- L-xylo-3-hexulose reductase is the missing link in the oxidoreductive pathway for D-galactose catabolism in filamentous fungi
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In addition to the well established Leloir pathway for the catabolism of D-galactose in fungi, the oxidoreductive pathway has been recently identified. In this oxidoreductive pathway, D-galactose is converted via a series of NADPH-dependent reductions and NAD+-dependent oxidations into D-fructose. The pathway intermediates include galactitol, L-xylo-3-hexulose, and D-sorbitol. This study identified the missing link in the pathway, the L-xylo-3-hexulose reductase that catalyzes the conversion of L-xylo-3-hexulose to D-sorbitol. In Trichoderma reesei (Hypocrea jecorina) and Aspergillus niger, we identified the genes lxr4 and xhrA, respectively, that encode the L-xylo-3-hexulose reductases. The deletion of these genes resulted in no growth on galactitol and in reduced growth on D-galactose. The LXR4 was heterologously expressed, and the purified protein showed high specificity for L-xylo-3-hexulose with a Km=2.0±0.5mM and a V max=5.5±1.0 units/mg. We also confirmed that the product of the LXR4 reaction is D-sorbitol.
- Mojzita, Dominik,Herold, Silvia,Metz, Benjamin,Seiboth, Bernhard,Richard, Peter
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Read Online
- Structure of a new ribitol teichoic acid-like O-polysaccharide of a serologically separate Proteus vulgaris strain, TG 276-1, classified into a new Proteus serogroup O53
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An unusual ribitol teichoic acid-like O-polysaccharide was isolated by mild acid degradation of the lipopolysaccharide from a previously non-classified Proteus vulgaris strain TG 276-1. Structural studies using chemical analyses and 2D 1H and 13C NMR spectroscopy showed that the polysaccharide is a zwitterionic polymer with a repeating unit containing 2-acetamido-4-amino-2,4,6-trideoxy-d-galactose (d-FucNAc4N) and two d-ribitol phosphate (d-Rib-ol-5-P) residues and having the following structure:{A figure is presented}where the non-glycosylated ribitol residue is randomly mono-O-acetylated. Based on the unique O-polysaccharide structure and the finding that the strain studied is serologically separate among Proteus bacteria, we propose to classify P. vulgaris strain TG 276-1 into a new Proteus serogroup, O53.
- Arbatsky, Nikolay P.,Kondakova, Anna N.,Senchenkova, Sof'ya N.,Siwinska, Malgorzata,Shashkov, Alexander S.,Zych, Krystyna,Knirel, Yuriy A.,Sidorczyk, Zygmunt
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Read Online
- Unexpected reactivity related to support effects during xylose hydrogenation over ruthenium catalysts
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Xylose is a major component of hemicelluloses. In this paper, its hydrogenation to xylitol in aqueous medium was investigated with two Ru/TiO2catalysts prepared with two commercial TiO2supports. A strong impact of the support on catalytic performance was evidenced. Ru/TiO2-R led to fast and selective conversion of xylose (100% conversion in 2 h at 120 °C with 99% selectivity) whereas Ru/TiO2-A gave a slower and much less selective transformation (58% conversion in 4 h at 120 °C with 17% selectivity) with the formation of several by-products. Detailed characterization of the catalysts with ICP, XRD, FTIR, TEM, H2chemisorption, N2porosimetry, TPR and acid-base titration was performed to elucidate the role of each support. TiO2-R has a small specific surface area with large ruthenium nanoparticles in weak interaction with the TiO2support and no acidity, whereas TiO2-A is a mesoporous material with a large specific surface area that is mildly acidic, and bears small ruthenium particles in strong interaction with the TiO2support. The former was very active and selective for xylose hydrogenation to xylitol whereas the latter was less active and poorly selective. Moreover, careful analysis of the reaction products also revealed that anatase TiO2can catalyze undesired side-reactions such as xylose isomerisation to various pentoses, and therefore the corresponding unexpected polyols (arabitol, ribitol) were produced during xylose conversion by hydrogenation. In a first kinetic approach, a simplified kinetic model was built to compare quantitatively intrinsic reaction rates of both catalysts. The kinetic constant for hydrogenation was 20 times higher for Ru/TiO2-R at 120 °C.
