摘要:
The enantioselectivity of the base-promoted cyclization of N-alkyl-N-chloroacetyl amino acid derivatives to beta-lactams is dependent on the substituents on the starting material. While Bu-t esters are preferred over Me esters, and N-Bzl-, N-Pmb, N-Nph and N-Mom groups gave similar e.e. values, only amino acid derivatives with branched side-chains at the gamma-position were able to show a good memory of chirality. (C) 2003 Elsevier Ltd. All rights reserved.