Table 1.

Calculated transition states, reaction barriers and reaction enthalpies in methanol solution for different conformers of the model inhibitors^a,^b

	thiirane	oxirane
(a)
(b)
(c)
(d)
(e)
(f)

^aIEF-PCM/B3LYP/6-311+G(d,p) energies with optimized geometries and zero point energies obtained with the 6-31+G(d) basis set. The reaction enthalpies are listed in the parenthesis. The color scheme is the same as in Figure 1.

^bUsing the most stable conformer for the reactant complex of the R and S enantiomers of 1 for reactants, and infinitely separated acetic acid and ring opened structures for products.