Thermal Synthesis of Polypeptides from N-t-Butyloxycarbonyltripeptide Derivatives without Reactive Side Chains

The thermal reactions of N-t-butyloxycarbonyl-aspartic acid (Boc-Asp-OH) and some N-t-butyloxycarbonyl derivatives of peptides in which the C-terminal is an aspartic residue as a reactive residue in Boc-Gly-Gly-L-Asp-OH are known. The two carboxy groups at C- zerminal are believed to form an anhydride or give peptide bonds directly. This research reports the thermal reactions of N-Boc-tripeptide derivatives such as Boc-Pro-Pro-Gly-OH, Boc-Pro-Pro-Gly-NH2, Boc-Pro-Pro-Gly-OCH3 and Boc-Ala- Ala-Ala-OH with a carboxy group at C-terminal. Thermal reactions were carried out at a constant temperature near their melting points for 1 to 24 h to afford polypeptides whose average molecular weight reached 2,500 Da.