| abstract |
A peptide having the formula A-B wherein A represents an N-terminal protected amino acid residue or an optionally N-terminal protected peptide residue and B represents an optionally C-terminal protected amino acid residue, is prepared by reacting a substrate component selected from the group consisting of (a) amino acid esters, peptide esters and depsipeptides of the formula A-OR1 or A-SR1 wherein A is as defined above and R1 represents alkyl, aryl, aralkyl or an alpha -des-amino fragment of an amino acid residue, (b) optionally N-substituted amino acid amides and peptide amides of the formula A-NHR2 wherein A is as defined above and R2 represents hydrogen, alkyl, aryl or aralkyl, and (c) optionally N-terminal protected peptides of the formula A-X wherein A is as defined above and X represents an amino acid with an amine component selected from the group consisting of (a) amino acids of the formula H-B-OH, (b) optionally N-substituted amino acid amides of the formula H-B-NHR3 wherein B is an amino acid residue and R3 represents hydrogen, hydroxy, amino or alkyl, aryl or aralkyl, and (c) amino acid esters of the formula H-B-OR4 or H-B-SR4 wherein B is an amino acid residue and R4 represents alkyl, aryl and aralkyl, in the presence of a carboxypeptidase enzyme in an aqueous solution or dispersion having a pH from 5 to 10.5, preferably at a temperature of from 20 DEG to 50 DEG C., to form a peptide, and subsequently cleaving a group R3 or R4 or an N-terminal protective group, if desired. |