A solution of 0.320 g of 2-(3-{(3-dimethylcarbamoylmethoxy-5-ethyl-2-fluorophenyl)-[4-(5-methyl-[1,2,4]oxadiazol-3-yl)phenylamino]methyl}-5-oxo-4,5-dihydro-1H-[1,2,4]triazol-1-yl)benzoic acid, 0.098 ml of triethylamine and 0.151 ml of diphenylphosphorylazide in 10 ml of t-butanol was stirred under a nitrogen atmosphere at room temperature for 20 hours and then at 70° C. for 36 hours. After adding 100 ml of ethyl acetate and 50 ml of water to the reaction mixture, the organic layer was dried over anhydrous magnesium sulfate, the desiccating agent was filtered off and the filtrate was concentrated under reduced pressure. The residue was purified by silica gel column chromatography (methanol-ethyl acetate) to give the title compound (0.135 g) as a white solid.
