37,103 results match your criteria Angewandte Chemie International Edition [Journal]


Total Synthesis Establishes the Biosynthetic Pathway to the Naphterpin and Marinone Natural Products.

Angew Chem Int Ed Engl 2018 Jun 23. Epub 2018 Jun 23.

University of Adelaide, School of Chemistry and Physics, North Terrace, SA5005, Adelaide, AUSTRALIA.

The naphterpins and marinones are naphthoquinone meroterpenoids with an unusual aromatic oxidation pattern that is biosynthesized from 1,3,6,8-tetrahydroxynaphthalene (THN). We propose that cryptic halogenation of THN derivatives by vanadium-dependent chloroperoxidase (VCPO) enzymes is key to this biosynthetic pathway, despite the absence of chlorine in these natural products. This speculation has inspired the total synthesis of the naphterpin/marinone biosynthetic pathway. Read More

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Discrimination of Avian Influenza Virus using Host-cell Infection Fingerprinting by Sulfinate-based Fluorescence Superoxide Probe.

Angew Chem Int Ed Engl 2018 Jun 22. Epub 2018 Jun 22.

Korea Institute of Science and Technology, Molecular Recognition Research Center, 39-1 Hawolgok-Dong, Seongbuk-Gu, 136-791, Seoul, KOREA, REPUBLIC OF.

Avian Influenza (AI) caused an annual epidemic outbreak that led to destroying tens of millions of poultry worldwide. Current gold standard AI diagnosis method is an embryonic egg-based hemagglutination assay followed by immunoblotting or PCR sequencing to confirm subtypes. It requires, however, specialized facilities to handle egg inoculation and incubation, and the subtyping methods relied on costly reagents. Read More

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June 2018
5 Reads

Diastereocontrolled Monoprotodeboronation of β-Sulfinimido gem-Bis(boronates): A General and Stereoselective Access to α,β-Disubstituted β-Aminoalkylboronates.

Angew Chem Int Ed Engl 2018 Jun 22. Epub 2018 Jun 22.

University of Alberta, Chemistry, 4-010 CCIS, T6G 2G2, Edmonton, CANADA.

β-Aminoalkylboronic acids are bioisosteres of the pharmaceutically important class of β-aminoacids. Few methods exist for their preparation. Here, a general methodology for 1,2-addition of lithiated 1,1-diborylalkanes onto chiral N-tert-butanesulfinyl aldimines produces β-sulfinimido gem-bis(boronates) in good to excellent yields with high diastereoselectivity. Read More

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Transmission of Unidirectional Molecular Motor Rotation to a Remote Biaryl Axis.

Angew Chem Int Ed Engl 2018 Jun 22. Epub 2018 Jun 22.

LMU München, Chemie, Butenandtstr. 5-13, 81377, München, GERMANY.

Molecular motors undergo directional motions upon external energy input. A profound challenge is the defined transfer of directional motor motions to remote entities at the molecular scale. In this work we present a molecular setup allowing to transfer the directional rotation of a light powered motor unit unto a remote biaryl axis via an ethylene-glycol chain link. Read More

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June 2018
1 Read

Hybrid organic-inorganic rotaxanes, including a hetero-hybrid [3]rotaxane featuring two distinct heterometallic rings and a molecular shuttle.

Angew Chem Int Ed Engl 2018 Jun 22. Epub 2018 Jun 22.

UNITED KINGDOM.

[2] and [3] hybrid rotaxanes are reported based on {Ti7M} rings (where M = a trivalent metal such as FeIII or GaIII}. NMR studies show that [2]rotaxanes can act as molecular shuttles, while EPR studies of [3]rotaxanes show weak interactions between the paramagnetic components of the supramolecular assemblies. Read More

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Hypervalent Iodine(III)-Catalyzed Balz-Schiemann Fluorination under Mild Conditions.

Angew Chem Int Ed Engl 2018 Jun 22. Epub 2018 Jun 22.

Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, CHINA.

An unprocedented hypervalent iodine(III)-catalyzed Balz-Schiemann reaction is described. The addition of hypervalent iodine compound enables the fluorination reaction to proceed under mild conditions (25-60 oC) with wide substrate scope and good functional group compatibility. Read More

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Tandem Payne/Dakin Reaction: A New Strategy for Hydrogen Peroxide Detection and Molecular Imaging.

Angew Chem Int Ed Engl 2018 Jun 22. Epub 2018 Jun 22.

The University of Hong Kong, Department of Chemistry, Pokfulam Road, 000, Hong Kong, CHINA.

