Mass spectrometry of bis-quinolizidine alkaloids: Lactams of sparteine and α-isosparteine

The mass spectral fragmentations of 2-oxosparteine (lupanine), 2-oxo-α-isosparteine (α-isolupanine), 15-oxosparteine, 17-oxosparteine and 10-oxosparteine (aphylline) are reinvestigated and discussed. Fragmentation pathways, elucidation of which were assisted by accurate mass measurements and metastable transitions, are proposed. The fragmentation assignments are not consistent with those previously reported in the literature. Many fragment species of the same m/z (low-resolution spectra) are composed of two or three fragment ions of different elemental compositions (high-resolution spectra). The obtained data create a safe basis for distinguishing structural and stero isomers.