Synthesis of an Exhaustive Library of Naturally Occurring Galf-Manp and Galp-Manp Disaccharides. Towards Fingerprinting According to the Ring Size by Advanced Mass Spectrometry-Based IM-MS and IRMPD.

Nature offers a huge diversity of glycosidic derivatives. Amongst numerous structural modulations, the nature of the ring size of hexosides may induce significant differences on both biological and physicochemical properties of the glycoconjugate of interest. On this assumption, we expect that small disaccharides bearing either a furanosyl entity or a pyranosyl residue would give a specific signature, even in the gas phase. On the basis of the scope of mass spectrometry, two analytical techniques to register those signatures were considered, i.e. the ion-mobility (IM) and the infra-red multiple photon dissociation (IRMPD), in order to build up cross-linked databases. D-Galactose occurs in natural products in both tautomeric forms and presents all possible regioisomers when linked to D-mannose. Consequently, the four reducing Galf-Manp disaccharides as well as the four Galp-Manp counterparts were firstly synthesized according to a highly convergent approach, and IM-MS and IRMPD-MS data were secondly collected. Both techniques used afforded signatures, specific to the nature of the connectivity between the two glycosyl entities.