Brominated labdane-type diterpenoids from an Okinawan Laurencia sp

From an unidentified species of Laurencia collected from Okinawan waters two novel brominated metabolites, 1 and 2, along with known halogenated compounds, 2,10-dibromo-3-chloro-alpha-chamigrene (3) and microcladallene A (4), were isolated and identified. The structures of these new compounds were established as ent-labdane-type bromoditerpenes, (1S,3R,5S,6S,8S,9S,10R,13R)-1-acetoxy-3-bromo-6-hydroxy-8,13-epoxy-labd-14-ene (1) and (3R,5S,6S,8S,9S,10R,13R)-3-bromo-6-hydroxy-8,13-epoxylabd-14-en-1-one (2), by interpretation of their spectroscopic data as well as by X-ray crystallographic analysis.