active as trans 4 cis 7 trideca dienyl acetate and that mixtures of the two compounds show a still better acitivity the invention comprises also a method for the preparation of the compound trans 4 cis 7 cis 10 trideca trienyl acetate which method has been shown schematically str1 in this method 2 6 chloro trans 4 hexenyloxy tetrahydropyran having formula 7 is coupled to 1 4 heptadiyn having formula 9 in the form of a grignard compound for the formation of 2 trans trideca 4 enyl 7 10 diynyl oxy tetrahydropyran having formula 10 then this compound is converted into trans trideca 4 enyl 7 10 diynyl acetate having formula 11 from which by selective reduction according to a method by brown et al j chem soc chem comm 1973 pp 553 and j org chem 38 pp 226 2230 the product desired is obtained the 2 6 chloro trans 4 hexenyloxy tetrahydropyran can for instance be prepared by firstly coupling 3 bromo propanol 1 having formula 3 to dihydropyran thus forming 2 3 bromopropyloxy tetrahydropyran having formula 4 then from this is obtained by conversion with propargylalcohol the compound 2 6 hydroxy hex 4 ynyloxy tetrahydropyran having formula 5 next this compound is reduced to 2 6 hydroxy trans 4 hexenyloxy tetrahydropyran having formula 6 from which the corresponding 6 chloro compound is prepared in the way known in the art the method of preparation is elucidated by means of the non restrictive example below showing in a the preparation.