反应详情

温度

75 °C

L-Xylose (5.00 g, 33.3 mmol), boric acid (4.50 g, 73.2 mmol), and glacial acetic acid (100 mL) were added into a 250 mL round bottom flask. The mixture was stirred at 80° C. until L-xylose and boric acid were dissolved in acetic acid. Acetic anhydride (50 mL) was added and the reaction mixture was stirred at 75° C. for 4 h. Analysis by TLC (EtOAc: MeOH: H2O, 10:3:1) showed that the L-xylose had been completely consumed. MeOH was then added to the reaction mixture, and the reaction mixture was concentrated to give a dark, orange-brown syrup. To this syrup, acetic anhydride (50 mL) and pyridine (50 mL) were added and the reaction mixture was stirred at room temperature for 4 h. The orange-brown mixture was pour into crushed ice and was extracted with Et2O (100 mL). The organic layer was washed with saturated aqueous NaHCO3 (50 mL), aqueous HCl, water, and saturated NaCl, dried over MgSO4 and concentrated to a yellow syrup. Purification by column chromatography on silica gel (Hexane:EtOAc, 2:1) yielded the tetra-O-acetylxylofuranose 49 (9.01 g, 85%) as a colorless syrup (α:β ratio 1:23). Data for the β (major) isomer.

1. additionwas added
2. customhad been completely consumed
3. additionMeOH was then added to the reaction mixture
4. concentrationthe reaction mixture was concentrated
5. customto give a dark, orange-brown syrup
6. stirringthe reaction mixture was stirred at room temperature for 4 h
7. additionThe orange-brown mixture was pour
8. custominto crushed ice
9. extractionwas extracted with Et2O (100 mL)
10. washThe organic layer was washed with saturated aqueous NaHCO3 (50 mL), aqueous HCl, water, and saturated NaCl
11. dry with materialdried over MgSO4
12. concentrationconcentrated to a yellow syrup
13. customPurification by column chromatography on silica gel (Hexane:EtOAc, 2:1)