Sulfuric Acid → 5-Amino-2-(4-amino-3-fluorophenyl)-7-ethoxycarbonyl-6,8-difluoro-4H-1-benzopyran-4-one

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Reaction Steps

740 mg (1.36 mol) of the above 7-ethoxycarbonyl-6,8-difluoro-2-(3-fluoro-4-pivaloylaminophenyl)-5-pivaloylamino-4H-1-benzopyran-4-one was subjected to the depivaloylation with concentrated sulfuric acid substantially in the same manner as that in Example 87 (2). The resulting solution was adjusted to pH 7 and extracted once with ethyl acetate. The organic layer was washed once with an aqueous saturated solution of sodium chloride and dried over anhydrous sodium sulfate. The solvent was distilled off under reduced pressure, and the residue was purified by silica gel column chromatography (chloroform) and recrystallized from ethyl acetate/n-hexane to give 259 mg of Compound 92 (yield: 50%) .

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