Resonance electron capture by the molecules of α- and β-C(14)-methoxy isomers of 10,12-dehydro-8,9-seco-8,9-dioxolappaconine and its oxo derivative

Abstract

The formation of negative ions of some diterpene alkaloid molecules having conjugated π_С=С and π_С=О bonds in their structure by resonance electron capture has been studied. The mass spectra of these compounds are due to electron capture onto the lowest unoccupied molecular orbital (LUMO), which is π*-_С=С or π*-_С=О in nature. It has been found that the partial conversion of the test compound molecules into the enol form is possible on transferring into a gas phase; for this purpose, the appearance potentials of the ions (M–H)^– and (M–OCH₃)^– have been compared with the calculated thermodynamic thresholds of their appearance in the keto and enol forms.