Gemcitabine → 2'-Deoxy-2',2'-difluorocytidine 5'-ethylenediphosphonate

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Reaction Steps

Ethylenediphosphonic acid (173 mg, 0.91 mmol) was treated with oxalyl chloride (2 mL, as solvent) and anhydrous DMF (0.1 ml, cat.). After heating at reflux for 10 minutes under argon, a solution was obtained and after a further 3 h the reaction mixture was cooled to room temperature and evacuated in vacuo. The residue was co-evaporated with anhydrous acetonitrile (3×10 ml). The residue was dissolved in anhydrous trimethyl phosphate (2 mL), cooled to −15° C. and 2′deoxy-2′,2′-difluorocytidine (93 mg, 0.46 mmol) was added under argon. After stirring for 2 h the reaction mixture was quenched with ice-cold TEAB solution (1.0 M, 5 mL) and stirred for 30 minutes. Purification by HPLC gave 7.8 mg of the titled compound 81.

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