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The enzyme galacturonate oxidoreductase PcGOR from Penicillium camemberti reduces the C-1 carbon of D-glucuronate and C-4 epimer D-galacturonate to their corresponding aldonic acids, important reactions in both pectin catabolism and ascorbate biosynthesis. PcGOR was active on both glucuronic acid and galacturonic acid, with similar substrate specificities (kcat/Km) using the preferred co-substrate NADPH. Substrate acceptance extended to lactone congeners, and D-glucurono-3,6-lactone was converted to L-gulono-1,4-lactone, an immediate precursor of ascorbate. Reaction with glucuronate showed only minor substrate inhibition, and the product L-gulonate and L-gulono-1,4-lactone were both found to be competitive inhibitors with Ki in the low mM range. In contrast, reaction with C-4 epimer galacturonate displayed marked substrate inhibition. Moreover, the product L-galactonate and L-galactono-1,4-lactone were observed to mitigate substrate inhibition by galacturonate, with the lactone having a greater effect than the acid.

Modern biorefining of cellulose and chitin requires the use of glycoside hydrolases (GHs) and lytic polysaccharide monooxygenases (LPMOs). LPMOs use molecular oxygen and two electrons from an external electron donor to cleave glycosidic bonds, by a mechanism that entails oxidization of the C1-carbon of glucose and N -acetylglucosamine, respectively, to produce δ-lactones. The equilibrium between these δ-lactones and their aldonic acids, which dominate at neutral pH, is of importance, since the former are potential inhibitors of GHs. We have used 13 C NMR to obtain more insight into the properties of the oxidized compounds and have studied the properties of N,N ′ ,N ″-triacetylchitotrionic acid, using 13 C NMR at various pHs and temperatures. Thus, we have determined the p K a of the aldonic acid to be 2.88 ± 0.05. The equilibrium constant for lactone at pH 1.41 was 0.137 ± 0.008 corresponding to a Δ G ° of 4.9 ± 0.2 kJ/mol. Using Van’t Hoff analysis Δ H ° and Δ S ° were determined to be 19.5 ± 1.6 kJ/mol and 49.0 ± 5.4 J/K mol, respectively.

We describe here the identification and characterization of two novel enzymes belonging to the IlvD/EDD protein family, the D-xylonate dehydratase from Caulobacter crescentus, Cc XyDHT, (EC 4.2.1.82), and the L-arabonate dehydratase from Rhizobium leguminosarum bv. trifolii, Rl ArDHT (EC 4.2.1.25), that produce the corresponding 2-keto-3-deoxy-sugar acids. There is only a very limited amount of characterization data available on pentonate dehydratases, even though the enzymes from these oxidative pathways have potential applications with plant biomass pentose sugars. The two bacterial enzymes share 41 % amino acid sequence identity and were expressed and purified from Escherichia coli as homotetrameric proteins. Both dehydratases were shown to accept pentonate and hexonate sugar acids as their substrates and require Mg2+ for their activity. Cc XyDHT displayed the highest activity on D-xylonate and D-gluconate, while Rl ArDHT functioned best on D-fuconate, L-arabonate and D-galactonate. The configuration of the OH groups at C2 and C3 position of the sugar acid were shown to be critical, and the C4 configuration also contributed substantially to the substrate recognition. The two enzymes were also shown to contain an iron-sulphur [Fe-S] cluster. Our phylogenetic analysis and mutagenesis studies demonstrated that the three conserved cysteine residues in the aldonic acid dehydratase group of IlvD/EDD family members, those of C60, C128 and C201 in Cc XyDHT, and of C59, C127 and C200 in Rl ArDHT, are needed for coordination of the [Fe-S] cluster. The iron-sulphur cluster was shown to be crucial for the catalytic activity (k(cat)) but not for the substrate binding (K-m) of the two pentonate dehydratases.

Organic compounds receive from industries as effluents are highly toxic and hazardous for the environment. Conventional oxidation process for the oxidation of organic compounds through use of N-bromophthalimide (NBP) is one of the significant process for conversion of organic compounds into environmental friendly or less harmful substances. The main scenario of this review is oxidation and kinetics of different organic compounds by NBP with different experimental methods—iodometric and potentiometric along with uncatalyzed, and catalyzed system. In addition to this we also summarize synthesis, properties and reactive species of NBP. Oxidation products obtained by oxidation of various organic compounds by NBP were acetic acid, aldehyde, carbon dioxide, ammonia, cyanide, aldonic acid etc. Present review, first time offers all aspects of NBP as an oxidizing agent for oxidation of organic compounds.