Hydrogen peroxide (H2O2) has been recognized as one of the most significant ROS (reactive oxygen species) in human health and disease. Due to the intrinsic attributes of H2O2 such as low reactivity under physiological pH, it is exceedingly challenging to develop small molecule fluorescent probes with high selectivity and sensitivity to visualize H2O2 in intricate biological milieux. To address this gap, we report a rationally designed tandem Payne/Dakin reaction that is specific to molecular recognition of H2O2, and demonstrate its application in developing novel biocompatible fluorescent probes. Read More

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On-Surface Bottom-Up Synthesis of Azine Derivatives Displaying Strong Acceptor Behavior.

Angew Chem Int Ed Engl 2018 Jun 21. Epub 2018 Jun 21.

ESISNA Group, Materials Science Factory., Institute of Materials Science of Madrid (ICMM-CSIC), Sor Juana Inés de la Cruz 3, 28049, Madrid, Spain.

On-surface synthesis is an emerging approach to obtain, in a single step, precisely defined chemical species that cannot be obtained by other synthetic routes. The control of the electronic structure of organic/metal interfaces is crucial for defining the performance of many optoelectronic devices. A facile on-surface chemistry route has now been used to synthesize the strong electron-acceptor organic molecule quinoneazine directly on a Cu(110) surface, via thermally activated covalent coupling of para-aminophenol precursors. Read More

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Redox-Triggered Orientational Responses of Liquid Crystals to Chlorine Gas.

Angew Chem Int Ed Engl 2018 Jun 22. Epub 2018 Jun 22.

University of Wisconsin-Madison, Chemical and Biological Engineering, 1415 Engineering Drive, 53706, Madison, UNITED STATES.

We report the design of surface-supported liquid crystals (LCs) that exhibit orientational and thus optical responses upon exposure to parts-per-billion concentrations of Cl2 gas. Computational chemistry methods identified Mn cations as candidate surface binding sites that undergo redox-triggered changes in strength of binding to nitrogen-based LCs upon exposure to Cl2 gas. Guided by these predictions, we prepared micrometer-thick films of nitrile- or pyridine-containing LCs on surfaces decorated with Mn2+ binding sites (as perchlorate salts). Read More

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Cu-catalyzed cross-dehydrogenative ortho-aminomethylation of phenols.

Angew Chem Int Ed Engl 2018 Jun 22. Epub 2018 Jun 22.

TU Kaiserslautern, FB chemie, Erwin-Schroedinger-Strasse Geb. 52 office, 67663, Kaiserslautern, GERMANY.

A highly selective Cu(II)-catalyzed cross-dehydrogenative ortho-aminomethylation of phenols with aniline derivatives is described. The corresponding C(sp2)-C(sp3) coupling products were obtained in moderate to excellent yields under mild reaction conditions and with a broad substrate scope. A radical mechanism is proposed. Read More

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Transformation of 14C-labeled Graphene to 14CO2 in the Shoots of Rice Plant.

Angew Chem Int Ed Engl 2018 Jun 21. Epub 2018 Jun 21.

UNITED STATES.

The exciting commercial application of graphene materials will increasingly lead to their release into soils, however, their potential transformation in agricultural crops and associated environmental effects are yet unknown due to difficulty in tracing the material. Our study focused on using carbon-14 labeled few-layer graphene (FLG) to determine its uptake, distribution, transformation, and depuration in rice plants. After 7 d hydroponic exposure to FLG suspension at 250 μg/L, roots accumulated 694. Read More

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Oxygen initiated and regulated controlled radical polymerization under ambient conditions.

Angew Chem Int Ed Engl 2018 Jun 21. Epub 2018 Jun 21.

CHINA.

A rapid oxygen-initiated and -regulated controlled radical polymerization was conducted under ambient temperature and atmosphere. The reaction between triethylborane and oxygen provides ethyl radicals which initiate and mediate the radical polymerization. The controlled radical polymerization was achieved using RAFT chain transfer agents (CTA) without any process of removing oxygen, providing well-defined polymers with almost full conversion (>95%) in short period (15 mins). Read More

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Difluorination at Boron leads to the First Electrophilic Ligated Boryl Radical (NHC-BF2*).

Angew Chem Int Ed Engl 2018 Jun 21. Epub 2018 Jun 21.

CNRS-Université de Lyon, C2P2, 43 bd du 11 novembre 1918, 69616, Villeurbanne, FRANCE.

1,3-Dimethylimidazol-2-ylidene difluoroborane (NHC-BF2H) was prepared in a one-pot, two-step reaction from the parent ligated borane (NHC-BH3). The derived difluoroboryl radical (NHC-BF2*) was generated by laser flash photolysis experiments and characterized by UV-spectroscopy and rate constant measurements. It is transient and reacts quickly with O2. Read More

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Radical Trifluoromethoxylation of Arenes Triggered by a Visible-Light-Mediated N-O Redox Fragmentation.

