Silver-catalyzed asymmetric amination of silyl enol ethers

2000 ◽  
Vol 78 (6) ◽  
pp. 666-672 ◽  
Author(s):  
Yasuhiro Yamashita ◽  
Haruro Ishitani ◽  
Shu Kobayashi
Keyword(s):  
Catalytic Activity ◽  
Amino Acid ◽  
Asymmetric Synthesis ◽  
Asymmetric Reactions ◽  
High Catalytic Activity ◽  
Enol Ethers ◽  
Chiral Catalyst ◽  
Silyl Enol Ethers ◽  
Catalytic Amination

Catalytic amination of silyl enol ethers with azo diester compounds was investigated. It was shown that Cu(OTf)2 or AgOTf had high catalytic activity and that AgOTf was the most efficient among the catalysts tested in the reactions. In asymmetric reactions, the AgClO4-BINAP system showed high enantioselectivity. In a mixture of toluene or mesitylene and THF, silyl enol ethers reacted with dibenzyl azodicarboxylate (DBnAD) smoothly to afford the corresponding amination adducts in excellent yields with up to 86% ee.Key words: amination, amino acid, asymmetric synthesis, chiral catalyst, silver.

scholarly journals Molecular cloning and heterologous expression of a cDNA encoding a mouse glutathione S-transferase Yc subunit possessing high catalytic activity for aflatoxin B1-8,9-epoxide

1992 ◽  
Vol 285 (1) ◽  
pp. 173-180 ◽  
Author(s):  
J D Hayes ◽  
D J Judah ◽  
G E Neal ◽  
T Nguyen
Keyword(s):  
Catalytic Activity ◽  
Amino Acid ◽  
Amino Acid Sequence ◽  
Rat Liver ◽  
Cdna Clone ◽  
Aflatoxin B1 ◽  
Mouse Liver ◽  
High Catalytic Activity ◽  
Glutathione S Transferase ◽  
E Coli

Resistance to the carcinogenic effects of aflatoxin B1 (AFB1) in the mouse is due to the constitutive expression of an Alpha-class glutathione S-transferase (GST), YcYc, with high detoxification activity towards AFB1-8,9-epoxide. A cDNA clone (pmusGST Yc) for a murine GST Yc polypeptide has been isolated. Sequencing has shown the cDNA insert of pmusGST Yc to be 922 bp in length, with an open reading frame of 663 bp that encodes a polypeptide of M(r) 25358. The primary structure of the murine GST Yc subunit predicted by pmusGST Yc is in complete agreement with the partial amino acid sequence of the aflatoxin-metabolizing mouse liver GST described previously [McLellan, Kerr, Cronshaw & Hayes (1991) Biochem. J. 276, 461-469]. A plasmid, termed pKK-musGST Yc, which permits the expression of the murine Yc subunit in Escherichia coli, has been constructed. The murine GST expressed in E. coli was purified and found to be catalytically active towards several GST substrates, including AFB1-8,9-epoxide. This enzyme was also found to possess electrophoretic and immunochemical properties closely similar to those of the GST Yc subunit from mouse liver. However, the GST synthesized in E. coli and the constitutive mouse liver Alpha-class GST exhibited small differences in their chromatographic behaviour during reverse-phase h.p.l.c. Automated Edman degradation revealed alanine to be the N-terminal amino acid in the GST Yc subunit expressed in E. coli, whereas the enzyme in mouse liver possesses a blocked N-terminus. Although sequencing showed that the purified Yc subunit from E. coli lacked the initiator methionine, the amino acid sequence obtained over the first eleven N-terminal residues agreed with that predicted from the cDNA clone, pmusGST Yc. Comparison of the deduced amino acid sequence of the mouse Yc polypeptide with the primary structures of the rat Alpha-class GST enzymes revealed that it is more closely related to the ethoxyquin-induced rat liver Yc2 subunit than to the constitutively expressed rat liver Yc1 subunit. The significance of the fact that both mouse Yc and rat Yc2 exhibit high catalytic activity towards AFB1-8,9-epoxide, whereas rat Yc1 possesses little activity towards this compound, is discussed in terms of structure/function.

