Steroidal sapogenins bearing a good leaving group at C23 undergo a completely stereospecificrearrangement under a variety of conditions via a mechanism involving neighboring-groupparticipation by the acetal oxygen atom in the departure of the nucleofuge from C23. The reactionsof equatorial (23S)-23-bromo- or (23S)-23-tosyloxyspirostanes with either the α (25R) or β (25S)oriented 25-methyl group lead to the bisfuran products with inversion of configuration at C23. Thereactions of the starting compounds with axial substituents (23R) at C23 require drastic conditionsand result in the formation of the corresponding olefin accompanied by the rearranged product (inthe case of the 25S isomer only).