Lytic polysaccharide monooxygenases are copper-dependent enzymes that perform oxidative cleavage of glycosidic bonds in cellulose and various other polysaccharides. LPMOs acting on cellulose use a reactive oxygen species to abstract a hydrogen from the C1 or C4, followed by hydroxylation of the resulting substrate radical. The resulting hydroxylated species is unstable, resulting in glycoside bond scission and formation of an oxidized new chain end. These oxidized chain ends are spontaneously hydrated at neutral pH, leading to formation of an aldonic acid or a gemdiol, respectively. LPMO activity may be characterized using a variety of analytic tools, the most common of which are high-performance anion exchange chromatography system with pulsed amperometric detection (HPAEC-PAD) and MALDI-TOF mass spectrometry (MALDI-MS). NMR may be used to increase the certainty of product identifications, in particular the site of oxidation. Kinetic studies of LPMOs have several pitfalls and to avoid these, it is important to secure copper saturation, avoid the presence of free transition metals in solution, and control the amount of reductant (i.e., electron supply to the LPMO). Further insight into LPMO properties may be obtained by determining the redox potential and by determining the affinity for copper. In some cases, substrate affinity can be assessed using isothermal titration calorimetry. These methods are described in this chapter.

Background: Lytic polysaccharide monooxygenase (LPMO) is a group of recently identified proteins that catalyze oxidative cleavage of the glycosidic linkages of cellulose and other polysaccharides. By utilizing the oxidative mode of action, LPMOs are able to enhance the efficiency of cellulase in the hydrolysis of cellulose. Particularly, auxiliary activity family 9 (AA9) is a group of fungal LPMOs that show a type-dependent regioselectivity on cellulose in which Types 1, 2, and 3 hydroxylate at C1, C4, and C1 and C4 positions, respectively. In this study, we investigated comparative characteristics of TtAA9E from Thielavia terrestris belonging to Type 1 and TaAA9A from Thermoascus aurantiacus belonging to Type 3 on cellulose and pretreated lignocellulose. Results: From product analysis, TtAA9E dominantly generated oligosaccharides with an aldonic acid form, which is an evidence of C1 oxidation, while TaAA9A generated oligosaccharides with both aldonic acid and 4-ketoaldose forms, which is evidence of C1 and C4 oxidations, respectively. For hydrolysis of cellulose (Avicel) by cellulase, higher synergism was observed for TtAA9E than for TaAA9A. For hydrolysis of pretreated lignocellulose using rice straw, synergistic behaviors of TtAA9E and TaAA9A were different depending on the pretreatment of rice straw. Specifically, on acid-pretreated rice straw, TtAA9E showed a higher synergism than TaAA9A while on alkali-pretreated rice straw, TaAA9A showed a higher synergism than TtAA9E. Conclusions: We show type-dependent action modes of TtAA9E and TaAA9A for cellulose oxidation together with substrate-dependent synergistic hydrolysis of cellulosic substrates. The results obtained from this study indicate the different behaviors of AA9s on cellulose and pretreated lignocellulose, suggesting a selection of AA9 proteins specific to substrates is required for industrial utilization.

The preparation of the δ-heptonolactones, 4- O -benzyl- D - glycero - D - D - gulo -heptono-1,5-lactoneand 4- O -benzyl- D - glycero - D - allo -heptono-1,5-lactone, by Kiliani reactions on 3- O -benzylglucose and 3- O -benzylallose are reported; acetonides of the two lactones are described.

Iodide ion induces a protected 5-formyl-2-iodo-1,5-lactone to undergo a reductive aldol condensation to give a fully substituted cyclopentane derivative in moderate yield; this strategy may provide a general synthesis of such highly functionalised carbocycles as mannostatins and allosamizolines.

The use of readily available sugar lactones in the synthesis of polyhydroxylated pyrrolidines is illustrated by the preparation of the glucosidase inhibitor 1,4-dideoxy-1, 4-imino-D-glucitol from D-galactonolactone and by the conversion of D-gulonolactone into 1,4-dideoxy-l,4-imino-D-allitol, 1,4-dideoxy-l,4-imino-D-ribitol, and (2S,3R,4S)-3,4-dihydroxyproline.

The syntheses of nojirimycin δ-1actam and of deoxynojirimycin from a divergent ido-furanose intermediate are reported.

