Innovative chiral capillary silica monoliths (CSMs) were developed based on DNA nanoflowers (DNFs). Baseline separation of enantiomers such as atenolol, tyrosine, histidine, and nefopam was achieved by using DNF-modified CSMs, and the obtained resolution value was higher than 1.78. To further explore the effect of DNFs on enantioseparation, different types of chiral columns including DNA strand containing the complementary sequence of the template (DCT)-modified CSMs, DNF2-modified CSMs, and DNF3-modified CSMs were prepared as well. It was observed that DNF-modified CSMs displayed better chiral separation ability compared with DCT-based columns. The intra-day and inter-day repeatability of model analytes\' retention time and resolution kept desirable relative standard deviation values of less than 8.28%. DNF2/DNF3-modified CSMs were able to achieve baseline separation of atenolol, propranolol, 2\'-deoxyadenosine, and nefopam enantiomers. Molecular docking simulations were performed to investigate enantioselectivity mechanisms of DNA sequences for enantiomers. To indicate the successful construction of DNFs and DNF-modified CSMs, various charaterization approaches including scanning electron microscopy, agarose gel electrophoresis, dynamic light scattering analysis, electroosmotic flow, and Fourier-transform infrared spectroscopy were utilized. Moreover, the enantioseparation performance of DNF-modified CSMs was characterized in terms of sample volume, applied voltage, and buffer concentration. This work paves the way to applying DNF-based capillary electrochromatography microsystems for chiral separation.

This work presents a new strategy to achieve the growth of copper sulfide nanoclusters with high nuclearity. Through a phosphine-assisted C-S reductive cleavage approach, an intrinsically chiral [Cu4] cluster passes through a [S-Cu9] cluster and transforms into a higher-nuclearity [S-Cu36] cluster, which features a core-shell structure with a [Cu4]4+ core encapsulated by a chiral [Cu20S12] shell. Interestingly, the spiral arrangement of the bidental ligands on the surface of the [S-Cu36] cluster leads to the L-/R-enantiomeric configurations. Moreover, by utilization of [Na(THF)6]+ as a chiral adaptive counterion, [S-Cu36] can be interlocked separately, thus enabling the isolation of homochiral clusters. Theoretical calculation suggests that the configuration transition between two enantiomeric [Na(THF)6]+ species is favorable at room temperature, thereby promoting the cocrystallization of resulting chiral products. This study introduces a novel perspective on the synthesis of chiral copper sulfide nanoclusters and presents an innovative approach to achieving the chiral separation of nanoclusters.

Porous organic cages (POCs) are a new type of molecular material. The well-defined cavities, abundant host-guest recognition ability, and good solubility of POCs render them attractive for use in various fields such as molecular recognition, gas adsorption, molecular containers, sensing, catalysis, chromatographic separation. In this study, a chiral POC (CPOC) was synthesized via the Schiff base condensation of 4,4\',4″,4″\'-(ethene-1,1,2,2-tetrayl)tetrabenzaldehyde with (R,R)-1,2-cyclohexanediamine. CPOC was characterized using nuclear magnetic resonance (NMR) spectroscopy, Fourier transform-infrared (FT-IR) spectroscopy, mass spectroscopy (MS), and thermogravimetric analysis (TGA). The FT-IR spectrum of CPOC showed a strong peak at 1638 cm-1, which was attributed to imine (-C=N-) absorption, as well as absorption peaks at 2928 and 2856 cm-1, which were attributed to the stretching vibrations of -CH2- and -CH-, respectively. MS analysis of CPOC revealed peaks at m/z=1801.9797, m/z=901.9914, and m/z=601.6631, corresponding to [M+H]+, [M+2H]2+, and [M+3H]3+, respectively, and indicating a molecular formula of CPOC (C126H120N12). The TGA curve of CPOC indicated high thermal stability up to 360 ℃; thus, the material is suitable for use as a stationary phase for gas chromatography (GC). CPOC was coated on the inner wall of a capillary column using the static coating method to prepare a GC column. Scanning electron microscopy (SEM) was used to characterize the coating condition of the fabricated column. The SEM images showed that the column had a uniform coating with a thickness of approximately 200 nm. Column efficiency was determined to be 3500 plates/m using n-dodecane as a target at 120 ℃. The polarity of the CPOC stationary phase was evaluated using McReynolds constants, which were measured using benzene, 1-nitropropane, 2-pentanone, pyridine, and 1-butanol as probe molecules at 120 ℃. The average McReynolds constant was 152, indicating that CPOC is a moderately polar stationary phase. The ability of the column to separate organic mixtures, isomers, and chiral compounds was subsequently investigated. All components of the four organic mixtures (n-alkanes, aromatics, n-alcohols, and Grob mixtures) tested achieved baseline separation on the column. In addition, nine positional isomers of disubstituted benzenes were well separated, and seven (o,m,p-nitrotoluene, o,m,p-nitrochlorobenzene, o,m,p-nitrobromobenzene, o,m,p-bromotoluene, o,m,p-dichlorobenzene, o,m,p-chloroaniline, and o,m,p-bromoaniline) achieved baseline separation. Some polar and apolar structural isomers, such as pentanol, dimethylphenol, dimethylaniline, butanol, and C9 aromatic hydrocarbon isomers, were also well separated on the column. Five cis/trans-isomers (nerol/geraniol, cis/trans-1,3-dichloropropene, cis/trans-1,2,3-trichloropropene, cis/trans-citral, and cis/trans-decahydronaphthalene) were baseline-separated on the column. More importantly, the column successfully separated 12 chiral compounds, indicating good chiral separation ability. Among these chiral compounds, five (ethyl 3-hydroxybutyrate, a valine derivative, a glutamic acid derivative, 1,2-butanediol diacetate, and 1,2-epoxybutane) achieved baseline separation. Six of these chiral compounds (ethyl 3-hydroxybutyrate, the valine derivative, the glutamic acid derivative, 1,2-epoxybutane, epichlorohydrin, and epibromohydrin) could not be separated on a β-DEX 120 column but were well separated on the developed column. Moreover, the separation efficiency of 1,2-butanediol diacetate and the isoleucine derivative on this column was better than that on the β-DEX 120 column. Separation of the glutamic acid derivative and o,m,p-nitrotoluene was performed before and after the column was used for repeated injections to explore its repeatability. The retention times and selectivity observed after 80, 160, and 500 injections were nearly unchanged compared with those obtained following the first use of the column, indicating that the column has good repeatability. The column was conditioned at 280 ℃ for a certain period to examine its thermal stability. Separation of 3-hydroxybutyrate and o,m,p-nitrochlorobenzene after the column was conditioned at 280 ℃ for 2, 4, or 8 h revealed no obvious changes compared with the first use of the column, indicating that the column had good thermal stability. Thus, CPOC is a stationary phase with good application potential for GC.

