Conformational free energy differences in steroids. Part III. Equilibration of 3α-hydroxy-, 3α-methoxy-, and 3α-acetoxy-5β-cholestan-6-ones with their 5α-isomers

Abstract

The equilibria mentioned in the title are influenced by electrostatic interactions between the 3α-substituents and the C-6 keto-group, calculated values for which are in accord with the observed effects. Restricted rotation in the axial hydroxy- and methoxy-groups is important in determining the magnitude of the interactions. The significance of the insensitivity of the 3α-methoxy-5α- and -5β-cholestan-6-one equilibrium to changing solvents is discussed. Equilibrium constants were determined by an optical rotatory dispersion technique.