Angew Chem Int Ed Engl 2018 Jun 21. Epub 2018 Jun 21.

SWITZERLAND.

A simple trifluoromethoxylation method enables non-directed functionalization of C-H bonds on a range of substrates to provide access to aryl trifluoromethyl ethers. This light-driven process is distinctly different than conventional protocols and occurs through an OCF3 radical mechanism mediated by a photoredox catalyst, triggering an N-O bond fragmentation. This pyridinium-based reagent is bench-stable and provides access to synthetic diversity in lead compounds in an operationally simple manner. Read More

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Phthalocyanine-Assembled Nanodots as Photosensitizers for Highly Efficient Type I Photoreactions in PDT.

Angew Chem Int Ed Engl 2018 Jun 21. Epub 2018 Jun 21.

Ewha Womans University, Department of Chemistry, 11-1 Daehyun-Dong, Seodaemun-Gu, 120-750, Seoul, KOREA, REPUBLIC OF.

Owing to their unique, nanoscale related optical properties, nanostructures assembled from molecular photosensitizers (PSs) have interesting applications in phototheranostics. However, most nanostructured PS assemblies are super-quenched, thus, preventing their use in photodynamic therapy (PDT). Although some of these materials undergo stimuli-responsive disassembly, which leads to partial recovery of PDT activity, their therapeutic potentials are unsatisfactory owing to a limited ability to promote generation reactive oxygen species (ROS), especially via type I photoreactions (i. Read More

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June 2018
1 Read

Swapping Interface Contacts in the Homodimeric tRNA Guanine Transglycosylase: An Option for Functional Regulation.

Angew Chem Int Ed Engl 2018 Jun 21. Epub 2018 Jun 21.

Univ. of Marburg, Inst. Pharmaceut. Chem., Marbacher Weg 6, D35032, Marburg, GERMANY.

The enzyme tRNA guanine transglycosylase, a target to fight Shigellosis, recognizes tRNA only as a homodimer and performs full nucleobase exchange at the wobble position. Active-site inhibitors block the enzyme function by competitively replacing tRNA. In solution, the wild-type homodimer dissociates only marginally, whereas mutated variants show substantial monomerization in solution. Read More

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The European 1,2-Dichloroethane Ban Should Liberate not Limit C-H Activation Research and Development.

Authors:
James Sherwood

Angew Chem Int Ed Engl 2018 Jun 21. Epub 2018 Jun 21.

University of York, Chemistry, Heslington, YO10 5DD, York, UNITED KINGDOM.

The popular solvent 1,2-dichloroethane (DCE, also known as ethylene dichloride) was recently subject to regulatory controls in the European Union that will severely limit its commercial use. Read More

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Sol-gel Synthesis of Metal-Phenolic Coordination Spheres and Their Derived Carbon Composites.

Angew Chem Int Ed Engl 2018 Jun 21. Epub 2018 Jun 21.

Xi'an Jiaotong University, School of Life Science and Technology, No.28, Xianning West Road, 710049, Xi'an, CHINA.

Metal-organic coordination spheres integrate the advantages of coordination polymers with spherical colloids, which are crucial for the fabrication of functional composites. However, it still lacks a universal strategy to develop chemically tailorable colloidal spheres from metal-organic coordination polymers. Here we report a formaldehyde-assisted metal-ligand crosslinking strategy for the synthesis of metal-phenolic coordination spheres based on the principle of sol-gel chemistry. Read More

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Non-enzymatic pathway with superoxide in intracellular terpenoid synthesis.

Angew Chem Int Ed Engl 2018 Jun 21. Epub 2018 Jun 21.

Niigata University, Department of Applied Biological Chemistry, 8050 Ikarashi-2, 950-2181, Niigata, JAPAN.

Non-C5-units terpenoids (norisoprenoids) having an acetonyl group are widely distributed in nature, especially in crustacean hormones, insect pheromones, plant odorants, and microbial volatiles. However, studies on the biosynthesis of norisoprenoids are scarce. In this study, we identified the C33 norisoprenoid, (all-E)-farnesylfarnesylacetone, from Bacillus spp. Read More

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June 2018
3 Reads

Photoswitching the efficacy of a small-molecule ligand for a peptidergic GPCR: from antagonism to agonism.

Angew Chem Int Ed Engl 2018 Jun 21. Epub 2018 Jun 21.

Amsterdam Institute for Molecules, Medicines and Systems. Vrije Universiteit Amsterdam, Division of Medicinal Chemistry, De Boelelaan 1108, 1081 HZ, Amsterdam, NETHERLANDS.

