The diunsaturated fatty acids 5,9-heneicosadienoic acid, 5,9-docosadienoic acid and 5,9-tricosadienoic acid, the brominated fatty acids 6-bromo- 5,9-heneicosadienoic acid and 6-bromo-5,9-docosadienoic acid, and the polyunsaturated fatty acids 5,9,13-eicosatrienoic acid and 5,9,13-docosatrienoic