Preparation and chiral recognition of a novel chiral stationary phase for HPLC,based on mono（6A-N- 1-（2-hydroxyl）- phenylethylimino-6A-deoxy）-β-cyclodextrin and covalently bonded silica gel

A novel chiral stationary phase （CSP） was prepared by immobilizing mono（6A-N-1-（2-hydroxyl）-phenylethylimino-6A- deoxy）-β-cyclodextrin onto the surface of silica gel via a longer spacer. This chiral stationary phase exhibited good enantioselectivity for a variety of chiral compounds under reversed-phase conditions.     

Preparation and chiral recognitio of a novel chiral stationary phase for HPLC,based on mono(6~A-N-1-(2-hydroxyl)-phenylethylimino-6~A-deoxy)-β-cyclodextrin and covalently bonded silica gel

A novel chiral stationary phase (CSP)was prepared by immobilizing mono(6~A-N-1-(2-hydroxyl)-phenylethylimino-6~A- deoxy)-β-cyclodextrin onto the surface of silica gel via a longer spacer.This chiral stationary phase exhibited good enantios- electivity for a variety of chiral compounds under reversed-phase conditions.     

A chiral stationary phase with special hydrophobic framework for ligand-exchange chromatography

A novel chiral stationary phase (CSP1) for ligand-exchange chromatography (CLEC) was prepared by firstly using dimethyl- chlorosilane as an endcapping reagent for decreasing residual silanol group on the surface of silica gel,and then introducing L-Pro as a chiral selector and hydrophobic octyl group to the silica gel surface simultaneously.The enantioseparations of 14 DL-amino acids on CSP1 were achieved with the enantioselectivityαranging from 1.09 to 2.44 and the resolution Rs being between 0.8 and 6.3.The chromatographic performances of CSP1 with the bonded phase (CSP2) prepared using reference method were compared.The results showed that the column efficiency and resolution Rs of chiral stationary phase could be improved by using the above modifying method.     

Preparation and chromatographic evaluation of a chiral stationary phase based on carboxymethyl-β-cyclodextrin for high-performance liquid chromatography

A novel chiral stationary phase (CSP) was prepared by chemically bonding carboxymethyl-β-cyclodextrin (CM-β-CD) onto 3-aminopropyl silica gel and showed excellent enantioseparation abilities for a broad range of chiral compounds and drugs.     

Stereoselective interactions of chiral dipeptides on amylose based chiral stationary phases

Dipeptides are stereo-specifically involved in several biological functions that are challenging to separate enantiomerically. Elution order of enantiomers is an important issue in chiral chromatography. Amylose tris-(3,5-dimethylphenylcarbamate) chiral stationary phase(CSP) is the best and most-widely-used CSP in chiral separations, but experimental data of enantiomeric separation of dipeptides on this CSP is lacking. Simulation studies were conducted to determine the order of elution and the chiral recognition mechanism of didpetides on this CSP. Results indicated that the docking energy of SR-enantiomers were higher than SS-antipodes. The range of docking energies for SR-enantiomers was -7.44 to -5.92 kcal/mol with CSP, but -7.15 to -5.87 kcal/mol for SS-stereoisomers. Therefore it is predicted that SS-enantiomer will elute first, followed by SR-antipode. Furthermore, hydrogen bondings, van der Waal’s interactions and electrostatic interactions were observed among SR- and SSenantiomers and chiral grooves of CSP. The number of hydrogen bonds was one in each enantiomer binding except S-Ala-R-Tyr, which contained two hydrogen bonds. No hydrogen bond was found in S-Ala-R-Trp, S-Leu-S-Trp, and S-Leu-S-Tyr dipeptides bindings. The chiral recognition mechanisms dictate different strengths of stereoselective bindings of the enantiomers on CSP.     

Preparation and Enantioseparation Property of Chiral Stationary Phases Based on Cellulose Tris(3,5-dimethylbenzoate)——A New Way to Prepare Polysaccharide-coating Type Chiral Stationary Phases

A new method to prepare polysaccharide-coating type chiral stationary phases （CSPs） was developed in this work. As a typical example, naked silica gel was coated by cellulose, which was then derivatized with 3,5-dimethylbenzoyl chloride to afford cellulose tris（3,5-dimethylbenzoate）-silica gel （CTDBS） complex. The silanols on CTDBS were end-capped with 3- aminopropyltriethoxysilane to obtain CSP 1. The amino groups on CSP 1 were further end-capped with 3,5-dimethylbenzoyl chloride to give CSP 2. The silanols on CTDBS were end-capped with methyltrimethoxysilane to yield CSP 3. CSPs 1-3 were characterized by FTIR, solid-state 13C-NMR and elemental analysis. The enantioseparation abilities of CSPs 1-3 were evaluated with structurally various chiral analytes. The enantioseparation results demonstrated that the end-capping moieties on CSPs 1 and 2 significantly affected enantioseparation. In addition, the effect of the structures of chiral analytes and end- capping moieties on the retention factors and the resolutions was discussed.     

