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Angewandte Chemie

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https://www.readbyqxmd.com/read/27910251/cloaked-caged-compounds-chemical-probes-for-two-photon-optoneurobiology
#1
Matthew T Richers, Joseph M Amatrudo, Jeremy P Olson, Graham C R Ellis-Davies
Caged neurotransmitters, in combination with focused light beams, enable precise interrogation of neuronal function, even at the level of single synapses. However, most caged transmitters are, surprisingly, severe antagonists of ionotropic gamma-aminobutyric acid (GABA) receptors. By conjugation of a large, neutral dendrimer to a caged GABA probe we introduce a "cloaking" technology that effectively reduces such antagonism to very low levels. Such cloaked caged compounds will enable the study of the signaling of the inhibitory neurotransmitter GABA in its natural state using two-photon uncaging microscopy for the first time...
December 2, 2016: Angewandte Chemie
https://www.readbyqxmd.com/read/27910250/a-large-%C3%AF-extended-carbon-nanoring-based-on-nanographene-units-bottom-up-synthesis-photophysical-properties-and-selective-complexation-with-fullerene-c70
#2
Dapeng Lu, Guilin Zhuang, Haotian Wu, Song Wang, Shangfeng Yang, Pingwu Du
Herein we report the organoplatinum-mediated bottom-up synthesis, characterization, and properties of a novel large π-extended carbon nanoring based on a nanographene hexa-peri-hexabenzocoronene (HBC) building unit. This tubular structure can be considered as an example of the longitudinal extension of the cycloparaphenylene scaffold to form a large π-extended carbon nanotube (CNT) segment. The cyclic tetramer of a tetramesityl HBC ([4]CHBC) was synthesized by the reaction of a 2,11-diborylated hexa-peri-hexabenzocoronene with a platinum complex, followed by reductive elimination...
December 2, 2016: Angewandte Chemie
https://www.readbyqxmd.com/read/27910244/total-syntheses-of-sarcandrolide%C3%A2-j-and-shizukaol%C3%A2-d-lindenane-sesquiterpenoid-4-2-dimers
#3
Changchun Yuan, Biao Du, Heping Deng, Yi Man, Bo Liu
The syntheses of members of a family of lindenane sesquiterpenoid [4+2] dimers led to the total syntheses of sarcandrolide J and shizukaol D. Inspired by a modified biosynthetic pathway, a cascade featuring furan formation/alkene isomerization/Diels-Alder cycloaddition was devised to construct the congested polycyclic architecture of the target molecules with the correct stereochemistry. This study presents a pioneering synthetic entry to this family of natural products and paves the way for fully exploring their biological functions...
December 2, 2016: Angewandte Chemie
https://www.readbyqxmd.com/read/27910233/a-genetically-encoded-allysine-for-the-synthesis-of-proteins-with-site-specific-lysine-dimethylation
#4
Zhipeng A Wang, Yu Zeng, Yadagiri Kurra, Xin Wang, Jeffery M Tharp, Erol C Vatansever, Willie W Hsu, Susie Dai, Xinqiang Fang, Wenshe R Liu
Using the amber suppression approach, N(ϵ) -(4-azidobenzoxycarbonyl)-δ,ϵ-dehydrolysine, an allysine precursor is genetically encoded in E. coli. Its genetic incorporation followed by two sequential biocompatible reactions allows convenient synthesis of proteins with site-specific lysine dimethylation. Using this approach, dimethyl-histone H3 and p53 proteins have been synthesized and used to probe functions of epigenetic enzymes including histone demethylase LSD1 and histone acetyltransferase Tip60. We confirmed that LSD1 is catalytically active toward H3K4me2 and H3K9me2 but inert toward H3K36me2, and methylation at p53 K372 directly activates Tip60 for its catalyzed acetylation at p53 K120...
December 2, 2016: Angewandte Chemie
https://www.readbyqxmd.com/read/27910228/regioselective-hydrohydroxyalkylation-of-styrene-with-primary-alcohols-or-aldehydes-via-ruthenium-catalyzed-c-c-bond-forming-transfer-hydrogenation
#5
Hongde Xiao, Gang Wang, Michael J Krische
Transfer hydrogenative coupling of styrene with primary alcohols using the precatalyst HClRu(CO)(PCy3 )2 modified by AgOTf or HBF4 delivers branched or linear adducts from benzylic or aliphatic alcohols, respectively. Related 2-propanol mediated reductive couplings also are described.
