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

•Oxidation of HA proceeds with quantitative yield of carboxy-HA.•Oxoammonium cation is reduced to hydroxylamine ТЕМРОН and radical ТЕМРО.•Upon alkali-induced TEMPO+Cl− decomposition dioxygen evolution is observed.•Oxidation of НА proceeds with participation of both cation TEMPO+ and molecular oxygen.•Oxidation of dermatan sulfate, water-soluble potato starch, methyl 2-acetamido-2-deoxy-β-d-glucopyranoside and ethanol occurs less effectively. 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-β-d-glucopyranoside and ethanol are presented.