Trimethylsilyl triflate → (2R,3R,4S,5S)-2-(2-amino-6-chloro-9H-purin-9-yl)-4-(benzoyloxy)-5-[(ethylamino)carbonyl]-tetrahydro-3-furanyl benzoate

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반응 단계

A suspension of 2-amino-6-chloropurine (4.60 g, 27.13 mmol) in 1,1,1-trichloroethane (230 ml) was treated with N,O-bis(trimethylsilyl)acetamide (20 ml, 81.4 mmol). The mixture was heated under reflux for 6 hours. The solution was allowed to cool to room temperature and the solvent was removed under reduced pressure. The residue was treated with a solution of (2S,3S,4R,5R)-5-(acetyloxy)-4-(benzoyloxy)-2-[(ethylamino)carbonyl]tetrahydro-3-furanyl benzoate and (2S,3S,4R,5S)-5-(acetyloxy)-4-(benzoyloxy)-2-[(ethylamino)carbonyl]tetrahydro-3-furanyl benzoate (Preparation 18) (14.39 g, 32.6 mmol) in anhydrous toluene (230 ml) and trimethylsilyl trifluoromethanesulfonate (20 ml, 108.5 mmol). The resulting solution was then heated at 90° C. under a nitrogen atmosphere for 90 minutes. The mixture was cooled to room temperature, diluted with ethyl acetate (250 ml) and washed with a saturated aqueous solution of sodium hydrogen carbonate (350 ml) and then brine (350 ml). The organic layer was separated, dried over anhydrous magnesium sulphate, filtered and evaporated under reduced pressure. The residue was purified by column chromatography on silica gel eluting with dichloromethane:methanol (98:2 by volume) to afford the title compound as a foam (8.1 g).

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