Thermal alteration of a cyclic fatty acid produced by a flaxseed extract

Methyl 8‐[2‐( cis ‐pent‐2′‐enyl)‐3‐oxo‐ cis ‐cyclopent‐4‐enyl] octanoate (I) is the methyl ester of a cyclic fatty acid synthesized enzymically from an incubation of linolenic acid with an extract of flaxseed ( Linum usitatissimum L.). A proposed trivial name for I is methyl 12‐oxo‐ cis ‐10, 15‐phytodienoate (12‐oxo‐PDA). The evidence presented indicated that compound I has the cis configuration of the carbon chains with respect to the cyclopentenone ring. Treatment with acid, base, or heat isomerized I to a second product (II) that has the trans configuration of the carbon chains. Prolonged heat treatment of II yielded a third cyclic product, methyl 12‐oxo‐9(13), cis ‐15‐phytodienoate (III).