Enantiomeric resolution of anionic R/ S-1,1′-binaphthyl-2,2′-diyl hydrogen phosphate by capillary electrophoresis using anionic cyclodextrin derivatives as chiral selectors

Abstract

The enantioseparation of racemic 1,1′-bi-2-naphthol (1), 1,1′-binaphthyl-2,2′-diyl hydrogen phosphate (2) and 1,1′-binaphthyl-2,2′-diamine (3) using native β-cyclodextrin (β-CD) and its anionic derivatives such as carboxymethyl-β-CD (CM-β-CD), sulfoethyl ether of β-cyclodextrin (SEE-β-CD) and sulfobutyl ether of β-cyclodextrin (SBE-β-CD) has been studied. The successful resolution of 2 in the anionic form using negatively charged cyclodextrin derivatives shows that the role of the Coulombic interactions is not critical for the chiral guest-host recognition in capillary electrophoresis (CE). The application of SEE-β-CD as a chiral selector in CE has been demonstrated for the first time. Comparison of the enantioseparation efficiencies of SEE-β-CD and SBE-β-CD shows that the spacer length and the substitution pattern are factors with rather low importance and that the resolution efficiency is mainly determined by the counter-current mobility of the chiral selector.