A method for simultaneous separation and quantitative determination of arabinose, galactose, glucose, xylose, xylonic acid, gluconic acid, galacturonic acid, and glucuronic acid was developed by using high performance anion-exchange chromatography coupled with pulsed amperometric detection (HPAEC-PAD). The separation was performed on a CarboPacTM PA-10 column (250 mm × 2 mm) with a various gradient elution of NaOH-NaOAc solution as the mobile phase. The calibration curves showed good linearity (R2 ≥ 0.9993) for the monosaccharides, uronic acids, and aldonic acids in the range of 0.1 to 12.5 mg/L. The detection limits (LODs) and the quantification limits (LOQs) were 4.91 to 18.75 μg/L and 16.36 to 62.50 μg/L, respectively. Relative standard deviations (RSDs) of the retention times and peak areas for the seven consecutive determinations of an unknown amount of mixture were 0.15% to 0.44% and 0.22% to 2.31%, respectively. The established method was used to separate and determine four monosaccharides, two uronic acids, and two aldonic acids in the prehydrolysate from dilute acid steam-exploded corn stover within 21 min. The spiked recoveries of monosaccharides, uronic acids, and aldonic acids ranged from 91.25% to 108.81%, with RSDs (n=3) of 0.04% ~ 6.07%. This method was applied to evaluate the quantitative variation of sugar and sugar acid content in biomass prehydrolysates.

In this work, the catalytic conversion of monosaccharides, such as d -glucose, d -fructose, d -mannose, d -galactose, and d -xylose, into lactic acid and aldonic acid in an alkaline media using supported noble metal catalysts under flowing air was investigated. Thus far, the conventional chemical conversions of d -glucose into lactic acid, such as alkaline degradations and hot water reactions, involved large amounts of by-products including unidentified compounds. To improve the atom economy for the d -glucose conversion, we examined a one-pot reaction of d -glucose into lactic acid and gluconic acid with the alkaline degradation and the air oxidation using supported metal catalysts. It succeeded in yielding about 45 C-% of lactic acid and about 45 C-% of gluconic acid from d -glucose using Pt/C catalysts with a 1.0 mol L −1 of sodium hydroxide aqueous solution at 353 K under flowing air.

Direct generation of electricity from monosaccharides of lignocellulosic biomass was examined using air cathode microbial fuel cells (MFCs). Electricity was generated from all carbon sources tested, including six hexoses (d-glucose, d-galactose, d(−)-levulose (fructose), l-fucose, lrhamnose, and d-mannose), three pentoses (d-xylose, d(−)-arabinose, and d(−)-ribose), two uronic acids (d-galacturonic acid and d-glucuronic acid) and one aldonic acid (d-gluconic acid). The mixed bacterial culture, which was enriched using acetate as a carbon source, adapted well to all carbon sources tested, although the adaptation times varied from 1 to 70 h. The maximum power density obtained from these carbon sources ranged from 1240 ± 10 to 2770 ± 30 mW m −2 at current density range of 0.76–1.18 mA cm −2 . d-Mannose resulted in the lowest maximum power density, whereas d-glucuronic acid generated the highest one. Coulombic efficiency ranged from 21 to 37%. For all carbon sources tested, the relationship between the maximum voltage output and the substrate concentration appeared to follow saturation kinetics at 120 � external resistance. The estimated maximum voltage output ranged between 0.26 and 0.44 V and half-saturation kinetic constants ranged from 111 to 725 mg L −1 . Chemical oxygen demand (COD) removal was over 80% for all carbon sources tested. Results from this study indicated that lignocellulosic biomass-derived monosaccharides might be a suitable resource for electricity generation using MFC technology. © 2007 Elsevier B.V. All rights reserved.

Synthetic polypeptides containing sugar moieties can find interesting applications as drug-delivery systems or as hydrogels. Only a few studies report on the successful synthesis of sugar-based polypeptides. The aim of this study is to access a range of well-defined polypeptides carrying linear gluconoyl moieties as side-groups, including homo-polypeptides and co-polypeptides with hydrophilic and hydrophobic sequences. The strategy consisted in first preparing the polypeptide via ring-opening polymerization of N-carboxyanhydrides using either an Al-Schiff's base metal complex or a primary amine. The free amino side-groups of the polylysine units are then reacted with gluconolactone, thus leading to a main polypeptide backbone and linear sugar moieties as pendant groups. Sugar moieties have also been attached to statistical and block co-polypeptides bearing hydrophilic and hydrophobic units such as L-lysine and L-leucine, respectively. The anchoring of linear gluconoyl moieties onto poly(L-lysine) and onto...

The lipid A from nitrogen-fixing bacterial species Rhizobium sin-1 is structurally unusual due to lack of phosphates and the presence of a 2-aminogluconolactone and a very long chain fatty acid, 27-hydroxyoctacosanoic acid (27OHC28:0), moiety. This structurally unusual lipid A can antagonize TNF-alpha production by human monocytes induced by Escherichia coli LPS. To establish the relevance of the unusual long chain 27-hydroxyoctacosanoic acid for antagonistic properties, a highly convergent strategy for the synthesis of several derivatives of the lipid A of R. sin-1 has been developed. Compound 1 is a natural R. sin-1 lipid A having a 27-hydroxyoctacosanoic acid at C-2', compound 2 contains an octacosanoic acid moiety at this position, and compound 3 is modified by a short chain tetradecanoic acid. Cellular activation studies with a human monocytic cell line have shown that the octacosanoic acid is important for optimal antagonistic properties. The hydroxyl of the natural 27-hydroxyoctacosanoic moiety does, however, not account for inhibitory activity. The resulting structure-activity relationships are important for the design of compounds for the treatment of septic shock.

