Efficient solution-phase synthesis of multiple O-phosphoseryl-containing peptides related to casein and statherin.

The multiple Ser(P)-containing peptides, H-Ser(P)-Ser(P)-Ser(P)-Glu-Glu-NHMe.TFA, H-Asp-Ser(P)-Ser(P)-Glu-Glu-NHMe.TFA and H-Glu-Ser(P)-Ser(P)-Glu-Glu-NHMe.TFA were prepared by the use of Boc-Ser(PO3Ph2)-OH in the Boc mode of solution phase peptide synthesis followed by platinum-mediated hydrogenolytic de-protection of the Ser(PO3Ph2)-containing peptides. The protected peptides were assembled using the mixed anhydride coupling methods with 40% TFA/CH2Cl2 used for removal of the Boc group from intermediate Boc-protected peptides.