Isonitrile derivatives of polysaccharides as supports for the covalent fixation of proteins and other ligands

A method for the introduction of side chains containing isonitrile (isocyanide, cyanide, N functional group) on the backbone of polysaccharides and other hydroxylic polymers was developed. The method was based on (a) ionization of some of the hydroxyl groups on the polymer by treatment with a strong base (tert-butoxide) in a polar aprotic solvent (dimethylsulfoxide), and (b) introduction of side chains containing isonitrile groups by nucleophilic attack of the polymeric alkoxide ions on a low molecular weight isonitrile containing a good leaving group in the ω-position, (1-tosyl-3-isocyanopropane). By this method, the side chains containing the -NC functional groups are attached to the polymeric backbone via stable ether bonds. The isonitrile derivatives of cellulose, linear and cross-linked dextran and cross-linked agarose were utilized for the covalent fixation of high and low molecular weight ligands by four-component reactions carried out in aqueous medium, at neutral pH.