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Tarak Karmakar, Sundaram Balasubramanian
Arylmalonate decarboxylase (AMDase) catalyzes the decarboxylation of α-aryl-α-methyl malonates to produce optically pure α-arylpropionates of industrial and medicinal importance. Herein, atomistic molecular dynamics simulations have been carried out to delineate the mechanism of the release of product molecules, phenylacetate (PAC) and carbon dioxide (CO2 ) from the wild-type (WT) and its G74C/C188S mutant enzymes. Both the product molecules follow a crystallographically characterized solvent-accessible channel to come out of the protein interior...
October 24, 2016: Journal of Physical Chemistry. B
Agostino Biafora, Thilo Krause, Dagmar Hackenberger, Florian Belitz, Lukas J Gooßen
A system consisting of catalytic amounts of [(p-cym)RuCl2 ]2 /PEt3 ⋅HBF4 , K2 CO3 as the base, and NMP as the solvent efficiently mediates the ortho-C-H arylation of benzoic acids with aryl bromides at 100 °C. Replacing the phosphine ligand with the amino acid dl-pipecolinic acid enables the analogous transformation with aryl chlorides. The key advantage of this broadly applicable transformation is the use of an inexpensive ruthenium catalyst in combination with simple carboxylates as directing groups, which can either be tracelessly removed or used as anchor points for decarboxylative ipso substitutions...
October 21, 2016: Angewandte Chemie
Stefan Hofbauer, Georg Mlynek, Lisa Milazzo, Dominic Pühringer, Daniel Maresch, Irene Schaffner, Paul G Furtmüller, Giulietta Smulevich, Kristina Djinović-Carugo, Christian Obinger
Heme biosynthesis in Gram positive bacteria follows a recently described coproporphyrin-dependent pathway with HemQ catalyzing the decarboxylation of coproheme to heme b. Here we present the first crystal structure of a HemQ (homopentameric coproproheme-HemQ from Listeria monocytogenes) at 1.69 Å resolution and the conversion of coproheme to heme b followed by UV-vis and resonance Raman spectroscopy as well as mass spectrometry. The ferric 5-coordinated coproheme iron of HemQ is weakly bound by a neutral proximal histidine H174...
October 18, 2016: FEBS Journal
Qipu Dai, Peihe Li, Nuannuan Ma, Changwen Hu
A novel approach has been developed for the synthesis of arylamines via the palladium-catalyzed intramolecular decarboxylative coupling (IDC) of aroyloxycarbamates, obtained in situ by reacting aryl carboxylic acids with hydroxycarbamates. The reaction offers facile access to structurally diverse arylamines with the site-specific formation of the C(sp(2))-N bond under mild conditions.
October 18, 2016: Organic Letters
Álvaro Gómez Baraibar, Dennis Reichert, Carolin Mügge, Svenja Seger, Harald Gröger, Robert Kourist
The combination of enzymes with traditional chemical catalysts unifies the high selectivity of the former with the versatility of the latter. A major challenge of this approach is the difference in the optimal reaction conditions for each catalyst type. In this work, we combined a cofactor-free decarboxylase with a ruthenium metathesis catalyst to produce high-value antioxidants from bio-based precursors. As suitable ruthenium catalysts did not show satisfactory activity under aqueous conditions, the reaction required the use of an organic solvent, which in turn significantly reduced enzyme activity...
October 18, 2016: Angewandte Chemie
S Binita Chanu, Samya Banerjee, Mithun Roy
Cancer-specific anticancer drugs are still an elusive goal. Using light as the temporal control to generate cytotoxic species from photo-activated prodrug in the presence or absence of molecular oxygen has shown potential application targeted chemotherapy as in photodynamic therapy (PDT). In the present work we explored the chemistry of several photo-active (μ-oxo)diiron(III) complexes of the following formulation [{Fe(μ-O) (L-his)(B)}2](ClO4)2 (1a-1c), [Fe2(μ-O)(H2O)2B4](ClO4)4 (2b, 2c) and [Fe2(μ-O)(μ-O2CMe)B4](ClO4)3 (3b, 3c), L-his = l-histidine, B is 2,2'-bipyridine, 1,10-phenanthroline (phen) and dipyrido[3,2-d:2',3'-f]quinoxaline (dpq) complexes for tumor-specific anticancer activity...
