Reaction Steps
To a solution of (1S,3R)-benzyl 3-((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-carboxamido)-2,2-dimethylcyclobutanecarboxylate (Example 2, about 0.140 g, 0.196 mmol) in MeOH:THF (2:1) (6 ml) at 0° C., 2N NaOH (2 ml) was added and allowed to stir at room temperature for about 6 hours. After completion of the reaction (monitored by TLC), the solvent was evaporated and acidified with 2N HCl, the aqueous layer was extracted with ethyl acetate and dried with Na2SO4. The solvent was evaporated and purified by silica gel column (100-200 mesh, elution 50% EtOAc in hexane) to afford the title compound as an off white solid. Wt: 0.105 g: Yield: 92%. 1H NMR (300 MHZ, CDCl3): δ 5.64 (d, 1H, J=7.8 Hz), 4.72 (s, 1H), 4.58 (s, 1H), 4.15 (q, 1H, J=9.3 Hz), 3.18 (dd, 1H, J=5.1, 10.8 Hz), 3.14-3.08 (m, 1H), 2.71-2.64 (m, 1H), 2.52-2.41 (m, 1H), 2.40-2.28 (m, 1H), 2.10-1.88 (m, 4H), 1.78-1.64 (m, 9H), 1.62-1.51 (m, 3H), 1.49-1.41 (m, 4H), 1.39-1.32 (m, 7H), 1.28-1.22 (m, 4H), 0.98 (s, 3H), 0.97 (s, 3H), 0.96 (s, 3H), 0.93 (s, 3H), 0.81 (s, 3H), 0.75 (s, 3H); Mass: [M+1]+ 582 (10%), [M+Na]+ 604 (100%); IR (KBr, cm−1): 3454, 3407, 2949, 2869, 1716, 1709, 1642, 1459, 1243, 1191, 1009, 885, 787; M.R: 174.6° C.-187.0° C.; HPLC: 90.33%.
