A 4-O-methylglucuronoxylan was converted into a hexenuronoxylan at high temperature and alkalinity similar to the conditions used during kraft pulping. The hexenuronoxylan was hydrolysed with enzymes, and acidic xylooligosaccharides were separated from the hydrolysate by anion-exchange and size-exclusion chromatography. The primary structure of the two main hexenuronic acid-substituted xylooligosaccharides (a tetramer and a pentamer) was determined by two-dimensional 1H and 13C NMR spectroscopy. The 4-deoxy-hexenutronic acid is not stable under the acid hydrolysis step of conventional carbohydrate analysis. Here, we have identified the acidic degradation products of 4-deoxy-hexenuronic acid by NMR spectroscopy. Two degradation pathways were observed, both resulting in a furan derivative.
Teleman, A., Hausalo, T., Tenkanen, M., & Vuorinen, T. (1996). Identification of the acidic degradation products of hexenuronic acid and characterisation of hexenuronic acid-substituted xylooligosaccharides by NMR spectroscopy. Carbohydrate Research, 280(2), 197-208. https://doi.org/10.1016/0008-6215(95)00309-6