2001 Volume 17 Issue 10 Pages 1183-1187
Enantiomer separation of mandelates and their analogs, which are important intermediates in asymmetric synthetic and pharmaceutical chemistry, was investigated by capillary gas chromatography using different cyclodextrin derivative chiral stationary phases (CD CSPs). The used cyclodextrin derivatives included permethylated β-CD (PMBCD), permethylated γ-CD, heptakis(2,6-di-O-butyl-3-O-butyryl)-β-CD, heptakis(2,6-di-O-pentyl-3-O-acetyl)-β-CD and heptakis(2,6-di-O-nonyl-3-O-trifluoroacetyl)-β-CD (DNTBCD), respectively. Among all the CSPs used, PMBCD and DNTBCD exhibited the broadest and best enantioselectivity for all the racemates investigated. Some thermodynamic parameters were evaluated and an enthalpy-entropy compensation effect was observed in enantiomer separation processes of mandelates and their analogs. Based on thermodynamic data and molecular mechanics calculations, the chiral recognition mechanism of mandelate derivatives on CD CSPs is discussed.