Oxirane ring conformational energy

Theoretical studies have indicated that the oxiranes display similar properties to compounds containing a double bond. For instance, the conformational energy of the A ring of 2,3-epoxylanostane is analogous to that of cyclohexene... 

Another way to maximize P is to limit the degree of free rotation at the chiral center and increase the energy difference between the two major conformations of the dipole at the chiral center. This can be achieved by incorporating the chiral center in a cyclic system such as in an oxirane [27, 82, 83]. The molecular dipole associated with an epoxide moiety is oriented normal to the tilt plane. The rigidity of the epoxide ring minimizes the conformational averaging out of the dipole moment and should lead to a high value for the P. Oxiranes are prepared by Sharpless epoxidation of allyl alcohols,... 

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