Chiral capillary electrophoresis with cationic pyrrolidinium‐β‐cyclodextrin derivatives as chiral selectors

New single‐isomer, cationic β‐cyclodextrins, including mono‐6‐deoxy‐6‐pyrrolidine‐β‐cyclodextrin chloride (pyCDCl), mono‐6‐deoxy‐6‐(N‐methyl‐pyrrolidine)‐β‐cyclodextrin chloride (N‐CH₃‐pyCDCl), mono‐6‐deoxy‐6‐(N‐(2‐hydroxyethyl)‐pyrrolidine)‐β‐cyclodextrin chloride (N‐EtOH‐pyCDCl), mono‐6‐deoxy‐6‐(2‐hydroxymethyl‐pyrrolidine)‐β‐cyclodextrin chloride (2‐MeOH‐pyCDCl) were synthesized and used as chiral selectors in capillary electrophoresis for the enantioseparation of carboxylic and hydroxycarboxylic acids and dansyl amino acids. The unsubstituted pyCDCl exhibited the greatest resolving ability. Most analytes were resolved over a wide range of pH from 6.0 to 9.0 with this chiral selector. In general, increasing pH led to a decrease in resolution. The effective mobilities of all the analytes were found to decrease with increasing CD concentration. The optimal concentration for most carboxylic acids and dansyl amino acid was in the range 5–7.5 mM and >15 mM for hydroxycarboxylic acids. ¹H NMR experiments provided direct evidence of inclusion in the CD cavity.     

Electrochemical Investigation of Myoglobin in Layer‐by‐Layer Films Assembled with Sulfonated‐β‐Cyclodextrin

In this work, myoglobin (Mb) and sulfonated‐β‐cyclodextrin (S‐CD) were assembled into {S‐CD/Mb}_n layer‐by‐layer films on solid substrates. In pH 7.0 buffers, the {S‐CD/Mb}_n films assembled on electrodes showed a pair of well‐defined and nearly reversible CV peaks at about ?0.35 V vs. SCE. The stable CV response of {S‐CD/Mb}_n films could be used to electrocatalyze reduction of oxygen and hydrogen peroxide in solution. For comparison, another modified β‐cyclodextrin, carboxyethyl‐β‐cyclodextrin (C‐CD), was also assembled with Mb into {C‐CD/Mb}_n multilayer films. The driving forces of the assembly were explored and discussed.     

Comparative evaluation of a one‐pot strategy for the preparation of β‐cyclodextrin‐functionalized monoliths: Effect of the degree of amino substitution of β‐cyclodextrin on the column performance

To further evaluate the feasibility and applicability of the one‐pot strategy in monolithic column preparation, two novel β‐cyclodextrin‐functionalized organic polymeric monoliths were prepared using two β‐cyclodextrin derivatives, i.e. mono(6‐amino‐6‐deoxy)‐β‐cyclodextrin and heptakis(6‐amino‐6‐deoxy)‐β‐cyclodextrin. In this improved method, mono(6‐amino‐6‐deoxy)‐β‐cyclodextrin or heptakis(6‐amino‐6‐deoxy)‐β‐cyclodextrin reacted with glycidyl methacrylate to generate the corresponding functional monomers and were subsequently copolymerized with ethylene dimethacrylate. The polymerization conditions for both monoliths were carefully optimized to obtain satisfactory column performance with respect to column efficiency, reproducibility, permeability, and stability. The obtained poly(glycidyl methacrylate‐mono(6‐amino‐6‐deoxy)‐β‐cyclodextrin‐co‐ethylene dimethacrylate) and poly(glycidyl methacrylate‐heptakis(6‐amino‐6‐deoxy)‐β‐cyclodextrin‐co‐ethylene dimethacrylate) monoliths exhibited a uniform structure, good permeability, and mechanical stability as indicated by scanning electron microscopy and micro‐high‐performance liquid chromatography experimental results. Because of the probable existence of multi‐glycidyl methacrylate linking spacers on the poly(glycidyl methacrylate‐heptakis(6‐amino‐6‐deoxy)‐β‐cyclodextrin‐co‐ethylene dimethacrylate) monolith, the effect of the ratio of glycidyl methacrylate/heptakis(6‐amino‐6‐deoxy)‐β‐cyclodextrin was especially studied, and satisfactory reproducibility could still be achieved by strictly controlling the composition of the polymerization mixture. To investigate the effect of the degree of amino substitution of β‐cyclodextrin on column performance, a detailed comparison of the two monoliths was also carried out using series of analytes including small peptides and chiral acids. It was found that the β‐cyclodextrin‐functionalized monolith with mono‐glycidyl methacrylate linking spacers demonstrated better chiral separation performance than that with multi‐glycidyl methacrylate linking spacers.     

