SESQUITERPENE LACTONES FROM THE CARIBBEAN SEA PLUME PSEUDOPTEROGORGIA-AMERICANA

In continuation of our chemical investigation of the Caribbean sea plu me Pseudopterogorgia americana from Puerto Rico, six previously undesc ribed guaiane lactones were recently discovered. The chemical structur es of metabolites 1-6, including their relative stereochemistry, were established largely by NMR. The constitution and relative configuratio ns of 1 were confirmed by a single-crystal X-ray diffraction study. In some instances, the new compounds generated NMR spectra characterized by an abundance of broad signals of very low intensity, suggesting th at the coalescence temperature for interconversion of different confor mations was near the NMR probe temperature.