Cyclopropanecarboxaldehyde → methyl 4-((1R,3aS,5aR,5bR,7aR,11aS,11bR,13aR,13bR)-3a-(cyclopropylmethylamino)-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

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Reaction Steps

To a solution of methyl 4-((1R,3aS,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)benzoate (0.022 g, 0.040 mmol) in DCE (0.25 mL) was added cyclopropanecarbaldehyde (2.84 mg, 0.040 mmol) and titanium (IV) isopropoxide (0.015 mL, 0.051 mmol). The mixture was stirred at rt for 1 h and sodium triacetoxyborohydride (0.017 g, 0.081 mmol) was added. After stirring the mixture for 16.75 h, the mixture was diluted with 3 mL of water and was filtered through a pad of celite, then was extracted with dichloromethane (3×4 mL). 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 title compound (0.024 g, 0.040 mmol, 99% yield) as a clear film. The crude product was used in the next step with no additional purification. LCMS: m/e 598.6 (M+H)+, 2.13 min (method 2).

Provenance & Evidence