Reaction Steps
To a solution of tert-butyl 4-((1R,3aS,5aR,5bR,7aR,11aS,11bR,13aR,13bR)-3a-formyl-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 (0.1 g, 0.167 mmol) in DCE (2 ml) was added acetic acid (0.019 ml, 0.334 mmol) and 3-(dimethylamino)propylamine (0.084 ml, 0.668 mmol). To the mixture was added sodium triacetoxyborohydride (0.177 g, 0.835 mmol) and it was stirred at rt for 72 h. After 72 h of stirring, the reaction was diluted with 7 ml of sat. NaHCO3 was extracted with dichloromethane (3×7 ml) and the combined organic layers were dried with Na2SO4. The drying agent was removed by filtration and the filtrate was concentrated under reduced pressure to give the expected product, tert-butyl 4-((1R,3aS,5aR,5bR,7aR,11aS,11bR,13aR,13bR)-3a-((3-(dimethylamino)propylamino)methyl)-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. The crude product was used in the next step with no additional purification. LCMS: m/e 685.6 (M−H)−, 2.92 min (method 6).