Synthesis of Polypyrrole Microtubes with Actinomorphic Morphology in the Presence of a β‐Cyclodextrin Derivative‐Methyl Orange Inclusion Complex

Summary: Polypyrrole (PPy) microtubes with an actinomorphic morphology are synthesized by a chemical method in the presence of an inclusion complex (IC) of mono [6‐deoxy‐6‐(2‐butenedinitrile‐2,3‐dimercapto sodium salt)]‐β‐cyclodextrin (6‐mnt‐β‐CD) with methyl orange (MO) as a dopant in aqueous solution. The morphologies of the obtained PPy were studied using transmission electron microscopy (TEM). It was found that the IC of 6‐mnt‐β‐CD with MO significantly affects the morphology of the resulting PPy.

The morphology of polypyrrole synthesized in the presence of 6‐mnt‐β‐CD/MO, determined by TEM.     

2-萘-(OCH2CH2)n-金刚胺与6-单取代环糊精衍生物的光诱导电子转移反应

A number of naphthalene donor compounds that possess an adamantanamine binding moiety and an (OCH2CH2)n (nn1, 2, 3, 4, 6, 8) spacer were synthesized. The fluorescence quenching between these donor substrates and mono-6-O-p-nitrobenzoyl-β-cyclodextrin (pNBCD) and mono-6-O-m-nitrobenzoyl-β-cyclodextrin(mNBCD) was studied in detail. It was found that very efficient fluorescence quenching could occur in these supramolecular systems. This quenching was attributed to the photoinduced electron transfer inside the supramolecular assembly between the naphthalene donors and cyclodextrin acceptors. Detailed Stern-Volmer constants were measured and they were partitioned into dynamic Stern-Volmer quenching constants and static binding constants. It was demonstrated that the binding constants between all the naphthalene compounds and cyclodextrins are the same as they possess the same binding site, i.e., adamantanamine.     

Synthesis and Conformational Analysis of 1′‐ and 3′‐Substituted 2‐Deoxy‐2‐fluoro‐D‐ribofuranosyl Nucleosides

Convergent syntheses of the 9‐(3‐X‐2,3‐dideoxy‐2‐fluoro‐β‐D ‐ribofuranosyl)adenines 5 (X=N₃) and 7 (X=NH₂), as well as of their respective α‐anomers 6 and 8 , are described, using methyl 2‐azido‐5‐O‐benzoyl‐2,3‐dideoxy‐2‐fluoro‐β‐D ‐ribofuranoside ( 4 ) as glycosylating agent. Methyl 5‐O‐benzoyl‐2,3‐dideoxy‐2,3‐difluoro‐β‐D ‐ribofuranoside ( 12 ) was prepared starting from two precursors, and coupled with silylated N⁶‐benzoyladenine to afford, after deprotection, 2′,3′‐dideoxy‐2′,3′‐difluoroadenosine ( 13 ). Condensation of 1‐O‐acetyl‐3,5‐di‐O‐benzoyl‐2‐deoxy‐2‐fluoro‐β‐D ‐ribofuranose ( 14 ) with silylated N²‐palmitoylguanine gave, after chromatographic separation and deacylation, the N⁷‐β‐anomer 17 as the main product, along with 2′‐deoxy‐2′‐fluoroguanosine ( 15 ) and its N⁹‐α‐anomer 16 in a ratio of ca. 42 : 24 : 10. An in‐depth conformational analysis of a number of 2,3‐dideoxy‐2‐fluoro‐3‐X‐D ‐ribofuranosides (X=F, N₃, NH₂, H) as well as of purine and pyrimidine 2‐deoxy‐2‐fluoro‐D ‐ribofuranosyl nucleosides was performed using the PSEUROT (version 6.3) software in combination with NMR studies.     

