Synthesis of protected decapeptide (B21--30) of human insulin.

The synthesis of the C-terminal decapeptide derivative B21--30 of the B-chain of human insulin (benzyloxycarbonyl-gamma-t-butoxyglutamyl-arginyl-glycyl-phenylalanyl-phenylalanyl-O-t-butyltyrosyl-O-t-butylthreonyl-prolyl-Nepsilon-t-butyl-oxycarbonyllysyl-O-t-butylthreonine t-butyl ester, (XIII) by the fragment condensation of the tripeptide B21--23 with the heptapeptide B24--30 is described. Two new routes for both the tripeptide and the heptapeptide were established. A simplified method for the purification of O-t-butylthreonine t-butyl ester was developed.