STEREOCHEMICAL STUDIES: IV. ACID-CATALYZED EQUILIBRATION OF α- AND β-FORMS OF 3-ALKOXY-4-OXA-5α-CHOLESTANES. THE ANOMERIC EFFECT

Abstract

The α- and β-anomers of 3-methoxy-, 3-isopropoxy-, 3-cyclohexyloxy-, and 3-phenoxy-4-oxa-5α-cholestane were separated by chromatography on alumina. The configurations of the anomers were assigned from a consideration of their optical rotations. Acid-catalyzed equilibration of the 3-alkoxy anomers favored formation of the axial isomer, the proportions of α- to β-forms being about 7:3. 2α-Phenoxy-4-oxa-5α-cholestane in acid solution was in equilibrium with phenol and 4-oxa-5α-cholest-2-ene.