Relationship between chromatographic resolution and amide structure of chiral 2-hydroxy acids as O-(−)-menthoxycarbonylated diastereomeric derivatives for enantiomeric separation on achiral gas chromatography

When comparing with our previous O-trifluoroacetylated(−)-menthyl ester derivatization method, the present results suggested that size differences between groups attached to the chiral center and conformational rigidity can have stronger effects on resolution than the distance between chiral centers. The elution of R- and S-stereoisomers was affected by the class of amine; i.e., primary, secondary, or cyclic, regardless of the substituents on the amine group, the structure of the 2-hydroxy acid, and the polarity of the column.