Acid-catalysed backbone rearrangement involving the C-D ring junction in normal steroid series

Protic and Lewis acids cause partial backbone rearrangement involving the C-D ring junction in the normal steroid series with ring contraction and formation of 12,14α-cyclo-12,13-seco-5α-cholest-13(17)-ene compounds. 12-Methylene rather than 13-methyl rearrangement is suggested and a revision of a previously proposed structure is given.