The replacement of the carboxylic acid functionality with a tetrazolic acid in the proline-catalyzed asymmetric aldol reaction between acetone and trimethylacetaldehyde has been studied using DFT methods at the B3LYP/6-31G** computational level. For the C-C bond-formation step, four reactive channels corresponding to the syn and anti arrangement of the enamine and the re and si attack modes have been analyzed. The B3LYP/6-31G** results allowed us to explain the stereo selectivity and the increase in reactivity relative to the proline-catalyzed process in DMSO. (c) 2005 Elsevier Ltd. All rights reserved.