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Angewandte Chemie

Duan-Jian Tao, Feng-Feng Chen, Zi-Qi Tian, Kuan Huang, Shannon M Mahurin, De-En Jiang, Sheng Dai
A novel method for the highly efficient and reversible capture of CO in carbanion-functionalized ionic liquids (ILs) by a C-site interaction is reported. Because of its supernucleophilicity, the carbanion in ILs could absorb CO efficiently. As a result, a relatively high absorption capacity for CO (up to 0.046 mol mol(-1) ) was achieved under ambient conditions, compared with CO solubility in a commonly used IL [Bmim][Tf2 N] (2×10(-3)  mol mol(-1) ). The results of quantum mechanical calculations and spectroscopic investigation confirmed that the chemical interaction between the C-site in the carbanion and CO resulted in the superior CO absorption capacities...
April 26, 2017: Angewandte Chemie
Nathan D Kirchhofer, Samantha R McCuskey, Cheng-Kang Mai, Guillermo C Bazan
We probe anaerobic respiration of bacteria in the presence of conjugated polyelectrolytes (CPEs). Three different CPEs were used to probe how structural variations impact biocurrent generation from Shewanella oneidensis MR-1. For the self-doped anionic CPE only, absorption spectroscopy shows that the addition of S. oneidensis MR-1 leads to the disappearance of the polaron (radical cation) band at >900 nm and an increase in the band at 735 nm due to the neutral species, consistent with electron transfer from microbe to polymer...
April 26, 2017: Angewandte Chemie
James I Murray, Nils J Flodén, Adriano Bauer, Nico D Fessner, Daniel L Dunklemann, Opetoritse Bob-Egbe, Henry S Rzepa, Thomas Bürgi, Jeffery Richardson, Alan C Spivey
The first catalytic kinetic resolution by N-sulfonylation is described. 2-Substituted indolines are resolved (s=2.6-19) using an atropisomeric 4-dimethylaminopyridine-N-oxide (4-DMAP-N-oxide) organocatalyst. Use of 2-isopropyl-4-nitrophenylsulfonyl chloride is critical to the stereodiscrimination and enables facile deprotection of the sulfonamide products with thioglycolic acid. A qualitative model that accounts for the stereodiscrimination is proposed.
April 26, 2017: Angewandte Chemie
Jia-Liang Yang, Hai-Lin Wu, Yang Li, Xing-Hong Zhang, Donald J Darensbourg
The preparation of perfectly alternating and regioslective copolymers derived from the copolymerization of carbonyl sulfide (COS) and epoxides by metal-free Lewis pair catalysts composed of a Lewis base (amidine, guanidine, or quaternary onium salts) and a Lewis acid (triethyl borane) is described. Colorless and highly transparent copolymers of poly(monothiocarbonate) were successfully obtained with over 99 % tail-to-head content and high molecular weight (up to 92.5 kg mol(-1) ). In most instances, oxygen-sulfur exchange reactions (O/S ERs), which would generate random thiocarbonate and carbonate units, were effectively suppressed...
April 26, 2017: Angewandte Chemie
Frederik Neuhaus, Dennis Mueller, Radu Tanasescu, Sandor Balog, Takashi Ishikawa, Gerald Brezesinski, Andreas Zumbuehl
Phospholipid liposomes are archetypical self-assembled structures. To minimize the surface tension, the vesicles typically are spherical. Deciphering the bilayer code, the basic physical interactions between phospholipids would allow these molecules to be utilized as building blocks for novel, non-spherical structures. A 1,2-diamidophospholipid is presented that self-assembles into a cuboid structure. Owing to intermolecular hydrogen bonding, the bilayer membranes form an exceptionally tight subgel packing, leading to a maximization of flat structural elements and a minimization of any edges...
April 26, 2017: Angewandte Chemie
Leonardus H Leijendekker, Jens Weweler, Tobias M Leuther, Jan Streuff
A titanium(III)-catalyzed radical cyclization to unprotected 3-aminoindoles, 3-aminopyrroles, or 3-iminoindolines is reported. The reaction is non-hazardous, scalable, and allows facile isolation of the free products by extraction. The method is demonstrated on a large substrate scope and it further allows the direct installation of various nitrogen protecting groups or the synthesis of building blocks for peptide chemistry in a single sequence. Fused bisindoles can be directly accessed from the cyclization products...
April 26, 2017: Angewandte Chemie
Jean-Pierre Dognon, Pekka Pyykkö
A Periodic System was proposed for the elements 1-172 by Pyykkö on the basis of atomic and ionic calculations. In it, the elements 121-138 were nominally assigned to a 5g row. We now perform molecular, relativistic four-component DFT calculations and find that the hexafluorides of the elements 125-129 indeed enjoy occupied 5g states.
