反应详情

A suspension of 24 (6.2 g, 25.4 mmol) and 23a (3.0 g, 16.9 mmol) in anhydrous methanol (40 mL) was stirred and heated to reflux for 10 min, then a solution of sodium methoxide 95% (3.65 g, 67.6 mmol) in methanol (40 mL) was slowly added. After refluxing for 24 h, 20 mL of 2.5N NaOH in water were added and the refluxing was maintained for additional 24 h. The mixture was allowed to cool to the room temperature methanol was removed under reduced pressure, 100 mL of water were added and the resultant mixture was extracted with AcOEt. The aqueous phase was separated and acidified to pH 5-6 with 2N HCl to form a precipitate which was collected by filtration, rinsed with water and dried to afford the desired carboxylic acid 25a (4.55 g, 14.8 mmol, 87%) as a white solid.

1. temperatureheated
2. temperatureto reflux for 10 min
3. temperatureAfter refluxing for 24 h
4. temperaturethe refluxing was maintained for additional 24 h
5. customwas removed under reduced pressure, 100 mL of water
6. additionwere added
7. extractionthe resultant mixture was extracted with AcOEt
8. customThe aqueous phase was separated
9. customto form a precipitate which
10. filtrationwas collected by filtration
11. washrinsed with water
12. customdried