Synthesis towards two sulphur-containing heterocyclic fatty acids

A total synthesis towards the methyl and ethyl esters of two sulphur-containing heterocyclic fatty acids that have been isolated from rapeseed oil, mustard oil, and garlic, was attempted. Since MS-EI analyses has been the sole method used for structure elucidation of these compounds, the aim of the synthesis was to obtain more extensive spectroscopic data of the fatty acids, and to confirm the proposed structures of the target molecules. Altogether, five synthetic strategies were explored, where the key carbon-extending reactions used in the various synthetic pathways included lithiation-alkylation, oxidative cross-couplings, and olefination reactions. Of the five synthetic strategies explored herein, only one pathway afforded the complete carbon-skeleton common to both target molecules, which in this case was constituted by ethyl (E)-8-(5-hexylthiophen-2-yl)oct-2-enoate. However, the α,β-unsaturated ester could not be purified to a satisfactory degree. With time being at its limit, optimisation of some of the low-yielding reaction steps leading to this intermediate, as well as conducting the remaining hydrogenation steps, was left for future work