The electrocatalytic oxidation of d-glucosamine (2-amino-2-deoxy-d-glucose) in alkaline and neutral solutions was examined using a carbon felt electrode modified with 2 nm core sized gold nanoparticles (Au2 nm nanoparticles) and a gold plate electrode. The electrocatalytic voltammetric oxidation curves of d-glucosamine were obtained in both solutions. The voltammetric responses for the electrocatalytic oxidation at a Au2 nm nanoparticle-modified electrode in both alkaline and neutral solutions were almost the same to those at a gold plate electrode. The oxidized product was identified to be d-glucosaminic acid (2-amino-2-deoxy- d-gluconic acid) generated by the 2-electron oxidation product of d-glucosamine by electrospray ionization time-of-flight mass spectra (ESI TOF-MS). The HPLC results also indicated that the oxidation product was d-glucosaminic acid.The controlled-potential electrolysis of d-glucosamine was performed at the Au2 nm nanoparticle-modified carbon felt electrodes in both alkaline and neutral solutions. In the alkaline solution, at a potential of −0.2 V, d-glucosaminic acid was formed with a current efficiency of 100%. In the neutral solution, electrolysis at 0.4 V on d-glucosaminic acid was obtained with current efficiencies of 70%. Keywords: Electrochemistry, Gold, Oxidation, Glucosamine, Glucosaminic acid, Electrolysis

Background Economical production of fuels and chemicals from plant biomass requires the efficient use of sugars derived from the plant cell wall. Neurospora crassa, a model lignocellulosic degrading fungus, is capable of breaking down the complex structure of the plant cell wall. In addition to cellulases and hemicellulases, N. crassa secretes lytic polysaccharide monooxygenases (LPMOs), which cleave cellulose by generating oxidized sugars—particularly aldonic acids. However, the strategies N. crassa employs to utilize these sugars are unknown. Results We identified an aldonic acid utilization pathway in N. crassa, comprised of an extracellular hydrolase (NCU08755), cellobionic acid transporter (CBT-1, NCU05853) and cellobionic acid phosphorylase (CAP, NCU09425). Extracellular cellobionic acid could be imported directly by CBT-1 or cleaved to gluconic acid and glucose by a β-glucosidase (NCU08755) outside the cells. Intracellular cellobionic acid was further cleaved to glucose 1-phosphate and gluconic acid by CAP. However, it remains unclear how N. crassa utilizes extracellular gluconic acid. The aldonic acid pathway was successfully implemented in Saccharomyces cerevisiae when N. crassa gluconokinase was co-expressed, resulting in cellobionic acid consumption in both aerobic and anaerobic conditions. Conclusions We successfully identified a branched aldonic acid utilization pathway in N. crassa and transferred its essential components into S. cerevisiae, a robust industrial microorganism. Electronic supplementary material The online version of this article (doi:10.1186/s13068-015-0303-2) contains supplementary material, which is available to authorized users.

The microbial oxidative cellulose degradation system is attracting significant research attention after the recent discovery of lytic polysaccharide mono-oxygenases. A primary product of the oxidative and hydrolytic cellulose degradation system is cellobionic acid (CbA), the aldonic acid form of cellobiose. We previously demonstrated that the intracellular enzyme belonging to glycoside hydrolase family 94 from cellulolytic fungus and bacterium is cellobionic acid phosphorylase (CBAP), which catalyzes reversible phosphorolysis of CbA into glucose 1-phosphate and gluconic acid (GlcA). In this report, we describe the biochemical characterization and the three-dimensional structure of CBAP from the marine cellulolytic bacterium Saccharophagus degradans. Structures of ligand-free and complex forms with CbA, GlcA, and a synthetic disaccharide product from glucuronic acid were determined at resolutions of up to 1.6 A. The active site is located near the dimer interface. At subsite +1, the carboxylate group of GlcA and CbA is recognized by Arg-609 and Lys-613. Additionally, one residue from the neighboring protomer (Gln-190) is involved in the carboxylate recognition of GlcA. A mutational analysis indicated that these residues are critical for the binding and catalysis of the aldonic and uronic acid acceptors GlcA and glucuronic acid. Structural and sequence comparisons with other glycoside hydrolase family 94 phosphorylases revealed that CBAPs have a unique subsite +1 with a distinct amino acid residue conservation pattern at this site. This study provides molecular insight into the energetically efficient metabolic pathway of oxidized sugars that links the oxidative cellulolytic pathway to the glycolytic and pentose phosphate pathways in cellulolytic microbes.

