C([NH:4][C:5]1[CH:6]=[C:7]([CH:11]=[CH:12][N:13]=1)[C:8]([OH:10])=[O:9])(=O)C.CO[C:16]1C=CC(CN2N=NC(CC(OCC)=O)=N2)=C[CH:17]=1.S(=O)(=O)(O)O.C(=O)([O-])O.[Na+]>C1(C)C=CC=CC=1.C(O)C>[NH2:4][C:5]1[CH:6]=[C:7]([CH:11]=[CH:12][N:13]=1)[C:8]([O:10][CH2:16][CH3:17])=[O:9]2-(Acetylamino)isonicotinic acid (13 g, 73.60 mmol) synthesized by the method of Example 7, (A) was added with ethanol (50 ml) and toluene (150 ml) and heated to 100-110° C. The mixture was added dropwise with concentrated sulfuric acid (7 ml) and heated for 11 hour with stirring. The reaction solution was returned to room temperature and poured into saturated aqueous sodium hydrogencarbonate cooled with ice. The mixture was extracted with chloroform and the collected organic layer was dried over magnesium sulfate and concentrated under reduced pressure to obtain 7.6 g (23% for the two steps) of the title compound as pale yellow crystals without purification.
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