Enantio-differentiation in the asymmetric hydrogenation of α-ketoesters to α-hydroxyesters over platinum catalysts modified with cinchona-alkaloid modifiers occurs through interaction of the ketoester with the cinchona modifier. The properties of the reactant and the structure of the probable transition complex methyl pyruvate (substrate) - cinchonidine (modifier) are calculated using quantum chemistry techniques.

The calculations suggest that protonated cinchonidine interacts with the substrate and that the crucial interaction occurs via hydrogen bonding of the protonated quinuclidine nitrogen and the oxygen of the α-carbonyl moiety of methyl pyruvate. In this complex the methyl pyruvate is stabilized in a half-hydrogenated state which may be the key for the enantio-differentiation.