Gas Chromatographic Enantiomer Separation of Atropisomeric PCBs Using Modified Cyclodextrins as Chiral Phases

Columns containing different types of cyclodextrin derivatives have been evaluated for chiral gas chromatographic separation of atropisomeric PCBs, o,p´‐DDT and o,p´‐DDD. Separation was attempted on columns containing mixed chiral selectors, and the performance of two closely related selectors was also examined. The cyclodextrins were: permethylated‐β‐CD (PM‐β‐CD), heptakis(2,3‐di‐O‐methyl‐6‐O‐tert‐butyldimethylsilyl)‐β‐CD (2,3‐M‐6‐TBDMS‐β‐CD), heptakis(2,3‐di‐O‐methyl‐6‐O‐tert‐hexyldimethylsilyl)‐β‐CD (2,3‐M‐6‐THDMS‐β‐CD), and heptakis(2,3‐di‐O‐ethyl‐6‐O‐tert‐hexyldimethylsilyl)‐β‐cyclodextrin (2,3‐E‐6‐THDMS‐β‐CD). The cyclodextrins were dissolved in OV‐1701 or in a dimethylsiloxane/silarylene copolymer containing 5% phenyl in the backbone. The application of mixed chiral selectors led to improved separations, however; at most eleven PCB congeners were separated on a single column. Chiral resolution of o,p´‐DDD was achieved. The use of a dimethylsiloxane/silarylene copolymer as a matrix for the cyclodextrins is a promising approach. With such a matrix, blocking of the CD cavities by silicone substituent groups can be avoided, and a reasonable CD solubility can be provided. The selectivity of heptakis(2,3‐di‐O‐ethyl‐6‐O‐tert‐hexyldimethylsilyl)‐β‐CD and heptakis(2,3‐di‐O‐methyl‐6‐O‐tert‐hexyldimethylsilyl)‐β‐CD was quite different, the former selector could separate four congeners, while the latter separated ten congeners.     

Combination of capillary electrophoresis and molecular modeling to study the enantiomer affinity pattern between β‐blockers and anionic cyclodextrin derivatives in a methanolic and water background electrolyte

In order to have deep insights into the mechanisms of enantiomer affinity pattern in both aqueous and non‐aqueous systems, an approach combining capillary electrophoresis and molecular modeling was undertaken. A chiral β‐blocker; acebutolol, was enantioseparated in aqueous capillary electrophoresis and non‐aqueous capillary electrophoresis using two anionic β‐cyclodextrin derivatives. The enantiomer affinity pattern of acebutolol was found to be opposite when an aqueous background electrolyte was replaced with non‐aqueous background electrolyte in the presence of heptakis(2,3‐di‐O‐acetyl‐6‐sulfo)‐β‐cyclodextrin but remained the same in the presence of heptakis(2,3‐di‐O‐methyl‐6‐sulfo)‐β‐cyclodextrin. Molecular docking of acebutolol into two β‐cyclodextrin derivatives indicated two distinct binding modes called ‘up’ and ‘down’ conformations. After structure optimization by molecular dynamics and energy minimization, both enantiomers of acebutolol were preferred to the ‘up’ conformation with heptakis(2,3‐di‐O‐methyl‐6‐sulfo)‐β‐cyclodextrin while ‘down’ conformation with heptakis(2,3‐di‐O‐acetyl‐6‐sulfo)‐β‐cyclodextrin. The further calculation of the complex energy with solvent effect indicated that heptakis(2,3‐di‐O‐acetyl‐6‐sulfo)‐β‐cyclodextrin had higher affinity to S‐acebutolol than R‐acebutolol in non‐aqueous capillary electrophoresis while it showed better binding to R‐acebutolol in aqueous capillary electrophoresis. However, the heptakis(2,3‐di‐O‐methyl‐6‐sulfo)‐β‐cyclodextrin bound better to R‐acebutolol in both aqueous and non‐aqueous capillary electrophoresis, implying that the binding mode played more important role in chiral separation of heptakis(2,3‐di‐O‐methyl‐6‐sulfo)‐β‐cyclodextrin while the solvent effect had prevailing impact on heptakis(2,3‐di‐O‐acetyl‐6‐sulfo)‐β‐cyclodextrin.     

