The use of a solvent with larger dielectric constant results in higher enantioselectivity in the hydrogenation of (E)-alpha-phenylcinnamic acid with a cinchonidine-modified Pd catalyst. The reaction in N,N-dimethylformamide containing 10vol% of water with a 5wt% Pd/TiO2 catalyst leads to an optical yield of 53% of S-(+)-2,3-diphenylpropionic acid.