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The production of labeled brominated metabolites with radioactive 82 Br in Laurencia species was investigated as part of a study of the biosynthesis of halogenated metabolites from species belonging to the red algal genus Laurencia (Rhodomelaceae, Ceramiales Br-containing metabolites. In the case of the laurencin-producing race of L. nipponica, laurencin and deacetyllaurencin were found to be produced in approximately 1:1 ratio, though laurencin is the major metabolite in the wild sample. Furthermore, when cultured in the dark, the production rates of brominated metabolites in Laurencia spp. were found to be diminished. The present study strongly indicates that the use of radiobromine [ 82 Br] in combination with the TLC-ARLG method is an effective approach for investigating the biosynthesis of brominated metabolites in Laurencia.3

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.

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