Total synthesis of bovine pancreatic ribonuclease A. Part 2. Synthesis of the protected hexatriacontapeptide ester (positions 89–124)

Abstract

Commencing with the protected C-terminal pentadecapeptide of bovine pancreatic RNase,Z(OMe)-(RNase 110–124)-OBzl, chain elongation was accomplished to form the hexatriacontapeptide, Z(OMe)-(RNase 89–124)-OBzl, by six successive azide condensations of the peptide fragments, Z(OMe)-Val-Ala-NHNH₂(4), Z(OMe)-Ile-Ile-NHNH₂(5), Z(OMe)-Asn-Lys(Z)-His-NHNH₂(6), Z(OMe)-Lys(Z)-Thr-Thr-Gln-Ala-NHNH₂(7), Z(OMe)-Tyr-Pro-Asn-Cys(MBzl)-Ala-Tyr-NHNH₂(8), and Z(OMe)-Ser-Ser-Lys(Z)-NHNH₂(9).