Human proinsulin VI. Synthesis of protected segment 46-70 of prohormone.

The synthesis of the protected pentacosapeptide Trt-Gly-Gly-Pro-Gly-Ala-Gly-Ser-(But)-Leu-Gln-Pro-Leu-Ala-Leu-Glu( OBut)-Gly-Ser (But)-Leu-Gln-Lys(Boc)-Arg-Gly-Ile-Val-Glu-(OBut)-Gln-OH (Pos. 46-70) of human proinsulin is described. This segment was prepared by the mixed anhydride condensation of the trityl-protected peptides (46-64) or (46-59) with the fragments 65-70 and 60-70, respectively. In both the cases the purification was effected by counter current distribution in a yield of 25% and 24%, respectively.