Reaction Steps
A mixture of 4-(((3aR,5aR,5bR,7aR,9S,11aR,11bR,13aS)-3a-((R)-1-acetoxy-2-((4-chlorobenzyl)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)oxy)-2,2-dimethyl-4-oxobutanoic acid (49) (150 mg, 0.192 mmol), Na2CO3 (20.37 mg, 0.192 mmol), in methanol (3 mL) was stirred for 3 h, then purified by preparative-HPLC to afford 4-(((3aR,5aR,5bR,7aR,9S,11aR,11bR,13aS)-3a-((R)-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 (74) (45 mg, 30%) as a white solid. Compound exists as a mixture of rotomers; 1H NMR (500 MHz, METHANOL-d4) δ=7.43-7.27 (m, 2H), 7.28-7.11 (m, 2H), 5.30-4.09 (m, 6H), 3.55-2.09 (m, 11H), 2.09-0.78 (m, 44H); LC/MS: m/z calculated 779.5. found 780.4 (M+1)+.
