Acetic Anhydride → 6-(4-Fluorobenzyl)-4-methoxy-1-[methyl(methylsulfonyl)amino]-5-oxo-5,6,7,8-tetrahydro-2,6-naphthyridin-3-yl acetate

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Reaction Steps

A solution of N-[6-(4-fluorobenzyl)-4-methoxy-2-oxido-5-oxo-5,6,7,8-tetrahydro-2,6-naphthyridin-1-yl]-N-methylmethanesulfonamide (0.36 g, 0.889 mmol) in acetic anhydride (10 mL) was heated to 110° C. for 3 hours, then evaporated to dryness to give the intermediate 6-(4-fluorobenzyl)-4-methoxy-1-[methyl(methylsulfonyl)amino]-5-oxo-5,6,7,8-tetrahydro-2,6-naphthyridin-3-yl acetate (ES MS (M+1)=452). The crude material was dissolved in methanol (6 mL) and treated with sodium methoxide (30% by weight in methanol, 0.5 mL, 2.6 mmol). After 1 hour, the product mixture was neutralized with 6 N HCl, then concentrated. The residue was partitioned between CHCl3 and 10% KHSO4. The organic extract was dried with Na2SO4, filtered, and concentrated under vacuum to provide the title compound.

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