The Experts below are selected from a list of 2046 Experts worldwide ranked by ideXlab platform
Carmen Najera - One of the best experts on this subject based on the ideXlab platform.
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Glyoxylic Acid versus ethyl glyoxylate for the aqueous enantio selective synthesis of α hydroxy γ keto Acids and esters by the n tosyl s a binam l prolinamide organocatalyzed aldol reaction
Synthesis, 2014Co-Authors: Fernando J N Moles, Carmen Najera, Gabriela Guillena, Enrique GomezbengoaAbstract:N-Tosyl-(S a)-binam- l -prolinamide is an efficient catalyst for the aqueous aldol reaction between ketones and Glyoxylic Acid, as the monohydrate or as an aqueous solution, or a 50% toluene solution of ethyl glyoxylate. These reactions led to the formation of chiral α-hydroxy-γ-keto carboxylic Acids and esters in high levels of diastereo- and enantioselectivities (up to 97% ee), providing mainly anti aldol products. Only cyclopentanone and cyclohexane-1,4-dione afforded an almost 1:1 mixture of the syn/anti-diastereoisomers; however, the reaction between 4-phenylcyclohexanone and ethyl glyoxylate gave the corresponding syn,syn-product as the major diastereoisomer.
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aqueous organocatalyzed aldol reaction of Glyoxylic Acid for the enantioselective synthesis of α hydroxy γ keto Acids
ChemInform, 2014Co-Authors: Fernando J N Moles, Gabriela Guillena, Carmen NajeraAbstract:Glyoxylic Acid is used as an electrophile in the stereoselective aldol reactions with unfunctionalized cyclic and non-cyclic ketones by using catalyst BPA.
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aqueous organocatalyzed aldol reaction of Glyoxylic Acid for the enantioselective synthesis of α hydroxy γ keto Acids
RSC Advances, 2014Co-Authors: Fernando J N Moles, Gabriela Guillena, Carmen NajeraAbstract:N-Tosyl-(Sa)-binam-L-prolinamide is an efficient catalyst for the aqueous aldol reaction, between Glyoxylic Acid, as monohydrate or aqueous solution, and ketones. This reaction led to the formation of chiral α-hydroxy-γ-keto carboxylic Acids in high levels of diastereo- and enantioselectivities achieving mainly anti aldol products.
Xiuhui Zhang - One of the best experts on this subject based on the ideXlab platform.
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clustering mechanism of oxocarboxylic Acids involving hydration reaction implications for the atmospheric models
Journal of Chemical Physics, 2018Co-Authors: Oona Kupiainenmaatta, Maofa Ge, Hanna Vehkamäki, Theo Kurten, Yunhong Zhang, Shaowen Zhang, Haijie Zhang, Hao Li, Jie Zhong, Xiuhui ZhangAbstract:The formation of atmospheric aerosol particles from condensable gases is a dominant source of particulate matter in the boundary layer, but the mechanism is still ambiguous. During the clustering process, precursors with different reactivities can induce various chemical reactions in addition to the formation of hydrogen bonds. However, the clustering mechanism involving chemical reactions is rarely considered in most of the nucleation process models. Oxocarboxylic Acids are common compositions of secondary organic aerosol, but the role of oxocarboxylic Acids in secondary organic aerosol formation is still not fully understood. In this paper, Glyoxylic Acid, the simplest and the most abundant atmospheric oxocarboxylic Acid, has been selected as a representative example of oxocarboxylic Acids in order to study the clustering mechanism involving hydration reactions using density functional theory combined with the Atmospheric Clusters Dynamic Code. The hydration reaction of Glyoxylic Acid can occur either in the gas phase or during the clustering process. Under atmospheric conditions, the total conversion ratio of Glyoxylic Acid to its hydration reaction product (2,2-dihydroxyacetic Acid) in both gas phase and clusters can be up to 85%, and the product can further participate in the clustering process. The differences in cluster structures and properties induced by the hydration reaction lead to significant differences in cluster formation rates and pathways at relatively low temperatures.
