The use of ethyl 2-(9-anthryl)-2-hydroxyacetate for assignment of the absolute configuration of carboxylic acids by 1H NMR

Abstract

Both theoretical and experimental evidences prove that the absolute configuration of an α-chiral carboxylic acid can be safely assigned by comparison of the 1H NMR spectra of its esters with ( R)- and ( S)-ethyl 2-(9-anthryl)-2-hydroxyacetate ( 5, AHA). A simplified conformational model, based on the dominance of the ap over the sp conformer and the selective effect of the anthryl group, allows the ( R/ S) assignment directly from the NMR chemical shifts.