Carbohydrate Research (v.346, #17)
Editorial board (IFC).
Graphical contents list (2643-2649).
Synthesis of a Forssman antigen derivative for use in a conjugate vaccine by Jianhao Feng; Rachel Hevey; Chang-Chun Ling (2650-2662).
The total chemical synthesis of a Forssman antigen analog is described. The pentasaccharide contains a functionalized tether which should facilitate future conjugation with immunogenic proteins. We found that the total synthesis can be efficiently achieved by following a convergent 2+3 strategy, and using N-Troc protected GalNAc thioglycoside as a donor.
Keywords: Forssman antigen; Oligosaccharides; Total synthesis; Glycosylation;
Synthesis and biological evaluation of RON-neoglycosides as tumor cytotoxins by Joseph M. Langenhan; Matthew M. Endo; Jeffrey M. Engle; Liane L. Fukumoto; Derek R. Rogalsky; Lauren K. Slevin; Lindsay R. Fay; Ryan W. Lucker; James R. Rohlfing; Kyle R. Smith; Anja E. Tjaden; Halina M. Werner (2663-2676).
Display Omitted► Conditions suitable for the convenient synthesis of neoglycosides have been identified. ► Sugar structure, rather than RON-glycosidic linkage, exerts the strongest influence on neoglycoside yield and stereochemistry. ► The structure of RON-neoglycosidic linkages influences both the potency and selectivity of digitoxin neoglycosides.Cardenolides such as digitoxin have been shown to inhibit cancer cell growth, to reduce cancer metastasis, and to induce apoptosis in tumor cells. Among the most potent digitoxin-based cytotoxins identified to date are MeON-neoglycosides generated via oxyamine neoglycosylation. Here, we report our studies of oxyamine neoglycosylation aimed at facilitating the elucidation of linkage-diversified digitoxin neoglycoside structure–activity relationships. We identified conditions suitable for the convenient synthesis of digitoxin neoglycosides and found that sugar structure, rather than RON-glycosidic linkage, exerts the strongest influence on neoglycoside yield and stereochemistry. We synthesized a library of digitoxin neoglycosides and assessed their cytotoxicity against eight human cancer cell lines. Consistent with previous findings, our data show that the structure of RON-neoglycosidic linkages influences both the potency and selectivity of digitoxin neoglycosides.
Keywords: Glycoconjugate; Glycosylalkoxylamines; Hydrolysis rates; Cardenolides; Digitoxin;
Synthesis of water-soluble multidentate aminoalcohol β-cyclodextrin derivatives via epoxide opening by K. Martina; M. Caporaso; S. Tagliapietra; G. Heropoulos; O. Rosati; G. Cravotto (2677-2682).
New highly soluble β-aminoalcohol β-cyclodextrin (β-CD) derivatives have been synthesized via nucleophilic epoxide opening reactions with mono-6-amino mono-6-deoxy-permethyl-β-CD and mono-6-amino mono-6-deoxy-β-CD. The binding properties of the β-CD were enhanced by linking aminoalcohol subunits which caused its solubility to improve markedly. The reaction conditions were optimised using microwave irradiation giving moderate-to-good yields with a series of epoxides. A regioselective epoxide opening reaction was observed in the reaction with styrene oxide while the stereoselectivity was strictly dependent on substrate structure.
Keywords: Cyclodextrin; Epoxides; Selectivity; Microwave activation; Solubilization in water;
Electrochemical bromochlorination of peracetylated glycals by Ivan Damljanović; Dragana Stevanović; Mirjana Vukićević; Rastko D. Vukićević (2683-2687).
Display Omitted► Cyclovoltammetric investigations of reaction conditions for the electrochemical halogenation of peracetylated glycals. ► Electrochemical generation of halogenating species. ► Synthesis of 2-bromoglycopyranosyl chlorides. ► Hemoselectivity in halogenation of peracetylated glycals.Peracetylated glycals—3,4,5-tri-O-acetyl-d-glucal (1a), 3,4,5-tri-O-acetyl-d-galactal (1b) and 3,4-di-O-acetyl-6-deoxy-l-glucal (1c)—have been bromochlorinated by a suitable halogenating agent, generated electrochemically from a mixture of bromides and chlorides in dichloromethane. The reaction was performed in two ways: (i) by a constant current electrolysis (2 F mol−1) of bromides and substrates in a milieu containing an excess of chlorides ( Br ⦵ /1/ Cl ⦵ = 1:1:6.8) and (ii) by anodic generation of free chlorine from chlorides (2 F mol−1) and subsequent addition of bromides and substrates in a ratio Br ⦵ /1 = 1:1. The corresponding 2-bromo-2-deoxy-glycopyranosyl chlorides were obtained in high yields.
