spliceosom als Angriffspunkt für Pharmaka
    • Authors: Brian León; Manoj K. Kashyap, Warren C. Chan, Kelsey A. Krug, Januario E. Castro, James J. La Clair, Michael D. Burkart
      Pages: 12218 - 12230
      Abstract: Seit seiner Entdeckung im Jahr 1977 hat die Untersuchung des alternativen RNA-Spleißens eine Vielzahl von Mechanismen zutage gefördert, die zuvor aus der Natur noch unbekannt waren. Die Erklärung dieser Umwandlungen und ihrer Resultate auf Ebene von Zellen und Organismen hat sich zu einer wichtigen Stoßrichtung der modernen chemischen Biologie entwickelt. Bis 2007 arbeiteten ausschließlich RNA-Biologen an diesem Thema. Durch die vor kurzem erfolgte Identifizierung von Naturstoffen und synthetischen Modulatoren des RNA-Spleißens sind aber auch chemische Untersuchungen des RNA-Spleißens möglich geworden. Gleichzeitig wurde die Bedeutung des Spleißens bei Erkrankungen erkannt, was eine neue Therapieplattform erschließt. Wie bei vielen natürlichen Systemen ist die Kenntnis mechanistischer Details auf molekularer Ebene der Schlüssel für das Verständnis der Funktion einer biologischen Maschine. Dieser Kurzaufsatz stellt aktuelle Erkenntnisse und Schlussfolgerungen zur Chemie und Biochemie des RNA-Spleißens vor.Wenn das Teilen schwer fällt: Seit zehn Jahren wird intensiv an der Entwicklung von Wirkstoffen gegen Spliceosomen gearbeitet. Die gefundenen synthetischen und natürlichen Spleißmodulatoren bieten neue Untersuchungsmöglichkeiten für krankheitsassoziierte Vorgänge rund um den Spleißvorgang. Dieser Kurzaufsatz präsentiert Fortschritte zu Chemie und chemischer Biologie des Spliceosoms und der Modulation seiner Funktion mit niedermolekularen Substanzen.
      PubDate: 2017-08-15T02:01:47.350306-05:
      DOI: 10.1002/ange.201701065
       
  • Magnesiumbatterien – ein Aufruf an Synthesechemiker: Elektrolyte und
           Kathoden dringend gesucht
    • Authors: John Muldoon; Claudiu B. Bucur, Thomas Gregory
      Pages: 12232 - 12253
      Abstract: Magnesiummetall ist ein hervorragendes Anodenmaterial mit einem negativen Reduktionspotential von −2.37 V gegen die Standardwasserstoffelektrode, dessen volumenspezifische Kapazität doppelt so hoch ist wie die von Lithiummetall. Ein Hauptvorteil gegenüber Lithiummetall ist, dass während des Aufladens kein Dendritenwachstum stattfindet. Dieser Aufsatz befasst sich mit aktuellen Entwicklungen bei Elektrolyten und Kathoden, und es werden wesentliche Herausforderungen auf dem Weg zu einer praktikablen Magnesiumbatterie diskutiert.100 Jahre nach dem Nobelpreis für Grignard: Die Aussicht auf eine Magnesiumbatterie, die mit Lithiumbatterien konkurrenzfähig ist, hat eine Renaissance der Magnesiumchemie ausgelöst. Dieser Aufsatz soll Synthesechemiker zur Beschäftigung mit diesem attraktiven Gebiet der Energiespeicherung anregen.
      PubDate: 2017-08-10T10:30:42.576498-05:
      DOI: 10.1002/ange.201700673
       
  • Facile One-Pot Synthesis of Functional Giant Polymeric Vesicles Controlled
           by Oscillatory Chemistry
    • Authors: Bishnu Prasad Bastakoti; Juan Perez-Mercader
      Pages: 12254 - 12259
      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.Mit Rhythmus: Eine oszillierende chemische Reaktion wurde für eine Eintopfsynthese riesiger Polymervesikel aus hydrophoben Polyethylenglykol(PEG)-Blöcken genutzt. Im Schema kennzeichnen grüne Schlangenlinien PEG, rote Sterne das Kettentransferagens (CTA), gelbe Rauten Komponenten der Belousov-Zhabotinsky-Reaktion und violette Kugeln die Monomereinheiten.
      PubDate: 2017-07-24T04:02:19.192377-05:
      DOI: 10.1002/ange.201703816
       
  • Ultrafast Light-Driven Substrate Expulsion from the Active Site of a
           Photoswitchable Catalyst
    • Authors: Manuel D. Pescher; Luuk J. G. W. van Wilderen, Susanne Grützner, Chavdar Slavov, Josef Wachtveitl, Stefan Hecht, Jens Bredenbeck
      Pages: 12260 - 12264
      Abstract: The photoswitchable piperidine general base catalyst is a prototype structure for light control of catalysis. Its azobenzene moiety moves sterically shielding groups to either protect or expose the active site, thereby changing the basicity and hydrogen-bonding affinity of the compound. The reversible switching dynamics of the catalyst is probed in the infrared spectral range by monitoring hydrogen bond (HB) formation between its active site and methanol (MeOH) as HB donor. Steady-state infrared (IR) and ultrafast IR and UV/Vis spectroscopies are used to uncover ultrafast expulsion of MeOH from the active site within a few picoseconds. Thus, the force generated by the azobenzene moiety even in the final phase of its isomerization is sufficient to break a strong HB within 3 ps and to shut down access to the active site.Lichtgesteuerte Katalyse: Das Schalten einer Azobenzol-Einheit auf ultraschneller Zeitskala verschiebt eine sterische Schutzgruppe, wodurch ein stark wasserstoffverbrückter Bindungspartner aus dem aktiven Zentrum herausgestoßen wird. Der Katalysator wird durch Blockade des Zugangs zum aktiven Zentrum deaktiviert.
      PubDate: 2017-08-24T00:55:37.447144-05:
      DOI: 10.1002/ange.201702861
       
  • Porphyrin Antennas on Carbon Nanodots: Excited State Energy and Electron
           Transduction
    • Authors: Francesca Arcudi; Volker Strauss, Luka Đorđević, Alejandro Cadranel, Dirk M. Guldi, Maurizio Prato
      Pages: 12265 - 12269
      Abstract: We report the synthesis and electron donor–acceptor features of a novel nanohybrid, in which the light-harvesting and electron-donating properties of a meso-tetraarylporphyrin (TArP) are combined with the electron-accepting features of nitrogen-doped carbon nanodots (NCNDs). In particular, in an ultrafast process (>1012 s−1), visible-light excitation transforms the strongly quenched porphyrin singlet excited states into short-lived (225 ps) charge-separated states. On the other hand, ultraviolet light excitation triggers a non-resolvable transduction of singlet excited state energy from the NCNDs to the porphyrins, followed by the same charge separation observed upon visible light excitation.Auf den Punkt gebracht: Ein neuartiges Hybrid-Nanomaterial wurde synthetisiert und bezüglich seiner Elektronen-Donor-Akzeptor-Eigenschaften untersucht. Es kombiniert die lichtsammelnden und Elektronen-donierenden Eigenschaften eines meso-Tetraarylporphyrins mit den Elektronen-akzeptierenden Charakteristika eines N-dotierten Kohlenstoff-Nanopunkts.
      PubDate: 2017-08-24T03:50:30.469755-05:
      DOI: 10.1002/ange.201704544
       
  • Nanoscale Metal–Organic Layers for Deeply Penetrating X-ray-Induced
           Photodynamic Therapy
    • Authors: Guangxu Lan; Kaiyuan Ni, Ruoyu Xu, Kuangda Lu, Zekai Lin, Christina Chan, Wenbin Lin
      Pages: 12270 - 12274
      Abstract: We report the rational design of metal–organic layers (MOLs) that are built from [Hf6O4(OH)4(HCO2)6] secondary building units (SBUs) and Ir[bpy(ppy)2]+- or [Ru(bpy)3]2+-derived tricarboxylate ligands (Hf-BPY-Ir or Hf-BPY-Ru; bpy=2,2′-bipyridine, ppy=2-phenylpyridine) and their applications in X-ray-induced photodynamic therapy (X-PDT) of colon cancer. Heavy Hf atoms in the SBUs efficiently absorb X-rays and transfer energy to Ir[bpy(ppy)2]+ or [Ru(bpy)3]2+ moieties to induce PDT by generating reactive oxygen species (ROS). The ability of X-rays to penetrate deeply into tissue and efficient ROS diffusion through ultrathin 2D MOLs (ca. 1.2 nm) enable highly effective X-PDT to afford superb anticancer efficacy.Schwere Hf-Atome in der sekundären Baueinheit dünner Metall-organischer Schichten (MOLs) absorbieren Röntgen-Strahlung und übertragen Energie auf Ir[bpy(ppy)2]+- oder [Ru(bpy)3]2+-Einheiten, die reaktive Sauerstoffspezies (ROS) für eine photodynamische Therapie (PDT) erzeugen. Die hohe Eindringtiefe der Röntgenstrahlung, hohe 1O2-Quantenausbeuten und eine effiziente ROS-Diffusion ermöglichen eine MOL-vermittelte PDT.
      PubDate: 2017-08-25T05:27:36.047566-05:
      DOI: 10.1002/ange.201704828
       
  • Chemical Origin of the Stability Difference between Copper(I)- and
           Silver(I)-Based Halide Double Perovskites
    • Authors: Zewen Xiao; Ke-Zhao Du, Weiwei Meng, David B. Mitzi, Yanfa Yan
      Pages: 12275 - 12279
      Abstract: Recently, CuI- and AgI-based halide double perovskites have been proposed as promising candidates for overcoming the toxicity and instability issues inherent within the emerging Pb-based halide perovskite absorbers. However, up to date, only AgI-based halide double perovskites have been experimentally synthesized; there are no reports on successful synthesis of CuI-based analogues. Here we show that, owing to the much higher energy level for the Cu 3d10 orbitals than for the Ag 4d10 orbitals, CuI atoms energetically favor 4-fold coordination, forming [CuX4] tetrahedra (X=halogen), but not 6-fold coordination as required for [CuX6] octahedra. In contrast, AgI atoms can have both 6- and 4-fold coordinations. Our density functional theory calculations reveal that the synthesis of CuI halide double perovskites may instead lead to non-perovskites containing [CuX4] tetrahedra, as confirmed by our material synthesis efforts.Tetraeder bevorzugt: Wegen der energiereichen 3d10-Orbitale von Kupfer ist für CuI die Sechsfachkoordination, wie sie für [CuX6]-Oktaeder erforderlich ist, energetisch ungünstig. DFT-Rechnungen und experimentelle Studien belegen, dass die CuI-Halogenid-Doppelperowskite thermodynamisch instabil sind und in [CuX4]-Tetraeder enthaltende Produkte zerfallen.
      PubDate: 2017-08-23T12:10:35.373721-05:
      DOI: 10.1002/ange.201705113
       
  • 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
      Pages: 12280 - 12284
      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: Das 15N2-Diazirin-Motiv erweist sich als geeignet, um im Rahmen der experimentell einfachen und kostengünstigen SABRE-SHEATH-Hyperpolarisationsmethode eine lang andauernde Polarisation zu unterstützen. Damit ist die 15N2-Gruppe ein vielversprechender molekularer Marker für die NMR/MRI-Bildgebung.
      PubDate: 2017-07-24T14:44:12.510698-05:
      DOI: 10.1002/ange.201704970
       
