Charged polysaccharides are important in nature, comprising important primary and secondary cell wall components of all plants, up to 40% by weight of kelp, and comprising nearly all of the complex glycosaminoglycans that are so vital to human health, to cite only a few examples. Charged derivatives of polysaccharides are commercially important as well. Carboxymethyl cellulose (CMC) is the highest volume commercial cellulose ether, useful in cleaning products, oilfield drilling, and many other applications. Hydroxypropyl methyl cellulose acetate succinate (HPMCAS) is one of the most useful polymers for creation of amorphous solid dispersions, which help to enhance aqueous solubility, and thus bioavailability, of otherwise poorly soluble drugs. Synthesis of charged polysaccharides can be very challenging; issues of chemo- and regioselectivity are exacerbated by the relatively unreactive nature of polysaccharides, and by their abundance of similarly reactive hydroxyl groups that are quite difficult to discriminate from one another in terms of reactivity. In addition, approach of charged reagents to polysaccharides that already have substituents of like charge is disfavored, in some cases limiting the amount of charge that can be attained. We will discuss here some of our recent work on applying new chemistries, and some more mature ones, to selective synthesis of charged polysaccharides. In all cases we will describe we see very good chemoselectivity, and in many cases the synthetic design enables us to achieve strong regioselectivity as well. The products are very interesting materials for application in drug delivery, tissue engineering, consumer products, and in many other potential applications.

Putting a charge into polysaccharides

255th National Meeting (2018)

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