STEREOSPECIFIC SYNTHESIS OF (R)-BACLOFEN AND (S)-BACLOFEN AND (R)-PCPGABA AND (S)-PCPGABA [4-AMINO-2-(4-CHLOROPHENYL)BUTYRIC ACID] VIA (R)-3-(4-CHLOROPHENYL)PYRROLIDINES AND (S)-3-(4-CHLOROPHENYL)PYRROLIDINES

(R)- and (S)-Baclofen and (R)- and (S)-PCPGABA [4-amino-2-(4-chlorophenyl)butyric acid] were stereospecifically synthesized via (R)- and (S)-3-(4-chlorophenyl)pyrrolidines, starting from trans-4-hydroxy-L-proline. The syntheses involve two key operations, namely, 1) a stereoselective hydrogenation of dehydroproline derivatives controlled by the C-2 carboxyl function and 2) an effective ruthenium tetroxide oxidation to prepare chiral 3- and 4-(4-chlorophenyl)pyrrolidio-2-ones, which are dehydrated precursors of the target molecules.