Rearrangement reactions in the positive and negative ion mass spectra of clausmarin A

The positive and negative ion mass spectra of clausmarin A, a naturally occurring tetracyclic coumarin, have been studied. The base peaks in the positive and negative ion spectra correspond to the complementary ions at m/z 143 and m/z 255, respectively, formed by a rearrangement reaction. The fragmentation pathways have been elucidated with the help of exact mass measurements and in situ deuterium labelling.