Reaction Steps
A solution of (3aR,5aR,5bR,7aR,9S,11aR,11bR,13aS)-3a-(2-((tert-butoxycarbonyl)amino)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 acetate (35) (5.8 g, 9.48 mmol), NaOH (11.37 g, 284 mmol) in methanol (4 mL), THF (6 mL), and Water (2 mL) was stirred at room temperature for 1 h. EtOAc was added and the reaction mixture was washed with water. The organic layer was separated, washed with water and brine, and dried (Na2SO4). Removal of the solvent provide tert-butyl (2-((3aR,5aR,5bR,7aR,9S,11aR,11bR,13aS)-9-hydroxy-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-3a-yl)ethyl)carbamate (36) (5.4 g, 7.87 mmol, 83% yield) as a white solid. 1H NMR (400 MHz, CHLOROFORM-d) δ=4.53-4.36 (m, 1H), 3.30-2.94 (m, 4H), 2.94-2.67 (m, 2H), 2.28 (d, J=18.8 Hz, 1H), 2.11-0.55 (m, 50H); LC/MS: m/z calculated 569.4. found 592.3 (M+Na)+.
