The enantioselective hydrogenation of alpha, beta-unsaturated acids catalyzed by cinchonidine-modified Pd/C was found to be highly dependent on the pretreatment temperature of the catalyst. An asymmetric yield as high as 92% was achieved in the hydrogenation of (E)-2,3-di(4-methoxyphenyl)propenoic acid using a conventional 5%Pd/C catalyst activated in situ at elevated temperatures before modification with cinchonidine. (c) 2005 Elsevier Inc. All rights reserved.