Tropical Marine Algae. IV. Novel Metabolites From the Red Alga Laurencia implicata (Rhodophyta, Rhodophyceae, Ceramiales, Rhodomelaceae)

The marine alga Laurencia implicata afforded four new C15-lipid' type metabolites: (3Z,6Z,9Z)-12-bromo-5,13-epoxypentadeca-3,6,9-trien-1-yne (6) with an unprecedented 1-oxacyclodecane ring, (3Z,6Z,92)-13-bromo-5,12-epoxypentadeca-3,6,9-trien-1-yne (7) with a nine-membered ether ring, (3E,6S,7S,9S,10S,12S,13R)-10,12-dibromo-6,9:7,13-bisepoxy-pentadec-3-en-l-yne (8), in which a chlorine atom in the known compound chlorofucin (9) has been replaced by bromine, (1R*,4R*,6S*,7S*)-9-acetoxy-1,10,12-tribromo-4,7:6,13-bisepoxypentadeca-1,2-diene (11) and the closely related known metabolite neolaurallene (10). In addition, a brominated sesquiterpene (1'R*,3'R*)-2-(3?-bromo-1',2',2'-trimethylcyclopentyl-5-methylphenol (14), The 2'-hydroxy derivative of a- bromocuparene (15), was identified. Structural elucidation of all metabolites was based on high-field n.m.r. studies and comparison with known metabolites.