Pyridine → 5'-O-(4,4'-dimethoxytrityl)-2'-O-(2-cyanoethoxymethyl)uridine

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Reaction Steps

2′-O-(2-Cyanoethoxymethyl)uridine (14 g, 43 mmol) was subjected to azeotropic distillation with pyridine, and then was dried with a vacuum pump for 30 minutes. The residue was dissolved in 300 mL of THF, and 68 g of pyridine (856 mmol), and 20 g of molecular sieve 4 A was added under an argon atmosphere, and the mixture was stirred for 10 minutes. To the solution was added 19.6 g of 4,4′-dimethoxytritylchloride (57.8 mmol) by 3 portions every 1 hour, and the mixture was further stirred for 1 hour. After 10 mL of methanol was added and the reaction solution was stirred for 2 minutes, the reaction solution was filtrated with a celite, and was washed with ethyl acetate. After concentrating the filtrate, the residue was dissolved in ethyl acetate, and was washed with a saturated aqueous sodium bicarbonate solution. After the organic layer was washed with saturated brine and dried over anhydrous magnesium sulfate, the solvent was distilled off. The obtained residue was purified by silica gel chromatography to obtain the objective compound (26.5 g, yield 98%).

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