- Fongarland, Pascal,Freitas, Victoria D. S.,Paez, Ana,Philippe, Régis,Veyre, Laurent,Vilcocq, Léa
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p. 39387 - 39398
(2021/12/27)
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- COMPOSITIONS AND METHODS OF MAKING RIBITOL
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The present disclosure describes compositions comprising substantially pure ribitol, pharmaceutical compositions of ribitol, and methods of making ribitol. The methods may include combining a reducing agent (e.g., borohydride) and ribose (e.g. D-ribose), optionally with stirring, to form a first reaction mixture; and contacting the first reaction mixture and an acidic quenching agent, optionally with stirring, to form a second reaction mixture, thereby forming ribitol.
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Page/Page column 17
(2020/12/11)
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- Effect of Cu addition to carbon-supported Ru catalysts on hydrogenation of alginic acid into sugar alcohols
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The objective of this study was to investigate the effect of Cu addition to carbon supported Ru catalysts on the hydrogenation of macroalgae-derived alginic acid into sugar alcohols, mainly sorbitol and mannitol. Both geometric and electronic effects were determined based on results of H2-TPR, H2- or CO-chemisorption, and XPS analyses after Cu was added to Ru. The addition of Cu to Ru caused blocking of active Ru surface and electron transfer between Ru and Cu. The intimate interaction between Ru and Cu formed RuCu bimetallic clusters which expedited hydrogen spillover from Ru to Cu. The highest yield of target sugar alcohols of 47.4% was obtained when 5 wt% of Ru and 1 wt% of Cu supported on nitric acid-treated activated carbon reacted at 180 °C for 2 h. The RuCu bimetallic catalyst exhibited deactivation upon repeated reactions due to the carbon deposition on the catalyst.
- Ban, Chunghyeon,Yang, Seungdo,Kim, Hyungjoo,Kim, Do Heui
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- Hydrogenolysis of sorbitol into valuable C3-C2 alcohols at low H2 pressure promoted by the heterogeneous Pd/Fe3O4 catalyst
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The hydrogenolysis of sorbitol and various C5-C3 polyols (xylitol; erythritol; 1,2- 1,4- and 2,3-butandiol; 1,2-propandiol; glycerol) have been investigated at low molecular hydrogen pressure (5 bar) by using Pd/Fe3O4, as heterogeneous catalyst and water as the reaction medium. Catalytic experiments show that the carbon chain of polyols is initially shortened through dehydrogenation/decarbonylation and dehydrogenation/retro-aldol mechanisms followed by a series of cascade reactions that include dehydrogenation/decarbonylation and dehydration/hydrogenation processes. At 240 °C, sorbitol is fully converted into lower alcohols with ethanol being the main reaction product in liquid phase.
- Gumina, Bianca,Mauriello, Francesco,Pietropaolo, Rosario,Galvagno, Signorino,Espro, Claudia
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p. 152 - 160
(2018/02/17)
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- CTAB-assisted sol-microwave method for fast synthesis of mesoporous TiO2 photocatalysts for photocatalytic conversion of glucose to value-added sugars
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Fabrication technique is an important factor for development of catalysts. Titanium dioxide (TiO2) is one of efficient photocatalysts. In this work, we firstly report the fabrication of TiO2 nanoparticles by sol-microwave method with cetyltrimethylammonium bromide (CTAB) surfactant. Absence of surfactant, microwave treatment significantly reduced the cluster sizes of TiO2, but high aggregations of TiO2 particles were observed. CTAB has great impact on morphology, cluster size and mesoporous structure of TiO2. Therefore, surface area of TiO2 synthesized by sol-microwave method with 0.108 M CTAB increased from 15.97 to 37.60 m2/g. Photocatalytic activity of TiO2 was tested via the glucose conversion to produce value-added chemicals (gluconic acid, xylitol, arabinose and formic acid). It was found that surface area, mesoporous structure and pore size of TiO2 are crucial properties for glucose conversion and product distribution. From the reaction test, 0.108 M CTAB/MW-TiO2 achieved the highest glucose conversion (62.28%).
