Synthesis and characterization of grafting β‐cyclodextrin with chitosan

Two new adsorbents [β‐cyclodextrin–chitosan (β‐CD–CTS) and β‐cyclodextrin‐6–chitosan (β‐CD‐6‐CTS)] were synthesized by the reaction of β‐cyclodextrin (β‐CD) with epoxy‐activated chitosan (CTS) and the sulfonation of the C‐6 hydroxyl group of β‐cyclodextrin with CTS, respectively. Their structures were confirmed by IR spectral analysis and X‐ray diffraction analysis, and their apparent amount of grafting was determined by ultraviolet spectroscopy. The adsorption properties of β‐CD‐CTS and β‐CD‐6‐CTS for p‐dihydroxybenzene were studied. The experimental results showed that the two new adsorbents exerted adsorption on the carefully chosen target. The highest saturated capacity of p‐dihydroxybenzene of β‐CD‐CTS and β‐CD‐6‐CTS were 51.68 and 46.41 mg/g, respectively. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 860–864, 2004     

Synthesis and Properties of Alkoxyethyl β‐d‐Xylopyranoside

In order to improve the water solubility of sugar‐based surfactants, alkyl β‐d‐ xylopyranosides, novel sugar‐based surfactants, 1,2‐trans alkoxyethyl β‐d‐ xylopyranosides, with alkyl chain length n = 6–12 were stereoselectively prepared by the trichloroacetimidate method. Their properties including hydrophilic–lipophilic balance (HLB) number, water solubility, surface tension, emulsification, foamability, thermotropic liquid crystal, and hygroscopicity were investigated. The results indicated that their HLB number decreased with increase of alkyl chain, the water solubility improved since the hydrophilic oxyethene (─OCH₂CH₂─) fragment was introduced. The dissolution process was entropy driven at 25–45 °C for alkyl chain length n = 6–10. Octyloxyethyl β‐d‐ xylopyranoside had the best foaming ability. Nonyloxyethyl β‐d‐ xylopyranoside had the best foam stability and the emulsifying ability was better in toluene/water system than in rapeseed oil/water system. The surface tension of in aqueous solution dropped to 27.8 mN m^?1 at the critical micelle concentration, and it also showed the most distinct thermotropic liquid phases with cross pattern texture upon heating and the fan schlieren texture on cooling. Hexyloxyethyl β‐d‐ xylopyranoside possessed the strongest hygroscopicity. Based on the effective improvement of water solubility, the prepared alkoxyethyl β‐d‐ xylopyranosides showed excellent surface activity and are expected to develop their practical application as a class of novel sugar‐based surfactants.     

Pervaporation behavior of PVA membrane containing β‐cyclodextrin for separating xylene isomeric mixtures

To evaluate molecular recognition function of β‐cyclodextrin to xylene isomers, β‐CD polymer of branching chain extension (β‐CD‐EGDE) was synthesized by crosslinking β‐CD with ethylene glycol diglycidyl ether (EGDE). The pervaporation blend membranes of β‐CD‐EGDE/PVA were prepared by casting an aqueous solution of PVA and β‐CD polymer mixture, and the membranes were used for separation of p‐/m‐ and p‐/o‐xylene mixtures. It was observed that the pristine PVA membrane almost had no selectivity for xylene isomer mixtures. The PVA membrane incorporating β‐CD polymer had molecular recognition function, which selectively facilitated the transport of the xylene isomers. To ascertain pervaporation behavior, the sorption and desorption processes of the membrane in xylenes were investigated. The sorption result showed that the complex formation constant between β‐CDs and xylenes played a key role in swelling behavior. There was a significant difference between diffusion coefficients D and D⁰, calculated from the sorption and desorption measurements, respectively, indicating that the diffusivity selectivity in desorption stage may have remarkable effect on the total selectivity during pervaporation process. © 2012 American Institute of Chemical Engineers AIChE J, 59: 604–612, 2013     

