Reaction Steps
To a solution of ethyl 5-((1R,3aS,5aR,5bR,7aR,11aS,11bR,13aR,13bR)-3a-(benzoyloxymethyl)-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)isoxazole-3-carboxylate (0.015 g, 0.022 mmol) in 1,4-Dioxane (2 mL) was added Water (0.5 mL) and Lithium hydroxide monohydrate (0.17 g, 4.05 mmol). The mixture was heated to 75° C. After 3.5 h the mixture was cooled to rt and was diluted with 1N HCl (7 mL) then was extracted with dichloromethane (4×7 mL). The combined organic layers were dried with Na2SO4. The drying agent was removed by filtration and the filtrate was concentrated under reduced pressure. The residue was purified by crystallization using dioxane, water, and methanol. The expected product, 5-((1R,3aS,5aR,5bR,7aR,11aS,11bR,13aR,13bR)-3a-(hydroxymethyl)-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)isoxazole-3-carboxylic acid (4 mg, 7.17 mmol, 31.9% yield), was isolated as a white solid. LCMS: m/e 536.35 (M+H)+, 2.03 min (method 7). 1H NMR (500 MHz, Pyr) δ ppm 0.87 (s, 3H), 0.96-1.88 (m, 20H), 1.04 (s, 3H), 1.05 (s, 3H), 1.17 (s, 3H), 1.21 (s, 3H), 1.81 (s, 3H), 2.14-2.27 (m, 1H), 2.39-2.53 (m, 1H), 2.59-2.74 (m, 1H), 3.70 (d, J=10.99 Hz, 1H), 4.12 (d, J=10.99 Hz, 1H), 4.80 (br. s., 1H), 4.94 (s, 1H), 6.40 (d, J=6.41 Hz, 1H), 7.08 (s, 1H).