- Payormhorm, Jiraporn,Chuangchote, Surawut,Laosiripojana, Navadol
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p. 546 - 555
(2017/09/01)
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- Xylitol Hydrogenolysis over Ruthenium-Based Catalysts: Effect of Alkaline Promoters and Basic Oxide-Modified Catalysts
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The aqueous-phase hydrogenolysis of xylitol into glycols over Ru/C was performed in the presence and absence of a wide range of concentrations of Ca(OH)2 to investigate the reaction pathway. Without base, epimerization and cascade decarbonylation were the predominant reactions with high selectivities to C5 and C4 alditols and light alkanes at full conversion. Glycol production was obtained by the addition of Ca(OH)2 to promote the retro-aldol reaction. It competed with reactions without base and became the main reaction for a OH?/ xylitol molar ratio Rmol(OH/xylitol) of 0.13, and high selectivities to glycols (56 %) and glycerol (16 %) were observed. However, lactate was a byproduct at up to 27 % with a high base amount (Rmol(OH/xylitol)=0.68). Bifunctional Ru/metal oxide/C catalysts (metal: Zn, Sn, Mn, Sr, W) were synthesized and were able to cleave the C?C bond into glycols without a base promoter. The 3.1 wt %Ru/MnO(4.5 %)/C catalyst was the most active (220 h?1) with reasonable selectivity to glycols (22 %) and glycerol (10 %) and a low production of lactate (1 %). Nevertheless, metal oxide leaching of the catalyst was observed likely because of the production of traces of lactate.
- Rivière, Maxime,Perret, Noémie,Cabiac, Amandine,Delcroix, Damien,Pinel, Catherine,Besson, Michèle
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p. 2145 - 2159
(2017/06/28)
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- Selective C?O Bond Cleavage of Sugars with Hydrosilanes Catalyzed by Piers’ Borane Generated In Situ
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Described herein is the selective reduction of sugars with hydrosilanes catalyzed by using Piers’ borane [(C6F5)2BH] generated in situ. The hydrosilylative C?O bond cleavage of silyl-protected mono- and disaccharides in the presence of a (C6F5)2BH catalyst, generated in situ from (C6F5)2BOH, takes place with excellent chemo- and regioselectivities to provide a range of polyols. A study of the substituent effects of sugars on the catalytic activity and selectivity revealed that the steric environment around the anomeric carbon (C1) is crucial.
- Zhang, Jianbo,Park, Sehoon,Chang, Sukbok
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supporting information
p. 13757 - 13761
(2017/10/09)
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- Preparation method of gamma-acetyl n-propanol
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The invention discloses a preparation method of gamma-acetyl n-propanol. The method includes the steps of (1) adding the hydrolysate of plant fiber or xylose and other raw materials into a reaction still, adding a two-phase reactive solvent and a catalyst, inletting hydrogen, and heating the reaction still to react for several hours; (2) carrying out standing, liquid separation and then solid-liquid separation on reaction materials in the reaction still, obtaining water phase, oil phase and the catalyst, and recycling the catalyst for reutilization; (3) concentrating water phase products, extracting 1, 4-pentanediol in the oil phase, mixing with the concentrated solution, and carrying out further separation to obtain a crude product of 1, 4-pentanediol; (4) pumping the crude product of 1, 4-pentanediol obtained from the water phase and the oil phase in step (3) to a fixed bed reactor, carrying out dehydrogenation to produce gamma-acetyl n-propanol under the action of a catalytic dehydrogenation catalyst or an oxydehydrogenation catalyst. According to the preparation method, raw materials have extensive sources, the production cost is low, no inorganic acid system is used, and the reaction process is environment-friendly.
