Synthesis and tandem mass spectrometry of chlorinated triacylglycerols

• New triacylglycerols containing one or two 9,10-dichlorooctadecanoyl groups were synthesized regioselectively.
• Hexachloro- and hexabromotriacylglycerols were prepared by halogenation of tri-(cis-9-octadecanoyl)glycerol.
• Upon CID-MS/MS, all chlorinated triacylglycerols showed characteristic double losses of HCl.
• HCl losses were consistent with sequential processes occuring from a single 9,10-dichlorooctadecanoyl group.
• A similar pattern of HBr losses were obtained upon CID-MS/MS of tri-(9,10-bibromooctadecanoyl)glycerol.

The incorporation of 9,10-dichlorooctadecanoyl groups using enzyme-catalyzed acylation and protecting group strategies yielded specific regioisomers of di- and tetrachlorinated triacylglycerols. Hexachloro- and hexabromotriacylglycerols were synthesized by addition of chlorine or bromine to tri-(cis-9-octadecenoyl)glycerol. Upon electrospray ionization and tandem mass spectrometry, the sodium adduct ions of all compounds containing a 9,10-dichlorooctadecanoyl group readily lost two molecules of HCl when subjected to collision-induced dissociation. A mechanism describing sequential HCl losses and the formation of a conjugated diene is proposed for the loss of both vicinal chlorine atoms from an alkyl chain. This characteristic fragmentation behavior and the availability of characterized standards will facilitate the development of quantitative analytical methods for the determination of chlorinated triacylglycerols in lipid mixtures isolated from marine and other biological sources.

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