Citric Acid → Smilagenin

Participants

Reaction Steps

Smilagenone (657 g) was dissolved in tetrahydrofuran (4000 ml) and the solution purged with nitrogen and cooled to provide an internal temperature of ca. −10° C. L-Selectride® (2400 ml 1M in THF) was added over ca. 50 minutes and stirred for 90 minutes. A solution of citric acid (600 g) in water (2000 ml) was added slowly, maintaining the temperature below 0° C. The mixture was allowed to warm to ambient temperature and stirred for 30 minutes. The aqueous layer was separated and extracted with dichloromethane (2000 ml) and the layers separated. The aqueous layer was extracted with dichloromethane (1500 ml). The combined organic extracts were washed with water (4000 ml) and dried over MgSO4. The organic extracts were evaporated to dryness to yield smilagenin.

Provenance & Evidence