Reaction Steps
To a stirred solution of (1R,3aS,5aR,5bR,7aR,9S,11aR,11bR,13aR,13bR)-9-acetoxy-5a,5b,8,8,11a-pentamethyl-1-(prop-1-en-2-yl)icosahydro-1H-cyclopenta[a]chrysene-3a-carboxylic acid (0.3 g, 0.602 mmol) in DCM (1 ml) a solution of (COCl)2 (0.52 ml, 6.02 mmol) in DCM (4 ml) was added at about 0° C. and the reaction mixture was allowed to stir at room temperature for about 3 hours. After completion of the reaction (monitored by TLC), the solvent was evaporated under nitrogen atmosphere and dissolved in DCM (4 ml), which was added to a stirred solution of ((1R,3S)-3-amino-2,2-dimethylcyclobutyl)(pyrrolidin-1-yl)methanone (Intermediate 13, 0.288 g, 1.023 mmol) in DCM (5 ml) and Et3N (0.16 ml, 1.204 mmol) at about 0° C. and allowed to stir at room temperature for about 16 hours. After completion of the reaction (monitored by TLC), the reaction mixture was diluted with DCM and washed with water, 1N HCl, water, brine and dried over Na2SO4, the solvent was evaporated and purified by silica gel column (100-200 mesh, elution 20% EtOAc in hexane) to afford the title compound as an off white solid. Wt: 0.230 g; Yield: 56.5%; 1H NMR (300 MHz, CDCl3): δ 6.38 (d, 1H, J=8.4 Hz), 4.73 (s, 1H), 4.58 (s, 1H), 4.50-4.42 (m, 1H), 4.13-4.02 (m, 1H), 3.56-3.28 (m, 5H), 3.18-3.07 (m, 1H), 2.79 (t, 1H, J=7.2 Hz), 2.55-2.33 (m, 2H), 2.27-2.18 (m, 1H), 2.04 (s, 3H), 2.00-1.74 (m, 8H), 1.72-1.10 (m, 20H), 0.95, 0.92, 0.88, 0.83 (s, 22H); Mass: [M+Na]+ 714 (100%); IR (KBr, cm−1): 3372, 2943, 2864, 1736, 1730, 1652, 1636, 1623, 1501, 1459, 1444, 1369, 1248, 1192, 1024, 979, 881, 853; M.R: 125.4° C.-135.5° C.
