Novel chiral metal organic frameworks functionalized composites for facile preparation of optically pure propranolol hydrochlorides

A nitrogen-doped graphene tube composite based on immobilized metal affinity chromatography for the capture of phosphopeptides

A novel immobilized metal affinity chromatography (IMAC) functional composite, mNi@N-GrT@PDA@Ti⁴⁺, was fabricated based on ultrathin magnetic nitrogen-doped graphene tube (mNi@N-GrT) after chelated Ti⁴⁺ with polydopamine, following as a magnetic solid-phase extraction sorbent for rapidly selective enrichment and mass spectrometry identification of phosphorylated peptides. After optimized, the composite exhibited high specificity in the enrichment of phosphopeptides from the digest mixture of β-casein and bovine serum albumin (BSA). The robust method presented the low detection limits (1 fmol, 200 μL) and excellent selectivity (1:100) in the molar ration mixture of β-casein and BSA digests. Furthermore, the selective enrichment of phosphopeptides in the complex bio-samples, was successfully carried out. The results showed that 28 phosphopeptides were finally detected in mouse brain, and 2087 phosphorylated peptides were identified in the HeLa cells extracts with specific selectivity of 95.6%. The enrichment performance of mNi@N-GrT@PDA@Ti⁴⁺ was satisfactory, suggesting that the functional composite provided a potential application in the enrichment of trace phosphorylated peptides from the complex biological matrix.

Enantioseparation/Recognition based on nano techniques/materials

Enantiomers show different behaviors in interaction with the chiral environment. Due to their identical chemical structure and their wide application in various industries, such as agriculture, medicine, pesticide, food, and so forth, their separation is of great importance. Today, the term "nano" is frequently encountered in all fields. Technology and measuring devices are moving towards miniaturization, and the usage of nanomaterials in all sectors is expanding substantially. Given that scientists have recently attempted to apply miniaturized techniques known as nano-liquid chromatography/capillary-liquid chromatography, which were originally accomplished in 1988, as well as the widespread usage of nanomaterials for chiral resolution (back in 1989), this comprehensive study was developed. Searching the terms "nano" and "enantiomer separation" on scientific websites such as Scopus, Google Scholar, and Web of Science yields articles that either use miniaturized instruments or apply nanomaterials as chiral selectors with a variety of chemical and electrochemical detection techniques, which are discussed in this article.

A chiral magnetic molybdenum disulfide nanocomposite for direct enantioseparation of RS-propranolol

We herein report a novel chiral magnetic molybdenum disulfide nanocomposite (MMoS₂/PNG-CD) with a high enantioselectivity and excellent thermosensitivity and magnetism. The prepared MMoS₂/PNG-CD shows temperature-dependent chiral discrimination and enantioselectivity toward a chiral drug RS-propranolol (RS-PPL), which is based on the molecular recognition ability of beta-cyclodextrin (β-CD) and the thermosensitivity of poly(N-isopropylacrylamide) (PNIPAM). The synthesized MMoS₂/PNG2-CD by using a monomer molar ratio of GMA to NIPAM of 2 : 1 demonstrates a high selectivity toward R-PPL over S-PPL due to the synergistic effect of the PNIPAM moieties and β-CD hosts. The thermo-induced volume phase transition (VPT) of the introduced PNIPAM moieties significantly affects the inclusion constants of the β-CD/R-PPL complex, and thus the loading and desorption of R-PPL on the MMoS₂/PNG2-CD. The enantioselectivity at temperatures below the lower critical solution temperature (LCST) of the PNG-β-CD grafting chains is much higher than that at temperatures above the LCST. As a result, the regeneration of the MMoS₂/PNG2-CD is easily achieved via simply changing the operating temperature. Moreover, the regenerated MMoS₂/PNG2-CD can be readily recovered from the RS-PPL solution under an external magnetic field for reuse. Such a multifunctional molybdenum disulfide nanocomposite with a high enantioselectivity and excellent thermosensitivity and regenerability is promising to serve as a high-performance nanoselector for direct resolution of various β-blocker drugs.

Metal-organic frameworks in chiral separation of pharmaceuticals

Stereoselective chiral molecules are responsible for specific biological functions in nature. At present, more than half of the prescribed drugs are chiral. Living organisms display divergent pharmacological responses to the enantiomers, leading to altered toxicity, pharmacokinetics, and pharmacodynamics. Thus, chiral analysis, separation, and extraction are crucial for ensuring enantiomeric purity to develop safe and effective medication. In recent times, metal-organic frameworks (MOFs) with appealing structures are gaining importance because of their fascinating properties as a sorbent and stationary phase. MOFs are crystalline porous solid materials built by interconnecting metal ions or clusters and organic linkers. This review explores the advancements in MOFs for the isolation and separation of chiral active pharmaceutical drugs.

