STRUCTURE ELUCIDATION OF EVERNINOMICIN-6, A NEW OLIGOSACCHARIDE ANTIBIOTIC, BY CHEMICAL DEGRADATION AND FAB-MS METHODS

The structural characterization of a new oligosaccharide antibiotic, E verninomicin-6 (EV-6), is described. Detailed fast-atom bombardment ma ss spectrometry (FAB-MS) studies along with NMR and chemical degradati on methods were conducted to elucidate the structure of EV-6. The effe cts of the use of various matrices, including salt addition, on the qu ality of the FAB-MS were explored. The use of 3-nitro benzyl alcohol, dimethyl sulfoxide (DMSO), and NaCl produced the best results: an inte nse sodiated molecular ion plus structurely informative fragmentation. FAB-MS yields information providing the complete sugar sequence infor mation for everninomicins, which is quite valuable to the elucidation of the structure of this complex oligosaccharide antibiotic. In additi on, the results of accurate mass work with the molecular ion are consi stent with the assigned structure. The use of electrospray ionization mass spectrometry (ESI-MS) and ESI-MS/MS for the study of EV-6 was inv estigated and was found to produce an abundant molecular ion with limi ted structural information. These results revealed that EV-6 resembled EV-D quite closely except for the absence of the nitrosugar and the r eplacement on ring g of the -CH2OCH3 group with a -CH2OH group. (C) 19 97 American Society for Mass Spectrometry.