Macrocycles play vital roles in supramolecular chemistry and chromatography. 1,1\'-Bi-2-naphthol (BINOL)-based chiral polyimine macrocycles are an emerging class of chiral macrocycles that can be constructed by one-step aldehyde-amine condensation of BINOL derivatives with other building blocks. These macrocycles exhibit good characteristics, such as facile preparation, rigid cyclic structures, multiple chiral centers, and defined molecular cavities, that make them good candidates as new chiral recognition materials for chromatographic enantioseparations. In this study, a BINOL-based [2+2] chiral polyimine macrocycle was synthesized by one-step condensation of enantiopure (S)-2,2\'-dihydroxy-[1,1\'-binaphthalene]-3,3\'-dicarboxaldehyde with (1R,2R)-1,2-diaminocyclohexane. The product was modified with 5-bromo-1-pentene and then attached to thiolated silica using click chemistry to construct a new chiral stationary phase (CSP). The enantioselectivity of the new CSP was explored by separating various racemates under normal phase (NP) and reversed phase (RP) high performance liquid chromatography (HPLC). Thirteen racemates and eight racemates were enantioseparated under the two separation modes, respectively, including chiral alcohols, phenols, esters, ketones, amines, and organic acids. Among them, nine racemates achieved baseline separation under NP-HPLC and seven racemates achieved baseline separation under RP-HPLC. High resolution separation was observed with benzoin (Rs = 5.10), epinephrine (Rs = 4.98), 3-benzyloxy-1,2-propanediol (Rs = 4.42), and 4,4\'-dimethylbenzoin (Rs = 4.52) in NP-HPLC, and with 4-methylbenzhydrol (Rs = 4.72), benzoin ethyl ether (Rs = 3.79), 1-phenyl-1-pentanol (Rs = 3.68), and 1-(3-bromophenyl)ethanol (Rs = 3.60) in RP-HPLC. Interestingly, the CSP complemented Chiralcel OD-H, Chiralpak AD-H, and CYCLOBOND I 2000 RSP columns for resolution of these test racemates, separating several racemic compounds that could not be well separated by the three commercially available columns. The influences of injected sample amount on separation were also evaluated. It was found that the column exhibited excellent stability and reproducibility after hundreds of injections, and the relative standard deviations (n = 5) of the retention time and resolution were less than 0.49% and 0.69%, respectively. This study indicates that the BINOL-based chiral macrocycle has great potential for HPLC enantioseparation.

A focused chemical investigation into the polar fractions of a well-known traditional Chinese medicine called Sang-Bai-Pi (the root bark of Morus alba) yielded a panel of prenylated flavanones. The new compounds were identified as four pairs of enantiomers (1a/1b-4a/4b) featuring the same constitution structure, on the basis of HRMS, NMR and ECD analyses. Several previously reported known racemic co-metabolites were also analyzed and separated by HPLC on chiral columns, and the absolute configurations of pure enantiomers were established via ECD technique for the first time. The inhibition of these isolates against the antidiabetic target a-glycosidase was further tested, with most of them showing decent inhibitory activity compared with the positive control acarbose. The interaction mechanism of two selected compounds (3a & 4b) was explored by kinetics experiment, which revealed a mixed type of inhibition pattern toward the enzyme.

