General and practical catalytic enantioselective Strecker reaction of ketoimines: Significant improvement through catalyst tuning by protic additives

Significant improvement in enantioselectivity and catalyst activity was achieved for the catalytic enantioselective Strecker reaction. Using a catalyst (1-2.5mol%) prepared from Gd(OⁱPr)₃ and D-glucose derived ligand 1, and in the presence of 2,6-dimethylphenol as an additive, high enantioselectivity was obtained from a wide range of ketoimines, including heteroaromatic and cyclic ketoimines. The new method was applied to an efficient catalytic asymmetric synthesis of sorbinil, a therapeutic agent for diabetic complications.