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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: 234)
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: 69)
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: 204)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 214)
Annales UMCS, Chemia     Open Access   (Followers: 1)
Annals of Clinical Chemistry and Laboratory Medicine     Open Access   (Followers: 2)
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: 293)
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: 4)
Bioorganic & Medicinal Chemistry     Hybrid Journal   (Followers: 124)
Bioorganic & Medicinal Chemistry Letters     Hybrid Journal   (Followers: 98)
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: 71)
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: 176)
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: 143)
Chemistry - An Asian Journal     Hybrid Journal   (Followers: 15)
Chemistry and Materials Research     Open Access   (Followers: 18)
Chemistry Central Journal     Open Access   (Followers: 4)
Chemistry Education Research and Practice     Free   (Followers: 5)
Chemistry in Education     Open Access   (Followers: 9)
Chemistry International     Hybrid Journal   (Followers: 2)
Chemistry Letters     Full-text available via subscription   (Followers: 45)
Chemistry of Materials     Full-text available via subscription   (Followers: 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: 9)
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: 18)

        1 2 3 | Last

Journal Cover Angewandte Chemie International Edition
  [SJR: 6.229]   [H-I: 397]   [214 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1433-7851 - ISSN (Online) 1521-3773
   Published by John Wiley and Sons Homepage  [1577 journals]
  • 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: 2017-09-19T04:40:53.517103-05:
      DOI: 10.1002/anie.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: 2017-09-19T04:40:43.086596-05:
      DOI: 10.1002/anie.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: 2017-09-19T03:41:10.839606-05:
      DOI: 10.1002/anie.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: 2017-09-19T02:41:05.220619-05:
      DOI: 10.1002/anie.201708176
  • 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.The severe line broadening in the intermediate exchange limits the applicability of NMR spectroscopy for interrogating the interaction modes of lead-like inhibitors with moderate affinities to target proteins. A 19F chemical exchange saturation transfer approach is used to retrieve the low-populated bound-state 19F pseudocontact shifts, which enable the identification of the best binding pose of the BRM bromodomain inhibitor.
      PubDate: 2017-09-19T00:35:52.936425-05:
      DOI: 10.1002/anie.201707114
  • 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.Energy conversion: Embedding an acceptor–donor–acceptor-structured organic semiconductor building block into a polymer main chain creates an excellent low-band-gap polymer acceptor with red-shifted absorption and high absorption coefficient. The polymer acceptor provides a record-high power conversion efficiency of 9.19 % for all-polymer solar cells.
      PubDate: 2017-09-19T00:35:47.184736-05:
      DOI: 10.1002/anie.201707678
  • 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.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, synthetic mRNA containing a poly A tail was complexed with PABPs in a stoichiometric manner.
      PubDate: 2017-09-19T00:35:25.802573-05:
      DOI: 10.1002/anie.201707466
  • 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.A weakness becomes an asset: The oxidative activity of catalytic nucleic acids in tandem with the much-maligned photosensitivity of the phenoxazine dye Amplex Red is leveraged to engineer an exponentially propagating reaction which creates a visible readout via multiple positive-feedback loops. This novel assay enables visible detection of the catalytic reporter from 1 μm to 100 pm.
      PubDate: 2017-09-19T00:31:18.980587-05:
      DOI: 10.1002/anie.201706163
  • 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.Cell watching: Cationic poly(phenylene ethynylene) (PPE) derivatives are explored for use as Raman probes for living cell imaging due to a synergetic-enhancement effect of alkyne vibrations in Raman-silent regions. The enhanced alkyne signals result from the integration of alkyne groups into the rigid polymer backbone. PPE-based conjugated polymer nanoparticles were also prepared as Raman-responsive nanomaterials for distinct imaging application.
      PubDate: 2017-09-19T00:30:58.147896-05:
      DOI: 10.1002/anie.201707042
  • 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: 2017-09-18T20:40:56.369484-05:
      DOI: 10.1002/anie.201708645
  • Catalytic Enantioselective Synthesis of Highly Functionalized
           Difluoromethylated Cyclopropanes
    • Authors: Maxence Bos; Wei-Sheng Huang, Thomas Poisson, Xavier Pannecoucke, André B. Charette, Philippe Jubault
      Abstract: The first catalytic asymmetric synthesis of highly functionalized difluoromethylated cyclopropanes is described. The method, based on a rhodium-catalyzed cyclopropanation of difluoromethylated olefins, gives access to a broad range of cyclopropanes bearing ester, ketone, or nitro functional groups. By using Rh2((S)-BTPCP)4 as a catalyst, the corresponding products were obtained in high yields and high diastereo- and enantioselectivities (up 20:1 d.r. and 99 % ee). This methodology allowed preparation of enantioenriched difluoromethylcyclopropanes for the first time.Small rings: The first catalytic asymmetric synthesis of difluorinated cyclopropanes is described. The methodology employs a rhodium catalyst and affords access to functionalized cyclopropanes in high yields with high diastereo- and enantioselectivities. PMP=para-methoxyphenyl.
      PubDate: 2017-09-18T11:39:39.13852-05:0
      DOI: 10.1002/anie.201707375
  • 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.Better together: Joint application of chemical biology and computational target prediction enabled the identification of the pyrazolo-imidazole derivative smoothib as a novel inhibitor of hedgehog signaling and the membrane protein smoothened as its target.
      PubDate: 2017-09-18T11:39:21.60015-05:0
      DOI: 10.1002/anie.201707394
  • Osmium-Mediated Transformation of 4-Thiouridine to Cytidine as Key To
           Study RNA Dynamics by Sequencing
    • Authors: Christian Riml; Thomas Amort, Dietmar Rieder, Catherina Gasser, Alexandra Lusser, Ronald Micura
      Abstract: To understand the functional roles of RNA in the cell, it is essential to elucidate the dynamics of their production, processing and decay. A recent method for assessing mRNA dynamics is metabolic labeling with 4-thiouridine (4sU), followed by thio-selective attachment of affinity tags. Detection of labeled transcripts by affinity purification and hybridization to microarrays or by deep sequencing then reveals RNA expression levels. Here, we present a novel sequencing method (TUC-seq) that eliminates affinity purification and allows for direct assessment of 4sU-labeled RNA. It employs an OsO4-mediated transformation to convert 4sU into cytosine. We exemplify the utility of the new method for verification of endogenous 4sU in tRNAs and for the detection of pulse-labeled mRNA of seven selected genes in mammalian cells to determine the relative abundance of the new transcripts. The results prove TUC-seq as a straight-forward and highly versatile method for studies of cellular RNA dynamics.RNA modification: The osmium-mediated conversion of thiouridine (4sU) to cytidine (C) is a so far disregarded reaction with great potential for comparative sequencing approaches.
      PubDate: 2017-09-18T11:39:12.37625-05:0
      DOI: 10.1002/anie.201707465
  • Conformationally Flexible Bis(9-fluorenylidene)porphyrin Diradicaloids
    • Authors: Hejian Zhang; Hoa Phan, Tun Seng Herng, Tullimilli Y. Gopalakrishna, Wangdong Zeng, Jun Ding, Jishan Wu
      Abstract: A stable 5,10-bis(9-fluorenylidene)porphyrin (Por-Fl) diradicaloid was synthesized. It shows a quinoidal, saddle-shaped geometry in the single crystal but can be thermally populated to a triplet diradical both in solution and in the solid state. Coordination with the Ni2+ ion (Por-Fl-Ni) does not significantly change the contorted conformation but reduces the singlet–triplet gap. Heat-induced geometric change can explain the observed paramagnetic properties as well as unusual hysteresis in SQUID measurements. On the other hand, protonation (Por-Fl-2H+) dramatically changes the conformation while maintains the closed-shell electronic structure. Our studies demonstrate how heat, coordination, and protonation affect the geometry, diradical character, and physical properties of conformationally flexible open-shell singlet diradicaloids.Protonation with a twist! A quinoidal bis(9-fluorenylidene)porphyrin and its NiII complex showed closed-shell saddle-shaped geometry in the crystalline state but they can be thermally populated to paramagnetic triplet species through geometric change. Protonation also dramatically changes the conformation and physical properties.
      PubDate: 2017-09-18T11:39:00.080679-05:
      DOI: 10.1002/anie.201707480
  • 4,5,9,10-Pyrene Diimides: A Family of Aromatic Diimides Exhibiting High
           Electron Mobility and Two-Photon Excited Emission
    • Authors: Ze-Hua Wu; Zhuo-Ting Huang, Rui-Xue Guo, Chun-Lin Sun, Li-Chuan Chen, Bing Sun, Zi-Fa Shi, Xiangfeng Shao, Hanying Li, Hao-Li Zhang
      Abstract: The design and synthesis of high-performance n-type organic semiconductors are important for the development of future organic optoelectronics. Facile synthetic routes to reach the K-region of pyrene and produce 4,5,9,10-pyrene diimide (PyDI) derivatives are reported. The PyDI derivatives exhibited efficient electron transport properties, with the highest electron mobility of up to 3.08 cm2 V−1 s−1. The tert-butyl-substituted compounds (t-PyDI) also showed good one- and two-photon excited fluorescence properties. The PyDI derivatives are a new family of aromatic diimides that may exhibit both high electron mobility and good light-emitting properties, thus making them excellent candidates for future optoelectronics.Conductive and emissive: Facile synthetic routes to reach the K-region of pyrene and produce 4,5,9,10-pyrene diimide (PyDI) derivatives are reported. The PyDI derivatives exhibited efficient electron transport properties, with the highest electron mobility of up to 3.08 cm2 V−1 s−1. The tert-butyl-substituted compounds (t-PyDI) also showed good one- and two-photon excited fluorescence properties.
      PubDate: 2017-09-18T11:38:49.246633-05:
      DOI: 10.1002/anie.201707529
  • 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.Under control: The low temperature oxidation activity of diesel oxidation catalysts was improved by unraveling the dynamic structural behavior of Pt nanoparticles on ceria using operando X-ray absorption spectroscopy (XAS) and environmental transmission electron microscopy (ETEM). This led to a general concept to finely adjust the size and structure of noble metal particles on strongly interacting supports during real operation.
      PubDate: 2017-09-18T11:38:41.127549-05:
      DOI: 10.1002/anie.201707842
  • 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.A space for RNA: The curation and analysis of the RNA-targeted BIoactive ligaNd Database (R-BIND) uncovered distinguishing 2D and 3D molecular properties that support the existence of an RNA-privileged chemical space. These guiding principles can facilitate the future design of selective ligands targeted toward therapeutically relevant RNAs.
      PubDate: 2017-09-18T11:37:58.014707-05:
      DOI: 10.1002/anie.201707641
  • Sensuke Ogoshi
    • PubDate: 2017-09-18T11:37:17.130585-05:
      DOI: 10.1002/anie.201708270
  • Heavy-Atom Tunneling Calculations in Thirteen Organic Reactions: Tunneling
           Contributions are Substantial, and Bell's Formula Closely Approximates
           Multidimensional Tunneling at ≥250 K
    • Authors: Charles Doubleday; Randy Armas, Dana Walker, Christopher V. Cosgriff, Edyta M. Greer
      Abstract: Multidimensional tunneling calculations are carried out for 13 reactions, to test the scope of heavy-atom tunneling in organic chemistry, and to check the accuracy of one-dimensional tunneling models. The reactions include pericyclic, cycloaromatization, radical cyclization and ring opening, and SN2. When compared at the temperatures that give the same effective rate constant of 3×10−5 s−1, tunneling accounts for 25–95 % of the rate in 8 of the 13 reactions. Values of transmission coefficients predicted by Bell's formula, κBell , agree well with multidimensional tunneling (canonical variational transition state theory with small curvature tunneling), κSCT. Mean unsigned deviations of κBell vs. κSCT are 0.08, 0.04, 0.02 at 250, 300 and 400 K. This suggests that κBell is a useful first choice for predicting transmission coefficients in heavy-atom tunnelling.Several common reaction types were studied to assess the importance of heavy-atom tunneling in organic reactions. The results are consistent with the hypothesis that heavy-atom tunneling is widespread. The success of Bell's formula suggests it is a useful first choice for predicting transmission coefficients in heavy-atom tunnelling.
      PubDate: 2017-09-18T11:33:53.124255-05:
      DOI: 10.1002/anie.201708489
  • Chan Beum Park
    • PubDate: 2017-09-18T11:33:49.24239-05:0
      DOI: 10.1002/anie.201709297
  • Octacyanidotungstate(IV) Coordination Chains Demonstrate a Light-Induced
    • Authors: Michał Magott; Olaf Stefańczyk, Barbara Sieklucka, Dawid Pinkowicz
      Abstract: A huge increase in the magnetization of two coordination chains based on tetravalent octacyanidometalates (WIV and MoIV) is observed on irradiation with 436 nm light, while no such behavior is observed for the NbIV analogue. A photomagnetic response based solely on [WIV(CN)8]4− is demonstrated for the first time. The observed behavior is attributed to the light-induced excited spin state trapping (LIESST) effect at the octacyanidometalate, and to the resulting magnetic exchange ON/OFF photoswitching between the MnII center and the photoinduced high-spin (S=1) WIV or MoIV centers.Let it shine! Octacyanidotungstate(IV) demonstrates a light-induced excited spin state trapping photomagnetic effect that can be used to produce very strong magnetic exchange photoswitching functionality in various bimetallic coordination polymers.
      PubDate: 2017-09-18T11:33:46.706192-05:
      DOI: 10.1002/anie.201703934
  • Native Desorption Electrospray Ionization Liberates Soluble and Membrane
           Protein Complexes from Surfaces
    • Authors: Stephen Ambrose; Nicholas G. Housden, Kallol Gupta, Jieyuan Fan, Paul White, Hsin-Yung Yen, Julien Marcoux, Colin Kleanthous, Jonathan T. S. Hopper, Carol V. Robinson
      Abstract: Mass spectrometry (MS) applications for intact protein complexes typically require electrospray (ES) ionization and have not been achieved via direct desorption from surfaces. Desorption ES ionization (DESI) MS has however transformed the study of tissue surfaces through release and characterisation of small molecules. Motivated by the desire to screen for ligand binding to intact protein complexes we report the development of a native DESI platform. By establishing conditions that preserve non-covalent interactions we exploit the surface to capture a rapid turnover enzyme–substrate complex and to optimise detergents for membrane protein study. We demonstrate binding of lipids and drugs to membrane proteins deposited on surfaces and selectivity from a mix of related agonists for specific binding to a GPCR. Overall therefore we introduce this native DESI platform with the potential for high-throughput ligand screening of some of the most challenging drug targets including GPCRs.Folded soluble and membrane proteins can be released directly from surfaces using a desorption electrospray ionization source coupled to a high-resolution mass spectrometer. Desorbed protein complexes maintain non-covalent interactions enabling rapid measurement of subunit stoichiometries and capturing specific ligand binding to a GPCR.
      PubDate: 2017-09-18T11:33:42.257735-05:
      DOI: 10.1002/anie.201704849
  • Optimizing Optical Absorption, Exciton Dissociation, and Charge Transfer
           of a Polymeric Carbon Nitride with Ultrahigh Solar Hydrogen Production
    • Authors: Guigang Zhang; Guosheng Li, Zhi-An Lan, Lihua Lin, Aleksandr Savateev, Tobias Heil, Spiros Zafeiratos, Xinchen Wang, Markus Antonietti
      Abstract: Polymeric or organic semiconductors are promising candidates for photocatalysis but mostly only show moderate activity owing to strongly bound excitons and insufficient optical absorption. Herein, we report a facile bottom-up strategy to improve the activity of a carbon nitride to a level in which a majority of photons are really used to drive photoredox chemistry. Co-condensation of urea and oxamide followed by post-calcination in molten salt is shown to result in highly crystalline species with a maximum π–π layer stacking distance of heptazine units of 0.292 nm, which improves lateral charge transport and interlayer exciton dissociation. The addition of oxamide decreases the optical band gap from 2.74 to 2.56 eV, which enables efficient photochemistry also with green light. The apparent quantum yield (AQY) for H2 evolution of optimal samples reaches 57 % and 10 % at 420 nm and 525 nm, respectively, which is significantly higher than in most previous experiments.Free to dissociate: The simultaneous modification of the electronic band structures, layer-stacking geometry, and crystallinity of carbon nitride polymers enables the liberation of Frenkel exciton dissociation and magnification of the hot-charges yield, which dramatically enhances the visible-light photocatalytic activities.
      PubDate: 2017-09-18T11:33:33.725104-05:
      DOI: 10.1002/anie.201706870
  • Solvation Accounts for the Counterintuitive Nucleophilicity Ordering of
           Peroxide Anions
    • Authors: Robert J. Mayer; Takahiro Tokuyasu, Peter Mayer, Jérôme Gomar, Stéphane Sabelle, Benedetta Mennucci, Herbert Mayr, Armin R. Ofial
      Abstract: The nucleophilic reactivities (N, sN) of peroxide anions (generated from aromatic and aliphatic peroxy acids or alkyl hydroperoxides) were investigated by following the kinetics of their reactions with a series of benzhydrylium ions (Ar2CH+) in alkaline aqueous solutions at 20 °C. The second-order rate constants revealed that deprotonated peroxy acids (RCO3−), although they are the considerably weaker Brønsted bases, react much faster than anions of aliphatic hydroperoxides (ROO−). Substitution of the rate constants of their reactions with benzhydrylium ions into the linear free energy relationship lg k=sN(N+E) furnished nucleophilicity parameters (N, sN) of peroxide anions, which were successfully applied to predict the rates of Weitz–Scheffer epoxidations. DFT calculations with inclusion of solvent effects by means of the Integral Equation Formalism version of the Polarizable Continuum Model were performed to rationalize the observed reactivities.Weak bases, but strong nucleophiles: Peroxybenzoate ions can be generated in aqueous solution under much less basic conditions than alkyl peroxide anions. Nevertheless, their nucleophilic reactivities exceed those of the alkyl peroxide anions significantly. Quantum chemical calculations reveal solvation to be the origin of the unexpected ordering of reactivity.
      PubDate: 2017-09-18T11:33:30.626286-05:
      DOI: 10.1002/anie.201707086
  • Enantioselective [2,3]-Sigmatropic Rearrangements: Metal-Bound or Free
           Ylides as Reaction Intermediates'
    • Authors: Katharina J. Hock; Rene M. Koenigs
      Abstract: Out of bounds: Enantioselective rearrangement reactions are a long-standing challenge in organic synthesis. Recent advances are highlighted that led to the development of the first enantioselective Doyle–Kirmse reaction and enantioselective rearrangement reactions of iodonium ylides.
      PubDate: 2017-09-18T11:33:25.808575-05:
      DOI: 10.1002/anie.201707092
  • 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.It's morphin’ time: Closely packed switchable micro-inclusions in a hydrogel matrix produce biphasic synergistic gel materials with switchable mechanics, self-healing capacity, and shape-memory properties.
      PubDate: 2017-09-18T11:33:03.120757-05:
      DOI: 10.1002/anie.201707239
  • An Active and Robust Bifunctional Oxygen Electrocatalyst through
           Carbon-Free Hierarchical Functionalization
    • Authors: Kevin Huang
      Abstract: A hierarchically functionalized hybrid electrode for Zn–air batteries is discussed that requires no carbon. Instead, an oxygen evolution reaction (OER)-active, porous, conductive, and corrosion-resistant nitride Ni3FeN is used as a support for oxygen reduction reaction (ORR)-active ordered intermetallic Fe3Pt NPs. The porosity in the Ni3FeN substrate is an important enabling factor for the high OER activity.
      PubDate: 2017-09-18T11:32:41.375911-05:
      DOI: 10.1002/anie.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.Give 'em the new one, two: A range of activated alkenes underwent rapid copper-catalyzed borylacylation at room temperature at low catalyst loadings (see scheme). The reaction involves borylcupration of the alkene and capture of the resulting alkyl–copper intermediate with an acid chloride. In the case of vinyl arenes, the transformation could be carried out in an enantioselective manner.
      PubDate: 2017-09-18T11:32:26.134404-05:
      DOI: 10.1002/anie.201707323
  • 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: 2017-09-18T10:40:38.196791-05:
      DOI: 10.1002/anie.201708732
  • Asymmetric Iron-Catalyzed C−H Alkylation Enabled by Remote Ligand
    • 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: 2017-09-18T09:41:38.38661-05:0
      DOI: 10.1002/anie.201709075
  • 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: 2017-09-18T09:41:24.784734-05:
      DOI: 10.1002/anie.201708474
  • Encapsulation of Isolated Luminophores within Supramolecular Cages
    • Authors: Marcel Handke; Takuji Adachi, Chunhua Hu, Michael D. Ward
      Abstract: The sequestration of luminophores within supramolecular polyhedral compartments of a crystalline zeolite-like hydrogen-bonded framework illustrates a unique approach to limiting the self-quenching ordinarily exhibited at the high concentrations achievable in this framework. A range of differently sized luminescent guests, namely coumarin 1, coumarin 4, fluorescein, [Ru(bpy)3]Cl2, and rhodamine B, can be encapsulated in amounts of up to one molecule per cage, equivalent to a concentration of 0.175 m, which is significantly higher than the concentration at which aggregation-induced quenching occurs in other media. The luminescence spectra of the encapsulated guests are consistent with the presence of isolated monomers and the absence of self-quenching. The emission color of the single crystals can be tuned readily from blue to red through the choice of guest molecules. These observations promise an approach to organic solid-state lasing compounds if crystals of sufficient size and quality can be prepared.The supramolecular cages of a zeolite-like framework were used to encapsulate and isolate molecular luminophores with a range of sizes and emission wavelengths. The luminescence spectra of these host–guest systems were consistent with the presence of isolated monomers and the absence of self-quenching.
      PubDate: 2017-09-18T08:58:22.532345-05:
      DOI: 10.1002/anie.201707097
  • Ultrafast Vibrational Dynamics of Membrane-Bound Peptides at the Lipid
           Bilayer/Water Interface
    • Authors: Junjun Tan; Baixiong Zhang, Yi Luo, Shuji Ye
      Abstract: Vibrational energy transfer (VET) of proteins at cell membrane plays critical roles in controlling the protein functionalities, but its detection is very challenging. By using a surface-sensitive femtosecond time-resolved sum-frequency generation vibrational spectroscopy with infrared pump, the detection of the ultrafast VET in proteins at cell membrane has finally become possible. The vibrational relaxation time of the N−H groups is determined to be 1.70(±0.05) ps for the α-helix located in the hydrophobic core of the lipid bilayer and 0.9(±0.05) ps for the membrane-bound β-sheet structure. The N−H groups with strong hydrogen bonding gain faster relaxation time. By pumping the amide A band and probing amide I band, the vibrational relaxation from N−H mode to C=O mode through two pathways (direct coupling and through intermediate states) is revealed. The ratio of the pathways depends on the NH⋅⋅⋅O=C hydrogen-bonding strength. Strong hydrogen bonding favors the coupling through intermediate states.The energy transfer within amide bonds along the backbone of membrane peptides has been studied. Femtosecond infrared-pump sum-frequency generation (SFG) vibrational spectroscopy was used to track the energy transfer from the N−H group to the C=O group within the peptide backbone.
      PubDate: 2017-09-18T08:57:54.0459-05:00
      DOI: 10.1002/anie.201706996
  • An Icosidodecahedral Supramolecule Based on Pentaphosphaferrocene: From a
           Disordered Average Structure to Individual Isomers
    • Authors: Claudia Heindl; Eugenia Peresypkina, Alexander V. Virovets, Ivan S. Bushmarinov, Michael G. Medvedev, Barbara Krämer, Birger Dittrich, Manfred Scheer
      Abstract: Pentaphosphaferrocenes [CpRFe(η5-P5)] (1) and CuI halides are excellent building blocks for the formation of discrete supramolecules. Herein, we demonstrate the potential of Cu(CF3SO3) for the construction of the novel 2D polymer [{Cp*Fe(μ4,η5:1:1:1-P5)}{Cu(CF3SO3)}]n (2) and the unprecedented nanosphere (CH2Cl2)1.4@[{CpBnFe(η5-P5)}12{Cu(CF3SO3)}19.6] (3). The supramolecule 3 has a unique scaffold beyond the fullerene topology, with 20 copper atoms statistically distributed over the 30 vertices of an icosidodecahedron. Combinatorics was used to interpret the average disordered structure of the supramolecules. In this case, only two pairs of enantiomers with D5 and D2 symmetry are possible for bidentate bridging coordination of the triflate ligands. DFT calculations showed that differences in the energies of the isomers are negligible. The benzyl ligands enhance the solubility of 3, enabling NMR-spectroscopic and mass-spectrometric investigations.With the CF3SO3− anion as a spacer, a new type of giant supramolecule was obtained from pentaphosphaferrocene and Cu+. With 20 copper atoms distributed over the 30 vertices of a giant icosidodecahedron, its unprecedented scaffold contains intrinsic vacancies and exists as four isomers.
      PubDate: 2017-09-18T08:57:49.291701-05:
      DOI: 10.1002/anie.201706756
  • Carboxylation of Aromatic and Aliphatic Bromides and Triflates with CO2 by
           Dual Visible-Light–Nickel Catalysis
    • Authors: Qing-Yuan Meng; Shun Wang, Burkhard König
      Abstract: We report the efficient carboxylation of bromides and triflates with K2CO3 as the source of CO2 in the presence of an organic photocatalyst in combination with a nickel complex under visible light irradiation at room temperature. The reaction is compatible with a variety of functional groups and has been successfully applied to the synthesis and derivatization of biologically active molecules. In particular, the carboxylation of unactivated cyclic alkyl bromides proceeded well with our protocol, thus extending the scope of this transformation. Spectroscopic and spectroelectrochemical investigations indicated the generation of a Ni0 species as a catalytic reactive intermediate.Not only good for plants, CO2 (formed in situ from K2CO3) and light enabled the efficient and mild carboxylation of bromides and triflates in the presence of an organic fluorophore and a nickel complex (see scheme). A variety of functional groups were tolerated, and non-activated cyclic alkyl bromides reacted well. The synthesis and derivatization of biologically active molecules demonstrated the applicability of the method in multistep synthesis.
      PubDate: 2017-09-18T08:57:34.880472-05:
      DOI: 10.1002/anie.201706724
  • Role of the Adsorbed Oxygen Species in the Selective Electrochemical
           Reduction of CO2 to Alcohols and Carbonyls on Copper Electrodes
    • Authors: Cécile S. Le Duff; Matthew J. Lawrence, Paramaconi Rodriguez
      Abstract: The electrochemical reduction of CO2 into fuels has gained significant attention recently as source of renewable carbon-based fuels. The unique high selectivity of copper in the electrochemical reduction of CO2 to hydrocarbons has called much interest in discovering its mechanism. In order to provide significant information about the role of oxygen in the electrochemical reduction of CO2 on Cu electrodes, the conditions of the surface structure and the composition of the Cu single crystal electrodes were controlled over time. This was achieved using pulsed voltammetry, since the pulse sequence can be programmed to guarantee reproducible initial conditions for the reaction at every fraction of time and at a given frequency. In contrast to the selectivity of CO2 reduction using cyclic voltammetry and chronoamperometric methods, a large selection of oxygenated hydrocarbons was found under alternating voltage conditions. Product selectivity towards the formation of oxygenated hydrocarbon was associated to the coverage of oxygen species, which is surface-structure- and potential-dependent.More oxygen, more oxygenation: Pulse voltammetry and copper single crystal electrodes were implemented to determine the influence of oxygen species adsorbed on copper electrodes in the electrochemical reduction of CO2. Product selectivity towards the formation of oxygenated hydrocarbons was associated to the coverage of oxygen species, which is surface-structure- and potential-dependent.
