Phosphoric Acid → (S)-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

Participants

Reaction Conditions

Reaction Steps

To a sealable vial was added (S)-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 (0.042 g, 0.067 mmol), 1-bromo-2-chloroethane (0.056 ml, 0.673 mmol) and phosphoric acid, potassium salt (0.071 g, 0.337 mmol). The mixture was diluted with acetonitrile (1 mL), was flushed with nitrogen, then was sealed and heated to 120° C. After 23 h of heating, the mixture was cooled to rt and the reaction mixture was filtered to remove solids. The solids were washed with dichloromethane and the filtrate was concentrated under reduced pressure to give (S)-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. The crude product was used in the next step with no additional purification. LCMS: m/e 650.8 (M+H)+, 2.26 min (method 1).

Provenance & Evidence