- Permanganate oxidation revisited: Synthesis of 3-deoxy-2-uloses via indium-mediated chain elongation of carbohydrates
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Application of the Barbier-type indium-mediated allylation method to suitable substrates offers access to carbohydrates bearing a terminal olefin moiety. The C-C bond, forming reaction generates a defined stereochemistry of the new chiral center and tolerates a wide variety of starting aldehydes thus allowing modifications in the carbohydrate backbone. Further transformations of the alkene moiety via an environmentally benign and subtle controlled protocol using potassium permanganate gives rise to the structural motif of 3-deoxy-2-uloses in good yields. The final part of the reaction sequence focuses on the deprotection of the acetyl groups essential for the success of the oxidation step. The acidic and labile 3-deoxy position of the target molecule is prone to elimination applying standard deacetylation conditions and therefore demands derivatisation of the molecule. The introduction of a thioketal moiety using microwave conditions shows promising results and subsequent standard transformations are applicable leading to the desired products.
- Schmoelzer, Christoph,Fischer, Michael,Schmid, Walther
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- Combined effect of promoter and surfactant on the chromium(VI) oxidation of D-ribose in aqueous media at room temperature
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Effect of polypyridine derivatives on chromium(VI) oxidation of D-ribose in aqueous media was studied spectrophotometrically. The oxidized product D-erythrose was detected by paper chromatography. The promoters 1,10-phenanthroline, 2,2-bipyridine, 2-picolinic acid, and 2,3-dipicolinic acid accelerated the oxidation, whereas isomeric 4,7-phenanthroline, 4,4-bipyridine, 4-picolinic acid, and 2,6-dipicolinic acid did not influence the oxidation. Formation of Cr(VI)-promoter complex was identified through fluorescence spectroscopy. Rate constants depended on promoter concentration. SDS and TX-100 enhanced the D-ribose oxidation, while CPC retarded the reaction. Location of D-ribose inside micelles was observed through 1H NMR. DLS study showed that the relative size of SDS and TX-100 micelles expanded in presence of chromium(VI).
- Sar, Pintu,Ghosh, Aniruddha,Malik, Susanta,Saha, Bidyut
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- Catalytic Action of Iron and Manganese Ions in the Photochemically-Induced Oxidation of D-Fructose with Atmospheric Oxygen
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D-fructose is susceptible to photochemically-induced oxidation by atmospheric oxygen in the presence of a catalytic amount of iron or manganese cations in a neutral to weakly basic pH range.Metal hydroxide does not precipitate from a solution in this pH range because of the high sequestering ability of D-fructose.Upon irradiation of Pyrex-filtered light, D-fructose degraded into D-erythrose and other fragments.This reaction is shown to proceed by coupling with an oxidation-reduction cycle involving a metal cation, i.e., the photooxidation of D-fructose by M(III) and the subsequent reoxidation of the resultant M(II) by atmospheric oxygen.
- Araki, Koji,Shiraishi, Shinsaku
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- PHOTOOXIDATION OF MONOSACCHARIDES WITH METAL CATALYSIS. OXIDATION WITH ATMOSPHERIC OXYGEN BY COUPLING WITH THE OXIDATION-REDUCTION CYCLE OF METAL IONS
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D-Fructose was oxidatively degraded to D-erythrose by atmospheric oxygen with irradiation of a Pyrex-filtered light in the presence of catalytic amount of FeCl3 at near neutral pH range.The reaction proceeded by coupling with the oxidation-reduction cycle of iron ion.D-Glucose-FeCl3 and D-fructose-MnCl2 systems were also found to be susceptible to the catalytic photooxidation.
- Araki, Koji,Shiraishi, Shinsaku
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- Anomerization of Furanose Sugars: Kinetics of Ring-Opening Reactions by 1H and 13C Saturation-Transfer NMR Spectroscopy
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With the tetroses D-threose and D-erythrose, kinetic and thermodynamic parameters for the interconversion of α- and β-furanoses and the acyclic hydrate with the intermediate aldehyde form have been obtained from 1H and 13C NMR measurements.Unidirectional rate constants for the various equilibria involving the aldehyde have been determined, and from them the overall rate constants for interconversion of the abundant species.The approach can be applied to systems in which only solutions at tautomeric equilibrium are available or in which interconversions are too rapid to observe by other methods.Analyses by 13C NMR were facilitated by the use of tetroses.Aqueous solutions of the tetroses were examined at 17-81 deg C by 13C and 1H NMR spectroscopy to evaluate tautomeric composition.Solutions of D-threose contain ca. 51percent α-furanose and ca. 38percent β-furanose at all temperatures, while the amount of aldehyde (a) increases from 0.7 to 4.7percent and the amount of hydrate (h) decreases from 10.2 to 7.1percent. ΔG (kcal mol-1), ΔH (kcal mol-1), and ΔS (cal mol-1 K-1) at 25 deg C were estimated for the reaction a -> α, -2.4, -6.0, and -12; a -> β, -2.2, -6.0, -13; a -> h, -1.4, -7.3, -20, respectively.Rate constants for ring opening of the tetroses in 2H2O were obtained by 1H and 13C saturation-transfer NMR spectroscopy by saturating H-1 or C-1 of the aldehyde, respectively, and observing the transfer of saturation to the α- and β-furanose and hydrate resonances.Rate constants (+/-10percent) for the ring-opening reactions of D-threose (unbuffered) are as follows: α-furanose, 0.034 s-1 (51 deg C), 0.10 s-1 (66 deg C); β-furanose, 0.083 s-1 (38 deg C), 0.53 s-1 (66 deg C).Ring-closing rate constants (+/-18percent), determined from equilibrium constants, and ring-opening rate constants are as follows: α-furanose, 0.74 s-1 (51 deg C), 1.5 s-1 (66 deg C); β-furanose, 2.0 s-1 (38 deg C), 5.9 s-1 (66 deg C).Activation energies were estimated for β-threofuranose ring-opening (14 +/- 3 kcal mol-1) and ring-closing (8 +/- 2 kcal mol-1) reactions.From the unidirectional rate constants, overall rate constants at 66 deg C for the conversion of α- and β-threofuranose were calculated as follows: kαβ = 0.08 +/- 0.01 s-1, kβα = 0.11 +/- 0.01 s-1.Rate constants for ring-opening of D-threose and D-erythrose in 50 mM sodium acetate (p2H 5.0) were compared.At 55 deg C, α-erythrose (0.40 s-1) > β-threose (0.36 s-1) > β-erythrose (0.19 s-1) > α-threose (0.11 s-1).Rate constants obtained by 13C and 1H ST NMR spectroscopy were in good agreement.
