Mass spectra of a series of natural Diels-Alder adducts obtained from root barks of Mulbbery tree were measured by electron impact (EI) and field desorption (FD) ionizations. A retro Diels-Alder fragmentation, which was observed in the spectra of all compounds, and the general fragmentation pattern of the adducts have been discussed. Furthermore, the fragmentation observed in a fast atom bombardment (FAB) study of some samples is also described.
