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Preparation of deuterium‐labelled methyl linoleate and its geometric isomers from natural seed oils
Author(s) -
Adlof R. O.,
Rakoff H.,
Emken E. A.
Publication year - 1991
Publication title -
journal of the american oil chemists' society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.512
H-Index - 117
eISSN - 1558-9331
pISSN - 0003-021X
DOI - 10.1007/bf02657681
Subject(s) - cis–trans isomerism , chemistry , isomerization , wittig reaction , toluene , saponification , catalysis , medicinal chemistry , organic chemistry , stereochemistry
Multi‐gram quantities of deuterium‐labelled methyl linoleate (methyl cis‐9,cis‐12‐octadecadienoate) and its geometric isomers are readily synthesized from Crépis alpina (70–80% cis‐9‐octadecen‐12‐ynoic acid) and Vernonia galamensis (70–80% 12,13‐epoxy‐cis‐9‐octadecenoic acid) seed oils. Methyl cis‐ 9,cis‐ 12‐ and trans‐ 9,cis‐ – octadecadienoate‐12,13‐d 2 were prepared by the Lindlar‐catalyzed reduction (with D 2 gas) of methyl cis‐ 9‐ and trans‐9‐octadecen‐12‐ynoates, respectively. Methyl trans‐ 9‐ octadecen‐12‐ynoate was synthesized by the p ‐toluene‐sulfinic acid‐catalyzed isomerization of the corresponding cis isomer. Methyl cis‐ 9fiis‐ 12., trans‐ 9fiis‐ 12 ; cis‐ 9,trans‐ 12‐ and trans‐ 9 , frans‐12‐octadecadienoate‐d 2 , d 4 and d 6 were prepared by the Wittig coupling (with stereochemical control) of the appropriate d 2 ‐, d 4 ‐ or de‐alkyltriphenyl‐phosphonium salt with methyl 12‐oxo‐cis‐9‐ or trans‐ 9‐ dodecenoate (prepared by the para‐periodic acid cleavage of methyl 12,13‐dihydroxy‐cis‐9‐ or trans‐9‐octadecenoate). The cis dihydroxy ester was synthesized from Vernonia galamensis seed oil by acetolysis, saponification and then esterification. The cis dihydroxy ester was isomerized by nitric acid/sodium nitrite to the trans form and purified by silver resin chromatography. Isotopic purities ranged from 88% (for the d 6 isomers) to 99% (for the d 2 isomers).