反应详情

N-Acetylgalactosamine 41 [3.0 g (13.56 mmol)] was suspended in acetyl chloride (6 ml), and stirred at room temperature overnight. The reaction mixture was diluted with chloroform (24 ml), poured into ice-water, and the chloroform layer was washed with saturated sodium bicarbonate. The organic layer dried over anhydrous magnesium sulfate, and the solvent was evaporated in vacuo to give an N-acetylgalactosamine chloride 43 (4.35 g). To a mixture of dexamethasone 6 [5.95 g (15.17 mmol)], the N-acetylgalactosamine chloride 43 [5.55 g (15.17 m mol)], trityl chloride [4.23 g (15.17 mmol)] and zinc chloride [2.07 g (15.17 mmol)] was added nitromethane (130 ml), and the resulting mixture was stirred under an argon atmosphere at room temperature overnight. The reaction solution was diluted with chloroform, and filtered to remove insoluble materials. The filtrate was washed successively with saturated solutions of sodium bicarbonate and sodium chloride. After drying the organic layer over anhydrous magnesium sulfate, the solvent was distilled off in vacuo, and the residue thus obtained was purified by silica gel column chromatography (acetone:toluene =2:3) to give fractions containing the desired product (950.8 mg). This fraction was further purified by HPLC using a reversed phase partition column (acetonitrile-water) to give α-anomer 44α [98.0 mg (yield 0.9%)] and β-anomer 44β [569.5 mg (yield 5.2%)], respectively, both as white powder.

1. washthe chloroform layer was washed with saturated sodium bicarbonate
2. dry with materialThe organic layer dried over anhydrous magnesium sulfate
3. customthe solvent was evaporated in vacuo