Enantiomeric separation of branched fatty acids having chiral centers remote from the carboxyl group by derivatization with chiral fluorescent-labelling reagents

Abstract

We have developed a highly sensitive fluorescent-derivatization reagent, 2-(2,3-anthracenedicarboximido)ethyl trifluoromethanesulfonate (AE-OTf), for carboxylic acids. The reagent has made it possible to detect fatty acids at sub-fmol levels. 1H-NMR studies of some AE-O-esters have suggested the possiblity of chiral discrimination of chiral carboxylic acids having chiral centers at a remote position from their carboxyl groups by labeling with chiral AE-OTf analogues. We prepared some chiral AE-OTf analogues and studied the discrimination of their diastereomeric derivatives of some branched fatty acids having a chiral methyl branch at the C2 - C12 position. After derivatizing with these reagents, it was possible to separate them on an ODS column below 0°C and to discrimine most of them by 1H-NMR. By fluorometric detection it was possible to detect them at fmol levels. These methods were successfully applied to determine the absolute configuration at the C15 position of a novel branched-chain fatty acid of a ceramido isolated from the Epiphytic Dinoflagellate, Coolia monotis, by using 80 μg of the ceramido.