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Decarboxylation

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https://www.readbyqxmd.com/read/28524922/3-4-alkadienyl-ketones-via-the-palladium-catalyzed-decarboxylative-allenylation-of-3-oxocarboxylic-acids
#1
Tonghao Zhu, Shengming Ma
In this communication, we report a palladium-catalyzed decarboxylative allenylation of benzyl carbonates and tert-butyl carbonates of 2,3-allenols with 3-oxocarboxylic acids. The reaction provides a new and straightforward approach to 3,4-dienyl ketones under mild conditions.
May 19, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28524664/nam-tms-mechanism-of-%C3%AE-amino-acid-n-carboxyanhydride-polymerization-a-dft-study
#2
Tianwen Bai, Jun Ling
The normal amine mechanism via proton transferring route (NAM-H) is widely accepted for synthesis of polypeptides with nonionic initiators. Besides proton, trimethylsilyl (TMS) group transferring process has been found in living/controlled polymerization initiated by N-TMS amine in experiments but the corresponding mechanism has never been proposed yet. In this work, we employed density functional theory (DFT) with solvation model to investigate the details of TMS-transfer mechanism, defined as NAM-TMS, for ring-opening polymerization of α-amino acid N-carboxyanhydride...
May 19, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28521505/orientation-and-conformation-of-osteocalcin-adsorbed-onto-calcium-phosphate-and-silica-surfaces
#3
Luisa A Scudeller, Selvi Srinivasan, Alexandre M Rossi, Patrick S Stayton, Gary P Drobny, David G Castner
Adsorption isotherms, circular dichroism (CD) spectroscopy, x-ray photoelectron spectroscopy (XPS), and time-of-flight secondary ion mass spectrometry (ToF-SIMS) were used to investigate the adsorption of human osteocalcin (hOC) and decarboxylated (i.e., Gla converted back to Glu) hOC (dhOC) onto various calcium phosphate surfaces as well as silica surfaces. The adsorption isotherms and XPS nitrogen signals were used to track the amount of adsorbed hOC and dhOC. The intensities of key ToF-SIMS amino acid fragments were used to assess changes in the structure of adsorbed hOC and dhOC...
May 18, 2017: Biointerphases
https://www.readbyqxmd.com/read/28514176/transition-metal-free-visible-light-enabled-decarboxylative-borylation-of-aryl-n-hydroxyphthalimide-esters
#4
Lisa Candish, Michael Teders, Frank Glorius
Herein, we report a conceptually novel borylation reac-tion via a mild photoinduced decarboxylation of redox-activated aromatic carboxylic acids. This work consti-tutes the first application of cheap and easily prepared N-hydroxyphthalimide (NHPI) esters as aryl radical precur-sors and does not require the use of expensive transition metals or ligands. The reaction is operationally simple, scalable, and displays broad scope and functional group tolerance.
May 17, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28514173/rh-iii-catalyzed-regio-and-chemoselective-4-1-annulation-of-azoxy-compounds-with-diazoesters-for-the-synthesis-of-2h-indazoles-roles-of-the-azoxy-oxygen-atom
#5
Zhen Long, Zhigang Wang, Danni Zhou, Danyang Wan, Jingsong You
A Rh(III)-catalyzed tandem C-H alkylation/intramolecular decarboxylative cyclization of azoxy compounds with diazoesters for the synthesis of 3-acyl-2H-indazoles is disclosed. The azoxy instead of the azo group enables a distinct approach for cyclative capture, leading to a [4 + 1]-annulation rather than a classic [4 + 2] manner. The azoxy oxygen atom is traceless after annulation, and further removal from the product is not required. This reaction features a complete regioselectivity for unsymmetrical azoxybenzenes and a compatibility of monoaryldiazene oxides...