Enantioselective comprehensive two‐dimensional gas chromatography of lavender essential oil

The enantiomeric composition of several chiral markers in lavender essential oil was studied by flow modulated comprehensive two‐dimensional gas chromatography operated in the reverse flow mode and hyphenated to flame ionization and quadrupole mass spectrometric detection. Two capillary column series were used in this study, 2,3‐di‐O‐ethyl‐6‐O‐tert‐butyldimethylsilyl‐β‐cyclodextrin or 2,3,6‐tri‐O‐methyl‐β‐cyclodextrin, as the chiral column in the first dimension and α polyethylene glycol column in the second dimension. Combining the chromatographic data obtained on these column series, the enantiomeric and excess ratios for α‐pinene, β‐pinene, camphor, lavandulol, borneol, and terpinen‐4‐ol were determined. This maybe a possible route to assess the authenticity of lavender essential oil.     

Enantioselective comprehensive two‐dimensional gas chromatography. A route to elucidate the authenticity and origin of Rosa damascena Miller essential oils

The analysis of Bulgarian and Turkish Rosa damascena Miller essential oils was performed by flow‐modulated comprehensive two‐dimensional gas chromatography using simultaneous detection of the second column effluent by flame ionization and quadrupole mass spectrometric detection. Enantioselective separations were obtained by running the samples on 2,3‐di‐O‐ethyl‐6‐O‐tert‐butyldimethylsilyl‐β‐cyclodextrin column as the first column and on polyethylene glycol as the second column. The determination of enantiomeric or diastereomeric excess of some terpenoic solutes is a possible route for quality or authenticity control as well as for the elucidation of the country of origin.     

Complexation of 4‐dimethylaminoazobenzene with various kinds of cyclodextrins: Effects of cyclodextrins on the thermal cis‐to‐trans isomerization

On the basis of the change in electronic and induced circular dichroism spectra for complex formation, the complexation of 4‐dimethylaminoazobenzene (DAAB) with four kinds of cyclodextrins (α‐ and β‐cyclodextrin (CD), heptakis(2,6‐di‐O‐methyl)‐β‐cyclodextrin, and heptakis(2,3,6‐tri‐O‐methyl)‐β‐cyclodextrin) was studied in methanol–water and dimethyl sulfoxide–water mixtures. It was found that the trans and cis isomers of DAAB form two different types of complex (inclusion and lid type) with CDs, depending on the kinds of CDs and solvents. Further, we have examined the effect of CDs on the thermal cis‐to‐trans isomerization of DAAB. The accelerated or decelerated effect on the thermal isomerization was observed upon adding CDs. The effects of CDs on the thermal isomerization are discussed in connection with the complexation of the cis‐isomer of DAAB with CDs. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 481–487, 2002     

Comparison of Different Di‐tert‐butyldimethyl‐Silylated Cyclodextrins as Chiral Stationary Phases in Capillary Gas Chromatography

Separation factors and thermodynamic data for the separation of various chiral analytes on different di‐O‐tert‐butyldimethyl‐silylated cyclodextrin derivatives are collected and described. Modifying the substitution pattern of the tert‐butyldimethylsilyl group in position 2 and 3 or changing from β‐ to γ‐cyclodextrin significantly affects the separation properties of the cyclodextrin derivatives.     

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.     

Chiral separation of 12 pairs of enantiomers by capillary electrophoresis using heptakis‐(2,3‐diacetyl‐6‐sulfato)‐β‐cyclodextrin as the chiral selector and the elucidation of the chiral recognition mechanism by computational methods

Chiral separation of 12 pairs of basic analyte enantiomers including oxybutynin, bambuterol, tradinterol, clenbuterol, clorprenaline, terbutaline, tulobuterol, citalopram, phencynonate, fexofenadine, salbutamol, and penehyclidine was conducted by capillary electrophoresis using a single‐isomer anionic β‐cyclodextrin derivative, heptakis‐(2,3‐diacetyl‐6‐sulfato)‐β‐cyclodextrin as the chiral selector. Parameters influencing separation were studied, including background electrolyte pH, heptakis‐(2,3‐diacetyl‐6‐sulfato)‐β‐cyclodextrin concentration, buffer concentration, and separation voltage. A background electrolyte consisting of 50 mM Tris‐H₃PO₄ and 6 mM heptakis‐(2,3‐diacetyl‐6‐sulfato)‐β‐cyclodextrin at pH 2.5 was found to be highly efficient for the separation of most enantiomers, with other conditions of normal polarity mode at 10 kV, detection wavelength of 210 nm using hydrodynamic injection for 3 s. Under the optimal conditions, baseline resolution (>1.50) for 11 pairs of enantiomers and somewhat lower resolution for penehyclidine enantiomers (1.17) were generated. Moreover, the possible mechanism of separation of clenbuterol, oxybutynin, salbutamol, and penehyclidine was investigated using a computational modeling method.     