Keywords: Peracetylated glycals; Bromochlorination; Electrochemical halogenation; Cyclic voltammetry; 2-Bromoglycopyranosyl chlorides;
Study of the inhibition of two human maltase-glucoamylases catalytic domains by different α-glucosidase inhibitors by Limei Ren; Xiaofang Cao; Peng Geng; Fang Bai; Gang Bai (2688-2692).
In humans, both the N-terminal catalytic domain (NtMGAM) and the C-terminal catalytic domain (CtMGAM) of small intestinal maltase glucoamylase (MGAM) are α-glycosidases that catalyze the hydrolysis of α-(1→4) glycosidic linkages in the process of starch digestion, and are considered to be the main therapeutic targets for type 2 diabetes. In this work, recombinant human CtMGAM has been cloned for the first time, and this, combined with the expression of NtMGAM in Pichia pastoris, made it possible for us to study the catalytic mechanism of MGAM in a well-defined system. The enzymatic kinetic assays of the two catalytic domains suggest that CtMGAM has the higher affinity for longer maltose oligosaccharides. Kinetic studies of commercially-available drugs such as 1-deoxynojirimycin (DNJ), miglitol, voglibose, and acarbose along with a series of acarviosine-containing oligosaccharides we isolated from Streptomyces coelicoflavus against NtMGAM, CtMGAM, and human pancreatic α-amylase (HPA) provide us an overall profile of the inhibitory ability of these inhibitors. Of all the inhibitors used in this paper, DNJ was the most effective inhibitor against MGAM; the K i values for the two catalytic domains were 1.41 and 2.04 μM for NtMGAM and CtMGAM, respectively. Acarviostatins 2-03 and 3-03 were the best inhibitors against HPA with relatively high inhibitory activity against CtMGAM. The acarviostatins 2-03 and 3-03 inhibition constants, K i, for HPA were 15 and 14.3 nM, and those for CtMGAM were 6.02 and 6.08 μM, respectively. These results suggest that NtMGAM and CtMGAM differ in their substrate specificities and inhibitor tolerance despite their structural relationship.
Keywords: Maltase-glucoamylase; Human pancreatic α-amylase; 1-Deoxynojirimycin; Acarviostatins;
Development of a chemical strategy to produce rare aldohexoses from ketohexoses using 2-aminopyridine by Kayo Hasehira; Nobumitsu Miyanishi; Wataru Sumiyoshi; Jun Hirabayashi; Shin-ichi Nakakita (2693-2698).
Rare sugars are monosaccharides that are found in relatively low abundance in nature. Herein, we describe a strategy for producing rare aldohexoses from ketohexoses using the classical Lobry de Bruyn–Alberda van Ekenstein transformation. Upon Schiff-base formation of keto sugars, a fluorescence-labeling reagent, 2-aminopyridine (2-AP), was used. While acting as a base catalyst, 2-AP efficiently promoted the ketose-to-aldose transformation, and acting as a Schiff-base reagent, it effectively froze the ketose–aldose equilibrium. We could also separate a mixture of Sor, Gul, and Ido in their Schiff-base forms using a normal-phase HPLC separation system. Although Gul and Ido represent the most unstable aldohexoses, our method provides a practical way to rapidly obtain these rare aldohexoses as needed.
Keywords: Rare sugar; 2-Aminopyridine; Aldohexose; Lobry de Bruyn–Alberda van Ekenstein transformation;
Cytotoxic and antioxidant triterpene saponins from Butyrospermum parkii (Sapotaceae) by Léon A. Tapondjou; Laurentine B.T. Nyaa; Pierre Tane; Massimo Ricciutelli; Luana Quassinti; Massimo Bramucci; Giulio Lupidi; Beaudelaire K. Ponou; Luciano Barboni (2699-2704).