  • Perfluoroaryl Azide Staudinger Reaction: A Fast and Bioorthogonal Reaction
    • Authors: Madanodaya Sundhoro; Seaho Jeon, Jaehyeung Park, Olof Ramström, Mingdi Yan
      Pages: 12285 - 12289
      Abstract: We report a fast Staudinger reaction between perfluoroaryl azides (PFAAs) and aryl phosphines, which occurs readily under ambient conditions. A rate constant as high as 18 m−1 s−1 was obtained between methyl 4-azido-2,3,5,6-tetrafluorobenzoate and methyl 2-(diphenylphosphanyl)benzoate in CD3CN/D2O. Furthermore, the iminophosphorane product was stable toward hydrolysis and aza-phosphonium ylide reactions. This PFAA Staudinger reaction proved to be an excellent bioothorgonal reaction. PFAA-derivatized mannosamine and galactosamine were successfully transformed into cell-surface glycans and efficiently labeled with phosphine-derivatized fluorophore-conjugated bovine serum albumin.Besser, schneller, stärker: Perfluorarylazide (PFAAs) reagieren mit Arylphosphanen in einer schnellen Staudinger-Reaktion bei Umgebungsbedingungen zu kinetisch stabilen Iminophosphoranen. Diese PFAA-Staudinger-Reaktion ist hoch bioorthogonal und konnte zur Markierung von Zelloberflächen eingesetzt werden.
      PubDate: 2017-09-01T03:45:48.37894-05:0
      DOI: 10.1002/ange.201705346
       
  • Functional Molecular Junctions Derived from Double Self-Assembled
           Monolayers
    • Authors: Sohyeon Seo; Eunhee Hwang, Yunhee Cho, Junghyun Lee, Hyoyoung Lee
      Pages: 12290 - 12294
      Abstract: Information processing using molecular junctions is becoming more important as devices are miniaturized to the nanoscale. Herein, we report functional molecular junctions derived from double self-assembled monolayers (SAMs) intercalated between soft graphene electrodes. Newly assembled molecular junctions are fabricated by placing a molecular SAM/(top) electrode on another molecular SAM/(bottom) electrode by using a contact-assembly technique. Double SAMs can provide tunneling conjugation across the van der Waals gap between the terminals of each monolayer and exhibit new electrical functions. Robust contact-assembled molecular junctions can act as platforms for the development of equivalent contact molecular junctions between top and bottom electrodes, which can be applied independently to different kinds of molecules to enhance either the structural complexity or the assembly properties of molecules.Mut zur Lücke: Funktionelle molekulare Übergänge aus zwei selbstorganisierten Monoschichten (SAMs) zwischen weichen Graphenelektroden wurden nach einem Kontaktverfahren zusammengebaut. Die Doppel-SAMs ermöglichen eine Tunnelkonjugation über die Van-der-Waals-Lücke zwischen den jeweiligen Monoschicht-Enden und verfügen über neue elektrischen Funktionen.
      PubDate: 2017-08-24T03:48:11.208676-05:
      DOI: 10.1002/ange.201705518
       
  • Microfluidic Lithography of Bioinspired Helical Micromotors
    • Authors: Yunru Yu; Luoran Shang, Wei Gao, Ze Zhao, Huan Wang, Yuanjin Zhao
      Pages: 12295 - 12299
      Abstract: Considerable efforts have been devoted to developing artificial micro/nanomotors that can convert energy into movement. A flow lithography integrated microfluidic spinning and spiraling system is developed for the continuous generation of bioinspired helical micromotors. Because the generation processes could be precisely tuned by adjusting the flow rates and the illuminating frequency, the length, diameter, and pitch of the helical micromotors were highly controllable. Benefiting from the fast online gelation and polymerization, the resultant helical micromotors could be imparted with Janus, triplex, and core–shell cross-sectional structures that have never been achieved by other methods. Owing to the spatially controlled encapsulation of functional nanoparticles in the microstructures, the helical micromotors can perform locomotion not only by magnetically actuated rotation or corkscrew motion but also through chemically powered catalytic reaction.Helikale Mikromotoren nach biologischem Vorbild mit Janus-, Triplex- und Kern-Schale-Profilen werden flusslithographisch in einem mikrofluidischen Dreh- und Wendelsystem erzeugt. Die helikalen Mikromotoren unterstützen eine Fortbewegung nicht nur bei magnetisch ausgelöster Rotation oder Spiralbewegung, sondern auch mit einer katalytischen chemischen Reaktion als Triebkraft.
      PubDate: 2017-08-23T12:10:55.695225-05:
      DOI: 10.1002/ange.201705667
       
  • Hydrogels with Reversible Mechanics to Probe Dynamic Cell
           Microenvironments
    • Authors: Adrianne M. Rosales; Sebastián L. Vega, Frank W. DelRio, Jason A. Burdick, Kristi S. Anseth
      Pages: 12300 - 12304
      Abstract: The relationship between ECM mechanics and cell behavior is dynamic, as cells remodel and respond to changes in their local environment. Most in vitro substrates are static and supraphysiologically stiff; thus, platforms with dynamic and reversible mechanical changes are needed. Herein, we developed hyaluronic acid-based substrates capable of sequential photodegradation and photoinitiated crosslinking reactions to soften and then stiffen the hydrogels over a physiologically relevant range of moduli. Reversible mechanical signaling to adhered cells was demonstrated with human mesenchymal stem cells. In situ hydrogel softening (from ca. 14 to 3.5 kPa) led to a decrease in the cell area and nuclear localization of YAP/TAZ, and subsequent stiffening (from ca. 3.5 to 28 kPa) increased the cell area and nuclear localization of YAP/TAZ. Each photoreaction was cytocompatible and tunable, rendering this platform amenable to studies of dynamic mechanics on cell behavior across many cell types and contexts.Hydrogele mit reversibel veränderlichen mechanischen Eigenschaften wurden entwickelt. Hyaluronsäure-Hydrogele, die photochemisch auf- und abgebaut werden können, geben Aspekte der Dynamik nativer Mikroumgebungen wieder. Mithilfe von humanen mesenchymalen Stammzellen wurde die zelluläre Mechanosensorik als Antwort auf geänderte mechanische Eigenschaften des Substrats demonstriert.
      PubDate: 2017-09-01T03:50:55.295449-05:
      DOI: 10.1002/ange.201705684
       
  • Capturing Elusive Cobaltacycle Intermediates: A Real-Time Snapshot of the
           Cp*CoIII-Catalyzed Oxidative Alkyne Annulation
    • Authors: Jesús Sanjosé-Orduna; Daniel Gallego, Alèria Garcia-Roca, Eddy Martin, Jordi Benet-Buchholz, Mónica H. Pérez-Temprano
      Pages: 12305 - 12309
      Abstract: Despite Cp*CoIII catalysts having emerged as a very attractive alternative to noble transition metals for the construction of heterocyclic scaffolds through C−H activation, the structure of the reactive species remains uncertain. Herein, we report the identification and unambiguous characterization of two long-sought cyclometalated Cp*CoIII complexes that have been proposed as key intermediates in C−H functionalization reactions. The addition of MeCN as a stabilizing ligand plays a crucial role, allowing the access to otherwise highly reactive species. Mechanistic investigations demonstrate the intermediacy of these species in oxidative annulations with alkynes, including the direct observation, under catalytic conditions, of a previously elusive post-migratory insertion seven-membered cobaltacycle.Ein intermediärer Cobaltacyclus in der Cp*CoIII-katalysierten Alkin-Anellierung unter C-H-Oxidation wurde beobachtet. Die außergewöhnliche Stabilisierung ansonsten hoch reaktiver Zwischenstufen durch MeCN gibt Einblicke in den Mechanismus dieser Transformationen.
      PubDate: 2017-06-28T06:47:20.926563-05:
      DOI: 10.1002/ange.201704744
       
  • Neodymium(III) Complexes Capable of Multi-Electron Redox Chemistry
    • Authors: Ezra J. Coughlin; Matthias Zeller, Suzanne C. Bart
      Pages: 12310 - 12313
      Abstract: A family of neodymium complexes featuring a redox-active ligand in three different oxidation states has been synthesized, including the iminoquinone (L0) derivative, (dippiq)2NdI3 (1-iq), the iminosemiquinone (L1−) compound, (dippisq)2NdI(THF) (1-isq), and the amidophenolate (L2−) [K(THF)2][(dippap)2Nd(THF)2] (1-ap) and [K(18-crown-6)][(dippap)2Nd(THF)2] (1-ap crown) species. Full spectroscopic and structural characterization of each derivative established the +3 neodymium oxidation state with redox chemistry occurring at the ligand rather than the neodymium center. Oxidation with elemental chalcogens showed the reversible nature of the ligand-mediated reduction process, forming the iminosemiquinone metallocycles, [K(18-crown-6)][(dippisq)2Nd(S5)] (2-isq crown) and [K(18-crown-6)(THF)][(dippisq)2Nd(Se5)] (3-isq crown), which are characterized to contain a 6-membered twist-boat ring.Eine neue Wendung in der Ln3+-Chemie: Eine Familie von Neodymkomplexen mit einem redoxaktiven Liganden in drei unterschiedlichen Oxidationszuständen wurde synthetisiert. Experimentelle Studien belegen das Vorliegen von NdIII-Zentren und zeigen Redoxprozesse am Liganden auf. Die reversible Natur des ligandvermittelten Reduktionsprozesses wird durch Oxidationen mit elementaren Chalkogenen nachgewiesen.
      PubDate: 2017-08-30T11:02:21.481566-05:
      DOI: 10.1002/ange.201705423
       
  • 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
      Pages: 12314 - 12317
      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) 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, the deformability of microspheres plays a crucial role on the adsorption kinetics, that is, soft hydrogel microspheres adsorb faster than harder elastomeric or rigid microspheres. These results should provide insight towards development of new colloidal nanomaterials that exhibit effective adsorption on specific sites in aqueous solution.Eine weiche Landung: Die detaillierten Adsorptions- und Deformationskinetiken von polymeren kolloidalen Mikrokugeln auf festen Oberflächen in wässriger Lösung unter Strömungsbedingungen wurden durch Hochgeschwindigkeits-Kraftmikroskopie (HS-AFM) untersucht. Die Elastizität (Verformbarkeit) der Mikrokugeln beeinflusst entscheidend ihre Adsorptionskinetiken.
      PubDate: 2017-08-25T05:28:28.642556-05:
      DOI: 10.1002/ange.201705808
       
  • Tailored Engineering of an Unusual (C4H9NH3)2(CH3NH3)2Pb3Br10
           Two-Dimensional Multilayered Perovskite Ferroelectric for a
           High-Performance Photodetector
    • Authors: Lina Li; Zhihua Sun, Peng Wang, Weida Hu, Sasa Wang, Chengmin Ji, Maochun Hong, Junhua Luo
      Pages: 12318 - 12322
      Abstract: Two-dimensional (2D) layered hybrid perovskites have shown great potential in optoelectronics, owing to their unique physical attributes. However, 2D hybrid perovskite ferroelectrics remain rare. The first hybrid ferroelectric with unusual 2D multilayered perovskite framework, (C4H9NH3)2(CH3NH3)2Pb3Br10 (1), has been constructed by tailored alloying of the mixed organic cations into 3D prototype of CH3NH3PbBr3. Ferroelectricity is created through molecular reorientation and synergic ordering of organic moieties, which are unprecedented for the known 2D multilayered hybrid perovskites. Single-crystal photodetectors of 1 exhibit fascinating performances, including extremely low dark currents (ca. 10−12 A), large on/off current ratios (ca. 2.5×103), and very fast response rate (ca. 150 μs). These merits are superior to integrated detectors of other 2D perovskites, and compete with the most active CH3NH3PbI3.Ein vielschichtiges Perowskit-Hybridferroelektrikum wurde durch Einbringen von gemischten organischen Kationen in den prototypischen 3D-Perowskit CH3NH3PbBr3 erhalten und in ferroelektrischen Einkristallphotodetektoren mit extrem niedrigem Dunkelstrom (ca. 10−12 A), hohem An/Aus-Stromverhältnis (ca. 2.5×103) und schneller Antwort (binnen ca. 150 μs) eingesetzt.
      PubDate: 2017-09-05T06:36:29.887099-05:
      DOI: 10.1002/ange.201705836
       
