A simple method of preparation of methyl trans-10,cis-12- and cis-9,trans-11-octadecadienoates from methyl linoleate |
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Authors: | O Berdeaux L Voinot E Angioni P Juanéda J L Sébédio |
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Affiliation: | (1) INRA, Unité de Nutrition Lipidique, 17 rue de Sully, BV 1540, 21034 Dijon Cedex, France |
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Abstract: | Pure conjugated isomers of linoleic acid were prepared on a large scale by alkali-isomerization of purified methyl linoleate.
The methyl esters of alkali-isomerized linoleic acid contained mainly the methyl cis-9,trans-11- and trans-10,cis-12-octadecadienoates (44 and 47%, respectively). These two isomers were then separated and purified by a series of low-temperature
crystallizations from acetone. The isomeric purity obtained for the cis-9,trans-11-octadecadienoate isomer was >90% and that of the trans-10,cis-12-octadecadienoate isomer was 89 to 97%. The isolated yield of the two isomers corresponded to 18 and 25.7%, respectively,
of the starting material. The structure of the two isomers was confirmed using partial hydrazine reduction, silver nitrate-thin-layer
chromatography of the resulting monoenes and gas chromatography coupled with mass spectrometry of the 4,4-dimethyloxazoline
derivatives. Fourier transform infrared spectroscopy of the monoenes gave the confirmation of the geometry of each double
bond. |
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Keywords: | Conjugated linoleic acid (CLA) 4 4-dimethyloxazoline derivative GC-FTIR GC-MS hydrazine reduction isomerization linoleic acid low-temperature crystallization NMR silver nitrate-thin layer chromatography UV |
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