Abstract
For studies into the relationship between their physical properties and chemical structure, several polyunsaturated fatty acids related to (Z,Z,Z)‐6,9,12‐octadecatrienoic acid and (Z,Z,Z)‐8,11,14‐eicosatrienoic acid were synthesized.
Methyl (E,Z,Z)‐2,11,14‐eicosatrienoate and methyl (E,Z,Z)‐2,9,12‐octadecatrienoate were prepared by E‐stereoselective coupling of (methoxycarbonylmethylene)triphenylphosphorane with (Z,Z)‐9,12‐octadecadienal and (Z,Z)‐7,10‐hexadecadienal respectively.
The synthesis of methyl (E,Z,Z)‐4,9,12‐octadecatrienoate started from 2,7‐octadiyn‐1‐ol which was reduced with lithium aluminium hydride. The (E)‐2‐octen‐7‐yn‐1‐ol thus obtained was coupled with 1‐bromo‐2‐octyne to give (E)‐2‐hexadecene‐7,10‐diyn‐ 1‐ol. This was converted into 1‐chloro‐(E)‐2‐hexadecene‐7,10‐diyne, which via malonic ester synthesis yielded (E)‐4‐octadecene‐9,12‐diynoic acid. Stereospecific hydrogenation and esterification finally afforded the desired compound, from which methyl (E,Z,Z)‐6,11,14‐eicosatrienoate was obtained by chain elongation.
Methyl (E,Z,Z)‐6,9,12‐octadecatrienoate was synthesized from 1,4‐dichloro‐(E)‐2‐butene which was converted into (E)‐4‐octen‐7‐ynoic‐7‐ynoic acid. Coupling the latter with 1‐bromo‐2‐octyne, esterification and reduction yielded (E‐4‐hexadecene‐7,10‐diyn‐ 1‐ol. Conversion into the corresponding chloro compound and stereospecific hydrogenation yielded 1‐chloro‐(E,Z,Z)‐4,7,1 O‐hexadecatriene. Malonic ester synthesis finally afforded the desired compound.
The synthesis of methyl (E,Z,Z)‐8,11,14‐eicosatrienoate started from 2‐octyne‐1,8‐diol which was reduced with lithium aluminium hydride; the resulting (E)‐octene‐1,8‐diol was converted into 1,8‐dichloro‐(E)‐2‐octene. The latter was coupled with 1,4‐decadiyne to give 1‐chloro‐(E)‐6‐octadecene‐9,12‐diyne, which was hydrogenated stereospecifically. Malonic ester synthesis finally completed the synthesis.