September 28, 2016: European Journal of Medicinal Chemistry
Salette Martinez, Robert P Hausinger
The ethylene-forming enzyme (EFE) from Pseudomonas syringae pv. phaseolicola PK2 is a member of the mononuclear non-heme Fe(II)- and 2-oxoglutarate (2OG)-dependent oxygenase superfamily. This enzyme is reported to simultaneously catalyze the conversion of 2OG into ethylene plus three CO2 and the Cδ hydroxylation of L-arginine (L-Arg) while oxidatively decarboxylating 2OG to form succinate and carbon dioxide. A new plasmid construct for expression in recombinant Escherichia coli cells allowed for the purification of large amounts of EFE with greater activity than previously recorded...
October 17, 2016: Biochemistry
John Lee
The molecular mechanisms of the bioluminescence systems of the firefly, bacteria, and those utilizing imidazopyrazinone luciferins such as coelenterazine, are gradually being uncovered using modern biophysical methods such as dynamic (ns-ps) fluorescence spectroscopy, NMR, X-ray crystallography, and computational chemistry. The chemical structures of all reactants are well defined and the spatial structures of the luciferases are providing important insight into interactions within the active cavity. It is generally accepted that the firefly and coelenterazine systems, although proceeding by different chemistries, both generate a dioxetanone high energy species that undergoes decarboxylation to form directly the product in its S1 state, the bioluminescence emitter...
October 17, 2016: Photochemistry and Photobiology
Yunhe Jin, Haijun Yang, Hua Fu
An efficient visible-light photoredox decarboxylative coupling of N-(acetoxy)phthalimides with aryl thiols has been developed. The reaction was performed well at room temperature with good tolerance of functional groups. Importantly, the visible-light photoredox decarboxylative arylthiation did not need an added photocatalyst.
October 14, 2016: Chemical Communications: Chem Comm
Dalip Kumar, V Arun, Meenakshi Pilania
Easily accessible heteroaromatic carboxylic acids and diaryliodonium salts were successfully employed to construct valuable 2-arylindoles and heteroaryl carboxylates in a regioselective fashion. C2-arylated indoles were produced via Pd-catalyzed decarboxylative strategy in water without any base, oxidant and ligand. Heteroaryl carboxylates were prepared under metal and base-free conditions. This protocol was successfully utilized to synthesize Paullone, a CDK inhibitor.
October 13, 2016: Chemistry, An Asian Journal
Patrick J Moon, Shengkang Yin, Rylan J Lundgren
We report decarboxylative carbonyl α-arylation by coupling arylboron nucleophiles with malonic acid derivatives. This process is enabled by the merger of aerobic oxidative Cu-catalysis with decarboxylative enolate interception reminiscent of malonyl-CoA reactivity in polyketide biosynthesis. This method allows for the synthesis of monoaryl acetate derivatives containing electrophilic functional groups that are incompatible with existing α-arylation reactivity paradigms. The utility of the reaction is demonstrated in drug intermediate synthesis and late-stage functionalization...
October 13, 2016: Journal of the American Chemical Society
Martin Pichette Drapeau, Lukas J Gooßen
The selective transformation of C-H bonds is one of the most desirable approaches to creating complexity from simple building blocks. Several directing groups are efficient in controlling the regioselectivity of catalytic C-H bond functionalizations. Among them, carboxylic acids are particularly advantageous, since they are widely available in great structural diversity and at low cost. The carboxylate directing groups can be tracelessly cleaved or may serve as the anchor point for further functionalization through decarboxylative couplings...
October 12, 2016: Chemistry: a European Journal
Clément Chauvier, Pierre Thuéry, Thibault Cantat
Silyl formates are investigated for the first time as surrogates of hydrosilanes. In the presence of a well-defined ruthenium catalyst, these reagents are shown to promote the chemoselective reduction of a variety of aldehydes by transfer hydrosilylation. Mechanistic investigations have shown that genuine hydrosilane species are avoided during catalysis. The mechanism involves a sequence of decarboxylation/insertion/transmetallation steps.
October 10, 2016: Angewandte Chemie
Xiao-Lan Xu, Wen-Tao Xu, Ji-Wei Wu, Jian-Bo He, Hua-Jian Xu
A general and effective method for the synthesis of amides through decarboxylative amidation of α-keto acids with amines has been developed. The reaction proceeded smoothly to afford the corresponding amide products in good yield under air and shows excellent functional group tolerance. In addition, the protocol can be further applied in the synthesis of heterocyclic compounds like benzimidazoles.
