[NH:1]1[C:9]2[C:4](=[CH:5][CH:6]=[CH:7][CH:8]=2)[CH:3]=[C:2]1[C:10]([O:12]C)=[O:11].C(=O)([O-])[O-].[Cs+].[Cs+].CS(O[CH2:25][CH2:26][CH2:27][CH2:28][O:29][CH3:30])(=O)=O>CC(N(C)C)=O>[CH3:30][O:29][CH2:28][CH2:27][CH2:26][CH2:25][N:1]1[C:9]2[C:4](=[CH:5][CH:6]=[CH:7][CH:8]=2)[CH:3]=[C:2]1[C:10]([OH:12])=[O:11]Methyl 1H-indole-2-carboxylate (0.67 g), cesium carbonate (1.9 g) and 4-methoxybutyl methanesulfonate (0.70 g) were suspended in DMA (20 ml), and the suspension was stirred at 60° C. for 4 hr. The reaction mixture was concentrated under reduced pressure, the residue was diluted with water, and the mixture was extracted with ethyl acetate. The extract was washed with saturated brine, dried over anhydrous magnesium sulfate and concentrated under reduced pressure. The obtained residue was subjected to silica gel chromatography, and a fraction eluted with ethyl acetate-hexane (0:10-4:6) was concentrated under reduced pressure. The obtained residue was dissolved in methanol (10 ml), 4N aqueous sodium hydroxide solution (5 ml) was added, and the mixture was heated at 80° C. for 2 hr. The mixture was allowed to cool to room temperature, acidified with 1N aqueous hydrochloric acid and extracted with ethyl acetate. The extract was washed with saturated brine, dried over anhydrous magnesium sulfate and concentrated under reduced pressure to give the object product (0.77 g).
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