Abstract
The use of the dimethylphosphinothioyl(Mpt) group for the protection of the hydroxyl function in the tyrosine side-chain was studied. N,O-Bis(Mpt)tyrosine was obtained directly by a Schotten-Baumann-type reaction of Mpt–Cl with tyrosine. The O-Mpt group was stable under acidic conditions, and it could be removed easily by alkaline hydrolysis or ester-exchange reaction. The usefulness of this new protecting group for the peptide synthesis was shown in the solid-phase synthesis of [d-Ala2, l-Leu5]-enkephalin(H–l-Tyr–d-Ala–Gly–l-Phe–l-Leu–OH) and its N-allyl derivative.