반응 단계
To a 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 (0.418 g, 0.749 mmol) was added methyl 6-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)spiro[3.3]hept-5-ene-2-carboxylate (0.250 g, 0.899 mmol), sodium carbonate monohydrate (0.232 g, 1.874 mmol) and tetrakis(triphenylphosphine)palladium(0) (0.026 g, 0.022 mmol). The mixture was diluted with 1,4-dioxane (4 mL) and water (1 mL), then was flushed with nitrogen and the vial was sealed and heated to 85° C. After 5.5 h of heating, the mixture was cooled to rt, concentrated under reduced pressure, adsorbed to silica gel, and purified by chromatography using a 0-45% ethyl acetate in hexanes gradient and a 40 g Thomson silica gel column. The fractions containing the expected product were combined and concentrated under reduced pressure to give methyl 6-((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)spiro[3.3]hept-5-ene-2-carboxylate (0.31 g, 0.554 mmol, 73.9% yield) as an off-white solid. 1H NMR showed a mixture of the two diastereomers (0.8:1 ratio) which were not separated and were used in the next step with no additional purification. LCMS: m/e 560.47 (M+H)+, 2.46 min (method 2). Mixture of diastereomers: 1H NMR (500 MHz, chloroform-d) δ=6.00 (s, 0.45H, minor diastereomer), 5.84 (s, 0.55H, major diastereomer), 5.54 (td, J=6.1, 2.2 Hz, 1H), 4.75 (d, J=2.0 Hz, 1H), 4.62 (dd, J=2.3, 1.3 Hz, 1H), 3.71 (m, 3H), 3.13-2.99 (m, 1H), 2.70-2.31 (m, 7H), 2.18-1.84 (m, 4H), 1.72 (s, 3H), 1.18 (d, J=3.5 Hz, 3H), 1.10-1.08 (m, 6H), 0.99 (s, 3H), 0.85 (s, 3H), 1.68-0.83 (m, 19H).