Display Omitted► The root bark of Butyrospermum parkii, a plant used in the traditional medicine, was studied. ► Three new triterpenoid saponins were isolated and elucidated. ► One of the new compounds showed a remarkable antiploriferative activity. ► As observed by other authors, the antiploriferative activity could be related to the presence of apiose units.Three new triterpenoid saponins, elucidated as 3-O-β-d-glucopyranosyloleanolic acid 28-O-β-d-xylopyranosyl-(1→4)-α-l-rhamnopyranosyl-(1→2)-β-d-xylopyranoside (parkioside A, 1), 3-O-[β-d-apifuranosyl-(1→3)-β-d-glucopyranosyl]oleanolic acid 28-O-[β-d-apifuranosyl-(1→3)-β-d-xylopyranosyl-(1→4)-[α-l-rhamnopyranosyl-(1→3)]-α-l-rhamnopyranosyl-(1→2)β-d-xylopyranoside (parkioside B, 2) and 3-O-β-d-glucuronopyranosyl-16α-hydroxyprotobassic acid 28-O-α-l-rhamnopyranosyl-(1→3)-β-d-xylopyranosyl-(1→4)-α-l-rhamnopyranosyl-(1→2)-β-d-xylopyranoside (parkioside C, 3), were isolated from the n-BuOH extract of the root bark of Butyrospermum parkii, along with the known 3-O-β-d-glucopyranosyloleanolic acid (androseptoside A). The structures of the isolated compounds were established on the basis of chemical and spectroscopic methods, mainly 1D and 2D NMR data and mass spectrometry. The new compounds were tested for both radical scavenging and cytotoxic activities. Compound 2 showed cytotoxic activity against A375 and T98G cell lines, with IC50 values of 2.74 and 2.93 μM, respectively. Furthermore, it showed an antioxidant activity comparable to that of Trolox or butylated hydroxytoluene (BHT), used as controls, against 2,2-diphenyl-1-picryl hydrazyl (DPPH), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), oxygen and nitric oxide radicals.
Keywords: Butyrospermun parkii; Butyrospermun paradoxum; Sapotaceae; Saponin; Cytotoxic activity; Antioxidant activity;
Structural characterization of the O-chain polysaccharide from an environmentally beneficial bacterium Pseudomonas chlororaphis subsp. aureofaciens strain M71 by Giuseppina Pieretti; Gerardo Puopolo; Sara Carillo; Astolfo Zoina; Rosa Lanzetta; Michelangelo Parrilli; Antonio Evidente; Maria Michela Corsaro (2705-2709).
Pseudomonas chlororaphis subsp. aureofaciens strain M71 was isolated from the root of a tomato plant and it was able to control in vivo Fusarium oxysporum f. sp. radicis-lycopersici responsible for the tomato crown and root rot. Recently, strain M71 was evaluated even for its efficacy in controlling Seiridium cardinale, the causal agent of bark canker of common cypress (Cupressus sempervirens L.). Strain M71 ability to persist on the tomato rhizosphere and on the aerial part of cypress plants could be related to the nature of the lipopolysaccharides (LPS) present on the outer membrane and in particular to the O-specific polysaccharide.A neutral O-specific polysaccharide was obtained by mild acid hydrolysis of the lipopolysaccharide from P. chlororaphis subsp. aureofaciens strain M71. By means of compositional analyses and NMR spectroscopy, the chemical repeating unit of the polymer was identified as the following linear trisaccharide.▪
Keywords: Biological control; Pseudomonas chlororaphis subsp. aureofaciens; Lipopolysaccharide; O-Specific polysaccharide; NMR spectroscopy;
Structure of the high molecular weight exopolysaccharide produced by Bifidobacterium animalis subsp. lactis IPLA-R1 and sequence analysis of its putative eps cluster by Shaun Leivers; Claudio Hidalgo-Cantabrana; Glenn Robinson; Abelardo Margolles; Patricia Ruas-Madiedo; Andrew P. Laws (2710-2717).
The bile adapted strain Bifidobacterium animalis subsp. lactis IPLA-R1 secretes a high molecular weight exopolysaccharide (HMW-EPS) when grown on the surface of agar-MRSC. This EPS is composed of l-rhamnopyranosyl, d-glucopyranosyl, d-galactopyranosyl and d-galactofuranosyl residues in the ratio of 3:1:1:1. Linkage analysis and 1D and 2D NMR spectroscopy were used to show that the EPS has a hexasaccharide repeating unit with the following structure:Display OmittedTreatment of the EPS with mild acid cleanly removed the terminal d-galactofuranosyl residue. The eps cluster sequenced for strain IPLA-R1 showed high genetic homology with putative eps clusters annotated in the genomes of strains from the same species. It is of note that several genes coding for rhamnose-precursors are present in the eps cluster, which could be correlated with the high percentage of rhamnose detected in its EPS repeated unit.
