To test this hypothesis, the relative energy differences between the two half-chairs possible of chelates 23 and 24 were -216.2 kcal mol -1 ΔG Binding = calculated using the same functional and basis set (Table ). Differences in free energies of 23 and 24 were then correlated to observed diastereomeric ratios of products (Figure ). All observed diastereomeric ratios correlated well with the magnitude of computed ΔG(23:24) with the exception of tertbutyl (Table , entries 4). Conformer 24e bearing pseudoaxial R 1 =t-Bu was the computed lowest energy chelate-conformer for the tert-butyl substituted chelate. However, on this conformer, Fürst-Plattner attack would result in the build-up of significant 1,3 diaxial strain analogous to the one depicted in conformer 15b (Figure ). So, while 24e is a competitive conformer to 23e, 23e is more reactive and leads to the anti product. This would be consistent with transition state energies reflecting the ultimate product ratios described by Curtin-Hammett principles for bulkier substituents like tertbutyl. On the other hand, diastereomeric ratios observed with smaller substituents on the chelate depend more closely on the energy differences between their chelate conformers.