反応手順
To a sealable vial containing (1R,3aS,5aR,5bR,7aR,11aR,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 trifluoromethanesulfonate (0.109 g, 0.195 mmol) was added methyl 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)cyclohex-3-enecarboxylate (0.078 g, 0.293 mmol), sodium carbonate hydrate (0.073 g, 0.586 mmol), and tetrakis(triphenylphosphine)palladium(0) (6.77 mg, 5.86 mmol). The mixture was diluted with 1,4-dioxane (2 mL) and water (0.5 mL) then was flushed with nitrogen, sealed and heated to 85° C. in an oil bath. After 20.5 h, the mixture was cooled to rt, diluted with water (10 mL) and extracted with dichloromethane (3×10 mL). The combined organic layers were dried with sodium sulfate. The drying agent was removed by filtration and the filtrate was concentrated under reduced pressure. The residue was adsorbed to silica gel and purified by chromatography using a 12 g Thomson silica gel column and a 10%-80% ethyl acetate in hexanes gradient. The fractions containing the expected product were combined and concentrated under reduced pressure to give methyl 4-((1R,3 aS,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)cyclohex-3-enecarboxylate (0.035 g, 0.064 mmol, 32.7% yield) as an off-white solid. 1H NMR (400 MHz, chloroform-d) δ=5.35 (br. s., 1H), 5.19 (d, J=5.8 Hz, 1H), 4.73 (s, 1H), 4.60 (br. s., 1H), 3.69 (s, 3H), 2.55 (td, J=10.7, 5.1 Hz, 2H), 2.31 (d, J=2.3 Hz, 2H), 2.22-1.94 (m, 6H), 1.70 (s, 3H), 1.07 (s, 3H), 1.79-0.81 (m, 34H).