Pancreas‐Specific Delivery of β‐Cell Proliferating Small Molecules

Our research groups recently described a series of small‐molecule inducers of β‐cell proliferation that could be used to increase β‐cell mass. To mitigate the risk of nonspecific proliferation of other cell types, we devised a delivery strategy built on the tissue specificity observed in the experimental β‐cell imaging agent (+)‐dihydrotetrabenazine (DTBZ). The β‐cell proliferator agent aminopyrazine (AP) was covalently linked with (+)‐DTBZ to afford conjugates that retain both the proliferation activity and binding affinity for vesicular monoamine transporter‐2 (VMAT2). In vivo mouse tissue distribution studies of a prototypical AP–DTBZ conjugate showed 15‐fold pancreas exposure over plasma. Tissue‐to‐plasma ratios in liver and kidneys were two‐ and five‐fold, respectively. This work is the first demonstration of enhanced delivery of β‐cell‐proliferating molecules to the pancreas by leveraging the intrinsic tissue specificity of a β‐cell imaging agent.     

气相低浓度甲苯在超稳Y分子筛的吸附-脱附性能

为提高Y分子筛对可挥发性有机废气的选择性吸附能力,采用高温水热处理技术对NaY分子筛进行骨架脱铝制备超稳Y分子筛(USY),并在固定床反应器中考察了USY在水汽存在下动态吸附低浓度甲苯的性能。结果表明,随着USY分子筛骨架Si/Al比的增加,虽然其微孔孔体积和比表面积发生了下降,但形成了较多的中孔结构。并且骨架硅含量增加后,USY对非极性的甲苯分子选择性吸附能力明显增加,当Si/Al为22左右,在相对湿度50%下,单位面积甲苯吸附量要比水吸附量大5.6倍。热重脱附研究表明,经过改性后,甲苯脱附温度可从NaY的300℃下降到超稳Y分子筛的160℃,具有优良的热再生性能。     

Preparation and coordination with Hg(II) of sulfur‐ and 2‐amino‐pyridine‐containing chelating resin

A novel chelating resin anchoring 2‐amino‐pyridine on macroporous crosslinked polystyrene beads via a sulfur‐containing spacer (PVBS‐AP) has been synthesized and its structures were characterized by FTIR, scanning electron microscopy, porous structure analysis, and elementary analysis. The results of scanning electron microscopy and pores analysis demonstrated that PVBS‐AP resin had meso‐macro porous structure. Its adsorption properties for Hg(II), Pd(II), Ni(II), Cu(II), Zn(II), Pb(II), and Cd(II) were investigated. Some factors affecting the adsorption of PVBS‐AP resin for Hg(II), such as temperature, contact time, ion concentration, and pH were also studied. The results showed that the increasing of temperature was beneficial to adsorption and Langmuir model was much better than Freundlich model to describe the isothermal process. PVBS‐AP resin had good adsorption selectivity for Hg(II). It could selective adsorb Hg(II) from such binary ions system as Hg(II)‐Ni(II), Hg(II)‐Zn(II), and Hg(II)‐Pb(II), their selective coefficients are α_Hg/Ni = ∞, α_Hg/Zn = 28.1, α_Hg/Pb = ∞, respectively. Five adsorption–desorption cycles demonstrate that this resin were suitable for reuse without considerable change in adsorption capacity. POLYM. ENG. SCI., 47:721–727, 2007. © 2007 Society of Plastics Engineers.     

The Kinetics and Equilibrium of Ethanol Adsorption from Aqueous Phase Using Calcined (Na‐1,6‐Hexanediol)‐ZSM‐5

Na‐ZSM‐5, synthesized using 1,6‐hexanediol as the structure directing agent, has been found to have a suitable selectivity and adsorbing capacity for ethanol adsorption from aqueous solutions. In contrast to quaternary ammonium based Na‐ZSM‐5 zeolites, this Na‐ZSM‐5 did not show any catalytic interaction with ethanol during thermal desorption. The dynamics of the adsorption process were investigated using the finite volume “uptake rate” route. The data predicted from the governing relations of the process were correlated with experimental results. The micro‐diffusion coefficient was determined as a function of temperature.The macropore diffusional mass transfer contribution for biporous zeolite particles was found to be negligible.     