- Serianni, Anthony S.,Pierce, John,Huang, Shaw-Guang,Barker, Robert
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- Synthesis, structure, and conformation of anti-tumor agents in the solid and solution states: Hydroxyl derivatives of ftorafur
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The pyrimidine antimetabolite Ftorafur [FT; 5-fluoro-1-(tetrahydro-2-furyl)uracil] has shown significant antitumor activity in several adenocarcinomas with a spectrum of activity similar to, but less toxic than, 5-fluorouracil (5-FU). It is considered as a prodrug that acts as a depot form of 5-FU, and hence the two drugs exhibit a similar spectrum ofchemotherapeutic activity. Ftorafur is metabolized in animals and humans when hydroxyl groups are introduced into the tetrahydrofuran moiety. These metabolites are also thought to be as active as ftorafur but less toxic than 5-FU. Hydroxyl derivatives: 2′-hydroxyftorafur (III), 3′-hydroxyftorafur (IV) and 2′,3′-dihydroxyftorafur (II) were synthesized and X-ray and NMR studies of these hydroxyl derivatives were undertaken in our laboratories to study the structural and conformational features of Ftorafur and its metabolites in the solid and solution states. X-ray crystallographic investigations were carried out with data collected on a CAD-4 diffractometer. The structures were solved and refined using the SDP crystallographic package of Enraf-Nonius on PDP 11/34 and Microvax computers. All of the compounds studied had the base in the anti conformation. The glycosidic torsion angles varied from -20 to 60 degrees. There is an inverse correlation between the glycosyl bond distances and the χ angle. Molecules with a lower χ angle have a larger bond distance and vice versa. The sugar rings show a wide variation of conformations ranging from C2′-endo through C3′-endo to C4′-exo. The crystal structures are stabilized by hydrogen bonds involving the base nitrogen atom N3 and the hydroxyl oxygen atoms of the sugar rings as donors and the keto oxygens O2 and O4 of the base and the hydroxyl oxygen atoms O2′ and O3′ as acceptors. The NMR studies were carried out on Brueker 400 and 600MHz instruments. Simulated proton spectra were obtained through Laocoon, and pseudorotational parameters were solved by Pseurot. Presence of syn or anti forms was demonstrated with the use of NOE experiments. The glycosyl conformations in solution vary more widely than in the solid state. The conformations of the sugar molecules are in agreement with the values obtained in the solid state. The studies of the structure and conformation in the solid and solution states give a model for the Ftorafur molecule that could be used in structure, function and biological activity correlation studies.
- Stokes, David M.,Paul, Brajeswar,Alderfer, James L.,Wollman, Robert M.,Srikrishnan, Thamarapu
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- Photothermal strategy for the highly efficient conversion of glucose into lactic acid at low temperatures over a hybrid multifunctional multi-walled carbon nanotube/layered double hydroxide catalyst
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The conversion of carbohydrates into lactic acid has attracted increasing attention owing to the broad applications of lactic acid. However, the current methods of thermochemical conversion commonly suffer from limited selectivity or the need for harsh conditions. Herein, a light-driven system of highly selective conversion of glucose into lactic acid at low temperatures was developed. By constructing a hybrid multifunctional multi-walled carbon nanotube/layered double hydroxide composite catalyst (CNT/LDHs), the highest lactic acid yield of 88.6% with 90.0% selectivity was achieved. The performance of CNT/LDHs for lactic acid production from glucose is attributed to the following factors: (i) CNTs generate a strong heating center under irradiation, providing heat for converting glucose into lactic acid; (ii) LDHs catalyze glucose isomerization, in which the photoinduced OVs (Lewis acid) in LDHs under irradiation further improve the catalytic activity; and (iii) in a heterogeneous-homogeneous synergistically catalytic system (LDHs-OH-), OH- ions are concentrated in LDHs, forming strong base sites to catalyze subsequent cascade reactions.
- Duo, Jia,Jin, Binbin,Jin, Fangming,Shi, Xiaoyu,Wang, Tianfu,Ye, Xin,Zhong, Heng
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p. 813 - 822
(2022/02/09)
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- Selective Reductive Dimerization of CO2into Glycolaldehyde
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The selective dimerization of CO2 into glycolaldehyde is achieved in a one-pot two-step process via formaldehyde as a key intermediate. The first step concerns the iron-catalyzed selective reduction of CO2 into formaldehyde via formation and controlled hydrolysis of a bis(boryl)acetal compound. The second step concerns the carbene-catalyzed C-C bond formation to afford glycolaldehyde. Both carbon atoms of glycolaldehyde arise from CO2 as proven by the labeling experiment with 13CO2. This hybrid organometallic/organic catalytic system employs mild conditions (1 atm of CO2, 25 to 80 °C in less than 3 h) and low catalytic loadings (1 and 2.5%, respectively). Glycolaldehyde is obtained in 53% overall yield. The appealing reactivity of glycolaldehyde is exemplified (i) in a dimerization process leading to C4 aldose compounds and (ii) in a tri-component Petasis-Borono-Mannich reaction generating C-N and C-C bonds in one process.