In order to obtain optical control of GPCR function, we set out to develop small-molecule ligands with photoswitchable efficacy in which both configurations bind the target protein but exert distinct pharmacological effects, i.e., stimulate or antagonise GPCR activation. Read More

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Cubosomes; the next generation of smart lipid nanoparticles?

Angew Chem Int Ed Engl 2018 Jun 21. Epub 2018 Jun 21.

Imperial College London, 208, Royal School of Mines, South Kensington Campus, SW7 2AZ, London, UNITED KINGDOM.

Cubosomes are highly stable nanoparticles formed from the lipid cubic phase and stabilized by a polymer based outer corona. Lipid cubic phases consist of a single lipid bilayer which forms a continuous periodic membrane lattice structure with pores formed by two interwoven water channels. Cubosome composition can be tuned to engineer pore sizes or include bioactive lipids, the polymer outer corona can be used for targeting and they are highly stable under physiological conditions. Read More

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A Deprotonation Approach to the Unprecedented Amino-Trimethylenemethane Chemistry: Regio-, Diastereo-, and Enantioselective Synthesis of Complex Amino Cycles.

Angew Chem Int Ed Engl 2018 Jun 20. Epub 2018 Jun 20.

Stanford University, Chemistry, 337 Campus Dr., 94305, Stanford, UNITED STATES.

Here we report the first realization of the amino-trimethylenemethane chemistry. The approach employs a deprotonation strategy which simplified the synthesis of the amino- trimethylenemethane donor, requiring only two steps from commercial and inexpensive materials. A broad scope of cycloaddition acceptors (seven different classes) participated in the chemistry, chemo-, regio-, diastereo-, and enantioselectively, generating various types of highly valuable complex amino cycles. Read More

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June 2018
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A Versatile One-Pot Synthesis of Polysubstituted Cyclopent-2-enimines from α,β-Unsaturated Amides via Imino-Nazarov Reaction.

Angew Chem Int Ed Engl 2018 Jun 20. Epub 2018 Jun 20.

CHINA.

The imino-Nazarov cyclization of the polysubstituted pentan-1,4-diene-3-imine is realized. To this aim, a one-pot procedure involving reductive alkenyliminylation of α,β-unsaturated secondary amides with potassium organotrifluoroborates followed by acid-catalyzed imino-Nazarov cyclization of the polysubstituted pentan-1,4-diene-3-imine intermediates is studied systematically. This mild, operationally simple, flexible, and high-yielding protocol efficiently affords polysubstituted pentan-1,4-diene-3-imines, cyclopentenimines, and α-amino cyclopentenones, which are useful scaffolds in organic synthesis. Read More

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June 2018
1 Read

Spotlights on our sister journals: Angew. Chem. Int. Ed. 26/2018.

Authors:

Angew Chem Int Ed Engl 2018 Jun;57(26):7558-7561

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Outstanding Methane Oxidation Performance of Pd-Embedded Ceria Catalysts Prepared by a One-step Dry Ball-Milling Method.

Angew Chem Int Ed Engl 2018 Jun 20. Epub 2018 Jun 20.

Università di Udine, Scienze e Tecnologie Chimiche, via Cotonificio 108, 33100, Udine, ITALY.

By carefully mixing Pd metal nanoparticles with CeO2 polycrystalline powder under dry conditions a new unpredicted arrangement of the Pd-O-Ce interface is obtained, where an amorphous shell containing Palladium species dissolved in Ceria is covering a core of CeO2 particles. The robust contact that is generated at nanoscale, along with mechanical forces generated during mixing, promotes the redox exchange between Pd and CeO2 and creates highly reactive and stable sites constituted by PdOx embedded into CeO2 surface layers. This specific arrangement outperforms conventional Pd/CeO2 reference catalysts in methane oxidation, by lowering light-off temperature by more than 50 degrees and boosting reaction rate. Read More

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White-Fluorescent Dual-Emission Mechanosensitive Membrane Probes that Function by Bending Rather than Twisting.

Angew Chem Int Ed Engl 2018 Jun 20. Epub 2018 Jun 20.

Department of Organic Chemistry, University of Geneva, Geneva, Switzerland.

Bent N,N'-diphenyl-dihydrodibenzo[a,c]phenazine amphiphiles are introduced as mechanosensitive membrane probes that operate by an unprecedented mechanism, namely, unbending in the excited state as opposed to the previously reported untwisting in the ground and twisting in the excited state. Their dual emission from bent or "closed" and planarized or "open" excited states is shown to discriminate between micelles in water and monomers in solid-ordered (S ), liquid-disordered (L ) and bulk membranes. The dual-emission spectra cover enough of the visible range to produce vesicles that emit white light with ratiometrically encoded information. Read More

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In Situ Depot for Continuous Evolution of Gaseous H2 Mediated by Magnesium Passivation/Activation Cycle for Treating Osteoarthritis.

