Reaction Steps
To a stirred solution of (1R,3aS,5aR,5bR,7aR,9S,11aR,11bR,13aR,13bR)-9-((1R,3S)-3-(tert-butoxycarbonyl)-2,2-dimethylcyclobutanecarbonyloxy)-5a,5b,8,8,11a-pentamethyl-1-(prop-1-en-2-yl)icosahydro-1H-cyclopenta[a]chrysene-3a-carboxylic acid (Example 3, about 0.160 g, 0.239 mmol) in 2M HCl in Dioxane (10 ml) was stirred at room temperature for about 12 hours. After completion of the reaction (monitored by TLC), the reaction mixture was diluted with EtOAc and washed with water, the organic layer dried over Na2SO4 and concentrated under reduced pressure. The resulting crude was purified by Silica gel column chromatography (100-200 Mesh, Elution: 20% EtOAc in Hexane) to afford the title compound as a white solid. Wt: 0.086 g; Yield: 59.0%; 1H NMR (300 MHZ, CDCl3): δ 4.74 (s, 1H), 4.61 (s, 1H), 4.47-4.43 (m, 1H), 3.03-2.97 (m, 1H), 2.87-2.74 (m, 2H), 2.63-2.51 (m, 1H), 2.31-2.24 (m, 2H), 2.19-1.90 (m, 3H), 1.69 (s, 3H), 1.78-1.68 (m, 5H), 1.52-1.41 (m, 12H), 1.29-1.02 (m, 9H), 0.97 (s, 3H), 0.93 (s, 3H), 0.85 (s, 9H); Mass: [M+Na]+ 633 (100%); IR (KBr, cm−1): 3427, 2951, 1730, 1706, 1698, 1456, 1376, 1242, 1190, 1107, 1020, 885; M. Range: 282.5-289.3° C.; HPLC: 92.2% % at RT 8.76 minutes.
