Novel thiol- amine- and amino acid functional xylan derivatives synthesized by thiol-ene reaction

In the present work, novel thioether xylans were synthesized via a simple procedure using water as solvent. First, allyl groups were introduced on the backbone of xylan by etherification of allyl chloride in aqueous alkaline conditions at 40 °C, providing degree of substitution (DS) values up to 0.49. On the second step, the allyl groups were reacted with thioacetic acid, cysteamine hydrochloride or cysteine providing novel thiol-, amine- or amino acid functionalized xylans. The presented modular approach offers broad possibilities for developing new polysaccharide based materials. The thioacetic acid - ene reaction is reported for the first time for polysaccharide modification, yielding a protected thiol that can be stored at atmospheric conditions and can be deprotected by simple hydrolysis just prior to use, providing a versatile water soluble polythiol. The free thiol-groups were utilized for hydrogel formation through thiol-thiol oxidative coupling, allowing good control over the hydrogel shape, such as 3D hydrogel scaffolds and cross-linked foams. Further, the thiol-containing xylan was used to modify filter paper surface by a simple dipping method, which provides a novel and convenient way for introducing thiol-functionality on paper surface.