October 7, 2016: Organic & Biomolecular Chemistry
Heng-Rui Zhang, Dao-Qian Chen, Ya-Ping Han, Yi-Feng Qiu, Dong-Po Jin, Xue-Yuan Liu
A photoredox-/copper-catalyzed decarboxylative difluoroacetylation reaction of α,β-unsaturated carboxylic acids has been developed. This reaction produces a variety of difluoroalkylated alkenes in moderate to excellent yields and exhibits satisfactory stereoselectivity and a broad substrate scope at ambient temperature. Furthermore, this decarboxylative difluoroacetylation protocol provides efficient and environment friendly access to the difluoroalkylated alkenes.
September 27, 2016: Chemical Communications: Chem Comm
Xiao-Bo Ding, Daniel P Furkert, Margaret A Brimble
The heronapyrroles are a family of antibiotic natural products containing the rare 2-nitropyrrole motif. We report here a second generation total synthesis that circumvents problems of selective pyrrole nitration and alkene formation that limited the utility of previous approaches. Stille sp(3)-sp(2) cross coupling of a novel 2-nitropyrrole fragment was developed to install the key C7,8 olefin with complete regiochemical control. An unusual Hunsdiecker-type decarboxylative halogenation was also identified, providing access to the complex vinyl stannane coupling partners required for formation of the natural product...
October 18, 2016: Chemical Communications: Chem Comm
B C Medeiros, A T Fathi, C D DiNardo, D A Pollyea, S M Chan, R Swords
Alterations to genes involved in cellular metabolism and epigenetic regulation are implicated in the pathogenesis of myeloid malignancies. Recurring mutations in isocitrate dehydrogenase (IDH) genes are detected in approximately 20% of adult patients with acute myeloid leukemia (AML) and 5% of adults with myelodysplastic syndromes (MDS). IDH proteins are homodimeric enzymes involved in diverse cellular processes, including adaptation to hypoxia, histone demethylation, and DNA modification. The IDH2 protein is localized in the mitochondria and is a critical component of the tricarboxylic acid (TCA, also called the 'citric acid' or Krebs) cycle...
October 10, 2016: Leukemia: Official Journal of the Leukemia Society of America, Leukemia Research Fund, U.K
Lars H Finger, Jannick Guschlbauer, Klaus Harms, Jörg Sundermeyer
Depending on the amount of methanol present in solution, CO2 adducts of N-heterocyclic carbenes (NHCs) and N-heterocyclic olefins (NHOs) have been found to be in fully reversible equilibrium with the corresponding methyl carbonate salts [EMIm][OCO2 Me] and [EMMIm][OCO2 Me]. The reactivity pattern of representative 1-ethyl-3-methyl-NHO-CO2 adduct 4 has been investigated and compared with the corresponding NHC-CO2 zwitterion: The protonation of 4 with HX led to the imidazolium salts [NHO-CO2 H][X], which underwent decarboxylation to [EMMIm][X] in the presence of nucleophilic catalysts...
November 2, 2016: Chemistry: a European Journal
Nicholas Drachman, Stephen Kadlecek, Mehrdad Pourfathi, Yi Xin, Harilla Profka, Rahim Rizi
PURPOSE: To optimize the production of hyperpolarized (13) C-bicarbonate from the decarboxylation of hyperpolarized [1-(13) C]pyruvate and use it to image pH in the lungs and heart of rats with acute lung injury. METHODS: Two forms of catalysis are compared calorimetrically to maximize the rate of decarboxylation and rapidly produce hyperpolarized bicarbonate from pyruvate while minimizing signal loss. Rats are injured using an acute lung injury model combining ventilator-induced lung injury and acid aspiration...
October 7, 2016: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
Jian Gu, Chun Cai
A copper mediated radical oxidative annulation of 2-(pyridin-2-yl)acetate derivatives with α,β-unsaturated carboxylic acids is developed. This study offers a new and expedient strategy for the synthesis of useful indolizines in moderate to good yields and exhibits a broad substrate scope and good functional group tolerance.
October 7, 2016: Organic & Biomolecular Chemistry
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