      PubDate: 2017-09-18T08:57:27.503736-05:
      DOI: 10.1002/anie.201706463
  • “Isolated” DyO+ Embedded in a Ceramic Apatite Matrix Featuring
           Single-Molecule Magnet Behavior with a High Energy Barrier for
           Magnetization Relaxation
    • Authors: Pavel E. Kazin; Mikhail A. Zykin, Valentina V. Utochnikova, Oxana V. Magdysyuk, Alexander V. Vasiliev, Yan V. Zubavichus, Walter Schnelle, Claudia Felser, Martin Jansen
      Abstract: Meeting the challenges of Moore's Law, predicting ambitious miniaturization rates of integrated circuits, requires to go beyond the traditional top-down approaches, and to employ synthetic chemistry methods, to use bottom-up techniques. During the recent decades, it has been shown that open-shell coordination compounds may exhibit intramolecular spontaneous magnetization, thus offering promising prospects for storage and processing of digital information. Against this background we regarded it rewarding to implement similar magnetic centers into a ceramic material, which would provide better long-term mechanical and chemical durability. Here we present new robust inorganic compounds containing separate DyO+ ions in an apatite matrix, which behave like single-molecule magnets. The materials exhibit a blocking temperature of 11 K and an energy barrier for spin reversal of a thousand inverse centimeters which is among the highest values ever achieved.Dy2O3-doped apatites show low-temperature hysteresis magnetization with a blocking temperature of up to 11 K and slow relaxation of magnetization with an energy barrier (Ueff) of up to 1043 cm−1. The barrier was determined by an electron spin tunneling through the third and fourth exited Kramers doublet for calcium and strontium compounds, respectively.
      PubDate: 2017-09-18T08:57:21.023596-05:
      DOI: 10.1002/anie.201706391
  • Divergent C–H Annulation for Multifused N-Heterocycles: Regio- and
           Stereospecific Cyclizations of N-Alkynylindoles
    • Authors: Khyarul Alam; Sung Won Hong, Kyung Hwan Oh, Jin Kyoon Park
      Abstract: N-Alkynylindoles were divergently cyclized for the synthesis of multifused N-heterocycles. An ortho-aryl palladium species was added to the α position of an ynamine to generate (Z)-6-alkylidene/benzylidene-6H-isoindolo[2,1-a]indoles, while Pt-catalyzed β-addition through π-activation gave 5-alkyl/arylindolo[2,1-a]isoquinolines. Double cyclizations using PdCl2 and oxidant afforded bright yellow benzo[7,8]indolizino[2,3,4,5-ija]quinolines, the synthesis of which was also demonstrated in a different synthetic route.A short fuse: N-Alkynylindoles were divergently cyclized to give multifused N-heterocycles. The Pd(OAc)2-catalyzed reaction with PPh3 led to 5-exo-dig cycloisomerization, while the PtCl2-catalyzed reaction led to 6-endo-dig cycloisomerization. With PdCl2 and oxidant, β-addition and tandem α-addition, followed by a second ring closure provided bright yellow benzo[7,8]indolizino[2,3,4,5-ija]quinoline, which was also synthesized by a different synthetic route.
      PubDate: 2017-09-18T08:57:14.994929-05:
      DOI: 10.1002/anie.201705514
  • Catalytic Reductive Pinacol-Type Rearrangement of Unactivated 1,2-Diols
           through a Concerted, Stereoinvertive Mechanism
    • Authors: Nikolaos Drosos; Gui-Juan Cheng, Erhan Ozkal, Bastien Cacherat, Walter Thiel, Bill Morandi
      Abstract: A catalytic pinacol-type reductive rearrangement reaction of internal 1,2-diols is reported herein. Several scaffolds not usually amenable to pinacol-type reactions, such as aliphatic secondary–secondary diols, undergo the transformation well without the need for prefunctionalization. The reaction uses a simple boron catalyst and two silanes and proceeds through a concerted, stereoinvertive mechanism that enables the preparation of highly enantiomerically enriched products. Computational studies have been used to rationalize the preference for migration over direct deoxygenation.Opportunities for insiders: A catalytic pinacol-type reductive rearrangement of 1,2-internal diols was developed by the use of a simple boron catalyst and two silanes (see scheme). The reaction occurs through a concerted, stereoinvertive mechanism and is applicable to several substrate scaffolds not usually amenable to pinacol-type reactions, such as aliphatic secondary–secondary diols, without the need for prefunctionalization.
      PubDate: 2017-09-18T08:56:37.651555-05:
      DOI: 10.1002/anie.201704936
  • Total Synthesis of Crocagin A
    • Authors: Filip Bihelovic; Desiree Stichnoth, Frank Surup, Rolf Müller, Dirk Trauner
      Abstract: Crocagin A (1) combines an attractive molecular structure with an unusual biosynthesis and bioactivity. An efficient synthesis of crocagin A is presented that hinges on an early formation of the heterotricyclic core, an electrophilic amination, and the stereoselective hydrogenation of a tetrasubstituted double bond. This synthesis confirms the absolute configuration of crocagin A and provides access to the natural product and derivatives thereof for further biological testing.Let it RiPP: A concise synthesis of the ribosomally produced and post-translationally modified peptides (RiPP) crocagin A is presented. The approach hinges on early formation of the heterotricyclic core, an electrophilic amination, and the stereoselective hydrogenation of a tetrasubstituted double bond.
      PubDate: 2017-09-18T08:56:27.86203-05:0
      DOI: 10.1002/anie.201612641
  • The Quest for Mononuclear Gold(II) and its Potential Role in
           Photocatalysis and Drug Action
    • Authors: Katja Heinze
      Abstract: The chemistry of gold strongly focuses on the ubiquitousoxidation states +I and +III. The intermediate oxidation state +II isgenerally avoided in mononuclear gold species. In recent years,gold(II) has been increasingly suggested as key intermediate inartificial photosynthesis systems with gold(III) moieties as electronacceptors or in gold-catalyzed photoredox catalysis and radicalchemistry. This Minireview provides a concise summary onconfirmed and characterized mononuclear open-shell gold(II)complexes. Recent findings on structural motifs and reactivitypatterns will be discussed. Exciting developments in the fields ofphotosynthesis, photocatalysis and potential roles in medicinalchemistry will be outlined.
      PubDate: 2017-09-18T08:40:51.220359-05:
      DOI: 10.1002/anie.201708349
  • Redox Modulatory Mn3O4 Nanozyme with Multi-enzyme Activity Provides
           Efficient Cytoprotection to Human Cells in Parkinson's Disease Model
    • Authors: Govindasamy Mugesh; Namrata Singh, Mohammed Azharuddin Savanur, Shubhi Srivastava, Patrick D’Silva
      Abstract: Nanomaterials with enzyme-like activities (nanozymes) attracts significant interest due to their therapeutic potential for the treatment of various diseases. Herein, we report that a Mn3O4 nanozyme functionally mimic three major antioxidant enzymes, i.e. superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) and the multienzyme activity is size as well as morphology-dependent. The redox modulatory effect of Mn3O4 plays a crucial role in protecting the cells from MPP+ induced cytotoxicity in a Parkinson disease (PD)-like cellular model, indicating that manganese-based nanomaterials having multi-enzyme activity can robustly rescue the cells from oxidative damage and thereby possess therapeutic potential to prevent ROS-mediated neurological disorders.
      PubDate: 2017-09-18T08:40:42.492209-05:
      DOI: 10.1002/anie.201708573
  • 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: 2017-09-18T08:40:21.248736-05:
      DOI: 10.1002/anie.201708646
  • Catalytic Enantioselective Carbopalladation/C-H Functionalization with
           Statistical Amplification of Product Enantiopurity: A Convertible Linker
    • Authors: Shuo Tong; Aurore Limouni, Qian Wang, Mei-Xiang Wang, Jieping Zhu
      Abstract: We demonstrated that combining a catalytic enantioselective reaction with dimerization in a single operation is an efficient way to upgrade the enantiomeric excesses (ee) of the product. Palladium-catalyzed reaction of N-(2-iodophenyl)-N-methyl methacrylamide derivatives with oxadiazole afforded, via a double enantioselective carbopalladation/intermolecular direct heteroarene C-H alkylation cascade, homodimers in good yields with excellent ee. The dimer was subsequently elaborated to the monomer in which the linker (oxadiazole) was incorporated into the target product
      PubDate: 2017-09-18T07:41:10.022023-05:
      DOI: 10.1002/anie.201709133
  • A Space-Charge Treatment of the Increased Concentration of Reactive
           Species at the Surface of a Ceria Solid Solution
    • Authors: Alexander F. Zurhelle; Xiaorui Tong, Andreas Klein, David S. Mebane, Roger A. De Souza
      Abstract: We apply a space-charge theory applicable to concentrated solid solutions—Poisson-Cahn theory—to describe quantitatively as a function of temperature and oxygen partial pressure published data obtained by in situ X-ray photoelectron spectroscopy (XPS) for the concentration of Ce3+ (the reactive species) at the surface of the oxide catalyst Ce0.8Sm0.2O1.9. In contrast to previous theoretical treatments, our calculations clearly indicate that the surface is positively charged and compensated by an attendant negative space-charge zone. The high space-charge potential that develops at the surface (> 0.8 V) is demonstrated to be hardly detectable by XPS measurements because of the short extent of the space-charge layer. Our approach emphasizes the need to take into account defect interactions and to allow deviations from local charge neutrality when considering the surfaces of oxide catalysts.
      PubDate: 2017-09-18T07:40:57.20805-05:0
      DOI: 10.1002/anie.201708118
  • Stoichiometric Reactions of CO2 and Indium-Silylamides and Catalytic
           Synthesis of Ureas
    • Authors: Maotong Xu; Andrew Jupp, Douglas Wade Stephan
      Abstract: The indium compounds In(N(SiMe3)2)2Cl*THF (2) and In(N(SiMe3)2)Cl2*(THF)n¬ (3) were shown to react with CO2 to give [(Me3Si)2N)InX(-OSiMe3)]2 (X = N(SiMe3)2 4, Cl 5). 0.05-2.0 mol% of the species 3 acts as a pre-catalyst for the conversion of aryl and alkyl silylamines under CO2 (2-3 atm.) to give the corresponding ureas in 70-99% yields. A proposed mechanism is supported by experimental and computational data.
      PubDate: 2017-09-18T07:40:34.023834-05:
      DOI: 10.1002/anie.201708921
  • Structural characterization of a covalent monolayer sheet obtained by
           two-dimensional polymerization at an air/water interface
    • Authors: Vivian Müller; Feng Shao, Milos Baljozovic, Mina Moradi, Yao Zhang, Thomas Jung, William B. Thompson, Benjamin T. King, Renato Zenobi, A. Dieter Schlüter
      Abstract: This work describes a two-dimensional polymerization at an air/water interface and provides, for the first time, direct spectroscopic evidence for the kind of cross-links formed and for the conversion reached in a covalently bonded monolayer sheet. This is achieved by a combination of a variety of monolayer characterization techniques before and after transfer onto solid substrates in particular by tip-enhanced Raman spectroscopy (TERS) and TERS mapping after transfer of both the monomer and polymer monolayer onto Au(111). This is a major advance for the field of 2D polymers synthesized at the air/water interface as it in principle allows to estimate crystallinity via percolation theory and to locate regions with defects.
      PubDate: 2017-09-18T06:40:34.892089-05:
      DOI: 10.1002/anie.201707140
  • Doubly N-Confused [36]Octaphyrin( Isomerization,
           Bis-Metal Coordination, and Topological Chirality
    • Authors: Hiroyuki Furuta; Koki Mitsuno, Takafumi Yoshino, Iti Gupta, Shigeki Mori, Satoru Karasawa, Masatoshi Ishida
      Abstract: A novel [36]octaphyrin analogue embedding two N-confused pyrrole units demonstrated unique prototropy-coupled isomerization between the figure-of-eight and dumbbell conformers. Upon bis-metal coordination, fixation of fully π-conjugated figure-of-eight structures were achieved as referred from the X-ray crystal structure. Chirogenesis of the helical enantiomers was proved by intense circular dichroism (CD) response in the near infrared (NIR) region.
      PubDate: 2017-09-18T05:41:53.198498-05:
      DOI: 10.1002/anie.201708253
  • Characterization of doubly ionic hydrogen bonds in protic ionic liquids by
           NMR deuteron quadrupole coupling constants - Differences to H-bonds in
           amides, peptides and proteins
    • Authors: Ralf Ludwig; Alexander E. Khudozhitkov, Peter Stange, Benjamin Golub, Dietmar Paschek, Alexander G. Stepanov, Daniil I. Kolokolov
      Abstract: We present the first deuteron quadrupole coupling constants (DQCC) for selected protic ionic liquids (PILs) measured by solid-state NMR spectroscopy. The experimental data are supported by dispersion-corrected density functional theory (DFT-D3) calculations and molecular dynamics (MD) simulations. The DQCCs of the N-D bond in the triethylammonium cations are the lowest reported for deuterons in PILs indicating strong doubly ionic hydrogen bonds. The NMR coupling parameters are compared to those in amides, peptides, and proteins. The DQCCs show characteristic behaviour with increasing interaction strength of the counterion and variation of the H-bond motifs. We report the similar presence of the quadrupolar splitting pattern and the narrow liquid line in the NMR spectra over large temperature ranges, indicating the heterogeneous nature of PILs. The knowledge of DQCC is a prerequisite for studying the rotational dynamics by means of NMR quadrupolar relaxation time experiments.
      PubDate: 2017-09-17T21:31:48.27565-05:0
      DOI: 10.1002/anie.201708340
  • Iridium-catalyzed direct C-H amidation polymerization: step-growth
           polymerization by C-N bond formation via C-H activation to give
           fluorescent polysulfonamides
    • Authors: Tae-Lim Choi; Jang Yoon-Jung, Soon-Hyeok Hwang
      Abstract: We report a powerful strategy for activation of C-H bonds to produce polysulfonamides by an atom-economical and green method using iridium-catalyzed direct C-H amidation polymerization (DCAP). After screening various directing groups, additives, silver salts, concentrations, and temperatures to optimize DCAP, high molecular-weight (up to 149 kDa) and defect-free polysulfonamides were synthesized from various bis-sulfonyl azides. Although these polymers do not have conventional fluorescent conjugated cores, they emit blue light with large Stokes shifts and high quantum yields upon photoexcitation, due to excited-state intramolecular proton transfer process.
      PubDate: 2017-09-15T23:31:22.243029-05:
      DOI: 10.1002/anie.201707446
  • Construction and Crystal Structure Analysis of Heme Acquisition Protein
           HasA Containing Iron(III)-5,15-Diphenylporphyrin and Derivatives Thereof
           as an Artificial Prosthetic Group
    • Authors: Hiromu Uehara; Yuma Shisaka, Tsubasa Nishimura, Hiroshi Sugimoto, Yoshitsugu Shiro, Yoshihiro Miyake, Hiroshi Shinokubo, Yoshihito Watanabe, Osami Shoji
      Abstract: Iron(III)-5,15-diphenylporphyrin (1) and its derivatives (2-7) were accommodated by the heme acquisition protein HasA secreted by Pseudomonas aeruginosa, despite possessing bulky substituents at the meso-position of the porphyrin. Crystal structure analysis revealed that the two phenyl groups at the meso-positions of porphyrin extend outside HasA. It was shown that growth of P. aeruginosa was inhibited in the presence of HasA coordinating the synthetic porphyrins under iron-limiting conditions, and that the structure of the synthetic porphyrins greatly affects the inhibition efficiency.
      PubDate: 2017-09-15T23:31:05.680221-05:
      DOI: 10.1002/anie.201707212
  • Enzymatic synthesis, amplification, and application of DNA with a
           functionalized backbone
    • Authors: Tingjian Chen; Floyd Eric Romesberg
      Abstract: The ability to amplify DNA along with its unprecedented sequence control has led to its use for different applications, but all are limited by the properties available to natural nucleotides. We previously reported the evolution of polymerase SFM4-3, which better tolerates 2'-modified substrates. To explore the utility of SFM4-3, we now report the characterization of its recognition of substrates with 2'-azido, 2'-chloro, 2'-amino, or arabinose sugars. We find that SFM4-3 can efficiently synthesize polymers composed of these nucleotides, and most interestingly, that SFM4-3 can also PCR amplify these modified oligonucleotides. When combined with post-amplification modification, the latter allows for the exponential amplification of polymers that may be functionalized with desired moieties arrayed in a controlled fashion, the utility of which we demonstrate with extensive small molecule functionalization and the production and initial characterization of a novel DNA hydrogel.
      PubDate: 2017-09-15T10:21:10.022421-05:
      DOI: 10.1002/anie.201707367
  • Wireless electrochemical actuation of conducting polymers
    • Authors: Bhavana Gupta; Bertrand Goudeau, Alexander Kuhn
      Abstract: Electrochemical actuation of conducting polymers usually requires a direct connection to an electric power supply. In this contribution, we suggest to overcome this issue by using the concept of bipolar electrochemistry. This allows changing the oxidation state of the polymer in a gradual and wireless way. Free standing polypyrrole films were synthesized with an intrinsic morphological asymmetry of their two faces in order to form a bilayer structure. Immersing such objects in an electrolyte solution and exposing them to a potential gradient leads to the asymmetric oxidation/reduction of the polymer, resulting in differential shrinking and swelling along the main axis. This additional asymmetry is responsible for a structural deformation. Optimization allowed highly efficient bending, which is expected to open up completely new directions in the field of actuation due to the wireless mode of action.
      PubDate: 2017-09-15T07:20:38.802574-05:
      DOI: 10.1002/anie.201709038
  • Frontispiece: A Binuclear Zinc Interaction Fold Discovered in the
           Homodimer of Alzheimer's Amyloid-β Fragment with Taiwanese Mutation D7H
    • Authors: Vladimir I. Polshakov; Alexey B. Mantsyzov, Sergey A. Kozin, Alexei A. Adzhubei, Sergey S. Zhokhov, Wouter van Beek, Alexandra A. Kulikova, Maria I. Indeykina, Vladimir A. Mitkevich, Alexander A. Makarov
      Abstract: Alzheimer′s DiseaseThe interaction of zinc ions with amyloid-β peptide fragments carrying the familial Taiwanese mutation D7H was studied by A. A. Makarov et al. In their Communication on page 11734 ff., a binuclear zinc interaction fold in the dimer structure is revealed.
      PubDate: 2017-09-15T06:38:09.602917-05:
      DOI: 10.1002/anie.201783961
  • The thermodynamic basis of the fuzzy interaction of an intrinsically
           disordered protein
    • Authors: San Hadži; Andrej Mernik, Črtomir Podlipnik, Remy Loris, Jurij Lah
      Abstract: Many intrinsically disordered proteins (IDP) that fold upon binding retain conformational heterogeneity in IDP-target complexes. The thermodynamics of such fuzzy interactions is poorly understood. Here we introduce a thermodynamic framework, based on analysis of ITC and CD spectroscopy data, that provides experimental description of IDP association in terms of folding and binding contributions which can be predicted using sequence folding propensities and molecular modeling. We show how IDP can modulate the entropy and enthalpy by adapting their bound-state structural ensemble to achieve optimal binding. This is explained in terms of a free energy landscape that provides the relationship between free energy, sequence folding propensity and disorder. The observed "fuzzy" behavior is possible not only because of IDP flexibility but also because backbone and side chain interactions are, to some extent, energetically decoupled allowing IDP to minimize energetically unfavorable folding.
      PubDate: 2017-09-15T06:28:22.434074-05:
      DOI: 10.1002/anie.201707853
  • A Catalytic Microwave Process for Superfast Preparation of High Quality
           Reduced Graphene Oxide
    • Authors: Runze Liu; Yu Zhang, Zhenjian Ning, Yuxi Xu
      Abstract: Herein we report that a small amount of graphite can unexpectedly act as the catalyst to greatly promote the microwave exfoliation and reduction of graphite oxide in ambient air. The reaction can be finished in a few seconds in contrast to more than ten minutes without catalyst. Meanwhile, the catalytic microwave exfoliated graphite oxide (CMEGO) shows much better quality than the traditional microwave exfoliated graphite oxide, including a much higher exfoliation degree with thinner graphene sheets and higher specific surface area (886 m2/g vs 466 m2/g), a much larger C/O ratio (19.4 vs 6.3) and a higher lattice crystallinity as well as significantly improved electrical conductivity (53180 S/m vs 5140 S/m). With such prominent features, the CMEGO is further used as anode for lithium-ion battery (LIB) and sodium-ion battery (SIB), and delivers ultrahigh reversible capacities, remarkable rate capabilities, and superior cycling stabilities in both LIB and SIB.
      PubDate: 2017-09-15T06:28:09.220023-05:
      DOI: 10.1002/anie.201708714
  • Ethers on Si(001): A prime example for the common ground between surface
           science and molecular organic chemistry
    • Authors: Lisa Pecher; Slimane Laref, Marc Raupach, Ralf Ewald Tonner
      Abstract: Using computational chemistry, we show that the adsorption of ether molecules on Si(001) under ultra-high vacuum conditions can be understood with textbook organic chemistry. The two-step reaction mechanism of (1) dative bond formation between the ether oxygen and a Lewis acidic surface atom and (2) a nucleophilic attack of a nearby Lewis basic surface atom is analysed in detail and found to mirror the acid-catalysed ether cleavage in solution. The O-Si dative bond is found to be the strongest of its kind and reactivity from this state defies the Bell-Evans-Polanyi principle. Electron rearrangement during the C-O bond cleavage is visualized using a newly developed bonding analysis method, which shows that the mechanism of nucleophilic substitutions on semiconductor surfaces is identical to molecular chemistry SN2 reactions. Our findings thus illustrate how the fields of surface science and molecular chemistry can mutually benefit and unexpected insight can be gained.
      PubDate: 2017-09-15T05:27:23.040222-05:
      DOI: 10.1002/anie.201707428
  • Fluorine Effects on Guiding Group Migration via Rh(V) Nitrenoid
    • Authors: Cheng-Qiang Wang; Yu Zhang, chao feng
      Abstract: An unprecedented Rh(III)-catalyzed hydroarylation of α,α-difluoromethylene alkynes with N-pivaloxyl aroylamides through sequential C−H activation and aryl migration was detailed herein. A large array of α,α-difluoromethylene alkynes and N-pivaloxyl aroylamides were well amenable to this transformation, thus providing a novel synthetic protocol for the construction of difluorinated 2-alkenylaniline derivatives in both high yields and excellent regioselectivity. Also of note, the unique fluorine effects were uncovered to underlie the thus unconventional reaction manifold.
      PubDate: 2017-09-15T05:27:12.032352-05:
      DOI: 10.1002/anie.201708505
  • A Freestanding SeS2 Cathode Based on CoS2-decorated Multichannel Carbon
           Fibers with Enhanced Lithium Storage Performance
    • Authors: Xiong-Wen (David) Lou
      Abstract: SeS2 shows attractive advantages beyond bare S and Se as a cathode material for lithium storage. Here, a freestanding lotus root-like carbon fiber network decorated with CoS2 nanoparticles (denoted as CoS2@LRC) has been designed and prepared as the SeS2 host for enhancing the lithium storage performance. The integrated electrode is constructed by three-dimensional interconnected multichannel carbon fibers, which can not only accommodate high content of SeS2 (70 wt.%), but also promise excellent electron and ion transport for achieving high capacity utilization of 1015 mAh g-1 at 0.2 A g-1. What's more, there are numerous CoS2 nanoparticles decorated all over the inner walls and surfaces of the carbon fibers, providing efficient sulfiphilic sites for restricting the dissolution of polysulfides and polyselenides during the electrochemical processes, thus successfully suppressing the shuttle effect and maintaining excellent cycling stability over 400 cycles at 0.5 A g-1.
      PubDate: 2017-09-15T05:20:51.260898-05:
      DOI: 10.1002/anie.201708105
  • Selective electrochemical reduction of CO2 to ethanol on B and N codoped
    • Authors: Yanming Liu; Yujing Zhang, Kai Chen, Xie Quan, Xinfei Fan, Yan Su, Shuo Chen, Huimin Zhao, Yaobin Zhang, Hongtao Yu, Michael R. Hoffmann
      Abstract: Electrochemical reduction of CO2 to ethanol, a clean and renewable liquid fuel with high heating value, is an attractive strategy for global warming mitigation and resource utilization. However, converting CO2 to ethanol remains great challenge due to the low activity, poor product selectivity and stability of electrocatalysts. Here, B and N codoped nanodiamond (BND) was reported as an efficient and stable electrode for selective reduction of CO2 to ethanol. Good ethanol selectivity was achieved on BND with high Faradaic efficiency of 93.2% (-1.0 V vs RHE), which overcame the limitation of low selectivity for multicarbon or high heating value fuels. Its superior performance was mainly originated from the synergistic effect of B and N codoping, high N content and overpotential for hydrogen evolution. The possible pathway for CO2 reduction revealed by DFT computation was CO2 *COOH *CO *COCO *COCH2OH *CH2OCH2OH CH3CH2OH.
      PubDate: 2017-09-15T04:21:20.014704-05:
      DOI: 10.1002/anie.201706311
  • Strand Displacement in Coiled-Coil Structures − Controlled Induction
           and Reversal of Proximity
    • Authors: Katharina Gröger; Georgina Gavins, Oliver Seitz
      Abstract: Coiled-coil peptides are frequently used to create new function upon self-assembly of supramolecular complexes. A multitude of coil peptide sequences provides control over specificity and stability of coiled-coil complexes. However, comparably little attention has been paid to the development of methods that allow for the reversal of complex formation under non-denaturing conditions. Herein, we present a reversible 2-state switching system. The process involves two peptide molecules for formation of a size-mismatched coiled-coil duplex and a third, disruptor peptide which targets an overhanging end. A real-time fluorescence assay revealed that proximity between two chromophores can be switched on and off, repetitively if desired. Showcasing the advantages provided by non-denaturing conditions the method permitted control over the bivalent interactions of the tSH2 domain of Syk kinase with a phosphopeptide ligand.
