Boronic ester-containing materials have been used in diverse settings including delivery vehicles, chromatographic media, and molecular sensors. An important class of these materials feature aryl boronic esters to confer oxidation-sensitivity, either by modulation of optical properties or through generation of self-immolating groups. Despite their widespread use, these boronic esters are nearly always made using a single diol. The use of pinacol in this role is so common that it is goes unquestioned, leaving huge swaths of chemical space unexplored. We have found that the choice of esterifying diol has important consequences for the properties of aryl boronic esters, especially in the context of polysaccharide-based materials. To explore these effects, arylboronic pinanediol ester groups were appended to polysaccharide backbones via carbonate linkages to generate organic-soluble polymers. The boronic esters on these polymers are susceptible to H<sub>2</sub>O<sub>2</sub>-triggered degradation. NMR-based reaction profiling was used to confirm that this degradation occurs by the expected mechanism: after oxidation of the C–B bond, 1,6-elimination removes the modifying groups, leading finally to the dissolution of the native polysaccharide. After processing into microparticles, their biocompatibility and ability to load with bioactive molecules was confirmed. Colorimetric quantification of polysaccharide release allowed for measurement of degradation kinetics at biologically relevant peroxide and particle concentrations. Finally, evaluation as a delivery vehicle for prophylactic immunotherapy of melanoma was carried out in mice. Beyond improving the properties of a particular class of materials, this work may have implications for improving and fine-tuning the wide range of already known boronic ester-containing materials.

Processable boronate-modified polysaccharides through high stability boronic esters

256th National Meeting (2018)

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