May 17, 2017: Organic Letters
https://www.readbyqxmd.com/read/28514140/properties-of-intermediates-in-the-catalytic-cycle-of-oxalate-oxidoreductase-and-its-suicide-inactivation-by-pyruvate
#6
Elizabeth Pierce, Steven O Mansoorabadi, Mehmet Can, George H Reed, Stephen W Ragsdale
Oxalate:ferredoxin oxidoreductase (OOR) is an unusual member of the thiamine pyrophosphate (TPP)-dependent 2-oxoacid:ferredoxin oxidoreductase (OFOR) family in that it catalyzes the coenzyme A (CoA)-independent conversion of oxalate into two moles of carbon dioxide. This reaction is surprising because binding of CoA to the acyl-TPP intermediate of other OFORs results in formation of a CoA ester and, in the case of pyruvate:ferredoxin oxidoreductase (PFOR), CoA binding generates the central metabolic intermediate acetyl-CoA and promotes a 10(5)-fold acceleration of the rate of electron transfer...
May 17, 2017: Biochemistry
https://www.readbyqxmd.com/read/28513162/radical-c-h-fluorination-using-unprotected-amino-acids-as-radical-precursors
#7
Alyssa M Hua, Duy N Mai, Ramon Martinez, Ryan D Baxter
We report a unique example of utilizing unprotected amino acids for benzylic C-H fluorination via a radical process. α-Aminoalkyl radicals are readily generated via oxidative decarboxylation of unprotected amino acids using a simple silver(I) catalyst and Selectfluor, which serves as both a mild oxidant and source of electrophilic fluorine. Mechanistic investigation shows that coordination of the unprotected amino acid plays a crucial role in lowering the oxidation potential of Ag(I), enabling oxidation under mild conditions...
May 17, 2017: Organic Letters
https://www.readbyqxmd.com/read/28512002/cell-surface-g-protein-coupled-receptors-for-tumor-associated-metabolites-a-direct-link-to-mitochondrial-dysfunction-in-cancer
#8
REVIEW
Bojana Ristic, Yangzom D Bhutia, Vadivel Ganapathy
Mitochondria are the sites of pyruvate oxidation, citric acid cycle, oxidative phosphorylation, ketogenesis, and fatty acid oxidation. Attenuation of mitochondrial function is one of the most significant changes that occurs in tumor cells, directly linked to oncogenesis, angiogenesis, Warburg effect, and epigenetics. In particular, three mitochondrial enzymes are inactivated in cancer: pyruvate dehydrogenase (PDH), succinate dehydrogenase (SDH), and 3-hydroxy-3-methylglutaryl CoA synthase-2 (HMGCS2). These enzymes are subject to regulation via acetylation/deacetylation...
May 13, 2017: Biochimica et Biophysica Acta
https://www.readbyqxmd.com/read/28510348/regioselective-synthesis-of-polycyclic-and-heptagon-embedded-aromatic-compounds-through-a-versatile-%C3%AF-extension-of-aryl-halides
#9
Wai Chung Fu, Zheng Wang, Wesley Ting Kwok Chan, Zhenyang Lin, Fuk Yee Kwong
A versatile π-extension reaction was developed based on the three-component cross-coupling of aryl halides, 2-haloarylcarboxylic acids, and norbornadiene. The transformation is driven by the direction and subsequent decarboxylation of the carboxyl group, while norbornadiene serves as an ortho-C-H activator and ethylene synthon via a retro-Diels-Alder reaction. Comprehensive DFT calculations were performed to account for the catalytic intermediates.
May 16, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28508504/aiba-aibb-induces-an-intramolecular-decarboxylation-in-isovalerate-biosynthesis-by-myxococcus-xanthus
#10
Tobias Bock, Eva Luxenburger, Judith Hoffmann, Vlad Schütza, Christian Feiler, Rolf Müller, Wulf Blankenfeldt
Isovaleryl coenzyme A (IV-CoA) is an important precursor for iso-fatty acids and lipids. It acts in the development of myxobacteria, which can produce this compound from acetyl-CoA through alternative IV-CoA biosynthesis (aib). A central reaction of aib is catalyzed by AibA/AibB, which acts as a cofactor-free decarboxylase despite belonging to the family of CoA-transferases. We developed an efficient expression system for AibA/AibB that allowed the determination of high-resolution crystal structures in complex with different ligands...