Synthesis of New Carnosine Derivatives of β‐Cyclodextrin and Their Hydroxyl Radical Scavenger Ability

Several in vitro and in vivo studies have suggested that carnosine can act as a scavenger of reactive oxygen species and intracellular proton buffer. On the other hand, carnosinase is a specific peptidase able to destroy the biological active dipeptide. To overcome this constraint, β‐cyclodextrin (β‐CD) was functionalized with carnosine to give the following new compounds: 6^A‐[(3‐{[(1S)‐1‐carboxy‐2‐(1H‐imidazol‐4‐yl)ethyl]amino}‐3‐oxopropyl)amino]‐6^A‐deoxy‐β‐cyclodextrin ( 1 ), 6^A‐[(β‐alanyl‐L ‐histidyl)amino]‐β‐cyclodextrin ( 2 ), and (2^AS,3^AR)‐3^A‐[(3‐{[(1S)‐1‐carboxy‐2‐(1H‐imidazol‐4‐yl)ethyl]amino}‐3‐oxopropyl)amino]‐3^A‐deoxy‐β‐cyclodextrin ( 3 ). Pulse‐radiolysis investigation showed that the β‐CD derivatives 1 – 3 are excellent scavengers of OH^. radicals. Their activity is not only due to the formation of the stable imidazole‐centered radical, but also to the scavenger ability of the glucose moieties of the macrocycle (Scheme). This effect is independent of the disposition of the imidazole ring. In fact, the quenching constant values are similar for the three compounds.     

Influence of graphene oxide incorporation and chemical cross‐linking on structure and mechanical properties of layer‐by‐layer assembled poly(Vinyl alcohol)‐Laponite free‐standing films

Functional fillers in multilayered films provide opportunity in tailoring the mechanical properties through chemical cross‐linking. In this study, Laponite‐graphene oxide co‐dispersion was used to incorporate graphene oxide (GO) easily into polyvinyl alcohol (PVA)/Laponite layer‐by‐layer (LBL) films. The LBL films were found to be uniform and the layer thickness increased linearly with number of depositions. The process was extended to a large number of depositions to investigate the macroscopic mechanical properties of the free‐standing films. The LBL films showed remarkable improvements in mechanical properties as compared to neat PVA film. The GO‐incorporated LBL films displayed higher enhancements in the tensile strength, ductility, and toughness as compared to that of PVA/Laponite LBL films, upon chemical cross‐linking. This suggests the advantageous effects of GO incorporation. Interestingly, cross‐linking of LBL films for longer time period (>1 h) and higher temperature (～80 °C) was not found to be much beneficial. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 2377–2387     

Preparation and characterization of polyvinyl alcohol/β‐cyclodextrin/GO‐Ag nanocomposite with improved antibacterial and strength properties

In this work, new hydrogel films based on polyvinyl alcohol (PVA) and β‐cyclodextrin (β‐CD) were prepared with the aim of studying their ability as an antibacterial and drug carrier system. Gallic acid (GA) was used as an antibacterial drug which was encapsulated into the β‐CD cavity, and finally, β‐CD inclusion complex (GA/βCD‐IC) was prepared. On the other hand, silver nanoparticles (AgNPs) were synthesized on the graphene oxide (GO) surface (GO‐Ag), and the obtained GO‐Ag was used to enhance the antibacterial properties and mechanical strength of their films. FT‐IR and DSC analysis approved the formation of cross‐linking with glutaraldehyde between the PVA and β‐CD. Hydrogel films were characterized using XRD and SEM. The disc diffusion method showed the antibacterial activity for the films containing GO‐Ag and GA. Due to the good strength, elasticity, WVP, and swelling ability, PVA/GA/βCD‐IC/GO‐Ag can be proposed as a potential antibacterial drug delivery system.     

