In order to prepare new ion-exchange materials, we proposed two methods for the synthesis of N-(1,2-dicarboxyethyl)chitosan from chitosan via polymer-analogous transformations: by nucleophilic addition—elimination with dimethyl ester of 2-oxosuccinic acid followed by reduction with sodium borohydride and by nucleophilic substitution with 2-bromosuccinic acid under the “synthesis in gel” conditions. When chitosan is treated with the 2-oxosuccinic acid derivatives, cross-linking of the polymer with the formation of amide functional groups occurs along with functionalization and leads to insoluble products. When sodium 2-bromosuccinate was used, water-soluble N-(1,2-dicarboxyethyl)-chitosan with the degree of functionalization up to 0.35 was synthesized. The ion-exchange properties were studied for the polymer additionally crosslinked with epichlorohydrin. The total static exchange capacity with respect to an equimolar mixture of CuII, NiII, CoII, and ZnII ions in an ammonium acetate buffer solution at pH 6.5 was 2 mmol g−1. The degree of extraction of the metal ions decreases in the series CuII (47%) > NiII (30%) > > ZnII (13%) > CoII (10%).