Sesquiterpenes of the liverwort Scapania undulata

Abstract

The essential oil of the liverwort Scapania undulata, collected in the Harz mountains, Northern Germany, was analysed by gas chromatography (GC), GC–mass spectrometry (MS) and several new components were isolated and investigated by various NMR techniques. As new natural compounds the sesquiterpene hydrocarbons (+)-helminthogermacrene ( 1) [the 4 Z-isomer of germacrene A ( 9)], (−)- cis-β-elemene ( 2) as a Cope-rearrangement product of 1, (+)-β-isolongibornene ( 3) and (−)-perfora-1,7-diene ( 4) could be identified. 1 has an identical mass spectrum and identical GC retention time on a non-polar stationary phase as germacrene A ( 9) but is considerably more stable than the latter. The Cope-rearrangement of 1 proceeds slowly at 350 °C and (−)- cis-β-elemene ( 2) is formed together with small amounts of other diastereoisomers.