We examined the chemical constitution of the red alga Laurencia saitoi Perestenko, collected from Katsuura, Boso Peninsula, Chiba Prefecture, Japan. This specimen produced a new polyhalogenated acetogenin, named katsuurallene (1), which structure was determined by the spectral methods, along with known diterpene, deoxyparguerol (2) and triterpene, thyrsiferol (3). In this paper we describe the structural elucidation of katsuurallene together with some biological activities.

We report on the chemical characteristics of the red alga Laurencia japonensis, collected off the coast of Yoshio, Katsuura, Boso Peninsula, Japan. We isolated two new brominated C 15 -acetogenins in this species, which we name katsuurenyne A (1) and katsuurenyne B (2), along with two already known halogenated terpenes [2,10-dibromo-3-chloro--chamigrene (7) and aplysiadiol (8)]. We extensively analysed spectral data (from IR, ESI-MS, 1D-NMR and 2D-NMR) to confirm the structure of these compounds.

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We examined the constitution of Laurencia mariannensis collected from the east coast of Tean Island, Thailand. The structure of a new brominated rearranged cyclolaurane-type sesquiterpene, named teanol (1), is reported. This is the first report on biology and chemistry of the Thailand red algal genus Laurencia (Rhodomelaceae, Ceramiales).