A new procedure for the preparation of poly(alpha-alkyl beta,L-aspartate)s based on the transesterification of polya-benzyl beta,L-aspartate) with alcohols in the presence of titanium tetrabutoxide is described. The reaction proceeded to almost total conversion without substantial racemization or imidation. Thermal properties of the resulting polymers were comparable to those of their homologues obtained by anionic ring-opening polymerization of beta-lactams and their thermal stability is even higher.