Direct separation of the enantiomers of reboxetine by liquid chromatography on different cellulose- and amylose-based chiral stationary phases

Racemic reboxetine, (R,S)-2[(R,S)-alpha-(2-ethoxyphenoxybenzyl] morpholine methane sulfonate, is a mixture of the (R,R) and (S,S) enantiomers. Separat ion oi the enantiomers of reboxetine by liquid chromatography has been inve stigated on three chiral stationary phases - cellulose tris(3,5-dimeihylphe nylcarbamate) (Chiralcel OD), cellulose tris-(phenylcarbamate) (Chiralcel O C), and amylose tris-(3,5-dimethylphenylcarbamate) (Chiralpak AD). On these stationary phases the resolution of the (R,R) and (S,S) enantiomers was hi ghly dependent on mobile-phase composition. When Chiralcel OD and OC were u sed, addition of diethylamine to the mobile phase greatly improved the sepa ration of the enantiomers. On Chiralpak AD enantioseparation was achieved w ithout the use of additives. Solute-mobile phase-stationary phase interacti ons which might participate in the mechanism of enantiorecognition are disc ussed.