Asymmetric Synthesis of α,α-Disubstituted α-Amino Acids Using (S,S)-Cyclohexane-1,2-diol as a Chiral Auxiliary
摘要:
Diastereoselective alkylation of ethyl 2-methyl- and/or 2-ethylacetoacetates using the (S,S)cyclohexane-1,2-diol as an acetal chiral auxiliary afforded enol ethers (2a-f and 5a-f) of 92 - > 95% de in 31-70% yields. Removal of the cyclohexane-l,2-diol with BF3-OEt2 afforded beta -keto esters (3 and 6) bearing a chiral quaternary carbon. The beta -keto esters could be easily converted into optically active alpha -methylated and/or alpha -ethylated alpha,alpha -disubstituted amino acids (12 and 13) in 21-99% yields using Schmidt rearrangement.
Enzymatic resolution of .alpha.-tertiary carboxylic acid esters
申请人:Genzyme Corporation
公开号:US05492830A1
公开(公告)日:1996-02-20
A method for the resolution of .alpha.-tertiary carboxylic acid esters by partial hydrolysis is disclosed. The partial hydrolysis is carried out by contacting the esters with an aqueous solution in the presence of a serine carboxypeptidase, and the hydrolysis product is separated from unreacted starting material to obtain the hydrolysis product or the unreacted starting material in enantiomerically enriched form. A novel ester hydrolase which is particularly useful in this method, and a nucleotide sequence encoding this enzyme, are also described.
Biocatalytic resolution of tertiary .alpha.-substituted carboxylic acid esters: efficient preparation of a quaternary asymmetric carbon center
作者:Christopher Yee、Todd A. Blythe、Thomas J. McNabb、Alan E. Walts
DOI:10.1021/jo00039a004
日期:1992.6
A method for resolving a variety of tertiary alpha-substituted carboxylic acid
EP1981831A2
申请人:——
公开号:EP1981831A2
公开(公告)日:2008-10-22
Kit for automated resolving agent selection and method thereof
申请人:Vaidya A. Niteen
公开号:US20070185346A1
公开(公告)日:2007-08-09
The present invention concerns an improved method and a tray or kit, which is useful to select quickly the optimum resolution agents, combinations and conditions to separate optical isomers. The tray of 24, 48, 96 or more samples is examined simultaneously visually or by standard analytical techniques.
KIT FOR AUTOMATED RESOLVING AGENT SELECTION AND METHOD THEREOF
申请人:Vaidya Niteen A.
公开号:US20120041225A1
公开(公告)日:2012-02-16
The present invention provides a means for the rapid selection of optimum resolving agents and solvents, combinations and conditions to separate optical isomers. The present invention combinedly describes and automates a full lifecycle of chiral separation method development and optimization through a series of kits and procedures providing screening, automation for screening, racemate recovery, enantiomer preparation, and method optimization.