  • Polyladderane Constructed from a Gemini Monomer through Photoreaction
    • Authors: Zhihan Wang; Benjamin Miller, Jonathan Butz, Katelyn Randazzo, Zijun D. Wang, Qianli R. Chu
      Pages: 12323 - 12327
      Abstract: Polyladderane, the first polymer to contain the ladderane functional group, was synthesized from a gemini monomer through photoreaction in the solid state. The modular design of the gemini monomers used to create polyladderane allowed specific structural modification, resulting in the formation of two distinct polymer products. Monomers were synthesized by connecting two photoreactive units, either sorbic acids (monomer I) or 2-furanacrylic acids (monomer II), with a 1,4-butanediol linker. Single-crystal X-ray diffraction analysis of the monomers confirmed that they packed in the desired head-to-tail orientation and within a viable distance for photoreaction by electronically complementary interaction. Pre-organized gemini monomers were irradiated with UV light and monitored by FT-IR. Two polyladderanes with cis,anti,cis-[3]-ladderane as a characteristic functional group were constructed stereospecifically in 24–36 hours.Zwei Polyladderane mit cis,anti,cis-[3]-Ladderan als charakteristischer funktioneller Gruppe wurden aus einem Zwillingsmonomer durch Photoreaktion im Festkörper erhalten. Ein in Einkristall-Einkristall-Experimenten abgefangenes Schlüsselintermediat und die Isolierung und Charakterisierung eines Ladderan-Dimers liefern direkten Beleg für neu gebildete Cyclobutanringe.
      PubDate: 2017-08-25T05:27:49.818706-05:
      DOI: 10.1002/ange.201705937
       
  • Organic Nanocrystals with Bright Red Persistent Room-Temperature
           Phosphorescence for Biological Applications
    • Authors: S. M. Ali Fateminia; Zhu Mao, Shidang Xu, Zhiyong Yang, Zhenguo Chi, Bin Liu
      Pages: 12328 - 12332
      Abstract: Persistent room-temperature phosphorescence (RTP) in pure organic materials has attracted great attention because of their unique optical properties. The design of organic materials with bright red persistent RTP remains challenging. Herein, we report a new design strategy for realizing high brightness and long lifetime of red-emissive RTP molecules, which is based on introducing an alkoxy spacer between the hybrid units in the molecule. The spacer offers easy Br−H bond formation during crystallization, which also facilitates intermolecular electron coupling to favor persistent RTP. As the majority of RTP compounds have to be confined in a rigid environment to quench nonradiative relaxation pathways for bright phosphorescence emission, nanocrystallization is used to not only rigidify the molecules but also offer the desirable size and water-dispersity for biomedical applications.Eine rein organische Substanz mit heller und beständiger roter Phosphoreszenz bei Raumtemperatur wurde synthetisiert. Nanokristalle dieser Verbindungen sind bioverträglich und in Wasser dispergierbar. Da ihre Phosphoreszenz auch in wässrigen Medien bestehen bleibt, haben sie großes Potenzial für die biologische Bildgebung.
      PubDate: 2017-08-23T12:11:29.886902-05:
      DOI: 10.1002/ange.201705945
       
  • On-Surface Formation of Cumulene by Dehalogenative Homocoupling of Alkenyl
           gem-Dibromides
    • Authors: Qiang Sun; Bay V. Tran, Liangliang Cai, Honghong Ma, Xin Yu, Chunxue Yuan, Meike Stöhr, Wei Xu
      Pages: 12333 - 12337
      Abstract: The on-surface activation of carbon–halogen groups is an efficient route to produce radicals for constructing various hydrocarbons and carbon nanostructures. To date, the employed halide precursors have only one halogen attached to a carbon atom. It is thus of interest to study the effect of attaching more than one halogen atom to a carbon atom with the aim of producing multiple unpaired electrons. By introducing an alkenyl gem-dibromide, cumulene products were fabricated on a Au(111) surface by dehalogenative homocoupling reactions. The reaction products and pathways were unambiguously characterized by a combination of high-resolution scanning tunneling microscopy and non-contact atomic force microscopy measurements together with density functional calculations. This study further supplements the database of on-surface synthesis strategies and provides a facile manner for incorporation of more complicated carbon scaffolds into surface nanostructures.Auf der Oberfläche: Cumulene entstehen als Produkte der dehalogenierenden Homokupplung von Alkenyl-gem-dibromiden auf einer Au(111)-Oberfläche.
      PubDate: 2017-08-28T12:43:09.405066-05:
      DOI: 10.1002/ange.201706104
       
  • Enzyme-Responsive LipoCEST Agents: Assessment of MMP-2 Activity by
           Measuring the Intra-liposomal Water 1H NMR Shift
    • Authors: Giuseppe Ferrauto; Enza Di Gregorio, Marta Ruzza, Valeria Catanzaro, Sergio Padovan, Silvio Aime
      Pages: 12338 - 12341
      Abstract: Mobile proton-containing solutes can be detected by MRI by the chemical exchange saturation transfer (CEST) method. CEST sensitivity is dramatically enhanced by using, as exchanging protons, the water molecules confined inside liposomes, 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. δIL of a spherical LipoCEST acts as a sensitive reporter of the distribution of streptavidin proteins anchored at the liposome surface by biotinylated phospholipids. This finding prompted the design of a MMP-2 responsive LipoCEST agent as the streptavidin moieties can be released from the liposome 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.Biotinylierte LipoCEST-Agentien ändern die chemische Verschiebung der Resonanz von intraliposomalem Wasser bei der Bindung an Streptavidin (grau). Wird eine spaltbare MMP-2-Einheit an das biotinylierte Substrat angefügt, so erhält man ein enzymresponsives LipoCEST-Agens. Die Änderung der chemischen Verschiebung von intraliposomalem Wasser liefert Informationen über die MMP-2-Aktivität. Biotin: blau, Tm-HPDO3A-Verschiebungsagens: gelbe Kreise.
      PubDate: 2017-08-25T05:28:44.533735-05:
      DOI: 10.1002/ange.201706271
       
  • Self-Assembled Luminescent Quantum Dots To Generate Full-Color and White
           Circularly Polarized Light
    • Authors: Shengwei Huo; Pengfei Duan, Tifeng Jiao, Qiuming Peng, Minghua Liu
      Pages: 12342 - 12346
      Abstract: The design and fabrication of quantum dots (QDs) with circularly polarized luminescence (CPL) has been a great challenge in developing chiroptical materials. We herein propose an alternative to the use of chiral capping reagents on QDs for the fabrication of CPL-active QDs that is based on the supramolecular self-assembly of achiral QDs with chiral gelators. Full-color-tunable CPL-active QDs were obtained by simple mixing or gelation of a chiral gelator and achiral 3-mercaptopropionic acid capped QDs. In addition, the handedness of the CPL can be controlled by the supramolecular chirality of the gels. Moreover, QDs with circularly polarized white light emission were fabricated for the first time by tuning the blending ratio of colorful QDs in the gel. The chirality transfer in the co-assembly of the achiral QDs with the gelator and the spacer effect of the capping reagents on the QD surface are also discussed. This work provides new insight into the design of functional chiroptical materials.Zirkular polarisierte Lumineszenz (CPL) tritt bei gemischten Gelen mit Nanoröhrenstruktur auf, die aus achiralen Quantenpunkten (QDs) und einem chiralen Gelator erzeugt wurden. Vollfarbige und weiße CPLs wurden durch gezieltes Mischen mehrerer verschiedenfarbiger QDs mit dem chiralen Gelator erhalten.
      PubDate: 2017-08-24T03:46:41.151856-05:
      DOI: 10.1002/ange.201706308
       
  • β-Lactam Synthesis through Diodomethane Addition to Amide Dianions
    • Authors: Alaa Zidan; Julian Garrec, Marie Cordier, Abeer M. El-Naggar, Nour E. A. Abd El-Sattar, Ali Khalil Ali, Mohamed Ali Hassan, Laurent El Kaim
      Pages: 12347 - 12351
      Abstract: We present a novel route for the quick and easy synthesis of a broad range of β-lactams. The synthesis involves a [3+1] cyclization of amide dianions with diiodomethane. In contrast to the seminal work of Hirai et al. from 1979, the reaction proved to be a general and efficient approach towards azetidinones. The ease of the process was confirmed by DFT calculations and its power demonstrated by a diversity-oriented synthesis of β-lactams with four points of diversity determined by the choice of Ugi adducts as starting materials.Vielfältige β-Lactame wurden über [3+1]-Cyclisierung von Amid-Dianionen mit Diiodmethan synthetisiert. Anders als die bahnbrechende Arbeit von Hirai et al. aus dem Jahr 1979 bietet diese Reaktion ein allgemeines und effizientes Verfahren zur Synthese von Azetidinonen. Bestätigt wird dies durch eine diversitätsorientierte Synthese von β-Lactamen mit vier Diversifizierungspunkten, die durch die Wahl von Ugi-Addukten als Ausgangsmaterialien festgelegt werden.
      PubDate: 2017-08-24T03:46:27.050827-05:
      DOI: 10.1002/ange.201706315
       
  • Highly Regioselective Alkylation of Hexabenzocoronenes: Fundamental
           Insights into the Covalent Chemistry of Graphene
    • Authors: Johannes Holzwarth; Konstantin Yu. Amsharov, Dmitry I. Sharapa, David Reger, Kateryna Roshchyna, Dominik Lungerich, Norbert Jux, Frank Hauke, Timothy Clark, Andreas Hirsch
      Pages: 12352 - 12358
      Abstract: Hexa-peri-hexabenzocoronides (HBC) was successfully used as a model system for investigating the complex mechanism of the reductive functionalization of graphene. The well-defined molecular HBC system enabled deeper insights into the mechanism of the alkylation of reductively activated nanographenes. The separation and complete characterization of alkylation products clearly demonstrate that nanographene functionalization proceeds with exceptionally high regio- and stereoselectivities on the HBC scaffold. Experimental and theoretical studies lead to the conclusion that the intact basal graphene plane is chemically inert and addend binding can only take place at either preexisting defects or close to the periphery.Intakt heißt inert: Experimente und Rechnungen ergeben, dass die intakte Basalebene von Graphen chemisch inert ist. Addenden können demnach nur entweder an bereits existierenden Defekten oder nahe der Peripherie binden. Die freie Bewegung von Alkylradikalen (siehe Bild) im neutralen Van-der-Waals-Komplex HBC-R. ist ein entscheidender Schritt der Sequenz. HBC=Hexa-peri-hexabenzocoronid.
      PubDate: 2017-08-23T12:11:43.428067-05:
      DOI: 10.1002/ange.201706437
       
  • Atomic-Level Insight into Optimizing the Hydrogen Evolution Pathway over a
           Co1-N4 Single-Site Photocatalyst
    • Authors: Yuanjie Cao; Si Chen, Qiquan Luo, Huan Yan, Yue Lin, Wei Liu, Linlin Cao, Junling Lu, Jinlong Yang, Tao Yao, Shiqiang Wei
      Pages: 12359 - 12364
      Abstract: Knowledge of the photocatalytic H2 evolution mechanism is of great importance for designing active catalysts toward a sustainable energy supply. An atomic-level insight, design, and fabrication of single-site Co1-N4 composite as a prototypical photocatalyst for efficient H2 production is reported. Correlated atomic characterizations verify that atomically dispersed Co atoms are successfully grafted by covalently forming a Co1-N4 structure on g-C3N4 nanosheets by atomic layer deposition. Different from the conventional homolytic or heterolytic pathway, theoretical investigations reveal that the coordinated donor nitrogen increases the electron density and lowers the formation barrier of key Co hydride intermediate, thereby accelerating H–H coupling to facilitate H2 generation. As a result, the composite photocatalyst exhibits a robust H2 production activity up to 10.8 μmol h−1, 11 times higher than that of pristine counterpart.Ein Einzelplatz für Co: Ein Katalysator mit einzeln gebundenen Co1-N4-Zentren auf g-C3N4 bewirkt eine effiziente und stabile photokatalytische H2-Entwicklung. Eine atomgenaue Charakterisierung gibt Einblicke in einen Stickstoff-optimierten H2-Entwicklungsmechanismus am aktiven Co-Zentrum.
      PubDate: 2017-08-28T12:42:46.452141-05:
      DOI: 10.1002/ange.201706467
       
