Acetic Anhydride → (3R,5R,8S,10S,13S,14S,Z)-17-Ethylidene-10,13-dimethyl-2,3,4,5,6,7,8,10,12,13,14,15,16,17-tetradecahydro-1H-cyclopenta[A]phenanthren-3-YL acetate

Participants

Reaction Conditions

Reaction Steps

Compound 1.5 (19.0 g, 63 mmol) was dissolved in CH2Cl2 (380 mL). Triethylamine (17.6 mL, 126.6 mmol), DMAP (0.772 g, 6 mmol) and acetic anhydride (8.98 mL, 94 mmol) were added sequentially at 25° C. under a nitrogen atmosphere. The resulting solution was stirred for 2 h at 25° C., at which point the reaction was determined by TLC to be complete. The reaction was quenched by the addition of ice-water (100 mL) and the phases were separated. The aqueous layer was extracted three times with DCM (3×150 mL). The organic fractions were combined and washed with saturated brine solution (100 mL), dried over anhydrous Na2SO4 (50 g), and filtered. The filtrate was concentrated under vacuum to afford compound 1.6a (22.0 g, 95% yield) as an off-white solid.

Provenance & Evidence