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Decarboxylation

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https://www.readbyqxmd.com/read/28440830/organocatalytic-decarboxylative-aldol-reaction-of-%C3%AE-ketoacids-with-%C3%AE-ketophosphonates-en-route-to-the-enantioselective-synthesis-of-tertiary-%C3%AE-hydroxyphosphonates
#1
Ganga B Vamisetti, Raghunath Chowdhury, Sunil K Ghosh
The first example of an asymmetric organocatalyzed decarboxylative aldol reaction of β-ketoacids (aroylacetic acids) with α-ketophosphonates that produces a quaternary chiral centre has been developed. A quinidine based bifunctional urea derivative was identified as the preferred catalyst affording γ-aroyl tertiary α-hydroxyphosphonates in good yield and enantioselectivity. The (31)P NMR spectroscopic study was performed to shed light on the reaction mechanism.
April 25, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28440651/iron-catalyzed-acyloxyalkylation-of-styrenes-using-hypervalent-iodine-reagents
#2
Zijia Wang, Motomu Kanai, Yoichiro Kuninobu
Iron-catalyzed acyloxyalkylation of styrene derivatives using hypervalent iodine reagents was achieved. The acyloxyalkylation reaction proceeded using various types of styrenes and hypervalent iodine reagents. The acyloxyalkylated products were obtained in moderate to good yields without loss of the functional groups. The reaction proceeded via the formation of radical species derived from hypervalent iodine reagents by decarboxylation.
April 25, 2017: Organic Letters
https://www.readbyqxmd.com/read/28436122/metabolic-engineering-of-escherichia-coli-for-production-of-2-phenylethylacetate-from-l-phenylalanine
#3
Daoyi Guo, Lihua Zhang, Hong Pan, Xun Li
In order to meet the need of consumer preferences for natural flavor compounds, microbial synthesis method has become a very attractive alternative to the chemical production. The 2-phenylethanol (2-PE) and its ester 2-phenylethylacetate (2-PEAc) are two extremely important flavor compounds with a rose-like odor. In recent years, Escherichia coli and yeast have been metabolically engineered to produce 2-PE. However, a metabolic engineering approach for 2-PEAc production is rare. Here, we designed and expressed a 2-PEAc biosynthetic pathway in E...
April 24, 2017: MicrobiologyOpen
https://www.readbyqxmd.com/read/28435050/the-human-krebs-cycle-2-oxoglutarate-dehydrogenase-complex-creates-an-additional-source-of-superoxide-hydrogen-peroxide-from-2-oxoadipate-as-alternative-substrate
#4
Natalia S Nemeria, Gary Gerfen, Elena Guevara, Pradeep Reddy Nareddy, Michal Szostak, Frank Jordan
Recently, we reported that the human 2-oxoglutarate dehydrogenase (hE1o) component of the 2-oxoglutarate dehydrogenase complex (OGDHc) could produce the reactive oxygen species superoxide and hydrogen peroxide (detected by chemical means) from its substrate 2-oxoglutarate (OG), most likely concurrently with one-electron oxidation by dioxygen of the thiamin diphosphate (ThDP)-derived enamine intermediate to a C2α-centered radical (detected by Electron Paramagnetic Resonance) [Nemeria et al., 2014; Ambrus et al...
April 20, 2017: Free Radical Biology & Medicine
https://www.readbyqxmd.com/read/28434121/intracellular-position-of-mitochondria-in-mesophyll-cells-differs-between-c3-and-c4-grasses
#5
Yuto Hatakeyama, Osamu Ueno
In C3 plants, part of the CO2 fixed during photosynthesis in chloroplasts is released from mitochondria during photorespiration by decarboxylation of glycine via glycine decarboxylase (GDC), thereby reducing photosynthetic efficiency. The apparent positioning of most mitochondria in the interior (vacuole side of chloroplasts) of mesophyll cells in C3 grasses would increase the efficiency of refixation of CO2 released from mitochondria by ribulose 1,5-bisphosphate carboxylase/​oxygenase (Rubisco) in chloroplasts...
