4-Chloro-1-(2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl)-indole (300 mg) obtained in Example 1-(3) and 2,3-dihydro-benzo[b]furan-5-carbonyl chloride (171 mg) were dissolved in dichloromethane (9 ml), and thereto was added aluminum chloride (166 mg) at 0° C. After being stirred at same temperature for 2.5 hours, the mixture was poured into ice-water (50 ml), and extracted with chloroform (30 ml) twice. The combined organic layer was washed with a saturated aqueous sodium hydrogen carbonate solution (10 ml) and dried over magnesium sulfate. The insoluble materials were filtered off, and the filtrate was evaporated under reduced pressure to give crude 4-chloro-1-(2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl)indol-3-yl 2,3-dihydrobenzo[b]furan-5-yl ketone (477 mg), which was partially deacetylated. This crude compound was dissolved in chloroform (9 ml), and thereto were added successively pyridine (0.151 ml), acetic anhydride (0.177 ml) and 4-(dimethyl-amino)pyridine (7.6 mg). After being stirred at room temperature for 16 hours, the solvent was evaporated under reduced pressure. The residue was dissolved in ethyl acetate (100 ml), and the mixture was washed with a 10% aqueous copper (II) sulfate solution (10 ml) twice and a saturated aqueous sodium hydrogen carbonate solution (10 ml), and dried over magnesium sulfate. The insoluble materials were filtered off, and the filtrate was evaporated under reduced pressure. The residue was purified by silica gel column chromatography (hexane:ethyl acetate=90:10-60:40) to give 4-chloro-1-(2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl)-indol-3-yl 2,3-dihydrobenzo[b]furan-5-yl ketone (346 mg) as a colorless powder. APCI-Mass m/Z 628/630 (M+H). 1H-NMR (DMSO-d6) δ 1.71 (s, 3H), 1.97 (s, 3H), 1.98 (s, 3H), 2.04 (s, 3H), 3.25 (td, J=8.8, 2.2 Hz, 2H), 4.08-4.14 (m, 2H), 4.30 (ddd, J=9.9, 5.3 and 3.0 Hz, 1H), 4.66 (t, J=8.8 Hz, 2H), 5.28 (t, J=9.8 Hz, 1H), 5.54 (t, J=9.6 Hz, 1H), 5.72 (t, J=9.4 Hz, 1H), 6.32 (d, J=9.0 Hz, 1H), 6.87 (d, J=8.3 Hz, 1H), 7.25 (d, J=7.7 Hz, 1H), 7.35 (t, J=8.0 Hz, 1H), 7.64 (dd, J=8.3, 1.6 Hz, 1H), 7.72 (br, 1H), 7.78 (d, J=8.3 Hz, 1H), 8.03 (s, 1H).
