Comparison of Chiral Recognition of Binaphthyl Derivatives with l-Undecyl-Leucine Surfactants in the Presence of Arginine and Sodium Counterions

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In this study the chiral selectivity of L-undecyl-leucine (und-leu) for binapthyl derivatives was examined with the use of arginine and sodium counterions at pH's ranging from 7 to 11. The objective of this project was to investigate whether a cationic amino acid, such as arginine would achieve enhanced chiral selectivity when utilized as the counterion in the place of sodium in micellar electrokinetic chromatography. The data indicate that und-leu has significantly improved chiral selectivity toward 1,1′-binaphthyl-2,2′-diyl hydrogenphosphate (BNP) enantiomers in the presence of arginine counterions in comparison to sodium and that, at least in the case of this study, the enantiomeric form of the arginine did not appear to play a role in the chiral selectivity. The maximum resolution (Rs) achieved for BNP when sodium was used as the counterion was ~0.6. However, when arginine was used as the counterion, the maximum resolution for BNP was ∼4.1. This was an increase in resolution of ∼ 7-fold. However, no significant difference was observed for the enantiomers of 1,1′-bi-2- naphthol. In order to learn more about why this might be the case, NMR studies were conducted to examine what role the counterion might play in enantiomeric recognition.

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