Under a nitrogen atmosphere, a mixture of 4-[3-(5,6-dimethyl-8-propyl-7H-imidazo[4,5-c]tetrazolo[1,5-a]pyridin-7-yl)propane-1-sulfonyl]benzoic acid (2.26 g, 4.95 mmol) and dichloromethane (50 mL) was cooled to 0° C. Oxalyl chloride (0.95 mL, 10.9 mmol) was added dropwise, and the reaction was stirred for two hours at room temperature. To one-third of the solution was added morpholine (0.43 mL, 4.9 mmol), and the reaction was stirred under nitrogen overnight. Additional morpholine (1.0 mL, 11 mmol) was added, and the reaction was stirred for two hours. A white precipitate formed, which was isolated by filtration, washed with ethyl acetate and water, and then dried for two hours in a vacuum oven at 80° C. to provide 0.75 g of {4-[3-(5,6-dimethyl-8-propyl-7H-imidazo[4,5-c]tetrazolo[1,5-a]pyridin-7-yl)propane-1-sulfonyl]phenyl}morpholin-4-ylmethanone as a white solid.