Keywords: Bifidobacterium; Exopolysaccharide; EPS structure; eps Cluster; Glycosyltransferase;
Morphology, molecular dynamics and electric conductivity of carbohydrate polymer films based on alginic acid and benzimidazole by Adam Rachocki; Katarzyna Pogorzelec-Glaser; Czesław Pawlaczyk; Jadwiga Tritt-Goc (2718-2726).
Display Omitted► The biodegradable films based on alginic acid and benzimidazole were synthesized. ► The materials were examined as potential membranes for electrochemical devices. ► The polymer films have shown the electric conductivity of ∼10−3 S/cm at 473 K. ► The molecular properties of the alginate systems were studied by NMR. ► The mechanism of the proton transport in the materials is the Grotthuss mechanism.The present paper describes a preparation method and molecular investigations of new biodegradable proton-conducting carbohydrate polymer films based on alginic acid and benzimidazole. Electric conductivity was studied in a wide temperature range in order to check the potential application of these compounds as membranes for electrochemical devices. Compared to pure alginic acid powder or its film, the biodegradable film of alginic acid with an addition of benzimidazole exhibits considerably higher conductivity in the range above water boiling temperature (up to approximately 10−3 S/cm at 473 K). Due to this important feature the obtained films can be considered as candidates for application in high-temperature electrochemical devices. The microscopic nature and mechanism of the conduction in alginate based materials were studied by proton nuclear magnetic resonance (NMR). The results show specific changes in morphology and molecular dynamics between pure alginate powders and the films obtained without and with the addition of benzimidazole molecules.
Keywords: Proton-conducting carbohydrate polymer films; Alginic acid and benzimidazole films; Morphology and microscopic structure; Molecular dynamics; Electric conductivity; NMR;
Structural and physicochemical characterisation of rye starch by S.V. Gomand; T. Verwimp; H. Goesaert; J.A. Delcour (2727-2735).
The gelatinisation, pasting and retrogradation properties of three rye starches isolated using a proteinase-based procedure were investigated and compared to those of wheat starch isolated in a comparable way. On an average, the rye starch granules were larger than those of wheat starch. The former had very comparable gelatinisation temperatures and enthalpies, but slightly lower gelatinisation temperatures than wheat starch. Under standardised conditions, they retrograded to a lesser extent than wheat starch. The lower gelatinisation temperatures and tendencies of the rye starches to retrograde originated probably from their higher levels of short amylopectin (AP) chains [degree of polymerisation (DP) 6–12] and their lower levels of longer chains (DP 13–24) than observed for wheat starch. The rapid visco analysis differences in peak and end viscosities between the rye starches as well as between rye and wheat starches were at least partly attributable to differences in the levels of AP short chains and in average amylose molecular weight. The AP average chain lengths and exterior chain lengths were slightly lower for rye starches, while the interior chain lengths were slightly higher than those for wheat starch.
Keywords: Rye starch; Wheat starch; Amylose/amylopectin fractionation; Amylopectin structure; Gelatinisation; Pasting;
The use of N,N′-diallylaldardiamides as cross-linkers in xylan derivatives-based hydrogels by Helinä Pohjanlehto; Harri Setälä; Kari Kammiovirta; Ali Harlin (2736-2745).
The preparation of a bio-based hydrogel by cross-linking derivatized xylan with sugar diacid based cross-linker. N,N′-Diallylaldardiamides (DA) were synthesized from galactaric, xylaric, and arabinaric acids, and used as cross-linkers together with xylan (X) derivatives to create new bio-based hydrogels. Birch pulp extracted xylan was derivatized to different degrees of substitution of 1-allyloxy-2-hydroxy-propyl (A) groups combined with 1-butyloxy-2-hydroxy-propyl (B) and/or hydroxypropyl (HP) groups. The hydrogels were prepared in water solution by UV induced free-radical cross-linking polymerization of derivatized xylan polymers without DA cross-linker (xylan derivative hydrogel) or in the presence of 1 or 5 wt % of DA cross-linker (DA hydrogel). Commercially available cross-linker (+)-N,N′-diallyltartardiamide (DAT) was also used. The degree of substitution (DS) of A, B, and HP groups in xylan derivatives was analyzed according to 1H NMR spectra. The DS values for the cross-linkable A groups of the derivatized xylans were 0.4 (HPX-A), 0.2 (HPX-BA), and 0.4 (X-BA). The hydrogels were examined with FT-IR and elemental analysis which proved the cross-linking successful. Water absorption of the hydrogels was examined in deionized water. Swelling degrees up to 350% were observed. The swollen morphology of the hydrogels was assessed by scanning electron microscopy (SEM). The presence of cross-linkers in DA hydrogels had only a small impact on the water absorbency when compared to xylan derivative hydrogels but a more uniform pore structure was achieved.