Synthesis of Novel Bis(β‐cyclodextrin)s Linked with Glycol and Their Inclusion Complexation with Organic Dyes

Three novel bis(β‐cyclodextrin (CD))s with flexible glycol linkers, i.e., ethylene glycol‐bridged bis(6‐hydroxy‐6‐deoxy‐β‐CD) ( 2 ), diethylene glycol‐bridged bis(6‐hydroxy‐6‐deoxy‐β‐CD) ( 3 ), and triethylene glycol‐bridged bis(6‐hydroxy‐6‐deoxy‐β‐CD) ( 4 ) have been synthesized by the reaction of mono[6‐O‐(p‐toluenesulfonyl)]‐β‐CD with corresponding materials. The inclusion complexation behaviors of these compounds 2 – 4 with organic dyes; that is, acridine red (=N‐[(3Z)‐6‐(methylamino)‐3H‐xanthen‐3‐ylidene]methanaminium chloride; AR), neutral red (=N⁸,N⁸,3‐trimethylphenazine‐2,8‐diamine hydrochloride; NR), ammonium 8‐anilinonaphthalene‐1‐sulfonate (ANS), sodium 6‐(p‐toluidinyl)‐naphthalene‐2‐sulfonate (TNS), rhodamine B (RhB) and brilliant green (=N‐(4‐{[4‐(diethylamino)cyclohexa‐2,5‐dien‐1‐yl](phenyl)methyl}cyclohex‐2‐en‐1‐ylidene)‐N‐ethyl‐ethanaminium hydrogen sulfate; BG), have been investigated at 25° in phosphate buffer (pH 7.20) by ultraviolet, fluorescence, and 2D‐NMR spectroscopy. The results indicate that the two linked CD units may cooperatively bind a guest, and the molecular binding ability toward dye guests, especially bent ANS, T‐shaped RhB, and triangular BG, can be extended. This cooperative binding mode is confirmed by Job's experiments and 2D‐NMR investigations. Furthermore, the complex stability depends greatly on the linker length of these glycol‐bridged bis(β‐CD)s and the size and shape of guest. The higher binding ability and selectivity of dye molecules by bis(β‐CD)s 2 – 4 are discussed from the viewpoint of size/shape‐fit concept and multiple recognition mechanism.     

Synthesis and application of a chiral ionic liquid functionalized β‐cyclodextrin as a chiral selector in capillary electrophoresis

A novel chiral ionic liquid functionalized β‐cyclodextrin, 6‐O‐2‐hydroxpropyltrimethylammonium‐β‐cyclodextrin tetrafluoroborate ([HPTMA‐β‐CD][BF₄]), was synthesized and used as a chiral selector in capillary electrophoresis. [HPTMA‐β‐CD][BF₄] not only increased the solubility in aqueous buffer in comparison with the parent compound, but also provided a stable reversal electroosmotic flow, and the enantioseparation of eight chiral drugs was examined in phosphate buffer containing [HPTMA‐β‐CD][BF₄] as the chiral selector. The effects of the [HPTMA‐β‐CD][BF₄] concentration and the background electrolyte pH were studied. Moreover, the chiral separation abilities of β‐CD and [HPTMA‐β‐CD][BF₄] were compared and possible mechanisms for the chiral recognition of [HPTMA‐β‐CD][BF₄] are discussed. Copyright © 2013 John Wiley & Sons, Ltd.     

