Methoxypropylamino β-cyclodextrin clicked AC regioisomer for enantioseparations in capillary electrophoresis

In this paper, we demonstrate:
• The click synthesis of a AC regioisomer cationic cyclodextrin (CD) as chiral selector.
• The good enantioselectivities (chiral resolution over 5) for acidic racemates.
• The strong chiral recognition of new CD by NMR study.
• Baseline enantioseparation of some acidic racemates at CD of 0.5 mM.

In this work, a novel methoxypropylamino β-cyclodextrin (β-CD) clicked AC regioisomer, 6A-4-hydroxyethyl-1,2,3-triazolyl-6C-3-methoxypropylamino β-cyclodextrin (HETz-MPrAMCD), was synthesized via nucleophilic addition and click chemistry. The chiral separation ability of this AC regioisomer cationic CD was evaluated toward 7 ampholytic and 13 acidic racemates by capillary electrophoresis. Dependence of enantioselectivity and resolution on buffer pH (5.5–8.0) and chiral selector concentration (0.5–7.5 mM) was investigated. Enantioselectivities (α ≥ 1.05) could be achieved for most analytes under optimal conditions except dansyl-dl-noreleucine and dansyl-dl-serine. The highest resolutions for 2-chloromandelic acid p-hydroxymandelic acid were 15.6 and 9.7 respectively. The inclusion complexation between HETz-MPrAMCD and each 3-phenyllactic acid enantiomer was also revealed with nuclear magnetic resonance study.

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