Smilagenone → Smilagenin

Participants

Reaction Steps

L-Selectride® (527 ml; 1M in tetrahydrofuran) was added to a solution of smilagenone (156 g) in tetrahydrofuran (obtained by hydrogenation of diosgenone) at ca. −10° C. under an atmosphere of nitrogen. The reaction mixture was stirred at this temperature for 30 minutes, allowed to warm to ambient temperature and stirred overnight. The mixture was quenched by addition to a mixture of aqueous citric acid (311 g in 3800 ml water) and dichloromethane (2200 ml), maintaining the internal temperature below 30° C. The aqueous phase was separated and re-extracted with dichloromethane (400 ml). The combined organic extracts were washed with aqueous citric acid (160 g in 2200 ml water) and distilled to low volume. 2-Propanol (3000 ml) was added and the mixture redistilled to ca. ½ volume. Additional 2-propanol (1500 ml) was added and the mixture distilled to ca. ½ volume. The mixture was heated to reflux and allowed to cool. The mixture was further cooled to 0-10° C. and filtered. The solid was dried in a vacuum oven at 60-65° C. to afford smilagenin. The yield is 94.0 g.

Provenance & Evidence