Synthesis of cis and trans methyl 8- and 13-octadecenoate-d2 and d4 isomers

The synthesis of deuterium labelled, unsaturated, isomeric fatty acids was required for a series of triple-labelled feeding experiments. The preparation of the cis and trans isomers of methyl 8-octadecenoate-17, 18-d2, methyl 8-octadecenoate-13, 13, 14, 14-d4, methyl 13-octadecenoate-17, 18-d2 and methyl 13-octadecenoate-17, 17, 18, 18-d4 is described. The syntheses utilize tris (triphenylphosphine) - chlororhodium(I) catalyst for the incorporation of deuterium. The double bond is introduced by coupling a deuterated alkyl triphenylphosphonium salt with the appropriate aldehydic ester using the Wittig reaction. Optimization of conditions has increased the overall yields for these syntheses to ∼50% and the isotopic purity to >95%.