Memory of chirality in the stereoselective synthesis of β-lactams: Importance of the starting amino acid derivative

Abstract

The enantioselectivity of the base-promoted cyclization of N-alkyl-N-chloroacetyl amino acid derivatives to β-lactams is dependent on the substituents on the starting material. While tBu 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 γ-position were able to show a good memory of chirality.