DIRECT CHIRAL HPLC SEPARATION OF THE ENANTIOMERS OF FLUORINATED N-ARYLAMINO-1-ARYLMETHYLPHOSPHONATE ESTERS - SUBSTITUENT EFFECTS ON THE ENANTIOSELECTIVITY

Racemic N-arylamino-1-arylmethylphosphonic acid diethyl esters with various fluorinated substituents in one or both aryl rings have been resolved in their enantiomers by a direct HPLC method, using chiral stationary phases. The chiral separation on Chiralcel OD strongly depends on the substitution pattern in the N-aryl and/or in the C-aryl moieties and it improves markedly with the polarity of the fluorinated substituent. A new Pirkle's chiral stationary phase (R)-alpha-Burke 1 is more efficient and in some cases more enantioselective than other Pirkle's phases. A chiral recognition model between this phase and the enantiomers of an analyte afforded to propose the absolute configuration of the optical isomers and to relate it to the chiroptical behaviour.