STEREOSPECIFIC REDUCTION OF SAPOGEN-3-ONES

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 high ly 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 t o useful steroidal sapogenins such as sarsasapogenin, episarsasapogenin, smilagenin, epismilagenin and esters thereof, from readily available or easi ly preparable starting materials (e.g. diosgenone, preparable from diosgenin).< /SDOAB>