The influence of thallium addition on the catalytic properties of palladium catalysts supported on SiO 2 in the reaction of aldoses (glucose and lactose) oxidation to aldonic acid was studied. It was found that thallium does not have any activity by itself, but acts as “promoter” for the catalytic activity and selectivity of monometallic Pd/SiO 2 catalysts. The XRD studies proved the presence of intermetallic compounds, which probably increases activity and selectivity of bimetallic catalysts in those reactions. The same interaction was found using ToF-SIMS. The TPO studies show that palladium oxidation occurs at much higher temperatures than in the case of thallium. A reaction involving bimetallic catalysts in oxidizing atmosphere at 333 K should not lead to surface oxidation of palladium and thus their deactivation.

A convenient method to obtain unknown chiral C2- and C3-functionalized aldono-1,4-lactone derivatives starting from l-ascorbic acid, which would be valuable in the synthesis of derivatives of various pharmacologically active agents for structure-activity studies, is described. The practicality of this approach is demonstrated by the synthesis of a series of 5,6-O-isopropylidene-2-allyl-3-keto-l-galactono-gamma-lactone and 5,6-O-isopropylidene-3-allyl-2-keto-l-galactono-gamma-lactone derivatives using the thermal Claisen rearrangement of the corresponding 3-O- and 2-O-allyl derivatives of 5,6-O-isopropylidene-l-ascorbic acid, respectively, followed by stereospecific reduction to the corresponding alcohols. The synthetic steps are shown to be efficient, and enantiospecific, and they proceed with high yields.

The indirect cathodic reduction of dispersed vat dyes CI Vat Yellow 1 and CI Vat Blue 5 was investigated by cyclic voltammetry and with batch electrolysis experiments. 0.01molL−1 solutions of the complexes Fe3‰+--gluconate and Ca2‰+-Fe3‰+--gluconate were studied. The addition of dispersed dyestuff to the mediator solution lead to a catalytic current. While the cathodic peak currents of both complexes is comparable, Fe3‰+-DGL shows higher enhancement factors, which are defined as quotient of catalytic peak current and cathodic peak current of the mediator system (Ip)c/(Ip)d. In the presence of 0.5gL−1 of dispersed vat dye enhancement factors of 1.8 were determined at scan rates of 0.005–0.010Vs−1. Galvanostatic batch reduction experiments with use of a laboratory multi-cathode cell confirmed the favourable properties of the Fe3‰+-DGL in comparison to the binuclear Ca2‰+-Fe3‰+-DGL. With use of the Fe3‰+-DGL mediator complete dyestuff reduction could be achieved. The batch reduction process was followed experimentally by photometry and redox potential measurement in the catholyte.

The standard (p∘ = 0.1 MPa) molar energies of combustion in oxygen, at T = 298.15 K, for crystalline d -, l -galactono-1,4-lactone, d -, l -gulono-1,4-lactone and l -mannono-1,4-lactone were measured by static-bomb calorimetry, by using paraffin oil as auxiliary substance and leading to the following results: d -galactono-1,4-lactone l -galactono-1,4-lactone d -gulono-1,4-lactone l -gulono-1,4-lactone l -mannono-1,4-lactone Δ c U m ∘ ( cr , 298.15 K ) / ( kJ · mol - 1 ) −2559.09 ± 0.47 −2559.66 ± 0.48 −2561.32 ± 0.51 −2560.91 ± 0.48 −2563.43 ± 0.37 Δ c H m ∘ ( cr , 298.15 K ) / ( kJ · mol - 1 ) −2557.85 ± 0.47 −2558.42 ± 0.48 −2560.08 ± 0.51 −2559.67 ± 0.75 −2562.19 ± 0.37 Δ f H m ∘ ( cr , 298.15 K ) / ( kJ · mol - 1 ) −1232.36 ± 0.65 −1231.79 ± 0.65 −1230.13 ± 0.65 −1230.54 ± 0.62 −1228.02 ± 0.65 ΔfusH(Tfus)/(kJ · mol−1) 35.77 ± 0.32 35.98 ± 0.06 40.13 ± 0.60 41.50 ± 0.36 36.13 ± 0.20 Tfus/K 410.32 ± 0.03 409.82 ± 0.03 459.30 ± 0.23 458.96 ± 0.05 426.52 ± 0.06 The values of standard molar enthalpies of formation in solid phase of the lactones were relationed with their molecular structures and hydrogen bonding.

