Practical resolution of an atropoisomeric α,α-disubstituted glycine with l-phenylalanine cyclohexylamide as chiral auxiliary
摘要:
L-Phenylalanine cyclohexylamide has been used as a chiral auxiliary for the medium-scale resolution of 2',1':1,2;1 ",2 ":3,4-dinaphthcyciohepta- 1,3-diene-6-amino-6-carboxylic acid (Bin), an alpha,alpha-disubstituted glycine with only axial dissymmetry. Coupling of X-Bin-OH (X=Ac; Bz) with H-(L)-Phe-NH-C6H11 by the EDC/HOBt method gave the dipeptide diastereoisomers X-(R)-Bin-(L)-Phe-NH-C6H11 and X-(S)-Bin-(L)-Phe-NH-C6H11, which were separated by crystallization (X=Bz) and/or chromatography. Extensive acidic hydrolysis, followed by esterification of the resulting free amino acid enantiomers, led to enantiomerically pure (-)-(R)-H-Bin-OMe and (+)-(S)-H-Bin-OMe with high yields. (C) 1998 Elsevier Science Ltd. All rights reserved.