Electron impact mass spectrometry of hemiterpenoid tricyclic quinoline alkaloids

The mass spectral behaviour of some quinoline-type alkaloids, 3,4-dihydro-2H,5H-pyrano3,2-c]quinolin-5-ones, isomeric 3,4-dihydro-2H,5H-pyrano2,3-b]quinolin-5-ones and 2H,5H-pyrano3,2-c]quinolin-5-ones, was studied in detail with the aid of linked scans, exact mass measurements and collisional spectrometry. The occurrence of a partial isomerization of the differently annulated isomers to a common, open-chain structure is discussed.