Coating of porous silica beads by in situ polymerization/crosslinking of 2‐hydroxypropyl β‐cyclodextrin for reversed‐phase high performance liquid chromatography applications

Porous silica beads were coated with a crosslinked β‐cyclodextrin polymer by in situ polymerization/crosslinking of 2‐hydroxypropyl β‐cyclodextrin with 1,6‐hexamethylenediisocyanate in anhydrous dimethylsulfoxide. This method was developed for the preparation of reversed‐phase high performance liquid chromatography stationary phases. The mass of polymer immobilized onto the silica surface was controlled by the amount of coupling agent, 1,6‐hexamethylenediisocyanate, added during the coating process. The influence of the polymer coating on the physical features of the beads was investigated by means of nitrogen adsorption/desorption methods, scanning electron microscopy and energy dispersion X‐ray analysis. The column lifetime was found to be primarily dependent on the extent of crosslinking of the stationary phase. Moreover, it was demonstrated that the synthesis of highly crosslinked stationary phases with a reasonable column lifetime gave rise to a phase separation of the β‐cyclodextrin polymer. To prove their usefulness as reversed‐phase packing materials, they were used to separate mixtures of nitrophenol positional isomers, four pesticides, and drugs. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1419–1426, 2004     

Viscometric Study of the Inclusion Complex Between β‐Cyclodextrin and HTAC in Aqueous Solution

The inclusion complex formed by β‐cyclodextrin (β‐CD) with the cationic surfactant hexadecyltrimethylammonium chloride (HTAC) was studied by viscometry using poly(ethylene oxide) (PEO)–HTAC aggregates as a viscosity indicator. The relative viscosity of β‐CD in aqueous PEO–HTAC solution profiles shows that the formation of the β‐CD/HTAC inclusion complex causes HTAC molecules to be stripped off the PEO chains, resulting in a decrease of aqueous solution viscosity as a result of the decrease in electrostatic repulsion between polymer‐bound HTAC micelles. The viscosity minimum at C_β‐CD/C_HTAC = 0.5 indicates that the molecular ratio of host molecule to guest molecule is 1:2 in the β‐CD/HTAC inclusion complex.     

Heptakis(2,3‐di‐O‐methyl‐6‐O‐sulfopropyl)‐β‐cyclodextrin: A Genuine Supramolecular Carrier for Aqueous Organometallic Catalysis

The behavior of heptakis(2,3‐di‐O‐methyl‐6‐O‐sulfopropyl)‐β‐cyclodextrin as inverse phase transfer catalyst in biphasic Tsuji–Trost and hydroformylation reactions has been investigated. In terms of activity, this methylated sulfopropyl ether β‐cyclodextrin is much more efficient than the randomly methylated β‐cyclodextrin, which was the most active cyclodextrin known to date. From a selectivity point of view, the intrinsic properties of the catalytic system are fully preserved in the presence of this cyclodextrin as the chemo‐ or regioselectivity was found to be identical to that observed without a mass transfer promoter in the hydroformylation reaction. The efficiency of this cyclodextrin was attributed to its high surface activity and to the absence of interactions with the catalytically active species and the water‐soluble phosphane used to dissolve the organometallic catalyst in the aqueous phase.     

