55750-63-5

6066-82-6

55750-53-3

55750-63-5

Under nitrogen protection, 4.7 g (22 mmol) of 6-maleimidohexanoic acid (MC) and 25 g (22 mmol) of N-hydroxybutanediimide (HOSu) were dissolved in 50 ml of acetonitrile. Another 4.5 g (22 mmol) of N,N'-dicyclohexylcarbodiimide (DCC) was dissolved in 25 ml of acetonitrile and the internal temperature was maintained. The DCC solution was slowly added dropwise to the reaction mixture at 0°C. The reaction mixture was stirred at 0 °C for 2 h. The reaction was then brought to room temperature and continued overnight. After completion of the reaction, the precipitate was removed by filtration and the filter cake was washed with acetonitrile (10 ml x 3). The filtrates were combined and concentrated to dryness under reduced pressure. The resulting oily product was dried under reduced pressure for 6 h at room temperature to give 6.4 g of a light brown solid, i.e., succinimidyl 6-(maleimido)hexanoate, in 95% yield.