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Paragraph 0036; 0037
(2017/12/09)
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- Kinetic insight into the effect of the catalytic functions on selective conversion of cellulose to polyols on carbon-supported WO3 and Ru catalysts
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Efficient conversion of cellulose, the most abundant biomass on Earth, to chemicals in high yields remains a formidable challenge. Here, we report the marked change in the distribution of polyol products in the cellulose reaction on Ru/C and WO3/C, strongly depending on the competitive reactions of the glucose intermediate. WO3 crystallites not only promote, as a solid acid, the efficient hydrolysis of cellulose to glucose, but also catalyze the selective cleavage of the C-C bonds in glucose and other C6 sugar intermediates, leading to the formation of ethylene glycol and propylene glycol, in competition with the sugar hydrogenation to the corresponding C6 polyols (e.g. sorbitol) on Ru/C. The basic C support, behaving similar to other solid bases (i.e. MgO), catalyzes the isomerization of glucose into fructose, leading to the favored formation of propylene glycol instead of ethylene glycol. Such strong dependence of the product distribution on the catalytic functions is clarified by the kinetic analysis of the three competitive reactions of glucose, including its hydrogenation, isomerization and C-C bond cleavage. Importantly, such kinetic analysis can predict the maximum selectivity ratio of propylene glycol to ethylene glycol, which is 2.5, for example, at 478 K under the reaction conditions in this work, corresponding to a maximum yield of propylene glycol of ～71%. These understandings shed new insights into the selective conversion of cellulose, which provides guidance for the rational design of catalyst functions and tuning of reaction parameters towards the controllable synthesis of specific products from cellulose.
- Liu, Yue,Liu, Haichao
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- Composite Material Consisting of a Catalyst/Phase-Change Material, Related Manufacturing Methods and Use of Such a Material in Catalytic Reactions
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Material with hybrid particles (1) each consisting of a particle (2) of a phase-change material (PCM) interfaced with a catalytic material (3) in solid form, the size of the hybrid particles being between 0.1 mm and 10 mm, preferably between 1 mm and 5 mm.
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Page/Page column
(2015/07/15)
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- Production of xylitol from glucose by a recombinant strain
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The present invention relates to a recombinant microbial host for the production of xylitol, the recombinant microbial host containing a nucleic acid sequence encoding a NAD+-specific D-arabitol 4-oxidoreductase (EC 1.1.1.11) using D-arabitol as substrate and producing D-xylulose as product, and a nucleic acid sequence encoding a NADPH-specific xylitol dehydrogenase using D-xylulose as substrate and producing xylitol as product.
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Paragraph 0229-0248
(2016/01/11)
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- Unravelling the Ru-Catalyzed Hydrogenolysis of Biomass-Based Polyols under Neutral and Acidic Conditions
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The aqueous Ru/C-catalyzed hydrogenolysis of biomass-based polyols such as erythritol, xylitol, sorbitol, and cellobitol is studied under neutral and acidic conditions. For the first time, the complete product spectrum of C2-C6 polyols is identified and, based on a thorough analysis of the reaction mixtures, a comprehensive reaction mechanism is proposed, which consists of (de)hydrogenation, epimerization, decarbonylation, and deoxygenation reactions. The data reveal that the Ru-catalyzed deoxygenation reaction is highly selective for the cleavage of terminal hydroxyl groups. Changing from neutral to acidic conditions suppresses decarbonylation, consequently increasing the selectivity towards deoxygenation.
- Hausoul, Peter J. C.,Negahdar, Leila,Schute, Kai,Palkovits, Regina
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p. 3323 - 3330
(2015/10/19)
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- Selective terminal C-C scission of C5-carbohydrates
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The selective catalytic production of C4-tetritols (erythritol and threitol) from C5-sugars is an attractive route for the conversion of non-digestible sugars to C4-building blocks from agro residues. Here we show that an unprecedented high selectivity of 20-25% C4-tertritols can be achieved under mild conditions (138 °C, 6 bar H2, and 24 h) in the aqueous conversion of xylose over a 5 wt% Ru/C catalyst. A mechanistic study revealed that the dominant reaction mechanism for C5-sugar conversion involves a formal decarbonylation step leading to the initial formation of the desired C4-tetritols. Subsequently the formed C4-tetritols undergo further terminal C-C scissions to glycerol and ethylene glycol. Remarkably, potentially competing reactions like internal C-C chain scission (fragmentation) or hydrodeoxygenation (HDO) do not occur to any significant extent under the applied conditions.