scholarly journals Single-molecule imaging analysis reveals the mechanism of a high-catalytic-activity mutant of chitinase A from Serratia marcescens

2020 ◽  
Vol 295 (7) ◽  
pp. 1915-1925 ◽  
Author(s):  
Akasit Visootsat ◽  
Akihiko Nakamura ◽  
Paul Vignon ◽  
Hiroki Watanabe ◽  
Takayuki Uchihashi ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Amino Acid ◽  
Serratia Marcescens ◽  
Kinetic Parameters ◽  
Single Molecule ◽  
Reaction Scheme ◽  
High Catalytic Activity ◽  
Single Molecule Imaging ◽  
Imaging Analysis ◽  
Chitinase A

Chitin degradation is important for biomass conversion and has potential applications for agriculture, biotechnology, and the pharmaceutical industry. Chitinase A from the Gram-negative bacterium Serratia marcescens (SmChiA) is a processive enzyme that hydrolyzes crystalline chitin as it moves linearly along the substrate surface. In a previous study, the catalytic activity of SmChiA against crystalline chitin was found to increase after the tryptophan substitution of two phenylalanine residues (F232W and F396W), located at the entrance and exit of the substrate binding cleft of the catalytic domain, respectively. However, the mechanism underlying this high catalytic activity remains elusive. In this study, single-molecule fluorescence imaging and high-speed atomic force microscopy were applied to understand the mechanism of this high-catalytic-activity mutant. A reaction scheme including processive catalysis was used to reproduce the properties of SmChiA WT and F232W/F396W, in which all of the kinetic parameters were experimentally determined. High activity of F232W/F396W mutant was caused by a high processivity and a low dissociation rate constant after productive binding. The turnover numbers for both WT and F232W/F396W, determined by the biochemical analysis, were well-replicated using the kinetic parameters obtained from single-molecule imaging analysis, indicating the validity of the reaction scheme. Furthermore, alignment of amino acid sequences of 258 SmChiA-like proteins revealed that tryptophan, not phenylalanine, is the predominant amino acid at the corresponding positions (Phe-232 and Phe-396 for SmChiA). Our study will be helpful for understanding the kinetic mechanisms and further improvement of crystalline chitin hydrolytic activity of SmChiA mutants.

Asymmetric synthesis of γ-cyano silyl enol ethers

1999 ◽  
Vol 10 (6) ◽  
pp. 1145-1151 ◽  
Author(s):  
Elena Dı́ez ◽  
Rosario Fernández ◽  
Eloı́sa Martı́n-Zamora ◽  
Carmen Pareja ◽  
Auxiliadora Prieto ◽  
...  
Keyword(s):  
Asymmetric Synthesis ◽  
Enol Ethers ◽  
Silyl Enol Ethers

Organocatalytic enantioselective Mukaiyama–Mannich reaction of fluorinated enol silyl ethers and cyclic N-sulfonyl ketimines

2016 ◽  
Vol 3 (3) ◽  
pp. 298-303 ◽  
Author(s):  
Jin-Sheng Yu ◽  
Jian Zhou
Keyword(s):  
Amino Acid ◽  
Mannich Reaction ◽  
Enantioselective Synthesis ◽  
Amino Acid Derivatives ◽  
Enol Ethers ◽  
Silyl Ethers ◽  
Silyl Enol Ethers ◽  
Catalytic Asymmetric ◽  
Enol Silyl Ethers

The first catalytic asymmetric Mukaiyama–Mannich reaction of fluorinated silyl enol ethers and ketimines is developed, allowing highly enantioselective synthesis of benzosultam based β-fluorinated Cα-tetrasubstituted α-amino acid derivatives.

ChemInform Abstract: Asymmetric Synthesis of γ-Cyano Silyl Enol Ethers.

ChemInform ◽  
2010 ◽  
Vol 30 (36) ◽  
pp. no-no
Author(s):  
Elena Diez ◽  
Rosario Fernandez ◽  
Eloisa Martin-Zamora ◽  
Carmen Pareja ◽  
Auxiliadora Prieto ◽  
...  
Keyword(s):  
Asymmetric Synthesis ◽  
Enol Ethers ◽  
Silyl Enol Ethers
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