反应详情

The product of Example 3 (2.0 g, 0.005 mol) was combined with trimethylorthoformate (10 ml, 0.09 mol) and para-toluenesulfonic acid monohydrate (50 mg, catalytic) in anhydrous methanol. The mixture was refluxed for 72 hours, cooled to room temperature, poured into diethyl ether, washed with a 1:1 mixture of 10% aqueous sodium hydroxide solution and concentrated aqueous sodium chloride solution (100 ml), water (100 ml) and saturated aqueous sodium chloride solution (100 ml). The organic phase was dried over magnesium sulfate, filtered and concentrated in vacuo to leave an oil that was purified by silica gel chromatography using a 3:1 hexane:dichloromethane solvent mixture. This provided the title compound as a white solid (1.83 g), m.p. about 93° C. Also prepared by this method: Compound 18.

1. temperatureThe mixture was refluxed for 72 hours
2. washwashed with a 1:1 mixture of 10% aqueous sodium hydroxide solution and concentrated aqueous sodium chloride solution (100 ml), water (100 ml) and saturated aqueous sodium chloride solution (100 ml)
3. dry with materialThe organic phase was dried over magnesium sulfate
4. filtrationfiltered
5. concentrationconcentrated in vacuo
6. customto leave an oil that
7. customwas purified by silica gel chromatography