- Noncovalently Functionalized Commodity Polymers as Tailor-Made Additives for Stereoselective Crystallization
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Stereoselective inhibition of the nucleation and crystal growth of one enantiomer aided by “tailor-made” polymeric additives is an efficient method to obtain enantiopure compounds. However, the conventional preparation of polymeric additives from chiral monomers are laborious and limited in structures, which impedes their rapid optimization and applicability. Herein, we report a “plug-and-play” strategy to facilitate synthesis by using commercially available achiral polymers as the platform to attach various chiral small molecules as the recognition side-chains through non-covalent interactions. A library of supramolecular polymers made up of two vinyl polymers and six small molecules were applied with seeds in the selective crystallization of seven racemates in different solvents. They showed good to excellent stereoselectivity in yielding crystals with high enantiomeric purities in conglomerates and racemic compound forming systems. This convenient, low-cost modular synthesis strategy of polymeric additives will allow for high-efficient, economical resolution of various racemates on different scales.
- Wan, Xinhua,Wang, Zhaoxu,Ye, Xichong,Zhang, Jie
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supporting information
p. 20243 - 20248
(2021/08/09)
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- Evaluation of the chiral recognition properties and the column performances of three chiral stationary phases based on cellulose for the enantioseparation of six dihydropyridines by high-performance liquid chromatography
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Separations of six dihydropyridine enantiomers on three commercially available cellulose-based chiral stationary phases (Chiralcel OD-RH, Chiralpak IB, and Chiralpak IC) were evaluated with high-performance liquid chromatography (HPLC). The best enantioseparation of the six chiral drugs was obtained with a Chiralpak IC (250?×?4.6?mm i.d., 5?μm) column. Then the influence of the mobile phase including an alcohol-modifying agent and alkaline additive on the enantioseparation were investigated and optimized. The optimal mobile phase conditions and maximum resolution for every analyte were as follows respectively: n-hexane/isopropanol (85:15, v/v) for nimodipine (R?=?5.80) and cinildilpine (R?=?5.65); n-hexane/isopropanol (92:8, v/v) for nicardipine (R?=?1.76) and nisoldipine (R?=?1.92); and n-hexane/isopropanol/ethanol (97:2:1, v/v/v) for felodipine (R?=?1.84) and lercanidipine (R?=?1.47). Relative separation mechanisms are discussed based on the separation results, and indicate that the achiral parts in the analytes' structure showed an important influence on the separation of the chiral column.
- Yu, Jia,Tang, Jing,Yuan, Xiaowei,Guo, Xingjie,Zhao, Longshan
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p. 147 - 154
(2017/04/24)
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- Enantioselective potential of polysaccharide-based chiral stationary phases in supercritical fluid chromatography
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The enantioselective potential of two polysaccharide-based chiral stationary phases for analysis of chiral structurally diverse biologically active compounds was evaluated in supercritical fluid chromatography using a set of 52 analytes. The chiral selectors immobilized on 2.5?μm silica particles were tris-(3,5-dimethylphenylcarmabate) derivatives of cellulose or amylose. The influence of the polysaccharide backbone, different organic modifiers, and different mobile phase additives on retention and enantioseparation was monitored. Conditions for fast baseline enantioseparation were found for the majority of the compounds. The success rate of baseline and partial enantioseparation with cellulose-based chiral stationary phase was 51.9% and 15.4%, respectively. Using amylose-based chiral stationary phase we obtained 76.9% of baseline enantioseparations and 9.6% of partial enantioseparations of the tested compounds. The best results on cellulose-based chiral stationary phase were achieved particularly with propane-2-ol and a mixture of isopropylamine and trifluoroacetic acid as organic modifier and additive to CO2, respectively. Methanol and basic additive isopropylamine were preferred on amylose-based chiral stationary phase. The complementary enantioselectivity of the cellulose- and amylose-based chiral stationary phases allows separation of the majority of the tested structurally different compounds. Separation systems were found to be directly applicable for analyses of biologically active compounds of interest.
- Kucerova, Gabriela,Kalikova, Kveta,Tesarova, Eva
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supporting information
p. 239 - 246
(2017/05/29)
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- Enantioselective retention of 4-aryl-1,4-dihydropyridine calcium-channel blockers on human serum albumin and α1-acid glycoprotein HPLC columns: Relationships with different scales of lipophilicity
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The enantioselective retention of eight 4-aryl-1,4-dihydropyridine (DHP) calcium-channel blockers on HPLC stationary phases supporting human serum albumin (HSA) or α1-acid glycoprotein (AGP) was investigated. All chiral neutral DHPs were resolved on the AGP column, whereas, on the HSA column, only isradipine showed a split chromatographic peak. Analyses performed on AGP with eluents containing dimethyloctylamine (DMOA) as thc displacer demonstrated that the protein has at least two binding sites for DHPs. The first family of binding sites is enantioselective, binds exclusively to the (R)-forms, and presumably interacts competitively with DMOA. The second family of binding sites appears to be non-enantioselective and is affected by a cooperative interaction with DMOA. For the selected set of DHPs, the lipophilicity scale in octan-1-ol/H2O (log P) was not collinear with log k(w)(IAM) values obtained with immobilized artificial membranes (IAM-HPLC) due to the inclusion of both neutral and basic congeners. Only for the neutral DHPs did log k(w)(IAM) behave as a better descriptor than log P for retention date on HSA and AGP. In fact, the behavior of the basic DHPs amlodipine and nicardipine on both proteins correlated better with the octan- 1-ol/H2O log P values. We, therefore, infer that the amphipathic nature of the IAM phase only mimics the interaction of non-ionizable compounds with serum proteins. In contrast, the IAM-HPLC retention data of protonated bases encode additional interaction mechanisms that are specific for phospholipids and not involved in ligand-protein interactions.
- Barbato, Francesco,Quaglia, Fabiana,Quercia, Maria Tiziana,La Rotonda, Maria Immacolata
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p. 767 - 776
(2007/10/03)
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