To a sealable flask containing ethyl 4-(((1R,3aS,5aR,5bR,7aR,11aS,11bR,13aR,13bR)-3a-amino-5a,5b,8,8,11a-pentamethyl-1-(prop-1-en-2-yl)-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)methylene)cyclohexanecarboxylate (0.015 g, 0.026 mmol) was added phosphoric acid, potassium salt (0.028 g, 0.130 mmol), potassium iodide (0.013 g, 0.078 mmol) and 4-(2-chloroethyl)thiomorpholine 1,1-dioxide (0.015 g, 0.078 mmol). The mixture was diluted with acetonitrile (1 mL), flushed with nitrogen, sealed, and heated to 100° C. After heating the mixture for 22 h, it was cooled to rt, diluted with water (5 mL), and extracted with dichloromethane (3×5 mL). The organic layers were dried with sodium sulfate, filtered, and concentrated under reduced pressure. The crude product was used in the next step with no additional purification. LCMS: m/e: 737.7 (M+H)1, 2.22 min (method 1).