Angew Chem Int Ed Engl 2018 Jun 20. Epub 2018 Jun 20.

National Tsing Hua University, Dept. of Chemical Engineering, 101, Section 2, Kuang Fu Road, 30013, Hsinchu, TAIWAN.

Inflammation is involved in many human pathologies, including osteoarthritis (OA). Hydrogen (H2) is known to have anti-inflammatory effects; however, the bioavailability of directly administered H2 gas is typically poor. Herein, a local delivery system that can provide a high therapeutic concentration of gaseous H2 at inflamed tissues is proposed. Read More

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June 2018
1 Read

Ambient Electro-Synthesis of Ammonia-Electrode Porosity and Composition Engineering.

Angew Chem Int Ed Engl 2018 Jun 20. Epub 2018 Jun 20.

AUSTRALIA.

Ammonia, key precursor for fertilizer production, convenient hydrogen carrier and emerging clean fuel, plays a pivotal role in sustaining life on earth. Currently, the main route for NH3 synthesis is via the heterogeneous catalytic Haber-Bosch process (N2+3H2→2NH3), which proceeds under extreme conditions of temperature and pressure with a very large carbon footprint. Herein we report that a pristine nitrogen-doped nanoporous graphitic carbon membrane (NCM) can electrochemically convert N2 into NH3 in an aqueous acidic solution under ambient conditions. Read More

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Palladium-Catalyzed Enantioselective Reductive Heck Reactions: Convenient Access to 3,3-Disubstituted 2,3-Dihydrobenzofuran.

Angew Chem Int Ed Engl 2018 Jun 20. Epub 2018 Jun 20.

CHINA.

The first example of highly enantioselective intramolecular hydroarylation of allyl aryl ethers was realized via palladium-catalyzed reductive heck reactions by utilizing a designed new chiral sulfonamide phosphine ligand (N-Me-XuPhos). N-Me-XuPhos can be easily prepared in a gram-scale from readily available starting materials via a 'one-pot' synthesis approach. A series of optically active 2,3-dihydrobenzofuran bearing a quaternary stereocenter were obtained in good yields with excellent enantioselectivities. Read More

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Terminal Hydride Species in [FeFe]-Hydrogenases are Vibrationally Coupled to the Active Site Environment.

Angew Chem Int Ed Engl 2018 Jun 19. Epub 2018 Jun 19.

JASRI, SPring-8, SPring-8/RIKEN, 1-1-1 Kouto, Sayo-cho,, Sayo-gun, Hyogo 679-5198, JAPAN, JAPAN.

A combination of NRVS and FT-IR spectroscopies and DFT calculations was used to observe and characterize Fe-H/D bending modes in CrHydA1 [FeFe]-hydrogenase Cys-to-Ser variant C169S. Mutagenesis of cysteine to serine at position 169 changes the functional group adjacent to the H-cluster from a -SH to -OH, thus altering the proton transfer pathway. C169S has a significant reduction in catalytic activity compared to the native CrHydA1, presumably due to less efficient transfer of protons to the H-cluster. Read More

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Dual Function Cobalt-Nickel Nanoparticles Tailored for High-Temperature Induction-Heated Steam Methane Reforming.

Angew Chem Int Ed Engl 2018 Jun 19. Epub 2018 Jun 19.

Haldor Topsøe A/S, Nymøllevej 55, DK-2800, Lyngby, DENMARK.

We present the tailored chemical synthesis of binary and ternary alloy nanoparticles with a uniform elemental composition and demonstrate their dual use as magnetic susceptors for induction heating and catalytic agent for steam reforming of methane to produce hydrogen at temperatures near and above 800oC. The heating and catalytic performance of two chemically synthesized samples of CoNi and Cu⊂CoNi, are compared and held against a traditional Ni-based reforming catalyst. The structural, magnetic and catalytic properties of the samples were characterized by X-ray diffraction, elemental analysis, magnetometry and reactivity measurements. Read More

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June 2018
1 Read

Ground-State Structure of the Proton-Bound Formate Dimer by Cold-Ion Infrared Action Spectroscopy.

Angew Chem Int Ed Engl 2018 Jun 19. Epub 2018 Jun 19.

Fritz-Haber-Institut der Max-Planck-Gesellschaft, Molecular Physics, Faradayweg 4-6, 14195, Berlin, GERMANY.

