[NH2:1][C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][C:3]=1[NH:8][C:9]([CH2:11][CH2:12][CH2:13][N:14]([CH3:25])[C:15](=[O:24])[O:16][CH2:17][C:18]1[CH:23]=[CH:22][CH:21]=[CH:20][CH:19]=1)=O.C1(C)C=CC(S(O)(=O)=O)=CC=1.O>C1(C)C=CC=CC=1>[N:8]1[C:3]2[CH:4]=[CH:5][CH:6]=[CH:7][C:2]=2[NH:1][C:9]=1[CH2:11][CH2:12][CH2:13][N:14]([CH3:25])[C:15](=[O:24])[O:16][CH2:17][C:18]1[CH:23]=[CH:22][CH:21]=[CH:20][CH:19]=120.1 g (59 mmol) of benzyl [3-[(2-aminophenyl)carbamoyl]propyl]methylcarbamate are dissolved in 450 ml of toluene and treated with 7 g (37 mmol) of p-toluenesulphonic acid. The reaction mixture is thereafter heated to reflux for 2 hours, whereby the water formed is removed from the reaction mixture by means of a water separator. After evaporation and dissolution of the residue in ethyl acetate the solution is washed twice with saturated aqueous sodium bicarbonate solution and twice with saturated aqueous soiium chloride solution. The organic phase is dried over magnesium sulphate and evaporated. Chromatography of the crude product on silica gel with ethyl acetate as the elution agent yields 11 g (58%) of benzyl [3-(2-benzimidazolyl)propyl]methylcarbamate, m.p. 83°-86°.
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