Synthesis of Casein-Related Peptides and Phosphopeptides. XVI. The Efficient Synthesis of the Casein-Related O-Phosphoseryl-Containing Peptide Ac-Glu-Ser(P)-Leu-Ser(P)-Ser(P)-Ser(P)-Glu-Glu-NHMe

Abstract

The multiple-O-phosphoseryl-containing peptide, Ac-Glu-Ser (P)-Leu-Ser (P)-Ser (P)-Ser (P)-Glu-Glu-NHMe, was prepared in high yield by the use of Boc-Ser(PO3Ph2)-OH in the Boc mode of peptide synthesis for the preparation of the protected Ser(PO3Ph2)-octapeptide followed by its one-step hydrogenolytic deprotection with platinum oxide. Peptide synthesis was performed by the repetitive excess mixed-anhydride coupling procedure and 40% CF3CO2H/CH2Cl2 for removal of the Boc group from intermediate peptides. The phosphopeptide was found to be greater than 99% pure by C8 r.p.-h.p.1.c. analysis, and was readily characterized by amino acid analysis, 13C n.m.r. spectroscopy and f.a.b. mass spectrometry.