D,L-α-氨基酸对映体在冠醚手性柱上的分离

Enantioseparation of D,L-α-Amine Acid on Crown Ester Chiral Stationary Phases

在(+)-(18-冠-6)-2,3,11,12-四羧酸手性固定相上对15种天然的D,L-α-氨基酸对映异构体进行手性分离研究。分别考察了流动相中有机添加剂甲醇的含量,酸性添加剂的种类和浓度对手性分离的影响,并初步探讨了溶质在手性柱上的手性识别的机理。可能是因为α-氨基酸上的伯胺基团与流动相中H+形成强极性的铵离子R-NH3+,由于两个对映体形成的R-NH3+在冠醚空腔内的氢键作用及适应性不同而发生手性识别。流动相中甲醇含量以及酸性添加剂种类和浓度的变化都影响了强极性的铵离子R-NH3+在流动相和固定相之间的平衡,导致手性识别的强弱差异。另外还考察了柱温变化对苯基丙氨酸和酪氨酸分离的影响,实验所选取的温度都低于对映体转折温度T=467.3K,因此在所研究的实验温度范围内,固定相构型未发生明显变化,保留机制及对映选择作用不变。ΔΔH0和ΔΔS0都为负,说明该化合物的拆分为焓驱动过程。

The enantioseparation of D, L-a-amine acid on （ ＋ ） -（ 18-crown-6 ） -2,3,11,12-tertcarboxyl acid chiral stationary phase （CSP）, and the influence of the methanol and acid addictives on the separation were investigated. The chiral recognition mechanism was also discussed. It is possible that the solute R-NH2 was protoned to R-NH3 , and the fitness and interaction in the crown ester cavity between the solutes and CSP were the dominant chiral recognition mechanism for the solutes. The concentration of methanol and composition of acid additive influenced the equilibrium of R-NH^3＋ between mobile phase and stationary phase, which resulted in the chiral recognition. In addition, the influence of column temperature on the enantiosepartion of phenylalanine and tyrosine was also investigated. And all the tested temperatures were lowered than the isotemperature T =467.3 K. The result showed that the configuratoin of stationary phase didn＇t have evidence changed, and reservation mechanism and enantiotropy selection action remained changeless. △△H^0and △△S^0 were negative which showed that the enantioseparation of two solutes was enthalpy control.