Crystal morphology tuning and green post-synthetic modification of metal organic framework for HPLC enantioseparation

Chiral metal-organic frameworks (CMOFs) served as chiral stationary phases (CSPs) show great potential in enantioseparation field. However, their performance improvement are still hindered by the difficult column packed and high back pressure due to the irregular morphology and broad size scope of CMOF particles. Here, the size and morphology of achiral Co-MOF-74 were effectively adjusted by controlling the synthetic route, temperature, the ratio of reactants and the amount of 2-methylimidazole (2-MI) at first. As a result, the uniformly spherical crystals in size of about 5 μm with good dispersion were obtained. Subsequently, a simple, green post-synthetic modification strategy was proposed for the fabrication of l-tyrosine functionalized Co-MOF-74, namely Co-MOF-74-L-Tyr in H₂O by incorporating l-tyrosine into the parent framework of Co-MOF-74 to construct chiral microenvironment. The homochiral Co-MOF-74-L-Tyr CSP gave superior enantioseparation performance for the eight chiral drugs and drug intermediates, such as nitrendipine, nimodipine, benzoin, 2,2'-furoin and bi-2-naphthol to the commercial columns under normal phase condition. The good repeatability and stability of this CSP was verified by the replicate enantioseparation for nimodipine and flavanone. Furthermore, the Co-MOF-74-L-Tyr packed column was successfully applied to detect the product N-1-(1-naphthyl)ethyltosylamide (HR-8) in the asymmetric reductive amination reaction. The size/morphology-controlled synthesis coupled with the green post-synthetic modification approach paves the way to fabricate target chiral MOFs with pre-designed functional groups, which is an effective complement for the preparation of CSPs in chiral chromatography.

Chiral magnetic hybrid materials constructed from macromolecules and their chiral applications

Chirality is a fundamental and ubiquitous feature of living organisms in nature. Magnetic materials, in particular magnetic nanoparticles (MNPs), show some interesting properties such as large specific surface area, easy surface modification, magnetic responsivity and separation ability. Integrating MNPs with chirality in a single material will undoubtedly create a large number of advanced multi-functional materials. Despite the great advancements made in this area, there have been no review articles to summarize the relevant studies. The present work reviews the major progress recently made in constructing chiral magnetic hybrid materials (CMHMs) using macromolecules, which are classified based on the primary chiral macromolecular organic components, namely, biological polymers and synthetic polymers, and the applications of the resulting chiral hybrids in chiral research fields, including asymmetric catalysis, enzymatic resolution, chromatographic separation, enantioselective crystallization and enantioselective adsorption, are also summarized. The challenges and prospects of related research fields are proposed in the last section.

Dispersive solid-phase extraction of racemic drugs using chiral ionic liquid-metal-organic framework composite sorbent

Nowadays, enantioseparation of racemic pharmaceuticals in preparations is a prime concern by drug authorities across the globe. In the present work, it was attempted to develop novel enantioselective extraction method for five clinically used drugs (atenolol, propranolol, metoprolol, racecadotril, and raceanisodamine in their tablets) as racemates. The enantioselective solid-liquid extraction of these racemic drugs was carried out successfully by the use of chiral ionic liquid (CIL) in combination with a metal organic framework (MOF) for the first time. The composite CIL@MOF was synthesized from tropine based chiral ionic liquids with L-proline anion ([C_nTr][L-Pro], n=3-6) and HKUST-1 type MOF, which was comprehensively characterized before being used as sorbent for enantioselective dispersive solid-liquid extraction. Preliminary selection of appropriate CIL was carried out on thin layer chromatography (TLC); under the joint participation of copper ion in the developing reagent, [C₃Tr][L-Pro] ionic liquid showed better resolution performance with ΔR_f value of 0.35 between the enantiomers was obtained for racemic atenolol. Moreover, the effect of copper salt dosage, amount of CIL, soli-liquid ratio and extraction time were investigated. The optimal conditions were obtained after thorough investigations; i.e. sample solution: ethanol, elution solvent: methanol, solid-liquid ratio: 12.5 mg:50 mL, amount of copper salt: 8 mg L^-1, amount of impregnated CIL: 30% and extraction time of 30 min. As a result, enantiomeric excess values are 90.4%, 95%, 92%, 81.6% and 83.2% for atenolol, propranolol, metoprolol, racecadotril and raceanisodamine, respectively. The developed enantioselective method was validated following ICH guidelines and it was proved to be simple, effective and enantioselective way for separation of racemic pharmaceuticals with similar behaviors.

Revelation of the chiral recognition of alanine and leucine in an l-phenylalanine-based metal–organic framework

An l-phenylalanine-based Zn-MOF, namely [Zn₂(l-Phe)₂(bpe)₂]_n, was designed for experimentally revealing the chiral recognition mechanism to alanine and leucine by means of ¹³C CP MAS NMR spectroscopy, XPS and control experiment.

Facile synthesis of a 3D flower-like SiO2-MOF architecture with copper oxide as a copper source for enantioselective capture

Facile synthesis of a 3D flower-like SiO₂–CuLBH architecture with copper oxide as a copper source for enantioselective capture.