反应详情

The product from Step B (11.5 g, 0.032 mol) was added to DMF (100 mL) containing imidazole (5.44 g, 0.08 mol) and t-butyldiphenylsilyl chloride (9.34 mL, 0.035 mol) and stirred at room temperature for 18 hr. The reaction mixture was evaporated to dryness and the residue was suspended in methylene chloride and filtered. The filtrate was concentrated and chromatographed (silica, methylene chloride) to provide a solid which was dissolved in THF (200 mL) and cooled to 5° C. A solution of pyridinium bromide perbromide (11.23 g, 0.035 mol) in THF (50 mL) was added dropwise and this mixture was stirred at 5° C. for 1 hr, at ambient temperature for 1 hr, and then evaporated to dryness. The residue was suspended in ethanol (150 mL) and cooled to 5° C. followed by the addition of sodium borohydride (3.59 g, 95 mmol). The reaction mixture was maintained at room temperature for 1 hr and then heated at reflux temperature for 1.5 hr. Water was carefully added and the ethanol evaporated. The aqueous mixture was neutralized and extracted with ethyl acetate (2×200 mL). The combined extracts were dried (MgSO4) and evaporated to a residue which was purified by column chromatography (silica, 15% ethyl acetate/hexane) to provide an amber syrup (8.2 g, 44%).

1. customThe reaction mixture was evaporated to dryness
2. filtrationfiltered
3. concentrationThe filtrate was concentrated
4. customchromatographed (silica, methylene chloride)
5. customto provide a solid which
6. temperaturecooled to 5° C
7. stirringthis mixture was stirred at 5° C. for 1 hr, at ambient temperature for 1 hr
8. customevaporated to dryness
9. temperaturecooled to 5° C.
10. temperatureThe reaction mixture was maintained at room temperature for 1 hr
11. temperatureheated
12. temperatureat reflux temperature for 1.5 hr
13. customthe ethanol evaporated
14. extractionextracted with ethyl acetate (2×200 mL)
15. dry with materialThe combined extracts were dried (MgSO4)
16. customevaporated to a residue which
17. customwas purified by column chromatography (silica, 15% ethyl acetate/hexane)