Chemical ionization mass spectra of acetals of beta-D-glycopyranosylnitromethanes

O-Isopropylidene and O-benzylidene acetals of common 2, 6-anhydro-1-deoxy-1-nitroalditols (beta-D-glycopyranosylnitromethanes) derived from D-glucose, D-galactose and D-mannose were studied by chemical ionization mass spectrometry (CIMS) using methane, isobutane, ammonia or pyridine as reaction gas. Production of [M+H](+) adduct ions dominates in the case of methane or isobutane possessing proton affinity values PA = 552 or 683 kJ mol(-1), respectively. The collision-induced dissociation time-of-flight product ion spectra of [M+H](+) ions differ characteristically according the stereochemical arrangement of the pyranoid ring. These differences can be helpful when assigning stereochemical arrangements for the pyranoid ring. The dominant process in ammonia (PA = 853 kJ mol(-1)) CIMS for most of the compounds studied is the production of the cluster ions [M+NH(4)](+). The cluster [M+pyridineH](+) ions are observable only for substances possessing the O-benzylidene group (PA of pyridine = 924 kJ mol(-1)). Copyright 2000 John Wiley & Sons, Ltd.

Electron ionization mass spectra of acetals of beta-D-glycopyranosylnitromethanes

O-Isopropylidene and O-benzylidene acetals of common 2, 6-anhydro-1-deoxy-1-nitroalditols (beta-D-glyco- pyranosylnitromethanes) derived from D-glucose, D-galactose and D-mannose were studied by electron ionization (EI) mass spectrometry. Fragment pathways of the title compounds were studied using accurate mass measurements, collision-induced dissociation, B/E and B2/E measurements of selected ions and mass spectra of O-deuterium-labelled compound. The fragmentation pathways and some differences found among the mass spectra of stereoisomers are discussed. Noteworthy is the splitting off of the (.)NO(2) radical and elimination of acetone from the molecular ions of 4, 6-O-benzylidene-2, 3-O-isopropylidene-beta-D-galactopyranosylnitromethane. This fragmentation route of relatively high abundance was not observed in the case of D-gluco and D-manno analogues. The differences in the EI mass spectra of stereoisomers may help to provide some information serving for the estimation of the stereochemical arrangement of compounds of this type. Copyright 1999 John Wiley & Sons, Ltd.

Stobadine is a potent modulator of endogenous endothelin-1 in human fibroblasts

Binding of endothelin (ET) peptides to their respective receptors with resulting proliferation of vascular smooth muscle has been implicated in the pathogenesis of arterial hypertension and atherosclerosis. Recently it was hypothesized that endothelin- (ET-1) bound to its two membrane receptors (ET(A) and ET(B)) continues to activate signal transducing proteins in cells. It was also shown that pyridoindole stobadine stabilized lysosomal membranes in myocardium in early ischemia. Therefore we decided to study the effects of stobadine on specific, subtype-selective binding and subsequent degradation of human, synthetic [125I]-ET-1 in human fibroblasts (HF). Our results indicate that stobadine significantly potentiated ET-1 binding by reductive ET(B) selective degradation of ET-1 in HF. Hence, it is very plausible that stobadine may modulate endogenous endothelin and its intracellular mitogenic and chemotactic factors, principally by affecting two presumably related processes, participating in the proliferative and mitogenic response, (1) potentiation of signal trasduction from ET(A) receptors, and (2) subtype-ET(B) selective intracellular processing.