      PubDate: 2017-09-15T03:20:52.613009-05:
      DOI: 10.1002/anie.201705339
  • Chemical functionalization strategies and intracellular applications of
    • Authors: Dominik Schumacher; Jonas Helma, Anselm F.L. Schneider, Heinrich Leonhardt, Christian Hackenberger
      Abstract: Nanobodies can be considered as next-generation life science tools for the recognition and modulation of antigens that are inaccessible to conventional antibodies. Due to their compact structure and high stability, nanobodies see frequent usage in basic research. Their chemical functionalization facilitates powerful diagnostic tools and opens the way towards promising therapeutic applications. In this review, central aspects of nanobody functionalization are given together with selected applications in molecular cell biology. While first-generation conjugation strategies rely on random modification of natural amino acids, more recent studies focus on a site-specific attachment of functional groups. Such techniques include chemoenzymatic approaches, expressed protein ligation and amber suppression in combination with bioorthogonal modification strategies. With an ever growing toolkit of protein synthesis and conjugation, functional applications are on the rise as well. Such recent applications range from sophisticated imaging and mass spectrometry to the delivery of nanobodies into living cells, enabling visualization and manipulation of intracellular antigens.
      PubDate: 2017-09-15T01:21:17.103468-05:
      DOI: 10.1002/anie.201708459
  • Merging [2 + 2] Cycloaddition with Radical 1,4-Addition: Metal-Free Access
           to Functionalized Cyclobuta[a]naphthalen-4-ols
    • Authors: Bo Jiang; Feng Liu, Jia-Yin Wang, Peng Zhou, guigen Li, Wen-Juan Hao, Shu-Jiang Tu
      Abstract: Metal-free [2 + 2] cycloaddition and S-centered radical-induced 1,4-addition cascades have been achieved by treating benzene-linked allene-ynes with aryldiazonium tetrafluoroborates and DABCO-bis(sulfur dioxide) in a one-pot operation; the reaction provides a greener and practical access to functionalized cyclobuta[a]naphthalen-4-ols of valuable applications. More than 50 examples were examined to achieve up to excellent diastereoselectivity and yields. The reaction pathway is proposed to proceed through the sequence of [2 + 2] cycloaddition, insertion of SO2, 1,4-addition, diazotization and tautomerization
      PubDate: 2017-09-14T22:21:35.335847-05:
      DOI: 10.1002/anie.201707615
  • Dynamic Molecular Invasion into Multiply Interlocked Catenane
    • Authors: Yasuyuki Yamada; Ryohei Ito, Sayaka Ogino, Tatsuhisa Kato, Kentaro Tanaka
      Abstract: A multiply interlocked catenane with a novel molecular topology was synthesized; a phthalocyanine bearing four peripheral crown ethers was quadruply interlocked with a cofacial porphyrin dimer bridged with four alkylammonium chains. The supramolecular conjugate has two nanospaces surrounded by a porphyrin, a phthalocyanine, and four alkyl chains to accommodate guest molecules. Because the phthalocyanine is movable along the alkyl chains, it acts as an adjustable wall, permitting the invasion of large molecules to the nanospaces without spoiling the affinity of the association. The dynamic molecular invasion allowed the intercalation of dianionic porphyrins into both the nanospaces with a high affinity. A photometric titration experiment revealed the two-step inclusion phenomenon. The multiply interlocked catenane complexed with three Cu2+ ions, and the spin-spin interaction was switched off by the intercalation of dianionic porphyrins.
      PubDate: 2017-09-14T21:36:46.597774-05:
      DOI: 10.1002/anie.201708248
  • Regioselective Intermolecular Allylic C-H Amination of Disubstituted
           Olefins via Rh-π-allyl Intermediates
    • Authors: Jacob S Burman; Simon B. Blakey
      Abstract: A method for catalytic intermolecular allylic C-H amination of trans-disubstituted olefins is reported. The reaction is efficient for a range of common nitrogen nucleophiles bearing electron withdrawing group and proceeds under mild conditions. Good levels of regioselectivity are observed for a wide range of electronically diverse trans-ß-alkyl styrene substrates.
      PubDate: 2017-09-14T21:36:17.162655-05:
      DOI: 10.1002/anie.201707021
  • A Chemical Disruptor of the ClpX Chaperone Complex Attenuates
           Multiresistant Staphylococcus aureus Virulence
    • Authors: Christian Fetzer; Vadim S Korotkov, Robert Thänert, Kyu Myung Lee, Martin Neuenschwander, Jens Peter von Kries, Eva Medina, Stephan Axel Sieber
      Abstract: The Staphylococcus aureus ClpXP protease is an important regulator of cell homeostasis and virulence. Here we utilize a high-throughput screen against the ClpXP complex and identify a specific inhibitor of the ClpX chaperone that disrupts its oligomeric state. Synthesis of 34 derivatives revealed that the molecular scaffold is restrictive for diversification with only minor changes tolerated. Subsequent analysis of the most active compound revealed strong attenuation of S. aureus toxin production which was quantified via a customized MS-based assay platform. Transcriptome and whole proteome studies further confirmed the global reduction of virulence and unraveled characteristic signatures of protein expression in compound treated cells. Although these partially matched the pattern of ClpX knockout cells, further depletion of toxins was observed leading to the intriguing perspective that additional virulence pathways may be directly or indirectly addressed by the small molecule.
      PubDate: 2017-09-14T07:22:13.20338-05:0
      DOI: 10.1002/anie.201708454
  • Because the Light is Better Here: Correlation-Time Analysis by NMR
    • Authors: Albert A. Smith; Matthias Ernst, Beat H. Meier
      Abstract: Relaxation data in NMR spectra are often used for dynamics analysis, by modeling motion in the sample with a correlation function consisting of one or more decaying exponential terms, each described by an order parameter, and a correlation time. This method has its origins in the Lipari–Szabo model-free approach, which originally considered overall tumbling plus one internal motion and was later expanded to several internal motions. Considering several of these cases in the solid state it is found that if the real motion is more complex than the assumed model, model fitting is biased towards correlation times where the relaxation data are most sensitive. This leads to unexpected distortions in the resulting dynamics description. Therefore dynamics detectors should be used, which characterize different ranges of correlation times and can help in the analysis of protein motion without assuming a specific model of the correlation function.Fighting bias: NMR Dynamics data are more sensitive to some correlation times than to others. Models of the correlation function tend to be biased towards where the light is better, that is, where the experiment is more sensitive, yielding an unreliable characterization of the motion. Replacing modeling by detectors that are sensitive to different ranges of correlation times could help to overcome this bias.
      PubDate: 2017-09-14T06:26:17.726482-05:
      DOI: 10.1002/anie.201707316
  • Cross-Coupling of α-Carbonyl Sulfoxonium Ylides with C−H Bonds
    • Authors: Manuel Barday; Christopher Janot, Nathan R. Halcovitch, James Muir, Christophe Aïssa
      Abstract: The functionalization of carbon–hydrogen bonds in non-nucleophilic substrates using α-carbonyl sulfoxonium ylides has not been so far investigated, despite the potential safety advantages that such reagents would provide over either diazo compounds or their in situ precursors. Described herein are the cross-coupling reactions of sulfoxonium ylides with C(sp2)−H bonds of arenes and heteroarenes in the presence of a rhodium catalyst. The reaction proceeds by a succession of C−H activation, migratory insertion of the ylide into the carbon–metal bond, and protodemetalation, the last step being turnover-limiting. The method is applied to the synthesis of benz[c]acridines when allied to an iridium-catalyzed dehydrative cyclization.A new alliance: The rhodium-catalyzed cross-coupling of sulfoxonium ylides with carbon–hydrogen bonds, in hexafluoroisopropanol at 60–90 °C, brings these reagents into the realm of C−H activation. When allied to an iridium-catalyzed dehydrative cyclization, this cross-coupling streamlines the synthesis of valuable heterocycles.
      PubDate: 2017-09-14T06:25:49.534279-05:
      DOI: 10.1002/anie.201706804
  • Enantioselective Light Harvesting with Perylenediimide Guests on
           Self-Assembled Chiral Naphthalenediimide Nanofibers
    • Authors: Ramarani Sethy; Jatish Kumar, Rémi Métivier, Marine Louis, Keitaro Nakatani, Nila Mohan Thazhe Mecheri, Akhila Subhakumari, K. George Thomas, Tsuyoshi Kawai, Takuya Nakashima
      Abstract: Self-assembling molecular systems often display amplified chirality compared to the monomeric state, which makes the molecular recognition more sensitive to chiral analytes. Herein, we report the almost absolute enantioselective recognition of a chiral perylenediimide (PDI) molecule by chiral supramolecular nanofibers of a bichromophoric naphthalenediimide (NDI) derivative. The chiral recognition was evaluated through the Förster resonance energy transfer (FRET) from the NDI-based host nanofibers to the guest PDI molecules. The excitation energy was successfully transferred to the guest molecule through efficient energy migration along the host nanofiber, thus demonstrating the light-harvesting capability of these hybrid systems. Furthermore, circularly polarized luminescence (CPL) was enantioselectively sensitized by the guest molecule as the wavelength band and sign of the CPL signal were switched in response to the chiral guest molecule.The enantioselective recognition of a chiral perylenediimide (PDI) molecule by chiral supramolecular nanofibers of a bichromophoric naphthalenediimide (NDI) derivative is described. The chiral recognition was evaluated through the Förster resonance energy transfer (FRET) from the NDI nanofibers to the PDI molecules, which demonstrated the light-harvesting capability of these hybrid systems.
      PubDate: 2017-09-14T06:25:35.342029-05:
      DOI: 10.1002/anie.201707160
  • Fully automated quantum chemistry based computation of spin-spin coupled
           nuclear magnetic resonance spectra for molecules
    • Authors: Stefan Grimme; Christoph Bannwarth, Sebastian Dohm, Andreas Hansen, Jana Pisarek, Philipp Pracht, Jakob Seibert, Frank Neese
      Abstract: We present a composite procedure for the quantum chemical computation of spin-spin coupled 1H-NMR spectra for general, flexible molecules in solution. It is based on four main steps, namely, conformer/rotamer ensemble (CRE) generation by the fast tight-binding method GFN-xTB and a newly developed search algorithm,relative free energy and NMR parameter computation, and solution of the spin-Hamiltonian. In this way the NMR-specific nuclear permutation problem is solved and the correct spin-symmetries are obtained. Energies, shieldings, and spin-spin couplings are computed at state-of-the-art DFT levels employing continuumsolvation. A few (in)organic and transition metal complexes are presented and very good, unprecedented agreement between theoretical and experimental spectra is achieved. The approach isroutinely applicable to systems with up to 100-150 atoms and may open new avenues for a detailed (conformational) structure elucidation of e.g. natural products or drug molecules.
      PubDate: 2017-09-14T05:20:45.271223-05:
      DOI: 10.1002/anie.201708266
  • Colloidal Synthesis and Photophysics of M3Sb2I9 (M = Cs and Rb)
           Nanocrystals: Lead-Free Perovskites
    • Authors: Jaya Pal; Suman Manna, Anirban Mondal, Shyamashis Das, K V Adarsh, Angshuman Nag
      Abstract: Here we report the colloidal synthesis of Cs3Sb2I9 and Rb3Sb2I9 perovskite nanocrystals, and explore their prospect for optoelectronic applications. Different morphologies such as nanoplatelets and nanorods of Cs3Sb2I9, and spherical Rb3Sb2I9 nanocrystals were prepared. All these samples show band-edge emissions in the yellow-red region. Exciton many-body interactions studied by femtosecond transient absorption spectroscopy of Cs3Sb2I9 nanorods reveals characteristic second-derivative-type spectral features, suggesting red-shifted excitons by as much as 79 meV. A high absorption cross-section of ~10-15 cm2 was estimated. All these results suggest that colloidal Cs3Sb2I9 and Rb3Sb2I9 nanocrystals are potential candidates for optical and optoelectronic applications in the visible region, though a better control of defect chemistry is required for efficient applications.
      PubDate: 2017-09-14T05:20:37.051651-05:
      DOI: 10.1002/anie.201709040
  • Stabilization of Low-Valent Iron(I) in a High-Valent Vanadium(V) Oxide
    • Authors: Montaha Anjass; Katharina Kastner, Florian Naegele, Mark Ringenberg, John Boas, Jie Zhang, Alan Bond, Timo Jacob, Carsten Streb
      Abstract: Low valent iron centers are critical intermediates in chemical and bio-chemical processes. Here, we show the first example of a low-valent FeI center stabilized in a high-valent polyoxometalate framework. Electrochemical studies show that the FeIII-functionalized molecular vanadium(V) oxide (DMA)[FeIIIClVV12O32Cl]3- (DMA - dimethyl ammonium) features two well-defined, reversible, iron-based electrochemical reductions which cleanly yield the FeI species (DMA)[FeIClVV12O32Cl]5-. Experimental and theoretical studies including electron paramagnetic resonance spectroscopy and density functional theory computations verify the formation of the FeI species. The study presents the first example for the seemingly paradoxical embedding of low-valent metal species in high-valent metal oxide anions and opens new avenues for reductive electron transfer catalysis by polyoxometalates.
      PubDate: 2017-09-14T04:22:52.392344-05:
      DOI: 10.1002/anie.201706828
  • Ring Expansion, Photo-isomerization, and Retro-cyclization of
    • Authors: Bochao Su; Yongxin Li, Rekesh Ganguly, Rei Kinjo
      Abstract: Diverse skeletal transformations of 1,4,2-diazaboroles (4,12) have been achieved through ring expansion, photo-isomerization and retro-cyclization, leading to the isolation of various BN-dihydroindole (3, 6), 1,3-azaborolidin-2-imine (7) and 1,4,2-diazaborol-3-imine (11) derivatives. These newly formed BN-heterocycles have been fully characterized by multiple NMR spectroscopy and X-ray diffraction analysis, and computational studies reveal their electronic properties.
      PubDate: 2017-09-14T04:22:39.737001-05:
      DOI: 10.1002/anie.201708720
  • Distribution of amyloid-like and oligomeric species from protein
           aggregation kinetics
    • Authors: Alexandra Silva; Bruno Almeida, Joana Sofia Fraga, Pablo Taboada, Pedro Miguel Martins, Sandra Ribeiro
      Abstract: Amyloid fibrils and soluble oligomers are two types of protein aggregates associated with neurodegeneration. Classic therapeutic strategies try to prevent the nucleation and spread of amyloid fibrils, whilst diffusible oligomers have emerged as promising drug targets affecting downstream pathogenic processes. We developed a generic protein aggregation model and validate it against measured compositions of fibrillar and non-fibrillar assemblies of ataxin-3, a protein implicated in Machado-Joseph disease. The derived analytic rate-law equations can be used to (i) identify the presence of parallel aggregation pathways and (ii) estimate the critical sizes of amyloid fibrils. The discretized population balance supporting our model is the first to quantitatively fit time-resolved measurements of size and composition of both amyloid-like and oligomeric species. The new theoretical framework can be used to screen a new class of drugs specifically targeting toxic oligomers.
      PubDate: 2017-09-14T04:22:11.474774-05:
      DOI: 10.1002/anie.201707345
  • Cascades in Compartments: En Route to Machine-Assisted Biotechnology
    • Authors: Kersten S. Rabe; Joachim Müller, Marc Skoupi, Christof M. Niemeyer
      Abstract: Biological compartmentalization is a fundamental principle of life that allows cells to metabolize, propagate, or communicate with their environment. Much research is devoted to understanding this basic principle and to harness biomimetic compartments and catalytic cascades as tools for technological processes. This Review summarizes the current state-of-the-art of these developments, with a special emphasis on length scales, mass transport phenomena, and molecular scaffolding approaches, ranging from small cross-linkers over proteins and nucleic acids to colloids and patterned surfaces. We conclude that the future exploration and exploitation of these complex systems will largely benefit from technical solutions for the integrated, machine-assisted development and maintenance of a next generation of biotechnological processes. These goals should be achievable by implementing microfluidics, robotics, and added manufacturing techniques supplemented by theoretical simulations as well as computer-aided process modeling based on big data obtained from multiscale experimental analyses.Machine-generated multienzyme cascades: The machine-assisted development of biomimetic compartments and catalytic cascades will pave the way towards a novel generation of biotechnological processes. Molecular scaffolds with small cross-linkers, proteins, nucleic acids, colloids, and patterned surfaces can be used to arrange the catalytic units. S: substrate, P: product.
      PubDate: 2017-09-14T04:16:22.122478-05:
      DOI: 10.1002/anie.201703806
  • Construction of Quaternary Stereogenic Centers in the Total Synthesis of
           Natural Products
    • Authors: Evgeny V. Prusov
      Abstract: Total syntheses of the tetracyclic terpene waihoensene and the densely functionalized tetracyclic compound ryanodol have recently been reported. Both approaches constitute examples of the efficient and innovative construction of multiple quaternary centers.
      PubDate: 2017-09-14T04:15:59.258934-05:
      DOI: 10.1002/anie.201706629
  • Flavylium Polymethine Fluorophores for Near- and Shortwave Infrared
    • Authors: Emily D. Cosco; Justin R. Caram, Oliver T. Bruns, Daniel Franke, Rachael A. Day, Erik P. Farr, Moungi G. Bawendi, Ellen M. Sletten
      Abstract: Bright fluorophores in the near-infrared and shortwave infrared (SWIR) regions of the electromagnetic spectrum are essential for optical imaging in vivo. In this work, we utilized a 7-dimethylamino flavylium heterocycle to construct a panel of novel red-shifted polymethine dyes, with emission wavelengths from 680 to 1045 nm. Photophysical characterization revealed that the 1- and 3-methine dyes display enhanced photostability and the 5- and 7-methine dyes exhibit exceptional brightness for their respective spectral regions. A micelle formulation of the 7-methine facilitated SWIR imaging in mice. This report presents the first polymethine dye designed and synthesized for SWIR in vivo imaging.Moving beyond the NIR: A series of polymethine dyes containing a 7-dimethylamino flavylium heterocycle were designed and synthesized. These dyes display distinctly red-shifted absorption and emission. The flavylium heptamethine dye is a bright shortwave infrared (SWIR) emitter and was employed for in vivo SWIR imaging.
      PubDate: 2017-09-14T04:12:38.802094-05:
      DOI: 10.1002/anie.201706974
  • Divergent Reactivity of a Dinuclear (NHC)Nickel(I) Catalyst versus
           Nickel(0) Enables Chemoselective Trifluoromethylselenolation
    • Authors: Alexander B. Dürr; Henry C. Fisher, Indrek Kalvet, Khai-Nghi Truong, Franziska Schoenebeck
      Abstract: We herein showcase the ability of NHC-coordinated dinuclear NiI–NiI complexes to override fundamental reactivity limits of mononuclear (NHC)Ni0 catalysts in cross-couplings. This is demonstrated with the development of a chemoselective trifluoromethylselenolation of aryl iodides catalyzed by a NiI dimer. A novel SeCF3-bridged NiI dimer was isolated and shown to selectively react with Ar−I bonds. Our computational and experimental reactivity data suggest dinuclear NiI catalysis to be operative. The corresponding Ni0 species, on the other hand, suffers from preferred reaction with the product, ArSeCF3, over productive cross-coupling and is hence inactive.A nickel(I) dimer catalyzes the chemoselective trifluoromethylselenolation of aryl iodides, and computational and experimental reactivity data suggest dinuclear NiI catalysis to be operative. The corresponding Ni0 species, on the other hand, suffers from preferred reaction with the product, ArSeCF3, over productive cross-coupling and is hence inactive.
      PubDate: 2017-09-14T04:05:44.075307-05:
      DOI: 10.1002/anie.201706423
  • Correct Modeling of Cisplatin: a Paradigmatic Case
    • Authors: Nicola Tasinato; Cristina Puzzarini, Vincenzo Barone
      Abstract: Quantum chemistry is a useful tool in modern approaches to drug and material design, but only when the adopted model reflects a correct physical picture. Paradigmatic is the case of cis-diaminodichloroplatinum(II), cis-[Pt(NH3)2Cl2], for which the correct simulation of the structural and vibrational properties measured experimentally still remains an open question. By using this molecule as a proof of concept, it is shown that state-of-the-art quantum chemical calculations and a simple model, capturing the basic physical flavors, a cis-[Pt(NH3)2Cl2] dimer, can provide the accuracy required for interpretative purposes. The present outcomes have fundamental implications for benchmark studies aiming at assessing the accuracy of a given computational protocol.Two are needed for a valid prediction: A dimer of cis-[Pt(NH3)2Cl2] as a quantum chemical model for cisplatin provides the first quantitative agreement with experiment for structural and vibrational properties. This result points out that a reliable in-silico drug design requires a model capturing the essential physical picture of the system and a proper theoretical protocol.
      PubDate: 2017-09-14T04:05:32.839522-05:
      DOI: 10.1002/anie.201707683
  • Analytical Description of NMR Relaxation Highlights Correlated Dynamics in
           Intrinsically Disordered Proteins
    • Authors: Nicola Salvi; Anton Abyzov, Martin Blackledge
      Abstract: The dynamic fluctuations of intrinsically disordered proteins (IDPs) define their function. Although experimental nuclear magnetic resonance (NMR) relaxation reveals the motional complexity of these highly flexible proteins, the absence of physical models describing IDP dynamics hinders their mechanistic interpretation. Combining molecular dynamics simulation and NMR, we introduce a framework in which distinct motions are attributed to local libration, backbone dihedral angle dynamics and longer-range tumbling of one or more peptide planes. This model provides unique insight into segmental organization of dynamics in IDPs and allows us to investigate the presence and extent of the correlated motions that are essential for function.Conformational dynamics of intrinsically disordered proteins (IDPs) define their biological function but remain poorly understood. By combining MD simulation and NMR distinct contributions to this motion are identified, including backbone dihedral jumps and longer-range segmental dynamics.
      PubDate: 2017-09-14T04:03:08.449031-05:
      DOI: 10.1002/anie.201706740
  • Evolution of the Ligand Shell Morphology during Ligand Exchange Reactions
           on Gold Nanoparticles
    • Authors: Zhi Luo; Jing Hou, Laure Menin, Quy Khac Ong, Francesco Stellacci
      Abstract: Ligand exchange reactions are used to achieve nanoparticles coated with a mixture of ligand molecules. Currently, nothing is known on the evolution of the morphology of the ligand shell during the reaction. Here, we use a recently developed method (based on MALDI-TOF) to follow the evolution of the ligand shell composition and morphology during the reaction. We observe the expected evolution in composition and we find that the ligand shell starts as a random mixture and gradually evolves towards a patchy morphology. When the composition has reached a plateau (i.e. when the reaction is generally assumed to be finished), the ligand shell morphology keeps evolving for days, slowly approaching its equilibrium configuration.Patchy ligand distributions: The evolution of the ligand shell morphology during ligand exchange reactions on surfaces of nanoparticles is elucidated for the first time. Kinetics and thermodynamics both play important roles on the formation of patchy domains at different reaction stages.
      PubDate: 2017-09-14T04:02:54.090413-05:
      DOI: 10.1002/anie.201708190
  • Electrochemically Enabled, Nickel-Catalyzed Amination
    • Authors: Chao Li; Yu Kawamata, Hugh Nakamura, Julien C. Vantourout, Zhiqing Liu, Qinglong Hou, Denghui Bao, Jeremy T. Starr, Jinshan Chen, Ming Yan, Phil S. Baran
      Abstract: Along with amide bond formation, Suzuki cross-coupling, and reductive amination, the Buchwald–Hartwig–Ullmann-type amination of aryl halides stands as one of the most employed reactions in modern medicinal chemistry. The work herein demonstrates the potential of utilizing electrochemistry to provide a complementary avenue to access such critical bonds using an inexpensive nickel catalyst under mild reaction conditions. Of note is the scalability, functional-group tolerance, rapid rate, and the ability to employ a variety of aryl donors (Ar−Cl, Ar−Br, Ar−I, Ar−OTf), amine types (primary and secondary), and even alternative X−H donors (alcohols and amides).Amination electrified: Arguably one of the most important types of bonds, the C−N bond, can now be forged under nickel-catalysis with the aid of electrochemistry. Broad scope, scalability, sustainability, mildness, and rapid reacion rates are some highlights of this interesting new reaction. Tf=trifluoromethanesulfonyl.
      PubDate: 2017-09-14T04:00:44.829819-05:
      DOI: 10.1002/anie.201707906
  • Synthesis of Acylborons by Ozonolysis of Alkenylboronates: Preparation of
           an Enantioenriched Amino Acid Acylboronate
    • Authors: Jumpei Taguchi; Toshiki Ikeda, Rina Takahashi, Ikuo Sasaki, Yasushi Ogasawara, Tohru Dairi, Naoya Kato, Yasunori Yamamoto, Jeffrey W. Bode, Hajime Ito
      Abstract: A concise synthesis of acylborons was achieved by ozonolysis of alkenyl MIDA (N-methyliminodiacetic acid) boronates. This reaction exhibits excellent functional group tolerance and is applicable to various acyl MIDA boronates and potassium acyltrifluroborates (KATs) that could not be synthesized by previous methods. In addition, α-amino acylborons, which would be essential for peptide ligations, were prepared for the first time. The acylboron of L-alanine was obtained in high enantiopurity and found to be configurationally stable. Oligopeptide synthesis between the α-amino KATs and amino acid in dilute aqueous media was studied.
      PubDate: 2017-09-14T02:06:53.766297-05:
      DOI: 10.1002/anie.201707933
  • Intrinsic Broadband White-Light Emission from Ultrastable, Cationic Lead
           Halide Layered Materials
    • Authors: Zewen Zhuang; Chengdong Peng, Guiyang Zhang, Huimin Yang, Jinlin Yin, Honghan Fei
      Abstract: We report a family of cationic lead halide layered materials, formulated as [Pb2X2]2+[−O2C(CH)2CO2−] (X = F, Cl, and Br), exhibiting pronounced broadband white-light emission in bulk form. These well-defined PbX-based structures achieve an external quantum efficiency as high as 11.8%, which is comparable to the highest reported value (~9%) for broadband phosphors based on layered organolead halide perovskites. More importantly, our cationic materials are long-sought ultrastable lead halide materials, which overcome the air/moisture-sensitivity problems of lead perovskites. In contrast to the perovskites and other bulk emitters, the white-light emission intensity of our materials remains undiminished after continuous UV irradiation for 30 days under atmospheric conditions (~60% relative humidity). Our initial mechanistic studies confirm that the broadband emission is ascribed to short-range electron-phonon coupling in the strongly deformable lattice and generated self-trapped carriers.
      PubDate: 2017-09-14T01:49:31.769728-05:
      DOI: 10.1002/anie.201706660
  • Toward Cost-effective Manufacturing of Si Solar Cells: Electrodeposition
           of High Quality Si Films in a CaCl2-based Molten Salt
    • Authors: Xiao Yang; Li Ji, Xingli Zou, Taeho Lim, Ji Zhao, Edward T Yu, Allen J. Bard
      Abstract: Electrodeposition of Si films from a Si-containing electrolyte is a cost-effective approach for the manufacturing of solar cells. Proposals relying on molten salts have suffered from low product quality due to difficulties in impurity control. Here we demonstrate a novel approach to electrodeposit high quality Si films from a CaCl2-based molten salt. Soluble SiIV−O anions generated from solid SiO2 are electrodeposited onto a graphite substrate to form a uniform layer of crystalline Si. Impurities in the deposited Si film are controlled at low concentrations (both B and P are less than 1 ppm). In the photoelectrochemical measurements, the Si film shows p-type semiconductor character and large photocurrent. A p-n junction fabricated from the deposited Si film exhibits clear photovoltaic effects. This study represents a first step to the ultimate goal of developing a cost-effective manufacturing process for Si solar cells based on electrodeposition.
