Reaction Steps
To a solution of 4-(((3aR,5aR,5bR,7aR,9S,11aR,11bR,13aS)-3a-((S)-1-acetoxy-2-(N-(4-chlorobenzyl)acetamido)ethyl)-1-isopropyl-5a,5b,8,8,11a-pentamethyl-2-oxo-3,3a,4,5,5a,5b,6,7,7a,8,9,10,11,11a,11b,12,13,13a-octadecahydro-2H-cyclopenta[a]chrysen-9-yl)oxy)-2,2-dimethyl-4-oxobutanoic acid (72) (150 mg, 0.182 mmol) in ethanol (2 mL) and toluene (2 mL) was added potassium hydroxide (40.9 mg, 0.729 mmol). The reaction mixture was stirred at rt for min. The reaction mixture was neutralized with aqueous 1 N HCl to pH=7 and concentrated to obtain a residue. The residue was extracted with DCM, washed with water and dried to yield the crude product which was purified by preparative-HPLC to afford 4-(((3aR,5aR,5bR,7aR,9S,11aR,11bR,13aS)-3a-((S)-2-(N-(4-chlorobenzyl)acetamido)-1-hydroxyethyl)-1-isopropyl-5a,5b,8,8,11a-pentamethyl-2-oxo-3,3a,4,5,5a,5b,6,7,7a,8,9,10,11,11a,11b,12,13,13a-octadecahydro-2H-cyclopenta[a]chrysen-9-yl)oxy)-2,2-dimethyl-4-oxobutanoic acid (73) (40 mg, 28%) as a white solid. Compound exists as a mixture of rotomers; 1H NMR (400 MHz, DMSO-d6) δ=12.18 (br. s., 1H), 7.52-7.14 (m, 4H), 5.03-3.77 (m, 5H), 3.39-2.80 (m, 3H), 2.62-2.54 (m, 1H), 2.27 (t, J=17.2 Hz, 1H), 2.20-0.58 (m, 51H);
