[NH2:1][C:2]1[CH:3]=[C:4]([CH:10]=[CH:11][C:12]=1[NH:13][CH2:14][CH3:15])[C:5]([O:7][CH2:8][CH3:9])=[O:6].[N:16]([O-])=O.[Na+].O.N.C(OCC)(=O)C>C(O)(=O)C>[CH2:14]([N:13]1[C:12]2[CH:11]=[CH:10][C:4]([C:5]([O:7][CH2:8][CH3:9])=[O:6])=[CH:3][C:2]=2[N:1]=[N:16]1)[CH3:15]Ethyl 3-amino-4-ethylaminobenzoate (1.80 g, 9.27 mmol) prepared in the same manner as in the Step 1-1-3 was dissolved in acetic acid (5 ml), and under an ice cooling sodium nitrite (1.28 g, 18.5 mmol) was added to the solution little by little. The mixture was stirred for 10 minutes under a water cooling. The mixture was cooled by ice again and neutralized with a 25% ammonia water. Thereafter, ethyl acetate was added to the mixture, and the resulting mixture was washed with a saturated saline solution and water in order. The washed mixture was dried over anhydrous magnesium sulfate and then concentrated. The residue was purified by silica gel column chromatography (n-hexane:ethyl acetate=3:1 to 1:1) to give the title compound (1.40 g, 69%) as a brown powder.
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