The hemicellulose xylan is well available and sustainable biopolymers, whose unique properties in terms of biocompatibility, bioactivity, and supramolecular self-assembling as well as chemical modification are currently not exploited to their full potential. The present work describes a modular synthesis approach for the chemical derivatization of xylan using xylan phenyl carbonates (XPC) as activated buildings blocks for the preparation of functional xylan carbamates (XC).<br/>Homogeneous synthesis of XPC was achieved using either dipolar aprotic solvents or ionic liquids (IL) as reaction media. Even fully functionalized derivatives with DS of 2 were accessible in good yield. The carbonate groups are introduced first at position 3, which activates the xylan backbone for subsequent derivatization at position 2. The derivatives obtained are well-defined with adjusting molecular structure and reactive towards nucleophilic compounds.<br/>XPC were converted into functional XC by reaction with a broad variety of different amines to demonstrate their versatility as activated intermediates. Non-charged primary and secondary alkyl amines reacted quantitatively with phenyl carbonate moieties in high reaction efficiencies. Thus, it is possible to reliably tailor XC properties by rational design of the molecular structure of XPC. It was also possible to directly convert XPC into novel charged xylan derivatives. Using the same intermediates, both cationic- (ammonium, phosphonium) and anionic (sulfonates, phosphates) groups could be introduced into the polymer backbone. Finally, it is demonstrated that the functionalization step can even be performed under aqueous conditions, e.g., on XPC based nanomaterials, which is particularly relevant for the immobilization of proteins and antibodies.

Xylan phenyl carbonates: An activated building block for modular synthesis of functional xylan derivatives

2019 Spring National Meeting

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