Chiral separation abilities of homogeneously synthesized cellulose 3,5-dimethylphenylcarbamates: Influences of degree of substitution and molecular weight

A series of cellulose 3,5-dimethylphenylcarbamates(CDMPCs) with different degrees of substitution(DS) and degrees of polymerization(DP) were homogeneously synthesized in 1-allyl-3-methylimidazolium chloride(Amim Cl). Then, the CDMPCs were coated on silica gel and used as chiral stationary phases(CSPs), and their chiral recognition abilities for seven racemates were evaluated by high performance liquid chromatography. The results showed that DS and DP of CDMPCs had a great influence on chiral recognition abilities of the CSPs. The CSPs with the DS ≈ 1 gives a low chiral recognition to most racemates. On the contrast, the CSPs with the DS ? 2 exhibited high chiral separation abilities. For example, six racemates could be separated on the CSP with CDMPC of DS ≈ 2(CSP-2). Especially, for the enantioseparation of 1-(2-naphthyl) ethanol and Tr?ger's base, CSP-2 gave the highest separation ability in all of CSPs. On the other hand, when the DP of cellulose was in a range from 39 to 220, the chiral separation abilities of CDMPCs increased as the DP increased. This work demonstrates that the structure of cellulose esters such as DS and DP has important effect on their chiral separation ability, and therefore provides a practical method to design and prepare desirable CSPs for different racemates.     

Enantiomeric separations of four basic drugs containing N-alkyl groups by a RP-HPLC system using SBE-β-CD as chiral mobile phase additive

The chiral separations of four pharmaceutical racemates which contain N-alkyl groups were satisfactorily resolved using SBE-β-CD as a chiral mobile phase additive(CMPA)in a RP-HPLC system(the resolution is 2.701 for ondansetron hydrochloride,1.996 for sulpiride,1.293 for clenbuterol hydrochloride and 0.816 for omeprazole).In addition,the effects of different parameters such as CD type and CD concentration were investigated.The separation mechanism arises through the combination of several potential interactions,including electrostatic interactions as well as hydrogen bonding interactions and hydrophobic inclusion interactions,which allow for the SBE-β-CD–drug complexation with strong stereoselectivity and stability.The resolution also relates to the number and location of N atoms in the enantiomers.This method will be applicable to the isolation of various types of biologically important enantiomers containing N-alkyl groups.     

改进的方法用于制备键合型纤维素－三（苯基氨基甲酸酯）手性固定相

The classical method for preparation of covalently boned cellulose derivative chiral stationary phases (CSP) with diisocyanate as spacer was improved. Diisocyanate was firstly allowed to react with 3-aminopropyltriethoxysilane, and the resulting product was then applied as the spacer reagent to immobilize cellulose derivatives onto silica gel. Influences of the amount and the length of the spacer on the optical resolution ability of the CSP were investigated. Comparing improved procedure to classical diisocyanate method, the cross-linking between the glucose units of the cellulose derivatives was avoided to the most extent. With the improved procedure, regio-nonselective ways could be adooted to prepare covalently bonded CSP, which showed an advantage for the rapid preparation.     

Scalable Cu(Ⅱ)-mediated intramolecular dehydrogenative phenol-phenol coupling:Concise synthesis of enantiopure axially chiral homo-and hetero-diphenols

An intramolecular dehydrogenative homo-and hetero-coupling of phenols has been successfully developed for quick preparation of enantiopure axial diphenols under mild Cu(Ⅱ)-mediated conditions,using((4 S,5 S)-2,2-dimethyl-1,3-dioxolane-4,5-diyl)dimethanol as the chiral auxiliary.The commercially available(R)-α-met hylbenzy la mine was identified as the best amine ligand for Cu(Ⅱ) in the reactions.A variety of homo/hetero bis-dihydroxylbenzoate substrates were examined,affording the corresponding axially chiral diphenols with satis factory to excellent diastereomeric ratios,and a representative scalable preparation was also attempted.A formal synthesis of natural product(+)-deoxyschizandrin has been achieved in this work using one axially chiral diphenol as the synthetic intermediate.     

