AbstractThe syntheses of derivatives of the L‐L tetrapeptides Gly‐Asp‐Ser‐Gly and Gly‐Glu‐Ser‐Gly have been described in preceding communications H. Kienhuis, A. van de Linde, J. P. J. van der Holst and A. Verweij, Rec. Trav. Chim. 80, 1278 (1961). A. van de Linde, H. Kienhuis, A. Verweij and J. P. J. van der Holst, ibid. 80,1305 (1961). H. Kienhuis, J. P. J. van der Holst and A. Verweij, ibid. 83, 1129 (1964). . These compounds were used as models for esterases. In order to study the effects of configuration and conformation in our model reactions, we synthesised the diastereoisomeric peptide derivatives containing D‐serine instead of L‐serine. In Fig. 1 the difference of the relative positions of the side chains of aspartic acid and serine is demonstrated for the stretched forms of the L‐L and L‐D peptides.