Analysis of neutral isomeric low molecular weight carbohydrates using ferrocenyl boronate derivatization and tandem electrospray mass spectrometry

A new analytical technique for small carbohydrates utilizing the cyclic fer rocenyl boronic esters (F(c)Bors) of several neutral mono- and disaccharide s is demonstrated. Distinction between the diastereomers of mono- and disac charides is obtained. Analysis is by tandem electrospray-mass spectrometry (ES-MS) using a modified ion-source that promotes the preformation of ions, Selection of the molecular ion produced during single-electron oxidation o f the ferrocene moiety of a specific population of saccharide isomers permi ts a variety of collisionally induced dissociation (CID) experiments. The r esultant MS2/MS3 spectra reflect the ensemble of possible cyclic esters in equilibrium. An array of stable cross pyranose ring fragment ions represent ing sequential carbon loss as 30 u is observed. Consequently, the system pr ovides an information-rich set of MSn spectra containing large amounts of s tructural information. Identification of D-glucose (D-Glc), its two commonl y found epimers (D-mannose and D-galactose), and the two major L-diastereom ers of 6-dideoxymonosaccharides, L-fucose (L-Fuc) and L-rhamnose (L-Rhm), a re demonstrated. Selected pairs of disaccharides can be distinguished in te rms of their anomeric linkage by reference to their MS3 spectra. Copyright (C) 2000 John Wiley & Sons, Ltd.