A suspension of methyl 6-[bis(methylsulfonyl)amino]-5-cyclopropyl-2-(4-fluorophenyl)-1-benzofuran-3-carboxylate (2.88 g, 5.98 mmol) in ethanol (50 mL) and water (25 mL) was treated with potassium hydroxide (6.71 g, 120 mmol) and heated at reflux for 1 hour (the suspension went into solution upon heating). The reaction was concentrated under vacuum, water (100 mL) was added and the solution acidified with 2M HCl (50 mL). The resulting precipitate was filtered, washed with 0.5 M HCl, then dissolved in methanol. This solution was evaporated to dryness and azeotroped twice with toluene to give 5-Cyclopropyl-2-(4-fluorophenyl)-6-[(methylsulfonyl)amino]-1-benzofuran-3-carboxylic acid. LCMS (m/z, ES+)=390 (M+H+).
