Halogenated monoterpenes from Plocamium costatum and their biological activity

From the dichloromethane solubles of the temperate red alga Plocamium costa tum, one new [1,4-dibromo-2,3,6-trichloro-3,7-dimethyl-7-octene] (1) and th ree previously reported polyhalogenated monoterpenes (2-4), and the known p hytol derivative 3,7,11,15-tetramethylhexadec-1-en-3-ol (1-phyten-3-ol, 5) were isolated. The structure of 1 was deduced from its spectroscopic data. For compound 3, complete H-1 and C-13 NMR data are reported for the first t ime. The CH2Cl2 extract and compounds 3 and 5 deterred settlement of barnac le larvae, suggesting a potential ecological role of these isolates.