[CH2:1]([O:3][C:4]([N:6]1[C:14]2[C:9](=[CH:10][C:11]([Cl:15])=[CH:12][CH:13]=2)[CH:8]=[C:7]1[O:16]C(OCC)=O)=[O:5])[CH3:2].Cl>CN(C)C=O.O>[CH2:1]([O:3][C:4]([N:6]1[C:14]2[C:9](=[CH:10][C:11]([Cl:15])=[CH:12][CH:13]=2)[CH:8]([C:4]([O:3][CH2:1][CH3:2])=[O:5])[C:7]1=[O:16])=[O:5])[CH3:2]To a solution of ethyl-5-chloro-2-[(ethoxycarbonyl)oxy]-1H-indole-1-carboxylate, intermediate 49, (36.87 g, 118.28 mmol) in N,N-dimethylformamide (100 ml) 4-dimethylaminopyridine (14.45 g, 118.28 mmol) was added portionwise at 0-5° C. such that the internal temperature did not exceed 5° C. A thick suspension was obtained, which was repeatedly diluted with N,N-dimethylformamide (total volume: 350 ml) to ease up stirring. After two hours at 0-5° C. a solution of hydrogen chloride (fuming, 37%; 9.8 ml) in water (480 ml) was added at such a rate that the internal temperature could be kept below 15° C. The precipitate was filtered, washed with water at 0-5° C. (2×100 ml) and dried to yield the title compound (27.45 g, 70%) as off-white powder (HPLC purity: 94%). MS (ESI+): 312.2; MS (ESI−): 310.2
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