- Zhang, Dan,Jarava-Barrera, Carlos,Bontemps, Sébastien
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p. 4568 - 4575
(2021/05/04)
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- Glucose oxidation to formic acid and methyl formate in perfect selectivity
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We report the highly remarkable discovery that glucose oxidation catalysed by polyoxometalates (POMs) in methanolic solution enables formation of formic acid and methyl formate in close to 100percent combined selectivity, thus with only negligible sugar oxidation to CO2. In detail, we report oxidation of a methanolic glucose solution using H8[PV5Mo7O40] (HPA-5) as catalyst at 90 °C and 20 bar O2 pressure. Experiments with 13C-labelled glucose confirm unambiguously that glucose is the only source of the observed formic acid and methyl formate formation under the applied oxidation conditions. Our results demonstrate a very astonishing solvent effect for the POM-catalysed glucose oxidation. In comparison to earlier work, a step-change in product yield and selectivity is achieved by applying an alcoholic reaction medium. The extremely high combined yields of formic acid and methyl formate greatly facilitate product isolation as low-boiling methyl formate (bp = 32 °C) can simply be isolated from the reaction mixture by distillation.
- Albert, Jakob,Bukowski, Anna,Kumpidet, Chiraphat,Maerten, Stephanie,Vo?, Dorothea,Wasserscheid, Peter
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p. 4311 - 4320
(2020/07/14)
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- Catalytic Gels for a Prebiotically Relevant Asymmetric Aldol Reaction in Water: From Organocatalyst Design to Hydrogel Discovery and Back Again
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This paper reports an investigation into organocatalytic hydrogels as prebiotically relevant systems. Gels are interesting prebiotic reaction media, combining heterogeneous and homogeneous characteristics with a structurally organized active solid-like catalyst separated from the surrounding environment, yet in intimate contact with the solution phase and readily accessible via liquid-like diffusion. A simple self-assembling glutamine amide derivative 1 was initially found to catalyze a model aldol reaction between cyclohexanone and 4-nitrobenzaldehyde, but it did not maintain its gel structure during reaction. In this study, it was observed that compound 1 could react directly with the benzaldehyde to form a hydrogel in situ based on Schiff base 2 as a low-molecular-weight gelator (LMWG). This new dynamic gel is a rare example of a two-component self-assembled LMWG hydrogel and was fully characterized. It was demonstrated that glutamine amide 1 could select an optimal aldehyde component and preferentially assemble from mixtures. In the hunt for an organocatalyst, reductive conditions were applied to the Schiff base to yield secondary amine 3, which is also a highly effective hydrogelator at very low loadings with a high degree of nanoscale order. Most importantly, the hydrogel based on 3 catalyzed the prebiotically relevant aldol dimerization of glycolaldehyde to give threose and erythrose. In buffered conditions, this reaction gave excellent conversions, good diastereoselectivity, and some enantioselectivity. Catalysis using the hydrogel of 3 was much better than that using non-assembled 3 - demonstrating a clear benefit of self-assembly. The results suggest that hydrogels offer a potential strategy by which prebiotic reactions can be promoted using simple, prebiotically plausible LMWGs that can selectively self-organize from complex mixtures. Such processes may have been of prebiotic importance.
- Hawkins, Kirsten,Patterson, Anna K.,Clarke, Paul A.,Smith, David K.
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supporting information
p. 4379 - 4389
(2020/03/05)
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- Catalysis and Stability Effect of Solvent Alcohol on the C6 Aldose Conversion toward Tetrose
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Conversions of biomass feedstock into various valuable chemicals are of great significance. As a typical route, retro-aldol condensation of monosaccharide greatly expands the variety of biomass-derived platform chemicals via a selective C?C splitting. Herein, we describe a solvent-catalysed strategy to high-selectively accumulate tetrose (four-carbon platform chemical) from C6 aldoses via the retro-aldol/aldol process. We find that alcohol solvents with Lewis acidity facilitate the C?C splitting process of hexose under the catalyst-free condition. The conversion is the fastest in methanol while it is the slowest in isopropanol. The product distribution is greatly influenced by the alcohols through shifting the equilibrium between tetrose and glycolaldehyde (GA). The addition of catalyst only accelerates the reaction rate, and does not change the product distribution. On the one hand, the acetalization of GA with methanol or ethanol shifts the equilibrium from tetrose toward GA, which results in a low yield of tetrose in methanol or ethanol solvent. On the other hand, tetrose can be well accumulated in isopropanol or n-butanol, and the yield of tetrose in isopropanol is higher than in n-butanol because tetrose can be well solvated and stabilized in it. This solvent-dependent reaction strategy provides a new possibility which contributes to the conversion of biomass feedback into valuable platform chemicals and accumulation of target products by utilizing the solvation effect.
- Hou, Wenrong,Yan, Yueer,Li, Gang,Zhan, Yulu,Feng, Lei,Zhang, Ruohong,Hua Li, Zhen,Zhang, Yahong,Tang, Yi
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p. 4182 - 4188
(2019/09/12)
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- Photocatalytic Solar Light H2 Production by Aqueous Glucose Reforming
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A series of tungsten and nitrogen doped Pt-TiO2 samples were prepared with the aim to extend the TiO2 absorption to the visible light region and to enhance the separation efficiency of the photogenerated electron/hole pairs. The physicochemical features of the powders were characterized by X-ray diffraction (XRD), UV/Vis reflectance spectra, specific surface area (SSA) determinations, and transmission electron microscopy (TEM) analyses. The influence of the presence of different doping agents was evaluated, under anaerobic conditions, in the aqueous photo-reforming of glucose to form H2 at ambient pressure and temperature under a halogen lamp or natural solar light irradiation. Arabinose, erythrose, and formic acid were the main glucose partial oxidation products observed in the liquid phase, whilst H2 and CO2 were measured in the gaseous phase. The highest H2 production was observed in the presence of the Pt-TiO2-W0.25 sample.
- Bellardita, Marianna,García-López, Elisa Isabel,Marcì, Giuseppe,Nasillo, Giorgio,Palmisano, Leonardo
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p. 4522 - 4532
(2018/09/29)
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- One-pot photoreforming of cellulosic biomass waste to hydrogen by merging photocatalysis with acid hydrolysis
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Environmental-friendly utilization and conversion of abundant lignocellulosic biomass waste into chemical fuels is considered as one of the efficient approaches developing renewable energy. Herein, we merge photocatalysis and acid hydrolysis to solve problems in biomass conversion and hydrogen production. Specifically, photocatalytic reforming cellulose to hydrogen has been accomplished by hydrolysis of cellulose in 0.6 M sulfuric acid solution at 403 K in the presence of a photocatalyst (e.g. platinized TiO2) under UV-light irradiation. Carbohydrates as the sacrificial electron donors are in situ generated via acid hydrolysis of cellulose. An unexpected production of 5-hydroxyl methyl furfural (HMF) has also been found during the combined process. In addition, efficient and repeatable hydrogen production has been achieved from photoreforming of raw biomass waste (paper pulp) as continuous supply of electron donors. Compared to traditional thermochemical gasification or pyrolysis of cellulose in high temperature and pressure, this work provides an alternative approach for producing hydrogen and valuable chemicals from lignocellulosic biomass.
