Reaction Steps
A suspension of (1R,3aS,5aR,5bR,7aR,11aR,11bR,13aR,13bR)-benzyl 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]chrysene-3a-carboxylate (4.0 g, 5.91 mmol), 3-fluoro-4-(methoxycarbonyl)phenylboronic acid (1.287 g, 6.50 mmol), sodium carbonate monohydrate (2.198 g, 17.73 mmol), and Pd(PPh3)4 (0.205 g, 0.177 mmol) in 1,4-dioxane (24 mL) and water (6 mL) was flushed with N2 and the mixture was heated to reflux. After 2 h of heating, the mixture was cooled to rt. The mixture was diluted with water (40 mL) and was extracted with dichloromethane (3×40 mL). The combined organic layers were dried with Na2SO4. The drying agent was removed by filtration and the filtrate was concentrated under reduced pressure. The residue was dissolved in DCM and was filtered through a pad of celite and silica gel, washing with a 25% EtOAc in hexanes solution. The filtrate was concentrated under reduced pressure to give the title compound (3.59 g, 5.27 mmol, 89% yield) as a dark grey foam. The crude product was used in the next step with no additional purification. 1H NMR (500 MHz, CHLOROFORM-d) δ ppm 7.80 (1H, t, J=7.8 Hz), 7.29-7.42 (5H, m), 6.96 (1H, d, J=7.9 Hz), 6.91 (1H, d, J=11.9 Hz), 5.28-5.33 (1H, m), 5.16 (1H, d, J=12.5 Hz), 5.09 (1H, d, J=12.2 Hz), 4.73 (1H, s), 4.59 (1H, br. s.), 3.92 (3H, s), 3.03 (1H, td, J=10.8, 4.7 Hz), 2.20-2.33 (2H, m), 2.09 (1H, dd, J=17.1, 6.4 Hz), 1.81-1.97 (2H, m), 1.68 (3H, s), 0.96 (3H, s), 0.92 (3H, s), 0.92 (3H, s), 0.91 (3H, s), 0.81 (3H, s), 0.79-1.75 (17H, m).
