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Natalja Vogt, Ilya I Marochkin, Anatolii N Rykov
The accurate molecular structure of picolinic acid has been determined from experimental data and computed at the coupled cluster level of theory. Only one conformer with the O[double bond, length as m-dash]C-C-N and H-O-C[double bond, length as m-dash]O fragments in antiperiplanar (ap) positions, ap-ap, has been detected under conditions of the gas-phase electron diffraction (GED) experiment (Tnozzle = 375(3) K). The semiexperimental equilibrium structure, rsee, of this conformer has been derived from the GED data taking into account the anharmonic vibrational effects estimated from the ab initio force field...
March 22, 2018: Physical Chemistry Chemical Physics: PCCP
Chaoqiang Xiao, Ying Han, Ying Liu, Jingpu Zhang, Chang-Qin Hu
Central nervous system (CNS) side effects are one of the most frequently reported adverse reactions of fluoroquinolones (FQs). However, the mechanism is not fully understood. In this study, zebrafish (Danio rerio) were used as a model system. We quantified neurobehavior by recording indicators with automated video-tracking and used liquid chromatography-tandem mass spectrometry (LC-MS/MS) to detect drug absorption in vivo. We studied embryotoxicity and effects on zebrafish locomotor activity of 17 typical FQs...
March 21, 2018: Chemical Research in Toxicology
Jeonghyo Lee, Sibin Wang, Miranda Callahan, Pavel Nagorny
This work describes the development of a new single-pot copper(II)-catalyzed decarboxylative Michael reaction between β-keto acids and enones, followed by in situ aldolization, which results in highly functionalized chiral and achiral cyclohexenones. The achiral version of this Robinson annulation features a hitherto unprecedented Michael reaction of β-keto acids with sterically hindered β,β'-substituted enones and provides access to all carbon quaternary stereocenter-containing cyclohexenones (11 examples, 43-83% yield)...
March 21, 2018: Organic Letters
Dian-Zhao Lin, Jing-Mei Huang
A new method for the synthesis of formamides has been developed through electrochemical decarboxylative N-formylation of amines with glyoxylic acid. This protocol provides an efficient approach to formamides with a broad range of functional group tolerance under ambient conditions.
March 20, 2018: Organic Letters
Shuaifei Wang, Xiaoyan Qian, Yuanyu Chang, Jiayue Sun, Xiujing Xing, Wendy Fields Ballard, Jason J Chruma
The impact of the steric and electronic factors in both the para-substituted benzaldimine and 2,2-diarylglycine components on the regioselectivity and enantioselectivity of the palladium-catalyzed decarboxylative allylation of allyl 2,2-diarylglycinate aryl imines was explored. These studies revealed that using 2,2-di(2-methoxyphenyl)glycine as the amino acid linchpin allowed for the exclusive synthesis of the desired homoallylic benzophenone imine regioisomers, independent of the nature of the imine moiety, in typically high yields...
March 20, 2018: Journal of Organic Chemistry
Harry R Beller, Andria V Rodrigues, Kamrun Zargar, Yu-Wei Wu, Avneesh K Saini, Renee M Saville, Jose H Pereira, Paul D Adams, Susannah G Tringe, Christopher J Petzold, Jay D Keasling
Microbial toluene biosynthesis was reported in anoxic lake sediments more than three decades ago, but the enzyme catalyzing this biochemically challenging reaction has never been identified. Here we report the toluene-producing enzyme PhdB, a glycyl radical enzyme of bacterial origin that catalyzes phenylacetate decarboxylation, and its cognate activating enzyme PhdA, a radical S-adenosylmethionine enzyme, discovered in two distinct anoxic microbial communities that produce toluene. The unconventional process of enzyme discovery from a complex microbial community (>300,000 genes), rather than from a microbial isolate, involved metagenomics- and metaproteomics-enabled biochemistry, as well as in vitro confirmation of activity with recombinant enzymes...
March 19, 2018: Nature Chemical Biology
R N Prasad Tulichala, Mallepalli Shankar, K C Kumara Swamy
Palladium-catalyzed ortho-amidation of indole-3-carboxylic acids with isothiocyanates by using the deciduous directing group nature of carboxyl functionality to afford indole-2-amides is demonstrated. Both C-H functionalization and decarboxylation took place in a one pot and hence this carboxyl group served as a unique, deciduous (or traceless) directing group. This reaction offers a broad substrate scope as demonstrated for several other heterocyclic carboxylic acids like chromene-3-carboxylic acid, imidazo[1,2-a]pyridine-2-carboxylic acid, benzofuran-2-carboxylic acid, pyrrole-2-carboxylic acid and thiophene-2-carboxylic acid...
