Reaktionsschritte
To a solution of tert-butyl 4-((1R,3aS,5aR,5bR,7aR,11aS,11bR,13aR,13bR)-3a-((2-(dimethylamino)ethylamino)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 (48 mg, 0.072 mmol) in DCE (2 ml) was added Hunig's base (0.037 ml, 0.215 mmol), 3-carboethoxypropionyl chloride (21.54 mg, 0.143 mmol), and DMAP (1 mg, 8.19 mmol). The mixture was stirred at rt for 5 h then was loaded directly onto a silica gel column and was purified using a 0-5% MeOH in dichloromethane gradient to afford tert-butyl 4-((1R,3aS,5aR,5bR,7aR,11aS,11bR,13aR,13bR)-3a-((N-(2-(dimethylamino)ethyl)-4-methoxy-4-oxobutanamido)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 as a white foam (53.8 mg, 0.051 mmol, 71.8% yield). LCMS: m/e 785.6 (M+H)+, 3.21 min (method 6).
