NOVEL DI-ENOIC, TRI-ENOIC, AND TETRAENOIC FATTY-ACIDS WITH BIS-METHYLENE-INTERRUPTED DOUBLE-BOND SYSTEMS FROM THE SPONGE HALICLONA CINEREA

Unusual fatty acids, with up to 34 carbon atoms and containing one or two bis-methylene-interrupted double-bond systems, have been identifie d in the sponge Haliclona cinerea from the Black Sea. These include th e dienes-5,9-16:2, 7,11-18:2, 9,13-20:2, 13,17-24:2, 15,19-26:2, 17,21 - 28:2, 19,23-30:2 and 21,25-32:2; trienes-5,9,23-30:3,5,9,24-31:3, 5, 9,25-32:3, and 5,9,27-34:3; and the tetraenes-5,9,19,23-30:4, 5,9,21,2 5-32:4, and 5,9,23,27-34:4. In addition, 5,9,13-eicosatrienoic acid wa s present. Many of these do not appear to have been described before, and only 5,9-16:2 and 5,9,23-30:3 are found often in sponges. They wer e identified by using silver-ion high-performance liquid chromatograph y to simplify the complex mixture of fatty acids for subsequent analys is by gas chromatography-mass spectrometry as picolinyl ester derivati ves. Deuteration with Wilkinson's catalyst in homogeneous solution con firmed the structures. We speculate that the di- and tetraenoic fatty acids arise by chain elongation of 5,9-hexadecadienoic acid, also a ma jor component of the lipids, followed by further insertion of double b onds in the 5 and 9 positions. The trienes may be formed from 9-hexade cenoic acid by similar mechanisms.