Capillary electrophoretic separation and computational modeling of inclusion complexes of β‐cyclodextrin and 18‐crown‐6 ether with primaquine and quinocide

The antimalarial drug primaquine (PQ) and its contaminant, the positional isomer quinocide (QC) have been successfully separated using capillary electrophoresis with either β‐cyclodextrin (β‐CD) or 18‐crown‐6 ether (18C6) as chiral mobile phase additive. The interactions of the drugs with cyclodextrins and 18C6 were studied by the semiempirical method (Parametric Model 3) PM3. Theoretical calculations for the inclusion complexes of PQ and QC with α‐CD, β‐CD and 18C6 were performed. Data from the theoretical calculations are correlated and discussed with respect to the electrophoretic migration behavior. More stable complexes are predicted for the PQ–β‐CD and PQ–18C6 complexes. The coelution of PQ and QC when α‐CD was used as buffer additive can be explained by their comparable stabilities of the inclusion complex formed, while significant differences in the complexation stabilities of the drugs with β‐CD is responsible for their separation. The stronger hydrogen bonding in PQ–18C6 system is responsible for the separation between PQ and QC when 18C6 was used as chiral mobile phase additive. Copyright © 2009 John Wiley & Sons, Ltd.     

保护的几丁寡糖及结构类似物的合成：复杂氨基寡糖合成的通用方法

建立了逐步合成具有重要生物活性的2-脱氧-2-氨基葡萄糖寡糖链的通用方法。采用邻苯二甲酰基保护氨基、硫代苯基为还原末端的离去基团,以氨基葡萄糖为起始原料,几种保护的几丁寡糖及结构类似物被合成：3-O-乙酰基-4,6-O-亚苄基-2-脱氧-2-邻苯二甲酰亚氨基-b-D-吡喃葡萄糖-（1→4）-（3-O-乙酰基-6-O-苄基-2-脱氧-2-邻苯二甲酰亚氨基）-b-D-吡喃葡萄糖甲苷（4）、3-O-乙酰基-4,6-O-亚苄基-2-脱氧-2-邻苯二甲酰亚氨基-b-D-吡喃葡萄糖-（1→4）-（3-O-乙酰基-6-O-苄基-2-脱氧-2-邻苯二甲酰亚氨基-b-D-吡喃葡萄糖）-（1→4）-（3-O-乙酰基-6-O-苄基-2-脱氧-2-邻苯二甲酰亚氨基）-b-D-吡喃葡萄糖甲苷（6）、3-O-乙酰基-4,6-O-亚苄基-2-脱氧-2-邻苯二甲酰亚氨基-b-D-吡喃葡萄糖-（1→3）-（4,6-O-亚苄基-2-脱氧-2-邻苯二甲酰亚氨基）-b-D-吡喃葡萄糖甲苷（8）、3-O-乙酰基-4,6-O-亚苄基-2-脱氧-2-邻苯二甲酰亚氨基-b-D-吡喃葡萄糖-（1→3）-（4,6-O-亚苄基-2-脱氧-2-邻苯二甲酰亚氨基-b-D-吡喃葡萄糖）- （1→3）-（4,6-O-亚苄基-2-脱氧-2-邻苯二甲酰亚氨基）- b-D-吡喃葡萄糖甲苷（10）。所合成化合物通过核磁共振和质谱分析确证了其化学结构。     

Photocatalytic Nanocomposite Films Fabricated by Layer‐by‐Layer Self‐assembly of TiO2 Nanoparticles and Lignosulfonates

