Chiral Separation of Racemates with Molecularly Imprinted Polymeric Membranes

本课题研究结果如下：研究了构建分子识别位点候选材料寡肽衍生物的氨基酸残基数目对手性识别能力的影响。采用选择性分子印迹法，由氨基酸残基数为3 ~ 6的寡肽衍生物形成手性识别位点。很明显，数字4，换句话说，四肽衍生物，是手性识别位点的最佳候选材料。以聚苯乙烯树脂为载体，制备了由d -氨基酸残基或l -氨基酸残基组成的四肽衍生物H-Asp(OcHex)- leu - asp (OcHex)- glu (OBzl)- och_2 - (DLDE)。用光学纯的Boc-Trps和外消旋Boc-Trps作为打印分子，将四肽衍生物转化为手性识别位点。手性识别能力取决于打印分子的绝对构型和构成氨基酸残基的绝对构型的结合。由d -氨基酸残基组成的DLDE衍生物制备并由Boc-D-Trp印迹的膜优先识别d -异构体而不是相应的l -异构体，反之亦然。在本研究中，还明确了外消旋打印分子在产生手性识别位点方面是有效的。所生成的手性识别位点的亲和常数为9.6 × 10^3 mol dm^<-3>，与分子印迹条件无关。通过电渗析实现对映选择性渗透。最佳选择性为5.9，与吸附选择性相对应。以Boc-D-Trp或Boc-L-Trp为印迹分子，利用不同的寡肽镊子制备了分子印迹聚合物膜。所形成的分子识别位点的手性识别能力取决于膜制备（分子印迹）过程中所采用的印迹分子的绝对构型，而候选寡肽镊子由l -氨基酸残基组成。换句话说，由d -异构体印迹的膜优先识别d -异构体而不是相应的l -异构体，反之亦然。寡肽镊子的靶分子与手性识别位点的亲和常数高于单链寡肽衍生物。这些膜选择性地运输对映体，通过透析优先纳入膜。这些膜的渗透选择性超过了它们的吸附选择性。以ac -d -色氨酸或ac - l -色氨酸为打印分子，制备了一种新型的含5元环碳酸酯的候选聚合物[（2-氧-1,3-二恶olan-4-基）甲基丙烯酸甲酯-共丙烯腈]，并将其转化为手性识别材料。分子印迹聚合物具有手性识别能力，被Ac-D-Trp的d -异构体印迹的材料优先识别d -异构体，反之亦然。分子印迹材料的吸附等温线证实了手性识别位点的形成。少

The following results have been obtained through the present research project : The effect of constituting amino acid residue number of oligopeptide derivatives, which are candidate materials to construct molecular recognition sites, on chiral recognition ability was investigated. Chiral recognition sites were formed from oligopeptide derivatives, of which constituting amino acid residue numbers were three to six, by adopting an alternative molecular imprinting. It was made clear that the number four, in other words, the tetrapeptide derivative, is the best candidate material to from a chiral recognition site.Molecularly imprinted polymeric membranes were prepared from polystyrene resin bearing tetrapeptide derivatives H-Asp(OcHex)-Leu-Asp(OcHex)-Glu(OBzl)-OCH_2- (DLDE) consisting of D-amino acid residues or L-amino acid residues. The tetrapeptide derivatives were converted into chiral recognition sites by using not only an optically pure Boc-Trp but also racemic Boc-Trps as a print mo … More lecule. The chiral recognition ability depends on the combination of the absolute configuration of the print molecule and that of constituting amino acid residues. The membrane prepared from DLDE derivative consisting of D-amino acid residues and imprinted by Boc-D-Trp recognized the D-isomer in preference to the corresponding L-isomer and vice versa. In the present study, it was also made clear that racemic print molecules were effective in generating chiral recognition sites. The affinity constant of the generated chiral recognition site was determined to be 9.6 x 10^3 mol dm^<-3>, which was independent of the molecular imprinting conditions. Enantioselective permeation was attained by applying electrodialysis. An optimum selectivity of 5.9, which corresponds to the adsorption selectivity, was attained.Molecularly imprinted polymeric membranes were prepared from various oligopeptide tweezers by the adoption of Boc-D-Trp or Boc-L-Trp as a print molecule. The chiral recognition ability of the formed molecular recognition sites was dependent on the absolute configuration of the print molecule adopted in the membrane preparation (molecular imprinting) process, whereas the candidate oligopeptide tweezers consisted of the L-amino acid residues. In other words, the membranes imprinted by the D-isomer recognized the D-isomer in preference to the corresponding L-isomer, and vice versa. The affinity constant between the target molecule and the chiral recognition site from oligopeptide tweezers was higher than that from a single-strand oligopeptide derivative. Those membranes selectively transported the enantiomer, which was preferentially incorporated into the membrane by dialysis. The permselectivities for these membranes exceeded their adsorption selectivities.A novel candidate polymeric material bearing 5-membered cyclic carbonate, poly[(2-oxo-1,3-dioxolan-4-yl)methyl methacrylate-co-acrylonitrile], converted into a chiral recognition material by adopting Ac-D-Trp or Ac-L-Trp as a print molecule. The molecularly imprinted polymer showed chiral recognition ability, and the material imprinted by the D-isomer of Ac-D-Trp recognized the D-isomer in preference to the corresponding L-isomer, and vice versa. The formation of the chiral recognition site was confirmed by apparent adsorption isotherms of the molecularly imprinted materials. Less