De Bruin T J, Marcelis A T, Zuilhof H, Rodenburg L M, Niederländer H A, Koudijs A, Overdevest P E, Van der Padt A, Sudhölter E J
Laboratory of Organic Chemistry, Wageningen University, Wageningen, The Netherlands.
Chirality. 2000 Aug;12(8):627-36. doi: 10.1002/1520-636X(2000)12:8<627::AID-CHIR5>3.0.CO;2-1.
A Micelle-enhanced ultrafiltration (MEUF) separation process was investigated that can potentially be used for large-scale enantioseparations. Copper(II)-amino acid derivatives dissolved in nonionic surfactant micelles were used as chiral selectors for the separation of dilute racemic amino acids solutions. For the alpha-amino acids phenylalanine, phenylglycine, O-methyltyrosine, isoleucine, and leucine good separation was obtained using cholesteryl L-glutamate and Cu(II) ions as chiral selector with an operational enantioselectivity (alpha(op)) up to 14.5 for phenylglycine. From a wide set of substrates, including four beta-amino acids, it was concluded that the performance of this system is determined by two factors: the hydrophobicity of the racemic amino acid, which results in a partitioning of the racemic amino acid over micelle and aqueous solution, and the stability of the diastereomeric complex formed upon binding of the amino acid with the chiral selector. The chiral hydrophobic cholesteryl anchor of the chiral selector also plays an active role in the recognition process, since inversion of the chirality of the glutamate does not yield the reciprocal enantioselectivities. However, if the cholesteryl group is replaced by a nonchiral alkyl chain, reciprocal operational enantioselectivities are found with enantiomeric glutamate selectors.
研究了一种胶束增强超滤（MEUF）分离过程，该过程有可能用于大规模对映体分离。溶解在非离子表面活性剂胶束中的铜（II）-氨基酸衍生物被用作手性选择剂，用于分离稀外消旋氨基酸溶液。对于α-氨基酸苯丙氨酸、苯甘氨酸、O-甲基酪氨酸、异亮氨酸和亮氨酸，使用胆固醇基L-谷氨酸和铜（II）离子作为手性选择剂可实现良好的分离，苯甘氨酸的操作对映选择性（α(op)）高达14.5。从包括四种β-氨基酸在内的多种底物中得出结论，该系统的性能由两个因素决定：外消旋氨基酸的疏水性，这导致外消旋氨基酸在胶束和水溶液之间分配；以及氨基酸与手性选择剂结合形成的非对映体复合物的稳定性。手性选择剂的手性疏水胆固醇基锚在识别过程中也起着积极作用，因为谷氨酸手性的反转不会产生相反的对映选择性。然而，如果胆固醇基被非手性烷基链取代，则使用对映体谷氨酸选择剂会发现相反的操作对映选择性。
