Structural Basis for Enantioselectivity in the Transfer Hydrogenation of a Ketone Catalyzed by an Artificial Metalloenzyme

The crystal structure of bovine β-lactoglobulin bound to a complex consisting of a (η5-Cp*)Rh(2,2′-dipyridylamine) head and a lauric acid derived hydrophobic tail has been solved at 1.85 A resolution. Previous work has shown that this hybrid catalyzes the transfer hydrogenation of an aryl ketone in neat water with formate as hydrogen donor with enantiomeric excess (ee) of about 26 %. Calculations using the X-ray model indicate that the complex head can adopt discrete conformations, which may explain the ee observed.