Amino acids and peptides. XVIII. Dipeptide formation during the synthesis of Z‐Asp(OBzl)‐OH

Abstract

During the benzyloxycarbonylation of H‐Asp(OBzl)‐OH by the Schotten‐Bauman reaction with benzyloxycarbonyl chloride in the presence of NaHCO3 or Na2CO3, besides Z‐Asp(OBzl)‐OH, Z‐Asp(OBzl)‐Asp(OBzl)‐OH was formed as side product, although the extent of the dipeptide formation differed depending on the base used (10% and 20% respectively). It was found that melting point, rotation value and Rf values upon thin‐layer chromatography of Z‐Asp(OBzl)‐Asp(OBzl)‐OH were quite similar to those of Z‐Asp(OBzl)‐OH.