Synthesis and analysis of electrospray ionization-generated five-coordinate diastereomeric Ni-N-glycoside complexes using a quadrupole ion trap mass spectrometer

Five-coordinate Ni N-glycoside complexes, consisting of a single tridentate N-glycoside ligand and a bidentate day ligand coordinated to a central Ni(II) ion, were synthesized for a series of diastereomeric monosaccharides. Following excitation of the precursor ions in a quadrupole ion trap, reproducibly distinct product ion spectra were obtained for each diastereomeric complex. Neutral losses resulted from cross-ring cleavages of the monosaccharide ring and/or losses of a bidentate day ligand. Isotopic labeling studies confirmed which particular carbon centers were lost from the precursor ion as a result of the: cross-ring cleavages. Synthesis of the Ni-N glycoside complex was achieved using as little as 21 mu g of monosaccharide. Production of the representative five-coordinate precursor ion was obtained over a wide range of metal-ligand:monosaccharide molar ratios and product ion spectra remained reproducible over this range. (C) 1999 Elsevier Science B.V.