Keywords: Hydrogel; N,N′-Diallylaldardiamides; Xylan; Renewable resources;
Structural and theoretical-experimental physicochemical study of trimethoprim/randomly methylated-β-cyclodextrin binary system by Daniela Kubota; Osmir Fabiano Lopes Macedo; George Ricardo Santana Andrade; Leila Souza Conegero; Luis Eduardo Almeida; Nivan Bezerra Costa; Iara F. Gimenez (2746-2751).
An inclusion complex of trimethoprim and randomly methylated β-cyclodextrin was prepared and characterized, evidencing the inclusion of the trimethoxyphenyl ring, in agreement with semiempirical molecular modeling.Here we report the structural characterization, physicochemical study and molecular modeling of the inclusion complex of trimethoprim in randomly methylated beta-cyclodextrin. The phase-solubility diagram obtained at pH 7.0 exhibited a linear behavior for the RAMEB concentrations studied suggesting a 1:1 stoichiometry and absence of aggregation in solution. From stoichiometric determination by the continuous variation method we confirmed a 1:1 stoichiometry. To make a detailed characterization of the inclusion mode, spectroscopic measurements by infrared and 1D and 2D 1H NMR spectroscopy provided evidence that the inclusion mode is characterized by inclusion of the trimethoxyphenyl ring in the cavity; interactions with methyl groups located in the border of the cavity were also detected. The structure proposed was also confirmed by semiempirical molecular modeling.
Keywords: Trimethoprim; Randomly methylated-β-cyclodextrin; Inclusion complex; Phase-solubility diagram; Semiempirical methods; PM3-D;
Mannan structural complexity is decreased when Candida albicans is cultivated in blood or serum at physiological temperature by Douglas W. Lowman; Harry E. Ensley; Rachel R. Greene; Kevin J. Knagge; David L. Williams; Michael D. Kruppa (2752-2759).
This report describes the reduction in mannan structural complexity when Candida albicans cells are cultured in the presence of host-derived blood components and physiological temperature.The Candida albicans cell wall provides an architecture that allows for the organism to survive environmental stress as well as interaction with host tissues. Previous work has focused on growing C. albicans on media such as Sabouraud or YPD at 30 °C. Because C. albicans normally colonizes a host, we hypothesized that cultivation on blood or serum at 37 °C would result in structural changes in cell wall mannan. C. albicans SC5314 was inoculated onto YPD, 5% blood, or 5% serum agar media three successive times at 30 °C and 37 °C, then cultivated overnight at 30 °C in YPD. The mannan was extracted and characterized using 1D and 2D 1H NMR techniques. At 30 °C cells grown in blood and serum contain less acid-stable terminal β-(1→2)-linked d-mannose and α-(1→2)-linked d-mannose-containing side chains, while the acid-labile side chains of mannan grown in blood and serum contain fewer β-Man-(1→2)-α-Man-(1→ side chains. The decrement in acid-stable mannan side chains is greater at 37 °C than at 30 °C. Cells grown on blood at 37 °C show fewer →6)-α-Man-(1→ structural motifs in the acid-stable polymer backbone. The data indicate that C. albicans, grown on media containing host-derived components, produces less complex mannan. This is accentuated when the cells are cultured at 37 °C. This study demonstrates that the C. albicans cell wall is a dynamic and adaptive organelle, which alters its structural phenotype in response to growth in host-derived media at physiological temperature.
Keywords: Mannan; NMR; Growth conditions;
Extraction of cellulose-synthesizing activity of Gluconacetobacter xylinus by alkylmaltoside by Akira Hashimoto; Kenji Shimono; Yoshiki Horikawa; Tsukasa Ichikawa; Masahisa Wada; Tomoya Imai; Junji Sugiyama (2760-2768).
