The asymmetric hydrogenation of trans-2-methyl-2-pentenoic acid in hexane over two well defined E-40692 and E-5220 Engelhard Pd/Al2O3 catalysts modified with cinchonidine was re-examined, the literature results have been reproduced and it was found that the E-40692 catalyst lead to the best conversions and %e.e. Deuteration experiments have been conducted under identical (solvent, catalyst, constituents ratios and temperature) conditions: percentage of H/D exchange (in the starting substrate and in the saturated product) as well as percentage of deuteration at all carbons have been determined by H-1 NMR and indicated that double bond migration and cis/trans isomerization occurred during hydrogenation/deuteration but that these processes contributed less at higher pressure (40 bar) and in the presence of cinchonidine. (C) 2002 Elsevier Science B.V. All rights reserved.