A method to stereospecifically prepare a steroidal sapogenin or a
derivative thereof by reducing a 3-keto,5.beta.-H steroidal sapogenin
with a hindered organoborane or an organo-aluminium hydride. A
3.beta.-hydroxy,5.beta.-H steroidal sapogenin or derivative thereof may
be prepared by reducing the 3-keto,5.beta.-H steroidal sapogenin using as
reducing agent a relatively highly hindered organoborane reagent or by SN
2 inversion of a 3.alpha.-hydroxy,5.beta.-H steroidal sapogenin or
derivative thereof. The organo-aluminium hydride may be used to prepare a
3.alpha.,5.beta.-H steroidal sapogenin or derivative thereof. The
invention provides a convenient route to useful steroidal sapogenins such
as sarsasapogenin, episarsasapogenin, smilagenin, epismilagenin and
esters thereof, from readily available or easily preparable starting
materials (e.g. diosgenone, preparable from diosgenin).