- Zou, Jing,Zhang, Guan,Xu, Xiaoxiang
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- Efficient Production of Biomass-Derived C4 Chiral Synthons in Aqueous Solution
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Carbohydrates are expected to replace petroleum and to become the base of industrial chemistry. Chirality is one particular area in which carbohydrates have a special potential advantage over petroleum resources. Herein, we report a catalytic approach for the direct production of d-tetroses [i.e., d-(?)-erythrose and d-(+)-erythrulose] from d-hexoses through a fast retro-aldol process at 190 °C that achieves a yield of 46 % and completely retains the chiral centers in the final chiral synthon. The d-tetrose products were further converted into their derivatives, thereby accomplishing transfer of chirality from natural chiral hexoses to high-value-added chiral chemicals. Our results also suggest that the product distribution for the conversion of d-hexoses was determined by their isomerization and epimerization trends that competed with their corresponding retro-aldol condensation processes.
- Lin, Shaoying,Guo, Xiao,Qin, Kai,Feng, Lei,Zhang, Yahong,Tang, Yi
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p. 4179 - 4184
(2017/12/02)
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- Borate-Stabilized Transformation of C6 Aldose to C4 Aldose
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Highly efficient transformations of biomass-derived sugars into various valuable chemicals are of topical interest. Tetrose with a four-carbon bone is the root of most of biomass-derived C4 products, but its extreme instability obstructs the blossoming of C4 products presently. Herein, we describe a borate-stabilized catalytic strategy to accumulate erythrose from C6 aldose in a highly selective manner via retro-aldol and aldol processes in alcohol solvent. In our proposed mechanism, borate can stabilize erythrose and avoid its further retro-aldol splitting or isomerization, and induce the production of erythrose again via the aldol condensation of the above-generated glycolaldehyde.
- Yan, Yueer,Feng, Lei,Li, Gang,Lin, Shaoying,Sun, Zhen,Zhang, Yahong,Tang, Yi
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p. 4473 - 4478
(2017/07/24)
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- Shape-selective Valorization of Biomass-derived Glycolaldehyde using Tin-containing Zeolites
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A highly selective self-condensation of glycolaldehyde to different C4 molecules has been achieved using Lewis acidic stannosilicate catalysts in water at moderate temperatures (40–100 °C). The medium-sized zeolite pores (10-membered ring framework) in Sn-MFI facilitate the formation of tetrose sugars while hindering consecutive aldol reactions leading to hexose sugars. High yields of tetrose sugars (74 %) with minor amounts of vinyl glycolic acid (VGA), an α-hydroxyacid, are obtained using Sn-MFI with selectivities towards C4 products reaching 97 %. Tin catalysts having large pores or no pore structure (Sn-Beta, Sn-MCM-41, Sn-SBA-15, tin chloride) led to lower selectivities for C4 sugars due to formation of hexose sugars. In the case of Sn-Beta, VGA is the main product (30 %), illustrating differences in selectivity of the Sn sites in the different frameworks. Under optimized conditions, GA can undergo further conversion, leading to yields of up to 44 % of VGA using Sn-MFI in water. The use of Sn-MFI offers multiple possibilities for valorization of biomass-derived GA in water under mild conditions selectively producing C4 molecules.
- Tolborg, S?ren,Meier, Sebastian,Saravanamurugan, Shunmugavel,Fristrup, Peter,Taarning, Esben,Sádaba, Irantzu
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p. 3054 - 3061
(2016/11/17)
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- A selective oxidation of glucose method of preparing high-value added chemical
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The invention provides a novel method for preparing high value-added chemicals by selectively photo-catalytically oxidizing glucose. The method is characterized in that glucose is directly converted into arabinose and erythrose by using rutile TiO2 loaded with a metallic promoter as a photocatalyst by a photo-catalytic dehydrogenating and oxidizing way under room temperature. The prepared arabinose and erythrose prepared by the method have the yields respectively reaching more than 45mol% and 26mol%; the reaction conditions are mild; no acid, alkali and organic solvents are added; and high-temperature and high-pressure conditions are not needed.
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Paragraph 0052; 0053; 0054
(2017/05/27)
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- METHOD FOR THE ENZYMATIC PRODUCTION OF D-ERYTHROSE AND ACETYL PHOSPHATE
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Described is a method for the production of D-erythrose and acetyl phosphate comprising the enzymatic conversion of D-fructose into D-erythrose and acetyl phosphate by making use of a phosphoketolase. The produced D-erythrose can further be converted into glycolaldehyde by a method for the production of glycolaldehyde comprising the enzymatic conversion of D-erythrose into glycolaldehyde by making use of an aldolase, wherein said aldolase is a 2- deoxyribose-5-phosphate aldolase (EC 4.1.2.4) or a fructose-bisphosphate aldolase (EC 4.1.2.13). The produced glycolaldehyde can finally be converted into acetyl phosphate by the enzymatic conversion of the thus produced glycolaldehyde into acetyl phosphate by making use of a phosphoketolase or a sulfoacetaldehyde acetyltransferase.
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Page/Page column 41-44
(2015/12/17)
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- Catalytic effect of aluminium chloride on the example of the conversion of sugar model compounds
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Abstract In this work, the catalytic effect of the Bronsted acid hydrochloric acid, the Bronsted base sodium hydroxide and the Lewis acid AlCl3 on the conversion of biomass derived carbohydrates is investigated. On the example of the glycolaldehyde conversion, it is shown that the Lewis acid catalyses the ketol-endiol-tautomerism, the dehydration, the retro-aldol-reaction and the benzilic-acid-rearrangement. The main products are C4- and C6-carbohydrates as well as their secondary products 2-hydroxybut-3-enoic acid 1 and several furans. Under the same reaction conditions hydrochloric acid catalyzes mainly the dehydration and sodium hydroxide the tautomerism and subsequent aldolization.