The versatile synthesis method for hierarchical micro‐ and mesoporous zeolite: An embedded nanocarbon cluster approach

In this work, we are reporting for the first time the synthesis of hierarchical micro‐ and mesoporous zeolite using silica–carbon (SiO₂/C) composites prepared by pyrolysis of carbonaceous gases in the presence of silica gel. The pyrolysis effectively yielded carbon deposited onto the raw silica material. The obtained SiO₂/C composites were utilised as a bifunctional material, mesoporous template and silica source, for the zeolite synthesis. Tetrapropylammonium hydroxide (TPAOH) was used as a microporous template. The combination of the obtained composites and the TPAOH for the hydrothermal synthesis resulted in the formation of hierarchical micro‐ and mesoporous ZSM‐5. The results from the SEM, TEM, and N₂ adsorption/desorption isotherms, and ²⁷Al MAS NMR characterisations of the synthesised samples obtained after the removal of the templates confirmed the successful formation of the micro‐ and mesoporous zeolites. The mesoporosity of the zeolites could be controlled by adjusting the carbon content in the SiO₂/C composites while the carbon content could be controlled by varying the deposition time and the concentration of the carbonaceous gases used. This controllable and efficient synthesis method is considered to be a promising method for creating hierarchical micro‐ and mesoporous zeolites. © 2011 Canadian Society for Chemical Engineering     

超稳Y型分子筛的骨架硅铝比对甘油气相脱水反应的影响

以铵交换和高温水热处理法制备了不同硅铝比的超稳Y型分子筛（USY）,利用X射线衍射、扫描电镜、氮气吸附脱附和吡啶红外等技术对USY进行了表征。以USY为催化剂,考察了USY的骨架硅铝比对气相甘油脱水制丙烯醛的影响。X射线衍射和扫描电镜结果表明,铵交换和高温水热处理只是提高USY的硅铝比,相对结晶度略有降低,而对Y型分子筛的结构和形貌没有影响。氮气吸附-脱附和吡啶红外结果表明,随USY骨架SiO₂/Al₂O₃比提高,总酸量和B酸酸量逐渐降低,L酸酸量有所增多,介孔孔体积和平均孔径有所增大。气相甘油脱水反应结果表明,催化剂织构性质对甘油转化率和丙烯醛选择性的影响大于酸性的影响,因而SiO₂/Al₂O₃比为29的USY催化剂的反应性能最好,甘油转化率和丙烯醛收率分别达到了84.5%和51.8%。     

Enzymes in Organic Chemistry, 11:[1] Hydrolase‐Catalyzed Resolution of α‐ and β‐Hydroxyphosphonates and Synthesis of Chiral,Non‐Racemic β‐Aminophosphonic Acids

The enantioselective acylation of racemic diisopropyl α‐ and β‐hydroxyphosphonates by hydrolases in t‐butyl methyl ether with isopropenyl acetate as acyl donor is limited by the narrow substrate specificity of the enzymes. High enantiomeric excesses (up to 99%) were obtained for the acetates of (S)‐diisopropyl 1‐hydroxy‐(2‐thienyl)methyl‐, 1‐hydroxyethyl‐ and 1‐hydroxyhexylphosphonate and (R)‐diisopropyl 2‐hydroxypropylphosphonate. The hydrolysis of a variety of β‐chloroacetoxyphosphonates by the lipase from Candida cylindracea and protease subtilisin in a biphasic system gives (S)‐β‐hydroxyphosphonates (ee 51–92%) enantioselectively. (S)‐2‐Phenyl‐2‐hydroxyethyl‐ and (S)‐3‐methyl‐2‐hydroxybutylphosphonates (ee 96% and 99%, respectively) were transformed into (R)‐2‐aminophosphonic acids of the same ee.     