December 2, 2016: Angewandte Chemie
https://www.readbyqxmd.com/read/27910202/isopropanol-dehydration-on-amorphous-silica-alumina-synergy-of-br%C3%A3-nsted-and-lewis-acidities-at-pseudo-bridging-silanols
#6
Kim Larmier, Céline Chizallet, Sylvie Maury, Nicolas Cadran, Johnny Abboud, Anne-Félicie Lamic-Humblot, Eric Marceau, Hélène Lauron-Pernot
The mechanism of isopropanol dehydration on amorphous silica-alumina (ASA) was unraveled by a combination of experimental kinetic measurements and periodic density functional theory (DFT) calculations. We show that pseudo-bridging silanols (PBS-Al) are the most likely active sites owing to the synergy between the Brønsted and Lewis acidic properties of these sites, which facilitates the activation of alcohol hydroxy groups as leaving groups. Isopropanol dehydration was used to specifically investigate these PBS-Al sites, whose density was estimated to be about 10(-1)  site nm(-2) on the silica-doped alumina surface under investigation, by combining information from experiments and theoretical calculations...
December 2, 2016: Angewandte Chemie
https://www.readbyqxmd.com/read/27910197/a-stable-manganese-pincer-catalyst-for-the-selective-dehydrogenation-of-methanol
#7
María Andérez-Fernández, Lydia K Vogt, Steffen Fischer, Wei Zhou, Haijun Jiao, Marcel Garbe, Saravanakumar Elangovan, Kathrin Junge, Henrik Junge, Ralf Ludwig, Matthias Beller
For the first time, structurally defined manganese pincer complexes catalyze the dehydrogenation of aqueous methanol to hydrogen and carbon dioxide, which is a transformation of interest with regard to the implementation of a hydrogen and methanol economy. Excellent long-term stability was demonstrated for the Mn-PNPiPr catalyst, as a turnover of more than 20 000 was reached. In addition to methanol, other important hydrogen carriers were also successfully dehydrogenated.
December 2, 2016: Angewandte Chemie
https://www.readbyqxmd.com/read/27910196/atomically-dispersed-iron-nitrogen-species-as-electrocatalysts-for-bifunctional-oxygen-evolution-and-reduction-reactions
#8
Pengzuo Chen, Tianpei Zhou, Lili Xing, Kun Xu, Yun Tong, Hui Xie, Lidong Zhang, Wensheng Yan, Wangsheng Chu, Changzheng Wu, Yi Xie
Rational design of non-noble materials as highly efficient, economical, and durable bifunctional catalysts for oxygen evolution and reduction reactions (OER/ORR) is currently a critical obstacle for rechargeable metal-air batteries. A new route involving S was developed to achieve atomic dispersion of Fe-Nx species on N and S co-decorated hierarchical carbon layers, resulting in single-atom bifunctional OER/ORR catalysts for the first time. The abundant atomically dispersed Fe-Nx species are highly catalytically active, the hierarchical structure offers more opportunities for active sites, and the electrical conductivity is greatly improved...
December 2, 2016: Angewandte Chemie
https://www.readbyqxmd.com/read/27910194/stereospecific-construction-of-contiguous-quaternary-all-carbon-centers-by-oxidative-ring-contraction
#9
Xin Yu, Jiadong Hu, Zhigao Shen, Hui Zhang, Jin-Ming Gao, Weiqing Xie
Oxidative ring contraction of cyclic α-formyl ketones was facilitated by the action of H2 O2 under operationally simple and environmentally benign reaction conditions. The process was highly regioselective and enables stereospecific construction of contiguous quaternary all-carbon centers from stereodefined all-substituted all-cyclic ketones. The asymmetric syntheses of (+)-cuparene and (+)-tochuinyl acetate were also successively achieved by taking advantage of this novel protocol.
December 2, 2016: Angewandte Chemie
https://www.readbyqxmd.com/read/27910186/diverse-activation-modes-in-the-hydroboration-of-aldehydes-and-ketones-with-germanium-tin-and-lead-lewis-pairs
#10
Julia Schneider, Christian P Sindlinger, Sarah M Freitag, Hartmut Schubert, Lars Wesemann
Intramolecular germylene, stannylene, and plumbylene Lewis pairs were reacted with hexanal and yielded the cyclic addition products only with the germanium and tin reagents. In further reactivity studies, the hydroboration of aldehydes and ketones catalyzed by intramolecular germylene, stannylene, and plumbylene Lewis pairs was studied. In the case of the cyclic germylene Lewis pair, the product of the oxidative addition of pinacolborane at the germylene moiety was observed. According to stoichiometric as well as catalytic experiments, the intramolecular germylene Lewis pair acts as a catalyst in the hydroboration of aldehydes and ketones...