      PubDate: 2017-09-13T13:23:57.815383-05:
      DOI: 10.1002/anie.201707635
  • A Self-Assembled Oligopeptide as a Versatile NMR Alignment Medium for the
           Measurement of Residual Dipolar Couplings in Methanol
    • Authors: Xinxiang Lei; Feng Qiu, Han Sun, Liwen Bai, Wen-Xuan Wang, Wensheng Xiang, Hongping Xiao
      Abstract: Residual dipolar coupling (RDC) is a powerful structural parameter for the determination of the constitution, conformation, and configuration of organic molecules. Herein, we report the first liquid crystal-based orienting medium that is compatible with MeOH, thus enabling RDC acquisitions of a wide range of intermediate to polar organic molecules. The liquid crystals were produced from self-assembled oligopeptide nanotubes (AAKLVFF), which are stable at very low concentrations. The presented alignment medium is highly homogeneous, and the size of RDCs can be scaled with the concentration of the peptide. To assess the accuracy of the RDC measurement by employing this new medium, seven bioactive natural products from different classes were chosen and analyzed. The straightforward preparation of the anisotropic alignment sample will offer a versatile and robust protocol for the routine RDC measurement of natural products.Alignment medium: A novel, robust, versatile anisotropic medium composed of self-assembled peptides, which are stable at very low concentrations, is used for the measurement of residual dipolar couplings (RDCs) in MeOH. The presented alignment medium is highly homogeneous, and the size of RDCs can be scaled with the concentration of the peptide.
      PubDate: 2017-09-13T13:07:05.512986-05:
      DOI: 10.1002/anie.201705123
  • The First Gold(III) Formate: Evidence for β-Hydride Elimination
    • Authors: Roopender Kumar; Jean-Philippe Krieger, Enrique Gómez-Bengoa, Thomas Fox, Anthony Linden, Cristina Nevado
      Abstract: The first stable gold(III) formate and experimental evidence for its β-hydride elimination are described. A catalytic dehydrogenation of formic acid together with mechanistic studies shed light on potential pathways operating in fundamental gold-catalyzed transformations.An anionic ligand exchange reaction on [(N^C^C)AuIIIF] in the presence of formic acid delivered the first example of a stable gold(III) formate. Its ability to undergo β-hydride elimination and its reactivity in the dehydrogenation of formic acid (FA) have been experimentally and computationally demonstrated.
      PubDate: 2017-09-13T13:06:47.848241-05:
      DOI: 10.1002/anie.201705557
  • Enzyme Activity by Design: An Artificial Rhodium Hydroformylase for Linear
    • Authors: Amanda G. Jarvis; Lorenz Obrecht, Peter J. Deuss, Wouter Laan, Emma K. Gibson, Peter P. Wells, Paul C. J. Kamer
      Abstract: Artificial metalloenzymes (ArMs) are hybrid catalysts that offer a unique opportunity to combine the superior performance of natural protein structures with the unnatural reactivity of transition-metal catalytic centers. Therefore, they provide the prospect of highly selective and active catalytic chemical conversions for which natural enzymes are unavailable. Herein, we show how by rationally combining robust site-specific phosphine bioconjugation methods and a lipid-binding protein (SCP-2L), an artificial rhodium hydroformylase was developed that displays remarkable activities and selectivities for the biphasic production of long-chain linear aldehydes under benign aqueous conditions. Overall, this study demonstrates that judiciously chosen protein-binding scaffolds can be adapted to obtain metalloenzymes that provide the reactivity of the introduced metal center combined with specifically intended product selectivity.Artificial metalloenzymes are hybrid catalysts that offer a unique opportunity to combine the superior performance of natural protein structures with the unnatural reactivity of transition-metal catalytic centers. An artificial rhodium hydroformylase has been developed that displays remarkable activities and selectivities in the biphasic production of long-chain linear aldehydes.
      PubDate: 2017-09-13T13:06:41.674987-05:
      DOI: 10.1002/anie.201705753
  • HKOH-1: A Highly Sensitive and Selective Fluorescent Probe for Detecting
           Endogenous Hydroxyl Radicals in Living Cells
    • Authors: Xiaoyu Bai; Yueyang Huang, Mingyang Lu, Dan Yang
      Abstract: The hydroxyl radical (.OH), one of the most reactive and deleterious reactive oxygen species (ROS), has been suggested to play an essential role in many physiological and pathological scenarios. However, a reliable and robust method to detect endogenous .OH is currently lacking owing to its extremely high reactivity and short lifetime. Herein we report a fluorescent probe HKOH-1 with superior in vitro selectivity and sensitivity towards .OH. With this probe, we have calibrated and quantified the scavenging capacities of a wide range of reported .OH scavengers. Furthermore, HKOH-1r, which was designed for better cellular uptake and retention, has performed robustly in detection of endogenous .OH generation by both confocal imaging and flow cytometry. Furthermore, this probe has been applied to monitor .OH generation in HeLa cells in response to UV light irradiation. Therefore, HKOH-1 could be used for elucidating .OH related biological functions.Highly sensitive and selective probes for hydroxyl radical detection have been developed. The fluorescent probe HKOH-1 has been applied in the screening of antioxidant capacities of several reported hydroxyl radical scavengers. Endogenous hydroxyl radical generation in multiple cell types has been detected with HKOH-1r by both confocal imaging and flow cytometry.
      PubDate: 2017-09-13T13:06:28.636869-05:
      DOI: 10.1002/anie.201705873
  • The Hydrophobic Gap at High Hydrostatic Pressures
    • Authors: Florian J. Wirkert; Christoph Hölzl, Michael Paulus, Paul Salmen, Metin Tolan, Dominik Horinek, Julia Nase
      Abstract: We have gained new insight into the so-called hydrophobic gap, a molecularly thin region of decreased electron density at the interface between water and a solid hydrophobic surface, by X-ray reflectivity experiments and molecular dynamics simulations at different hydrostatic pressures. Pressure variations show that the hydrophobic gap persists up to a pressure of 5 kbar. The electron depletion in the interfacial region strongly decreases with an increase in pressure, indicating that the interfacial region is compressed more strongly than bulk water. The decrease is most significant up to 2 kbar; beyond that, the pressure response of the depletion is less pronounced.The hydrophobic gap, a thin layer of decreased electron density at the interface between water and a solid hydrophobic surface, was studied by X-ray reflectivity experiments and molecular dynamics simulations. The electron depletion in the interfacial region strongly decreases with increasing hydrostatic pressure, which indicates that the interfacial region is compressed more strongly than bulk water. OTS=octadecyltrichlorosilane.
      PubDate: 2017-09-13T13:06:17.487731-05:
      DOI: 10.1002/anie.201706662
  • Highly Efficient Nondoped OLEDs with Negligible Efficiency Roll-Off
           Fabricated from Aggregation-Induced Delayed Fluorescence Luminogens
    • Authors: Jian Huang; Han Nie, Jiajie Zeng, Zeyan Zhuang, Shifeng Gan, Yuanjing Cai, Jingjing Guo, Shi-Jian Su, Zujin Zhao, Ben Zhong Tang
      Abstract: Purely organic emitters that can efficiently utilize triplet excitons are highly desired to cut the cost of organic light-emitting diodes (OLEDs), but most of them require complicated doping techniques for their fabrication and suffer from severe efficiency roll-off. Herein, we developed novel luminogens with weak emission and negligible delayed fluorescence in solution but strong emission with prominent delayed components upon aggregate formation, giving rise to aggregation-induced delayed fluorescence (AIDF). The concentration-caused emission quenching and exciton annihilation are well-suppressed, which leads to high emission efficiencies and efficient exciton utilization in neat films. Their nondoped OLEDs provide excellent electroluminescence efficiencies of 59.1 cd A−1, 65.7 lm W−1, and 18.4 %, and a negligible current efficiency roll-off of 1.2 % at 1000 cd m−2. Exploring AIDF luminogens for the construction of nondoped OLEDs could be a promising strategy to advance device efficiency and stability.Neat films of luminogens with aggregation-induced delayed fluorescence (AIDF) were employed in nondoped OLEDs. These systems afford remarkable current, power, and external quantum efficiencies as the concentration-caused emission quenching and exciton annihilation are well suppressed, which leads to high emission efficiencies and efficient exciton utilization in the neat films.
      PubDate: 2017-09-13T13:06:13.179823-05:
      DOI: 10.1002/anie.201706752
  • Selective Ring-Opening Polymerization of Non-Strained γ-Butyrolactone
           Catalyzed by A Cyclic Trimeric Phosphazene Base
    • Authors: Na Zhao; Chuanli Ren, Huaike Li, Yunxin Li, Shaofeng Liu, Zhibo Li
      Abstract: A new superbase, the cyclic trimeric phosphazene base (CTPB), was prepared with high yield and purity. In the presence of alcohol, the CTPB serves as a highly efficient organocatalyst for ring-opening polymerization of the “non-polymerizable” γ-butyrolactone to offer well-defined poly(γ-butyrolactone) with high conversions (up to 98 %) at −60 °C. The produced polymers have high molecular weights (up to 22.9 kg mol−1) and low polydispersity distributions (1.27–1.50). NMR analysis of initiation process and the structural analysis of resulting polymers by MALDI-TOF suggest a mechanism involving an activating initiator which leads only to linear polymers with BnO/H chain ends.Superbase! Sustainable poly(γ-butyrolactone) was prepared by ring-opening polymerization using a metal-free superbase, that is, a cyclic trimeric phosphazene base. The reaction features high conversion (up to 98%), high molecular weights (up to 22.9 kDa), and selective synthesis of the linear polymer.
      PubDate: 2017-09-13T13:06:07.459335-05:
      DOI: 10.1002/anie.201707122
  • High-Fidelity Multistate Switching with Anion–Anion and Acid–Anion
           Dimers of Organophosphates in Cyanostar Complexes
    • Authors: Wei Zhao; Bo Qiao, Chun-Hsing Chen, Amar H. Flood
      Abstract: The acid–base switching of complexes formed from anti-electrostatic anion–anion homodimers of organophosphates and cyanostar macrocycles was investigated for the first time. High-fidelity 2:2 complexes were selected by using suitably sized organo substituents. Reversible and direct switching occurs with triflic acid and hydroxide base. An unexpected acid⋅⋅⋅anion heterodimer was discovered with weaker picric acid, which helped reveal some of the elementary steps. Switching can also proceed in a cooperative (strong anion then weak acid) or stepwise manner (weak acid then strong anion).On–off relationship: Anions in high-fidelity 2:2 complexes formed from phosphate homodimers and cyanostar macrocycles switch directly in and out of the macrocycles when a strong base and acid is added, respectively. An unexpected complex of an acid–anion heterodimer was discovered in step-wise switching with weaker acids.
      PubDate: 2017-09-13T13:06:03.377165-05:
      DOI: 10.1002/anie.201707869
  • Between Localization and Delocalization: Ru(cod)2+ Units in the Zintl
           Clusters [Bi9{Ru(cod)}2]3− and [Tl2Bi6{Ru(cod)}]2−
    • Authors: Niels Lichtenberger; Nils Spang, Andreas Eichhöfer, Stefanie Dehnen
      Abstract: Reactions of [K(crypt-222)]2(TlBi3)⋅0.5 en (1 b) with [Ru(cod)(H2CC(Me)CH2)2] (A) in 1,2-diaminoethane (en) led to the formation of two compounds with new bismuth-rich cluster anions, [K(crypt-222)]3[Bi9{Ru(cod)}2]⋅1.5 en (2) and [K(crypt-222)]2[Tl2Bi6{Ru(cod)}]⋅2 tol (3), alongside the salt of a binary nido cluster, [K(crypt-222)]3(Tl4Bi5)⋅2 en (4). The anions in 2 and 3 are two further examples of rare heterometallic clusters containing Ru atoms. As one cod ligand is retained on each Ru atom in both clusters, the anions may be viewed as intermediates on the way towards larger, ligand-free intermetalloid clusters. Quantum-chemical studies provided insight into the bonding situation in these clusters. According to these studies, the anion of 2 features both electron-precise and electron-deficient parts. Electrospray ionization mass spectrometry analysis indicated that the clusters undergo stepwise fragmentation.A little bit of each: DFT studies confirm a hybrid bonding situation in [Bi9{Ru(cod)}2]3− with both localized and delocalized bonds. This cluster and [Tl2Bi6{Ru(cod)}]2− were obtained upon reaction of the binary Zintl anion (TlBi3)2− with [Ru(cod)(H2CC(Me)CH2)2]. Both clusters are rare examples of Zintl anions comprising Ru atoms and illustrate the electronic flexibility of Group 15 polyanions with (pseudo)atoms of other groups.
      PubDate: 2017-09-13T13:05:49.975701-05:
      DOI: 10.1002/anie.201707632
  • Rocking-Chair Ammonium-Ion Battery: A Highly Reversible Aqueous Energy
           Storage System
    • Authors: Xianyong Wu; Yitong Qi, Jessica J. Hong, Zhifei Li, Alexandre S. Hernandez, Xiulei Ji
      Abstract: Aqueous rechargeable batteries are promising solutions for large-scale energy storage. Such batteries have the merit of low cost, innate safety, and environmental friendliness. To date, most known aqueous ion batteries employ metal cation charge carriers. Here, we report the first “rocking-chair” NH4-ion battery of the full-cell configuration by employing an ammonium Prussian white analogue, (NH4)1.47Ni[Fe(CN)6]0.88, as the cathode, an organic solid, 3,4,9,10-perylenetetracarboxylic diimide (PTCDI), as the anode, and 1.0 m aqueous (NH4)2SO4 as the electrolyte. This novel aqueous ammonium-ion battery demonstrates encouraging electrochemical performance: an average operation voltage of ca. 1.0 V, an attractive energy density of ca. 43 Wh kg−1 based on both electrodes’ active mass, and excellent cycle life over 1000 cycles with 67 % capacity retention. Importantly, the topochemistry results of NH4+ in these electrodes point to a new paradigm of NH4+-based energy storage.Charging ahead: An ammonium Prussian white analogue serves as the cathode, an organic solid, 3,4,9,10-perylenetetracarboxylic diimide (PTCDI), as the anode, and 1.0 m (NH4)2SO4 as the electrolyte in an aqueous rocking-chair ammonium-ion battery. The topochemistry of NH4+ in these electrodes points to a new paradigm of NH4+-based energy storage.
      PubDate: 2017-09-13T13:05:35.939994-05:
      DOI: 10.1002/anie.201707473
  • A Material Showing Colossal Positive and Negative Volumetric Thermal
           Expansion with Hysteretic Magnetic Transition
    • Authors: Ji-Xiang Hu; Yang Xu, Yin-Shan Meng, Liang Zhao, Shinya Hayami, Osamu Sato, Tao Liu
      Abstract: It is an ongoing challenge to design and synthesize magnetic materials that undergo colossal thermal expansion and that possess potential applications as microscale or nanoscale actuators with magnetic functionality. A paramagnetic metallocyanate building block was used to construct a cyanide-bridged Fe-Co complex featuring both positive and negative colossal volumetric thermal-expansion behavior. A detailed study revealed that metal-to-metal charge transfer between 180 and 240 K induced a volumetric thermal expansion coefficient of 1498 MK−1 accompanied with hysteretic spin transition. Rotation of the magnetic building blocks induced change of π⋅⋅⋅π interactions, resulting in a negative volume expansion coefficient of −489 MK−1, and another hysteretic magnetic transition between 300 and 350 K. This work presents a strategy for incorporating both colossal positive and negative volumetric thermal expansion with shape and magnetic memory effects in a material.We got both kinds of expansion: A Fe−Co layered network was synthesized. This material exhibits colossal positive and negative thermal expansion (PTE and NTE) at different temperature regions accompanying hysteretic magnetic transitions.
      PubDate: 2017-09-13T13:05:29.504671-05:
      DOI: 10.1002/anie.201707258
  • Cationic Nitrogen Doped Helical Nanographenes
    • Authors: Kun Xu; Xinliang Feng, Reinhard berger, Alexey A Popov, Jan J Weigand, Ilka Vincon, Peter Machata, Felix Hennersdorf, Youjia Zhou, Yubin Fu
      Abstract: Herein, we report on the synthesis of a series of novel cationic nitrogen doped nanographenes (CNDN) by rhodium catalyzed annulation reactions. This powerful method allows for the synthesis of cationic nanographenes with non-planar, axial chiral geometries. Single-crystal X-ray analysis reveals helical and cove-edged structures. Compared to their all-carbon analogues, the CNDN exhibit energetically lower lying frontier orbitals with a reduced optical energy gap and an electron accepting behavior. All derivatives show quasi reversible reductions in cyclic voltammetry. Depending on the number of nitrogen dopant, in situ spectroelectrochemistry proves the formation of neutral radicals (one nitrogen dopant) or radical cations (two nitrogen dopants) upon reduction. The developed synthetic protocol paves the way for the design and synthesis of expanded nanographenes or even graphene nanoribbons containing cationic nitrogen doping.
      PubDate: 2017-09-13T11:15:32.323487-05:
      DOI: 10.1002/anie.201707714
  • Multidimensional Correlations in Asymmetric Catalysis via Parameterization
           of Uncatalyzed Transition States
    • Authors: Manuel Orlandi; F. Dean Toste, Matthew S. Sigman
      Abstract: The study of the chiral anion phase transfer (CAPT) catalyzed oxidative amination of tetrahydroisoquinolines via multidimensional correlation analysis (MCA) is revisited. The parameterization of the transition states (TSs) for the uncatalyzed reaction, the introduction of conformational descriptors, and the use of computed interaction energies and distances as parameters allowed access to a considerably simplified mathematical correlation of substrate and catalyst structure to enantioselectivity. The equation obtained is suggestive of key interactions occurring at the TS. Specifically, the CAPT catalyst is proposed to coordinate the intermediate iminium cation by P=O∙∙∙H-O hydrogen bond and by N∙∙∙H-C electrostatic interaction. The conformational freedom of the substrate's benzyl substituent is also found to be important in order to provide an efficient mode of molecular recognition.
      PubDate: 2017-09-13T10:15:25.727454-05:
      DOI: 10.1002/anie.201707644
  • Real-time control of the enantioselectivity of a supramolecular catalyst
           allows selecting the configuration of consecutively formed stereogenic
    • Authors: Jeremy M. Zimbron; Xavier Caumes, Yan Li, Christophe M. Thomas, Matthieu Raynal, Laurent Bouteiller
      Abstract: The enantiomeric state of a supramolecular copper catalyst can be switched in situ in ca. five seconds. The dynamic property of the catalyst is provided by the non-covalent nature of the helical assemblies supporting the copper centres. These assemblies are formed by mixing an achiral benzene-1,3,5-tricarboxamide (BTA) phosphine ligand (for copper coordination) and both enantiomers of a chiral phosphine-free BTA co-monomer (for chirality amplification). The enantioselectivity of the hydrosilylation reaction is fixed by the BTA enantiomer in excess, which can be altered by simple BTA addition. As a result of the complete and fast stereochemical switch, any combination of the enantiomers was obtained during the conversion of a mixture of two substrates.
      PubDate: 2017-09-13T08:13:21.965298-05:
      DOI: 10.1002/anie.201706757
  • Enzyme Encapsulation by a Ferritin Cage
    • Authors: Stephan Tetter; Donald Hilvert
      Abstract: Ferritins, conserved across all kingdoms of life, are protein nanocages that evolved to mineralize iron. The last several decades have shown that these cages have considerable technological and medical potential owing to their stability and tolerance to modification, as well as their ability to template nanoparticle synthesis and incorporate small molecules. Here we show that it is possible to encapsulate proteins in a ferritin by exploiting electrostatic interactions with the negatively charged interior of the cage. Positively supercharged green fluorescent protein is efficiently taken up by Archaeoglobus fulgidus ferritin in a tunable fashion. By genetic tethering to the fluorescent protein, enzymes could be incorporated into the ferritin cage. The fusion proteins retained high catalytic activity, and showed increased tolerance to proteolysis and heat. Equipping ferritins with enzymatic activity paves the way for many new nanotechnological and pharmacological applications.
      PubDate: 2017-09-13T08:11:08.059102-05:
      DOI: 10.1002/anie.201708530
  • Laser-initiated Radical Trifluoromethylation of Peptides and Proteins and
           Its Application to Mass Spectrometry-Based Protein Footprinting
    • Authors: Ming Cheng; Bojie Zhang, Weidong Cui, Michael L. Gross
      Abstract: We describe a novel, laser-initiated radical trifluoromethylation for protein footprinting and establish its broad residue coverage. *CF3 reacts with 18 of 20 common amino acids including Gly, Ala, Ser, Thr, Asp, Glu that are relatively "silent" with *OH. This new approach to footprinting is a bridge between trifluoromethylation in materials and medicinal chemistry and structural biology and biotechnology. Its application to a membrane protein and to myoglobin show that the approach is sensitive to protein conformational change and solvent accessibility.
      PubDate: 2017-09-13T03:27:34.327998-05:
      DOI: 10.1002/anie.201706697
  • Catanionic coacervate micro-droplets as a surfactant-based membrane-free
           protocell model
    • Authors: Jean-Paul Douliez; Nicolas MARTIN, Stephen Mann, Cédric Gaillard, Thomas Beneyton, Jean-Christophe Baret, Laure Beven
      Abstract: We report on the formation of surfactant complex catanionic coacervate micro-droplets in mixtures of decanoic acid and cetyl pyridinium chloride or cetyl trimethyl ammonium bromide. We show that coacervation occurs over a broad range of composition, pH and ionic strength. The catanionic coacervates consist of elongated micelles, sequester a wide range of solutes including water-soluble organic dyes, polysaccharides, proteins, enzymes and DNA, and can be structurally stabilized by sodium alginate or gelatin-based hydrogelation. Taken together, the results suggest that catanionic coacervates could be exploited as a novel surfactant-based membrane-free protocell model
      PubDate: 2017-09-13T03:26:15.100469-05:
      DOI: 10.1002/anie.201707139
  • In Situ Generated Piers' Borane-Catalyzed Selective C-O Bond Cleavage of
           Sugars with Hydrosilanes
    • Authors: Sukbok Chang; Jianbo Zhang, Sehoon Park
      Abstract: Described herein is the Piers' borane (C6F5)2BH-catalyzed selective reduction of sugars with hydrosilanes. The hydrosilylative C-O bond cleavage of silyl-protected mono- and disaccharides in the presence of (C6F5)2BH catalyst, in situ generated from (C6F5)2BOH, takes place with excellent chemo- and regioselectivities to provide a range of polyols. Study of the substituent effects of sugars on the catalytic activity and selectivity revealed that the steric environment around the anomeric carbon (C1) is crucial.
      PubDate: 2017-09-12T21:25:50.372093-05:
      DOI: 10.1002/anie.201708109
  • Multi-Photon Absorption in Metal-Organic Frameworks
    • Authors: Raghavender Medishetty; Lydia Nemec, Venkatram Nalla, Sebastian Henke, Marek Samoc, Karsten Reuter, Roland A. Fischer
      Abstract: Multi-photon absorption (MPA) is among the most prominent nonlinear optical (NLO) effects and has applications, for example in telecommunications, defense, photonics and bio-medicines. Established MPA materials include dyes, quantum dots, organometallics and conjugated polymers, most often dispersed in solution. We demonstrate how metal-organic frameworks (MOFs), a novel NLO solid-state materials class, can be designed for exceptionally strong MPA behavior. MOFs consisting of zirconium- and hafnium-oxo-clusters and featuring a chromophore linker based on the tetraphenylethene (TPE) molecule exhibit record high two-photon absorption (2PA) cross section values, up to 3600 GM. The unique modular building-block principle of MOFs allows enhancing and optimizing their MPA properties in a theory guided approach by combining tailored charge polarization, conformational strain, three-dimensional arrangement and alignment of the chromophore linkers in the crystal.
      PubDate: 2017-09-12T08:20:53.691021-05:
      DOI: 10.1002/anie.201706492
  • Palladium-Catalyzed [3+3] Annulation of Vinyl Chromium(0) Carbene
           Complexes through Carbene Migratory Insertion/Tsuji–Trost Reaction
    • Authors: Kang Wang; Yifan Ping, Taiwei Chang, Jianbo Wang
      Abstract: Vinyl chromium(0) Fischer carbene complexes were employed as the source of π-allylic palladium species for catalytic [3+3] annulation under palladium catalysis. Mechanistically, this transformation is proposed to involve carbene migratory insertion and intramolecular Tsuji–Trost reaction as the key steps. Substituted six-membered heterocyclic flavonones and quinolines are obtained, depending on the nucleophilic functional group on the coupling partners.Give me a ring: Vinyl chromium(0) carbenes were employed as the three-carbon unit for carbene-based migratory insertion/Tsuji–Trost-type coupling. The annulation of α,β-unsaturated chromium(0) Fischer carbene complexes with 2-iodophenol and 2-iodoanilines was realized through palladium catalysis.
      PubDate: 2017-09-12T07:41:24.135352-05:
      DOI: 10.1002/anie.201707590
  • Reversible DNA-protein cross-linking at epigenetic DNA marks
    • Authors: Shaofei Ji; Hongzhao Shao, Qiyuan Han, Christopher L Seiler, Natalia Tretyakova
      Abstract: 5-Formylcytosine (5fC) is an endogenous DNA modification frequently found within regulatory elements of mammalian genes. Although 5fC is an oxidation product of 5-methylcytosine (5mC), the two epigenetic marks show distinct genome-wide distributions and protein affinities, suggesting that they perform different functions in epigenetic signaling. A unique feature of 5fC is the presence of a potentially reactive aldehyde group in its structure. Here, we show that 5fC bases in DNA readily form Schiff base conjugates with Lys side chains of nuclear proteins in vitro and in vivo. These covalent protein-DNA complexes are reversible (t1/2, 1.8 h), suggesting that they contribute to transcriptional regulation and chromatin remodeling. On the other hand, 5fC mediated DNA-protein cross-links, if present at replication forks or actively transcribed regions, may interfere with DNA replication and transcription.