A stereoseletive synthesis of 2,7-anhydrosialic acid derivative 18 was achieved from d-glucono-delta-lactone. A highly syn-selective addition of Grignard reagent to theN-benzylimine 8 served as a key step.

A study has been conducted of the separation of sugar acids (gluconic, galacturonic and glucuronic acids) by capillary electrophoresis using indirect UV detection. We have tested various background electrolytes: p-hydroxibenzoic acid, sorbic acid, potassium hydrogen phthalate, protocatechuic acid, α-resorcylic acid and β-resorcylic acid. The choice between these electrolytes was made on the basis of studies of electrophoretic mobility and absorbance values at the wavelengths of our CE system. Of all the electrolytes tested, it was found that β-resorcylic acid best met the required characteristics. The best separation of the three acid was achieved with a time of 8 min, for an electrolyte consisting of 5 mM β-resorcylic acid, 1 mM TTAOH (pH 3.0), indirect detection at 214 nm, -20 kV of run voltage and capillary of 60 cm length and 75 µm i.d. It was found that the proposed method is applicable to samples of both must and wine, and that the samples do not require any prior treatment apart from centrifugation (only in the case of must), filtration and dilution in suitable proportion.

Solubilities of l -glutamic acid, 3-nitrobenzoic acid, p -toluic acid, calcium- l -lactate, calcium gluconate, magnesium- dl -aspartate, and magnesium- l -lactate in water were determined in the temperature range 278 K to 343 K. The apparent molar enthalpies of solution at T = 298.15 K as derived from these solubilities are Δ sol H m ( l -glutamic acid, m sat = 0.0565 mol · kg − 1 ) = 30.2 kJ · mol − 1 , Δ sol H m (3-nitrobenzoic acid, m = 0.0188 mol · kg − 1 ) = 28.1 kJ · mol − 1 , Δ sol H m ( p - toluic acid, m = 0.00267 mol · kg − 1 ) = 23.9 kJ · mol − 1 , Δ sol H m (calcium- l -lactate tetrahydrate, m = 0.2902 mol · kg − 1 ) = 25.8 kJ · mol − 1 , Δ sol H m (calcium gluconate, m = 0.0806 mol · kg − 1 ) = 22.1 kJ · mol − 1 , Δ sol H m (magnesium- dl -aspartate tetrahydrate, m = 0.1469 mol · kg − 1 ) = 11.5 kJ · mol − 1 , and Δ sol H m (magnesium- l -lactate trihydrate, m = 0.3462 mol · kg − 1 ) = 3.81 kJ · mol − 1 .

Graft Copolymers Having Hydrophobic Backbone and Hydrophilic Branches XXI. Preparation of Galactose Surface-Accumulated Polystyrene Nanospheres and Their Interaction with Lectin

Vapour pressures of water over saturated solutions of dl -2-aminobutyric acid, 4-aminobutyric acid, sodium- d -gluconate, sodium hippurate, and potassium magnesium- l -aspartate were determined over the (278 to 322) K temperature range. The determined vapour pressures were used to obtain the water activities, the molar enthalpies of vaporization, and the osmotic coefficients of sodium- d -gluconate.

Seven new tannins, elaeagnatins A-G, have been isolated from the leaves of Elaeagnus umbellata (Elaeagnaceae) together with fifteen known tannins and related polyphenols, and their structures have been characterized as monomeric and dimeric C-glucosidic ellagitannins on the basis of spectral and chemical evidence. Elaeagnatins B, C and F are the first dimers composed of C-glucosidic monomer and ellagitannin monomer with a gluconic acid core.

The oxidation of D-ribose and 2-deoxy-D-ribose by CrVI yields the aldonic acid and Cr3+ as final products when an excess of sugar over CrVI is used. The redox reaction occurs through CrVI–>CrIII and CrVI–>CrV–>CrIII paths. The complete rate laws for the CrVI oxidation reactions are expressed by -d[CrVI]/dt = kH[H+]2 [ribose][CrVI], where kH = (5.9 ± 0.1) × 10-2 mol-3 dm9 s-1, and -d[CrVI]/dt = (k0 + kH'[H+]2) [2-deoxyribose][CrVI], where k0 = (1.3 ± 0.5) × 10-3 mol-1 dm3 s-1 and kH' = (4.2 ± 0.1) × 10-2 mol-3 dm9 s-1, at 33°C. An intermediate sugar alkoxide radical could be trapped with DMPO and observed by EPR as a multiline signal at g = 2.003. CrV is formed in a rapid step by reaction of the sugar radical with CrVI. CrV reacts with the substrate faster than CrVI does. The EPR spectra show that five- and six-coordinate oxochromate(V) intermediates are formed, and the distribution of these CrV species in the reaction mixture essentially depends on the solution acidity.Key words: ribose, 2-deoxyribose, chromium, redox, mechanism, kinetics.

