Regioselectivity Control of Enone Reduction Mediated by Aqueous Baker's Yeast with Addition of Ionic Liquid [bmim(PF6)]

A methodology that controls the reaction regioselectivity of a substrate with two reactive functions using a whole cell biocatalyst in a biphasic water/[(bmim)PF6] medium is described. While the aqueous baker's yeast reduction of ethyl (E/Z)−2-acetyl-3-phenylpropenoate 1a produces ethyl 2-benzyl-3-hydroxybutanoate 3a due to tandem reactions of C˭C and C˭O bond reduction, the bioreduction performed by the same microorganism in a biphasic water/[(bmim)PF6] medium gives ethyl 2-benzyl-3-oxobutanoate 2a by reducing only the C˭C bond. This result is due to substrate and intermediate partitioning between water and hydrophobic IL, thereby decreasing the concentration of the substrate and intermediate species in water as well as the difference in KM values of ene-reductase and ketoreductase operating in the baker's yeast cells. The same methodology was applied to the bioreduction of the analogs of 1a to obtain the corresponding products, where only the C˭C bond was reduced.