Enantioselectivity vs. kinetic resolution in antibody catalysis: Formation of the (S) product despite preferential binding of the (R) intermediate

Antibody 14D9, which catalyzes the stereoselective transformation of achiral enol ethers into the corresponding (S)-ketals, resolves a racemic mixture of structurally similar chiral enol ethers by selective conversion of the (R)-enol ether into the (R)-ketal, raising the possibility that the (S) transition state is preferencially stabilized by the antibody despite a better binding of the (R) intermediate.