title: Water-soluble aminocurdlan derivatives by chemoselective azide reduction using NaBH4.
abstract: Water-solubility can often enhance the utility of polysaccharide derivatives, for example in pharmaceutical and biomedical applications. Synthesis of water-soluble aminopolysaccharides, particularly those bearing other sensitive functional groups, can be a challenging endeavor. Curdlan is a bioactive β-1,3-glucan with considerable promise for biomedical applications. Aminocurdlans are intriguing target molecules for study of, for example, their interactions with the proteins that form tight junctions between enterocytes. Herein we report the preparation of two water-soluble 6-aminocurdlans starting from 6-bromo-6-deoxycurdlan. The 6-bromide was first displaced by nucleophilic substitution with sodium azide in dimethyl sulfoxide. The O-2 groups were acylated with hydrophilic oligo (ethylene oxide) esters, so as to enhance aqueous solubility. The resultant 6-azido-6-deoxy-2,4-di-O-trioxadecanoylcurdlan was then treated with excess sodium borohydride to reduce the azide; unexpectedly, the water-soluble product proved to be the amide, 6-trioxadecanamido-6-deoxycurdlan. Regioselectivity and degree of substitution (DS) of those derivatives were characterized by means of (1)H NMR, (13)C NMR and FTIR-spectroscopy, elemental analysis, and titration. Alternatively, direct borohydride reduction of the parent 6-azido-6-deoxycurdlan afforded 6-amino-6-deoxycurdlan that was also water-soluble.
authors: Macromolecules and Interfaces Institute, Virginia Tech, Blacksburg, VA 24061, United States.
authors: Ruoran
authors: R
authors: Zhang
authors: Macromolecules and Interfaces Institute, Virginia Tech, Blacksburg, VA 24061, United States; Department of Sustainable Biomaterials, College of Natural Resources and Environment, Virginia Tech, Blacksburg, VA 24061, United States. Electronic address: kjedgar@vt.edu.
authors: Kevin J
authors: KJ
authors: Edgar
mesh_terms: D001386:Azides / Q000737:chemistry*; D001894:Borohydrides / Q000737:chemistry*; D010084:Oxidation-Reduction; D012995:Solubility; D013237:Stereoisomerism; D014867:Water / Q000737:chemistry*; D047071:beta-Glucans / Q000138:chemical synthesis / Q000737:chemistry*
chemical_list: D001386:Azides; D001894:Borohydrides; D047071:beta-Glucans; D014867:Water; C038459:curdlan; C025364:sodium borohydride
keywords: Amidocurdlan; Aminocurdlan; Regioselectivity; Sodium borohydride; Water-soluble