Enantioselective Syntheses of (-)-(R)-Rolipram, (-)-(R)-Baclofen and Other GABA Analogues via Rhodium-Catalyzed Conjugate Addition of Arylboronic Acids

Highly enantioselective syntheses of two important γ-aminobutyric acid (GABA) analogues, the antispastic drug (-)-(R)-Baclofen and the antidepressant agent (-)-(R)-Rolipram, are reported. Key-steps in both syntheses are the Rh-catalyzed asymmetric 1,4-additions of arylboronic acids to 4-aminobut-2,3-enoic acid derivatives.