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Decarboxylation

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https://www.readbyqxmd.com/read/28920985/enantioselective-synthesis-of-sterically-hindered-%C3%AE-allyl-%C3%AE-aryl-oxindoles-via-palladium-catalysed-decarboxylative-asymmetric-allylic-alkylation
#1
Mark Jackson, Calvin Quince O'Broin, Helge Müller-Bunz, Patrick J Guiry
The highly enantioselective synthesis of sterically hindered α-allyl-α-aryl oxindoles possessing an all-carbon quaternary stereocenter at the oxindole 3-position has been developed. The key step in the synthetic route employed was a novel one-pot, two-step synthesis of α-aryl-β-amido allyl ester substituted oxindoles in good yields of 41-75% (13 examples) by interception of an unstable allyl ester intermediate through reaction with aryllead triacetate reagents. Pd-Catalyzed decarboxylative asymmetric allylic alkylation (DAAA) was optimized with 2,4,6-trimethoxyphenyl as the aryl-containing substrate...
September 18, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28920440/unrestricted-mass-spectrometric-data-analysis-for-identification-localization-and-quantification-of-oxidative-protein-modifications
#2
Martin Rykær, Birte Svensson, Michael J Davies, Per Hägglund
Oxidation generates multiple diverse post-translational modifications resulting in changes in protein structure and function, associated with a wide range of diseases. Of these modifications, carbonylations have often been used as hallmarks of oxidative damage. However, accumulating evidence supports the hypothesis that other oxidation products may be quantitatively more important under physiological conditions. To address this issue we have developed a holistic mass spectrometry-based approach for simultaneous identification, localization and quantification of a broad range of oxidative modifications based on so-called 'dependent peptides'...
September 18, 2017: Journal of Proteome Research
https://www.readbyqxmd.com/read/28917116/thermal-and-photo-induced-degradation-of-perfluorinated-carboxylic-acids-kinetics-and-mechanism
#3
Jiaoqin Liu, Ruijuan Qu, Zunyao Wang, Itza Mendoza-Sanchez, Virender K Sharma
Perfluorinated carboxylic acids (PFCAs) of different carbon chain lengths are chemicals of concern to human health and their removal, using conventional remediation technologies, is challenging. The present paper pursuits thermal and photo-induced degradation of PFCAs (F(CF2)nCOOH, n = 1-9) under various concentrations of four different acids (HNO3, H2SO4, HCl, and H3PO4) covering a range of strong acidic to basic pH. For thermal-induced experiments, the temperature was set at 40 °C, 60 °C, and 80 °C at acid strengths of 0...
September 6, 2017: Water Research
https://www.readbyqxmd.com/read/28915313/a-metabolomic-approach-applied-to-a-liquid-chromatography-coupled-to-high-resolution-tandem-mass-spectrometry-method-hplc-esi-hrms-ms-towards-the-comprehensive-evaluation-of-the-chemical-composition-of-cannabis-medicinal-extracts
#4
Cinzia Citti, Umberto Maria Battisti, Daniela Braghiroli, Giuseppe Ciccarella, Martin Schmid, Maria Angela Vandelli, Giuseppe Cannazza
INTRODUCTION: Cannabis sativa L. is a powerful medicinal plant and its use has recently increased for the treatment of several pathologies. Nonetheless, side effects, like dizziness and hallucinations, and long-term effects concerning memory and cognition, can occur. Most alarming is the lack of a standardised procedure to extract medicinal cannabis. Indeed, each galenical preparation has an unknown chemical composition in terms of cannabinoids and other active principles that depends on the extraction procedure...
September 15, 2017: Phytochemical Analysis: PCA
https://www.readbyqxmd.com/read/28914321/photoredox-catalysis-enabled-alkylation-of-alkenyl-carboxylic-acids-with-n-acyloxy-phthalimide-via-dual-decarboxylation
#5
Kun Xu, Zhoumei Tan, Haonan Zhang, Juanli Liu, Sheng Zhang, Zhiqiang Wang
A ruthenium based photoredox catalyst in combination with a substoichiometric amount of 1,4-diazabicyclo[2.2.2]octane (DABCO) efficiently catalyzed dual decarboxylative couplings between alkenyl carboxylic acids and N-(acyloxy)phthalimides derived from aliphatic carboxylic acids, delivering alkylated styrene derivatives in a high regio- and stereo-selective manner under mild reaction conditions. Various types of secondary, tertiary, and quaternary aliphatic carboxylic acids as well as α-amino acids can be used as suitable substrates...