- Van Der Klis, Frits,Gootjes, Linda,Van Haveren, Jacco,Van Es, Daan S.,Bitter, Johannes H.
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p. 3900 - 3909
(2015/07/15)
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- Aqueous-phase hydrogenation and hydrodeoxygenation of biomass-derived oxygenates with bimetallic catalysts
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The reaction rate on a per site basis for aqueous-phase hydrogenation (APH) of propanal, xylose, and furfural was measured over various alumina-supported bimetallic catalysts (Pd-Ni, Pd-Co, Pd-Fe, Ru-Ni, Ru-Co, Ru-Fe, Pt-Ni, Pt-Co, and Pt-Fe) using a high-throughput reactor (HTR). The results in this paper demonstrate that the activity of bimetallic catalysts for hydrogenation of a carbonyl group can be 110 times higher than monometallic catalysts. The addition of Fe to a Pd catalyst increased the activity for hydrogenation of propanal, xylose, and furfural. The Pd1Fe3 catalyst had the highest reaction rate for APH of propanal among all catalysts tested in the HTR. The addition of Fe to the Pd catalyst increased the reaction rate for xylose hydrogenation by a factor of 51, compared to the monometallic Pd catalyst. However, no bimetallic catalyst tested in this study was more active than the monometallic Ru catalyst for hydrogenation of xylose. The Pd1Fe 3 catalyst had the highest reaction rate for APH of furfural, which was 9 times higher than the rate of the Pd catalyst. The Pd1Fe 3/Zr-P, a bimetallic bifunctional catalyst, was 14 times more active on a per site basis than a Pd/Zr-P catalyst for aqueous-phase hydrodeoxygenation (HDO) of sorbitol in a continuous flow reactor. The addition of Fe to the Pd catalyst increased the rate of C-C cleavage reactions and promoted the conversion of sorbitan and isosorbide in HDO of sorbitol. Pd1Fe 3/Zr-P also had a higher yield of gasoline-range products than the Pd/Zr-P catalyst.
- Lee, Jechan,Kim, Yong Tae,Huber, George W.
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supporting information
p. 708 - 718
(2014/02/14)
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- Promoting effect of SnOx on selective conversion of cellulose to polyols over bimetallic Pt-SnOx/Al2O3 catalysts
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Cellulose is the most abundant source of biomass in nature, and its selective conversion into polyols provides a viable route towards the sustainable synthesis of fuels and chemicals. Here, we report the marked change in the distribution of polyols in the cellulose reaction with the Sn/Pt atomic ratios in a wide range of 0.1-3.8 on the SnOx-modified Pt/Al 2O3 catalysts. Such a change was found to be closely related to the effects of the Sn/Pt ratios on the activity for the hydrogenation of glucose and other C6 sugar intermediates involved in the cellulose reaction as well as to the notable activity of the segregated SnO x species for the selective degradation of the sugar intermediates on the Pt-SnOx/Al2O3 catalysts. At lower Sn/Pt ratios of 0.1-1.0, there existed electron transfer from the SnOx species to the Pt sites and strong interaction between the catalysts, as characterized by temperature-programmed reduction in H2 and infrared spectroscopy for CO adsorption, which led to their superior hydrogenation activity (per exposed Pt atom), and in-parallel higher selectivity to hexitols (e.g. sorbitol) in the cellulose reaction, as compared to Pt/Al 2O3. The hexitol selectivity reached the greatest value of 82.7% at the Sn/Pt ratio of 0.5, nearly two times that of Pt/Al 2O3 at similar cellulose conversions (～20%). As the Sn/Pt ratios exceeded 1.5, the Pt-SnOx/Al2O3 catalysts exhibited inferior hydrogenation activity (per exposed Pt atom), due to the formation of the crystalline Pt-Sn alloy, which led to the preferential conversion of cellulose to C2 and especially C3 products (e.g. acetol) over hexitols, most likely involving the isomerization of glucose to fructose and retro-aldol condensation of these sugars on the segregated SnOx species, apparently in the form of Sn(OH)2. These findings clearly demonstrate the feasibility for rational control of the cellulose conversion into the target polyols (e.g. acetol or propylene glycol), for example, by the design of efficient catalysts based on the catalytic functions of the SnOx species with tunable hydrogenation activity.
