Structure-Based Analysis and Optimization of a Highly Enantioselective Catalyst for the Strecker Reaction

A mechanistic investigation of the asymmetric Strecker reaction catalyzed by a metal-free Schiff base catalyst was conducted. The active site of the catalyst, the relevant stereoisomer of the imine substrate, and the solution structure of the imine-catalyst complex were elucidated using a series of kinetics, structure-activity, and NMR experiments. An unusual bridging interaction between the imine and the urea hydrogens of the catalyst was identified and supported by computation. Rational optimization of catalyst structure based on the mechanistic insight led to an improved catalyst for the asymmetric Strecker reaction.