The proton-bound dicarboxylate motif, RCOO-·H+·-OOCR, is a prevalent chemical configuration found in many condensed phase systems. We study the archetypal proton-bound formate dimer, HCOO-·H+·-OOCH, utilizing cold-ion infrared action spectroscopy in the photon energy range of 400-1800 cm-1. The spectrum obtained at ~0. Read More

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Over 12% Polarization and 20 Minute Lifetime of 15N on Choline Derivative Utilizing Parahydrogen and Rh Nanocatalyst in Water.

Angew Chem Int Ed Engl 2018 Jun 19. Epub 2018 Jun 19.

University of California, Los Angeles UCLA, Department of Chemistry and Biochemistry, 607 Charles E Young Drive East, Young Hall 3048B, 90095, Los Angeles, UNITED STATES.

Hyperpolarization techniques are key to extending the capabilities of MRI for the investigation of structural, functional and metabolic processes in vivo. Recent heterogeneous catalyst development has produced high polarization in water using parahydrogen with biologically relevant contrast agents. Here we introduce a novel heterogeneous ligand-stabilized Rh catalyst capable of achieving 15N polarization of 12. Read More

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June 2018
2 Reads

Hydrogenation of Pyridines using a Nitrogen-Modified Titania Supported Cobalt Catalyst.

Angew Chem Int Ed Engl 2018 Jun 19. Epub 2018 Jun 19.

Leibniz-Institut für Katalyse, Homogeneous Catalysis, Albert-Einstein-Straße 29a, 18059, Rostock, GERMANY.

Novel heterogeneous catalysts were prepared by impregnation of titania with a solution of cobalt acetate/melamine and subsequent pyrolysis. The resulting materials show an unusual nitrogen-modified titanium structure through partial implementation of nitrogen into the support. The optimal catalyst displayed good activity and selectivity for challenging pyridine hydrogenation under acid free conditions in water as solvent. Read More

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Formation of Polypyrrole-Coated Sb2Se3 Microclips with Enhanced Sodium Storage Properties.

Angew Chem Int Ed Engl 2018 Jun 19. Epub 2018 Jun 19.

Nanyang Technological University, School of Chemical and Biomedical Eng, 62 Nanyang Drive, #N1.2-B1-09, 637459, Singapore, SINGAPORE.

Sb-based electrode materials with high specific capacity have aroused considerable interest as anode materials for sodium-ion batteries (SIBs). However, their practical application is still hindered by the poor rate capability and rapid capacity fading, which are largely due to their low electronic conductivity and the severe volume expansion during Na+ ions uptake. Tuning the nanostructure, increasing the conductivity and constructing a buffer layer are effective strategies to address these issues. Read More

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June 2018
1 Read

Floxuridine Homomeric Oligonucleotides "Hitchhike" with Albumin In Situ for Cancer Chemotherapy.

Angew Chem Int Ed Engl 2018 Jun 19. Epub 2018 Jun 19.

Molecular Science and Biomedicine Laboratory, State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, College of Life Sciences, Aptamer Engineering Center of Hunan Province, Hunan University, Changsha, Hunan, 410082, China.

Automated attachment of chemotherapeutic drugs to oligonucleotides through phosphoramidite chemistry and DNA synthesis has emerged as a powerful technology in constructing structure-defined and payload-tunable oligonucleotide-drug conjugates. In practice, however, in vivo delivery of these oligonucleotides remains a challenge. Inspired by the systemic transport of hydrophobic payloads by serum albumin in nature, we report the development of a lipid-conjugated floxuridine homomeric oligonucleotide (LFU20) that "hitchhikes" with endogenous serum albumin for cancer chemotherapy. Read More

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Enantioselective Synthesis of (-)-Halenaquinone.

Angew Chem Int Ed Engl 2018 Jun 19. Epub 2018 Jun 19.

Department of Chemistry, Oregon State University, Corvallis, OR, 97331, USA.

The efficient, 12-14 step (LLS) total synthesis of (-)-halenaquinone has been achieved. Key steps in the synthetic sequence include: (a) proline sulfonamide-catalyzed, Yamada-Otani reaction to establish the C6 all-carbon quaternary stereocenter, (b) multiple, novel palladium-mediated oxidative cyclizations to introduce the furan moiety, and (c) oxidative Bergman cyclization to form the final quinone ring. Read More

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Central Doping of a Foreign Atom into the Silver Cluster for Catalytic Conversion of CO2 toward C-C Bond Formation.

Angew Chem Int Ed Engl 2018 Jun 19. Epub 2018 Jun 19.

Nanjing University, Chemistry, No. 163 Xianlin Road, 210093, Nanjing, CHINA.

