New Geometric Isomers of Oxooctadecadienoate in Copper-catalyzed Decomposition Products of Linoleate Hydroperoxide

Methyl linoleate hydroperoxide produced by autoxidation was refluxed with 10(-4) M Cu-naphthenate in benzene. Two new geometrical isomers of oxooctadecadienoate (compounds I and II) were found in addition to the four known isomers. They were isolated by a Sephadex LH-20 column chromatography with chloroform-hexane (2:1) and purified by HPLC on Nucleosil ®100-5 and Zorbax ODS columns. UV, IR, MS, and (1)H-NMR spectra were measured. The geometry of conjugated dienes were assigned from the coupling constants of the olefinic protons. Compounds I and II were identified as 13-oxo-trans-9, cis-11- and 9-oxo-cis-10, trans-12-octadecadienoate, respectively. Each of them had a cis double bond adjacent to the oxo group. The hydroperoxides of the same geometry as compounds I and II were also detected in autoxidation products.