September 15, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28912830/in-vitro-oxidative-decarboxylation-of-free-fatty-acids-to-terminal-alkenes-by-two-new-p450-peroxygenases
#6
Huifang Xu, Linlin Ning, Wenxia Yang, Bo Fang, Cong Wang, Yun Wang, Jian Xu, Severine Collin, Frederic Laeuffer, Laurent Fourage, Shengying Li
BACKGROUND: P450 fatty acid decarboxylases represented by the unusual CYP152 peroxygenase family member OleTJE have been receiving great attention recently since these P450 enzymes are able to catalyze the simple and direct production of 1-alkenes for potential applications in biofuels and biomaterials. To gain more mechanistic insights, broader substrate spectra, and improved decarboxylative activities, it is demanded to discover and investigate more P450 fatty acid decarboxylases. RESULTS: Here, we describe for the first time the expression, purification, and in vitro biochemical characterization of two new CYP152 peroxygenases, CYP-Aa162 and CYP-Sm46Δ29, that are capable of decarboxylating straight-chain saturated fatty acids...
2017: Biotechnology for Biofuels
https://www.readbyqxmd.com/read/28911770/primary-deuterium-kinetic-isotope-effects-from-product-yields-rationale-implementation-and-interpretation
#7
Tina L Amyes, John P Richard
A simple and convenient method is described to determine primary deuterium kinetic isotope effects (1°DKIEs) on reactions where the hydron incorporated into the reaction product is derived from solvent water. The 1°DKIE may be obtained by (1)H NMR analyses as the ratio of the yields of H- and D-labeled products from a reaction in 50:50 (v/v) HOH/DOD. The procedures for these (1)H NMR analyses are reviewed. This product deuterium isotope effect (PDIE) is defined as 1/ϕEL for fractionation of hydrons between solvent and the transition state for the reaction examined...
2017: Methods in Enzymology
https://www.readbyqxmd.com/read/28905627/an-aminocatalyzed-michael-addition-iron-mediated-decarboxylative-cyclization-sequence-for-the-preparation-of-2-3-4-6-tetrasubstituted-pyridines-scope-and-mechanistic-insights
#8
Mateus L Stivanin, Marcelo Duarte, Camila Sartori, Naylil M R Capreti, Celio F F Angolini, Igor D Jurberg
A novel, scalable strategy for the preparation of 2,3,4,6-tetrasubstituted pyridines is described. This protocol has two steps: an aminocatalyzed addition of ketones to alkylidene isoxazol-5-ones, followed by an iron-mediated decarboxylative cyclization event. Mechanistic insights for both steps are provided based on HRMS-ESI(+) studies.
September 14, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28905058/a-transition-metal-free-fast-track-to-flavones-and-3-arylcoumarins
#9
Mostafa Golshani, Mehdi Khoobi, Nafiseh Jalalimanesh, Farnaz Jafarpour, Alireza Ariafard
A highly regioselective and transition-metal free one-pot arylation of chromenones with arylboronic acids has been achieved employing K2S2O8. The procedure consists of a sequence of some reactions including an arylation/decarboxylation cascade and proceeds well in aqueous media to afford biologically interesting flavones and 3-arylcoumarins. This method exhibited excellent selectivity and functional group tolerance under mild conditions. The reaction also showed perfect efficacy for the preparation of styryl coumarins...
September 14, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28901769/enantioselective-pd-catalyzed-decarboxylative-allylic-alkylation-of-thiopyranones-access-to-acyclic-stereogenic-%C3%AE-quaternary-ketones
#10
Eric J Alexy, Scott C Virgil, Michael D Bartberger, Brian M Stoltz
A catalytic, enantioselective decarboxylative allylic alkylation of 4-thiopyranones is reported. The α-quaternary 4-thiopyranones produced are challenging to access by standard enolate alkylation owing to facile ring-opening β-sulfur elimination. In addition, reduction of the carbon-sulfur bonds provides access to elusive acyclic α-quaternary ketones. The alkylated products are obtained in up to 92% yield and 94% enantiomeric excess.
