Reaction Steps
To a solution of methyl 4-((1R,3aS,5aR,5bR,7aR,11aS,11bR,13aR,13bR)-3a-((2-fluoropyridin-4-yl)methylamino)-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)benzoate, TFA (77.7 mg, 0.101 mmol) in THF (3 mL) was added a 0.753 molar aqueous solution of LiOH.H2O (0.539 mL, 0.405 mmol). The reaction mixture was heated to 75° C. After 4 h, the reaction mixture was concentrated. The crude residue was dissolved in THF (1.5 mL) and MeOH (200 μL), filtered and purified by reverse phase preparative HPLC using HPLC method 3 to give 4-((1R,3aS,5aR,5bR,7aR,11aS,11bR,13aR,13bR)-3a-((2-fluoropyridin-4-yl)methylamino)-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)benzoic acid, TFA (30.6 mg, 0.037 mmol, 36.1% yield) as a white solid. LCMS: m/e 637.7 (M−H)−, 3.12 min (method 6). 1H NMR (500 MHz, 1:1 CDCl3:MeOD) δ=8.24 (d, J=5.2 Hz, 1H), 7.92 (d, J=8.2 Hz, 2H), 7.43 (d, J=5.2 Hz, 1H), 7.24 (s, 1H), 7.20 (d, J=8.5 Hz, 2H), 5.29 (dd, J=1.7, 6.3 Hz, 1H), 4.78 (s, 1H), 4.17 (br. s., 2H), 2.78-2.69 (m, 1H), 2.18-2.10 (m, 2H), 2.09-2.01 (m, 2H), 1.98 (dd, J=3.1, 11.9 Hz, 1H), 1.96-1.88 (m, 1H), 1.83-1.76 (m, 1H), 1.72 (s, 3H), 1.70-1.64 (m, 1H), 1.63-1.40 (m, 10H), 1.39-1.31 (m, 1H), 1.31-1.23 (m, 2H), 1.13 (s, 3H), 1.07 (s, 3H), 1.02 (s, 3H), 0.95 (s, 3H), 0.94 (s, 3H). 13C NMR (1:1 CDCl3:MeOD) d ppm 15.3, 16.6, 17.4, 19.5, 20.6, 21.8, 22.2, 26.1, 27.6, 29.0, 29.5, 30.2, 33.9, 34.6, 37.2, 38.2, 38.4, 41.8, 42.8, 43.1, 45.7, 47.2, 49.7, 49.9, 50.3, 50.5, 53.9, 78.8, 123.1, 123.2, 124.9, 129.3, 129.7, 131.0, 147.4, 149.7, 164.0, 166.0, 170.1.
