反应详情

To Intermediate 3 (3.5 g) in tetrahydrofuran (100 ml) at −70° C. was added lithium hexamethyldisilazide (20 ml). After ¼ h, benzyl chloroformate (2.8 ml) was added. The mixture was warmed to room temperature for 1 h and 1 M hydrochloric acid (25 ml) added. After extraction with ethyl acetate (3×25 ml), the combined extracts were washed with 2% ammonia solution, 2M hydrochloric acid and brine, then dried (MgSO4). After solvent removal, the white solid was recrystallised from ethyl acetate: hexane 5:1 to give the title compound (4.2 g), T.l.c. silica (18:2 ethyl acetate: methanol) Rf 0.7.

1. waitAfter ¼ h
2. extractionAfter extraction with ethyl acetate (3×25 ml)
3. washthe combined extracts were washed with 2% ammonia solution, 2M hydrochloric acid and brine
4. dry with materialdried (MgSO4)
5. customAfter solvent removal
6. customthe white solid was recrystallised from ethyl acetate: hexane 5:1