  • C−H Activation from Iron(II)-Nitroxido Complexes
    • Authors: Claudia Kleinlein; Andrew J. Bendelsmith, Shao-Liang Zheng, Theodore A. Betley
      Pages: 12365 - 12369
      Abstract: The reaction of nitroxyl radicals TEMPO (2,2′,6,6′-tetramethylpiperidinyloxyl) and AZADO (2-azaadamantane-N-oxyl) with an iron(I) synthon affords iron(II)-nitroxido complexes (ArL)Fe(κ1-TEMPO) and (ArL)Fe(κ2-N,O-AZADO) (ArL=1,9-(2,4,6-Ph3C6H2)2-5-mesityldipyrromethene). Both high-spin iron(II)-nitroxido species are stable in the absence of weak C−H bonds, but decay via N−O bond homolysis to ferrous or ferric iron hydroxides in the presence of 1,4-cyclohexadiene. Whereas (ArL)Fe(κ1-TEMPO) reacts to give a diferrous hydroxide [(ArL)Fe]2(μ-OH)2, the reaction of four-coordinate (ArL)Fe(κ2-N,O-AZADO) with hydrogen atom donors yields ferric hydroxide (ArL)Fe(OH)(AZAD). Mechanistic experiments reveal saturation behavior in C−H substrate and are consistent with rate-determining hydrogen atom transfer.Nitroxylradikale reagieren mit dem Eisen(I)-Synthon (ArL)Fe zu Eisen(II)-Nitroxidokomplexen. Die High-Spin-Eisen(II)-Verbindungen sind stabil in Abwesenheit von schwachen C-H-Bindungen, zersetzen sich aber in Gegenwart labiler C-H-Bindungen über N-O-Bindungshomolyse zu FeII/III-Hydroxiden.
      PubDate: 2017-08-25T05:29:30.719284-05:
      DOI: 10.1002/ange.201706594
       
  • Hierarchical Nanotubes Constructed by Carbon-Coated Ultrathin SnS
           Nanosheets for Fast Capacitive Sodium Storage
    • Authors: Peilei He; Yongjin Fang, Xin-Yao Yu, Xiong Wen (David) Lou
      Pages: 12370 - 12373
      Abstract: Tin(II) sulfide (SnS) has been an attractive anode material for sodium ion batteries. Herein, an elegant templating method has been developed for the rational design and synthesis of hierarchical SnS nanotubes composed of ultrathin nanosheets. In order to enhance the electrochemical performance, carbon coated hierarchical SnS nanotubes (denoted as SnS@C nanotubes) have also been obtained by simply adding glucose into the reaction system. Benefiting from their unique structural merits, the SnS@C nanotubes exhibit enhanced sodium storage properties in terms of good cycling performance and superior rate capability.Eine einfache Templatmethode liefert hierarchische Nanoröhren bestehend aus kohlenstoffbeschichteten ultradünnen SnS-Nanoschichten. Die besonderen Struktureigenschaften dieser SnS@C-Nanoröhren sorgen für ein sehr gutes Natriumspeicherverhalten mit langer Zyklenlebensdauer und exzellenter Ratenkapazität.
      PubDate: 2017-08-24T01:01:31.306857-05:
      DOI: 10.1002/ange.201706652
       
  • Enantioselective Tandem Cyclization of Alkyne-Tethered Indoles Using
           Cooperative Silver(I)/Chiral Phosphoric Acid Catalysis
    • Authors: Yugen Zhu; Wei He, Wei Wang, Chloe E. Pitsch, Xiaotai Wang, Xiang Wang
      Pages: 12374 - 12377
      Abstract: Reported is the enantioselective synthesis of tetracyclic indolines using silver(I)/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.Dual und kooperativ: Eine hoch enantioselektive Synthese tetracyclischer Indoline beruht auf kooperativer Katalyse mit Silber(I) und einem chiralen Phosphorsäurederivat. Mechanistische Untersuchungen offenbaren eine doppelte Rolle des chiralen Phosphats.
      PubDate: 2017-08-23T12:12:19.79316-05:0
      DOI: 10.1002/ange.201706694
       
  • Photochemical Intramolecular C−H Addition of
           Dimesityl(hetero)arylboranes through a [1,6]-Sigmatropic Rearrangement
    • Authors: Naoki Ando; Aiko Fukazawa, Tomokatsu Kushida, Yoshihito Shiota, Shuhei Itoyama, Kazunari Yoshizawa, Yasunori Matsui, Yutaro Kuramoto, Hiroshi Ikeda, Shigehiro Yamaguchi
      Pages: 12378 - 12382
      Abstract: A new reaction mode for triarylboranes under photochemical conditions was discovered. Photoirradiation of dimesitylboryl-substituted (hetero)arenes produced spirocyclic boraindanes, where one of the C−H bonds in the ortho-methyl groups of the mesityl substituents was formally added in a syn fashion to a C−C double bond of the (hetero)aryl group. Quantum chemical calculations and laser flash photolysis measurements indicated that the reaction proceeds through a [1,6]-sigmatropic rearrangement. This behavior is reminiscent of the photochemical reaction mode of arylalkenylketones, thus demonstrating the isosteric relation between tricoordinate organoboron compounds and the corresponding pseudo-carbocationic species in terms of pericyclic reactions. Despite the disrupted π-conjugation, the resulting spirocyclic boraindanes exhibited a characteristic absorption band at relatively long wavelengths (λ=370—400 nm).Die lichtinduzierte Isomerisierung von Dimesitylboryl-substituierten (Hetero)Arenen liefert spirocyclische Boraindane. Der Prozess verläuft als sigmatrope [1,6]-Umlagerung mit anschließender intramolekularer C-C-Kupplung. Am ersten Schritt ist das freie p-Orbital des Bors beteiligt, sodass sich eine neue Reaktivität für Triarylborane ergibt. Die spirocyclischen Boraindane zeigen ein charakteristisches Absorptionsverhalten.
      PubDate: 2017-08-23T12:16:28.822319-05:
      DOI: 10.1002/ange.201706929
       
  • Beyond Bleaney's Theory: Experimental and Theoretical Analysis of Periodic
           Trends in Lanthanide-Induced Chemical Shift
    • Authors: Elizaveta A. Suturina; Kevin Mason, Carlos F. G. C. Geraldes, Ilya Kuprov, David Parker
      Pages: 12383 - 12386
      Abstract: A detailed analysis of paramagnetic NMR shifts in a series of isostructural lanthanide complexes relavant to PARASHIFT contrast agents reveals unexpected trends in the magnetic susceptibility anisotropy that cannot be explained by the commonly used Bleaney's theory. Ab initio calculations reveal that the primary assumption of Bleaney's theory—that thermal energy is larger than the ligand field splitting—does not hold for the lanthanide complexes in question, and likely for a large fraction of lanthanide complexes in general. This makes the orientation of the magnetic susceptibility tensor differ significantly between complexes of different lanthanides with the same ligand: one of the most popular assumptions about isostructural lanthanide series is wrong.Theorie und Praxis: Zuordnung und Kurvenanpassung der paramagnetischen Protonen-NMR-Spektren isostruktureller Serien von Lanthanoid(III)-Komplexen offenbaren deutliche Abweichungen von der üblicherweise angewendeten Bleany-Theorie. Berechnungen zeigen, dass die primäre Annahme der Bleany-Theorie, nämlich dass die thermische Energie größer ist als die Ligandenfeldaufspaltung, für die fraglichen Lanthanoidkomplexe nicht gilt.
      PubDate: 2017-08-24T03:45:27.322323-05:
      DOI: 10.1002/ange.201706931
       
  • Exclusive Formation of Formic Acid from CO2 Electroreduction by a Tunable
           Pd-Sn Alloy
    • Authors: Xiaofang Bai; Wei Chen, Chengcheng Zhao, Shenggang Li, Yanfang Song, Ruipeng Ge, Wei Wei, Yuhan Sun
      Pages: 12387 - 12391
      Abstract: Conversion of carbon dioxide (CO2) into fuels and chemicals by electroreduction has attracted significant interest, although it suffers from a large overpotential and low selectivity. A Pd-Sn alloy electrocatalyst was developed 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 favorable over the Pd-Sn alloy catalyst surface with an atomic composition of PdSnO2, consistent with experiments.Gut für O: PdSn-Legierungen auf Trägern wurden als Elektrokatalysatoren der CO2-Reduktion in wässriger Lösung entwickelt. Über PdSn/C verlief die Ameisensäurebildung bei sehr niedrigem Überpotential (−0.26 V) mit nahezu perfektem Faraday-Wirkungsgrad. Dieses Resultat wird mit einer optimalen Oberflächenoxid-Konfiguration erklärt.
      PubDate: 2017-08-24T03:45:43.672051-05:
      DOI: 10.1002/ange.201707098
       
  • Rapid Access to Nanographenes and Fused Heteroaromatics by
           Palladium-Catalyzed Annulative π-Extension Reaction of Unfunctionalized
           Aromatics with Diiodobiaryls
    • Authors: Wataru Matsuoka; Hideto Ito, Kenichiro Itami
      Pages: 12392 - 12396
      Abstract: Efficient and rapid access to nanographenes and π-extended fused heteroaromatics is important in materials science. Herein, we report a palladium-catalyzed efficient one-step annulative π-extension (APEX) reaction of polycyclic aromatic hydrocarbons (PAHs) and heteroaromatics, producing various π-extended aromatics. In the presence of a cationic Pd complex, triflic acid, silver pivalate, and diiodobiaryls, diverse unfunctionalized PAHs and heteroaromatics were directly transformed into larger PAHs, nanographenes, and π-extended fused heteroaromatics in a single step. In the reactions that afford [5]helicene substructures, simultaneous dehydrogenative ring closures occur at the fjord regions to form unprecedented larger nanographenes. This successive APEX reaction is notable as it stiches five aryl–aryl bonds by C−H functionalization in a single operation. Moreover, the unique molecular structures, crystal-packing structures, photophysical properties, and frontier molecular orbitals of the thus-formed nanographenes were elucidated.Eine Stufe reicht: Eine neuartige π-Expansionsreaktion bietet schnellen Zugang zu polycyclischen aromatischen Kohlenwasserstoffen, kondensierten Heteroarenen und Nanographenen. In Gegenwart eines Palladiumkatalysators, von Silberpivalat und Trifluormethansulfonsäure werden die unfunktionalisierten aromatischen Template mit einer Vielzahl an Diiodbiarylen als π-expandierende Reagentien mit guten Ausbeuten und Regioselektivitäten erweitert.
      PubDate: 2017-08-24T03:46:04.569758-05:
      DOI: 10.1002/ange.201707486
       
