Regio- and stereochemical analysis of trihydroxyoctadecenoic acids derived from linoleic acid 9- and 13-hydroperoxides |
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Authors: | Mats Hamberg |
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Affiliation: | (1) Department of Physiological Chemistry, Karolinska Institutet, Box 60400, S-104 01 Stockholm, Sweden |
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Abstract: | The methyl esters of 9S,10S,13R-trihydroxy-11E-octadecenoic acid, 9S,10R,13S-trihydroxy-11E-octadecenoic acid, and 9S,10R,13R-trihydroxy-11E-octadecenoic acid were prepared from 9S-hydroperoxy-10E,12Z-octadecadienoic acidvia the epoxy alcohols methyl 10R,11R-epoxy-9S-hydroxy-12Z-octadecenoate and methyl 10S,11S-epoxy-9S-hydroxy-12Z-octadecenoate. The trihydroxyesters, as well as four stereoisomeric methyl 9,12,13-trihydroxy-10E-octadecenoates earlier prepared Hamberg, M.,Chem. Phys. Lipids 43, 55–67 (1987)], were characterized by thin-layer chromatography, gas-liquid chromatography, mass spectrometry, and by chemical
degradation. Availability of these chemically defined trihydroxyoctadecenoates made it possible to design a method for regio-
and stereochemical analysis of 9,10,13- and 9,12,13-trihydroxyoctadecenoic acids obtained from various sources. Application
of the method revealed that the mixture of 9,10,13- and 9,12,13-trihydroxyoctadecenoic acids formed during autoxidation of
linoleic acid in aqueous medium contained comparable amounts of the sixteen possible regio- and stereoisomers. Furthermore,
hydrolysis of the allylic epoxy alcohol, methyl 9S,10R-epoxy-13S-hydroxy-11E-octadecenoate, yielded a major trihydroxyoctadecenoate,i.e., methyl 9S,10S,13S-trihydroxyl-11E-octadecenoate, together with smaller amounts of methyl 9S,10R,13S-trihydroxy-11E-octadecenoate, methyl 9S,12R,13S-trihydroxy-10E-octadecenoate, and methyl 9S,12S,13S-trihydroxy-10E-octadecenoate. |
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