[CH2:1]([O:8][C:9]1[CH:10]=[C:11]([CH:15]=[CH:16][C:17]=1[O:18][CH3:19])[C:12](Cl)=[O:13])[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.[NH2:20][CH2:21][CH2:22][CH2:23][C:24]([OH:26])=[O:25].[OH-].[Na+].Cl>O1CCCC1.O>[CH2:1]([O:8][C:9]1[CH:10]=[C:11]([CH:15]=[CH:16][C:17]=1[O:18][CH3:19])[C:12]([NH:20][CH2:21][CH2:22][CH2:23][C:24]([OH:26])=[O:25])=[O:13])[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=114.0 g of 3-benzyloxy-4-methoxybenzoyl chloride are added in one portion at 26° C. to 15.6 g of 4-aminobutyric acid, 12.1 g of sodium hydroxide and 160 ml of ion-free water and subsequently 30 ml of tetrahydrofuran are added dropwise within 10 minutes. After 2 hours, the mixture is acidified with concentrated hydrochloric acid at a temperature below 10° C. The precipitate is separated and stirred with ethyl acetate. The mixture is filtered and the filter cake is washed with ethyl acetate. There is obtained 4-[(3-benzyloxy-4-methoxybenzoyl)amino]butyric acid which, after recrystallisation from ethyl acetate, melts at 156°-158° C.
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