A method to stereospecifically prepare a steroidal sapogenin or a derivative thereof by reducing a 3-keto,5β-H steroidal sapogenin with a hindered organoborane or an organo-aluminium hydride. A 3β-hydroxy,5β-H steroidal sapogenin or derivative thereof may be prepared by reducing the 3-keto,5β-H steroidal sapogenin using as reducing agent a relatively highly hindered organoborane reagent or by SN 2 inversion of a 3α-hydroxy,5β-H steroidal sapogenin or derivative thereof. The organo-aluminium hydride may be used to prepare a 3α,5β-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).
一种立体选择性制备类
固醇皂苷或其衍
生物的方法,通过使用有阻碍的有机
硼烷或
有机铝氢化物还原3-酮,5β-H类
固醇皂苷。使用相对高度受阻的有机
硼烷试剂还原3-酮,5β-H类
固醇皂苷或通过SN 2 反转3α-羟基,5β-H类
固醇皂苷或其衍
生物可制备3β-羟基,5β-H类
固醇皂苷或其衍
生物。
有机铝氢化物可用于制备3α,5β-H类
固醇皂苷或其衍
生物。该发明提供了一种方便的途径,从易得到的或易于制备的起始材料(例如从蕃薯草甙制备的蕃薯草酮)中制备有用的类
固醇皂苷,例如薯蕉
皂苷、薯蕉
皂苷E、野菜
皂苷、野菜
皂苷E及其
酯类。