Stereoselective synthesis of (S)-MPPG, (S)-MTPG and (S)-(+)-αM4CPG from (R)-4-hydroxyphenylglycine

Abstract

(R)-4-Hydroxyphenylglycine was protected with a benzyl group and a methyl group was introduced at the α position by using the self-regeneration-of-stereocentre method. After the 4-hydroxy group had been converted into the corresponding trifluoromethanesulfonate (triflate), three palladium-catalyzed reactions were employed to furnish (S)-α-methyl-4-phosphonophenylglycine [(S)-MPPG], (S)-α-methyl-4-(tetrazol-5-yl)phenylglycine [(S)-MTPG] and (S)-4-carboxyphenyl-α-methylglycine [(S)-αM4CPG], a class of new and selective antagonists of metabotropic glutamate receptors.