September 13, 2017: Organic Letters
https://www.readbyqxmd.com/read/28901144/visible-light-enabled-decarboxylative-mono-and-difluoromethylation-of-cinnamic-acids-under-metal-free-conditions
#11
Wei-Ke Tang, Yi-Si Feng, Zhuo-Wei Xu, Zhi-Fei Cheng, Jun Xu, Jian-Jun Dai, Hua-Jian Xu
Several new mono- and difluoromethylation reactions of cinnamic acids using an Eosin Y catalytic system are reported. An efficient alkene fluoromethylation of α,β-unsaturated carboxylic acids was accomplished under ambient temperature and metal-free conditions, with a wide range of functional group tolerance. A mechanism that involves a radical process is proposed for this reaction.
September 13, 2017: Organic Letters
https://www.readbyqxmd.com/read/28901047/mild-decarboxylative-c-h-alkylation-computational-insights-for-solvent-robust-ruthenium-ii-domino-manifold
#12
Phani Kumar, Torben Rogge, Santhivardhana Reddy Yetra, Alexander Bechtholdt, Eric Clot, Lutz Ackermann
Computational studies on decarboxylative C-H alkenylations provided key insights into the solvent-independent nature of C-H activation/decarboxylation domino reactions, which was exploited for ruthenium(II)-catalyzed C-H alkylations by decarboxylative ruthenium(II) catalysis with ample scope under copper- and silver-free reaction conditions.
September 12, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28892875/development-of-parafollicular-cells-and-their-relationship-with-developing-thyroid-follicles-in-human-foetuses
#13
Sushant Swaroop Das, Sabita Mishra, J M Kaul
INTRODUCTION: The parafollicular cells or clear (C) cells in man are part of neuroendocrine system under Amine Precursor Uptake and Decarboxylation (APUD) cells. Their role in adults has been reputable but in foetus is still unclear. AIM: The present study was a baseline study endeavouring to describe the chronological development of the parafollicular cells with particular focus on its correlation with developing human thyroid follicles. MATERIALS AND METHODS: The study was conducted on 10 aborted foetuses (14-28 weeks), procured from the Department of Obstetrics and Gynaecology, Lok Nayak Hospital, New Delhi, India...
July 2017: Journal of Clinical and Diagnostic Research: JCDR
https://www.readbyqxmd.com/read/28881427/active-site-geometry-of-a-novel-aminopropyltransferase-for-biosynthesis-of-hyperthermophile-specific-branched-chain-polyamine
#14
Ryota Hidese, Ka Man Tse, Seigo Kimura, Eiichi Mizohata, Junso Fujita, Yuhei Horai, Naoki Umezawa, Tsunehiko Higuchi, Masaru Niitsu, Tairo Oshima, Tadayuki Imanaka, Tsuyoshi Inoue, Shinsuke Fujiwara
Branched-chain polyamines are found exclusively in thermophilic bacteria and Euryarchaeota and play essential roles in survival at high temperatures. In the present study, kinetic analyses of a branched-chain polyamine synthase from the hyperthermophilic archaeon Thermococcus kodakarensis (Tk-BpsA) were conducted, showing that N(4) -bis(aminopropyl)spermidine was produced by sequential additions of decarboxylated S-adenosyladenosine (dcSAM) aminopropyl groups to spermidine, through bifunctional catalytic action...
September 7, 2017: FEBS Journal
https://www.readbyqxmd.com/read/28879605/in-vitro-evaluation-of-limitations-and-possibilities-for-the-future-use-of-intracorporeal-gas-exchangers-placed-in-the-upper-lobe-position
#15
Erin Schumer, Klaus Höffler, Christian Kuehn, Mark Slaughter, Axel Haverich, Bettina Wiegmann
The lack of donor organs has led to the development of alternative "destination therapies", such as a bio-artificial lung (BA) for end-stage lung disease. Ultimately aiming at a fully implantable BA, general capabilities and limitations of different oxygenators were tested based on the model of BA positioning at the right upper lobe. Three different-sized oxygenators (neonatal, paediatric, and adult) were tested in a mock circulation loop regarding oxygenation and decarboxylation capacities for three respiratory pathologies...
