122555-91-3

5292-43-3

294-90-6

122555-91-3

Under nitrogen protection, 1,4,7,10-tetraazacyclododecane (1 g, 5.81 mmol) was dissolved in anhydrous acetonitrile (20 ml) and cooled to 0 °C. Sodium bicarbonate (1.464 g, 17.44 mmol) was added to the reaction system under stirring conditions. Subsequently, anhydrous acetonitrile solution (10 ml) of tert-butyl bromoacetate (3.4 g, 17.44 mmol) was slowly added through a dropping funnel over a period of 1 hour. The reaction mixture was continued to be stirred at 0 °C for 3 h, followed by raising to room temperature and stirring for 45 h. The progress of the reaction was monitored by thin layer chromatography (TLC) with the unfolding agent being dichloromethane (DCM): methanol (9:1), and the target product had an Rf value of 0.67. Upon completion of the reaction, the reaction mixture was filtered and the filtrate was concentrated to dryness under reduced pressure. The crude product was purified by silica gel column chromatography with the eluent being dichloromethane solution containing 2% methanol to afford tri-tert-butyl 1,4,7,10-tetraazacyclododecane-1,4,7-triacetate (Compound 2) as a white powder in 83.5% yield.