[NH2:1][C:2]1[CH:3]=[C:4]([CH:8]=[CH:9][CH:10]=1)[C:5]([OH:7])=[O:6].C(=O)(O)[O-].[Na+].Cl[C:17]([O:19][CH2:20][CH3:21])=[O:18]>Cl>[CH2:20]([O:19][C:17]([NH:1][C:2]1[CH:3]=[C:4]([CH:8]=[CH:9][CH:10]=1)[C:5]([OH:7])=[O:6])=[O:18])[CH3:21]A mixture composed of 3-aminobenzoic acid (20 g), 1 M aqueous sodium bicarbonate solution (730 cc) and ethyl chloroformate (14 cc) is left with stirring for 30 minutes at 5° C. 2.5 N hydrochloric acid (300 cc) is then added to the reaction mixture. The precipitate formed is separated by filtration, washed with water (3×200 cc) and dried at 40° C. under reduced pressure (0.07 kPa). 3-Ethoxycarbonylaminobenzoic acid (25 g), m.p. 198° C., is thereby obtained.
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