Photocatalytic multilayer nanocomposite films composed of anatase TiO₂ nanoparticles and lignosulfonates (LS) were fabricated on quartz slides by the layer‐by‐layer (LBL) self‐assembly technique. X‐ray photoelectron spectroscopy (XPS), UV‐vis spectroscopy and atomic force microscopy (AFM) were used to characterize the TiO₂/LS multilayer nanocomposite films. Moreover, the photocatalytic properties (decomposition of methyl orange and bacteria) of multilayer nanocomposite films were investigated. XPS results indicated that the intensities of titanium and sulfur peaks increased with the LBL deposition process. A linear increase in absorbance at 280 nm was found by UV‐Vis spectroscopy, suggesting that stepwise multilayer growth occurs on the substrate and this deposition process is highly reproducible. AFM images showed that quartz slide was completely covered by TiO₂ nanoparticles when a 10‐bilayer multilayer film was formed. The decomposition efficiency of methyl orange by TiO₂/LS multilayer films under the same UV irradiation time increased linearly with the number of TiO₂ layers, and the results of decomposition of bacteria under UV irradiation showed that TiO₂/LS multilayer nanocomposite films exhibited excellent decomposition activity of bacteria (Escherichia coil).     

Layer—by—layer Multilaryer Films Self—assembled from a Rare—earth—containing Poly—oxometalate,Na9[Eu（W5O18）2] and Poly （allylamine hydrochloride） and Their Photoluminescent Properties

Ultrathin multilayer films of a rare-earth-containing polyoxometalate Na9[Eu(W5O18)2](EW) and poly (allymamine hydrochloride)(PAH) have been prepared by layer-by-layer self-assembly from dilute aqueous solution.The fabrication process of the EW/PAH multilaryer films was followed by UV-vis spectroscopy and ellipsometry,which show that the deposition process is linear and highly reproducible from layer to layer.An average EW/PAH bilayer thickness of ca.2.1nm was determined by ellipsometry.In addition,the scanning electron microscopy(SEM) image of the EW/PAH film indicates that the film surface is relatively uniform and smooth.The photoluminescent properties of these films were also investigated by fluorescence spectroscopy.     

羟丙基-β-环糊精磁性复合微粒的合成及作为阿霉素载体的体外释药研究

羟丙基-β-环糊精因具有内部疏水和外部亲水锥形圆筒空腔结构和良好的生物相容性在磁性药物载体方面有潜在应用价值。本研究将羟丙基-β-环糊精修饰在超顺磁性纳米四氧化三铁粒子表面制备磁性复合微粒,用红外光谱,透射电镜,振动磁强计,电感耦合等离子发射等方法对该复合微粒进行了表征,并将其用于抗肿瘤药物阿霉素的体外载药与释药实验研究。结果表明该复合微粒的粒径大小在10-20nm,饱和磁化强度59.9 emu/g,铁含量55.4%。对阿霉素的载药量为87.8 μg/mg。体外释药结果显示载药复合粒子在PBS中1天,4天,10天的累积释药量分别为35.5%, 49.3%, 76.5%,表明该载体具有一定的药物缓释功能。由此可知,羟丙基-β-环糊精磁性复合微粒可作为磁性靶向给药系统的有效载体。     

Chemo‐Enzymatic Synthesis of 3‐Deoxy‐β‐D‐ribofuranosyl Purines

9‐(3‐Deoxy‐β‐D ‐erythro‐pentofuranosyl)‐2,6‐diaminopurine ( 6 ) was synthesized by an enzymatic transglycosylation of 2,6‐diaminopurine ( 2 ) with 3′‐deoxycytidine ( 1 ) as a donor of 3‐deoxy‐D ‐erythro‐pentofuranose moiety. This transformation comprises i) deamination of 1 to 3′‐deoxyuridine ( 3 ) under the action of whole cell (E. coli BM‐11) cytidine deaminase (CDase), ii) the phosphorolytic cleavage of 3 by uridine phosphorylase (UPase) giving rise to the formation of uracil ( 4 ) and 3‐deoxy‐α‐D ‐erythro‐pentofuranose‐1‐O‐phosphate ( 5 ), and iii) coupling of the latter with 2 catalyzed by whole cell (E. coli BMT‐4D/1A) purine nucleoside phosphorylase (PNPase). Deamination of 6 by adenosine deaminase (ADase) gave 3′‐deoxyguanosine ( 7 ). Treatment of 6 with NaNO₂ afforded 9‐(3‐deoxy‐β‐D ‐erythro‐pentofuranosyl)‐2‐amino‐6‐oxopurine (3′‐deoxyisoguanosine; 8 ). Schiemann reaction of 6 (HF/HBF₄+NaNO₂) gave 9‐(3‐deoxy‐β‐D ‐erythro‐pentofuranosyl)‐2‐fluoroadenine ( 9 ).     

