Fmoc/solid-phase synthesis of Tyr(P)-containing peptides through t-butyl phosphate protection

The synthesis of Tyr(P)-containing peptides by the use of Fmoc-Tyr(PO3Me2)-OH in Fmoc/solid phase synthesis is complicated since, firstly, piperidine causes cleavage of the methyl group from the -Tyr(PO3Me2)-residue during peptide synthesis and, secondly, harsh conditions are needed for its final cleavage. A very simple method for the synthesis of Tyr(P)-containing peptides using t-butyl phosphate protection is described. The protected phosphotyrosine derivative, Fmoc-Tyr(PO3tBu2)-OH was prepared in high yield from Fmoc-Tyr-OH by a one-step procedure which employed di-t-butyl N,N-diethyl-phosphoramidite as the phosphorylation reagent. The use of this derivative in Fmoc/solid phase peptide synthesis is demonstrated by the preparation of the Tyr(P)-containing peptides, Ala-Glu-Tyr(P)-Ser-Ala and Ser-Ser-Ser-Tyr(P)-Tyr(P).