Three new fatty acid metabolites didemnilactones A (1) and B (2) and neodidemnilactone (3) were isolated from the tunicate Didemnum moseleyi (Herdman). Their structures including absolute stereochemistry were established on the basis of spectral studies and chemical synthesis. Didemnilactones exhibited inhibitory activity against lipoxygenase and weak binding activity to leukotriene B4 receptors.