From the water-soluble portion of the methanolic extract of fennel, seven new sugar alcohols (two deoxybutitols, four deoxypentitols and one deoxyhexitol) and a sugar lactone were isolated, together with seven known glucides, four nucleosides, (3R)-2-hydroxymethylbutane-1, 2, 3, 4-tetrol and uracil. From the results of spectral investigation, the new compounds were characterized as 1-deoxythreitol (9), (2R)-butane-1, 2, 4-triol (10), 1-deoxy-D-ribitol (11), 1-deoxy-D-xylitol (12), 2-deoxy-D-ribitol (13), 3-deoxyarabinitol (14), 1-deoxy-D-glucitol (16) and 2-deoxy-D-ribono-1, 4-lactone (15), respectively.

Tctrasaccharide Galβ1→4(GlcNAc) 3 was synthesized from N,N',N-triacetylchitotriose (GlcNAc) 3 and lactose using transglycosylation with a β-D-galactosidase from Bacillus circulans. The reducing terminal of Galβ1 →4(GlcNAc) 3 was oxidized and connected to p-vinylbenzylamine via amide linkage, and the resulting oligosaccharide-substituted styrene monomer was polymerized with the radical initiator 2,2'-azobis( 2-amidinopropane) dihydrochloride at 60 C. Glycopolystyrene was found to bind strongly with wheat germ agglutinin (WGA) and tomato (Lycopersicon esculentum) agglutinin (LEA) by inhibition of hemagglutination and double diffusion.

Nonionic surfactants each bearing one alkyl chain and two gluconamides, maltobionamides, lactobionamides, or maltotrionamides were prepared by the monoalkylation of malononitrile with alkyl bromide, reduction of two nitrile groups with LiAlH4/AlCl3, and reaction of the alkyldiamine thus produced with the sugar lactone. The surfactants possessed good water solubility. That the surfactants bearing two gluconamide groups showed higher water solubility than the conventional N-alkylgluconamide [RNHCO (CHOH) 4CH2OH] or dialkylbisgluconamide [R2C (CH2NHCO (CHOH) 4CH2OH) 2] with the same alkyl chain length is of particular interest. The critical micelle concentrations (cmcs) of the surfactants decreased with increase in carbon number of the alkyl chain, while the number of sugar unit in hydrophilic portions had little effect on cmcs. Surfactants bearing terminal glucopyranoside residues had remarkable binding affinity toward the sugar-binding protein, Concanavalin A (Con A), while the one with terminal galactopyranoside residues did not. Terminal sugar residues in the surfactants are thus specifically distinguished by Con A.

Non-ionic surfactants based on sugars are of interest to both chemists and biochemists. They have potential pharmaceutical (biocompatible formulation) biochemical (extraction of membrane proteins) and medicinal applications; generally these derivatives are not readily synthesized as the starting sugars require protection. We present here routes, avoiding protection of the starting sugars, to new series of surfactants derived from lactose, glucose, gluconic or lactobionic acids. By changing the tail or the hydrophobic body bonded to the sugar heads, we have synthesized sugar-based amphiphilic compounds having (1) one chain, (2) one fluorinated chain, (3) a double chain or (4) two sugar heads (bolaamphiphilic compounds) All these compounds form aggregates in solution: direct, reverse micelles, or vesicles. Fluorinated molecules give gels in aqueous or non-aqueous media. Some of them are interesting products to extract membrane proteins or to formulate solution of hydrophobic acids to realize enzymatic reactions. Finally soluble analogs of Galcer possess activity against both HIV andAspergillus fumigatus, a yeast responsible for opportunistic infections in AIDS patients.

Glucose-fructose oxidoreductase from Zymomonas mobilis catalyzed the oxidation of various aldose sugars to the corresponding aldonic acids. The enzyme was used for the selective and high-yield conversion of lactose to lactobionic acid in batch, fed-batch and continous reaction mode. A productivity of 110 g L d was obtained in an ultrafiltration membrane reactor, operated for 70 h.

Synthesized glycolipids have been reported as hydrolase models, and their active sites could be explained on the basis of 2, 3-hydroxyl groups of the sugar moiety. In this study, a glycolipid was found to exhibit acidic nature in water, reflecting the dissociation of the hydroxyl group, and the conjugated base to be concerned with the hydrolysing activity. The 2- or 3-deoxy-glycolipids then were synthesized and used in the hydrolysis of phenylalanine p-nitrophenyl ester. 3-Deoxy-glycolipid showed only a little lower hydrolysing activity than the perfect glycolipid, while 2-deoxy-glycolipid, considerably lower activity. The hydroxyl group on 2-position is thus shown to be a predominant active site, although 3-hydroxyl one also is a weaker active site. That is, the oxy anion on 2-position of a sugar moiety is esti-mated as active species that attack the carbonyl carbon of an ester nucleophilically with consequent bond cleavage.

