반응 단계
To a vial containing (1R,3aS,5aR,5bR,7aR,11aR,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 trifluoromethanesulfonate (0.65 g, 1.165 mmol) was added phosphoric acid, potassium salt (0.742 g, 3.50 mmol), (R)-benzyl 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)cyclohex-3-enecarboxylate (0.8 g, 2.338 mmol) (enantiomer 1 prepared above), 2-dicyclohexylphosphino-2′,6′-dimethoxy-1,1′-biphenyl (S-phos) (0.072 g, 0.175 mmol) and palladium(II) acetate (0.026 g, 0.117 mmol). The mixture was diluted with 1,4-dioxane (10 mL) and water (1 mL), flushed with nitrogen, then the vial was sealed and heated to 75° C. After 6 h of heating, the mixture was cooled to rt, diluted with water (20 mL) and brine (20 mL), and was extracted with dichloromethane (5×40 mL). The organic layers were dried with sodium sulfate, filtered, and concentrated under reduced pressure. The residue was purified by flash chromatography using a 10-60% ethyl acetate in hexanes gradient and a 40 g silica gel column. The fractions containing the expected product were combined and were concentrated under reduced pressure to give (R)-benzyl 4-((1R,3 aS,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)cyclohex-3-enecarboxylate (0.488 g, 0.782 mmol, 67.1% yield) as an off-white solid. LCMS: m/e 624.65 (M+H)+, 2.18 min (method 1). 1H NMR (500 MHz, chloroform-d) δ=7.40-7.30 (m, 5H), 5.35 (br. s., 1H), 5.18 (dd, J=6.2, 1.8 Hz, 1H), 5.14 (s, 2H), 4.73 (d, J=2.0 Hz, 1H), 4.60 (s, 1H), 2.65-2.50 (m, 2H), 2.38-2.30 (m, 2H), 2.25-1.94 (m, 5H), 1.70 (s, 3H), 1.07 (s, 3H), 0.96 (s, 3H), 0.94 (s, 3H), 0.92 (s, 3H), 0.86 (s, 3H), 1.80-0.83 (m, 23H).
