Studies of Unusual Amino Acids and Their Peptides. XIII. The Chemistry of N-(Carboxy methyl) amino Acids. II. The Synthesis of Peptides Containing N-(Carboxymethyl) amino Acids

Abstract

Abstract The basic problems in the synthesis of peptides with N-carboxymethyl(Cm-)amino acids were investigated. Several kinds of N-protected derivatives of a free Cm-amino acid and the N-benzyloxycarbonyl (Z) derivative of its monoester were obtained by the conventional methods used for the parent amino acid. The peptide-bond formation at either carboxyl group of a Cm-amino acid proved to be achievable by the usual methods, such as the carbodiimide, dicyclohexylcarbodiimide–1-hydroxybenzotriazole, or mixed anhydride method, as illustrated by the examples using the Z–Cm-amino acid derivatives as the carboxyl components. On the other hand, a peptide using a Cm-amino acid diester as the amino component could not be prepared by the usual methods mentioned above. The desired compound was eventually obtained by the acid chloride method. A peptide containing a Cm-amino acid with the free imino group was also prepared by the condensation of a bromoacetylated amino acid ester with an amino acid or peptide ester.