反应详情

To a solution of 103 (1.2 g, 1.945 mmol) in acetonitrile (20 ml) and water (5.00 ml) stirred in air at rt was added NBS (1.385 g, 7.78 mmol) in one charge. The reaction mixture was stirred at rt for 0.5 h, then quenched with Na2SO3 (solid), concentrated and the residue was extracted with EtOAc. The organic phase was washed with water and saturated brine, dried over sodium sulphate and concentrated in vacuo to give (3aR,5aR,5bR,7aR,9S,11aR,11bR,13aS)-3a-(1-hydroxy-2-oxoethyl)-1-isopropyl-5a,5b,8,8,11a-pentamethyl-2-oxo-3,3a,4,5,5a,5b,6,7,7a,8,9,10,11,11a,11b,12,13,13a-octadecahydro-2H-cyclopenta[a]chrysen-9-yl acetate (104) (1.09 g, 1.083 mmol, 55.7% yield) as a light yellow solid which was used without further purification.

1. additioncharge
2. customquenched with Na2SO3 (solid)
3. concentrationconcentrated
4. extractionthe residue was extracted with EtOAc
5. washThe organic phase was washed with water and saturated brine
6. dry with materialdried over sodium sulphate
7. concentrationconcentrated in vacuo