- Deng, Tianyin,Liu, Haichao
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p. 116 - 124
(2013/02/26)
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- Yarrowia lipolytica dehydrogenase/reductase: An enzyme tolerant for lipophilic compounds and carbohydrate substrates
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Yarrowia lipolytica short chain dehydrogenase/reductase (YlSDR) was expressed in Escherichia coli, purified and characterized in vitro. The substrate scope for YlSDR mediated oxidation was investigated with alcohols and unprotected carbohydrates spectrophotometrically, revealing a preference for secondary compared to primary alcohols. In reduction direction, YlSDR was highly active on ribulose and fructose, suggesting that the enzyme is a mannitol-2-dehydrogenase. In order to explore substrate tolerance especially for space-demanding, lipophilic protecting groups, 5-O-trityl-d-ribitol and 5-O-trityl-α,β-d-ribose were investigated as substrates: YlSDR oxidized 5-O-trityl-d-ribitol and 5-O-trityl-α,β-d-ribose and reduced the latter at the expense of NADP(H).
- Napora, Kamila,Wrodnigg, Tanja M.,Kosmus, Patrick,Thonhofer, Martin,Robins, Karen,Winkler, Margit
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supporting information
p. 3393 - 3395
(2013/06/27)
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- Probing the ruthenium-catalyzed higher polyol hydrogenolysis reaction through the use of stereoisomers
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Nine polyol stereoisomers ranging from three to six carbons in length were reacted under hydrogenolysis conditions (205-240°C, 100 bar H2) over a Ru-C catalyst to better understand the reaction mechanism. Previous reports have postulated the retro-aldol mechanism as the main pathway leading to C-C scission. However, the retro-aldol mechanism was insufficient in explaining the product distribution of tetritols from pentitols, while the decarbonylation mechanism could explain the selectivity results of terminal C-C scission. Retro-aldol scission of internal C-C bonds was confirmed to occur by the tetritol product distribution from hexitols. Therefore, the presence or role of 3-keto and 4-keto intermediates had a negligible effect on the C-C hydrogenolysis of polyols when compared to aldehyde intermediates. The reaction rates of the polyols depended on the configuration of the polyol stereoisomers. The reactivity of the stereoisomers was correlated to the presence of erythro sequences of hydroxyl groups and was independent of the carbon chain length. The Royal Society of Chemistry.
- Deutsch, Keenan L.,Lahr, Daniel G.,Shanks, Brent H.
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p. 1635 - 1642
(2013/02/23)
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- Selective hydrogenolysis of biomass-derived xylitol to ethylene glycol and propylene glycol on supported Ru catalysts
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The selective hydrogenolysis of biomass-derived xylitol to ethylene glycol and propylene glycol was carried out on different catalysts in the presence of Ca(OH)2. The catalysts included Ru supported on activated carbon (C) and, for comparison, on metal oxides, Al2O3, TiO 2, ZrO2 and Mg2AlOx as well as C-supported other noble metals, Rh, Pd and Pt, with similar particle sizes (1.6-2.0 nm). The kinetic effects of H2 pressures (0-10 MPa), temperatures (433-513 K) and solid bases including Ca(OH)2, Mg(OH)2 and CaCO3 were examined on Ru/C. Ru/C exhibited superior activities and glycol selectivities than Ru on TiO2, ZrO2, Al2O3 and Mg2AlOx, and Pt was found to be the most active metal. Such effects of the metals and supports are attributed apparently to their different dehydrogenation/ hydrogenation activities and surface acid-basicities, which consequently influenced the xylitol reaction pathways. The large dependencies of the activities and selectivities on the H2 pressures, reaction temperatures, and pH values showed their effects on the relative rates for the hydrogenation and base-catalyzed reactions involved in xylitol hydrogenolysis, reflecting the bifunctional nature of the xylitol reaction pathways. These results led to the proposition that xylitol hydrogenolysis to ethylene glycol and propylene glycol apparently involves kinetically relevant dehydrogenation of xylitol to xylose on the metal surfaces, and subsequent base-catalyzed retro-aldol condensation of xylose to form glycolaldehyde and glyceraldehyde, followed by direct glycolaldehyde hydrogenation to ethylene glycol and by sequential glyceraldehyde dehydration and hydrogenation to propylene glycol. Clearly, the relative rates between the hydrogenation of the aldehyde intermediates and their competitive reactions with the bases dictate the selectivities to the two glycols. This study provides directions towards efficient synthesis of the two glycols from not only xylitol, but also other lignocellulose-derived polyols, which can be achieved, for example, by optimizing the reaction parameters, as already shown by the observed effects of the catalysts, pH values, and H2 pressures.