  • A Stereoselective [3+1] Ring Expansion for the Synthesis of Highly
           Substituted Methylene Azetidines
    • Authors: Steven C. Schmid; Ilia A. Guzei, Jennifer M. Schomaker
      Pages: 12397 - 12401
      Abstract: The reaction of rhodium-bound carbenes with strained bicyclic methylene aziridines results in a formal [3+1] ring expansion to yield highly substituted methylene azetidines with excellent regio- and stereoselectivity. The reaction appears to proceed through an ylide-type mechanism, where the unique strain and structure of the methylene aziridine promotes a ring-opening/ring-closing cascade that efficiently transfers chirality from substrate to product. The resultant products can be elaborated into new azetidine scaffolds containing vicinal tertiary-quaternary and even quaternary-quaternary stereocenters.3+1: Bei der Umsetzung mit einer Rhodium-Carben-Spezies kommt es zu einer effizienten Ringerweiterung von Methylenaziridinen um ein Kohlenstoffatom zu Methylenazetidinen. Die Produkte der 3+1-Ringerweiterung werden hoch stereoselektiv und in hohen Ausbeuten erhalten.
      PubDate: 2017-09-01T03:40:34.129637-05:
      DOI: 10.1002/ange.201705202
       
  • Enzymatic C−H Oxidation–Amidation Cascade in the Production of Natural
           and Unnatural Thiotetronate Antibiotics with Potentiated Bioactivity
    • Authors: Jie Li; Xiaoyu Tang, Takayoshi Awakawa, Bradley S. Moore
      Pages: 12402 - 12407
      Abstract: The selective activation of unreactive hydrocarbons by biosynthetic enzymes has inspired new synthetic methods in C−H bond activation. Herein, we report the unprecedented two-step biosynthetic conversion of thiotetromycin to thiotetroamide C involving the tandem oxidation and amidation of an unreactive ethyl group. We detail the genetic and biochemical basis for the terminal amidation in thiotetroamide C biosynthesis, which involves a uniquely adapted cytochrome P450–amidotransferase enzyme pair and highlights the first oxidation–amidation enzymatic cascade reaction leading to the selective formation of a primary amide group from a chemically inert alkyl group. Motivated by the ten-fold increase in antibiotic potency of thiotetroamide C ascribed to the acetamide group and the unusual enzymology involved, we enzymatically interrogated diverse thiolactomycin analogues and prepared an unnatural thiotetroamide C analogue with potentiated bioactivity compared to the parent molecule.Enzymatische Oxidation/Amidierung: Studien der biochemischen Bildung der terminalen Amidgruppe von Thiotetroamid C förderten ein einzigartiges adaptiertes Enzympaar aus Cytochrom P450 und Amidotransferase zu Tage, das eine unreaktive Ethylgruppe selektiv und sequenziell oxidiert und amidiert, einhergehend mit einem deutlichen Anstieg der antibiotischen Wirkung. Die Substratpromiskuität dieses Enzympaares eröffnet Möglichkeiten für die chemoenzymatische Synthese.
      PubDate: 2017-09-01T03:45:56.183952-05:
      DOI: 10.1002/ange.201705239
       
  • Band-Gap Opening in Metallic Single-Walled Carbon Nanotubes by
           Encapsulation of an Organic Salt
    • Authors: Belén Nieto-Ortega; Julia Villalva, Mariano Vera-Hidalgo, Luisa Ruiz-González, Enrique Burzurí, Emilio M. Pérez
      Pages: 12408 - 12412
      Abstract: The encapsulation of viologen derivatives into metallic single-walled carbon nanotubes (SWNTs) results in the opening of a band gap, making the SWNTs semiconducting. Raman spectroscopy, thermogravimetric analysis, and aberration-corrected high-resolution transmission electron microscopy confirm the encapsulation process. Through the fabrication of field-effect transistor devices, the change of the electronic structure of the tubes from metallic to semiconducting upon the encapsulation is confirmed. The opening of a gap in the band structure of the tubes was not detected in supramolecular controls.Bandlücke, öffne Dich! Bei der Verkapselung von Viologensalzen in einwandigen Kohlenstoffnanoröhren ändert sich die elektronische Bandlücke der Röhren. An die Stelle metallischer Eigenschaften treten hochwertige Halbleitereigenschaften.
      PubDate: 2017-08-24T03:50:48.383286-05:
      DOI: 10.1002/ange.201705258
       
  • Activation of Remote meta-C−H Bonds in Arenes with Tethered Alcohols: A
           Salicylonitrile Template
    • Authors: Lanlan Zhang; Chaoyue Zhao, Yang Liu, Jiancong Xu, Xiufang Xu, Zhong Jin
      Pages: 12413 - 12417
      Abstract: Palladium-catalyzed activation of remote meta-C−H bonds in arenes containing tethered alcohols was achieved with high regioselectivity by using a nitrile template. Computational studies on the macrocyclic transition state of the regioselectivity-determining C−H activation steps revealed that both the C-N-Ag angles and gauche comformations of phenyl ether play an extremely important role in the meta selectivity.Fernwirkung: Die selektive palladiumkatalysierte Aktivierung entfernter meta-C(Aren)-H-Bindungen in langkettigen Alkoholen gelingt mithilfe einer Salicylnitril-Funktion. DFT-Rechnungen zufolge hängt die Regioselektivität stark vom C-N-Ag-Winkel und der gauche-Konformation des Phenylethers im makrocyclischen Übergangszustand ab.
      PubDate: 2017-08-23T12:17:07.295979-05:
      DOI: 10.1002/ange.201705495
       
  • An Asymmetric Pathway to Dendrobine by a Transition-Metal-Catalyzed
           Cascade Process
    • Authors: Yujin Lee; Elise M. Rochette, Junyong Kim, David Y.-K. Chen
      Pages: 12418 - 12422
      Abstract: An asymmetric pathway to the caged tetracyclic pyrrolidine alkaloid, dendrobine, is reported. The successful synthetic strategy features a one-pot, sequential palladium-catalyzed enyne cycloisomerization and rhodium-catalyzed diene-assisted pyrrolidine formation by allylic CH activation. The developed transition-metal-catalyzed cascade process permits rapid access to the dendrobine core structure and circumvents the handling of labile intermediates. An intramolecular aldol condensation under carefully defined reaction conditions takes place with a concomitant detosylation, followed by reductive amine methylation, to afford a late-stage intermediate (previously identified by several prior dendrobine syntheses) in only 10 synthetic steps overall.Das polycyclische Alkaloid Dendrobin ist über eine Eintopfsequenz aus palladiumkatalysierter Enin-Cycloisomerisierung und rhodiumkatalysierter, Dien-unterstützter Pyrrolidinbildung unter allylischer C-H-Aktivierung in einer asymmetrischen Synthese zugänglich. Intramolekulare Aldolkondensation mit Detosylierung und anschließende reduktive Aminierung führen in nur 10 Stufen zu einer fortgeschrittenen Zwischenstufe.
      PubDate: 2017-08-24T03:47:07.891578-05:
      DOI: 10.1002/ange.201705713
       
  • Photochemical Dual-Catalytic Synthesis of Alkynyl Sulfides
    • Authors: Jeffrey Santandrea; Clémentine Minozzi, Corentin Cruché, Shawn K. Collins
      Pages: 12423 - 12427
      Abstract: A photochemical dual-catalytic cross-coupling to form alkynyl sulfides via C(sp)−S bond formation is described. The cross-coupling of thiols and bromoalkynes is promoted by a soluble organic carbazole-based photocatalyst using continuous flow techniques. Synthesis of alkynyl sulfides bearing a wide range of electronically and sterically diverse aromatic alkynes and thiols can be achieved in good to excellent yields (50–96 %). The simple continuous flow setup also allows for short reaction times (30 min) and high reproducibility on gram scale. In addition, we report the first application of photoredox/nickel dual catalysis towards macrocyclization, as well as the first example of the incorporation of an alkynyl sulfide functional group into a macrocyclic scaffold.Katalytische Partnerschaft: Eine photochemische dual-katalytische Kreuzkupplung zur Bildung von Alkinylsulfiden durch C(sp)-S-Bindungsbildung wird von einem Carbazol-Photokatalysator in einer Durchflusssynthese bei kurzen Reaktionszeiten vermittelt (50–96 %, 30 min). Außerdem wurde die Einführung einer Alkinylsulfidgruppe in ein makrocyclisches Grundgerüst als erste Anwendung dieser dualen Photoredox/Nickel-Katalyse in der Makrocyclisierung demonstriert.
      PubDate: 2017-08-24T03:47:00.821889-05:
      DOI: 10.1002/ange.201705903
       
  • Highly Selective and Efficient Ring Hydroxylation of Alkylbenzenes with
           Hydrogen Peroxide and an Osmium(VI) Nitrido Catalyst
    • Authors: Hoi-Ki Kwong; Po-Kam Lo, Shek-Man Yiu, Hajime Hirao, Kai-Chung Lau, Tai-Chu Lau
      Pages: 12428 - 12431
      Abstract: The OsVI 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 at room temperature. 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 up to 6360, 5670, and 3880 can be achieved for the oxidation of p-xylene, ethylbenzene, and mesitylene, respectively. Density functional theory calculations suggest that the active intermediate is an OsVIII nitrido oxo species.Der Trick mit Ring und Kette: Der OsVI-Nitridokomplex OsVI(N)(2-Quin)2(OTs) (Quin=2-Chinaldinat, OTs=Tosylat) katalysiert die Hydroxylierung von Alkylbenzolen mit H2O2 und erzielt dabei ein Verhältnis von Ring- zu Seitenketten-Oxidation von bis zu 99.9:0.1 sowie Umsatzzahlen (TONs) über 6300.
      PubDate: 2017-08-23T12:11:33.837689-05:
      DOI: 10.1002/ange.201705986
       
  • A Nucleophilic Gold(III) Carbene Complex
    • Authors: Anthony Pujol; Mathieu Lafage, Feriel Rekhroukh, Nathalie Saffon-Merceron, Abderrahmane Amgoune, Didier Bourissou, Noel Nebra, Marie Fustier-Boutignon, Nicolas Mézailles
      Pages: 12432 - 12435
      Abstract: The first AuIII carbene complex was prepared by reacting a geminal dianion with a (P,C) cyclometalated AuIII precursor. Its structure and bonding situation have been thoroughly investigated by experimental and computational means. The presence of a high-energy highest occupied molecular orbital (HOMO) centered at the carbene center suggests nucleophilic character for the AuIII carbene complex. This unprecedented feature was confirmed by reactions with two electrophiles (PhNCS and CS2), resulting in two types of C=C coupling reactions.Das etwas andere Goldcarben: Ein Gold(III)-Carben-Komplex wurde ausgehend von einem geminalen Dianion und einer P,C-cyclometallierten Gold(III)-Vorstufe hergestellt. Im Unterschied zu Gold(I)-Carben-Komplexen verhält sich der Titelkomplex nukleophil, und er geht C=C-Kupplungen mit Elektrophilen ein.
      PubDate: 2017-08-24T03:46:55.85561-05:0
      DOI: 10.1002/ange.201706197
       
  • Group 6 Transition-Metal/Boron Frustrated Lewis Pair Templates Activate
           N2 and Allow its Facile Borylation and Silylation
    • Authors: Antoine Simonneau; Raphaël Turrel, Laure Vendier, Michel Etienne
      Pages: 12436 - 12440
      Abstract: The reaction of trans-[M(N2)2(dppe)2] (M=Mo, 1Mo, M=W, 1W) with B(C6F5)3 (2) provides the adducts [(dppe)2M=N=N-B(C6F5)3] (3) which can be regarded as M/B transition-metal frustrated Lewis pair (TMFLP) templates activating dinitrogen. Easy borylation and silylation of the activated dinitrogen ligands in complexes 3 with a hydroborane and hydrosilane occur by splitting of the B−H and Si−H bonds between the N2 moiety and the perfluoroaryl borane. This reactivity of 3 is reminiscent of conventional frustrated Lewis pair chemistry and constitutes an unprecedented approach for the functionalization of dinitrogen.Distickstoff ist eines der kleinen Moleküle, die durch frustrierte Lewis-Paare (FLPs) noch nicht aktiviert werden können. Dies gelingt jedoch mit einer Borverbindung eines Gruppe-6-Metalls (Mo oder W) in ähnlicher Weise wie für herkömmliche FLPs üblich. Borylierungen und Silylierungen unter milden Bedingungen folgen einem Mechanismus, bei dem koordiniertes N2 als FLP-Lewis-Base-Komponente auftritt.
      PubDate: 2017-08-29T04:36:30.606336-05:
      DOI: 10.1002/ange.201706226
       
