SYNTHESIS OF AN OPEN-CHAIN ASYMMETRICAL CYSTINE PEPTIDE CORRESPONDING TO THE SEQUENCE A18-21 -B19-26 OF BOVINE INSULIN BY SOLID PHASE FRAGMENT CONDENSATION

Abstract

An insulin fragment containing residues A18-21 and B19-26 linked by the disulfide bond between residues A20 and B19 was synthesized. The sequence B21-26 was assembled on a solid support by the Merrifield technique. The protected fragments A18-21 and B19-20 were prepared by conventional methods. After forming the disulfide bridge through cleavage of the S-thiocarbonate derivative of A18-21 by the thiol peptide B19-20, the resulting asymmetrical cystine peptide A18-21-B19-20 was coupled via the carboxyl group of residue B20 to the free NH2-terminal amino group of the protected B21-26 resin. The product was deprotected, cleaved from the resin and purified to give the homogeneous dodecapeptide A18-21-B19-26.