Physical properties of diblock methylcellulose derivatives with regioselective functionalization patterns: First direct evidence that a sequence of 2,3,6‐tri‐O‐methyl‐glucopyranosyl units causes thermoreversible gelation of methylcellulose

This article describes detailed structure‐property relationships of 5 regioselectively methylated celluloses and 10 diblock cellulose derivatives with regioselective functionalization patterns: methyl 2,3,6‐tri‐O‐ ( 1 , 236MC), methyl 2,3‐di‐O‐ ( 2 , 23MC), methyl 2,6‐di‐O‐ ( 3 , 26MC), methyl 3‐O‐ ( 4 , 3MC), methyl 6‐O‐methyl‐cellulosides ( 5 , 6MC), methyl β‐D‐glucopyranosyl‐(1→4)‐2,3,6‐tri‐O‐methyl‐ ( 6 , G‐236MC), methyl β‐D‐glucopyranosyl‐(1→4)‐2,3‐di‐O‐methyl‐ ( 7 , G‐23MC), methyl β‐D‐glucopyranosyl‐(1→4)‐2,6‐di‐O‐methyl‐ ( 8 , G‐26MC), methyl β‐D‐glucopyranosyl‐(1→4)‐3‐O‐methyl‐ ( 9 , G‐3MC), methyl β‐D‐glucopyranosyl‐(1→4)‐6‐O‐methyl‐ ( 10 , G‐6MC), methyl β‐D‐glucopyranosyl‐(1→4)‐β‐D‐glucopyranosyl‐(1→4)‐2,3,6‐tri‐O‐methyl‐ ( 11 , GG‐236MC), methyl β‐D‐glucopyranosyl‐(1→4)‐β‐D‐glucopyranosyl‐(1→4)‐2,3‐di‐O‐methyl‐ ( 12 , GG‐23MC), methyl β‐D‐glucopy‐ranosyl‐(1→4)‐β‐D‐glucopyranosyl‐(1→4)‐2,6‐di‐O‐methyl‐ ( 13 , GG‐26MC), methyl β‐D‐glucopyranosyl‐(1→4)‐β‐D‐glucopyranosyl‐(1→4)‐3‐O‐methyl‐ ( 14 , GG‐3MC), and methyl β‐D‐glucopyranosyl‐(1→4)‐β‐D‐glucopyranosyl‐(1→4)‐6‐O‐methyl‐cellulosides ( 15 , GG‐6MC). Surface tension, differential scanning calorimetry, fluorescence, and dynamic light scattering measurements of aqueous solutions of compounds 1 – 15 revealed that there was no relationship between aggregation behaviors and gel formation, gelation occurred only when the hydrophobic environments formed by hydrophobic interactions between the sequences of 2,3,6‐tri‐O‐methyl‐glucopyranosyl units upon heating. The diblock structure consisting of cellobiosyl block and approx. ten 2,3,6‐tri‐O‐methyl‐glucopyranosyl units was of crucial importance for thermoreversible gelation of methylcellulose. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 1539–1546, 2011     

6‐TIPS‐β‐Cyclodextrin‐Modified Fe3O4 for Facile Enantioseparation of 1‐(1‐Naphthyl)ethylamine

A new type of chiral magnetic nanoparticle was prepared from covalently linked magnetic nanoparticles (Fe₃O₄) and heptakis‐(6‐O‐triisopropylsilyl)‐β‐cyclodextrin (6‐TIPS‐β‐CD). The resulting selectors (TIPS‐β‐CD‐MNPs) combined the good magnetic properties Fe₃O₄ and efficient chiral recognition ability of 6‐TIPS‐β‐CD. The enantioselectivity of TIPS‐β‐CD‐MNPs towards 1‐(1‐naphthyl)ethylamine was six times higher than that of the parent β‐CD modified Fe₃O₄ particles.     