March 19, 2018: Journal of Organic Chemistry
Aurélie Fossey-Jouenne, Carine Vergne-Vaxelaire, Anne Zaparucha
Amino alcohols are versatile compounds with a wide range of applications. For instance, they have been used as chiral scaffolds in organic synthesis. Their synthesis by conventional organic chemistry often requires tedious multi-step synthesis processes, with difficult control of the stereochemical outcome. We present a protocol to enzymatically synthetize amino alcohols starting from the readily available L-lysine in 48 h. This protocol combines two chemical reactions that are very difficult to conduct by conventional organic synthesis...
February 16, 2018: Journal of Visualized Experiments: JoVE
Joseph D Wani Lako, Jada P Yengkopiong, William H L Stafford, Marla Tuffin, Don A Cowan
The Bacillus licheniformis ydaP gene encodes for a pyruvate oxidase that catalyses the oxidative decarboxylation of pyruvate to acetate and CO2 . The YdaP form of this enzyme was purified about 48.6-folds to homogeneity in three steps. The enzyme was recovered in a soluble form and demonstrated significant activity on pyruvate using 2, 6-dichlorophenolindophenol (DCPIP) as an artificial electron acceptor. HPLC analysis of the YdaP-enzyme catalysed conversion of pyruvate showed acetate as the sole product, confirming the putative identity of pyruvate oxidase...
March 15, 2018: Acta Biochimica Polonica
Meng-Jun Qiu, Yao-Bing Chen, Sheng-Li Yang, Xiao-Xiao He, Zhi-Fan Xiong
BACKGROUND: Neuroendocrine tumors (NETs) are uncommon type of cancers, also known as APUD (amine precursor uptake decarboxylation) tumors, which are becoming increasingly prevalent. Alkaline phosphatase (ALP) is a poor prognosis factor in a number of hepatic diseases. However, its distribution and prognostic value in primary hepatic neuroendocrine tumors (PHNETs) are still not clear. In this study, our aim is to investigate the correlations between ALP and clinicopathological features and prognostic factors of PHNETs...
March 13, 2018: Clinica Chimica Acta; International Journal of Clinical Chemistry
Tianhua Yang, Jian Wang, Bingshuo Li, Xingping Kai, Wanli Xing, Rundong Li
This study extended previous work investigating two-step liquefaction by supercritical ethanol of rice straw under CO2 atmosphere at temperatures of 270-345 °C. Subcritical CO2 -subcritical ethanol (SubCO2 -SubEtOH) pretreatment decreased the content of lignin in the rice stalk from 22.94 to 21.43 wt%. The results showed that although oxygen-transfer reaction, transesterification, carbonylation, and other reactions may occur with the supercritical CO2 -supercritical ethanol (ScCO2 -ScEtOH) liquefaction reactions, transesterification was the main reaction...
February 23, 2018: Bioresource Technology
Nuannuan Ma, Peihe Li, Zheng Wang, Qipu Dai, Changwen Hu
An efficient Pd-catalyzed decarboxylation/cyclization of aroyloxycarbamates to realize substituted indoles has been disclosed. Terminal alkynes as the coupling partners lead to site specific 2-substituted indoles through two pathways, while internal alkynes with aroyloxycarbamates can be transformed to 2,3-disubstituted indoles directly. This protocol is further demonstrated by the efficient synthesis of indoles as well as the success of employing inexpensive aryl acids as starting materials to construct C-N bonds by releasing CO2...
March 16, 2018: Organic & Biomolecular Chemistry
Per Strøman, Kim Ib Sørensen, Patrick M F Derkx, Ana Rute Neves
Biogenic amines have been widely studied because of their potential toxicity in fermented foods. Several lactic acid bacteria have the potential to decarboxylate the amino acid tyrosine to tyramine. In this work, we identified two strains of Lactobacillus curvatus, Lbc1 and Lbc2, endowed with the ability to produce tyramine, a metabolic feature that limits their application in starter cultures for fermented meat. To overcome this limitation, we set out to eliminate tyramine production from L. curvatus strains by using classical strain improvement...
