Having established the scope of this novel aluminate catalyzed epoxidation reaction, we turned our attention to elucidate the mechanistic underpinnings of this reaction. In particular, we were interested in a comparison of the asymmetric epoxidation reaction enabled by the borate and aluminate complex in order to understand the origin of enantiodivergence induced by changing the Lewis acidic center from boron to aluminum. Accordingly, we modeled key transition states (TS) in the reactions of benzaldehyde 18 and diazoacetamide 1a resulting in the cis-epoxide 24a catalyzed by either the (R)-VANOL borate or the (R)-VANOL aluminate using B3LYP 8 -D3 9 /6-31G(d) 10 as implemented in Gaussian High-level single point energy calculations were performed for all stationary points using M06-2x 12 /6-311++G** PCM 13 (toluene). The Gibbs free energies reported in the manuscript are obtained by adding the free energy correction from the optimizations to the high-level single point energy calculations. The free energies were corrected using Grimme's quasi rigid rotor -harmonic oscillator (qRRHO) approach. This approach is routinely utilized and is well-established to evaluate reactivity and selectivity in similar catalytic systems. Based on prior catalyst structure studies , we assumed that both the aluminum and boron catalysts have incorporated two molecules of the VANOL ligand. We envisioned three viable mechanistic pathways for aldehyde We initiated our DFT study by locating TSCC and TSRC steps for LA, BLA and BA pathways for both the boron and aluminum catalyst systems. Our first goal was to identify the mode of catalysis in these reactions (LA/BLA/BA). The second objective was to identify the rate-and enantioselectivitydetermining step (TSCC or TSRC) within the operative mechanism for each catalyst system. Once we identify the enantioselectivity-determining step, our final goal was to understand the origin of enantioselectivity in each catalyst system and the origin of enantiodivergence observed across the two catalysts.