6β-Bromo-4, 4-dimethyl-lα, 2α-epoxy-3α, 5α-oxidocholestane (1) was derived from 4, 4-dimethyl-lα, 2α-epoxy-5-cholesten-3α-ol (6). The A/B ring of the bromo-epoxy-oxide (1) was found to be transformed into a 5/7 membered ring (3a) on acidic treatment. From the product (3a), the 2α, 5β-dihydroxy-3α, 6α-oxide (16) and the 3α, 5β-dihydroxy-2α, 6α-oxide (20) were synthesized. The mechanisms of the transformation were discussed.
