Mass spectrometric characteristics of two novel series of ring‐C monounsaturated tricyclic terpenes found in Tasmanian tasmanite

Abstract

Electron impact and methane chemical ionization mass spectra were measured for two homologous series of monounsaturated tricyclic terpenes, A9'' ') and A13(14). The double bond position was inferred by interpretation of their mass spectra, comparisons with the known saturated and ring-C monoaromatic series, published mass spectrometric data on other terpenoids and MM2 calculations. The distributions of and 6,'' "-monounsaturated tricyclic terpene isomers were shown by theory and from experimental data to be dependent on the chain length at position 14. These two series coexist in the same geological sample. A9(' ')-Monounsaturated tricyclic terpenes can be derived from the compounds by isomerization of the double bond. The A9(' "-monounsaturated tricyclic terpene series extends from C,, to C,, and the A"(14) series from C,, to C.,,. The diastereomers >C2,, for both series could be resolved by gas chromatography.