April 22, 2017: Journal of Plant Research
https://www.readbyqxmd.com/read/28433904/biodegradation-of-naproxen-by-freshwater-algae-cymbella-sp-and-scenedesmus-quadricauda-and-the-comparative-toxicity
#6
Tengda Ding, Kunde Lin, Bo Yang, Mengting Yang, Juying Li, Wenying Li, Jay Gan
Naproxen is one of the most prevalent pharmaceuticals and of great environment concern. Information about bioremediation of naproxen by algae remains limited and no study has been reported on the degradation mechanism and the toxicity of NPX on algae. In this study, both Cymbella sp. and Scenedesmus quadricauda showed complete growth inhibition (100%) at 100mgL(-1) within 24h. Biochemical characteristics including chlorophyll a, carotenoid contents and enzyme activities for these two microalgae were affected by NPX at relatively high concentrations after 4d of exposure...
April 8, 2017: Bioresource Technology
https://www.readbyqxmd.com/read/28429316/c2-metabolism-in-euglena
#7
Masami Nakazawa
Euglenoids are able to assimilate fatty acids and alcohols with various carbon-chain lengths, and ethanol is known to be one of the best carbon sources to support the growth of Euglena gracilis. Ethanol is first oxidized to acetate by the sequential reactions of alcohol dehydrogenase and acetaldehyde dehydrogenase in the mitochondria, and then converted to acetyl coenzyme A (acetyl-CoA). Acetyl-CoA is metabolized through the glyoxylate cycle which is a modified tricarboxylic acid (TCA) cycle in which isocitrate lyase (ICL) and malate synthase (MS) function to bypass the two decarboxylation steps of the TCA cycle, enabling the net synthesis of carbohydrates from C2 compounds...
2017: Advances in Experimental Medicine and Biology
https://www.readbyqxmd.com/read/28424520/decarboxylative-alkenylation
#8
Jacob T Edwards, Rohan R Merchant, Kyle S McClymont, Kyle W Knouse, Tian Qin, Lara R Malins, Benjamin Vokits, Scott A Shaw, Deng-Hui Bao, Fu-Liang Wei, Ting Zhou, Martin D Eastgate, Phil S Baran
Olefin chemistry, through pericyclic reactions, polymerizations, oxidations, or reductions, has an essential role in the manipulation of organic matter. Despite its importance, olefin synthesis still relies largely on chemistry introduced more than three decades ago, with metathesis being the most recent addition. Here we describe a simple method of accessing olefins with any substitution pattern or geometry from one of the most ubiquitous and variegated building blocks of chemistry: alkyl carboxylic acids...
April 19, 2017: Nature
https://www.readbyqxmd.com/read/28421770/selective-synthesis-of-e-and-z-allyl-nitriles-via-decarboxylative-reactions-of-alkynyl-carboxylic-acids-with-azobis-alkylcarbonitriles
#9
Francis Mariaraj Irudayanathan, Sunwoo Lee
Allyl nitriles were synthesized from the reactions of arylpropiolic acids with azobis(alkylcarbonitriles) (AIBN or ACCN). In the presence of Cu(OAc)2 as a catalyst and pyridine as the solvent, the (E)-stereoisomer was formed as the major product. This transformation shows good tolerance toward alkoxy, halogen, alcohol, amine, ester, and ketone functional groups. When the reaction was conducted with the sterically bulky amine, ethyldiisopropylamine, in the absence of a copper catalyst, the corresponding (Z)-stereoisomers were formed preferentially...
April 19, 2017: Organic Letters
https://www.readbyqxmd.com/read/28414446/radical-decarboxylation-annulation-of-acrylamides-with-aliphatic-acyl-peroxides
#10
Changduo Pan, Yu Fu, Qingting Ni, Jin-Tao Yu
A radical decarboxylation/annulation of acrylamides with aliphatic acyl peroxides was developed, giving a series of linear alkylated oxindoles in moderate to good yields. The reaction used aliphatic acyl peroxides as the linear alkyl radical source and tolerated a broad scope of substrates under metal-free conditions, offering a simple and efficient approach toward alkylated oxindoles.