- Schwiderski, Martin,Kruse, Andrea
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- Photocatalytic conversion of glucose in aqueous suspensions of heteropolyacid-TiO2 composites
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Commercial and home prepared TiO2 samples were functionalized with a commercial Keggin heteropolyacid (HPA) H 3PW12O 40 (PW12) or with a hydrothermally home prepared K 7PW11O 39 salt (PW11). All the materials were characterized by specific surface area measurements (BET), XRD analyses, Raman, DRS along with SEM observations and they have been used for glucose photocatalytic conversion in an aqueous suspension. Different reaction extents and distribution of intermediate oxidation products were observed depending on the photocatalyst. Gluconic acid, arabinose, erythrose and formic acid were observed as oxidation products when bare TiO2 or HPA/TiO2 composite materials were used. Glucose isomerization to form fructose was also observed and in some runs traces of glucaric acid and glyceraldehyde were also found. The carbon mass balance was accomplished in the presence of the commercial Evonik P25 TiO2 powder and the composites where TiO2 was present, whereas the presence of the solvothermically prepared TiO2 gave rise to a carbon unbalance, due to strong adsorption of the products on the photocatalyst surface. No reactivity was observed in the presence of PW12 alone while PW11 induced only isomerization of the glucose.
- Bellardita,García-López,Marcì,Megna,Pomilla,Palmisano
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p. 59037 - 59047
(2016/06/09)
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- Tertiary Amine Promoted Asymmetric Aldol Reaction of Aldehydes
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The direct asymmetric self-aldol reactions of various α-oxyaldehydes catalyzed by tertiary amines have been demonstrated. By using 10 mol-% of quinine catalyst, dimerization products have been prepared in high yields, with good anti-diastereocontrol, and up to 80% ee. The presented enolate-mediated synthesis of protected tetrose sugars has never been accomplished before by chiral tertiary amine organocatalysts.
- Gut, Bartosz,Mlynarski, Jacek
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p. 5075 - 5078
(2015/08/18)
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- Zeolite-catalyzed isomerization of tetroses in aqueous medium
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The isomerization of erythrose (ERO) was studied in water over commercially available large-pore zeolites, e.g. H-Y, H-USY and H-beta. Among the employed zeolites, H-USY(6) was found to efficiently isomerize the sugar, yielding 45% erythrulose (ERU), 42% ERO and 3% of the epimer threose (THO) (corresponding to the equilibrium mixture), i.e. total tetrose yield 90%, after reaction for 5-7 h at 120 °C. Changing the solvent from water to methanol decreased the yield of ERU markedly to 18% and gave only a total yield of tetroses of 27% which is significantly lower than that obtained in water. Hence, the results demonstrate that water is the preferred solvent compared to lower alcohols for zeolite-catalyzed tetrose isomerization, which is opposite to what has been found previously for analogous pentose and hexose isomerization. A reuse study revealed further that H-USY(6) could be applied for at least five reaction runs with essentially unchanged activity and without significant aluminum leaching from the catalyst. The use of benign reaction conditions and an industrially pertinent solid catalyst in combination with water establishes a new, green tetrose isomerization protocol. the Partner Organisations 2014.
- Saravanamurugan, Shunmugavel,Riisager, Anders
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p. 3186 - 3190
(2014/08/18)
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- Selective conversion of aqueous glucose to value-added sugar aldose on TiO2-based photocatalysts
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We describe here a photocatalytic process for direct conversion of glucose to value-added chemicals (arabinose and erythrose) and H2 in water under mild reaction conditions without additional acid or base. The total selectivity for the production of arabinose and erythrose on rutile TiO 2-based photocatalyst reaches 91% at 65% conversion. More importantly, it has been demonstrated for the first time that the photodegradation of glucose initially involves C1-C2 bond cleavage (α-scission) to produce arabinose in the presence of water as solvent. To unravel the high selectivity on rutile TiO2, EPR and glucose reaction were carried out on rutile TiO2 in the presence of H 2O2. It was found that the selectivity of the products is mainly dependent on the reactive oxygen species: the hydroxyl radicals (OH) may lead to low selectivity, while the peroxy species lead to a high selectivity. The advantages of the photocatalytic approach for conversion of biomass to value-added chemicals include (1) operation at low reaction temperature, (2) benign environmental effects due to using only water as both solvent and oxidant precursor, and (3) being wasteless due to high selectivity with H2 as the by-product.
- Chong, Ruifeng,Li, Jun,Ma, Yi,Zhang, Bao,Han, Hongxian,Li, Can
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p. 101 - 108
(2014/05/20)
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- Asymmetric organocatalytic formation of protected and unprotected tetroses under potentially prebiotic conditions
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Esters of proteinogenic amino acids efficiently catalyse the formation of erythrose and threose under potentially prebiotic conditions in the highest yields and enantioselectivities yet reported. Remarkably while esters of (l)-proline yield (l)-tetroses, esters of (l)-leucine, (l)-alanine and (l)-valine generate (d)-tetroses, offering the potential to account for the link between natural (l)-amino acids and natural (d)-sugars. The effect of pH and NaCl on the yields and enantioselectivities was also investigated and was shown to be significant, with the optimal enantioselectivities occurring at pH 7.
- Burroughs, Laurence,Clarke, Paul A.,Forintos, Henrietta,Gilks, James A. R.,Hayes, Christopher J.,Vale, Matthew E.,Wade, William,Zbytniewski, Myriam
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experimental part
p. 1565 - 1570
(2012/04/05)
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- Efficient asymmetric organocatalytic formation of erythrose and threose under aqueous conditions
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Esters of proteinogenic amino acids efficiently catalyse the formation of erythrose and threose under aqueous conditions in the highest yields and enantioselectivities yet reported. Remarkably while esters of (l)-proline yield (l)-carbohydrates, esters of (l)-leucine and (l)-alanine generate (d)-carbohydrates, offering the potential to account for the prebiotic link between natural (l)-amino acids and natural (d)-sugars.
