Schiff Bases of Amino Acid Esters as New Substrates for the Enantioselective Enzymatic Hydrolysis and Accompanied Asymmetric Transformations in Aqueous Organic Solvents1,2
摘要:
The enzyme (lipases and chymotrypsin)-catalyzed hydrolysis of Schiff bases derived from racemic amino acid esters and aromatic aldehydes has been investigated. The reactions were successfully carried out in different aqueous organic solvents at ambient temperature, but the aqueous acetonitrile (5.4% water content by volume) was the solvent of choice. The L-amino acid (ee 98%) precipitated out from the solution as the reaction progressed, and the liberated aldehyde and unhydrolyzed D-ester (ee 40-98%) remained in the solution. The range of substrates included amino acids having different types of side chains. The addition of an organic base (DABCO) into the solution resulted in the racemization of the remaining D-ester and the additional hydrolysis of the substrate, thus leading to the effective asymmetric transformation of the initial ester. Upto 87.5% of the initial racemate was converted into the L-enantiomer.
Mono- vs. dialkylation of carbanions. Effects of absolute and relative acidity of the conjugate carbon acids in selectivity control
作者:Luděk Ridvan、Jiří Závada
DOI:10.1016/s0040-4020(97)00989-7
日期:1997.10
in the reaction of the dibromide 1 with carbanions 2a – 2g covering a range greater than 15 pK units in DMSO. It was found that the bis(monoalkylated) product 3 arises exclusively or predominantly from the carbanions 2d – 2g derived from the less acidic carbon acids 7d – 7g whereas the cyclic product of dialkylation 4 prevails in the reaction of the carbanions 2a – 2c derived from the more acidic carbon
Enantio- and diastereodivergent synthesis of fused indolizines enabled by synergistic Cu/Ir catalysis
作者:Bing-Ke Zhu、Hui Xu、Lu Xiao、Xin Chang、Liang Wei、Huailong Teng、Yanfeng Dang、Xiu-Qin Dong、Chun-Jiang Wang
DOI:10.1039/d3sc00118k
日期:——
Highly diastereo-/enantioselectiveassembly of 2,3-fused indolizine derivatives could be easily available through a cascade allylation/Friedel–Craftstype reaction enabled by a synergistic Cu/Ir catalysis. This designed protocol provides an unprecedented and facile route to enantioenriched indolizines bearing three stereogenic centers in moderate to high yields with excellent stereoselective control
Phenylation of amino acid derivatives: A new route to α-phenyl-α-substituted amino acids
作者:Martin J. O'Donnell、William D. Bennett、William N. Jacobsen、You-an Ma
DOI:10.1016/s0040-4039(00)99282-7
日期:1989.1
Schiff Bases of Amino Acid Esters as New Substrates for the Enantioselective Enzymatic Hydrolysis and Accompanied Asymmetric Transformations in Aqueous Organic Solvents<sup>1</sup><sup>,</sup><sup>2</sup>
作者:Virinder S. Parmar、Amarjit Singh、Kirpal S. Bisht、Naresh Kumar、Y. N. Belokon、K. A. Kochetkov、N. S. Ikonnikov、S. A. Orlova、V. I. Tararov、T. F. Saveleva
DOI:10.1021/jo941734v
日期:1996.1.1
The enzyme (lipases and chymotrypsin)-catalyzed hydrolysis of Schiff bases derived from racemic amino acid esters and aromatic aldehydes has been investigated. The reactions were successfully carried out in different aqueous organic solvents at ambient temperature, but the aqueous acetonitrile (5.4% water content by volume) was the solvent of choice. The L-amino acid (ee 98%) precipitated out from the solution as the reaction progressed, and the liberated aldehyde and unhydrolyzed D-ester (ee 40-98%) remained in the solution. The range of substrates included amino acids having different types of side chains. The addition of an organic base (DABCO) into the solution resulted in the racemization of the remaining D-ester and the additional hydrolysis of the substrate, thus leading to the effective asymmetric transformation of the initial ester. Upto 87.5% of the initial racemate was converted into the L-enantiomer.