Synthesis of substituted cis‐8,cis‐11,cis‐14‐eicosatrienoic acids, precursors of correspondingly substituted prostaglandins

The synthesis of the following groups of acids is described: (a) 3-Methyl-c-2,c-8,c-11,c-14-, and 3-methyl-t-2,c-8,c-11,c-14-eicosatetraenoic acid and 3-methyl-c-8,c-11,c-14-eicosatrienoic acid, (b) c-8,c-11,c-14-eicosatrien-5-ynoic acid, (c) c-2,3-methylene-,t-2,3-methylene-,3,3-dimethyl- and 4,4-dimethyl-c-8,c-11,c-14-eicosatrienoic acid, (d) 18-methyl-, (S)-18-methyl- and 19-methyl-c-8,c-11,c-14-eicosatrienoic acid. They were obtained via coupling of (a) c-7,c-10,c-13-nonadecatrien-2-one with ethoxycarbonylmethylenetriphenylphosphorane and c-7,c-10,c-13-nonadecatrien-2-yl methane sulfonate with diethyl malonate, (b) l-bromo-c-2,c-5,c-8-tetradecatriene with 5-hexynoic acid, (c) 1-bromo-2,5-undecadiyne with the appropriately substituted 8-nonynoic acids and (d) from the correspondingly substituted 1-bromo pentanes, using standard procedures.