[Cl:1][C:2]1[CH:22]=[CH:21][C:5]2[C:6](=[O:20])[C:7]3[C:14]([C:15]([O:17][CH2:18][CH3:19])=[O:16])=[N:13][NH:12][C:8]=3[C:9](=[O:11])[NH:10][C:4]=2[CH:3]=1.[CH3:23]C(O)C>Cl>[Cl:1][C:2]1[CH:22]=[CH:21][C:5]2[C:6](=[O:20])[C:7]3[C:14]([C:15]([O:17][CH:18]([CH3:23])[CH3:19])=[O:16])=[N:13][NH:12][C:8]=3[C:9](=[O:11])[NH:10][C:4]=2[CH:3]=1A solution of 7-chloro-3-(ethoxycarbonyl)pyrazolo[3,4-c][1]benzazepine-4,10(1H,9H)-dione (500 mg, 1.56 mmol), 2-propanol (60 mL), and concentrated hydrochloric acid (3 drops) was subjected to three cycles of partial solvent removal by slow distillation (over 6 hours) followed by overnight reflux. After the third cycle, solvent was removed by rotary evaporation and the crude product was purified by flash chromatography eluting with dichloromethane:2-propanol (95:5-85:15) to yield the title compound as a white solid (256 mg, 48%, m.p. 291° C.). Alternatively, the title compound can be prepared as described in Example 18 shown hereinbelow in Table 1.
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