Oxachamigrenes, New Halogenated Sesquiterpenes from Laurencia obtusa

Abstract
Two new sesquiterpenes belonging to a novel oxacyclic structural type of chamigrene skeleton, oxachamigrene (1) and 5-acetoxyoxachamigrene (2), have been isolated from the red alga Laurenciaobtusa. The structures of the compounds were determined on the basis of spectroscopic evidence. A biogenetic route for these metabolites has been proposed.