Reaktionsschritte
To a sealable vial was added (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 (0.075 g, 0.120 mmol), 1-bromo-2-chloroethane (0.100 mL, 1.202 mmol), and phosphoric acid, potassium salt (0.128 g, 0.601 mmol). The mixture was diluted with acetonitrile (1.5 mL), flushed with nitrogen, then the vial was sealed and heated to 120° C. After 24 h of heating, the mixture was cooled to rt and was filtered to remove solids. The solids were washed with dichloromethane and the filtrate was concentrated under reduced pressure to give (R)-benzyl 4-((1R,3aS,5aR,5bR,7aR,11aS,11bR,13aR,13bR)-3a-(aziridin-1-yl)-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 as an off-white solid that was used in the next step with no additional purification. LCMS: m/e 650.7 (M+H)+, 2.22 min (method 1).