  • Iminyl-Radicals by Oxidation of α-Imino-oxy Acids: Photoredox-Neutral
           Alkene Carboimination for the Synthesis of Pyrrolines
    • Authors: Heng Jiang; Armido Studer
      Pages: 12441 - 12444
      Abstract: The visible-light-promoted decarboxylation of α-imino-oxy propionic acids for the generation of iminyl radicals has been accomplished through the use of Ir(dFCF3ppy)2(dtbbpy)PF6 as a photoredox catalyst. Different from visible-light-promoted homolysis and single-electron reduction of oxime derivatives, this strategy provides a novel catalytic cycle for alkene carboimination through a sequence comprising N-radical generation, iminyl radical cyclization, intermolecular conjugate addition to a Michael acceptor, and single-electron reduction to afford various pyrroline derivatives in an overall redox-neutral process. The indolizidine alkaloid skeleton could be easily constructed from a pyrroline derivative prepared by this synthetic method.Radikalischer Ringschluss: Eine redoxneutrale radikalische Reaktionskaskade von α-Iminooxypropionsäuren mit verschiedenen Michael-Akzeptoren führt unter Iridium-Photoredoxkatalyse zu wertvollen Pyrrolinen. Diese Reaktionskaskaden umfassen die oxidative Bildung eines Iminylradikals, eine carboaminierende Cyclisierung und eine intermolekulare radikalische konjugierte Addition.
      PubDate: 2017-09-05T06:26:23.53275-05:0
      DOI: 10.1002/ange.201706270
       
  • Total Synthesis of Actinophyllic Acid
    • Authors: Yu Yoshii; Hidetoshi Tokuyama, David Y.-K. Chen
      Pages: 12445 - 12449
      Abstract: Herein we report a total synthesis of the indolohydroazocine natural product actinophyllic acid. The target molecule was retrosynthetically deconvoluted to render a greatly simplified and symmetrical [4.4.1] bicyclic trienone, the desymmetrization of which was carefully examined under a variety of conditions, including oxidative, reductive, and transition-metal-catalyzed transformations. Ultimately, the successful synthetic strategy featured chemoselective catalytic dihydroxylation, desymmetrizing nitrile oxide dipolar cycloaddition, and palladium-catalyzed aminoarylation to sequentially modify the three olefins within the trienone, followed by a late-stage reductive cascade indolization and alkylation to complete the target molecule.Zerbrochener Spiegel: Der Indolohydroazocin-Naturstoff Actinophyllsäure wurde über die Desymmetrisierung eines Trienons synthetisiert. Die entscheidenden Schritte dieser Synthese waren eine chemoselektive katalytische Dihydroxylierung, eine desymmetrisierende dipolare Nitriloxid-Cycloaddition und eine palladiumkatalysierte Aminoarylierung.
      PubDate: 2017-08-24T03:46:34.441607-05:
      DOI: 10.1002/ange.201706312
       
  • Aryloxide-Facilitated Catalyst Turnover in Enantioselective
           α,β-Unsaturated Acyl Ammonium Catalysis
    • Authors: Anastassia Matviitsuk; Mark D. Greenhalgh, Diego-Javier Barrios Antúnez, Alexandra M. Z. Slawin, Andrew D. Smith
      Pages: 12450 - 12455
      Abstract: A new general concept for α,β-unsaturated acyl ammonium catalysis is reported that uses p-nitrophenoxide release from an α,β-unsaturated p-nitrophenyl ester substrate to facilitate catalyst turnover. This method was used for the enantioselective isothiourea-catalyzed Michael addition of nitroalkanes to α,β-unsaturated p-nitrophenyl esters in generally good yield and with excellent enantioselectivity (27 examples, up to 79 % yield, 99:1 er). Mechanistic studies identified rapid and reversible catalyst acylation by the α,β-unsaturated p-nitrophenyl ester, and a recently reported variable-time normalization kinetic analysis method was used to delineate the complex reaction kinetics.Hilfe für den Katalysator: Ein neues Konzept in der Katalyse mit α,β-ungesättigten Acylammonium-Intermediaten nutzt die Freisetzung von Aryloxid aus einem α,β-ungesättigten Arylester zur Beschleunigung des Katalysatorumsatzes. Die enantioselektive Isothioharnstoff-katalysierte Michael-Addition von Nitroalkanen an α,β-ungesättigte p-Nitrophenylester gelang in guten Ausbeuten und mit exzellenter Enantioselektivität.
      PubDate: 2017-08-25T05:28:52.728027-05:
      DOI: 10.1002/ange.201706402
       
  • Palladium-Catalyzed Alkylation with Alkyl Halides by C(sp3)−H
           Activation
    • Authors: Zhuo Wu; Ding Ma, Bo Zhou, Xiaoming Ji, Xiaotian Ma, Xiaoling Wang, Yanghui Zhang
      Pages: 12456 - 12459
      Abstract: Utilizing halogens as traceless directing goups represents an attractive strategy for C−H functionalization. A two C−H alkylation system, initiated by the oxidative addition of organohalides to Pd0, has been developed. The first reaction involves an intermolecular alkylation of palladacycles to form C(sp3)−C(sp2) bonds followed by C(sp2)−H activation/cyclization to deliver alkylated benzocyclobutenes as the final products. In the second reaction, two C−C bonds are formed by the reaction of palladacycles with CH2Br2, and provides a facile and efficient method for the synthesis of indanes. The alkylated benzocyclobutene products can be transformed into tricyclic hyrocarbons, and the indane derivatives are essential structural motifs in bioactive and odorant molecules.6,4 oder 6,5: Die Titelreaktionen von Arylhalogeniden unter C(sp3)-H-Aktivierung verlaufen als Tandemprozesse, in denen zwei C(sp2)-C(sp3)-Bindungen geknüpft und alkylierte Benzocyclobutene als Produkte gebildet werden. Für die Reaktion mit CH2Br2 wurde auch eine katalytische Variante entwickelt, die Indane liefert.
      PubDate: 2017-08-24T03:46:19.799751-05:
      DOI: 10.1002/ange.201706418
       
  • Catalytic Divergent [3+3]- and [3+2]-Cycloaddition by Discrimination
           Between Diazo Compounds
    • Authors: Yongming Deng; Lynée A. Massey, Yeray A. Rodriguez Núñez, Hadi Arman, Michael P. Doyle
      Pages: 12460 - 12464
      Abstract: Highly selective divergent cycloaddition reactions of enoldiazo compounds and α-diazocarboximides catalyzed by copper(I) or dirhodium(II) have been developed. With tetrakis(acetonitrile)copper(I) tetrafluoroborate as the catalyst epoxypyrrolo[1,2-a]azepine derivatives were prepared in good yields and excellent diastereoselectivities through the first reported [3+3]-cycloaddition of a carbonyl ylide. Use of Rh2(pfb)4 or Rh2(esp)2 directs the reactants to regioselective [3+2]-cycloaddition generating cyclopenta[2,3]pyrrolo[2,1-b]oxazoles with good yields and excellent diastereoselectivities.Katalytische Divergenz: Mit Kupfer(I)- oder Dirhodium(II)-Katalysatoren gelingt die Titelreaktion zwischen Enoldiazoverbindungen und α-Diazocarboximiden mit hoher Diastereokontrolle und Kreuzselektivität. Drei heterocyclische Produkte mit multicyclischen Azepin-, Pyrrolizin- und Oxazol-Gerüsten wurden aus den gleichen Diazoverbindungen synthetisiert.
      PubDate: 2017-08-24T03:46:11.267334-05:
      DOI: 10.1002/ange.201706639
       
  • Formation of Binuclear Zigzag Hexapentaene Titanium Complexes via a
           Titanacumulene [Ti=C=C=CH2] Intermediate
    • Authors: Tim Oswald; Tina Gelert, Christian Lasar, Marc Schmidtmann, Thorsten Klüner, Rüdiger Beckhaus
      Pages: 12465 - 12469
      Abstract: The reaction of bis(η5:η1-pentafulvene)titanium complexes with an allylidenephosphorylide Ph3P=C(H)- C(H)=CH2 leads to binuclear zigzag hexapentaene titanium complexes (Ti2a, Ti2b). The formation of the central C6H4 unit can be described as a spontaneous double C−H bond activation process, leading to an R3P=C=C=CH2 intermediate, as a synthon for a titanabutatriene fragment [(CpR)2Ti=C=C=CH2] (R: 2-adamantyl, CH(p-tol)2). In a subsequent dimerization Ti2a and Ti2b are formed, proofed by single-crystal X-ray diffraction and NMR measurements. The reaction sequence is confirmed by DFT calculations.Nicht nur in der Atmosphäre des Saturnmondes Titan, sondern auch in der Koordinationssphäre des Elements Titan kann sich das ungewöhnliche Hexapentaen H2C=C=C=C=C=CH2 bilden. Die doppelte C-H-Aktivierung eines Phosphorylids erzeugt eine Phosphacumulen-Zwischenstufe, die mit einem Titanocenfragment unter PPh3-Eliminierung zu [Cp′2Ti=C=C=CH2] reagiert, das durch Dimerisierung die Titanhexapentaen-Komplexe liefert.
      PubDate: 2017-08-23T12:11:55.563088-05:
      DOI: 10.1002/ange.201706674
       
  • Sono-RAFT Polymerization in Aqueous Medium
    • Authors: Thomas G. McKenzie; Enrico Colombo, Qiang Fu, Muthupandian Ashokkumar, Greg G. Qiao
      Pages: 12470 - 12474
      Abstract: The ultrasonic irradiation of aqueous solution is demonstrated to be a suitable source of initiating radicals for a controlled radical polymerization when conducted in the presence of a thiocarbonylthio-containing reversible addition–fragmentation chain transfer (RAFT) agent. This allows for a highly “green” method of externally regulated/controlled polymerization with a potentially broad scope for polymerizable monomers and/or polymer structures.Schallende Synthese: Eine sonochemisch induzierte RAFT-Polymerisation nutzt hochfrequenten Ultraschall zur effizienten zeitlichen Steuerung der Reaktion. Anders als die niedrigen Frequenzen, die bei mechanisch induzierten Polymerisationen angewendet werden, erzeugen hohe Frequenzen nur geringe Scherkräfte, wodurch kettenspaltende Depolymerisationen verhindert werden.
      PubDate: 2017-09-01T06:30:51.320642-05:
      DOI: 10.1002/ange.201706771
       
  • Selective α-Oxyamination and Hydroxylation of Aliphatic Amides
    • Authors: Xinwei Li; Fengguirong Lin, Kaimeng Huang, Jialiang Wei, Xinyao Li, Xiaoyang Wang, Xiaoyu Geng, Ning Jiao
      Pages: 12475 - 12479
      Abstract: Compared to the α-functionalization of aldehydes, ketones, even esters, the direct α-modification of amides is still a challenge because of the low acidity of α-CH groups. The α-functionalization of N−H (primary and secondary) amides, containing both an unactived α-C−H bond and a competitively active N−H bond, remains elusive. Shown herein is the general and efficient oxidative α-oxyamination and hydroxylation of aliphatic amides including secondary N−H amides. This transition-metal-free chemistry with high chemoselectivity provides an efficient approach to α-hydroxy amides. This oxidative protocol significantly enables the selective functionalization of inert α-C−H bonds with the complete preservation of active N−H bond.Aktiv ist relativ: Ein allgemeines Verfahren für die effiziente α-Oxyaminierung aliphatischer Amide, darunter auch sekundärer N-H-Amide, verzichtet auf Übergangsmetalle und führt hoch chemoselektiv zu α-Hydroxyamiden. Durch das oxidative Verfahren gelingt eine selektive Funktionalisierung inerter α-C-H-Bindungen, bei der die aktive N-H-Bindung erhalten bleibt.
      PubDate: 2017-09-05T06:21:27.175618-05:
      DOI: 10.1002/ange.201706963
       
