Synthesis and mass spectral characterization of metal coordinated oligosaccharides

Formation of an N-glycoside between a hexose and diethylenetriamine ( dien) allows introduction of various transition metals to form coordination complexes. The Zn(dien)(N-hexosyl) complexes (where hexosyl = glucosyl, galactosyl, or mannosyl) dissociate by unique pathways when subjected to sequential stages of mass spectrometry (MSn) in a quadrupole ion trap, thus distinguishing the three most common hexoses in mammalian tissue. Similar Zn-dien coordination complexes of 1,3, 1,4, and 1,6 linked disaccharides give dissociation patterns that coincide with the position and anomeric configuration of the O-glycosidic linkage. MSn on 13C labeled, 2H labeled, and deoxy analogues of the diastereomeric monosaccharide complexes are used to probe the dissociation mechanisms.; To apply these methods to oligosaccharides, a partial acid hydrolysis procedure is presented using a cation exchange resin as the acid catalyst. The resulting mono- and disaccharides are allowed to form Zn(dien )(N-glycosyl) complexes that are subsequently analyzed by MS n as above.; The N-glycoside ligands themselves also could be conveniently synthesized and purified. A series of five such ligands was synthesized and structurally characterized. One compound (1,3-N,N-di-beta-D-glucopyranosyl-diethylenetriamine) tested positive for anti-cancer activity in four cancer cell lines, including breast and ovarian cancers. In addition, these synthesized ligands facilitated substitution of a series of transition metals (Co, Ni, Cu, and Zn) for the central coordinating metal cation. The resulting complexes were used to probe the influence of metal coordination on MSn of organic molecules. The results indicate that both coordination number of the metal and coordination geometry play an important role in dictating the observed dissociation pathways.; Finally, a model lipooligosaccharide (LOS) isolated from Salmonella typhimurium and previously uncharacterized LOS from Haemophilus influenzae were examined. Alkali metal coordination followed by MS n was used to determine the monosaccharide sequence and linkages within the oligosaccharide. The overall topology of the structure was determined using a computer algorithm described in this work in conjunction with MS n data of sodiated precursor ions. In addition, partial acid hydrolysis was used to release hexose monosaccharides from the S. typhimurium oligosaccharide, and the stereochemistry of these components was identified using Zn-dien coordination followed by MS n.