In the 1,5-lactone compound, C 6 H 8 O 4 , the lactone ring adopts a conformation between sofa and half-chair. The five-membered ring in the 1,4-lactone, C 6 H 8 O 4 , is planar and the side chain is in a staggered conformation. The crystal structure of the 1,5-lactone is stabilized by both O-H...O and C-H...O hydrogen bonds and that of the 1,4-lactone by O-H...O hydrogen bonds.

The heterogeneous selective liquid-phase oxidation of aldonic acids to the corresponding 2-keto-acids over a lead- or bismuth-modified platinum catalyst was reinvestigated. The influence of the pH (pH range 2–9) on the nature and the stability of the chelate complex formed between aldonic acid and the promotor (Pb, Bi), which is assumed to govern the selectivity, was found to be important for the performance of the catalyst. The non-selective complexation in alkaline medium of the promotor with 2-keto-aldonic acid was assumed to be the cause of the decrease of the selectivity at higher conversion. In weakly acidic medium (pH

The title compounds were synthesized from 3-deoxy-D-glycero-D-galacto-2-nonulosonic acid (5, KDN) by a new method which is similar to the Ritter reaction. The structures on these compounds were elucidated from the MS, elemental analysis, 1H-NMR and 13C-NMR, data, and the stereochemistry of methyl 4-benzoylamino-5, 7, 8, 9-tetra-O-acetyl-2, 6-anhydro-2, 3-dideoxy-D-glycero-D-galacto-non-2-enonate (13) was determined by X-ray crystallographic analysis.

The bulk terrestrial biomass resource in a future bio-economy will be lignocellulosic biomass, which is recalcitrant and challenging to process. Enzymatic conversion of polysaccharides in the lignocellulosic biomass will be a key technology in future biorefineries and this technology is currently the subject of intensive research. We describe recent developments in enzyme technology for conversion of cellulose, the most abundant, homogeneous and recalcitrant polysaccharide in lignocellulosic biomass. In particular, we focus on a recently discovered new type of enzymes currently classified as CBM33 and GH61 that catalyze oxidative cleavage of polysaccharides. These enzymes promote the efficiency of classical hydrolytic enzymes (cellulases) by acting on the surfaces of the insoluble substrate, where they introduce chain breaks in the polysaccharide chains, without the need of first “extracting” these chains from their crystalline matrix.

Triphenylphosphine and tetrachloromethane react cleanly in refluxing tetrahydrofuran with substituted γ- and δ-lactones and some esters to afford the corresponding dichloroolefins in good yields. This new Wittig-type reaction provides an easy entry to this new class of compounds and tolerates a large variety of protecting groups. Application of this methodology to the dichloroolefination of simple lactones, sugar-derived lactones, and other biologically significant lactones is described

6-epi-Trehazolin was synthetized in a stereocontrolled manner, and this synthesis proved that an oxazine structural isomer of 6-epi-trehazolin does not exist

The geometries of the lactone rings in the two structures are similar. Differences between C 7 H 12 O 7 (I) and C 21 H 24 O 11 S 2 (II) occur in the conformation of the side chain with respect to the lactone ring, and in the crystal packing, with that of (I) being more influenced by hydrogen bonding. A weak intramolecular hydrogen bond of 2.718 (6) A is present in (II)

The geometries of the lactone rings in the three structures are similar. Differences between C 8 H 14 O 10 S 2 (III), C 8 H 14 O 10 S 2 (IV) and C 8 H 14 O 10 S 2 (V) arise in the conformation of the side chain and in the crystal packing of the structures

We report the convenient preparation of 3-O- and 2-O-allylated derivatives of 5,6-O-isopropylidene L-ascorbic acid (1) with various allyl substituents in high yield and their quantitative thermal Claisen rearrangement to the corresponding 2-C- and 3-C-allylated derivatives with high regio- and stereoselectivity under relatively mild conditions. This reaction will now allow the synthesis of heretofore unknown 3-C-allylated derivatives of L-ascorbic acid in high yield. The high chiral induction at the substituents of the allylic carbon, especially in the case of the 3-O-methyl-2-O-crotyl derivative, is intriguing. This general method of preparation of 2-C- and 3-C-allylated derivatives of ascorbic acid may have important applications in synthetic organic and pharmaceutical chemistry