Enantioselective Catalytic Synthesis of α‑Halogenated α‑Aryl‑β^2,2-amino Acid Derivatives

The enantioselective synthesis of a broad variety of novel differently functionalized α-halogenated α-aryl-β2,2-amino acid derivatives by means of an ammonium-salt-catalyzed asymmetric α-halogenation of isoxazolidin-5-ones was accomplished. Key to success to obtain high levels of enantioselectivities was the use of Maruoka’s spirocyclic binaphthyl-based ammonium salts, and detailed accompanying mechanistic studies using density functional theory methods revealed the key features for the catalyst–substrate interactions.