Study of the mechanism of enantioseparation.: IV.: Study of enantioseparation of some derivatives of phenylcarbamic acid using π-complex stationary phase in HPLC

The Whelk-O 1 chiral stationary phase (CSP) is an useful column for the high performance liquid chromatographic (HPLC) resolution of enantiomers of 2-methoxy-1-[(4-methylpiperazino)methyl]ethyl esters of N-(2-,3-, and 4-alkoxyphenyl)carbamic acid (group of the local anaesthetic drugs) in the organic mode and the reversed mode. According to the results of enantiomeric separations in different mobile phases [containing organic modifiers (methanol, acetonitrile, water), with different additives of acetic acid and trimethylamine], it can be postulated that the piperazino part of the phenylcarbamic acid compound is essential because the separation of piperidino, pyrrolidino, and perhydroazepino esters of alkoxy phenylcarbamic acid were not observed. Also the influence of the environment near the analyte's stereogenic is important for enantioseparation. A comparison of the enantiomeric elution order and the configuration of the chiral selector shows that R-(-) enantiomers are more retained on the (R,R) Whelk-O 1 column and S-(+) enantiomers are more retained on the (S,S) Whelk-O 1 column.