      PubDate: 2017-09-12T06:48:29.579278-05:
      DOI: 10.1002/anie.201708286
  • Near Infrared Free Radical and Free Radical Promoted Cationic
           Photopolymerizations by Insource Lightening Using Upconverting Glass
    • Authors: Azra Kocaarslan; Sevcan Tabanli, Gonul Eryurek, Yusuf Yagci
      Abstract: A novel methodology for the initiation of free radical and free radical promoted cationic photopolymerizations by insource lightening in the near infrared (NIR) region using upconverting glass (UCG) is reported. This approach pertains to the laser irradiation of UCG at 975 nm in the presence of Fluorescein (FL) and pentamethyldiethylene triamine (PMDETA). FL excited by blue light emitted from the UCG undergoes electron transfer reactions with PMDETA to form free radicals capable of initiating polymerization of methyl methacrylate. To execute the corresponding free-radical-promoted cationic polymerization of cyclohexene oxide, isobutyl vinyl ether and N-vinyl carbazole we use FL, dimethyl aniline (DMA) and diphenyliodonium hexafluorophosphate as sensitizer, co-initiator and oxidant, respectively. Iodonium ions promptly oxidize DMA radicals formed to the corresponding cations. Thus, cationic polymerization with an efficiency comparable to the conventional irradiation source is initiated
      PubDate: 2017-09-12T06:15:44.833729-05:
      DOI: 10.1002/anie.201707944
  • Spin State-Controlled Photodissociation of Iron(III) Azide to Iron(V)
           Nitride Complex
    • Authors: Erik Andris; Rafael Navratil, Juraj Jasik, Gerard Sabenya, Miquel Costas, Martin Srnec, Jana Roithová
      Abstract: We report the generation of iron(V) nitride complexes, which are targets of biomimetic chemistry. Temperature-dependent ion spectroscopy shows that this reaction is governed by the spin state population of their iron(III) azide precursors and can be tuned by temperature. The complex [(MePy2TACN)Fe(N3)]2+ exists as a mixture of sextet and doublet spin states at 300 K, whereas only the doublet state is populated at 3 K. Photofragmentation of the sextet state complex leads to the reduction of the iron centre. The doublet state complex photodissociates to the desired iron(V) nitride complex. To generalize these findings, we show results for complexes with cyclam-based ligands.
      PubDate: 2017-09-12T05:21:48.634597-05:
      DOI: 10.1002/anie.201707420
  • CsB4O6F: A Congruent-melting Deep-ultraviolet Nonlinear Optical Material
           with Superior Functional Units Recombination
    • Authors: Xuefei Wang; Ying Wang, Bingbing Zhang, Fangfang Zhang, Zhihua Yang, Shilie Pan
      Abstract: The discovery of new nonlinear optical (NLO) materials for coherent light generation in the deep-ultraviolet (DUV, wavelength below 200 nm) region is essential for the development of laser technologies. Herein, we report a new material CsB4O6F (CBF), which combines the superior structural genes of two famous NLO materials—β-BaB2O4 (BBO) and KBe2BO3F2 (KBBF). CBF exhibits excellent DUV optical properties including a short cutoff edge (155 nm), a large SHG response (~1.9 × KDP), and a suitable birefringence that enables frequency doubling down to 171.6 nm. Remarkably, CBF melts congruently and show an improved growth habit. In addition, our rational design strategy will contribute to the discovery of DUV NLO materials.
      PubDate: 2017-09-12T04:21:25.752392-05:
      DOI: 10.1002/anie.201708231
  • Protecting and Leaving Functions of Trimethylsilyl Groups in
           Trimethylsilylated Silicates for the Synthesis of Alkoxysiloxane Oligomers
    • Authors: Masashi Yoshikawa; Yasuhiro Tamura, Ryutaro Wakabayashi, Misa Tamai, Atsushi Shimojima, Kazuyuki Kuroda
      Abstract: The concept of protecting groups and leaving groups in organic synthesis was applied to the synthesis of siloxane-based molecules. Alkoxy-functionalized siloxane oligomers composed of SiO4, RSiO3, or R2SiO2 units were chosen as targets; however, synthetic methods are limited. Here we describe a novel synthesis of alkoxysiloxane oligomers based on the substitution reaction of trimethylsilyl (TMS) groups with alkoxysilyl groups. Oligosiloxanes possessing TMS groups were reacted with alkoxychlorosilane in the presence of BiCl3 as a catalyst. TMS groups were substituted with alkoxysilyl groups, leading to the synthesis of alkoxysiloxane oligomers. Siloxane oligomers composed of RSiO3 and R2SiO2 units were synthesized more efficiently than those composed of SiO4 units, suggesting that the steric hindrance around the TMS groups of the oligosiloxanes makes a difference in the degree of substitution. This reaction uses TMS groups as both protecting and leaving groups of SiOH/SiO- groups.
      PubDate: 2017-09-12T03:21:29.61747-05:0
      DOI: 10.1002/anie.201705942
  • Rational Optimization of Supramolecular Catalysts for the
           Rhodium-Catalyzed Asymmetric Hydrogenation Reaction
    • Authors: Julien Daubignard; Remko J. Detz, Anne C. H. Jans, Bas de Bruin, Joost N. H. Reek
      Abstract: Rational design of catalysts for asymmetric transformations is a longstanding challenge in the field of catalysis. In the current contribution we report a catalyst in which a hydrogen bond between the substrate and the catalyst plays a crucial role in determining the selectivity and the rate of the catalytic hydrogenation reaction, as is evident from a combination of experiments and DFT calculations. Detailed insight allowed in silico mutation of the catalyst such that only this hydrogen bond interaction is stronger, predicting that the new catalyst is faster. Indeed, we experimentally confirmed that optimization of the catalyst can be realized by increasing the hydrogen bond strength of this interaction by going from a urea to phosphine oxide H-bond acceptor on the ligand.How to make a catalyst run better: For the first time the computer-based optimization of a supramolecular catalyst for asymmetric hydrogenation reactions is demonstrated. According to DFT calculations and experiments two hydrogen bonds between the catalyst and the substrate exist; increasing the strength of this hydrogen bond interaction by replacing one ligand results in higher reaction rates and higher selectivities.
      PubDate: 2017-09-12T01:48:31.333175-05:
      DOI: 10.1002/anie.201707670
  • Ligand-Controlled Regiodivergent and Enantioselective Copper-Catalyzed
           Hydroallylation of Alkynes
    • Authors: Guoxing Xu; Haiyan Zhao, Bin Fu, Aijie Cang, Ge Zhang, Qian Zhang, Tao Xiong, Qian Zhang
      Abstract: A ligand-controlled regiodivergent and enantioselective copper-catalyzed intermolecular hydroallylation of alkynes with allylic phosphates and hydrosilanes has been achieved for the first time. The chiral bidentate sulfonate-containing N-heterocyclic carbene ligated CuCl complex leads to enantioenriched SN2′-type products, whereas the use of the IMesCuCl catalyst affords SN2-type products. Thus a range of chiral branched and achiral linear 1,4-dienes could be facilely synthesized from readily available alkynes in a regiodivergent manner.Under control: A ligand-controlled regiodivergent and enantioselective copper-catalyzed intermolecular hydroallylation of alkynes with allylic phosphates and hydrosilanes has been achieved. Chiral branched or achiral linear dienes can be obtained by proper choice of the ancillary N-heterocyclic carbene ligand.
      PubDate: 2017-09-12T01:48:13.634849-05:
      DOI: 10.1002/anie.201707070
  • Nickel-Catalyzed Reductive Allylation of Tertiary Alkyl Halides with
           Allylic Carbonates
    • Authors: Haifeng Chen; Xiao Jia, Yingying Yu, Qun Qian, Hegui Gong
      Abstract: The construction of all C(sp3) quaternary centers has been successfully achieved under Ni-catalyzed cross-electrophile coupling of allylic carbonates with unactivated tertiary alkyl halides. For allylic carbonates bearing C1 or C3 substituents, the reaction affords excellent regioselectivity through the addition of alkyl groups to the unsubstituted allylic carbon terminus. The allylic alkylation method also exhibits excellent functional-group compatibility, and delivers the products with high E selectivity.All at C: Ni-catalyzed reductive coupling of tertiary alkyl bromides with allylic carbonates enables the formation of all-C(sp3) quaternary centers in good to excellent yields. The reactions exhibit excellent regioselectivity and functional-group tolerance, and a broad substrate scope.
      PubDate: 2017-09-12T01:47:51.008645-05:
      DOI: 10.1002/anie.201705521
  • Release of Enzymatically Active Deubiquitinating Enzymes upon Reversible
           Capture by Disulfide Ubiquitin Reagents
    • Authors: Annemieke de Jong; Katharina Witting, Raymond Kooij, Dennis Flierman, Huib Ovaa
      Abstract: Deubiquitinating enzymes (DUBs) catalyze the cleavage of ubiquitin from target proteins. Ubiquitin is post-translationally attached to proteins and serves as an important regulatory signal for key cellular processes. In this study, novel activity-based probes to study DUBs were synthesized that comprise a ubiquitin moiety and a novel disulfide warhead at the C-terminus. These reagents can bind DUBs covalently by forming a disulfide bridge between the active-site cysteine residue and the ubiquitin-based probe. As disulfide bridges can be broken by the addition of a reducing agent, these novel ubiquitin reagents can be used to capture and subsequently release catalytically active DUBs, whereas existing capturing agents bind irreversibly. These novel reagents allow for the study of these enzymes in their active state under various conditions.Capture and release: Ubiquitin-based activity probes were developed that are the first of their kind to yield active deubiquitinating enzymes (DUBs) after capture and release. These reagents form disulfide linkages with the active-site cysteine residue of DUBs. After capture from cell extract using an affinity resin, the disulfide linkage can be mildly cleaved with reducing agents to yield active DUBs.
      PubDate: 2017-09-12T01:46:17.591664-05:
      DOI: 10.1002/anie.201706738
  • Compartmentalizing Supramolecular Hydrogels Using Aqueous Multi-phase
    • Authors: Serhii Mytnyk; Alexandre G. L. Olive, Frank Versluis, Jos M. Poolman, Eduardo Mendes, Rienk Eelkema, Jan H. van Esch
      Abstract: A generic method is used for compartmentalization of supramolecular hydrogels by using water-in-water emulsions based on aqueous multi-phase systems (AMPS). By forming the low-molecular-weight hydrogel throughout all phases of all-aqueous emulsions, distinct, micro-compartmentalized materials were created. This structuring approach offers control over the composition of each type of the compartments by directing the partitioning of objects to be encapsulated. Moreover, this method allows for barrier-less, dynamic exchange of even large hydrophilic solutes (MW≈60 kDa) between separate aqueous compartments. These features are expected to find use in the fields of, for instance, micro-structured catalysts, templating, and tissue engineering.Hydrogel compartments: A versatile approach is used to create aqueous microcompartments inside low-molecular-weight hydrogels using polymer phase separation. Distinct micrometer-sized domains are thus created with controlled composition and unrestricted exchange of even large polar solutes. The method may potentially find use for templating porous soft materials or in the fabrication of tissue engineering scaffolds.
      PubDate: 2017-09-12T01:45:59.444409-05:
      DOI: 10.1002/anie.201706272
  • Graphene Oxide Facilitates Solvent-Free Synthesis of Well-Dispersed,
           Faceted Zeolite Crystals
    • Authors: Hui Li; Xing Liu, Siqi Qi, Linli Xu, Guosheng Shi, Yihong Ding, Xiaoying Yan, Yong Huang, Jianxin Geng
      Abstract: Zeolites with molecular dimension pores are widely used in petrochemical and fine-chemical industries. While traditional solvothermal syntheses suffer from environmental, safety, and efficiency issues, the newly developed solvent-free synthesis is limited by zeolite crystal aggregation. Herein, we report well-dispersed and faceted silicalite ZSM-5 zeolite crystals obtained using a solvent-free synthesis facilitated by graphene oxide (GO). The selective interactions between the GO sheets and different facets, which are proven by molecular dynamics simulations, result in oriented growth of the ZSM-5 crystals along the c-axis. More importantly, the incorporation of GO sheets into the ZSM-5 crystals leads to the formation of mesopores. Consequently, the faceted ZSM-5 crystals exhibit hierarchical pore structures. The developed synthetic method is superior to conventional approaches because of the aforementioned features of the ZSM-5 zeolite.
      PubDate: 2017-09-11T21:24:36.986358-05:
      DOI: 10.1002/anie.201707823
  • Remote Loading of Small Molecule Therapeutics into Cholesterol-Enriched
           Cell Membrane-Derived Vesicles
    • Authors: Xinxin Zhang; Pavimol Angsantikul, Man Ying, Jia Zhuang, Qiangzhe Zhang, Xiaoli Wei, Yao Jiang, Yue Zhang, Diana Dehaini, Mengchun Chen, Yijie Chen, Weiwei Gao, Ronnie Fang, Liangfang Zhang
      Abstract: The increasing popularity of biomimetic design principles in nanomedicine has led to therapeutic platforms with enhanced performance and biocompatibility. This includes the direct use of naturally derived cell membranes, which can bestow nanocarriers with cell-specific functionalities. Herein, we report on a strategy enabling the efficient encapsulation of drugs via remote loading into membrane vesicles derived from red blood cells. This is accomplished by supplementing the membrane with additional cholesterol, stabilizing the nanostructure and facilitating the retention of a pH gradient. We demonstrate the loading of two model drugs: the chemotherapeutic doxorubicin and the antibiotic vancomycin. The therapeutic implications of these naturally derived, remote-loaded nanoformulations are studied both in vitro and in vivo using animal disease models. Ultimately, this approach could be used to design new biomimetic nanoformulations with higher efficacy and improved safety profiles.
      PubDate: 2017-09-11T14:15:52.515655-05:
      DOI: 10.1002/anie.201707598
  • Single Turnover at Molecular Polymerization Catalysts Reveals
           Spatiotemporally Resolved Reactions
    • Authors: Suzanne A. Blum; Quinn T. Easter
      Abstract: Multiple active individual molecular ruthenium catalysts were pinpointed within growing polynorbornene, revealing reaction dynamics and location information that is unavailable through traditional ensemble experiments. These experiments are the first single-turnover fluorescence microscopy imaging at any molecular catalyst and achieve the detection of individual monomer reactions at an industrially important molecular ruthenium ring-opening metathesis polymerization (ROMP) catalyst under synthetically relevant catalytic conditions (e.g., unmodified industrial catalyst, ambient pressure, condensed phase, ~0.03 M monomer). These results further establish the key fundamentals of this imaging technique for characterizing the reactivity and location of molecular catalysts even when they are the minor components.
      PubDate: 2017-09-11T13:15:53.352337-05:
      DOI: 10.1002/anie.201708284
  • Electron Transfer and Hydride Transfer Pathways in the Stoltz-Grubbs
           Reducing System (KOtBu-Et3SiH)
      Abstract: Recent studies by Stoltz, Grubbs et al. have shown that triethylsilane and potassium tert-butoxide react to form a highly attractive and versatile system that shows (reversible) silylation of arenes and heteroarenes as well as reductive cleavage of C-O bonds in aryl ethers and C-S bonds in aryl thioethers. Their extensive mechanistic studies indicate a complex network of reactions with a number of possible intermediates and mechanisms, but their reactions likely feature silyl radicals undergoing addition reactions and SH2 reactions. This paper focuses on the same system, but through computational and experimental studies, reports complementary facets of its chemistry based on (a) single electron transfer (SET), and (b) hydride delivery reactions to arenes
      PubDate: 2017-09-11T12:15:48.148355-05:
      DOI: 10.1002/anie.201707914
  • Chemical modification improves biocompatibility of black phosphorus
    • Authors: Guangbo Qu; Wei Liu, Yuetao Zhao, Jie Gao, Tian Xia, Jianbo Shi, Ligang Hu, Wenhua Zhou, Jiejun Gao, Huaiyu Wang, Qian Luo, Qunfang Zhou, Sijin Liu, Xuefeng Yu, Guibin Jiang
      Abstract: Black phosphorus nanosheets (BPs) have exhibited great potential for various applications including biomedicine, thus their potential side effects and corresponding improvement strategy deserve investigation. Here, in vitro and in vivo biological effects of BPs with and without titanium sulfonate ligand (TiL4) modification are investigated. Comparing to bare BPs, BPs with TiL4 modification (TiL4@BPs) can efficiently escape from macrophages uptake, and reduce the cytotoxicity and proinflammation. When intravenously injected into mice, bare BPs trigger significant inflammatory responses, including an increase in peripheral neutrophils accompanied by elevation of a group of inflammatory cytokines, while TiL4@BPs exhibit no such adverse immune responses. The corresponding mechanisms are also discussed. These findings may not only guide the applications of BPs, but also propose an efficient strategy to further improve the biocompatibility of BPs.
      PubDate: 2017-09-11T11:15:46.97411-05:0
      DOI: 10.1002/anie.201706228
  • Evidence of Organic Luminescent Centers in Sol-Gel Synthesized Yttrium
           Aluminum Borate Matrix Leading to Bright Visible Emission
    • Authors: Pauline BURNER; Atul D. Sontakke, Mathieu Salaün, Michel Bardet, Jean-Marie Mouesca, Serge Gambarelli, Anne-Laure Barra, Alban Ferrier, bruno Viana, Alain Ibanez, Vincent Maurel, Isabelle Gautier-Luneau
      Abstract: Yttrium aluminum borate (YAB) powders prepared by sol-gel process have been investigated to understand their photoluminescence (PL) mechanism. The amorphous YAB powders exhibit bright visible PL from blue emission for powders calcined at 450 °C to broad white PL for higher calcination temperature. Thanks to 13C labelling, NMR and EPR studies show that propionic acid initially used to solubilize the yttrium nitrate is decomposed into aromatic molecules confined within the inorganic matrix. DTA-TG-MS analyses show around 2 wt % of carbogenic species. The PL broadening corresponds to the apparition of a new band at 550 nm, associated with the formation of aromatic species. Furthermore, pulsed ENDOR spectroscopy combined with DFT calculations enables us to ascribe EPR spectra to free radicals derived from small (2 to 3 rings) polycyclic aromatic hydrocarbons (PAH). PAH molecules are thus at the origin of the PL as corroborated by slow afterglow decay and thermoluminescence experiments.
      PubDate: 2017-09-11T11:15:36.185929-05:
      DOI: 10.1002/anie.201706070
  • Cover Picture: Structural Basis for Expansion of the Genetic Alphabet with
           an Artificial Nucleobase Pair (Angew. Chem. Int. Ed. 39/2017)
    • Authors: Karin Betz; Michiko Kimoto, Kay Diederichs, Ichiro Hirao, Andreas Marx
      Pages: 11655 - 11655
      Abstract: Expansion of the genetic alphabet … … with hydrophobic artificial base pairs is a promising approach. In their Communication on page 12000 ff., A. Marx, I. Hirao, and co-workers present a high-resolution crystal structure of the dDs–dPx pair in the active site of a DNA polymerase. They show that the artificial base pair adopts a planar structure just like a natural nucleobase pair. Its varying size and shape, however, cause minor alterations near the active site.
      PubDate: 2017-07-07T04:00:26.249256-05:
      DOI: 10.1002/anie.201706478
  • Inside Cover: Antimonene Quantum Dots: Synthesis and Application as
           Near-Infrared Photothermal Agents for Effective Cancer Therapy (Angew.
           Chem. Int. Ed. 39/2017)
    • Authors: Wei Tao; Xiaoyuan Ji, Xiaoding Xu, Mohammad Ariful Islam, Zhongjun Li, Si Chen, Phei Er Saw, Han Zhang, Zameer Bharwani, Zilei Guo, Jinjun Shi, Omid C. Farokhzad
      Pages: 11656 - 11656
      Abstract: Antimonene quantum dots synthesized by a controllable liquid exfoliation method are reported by O. C. Farokhzad, J. Shi, H. Zhang et al. in their Communication on page 11896 ff., The particles showed a high photothermal conversion efficiency (45.5%), near-infrared-induced degradability, and biocompatibility, thus making them ideal photothermal agents. This study will open up exciting and novel research on antimonene for biomedical applications.
      PubDate: 2017-08-03T05:01:26.266693-05:
      DOI: 10.1002/anie.201707385
  • Graphical Abstract: Angew. Chem. Int. Ed. 39/2017
    • Pages: 11659 - 11675
      PubDate: 2017-09-15T06:37:58.735732-05:
      DOI: 10.1002/anie.201783911
  • Corrigendum: Digital Quantification of DNA Replication and Chromosome
           Segregation Enables Determination of Antimicrobial Susceptibility after
           only 15 Minutes of Antibiotic Exposure
    • Authors: Nathan G. Schoepp; Eugenia M. Khorosheva, Travis S. Schlappi, Matthew S. Curtis, Romney M. Humphries, Janet A. Hindler, Rustem F. Ismagilov
      Pages: 11675 - 11675
      PubDate: 2017-09-15T06:38:05.883721-05:
      DOI: 10.1002/anie.201707742
  • Spotlights on our sister journals: Angew. Chem. Int. Ed. 39/2017
    • Pages: 11678 - 11681
      PubDate: 2017-09-15T06:38:05.417415-05:
      DOI: 10.1002/anie.201783913
  • Daniel Romo
    • Pages: 11682 - 11682
      Abstract: “I celebrate success by giving thanks to God and “chillin” with my family. The best advice I have ever been given is “Romo, when you begin your independent career, be sure to do some chemistry that will become associated with your name” (A. I. Meyers). ...” This and more about Daniel Romo can be found on page 11682.
      PubDate: 2017-06-06T07:01:01.01296-05:0
      DOI: 10.1002/anie.201703689
  • Mukaiyama Award: F. Glorius and Y. Nakao Wissenschaftspreis der Stadt Ulm:
           C. Streb BioTrans Senior Award: M. T. Reetz BioTrans Junior Award: F.
    • Pages: 11683 - 11683
      PubDate: 2017-08-23T12:35:20.406479-05:
      DOI: 10.1002/anie.201708171
  • Comment on “A Liposomal System Capable of Generating CO2 Bubbles to
           Induce Transient Cavitation, Lysosomal Rupturing and Cell Necrosis”
    • Authors: Peter Tiefenboeck; Jong Ah Kim, Ferdinand Trunk, Jean-Christophe Leroux
      Pages: 11686 - 11689
      Abstract: In 2012 Sung et al. reported temperature-sensitive liposomes encapsulating ammonium bicarbonate (ABC), supposedly releasing their payload above 42 °C owing to ABC decomposition, subsequent CO2 bubbles generation, and transient cavitation. In attempts to reproduce the system, insurmountable difficulties have been encountered. New results presented herein cast doubts on the thermoresponsiveness of these liposomes.
      PubDate: 2017-07-06T07:08:38.922458-05:
      DOI: 10.1002/anie.201703740
  • Response to Comment on “A Liposomal System Capable of Generating CO2
           Bubbles to Induce Transient Cavitation, Lysosomal Rupturing and Cell
    • Authors: Wei-Lin Wan; Min-Fan Chung, Po-Chien Shih, Hsing-Wen Sung
      Pages: 11690 - 11692
      Abstract: Leroux et al. performed a set of experiments reported in our study and claim that they failed to reproduce the thermoresponsive liposomal system containing ammonium bicarbonate (ABC) that could trigger drug release under mild heating. We disagree with their assessments and speculate that the different method used by Leroux et al. to prepare the aqueous ABC is the culprit.
      PubDate: 2017-08-16T02:25:38.051862-05:
      DOI: 10.1002/anie.201706509
  • Acidity Strength of Solid Catalysts Probed by Hyperpolarized Natural
           Abundance 17O NMR Spectroscopy
    • Authors: Frédéric Blanc
      Pages: 11694 - 11696
      Abstract: Observation of Brønsted acid sites: By enhancing the solid-state NMR signals of 17O at natural abundance with dynamic nuclear polarization (DNP), Pruski et al. were able to measure oxygen–proton distances accurately with sub-picometer precision. The results give insight into the Brønsted acidity of a range of solid acid catalysts.
      PubDate: 2017-07-10T10:41:10.772624-05:
      DOI: 10.1002/anie.201705933
  • Structure Determination Techniques Flex Their Muscles
    • Authors: Alexander J. Blake
      Pages: 11697 - 11698
      Abstract: A historical challenge: Gas-phase electron diffraction and single-crystal X-ray diffraction are both established techniques, but they were both pushed to their limits by the challenge posed by the highly flexible tetranitromethane molecule. New approaches had to be developed for the structure of the molecule to be elucidated.
      PubDate: 2017-08-02T06:21:37.971365-05:
      DOI: 10.1002/anie.201706526
  • Asymmetric Synthesis of Secondary and Tertiary Boronic Esters
    • Authors: Beatrice S. L. Collins; Claire M. Wilson, Eddie L. Myers, Varinder K. Aggarwal
      Pages: 11700 - 11733
      Abstract: Non-racemic chiral boronic esters are recognised as immensely valuable building blocks in modern organic synthesis. Their stereospecific transformation into a variety of functional groups—from amines and halides to arenes and alkynes—along with their air and moisture stability, has established them as an important target for asymmetric synthesis. Efforts towards the stereoselective synthesis of secondary and tertiary alkyl boronic esters have spanned over five decades and are underpinned by a wealth of reactivity platforms, drawing on the unique and varied reactivity of boron. This Review summarizes strategies for the asymmetric synthesis of alkyl boronic esters, from the seminal hydroboration methods of H. C. Brown to the current state of the art.Non-racemic chiral boronic esters are immensely valuable building blocks in modern organic synthesis. Their stereospecific transformation into a variety of functional groups, along with their air and moisture stability, has established them as an important target for asymmetric synthesis. Methods for their asymmetric synthesis now span a wealth of reactivity platforms.
      PubDate: 2017-08-09T07:12:15.95455-05:0
      DOI: 10.1002/anie.201701963
  • A Binuclear Zinc Interaction Fold Discovered in the Homodimer of
           Alzheimer's Amyloid-β Fragment with Taiwanese Mutation D7H
    • Authors: Vladimir I. Polshakov; Alexey B. Mantsyzov, Sergey A. Kozin, Alexei A. Adzhubei, Sergey S. Zhokhov, Wouter van Beek, Alexandra A. Kulikova, Maria I. Indeykina, Vladimir A. Mitkevich, Alexander A. Makarov
      Pages: 11734 - 11739
      Abstract: Zinc-induced oligomerization of amyloid-β peptide (Aβ) produces potentially pathogenic agents of Alzheimer's disease. Mutations and modifications in the metal binding domain 1–16 of Aβ peptide crucially affect its zinc-induced oligomerization by changing intermolecular zinc mediated interface. The 3D structure of this interface appearing in a range of Aβ species is a prospective drug target for disease modifying therapy. Using NMR spectroscopy, EXAFS spectroscopy, mass spectrometry, and isothermal titration calorimetry the interaction of zinc ions with Aβ fragments 1–7 and 1–10 carrying familial Taiwanese mutation D7H was studied. Zinc ions induce formation of a stable homodimer formed by the two peptide chains fastened by two zinc ions and stacking interactions of imidazole rings. A binuclear zinc interaction fold in the dimer structure was discovered. It can be used for designing zinc-regulated proteins and zinc-mediated self-assembling peptides.Do zinc twice: The interaction of zinc ions with amyloid-β peptide fragments 1–7 and 1–10 carrying familial Taiwanese mutation D7H was studied. Zinc ions induce formation of a stable homodimer formed by the two peptide chains fastened by two zinc ions and stacking interactions between imidazole rings. A binuclear zinc interaction fold in the dimer structure was discovered.
