N[C:2]1[N:7]=[CH:6][C:5]([S:8]([NH:11][C:12]2[CH:13]=[CH:14][CH:15]=[C:16]3[C:20]=2[NH:19][CH:18]=[C:17]3[Cl:21])(=[O:10])=[O:9])=[CH:4][CH:3]=1.N([O-])=[O:23].[Na+].C(=O)(O)[O-].[Na+]>C(O)(=O)C>[Cl:21][C:17]1[C:16]2[C:20](=[C:12]([NH:11][S:8]([C:5]3[CH:6]=[N:7][C:2]([OH:23])=[CH:3][CH:4]=3)(=[O:10])=[O:9])[CH:13]=[CH:14][CH:15]=2)[NH:19][CH:18]=1Under ice-cooling, into a solution of the compound of Example 33a (100 mg, 0.31 mmol) dissolved in 2 ml of glacial acetic acid was added dropwise 1 ml of an aqueous solution containing 32 mg (0.46 mmol) of sodium nitrite. After stirring for one hour, the mixture was adjusted to about pH 8 by adding an aqueous sodium bicarbonate and further stirred for 10 minutes. The reaction mixture was extracted with ethyl acetate, and the extract was washed with water, dried over magnesium sulfate and concentrated. Then, the residue was purified by silica gel thin layer chromatography, to give 54 mg of the title compound.
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