Asymmetric reduction of α-hydroxy aromatic ketones to chiral aryl vicinal diols using carrot enzymes system

Asymmetric reduction ofα-hydroxy aromatic ketones was carried out by using carrot enzymes system,yielding corresponding chiral vicinal diols with special functional groups.The optimum reaction conditions were obtained after investigation of various influencing factors.Chiral aryl vicinal diols were produced with good yields and excellent enantiomeric excesses under appropriate conditions.Meanwhile,the steric factors and electronic effects of the substituents on the aromatic ring were shown to have an interesting influence on both yield and enantioselectivity.     

超声波技术制备功能化二氧化硅在苯酚和碳酸二甲酯甲基化反应中的应用

Porous silica modified with -（CH2）3NH2 （primary amine）, -（CH2）3NHCH2CH2NH2 （secondary/primary amine） and -（CH2）3N-cycl-（CH2）4 （tertiary amine） were synthesized by ultrasonic technique under mild conditions. The samples were characterized by BET, elemental analysis and TG, showing that the organosilane moieties were grafted onto the surface of porous silica by covalent bond. The structure of the organosilane moieties and ultrasonic treatment time were all significant for the quantities of grafted amino groups. The samples exhibited promising catalytic properties towards the methylation reaction of phenol with dimethyl carbonate （DMC）. The methylation reaction with the modified samples featured high selectivity at high conversion. The samples were subjected to utilization for a few recycles without obvious loss of activity to indicate that ultrasonic technique was effective for the preparation of organically modified porous silica catalysts.     

Enantioseparation of Novel Chiral Tetrahedral Clusters on an Amylosoe Tris-（3,5-dimethylphenylcarbamate） Chiral Stationary Phase by Normal Phase HPLC

Amylose tris(3,5-dimethylphenylcarbamate) (ADMPC) coated on a kind of small particle silica gel was prepared. On this ADMPC chiral stationary phase (CSP), the direct enantiomeric separation of six novel chiral transition metal tetrahedral clusters has firstly been achieved using n-hexane as the mobile phase containing various alcohols as modifiers. The effect of mobile phase modifiers and the structural variation of the solutes on their retention factors (k‘) and resolutions (Rs) were investigated. The result suggests that not only the structure and concentration of alcohol in mobile phase, but also the structural differences in racemates can have a pronounced effect on enantiomeric separation. ADMPC-CSP is a suitable CSP for the optical resolution of chiral tetrahedral cluster by HPLC.     

浸渍硅胶薄层色谱板分离钴和镍及数字图像分析法定量(英文)

Thin layer chromatography(TLC) of cobalt and nickel has been performed on silica gel layers induced with alkali mediated cellulose extract.A novel combination of 10% aqueous solutions of Tween-20 and potassium thiocyanate in 1∶1(v/v) was identified as the best mobile phase for the selective separation of Co2+from Ni2+on the impregnated Silica Gel G layers.The chromatographic characteristics of the cations were studied and the limits of detection as well as the limits of quantification for Co2+and Ni2+were determined.The quantitative estimation of the cations was achieved from the digital image analysis of respective chromatograms.The proposed quantitative method was successfully applied with 0-0.50% error for the determination of Co2+from Ni2+in spiked samples of bauxite,soil and rock containing common cations such as Al3+,Fe2+,Ti4+,Zn2+,Mn2+,Cu2+,Cr6+,Mg2+,etc.under the optimized chromatographic conditions.     

ADSORPTION BEHAVIOR OF Pb（II） ON POTASSIUM HEXATITANATE WHISKER BY FAAS

Based on the advantage of high surface area and strong adsorption ability of potassium hexatitanate whisker, a method to determine trace Pb（II） content by combining solid phase extraction with Flame atomic absorption spectrometry （FAAS） was established. The adsorptive behavior of potassium hexatitanate whisker to Pb（II）, primary influencing factors of adsorption and elution and effect of coexistence ions were investigated systemically. The optimal analytical conditions were discussed and examined. It was found that the adsorption rate of potassium hexatitanate whisker to Pb（II） was 100% at pH 4.0. Pb（II） could be eluted from potassium tetratitanate whisker with HCl （2mol/L） under boiling water for 30min. The detection limit was 5.75ng/mL, and relative standard deviation was 1.66% （n=9, Cpb=2.0μg/mL）.     

