pH-Dependent Chemoselective Synthesis of α-Amino Acids. Reductive Amination of α-Keto Acids with Ammonia Catalyzed by Acid-Stable Iridium Hydride Complexes in Water

An acid-stable hydride complex [Cp*Ir^III(bpy)H]⁺ {1, Cp* = η⁵-C₅Me₅, bpy = 2,2′-bipyridine} serves as the active catalyst for the highly chemoselective synthesis of α-amino acids by reductive amination of α-keto acids with aqueous NH₃ and HCOO^- in water at pH 5?8. pH-dependent catalytic ¹⁵N- and ²H-double-labeling has also been accomplished by using ¹⁵NH₃ and DCOONa, which are ideal amine and hydride ion sources, respectively.