- Burroughs, Laurence,Vale, Matthew E.,Gilks, James A. R.,Forintos, Henrietta,Hayes, Christopher J.,Clarke, Paul A.
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supporting information; experimental part
p. 4776 - 4778
(2010/09/05)
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- Methods for the electrolytic production of erythrose or erythritol
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Methods for the production of erythrose and/or erythritol are provided herein. Preferably, the methods include the step of electrolytic decarboxylation of a ribonic acid or arabinonic acid reactant to produce erythrose. Optionally, the reactant can be obtained from a suitable hexose sugar, such as allose, altrose, glucose, fructose or mannose. The erythrose product can be hydrogenated to produce erythritol.
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Page/Page column 8-9
(2008/06/13)
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- Kinetics and mechanism of oxidation of D-fructose by tetraethylammonium chlorochromate in aqueous acetic acid
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In an attempt for developing new oxochromium(VI) reagents for effective and selective oxidation of organic substrates under mild conditions we report in the present paper the kinetic and mechanistic study of the oxidation of D-fructose by tetraethylammonium chlorochromate (C2H 5)4NCrO3Cl. The reaction has been carried out in aqueous acetic acid 50% (v/v) medium in presence of perchloric acid at constant ionic strength. The reaction has been found to be first-order with respect to each of the oxidant and substrate under pseudo first-order conditions. The reaction is catalysed by acid and follows a first-order dependence on H+ ion concentration. The ionic strength variation has no effect on the reaction rate. The decrease in dielectric constant of the medium increases the rate of reaction. A 1:1 stoichiometry is observed in the oxidation and the reaction rate is not retarded by the addition of radical trapping agent acrylonitrile. Effect of temperature on the rate of oxidation has been studied to show the validity of Arrhenius equation and various activation parameters have been computed. The products of oxidation are identified to be D-erythrose and glycollic acid. On the observed facts a hydride ion transfer mechanism is proposed.
- Tomar, Ashish,Kumar, Arun
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p. 1153 - 1157
(2008/02/07)
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- Mitochondrially targeted antioxidants
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The invention provides mitochondrially targeted antioxidant compounds comprising a lipophilic cation moiety covalently coupled to a glutathione peroxidase mimetic. These compounds can be used to treat patients who would benefit from the reduction of oxidative stress.
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- Prebiotic carbohydrate synthesis: Zinc-proline catalyzes direct aqueous aldol reactions of α-hydroxy aldehydes and ketones
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Zn-proline catalyzed aldolisation of glycoladehyde gave mainly tetroses whereas in the cross-aldolisation of glycoladehyde and rac-glyceraldehyde, pentoses accounted for 60% of the sugars formed with 20% of ribose. The Royal Society of Chemistry 2005.
- Kofoed, Jacob,Reymond, Jean-Louis,Darbre, Tamis
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p. 1850 - 1855
(2007/10/03)
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- The catalysis of the Ruff oxidative degradation of aldonic acids by copper(II)-containing solids
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The catalysis of the Ruff oxidative degradation of calcium D-gluconate to D-arabinose by aqueous diluted hydrogen peroxide was investigated using copper(II)-containing solids: zeolites and resins. Among zeolites, copper(II)-exchanged Y faujasite has given
- Hourdin, Gwenaelle,Germain, Alain,Moreau, Claude,Fajula, Francois
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p. 217 - 224
(2007/10/03)
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- Methods for treating plants and enhancing plant growth using polyacylglycosides and/or polyalkylglycosides and formulations for same
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Methods and formulations for treating plants and enhancing plant growth and for safening high concentrations of one or more phytocatalysts, wherein one or more formulations, comprising, a high concentration of one or more phytocatalysts, and an effective amount of one or more polyacylglycosides and polyalkylglycosides; and isomers, and metabolites, salts, hydrates, esters, amines, and derivatives of the polyacylglycosides and polyalkylglycosides, and combinations thereof, is applied to the plants.
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- Kinetics and mechanism of electron transfer reactions of aquo- thallium(III) perchlorate with aldopentoses
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The kinetics of electron transfer reactions of aquo-thallium(III) perchlorate with D-xylose, D-arabinose and D-ribose have been studied under the pseudo-first order condition. The fractional order with respect to aldopentose concentrations suggest the Michaelis-Menten type of kinetics. The rate decreases with acid concentration, and is strongly inhibited by the complexing chloride, acetate ions and acetic acid. A free radical mechanism involving aldopentose derived free radical has proposed for these reactions. Rate law consistent with the experimental data has been also derived.
- Fadnis, Anand G.,Arzare, Sapana
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p. 235 - 237
(2007/10/03)
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- The reaction of hyaluronic acid and its monomers, glucuronic acid and N- acetylglucosamine, with reactive oxygen species
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Synovial fluid is a ~0.15% (w/v) aqueous solution of hyaluronic acid (HA), a polysaccharide consisting of alternating units of GlcA and GlcNAc. In synovial fluid of patients suffering from rheumatoid arthritis, HA is thought to be degraded either by radicals generated by Fenton chemistry (Fe2+/H2O2) or by NaOCl generated by myeloperoxidase. We investigated the course of model reactions of these two reactants in physiological buffer with HA, and with the corresponding monomers GlcA and GlcNAc. meso-Tartaric acid, arabinuronic acid, arabinaric acid and glucaric acid were identified by GC-MS as oxidation products of glucuronic acid. When GlcNAc was oxidised, erythronic acid, arabinonic acid, 2-acetamido-2-deoxy-gluconic acid, glyceric acid, erythrose and arabinose were formed. NaOCl oxidation of HA yielded meso-tartaric acid; in addition, arabinaric acid and glucaric acid were obtained by oxidation with Fe2+/H2O2. These results indicate that oxidative degradation of HA proceeds primarily at glucuronic acid residues. meso-Tartaric acid may be a useful biomarker of hyaluronate oxidation since it is produced by both NaOCl and Fenton chemistry.
