Diisopropylcarbodiimide (364 μL, 2.37 mmol) was added to the dimethylformamide solution of UTP tributylamine salt prepared above in (1), and the mixture was stirred at room temperature for three hours. To the mixture were added the 0.184 M dimethylformamide solution of UMP tributylamine salt prepared above in (2) and a solution of anhydrous magnesium chloride (207.5 mg, 2.179 mmol) in dimethylformamide (4.9 mL), followed by stirring at room temperature for 255 minutes. The resultant reaction mixture was analyzed through HPLC (262 nm). As a result, Up4U (i.e., target product) was found to be produced from UTP at a synthesis yield of 84.2%.