      PubDate: 2017-06-27T06:33:51.075542-05:
      DOI: 10.1002/anie.201704615
  • Solid-State Transformation of Amorphous Calcium Carbonate to Aragonite
           Captured by CryoTEM
    • Authors: Jessica M. Walker; Bartosz Marzec, Fabio Nudelman
      Pages: 11740 - 11743
      Abstract: Early-stage reaction mechanisms for aragonite-promoting systems are relatively unknown compared to the more thermodynamically stable calcium carbonate polymorph, calcite. Using cryoTEM and SEM, the early reaction stages taking place during aragonite formation were identified in a highly supersaturated solution using an alcohol–water solvent, and an overall particle attachment growth mechanism was described for the system. In vitro evidence is provided for the solid-state transformation of amorphous calcium carbonate to aragonite, demonstrating the co-existence of both amorphous and crystalline material within the same aragonite needle. This supports non-classical formation of aragonite within both a synthetic and biological context.Solid-state transformation: By observing early stages of aragonite formation using cryoTEM, it was demonstrated that a non-classical mechanism is involved, including the co-existence of amorphous and crystalline material. This offers key evidence to support nanoparticle assembly mechanisms in both synthetic and biological systems.
      PubDate: 2017-08-15T02:17:25.719711-05:
      DOI: 10.1002/anie.201703158
  • Branched Aramid Nanofibers
    • Authors: Jian Zhu; Ming Yang, Ahmet Emre, Joong Hwan Bahng, Lizhi Xu, Jihyeon Yeom, Bongjun Yeom, Yoonseob Kim, Kyle Johnson, Peter Green, Nicholas A. Kotov
      Pages: 11744 - 11748
      Abstract: Interconnectivity of components in three-dimensional networks (3DNs) is essential for stress transfer in hydrogels, aerogels, and composites. Entanglement of nanoscale components in the network relies on weak short-range intermolecular interactions. The intrinsic stiffness and rod-like geometry of nanoscale components limit the cohesive energy of the physical crosslinks in 3DN materials. Nature realizes networked gels differently using components with extensive branching. Branched aramid nanofibers (BANFs) mimicking polymeric components of biological gels were synthesized to produce 3DNs with high efficiency stress transfer. Individual BANFs are flexible, with the number of branches controlled by base strength in the hydrolysis process. The extensive connectivity of the BANFs allows them to form hydro- and aerogel monoliths with an order of magnitude less solid content than rod-like nanocomponents. Branching of nanofibers also leads to improved mechanics of gels and nanocomposites.Branching needed: The production of 3D networks with efficient stress transfer is enabled by branched aramid nanofibers (BANFs). The extensive connectivity of the BANFs leads to the formation of hydro- and aerogel monoliths with much less solid content than rod-like nanocomponents. The branching also leads to improved gel mechanics, allowing the preparation of continuous microscale luminescent fibers and high-performance nanocomposites.
      PubDate: 2017-08-18T05:06:01.894694-05:
      DOI: 10.1002/anie.201703766
  • An Esterase-Sensitive Prodrug Approach for Controllable Delivery of
           Persulfide Species
    • Authors: Yueqin Zheng; Bingchen Yu, Zhen Li, Zhengnan Yuan, Chelsea L. Organ, Rishi K. Trivedi, Siming Wang, David J. Lefer, Binghe Wang
      Pages: 11749 - 11753
      Abstract: A strategy to deliver a well-defined persulfide species in a biological medium is described. Under near physiological conditions, the persulfide prodrug can be activated by an esterase to generate a “hydroxymethyl persulfide” intermediate, which rapidly collapses to form a defined persulfide. Such persulfide prodrugs can be used either as chemical tools to study persulfide chemistry and biology or for future development as H2S-based therapeutic reagents. Using the persulfide prodrugs developed in this study, the reactivity between S-methyl methanethiosulfonate (MMTS) with persulfide was unambiguously demonstrated. Furthermore, a representative prodrug exhibited potent cardioprotective effects in a murine model of myocardial ischemia-reperfusion (MI/R) injury with a bell shape therapeutic profile.A strategy to deliver a well-defined persulfide species in a biological medium is described. Under near physiological conditions, a persulfide prodrug is activated by an esterase to generate a hydroxymethyl persulfide intermediate, which rapidly collapses to form a persulfide. Such prodrugs can be used to study persulfide chemistry and biology or for development as H2S-based therapeutic reagents.
      PubDate: 2017-08-16T07:45:31.381713-05:
      DOI: 10.1002/anie.201704117
  • Controlled Supramolecular Self-Assembly of Super-charged β-Lactoglobulin
           A–PEG Conjugates into Nanocapsules
    • Authors: Amit Kumar Khan; Sushanth Gudlur, Hans-Peter M. de Hoog, Winna Siti, Bo Liedberg, Madhavan Nallani
      Pages: 11754 - 11758
      Abstract: The synthesis and characterization of a new protein–polymer conjugate composed of β lactoglobulin A (βLG A) and poly(ethylene glycol) PEG is described. βLG A was selectively modified to self-assemble by super-charging via amination or succinylation followed by conjugation with PEG. An equimolar mixture of the oppositely charged protein–polymer conjugates self-assemble into spherical capsules of 80–100 nm in diameter. The self-assembly proceeds by taking simultaneous advantage of the amphiphilicity and polyelectrolyte nature of the protein–polymer conjugate. These protein–polymer capsules or proteinosomes are reminiscent of protein capsids, and are capable of encapsulating solutes in their interior. We envisage this approach to be applicable to other globular proteins.Super-charged self-assembly: The protein β lactoglobulin A (βLG A) was selectively modified to self-assemble by amination or succinylation followed by conjugation with poly(ethylene glycol) (PEG). An equimolar mixture of the oppositely charged protein–polymer conjugates self-assemble into spherical capsules of 80–100 nm in diameter.
      PubDate: 2017-08-17T08:45:58.671042-05:
      DOI: 10.1002/anie.201704298
  • Control of Redox Events by Dye Encapsulation Applied to Light-Driven
           Splitting of Hydrogen Sulfide
    • Authors: Xu Jing; Yang Yang, Cheng He, Zhiduo Chang, Joost N. H. Reek, Chunying Duan
      Pages: 11759 - 11763
      Abstract: Solar production of hydrogen by consuming low-value waste products is an attractive pathway that has both economic and environmental benefits. Inspired by the reactive pocket of enzymes, a synthetic platform to combine photocatalytic hydrogen evolution with sulfide oxidation in a one-pot process via control over the location of the electron-transfer steps is developed. The redox-active coordination vessel Ni-TFT, which has an octahedral pocket, encapsulates an organic dye to pre-organize for photocatalytic proton reduction via an oxidative quenching pathway using the nickel corners as catalysts, generating molecular hydrogen and the oxidized dye. The oxidized dye is displaced by a neutral dye and oxidizes sulfide once outside the pocket to give element sulfur. The overall reaction constitutes hydrogen sulfide splitting, forming molecular hydrogen and elemental sulfur, which is analogous to the water-splitting reaction.Split and run: A supramolecular cage that allows photocatalytic hydrogen evolution to be combined with sulfide oxidation in a one-pot process was developed through preorganization of the dye controlling the crucial electron-transfer steps. The overall reaction is hydrogen sulfide splitting to form molecular hydrogen and elemental sulfur, which is analogous to the water-splitting reaction.
      PubDate: 2017-08-16T09:02:06.739073-05:
      DOI: 10.1002/anie.201704327
  • Fractal MTW Zeolite Crystals: Hidden Dimensions in Nanoporous Materials
    • Authors: Lei Wang; Sheng-cai Zhu, Mei-kun Shen, Hai-wen Tian, Song-hai Xie, Hong-bin Zhang, Ya-hong Zhang, Yi Tang
      Pages: 11764 - 11768
      Abstract: Screw dislocation structures in crystals are an origin of symmetry breaking in a wide range of dense-phase crystals. Preparation of such analogous structures in framework-phase crystals is of great importance in zeolites but is still a challenge. On the basis of crystal-structure solving and model building, it was found that the two specific intergrowths in MTW zeolite produce this complex fractal and spiral structure. With the structurally determined parameters (spiral pitch h, screw angle θ, and spatial angle ψ) of Burgers circuit, the screw dislocation structure can be constructed by two different dimensional intergrowth sections. Thus the reported complexity of various dimensions in diverse crystals can be unified.Hunting hidden dimensions: It is revealed that the experimentally observed screw dislocation structure in MTW zeolite is constructed by two specific rational intergrowth processes along different dimensions.
      PubDate: 2017-08-17T05:56:52.803691-05:
      DOI: 10.1002/anie.201704499
  • Mechanochemistry Induced Using Force Exerted by a Functionalized
           Microscope Tip
    • Authors: Yajie Zhang; Yongfeng Wang, Jing-Tao Lü, Mads Brandbyge, Richard Berndt
      Pages: 11769 - 11773
      Abstract: Atomic-scale mechanochemistry is realized from force exerted by a C60-functionalized scanning tunneling microscope tip. Two conformers of tin phthalocyanine can be prepared on coinage-metal surfaces. A transition between these conformers is induced on Cu(111) and Ag(100). Density-functional calculations reveal details of this reaction. Because of the large energy barrier of the reaction and the strong interaction of SnPc with Cu(111), the process cannot be achieved by electrical means.Tipp off: Atomic-scale mechanochemistry is realized from a force exerted by a C60-functionalized scanning tunneling microscope tip. Two conformers of tin phthalocyanine can be prepared on coinage-metal surfaces. A transition between these conformers is induced on Cu(111) and Ag(100).
      PubDate: 2017-08-22T02:25:47.11611-05:0
      DOI: 10.1002/anie.201704940
  • A Crystalline π-Stack Containing Five Stereoisomers: Insights into
           Conformational Isomorphism, Chirality Inversion, and Disorder
    • Authors: Agnieszka Nowak-Król; Merle I. S. Röhr, David Schmidt, Frank Würthner
      Pages: 11774 - 11778
      Abstract: An unprecedented crystal-packing arrangement of a tetramethoxy-bay-substituted perylene bisimide (PBI) consists of three crystallographically independent molecules, that is, an achiral (AC) PBI of saddle-shaped geometry along with two pairs of propeller-like twisted (P)- and (M)-enantiomeric PBI frameworks. All these five conformations are observed within a single π-stack revealing an intriguing packing sequence with an inversion of chirality from P to M via AC. Nudged elastic band calculations for the isolated molecule show that AC is a local minimum of the P to M interconversion path. In addition, two minor conformations were observed in the crystal, one of which resembles a transition-state molecule. Theoretical studies of dimeric and trimeric stacks reveal that the coexistence of all these structures in the crystal lattice is aided by the strong dispersion interactions between PBI cores and perfectly interdigitated dodecyl chains which stabilize energetically higher conformations.From hand to hand: A unique crystal-packing arrangement of bay-substituted perylene bisimide consists of propeller-like twisted and achiral stereoisomers. All the conformations are assembled in a single regular π-stack showing an inversion of chirality from P to M via an achiral molecule. Coexistence of these conformations in the crystal lattice is attributed to the strong dispersion forces.
      PubDate: 2017-08-18T04:05:38.276484-05:
      DOI: 10.1002/anie.201705445
  • NOAH: NMR Supersequences for Small Molecule Analysis and Structure
    • Authors: Ēriks Kupče; Tim D. W. Claridge
      Pages: 11779 - 11783
      Abstract: Nested NMR experiments combining up to five conventional NMR pulse sequences into one supersequence are introduced. The core 2D NMR techniques routinely employed in small molecule NMR spectroscopy, such as HSQC, HMQC, HMBC, COSY, NOESY, TOCSY, and similar, can be recorded in a single measurement. In this way the data collection time may be dramatically reduced and sample throughput increased for basic NMR applications, such as structure elucidation and verification in synthetic, medicinal, and natural product chemistry.NOAH's Ark: The nesting of up to five conventional NMR pulse sequences into one “NOAH supersequence”, employing only a single recovery delay, saves a significant amount of time during data collection for the analysis of small molecules. These experiments do not require specialist spectrometer hardware.
      PubDate: 2017-08-18T04:05:29.323715-05:
      DOI: 10.1002/anie.201705506
  • Enzymatic Synthesis of Homogeneous Chondroitin Sulfate Oligosaccharides
    • Authors: Jine Li; Guowei Su, Jian Liu
      Pages: 11784 - 11787
      Abstract: Chondroitin sulfate (CS) is a sulfated polysaccharide that plays essential physiological roles. Here, we report an enzyme-based method for the synthesis of a library of 15 different CS oligosaccharides. This library covers 4-O-sulfated and 6-O-sulfated oligosaccharides ranging from trisaccharides to nonasaccharides. We also describe the synthesis of unnatural 6-O-sulfated CS pentasaccharides containing either a 6-O-sulfo-2-azidogalactosamine or a 6-O-sulfogalactosamine residue. The availability of structurally defined CS oligosaccharides offers a novel approach to investigate the biological functions of CS.In large numbers: An enzyme-based method enabled the synthesis of 15 chondroitin sulfate (CS) oligosaccharides. This library covers 4-O- and 6-O-sulfated oligosaccharides ranging from trisaccharides to nonasaccharides. Unnatural 6-O-sulfated CS pentasaccharides containing either a 6-O-sulfo-2-azidogalactosamine or a 6-O-sulfogalactosamine residue were also synthesized.
      PubDate: 2017-08-17T07:02:54.635544-05:
      DOI: 10.1002/anie.201705638
  • In Situ Localization of Enzyme Activity in Live Cells by a Molecular Probe
           Releasing a Precipitating Fluorochrome
    • Authors: Hong-Wen Liu; Ke Li, Xiao-Xiao Hu, Longmin Zhu, Qiming Rong, Yongchao Liu, Xiao-Bing Zhang, Jens Hasserodt, Feng-Li Qu, Weihong Tan
      Pages: 11788 - 11792
      Abstract: Current enzyme-responsive, fluorogenic probes fail to provide in situ information because the released fluorophores tend to diffuse away from the reaction sites. The problem of diffusive signal dilution can be addressed by designing a probe that upon enzyme conversion releases a fluorophore that precipitates. An excited-state intramolecular proton transfer (ESIPT)-based solid-state fluorophore HTPQ was developed that is strictly insoluble in water and emits intense fluorescence in the solid state, with λex/em=410/550 nm, thus making it far better suited to use with a commercial confocal microscope. HTPQ was further utilized in the design of an enzyme-responsive, fluorogenic probe (HTPQA), targeting alkaline phosphatase (ALP) as a model enzyme. HTPQA makes possible diffusion-resistant in situ detection of endogenous ALP in live cells. It was also employed in the visualizing of different levels of ALP in osteosarcoma cells and tissue, thus demonstrating its interest for the diagnosis of this type of cancer.A solid-state fluorophore (HTPQ) that is well-suited to confocal microscopy was developed. HTPQ was used to design an enzyme-responsive, fluorogenic probe (HTPQA) targeting alkaline phosphatase (ALP) as a model enzyme. HTPQA makes possible diffusion-resistant detection of endogenous ALP in live cells and visualization of ALP levels in Saos-2 and U-2OS osteosarcoma cells and tissue.
      PubDate: 2017-08-15T02:12:06.751731-05:
      DOI: 10.1002/anie.201705747
  • A Highly Efficient Chemiluminescence Probe for the Detection of Singlet
           Oxygen in Living Cells
    • Authors: Nir Hananya; Ori Green, Rachel Blau, Ronit Satchi-Fainaro, Doron Shabat
      Pages: 11793 - 11796
      Abstract: Singlet oxygen is among the reactive oxygen species (ROS) with the shortest life-times in aqueous media because of its extremely high reactivity. Therefore, designing sensors for detection of 1O2 is perhaps one of the most challenging tasks in the field of molecular probes. Herein, we report a highly selective and sensitive chemiluminescence probe (SOCL-CPP) for the detection of 1O2 in living cells. The probe reacts with 1O2 to form a dioxetane that spontaneously decomposes under physiological conditions through a chemiexcitation pathway to emit green light with extraordinary intensity. SOCL-CPP demonstrated promising ability to detect and image intracellular 1O2 produced by a photosensitizer in HeLa cells during photodynamic therapy (PDT) mode of action. Our findings make SOCL-CPP the most effective known chemiluminescence probe for the detection of 1O2. We anticipate that our chemiluminescence probe for 1O2 imaging would be useful in PDT-related applications and for monitoring 1O2 endogenously generated by cells in response to different stimuli.Illuminating singlet oxygen: A chemiluminescence probe for singlet oxygen based on dioxetane formation is described. The dioxetane decomposes through a highly efficient chemiexcitation process to emit green light. The probe was used to detect and image intracellular 1O2 produced by a photosensitizer in HeLa cells during photodynamic therapy.
      PubDate: 2017-08-16T02:30:42.975679-05:
      DOI: 10.1002/anie.201705803
  • Asymmetric Synthesis of α,α-Disubstituted Allylic Amines through
           Palladium-Catalyzed Allylic Substitution
    • Authors: Wusheng Guo; Aijie Cai, Jianing Xie, Arjan W. Kleij
      Pages: 11797 - 11801
      Abstract: The first asymmetric synthesis of important α,α-disubstituted N-alkyl allyl amine scaffolds through allylic substitution is reported. This approach is based on palladium catalysis and features ample scope with respect to both the allylic precursor and amine reagent, and high asymmetric induction with enantiomeric ratios (e.r.) up to 98.5:1.5. The use of less-reactive anilines is also feasible, providing enantioenriched α,α-disubstituted N-aryl allylic amines.Take a walk on the wide side: The first asymmetric synthesis of invaluable α,α-disubstituted N-alkyl allylic amines was developed using an allylic substitution approach. The catalytic method relies on Pd catalysis, is user-friendly, and can be accomplished under mild and additive-free conditions. The wide product scope for these challenging allylic amine scaffolds is the most impressive reported to date, with e.r. values of up to 98.5:1.5.
      PubDate: 2017-08-23T12:38:23.445602-05:
      DOI: 10.1002/anie.201705825
  • Ultrathin Cell-Membrane-Mimic Phosphorylcholine Polymer Film Coating
           Enables Large Improvements for In Vivo Electrochemical Detection
    • Authors: Xiaomeng Liu; Tongfang Xiao, Fei Wu, Mo-Yuan Shen, Meining Zhang, Hsiao-hua Yu, Lanqun Mao
      Pages: 11802 - 11806
      Abstract: Resisting biomolecule adsorption onto the surface of brain-implanted microelectrodes is a key issue for in vivo monitoring of neurochemicals. Herein, we demonstrate that an ultrathin cell-membrane-mimic film of ethylenedioxythiophene tailored with zwitterionic phosphorylcholine (EDOT-PC) electropolymerized onto the surface of a carbon fiber microelectrode (CFE) not only resists protein adsorption but also maintains the sensitivity and time response for in vivo monitoring of dopamine (DA). As a consequence, the as-prepared PEDOT-PC/CFEs could be used as a new reliable platform for tracking DA in vivo and would help understand the physiological and pathological functions of DA.Time to measure your dopamine levels, Pinky: An ultrathin cell-membrane-mimic film of ethylenedioxythiophene tailored with a zwitterionic phosphorylcholine (EDOT-PC) electropolymerized onto the surface of a carbon fiber microelectrode (CFE) was found to not only resist protein adsorption but also maintain sensitivity and temporal resolution for the in vivo monitoring of dopamine (DA).
      PubDate: 2017-08-21T07:35:26.185654-05:
      DOI: 10.1002/anie.201705900
  • Nucleophilic Amination of Methoxy Arenes Promoted by a Sodium
           Hydride/Iodide Composite
    • Authors: Atsushi Kaga; Hirohito Hayashi, Hiroyuki Hakamata, Miku Oi, Masanobu Uchiyama, Ryo Takita, Shunsuke Chiba
      Pages: 11807 - 11811
      Abstract: A method for the nucleophilic amination of methoxy arenes was established by using sodium hydride (NaH) in the presence of lithium iodide (LiI). This method offers an efficient route to benzannulated nitrogen heterocycles. Mechanistic studies showed that the reaction proceeds through an unusual concerted nucleophilic aromatic substitution.Come full circle: A method for the nucleophilic amination of methoxy arenes was established by using sodium hydride (NaH) in the presence of lithium iodide (LiI). This method offers an efficient route to benzannulated nitrogen heterocycles. Mechanistic studies showed that the reaction proceeds through an unusual concerted nucleophilic aromatic substitution.
      PubDate: 2017-08-16T09:02:36.681662-05:
      DOI: 10.1002/anie.201705916
  • Pot Economy in the Total Synthesis of Estradiol Methyl Ether by Using an
    • Authors: Yujiro Hayashi; Seitaro Koshino, Kanna Ojima, Eunsang Kwon
      Pages: 11812 - 11815
      Abstract: Enantioselective total synthesis of estradiol methyl ether has been accomplished in a pot-economical manner using five reaction vessels and four purifications. The key reaction is a diphenylprolinol silyl ether mediated domino Michael/aldol reaction to afford bicyclo[4.3.0]nonane derivatives, containing the A, C, and D rings of steroids, as a single isomer with excellent enantioselectivity. Six reactions such as oxidation, hydrogenation, formation of acid chloride, Friedel–Crafts reaction, deprotection, and reduction can be carried out in the last one-pot sequence.Pot luck: Estradiol methyl ether was synthesized using only five reaction vessels and four purification steps. The key step involved a diphenylprolinol silyl ether mediated Michael reaction. The last one-pot sequence of the reaction involves six reactions, and highlights the pot-economical aspect of the synthesis. TMS=trimethylsilyl.
      PubDate: 2017-08-21T07:30:44.392745-05:
      DOI: 10.1002/anie.201706046
  • A Suite of “Minimalist” Photo-Crosslinkers for Live-Cell Imaging and
           Chemical Proteomics: Case Study with BRD4 Inhibitors
    • Authors: Sijun Pan; Se-Young Jang, Danyang Wang, Si Si Liew, Zhengqiu Li, Jun-Seok Lee, Shao Q. Yao
      Pages: 11816 - 11821
      Abstract: Affinity-based probes (AfBPs) provide a powerful tool for large-scale chemoproteomic studies of drug–target interactions. The development of high-quality probes capable of recapitulating genuine drug–target engagement, however, could be challenging. “Minimalist” photo-crosslinkers, which contain an alkyl diazirine group and a chemically tractable tag, could alleviate such challenges, but few are currently available. Herein, we have developed new alkyl diazirine-containing photo-crosslinkers with different bioorthogonal tags. They were subsequently used to create a suite of AfBPs based on GW841819X (a small molecule inhibitor of BRD4). Through in vitro and in situ studies under conditions that emulated native drug–target interactions, we have obtained better insights into how a tag might affect the probe's performance. Finally, SILAC-based chemoproteomic studies have led to the discovery of a novel off-target, APEX1. Further studies showed GW841819X binds to APEX1 and caused up-regulation of endogenous DNMT1 expression under normoxia conditions.Tagging for more: New “minimalist” alkyl diazirine-containing photo-crosslinkers with different bioorthogonal tags were developed and used to create a suite of affinity-based probes (AfBPs) based on a known small-molecule inhibitor of BRD4.
      PubDate: 2017-08-25T05:22:25.893944-05:
      DOI: 10.1002/anie.201706076
  • Shaping Antiaromatic π-Systems by Metalation: Synthesis of a Bowl-Shaped
           Antiaromatic Palladium Norcorrole
    • Authors: Tsubasa Yonezawa; Siham A. Shafie, Satoru Hiroto, Hiroshi Shinokubo
      Pages: 11822 - 11825
      Abstract: The synthesis of a bowl-shaped antiaromatic molecule was achieved through the deformation of a planar antiaromatic porphyrinic π-conjugation system by insertion of palladium into the small cavity of a metal-free norcorrole. The bowl-to-bowl inversion dynamics of the antiaromatic Pd-coordinated norcorrole was determined by variable-temperature 1H NMR spectroscopy. The metal-free norcorrole was prepared from acid-induced demetalation of a copper norcorrole, which was obtained from the intramolecular coupling of a bis(diiododipyrrin) copper complex with copper thiophenecarboxylate.A bowl-shaped antiaromatic molecule was synthesized by deformation of a planar antiaromatic π-conjugation system upon insertion of palladium into the small cavity of a metal-free norcorrole. The latter was prepared through demetalation of a copper norcorrole obtained from the intramolecular coupling of a bis(diiododipyrrin) copper complex with copper thiophenecarboxylate.
      PubDate: 2017-08-16T02:31:30.843928-05:
      DOI: 10.1002/anie.201706134
  • An Ionophore-Based Anion-Selective Optode Printed on Cellulose Paper
    • Authors: Xuewei Wang; Qi Zhang, Changwoo Nam, Michael Hickner, Mollie Mahoney, Mark E. Meyerhoff
      Pages: 11826 - 11830
      Abstract: A general anion-sensing platform is reported based on a portable and cost-effective ion-selective optode and a smartphone detector equipped with a color analysis app. In contrast to traditional anion-selective optodes using a hydrophobic polymer and/or plasticizer to dissolve hydrophobic sensing elements, the new optode relies on hydrophilic cellulose paper. The anion ionophore and a lipophilic pH indicator are inkjet-printed and adsorbed on paper and form a “dry” hydrophobic sensing layer. Porous cellulose sheets also allow the sensing site to be modified with dried buffer that prevents any sample pH dependence of the observed color change. A highly selective fluoride optode using an AlIII-porphyrin ionophore is examined as an initial example of this new anion sensing platform for measurements of fluoride levels in drinking water samples. Apart from Lewis acid–base recognition, hydrogen bonding recognition is also compatible with this sensing platform.Cellulose paper as a sole substrate allows adsorption of a lipophilic anion ionophore and pH-sensitive indicator dye to enable heterogeneous anion sensing via an anion-proton co-extraction mechanism. This platform also enables adsorption of a buffer salt as the sample pH adjuster to prevent pH dependence of the optical anion response.
      PubDate: 2017-08-16T02:31:35.418434-05:
      DOI: 10.1002/anie.201706147
  • Directing the Activation of Donor–Acceptor Cyclopropanes Towards
           Stereoselective 1,3-Dipolar Cycloaddition Reactions by Brønsted Base
    • Authors: Jakob Blom; Andreu Vidal-Albalat, Julie Jørgensen, Casper L. Barløse, Kamilla S. Jessen, Marc V. Iversen, Karl Anker Jørgensen
      Pages: 11831 - 11835
      Abstract: The first stereoselective organocatalyzed [3+2] cycloaddition reaction of donor-acceptor cyclopropanes is presented. It is demonstrated that by applying an optically active bifunctional Brønsted base catalyst, racemic di-cyano cyclopropylketones can be activated to undergo a stereoselective 1,3-dipolar reaction with mono- and polysubstituted nitroolefins. The reaction affords functionalized cyclopentanes with three consecutive stereocenters in high yield and stereoselectivity. Based on the stereochemical outcome, a mechanism in which the organocatalyst activates both the donor-acceptor cyclopropane and nitroolefin is proposed. Finally, chemoselective transformations of the cycloaddition products are demonstrated.Polar ends: The first stereoselective organocatalyzed [3+2] cycloaddition reaction of donor-acceptor cyclopropanes is presented. By using an optically active bifunctional Brønsted base catalyst, racemic di-cyano cyclopropylketones can be activated to undergo a stereoselective 1,3-dipolar reaction with mono- and polysubstituted nitroolefins. The reaction affords functionalized cyclopentanes with three contiguous stereocenters in high yield and stereoselectivity.