  • Synergistic Cu/Pd Catalysis for Enantioselective Allylic Alkylation of
           Aldimine Esters: Access to α,α-Disubstituted α-Amino Acids
    • Authors: Liang Wei; Shi-Ming Xu, Qiao Zhu, Chao Che, Chun-Jiang Wang
      Pages: 12480 - 12484
      Abstract: An unprecedented enantioselective allylic alkylation of readily available aldimine esters has been developed, and is catalyzed by a synergistic Cu/Pd catalyst system. This strategy provides facile access to nonproteinogenic α,α-disubstituted α-amino acids in high yield with excellent enantioselectivity. The more challenging double allylic alkylation of glycinate-derived imine esters was also realized. Furthermore, this methodology was applied for the construction of the key intermediate of PLG peptidomimetics.Kooperativer Ansatz: Eine enantioselektive allylische Alkylierung von Aldiminestern unter synergistischer Cu/Pd-Katalyse liefert nichtproteinogene α,α-disubstituierte α-Aminosäuren in hohen Ausbeuten bei hervorragender Enantioselektivität. Auch die schwierigere doppelte allylische Alkylierung von Glycinat-abgeleiteten Iminestern wurde realisiert. LG=Abgangsgruppe.
      PubDate: 2017-08-23T12:16:02.14783-05:0
      DOI: 10.1002/ange.201707019
       
  • A meso–meso β-β β-β Triply Linked Subporphyrin
           Dimer
    • Authors: Yasuhiro Okuda; Norihito Fukui, Jinseok Kim, Taeyeon Kim, Hua-Wei Jiang, Graeme Copley, Masaaki Kitano, Dongho Kim, Atsuhiro Osuka
      Pages: 12485 - 12489
      Abstract: A meso–meso β-β β-β triply linked subporphyrin dimer 6 was synthesized by stepwise reductive elimination of β-to-β doubly PtII-bridged subporphyrin dimer 9. Dimer 6 was characterized by spectroscopic and electrochemical measurements, theoretical calculations, and picosecond time-resolved transient absorption spectroscopy. X-ray diffraction analysis reveals that 6 has a bowl-shaped structure with a positive Gaussian curvature. Despite the curved structure, 6 exhibits a remarkably red-shifted absorption band at 942 nm and a small electrochemical HOMO–LUMO gap (1.35 eV), indicating an effectively conjugated π-electronic network.Ein dreifach verbrücktes Subporphyrin-Dimer wurde durch stufenweise reduktive Eliminierung aus einem doppelt β-zu-β-PtII-verbrückten Subporphyrin-Dimer unter zusätzlicher Bildung der meso-meso-Bindung erhalten. Infolge effektiver π-Konjugation zeigt das dreifach verbrückte Dimer trotz seiner gewölbten Struktur eine rotverschobene Absorption und einen kleinen elektrochemischen HOMO-LUMO-Abstand.
      PubDate: 2017-08-23T12:15:54.940381-05:
      DOI: 10.1002/ange.201707123
       
  • Strategic Construction of Directly Linked Porphyrin–BODIPY Hybrids
    • Authors: Lei Xu; Bin Wen, Gakhyun Kim, Taeyeon Kim, Fei Cheng, Mingbo Zhou, Ling Xu, Takayuki Tanaka, Bangshao Yin, Atsuhiro Osuka, Dongho Kim, Jianxin Song
      Pages: 12490 - 12494
      Abstract: A powerful and concise synthesis of directly linked porphyrin-BODIPY hybrids has been demonstrated, which consists of condensation of directly linked meso-pyrroyl NiII-porphyrin with arylaldehyde, oxidation with p-chloranil, and complexation with BF3⋅Et2O. Synthesized hybrids include porphyrin dimer 6Ni, trimers 8Ni, 9Ni, tetramer 12Ni, pentamer 16Ni, hexamer 13Ni, and nonamers 17Ni and 18Ni. The structures of 6Ni, 9Ni and 12Ni were unambiguously confirmed by X-ray diffraction analysis. Some NiII porphyrins were effectively converted to the corresponding ZnII porphryins. In these hybrids, the pigments are three-dimensionally arranged with a face-to-face dimeric porphyrin unit in a well-defined manner, featuring their potential as light-harvesting antenna and functional hosts.Oligomere Hybride aus Nickel(II)- porphyrin und BODIPY (n-mere: n=2–6, 9) wurden durch eine kurze und effiziente Synthese aufgebaut und zum Teil in die entsprechenden ZnII-Komplexe umgewandelt. Die Hybride nehmen eine dreidimensionale Struktur mit flächig angeordneten Porphyrinteilen an und zeigen Potenzial als Lichtsammelantennen und funktionelle Wirte.
      PubDate: 2017-08-25T05:21:56.478332-05:
      DOI: 10.1002/ange.201707237
       
  • Total Synthesis of (−)-Vindorosine
    • Authors: Wen Chen; Xiao-Dong Yang, Wen-Yun Tan, Xiang-Yang Zhang, Xia-Li Liao, Hongbin Zhang
      Pages: 12495 - 12499
      Abstract: Outlined herein is a novel and scalable synthesis of (−)-vindorosine based on two key transformations. A highly diastereoselective vinylogous Mannich addition of dioxinone-derived lithium dienolates with indolyl N-tert-butanesulfinyl imines has been developed. In addition, an intramolecular Heathcock/aza-Prins cyclization was introduced to construct both the C, and the highly substituted E rings for the synthesis of (−)-vindorosine and related alkaloids.Kommen wir zum Kern: Eine neue Strategie für die Synthese von (−)-Vindorosin und verwandten Alkaloiden enthält als Schlüsselschritte eine asymmetrische vinyloge Mannich-Addition von Dioxinon-abgeleiteten Lithiumdienolaten zu Indolyl-N-tert-butansulfinyliminen und eine intramolekulare Heathcock/Aza-Prins-Cyclisierung zum Aufbau der C- und E-Ringe.
      PubDate: 2017-08-24T03:45:36.878552-05:
      DOI: 10.1002/ange.201707249
       
  • Biomimetische Synthese komplexer Flavonoide isoliert aus
           Daemonorops-“Drachenblut”
    • Authors: Matthias Schmid; Dirk Trauner
      Pages: 12500 - 12504
      Abstract: Dragonbloodin A1 und A2 sind ein Paar komplexer Flavonoidtrimere, die aus der Palmenart Daemonorops draco isoliert wurden. Wir präsentieren hier eine kurze Synthese, die ihre relative Konfiguration sowie ihren natürlichen Ursprung aufklärt. Die Synthese zeichnet sich durch biomimetische Reaktionskaskaden aus, an denen sowohl ionische als auch radikalische Intermediate beteiligt sind. Außerdem wird die Beziehung zwischen Dracorhodin, den Dracoflavanen C sowie den Dragonbloodinen A1 und A2 behandelt.Dragonbloodin A1 und A2 sind ein Paar komplexer Flavonoidtrimere, die aus der Palmenart Daemonorops draco isoliert wurden, die eine der Quellen von „Drachenblut” stellt. Durch eine effiziente Synthese wird ihre relative Konfiguration aufgeklärt und dadurch auch die Vermutung nahelegt, dass sich diese komplexen Moleküle spontan aus den Inhaltstoffen des Drachenbluts unter Lufteinfluss bilden.
      PubDate: 2017-08-16T02:25:48.33425-05:0
      DOI: 10.1002/ange.201705390
       
  • Durch sichtbares Licht vermittelte Deaminierung zur Erzeugung von
           Alkylradikalen
    • Authors: Felix J. R. Klauck; Michael J. James, Frank Glorius
      Pages: 12505 - 12509
      Abstract: Eine Deaminierungsstrategie für die durch sichtbares Licht vermittelte Erzeugung von Alkylradikalen aus redoxaktivierten primären Amin-Vorstufen wird beschrieben. Häufig vorkommende und preiswerte primäre Amine, einschließlich der Aminosäuren, wurden in einem Schritt in redoxaktive Pyridiniumsalze und anschließend in Alkylradikale durch Umsetzung mit einem angeregten Photokatalysator umgesetzt. Das Potenzial dieses Protokolls für Synthesen wurde durch die einfach durchzuführende Alkylierung einer Anzahl von Heteroarenen unter milden Bedingungen nachgewiesen.Radikaler Schnitt: Die Titelreaktion erzeugt Alkylradikale aus redoxaktivierten primären Aminvorstufen. In der Natur häufig vorkommende preiswerte primäre Amin-Rohstoffe, einschließlich Aminosäuren, wurden in einem Schritt in redoxaktive Pyridiniumsalze und anschließend in Alkylradikale durch Umsetzung mit einem angeregten Photokatalysator umgesetzt. Das Potenzial der Methode wurde anhand der Alkylierung einer Reihe von Heteroarenen gezeigt.
      PubDate: 2017-08-29T11:21:17.490748-05:
      DOI: 10.1002/ange.201706896
       
  • Metall-Metall-Mehrfachbindung oder keine Bindung' Die elektronische
           Struktur von V2O2
    • Authors: Olaf Hübner; Hans-Jörg Himmel
      Pages: 12510 - 12514
      Abstract: Die detaillierte Kenntnis der elektronischen Struktur von Vanadiumoxidclustern bildet die Basis für das Verständnis und die Abstimmung ihrer wichtigen katalytischen Eigenschaften. Allerdings existieren in der Literatur schon für das einfache vieratomige V2O2-Molekül widersprüchliche Berichte bezüglich des elektronischen Grundzustandes und einer möglichen Vanadium-Vanadium-Bindung. Mit einer Kombination aus experimentellen (Matrixisolation) und theoretischen Ergebnissen zeigen wir hier, dass eine Vanadium-Vanadium-Bindung in diesem prototypischen Vanadiumoxidmolekül gebildet wird.Wohin mit den Elektronen' Die Aufklärung der elektronischen Struktur des scheinbar einfachen V2O2-Moleküls, einer prototypischen Verbindung für katalytisch aktive Vanadiumoxide, erfordert eine gründliche kombinierte experimentelle und theoretische Studie.
      PubDate: 2017-08-24T03:46:44.243918-05:
      DOI: 10.1002/ange.201706266
       
  • Strukturelle und elektronische Flexibilität in Hydriden von Zintl-Phasen
           mit Tetrel-Wasserstoff- und Tetrel-Tetrel-Bindung
    • Authors: Henry Auer; Robert Schlegel, Oliver Oeckler, Holger Kohlmann
      Pages: 12515 - 12518
      Abstract: Die Hydrierung von Zintl-Phasen ermöglicht die Bildung neuer Strukturmotive mit Hauptgruppenelement-Wasserstoff-Bindungen im Festkörper. Die Hydrierung von SrSi, BaSi und BaGe führt zu den Hydriden SrSiH5/3-x, BaSiH5/3-x und BaGeH5/3-x. Die Kristallstrukturen wurden durch eine Kombination von Röntgen-, Neutronen- und Elektronenbeugung sowie unter Zuhilfenahme von DFT-Rechnungen gelöst und zeigen eine sechsfache Überstruktur im Vergleich zur wasserstofffreien Zintl-Phase. Schichten aus verknüpften HSr4-(HBa4-)Tetraedern, die ein Hydridanion enthalten, wechseln sich mit Schichten aus polyanionischen Einfach- und Doppelketten ab, in denen Wasserstoff kovalent an Silicium oder Germanium gebunden ist. Die idealisierten chemischen Formeln EaTtH5/3 (Ea=Erdalkalimetall, Tt=Tetrelatom) lassen sich mit dem Zintl-Klemm-Konzept als (Ea2+)3(TtH−)(Tt2H2−)(H−)3 beschreiben, wobei alle Tt-Atome dreibindig sind. Die Nichtstöchiometrie (SrSiH5/3-x, x=0.17(2); BaGeH5/3-x, x=0.10(3)) ist durch zusätzliche π-Bindungsanteile zu erklären.Die Zintl-Phasen SrSi, BaSi und BaGe bilden Hydride der Form EaTtH5/3-x (Ea=Sr, Ba; Tt=Si, Ge). Die Polyanionen dieser Phasen liegen als Einfach- und Doppelketten vor, die zusätzliche Tetrel-Wasserstoff- sowie Tetrel-Tetrel-Bindungen aufweisen.
      PubDate: 2017-08-25T05:28:58.777235-05:
      DOI: 10.1002/ange.201706523
       