September 6, 2017: Journal of Artificial Organs: the Official Journal of the Japanese Society for Artificial Organs
https://www.readbyqxmd.com/read/28876954/base-controlled-reactions-through-an-aldol-intermediate-formed-between-2-oxoaldehydes-and-malonate-half-esters
#16
Atul Kumar, Shahnawaz Khan, Qazi Naveed Ahmed
A practical, atom-economical, base-directed, and highly efficient method for the generation of different selective products through a common aldol intermediate of 2-oxoaldehydes and malonate half esters is successfully developed. The addition of a strong basic environment (potassium tert-butoxide) catalyzed the synthesis of stable decarboxylative aldol products (α-hydroxy ketones), while the Doebner modification procedure resulted in decarboxylative elimination to (E)-α,β-unsaturated esters in good yields...
September 6, 2017: Organic Letters
https://www.readbyqxmd.com/read/28876945/enantioselective-decarboxylative-%C3%AE-alkynylation-of-%C3%AE-ketocarbonyls-via-a-catalytic-%C3%AE-imino-radical-intermediate
#17
Dehong Wang, Long Zhang, Sanzhong Luo
A distinctive aminocatalysis via α-imino radical is reported on the basis of SET oxidation of a secondary enamine. The combination of chiral primary amine catalysis and visible-light photoredox catalysis enables the enantioselective decarboxylative coupling of propiolic acid and β-ketocarbonyls to afford alkynylation adducts with high enantioselectivity. Mechanism studies indicate the reaction proceeds via an α-imino radical addition.
September 6, 2017: Organic Letters
https://www.readbyqxmd.com/read/28874750/amixicile-a-novel-strategy-for-targeting-oral-anaerobic-pathogens
#18
Justin A Hutcherson, Kathryn M Sinclair, Benjamin R Belvin, Qin Gui, Paul S Hoffman, Janina P Lewis
The oral microflora is composed of both health-promoting as well as disease-initiating bacteria. Many of the disease-initiating bacteria are anaerobic and include organisms such as Porphyromonas gingivalis, Prevotella intermedia, Fusobacterium nucleatum, and Tannerella forsythia. Here we investigated a novel therapeutic, amixicile, that targets pyruvate:ferredoxin oxidoreductase (PFOR), a major metabolic enzyme involved in energy generation through oxidative decarboxylation of pyruvate. PFOR is present in these anaerobic pathogenic bacteria and thus we hypothesized that amixicile would effectively inhibit their growth...
September 5, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28872321/oleb-from-bacterial-hydrocarbon-biosynthesis-is-a-%C3%AE-lactone-decarboxylase-sharing-key-features-with-haloalkane-dehalogenases
#19
James K Christenson, Serina L Robinson, Tiffany A Engel, Jack Eugene Richman, An N Kim, Lawrence P Wackett
OleB is an α/β-hydrolase found in bacteria that biosynthesize long-chain olefinic hydrocarbons, but its function has remained obscure. We report that OleB from the gram-negative bacterium Xanthomonas campestris performs an unprecedented β-lactone decarboxylation reaction, to complete cis-olefin biosynthesis. OleB reactions monitored by (1)H-NMR spectroscopy revealed a selectivity for decarboxylating cis-β-lactones and no discernable activity with trans-β-lactones, consistent with the known configuration of pathway intermediates...
September 5, 2017: Biochemistry
https://www.readbyqxmd.com/read/28872178/unique-structural-micro-adjustments-in-a-new-benzothiadiazole-derived-zn-ii-metal-organic-framework-via-simple-photochemical-decarboxylation
#20
Xiao Han, Qing Cheng, Xiangru Meng, Zhichao Shao, Ke Ma, Donghui Wei, Jie Ding, Hongwei Hou
The first example of micro-adjustments of a metal organic framework (MOF) structure was observed in a new Zn(ii) MOF (Zn-BTDC-M1) derived from a benzothiadiazole-4,7-dicarboxylic acid (H2BTDC) ligand using a light-driven decarboxylation process. Interestingly, such decarboxylation occurs at the non-chelated wing of the ligand, which induced a change in the capability of the MOF for physical N2 adsorption and chemical NH3 gas adsorption.
September 14, 2017: Chemical Communications: Chem Comm
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