This study represents the initial examination of the herbicidal efficacy, crop safety, and degradation patterns of 2,4-D ethylhexyl ester (2,4-D EHE) at the enantiomeric level. Baseline separation of 2,4-D EHE enantiomers was achieved using a superchiral R-AD column, with their absolute configurations determined through chemical reaction techniques. Evaluation of weed control efficacy against sensitive species such as sun spurge and flixweed demonstrated significantly higher inhibition rates for S-2,4-D EHE compared to R-2,4-D EHE. Conversely, no stereoselectivity was observed in the fresh-weight inhibition rates of both enantiomers on crops or nonsensitive weeds. A sensitive HPLC-MS/MS method was developed to simultaneously detect two enantiomers and the metabolite 2,4-D in plants. Investigation into degradation kinetics revealed no substantial difference in the half-lives of R- and S-2,4-D EHE in maize and flixweed. Notably, the metabolite 2,4-D exhibited prolonged persistence at elevated levels on flixweed, while it degraded rapidly on maize.

Chiral resolution of racemic compounds represents an important task in research and development and, most importantly, in the large-scale production of pharmaceuticals. Zeolites, which are already frequently utilized for their unique properties, represent materials that can be used for the development of new chiral stationary phases for liquid chromatography, simulated moving bed or enantioselective membranes. The aim of this study was to modify a series of MWW zeolites by a chiral anion-exchange type selector thereby creating a chiral stationary phase for enantiomeric resolution of acidic compounds. To evaluate the applicability of the prepared chiral stationary phase in liquid chromatography, we used N-protected amino acids as model analytes. First, we tested the new sorbents preferential sorption using N-(3,5-dinitrobenzoyl)leucine. We observed outstanding sorption properties of a zeolite-based sorbent (MCM-36), which were comparable to spherical chromatographic silica. This particular material was subsequently packed into a chromatographic column, which was tested under polar organic mode HPLC conditions facilitating baseline resolution of 5 out of 8 N-protected amino acids. Although the chromatographic performance shows several drawbacks (high backpressure, low column efficiency), it clearly documents the potential of the novel materials in chiral separation. To the best of our knowledge, this is the first example of the preparation of the chiral stationary phase based on MWW zeolites ever.

Developing novel chiral stationary phases (CSPs) with versatility is of great importance in enantiomer separation. This study fabricated a dual-chiral covalent organic framework (PA-CA COF) via successive post-synthetic modifications. The chiral trans-1,2-cyclohexanediamine (CA) and (D)-penicillamine (PA) groups were periodically aligned within nanochannels of the COF, allowing selective recognition of enantiomers through intermolecular interactions. It can be a versatile high-performance liquid chromatography (HPLC) CSP for separating a wide range of enantiomers, including chiral pharmaceutical intermediates and chiral drugs. With separation performance comparable to commercial chiral columns and even greater versatility, the PA-CA COF@SiO2 column held promise for practical applications. Chiral separation results combined with molecular simulation indicated that the mixed mode of PA and CA resulted in the broad separation capability of PA-CA COF. The introduction of the dual-chiral COFs concept opens up a new avenue for chiral recognition and separation, holding great potential for practical enantiomer separation.

In this paper, the preparation of three new polysaccharide-type chiral stationary phases (CSPs) based on levan carbamates (3,5-dimethylphenyl, 4-methylphenyl, and 1-naphthyl) is described. The enantioseparation of (±)-trans-β-lactam ureas 1a-h was investigated by high-performance liquid chromatography (HPLC) on six different chiral columns (Chiralpak AD-3, Chiralcel OD-3, Chirallica PST-7, Chirallica PST-8, Chirallica PST-9, and Chirallica PST-10) in the polar organic mode, using pure methanol (MeOH), ethanol (EtOH), and acetonitrile (ACN). Apart from the Chirallica PST-9 column (based on levan tris(1-naphthylcarbamate), the columns exhibited a satisfactory chiral recognition ability for the tested trans-β-lactam ureas 1a-h.

The current work describes the efficient creation and employment of a new S-citalopram selective polymeric sorbent, made from poly(divinylbenzene-maleic anhydride-styrene). The process began by using suspension polymerization technique in the synthesis of poly(styrene-maleic anhydride-divinylbenzene) microparticles. These were then modified with ethylenediamine, developing an amido-succinic acid-based polymer derivative. The S-citalopram, a cationic molecule, was loaded onto these developed anionic polymer particles. Subsequently, the particles were post-crosslinked using glyoxal, which reacts with the amino group residues of ethylenediamine. S-citalopram was extracted from this matrix using an acidic solution, which also left behind stereo-selective cavities in the S-citalopram imprinted polymer, allowing for the selective re-adsorption of S-citalopram. The attributes of the polymer were examined through methods such as 13C NMR, FTIR, thermogravemetric and elemental analyses. SEM was used to observe the shapes and structures of the particles. The imprinted polymers demonstrated a significant ability to adsorb S-citalopram, achieving a capacity of 878 mmol/g at a preferred pH level of 8. It proved efficient in separating enantiomers of (±)-citalopram via column methods, achieving an enantiomeric purity of 97 % for R-citalopram upon introduction and 92 % for S-citalopram upon release.