Structure of the Products of 4-Mercaptobutyric Acid Hydrazide Condensation with a Series of Aldoses as Promising Ligands of Gold Glyconanoparticles for Biomedical Application

The structure of previously unknown condensation products of a series of aldoses (N-acetyl-D-glucosamine, D-mannose, D-galactose, and L-fucose) with 4-mercaptobutyric acid hydrazide, promising glyco-ligands of noble metal nanoparticles, has been studied by means of ¹H and ¹³C NMR spectroscopy. It has been shown that the derivatives of N-acetyl-D-glucosamine, D-mannose, and D-galactose exist as a tautomeric mixture of open hydrazone and cyclic pyranose forms in the solution in DMSO-d₆. The linear hydrazone form is represented by a set of Z′,E′-conformational isomers, differing in the arrangement of substituents relative to the amide C–N bond, in comparable quantities. The condensation product obtained from L-fucose is an exclusively cyclic pyranose structure in the crystalline state and in solutions in DMSO-d₆, represented by a single β-configuration isomer.