Total synthesis of bovine pancreatic ribonuclease A. Part 5. Synthesis of the protected S-protein (positions 21–124) and the protected S-peptide (positions 1–20)

Abstract

Starting from the protected tetraoctacontapeptide corresponding to the sequence Z(OMe)-(41–124)-OBzl of bovine pancreatic RNase, the protected S-protein Z(OMe)-(RNase 21–124)-OBzl was synthesized by six successive azide condensations of the peptide fragments Z(OMe)-Asp(OBzl)-Arg(MBS)-Cys(MBzl)-NHNH-Troc (23), Z(OMe)-Arg(MBS)-Asn-Leu-Thr-Lys(Z)-NHNH₂(24), Z(OMe)-Met(O)-Lys(Z)-Ser-NHNH₂(25), Z(OMe)-Asn-Gln-Met(O)-NHNH₂(26), Z(OMe)-Asn-Tyr-Cys(MBzl)-NHNH₂(27), and Z(OMe)-Ser-Ser-Ser-NHNH₂(28). In addition, the S-peptide was synthesized in a protected form, Z-Lys(Z)-Glu(OBu^t)-Thr-Ala-Ala-Ala-Lys(Z)-Phe-Glu(OBzl)-Arg(MBS)-Gln-His-Met(O)-Asp-Ser-Ser-Thr-Ser-Ala-Ala-NHNH₂, by assembling three sub-units: (A)(14–20), (B)(9–13), and (C)(1–8).