Lithium diisopropylamide → Dihydro-7-(2-acetylthioethyl)-1-pyrindine-6,6-bisphosphonic acid, tetraethyl ester

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Reaction Steps

To a solution of dihydro-1-pyrindine-6,6-bisphosphonic acid, tetraethyl ester (7.0 mmol) [prepared as described in Example A, Part I] in anhydrous THF (100 ml) at -78° C. under argon is added dropwise a pregenerated solution of lithium diisopropyl amide (7.0 mmol) in THF (10 ml). After stirring 30 minutes, to this is added 2-acetylthio-1-iodoethane (7.5 mmol) in THF (25 ml). The reaction mixture is stirred at -78° C. for 5 hours then allowed to warm to room temperature and stirred overnight. The reaction is quenched by the addition of saturated aqueous ammonium chloride and then extracted with diethyl ether. The organic layers are combined, dried over sodium sulfate, filtered and concentrated under reduced pressure. The desired product is purified by flash chromatography using a 5-10% isopropanol in methylene chloride gradient on silica gel.

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