      PubDate: 2017-08-16T02:26:17.009625-05:
      DOI: 10.1002/anie.201706150
  • Large-Scale Syntheses of Zinc Sulfide⋅(Diethylenetriamine)0.5 Hybrids as
           Precursors for Sulfur Nanocomposite Cathodes
    • Authors: Tao Ma; Fei Zhou, Tian-Wen Zhang, Hong-Bin Yao, Ting-Yu Su, Zhi-Long Yu, Yi Li, Lei-Lei Lu, Shu-Hong Yu
      Pages: 11836 - 11840
      Abstract: Nanostructured metal sulfide–amine hybrid materials have attracted attention because of their unique properties and versatility as precursors for functional inorganic nanomaterials. However, large-scale synthesis of metal sulfide–amine hybrid nanomaterials is limited by hydrothermal and solvothermal preparative reaction conditions; consequently, incorporation of such materials into functional nanomaterials is hindered. An amine molecule-assisted refluxing method was used to synthesize highly uniform zinc sulfide⋅(diethylenetriamine)0.5 (ZnS⋅(DETA)0.5) hybrid nanosheets and nanobelts in a large scale. The obtained ZnS⋅(DETA)0.5 hybrid nanomaterials can be used as efficient precursors to fabricate functional ZnS nanomaterials and carbon encapsulated sulfur (S@C) nanocomposite cathodes for Li–S batteries.Semiconducting hybrid nanomaterials for sulfur nanocomposite cathodes were prepared by an amine molecule-assisted refluxing technique. Uniform zinc sulfide⋅(diethylenetriamine)0.5 hybrid nanomaterials were synthesized in a 15 g yield per one-pot reaction. The material was used to fabricate functional zinc sulfide nanomaterials and encapsulated sulfur nanocomposites.
      PubDate: 2017-08-04T06:16:05.285951-05:
      DOI: 10.1002/anie.201706199
  • RadH: A Versatile Halogenase for Integration into Synthetic Pathways
    • Authors: Binuraj R. K. Menon; Eileen Brandenburger, Humera H. Sharif, Ulrike Klemstein, Sarah A. Shepherd, Michael F. Greaney, Jason Micklefield
      Pages: 11841 - 11845
      Abstract: Flavin-dependent halogenases are useful enzymes for providing halogenated molecules with improved biological activity, or intermediates for synthetic derivatization. We demonstrate how the fungal halogenase RadH can be used to regioselectively halogenate a range of bioactive aromatic scaffolds. Site-directed mutagenesis of RadH was used to identify catalytic residues and provide insight into the mechanism of fungal halogenases. A high-throughput fluorescence screen was also developed, which enabled a RadH mutant to be evolved with improved properties. Finally we demonstrate how biosynthetic genes from fungi, bacteria, and plants can be combined to encode a new pathway to generate a novel chlorinated coumarin “non-natural” product in E. coli.Unnatural high: The fungal halogenase RadH regioselectively halogenates a range of bioactive scaffolds. Structure-guided mutagenesis provided insight into the selectivity and mechanism of RadH and related halogenases. A high-throughput fluorescence screen was developed to evolve a RadH mutant with improved activity. The improved RadH was assembled with other enzymes from diverse origins in E. coli to create a novel chlorinated “non-natural” product.
      PubDate: 2017-08-18T06:06:17.633024-05:
      DOI: 10.1002/anie.201706342
  • Synthesis of a Doubly Boron-Doped Perylene through NHC-Borenium
           Hydroboration/C−H Borylation/Dehydrogenation
    • Authors: Jeffrey M. Farrell; David Schmidt, Vincenzo Grande, Frank Würthner
      Pages: 11846 - 11850
      Abstract: Reaction of an N-heterocyclic carbene (NHC)–borenium ion with 9,10-distyrylanthracene forms four B−C bonds through two selective, tandem hydroboration–electrophilic C−H borylations to yield an isolable, crystallographically characterizable polycyclic diborenium ion as its [NTf2]− salt (1). Dehydrogenation of 1 with TEMPO radical followed by acidic workup yields a 3,9-diboraperylene as its corresponding borinic acid (2). This sequence can be performed in one pot to allow the facile, metal-free conversion of an alkene into a small molecule containing a boron-doped graphene substructure. Doubly boron-doped perylene 2 exhibits visible range absorbance and fluorescence in chloroform solution (Φ=0.63) and undergoes two reversible one-electron reductions at moderate potentials of −1.30 and −1.64 eV vs. ferrocenium/ferrocene in DMSO. Despite sterically accessible boron centers and facile electrochemical reductions, compound 2 is air-, moisture-, and silica gel-stable.Keen to B graphene: A one-pot strategy is used to convert an unfunctionalized alkene into a stable, electron-deficient, doubly boron-doped perylene. Key to this strategy is a highly selective sequence of N-heterocyclic carbene (NHC)-borenium hydroborations and electrophilic C−H borylations. The synthetic strategy presented herein is a new, direct, facile and complimentary approach to B-doped graphene substructures.
      PubDate: 2017-08-18T01:26:05.758909-05:
      DOI: 10.1002/anie.201706346
  • Efficient Photoelectrochemical Reduction of Carbon Dioxide to Formic Acid:
           A Functionalized Ionic Liquid as an Absorbent and Electrolyte
    • Authors: Weiwei Lu; Bo Jia, Beilei Cui, Yuan Zhang, Kaisheng Yao, Yuling Zhao, Jianji Wang
      Pages: 11851 - 11854
      Abstract: Photoelectrochemical (PEC) reduction of carbon dioxide (CO2) is a potential method for production of fuels and chemicals from a C1 feedstock accumulated in the atmosphere. However, the low solubility of CO2 in water, and complicated processes associated with capture and conversion, render CO2 conversion inefficient. A new concept is proposed in which a PEC system is used to capture and convert CO2 into formic acid. The process is assisted by an ionic liquid (1-aminopropyl-3-methylimidazolium bromide) aqueous solution, which functions as an absorbent and electrolyte at ambient temperature and pressure. Within this PEC reduction strategy, the ionic liquid plays a critical role in promoting the conversion of CO2 to formic acid and suppressing the reduction of H2O to H2. At an applied voltage of 1.7 V, the Faradaic efficiency for formic acid production is as high as 94.1 % and the electro-to-chemical efficiency is 86.2 %.Capture and conversion: A functionalized ionic liquid (IL) was used as an absorbent and electrolyte in photoelectrocatalytic reduction of CO2. The IL was critical for promoting conversion of CO2 to formic acid (FA) and suppressing reduction of H2O to H2. A 94.1 % faradaic efficiency and 86.2 % electro-to-chemical efficiency were achieved at 1.7 V for FA production. PEM=proton exchange membrane.
      PubDate: 2017-08-18T01:21:20.343643-05:
      DOI: 10.1002/anie.201703977
  • Structural Revision and Biomimetic Synthesis of Goupiolone B
    • Authors: Yosuke Matsuo; Ayane Yoshida, Yoshinori Saito, Takashi Tanaka
      Pages: 11855 - 11859
      Abstract: Goupiolones A and B are unique phenolic compounds with significant DNA-damaging activity. In this study, the structure of goupiolone B was revised on the basis of DFT calculations of the 13C NMR chemical shifts and biosynthetic considerations. The dibenzobicyclo[3.2.2]nonane skeleton of the revised structure suggested that goupiolone B was produced by oxidative coupling between catechol and goupiolone A, which was strongly supported by biomimetic synthesis. Furthermore, racemization of goupiolone B was observed during the attempted resolution of its racemic mixture. A plausible racemization mechanism involving α-ketol rearrangement is proposed.Which one is real' Goupiolones A and B are unique phenolic compounds with DNA-damaging activity. The structure of goupiolone B has now been revised on the basis of DFT calculations of 13C NMR chemical shifts and biosynthetic considerations. The dibenzobicyclo[3.2.2]nonane skeleton of the revised structure suggests that goupiolone B is produced by oxidative coupling between catechol and goupiolone A (see scheme).
      PubDate: 2017-08-18T01:21:10.527747-05:
      DOI: 10.1002/anie.201706532
  • Macroscopic Polarization Enhancement Promoting Photo- and
           Piezoelectric-Induced Charge Separation and Molecular Oxygen Activation
    • Authors: Hongwei Huang; Shuchen Tu, Chao Zeng, Tierui Zhang, Ali H. Reshak, Yihe Zhang
      Pages: 11860 - 11864
      Abstract: Efficient photo- and piezoelectric-induced molecular oxygen activation are both achieved by macroscopic polarization enhancement on a noncentrosymmetric piezoelectric semiconductor BiOIO3. The replacement of V5+ ions for I5+ in IO3 polyhedra gives rise to strengthened macroscopic polarization of BiOIO3, which facilitates the charge separation in the photocatalytic and piezoelectric catalytic process, and renders largely promoted photo- and piezoelectric induced reactive oxygen species (ROS) evolution, such as superoxide radicals (.O2−) and hydroxyl radicals (.OH). This work advances piezoelectricity as a new route to efficient ROS generation, and also discloses macroscopic polarization engineering on improvement of multi-responsive catalysis.Macroscopic polarization enhancement by V5+ replacement in the piezoelectric semiconductor BiOIO3 can greatly facilitate charge separation and provide efficient photo- and piezoelectric-induced molecular oxygen activation. Powerful superoxide and hydroxyl radicals can be thereby produced in abundance.
      PubDate: 2017-08-16T03:51:03.805757-05:
      DOI: 10.1002/anie.201706549
  • Unified Total Synthesis of Polyoxins J, L, and Fluorinated Analogues on
           the Basis of Decarbonylative Radical Coupling Reactions
    • Authors: Haruka Fujino; Masanori Nagatomo, Atmika Paudel, Suresh Panthee, Hiroshi Hamamoto, Kazuhisa Sekimizu, Masayuki Inoue
      Pages: 11865 - 11869
      Abstract: Polyoxins J (1 a) and L (1 b) are important nucleoside antibiotics. The complex and densely functionalized dipeptide structures of 1 a and 1 b contain thymine and uracil nucleobases, respectively. Herein we report the unified total synthesis of 1 a, 1 b, and their artificial analogues 1 c and 1 d with trifluorothymine and fluorouracil structures. Decarbonylative radical coupling between α-alkoxyacyl tellurides and a chiral glyoxylic oxime ether led to chemo- and stereoselective construction of the ribonucleoside α-amino acid structures of 1 a–d without damaging the preinstalled nucleobases. The high applicability of the radical-based methodology was further demonstrated by preparation of the trihydroxynorvaline moiety of 1 a–d. The two amino acid fragments were connected and elaborated into 1 a–d (longest linear sequence: 11 steps). Compounds 1 a and 1 b assembled in this way exhibited potent activity against true fungi, while only 1 d was active against Gram-positive bacteria.On the double: The important nucleoside antibiotics polyoxins J and L were synthesized along with two fluorinated analogues by a newly developed radical-based strategy that enabled rapid assembly of the four polyoxins in a unified fashion. Preliminary biological evaluation show the distinct antimicrobial spectra of the synthesized polyoxins.
      PubDate: 2017-08-17T08:12:32.358744-05:
      DOI: 10.1002/anie.201706671
  • Nickel-Catalyzed Enantioselective Conjunctive Cross-Coupling of 9-BBN
    • Authors: Matteo Chierchia; Chunyin Law, James P. Morken
      Pages: 11870 - 11874
      Abstract: Catalytic enantioselective conjunctive cross-coupling between 9-BBN borate complexes and aryl electrophiles can be accomplished with Ni salts in the presence of a chiral diamine ligand. The reactions furnish chiral 9-BBN derivatives in an enantioselective fashion and these are converted to chiral alcohols and amines, or engaged in other stereospecific C−C bond forming reactions.Conjunctive coupling: Ni-Catalyzed conjunctive couplings furnish chiral 9-BBN derivatives in an enantioselective fashion and these are converted to chiral alcohols and amines, or they can be engaged in other stereospecific C−C bond forming reactions.
      PubDate: 2017-08-17T07:08:36.19908-05:0
      DOI: 10.1002/anie.201706719
  • Forging Fluorine-Containing Quaternary Stereocenters by a Light-Driven
           Organocatalytic Aldol Desymmetrization Process
    • Authors: Sara Cuadros; Luca Dell'Amico, Paolo Melchiorre
      Pages: 11875 - 11879
      Abstract: Reported herein is a light-triggered organocatalytic strategy for the desymmetrization of achiral 2-fluoro-substituted cyclopentane-1,3-diketones. The chemistry is based on an intermolecular aldol reaction of photochemically generated hydroxy-o-quinodimethanes and simultaneously forges two adjacent fully substituted carbon stereocenters, with one bearing a stereogenic carbon–fluorine unit. The method uses readily available substrates, a simple chiral organocatalyst, and mild reaction conditions to afford an array of highly functionalized chiral 2-fluoro-3-hydroxycyclopentanones.Symmetry-breaking! The desymmetrization of achiral 2-fluoro-substituted cyclopentane-1,3-diketones (1) leads to the stereoselective construction of valuable fluorine-containing quaternary stereocenters. The chemistry exploits the ability of a readily available amido-thiourea catalyst to selectively activate one of the enantiotopic carbonyl groups within 1 and promote an intermolecular aldol reaction of hydroxy-o-quinodimethanes, which are photochemically generated from 2.
      PubDate: 2017-08-18T04:10:47.144041-05:
      DOI: 10.1002/anie.201706763
  • A Simple Route to Calcium and Strontium Hydride Clusters
    • Authors: Brant Maitland; Michael Wiesinger, Jens Langer, Gerd Ballmann, Jürgen Pahl, Holger Elsen, Christian Färber, Sjoerd Harder
      Pages: 11880 - 11884
      Abstract: The first strontium hydride complex has been obtained by simply treating Sr[N(SiMe3)2]2 with PhSiH3 in the presence of PMDTA. The Sr complex Sr6H9[N(SiMe3)2]3⋅(PMDTA)3 crystallizes as an “inverse cryptand”: an interstitial H− is surrounded by a Sr6H84+ cage decorated with amide and PMDTA ligands. The analogous Ca complex could also be obtained and both retain their solid-state structures in solution: 1H NMR spectra in C6D6 show two doublets and one nonet (4:4:1). Up to 90 °C, no coalescence is observed. The Ca cluster was investigated by DFT calculations and shows atypically low charges on Ca (+1.14) and H (−0.59) which signifies an unexpectedly low ionicity. AIM analysis shows hydride⋅⋅⋅hydride bond paths with considerable electron densities in the bond critical point. The clusters thermally decompose into larger, undefined, metal hydride aggregates.Hydride Sr. The first strontium hydride complex has been prepared by a surprisingly simple reaction. The cluster consists of an interstitial hydride, surrounded by an Sr6 octahedron that has eight hydrides capping its faces and is decorated with ligands. Together with its calcium analogue these clusters can be seen as “inverse cryptands”. 1H NMR spectroscopy shows hydride⋅⋅⋅hydride magnetic coupling.
      PubDate: 2017-08-23T12:37:27.274617-05:
      DOI: 10.1002/anie.201706786
  • The Effect of Additives on the Early Stages of Growth of Calcite Single
    • Authors: Yi-Yeoun Kim; Colin L. Freeman, Xiuqing Gong, Mark A. Levenstein, Yunwei Wang, Alexander Kulak, Clara Anduix-Canto, Phillip A. Lee, Shunbo Li, Li Chen, Hugo K. Christenson, Fiona C. Meldrum
      Pages: 11885 - 11890
      Abstract: As crystallization processes are often rapid, it can be difficult to monitor their growth mechanisms. In this study, we made use of the fact that crystallization proceeds more slowly in small volumes than in bulk solution to investigate the effects of the soluble additives Mg2+ and poly(styrene sulfonate) (PSS) on the early stages of growth of calcite crystals. Using a “Crystal Hotel” microfluidic device to provide well-defined, nanoliter volumes, we observed that calcite crystals form via an amorphous precursor phase. Surprisingly, the first calcite crystals formed are perfect rhombohedra, and the soluble additives have no influence on the morphology until the crystals reach sizes of 0.1–0.5 μm for Mg2+ and 1–2 μm for PSS. The crystals then continue to grow to develop morphologies characteristic of these additives. These results can be rationalized by considering additive binding to kink sites, which is consistent with crystal growth by a classical mechanism.Rooms for crystals: By precipitating calcite crystals within confined volumes, where growth proceeds more slowly, in a “Crystal Hotel”, it is shown that additives only affect the shape of the crystals once they have reached sizes of at least 100 nm. As a crystal grows, the density of specific surface (kink) sites to which the additives bind increases. Changes in the crystal shape will only become evident when this density is high enough.
      PubDate: 2017-08-18T06:06:31.215092-05:
      DOI: 10.1002/anie.201706800
  • Enantioselective Crossed Photocycloadditions of Styrenic Olefins by Lewis
           Acid Catalyzed Triplet Sensitization
    • Authors: Zachary D. Miller; Byung Joo Lee, Tehshik P. Yoon
      Pages: 11891 - 11895
      Abstract: The synthesis of unsymmetrical cyclobutanes by controlled heterodimerization of olefins remains a substantial challenge, particularly in an enantiocontrolled fashion. Shown herein is that chiral Lewis acid catalyzed triplet sensitization enables the synthesis of highly enantioenriched diarylcyclobutanes by photocycloaddition of structurally varied 2′-hydroxychalcones with a range of styrene coupling partners. The utility of this reaction is demonstrated through the direct synthesis of a representative norlignan cyclobutane natural product.Cross-products: Lewis acid catalyzed triplet sensitization enables the highly enantioselective crossed cycloaddition of chalcones and styrenes to forge cyclobutane cores. These cores are found in multiple bioactive natural products.
      PubDate: 2017-08-30T11:09:10.346451-05:
      DOI: 10.1002/anie.201706975
  • Antimonene Quantum Dots: Synthesis and Application as Near-Infrared
           Photothermal Agents for Effective Cancer Therapy
    • Authors: Wei Tao; Xiaoyuan Ji, Xiaoding Xu, Mohammad Ariful Islam, Zhongjun Li, Si Chen, Phei Er Saw, Han Zhang, Zameer Bharwani, Zilei Guo, Jinjun Shi, Omid C. Farokhzad
      Pages: 11896 - 11900
      Abstract: Photothermal therapy (PTT) has shown significant potential for cancer therapy. However, developing nanomaterials (NMs)-based photothermal agents (PTAs) with satisfactory photothermal conversion efficacy (PTCE) and biocompatibility remains a key challenge. Herein, a new generation of PTAs based on two-dimensional (2D) antimonene quantum dots (AMQDs) was developed by a novel liquid exfoliation method. Surface modification of AMQDs with polyethylene glycol (PEG) significantly enhanced both biocompatibility and stability in physiological medium. The PEG-coated AMQDs showed a PTCE of 45.5 %, which is higher than many other NMs-based PTAs such as graphene, Au, MoS2, and black phosphorus (BP). The AMQDs-based PTAs also exhibited a unique feature of NIR-induced rapid degradability. Through both in vitro and in vivo studies, the PEG-coated AMQDs demonstrated notable NIR-induced tumor ablation ability. This work is expected to expand the utility of 2D antimonene (AM) to biomedical applications through the development of an entirely novel PTA platform.Antimonene quantum dots (AMQDs) were synthesized through a liquid exfoliation method. The poly(ethylene glycol)-coated AMQDs were shown to have high photothermal conversion efficiency (45.5 %), near-infrared-induced degradability, and biocompatibility, making them a new generation of ideal photothermal agents for effective cancer treatment. The study opens up an exciting and novel research direction of AM for biomedical applications.
      PubDate: 2017-07-17T06:25:33.24265-05:0
      DOI: 10.1002/anie.201703657
  • Reductive Decarboxylative Alkynylation of N-Hydroxyphthalimide Esters with
    • Authors: Liangbin Huang; Astrid M. Olivares, Daniel J. Weix
      Pages: 11901 - 11905
      Abstract: A new method for the synthesis of terminal and internal alkynes from the nickel-catalyzed decarboxylative coupling of N-hydroxyphthalimide esters and bromoalkynes is presented. This reductive cross-electrophile coupling is the first to use a C(sp)−X electrophile, and appears to proceed via an alkynylnickel intermediate. The internal alkyne products are obtained in yields of 41–95 % without the need for a photocatalyst, light, or a strong oxidant. The reaction displays a broad scope of carboxylic acid and alkyne coupling partners, and can tolerate an array of functional groups, including carbamate NH, halogen, nitrile, olefin, ketone, and ester moieties. Mechanistic studies suggest that this process does not involve an alkynylmanganese reagent and instead proceeds through nickel-mediated bond formation.Terminal and internal alkynes can be synthesized by a nickel-catalyzed decarboxylative coupling of N-hydroxyphthalimide esters and bromoalkynes. The reaction displays a broad scope of carboxylic acid and alkyne coupling partners, and tolerates an array of functional groups, including carbamate, halogen, nitrile, olefin, ketone, and ester moieties.
      PubDate: 2017-08-17T07:05:58.883522-05:
      DOI: 10.1002/anie.201706781
  • Decarboxylative Alkynylation
    • Authors: Joel M. Smith; Tian Qin, Rohan R. Merchant, Jacob T. Edwards, Lara R. Malins, Zhiqing Liu, Guanda Che, Zichao Shen, Scott A. Shaw, Martin D. Eastgate, Phil S. Baran
      Pages: 11906 - 11910
      Abstract: The development of a new decarboxylative cross-coupling method that affords terminal and substituted alkynes from various carboxylic acids is described using both nickel- and iron-based catalysts. The use of N-hydroxytetrachlorophthalimide (TCNHPI) esters is crucial to the success of the transformation, and the reaction is amenable to in situ carboxylic acid activation. Additionally, an inexpensive, commercially available alkyne source is employed in this formal homologation process that serves as a surrogate for other well-established alkyne syntheses. The reaction is operationally simple and broad in scope while providing succinct and scalable avenues to previously reported synthetic intermediates.All kinds of alkynes: A convenient method for the decarboxylative alkynylation of redox-active esters has been developed. The reaction is broad, chemoselective, and provides access to alkynes that are both terminal and substituted using either nickel or iron catalysis. It was used to swiftly synthesize a variety of alkynyl intermediates that were previously difficult to access.
      PubDate: 2017-08-01T08:41:36.124619-05:
      DOI: 10.1002/anie.201705107
  • Synthesis and Reactivity of Fluoroalkyl Copper Complexes by the
           Oxycupration of Tetrafluoroethylene
    • Authors: Masato Ohashi; Takuya Adachi, Naoyoshi Ishida, Kotaro Kikushima, Sensuke Ogoshi
      Pages: 11911 - 11915
      Abstract: The copper(I)-mediated generation of -OCF2CF2- moieties by the oxycupration of tetrafluoroethylene (TFE) using either copper aryloxides or alkoxides is disclosed. The key intermediates, 2-aryloxy-1,1,2,2-tetrafluoroethyl and 2-alkoxy-1,1,2,2-tetrafluoroethyl copper complexes, were obtained from the reaction of the corresponding aryloxy and alkoxy copper complexes with TFE, and their structures in solution and in the solid state were unambiguously determined by multinuclear NMR spectroscopy and X-ray diffraction analysis. These copper complexes subsequently reacted with aryl iodides (ArI) to afford ROCF2CF2Ar (R=aryl or alkyl) in high yields.The copper(I)-mediated generation of -OCF2CF2- moieties by the oxycupration of tetrafluoroethylene (TFE) using either copper aryloxides or alkoxides is disclosed. The key intermediates, 2-aryloxy- and 2-alkyloxy-1,1,2,2-tetrafluoroethyl copper complexes, were obtained from the reaction of the corresponding aryloxy and alkoxy copper complexes with TFE. These copper complexes subsequently reacted with aryl iodides to afford ROCF2CF2Ar (R=aryl or alkyl) in high yields.
      PubDate: 2017-07-14T00:36:16.639611-05:
      DOI: 10.1002/anie.201703923
  • Aptamer/AuNP Biosensor for Colorimetric Profiling of Exosomal Proteins
    • Authors: Ying Jiang; Muling Shi, Yuan Liu, Shuo Wan, Cheng Cui, Liqin Zhang, Weihong Tan
      Pages: 11916 - 11920
      Abstract: Exosomes constitute an emerging biomarker for cancer diagnosis because they carry multiple proteins that reflect the origins of parent cells. Assessing exosome surface proteins provides a powerful means of identifying a combination of biomarkers for cancer diagnosis. We report a sensor platform that profiles exosome surface proteins in minutes by the naked eye. The sensor consists of a gold nanoparticle (AuNP) complexed with a panel of aptamers. The complexation of aptamers with AuNPs protects the nanoparticles from aggregating in a high-salt solution. In the presence of exosomes, the non-specific and weaker binding between aptamers and the AuNP is broken, and the specific and stronger binding between exosome surface protein and the aptamer displaces aptamers from the AuNP surface and results in AuNP aggregation. This aggregation results in a color change and generates patterns for the identification of multiple proteins on the exosome surface.A coat of many colors: A gold nanoparticle/aptamer biosensor (AuNP/AptX) provides a colorimetric platform for rapid and multiplexed protein analysis of exosomes.
      PubDate: 2017-08-21T07:40:21.492376-05:
      DOI: 10.1002/anie.201703807
  • Processable and Moldable Sodium-Metal Anodes
    • Authors: Aoxuan Wang; Xianfei Hu, Haoqing Tang, Chanyuan Zhang, Shan Liu, Ying-Wei Yang, Quan-Hong Yang, Jiayan Luo
      Pages: 11921 - 11926
      Abstract: Sodium-ion batteries are similar in concept and function to lithium-ion batteries, but their development and commercialization lag far behind. One obstacle is the lack of a standard reference electrode. Unlike Li foil reference electrodes, sodium is not easily processable or moldable and it deforms easily. Herein we fabricate a processable and moldable composite Na metal anode made from Na and reduced graphene oxide (r-GO). With only 4.5 % percent r-GO, the composite anodes had improved hardness, strength, and stability to corrosion compared to Na metal, and can be engineered to various shapes and sizes. The plating/stripping cycling of the composite anode was significantly extended in both ether and carbonate electrolytes giving less dendrite formation. We used the composite anode in both Na-O2 and Na-Na3V2(PO4)3 full cells.Sodium to GO: An obstacle to the development of sodium-based energy systems is the lack of a standard reference electrode. Sodium deforms easily and if rolled into a film to be used as the reference electrode it is difficult to control its shape and thickness. But sodium with 4.5 % reduced graphene oxide (r-GO) gives Na@r-GO composite anodes that can be processed and molded and have improved electrochemical properties.
