The mass spectra of some naturally‐occurring 3,4‐dialkoxy furocoumarins and their nor‐derivatives

The mass spectral fragmentations of several naturally‐occurring 3,4‐dialkoxy furocoumarins from the Halfordia species and their nor‐derivatives have been studied using deuterium labelling and metastable analysis. Halfordin (I), isohalfordin (VI) and halkendin (X) show a common major breakdown pathway involving initial loss of a methyl radical from the 3‐methoxy group followed by expulsion of CO, then loss of C2H3O, the latter fragment containing the methyl group from the 4‐position.