Stoichiometric C6-oxidation of hyaluronic acid by oxoammonium salt TEMPO+Cl- in an aqueous alkaline medium

This paper reports the selective oxidation of hyaluronic acid (HA) by stoichiometric quantity of 2,2,6,6-tetramethylpiperidine-1-oxoammonium chloride (TEMPO) in aqueous alkaline medium. High efficiency of the HA oxidation and quantitative yield of carboxy-HA per starting TEMPO, as well as unusual behavior of the oxidation system generating an oxygen upon alkali-induced oxoammonium chloride decomposition are demonstrated. The scheme for HA oxidation involving both TEMPO and oxygen produced upon the TEMPO+Cl- decomposition and/or air oxygen is proposed. For comparison, the data on stoichiometric oxidation of such substrates as dermatan sulfate, water-soluble potato starch, methyl 2-acetamido-2-deoxy-beta-D-glucopyranoside and ethanol are presented. (C) 2015 Elsevier Ltd. All rights reserved.