This study reinvestigated the synthesis of cellulose in vitro with a well-known cellulose-producing bacterium, Gluconacetobacter xylinus. Alkylmaltoside detergents, which are more frequently used in recent structural biological researches, are uniquely used in this study to solubilize cellulose-synthesizing activity from the cell membrane of G. xylinus. Activity comparable to that previously reported is obtained, while the synthesized cellulose is crystallized into a non-native polymorph of cellulose (cellulose II) as well as the previous studies. In spite of this failure to recover the native activity to synthesize cellulose I microfibril in vitro, the product is a polymer with a degree of polymerization greater than 45 as determined by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). It was thus concluded that the established protocol can solubilize cellulose-synthesizing activity of G. xylinus with polymerizing activity.
Keywords: Cellulose synthase; CesA/BcsA; CesB/BcsB; Cellulose I; Gluconacetobacter xylinus; Membrane protein enzyme;
Sulfated polysaccharides from brown seaweeds Saccharina japonica and Undaria pinnatifida: isolation, structural characteristics, and antitumor activity by Olesya S. Vishchuk; Svetlana P. Ermakova; Tatyana N. Zvyagintseva (2769-2776).
Display Omitted► The galactofucans were isolated from brown algae U. pinnatifida and S. japonica. ► Sulfated polysaccharides differed in their structural characteristics. ► The galactofucan from U. pinnatifida possessed high antitumor activity in vitro.During the last decade brown seaweeds attracted much attention as a source of polysaccharides, namely laminarans, alginic acids, and sulfated polysaccharides—fucoidans, with various structures and biological activities.In this study, sulfated polysaccharides were isolated from brown seaweeds Saccharina japonica (formerly named Laminaria) and Undaria pinnatifida and their antitumor activity was tested against human breast cancer T-47D and melanoma SK-MEL-28 cell lines.The sulfated polysaccharide form S. japonica was highly branched partially acetylated sulfated galactofucan, built up of (1→3)-α-l-fucose residues. The sulfated polysaccharide from U. pinnatifida was partially acetylated highly sulfated galactofucan consisting of (1→3)- or (1→3);(1→4)-α-l-fucose residues.Fucoidans from S. japonica and U. pinnatifida distinctly inhibited proliferation and colony formation in both breast cancer and melanoma cell lines in a dose-dependent manner. These results indicated that the use of sulfated polysaccharides from brown seaweeds S. japonica and U. pinnatifida might be a potential approach for cancer treatment.
Keywords: Brown seaweed; Saccharina japonica; Undaria pinnatifida; Sulfated polysaccharide; Galactofucan; Antitumor activity;
Preparation and characterization of new and improved soluble-starches, -amylose, and -amylopectin by reaction with benzaldehyde/zinc chloride by David A. Johnston; Rupendra Mukerjea; John F. Robyt (2777-2784).
Structure of a benzaldehyde-modified starch fragment, containing two nonreducing-ends with 4,6-benzylidene groups.Seven different starches from potato, rice, maize, waxymaize, amylomaize-VII, shoti, and tapioca, and potato amylose and potato amylopectin have been reacted with benzaldehyde, catalyzed by ZnCl2, to give new water-soluble starches and water soluble-amylose and soluble-amylopectin. In contrast to the native starches, aqueous solutions of the modified starches could not be precipitated with 2-, 3-, or 4-volumes of ethanol. β-Amylase gave no reaction with the modified starches, in contrast to the native starches, indicating that the modification occurred exclusively at the nonreducing-ends, giving 4,6-benzylidene-d-glucopyranose at the nonreducing-ends. Reactions of α-amylase with native and modified potato and rice starches gave a decrease in the triiodide blue color and an increase in the reducing-value that were similar for the native- and modified-starches, indicating the modified starches had not been significantly altered by the modification. The benzaldehyde-modified starches and benzaldehyde-modified potato amylose and potato amylopectin components, therefore, have a starch structure very much like their native counterparts, in contrast to the Lintner, Small, and the alcohol/acid-hydrolyzed soluble-starches that have undergone acid hydrolysis. The benzaldehyde-modified starches and starch components have significantly higher water solubility than their native counterparts even though the structures of the modified starches had only been slightly altered from the structures of their native counterparts. They all gave crystal-clear solutions that did not retrograde.