Synthesis and Enzymic Hydrolysis of Acylated Adenosine Derivatives

Abstract

Various derivatives of adenosine were prepared by acylation of adenosine (6‐amino‐9‐(β‐D‐ribofuranosyl)purine (1) with different molar equivalents of acetic anhydride and/or pivaloyl chloride in pyridine. Compounds 6‐acetylamino‐9‐[(2,3,5‐tri‐O‐acetyl)‐β‐D‐ribofuranosyl]purine (3), 6‐amino‐9‐[(2,3,5‐tri‐O‐acetyl)‐β‐D‐ribofuranosyl]purine (4), and 6‐pivaloylamino‐9‐[(2,3,5‐tri‐O‐pivaloyl)‐β‐D‐ribofuranosyl]purine (5) were subsequently submitted to hydrolysis catalyzed by a number of hydrolytic enzymes. Regioselective enzymic deacetylation at the primary hydroxyl group of 3 and 4 with butyrylcholinesterase (BChE) produced 6‐acetylamino‐9‐[(2,3‐di‐O‐acetyl)‐β‐D‐ribofuranosyl]purine (9) and 6‐amino‐9‐[(2,3‐di‐O‐acetyl‐β‐D‐ribofuranosyl]purine (10), respectively. All structures were established by ¹H and ¹³C NMR spectroscopies.     

Gas phase isomeric differentiation of oleanolic and ursolic acids associated with heptakis‐(2,6‐di‐O‐methyl)‐β‐cyclodextrin by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry

Oleanolic acid (OA) and ursolic acid (UA) are isomeric triterpenoid compounds with similar pharmaceutical properties. Usually, modern chromatographic and electrophoretic methods are widely utilized to differentiate these two compounds. Compared with mass spectrometric (MS) methods, these modern separation methods are both time‐ and sample‐consuming. Herein, we present a new method for structural differentiation of OA and UA by Fourier transform ion cyclotron resonance mass spectrometry (FT‐ICR MS) with the association of heptakis‐(2,6‐di‐O‐methyl)‐β‐cyclodextrin (DM‐β‐CD). Exact MS and tandem MS (MS/MS) data showed that there is no perceptible difference between OA and UA, as well as their β‐cyclodextrin and γ‐cyclodextrin complexes. However, there is a remarkable difference in MS/MS spectra of DM‐β‐CD complexes of OA and UA. The peak corresponding to the neutral loss of a formic acid and a water molecule could only be observed in the MS/MS spectrum of the complex of DM‐β‐CD : OA. Molecular modeling calculations were also employed to further investigate the structural differences of DM‐β‐CD : OA and DM‐β‐CD : UA complexes. Therefore, by employing DM‐β‐CD as a reference reagent, OA and UA could be differentiated with purely MS method. Copyright © 2010 John Wiley & Sons, Ltd.     

Comparative analysis of the full set of methylated β‐cyclodextrins as chiral selectors in capillary electrophoresis

The chiral separation ability of the full library of methylated‐β‐cyclodextrins towards pharmacologically significant racemic drugs including basic compounds was studied by chiral CE. The syntheses of all the methylated, single isomer β‐cyclodextrins were revised and optimized and the aqueous solubility of the derivatives was unambiguously established. The three most relevant commercially available methylated isomeric mixtures were also included in the screening, so a total of ten various methylated CDs were investigated. The effects of the selector concentration on the enantiorecognition properties at acidic pH were investigated. Among the dimethylated β‐cyclodextrins, the heptakis (2,6‐di‐O‐methyl)‐β‐cyclodextrin isomer (2,6‐DIMEB) resulted to be the most versatile chiral selector. Terbutaline was selected as a model compound for the in‐depth investigation of host‐guest enantiodiscrimination ability. The association constants between the two terbutaline enantiomers and 2,6‐DIMEB were determined in order to support that the enantioseparation is driven by differences is host‐guest binding. The migration order of the enantiomers was confirmed by performing spiking experiments with the pure enantiomers. 1D and 2D NMR spectroscopy was applied to the 2,3‐, and 2,6‐DIMEB/terbutaline systems to rationalize at molecular level the different enantioseparation ability of the dimethylated β‐cyclodextrin selectors.     

