title: Synthesis of four isomers of parinaric acid.
abstract: A simple and reliable method for synthesizing four isomers of parinaric acid from alpha-linolenic acid (ALA) in high yields is described. The methylene-interrupted, cis triene system (1,4,7-octatriene) of ALA and common to other naturally occurring polyunsaturated fatty acids was transformed to a conjugated tetraene system (1,3,5,7-octatetraene). The synthesis involves bromination of ALA using 0.l M Br(2) in a saturated solution of NaBr in methanol, esterification of the fatty acid dibromides, double dehydrobromination by 1,8-diazabicyclo[5.4.0]undec-7-ene and saponification of the conjugated esters to a mixture of free conjugated acids. Addition of one molecule of bromine to the 12,13-double bond of ALA and subsequent dehydrobromination produces alpha-parinaric acid (9Z,11E,13E,15Z-octadecatetraenoic acid); addition of Br(2) to the 9,10-double bond or 15,16-double bond and then dehydrobromination and rearrangement yields 9E,11E,13E,15Z-octadecatetraenoic or 9E,11E,13E,15Z-octadecatetraenoic acids, respectively. The mixture of parinaric acid isomers is obtained in 65% yield, and the isomers can be purified by preparative HPLC; alternatively, the isomers can be converted by base catalyzed cis-trans isomerization (or by treatment with I(2)) to exclusively beta-parinaric acid (9E,11E,13E,15E-octadecatetraenoic acid). The various parinaric acid isomers were characterized by (1)H NMR, (13)C NMR, UV, GLC, HPLC and mass spectrometry.
authors.affiliation: Department of Biological Chemistry, University of Michigan Medical School, 5416 Medical Science I, 1301 E, Catherine Street, Ann Arbor, MI 48109, USA.
authors.forename: Dmitry V
authors.initials: DV
authors.lastname: Kuklev
authors.forename: William L
authors.initials: WL
authors.lastname: Smith
mesh_terms: D005227:Fatty Acids / Q000138:chemical synthesis* / Q000737:chemistry; D005231:Fatty Acids, Unsaturated / Q000138:chemical synthesis* / Q000737:chemistry; D007536:Isomerism; D017962:alpha-Linolenic Acid / Q000138:chemical synthesis* / Q000737:chemistry
chemical_list: D005227:Fatty Acids; D005231:Fatty Acids, Unsaturated; D017962:alpha-Linolenic Acid; C013641:parinaric acid