Synthesis,Structure–Activity,and Structure–Stability Relationships of 2‐Substituted‐N‐(4‐oxo‐3‐oxetanyl) N‐Acylethanolamine Acid Amidase (NAAA) Inhibitors

N‐Acylethanolamine acid amidase (NAAA) is a cysteine amidase that preferentially hydrolyzes saturated or monounsaturated fatty acid ethanolamides (FAEs), such as palmitoylethanolamide (PEA) and oleoylethanolamide (OEA), which are endogenous agonists of nuclear peroxisome proliferator‐activated receptor‐α (PPAR‐α). Compounds that feature an α‐amino‐β‐lactone ring have been identified as potent and selective NAAA inhibitors and have been shown to exert marked anti‐inflammatory effects that are mediated through FAE‐dependent activation of PPAR‐α. We synthesized and tested a series of racemic, diastereomerically pure β‐substituted α‐amino‐β‐lactones, as either carbamate or amide derivatives, investigating the structure–activity and structure–stability relationships (SAR and SSR) following changes in β‐substituent size, relative stereochemistry at the α‐ and β‐positions, and α‐amino functionality. Substituted carbamate derivatives emerged as more active and stable than amide analogues, with the cis configuration being generally preferred for stability. Increased steric bulk at the β‐position negatively affected NAAA inhibitory potency, while improving both chemical and plasma stability.     

Temperature Dependence of Electrical Resistivity (4–300 K) in Aluminum‐ and Boron‐Doped SiC Ceramics

Al‐ and B‐doped 3C–SiC ceramics were prepared by hot‐pressing powder compacts containing submicrometer‐sized β‐SiC, precursors of 5 wt% nanosized β‐SiC, and an optional additive (Al or B) in an Ar atmosphere. Electron probe microanalysis (EPMA) investigation on the obtained specimens revealed that a portion of the doped Al and B atoms substituted the zinc blende lattice sites. The temperature‐dependent electrical resistivity data of the Al‐ and B‐doped SiC specimens were measured in the 4–300 K range and compared with those of an undoped specimen. The Al‐ and B‐doped SiC specimens exhibited resistivities that were as high as ~10³ Ω cm at room temperature and ~10⁵ and ~10⁴ Ω cm, respectively, below 100 K. These values are larger than those of the undoped SiC specimen by a factor of ~10⁴. Such high resistivities of the impurity‐doped specimens are attributable to the carrier compensation by the Al‐ and B‐derived acceptors located well above the valence‐band edge of 3C–SiC. Photoluminescence investigation revealed that the Al‐ and B‐doped specimens exhibited emission profile below 2 eV, implying the existence of the acceptors.     

6‐Amino‐6‐deoxy‐5,6‐di‐N‐(N′‐octyliminomethylidene)nojirimycin: Synthesis,Biological Evaluation,and Crystal Structure in Complex with Acid β‐Glucosidase

6‐Amino‐6‐deoxy‐5,6‐di‐ N ‐( N ′‐octyliminomethylidene)nojirimycin , a reducing analogue of N‐nonyl‐1‐deoxynojirimycin, proved to be a potent and very selective inhibitor of β‐glucosidases, including human acid β‐glucosidase. Structural studies of the enzyme–inhibitor complex showed a binding mode in which the anomeric hydroxy group is accommodated in the “wrong” α configuration.

     

Behavior of α‐ and β‐cyclodextrin‐encapsulated allyl isothiocyanate as slow‐release additives in polylactide‐co‐polycaprolactone films

The natural antibacterial agent allyl isothiocyanate (AITC) encapsulated in either α‐ or β‐cyclodextrin (CD) has previously been evaluated as a slow‐release additive in polylactide‐co‐polycaprolactone (PLA–PCL) films designed for use in cheese packaging. In the research described in this article, thermogravimetric analysis (TGA) and thermogravimetric analysis in tandem with mass spectrometry (TGA–MS) were used to explore the thermal properties of CD‐encapsulated AITC complexes as well as those of PLA–PCL films containing these complexes. To our knowledge, this is the first reported application of the TGA–MS technique to explore the thermal stability of CD‐entrapped AITC and the first study to report differences in thermal stability of AITC in α‐and β‐CD cavities in the solid state. Observed differences in the thermal degradation profile of films containing the CD complexes can be explained if AITC binds more strongly to β‐CD than to α‐CD. This hypothesis has been reinforced by gas chromatography (GC) and high performance liquid chromatography (HPLC) studies, the results of which suggest that a new covalently bound AITC–CD complex may be formed when incorporating the β‐CD complex of AITC in PLA–PCL films but not when incorporating the α‐CD complex of AITC. This finding means that the α‐CD complex of AITC would be preferred in situations where adequate long‐term controlled release of AITC from polymer films is required, as for example in the case of active packaging applications. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Effects of micro and nano β‐TCP fillers in freeze‐gelled chitosan scaffolds for bone tissue engineering

