STEREOSPECIFIC DECOMPOSITIONS INDUCED BY LOW-ENERGY COLLISION-INDUCEDDISSOCIATION OF MH(+) IONS OF EPIMERIC ALKALOIDS

Several studies have investigated stereochemical effects observed in t he electron ionization and low-energy collision-induced dissociation ( CID) mass spectra of molecular ions from synthetic and natural alkaloi ds, More recently, it has been shown that low-collision-energy CID spe ctra of protonated epimeric alkaloids can yield additional information , For instance, three epimeric tetracyclic alkaloids studied in the pr esent work are characterized by different cis/trans ring junction geom etries and by different configurations of the ethyl group linked to th e C-ring, Low-energy collisional spectra of the epimeric MH(+) ions sh ow large differences depending both on the ring junction geometry and the stereochemistry of the side chain. Interpretation of certain speci fic processes invokes ion-dipole formation, allowing internal electron transfer, Consecutive decompositions have also been scrutinized.