ISOLATION OF BROMINATED LONG-CHAIN FATTY-ACIDS FROM THE PHOSPHOLIPIDSOF THE TROPICAL MARINE SPONGE AMPHIMEDON TERPENENSIS

Preliminary investigation of the phospholipid fatty acid composition o f the tropical marine sponge Amphimedon terpenensis by gas chromatogra phy/mass spectrometry revealed the presence of some novel brominated f atty acids. Two new brominated fatty acids, (5E, 9Z)-6-bromo-5,9-tetra cosadienoic acid (2a) and (5E, 9Z)-6-bromo-5,9-pentacosadienoic acid ( 3a) were subsequently isolated from a chloroform/methanol (3:1, vol/vo l) extract of the sponge and characterized as their methyl esters 2b a nd 3b. The known brominated fatty acid (5E, SZ)-6-bromo-5,9-hexacosadi enoic acid (4a) was also isolated. The new fatty acid methyl esters we re confirmed as brominated Delta 5,9 acid derivatives by chemical ioni zation mass spectrometry. The position of the bromine substituent was determined to be C-6 by nuclear magnetic resonance techniques while th e stereochemistry of the two double bonds was deduced by nuclear Overh auser enhancement difference spectroscopy. The biosynthetic implicatio ns of the co-occurrence of the three brominated acids are discussed.