Colorimetric and fluorescence dual-mode detection of arsenic（v） based on cobalt oxyhydroxide nanoplatesEI北大核心CSCD

The oxidase-like activity of cobalt oxyhydroxide （CoOOH） nanosheets is inhibited by arsenic （V） in the system, thereby attenuating the oxidation of p-phenylenediamine （PPD） by CoOOH nanosheets, and changing the absorbance of the solution. Based on this principle, and the fluorescence inner filter effect （IFE） of p-phenylenediamine oxide （oxPPD） on the dye acridine orange （AO）, a colorimetric and fluorescence dualmode method for the quantitative detection of As（V） was established. The variation of absorbance and fluorescence intensity of As（V） with different concentrations was investigated, and the effects of the concentrations of CoOOH nanosheet and PPD, pH of buffer solution, and temperature of reaction were optimized. The results showed that under the optimized conditions, the concentration of As（Ⅴ） had a good linear relationship with the corresponding signal intensity, and the detection limits of colorimetric and fluorescence method were 5 and 10 nmol/L, respectively. The method has been used for the determination of arsenic（V） in lake water located the city center. © 2023, Youke Publishing Co.,Ltd. All rights reserved.     

Supercritical carbon dioxide assisted synthesis of amphiphilic graft copolymers based on poly(styrene-co-maleic anhydride) with methoxyl poly(ethylene glycol) side chains

Supercritical carbon dioxide（scCO₂） was used as a reaction medium in synthesizing amphiphilic graft copolymers composed of poly（styrene-co-maleic anhydride）（SMA） backbones and methoxyl poly（ethylene glycol）（MPEG） side chains via esterification.The synthesized copolymers were characterized by Fourier transform infrared spectroscopy（FTIR）,gel permeation chromatography（GPC）,¹H-NMR,thermo-gravimetric analysis（TGA） and differential scanning calorimetric analysis（DSC）.The gelation phenomenon was suppressed effectively by tuning reaction conditions.The influences of scCO₂ temperature and pressure on the conversion of anhydride were investigated.It was found that the highest conversion ratio occurred at 80℃under a constant pressure of 14 MPa or 26 MPa.With the increase of scCO₂ pressure,the conversion ratio increased first,and then leveled off.The conversion ratio of anhydride could be controlled by regulating the reaction conditions.It was also revealed that using low molecular weight MPEG brought a high conversion ratio of anhydride.     

Preparation of novel chiral stationary phase based on click chemistry for ligand exchange chromatography

Click chemistry was applied to immobilize L-proline derivative onto azide-modified silica gel to give a novel chiral stationary phase(denoted as click-CSP) for ligand exchange chromatography.The developed protocol combines the benefits of operational simplicity,exceptionally mild conditions and high surface loadings.The enantioselectivityαof some DL-amino acids on the click-CSP were found to be in the range from 1.13 to 3.46.The chromatographic resolutions of some DL-amino acids and the stability study f...     

Pillar[5]arene-functionalized nanochannel platform for detecting chiral drugs

Chirality is a fascinating and essential feature of life and highly associated with many significant pharmaceutical,chemical,and biological processes.The construction of chiral recognition platform is a hot research topic and challenging assignment.Herein,we report an electrochemical method by diffe rential pulse voltammetry(DPV) for the enantioselective recognition of chiral drug propranolol(R/SPPL) through a nanochannel platform based on the N-acetyl-L-cysteine functionalized pillar[5]arenes derivative NALC-P5 and the porous polycarbonate membrane.The chiral discrimination depends on the diffe rence in the supramolecular host-guest interaction between the chiral NALC-P5 and the R/S-PPL.The transmission rate of the R/S-PPL can be regulated in the nanochannel and we can achieve the selective transport of the chiral drugs.This simple electrochemical technique has potential applications as a general platform for the recognition of chiral molecules.     

Synthesis of Chlorogenic Acid Imprinted Chromatographic Packing by Surface-initiated Atom Transfer Radical Polymerization and Its Application

A novel chromatographic packing of chlorogenic acid（CGA） molecularly imprinted polymer（MIP） based on the 5.0 ~tm silica was prepared by surface initiated atom transfer radical polymerization（SI-ATRP） with 4-vinylpyridine（4-VP） as functional monomer, ethyl glycol dimethacrylate（EDMA） as cross-linker in the mixture of methanol and water（7：3, volume ratio） under mild reaction conditions. The characteristics of CGA MIP were investi- gated by elemental analysis, thermogravimetric analysis（TGA）, Fourier transform infrared spectrometry（FTIR） and atomic force microscopy（AFM）. The effects of some chromatographic conditions such as mobile phase composition and temperature on the retention time were investigated. The adsorption capacity of the stationary phase for com- pounds was determined by frontal chromatographic technique. The results show that Freundlich isotherm fits the ex- perimental adsorption isotherm data better than Langmuir model does. The relatively high heterogeneity index values regressed with the Freundlich isotherm suggest the formation of fairly homogeneous MIP. Thermodynamic data（AAH and AAS） obtained by van＇t Hoff plots reveal an entropy-controlled separation. The CGA MIP column was shown to be successful for the separation and purification of chlorogenic acid from the extract of Honeysuckle.