April 20, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28412574/work-place-drug-testing-of-police-officers-after-thc-exposure-during-large-volume-cannabis-seizures
#11
Gregory S Doran, Ralph Deans, Carlo De Filippis, Chris Kostakis, Julia A Howitt
Police officers responsible for the seizure and removal of illegally grown cannabis plants from indoor and outdoor growing operations face the prospect of THC exposure while performing their work duties. As a result, a study investigating the amount of THC on hands and uniforms of officers during raids on cannabis growing houses (CGHs) and forest cannabis plantations (FCPs) and in the air at these sites was conducted. Swabs of gloves/hands, chests, and heads/necks were collected and analysed for THC. Results of hand swabs indicated that officers removing plants from FCPs were exposed to THC concentrations up to 20 times those involved in raids at CGHs, which was mainly associated with the number and size of plants seized...
April 2, 2017: Forensic Science International
https://www.readbyqxmd.com/read/28411403/ni-ir-catalyzed-photoredox-decarboxylative-coupling-of-s-substituted-thiolactic-acids-with-hetero-aryl-bromides-short-synthesis-of-sulfoxaflor-and-its-sf5-analog
#12
William Dolbier, Oleksandr Kanishchev
Metallaphotoredox cross-coupling reactions have recently emerged as a powerful tool for the construction of C(sp2)-C(sp3) bonds between alkyl chains and aromatic systems, including electron-deficient hetero(aryls) which are known to be the most challenging coupling partners. In this article we disclose Ni/Ir-catalyzed photoredox decarboxylative coupling of readily available S-substituted thiolactic acids with electron-deficient (hetero)aryl bromides, which resulted in the formation of simple but otherwise not easily accessible hetero(arenes) with alkylsulfide side chain...
April 15, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28411241/2-alkylquinolone-alkaloid-biosynthesis-in-the-medicinal-plant-evodia-rutaecarpa-involves-collaboration-of-two-novel-type-iii-polyketide-synthases
#13
Takashi Matsui, Takeshi Kodama, Takahiro Mori, Tetsuhiro Tadakoshi, Hiroshi Noguchi, Ikuro Abe, Hiroyuki Morita
2-Alkylquinolone (2AQ) alkaloids are pharmaceutically and biologically important natural products produced by both bacteria and plants, with a wide range of biological effects, including antibacterial, cytotoxic, anticholinesterase, and quorum-sensing signaling activities. These diverse activities and 2AQ occurrence in vastly different phyla have raised much interest in the biosynthesis pathways leading to their production. Previous studies in plants have suggested that type III polyketide synthases (PKSs) might be involved in 2AQ biosynthesis, but this hypothesis is untested...
April 14, 2017: Journal of Biological Chemistry
https://www.readbyqxmd.com/read/28408721/decarboxylative-borylation
#14
Chao Li, Jie Wang, Lisa M Barton, Shan Yu, Maoqun Tian, David S Peters, Manoj Kumar, Anthony W Yu, Kristen A Johnson, Arnab K Chatterjee, Ming Yan, Phil S Baran
The widespread use of alkyl boronic acids and esters is frequently hampered by the challenges associated with their preparation. Herein we describe a simple and practical method to rapidly access densely functionalized alkyl boronate esters from abundant carboxylic substituents. This broad-scope Ni-catalyzed reaction uses the same activating principle as amide bond formation to replace a carboxylic acid with a boronate ester. Application to peptides allowed expedient preparations of α-amino boronic acids, often with high stereoselectivity, facilitating the synthesis of both FDA approved alkyl boronic acid drugs (Velcade and Ninlaro) as well as a boronic acid version of the iconic antibiotic vancomycin...
April 13, 2017: Science
https://www.readbyqxmd.com/read/28407894/acrylamide-and-5-hydroxymethylfurfural-formation-during-biscuit-baking-part-ii-effect-of-the-ratio-of-reducing-sugars-and-asparagine
#15
Ha T Nguyen, H J Ine van der Fels-Klerx, M A J S van Boekel
This study investigated acrylamide and 5-hydroxymethylfurfural (HMF) formation during biscuit baking. Four types of wheat flour with different molar ratios of total fructose and glucose to asparagine were investigated. Nevertheless, the molar ratio in all four biscuit doughs exceeded one after proofing due to enzyme action. Data obtained after baking were used to develop a mechanistic model, based on the asparagine-related pathway, for acrylamide and HMF formation in the four baked biscuit types. Asparagine reacted with fructose to form a Schiff base before decarboxylation to produce acrylamide without Amadori rearrangement product and sugar fragmentation...
