Investigations into the relationship of oxazaborolidine structure to the enantioselectivity obtained in the reduction of prochiral ketones revealed the intrinsic power of the molecular recognition element in the catalytic reduction. This molecular recognition, two-point binding of borane and the ketonic oxygen atom by the oxazaborotidine, assembles a trimolecular complex which provides high enantiomeric excess. Enantiomeric excess was demonstrated to be dependent on the extent to which one oxazaborolidine face was precluded from attaining two-point binding and on nonbonded interactions that developed during formation of the borane-oxazaborolidine complex. As a result, erythro-substituted oxazaborolidines were demonstrated to be useful catalysts for enantioselective reduction of prochiral ketones. Ab initio molecular orbital calculations have been used to locate possible complexes and transition state assemblies that correspond to catalyst-borane and the trimolecular complex on a proposed reduction pathway. Geometry optimizations were carried out at the 3-21G, 6-31G(d), and MP2/6-31G(d) levels of theory. Correlation energies were computed via Moller-Plesset perturbation theory to the second order (MP2). Relative activation energies establish correctly the observed enantioselectivity of the two best oxazaborolidine catalysts in this study. Additionally, the diminished enantioselectivity of N-methyl-substituted catalysts was traced to conformational changes in the exo transition state. Though the relative energies obtained from the various levels of theory are similar, absolute complexation and activation energies are found to vary considerably with the level of theory employed. The existence of key intermediates was found to depend on the level of theory.