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

Both theoretical and experimental evidences prove that the absolute configuration of an cx-chiral carboxylic acid can be safely assigned by comparison of the H-1 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 (WS) assignment directly from the NMR chemical shifts. (C) 1997 Elsevier Science Ltd.