Spontaneous acetyl group migration between xylose and arabinose in arabinoxylan-derived oligosaccharide

Abstract

Previously, a synthetic β-1,4-xylooligosaccharide having the non-reducing-end xylopyranosyl residue both acetylated and arabinosylated was reported to undergo an acetyl group migration [Bella et al., 2023]. This process was further investigated in this work by NMR spectroscopy. It was found that the spontaneous transesterification reaction was regioselective involving the acetyl group transfer from position O-2 of the xylopyranosyl residue exclusively to position O-2 of the α-l-arabinofuranosyl moiety linked to position 3 of the same xylose. Finally, the acetyl group migration resulted in an equilibrium, where the arabinose 2-acetate predominated over the xylose 2-acetate. This is the first report of acetyl group migration between different pentoses, which are in addition, glycosidically interconnected. This intramolecular transacetylation may have significant consequences on the structure of acetylated fragments generated in arabinoxylan hydrolyzates. In turn, it can broaden enzyme repertoire related to biotechnological exploitation of the esterified arabinoxylan fragments, e.g., through its enzyme-catalyzed deesterification of 2-acetylated arabinose moiety.