Novel Hydroxyicosatetraenoic and Hydroxyicosapentaenoic Acids and a 13‐Oxo Analog. Isolation from a Mixture of the Calcareous Red Algae Lithothamnion corallioides and Lithothamnion calcareum of Brittany Waters

A mixture of the red calcareous algae Lithothamnion corallioides C ROUAN and Lithothamnion calcareum (P ALLAS ) A RESCHOUGH , from Brittany waters, gives, on ethanolic extraction, the novel icosanoids ethyl 13‐hydroxy‐arachidonate (=(+)‐all‐ Z ‐ethyl 13‐hydroxyicosa‐5,8, 11,14,‐tetraenoate; (+)‐ 1 )), ethyl 13‐hydroxytimnodonate (=(+)‐(all‐ Z )‐ethyl 13‐hydroxyicosa‐5,8,11,14,17‐pentaenoate ((+)‐ 2 ), and (5 Z ,9 E ,11 E ,14 E )‐ethyl 8‐hydroxy‐13‐oxoicosa‐5,9,11,14‐tetraenoate ( 3 ). Moreover, the ethyl esters of four known icosatetraenoic acids are contained in the above algae. Structural elucidations of these metabolites are based mainly on NMR data.