ENANTIOMERIC SEPARATION OF AMINES BY GAS CHROMATOGRAPHY USING DERIVATIZED CYCLODEXTRINS AS STATIONARY PHASES

Abstract

Thirty-two amines with different types and positions of substitution including 1-phenylethylamines, 1-phenylpropyamines, and 1-aminoindanes were synthesized by reductive amination. All synthesized amines were derivatized to trifluoroacetyl (TFA) derivatives. Enantioseparation of all TFA amine derivatives were studied by capillary gas chromatography using 2,3-di-O-methyl-6-O-tert-butyldimethylsilyl derivative of alpha, beta, and gamma cyclodextrins (ASiMe, BSiMe, and GSiMe, respectively) as chiral stationary phases. The influence of temperature, cyclodextrin ring size, and structure of amines on retention and enantioselectivity were studied. Both type and position of substituents on amine structures strongly influence enantioseparation on three chiral columns. In addition, cyclodextrin ring size also affects the enantioseparation as well. ASiMe column could separate twenty-four enantiomers of TFA amine derivatives. Meta-substituted TFA amine derivatives show good enantioseparation, except for trifluoromethyl group. All ortho-substituted TFA amine derivatives could be separated. Unfortunately, para-substituted TFA amine derivatives show poor enantioseparation or could not be separated. BSiMe column could also separate twenty-four enantiomers of TFA amine derivatives. Ortho- and meta-substitution of halogenated TFA amine derivatives seemed to promote the enantioseparation. All TFA 1-aminoindanes could be separated, except for 5ClA. GSiMe column could separate only thirteen TFA amine derivatives. Most of TFA amine derivatives show poorer enantioseparation than both ASiMe and BSiMe columns, except for 4Me, 4MeP, 4CFP. Moreover, all TFA amine derivatives could be successfully enantioseparated with at least one column, except for 4OMeP.