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gas phase hydration of Glyoxylic Acid kinetics and atmospheric implications
Chemosphere, 2017Co-Authors: Ling Liu, Xiuhui Zhang, Yunhong ZhangAbstract:Oxocarboxylic Acids are one of the most important organic species found in secondary organic aerosols and can be detected in diverse environments. But the hydration of oxocarboxylic Acids in the atmosphere has still not been fully understood. Neglecting the hydration of oxocarboxylic Acids in atmospheric models may be one of the most important reasons for the significant discrepancies between field measurements and abundance predictions of atmospheric models for oxocarboxylic Acids. In the present paper, Glyoxylic Acid, as the most abundant oxocarboxylic Acids in the atmosphere, has been selected as an example to study whether the hydration process can occur in the atmosphere and what the kinetic process of hydration is. The gas-phase hydration of Glyoxylic Acid to form the corresponding geminal diol and those catalyzed by atmospheric common substances (water, sulfuric Acid and ammonia) have been investigated at the CCSD(T)-F12/cc-pVDZ-F12//M06-2X/6-311++G(3df,3pd) level of theory. The contour map of electron density difference of transition states have been further analyzed. It is indicated that these atmospheric common substances can all catalyze on the hydration to some extent and sulfuric Acid is the most effective reducing the Gibbs free energy of activation to 9.48 kcal/mol. The effective rate constants combining the overall rate constants and concentrations of the corresponding catalysts have shown that water and sulfuric Acid are both important catalysts and the catalysis of sulfuric Acid is the most effective for the gas-phase hydration of Glyoxylic Acid. This catalyzed processes are potentially effective in coastal regions and polluted regions.
M. W. Anders - One of the best experts on this subject based on the ideXlab platform.
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glutathione transferase zeta catalyzed biotransformation of dichloroacetic Acid and other alpha haloAcids
Chemical Research in Toxicology, 1998Co-Authors: Zeen Tong, Philip G. Board, M. W. AndersAbstract:Dichloroacetic Acid (DCA) is a common drinking-water contaminant, is hepatocarcinogenic in rats and mice, and is a therapeutic agent used clinically in the management of lactic Acidosis. Recent studies show that glutathione transferase Zeta (GSTZ) catalyzes the oxygenation of DCA to Glyoxylic Acid [Tong et al. (1998) Biochem. J. 331, 371-374]. In the present studies, the substrate selectivity of GSTZ, the kinetics of DCA metabolism, and the fate of DCA and glutathione were investigated. The results showed that GSTZ catalyzed the oxygenation of bromochloro-, bromofluoro-, chlorofluoro-, dibromo-, and dichloroacetic Acid, but not difluoroacetic Acid, to Glyoxylic Acid. GSTZ also catalyzed the biotransformation of fluoroacetic Acid to S-(carboxymethyl)glutathione, and of (R,S)-2-bromopropionic Acid, (R)-, (S)-, and (R,S)-2-chloropropionic Acid, and (R, S)-2-iodopropionic Acid, but not (R,S)-2-fluoropropionic Acid, to S-(alpha-methylcarboxymethyl)glutathione; and of 2, 2-dichloropropionic Acid to pyruvate. No biotransformation of 3, 3-dichloropropionic Acid was detected, and no GSTZ-catalyzed fluoride release from ethyl fluoroacetate and fluoroacetamide was observed. The relative rates of DCA biotransformation by hepatic cytosol were mouse > rat > human. Immunoblotting showed the presence of GSTZ in mouse, rat, and human liver cytosol. 13C NMR spectroscopic studies showed that [2-13C]Glyoxylic Acid was the only observable, stable metabolite of [2-13C]DCA. Also, glutathione was required, but was neither consumed nor oxidized to glutathione disulfide, during the oxygenation of DCA to Glyoxylic Acid. These results are consistent with a reaction mechanism that involves displacement of chloride from DCA by glutathione to afford S-(alpha-chlorocarboxymethyl)glutathione, which may undergo hydrolysis to give the hemithioacetal S-(alpha-hydroxycarboxymethyl)glutathione. Elimination of glutathione from the hemithioacetal would give Glyoxylic Acid.
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glutathione transferase zeta catalyses the oxygenation of the carcinogen dichloroacetic Acid to Glyoxylic Acid
Biochemical Journal, 1998Co-Authors: Zeen Tong, Philip G. Board, M. W. AndersAbstract:Dichloroacetic Acid (DCA), a common drinking-water contaminant, is hepatocarcinogenic in rats and mice, and is a therapeutic agent used clinically in the management of lactic Acidosis. DCA is biotransformed to Glyoxylic Acid by glutathione-dependent cytosolic enzymes in vitro and is metabolized to Glyoxylic Acid in vivo. The enzymes that catalyse the oxygenation of DCA to Glyoxylic Acid have not, however, been identified or characterized. In the present investigation, an enzyme that catalyses the glutathione-dependent oxygenation of DCA was purified to homogeneity (587-fold) from rat liver cytosol. SDS/PAGE and HPLC gel-filtration chromatography showed that the purified enzyme had a molecular mass of 27-28 kDa. Sequence analysis showed that the N-terminus of the purified protein was blocked. An internal sequence of 30 amino Acid residues was obtained that matched the recently discovered human glutathione transferase Zeta well [Board, Baker, Chelvanayagam and Jermiin (1997) Biochem. J. 328, 929-935]. Western-blot analysis showed that the purified rat-liver enzyme cross-reacted with rabbit antiserum raised against recombinant human glutathione transferase Zeta. The apparent Km and Vmax values of the purified enzyme with DCA as the variable substrate were 71.4 microM and 1334 nmol/min per mg of protein, respectively; the Km for glutathione was 59 microM. Both the purified rat-liver enzyme and the recombinant human enzyme showed high activity with DCA as the substrate. These results demonstrate that the glutathione-dependent oxygenation of DCA to Glyoxylic Acid is catalysed by a Zeta-class glutathione transferase.
