Determination of the Absolute Configuration of Amines and α-Amino Acids by 1H NMR of (R)-O-Aryllactic Acid Amides
- 1 January 1996
- journal article
- research article
- Published by American Chemical Society (ACS) in The Journal of Organic Chemistry
- Vol. 61 (21) , 7285-7290
- https://doi.org/10.1021/jo9604191
Abstract
(R)-O-Aryllactic acid (ROAL) amides derived from α-chiral primary amines and α-amino acid esters show different chemical shifts in 1H NMR spectroscopy (300 MHz) depending on their configuration. Molecular mechanics, semiempirical calculations, and 1H NMR studies suggest that, in solution, these amides prefer an ap-Z conformation with the CαOAr and CO groups close to anti-periplanar as in the case of mandelic acid amides. The proposed conformational preference is different from that of the ROAL esters (CαH and CO groups in a syn-periplanar conformation). The conformational model for ROAL amides allows the absolute configuration assignment of primary amines and α-amino acid esters according to the relative position of the aryl group and the substituents on the amine moiety, and also their enantiomeric composition.Keywords
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