Facile synthesis of cyclic tetrapeptides from nonactivated peptide esters on metal centers

Abstract

The cyclization of dipeptide esters of α-, β-, γ, and δ-amino acids can be achieved by using Ni(II), Pd(II), or Cu(II) templates. The structure of one of the complexes (1) obtained, which was determined by X-ray crystallography, reveals that the anions form layers and are linked to water molecules by hydrogen bonds.