The enantioselective hydrogenation of 5,6-dihydro-2H-pyran-3-carboxylic acid over a cinchona alkaloid-modified palladium catalyst:: asymmetric synthesis of a cockroach attractant

A novel application of a cinchona-modified supported Pd catalyst is presented. The key step in the asymmetric synthesis of the cockroach attractant methyl (+)-tetrahydro-2H-pyran-3-carboxylate was the enantioselective hydrogenation of 5,6-dihydro-2H-pyran-3-carboxylic acid over 5% Pd/Al(2)O(3) modified by cinchonidine, which afforded the saturated product in up to 89% optical purity.