Determination of the side-products formed during the nitroxide-mediated bleach oxidation of glucose to glucaric acid

The side products formed in the TEMPO-mediated oxidation of glucose to glucaric acid were determined by GC. Next to glucaric acid, gluconic acid, the intermediate in the oxidation, the degradation products, oxalic acid, tartronic acid, meso- (erythraric) and dl-threaric (tartaric) acid were detected. Chiral GC determined the dl-tartaric acid to be non-racemic mixtures of l- and d-tartaric acids, with inverse d/l-ratios depending on the oxidation of d- or l-glucose. The origin of all degradation products is rationalized. This study details a fast screening method to optimize the reaction conditions toward minimal degradation.