Chemical modifications of 1→4-2-amino-2-deoxy-α-d-galactan

Oxidation of 1→4-2-amino-2-deoxy-α-d-galactan (poly-α-d-galactosamine) with nitrogen oxides allowed the formation of a carboxyl group at the C-6 position. The carboxylated polysaccharide by acetylation afforded a derivative similar to the antigenic Vi polysaccharide of Salmonella typhi. The reaction of the modified poly-α-d-galactosamine with caprolactam assisted by carbodiimide introduced at the C-6 position a secondary amide function with a new terminal acidic group. The caproic acid residue was used as a linker for the conjugation of the modified poly-α-d-galactosamine with tetanus toxoid and with bovine serum albumin.