Lin Ching-Erh, Lin Sheng-Li, Fang I-Ju, Liao Wei-Ssu, Chen Chia-Chong
Department of Chemistry, National Taiwan University, Taipei, Taiwan.
Electrophoresis. 2004 Aug;25(16):2786-94. doi: 10.1002/elps.200405968.
We investigated the enantioseparations of racemic hydrobenzoin, together with benzoin and benzoin methyl ether, in capillary electrophoresis (CE) using the single-isomer heptakis(2,3-dihydroxy-6-O-sulfo)-beta-cyclodextrin (SI-S-beta-CD) as a chiral selector in the presence and absence of borate complexation and enantiomer migration reversal of hydrobenzoin with a dual CD system consisting of SI-S-beta-CD and beta-CD in the presence of borate complexation at pH 9.0 in a borate buffer. The enantioselectivity of hydrobenzoin increased remarkably with increasing SI-S-beta-CD concentration and the enantioseparation depended on CD complexation between hydrobenzoin-borate and SI-S-beta-CD. The (S,S)-enantiomer of hydrobenzoin-borate complexes interacted more strongly than the (R,R)-enantiomer with SI-S-beta-CD. The enantiomers of hydrobenzoin could be baseline-resolved in the presence of SI-S-beta-CD at a concentration as low as 0.1% w/v, whereas the three test analytes were simultaneously enantioseparated with addition of 0.3% w/v SI-S-beta-CD or at concentrations >2.0% w/v in a borate buffer and 0.5% w/v in a phosphate background electrolyte at pH 9.0. Compared with the results obtained previously using randomly sulfated beta-CD (MI-S-beta-CD) in a borate buffer, enantioseparation of these three benzoin compounds is more advantageously aided by SI-S-beta-CD as the chiral selector. The enantioselectivity of hydrobenzoin depended greatly on the degree of substitution of sulfated beta-CD. Moreover, binding constants of the enantiomers of benzoin compounds to SI-S-beta-CD and those of hydrobenzoin-borate complexes to SI-S-beta-CD were evaluated for a better understanding of the role of CD complexation in the enantioseparation and chiral recognition. Enantiomer migration reversal of hydrobenzoin could be observed by varying the concentration of beta-CD, while keeping SI-S-beta-CD at a relatively low concentration. SI-S-beta-CD and beta-CD showed the same chiral recognition pattern but they exhibited opposite effects on the mobility of the enantiomers.
我们研究了外消旋氢化苯偶姻以及苯偶姻和苯偶姻甲醚在毛细管电泳(CE)中的对映体拆分,使用单异构体七(2,3 - 二羟基 - 6 - O - 磺基)-β-环糊精(SI - S -β-CD)作为手性选择剂,研究了有无硼酸盐络合的情况,以及在pH 9.0的硼酸盐缓冲液中,在硼酸盐络合存在下,使用由SI - S -β-CD和β-CD组成的双环糊精系统使氢化苯偶姻对映体迁移反转的情况。氢化苯偶姻的对映选择性随着SI - S -β-CD浓度的增加而显著提高,对映体拆分取决于氢化苯偶姻 - 硼酸盐与SI - S -β-CD之间的环糊精络合。氢化苯偶姻 - 硼酸盐络合物的(S,S)-对映体与SI - S -β-CD的相互作用比(R,R)-对映体更强。在硼酸盐缓冲液中,当SI - S -β-CD浓度低至0.1% w/v时,氢化苯偶姻的对映体可以实现基线分离,而在pH 9.0的硼酸盐缓冲液中添加0.3% w/v的SI - S -β-CD或浓度>2.0% w/v,以及在磷酸盐背景电解质中添加0.5% w/v时,三种测试分析物可以同时实现对映体分离。与之前在硼酸盐缓冲液中使用随机硫酸化β-环糊精(MI - S -β-CD)获得的结果相比,SI - S -β-CD作为手性选择剂更有利于这三种苯偶姻化合物的对映体分离。氢化苯偶姻的对映选择性很大程度上取决于硫酸化β-环糊精的取代度。此外,评估了苯偶姻化合物对映体与SI - S -β-CD的结合常数以及氢化苯偶姻 - 硼酸盐络合物与SI - S -β-CD的结合常数,以便更好地理解环糊精络合在对映体分离和手性识别中的作用。通过改变β-CD的浓度,同时保持SI - S -β-CD处于相对较低的浓度,可以观察到氢化苯偶姻对映体迁移反转。SI - S -β-CD和β-CD表现出相同的手性识别模式,但它们对映体迁移率的影响相反。