Keywords: New soluble starches; 4,6-Benzylidene starches; Native- and benzylidene-starches react similarly with α-amylase; Modified-starches 4–16 times more soluble than their native starches; β-Amylase gave no products from the benzylidene-starches;
Catalytic dehydration of xylose to furfural: vanadyl pyrophosphate as source of active soluble species by Irantzu Sádaba; Sérgio Lima; Anabela A. Valente; Manuel López Granados (2785-2791).
Display Omitted► The dehydration of xylose into furfural is effectively carried out in the presence of vanadium phosphates catalysts. ► Based on catalytic tests and solid state characterisation, (VO)2P2O7 is a fairly stable solid acid. ► (VO)2P2O7 is a source of active water-soluble species. ► A concentration of (VO)2P2O7 as low as 5 mM, gave ca. 56% furfural yield, at 170 °C/6 h reaction.The acid-catalysed, aqueous phase dehydration of xylose (a monosaccharide obtainable from hemicelluloses, e.g., xylan) to furfural was investigated using vanadium phosphates (VPO) as catalysts: the precursors, VOPO4·2H2O, VOHPO4·0.5H2O and VO(H2PO4)2, and the materials prepared by calcination of these precursors, that is, γ-VOPO4, (VO)2P2O7 and VO(PO3)2, respectively. The VPO precursors were completely soluble in the reaction medium. In contrast, the orthorhombic vanadyl pyrophosphate (VO)2P2O7, prepared by calcination of VOHPO4·0.5H2O at 550 °C/2 h, could be recycled by simply separating the solid acid from the reaction mixture by centrifugation, and no drop in catalytic activity and furfural yields was observed in consecutive 4 h-batch runs (ca. 53% furfural yield, at 170 °C). However, detailed catalytic/characterisation studies revealed that the vanadyl pyrophosphate acts as a source of active water-soluble species in this reaction. For a concentration of (VO)2P2O7 as low as 5 mM, the catalytic reaction of xylose (ca. 0.67 M xylose in water, and toluene as solvent for the in situ extraction of furfural) gave ca. 56% furfural yield, at 170 °C/6 h reaction.
Keywords: Xylose; Furfural; Acid catalysis; Vanadyl pyrophosphate; Homogeneous catalysis;
Synthesis, separation, and characterization of amphiphilic sulfated oligosaccharides enabled by reversed-phase ion pairing LC and LC–MS methods by Amanda M. Fenner; Robert J. Kerns (2792-2800).
Synthesis of amphiphilic oligosaccharides is problematic because traditional methods for separating and purifying oligosaccharides, including sulfated oligosaccharides, are generally not applicable to working with amphiphilic sugars. We report here RPIP-LC and LC–MS methods that enable the synthesis, separation, and characterization of amphiphilic N-arylacyl O-sulfonated aminoglycosides, which are being pursued as small-molecule glycosaminoglycan mimics. The methods described in this work for separating and characterizing these amphiphilic saccharides are further applied to a number of uses: monitoring the progression of sulfonation reactions with analytical RP-HPLC, characterizing sulfate content for individual molecules with ESI-MS, determining the degree of sulfation for products having mixed degrees of sulfation with HPLC and LC–MS, and purifying products with benchtop C18 column chromatography. We believe that the methods described here will be broadly applicable to enabling the synthesis, separation, and characterization of amphiphilic, sulfated, and phosphorylated oligosaccharides and other types of molecules substituted to varying degrees with both anionic and hydrophobic groups.
Keywords: Biomimetic synthesis; Aliphatic oligosaccharide; Mass spectrometry; Reversed-phase ion-pairing; Sulfation; Electrospray ionization;
Efficient and selective removal of chloroacetyl group promoted with tetra-n-butylammonium fluoride (TBAF) by Guofeng Gu; Min Fang; Yuguo Du (2801-2804).
A practical method for the efficient and selective cleavage of chloroacetyl protecting group using tetra-n-butylammonium fluoride (TBAF) in THF solution at rt was disclosed.
Keywords: Chloroacetyl group; Tetra-n-butylammonium fluoride; Chemoselective deprotection;
Synthesis of a novel pentasaccharide core component from the lipooligosaccharide of Moraxella catarrhalis by Andrew G. Pearson; Ian R. Peak; Jennifer C. Wilson; I. Darren Grice (2805-2811).
