Enantioselective Pictet-Spengler Reaction of Acyclic α-Ketoesters Using Chiral Imidazoline-Phosphoric Acid Catalysts.

The first enantioselective Pictet-Spengler reaction of acyclic α-ketoesters with tryptamines has been developed. Excellent yields and enantioselectivity were obtained for the reaction using chiral imidazoline-phosphoric acid catalysts. Density functional theory calculations suggested possible transition states that explain the origin of chiral induction. This process provides an efficient route for the synthesis of tetrahydro-β-carboline derivatives.