Selectivity is a key issue in modification of abundant, natural polysaccharides. In order to exploit the diverse structures, functionality, and renewable nature of these useful materials, it is essential that we achieve a high level of regio- and chemoselectivity in polysaccharide modification. We must achieve this despite the presence of multiple, chemically non-equivalent groups that have similar reactivity. We must overcome the overall low reactivity of polysaccharide functional groups, due largely to limited approach angles, and the limited variety of solvents that will dissolve most natural polysaccharides. We will describe herein two approaches that have recently been developed in our lab, where we achieve substantial selectivity, through different approaches, and obtain derivatives with useful structures and function. In both cases, the modifications permit formation of architectures that may have considerable utility. We will describe an approach to selective oxidation of polysaccharides, that permits introduction either of carboxylic acids or ketone groups, depending on the details of the method used. Some of these products have potential use in amorphous solid dispersion of otherwise poorly soluble drugs, while others are ideally constructed as component backbones of polymeric prodrugs, or as precursors to dynamic, self-healing, readily processes hydrogels. We will also discuss new approaches to conversion of polysaccharides and their derivatives to excellent precursors to di- and triblock copolymers, thereby enabling useful properties by stitching together segments of dissimilar properties.

Selective modification of polysaccharides: Towards controlled and useful architectures

256th National Meeting (2018)

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