September 1, 2017: Food Chemistry
https://www.readbyqxmd.com/read/28407542/diclofenac-degradation-in-water-by-feceox-catalyzed-h2o2-influencing-factors-mechanism-and-pathways
#16
Shan Chong, Guangming Zhang, Nan Zhang, Yucan Liu, Ting Huang, Huazhen Chang
The degradation of diclofenac in a like Fenton system, FeCeOx-H2O2, was studied in details. The influencing factors, reaction kinetics, reaction mechanism and degradation pathways of diclofenac were investigated. The optimum conditions were at a solution pH of 5.0, H2O2 concentration of 3.0mmol/L, diclofenac initial concentration of 0.07mmol/L, FeCeOx dosage of 0.5g/L, and 84% degradation of diclofenac was achieved within 40min. The kinetics of FeCeOx catalyzed H2O2 process involved adsorption-dominating and degradation-dominating stages and fitted pseudo-second order model and pseudo-first order model, respectively...
April 5, 2017: Journal of Hazardous Materials
https://www.readbyqxmd.com/read/28406521/dissection-of-the-neocarazostatin-a-c4-alkyl-side-chain-biosynthesis-by-in-vitro-reconstitution
#17
Li Su, Rui Zhang, Kwaku Kyeremeh, Zixin Deng, Hai Deng, Yi Yu
Neocarazostatin A (1) is a potent free radical scavenger possessing an intriguing tricyclic carbazole nucleus with a C4 alkyl side chain attached to ring "A". Although the biosynthetic gene cluster of 1 (nzs) has been identified, and several key steps of the pathway have been well characterized, the enzyme(s) involved in the biosynthesis of the C4 unit still remains obscure. In this work, we demonstrate that three enzymes, including one (MA37-FabG) from primary fatty acid metabolism and two pathway-specific ones (NzsE and NzsF), are responsible for the formation of the side chain precursor...
April 13, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28406311/organocatalytic-asymmetric-decarboxylative-amination-of-%C3%AE-keto-acids-access-to-optically-active-%C3%AE-amino-ketones-and-1-2-amino-alcohols
#18
Yi Wei, Heng-Xia Zhang, Jun-Liang Zeng, Jing Nie, Jun-An Ma
An organocatalytic asymmetric decarboxylative amination reaction of β-keto acids is described. Under mild reaction conditions, a series of chiral α-amino ketones were obtained in good to high yields (up to 99%) and enantioselectivities (up to 95% ee). A chiral 1,2-amino alcohol was synthesized from the corresponding decarboxylative amination product in several steps without loss of enantioselectivity.
April 13, 2017: Organic Letters
https://www.readbyqxmd.com/read/28400403/molecular-imaging-in-the-investigation-of-hypoglycaemic-syndromes-and-their-management
#19
David A Pattison, Rodney J Hicks
There has been recent progress in molecular imaging using a variety of cellular targets for the investigation of adult non-diabetic hypoglycaemic syndromes and its integration into patient management. These targets include peptide receptors - somatostatin receptors (SSTR) and glucagon-like peptide-1 receptor (GLP-1R) - the Amine Precursor Uptake and Decarboxylation system utilising the diphydroxyphenylaline (DOPA) analogue 6-[18F]-L-fluoro-L-3, 4-dihydroxyphenylalanine (18F-FDOPA), and glycolytic metabolism with 2-[18F]Fluoro-2-Deoxy-D-Glucose (FDG)...
April 11, 2017: Endocrine-related Cancer
https://www.readbyqxmd.com/read/28398754/reversing-the-cytotoxicity-of-bile-acids-by-supramolecular-encapsulation
#20
Ying-Ming Zhang, Xun Xu, Qilin Yu, Yao-Hua Liu, Yu-Hui Zhang, Li-Xia Chen, Yu Liu
Supramolecular encapsulation has been developed into a powerful tool in clearance of toxic substances and hazardous waste from living body and external environments. Herein we tested the special efficacy of tyramine-modified β-cyclodextrin (1) in inhibiting and reversing of the inherent cytotoxicity of deoxycholic acid (DCA). The decarboxylation from tyrosine to tyramine in 1 is crucial to the mutual electrostatic communication, ultimately leading to great enhancement in binding affinity and molecular selectivity toward bile acids...
April 18, 2017: Journal of Medicinal Chemistry
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