STEREOSELECTIVE SYNTHESIS OF (S)-MPPG, (S)-MTPG AND (S)-(-ALPHA-M4CPGFROM (R)-4-HYDROXYPHENYLGLYCINE())

(R)-4-Hydroxyphenylglycine was protected with a benzyl group and a met hyl group was introduced at the a position by using the self-regenerat ion-of-stereocentre method. After the 4-hydroxy group had been convert ed into the corresponding trifluoromethanesulfonate (triflate), three palladium-catalyzed reactions were employed to furnish (S)-alpha-methy l-4-phosphonophenylglycine [(S)-MPPG], (S)-alpha-methyl-4-(tetrazol-5- yl)phenylglycine [(S)-MTPG] and (S)-4-carboxyphenyl-alpha-methylglycin e [(S)-alpha M4CPG], a class of new and selective antagonists of metab otropic glutamate receptors.