Inherently chiral dialkyloxy-calix[4]arene acetic acids as enantiodiscriminating additives for high-performance liquid chromatography separation of d,l-amino acids

Inherently chiral dialkyloxy-calix[4]arene acetic acids with asymmetric placement of substituents on the lower rim of the macrocycle were first studied as enantiodiscriminating additives to the mobile phase MeCN/H2O/HCOOH (75/25/0.02 by volume) in the high-performance liquid chromatography (HPLC) separation of d,l-alanine and d,l-valine on the achiral stationary phase ZORBAX Original CN. The dependence of enantio-binding properties on the position of alkyl groups is demonstrated. The highest resolution (1.65) and enantioselectivity (1.80) were obtained for the 1,2-dipropyloxy-calix[4]arene acetic acid.

Automated summary

In this study, inherently chiral dialkyloxy-calix[4]arene acetic acids were investigated as enantiodiscriminating additives in HPLC separations, showing a significant impact on the separation of d,l-alanine and d,l-valine. The study also revealed the dependence of enantio-binding properties on the position of alkyl groups within the macrocycle, with the highest resolution and enantioselectivity achieved with the 1,2-dipropyloxy-calix[4]arene acetic acid.