Direct High-Performance Liquid Chromatographic Separation of Peptide Enantiomers: Study on Chiral Recognition by Systematic Evaluation of the Influence of Structural Features of the Chiral Selectors on Enantioselectivity
作者:Christoph Czerwenka、Michael Lämmerhofer、Norbert M. Maier、Kari Rissanen、Wolfgang Lindner
DOI:10.1021/ac020372l
日期:2002.11.1
All-R/all-S enantiomers of oligoalanines (Alan, n = 1−10) with N-terminal protection group have been separated by HPLC on chiral stationary phases based on various cinchona alkaloid selectors. Structure−enantioselectivity relationships derived by extensive selector structure optimization provided insights into binding mechanisms and chiral recognition. Their interpretation was supported by X-ray crystal structures of amino acid and dipeptide, respectively, in complex with chiral selector. Optimized selectors have bulky elements representing steric barriers and deep binding pockets that afforded very high enantioselectivities; e.g., for the all-R and all-S enantiomers of N-(3,5-dinitrobenzoyl)alanylalanine, an α-value of 20.0 (corresponding to ΔΔG of −7.43 kJ/mol) was obtained with a chiral stationary phase based on 6‘-(neopentoxy)-9-O-tert-butylcarbamoylcinchonidine. Further, a chiral stationary phase based on 1,4-bis(9-O-quinidinyl)phthalazine was able to distinguish between the all-R and all-S enantiomers of hepta- to decaalanine peptides with enantioselectivity values between 1.8 and 1.9, corresponding to ΔΔG of −1.46 and −1.59 kJ/mol, respectively.
利用基于各种金鸡纳生物碱选择剂的手性固定相,通过高效液相色谱法分离了带有 N 端保护基团的低聚丙氨酸(Alan,n = 1-10)的全 R/ 全 S 对映异构体。通过对选择剂结构的广泛优化,得出了结构-对映体选择性关系,从而深入了解了结合机制和手性识别。氨基酸和二肽分别与手性选择剂复合的 X 射线晶体结构支持了对它们的解释。优化后的选择子具有代表立体障碍的笨重元素和深结合口袋,可提供非常高的对映选择性;例如,全 R 和全 S 手性选择子的对映选择性都非常高、对于 N-(3,5-二硝基苯甲酰)丙氨酰丙氨酸的全-R 和全-S 对映体,使用基于 6'-(新戊氧基)-9-O-叔丁基氨基甲酰基辛可尼丁的手性固定相,可获得 20.0 的 α 值(对应于 -7.43 kJ/mol 的 ΔΔG)。此外,基于 1,4-双(9-O-奎宁基)酞嗪的手性固定相能够区分七至十丙氨酸肽的全 R 和全 S 对映体,对映体选择性值介于 1.8 和 1.9 之间,对应的 ΔΔG 分别为 -1.46 和 -1.59 kJ/mol。