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温度

0 °C

To a solution of 16 (13.4 g, 29.9 mmol) and pyridine (9.7 mL, 120 mmol) in anhydrous chloroform (60 mL) at 0° C. was added dropwise a solution of methyl chloroformate (9.2 mL, 120 mmol) in chloroform (30 mL). The mixture was stirred 1 h at 0° C., and then was washed with 2 N HCl (2×60 mL). The organic phase was dried over Na2SO4, filtered and concentrated under reduced pressure to give a yellow oil. The oil (mixture of 16 and 17) was treated with pyridine (5 mL, 62 mmol) and methyl chloroformate (4.6 mL, 60 mmol) under the same conditions above another four times to achieve approximately 90% conversion. The crude product, a yellow oil, was purified on an AnaLogix chromatography system with 33-50% EtOAc/heptanes to give 7.6 g (50%, greater than 98% purity) of 17 as a colorless oil.

1. washwas washed with 2 N HCl (2×60 mL)
2. dry with materialThe organic phase was dried over Na2SO4
3. filtrationfiltered
4. concentrationconcentrated under reduced pressure
5. customto give a yellow oil
6. customThe crude product, a yellow oil, was purified on an AnaLogix chromatography system with 33-50% EtOAc/heptanes