N-Acetyl-β- -glucosamine is an ubiquitous glycan constituent in living organisms. On the one hand, it is widely encountered in its 3-O-glycosylated form in structures of highly diverse origins, including hyaluronan, human glycolipids and glycopro-teins, insects, parasites, or bacteria. In particular, 2-N-acyl-3-O-substituted-β–glucosamines are major components of the cell wall peptidoglycan and bacterial lipid A. On the other hand, N-acetyl-β- -glucosamine residues are often present in their 4-O-or 6-O-substituted forms. These substitution patterns are also highly diversied, both in terms of the nature of substitutions and species in which they occur. For example, β-(1→6)-linked poly-N-acetyl–glucosamine has been iden-tied as a conserved component of major bacterial, fungal, and protozoal parasites.