SO3H‐functionalized nano‐MGO‐D‐NH2: Synthesis,characterization and application for one‐pot synthesis of pyrano[2,3‐d]pyrimidinone and tetrahydrobenzo[b]pyran derivatives in aqueous media

An SO₃H‐functionalized nano‐MGO‐D‐NH₂ catalyst has been prepared by multi‐functionalization of a magnetic graphene oxide (GO) nanohybrid and evaluated in the synthesis of tetrahydrobenzo[b]pyran and pyrano[2,3‐d]pyrimidinone derivatives. The GO/Fe₃O₄ (MGO) hybrid was prepared via an improved Hummers method followed by the covalent attachment of 1,4‐butanesultone with the amino group of the as‐prepared polyamidoamine‐functionalized MGO (MGO‐D‐NH₂) to give double‐functionalized magnetic nanoparticles as the catalyst. The prepared nanoparticles were characterized to confirm their synthesis and to precisely determine their physicochemical properties. In summary, the prepared catalyst showed marked recyclability and catalytic performance in terms of reaction time and yield of products. The results of this study are hoped to aid the development of a new class of heterogeneous catalysts to show high performance and as excellent candidates for industrial applications.     

A family of single‐isomer,dicationic cyclodextrin chiral selectors for capillary electrophoresis: Mono‐6A‐ammonium‐6C‐butylimidazolium‐β‐cyclodextrin chlorides

The first member of the single‐isomer, dicationic cyclodextrin (CD) family, 6^A‐ammonium‐6^C‐butylimidazolium‐β‐cyclodextrin chlorides (AMBIMCD), has been synthesized, analytically characterized, and used to separate a variety of acidic enantiomers and amino acids by CE. Starting from mono‐6^A‐azido‐β‐cyclodextrin, the cationic imidazolium and ammonium moieties were subsequently introduced onto primary ring of β‐cyclodextrin via nucleophilic addition and Staudinger reaction. The analytically pure AC regio‐isomer CD was further obtained via column chromatography. This dicationic CD exhibited excellent enantioselectivities for selected analytes at concentration as low as 0.5 mM, which were even better than those of its mono‐imidazolium or ammonium‐substitued counterpart CDs at 10 equivalent concentrations. The effective mobilities of all studied analytes were found to decrease with the concentration of AMBIMCD. Inclusion complexation in combination with eletrostatic interactions seemed to account for the enhanced chiral discrimination process.     

Fabrication and Electrochemical Behavior of Vanadium‐Substituted Keggin‐Type Polyoxometalates Multilayer Films on 4‐Aminobenzoic Acid Modified Glassy Carbon Electrodes

Two Vanadium‐substituted Keggin‐type polyoxometalates, K₃H₂[α‐SiVW₁₁O₄₀]?6H₂O (SiVW₁₁) and K₄H₂[γ(1, 2)‐SiV₂W₁₀O₄₀]?4H₂O (SiV₂W₁₀) were first successfully immobilized on 4‐aminobenzoic acid modified glass carbon electrodes respectively by layer‐by‐layer assembly with poly (ethylenimine) (PEI) as counterions. The regular growth processes were monitored by cyclic voltammetry (CV), and it was proved that the multilayer films were uniform and stable. The cyclic voltammetry results indicated that the electrochemical behavior of two multilayer films was similar, and their redox couples are pH‐ and scan rate‐dependent. The multilayer films show favorable electrocatalytic active toward the reduction of NO₂^?, IO₃^? and H₂O₂.