- Jahn, Michael,Baynes, John W.,Spiteller, Gerhard
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p. 228 - 234
(2007/10/03)
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- Electrooxidation of mesoerythritol on platinum, modified or not by adatoms, in acid medium
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The electrocatalytic oxidation of meso-erythritol has been studied in 0.1 M HClO4 on platinum and on adatoms modified platinum. Preliminary investigations by cyclic voltammetry showed that erythritol was not reactive on a Pt electrode. Underpotential deposition of lead or thallium adatoms at platinum allowed to increase significantly the current densities. Long-time electrolyses were carded out using a three potential plateau program with different values of the oxidation potentials. Chromatographic analyses showed that the oxidation of erythritol led mainly to erythrose, erythrulose and to erythronic acid. Otherwise, electrolysis of erythritol on a Pt-Tl modified electrode orientated selectively the distribution of the reaction products towards the formation of erythrulose.
- Cherqaoui,Chbihi,Takky,Kokoh,Leger,Lamy
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p. 510 - 521
(2007/10/03)
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- Process for isomerization of compound of aldose structure into compound of ketose structure, and isomerization agent or accelerator used therein
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A process is provided which comprises isomerizing a compound having a ketose structure by the use of or in the presence of an organogermanium compound having a structural portion represented by formula (I): STR1 Due to the use or presence of the organogermanium compound, the process is free from the problems of the prior art, and is capable of isomerizing a compound having an aldose structure into a compound having a ketose structure at a high isomerization ratio without requiring any special apparatus or any complicated operation.
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- Compounds and methods for monosaccharide analysis
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Compounds and methods are provided for use in monosaccharide analysis. The present invention discloses hydrazino monosaccharide derivatives. Methods for preparing and using hydrazino monosaccharide derivatives for structural analysis of aldose and ketose monosaccharides are also disclosed.
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- PREPARATION OF D-ARABINOSE IN A LABORATORY FLUIDIZED BED ELECTRODE CELL
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Results of experimental work employing and electrochemical reactor with the fluidized bed electrode to prepare D-arabinose by direct degradative oxidation of sodium D-gluconate without chemical oxidizing agents are presented.The observed yield of D-arabinose exceeded 70percent by mass related to the theoretically obtainable amount with the selectivity ranging between 96 and 98.1percent.The undesirable product was mainly D-erythrose produced by consecutive reaction from D-arabinose.Typical specific electric power consumption ranged between 7.5 and 14 kWh per kg of D-arabinose.
- Jiricny, Vladimir,Stanek, Vladimir
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p. 863 - 874
(2007/10/02)
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- 4-Isopropyl-2-oxazolin-5-one anion as a new convenient formyl anion equivalent for conjugate addition and aldol reactions
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The anion of the title compound, simply generated in the presence of catalytic amount of triethylamine, acts as nucleophilic acylating equivalent of formaldehyde reacting with both common electrophilic olefins or aldehydes to give moderate to good yield of Michael or aldol adducts respectively, which are easily hydrolized by dilute acid at ambient to temperature to afford the corresponding aldehydes.
- Barco, Achille,Benetti, Simonetta,De Risi, Carmela,Pollini, Gian P.,Spalluto, Giampiero,Zanirato, Vinicio
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p. 3907 - 3910
(2007/10/02)
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- Metal-mediated decarbonylation and dehydration of ketose sugars
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Ketose sugars can be decarbonylated and/or dehydrated by the action of certain metal complexes. Fructose reacts with 1 equiv of RhCl(PPh3)3 (1) in N-methyl-2-pyrrolidinone (NMP) at 130°C to give furfuryl alcohol, Rh(CO)Cl(PPh3)2 (2), and a small amount of 1-deoxyerythritol. 1,3-Dihydroxyacetone consumes 2 equiv of 1, giving methane and ca. 2 mol of 2. With manno-2-heptulose the primary product is 2,7-anhydromanno-2-heptulopyranose. The mechanisms of these unusual reactions have been studied by using 13C-labeling experiments and model reactions employing Pd(II) and HCl. Attempts to make the reactions catalytic using [Rh(Ph2PCH2CH2CH2PPh 2)2]+[BF4]- in place of 1 were not successful. The use of NMP as a solvent offers some advantages in the acid-catalyzed synthesis of certain carbohydrate dehydration products, as exemplified by the conversion of manno-2-heptulose to its 2,7-anhydride and of 2-deoxyglucose to 1-(2-furanyl)-1,2-ethanediol.
- Andrews, Mark A.
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p. 2703 - 2708
(2008/10/08)
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- NOVEL SYNTHETIC EQUIVALENTS OF DIFFERENTIALLY PROTECTED TARTARIC ALDEHYDES. A SIMPLE ROUTE TO USEFUL C-4 CHIRAL SYNTHONS.
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The synthesis of 4-acetoxy-3-O-benzyl-1,2-O-isopropylidene aldotetroses from D-glucose is reported.These synthetic equivalents of tartaric aldehydes are chemoselectively reduced at the acetoxylated center leading to a series of useful differentially protected C-4 chiral synthons.
- Dhavale, Dilip D.,Tagliavini, Emilio,Trombini, Claudio,Umani-Ronchi, Achille
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p. 6163 - 6166
(2007/10/02)
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- FURANOSE RING ANOMERIZATION: A KINETIC STUDY OF THE 5-DEOXYPENTOSES AND 5-O-METHYLPENTOSES
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The anomerzation of 5-deoxy-L-pentoses (1-4) and 5-O-methyl-D-pentoses (5-8) in aqueous solution has been studied by (13)C saturation-transfer n.m.r. (s.t.-n.m.r.) spectroscopy, using compounds substituted with (13)C at the anomeric carbon atom.Unidirectional rate-constants of ring-opening (kopen) and ring closing (kclose) have been obtained for these compounds under identical solution conditions (50mM acetate buffer, pH 4.0 at 60 deg C), and have been compared to those measured for the D-tetroses (9 and 10) and four D-pentose 5-phosphates (11-14).Based on these comparisons, several correlations between furanose structure and reactivity have been revealed, and models have been proposed to explain the observed kinetic behavior of compounds 1-10.The effect of exocyclic structure on acid-catalyzed rate-constants was also examined by comparing the behavior of 5-deoxy-L-lyxose and 5-O-methyl-D-lyxose.Some consideration has been given to identifying the factors (enthalpic and entropic) that may play roles in determining the effect of structure on anomerization reactivity.