December 2, 2016: Angewandte Chemie
https://www.readbyqxmd.com/read/27910183/on-the-origin-of-the-remarkably-variable-reactivities-of-alceox-x-2-4-towards-methane-as-a-function-of-oxygen-content
#11
Shaodong Zhou, Jilai Li, Maria Schlangen, Helmut Schwarz
The thermal gas-phase reactions of the closed-shell heteronuclear metal-oxide clusters [AlCeOx ](+) (x=2-4) with methane have been explored by FT-ICR mass spectrometry and high-level quantum-chemical calculation. Whereas [AlCeO2 ](+) and [AlCeO4 ](+) are inert towards methane under ambient conditions, [AlCeO3 ](+) spontaneously abstracts one hydrogen atom from methane. Mechanistic aspects have been addressed to reveal the reasons for the rather distinct reactivities of the [AlCeOx ](+) /CH4 couples, and the electronic origins of the unprecedented single hydrogen-atom abstraction from methane by closed-shell [AlCeO3 ](+) are discussed...
December 2, 2016: Angewandte Chemie
https://www.readbyqxmd.com/read/27910182/catalyst-free-polyhydroboration-of-dodecaborate-yields-highly-photoluminescent-ionic-polyarylated-clusters
#12
Mark W Lee
The incorporation of polyhedral boranes into novel photoluminescent materials is an area with increasing interest. While the neutral carboranes have been widely investigated for this purpose, the dodecaborate ion has received much less attention. Herein we report a significant expansion to the scope of substitution reactions for the dodecaborate ion, whereby this cluster was observed to react directly with a wide range of arenes in a step-wise and controlled manner. In the products of these reactions, the dodecaborate ion serves as a core upon which up to nine mono- or polycyclic aromatic hydrocarbon ligands are exohedrally bonded...
December 2, 2016: Angewandte Chemie
https://www.readbyqxmd.com/read/27910179/stereocontrolled-total-syntheses-of-rotenone-and-dalpanol-by-1-2-rearrangement-and-sn-ar-oxycyclizations
#13
Kayo Nakamura, Ken Ohmori, Keisuke Suzuki
The total syntheses of (-)-rotenone and (-)-dalpanol have been achieved by a group-selective, stereospecific 1,2-shift of an epoxy alcohol and SN Ar cyclizations. Three oxacycles are constructed, thus illustrating a versatile synthetic route to various rotenoids.
December 2, 2016: Angewandte Chemie
https://www.readbyqxmd.com/read/27910176/visible-light-accelerated-c-h-sulfinylation-of-heteroarenes
#14
Andreas Uwe Meyer, Alexander Wimmer, Burkhard König
Heteroaromatic sulfoxides are a frequent structural motif in natural products, drugs, catalysts, and materials. We report a metal-free visible-light-accelerated synthesis of heteroaromatic sulfoxides from sulfinamides and peroxodisulfate. The reaction proceeds at room temperature with blue-light irradiation and allows the C-H sulfinylation of electron-rich heteroarenes, such as pyrroles and indoles. An electrophilic aromatic substitution mechanism is proposed based on the substrate scope, substitution selectivity, and competition experiments with different nucleophiles...
December 2, 2016: Angewandte Chemie
https://www.readbyqxmd.com/read/27911472/solid-state-emission-of-the-anthracene-o-carborane-dyad-from-the-twisted-intramolecular-charge-transfer-in-the-crystalline-state
#15
Hirofumi Naito, Kenta Nishino, Yasuhiro Morisaki, Kazuo Tanaka, Yoshiki Chujo
The emission process of the o-carborane dyad with anthracene originating from the twisted intramolecular charge transfer (TICT) state in the crystalline state is described. The anthracene-o-carborane dyad was synthesized and its optical properties were investigated. Initially, the dyad had aggregation- and crystallization-induced emission enhancement (AIEE and CIEE) properties via the intramolecular charge transfer (ICT) state. Interestingly, the dyad presented the dual-emissions assigned to both locally excited (LE) and ICT states in solution...
