In the present study, three representative residual chromophores recently isolated from highly bleached and aged pulps, 2,5-dihydroxy-w1,4x-benzoquinone (1), 5,8-dihydroxy-w1,4x-naphthoquinone (2), and 2,6-dihydroxyacetophenone (3), were selected to study their effects with regard to cellulose degradation under bleaching conditions, similar to those typically used in the pulp and paper industries.

Summary: The present study describes two approaches to synthesize hexenuronic acid model compounds in which the xylan backbone is replaced by a simple substituent, either methyl or phenyl. To general pathways towards the two products are offered: the first one, starting from glucuronic acid and involving formation and reopening of the 1,6-lactone, was especially suitable to afford the phenyl derivative 8. The second one, by contrast, is more appropriate for the methyl compound 12; it starts from galactose and involves TEMPO oxidation and conversions of the intermediate 1,3-lactone. Both pathways were optimized on a mg scale and subsequently upscaled to afford the targets in gram amounts. The ''detour'' via the methyl glucopyranosiduronate -instead of using the free acid -proved to be crucial in boosting the yield in the elimination step.