Solid state structure of sodium β-1-thiophenyl glucuronate identifies 5-coordinate sodium with three independent glucoronates

Glucuronic acid is a key component of the glycosaminoglycans (GAGs) Chrondroitin Sulfate (CS), Heparin/Heparan sulfate (HS) and Hyaluronic Acid (HA), as well an important metabolite derivative. In biological systems the carboxylate of uronic acids in GAGs is involved in important H-binding interactions, and the role of metal coordination, such as sodiated systems, has indications associated with a number of biological effects, and physiological GAG-related processes. In synthetic approaches to GAG fragments, thioglycoside intermediates, or derivatives from these, are commonly employed. Of the reported examples of sodium coordination in carbohydrates, 6-coordinate systems are usually observed often with water ligands involved, Herein we report an unexpected 5-coordinate sodiated GlcA crystal structure of the parent GlcA, but as a thioglycoside derivative, whose crystal coordination differs from previous examples, with no involvement of water as a ligand and containing a distorted trigonal bypramidal sodium with each GlcA having five of 6 oxygens sodium-coordinated. [Display omitted] •Unusual 5-coordinate sodiated GlcA thioglucoside crystal structure with all ligands from carbohydrate oxygens.•The GlcA thioglycoside is a new derivative.•Shows 3 sodium environments per sugar, two chelated (one each from the carboxylate) and the third only monocoordinate O3.•New example of geometries that are accessible for the GlcA fragment which may be of relevance in biological GlcA structures.