Reaction Steps
To a sealable vial containing ethyl 5-(tributylstannyl)isoxazole-3-carboxylate (0.052 g, 0.122 mmol) was added ((1R,3aS,5aR,5bR,7aR,11aR,11bR,13aR,13bR)-5a,5b,8,8,11a-pentamethyl-1-(prop-1-en-2-yl)-9-(trifluoromethylsulfonyloxy)-2,3,3a,4,5,5a,5b,6,7,7a,8,11,11a,11b,12,13,13a,13b-octadecahydro-1H-cyclopenta[a]chrysen-3a-yl)methyl benzoate (0.075 g, 0.111 mmol), lithium chloride (0.014 g, 0.332 mmol), and tetrakis(triphenylphosphine)palladium(0) (6.40 mg, 5.54 μmol). The mixture was diluted with 1,4-Dioxane (2 mL) and was flushed with N2. The vial was sealed and heated to 85° C. After 15.5 h of heating, the mixture was cooled to rt, was diluted with water (4 mL), and was extracted with dichloromethane (3×4 mL). The combined organic layers were dried over Na2SO4. The drying agent was removed by filtration and the filtrate was concentrated under reduced pressure. The residue was purified by Biotage flash chromatography using a 0-10% EtOAc in hexanes gradient. The fractions containing the expected product were combined and concentrated under reduced pressure. Ethyl 5-((1R,3aS,5aR,5bR,7aR,11aS,11bR,13aR,13bR)-3a-(benzoyloxymethyl)-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)isoxazole-3-carboxylate was isolated as an off-white foam (0.015 g total mass, 0.022 mmol, 20.3% yield). LCMS: m/e 668.53 (M+H)+, 3.11 min (method 1).