- Sun, Jiying,Liu, Haichao
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experimental part
p. 135 - 142
(2011/04/15)
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- Heteropoly acids as efficient acid catalysts in the one-step conversion of cellulose to sugar alcohols
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Cellulose and even spruce can be converted efficiently into valuable platform chemicals via combined hydrolysis and hydrogenation in the aqueous phase. Thereby, heteropoly acids together with supported ruthenium catalysts show not only high activity but also remarkable selectivity to sugar alcohols reaching up to 81% yield of C4 to C6 sugar alcohols in only 7 h at 160 °C.
- Palkovits, Regina,Tajvidi, Kameh,Ruppert, Agnieszka M.,Procelewska, Joanna
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supporting information; experimental part
p. 576 - 578
(2011/03/17)
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- Hydrogenolysis of cellulose combining mineral acids and hydrogenation catalysts
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A catalytic system capable of reaching high performance in the hydrogenolysis of cellulose at low reaction temperature and short reaction times has been developed. Therefore, supported noble metal catalysts based on Pt, Pd and Ru have been combined with dilute mineral acids. A broad variable set in terms of type of noble metal, type of acid, acid concentration and reaction time could be evaluated based on chemical interpretation and supported by a Design of Experiment (DoE) approach. The variables significantly influenced conversion of cellulose, product range and selectivity towards sugar alcohol formation. Thus, at 160 °C, above 60% yield in sugars and sugar alcohols with 84% selectivity at a cellulose conversion of 72% could be reached. Besides, glycerol, propylene glycol, ethylene glycol and methanol were formed as additional valuable by-products leading to an overall carbon utilization above 89%. Furthermore, the concept was successfully transferred to real feedstocks in the form of spruce reaching close to 60% conversion in only one hour reaction time.
- Palkovits, Regina,Tajvidi, Kameh,Procelewska, Joanna,Rinaldi, Roberto,Ruppert, Agnieszka
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scheme or table
p. 972 - 978
(2010/08/19)
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- Sorbitol Conversion Process
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A process for converting aqueous sorbitol to xylitol and isosorbide in the presence of an acid catalyst, and in the absence of an enzyme or of a hydrogenating catalyst, is disclosed. In the process, a sorbitol solution is reacted with an acid zeolite to produce xylitol and isosorbide.
