Pinguisane-type sesquiterpenes from the South American liverwort Porella recurva (Taylor) Kuhnemann.

The chemical composition of a dichloromethane extract of the South American liverwort Porella recurva has been examined. Two new pinguisane-type norsesquiterpenoid natural products were isolated: 6,11-epoxy-15-nor-3,4-dioxo-5,10-pinguisadien-12-acetate and 6,11-epoxy-15-nor-4-oxo-5,10-pinguisadien-12-acetate. In addition two known pinguisane-type sesquiterpenes were also isolated: norpinguisone and norpinguisone methyl ester. All structures were elucidated by means of NMR spectroscopic techniques and mass spectrometry.