Purified BF3-etherate reacts with 3β-acetoxy-5, 6α-epoxy-5α-cholestane (I) at high concentrations in benzene to give the unsymmetrical di-steroidal ether (IIa). The formation of the ether (IIa) involves a novel “backbone rearrangement” of one of the steroidal skeletons, giving the 5β, 14β-dimethyl 18, 19-bisnor structure with all ring junction configurations inverted. 3, 3-Ethylene dioxy-5, 6β-epoxy-5β-cholestane reacts with BF3-etherate to give ...
