反应详情

25.81 g of N-bromosuccinimide (145 mmol) was added to a solution of 21.20 g of (2S,4E)-6-(benzyloxy)-2-isopropylhex-4-enoic acid dimethylamide obtained in Example (1c) (72.5 mmol) and 8.3 ml of acetic acid (145 mmol) in a mixed solvent of tetrahydrofuran (290 ml) and water (145 ml) under ice-cooling, and the mixture was stirred at the same temperature for three hours. 100 ml of a saturated sodium bicarbonate aqueous solution and 100 ml of a 1.5 M sodium sulfite aqueous solution were added to the reaction mixture, and the mixture was further stirred at room temperature for 30 minutes. The reaction mixture was concentrated under reduced pressure to about ⅔ of the volume, followed by extraction with ethyl acetate. Then, the organic layer was washed with water and brine and dried over anhydrous magnesium sulfate. After filtration, the solvent was evaporated under reduced pressure, and the residue was purified by silica gel column chromatography (elution solvent:n-hexane/ethyl acetate=6/1-5/1) to obtain 22.73 g of the title compound (total yield over three steps: 50%).

1. temperaturecooling
2. stirringthe mixture was further stirred at room temperature for 30 minutes
3. concentrationThe reaction mixture was concentrated under reduced pressure to about ⅔ of the volume
4. extractionfollowed by extraction with ethyl acetate
5. washThen, the organic layer was washed with water and brine
6. dry with materialdried over anhydrous magnesium sulfate
7. filtrationAfter filtration
8. customthe solvent was evaporated under reduced pressure
9. customthe residue was purified by silica gel column chromatography (elution solvent:n-hexane/ethyl acetate=6/1-5/1)