Citric Acid → 6-[4-Methoxy-3-(3,3,6,6-tetramethyl-1,8-dioxo-2,3,4,5,6,7,8,9-octahydro-1H-xanthen-9-yl)phenyl]-N-(methylsulfonyl)pyridine-2-carboxamide

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Reaction Steps

1,1′-Carbonyldiimidazole (54.6 mg, 0.34 mmol) was added to a solution of the 6-[4-methoxy-3-(3,3,6,6-tetramethyl-1,8-dioxo-2,3,4,5,6,7,8,9-octahydro-1H-xanthen-9-yl)phenyl]pyridine-2-carboxylic acid produced in Example 1-2 (130 mg, 0.26 mmol) in DMF (2.6 ml) at room temperature, and the mixture thus obtained was then stirred at the same temperature as above for 2 hours. Thereafter, methanesulfonamide (32.1 mg, 0.34 mmol) and 1,8-diazabicyclo[5.4.0]undec-7-ene (0.050 ml, 0.34 mmol) were added to the resulting solution at room temperature, and the mixture thus obtained was then stirred at the same temperature as above for 71 hours. Thereafter, an aqueous solution of citric acid (249 mg, 1.30 mmol) was added to the reaction solution, and the mixed solution was then extracted with ethyl acetate. The organic layer thus obtained was washed with water, and was then dried over anhydrous sodium sulfate. The solvent was distilled away under reduced pressure, and the residue thus obtained was then purified by silica gel column chromatography (methanol:dichloromethane=0:1 to 1:9, v/v). Ethanol was added to the fraction thus obtained, and the generated solid was then collected by filtration and dried to obtain the title compound (84.4 mg, yield: 56%).

Provenance & Evidence