      PubDate: 2017-08-16T06:17:21.559719-05:
      DOI: 10.1002/anie.201703937
  • Rhodium-Catalyzed Enantioselective Reductive Arylation: Convenient Access
           to 3,3-Disubstituted Oxindoles
    • Authors: Young Jin Jang; Egor M. Larin, Mark Lautens
      Pages: 11927 - 11930
      Abstract: A rhodium-Josiphos(L*) catalyzed enantioselective intramolecular hydroarylation reaction is described. The reductive cyclization of o-bromoaniline-derived acrylamides provides convenient access to 3,3-disubstituted oxindoles in good yields and with excellent enantioselectivity across a range of substrates. We propose that the key cyclization proceeds via a rhodium(III) intermediate. Overall, this method represents an unusual mode of reactivity for rhodium catalysis and is complementary to palladium(0)-catalyzed α-arylation methods.All systems Ar go: A novel approach for the synthesis of 3,3-disubstituted oxindoles was developed using a rhodium-Josiphos chiral catalyst system. This unusual enantioselective rhodium-catalyzed reductive arylation, which functions across a range of substrates, serves as an alternative to palladium(0)-catalyzed α-arylation and does not require the use of a strong base for enolate formation.
      PubDate: 2017-08-14T03:36:45.445812-05:
      DOI: 10.1002/anie.201704922
  • Switchable Stereoselectivity in Bromoaminocyclization of Olefins: Using
           Brønsted Acids of Anionic Chiral Cobalt(III) Complexes
    • Authors: Hua-Jie Jiang; Kun Liu, Jie Yu, Ling Zhang, Liu-Zhu Gong
      Pages: 11931 - 11935
      Abstract: Brønsted acids of anionic chiral CoIII complexes act as bifunctional phase-transfer catalysts to shuttle the substrates across the solvent interface and control stereoselectivity. The diastereomeric chiral CoIII-templated Brønsted acids, with the same chiral ligands, enabled a switch in the enantioselective bromoaminocyclization of olefins to afford the two enantiomers of 2-substituted pyrrolidines with high enantioselectivities (up to 99:1 e.r.).Flip of the switch: Brønsted acids of anionic chiral CoIII complexes act as bifunctional phase-transfer catalysts to shuttle the substrates across the solvent interface and control stereoselectivity. The diastereomeric chiral CoIII-templated Brønsted acids, with the same chiral ligands, enabled a switch in the enantioselective bromoaminocyclization of olefins to afford the two enantiomers of the 2-substituted pyrrolidines with high stereoselectivities.
      PubDate: 2017-08-16T09:02:23.032587-05:
      DOI: 10.1002/anie.201705066
  • Amine-Urea-Mediated Asymmetric Cycloadditions between Nitrile Oxides and
           o-Hydroxystyrenes by Dual Activation
    • Authors: Hiroyuki Suga; Yohei Hashimoto, Yasunori Toda, Kazuaki Fukushima, Hiroyoshi Esaki, Ayaka Kikuchi
      Pages: 11936 - 11939
      Abstract: The first example of asymmetric 1,3-dipolar cycloadditions between nitrile oxides and o-hydroxystyrenes, mediated by cinchona-alkaloid-based amine-ureas is reported. The method is based on a dual activation involving both LUMO and HOMO activations. In addition to the stoichiometric asymmetric induction, a catalytic amount of amine-urea enables the cycloadditions to proceed in an enantioselective manner. Computational studies strongly support the HOMO activation of o-hydroxystyrenes and LUMO activation of nitrile oxides by hydrogen-bonding interactions with the Brønsted acid/base bifunctional catalyst.Agreeable interactions: The first example of 1,3-dipolar cycloadditions between nitrile oxides and o-hydroxystyrenes, mediated by a cinchona-alkaloid-based amine-urea catalyst, is reported. The reaction involves the dual activation of both the LUMO of the nitrile oxide and HOMO of the o-hydroxystyrene, as confirmed by computational studies. The activation is facilitated by hydrogen-bonding interactions with the bifunctional catalyst.
      PubDate: 2017-08-24T03:52:36.959141-05:
      DOI: 10.1002/anie.201705662
  • Oxygenation of Simple Olefins through Selective Allylic C−C Bond
           Cleavage: A Direct Approach to Cinnamyl Aldehydes
    • Authors: Jianzhong Liu; Xiaojin Wen, Chong Qin, Xinyao Li, Xiao Luo, Ao Sun, Bencong Zhu, Song Song, Ning Jiao
      Pages: 11940 - 11944
      Abstract: A novel metal-free allylic C−C σ-bond cleavage of simple olefins to give valuable cinnamyl aldehydes is reported. 1,2-Aryl or alkyl migration through allylic C−C bond cleavage occurs in this transformation, which is assisted by an alkyl azide reagent. This method enables O-atom incorporation into simple unfunctionalized olefins to construct cinnamyl aldehydes. The reaction features simple hydrocarbon substrates, metal-free conditions, and high regio- and stereoselectivity.Cut and paste: A novel metal-free allylic C−C bond cleavage of simple unfunctionalized olefins was developed for the synthesis of valuable cinnamyl aldehyde derivatives with high regio- and stereoselectivity. This method not only provides a new approach to cinnamyl aldehydes, but also expands the application of alkyl azides as well as the recombination of olefins in organic synthesis.
      PubDate: 2017-08-18T04:05:57.995705-05:
      DOI: 10.1002/anie.201705671
  • Decacene: On-Surface Generation
    • Authors: Justus Krüger; Fátima García, Frank Eisenhut, Dmitry Skidin, José M. Alonso, Enrique Guitián, Dolores Pérez, Gianaurelio Cuniberti, Francesca Moresco, Diego Peña
      Pages: 11945 - 11948
      Abstract: Acenes are intriguing molecules with unique electronic properties. The difficulties in their preparation owing to low stability under ambient conditions are apparent because successful syntheses of long unsubstituted acenes are still scarce, in spite of the great attention they have attracted. Only unsubstituted acenes up to heptacene have been isolated in bulk, with nonacene being the largest acene detected to date. Herein we use on-surface assisted reduction of tetraepoxy decacene precursors on Au(111) as the key step to generate unprecedented decacene which is visualized and its electronic resonances studied by scanning tunneling microscopy (STM) and spectroscopy (STS).Decathletes: Combined efforts of organic synthesis and on-surface chemistry have led to the preparation of decacene for the first time. An iterative sequence of aryne cycloadditions was used to synthesize stable tetraepoxy precursors which were reduced on Au(111) to obtain unprecedented decacene as visualized by scanning tunneling microscopy (STM).
      PubDate: 2017-08-17T04:50:46.374856-05:
      DOI: 10.1002/anie.201706156
  • Base-Free Asymmetric Transfer Hydrogenation of 1,2-Di- and Monoketones
           Catalyzed by a (NH)2P2-Macrocyclic Iron(II) Hydride
    • Authors: Lorena De Luca; Antonio Mezzetti
      Pages: 11949 - 11953
      Abstract: The hydride isonitrile complex [FeH(CNCEt3)(1 a)]BF4 (2) containing a chiral P2(NH)2 macrocycle (1 a), in the presence of 2-propanol as hydrogen donor, catalyzes the base-free asymmetric transfer hydrogenation (ATH) of prostereogenic ketones to alcohols and the hemihydrogenation of benzils to benzoins, which contain a base-labile stereocenter. Benzoins are formed in up to 83 % isolated yield with enantioselectivity reaching 95 % ee. Ketones give the same enantioselectivity observed with the parent catalytic system [Fe(CNCEt3)2(1 a)] (3 a) that operates with added NaOtBu.Base' No thanks! A hydride isonitrile iron(II) complex bearing a C2-symmetric diamino (NH)2P2 macrocyclic ligand catalyzes the asymmetric transfer hydrogenation of ketones under base-free conditions with excellent enantioselectivity (up to 99 % ee). Base-labile benzoins are formed from the corresponding benzils with up to 95 % ee.
      PubDate: 2017-08-18T04:00:51.196499-05:
      DOI: 10.1002/anie.201706261
  • Recognition-then-Reaction Enables Site-Selective Bioconjugation to
           Proteins on Live-Cell Surfaces
    • Authors: Cheng Cui; Hui Zhang, Ruowen Wang, Sena Cansiz, Xiaoshu Pan, Shuo Wan, Weijia Hou, Long Li, Meiwan Chen, Yuan Liu, Xigao Chen, Qiaoling Liu, Weihong Tan
      Pages: 11954 - 11957
      Abstract: Site-selective protein modification is a key step in facilitating protein functionalization and manipulation. To accomplish this, genetically engineered proteins were previously required, but the procedure was laborious, complex, and technically challenging. Herein we report the development of aptamer-based recognition-then-reaction to guide site-selective protein/DNA conjugation in a single step with outstanding selectivity and efficiency. As models, several proteins, including human thrombin, PDGF-BB, Avidin, and His-tagged recombinant protein, were studied, and the results showed excellent selectivity under mild reaction conditions. Taking advantage of aptamers as recognition elements with extraordinary selectivity and affinity, this simple preparation method can tag a protein in a complex milieu. Thus, with the aptamer obtained from cell-SELEX, real-time modification of live-cell membrane proteins can be achieved in one step without any pre-treatment.Aptamers with aptitude: Aptamer-based recognition-then-reaction is used to guide site-selective protein/DNA conjugation in a single step with outstanding selectivity and efficiency. Real-time modification of live-cell membrane proteins can be achieved in one step without any pre-treatment.
      PubDate: 2017-08-25T05:22:10.855885-05:
      DOI: 10.1002/anie.201706285
  • Selective Palladium(II)-Catalyzed Carbonylation of Methylene β-C−H
           Bonds in Aliphatic Amines
    • Authors: Jaime R. Cabrera-Pardo; Aaron Trowbridge, Manuel Nappi, Kyohei Ozaki, Matthew J. Gaunt
      Pages: 11958 - 11962
      Abstract: Palladium(II)-catalyzed C−H carbonylation reactions of methylene C−H bonds in secondary aliphatic amines lead to the formation of trans-disubstituted β-lactams in excellent yields and selectivities. The generality of the C−H carbonylation process is aided by the action of xantphos-based ligands and is important in securing good yields for the β-lactam products.The ligand is key: Palladium(II)-catalyzed C−H carbonylation reactions of methylene C−H bonds in secondary aliphatic amines lead to the formation of trans-disubstituted β-lactams in excellent yields and selectivities. The generality of the C−H carbonylation process is aided by the action of xantphos-based ligands.
      PubDate: 2017-08-21T07:31:36.167299-05:
      DOI: 10.1002/anie.201706303
  • A 2-O-Methylriboside Unknown Outside the RNA World Contains Arsenic
    • Authors: Ronald A. Glabonjat; Georg Raber, Kenneth B. Jensen, Nikolaus Guttenberger, Klaus Zangger, Kevin A. Francesconi
      Pages: 11963 - 11965
      Abstract: Lipid-soluble arsenic compounds, also called arsenolipids, are ubiquitous marine natural products of currently unknown origin and function. In our search for clues about the possible biological roles of these compounds, we investigated arsenic metabolism in the unicellular green alga Dunaliella tertiolecta, and discovered an arsenolipid fundamentally different from all those previously identified; namely, a phytyl 5-dimethylarsinoyl-2-O-methyl-ribofuranoside. The discovery is of particular interest because 2-O-methylribosides have, until now, only been found in RNA. We briefly discuss the significance of the new lipid in biosynthesis and arsenic biogeochemical cycling.A little stranger: Studies of the arsenic metabolism in the unicellular green alga Dunaliella tertiolecta revealed an arsenolipid fundamentally different from all those previously identified, namely, a phytyl 5-dimethylarsinoyl-2-O-methyl-ribofuranoside (see picture). The discovery is of particular interest because 2-O-methylribosides have, until now, only been found in RNA.
      PubDate: 2017-08-17T07:02:14.082997-05:
      DOI: 10.1002/anie.201706310
  • How Understanding the Role of an Additive Can Lead to an Improved
           Synthetic Protocol without an Additive: Organocatalytic Synthesis of
           Chiral Diarylmethyl Alkynes
    • Authors: Min Chen; Jianwei Sun
      Pages: 11966 - 11970
      Abstract: The use of additives for organic synthesis has become a common tactic to improve the outcome of organic reactions. Herein, by using an organocatalytic process for the synthesis of chiral diarylmethyl alkynes as a platform, we describe how an additive is involved in the improvement of the process. The evolution of an excellent synthetic protocol has been achieved in three stages, from 1) initially no catalyst turnover, to 2) good conversion and enantioselectivity with a superior additive, and eventually 3) even better efficiency and selectivity without an additive. This study is an important and rare demonstration that understanding the role of additive can be so beneficial as to obviate the need for the additive.Addition and subtraction: On the basis of an organocatalytic process, it is shown how a reaction can be evolved from an initial stage without catalyst turnover to a highly efficient and enantioselective transformation in the presence of an additive, and eventually without the additive (see picture). Thus, by understanding the role of an additive, it was possible to redesign and significantly improve the synthetic protocol.
      PubDate: 2017-08-17T07:03:03.913444-05:
      DOI: 10.1002/anie.201706579
  • Rational Control of the Selectivity of a Ruthenium Catalyst for
           Hydrogenation of 4-Nitrostyrene by Strain Regulation
    • Authors: Junjie Mao; Wenxing Chen, Wenming Sun, Zheng Chen, Jiajing Pei, Dongsheng He, Chunlin Lv, Dingsheng Wang, Yadong Li
      Pages: 11971 - 11975
      Abstract: Tuning the selectivity of metal catalysts is of paramount importance yet a great challenge. A new strategy to effectively control the selectivity of metal catalysts, by tuning the lattice strain, is reported. A certain amount of Co atoms is introduced into Ru catalysts to compress the Ru lattice, as confirmed by aberration-corrected high-resolution transmission electron microscopy (HRTEM) and X-ray absorption fine structure (XAFS) measurements. We discover that the lattice strain of Ru catalysts can greatly affect their selectivity, and Ru with 3 % lattice compression exhibits extremely high catalytic selectivity for hydrogenation of 4-nitrostyrene to 4-aminostyrene compared to pristine Ru (99 % vs. 66 %). Theoretical studies confirm that the optimized lateral compressive strain facilitates hydrogenation of the nitro group but impedes the hydrogenation of the vinyl group. This study provides a new guideline for designing metal catalysts with high selectivity.Taking the strain: Introducing Co atoms into a Ru catalyst compressed the Ru lattice strain, thus further affecting catalytic selectivity for hydrogenation of 4-nitrostyrene to 4-aminostyrene. Theoretical studies reveal that the optimized lateral compressive strain facilitates hydrogenation of the nitro group but impedes the hydrogenation of the vinyl group.
      PubDate: 2017-08-15T02:12:13.641771-05:
      DOI: 10.1002/anie.201706645
  • Markovnikov-Selective Palladium Catalyst for Carbonylation of Alkynes with
    • Authors: Jie Liu; Haoquan Li, Ricarda Dühren, Jiawang Liu, Anke Spannenberg, Robert Franke, Ralf Jackstell, Matthias Beller
      Pages: 11976 - 11980
      Abstract: A new class of palladium catalysts, based on heterocyclic diphosphines, was rationally designed and synthesized. Application of one of these catalysts allows novel Markovnikov-selective carbonylation of non-activated alkynes with heteroarenes to give the corresponding branched α,β-unsaturated ketones in excellent yields (up to 97 %) and regioselectivities (b/l up to 99:1). In addition to heteroarenes, other common nucloephiles (alcohol, phenol, amine, and amide) furnish the desired carbonylation products smoothly in high yields.Cool cat: The ligand L1 [bis(2-(diphenylphosphanyl)-1H-pyrrol-1-yl)methane] allows a general palladium-catalyzed carbonylation of unactivated alkynes with heteroarenes. The reaction proceeds smoothly to give the corresponding branched α,β-unsaturated ketones in good yields and often with high Markovnikov selectivity. b=branched, l=linear.
      PubDate: 2017-08-25T05:21:50.792722-05:
      DOI: 10.1002/anie.201706794
  • Palladium-Catalyzed Suzuki–Miyaura Cross-Coupling of Secondary
           α-(Trifluoromethyl)benzyl Tosylates
    • Authors: Marta Brambilla; Matthew Tredwell
      Pages: 11981 - 11985
      Abstract: A palladium-catalyzed C(sp3)−C(sp2) Suzuki–Miyaura cross-coupling of aryl boronic acids and α-(trifluoromethyl)benzyl tosylates is reported. A readily available, air-stable palladium catalyst was employed to access a wide range of functionalized 1,1-diaryl-2,2,2-trifluoroethanes. Enantioenriched α-(trifluoromethyl)benzyl tosylates were found to undergo cross-coupling to give the corresponding enantioenriched cross-coupled products with an overall inversion in configuration. The crucial role of the CF3 group in promoting this transformation is demonstrated by comparison with non-fluorinated derivatives.Only with fluorine: A palladium-catalyzed cross-coupling of secondary α-(trifluoromethyl)benzyl tosylates with (hetero)aryl boronic acids enables the stereoselective synthesis of more than twenty 1,1-diaryl-2,2,2-trifluoroethanes. The cross-coupling was shown to occur with predominant inversion of configuration.
      PubDate: 2017-08-15T02:11:39.103059-05:
      DOI: 10.1002/anie.201706631
  • Enantioselective Construction of Trifluoromethoxylated Stereogenic Centers
           by a Nickel-Catalyzed Asymmetric Suzuki–Miyaura Coupling of Secondary
           Benzyl Bromides
    • Authors: Weichen Huang; Xiaolong Wan, Qilong Shen
      Pages: 11986 - 11989
      Abstract: Trifluoromethoxy-substituted stereogenic centers can be constructed with high enantioselectivity by a nickel-catalyzed Suzuki–Miyaura coupling of readily available α-bromobenzyl trifluoromethyl ethers with a variety of aryl pinacol boronates. The coupling proceeds under mild reaction conditions, and a variety of common functional groups, such as fluoride, chloride, bromide, ester, enolizable ketone, nitro, cyano, amino, and vinyl moieties, were well tolerated. Furthermore, the reaction can be easily scaled up to gram quantities without a decrease in enantioselectivity.Trifluoromethoxy-substituted stereogenic centers were constructed with high enantioselectivity in a nickel-catalyzed Suzuki–Miyaura coupling of readily available α-bromobenzyl trifluoromethyl ethers with a variety of aryl pinacol boronates. The coupling proceeds under mild reaction conditions, and a variety of common functional groups are well tolerated.
      PubDate: 2017-08-21T02:45:36.224886-05:
      DOI: 10.1002/anie.201706868
  • Synthesis, Isolation, and Trifluoromethylation of Two Isomers of C84-Based
           Monometallic Cyanide Clusterfullerenes: Interplay between the Endohedral
           Cluster and the Exohedral Addends
    • Authors: Fei Jin; Song Wang, Nadezhda B. Tamm, Shangfeng Yang, Sergey I. Troyanov
      Pages: 11990 - 11994
      Abstract: As an emerging member of endohedral fullerenes, metal cyanide clusterfullerenes (CYCF) are unique in terms of the encapsulation of a monometallic cluster. To date the reported carbon cages of CYCFs are limited to C82 and C76, and little is known about the chemical reactivity of CYCFs. Herein, two isomers of the first C84-based CYCFs, YCN@C84, were isolated as trifluoromethyl derivatives, including YCN@C84(23)(CF3)18 and three isomers of YCN@C84(13)(CF3)16, which are based on a unique chiral C2-C84(13) cage. As a common feature of the CF3 addition patterns, the YCN@C84(CF3)16/18 compounds are stabilized by the formation of isolated C=C bonds and benzenoid rings on the carbon cages. The interplay between the endohedral YCN cluster and the exhohedral CF3 addends was unveiled according to single-crystal X-ray diffraction studies, thus offering new insight into the chemical reactivity of CYCFs.A metal within: Two isomers of the first C84-based metal cyanide clusterfullerene (CYCF), YCN@C84, were synthesized, isolated, and identified as the trifluoromethyl derivatives YCN@C84(CF3)16/18. The interplay between the endohedral YCN cluster and the exhohedral CF3 addends was unveiled by single-crystal X-ray diffraction studies.
      PubDate: 2017-08-21T07:36:36.023326-05:
      DOI: 10.1002/anie.201707298
  • Stoichiometric and Catalytic C−C and C−H Bond Formation with B(C6F5)3
           via Cationic Intermediates
    • Authors: Yashar Soltani; Lewis C. Wilkins, Rebecca L. Melen
      Pages: 11995 - 11999
      Abstract: This work showcases a new catalytic cyclization reaction using a highly Lewis acidic borane with concomitant C−H or C−C bond formation. The activation of alkyne-containing substrates with B(C6F5)3 enabled the first catalytic intramolecular cyclizations of carboxylic acid substrates using this Lewis acid. In addition, intramolecular cyclizations of esters enable C−C bond formation as catalytic B(C6F5)3 can be used to effect formal 1,5-alkyl migrations from the ester functional groups to unsaturated carbon–carbon frameworks. This metal-free method was used for the catalytic formation of complex dihydropyrones and isocoumarins in very good yields under relatively mild conditions with excellent atom efficiency.The Lewis acidic borane B(C6F5)3 activates alkynes towards an intramolecular cyclization with carboxylic acids. Analogous intramolecular cyclizations of esters via C−C bond formation proceed in good to excellent yields in the presence of catalytic amounts of B(C6F5)3. This process involves a 1,5-alkyl migration from the ester functional group to the unsaturated carbon framework.
      PubDate: 2017-08-18T03:56:10.965887-05:
      DOI: 10.1002/anie.201704789
  • Structural Basis for Expansion of the Genetic Alphabet with an Artificial
           Nucleobase Pair
    • Authors: Karin Betz; Michiko Kimoto, Kay Diederichs, Ichiro Hirao, Andreas Marx
      Pages: 12000 - 12003
      Abstract: Hydrophobic artificial nucleobase pairs without the ability to pair through hydrogen bonds are promising candidates to expand the genetic alphabet. The most successful nucleobase surrogates show little similarity to each other and their natural counterparts. It is thus puzzling how these unnatural molecules are processed by DNA polymerases that have evolved to efficiently work with the natural building blocks. Here, we report structural insight into the insertion of one of the most promising hydrophobic unnatural base pairs, the dDs–dPx pair, into a DNA strand by a DNA polymerase. We solved a crystal structure of KlenTaq DNA polymerase with a modified template/primer duplex bound to the unnatural triphosphate. The ternary complex shows that the artificial pair adopts a planar structure just like a natural nucleobase pair, and identifies features that might hint at the mechanisms accounting for the lower incorporation efficiency observed when processing the unnatural substrates.Complementing A–T and G–C: Hydrophobic artificial base pairs have great potential to expand the genetic code. In the active site of the KlenTaq DNA polymerase, the promising candidate dDs–dPxTP pairs edge-to-edge, just like a cognate Watson–Crick pair. Its varying size and shape, however, cause minor alterations near the active site.
      PubDate: 2017-06-27T06:22:50.704265-05:
      DOI: 10.1002/anie.201704190
  • Pristine DNA Hydrogels from Biotechnologically Derived Plasmid DNA
    • Authors: Tanja Nöll; Sabine Wenderhold-Reeb, Holger Schönherr, Gilbert Nöll
      Pages: 12004 - 12008
      Abstract: DNA hydrogels are of great interest for a variety of biomedical applications owing to their biocompatibility and biodegradability but the advantages of DNA hydrogels have not been exploited yet because of their limited availability. Thus far, DNA hydrogels have been prepared from synthetically derived building blocks, and their production on large scale would be far too expensive. As an alternative, here the generation of DNA hydrogels from plasmid DNA is reported. Plasmid DNA can be prepared on large scale at reasonable costs by a fermentation process. The desired linear DNA building blocks are then obtained from the plasmid DNA by enzymatic digestion. Gel formation is carried out by covalent bond formation between individual building blocks via enzymatic ligation. The generation of pristine DNA hydrogels from plasmid DNA is thus presented for the first time. The viscoelastic properties of the hydrogels were studied by rheology, which confirmed that the gels have storage moduli G′ of >100 Pa.(De)construction: Pristine DNA hydrogels were formed from biotechnologically derived plasmid DNA through ligation of longer or shorter fragments, obviating the need for DNA building blocks prepared by solid-phase synthesis. The rheological properties of the hydrogels can be adjusted by varying the length and sequence of the employed fragments as well as the experimental conditions.
      PubDate: 2017-08-17T06:46:15.289205-05:
      DOI: 10.1002/anie.201705001
  • Carbon–Halogen Bond Activation by Selenium-Based Chalcogen Bonding
    • Authors: Patrick Wonner; Lukas Vogel, Maximilian Düser, Luís Gomes, Florian Kniep, Bert Mallick, Daniel B. Werz, Stefan M. Huber
      Pages: 12009 - 12012
      Abstract: Chalcogen bonding is a little explored noncovalent interaction similar to halogen bonding. This manuscript describes the first application of selenium-based chalcogen bond donors as Lewis acids in organic synthesis. To this end, the solvolysis of benzhydryl bromide served as a halide abstraction benchmark reaction. Chalcogen bond donors based on a bis(benzimidazolium) core provided rate accelerations relative to the background reactivity by a factor of 20–30. Several comparative experiments provide clear indications that the observed activation is due to chalcogen bonding. The performance of the chalcogen bond donors is superior to that of a related brominated halogen bond donor.Activation Se(en) from a different angle: Chalcogen bond donors (chalcogen-based Lewis acids) accelerate a halide abstraction benchmark reaction by a factor of 20–30. Several comparative experiments provide clear indications that the observed activation is due to chalcogen bonding.
      PubDate: 2017-07-06T11:01:00.01138-05:0
      DOI: 10.1002/anie.201704816
  • Inside Back Cover: Carbon–Halogen Bond Activation by Selenium-Based
           Chalcogen Bonding (Angew. Chem. Int. Ed. 39/2017)
    • Authors: Patrick Wonner; Lukas Vogel, Maximilian Düser, Luís Gomes, Florian Kniep, Bert Mallick, Daniel B. Werz, Stefan M. Huber
      Pages: 12013 - 12013
      Abstract: Selenium compounds may form noncovalent interactions, so-called chalcogen bonds, with Lewis bases under certain conditions. In their Communication on page 12009 ff., S. M. Huber and co-workers show that such chalcogen bond donors activate a benchmark reaction. Control experiments with non-selenated reference compounds confirmed the crucial role of the selenium substituent. The corresponding brominated halogen bond donor was somewhat less active.
      PubDate: 2017-07-26T07:55:21.810609-05:
      DOI: 10.1002/anie.201707295
  • Back Cover: Synthesis and Reactivity of Fluoroalkyl Copper Complexes by
           the Oxycupration of Tetrafluoroethylene (Angew. Chem. Int. Ed. 39/2017)
    • Authors: Masato Ohashi; Takuya Adachi, Naoyoshi Ishida, Kotaro Kikushima, Sensuke Ogoshi
      Pages: 12014 - 12014
      Abstract: Copper(I)-mediated generation of −OCF2CF2− moieties through the oxycupration of tetrafluoroethylene using either copper aryloxides or alkoxides is described by S. Ogoshi et al. on page 11911 ff. The key intermediates, 2-aryloxy- and 2-alkyloxy-1,1,2,2-tetrafluoroethyl copper complexes, were obtained and subsequently reacted with aryl iodides to afford ROCF2CF2Ar (R=aryl or alkyl) in high yields.
      PubDate: 2017-08-09T07:00:23.969441-05:
      DOI: 10.1002/anie.201707624
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