Stereochemistry of the reductive amination of 4-oxoproline derivatives with glycine esters

Abstract

An amination of 4-oxoproline derivatives with glycine methyl or benzyl ester and sodium cyanoborohydride led to the mixtures of corresponding diastereomeric 4-cis- and 4-trans-glycinoproline derivatives. We found that the ratio of diastereomers mainly depends on the structure of 4-oxoproline ester groups and, to a lesser extent, on the structure of N-acyl substituents. The best results were achieved with tert-butyl ester group; it ensured good yields of the amination products and the greatest prevalence of 4-cis-isomers. The structure of ester group in glycine molecule only scarcely affected the resulting ratio of N-(N-benzyloxycarbonylglycyl)-4-glycinoprolines. The English version of the paper: Russian Journal of Bioorganic Chemistry, 2002, vol. 28, no. 6; see also http://www.maik.ru.