Iridium-Catalyzed Asymmetric Hydrogenation of γ- and δ-Ketoacids for Enantioselective Synthesis of γ- and δ-Lactones.

A highly efficient asymmetric hydrogenation of γ- and δ-ketoacids was developed by using a chiral spiro iridium catalyst (S)-1a, affording the optically active γ- and δ-hydroxy acids/lactones in high yields with excellent enantioselectivities (up to >99% ee) and turnover numbers (TON up to 100000). This protocol provides an efficient and practical method for enantioselective synthesis of Ezetimibe.