Scheme 2. Schematic of synthetic route for Dex-Mal. The scheme 2 presents the synthetic procedure to synthesize dextran (MW = 100 kDa) with maleimide groups (Dex-Mal). Briefly, Dex-Mal was prepared through DCC mediated esterification of the hydroxyl group of the dextran with N-maleoylamino acid, which was obtained through a procedure reported previously. Typically, N-maleoylamino acids (0.72 g, 3.1 mmol) was dissolved in 20 mL DMSO followed by addition of DPTS (0.145 g, 0.45 mmol) and DCC (0.96 g, 4.65 mmol). Dextran (0.92 g, 5.15 mmol anhydroglucose (AHG) units) was dissolved in 10 mL DMSO and added to the reaction mixture slowly. After stirring for 24 h at room temperature, the formed N,N'-dicyclohexylurea salt was removed by filtration, and the crude product was obtained by precipitation in cold ethanol. The precipitate was collected by filtration and washed with ethanol and then dissolved in water and purified by ultrafiltration.