Clusters with an exact number of atoms are of particular research interest in catalysis. Their catalytic behaviors can be potentially altered with the addition or removal of a single atom. Herein we explore the effects of the single-foreign-atom (Au, Pd and Pt) doping into the core of an Ag cluster with 25-atoms on the catalytic properties, where the foreign atom is protected by 24 Ag atoms (i. Read More

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June 2018
1 Read

Thiourea-catalyzed asymmetric Michael addition of carbazolones to 2-chloroacrylonitrile: Total synthesis of 5,22-dioxokopsane, kopsinidine C and demethoxycarbonylkopsin.

Angew Chem Int Ed Engl 2018 Jun 19. Epub 2018 Jun 19.

CHINA.

A modified Takemoto's catalyst enabled the asymmetric Michael addition of carbazolones to 2-chloroacrylonitrile to afford 3,3-disubstituted carbazolones with excellent enantioselectivity. This method was successfully applied to the total synthesis of three kopsia alkaloids which featured an unprecedented Mn(III)-mediated oxidative cyclization to create the caged ring system, a SmI2-mediated reductive coupling and a ketol rearrangement as the key steps. Read More

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Competition between H and CO for active sites governs Cu mediated electrosynthesis of hydrocarbon fuels.

Angew Chem Int Ed Engl 2018 Jun 19. Epub 2018 Jun 19.

Massachusetts Institute of Technology, Chemistry, 77 Mass Ave., Rm. 18-292, 02139, Cambridge, UNITED STATES.

We investigate the dynamics of carbon monoxide on Cu surfaces during CO reduction and provide insight into the mechanism leading to the formation of hydrogen, methane and ethylene, the three key products in the electrochemical reduction of CO2. Reaction order experiments were conducted at low temperature in an ethanol medium affording high solubility and surface-affinity for carbon monoxide. Surprisingly, we find that the methane production rate is suppressed by increasing the pressure of CO, whereas ethylene production remains largely unaffected. Read More

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Iron Porphyrins Embedded into a Supramolecular Porous Organic Cage for Electrochemical CO2 Reduction in Water.

Angew Chem Int Ed Engl 2018 Jun 19. Epub 2018 Jun 19.

University of California, Department of Chemistry, 532A Latimer Hall, 94720-1460, Berkeley, UNITED STATES.

We report the use of a porous organic cage composed of six iron tetraphenylporphyrins as a supramolecular catalyst for electrochemical CO2-to-CO conversion. This strategy enhances active site exposure and substrate diffusion relative to the monomeric catalyst, resulting in CO generation with near-quantitative Faradaic efficiency in pH 7.3 water, with activities reaching 55,250 turnovers. Read More

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Peapod-like CoP@C nanostructure from phosphorization in low-temperature molten salt for high-performance lithium ion batteries.

Angew Chem Int Ed Engl 2018 Jun 19. Epub 2018 Jun 19.

CHINA.

A mild phosphorization process in low-temperature molten salt (NaCl-KCl-AlCl3) is developed to synthesize peapod-like CoP@C nanostructures by using low-toxic industrial PCl3 as the phosphorus source and Mg as the reductant at 250 ºC. Importantly, high using efficiency of the phosphorous source is achieved since only stoichiometric PCl3 is required to complete the reaction. The molten NaCl-KCl-AlCl3 not only provide a liquid environment but also participate in the electron transport by the reversible conversion of Al3+/Al redox couple. Read More

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Efficient Oxygen Reduction Reaction (ORR) Catalysts Based on Single Iron Atoms Dispersed on a Hierarchically Structured Porous Carbon Framework.

Angew Chem Int Ed Engl 2018 Jun 19. Epub 2018 Jun 19.

Center of Advanced Science and Engineering for Carbon (Case4carbon), Department of Macromolecular Science and Engineering, Case Western Reserve University, Cleveland, OH, 44106, USA.

Single Fe atoms dispersed on hierarchically structured porous carbon (SA-Fe-HPC) frameworks are prepared by pyrolysis of unsubstituted phthalocyanine/iron phthalocyanine complexes confined within micropores of the porous carbon support. The single-atom Fe catalysts have a well-defined atomic dispersion of Fe atoms coordinated by N ligands on the 3D hierarchically porous carbon support. These SA-Fe-HPC catalysts are comparable to the commercial Pt/C electrode even in acidic electrolytes for oxygen reduction reaction (ORR) in terms of the ORR activity (E =0. Read More

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June 2018
1 Read

Precise Activation of Ammonia and Carbon Dioxide by an Iminodisilene.

Angew Chem Int Ed Engl 2018 Jun 19. Epub 2018 Jun 19.