Cyclodextrin encapsulation of the functional group diminishes an antioxidant's free radical scavenging rates

Scavenging rates of cyclodextrin‐solubilized lipophilic antioxidants, namely catechin, epicatechin, epigallocatechin gallate, and resveratrol, against alkoxyl (RO^?) radical were measured with the use of electron paramagnetic resonance (EPR) spin‐trapping method. Results indicated that the scavenging rates of catechin and resveratrol were notably dependent on the solubilizer used, i.e., native β‐cyclodextrin (β‐CD) or heptakis(2,6‐di‐O‐methyl)‐β‐cyclodextrin (DM‐β‐CD). But, epicatechin and epigallocatechin gallate showed almost no dependence on the cyclodextrin used. Catechin's scavenging rate in β‐CD was 66% lower than in DM‐β‐CD; in contrast, resveratrol in β‐CD showed 45% higher rate than in DM‐β‐CD. Based on the reported solution‐NMR structure of the inclusion complex of these antioxidants, it was concluded that the scavenging rate is decreased when the cyclodextrin cavity preferentially encapsulates the antioxidant‐function bearing group, i.e., O‐ and p‐quinolinol group in catechin and resveratrol, respectively. The depth of inclusion of the functional group determines the extent of the scavenging rate difference, suggesting that the cavity wall of the cyclodextrin acts like a barrier that hinders the approach of attacking free radicals. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 44: 598–603, 2012     

Synthesis and Silica‐Based Immobilization of Monofunctionalized Heptakis(2,6‐di‐O‐methyl‐3‐O‐pentyl)‐β‐cyclodextrin for Enantioselective Capillary‐HPLC

Heptakis(2,6‐di‐O‐methyl‐3‐O‐pentyl)‐β‐cyclodextrin was monofunctionalized by the regioselective introduction of exactly one ω‐epoxyoctyl group at the primary site of the cyclodextrin. The site‐specifically substituted cyclodextrin was immobilized to commercially available aminopropyl silica by nucleophilic opening of the epoxy function of the spacer substituent resulting in a lipophilic chiral stationary phase with broad applicability for enantiomer separations in capillary‐HPLC under reversed‐phase conditions.     

Enantiomeric separation of some common controlled stimulants by capillary electrophoresis with contactless conductivity detection

CE methods with capacitively coupled contactless conductivity detection (C⁴D) were developed for the enantiomeric separation of the following stimulants: amphetamine (AP), methamphetamine (MA), ephedrine (EP), pseudoephedrine (PE), norephedrine (NE) and norpseudoephedrine (NPE). Acetic acid (pH 2.5 and 2.8) was found to be the optimal background electrolyte for the CE‐C⁴D system. The chiral selectors, carboxymethyl‐β‐cyclodextrin (CMBCD), heptakis(2,6‐di‐O‐methyl)‐β‐cyclodextrin (DMBCD) and chiral crown ether (+)‐(18‐crown‐6)‐2,3,11,12‐tetracarboxylic acid (18C6H₄), were investigated for their enantioseparation properties in the BGE. The use of either a single or a combination of two chiral selectors was chosen to obtain optimal condition of enantiomeric selectivity. Enantiomeric separation of AP and MA was achieved using the single chiral selector CMBCD and (hydroxypropyl)methyl cellulose (HPMC) as the modifier. A combination of the two chiral selectors, CMBCD and DMBCD and HPMC as the modifier, was required for enantiomeric separation of EP and PE. In addition, a combination of DMBCD and 18C6H₄ was successfully applied for the enantiomeric separation of NE and NPE. The detection limits of the enantiomers were found to be in the range of 2.3–5.7 μmol/L. Good precisions of migration time and peak area were obtained. The developed CE‐C⁴D method was successfully applied to urine samples of athletes for the identification of enantiomers of the detected stimulants.     

