Reaction Steps
To a cloudy solution of methyl 4-((1R,3aS,5aR,5bR,7aR,11aS,11bR,13aR,13bR)-3a-(3-(2-(dimethylamino)ethyl)ureido)-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)benzoate (0.255 g, 0.388 mmol) in THF (5 mL) was added a solution of lithium hydroxide monohydrate (0.049 g, 1.16 mmol) in water (1.00 mL). The reaction mixture was heated to 75° C. for 18 h. Then, the reaction was treated with 1N HCl (1 mL) and concentrated in vacuo, absorbed onto silica gel (3.5 g), loaded onto a silica gel column (12 g cartridge) and eluted with 90:10 DCM:MeOH to give the title compound (237 mg, 0.368 mmol, 95% yield) as a white solid. LCMS: m/e 644.4 (M+H)+, 3.95 min (method 8). 1H NMR (500 MHz, MeOD) δ ppm 7.9 (2H, d, J=8.2 Hz), 7.2 (2H, d, J=8.2 Hz), 5.9 (1H, s), 5.3-5.3 (1H, m), 4.8 (1H, d, J=1.8 Hz), 4.6 (1H, s), 3.7-3.8 (1H, m), 3.4-3.6 (2H, m), 3.4 (1H, s), 3.2-3.3 (2H, m), 2.9 (6H, s), 2.7 (1H, td, J=11.1, 5.0 Hz), 2.6 (1H, dd, J=10.2, 3.2 Hz), 2.4 (1H, dd, J=12.1, 8.1 Hz), 2.2 (1H, dd, J=17.4, 6.4 Hz), 1.9-2.0 (2H, m), 1.8 (1H, d, J=13.4 Hz), 1.7 (3H, s), 1.7 (1H, br. s.), 1.7-1.7 (1H, m), 1.6-1.6 (2H, m), 1.5-1.6 (4H, m), 1.4-1.4 (5H, m), 1.3-1.4 (3H, m), 1.2 (3H, s), 1.1-1.1 (1H, m), 1.0-1.1 (6H, m), 1.0 (3H, s), 1.0 (3H, s). 13C NMR (MeOD) δ ppm 14.5, 16.3, 16.8, 19.2, 20.6, 21.3, 22.2, 26.3, 28.2, 29.7, 30.4, 30.5, 34.5, 36.2, 36.4, 37.1, 38.2, 38.4, 41.5, 42.6, 42.8, 43.6, 48.1, 49.0, 49.3, 49.3, 50.4, 50.6, 54.0, 55.6, 59.9, 64.9, 110.3, 111.1, 124.8, 129.3, 130.7, 147.5, 150.9, 160.4.