Tissue engineering holds an exciting promise in providing a long‐term cure to bone‐related defects and diseases. However, one of the most important prerequisites for bone tissue engineering is an ideal platform that can aid tissue genesis by having biomimetic, mechanostable, and cytocompatible characteristics. Chitosan (CS) was chosen as the base polymer to incorporate filler, namely beta‐tri calcium phosphate (β‐TCP). This research deals with a comparative study on the properties of CS scaffolds prepared using micro‐ and nano‐sized β‐TCP as filler by freeze gelation method. The scaffolds were characterized for their morphology, porosity, swelling, structural, chemical, biodegradation, and bioresorption properties. Rheological behavior of polymer and polymer‐ceramic composite suspensions were analyzed and all the suspensions with varying ratios of β‐TCP showed non‐Newtonian behavior with shear thinning property. Pore size, porosity of micro‐ and nano‐sized composite scaffolds are measured as 48–158 μm and 77% and 43–155 μm and 81%, respectively. The scaffolds containing nano β‐TCP possess higher compressive strength (～2.67 MPa) and slower degradation rate as compared to composites prepared with micro‐sized β‐TCP (～1.52 MPa). Bioresorbability, in vitro cell viability by 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) assay, proliferation by Alamar blue assay, cell interaction by scanning electron microscope, and florescence microscopy further validates the potentiality of freeze‐gelled CS/β‐TCP composite scaffolds for bone tissue engineering applications. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41025.     

Kinetic study of 1‐butanol dehydration to di‐n‐butyl ether over Amberlyst 70

Kinetics of the catalytic dehydration of 1‐butanol to di‐n‐butyl ether (DNBE) over Amberlyst 70 was investigated. Experiments were performed in liquid phase at 4 MPa and 413–463 K. Three elementary reaction mechanisms were considered: a Langmuir–Hinselwood–Hougen–Watson (LHHW) formulation; an Eley–Rideal (ER) formulation in which DNBE remains adsorbed; an ER formulation in which water remains adsorbed. Two kinetic models explain satisfactorily the dehydration of 1‐butanol to DNBE: a LHHW formalism in which the surface reaction between two adjacent adsorbed molecules of 1‐butanol is the rate limiting step (RLS) and where the adsorption of water is negligible, and a mechanism in which the RLS is the desorption of water being the adsorption of DNBE negligible. In both models, the strong inhibiting effect of water was successfully taken into account by means of a correction factor derived from a Freundlich adsorption isotherm. Both models present similar values of apparent activation energies (122 ± 2 kJ/mol). © 2015 American Institute of Chemical Engineers AIChE J, 62: 180–194, 2016     

Enantioselective Copper(II)‐Catalyzed Conjugate Addition of Indoles to β‐Substituted Unsaturated Acyl Phosphonates

The first copper‐catalyzed enantioselective conjugate addition of indoles to β‐substituted unsaturated acyl phosphonates was successfully realized by using a heteroarylidene‐tethered bis(oxazoline) ligand. The reaction features high efficiency, cheap catalyst and broad generality. In the case of either β‐alkyl‐ or β‐aryl‐substituted unsaturated acyl phosphonates, the 3‐indolyl adducts were achieved in high yields with good to excellent enantioselectivities (up to 97% ee). The 3‐indolyl adducts can serve as important intermediates in the synthesis of indole alkaloids.