March 15, 2018: Journal of Food Protection
Jaya Kumar, Srijit Das, Seong Lin Teoh
Acrylamide (AA) is a water soluble white crystalline solid commonly used in industries. It was listed as an industrial chemical with potential carcinogenic properties. However to date, AA was used to produce polyacrylamide polymer, which was widely used as a coagulant in water treatment; additives during papermaking; grouting material for dams, tunnels, and other underground building constructions. AA in food could be formed during high-temperature cooking via several mechanisms, i.e., formation via acrylic acid which may be derived from the degradation of lipid, carbohydrates, or free amino acids; formation via the dehydration/decarboxylation of organic acids (malic acid, lactic acid, and citric acid); and direct formation from amino acids...
2018: Frontiers in Nutrition
Hao Chen, Xuehe Lu, Xuejian Xia, Qiongqiong Zhu, Yanhong Song, Jie Chen, Weiguo Cao, Xiaoyu Wu
A decarboxylative formal [4 + 2] cycloaddition reaction between ethynyl benzoxazinanones and 5-substituted 2-silyloxyfurans catalyzed by chiral Cu-Pybox complex is described. This method allows the formation of intriguing tetrahydroquinolines fused with a butyrolactone moiety featuring three contiguous chiral centers in high yields with excellent diastereo- and enantioselectivities in most cases. The utility of this method was exemplified by the removal of the N-protecting groups and derivatization on the terminal alkyne functionality of the cyclization products...
March 14, 2018: Organic Letters
Chi-Hao Chang, Chih-Ming Chou
This study explores a Pd-catalyzed decarboxylative Heck-type Csp3 -Csp2 coupling reaction of 2,5-cyclohexadiene-1-carboxylic acid derivatives with vinyl halides to provide γ-olefination products. The olefinated 1,3-cyclohexadienes can be further oxidized to produce meta-alkylated stilbene derivatives. Additionally, the conjugated diene products can also undergo a Diels-Alder reaction to produce a bicyclo[2.2.2]octadiene framework.
March 14, 2018: Organic Letters
Srinivas Angapelly, P V Sri Ramya, Rohini Sodhi, Andrea Angeli, Krishnan Rangan, Narayana Nagesh, Claudiu T Supuran, Mohammed Arifuddin
A practical and transition metal-free one-pot domino synthesis of diversified (1,3,4-oxadiazol-2-yl)anilines has been developed employing isatins and hydrazides as the starting materials, in the presence of molecular iodine. The prominent feature of this domino process involves consecutive condensation, hydrolytic ring cleavage, and an intramolecular decarboxylation, in a one-pot process that leads to the oxidative formation of a C-O bond. Fluorescence properties of some of the representative molecules obtained in this way were studied...
December 2018: Journal of Enzyme Inhibition and Medicinal Chemistry
Junsei Taira, Rin Toyoshima, Nana Ameku, Akira Iguchi, Yasutomo Tamaki
Vanillin is valuable and popular flavor used in foods and cosmetics. Many bacteria species have the ability to decarboxylate substituted cinnamic acids in order to form vanillin. However, the phenolic biotransformation including vanillin production in a common fungus, the Aspergillus luchuensis, which is used in distilled beverages, has not yet been clarified. This study focused on elucidating the vanillin production due to phenolic biotransformation in A. luchuensis during fermentation. The phenolic metabolites were extracted by a solid phase column and they were determined using on LC/MS and LC/MS/MS in a selective ion mode...
March 13, 2018: AMB Express
Shuai Yang, Wenkai Hua, Yanqi Wu, Tao Hu, Feng Wang, Xingxian Zhang, Fengzhi Zhang
Here we report a site-selective synthesis of functionalized dibenzo[f,h]quinolines and their derivatives, which could be used as OLED materials. The key step is the double cross coupling reaction between the 2-chloropyridinyl acids and the cyclic diaryliodonium salts, where the carboxylic acid was unprecedentedly employed as both a traceless directing group and a functional handle in a one-pot atom- and step-economical process.
March 14, 2018: Chemical Communications: Chem Comm
T J Thomas, Thresia Thomas
Polyamine levels are elevated in breast tumors compared to those of adjacent normal tissues. The female sex hormone, estrogen is implicated in the origin and progression of breast cancer. Estrogens stimulate and antiestrogens suppress the expression of polyamine biosynthetic enzyme, ornithine decarboxylate (ODC). Using several bis(ethyl)spermine analogues, we found that these analogues inhibited the proliferation of estrogen receptor-positive and estrogen receptor negative breast cancer cells in culture. There was structure-activity relationship in the efficacy of these compounds in suppressing cell growth...
March 13, 2018: Medical Sciences: Open Access Journal
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