Studies on the Development of Selectively Modified Cyclodextrin Stationary Phases for HPLC

建立了选择性分离甲基化的β-和γ-环糊精(CD)衍生物的方法。它们在2-位(2-MM-)、3-位(3-MM-)、2-和3-位(2，3-DM-)和2-、3-和6-位(2，3，6-TM-)上的羟基均被甲基化。用MM-、DM-和TM-分别对未修饰的CD进行前处理，得到单甲基化、双甲基化和三甲基化的CD衍生物，单烯丙氧基乙基化后，用二甲氧基甲基硅烷处理，然后在硅胶表面偶联。因此，可以得到选择性甲基化的CD键合高效液相色谱固定相，而不需要未反应的间隔臂。这种Cd固定相的制备方法能够准确地估计Cd的固定量，并且易于固定伽马-Cd衍生物和β-Cd衍生物。未修饰的Gamma-Cd和3-MM-Gamma-Cd固定相能拆分大部分对映体，而2-MM-Gamma-Cd和2，3，6-Tm-Gamma-Cd固定相不能拆分。这些结果积极地表明，2-羟基对这些溶质的手性识别有重要贡献。结果表明，选择性甲基化的伽马-镉固定相具有较高的对映体选择性。对选择性甲基化的β-CD固定相的类似研究目前正在进行中。

The method to isolate selectively methylated beta-and gamma-cyclodextrin (CD) derivatives could be established. Their hydroxyl groups at 2-position (2-MM-) 3-position (3-MM-), both 2- and 3-positions (2,3-DM-) and 2-, 3-and 6-positions (2,3,6-TM-) were methylated. The mono-, di- and trimethylated CD derivatives are donared by prefixing the unmodified CD with MM-, DM- and TM-, respectively.After monoallyloxyethylation, the unmodified and methylated CDs were treated with dimethoxymethylsilane, followed by coupling on the silica gel surface. Selectively methylated CD-bonded stationary phases for HPLC without an unreacted spacer arm could be thus obtained. This preparation method of the CD stationary phases brought about a ready estimation of the precise amount of CD immobilized and easy immobilization of the gamma-CD derivatives as well as the beta-CD ones.The chiral recognition abilities of the resulting gamma-CD stationary phases were evaluated using dansylamino acids as model solutes. Unmodified gamma-CD and 3-MM-gamma-CD stationary phases could resolve most of their enantiomers, while 2-MM-gamma-CD and 2,3,6-TM-gamma-CD stationary phases could not at all. These results positively suggest an important contribution of the 2-hydroxyl group to the chiral recognition for these solutes. It is found that the selectively methylated gamma-CD stationary phases exhibit the high enantioselectivities as expected. Similar investigation is now in progress on the selectively methylated beta-CD stationary phases.