The novel pentasaccharide [p-(trifluoroacetamido)phenyl]ethyl 3-O-β-d-glucopyranosyl-4-O-β-d-glucopyranosyl-6-O-[2-O-(α-d-glucopyranosyl)-β-d-glucopyranosyl]-α-d-glucopyranoside (1), which includes a linker moiety to enable facile coupling to an antigenic protein, was synthesised as a component of a potential vaccine candidate against the Gram-negative bacterium Moraxella catarrhalis. This microorganism is one of three principal causative agents of otitis media in children. The pentasaccharide represents a common cross-serotype (A, B and C) structure from the lipooligosaccharides of Moraxella catarrhalis.
Keywords: Moraxella catarrhalis; Pentasaccharide; Linker; Lipooligosaccharide;
Structure and gene cluster of the O-antigen of Escherichia coli O19ab by Andrei V. Perepelov; Hongfei Zhu; Sof’ya N. Senchenkova; Quan Wang; Alexander S. Shashkov; Lei Wang; Yuriy A. Knirel (2812-2815).
The O-polysaccharide (O-antigen) of Escherichia coli O19ab was studied by sugar analysis along with 1D and 2D 1H and 13C NMR spectroscopy. The following structure of the linear pentasaccharide repeating unit was established: → 2 ) - α -l-Rha p - ( 1 → 2 ) - α -l-Rha p - ( 1 → 2 ) - α -l-Rha p - ( 1 → 2 ) - α -d-Glc p - ( 1 → 3 ) - α -d-Glc p NAc 6 Ac- ( 1 → where the degree of O-acetylation of GlcNAc is ∼33%. The O-antigen gene cluster of E. coli O19ab was sequenced. The gene functions were tentatively assigned by comparison with sequences in the available databases and found to be in full agreement with the E. coli O19ab-antigen structure.
Keywords: Escherichia coli; Bacterial polysaccharide structure; O-antigen; Lipopolysaccharide; O-antigen gene cluster;
Chemical structure of wall teichoic acid isolated from Enterococcus faecium strain U0317 by Anna Bychowska; Christian Theilacker; Małgorzata Czerwicka; Kinga Marszewska; Johannes Huebner; Otto Holst; Piotr Stepnowski; Zbigniew Kaczyński (2816-2819).
Wall teichoic acid (WTA) was isolated from Enterococcus faecium strain U0317 and structurally characterized using 1H, 13C, and 31P NMR spectroscopy, including two-dimensional COSY, TOCSY, ROESY, HMQC, and HMBC experiments. Further compositional determination was undertaken using classical chemical methods and HF treatment followed by GLC and GLC–MS analyses. The repeating unit of WTA consisted of two residues of 2-acetamido-2-deoxy-d-galactose, glycerol (Gro), and phosphate, and has the structure shown below: → 6 ) - α -d-Gal p NAc- ( 1 → 3 ) - β -d-Gal p NAc- ( 1 → 2 ) -Gro- ( 3 → P →
Keywords: Enterococcus faecium; U0317 strain; Polysaccharide; Wall teichoic acid; NMR; Structure;
Interactions of D-cellobiose with p-toluenesulfonic acid in aqueous solution: a 13C NMR study by Ananda S. Amarasekara; Onome S. Owereh; Brian Ezeh (2820-2822).
The effects of adding D2SO4, and p-toluenesulfonic acid-d to D-cellobiose dissolved in D2O were investigated at 23 °C by plotting 13C NMR chemical shift changes (Δδ) against the acid to D-cellobiose molar ratio. 13C Chemical shifts of all 18 carbon signals from α and β anomers of D-cellobiose showed gradual decreases due to increasing acidity in aqueous D2SO4 medium. The C-1 of the α anomer showed a slightly higher response to increasing D+ concentration in the surrounding. In the aqueous p-toluenesulfonic acid-d medium, C-6′ and C-4′ carbons of both α, and β anomeric forms of D-cellobiose are significantly affected by increasing the sulfonic acid concentrations, and this may be due to a 1:1 interaction of p-toluenesulfonic acid-d with the C-6′, C-4′ region of the cellobiose molecule.
Keywords: Cellobiose; p-Toluenesulfonic acid; Sulfuric acid; 13C NMR;
Corrigendum to ‘‘Transformation of aldose formazans. Novel synthesis of 2-acetamido-2-deoxypentonolactones and a new pent-2-enose formazan” [Carbohydr. Res. 346 (2011) 1534–1540] by Virág Zsoldos-Mády; István Pintér; Mária Peredy-Kajtár; András Perczel (2823).