December 1, 2016: Angewandte Chemie
https://www.readbyqxmd.com/read/27907246/modern-synthetic-avenues-for-the-preparation-of-functional-fluorophores
#16
Fabio De Moliner, Nicola Kielland, Rodolfo Lavilla, Marc Vendrell
Biomedical research relies on the fast and accurate profiling of specific biomolecules and cells in a non-invasive manner. Functional fluorophores have consolidated as powerful tools for such studies. Since these sophisticated structures are often difficult to access through conventional synthetic strategies, novel chemical processes have been developed in the last years. In this Minireview we describe the most recent advances in the design, preparation and fine-tuning of fluorophores by means of multicomponent reactions, C-H activation processes, cycloadditions and biomolecule-based chemical transformations...
December 1, 2016: Angewandte Chemie
https://www.readbyqxmd.com/read/27906528/a-new-domain-of-reactivity-for-high-valent-dinuclear-m-%C3%AE-o-2-m-complexes-in-oxidation-reactions
#17
Xenia Engelmann, Shenglai Yao, Erik R Farquhar, Tibor Szilvási, Uwe Kuhlmann, Peter Hildebrandt, Matthias Driess, Kallol Ray
The strikingly different reactivity of a series of homo- and heterodinuclear [(M(III) )(μ-O)2 (M(III) )'](2+) (M=Ni; M'=Fe, Co, Ni and M=M'=Co) complexes with β-diketiminate ligands in electrophilic and nucleophilic oxidation reactions is reported, and can be correlated to the spectroscopic features of the [(M(III) )(μ-O)2 (M(III) )'](2+) core. In particular, the unprecedented nucleophilic reactivity of the symmetric [Ni(III) (μ-O)2 Ni(III) ](2+) complex and the decay of the asymmetric [Ni(III) (μ-O)2 Co(III) ](2+) core through aromatic hydroxylation reactions represent a new domain for high-valent bis(μ-oxido)dimetal reactivity...
December 1, 2016: Angewandte Chemie
https://www.readbyqxmd.com/read/27906493/achiral-inorganic-gypsum-acts-as-an-origin-of-chirality-through-its-enantiotopic-surface-in-conjunction-with-asymmetric-autocatalysis
#18
Arimasa Matsumoto, Yoshiyasu Kaimori, Mizuki Uchida, Haruna Omori, Tsuneomi Kawasaki, Kenso Soai
Achiral inorganic gypsum (CaSO4 ⋅2 H2 O) triggers the asymmetric autocatalysis of pyrimidyl alkanol on its two-dimensional enantiotopic faces to give highly enantioenriched alkanol products with absolute configurations corresponding to the respective enantiotopic surfaces. This is the first example of highly enantioselective synthesis on the enantiotopic surface of an achiral mineral.
December 1, 2016: Angewandte Chemie
https://www.readbyqxmd.com/read/27905166/50-and-more-years-of-propellane-chemistry-from-a-chemical-curiosity-to-explosive-applications-in-material-sciences-and-natural-product-chemistry
#19
Alicia Merve Dilmac, Eduard Spuling, Armin de Meijere, Stefan Bräse
Propellanes are a unique class of compounds with well over 10000 members with an inverted tetrahedral configuration featuring a weak single bond between two carbon atoms linked by three additional bridge. Not only structurally interesting, these propella-type compounds exhibit unusual reactivities. In this review, we highlight their synthesis and applications in material sciences, natural product chemistry and medicinal chemistry. We feature the chemistry of [1.1.1]propellane like the synthesis of oligomeric and polymeric structures derived from it such as bicyclo[1...
November 30, 2016: Angewandte Chemie
https://www.readbyqxmd.com/read/27902877/the-discovery-of-electrokinetic-phenomena-setting-the-record-straight
#20
REVIEW
Christian J C Biscombe
Electro-osmosis and electrophoresis were discovered by F. F. Reuss in Moscow in 1807. Or so the story goes. This essay critically examines the contributions of three scientists to the discovery of electrokinetic phenomena. The evidence suggests that Reuss did indeed discover electro-osmosis, which takes its name (indirectly) from the work of Porrett. Contrary to current consensus, Gautherot made the earliest known observation of electrophoresis.
November 30, 2016: Angewandte Chemie
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