Reaktionsschritte
To a vial containing (1R,3 aS,5aR,5bR,7aR,11aR,11bR,13 aR,13bR)-3a-amino-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 trifluoromethanesulfonate (1.54 g, 2.76 mmol) was added diisopropyl 6-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)spiro[3.3]hept-5-ene-2,2-dicarboxylate (1.044 g, 2.66 mmol), sodium carbonate monohydrate (0.856 g, 6.90 mmol) and tetrakis(triphenylphosphine)palladium(0) (0.096 g, 0.083 mmol). The mixture was diluted with 1,4-dioxane (12 mL) and water (3 mL), then was flushed with nitrogen and the vial was sealed and heated to 85° C. After 5.5 h of heating, the mixture was cooled to rt. The mixture was diluted with water (40 mL) and extracted with dichloromethane (3×40 mL). The combined organic layers were dried over sodium sulfate. The drying agent was removed by filtration and the filtrate was concentrated under reduced pressure. The residue was purified by flash chromatography using a 0-50% ethyl acetate in hexanes gradient and a Thomson 80 g silica gel column. The fractions containing the expected product were combined and concentrated under reduced pressure to give diisopropyl 6-((1R,3aS,5aR,5bR,7aR,11aS,11bR,13aR,13bR)-3a-amino-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)spiro[3.3]hept-5-ene-2,2-dicarboxylate (1.19 g, 1.766 mmol, 63.9% yield) as an off-white solid. LCMS: m/e 674.7 (M+H)+, 2.30 min (method 1). 1H NMR (500 MHz, chloroform-d) δ=5.87 (s, 1H), 5.52 (dd, J=6.4, 1.8 Hz, 1H), 5.13-5.01 (m, 2H), 4.73 (br. s., 1H), 4.61 (br. s., 1H), 2.74-2.66 (m, 4H), 2.63-2.51 (m, 3H), 2.14-1.99 (m, 2H), 1.70 (s, 3H), 1.27-1.23 (m, 12H), 1.15 (s, 3H), 1.07 (br. s., 3H), 1.06 (s, 3H), 0.97 (s, 3H), 0.83 (s, 3H), 1.76-0.80 (m, 20H).
