With respect to the limitations of fossil-based materials, exploration and innovative use of bioresources become increasingly important. Agarose, an abundant seaweed polysaccharide (PS) that is renowned for its thermoreversible gelation, has considerable potential in this context for the preparation of functional biomaterials, e.g., hydrogels and tissue-scaffolds. It is non-ionic and provides a large density of OH-groups, i.e., agarose is well suited for polymer analogues chemical modification.<br/>Tosylated polysaccharides are key-intermediates that can be converted with a vast variety of nucleophiles to yield functional derivatives with specific features. Based on knowledge on the preparation of ‘classical’ PS-derivatives, e.g., derived from cellulose or starch, tosylation of agarose was studied with respect to the effects of the reaction parameters (type of PS-solvent, time, amount of tosylation reagent) on the molecular structure of the products. Tosyl agaroses (TOSA) with high DS<sub>tosyl</sub> ≤ 1.81 were obtained in completely homogeneous reactions and characterized by FT-IR and 1D-/2D-NMR spectroscopy. Despite the structural resemblance of agarose and cellulose, TOSA showed a unique substitution pattern that could be triggered from non-preferential to regioselective tosylation by performing the reaction with or without LiCl. Finally, the nucleophilic displacement reaction of TOSA was studied using azide and ethylendiamine with the aim to yield products (i) for “click-chemistry” approaches, (ii) with specific surface affinity/self-assembling properties. The novel deoxy-agarose derivatives obtained partly showed thermoreversible gelation and will be used for creating functional bio-based materials.

Homogeneous tosylation of agarose as an approach towards functional bio-based materials

249th National Meeting (2015)

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