  • Eigenschaften von Wasser in den Poren von periodisch mesoporösen
           Organosilicas – Nanoabprägung der lokalen Struktur
    • Authors: J. Benedikt Mietner; Felix J. Brieler, Young Joo Lee, Michael Fröba
      Pages: 12519 - 12523
      Abstract: Die Eigenschaften von Gastmolekülen in den Poren poröser Materialien sind sowohl aus wissenschaftlicher wie auch aus technologischer Perspektive hochinteressant. Entscheidenden Einfluss auf die durch eine geometrische Beschränkung hervorgerufenen Effekte haben insbesondere die Topologie, Größe und Oberflächenpolarität der Poren. Allerdings ist über die Kontaktfläche zwischen Gastmolekül und Porenwand noch zu wenig bekannt. Hier wird gezeigt, dass die Mobilität von Wassermolekülen in den Poren von periodisch mesoporösen Organosilicas (PMOs) stark von der Polarität der organischen Einheit abhängt. Mithilfe mehrdimensionaler Festkörper-NMR-Spektroskopie wurde die räumliche Anordnung von Wasser im Inneren von Poren bestimmt. Wassermoleküle interagieren, abhängig von der alternierenden Oberflächenpolarität, entweder nur mit den anorganischen Silicatschichten oder auch mit den organischen Schichten. Als Ergebnis wird in Abhängigkeit von den PMO-Typen entweder eine modulierte oder eine gleichmäßige Porenfüllung mit Wasser vorgeschlagen.Topologie, Größe und Oberflächenpolarität von Nanoporen sind wesentlich für Größenbeschränkungseffekte. Die molekulare Mobilität und die räumliche Anordnung von Wasser innerhalb periodisch mesoporöser Organosilicas (PMOs) wurden mit mehrdimensionaler Festkörper-NMR-Spektroskopie ermittelt; es zeigt sich, dass das Wasser entweder nur mit der Silicatschicht oder auch zusätzlich mit den organischen Schichten wechselwirkt.
      PubDate: 2017-08-23T12:11:03.703263-05:
      DOI: 10.1002/ange.201705707
       
  • Enzymatische Synthese von Psilocybin
    • Authors: Janis Fricke; Felix Blei, Dirk Hoffmeister
      Pages: 12524 - 12527
      Abstract: Psilocybin ist der psychotrope, vom Tryptamin abgeleitete Naturstoff der Psilocybe-Fruchtkörper, der so genannten “Zauberpilze”. Obwohl dessen Struktur seit 60 Jahren bekannt ist, blieb die enzymatische Grundlage ihrer Biosynthese ungeklärt. Wir charakterisierten vier Psilocybin-Biosyntheseenzyme, nämlich i) PsiD, welches zu einer neuen Klasse pilzlicher l-Tryptophan-Decarboxylasen gehört, ii) PsiK, welches den Phosphotransfer-Schritt katalysiert, iii) die Methyltransferase PsiM, welche einen wiederholten N-Methyltransfer als abschließenden Biosyntheseschritt katalysiert, sowie iv) PsiH, eine Monooxygenase. In einer kombinierten Reaktion mit PsiD, PsiK und PsiM wurde Psilocybin vom 4-Hydroxy-l-tryptophan ausgehend nach einer schrittökonomischen Route synthetisiert. Angesichts des wieder aufkommenden pharmazeutischen Interesses an Psilocybin könnten unsere Ergebnisse die Grundlage für dessen biotechnologische Produktion schaffen.Das Tryptaminderivat Psilocybin ist der psychoaktive Inhaltsstoff der Psilocybe-Arten, der so genannten „Zauberpilze”. Die Decarboxylase PsiD, die Kinase PsiK sowie die Methyltransferase PsiM wurden in Psilocybe cubensis als Biosynthese-enzyme identifiziert und eingesetzt, um Psilocybin enzymatisch in einer Eintopfreaktion zu synthetisieren.
      PubDate: 2017-08-25T05:27:43.272746-05:
      DOI: 10.1002/ange.201705489
       
  • Auf dem Weg vom Fenestrindan zu sattelförmigen Nanographenen mit einem
           tetrakoordinierten Kohlenstoff-Atom
    • Authors: Wai-Shing Wong; Chun-Fai Ng, Dietmar Kuck, Hak-Fun Chow
      Pages: 12528 - 12532
      Abstract: Die Synthese zweier polycyclischer aromatischer Verbindungen (8 a und 8 b) mit aufgrund eines all-cis-[5.5.5.5]Fenestran-Kerns und eines o,p,o,p,o,p,o,p-Cyclooctaphenylen-Gürtels sattelförmiger Molekülstruktur sowie ihre Charakterisierung durch NMR-Spektroskopie und Massenspektrometrie wird beschrieben. Der Schlüsselschritt der Synthese besteht in einer nichtklassischen Scholl-Reaktion der entsprechenden elektronenreichen 1,4,9,12-Tetraarylfenestrindan-Derivate 7 a und 7 b unter Bildung von vier Cycloheptatrien-Ringen. Die strukturellen Details des D2d-symmetrischen Sattels 8 a wurden durch Röntgenstrukturanalyse ermittelt, und die UV-vis- und emissionsspektroskopischen und cyclovoltammetrischen Eigenschaften von 8 a und 8 b wurden ebenfalls untersucht.Gekrümmtes Nanographen: Zwei in allen vier Buchten vollständig überbrückte Fenestrindan-Derivate wurden in guten Ausbeuten mittels einer nichtklassischen Scholl-Cyclisierung synthetisiert, was einen Weg zu sattelförmigen Nano-graphenen eröffnet.
      PubDate: 2017-08-29T04:35:42.367134-05:
      DOI: 10.1002/ange.201707505
       
  • Cyanid-freie und breit anwendbare enantioselektive Syntheseplattform für
           chirale Nitrile durch einen biokatalytischen Zugang
    • Authors: Tobias Betke; Philipp Rommelmann, Keiko Oike, Yasuhisa Asano, Harald Gröger
      Pages: 12533 - 12538
      Abstract: Eine Cyanid-freie Plattformtechnologie zur Synthese von chiralen Nitrilen durch eine biokatalytische, enantioselektive Dehydratisierung zahlreicher Aldoxime wurde entwickelt. Die Nitrile wurden in vielen Fällen mit Enantiomerenüberschüssen von>90 % ee (bis zu 99 % ee) erhalten, und eine “privilegierte Substratstruktur” in Hinblick auf das Erzielen einer hohen Enantioselektivität wurde identifiziert. Des Weiteren wurde ein überraschendes Phänomen bei der Enantiospezifität beobachtet, das normalerweise in der Biokatalyse nicht auftritt: In Abhängigkeit vom E- und Z-Isomer des racemischen Aldoximsubstrats wurde mit demselben Enzym das gegensätzliche Enantiomer des gebildeten Nitrils als bevorzugtes Produkt erhalten.Eine Cyanid-freie Plattformtechnologie für die Synthese chiraler Nitrile über biokatalytische, enantioselektive Dehydratisierung einer großen Bandbreite einfach zugänglicher Aldoxime führt in vielen Fällen zu den jeweiligen Nitrilen mit hohen Enantiomerenüberschüssen von>90 % ee (und bis zu 99 % ee). Diese Studie offenbart auch eine „privilegierte Substratstruktur” im Hinblick auf eine gute Aktivität und hohe Enantioselektivität. Oxd=Aldoximdehydratase.
      PubDate: 2017-08-29T04:36:52.484513-05:
      DOI: 10.1002/ange.201702952
       
  • Calciumhydrid-Kation [CaH]+ stabilisiert durch einen makrocyclischen
           NNNN-Liganden: ein selektiver Katalysator für die Hydrierung von Olefinen
           
    • Authors: Danny Schuhknecht; Carolin Lhotzky, Thomas P. Spaniol, Laurent Maron, Jun Okuda
      Pages: 12539 - 12543
      Abstract: Die Reaktion des Dibenzylcalcium-Komplexes [Ca(Me4TACD)(CH2Ph)2], stabilisiert durch den neutralen, makrocyclischen Liganden 1,4,7,10-Tetramethyl-1,4,7,10-tetra
      PubDate: 2017-08-29T04:35:57.808353-05:
      DOI: 10.1002/ange.201706848
       
  • Innenrücktitelbild: Biomimetische Synthese komplexer Flavonoide isoliert
           aus Daemonorops-“Drachenblut” (Angew. Chem. 40/2017)
    • Authors: Matthias Schmid; Dirk Trauner
      Pages: 12545 - 12545
      Abstract: Eine oxidative Reaktionskaskade offenbart den Ursprung der komplexen Flavonoide Dragonbloodin A1 und A2, die aus Daemonorops draco oder “Drachenblut” isoliert wurden. In ihrer Zuschrift auf S. 12500 präsentieren D. Trauner und M. Schmid eine kurze Synthese von Dragonbloodin A1 und A2 über eine biomimetische Trimerisierung und eine autoxidative radikalische Cyclisierung. Dadurch konnte die relative und absolute stereochemische Konfiguration der Produkte klargestellt werden.
      PubDate: 2017-08-24T00:54:39.805291-05:
      DOI: 10.1002/ange.201708380
       
  • Rücktitelbild: Cyanid-freie und breit anwendbare enantioselektive
           Syntheseplattform für chirale Nitrile durch einen biokatalytischen Zugang
           (Angew. Chem. 40/2017)
    • Authors: Tobias Betke; Philipp Rommelmann, Keiko Oike, Yasuhisa Asano, Harald Gröger
      Pages: 12546 - 12546
      Abstract: Eine cyanidfreie Plattformtechnologie …… für die Synthese chiraler Nitrile durch biokatalytische Dehydratisierung einer großen Bandbreite an Aldoximen liefert die Produkte in vielen Fällen mit hoher Enantioselektivität. In der Zuschrift auf S. 12533 beschreiben Y. Asano, H. Gröger et al. zudem ein überraschendes Phänomen bezüglich der Enantiospezifität: In Abhängigkeit vom E- oder Z-Isomer des racemischen Substrats wird mit demselben Enzym das entgegengesetzte Enantiomer des Nitrils bevorzugt gebildet.
      PubDate: 2017-09-01T03:56:02.3368-05:00
      DOI: 10.1002/ange.201707179
       
 
 
JournalTOCs
School of Mathematical and Computer Sciences
Heriot-Watt University
Edinburgh, EH14 4AS, UK
Email: journaltocs@hw.ac.uk
Tel: +00 44 (0)131 4513762
Fax: +00 44 (0)131 4513327
 
Home (Search)
Subjects A-Z
Publishers A-Z
Customise
APIs
Your IP address: 54.156.69.204
 
About JournalTOCs
API
Help
News (blog, publications)
JournalTOCs on Twitter   JournalTOCs on Facebook

JournalTOCs © 2009-2016