Betulin → (+)-Betulonic acid

Participants

Reaction Conditions

Reaction Steps

To a solution of betulin (1, 1.0 g, 2.26 mmol) in acetone (50 mL), cooled to 0° C., freshly prepared Jones' reagent was added dropwise. The resulting mixture was stirred for about 1.5 hours at 0° C., quenched with methanol (25 mL), stirred for an additional 5 minutes, then water (40 mL) was added. The acetone was removed under vacuum and the aqueous residue was extracted two times with 40 mL of ethyl acetate (EtOAc). The ethyl acetate layer was separated from the aqueous layer, then the ethyl acetate layer was washed first with water (20 mL) and then with brine (15 mL). The ethyl acetate layer was dried over magnesium sulfate (MgSO4), then filtered, and finally the ethyl acetate was removed under vacuum. The residue was column chromatographed over silica gel (60-200 mesh) using petroleum ether/EtOAc (4:1 volume ratio) to yield 770 mg of betulonic acid, having a melting point (mp) of 247°-249° C. (literature mp 246°-2470° C.). The reaction provided a 75% yield of betulonic acid.

Provenance & Evidence