Fernando J N Moles - One of the best experts on this subject based on the ideXlab platform.
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Glyoxylic Acid versus ethyl glyoxylate for the aqueous enantio selective synthesis of α hydroxy γ keto Acids and esters by the n tosyl s a binam l prolinamide organocatalyzed aldol reaction
Synthesis, 2014Co-Authors: Fernando J N Moles, Carmen Najera, Gabriela Guillena, Enrique GomezbengoaAbstract:N-Tosyl-(S a)-binam- l -prolinamide is an efficient catalyst for the aqueous aldol reaction between ketones and Glyoxylic Acid, as the monohydrate or as an aqueous solution, or a 50% toluene solution of ethyl glyoxylate. These reactions led to the formation of chiral α-hydroxy-γ-keto carboxylic Acids and esters in high levels of diastereo- and enantioselectivities (up to 97% ee), providing mainly anti aldol products. Only cyclopentanone and cyclohexane-1,4-dione afforded an almost 1:1 mixture of the syn/anti-diastereoisomers; however, the reaction between 4-phenylcyclohexanone and ethyl glyoxylate gave the corresponding syn,syn-product as the major diastereoisomer.
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aqueous organocatalyzed aldol reaction of Glyoxylic Acid for the enantioselective synthesis of α hydroxy γ keto Acids
ChemInform, 2014Co-Authors: Fernando J N Moles, Gabriela Guillena, Carmen NajeraAbstract:Glyoxylic Acid is used as an electrophile in the stereoselective aldol reactions with unfunctionalized cyclic and non-cyclic ketones by using catalyst BPA.
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aqueous organocatalyzed aldol reaction of Glyoxylic Acid for the enantioselective synthesis of α hydroxy γ keto Acids
RSC Advances, 2014Co-Authors: Fernando J N Moles, Gabriela Guillena, Carmen NajeraAbstract:N-Tosyl-(Sa)-binam-L-prolinamide is an efficient catalyst for the aqueous aldol reaction, between Glyoxylic Acid, as monohydrate or aqueous solution, and ketones. This reaction led to the formation of chiral α-hydroxy-γ-keto carboxylic Acids in high levels of diastereo- and enantioselectivities achieving mainly anti aldol products.
Jeanne Crassous - One of the best experts on this subject based on the ideXlab platform.
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synthesis of carbo 6 helicene derivatives grafted with amino or aminoester substituents from enantiopure 6 helicenyl boronates
Journal of Organic Chemistry, 2018Co-Authors: Nora Hellou, Aurelie Mace, Clothilde Martin, Vincent Dorcet, Thierry Roisnel, Marion Jean, Nicolas Vanthuyne, Fabienne Berree, Bertrand Carboni, Jeanne CrassousAbstract:Enantiopure carbo[6]helicenyl boronates were synthesized using a photocyclization reaction as the key step. These compounds were further converted to various amino derivatives using copper-catalyzed azidation or amination and reductive alkylation of benzylazide by a helicenyl dichloroborane. Asymmetric Petasis condensation with Glyoxylic Acid and morpholine controlled by the helical chirality afforded the corresponding amino esters.
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Synthesis of Carbo[6]helicene Derivatives Grafted with Amino or Aminoester Substituents from Enantiopure [6]Helicenyl Boronates
2017Co-Authors: Nora Hellou, Clothilde Martin, Vincent Dorcet, Thierry Roisnel, Marion Jean, Nicolas Vanthuyne, Bertrand Carboni, Aurélie Macé, Fabienne Berrée, Jeanne CrassousAbstract:Enantiopure carbo[6]helicenyl boronates were synthesized using a photocyclization reaction as the key step. These compounds were further converted to various amino derivatives using copper-catalyzed azidation or amination and reductive alkylation of benzylazide by a helicenyl dichloroborane. Asymmetric Petasis condensation with Glyoxylic Acid and morpholine controlled by the helical chirality afforded the corresponding amino esters