Lichen substances—128 Mass spectroscopy of natural products—12. Comparative positive and negative ion mass spectroscopy of nitrogen-containing and ring C cleaved usnic acid derivatives

Abstract

The mass spectral fragmentation behaviour of some nitrogen-containing and ring C cleaved usnic acid derivatives has been studied. The principal fragmentation pathway is drastically changed in the nitrogen-containing compounds when compared to that observed with the ring C cleaved derivatives. The main fragment ions of the ring C derivatives are also present in the mass spectrum of usnic acid itself.