- Snyder, Joseph R.,Serianni, Anthony S.
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- EFFECT OF PRESSURE ON THE RATES OF OXIDATION OF MONOSACCHARIDES WITH VANADIUM(V)
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The effect of pressure on the rates of the oxidation of D-galactose, D-glucose, D-mannose, D-fructose, L-sorbose, L-arabinose, D-ribose, and D-xylose with vanadium(V) in perchloric acid was studied.The activation volumes for the monosaccharides were positive and approximately equal (7.5+/-1.3 mL*mol-1), with negligible dependence on pressure up to 200 MPa at least.These observations indicate the same mechanism for the formation of the activated complexes.A mechanism involving formation of a radical by hydrogen atom transfer in the rate-determining decomposition of a monosaccharide-vanadium(V) complex is proposed.
- Virtanen, Pentti O. I.,Koukkanen, Toivo,Rauma, Touko
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- KINETICS OF OXIDATION OF MONOSACCHARIDES WITH CERIUM(IV)
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The kinetics of the oxidation of D-galactose, D-glucose, D-mannose, D-fructose, L-sorbose, L-arabinose, D-ribose, and D-xylose with cerium(IV) in perchloric acid were studied.Two complexes were found to form in each case.The first complex forms in a pre-equilibrium reaction during mixing in the stopped-flow apparatus.Michaelis-Menten kinetics were observed for this oxidation.The values of the complex-formation and dissociation rate-constants were determined in 1.0 M HClO4.The dissociation partly involves the oxidation of the first complex and partly, the formation of a second, more-stable complex.This second complex is oxidized much more slowly than the first, and the values of the pseudo-first-order rate-constant were again determined in 1.0 M HClO4.The values proved to be almost constant in the range of 0.1 M to 1.0 M , from which it was concluded that practically all of the Ce(IV) was complexed.
- Virtanen, Pentti O. I.,Lindroos, Raija,Oikarinen, Eija,Vaskuri, Juhani
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- OXIDATIVE DEGRADATION OF MONOSACCHARIDES BY IRON(III) CHLORIDES WITH A NEAR-UV TO VISIBLE LIGHT UNDER AEROBIC ATMOSPHERE.
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Monosaccharides were oxidatively degraded by FeCl//3 with irradiation of a near-UV to visible light under aerobic atmosphere. D-Fructose and D-arabinose were degraded to D-erythrose in a yield of more than 80 mol%. D-Glucose and D-mannose were at first degraded to D-arabinose, which was subsequently degraded to D-erythrose, while d-ribose was directly degraded to d-erythrose and D-glyceraldehyde. The degradation processes were selective, and these reactions were shown to proceed via formation of an Fe(III)-monosaccharide complex. The kinetic data and other features of these reactions are also discussed.
- Araki,Sakuma,Shiraishi
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p. 997 - 1002
(2007/10/02)
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- Kinetics, Catalysis, and Mechanism of the Secondary Reaction in the Final Phase of the Formose Reaction
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In the final phase of the formose reaction sugars are formed by the reaction of glycolaldehyde, glyceraldehyde and dihydroxyacetone.The application of high-pressure liquid chromatography allows for the first time to investigate intermediate and final products quantitatively.The results of kinetical investigations allow to suggest a reaction mechanism for the secondary reaction in the final phase of the formose reaction.This mechanism is compared with that of the starting phase and other known mechanisms.From the results metal ion-catalyzed aldol reactions have to be assumed.
- Harsch, Guenther,Bauer, Hermann,Voelter, Wolfgang
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p. 623 - 635
(2007/10/02)
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- THE FORMOIN REACTION
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The formoin reaction, i.e., the autocondensation of formaldehyde in an aprotic solvent catalysed by the conjugate base of a thiazolium ion, has been studied in detail.Glucose, galactose, dihyroxyacetone dimer, xylose, and arabinose have been identified as products.The influence of catalysts, temperature, basicity, and reaction time is documented.N,N-Dimethylformamide is a more convenient solvent than ether, benzene, or diglyme.Ethyldi-isopropylamine affords better yields of carbohydrate material than triethylamine.At =60 deg, aldol condensations are reduced to a minimum.After 1-2 h of reaction (depending on the conditions), the yields begin to decrease and become zero after ca. 24 h.
- Castells, Josep,Lopez-Calahorra, Francisco,Geijo, Fernando
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p. 197 - 208
(2007/10/02)
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- PHOTOLYSIS OF D-FRUCTOSE IN AQUEOUS SOLUTION
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In the 254-nm photolysis of aqueous solutions of D-fructose, only the open-chain form, which is present to an extent of ca. 0.8percent in equilibrium with the cyclic forms, absorbs the light.A study of the products and their quantum yields reveals that the main, primary process is C-C bond cleavage α to the carbonyl group.In the absence of oxygen, the subsequent reactions of the resulting radicals are (a) loss of CO from the hydroxyalkylacyl radicals (estimated rate constant k ca. 3*1E6 s-1); (b) consecutive elimination of two molecules of water from the tetritol radicals; and (c) disproportionation and combination reactions.A peculiar product is trans-4-hydroxy-2-butenal, whose precursor is formed from the tetritol radical through elimination of two molecules of water.This compound is a good radical-scavenger and during photolysis quickly attains a low steady-state concentration.One of the products derived from it is a 2,3-dideoxy-2,3-di-C-hydroxymethyltetrose.In the presence of oxygen, the CO elimination process is partly, and the water elimination reactions are fully, suppressed by the fast addition of oxygen to the acylalkyl and hydroxyalkyl radicals.The peroxyl radicals react through unimolecular elimination of HO2. from α-hydroxyalkylperoxyl radicals and bimolecular dismutation with loss of O2, accompanied by loss of CO2 when hydroxyalkylacylperoxyl radicals are involved.
- Triantaphylides, Christian,Schuchmann, Heinz-Peter,Sonntag, Clemens von
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p. 131 - 142
(2007/10/02)
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