Reaction Steps
To a solution of methyl 4-((1R,3aS,5aR,5bR,7aR,11aS,11bR,13aR,13bR)-3a-isocyanato-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)benzoate (600 mg, 1.053 mmol) and N,N-diisopropyethyllamine (0.734 mL, 4.21 mmol) in THF (6 mL) was added tert-butyl 1-(aminomethyl)cyclopropylcarbamate (294 mg, 1.579 mmol). The resulting mixture was stirred at rt. After 16 h, the solvent was concentrated. The crude material was dissolved in THF (1 mL) and MeOH (2 mL), filtered and purified by reverse phase preparative HPLC (method 1) to give the title compound (499.5 mg, 58% yield) as a white solid. LCMS: m/e 756.7 (M+H)+, 2.75 min (method 7). 1H NMR (500 MHz, CHLOROFORM-d) δ ppm 8.0 (2H, d, J=8.5 Hz), 7.2 (2H, d, J=8.5 Hz), 5.3-5.3 (1H, m), 5.1 (1H, br. s.), 4.8 (1H, s), 4.7 (1H, s), 3.9 (3H, s), 3.5-3.5 (1H, m), 3.4 (1H, d, J=14.3 Hz), 2.8 (1H, br. s.), 2.6 (1H, d, J=12.8 Hz), 2.4 (1H, dd, J=12.2, 8.2 Hz), 2.1 (1H, dd, J=17.4, 6.4 Hz), 1.9-2.1 (2H, m), 1.8 (1H, d, J=13.4 Hz), 1.7-1.8 (1H, m), 1.7 (3H, s), 1.7-1.7 (2H, m), 1.5-1.7 (3H, m), 1.5 (9H, s), 1.4-1.5 (5H, m), 1.2-1.3 (1H, m), 1.1-1.2 (2H, m), 1.1 (3H, s), 1.0 (3H, s), 1.0 (3H, s), 0.9 (6H, s), 0.8-0.9 (3H, m). 13C NMR (CHLOROFORM-d) δ ppm 14.1, 15.4, 16.1, 19.0, 19.5, 20.7, 20.8, 24.8, 27.0, 28.1, 29.1, 29.2, 29.4, 31.4, 33.2, 35.1, 36.0, 36.6, 37.2, 40.4, 41.4, 41.6, 46.0, 49.1, 49.6, 51.7, 52.5, 77.3, 80.1, 109.9, 123.7, 127.6, 128.2, 129.8, 146.0, 148.4, 149.2, 167.0.
