Synthesis Of Novel β-cyclodextrins And Chiral Separation In Capillary Electrophoresis

When people realize that two enantiomers of aracemic drug may have opposite effect in pharmacological treatment,the study of chiral separation is becoming demanding. In recent years, chiral separation has been an emphasis.Among all chiral selectors in use,cyclodextrins have recieved a lot of attention in academic research and industrial applications. In continuation to the research in our laboratory, in this thesis we have developed new series of imidazole-functionalized cyclodextrinsfor the application of chiral separation.By introducing methoxy group (-OCH3) and hydroxy group (-OH) at the end of the imidazole groups, theymayform hydrogen-bonds with analytes, which can enhance the interactions between cyclodextrins andanalytes to improve the effect of separation.In this paper, the first cationic CD we developed is6A-(3-methoxy-propyl imidazole)-β-cyclodextrin chloride (MPrIMCDCl). On the basis of6A-(3-propyl imidazolium)-β-cyclodextrinchloride salt (PrIMCDCl), we introduced a methoxy group that can form hydrogen-bonding with analytes and enhance the interactions between cyclodextrin andanalytes and thus the chiral recognition. In subsequent capillary electrophoresis separation experiments, the increased chiral separation was demonstrtaed owing to the introduction of methoxy. From the chiral separation at varied chiral selector concentrations, the equilibrium constants(K) between CD and analytes were further calculated and compared. And the role of hydrogen bonding in enhancing chiral recognition was correlated. In the study, the as-developed6A-(3-methoxy-propyl imidazole)-β-cyclodextrin chloride (MPrIMCDCl) was found to present much better chiral separation towards dansyl amino acids than the reference CD,6A-(3-methoxy-propyl ammonium)-β-cyclodextrin chloride (MPrAMCD).The second series are disubstituted positively charged β-cyclodextrin:6A-(4hydroxyethyl)-1,2,3-triazole-6c-[1-(2-methoxyethyl)]imidazolium-β-cyclodextrin chloride and6A-(4-hydroxyethyl)-1,2,3-triazole-6c-[1-(2-methoxy-propyl)] imidazolium β-cyclodextrin chloride. On the basis of the first category cyclodextrins, we introduce hydroxyl-terminated triazole group toachieve furrther enhanced hydrogen bonding with oxygen atoms. Such disubstituted positively charged β-cyclodextrins were developedby the use of click chemistry to introduceboth methoxy-terminated imidazole groups and hydroxyl-terminated triazole groups onto A, C positions of the primary rim of β-cyclodextrins.