Reaction Steps
2,2-Dimethylsuccinic anhydride (238 mg) was added to a stirred solution of (1R,3aS,5aR,5bR,7aR,9S,11aR,11bR,13aR,13bR)-N-((1S,3R)-3-(4-ethylpiperazine-1-carbonyl)-2,2-dimethylcyclobutyl)-9-hydroxy-5a,5b,8,8,11a-pentamethyl-1-(prop-1-en-2-yl)icosahydro-1H-cyclopenta[a]chrysene-3a-carboxamide (Example 67, 125 mg) and DMAP (45 mg) in dry pyridine (10 mL) at room temperature. After addition, the reaction mixture was refluxed for 14 hours. After completion of the reaction (monitored by TLC), it was diluted with EtOAc, the organic layer was washed with aqueous 1N HCl, then washed with water and brine, and dried with Na2SO4. The solvent was evaporated and purified by silica gel column (100-200, elution 35% EtOAc in hexane) to afford 90 mg of title compound (60.8% yield) as an off white solid with 81.67% HPLC purity. 1H-NMR (300 MHz, CDCl3): δ 5.92 (d, J=7.8 Hz, 1H), 4.73 (s, 1H), 4.58 (s, 1H), 4.52-4.44 (m, 1H), 4.19-4.09 (m, 1H), 3.90 (m, 2H), 3.7 (m, 2H), 3.15-3.04 (m, 1H), 2.87-2.82 (m, 6H), 2.60 (m, 3H), 2.5-2.3 (m, 3H), 2.00-1.91 (m, 3H), 1.75-1.10 (m, 36H), 0.947, 0.914, 0.900 (s, 18H); Mass: [M+1]+ 806 (100%); IR (KBr, cm−1): 3394, 2957, 2873, 1724, 1623, 1455, 1374, 1367, 1244, 1188, 1146, 980, 883, 765; M.R: 63.8° C.-122.5° C.
