Kinetic Studies of Acetyl Group Migration between the Saccharide Units in an Oligomannoside Trisaccharide Model Compound and a Native Galactoglucomannan Polysaccharide

Mechanism of Acyl Group Migration in Carbohydrates

Acyl group migration has been the subject of several studies. Such migration processes may cause problems during synthesis, isolation, and purification of different acyl-bearing compounds, and have biological relevance, for example, in the metabolism of pharmaceuticals. Considering the recent evidence of acyl group migration being possible even over glycosidic bonds, it could be hypothesized to be involved also in the regulation of biological activity of natural polysaccharides in the host cells. Migrations are mostly observed in carbohydrates, typically having several hydroxyl groups near each other. Several studies have investigated the migration in a single or only a few different carbohydrate molecules, providing different suggestions for the mechanisms of migration, seldom supported by comprehensive computational investigations. In this concept article we discuss the recent progress on the mechanistic aspects of acyl group migration, with carbohydrates in particular focus.

Acetyl Group Migration in Xylan and Glucan Model Compounds as Studied by Experimental and Computational Methods

It was recently demonstrated by us that acetyl groups in oligosaccharides can migrate not only within one saccharide unit but also between two different saccharide units. Kinetics of this phenomenon were previously investigated in both mannan model compounds and a naturally occurring polysaccharide. In addition to mannans, there are also several other naturally acetylated polysaccharides, such as xyloglucans and xylans. Both xyloglucans and xylans are some of the most common acetylated polysaccharides in nature, displaying important roles in the plant cells. Considering the various biological roles of natural polysaccharides, it could be hypothesized that the intramolecular migration of acetyl groups might also be associated with regulation of the biological activity of polysaccharides in nature. Consequently, a better understanding of the overall migration phenomenon across the glycosidic bonds could help to understand the potential role of such migrations in the context of the biological activity of polysaccharides. Here, we present a detailed investigation on acetyl group migration in the synthesized xylan and glucan trisaccharide model compounds by a combination of experimental and computational methods, showing that the migration between the saccharide units proceeds from a secondary hydroxyl group of one saccharide unit toward a primary hydroxyl group of the other unit.