Fosmidomycin → 3-(N-benzoyloxy-N-formylamino)propylphosphonic acid

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Reaction Steps

A solution of benzoyl chloride (700 mg) in dry acetone (6 ml) was added dropwise to a solution of sodium salt of 3-(N-formyl-N-hydroxyamino)propylphosphonic acid (820 mg) in a mixture of water (15 ml) and acetone (15 ml) under ice-cooling, while stirring. During this period, pH of the mixture was kept at around 7.5-7.7 with 1 N aqueous sodium hydroxide solution. The stirring was continued at the same temperature for 10 minutes and then acetone was evaporated under reduced pressure. The resulting aqueous solution was adjusted to pH 3.5 with 1N hydrochloric acid and ether (40 ml) was added thereto. After removal of the precipitated impurities, the aqueous layer was adjusted to pH 1.6 with 1N hydrochloric acid and extracted three times with ethyl acetate (50 ml, 20 ml×2). The combined ethyl acetate layer was washed with saturated aqueous sodium chloride solution, dried over magnesium sulfate and evaporated to dryness to give crystals, which were washed with ether to give crystalline 3-(N-benzoyloxy-N-formylamino)propylphosphonic acid (620 mg). Mp 149°-153° C. (dec.).

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