May 16, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28503693/exploiting-the-unusual-effects-of-fluorine-in-methodology
#11
Douglas L Orsi, Ryan A Altman
Fluorination of organic molecules significantly impacts the basic physicochemical properties of small and large biologically active molecules, agrichemicals, and materials. Thus, the development of synthetic reactions to access these substructures is important for many applied fields of chemistry. However, these fluorine-induced perturbations of chemical properties can inhibit standard chemical transformations, which provides unique challenges for synthetic organic chemists. In addition, the physicochemical properties imparted by fluorinated substituents can enable distinct reactivity patterns relative to non-fluorinated substrates, thus making synthetic organofluorine chemistry a fertile ground for developing new, exciting transformations...
May 15, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28501642/a-novel-method-for-photo-oxidative-degradation-of-diatrizoate-in-water-via-electromagnetic-induction-electrodeless-lamp
#12
Lingjun Meng, Shaogui Yang, Cheng Sun, Huan He, Qiming Xian, Shiyin Li, Guoxiang Wang, Limin Zhang, Dong Jiang
In this study, an electromagnetic induction electrodeless lamp (EIEL) was first introduced into UV advanced oxidation processes (AOPs) for photodegradation of Diatrizoate (DTZ), which was the most persistent iodinated X-ray contrast medium (ICM), and traditional Hg lamps were taken as references. Direct photolysis rate of DTZ under EIEL irradiation was 1.34 times as that under Hg irradiation, but the electric energy consumption was 0.87 times. In this sense, the combination of EIEL and oxidants (O2, H2O2 and S2O8(2-)(PS)) was further investigated...
May 5, 2017: Journal of Hazardous Materials
https://www.readbyqxmd.com/read/28500042/carboxyl-analogue-of-mutacin-1140-a-scaffold-for-lead-antibacterial-discovery
#13
Jerome Escano, Akshaya Ravichandran, Bita Salamat, Leif Smith
Mutacin 1140 belongs to the epidermin group of lantibiotics. Epidermin class lantibiotics are ribosomally synthesized and post translationally modified antibiotics with potent activity against Gram-positive bacteria. In particular, this class is effective at targeting drug resistant Streptococcus pneumoniae, MRSA,Mycobacterium tuberculosis, and Clostridium difficile A C-terminal S-[(Z)-2-aminovinyl]-D-cysteine (AviCys) residue is derived from a decarboxylation of a terminal cysteine that is involved in one of the lanthionine ring formation...
May 12, 2017: Applied and Environmental Microbiology
https://www.readbyqxmd.com/read/28498678/mechanisms-and-origins-of-chemo-and-regioselectivities-of-ru-ii-catalyzed-decarboxylative-c-h-alkenylation-of-aryl-carboxylic-acids-with-alkynes-a-computational-study
#14
Jing-Lu Yu, Shuo-Qing Zhang, Xin Hong
The mechanisms and chemo- and regioselectivities of Ru(II)-catalyzed decarboxylative C-H alkenylation of aryl carboxylic acids with alkynes were investigated with density functional theory (DFT) calculations. The catalytic cycle involves sequential carboxylate-directed C-H activation, alkyne insertion, decarboxylation and protonation. The facile tether-assisted decarboxylation step directs the intermediate toward the desired decarboxylative alkenylation, instead of typical annulation and double alkenylation pathways...
May 22, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28496208/ethylenation-of-aldehydes-to-3-propanal-propanol-and-propanoic-acid-derivatives
#15
Daniel T Payne, Yiming Zhao, John S Fossey
Methodology has been developed for the synthesis of 3-propanaldehydes through a five-step process in 11-67% yield from aldehydes. Aldehydes were reacted with Meldrum's acid through a Knoevenagel condensation to give materials that upon reduction with sodium borohydride and subsequent hydrolysis decarboxylation generated the corresponding 3-propanoic acid derivatives. The -propanoic acid derivatives were reduced to give 3-propanol derivatives, which were readily oxidised to target 3-propanal derivatives.
