Diversity of polysaccharide structures designed by aqueous Ugi-multi-compound reaction

Carboxymethyl ethers of xylan, cellulose, and pullulan could be efficiently modified applying the Ugi-reaction in the “green” solvent water. Using different components, namely an aldehyde, an amine, and an isonitrile, the reaction led to novel polysaccharide derivatives with peptide-like substituents. The reactions were carried out applying 2-methoxyethylamine and propargyl amine, paraformaldehyde and benzaldehyde as well as tert-butylisonitrile at room temperature. The characterization of the products was performed by ¹³C-NMR spectroscopy. In any case, a high conversion of the carboxyl groups could be realized. The products isolated possessed a lower degree of substitution compared to the starting material, which may result from a hydrolytic cleavage of ether bonds. Nevertheless, the results indicated that carboxymethylated polysaccharides are useful starting materials for new polysaccharide derivatives in a toolbox reaction.