April 26, 2017: Angewandte Chemie
Daniel Lauster, Maria Glanz, Markus Bardua, Kai Ludwig, Markus Hellmund, Ute Hoffmann, Alf Hamann, Christoph Böttcher, Rainer Haag, Christian P R Hackenberger, Andreas Herrmann
To inhibit binding of the influenza A virus to the host cell glycocalyx, we generate multivalent peptide-polymer nanoparticles binding with nanomolar affinity to the virus via its spike protein hemagglutinin. The chosen dendritic polyglycerol scaffolds are highly biocompatible and well suited for a multivalent presentation. We could demonstrate in vitro that by increasing the size of the polymer scaffold and adjusting the peptide density, viral infection is drastically reduced. Such a peptide-polymer conjugate qualified also in an in vivo infection scenario...
April 26, 2017: Angewandte Chemie
Yuwei Hu, Alessandro Cecconello, Andrea Idili, Francesco Ricci, Itamar Willner
Triplex nucleic acids attract recent interest as part of the rich "tool-box" of structures used to develop DNA-based nanostructures and materials. This review addresses the use of DNA triplexes to assemble sensing platforms and molecular switches. Furthermore, the pH-induced, switchable assembly and dissociation of triplex DNA-bridged nanostructures are presented. Specifically, the aggregation/deaggregation of nanoparticles and the reversible oligomerization of "origami" tiles or DNA circles are described. Also, the use of triplex-DNA structures as functional units to assemble pH-responsive systems and materials are presented...
April 26, 2017: Angewandte Chemie
Areetha D'Souza, Xiangyang Wu, Edwin Kok Lee Yeow, Surajit Bhattacharjya
The structure and function of naturally occurring proteins are governed by a large number of amino acids (≥100). The design of miniature proteins with desired structures and functions not only substantiates our knowledge about proteins but can also contribute to the development of novel applications. Excellent progress has been made towards the design of helical proteins with diverse functions. However, the development of functional β-sheet proteins remains challenging. Herein, we describe the construction and characterization of four-stranded β-sheet miniproteins made up of about 19 amino acids that bind heme inside a hydrophobic binding pocket or "heme cage" by bis-histidine coordination in an aqueous environment...
April 25, 2017: Angewandte Chemie
Hyun-Joo Koo, Elijah E Gordon, Myung-Hwan Whangbo
The feasibility of a single-domain ferromagnet based on uniaxial magnetic ions was examined. For a noncentrosymmetric uniaxial magnetic ion of magnetic moment μ at a site of local electric dipole moment p, it is unknown to date whether μ prefers to be parallel or antiparallel to μ. The nature of this magnetoelectric interaction was probed in terms of analogical reasoning based on the Rashba effect and density functional theory (DFT) calculations. We show that μ and p prefer an antiparallel arrangement, predict that Fe-doped CaZnOS is a single-domain ferromagnet like a bar magnet, and find the probable cause for the ferromagnetism and weak magnetization hysteresis in Fe-doped hexagonal ZnO and ZnS at very low dopant concentrations...
April 25, 2017: Angewandte Chemie
Philip Brandt, María García-Altares, Markus Nett, Christian Hertweck, Dirk Hoffmeister
The antilarval mushroom polyenes 18-methyl-19-oxoicosaoctaenoic acid and 20-methyl-21-oxodocosanonaenoic acid appear in response to injury of the mycelium of the stereaceous mushroom BY1. We identified a polyketide synthase (PPS1) which belongs to a hitherto completely uncharacterized clade of polyketide synthases. Expression of the PPS1 gene is massively upregulated following mycelial damage. The synthesis of the above polyenes was reconstituted in the mold Aspergillus niger as a heterologous host. This demonstrates that PPS1 1) synchronously produces branched-chain polyketides of varied lengths, and 2) catalyzes the unprecedented shift of eight or nine double bonds...
April 25, 2017: Angewandte Chemie
Sabine Laschat, Ursula Bilitewski, Joshua Blodgett, Anne-Kathrin Duhme-Klair, Sabrina Dallavalle, Anne Routledge, Rainer Schobert
Upon bacterial infection one of the defense mechanisms of the host is the withdrawal of essential metal ions, in particular iron leading to "nutritional immunity". However, bacteria have evolved strategies to overcome iron starvation, e.g. by stealing iron from the host or other bacteria by specific iron chelators with high binding affinity. Fortunately, these complex interactions between host and pathogen regarding metal homeostasis provide several opportunities for interception and thus allow the development of novel antibacterials...
