Asymmetric Synthesis of Functionalized Phenylalanine Derivatives via Rh-Catalyzed Conjugate Addition and Enantioselective Protonation Cascade.

The asymmetric conjugate addition of arylboronic acids to -phthalimidodehydroalanine catalyzed by Rh(I)/ enables the facile preparation of chiral functionalized phenylalanines. The reaction proceeds by a conjugate addition and enantioselective protonation cascade, affording a rhodium enolate that undergoes -face protonation. The reaction tolerates various arylboronic acids and can be used in the gram-scale synthesis of ()-phenylalanine hydrochloride, demonstrating the reaction scope and the synthetic feasibility of the process.