Reaction Steps
To a solution of 4-((1R,3aS,5aR,5bR,7aR,11aS,11bR,13aR,13bR)-3a-(aminomethyl)-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 (20 mg, 0.037 mmol) in DCM (2 ml) was added dihydrofuran-2,5-dione (11.04 mg, 0.110 mmol) followed by DMAP (4.49 mg, 0.037 mmol) and DIPEA (6.42 μl, 0.037 mmol). The mixture was stirred at rt for 18 h. The solvent was removed in vacuo and the resulting residue was purified by prep. HPLC. The product was isolated as a white solid (5 mg, 21.1%). LCMS: m/e 644.5 (MH+), 2.80 min (method 3). 1H NMR (400 MHz, MeOD) δ ppm 7.94 (d, J=8.5 Hz, 2H), 7.16-7.34 (m, 2H), 5.32 (dd, J=6.4, 1.6 Hz, 1H), 4.74 (d, J=2.0 Hz, 1H), 4.62 (s, 1H), 3.54 (d, J=13.6 Hz, 1H), 3.04 (d, J=13.8 Hz, 1H), 2.57-2.71 (m, 2H), 2.44-2.57 (m, 2H), 2.17 (dd, J=17.2, 6.4 Hz, 1H), 2.09 (dd, J=13.1, 1.8 Hz, 1H), 1.85 (dd, J=12.2, 3.4 Hz, 2H), 1.65-1.82 (m, 8H), 1.61 (br. s., 2H), 1.53 (d, J=10.5 Hz, 3H), 1.48 (d, J=2.0 Hz, 1H), 1.35-1.45 (m, 3H), 1.24-1.35 (m, 3H), 1.16-1.24 (m, 4H), 1.02-1.16 (m, 8H), 0.99 (s, 3H), 0.95 (s, 3H).
