Direct Chiral Separation of Binaphthyl Derivatives Using Atroposelective Antibodies

Abstract

A simple procedure for chiral separation based on the difference in the molecular weights of the antigen-antibody complex and analyte is developed. We raise monoclonal antibodies (mAbs) highly specific for the R-or S-isomer of a binaphthyl derivative (BN) by immunizing mice with the corresponding BN enantiomer. Aqueous solutions of racemic BN are mixed with mAbs. The free BN is separated by ultrafiltration. The enantiomers of BN are obtained with a high e.e. using atroposelective antibodies.Chirality is crucial in various scientific fields such as pharmaceuticals, [1] chemistry, [2][3][4] and materials science. [5] For example, in pharmaceutical applications employing a specific enantiomer is especially important. Often one enantiomer displays the desired effect, while the other elicits serious side effects. Therefore, chiral separations on both industrial and laboratory scales are important. High-performance liquid chromatography is a popular chiral separation methodology. [6] To date, many researchers have devoted much effort to develop chiral stationary phases (CSPs) such as synthetic polymers, [7] saccharides, [8,9] biomacromolecules, etc. [10][11][12] However, trial and error is still required for developing CSPs. One promising approach toward a straightforward chiral separation strategy is to use antibodies that precisely recognize the chirality of the target molecule. [13] With the advent of cell technology, [14] it is now possible to prepare individual antibodies, monoclonal antibodies (mAbs), in large amounts and in a homogeneous form semi-permanently.Many researchers have developed mAbs against optically active compounds for various purposes. [15][16][17][18][19][20] Among them, the use of mAbs as CSP of immuno affinity chiral columns has been extensively studied. [21] However, harsh elution conditions are necessary due to the high affinity of mAbs against target molecules. Eluting a tightly bound enantiomer while maintaining the stability of mAbs is problematic. [22][23][24] In addition, optimization of the immobilization method of mAbs onto columns is necessary to retain the binding affinity of mAbs. [25] To fully utilize the characteristic of mAbs, a more convenient methodology without columns for chiral separation is necessary.Our research focuses on the basic properties of mAbs, including high specificity for the target molecule and the molecular weight. Unlike chromatographic methods, the high molecular recognition ability of mAb can separate enantiomers with a one-step physical event. The large difference in the molecular weights between the analyte and mAbs realizes the separation of the free analyte by ultrafiltration. In addition, both enantiomers can be obtained by a simple one-step procedure where mAbs are prepared for each enantiomer.Herein, we report a convenient column-free methodology for chiral separation. This study provides insight on how to avoid difficulties when using mAbs. We chose a binaphthyl derivative with axial chirality, which is a well known asymmetric ligand, as a target ...

Artificial Metalloenzymes: From Selective Chemical Transformations to Biochemical Applications

“…Recently, Harada and coworkers employed monoclonal antibodies (mAbs) as protein scaffolds for ArMs catalyzing Friedel–Crafts reactions [ 66 ]. They previously developed atroposelective mAbs by immunological optimization of mAbs over binaphthyl (BN) derivatives [ 67 , 68 ]. These anti-BN mAbs could bind 1,1′-bi-isoquinoline (BIQ)-based metal catalysts and provide a chiral environment for the selective reaction.…”

Atroposelective antibodies as a designed protein scaffold for artificial metalloenzymes

“…Recently, we revealed that mAbs prepared by immunization with R -and S -4,4′-([1,1′-binaphthalene]-2,2′-diylbis(oxy))dibutanoic acid (BN ( R ) and BN ( S ) in Fig. 1a) or racemic BN precisely recognize the axial chirality of BN 43,44 . Hence, we defined the anti-BN mAbs as an atroposelective antibody.…”

“…Hence, we defined the anti-BN mAbs as an atroposelective antibody. The chiral recognition ability has been applied to operationally simple and rapid chiral separation and chiral sensing systems 43,45 .

Figure 1Design strategy for artificial metalloenzymes based on atroposelective antibodies. Atroposelective antibodies generated against a structurally simple binaphthyl derivative (BN) ( a ) are used to accommodate various BIQ-based metal catalysts ( b ).

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Visualization of Chiral Binaphthyl Recognition by Atroposelective Antibodies with Thermoresponsive Polymers

“…The atroposelectivity of mAbs has been exploited in a column-free chiral separation with a one-step simple procedure. 29 We expect that optical isomers can be distinguished by the naked eye without any special instruments. 3034 Here we demonstrate that one of the mAbs elicited against the S-isomer of BN [BN (S)] can be used to differentiate BN (S) from BN (R).…”