Syntheses of some polyunsaturated sulfur- and oxygen-containing fatty acids related to eicosapentaenoic and docosahexaenoic acids

With the aim of enhancing selectively the beneficial biological effects of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) a number of poly unsaturated Fatty acids containing sulfur or oxygen atoms in the chain has been synthesized starting from EPA and DHA, respectively. Oxidative degrada tion of these acids led to the corresponding aldehydes all-(Z)-3,6,9,12-pen tadecatetraenal and all-(2)-3,6,9,12,15-octadecapentaenal. Reactions with D BU converted these aldehydes quantitatively into the conjugated isomers (2E ,6Z,9Z,12Z)-pentadecatetraenal and (2E,6Z,9Z,12Z,15Z)-octadecapentaenal, re spectively. The four aldehydes were transformed by a sequence of reactions comprising reduction to the alcohols, halogenation and substitution with me rcapto esters into the corresponding sulfur containing polyunsaturated fatt y acid eaters. The oxygen containing esters were prepared from the respecti ve alcohol by boron trifluoride catalysed reaction with ethyl diazoacetate.