Reaction #172733

Reaction equation

(1R,3aS,5aR,5bR,7aR,11aS,11bR,13aR,13bR)-tert-butyldimethylsilyl 9-(4-(methoxycarbonyl)phenyl)-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]chrysene-3a-carboxylate

TBAF

→

title compound

Yield 99.1%

(1R,3aS,5aR,5bR,7aR,11aS,11bR,13aR,13bR)-9-(4-(methoxycarbonyl)phenyl)-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]chrysene-3a-carboxylic acid

Yield 99.1%

Solvents

dioxane

HCl

water

Conditions

Workup

1. 1
   Extractionextracted with dichloromethane (3×100 mL)
2. 2
   DryingThe combined organic layers were dried over Na2SO4
3. 3
   Filtrationfiltered
4. 4
   Concentrationpartially concentrated under reduced pressure to about 10 mL volume
5. 5
   workup.ADDITIONTo the partially concentrated mixture was added 1N HCl (50 mL)
6. 6
   OtherThe solids that formed
7. 7
   Filtrationwere collected by filtration
8. 8
   Washwashed with water

Procedure

To solution of (1R,3aS,5aR,5bR,7aR,11aS,11bR,13aR,13bR)-tert-butyldimethylsilyl 9-(4-(methoxycarbonyl)phenyl)-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]chrysene-3a-carboxylate (3.12 g, 4.54 mmol) in dioxane (25 mL) was added TBAF (75% wt in water) (2.375 g, 6.81 mmol) and the mixture was stirred at rt for 4 h. The reaction mixture was diluted with 1N HCl (25 mL) and water (5 mL) and extracted with dichloromethane (3×100 mL). The combined organic layers were dried over Na2SO4, filtered, and partially concentrated under reduced pressure to about 10 mL volume. To the partially concentrated mixture was added 1N HCl (50 mL). The solids that formed were collected by filtration and washed with water to give the title compound (2.58 g, 4.50 mmol, 99% yield) as a white solid. LCMS: m/e 571.47 (M−H)−, 3.60 min (method 1). 1H NMR (500 MHz, CHLOROFORM-d) δ ppm 9.80 (br. s., 1H), 7.92 (d, J=8.24 Hz, 2H), 7.18 (d, J=8.24 Hz, 2H), 5.32-5.26 (m, 1H), 4.75 (s, 1H), 4.62 (br. s., 1H), 3.90 (s, 3H), 3.07-2.99 (m, 1H), 2.33-2.21 (m, 2H), 2.10 (dd, J=17.09, 6.10 Hz, 1H), 2.06-1.94 (m, 2H), 1.70 (s, 3H), 1.01 (br. s., 3H), 1.00 (br. s., 3H), 0.98 (s, 3H), 0.91 (s, 6H), 1.79-0.89 (m, 17H).

Source