April 25, 2017: Angewandte Chemie
Johanna Hofmann, Kevin Pagel
Carbohydrates form one of the major classes of biological macromolecules in living organisms. To investigate their properties and function, an in-depth knowledge of their underlying structure is essential. However, the inherent structural complexity of glycans represents a major challenge. Carbohydrates are often branched and exhibit diverse regio- and stereochemistry. This in turn leads to a vast number of possible isomers, which are difficult to distinguish using established analytical tools. In the last decade, ion mobility-mass spectrometry, a technique that separates ions based on their mass, charge, size and shape, emerged as a powerful alternative for isomer distinction...
April 24, 2017: Angewandte Chemie
Yongxing Tang, Lauren A Mitchell, Gregory H Imler, Damon A Parrish, Jean'ne M Shreeve
3,5-Dinitrimino-1,2,4-triazole (2) with three protons has the potential of deprotonation to form energetic salts. Neutralization of 2 with 50 % hydroxylamine in varying molar ratios leads to the formation of the corresponding mono/dihydroxylammonium energetic salts. Additionally compound 5, an ammonia oxide adduct of dihydroxylammonium 3,5-dinitramino-1,2,4-triazolate, was prepared when excess hydroxylamine was used. The structures of 3-5 are supported by single-crystal X-ray diffraction. The energetic properties of the new materials are competitive...
April 24, 2017: Angewandte Chemie
Florian Gallier, Arnaud Martel, Gilles Dujardin
The Robinson annulation is a reaction that has been useful for numerous syntheses since its discovery in 1935, especially in the field of the steroid synthesis. The products are usually obtained after 3 consecutive steps which are the formation of an enolate (or derivative), a conjugate addition and an aldol reaction. Over the years, several methodological improvements were made for each individual step or alternative routes were devised to access the Robinson annulation products. The first part of this review outlines the most relevant developments towards the formation of Monocarbonyl-derived Robinson Annulation Products (MRA Products, MRAP) and Activated Monocarbonyl-derived Robinson Annulation Products (AMRA Products, AMRAP)...
April 24, 2017: Angewandte Chemie
Heiko Sommer, James Y Hamilton, Alois Fürstner
Treatment of alkenylstannanes with Cu(OAc)2 /Et3 N affords the corresponding enol esters or ketones under conditions that proved compatible with many common functionalities; these include groups that would neither survive under the standard Tamao-Fleming conditions for the oxidation of Csp2 -SiR3 bonds nor under the conditions commonly used to oxidize C-B bonds. Chiral centers adjacent to the unveiled carbonyls are not racemized and competing protodestannation is marginal, even if the substrate carries unprotected -OH groups as internal proton sources...
April 24, 2017: Angewandte Chemie
Hua Wu, Qian Wang, Jieping Zhu
We report an unprecedented organocatalytic enantioselective acyloin rearrangement of α,α-disubstituted α-hydroxy acetals. In the presence of a catalytic amount of chiral binol-derived N-triflyl phosphoramide, α-hydroxy acetals rearranged to α-alkoxy ketones in good to high yields with high enantioselectivities. Formation of an ion pair between the in situ generated oxocarbenium ion and the chiral phosphoramide anion was proposed to be responsible for the highly efficient transfer of chirality. Conditions for removal of cyclohexyl and cyclopentyl groups from the corresponding α-alkoxy ketones were uncovered underpinning their potential general utility as hydroxy protecting groups...
April 24, 2017: Angewandte Chemie
G K Surya Prakash
George Andrew Olah, Founding Director, Loker Hydrocarbon Research Institute at the University of Southern California, passed away on March 8, 2017. Olah was awarded the Nobel Prize in Chemistry 1994 for his work on the stabilization of carbocations in superacids. In recent years he was highly active in establishing a methanol economy, in which carbon dioxide is converted to methanol for use as a fuel or feedstock.
April 24, 2017: Angewandte Chemie
Yuya Ikeuchi, Hiroshi Takatsu, Cédric Tassel, Yoshihiro Goto, Taito Murakami, Hiroshi Kageyama
A high-pressure reaction yielded the fully occupied tetragonal tungsten bronze K3 W5 O15 (K0.6 WO3 ). The terminal phase shows an unusual transport property featuring slightly negative temperature-dependence in resistivity (dρ/dT<0) and a large Wilson ratio of RW =3.2. Such anomalous metallic behavior possibly arises from the low-dimensional electronic structure with a van Hove singularity at the Fermi level and/or from enhanced magnetic fluctuations by geometrical frustration of the tungsten sublattice...
April 24, 2017: Angewandte Chemie
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