The lindlar-catalyzed reduction of methyl santalbate: a facile preparation of methyl 9-cis,11-trans-Octadecadienoate-9,10-d2

Conjugated linoleic acid (CLA) has been associated with the reduction of chemically induced cancers in mice and rats and the suppression of atherosclerosis in rats. We have found seed oils to be a valuable source of precursors for the rapid preparation of gram quantities of deuterium-labeled fats. Methyl santalbate (methyl 11-trans-octadecen-9-ynoate), obtained from Santalum album (Linn.) seed, was reduced with Lindlar catalyst, quinoline, and deuterium gas to produce, in yields of 65–75%, the gram quantities of methyl 9-cis,11-trans-octadecadienoate-9,10-d₂ (CLA-d₂) we required for metabolism and oxidation studies. Unlike monoacetylenic and methylene-interrupted polyacetylenic fatty acid methyl esters, the conjugated system was reduced with no noticeable break in the rate of deuterium uptake. The quantity of poison (quinoline) present did influence the amount of CLA-d₂ produced, but the production of overreduced fatty acid methyl esters (perhaps because of the conjugated system) could not be prevented. Fractionation of the reaction mixture by silver resin chromatography resulted in the isolation of >99% chemically pure CLA-d₂ in yields of 60–70%.