BIOSYNTHESIS OF PHEROMONES IN FEMALE GAMETES OF MARINE BROWN-ALGAE (PHAEOPHYCEAE)

Female gametes of the brown algae Ectocarpus siliculosus and Sphacelar ia rigidula as well as thalli of Giffordia mitchellae metabolise exter nally added [H-2(n)]icosanoic acids into the hydrocarbon pheromones ec tocarpene (1), dictyotene (2) and finavarrene (5). The series of the C 11H16 hydrocarbons originates from all-cis-5,8,11,-14,17-icosapentaeno ic acid (7); the C11H18 compound dictyotene (2) is produced from all-c is-5,8,11,14-icosate-traenoic acid (8) (arachidonic acid). The key ste p in the biosynthesis of giffordene (6) is a thermally allowed [1,7]-h ydrogen shift of an 1,3Z,5Z,8Z-undecatetraene (21) intermediate derive d from 7.