Supramolecular Complexation in Biological Media: NMR Study on Inclusion of an Anionic Tetraarylporphyrin into a Per‐O‐Methylated β‐Cyclodextrin Cavity in Serum,Blood, and Urine

The supramolecular complexation of 5,10,15,20‐tetrakis(4‐sulfonatophenyl)porphyrin (TPPS) with heptakis(2,3,6‐tri‐O‐methyl)‐β‐cyclodextrin (TMCD) has been known to be highly specific in aqueous media. In this study, we have used NMR spectroscopy to reveal that this supramolecular system also works even in biologically crowded media such as serum, blood, and urine. A ¹³C‐labeled heptakis(2,3,6‐tri‐O‐methyl‐¹³C)‐β‐cyclodextrin (¹³C‐TMCD) was synthesized and studied using one‐dimensional (1D) HMQC spectroscopy in serum and blood. The 1D HMQC spectrum of ¹³C‐TMCD showed clear signals due to the 2‐, 3‐, and 6‐O¹³CH₃ groups, whose chemical shifts changed upon addition of TPPS due to quantitative formation of the ¹³C‐TMCD/TPPS=2/1 inclusion complex in such biological media. The ¹H NMR signals of non‐isotope‐labeled TPPS included by ¹³C‐TMCD were detected using the ¹³C‐filtered ROESY technique. A pharmacokinetic study of ¹³C‐TMCD and its complex with TPPS was carried out in mice using the 1D HMQC method. The results indicated that (1) 1D HMQC is an effective technique for monitoring the inclusion phenomena of ¹³C‐labeled cyclodextrin in biological media and (2) the intermolecular interaction between ¹³C‐TMCD and TPPS is highly selective even in contaminated media like blood, serum, and urine.     

Synthesis of benzyl O-(2,3,3'-tri-O-acetyl-β-D-apiofuranosyl)-(1→3)-2,4-di-O-benzoyl-α-D-xylopyranoside and its X-ray structure

The protected apiose-containing disaccharide, benzyl O-(2,3, 3'-tri-O-acetyl-β-D-apiofuranosyl)-( 1→3)-2, 4-di-O-benzoyl-α-D-xylopyranoside, was synthesized and its X-ray structure provided.     

A mixed cyclodextrin‐biphenyl thermotropic liquid crystal: Synthesis,liquid‐crystalline properties,and supramolecular organization

A well‐defined structure liquid crystal heptakis [6‐deoxy‐6‐(1‐H‐1,2,3‐triazol‐4‐yl)(methyl)6‐(4‐methoxybiphenyl‐4′‐yloxy) hexanoyl]‐β‐cyclodextrin (H6B‐β‐CD) was synthesized from propargyl 6‐(4‐methoxybiphenyl‐4′‐yloxy) hexanoate (P6B) and heptakis (6‐deoxy‐6‐azido)‐β‐cyclodextrin ((N₃)₇‐β‐CD) by click reaction. The chemical structure of H6B‐β‐CD was confirmed by ¹H NMR, FTIR, and MALDI‐TOF MS. The thermal stability of the compound was investigated by thermogravimetric analysis (TGA). The liquid crystalline behavior was studied by differential scanning calorimetry (DSC), polarizing optical microcopy (POM), and wide‐angle X‐ray diffraction (WAXD) measurement. These investigations have shown that the supramolecular structure of H6B‐β‐CD are consisted of a large scale ordered lamellar structure and a small scale ordered structure (SmE) at low temperature region. As the temperature increases, the small scale structure becomes disordered relatively in the first instance, from smectic E to smectic A. Then, the lamellar structure collapses and nematic phase and isotropic phase are observed in sequence. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2838–2845, 2010     

A comparative analysis of mono‐ and disaccharide benzyl fucopyranosides

The syntheses and X‐ray analyses of two fuco­pyran­osides, the monosaccharide benzyl 3,4‐di‐O‐acetyl‐2‐hydro­xy‐β‐d ‐fuco­pyran­oside, C₁₇H₂₂O₇, and the disaccharide 1‐benzyl O‐(2,3‐di‐O‐acetyl‐4,6‐O‐benzyl­idene‐β‐d ‐gluco­pyran­osyl)‐(12)‐3,4‐O‐iso­propyl­idene‐β‐d ‐fuco­pyran­oside, C₃₃H₄₀O₁₂, are de­scribed. The different substituents induce small conformational changes on the fuco­pyran­oside ring. However, the conformation of the benzyl group varies from (+)gauche for the monosaccharide to synperiplanar for the disaccharide.