Reaction Steps
To a solution of ethyl 3-((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)-1H-pyrazole-5-carboxylate (0.07 g, 0.105 mmol) in 1,4-Dioxane (4 mL) was added Water (1 mL) and lithium hydroxide monohydrate (0.085 g, 2.026 mmol). The mixture was heated to 75° C. for 18.25 h, was cooled to rt, and was quenched with 1N HCl (7 mL). The mixture was extracted with dichloromethane (4×7 mL) and the combined organic layers were dried with Na2SO4. The drying agent was removed by filtration and the filtrate was concentrated under reduced pressure. Purification was accomplished by crystallization from dioxane and water to give 3-((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)-1H-pyrazole-5-carboxylic acid (0.03 g, 0.052 mmol, 49.2% yield) as a white solid. LCMS: m/e 533.60 (M−H)−, 1.24 min (method 1). 1H NMR (500 MHz, Pyr) δ ppm 0.86 (t, J=7.48 Hz, 3H), 0.95 (s, 3H), 1.06 (s, 6H), 1.06-1.99 (m, 22H), 1.80 (s, 3H), 2.14-2.24 (m, 2H), 2.40-2.51 (m, 2H), 2.65 (dt, J=10.99, 5.49 Hz, 1H), 3.69 (d, J=10.68 Hz, 1H), 4.12 (d, J=10.68 Hz, 1H), 4.79 (s, 1H), 4.93 (d, J=2.14 Hz, 1H), 6.13 (br. s., 1H), 7.33 (s, 1H).
