Reaction Steps
To a solution of diisopropyl 6-((1R,3aS,5aR,5bR,7aR,11aS,11bR,13aR,13bR)-3a-((tert-butoxycarbonyl)amino)-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)spiro[3.3]hept-5-ene-2,2-dicarboxylate (15 mg, 0.019 mmol) in dioxane (2 mL) and MeOH (1 mL) was added 1N NaOH (1 mL, 1 mmol). The mixture was stirred at 50° C. for 4 h. The solvent was removed in vacuo. The crude product was dissolved in dioxane (1 mL) and MeOH (1 mL). H2O was added dropwise, the solid formed was collected by filtration to give desired product in 88% yield. MS: m/e 688.6 (M−H)−, 2.72 min (method 5). 1H NMR (400 MHz, METHANOL-d4) δ 5.88 (s, 1H), 5.57-5.52 (m, 1H), 4.74 (d, J=1.8 Hz, 1H), 4.61 (s, 1H), 2.69 (s, 2H), 2.68-2.48 (m, 4H), 2.33-2.25 (m, 1H), 2.14 (dd, J=17.9, 6.7 Hz, 1H), 1.99-1.83 (m, 2H), 1.77-0.81 (m, 19H), 1.70 (s, 3H), 1.45 (s, 9H), 1.16 (s, 3H), 1.09 (s, 3H), 1.08 (s., 3H), 1.00 (s, 3H), 0.86 (s, 3H).