May 11, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28490063/characterisation-of-a-thiamine-diphosphate-dependent-alpha-keto-acid-decarboxylase-from-proteus-mirabilis-jn458
#16
Biying Wang, Yajun Bai, Taiping Fan, Xiaohui Zheng, Yujie Cai
Alpha-keto acid decarboxylases can convert keto acids to their corresponding aldehydes, which are often volatile aroma compounds. The gene encoding α-keto acid decarboxylase in Proteus mirabilis JN458 was cloned, and the enzyme overexpressed in Escherichia coli BL21 (DE3), purified in high yield, and characterised. The molecular weight is 62.291kDa by MALDI-TOF MS, and optimum activity at pH 6.0 and 40-50°C. The enzyme is a typical decarboxylase, dependent on thiamine diphosphate and Mg(2+) as cofactors. For the decarboxylation reaction, the enzyme displayed a broad substrate range...
October 1, 2017: Food Chemistry
https://www.readbyqxmd.com/read/28489402/iodine-catalyzed-facile-approach-to-sulfones-employing-tosmic-as-a-sulfonylating-agent
#17
Lingaswamy Kadari, Radha Krishna Palakodety, Lakshmi Prapurna Yallapragada
A novel iodine-catalyzed functionalization of a variety of olefins and alkynes and direct decarboxylative functionalization of cinnamic and propiolic acids with TosMIC to provide access to various vinyl, allyl, and β-iodo vinylsulfones is described. This simple, efficient, and environmentally benign approach employing inexpensive molecular iodine as a catalyst demonstrates a versatile protocol for the synthesis of highly valuable sulfones, rendering it attractive to both synthetic and medicinal chemistry.
May 10, 2017: Organic Letters
https://www.readbyqxmd.com/read/28486485/hydrogen-peroxide-inhibition-of-bicupin-oxalate-oxidase
#18
John M Goodwin, Hassan Rana, Joan Ndungu, Gaurab Chakrabarti, Ellen W Moomaw
Oxalate oxidase is a manganese containing enzyme that catalyzes the oxidation of oxalate to carbon dioxide in a reaction that is coupled with the reduction of oxygen to hydrogen peroxide. Oxalate oxidase from Ceriporiopsis subvermispora (CsOxOx) is the first fungal and bicupin enzyme identified that catalyzes this reaction. Potential applications of oxalate oxidase for use in pancreatic cancer treatment, to prevent scaling in paper pulping, and in biofuel cells have highlighted the need to understand the extent of the hydrogen peroxide inhibition of the CsOxOx catalyzed oxidation of oxalate...
2017: PloS One
https://www.readbyqxmd.com/read/28485458/copper-catalyzed-fluoroalkylation-of-alkynes-and-alkynyl-vinyl-carboxylic-acids-with-fluoroalkyl-halides
#19
Jing-Jing Ma, Wen-Bin Yi
Copper-catalyzed fluoroalkylation of alkynes and alkynyl carboxylic acids has been achieved with high functional-group tolerance and excellent regio- and stereoselectivities. A variety of fluoroalkyl halides including ethyl bromodifluoroacetate can be employed. Additionally, an unprecedented decarboxylative fluoroalkylation of α, β-unsaturated carboxylic acids has been achieved via a radical pathway.
May 9, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28485262/biological-significance-of-phosphoenolpyruvate-carboxykinase-in-a-cestode-parasite-raillietina-echinobothrida-and-effect-of-phytoestrogens-on-the-enzyme-from-the-parasite-and-its-host-gallus-domesticus
#20
Ramnath, Asim Kumar Dutta, Barilin Dkhar, Veena Tandon, Bidyadhar DAS
Phosphoenolpyruvate carboxykinase (PEPCK) is involved in glycolysis in the cestode parasite, Raillietina echinobothrida; whereas, it executes a gluconeogenic role in its host, Gallus domesticus. Because of its differing primary function in the cestode parasite and its host, this enzyme is regarded as a plausible anthelmintic target. Hence, the biological significance of PEPCK in the parasite was analysed using siRNA against PEPCK from R. echinobothrida (RePEPCK). In order to find out the functional differences between RePEPCK and GdPEPCK (PEPCK from its host, G...
May 9, 2017: Parasitology
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