[Cl:1][C:2]1[CH:24]=[CH:23][C:5]([C:6]([C:8]2[N:12]([CH3:13])[C:11]([CH2:14][C:15]([OH:17])=[O:16])=[C:10](C(O)=O)[C:9]=2[O:21][CH3:22])=[O:7])=[CH:4][CH:3]=1.FC(F)(F)C(O)=O>>[Cl:1][C:2]1[CH:3]=[CH:4][C:5]([C:6]([C:8]2[N:12]([CH3:13])[C:11]([CH2:14][C:15]([OH:17])=[O:16])=[CH:10][C:9]=2[O:21][CH3:22])=[O:7])=[CH:23][CH:24]=1According to scheme (b), the precursor of formula IIb is decarboxylated under acidic, mild conditions. For example, 5-(p-chlorobenzoyl)-3-hydroxycarbonyl-4-methoxy-1-methylpyrrole-2-acetic acid or its corresponding di(t-butyl) ester is treated with refluxing trifluoroacetic acid to afford 5-(p-chlorobenzoyl)-4-methoxy-1-methylpyrrole-2-acetic acid. Other acids may also be used. For example, those listed below in Table III.
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