TU München - Technische Chemie, Wacker Lehrstuhl für Makromolekulare Chemie, Lichtenbergstr. 4, 85748, Garching, GERMANY.

The activation of NH₃ and CO₂ is still an ambitious target for multiply bonded sub-valent silicon compounds. Herein, we present the precise splitting of the N-H bond of ammonia by (Z)-imino(silyl)disilene 1 to give trans-1,2-adduct 2a at low temperatures (-78 °C). According to DFT calculations, the stereospecific hydroamination follows a similar mechanism as the recently reported anti-addition of H₂ to the Si=Si bond of 1. Read More

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Ultrasmall Zeolite L Crystals Prepared from Highly-Interdispersed Alkali-Silicate Precursors.

Angew Chem Int Ed Engl 2018 Jun 19. Epub 2018 Jun 19.

University of Houston, Chemical and Biomolecular Engineering, 4726 Calhoun Road, S222 Engineering Building 1, 77204, Houston, UNITED STATES.

The preparation of nanosized zeolites is critical for applications where mass transport limitations within microporous networks hinder their performance. Oftentimes the ability to generate ultrasmall zeolite crystals is dependent upon the use of expensive organics with limited commercial relevance. Here, we report the generation of zeolite L crystals with uniform sizes less than 30 nm using a facile, organic-free method. Read More

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Jochen Block Prize for Andreas Vorholt / Otto Bayer Award for Tobias Erb.

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Angew Chem Int Ed Engl 2018 Jun 19. Epub 2018 Jun 19.

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Blood-Catalyzed RAFT Polymerization.

Angew Chem Int Ed Engl 2018 Jun 19. Epub 2018 Jun 19.

The University of Melbourne, Department of Chemical and Biomolecular Engineering, The University of Melbourne, 3010, Melbourne, AUSTRALIA.

The use of hemoglobin (Hb) contained within red blood cells to drive a controlled radical polymerization via a reversible addition-fragmentation chain transfer (RAFT) process is reported for the first time. No pre-treatment of the Hb or cells was required prior to their use as polymerization catalysts, indicating the potential for synthetic engineering in complex biological microenvironments without the need for ex vivo techniques. Due to the naturally-occurring prevalence of the reagents employed in the catalytic system (Hb and hydrogen peroxide), this approach may facilitate the development of new strategies for in vivo cell engineering with synthetic macromolecules. Read More

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Organocatalytic Formation of Chiral Trisubstituted Allenes and Chiral Furan Derivatives.

Angew Chem Int Ed Engl 2018 Jun 19. Epub 2018 Jun 19.

DENMARK.

A novel reaction concept providing chiral allenes by amino catalytic activation of aldehydes or alpha,beta-unsaturated aldehydes reacting with alkynyl-substituted enones is presented. The reaction proceeds to form a variety of trisubstituted allenes in high yields and excellent stereoselectivities. The utility of the reaction concept is further demonstrated by the synthesis of chiral furan derivatives in high yields and stereoselectivities. Read More

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High-Throughput Design of Biocompatible Enzyme-Based Hydrogel Microparticles with Autonomous Movement.

Angew Chem Int Ed Engl 2018 Jun 19. Epub 2018 Jun 19.

Radboud Universiteit Institute for Molecules and Materials, Systems Chemistry, Heyendaalseweg 135, 6525 AJ, Nijmegen, NETHERLANDS.

Micro- and nanomotors and their use for biomedical applications have received recently increased attention. However, most designs use top-down methods to construct inorganic motors, which are labour-intensive and not suitable for biomedical use. Herein, we report a high throughput design of asymmetric hydrogel microparticle with autonomous movement using a microfluidic chip generating asymmetric aqueous two-phase separating droplets consisting of PEGDA and dextran with the biocatalyst placed in the PEGDA phase. Read More

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June 2018
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Purification of Uranium-based Endohedral Metallofullerenes (EMFs) by Selective Supramolecular Encapsulation and Release.

Angew Chem Int Ed Engl 2018 Jun 19. Epub 2018 Jun 19.

Universitat de Girona, Institut de Química Computacional i Catàlisi and Departament de Química, Campus Montilivi, Facultat de Ciències, 17071, Girona, SPAIN.

Supramolecular nanocapsule 1·(BArF)8 is able to sequentially and selectively entrap recently discovered U2@C80 and unprecedented Sc2CU@C80, simply by soaking crystals of 1·(BArF)8 in a toluene solution of arc-produced soot. These species, selectively and stepwise absorbed by 1·(BArF)8, are easily released, obtaining highly pure fractions of U2@C80 and Sc2CU@C80 in one step. Sc2CU@C80 represents the first example of a mixed metal actinide-based endohedral metallofullerene (EMF). Read More

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