Stereospecific decompositions induced by low-energy collision-induced dissociation of MH+ ions of epimeric alkaloids


  • Presented at the 11th Annual Meeting of the French Mass Spectrometry Society, held at Rouen, 20–22 September 1994.


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