[O:1]=[C:2]1[N:6]([CH2:7][C:8]2[CH:17]=[CH:16][C:11]3[NH:12][C:13](=[O:15])[NH:14][C:10]=3[CH:9]=2)[C:5]2[CH:18]=[C:19]([C:22]([O:24]C)=[O:23])[CH:20]=[CH:21][C:4]=2[O:3]1.Cl>O>[O:1]=[C:2]1[N:6]([CH2:7][C:8]2[CH:17]=[CH:16][C:11]3[NH:12][C:13](=[O:15])[NH:14][C:10]=3[CH:9]=2)[C:5]2[CH:18]=[C:19]([C:22]([OH:24])=[O:23])[CH:20]=[CH:21][C:4]=2[O:3]11.1 g (3.24 mmol) of methyl 2-oxo-3-(2-oxo-2,3-dihydro-1H-benzimidazol-5-ylmethyl)-2,3-dihydrobenzoxazole-5-carboxylate are suspended in 20 ml of water, 30 ml of conc. hydrochloric acid are added, and the mixture is stirred at a bath temperature of 100° C. for 24 h. A further 20 ml of conc. HCl are added, and the reaction mixture is stirred at a bath temperature of 130° C. for 3 days. The suspension is filtered and washed with water, and the residue is dried at 50° C. in a drying cabinet; product: 996 mg; m.p. 230-231° C.; ESI 326; HPLC: Rt=4.24 min (method A).
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