Three new sesquiterpenes from the red alga Laurencia perforata.

From the lipophilic extract of the red alga Laurencia perforata three new sesquiterpenes, (1S,2S,4S,5S, 6S,8R)-4-hydroxy-2,5,6-trimethyl-11-methylenetricyclo[6.2.1.0(1,6)]undecan-3-one (1, 4-hydroxy-1,8-epi-isotenerone), (3R,4R,4aR,9R)-3,9-dihydroxy-1,4,4a,7-tetramethyl-3,4,4a,5,8,9-hexahydro-2H-benzo[a]cyclohepten-2-one (9-hydroxy-3-epi-perforenone A, 2), and 3-epi-perforenone A (3), were isolated. The structures of all isolates were determined from their spectroscopic data (NMR, MS, IR, UV). Unusual for a species of this algal genus was the apparent absence of halogenated compounds.