New Halogenated Diterpenes from Red Alga Laurencia perforata

Article abstract of DOI:10.1021/jo00208a021

The red alga Laurencia perforata contains a variety of secondary metabolites, some of which have previously been described from other sources.We report here the isolation and structural determination of three new diterpenoids.The bicarbocyclic diterpene 1 was shown to be related with the also isolated, and previously known, isoaplysin-20 (2).The structures of the two more polar diterpenes isolated from the extract were shown to be 3,15-dibromo-7,16-dihydroxyisopimar-9(11)-ene (5) and 3,15-dibromo-7,12,16-trihydroxyisopimar-9(11)-ene (7).Extensive 1H NMR decoupling studies and some degradative experiments were used to establish the structures.