title: Diesters of alkane diols and 2-hydroxy fatty acids: identification and discrimination of isomers with the aid of NMR spectroscopy.
abstract: High resolution nuclear magnetic resonance spectroscopy has been shown to be extremely useful for the identification and discrimination of naturally occurring diesters of 1,2- and 2,3-alkanediols as well as for fatty alkyl esters of acylated 2-hydroxy fatty acids. A comparison of 220 MHz spectra of 1,2 and erythro- 2,3-alkanediol diesters exhibits the following distinguishing features: (1) two non-equivalent methylene protons from the glycol group of 1,2-alkanediol diesters resonate at 3.87 ppm and 4.17 ppm respectively while these resonances are completely absent in the spectrum of 2,3-isomer; (2) methylene protons adjacent to esther carbonyl groups appear as two overlapping triplets at 2.22 ppm in 1,2-alkanediol diesters while the corresponding protons in the 2,3-isomer are displayed as two partially overlapping triplets centered at 2.15 ppm and 2.2 ppm respectively; and (3) methyl protons adjacent to glycol group in 2,3-isomer appear as downfield doublet at 1.13 ppm; this downfield doublet is not shown by 1,2-alkanediol diesters. Erythro- and threo-2,3-alkanediol diesters have also been distinguished from each other; two alpha-methylenes in erythro isomers appear as partially overlapping triplets while these protons in threo isomer display an apparent quartet centered at 2.22 ppm. Fatty alkyl esters of acylated 2-hydroxy fatty acids display a triplet at 4.79 for 2-position methylene proton, a distinguishing feature not shown by diacyl alkanediols. A distinction between diester lipids and other classes of neutral lipids has also been achieved by the study of nuclear magnetic resonance spectra, particularly in the region of 3-6 ppm.
mesh_terms: D000818:Animals; D004952:Esters; D005233:Fatty Alcohols / Q000032:analysis; D006880:Hydroxy Acids / Q000032:analysis; D007536:Isomerism; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D012627:Sebaceous Glands / Q000032:analysis; D014422:Turkeys; D014885:Waxes / Q000032:analysis
chemical_list: D004952:Esters; D005233:Fatty Alcohols; D006880:Hydroxy Acids; D014885:Waxes