Reaction Steps
To a solution of methyl 4-((1R,3aS,5aR,5bR,7aR,11aS,11bR,13aR,13bR)-3a-(((1,1-dioxido-4-thiomorpholinyl)acetyl)amino)-1-isopropenyl-5a,5b,8,8,11a-pentamethyl-2,3,3a,4,5,5a,5b,6,7,7a,8,11,11a,11b,12,13,13a,13b-octadecahydro-1H-cyclopenta[a]chrysen-9-yl)benzoate (0.05 g, 0.071 mmol) in dichloroethane (1 mL) and Hunig's base (0.062 mL, 0.355 mmol) was added acetyl chloride (0.020 mL, 0.284 mmol). The mixture was heated to 50° C. After heating the mixture for 71.25 h, the mixture was cooled to rt and was directly loaded onto a 12 g Thomson silica gel column and was purified by Biotage flash chromatography using a 0-5% MeOH in dichloromethane gradient. The fractions containing the expected product were combined and were concentrated under reduced pressure to give methyl 4-((1R,3aS,5aR,5bR,7aR,11aS,11bR,13aR,13bR)-3a-(acetyl(2-(1,1-dioxido-4-thiomorpholinyl)ethyl)amino)-1-isopropenyl-5a,5b,8,8,11a-pentamethyl-2,3,3a,4,5,5a,5b,6,7,7a,8,11,11a,11b,12,13,13a,13b-octadecahydro-1H-cyclopenta[a]chrysen-9-yl)benzoate (40 mg, 0.054 mmol, 75%) as a clear, colorless film. LCMS: m/e 747.5 (M+H)+, 2.26 min (method 2).