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Page/Page column 2
(2008/12/04)
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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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- Multiple Forms of Xylose Reductase in Candida intermedia: Comparison of Their Functional Properties Using Quantitative Structure-Activity Relationships, Steady-State Kinetic Analysis, and pH Studies
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The xylose-fermenting yeast Candida intermedia produces two isoforms of xylose reductase: one is NADPH-dependent (monospecific xylose reductase; msXR), and another is shown here to prefer NADH ≈4-fold over NADPH (dual specific xylose reductase; dsXR). To compare the functional properties of the isozymes, a steady-state kinetic analysis for the reaction D-xylose + NAD(P)H + H + ? xylitol + NAD(P)+ was carried out and specificity constants (kcat/Kaldehyde) were measured for the reduction of a series of aldehydes differing in side-chain size as well as hydrogen-bonding capabilities with the substrate binding pocket of the enzyme. dsXR binds NAD(P)+ (KiNAD+ = 70 μM; KiNADP+ = 55 μM) weakly and NADH (Ki = 8 μM) about as tightly as NADPH (Ki = 14 μM). msXR shows uniform binding of NADPH and NADP + (KiNADP+ ≈ KiNADPH = 20 μM). A quantitative structure-activity relationship analysis was carried out by correlating logarithmic kcat/Kaldehyde values for dsXR with corresponding logarithmic kcat/Kaldehyde values for msXR. This correlation is linear with a slope of ≈1 (r2 = 0.912), indicating that no isozyme-related pattern of substrate specificity prevails and aldehyde-binding modes are identical in both XR forms. Binary complexes of dsXR-NADH and msXR-NADPH show the same macroscopic pK of ≈9.0-9.5, above which the activity is lost in both enzymes. A lower pK of 7.4 is seen for dsXR-NADPH. Specificity for NADH and greater binding affinity for NAD(P)H than NAD(P)+ are thus the main features of enzymic function that distinguish dsXR from msXR.
- Nidetzky, Bernd,Brueggler, Kaspar,Kratzer, Regina,Mayr, Peter
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p. 7930 - 7935
(2007/10/03)
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- Catalytic hydrogenation of arabinonic acid and lactones to arabitol
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Aqueous solutions (20 wt%) of arabinonic acid in equilibrium with arabinonolactones were hydrogenated on ruthenium catalysts at 100°C or lower temperatures in a batch reactor. The highest selectivity to arabitol was 98.9% at 98% conversion, with a reaction rate of 73 mmol h-1 gRu-1 at 80°C. Reaction modeling was achieved by a detailed kinetic analysis of reaction data under various reaction conditions. The conversion of substrate follows a rate equation established with the Horiuti-Polanyi mechanism. The selectivity was higher on small particles supported on carbon supports because of an electron-donating effect of the support on the ruthenium particles, which decreases the rate of dehydroxylation reactions leading to unwanted deoxy products. The most important factor enhancing the selectivity was the presence of anthraquinone-2-sulfonate (A2S), which decreased the formation of deoxy products. With an optimum amount of A2S the selectivity at 100°C was improved from 93.6 to 96.7%. The molecule acted as a permanent surface modifier since the catalyst was recycled with the same selectivity without further addition of A2S. The molecule could act as an electron-donating surface ligand decreasing the rate of dehydroxylation reactions.
- Fabre, Lionel,Gallezot, Pierre,Perrard, Alain
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p. 247 - 254
(2007/10/03)
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- Scorzonerosides A, B and C, novel triterpene oligoglycosides with hepatoprotective effect from Chinese Bupleuri radix, the roots of Bupleurum scorzonerifolium Willd.
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Triterpene glycoside adonitol esters, scorzonerosides A, B, and C, were isolated from Chinese Bupleuri Radix, the roots of Bupleurum scorzonerifolium. Their absolute stereostructures were elucidated on the physicochemical and chemical evidence, which included the synthesis of the adonitol moiety from D-ribose. Scorzonerosides A, B, and C were found to show hepatoprotective effect on liver injury induced by D-galactosamine and lipopolysaccharide in mice.
- Yoshikawa, Masayuki,Murakami, Toshiyuki,Hirano, Kazuhiro,Inadzuki, Masahiro,Ninomiya, Kiyofumi,Matsuda, Hisashi
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p. 7395 - 7398
(2007/10/03)
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- Stereospecific carbon-carbon bond formation using rabbit muscle aldolase
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Approaches to the enantiospecific syntheses of shikimic acid and immunoactivator FR 900483 utilising Rabbit Muscle Aldolase condensations have been described.
- Sawden, J,Turner, N J
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- Synthesis of D-erythro-2-pentulose and D-threo-2-pentulose and analysis of the 13C- and 1H-n.m.r. spectra of the 1-13C- and 2-13C-substituted sugars.
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The pentuloses D-erythro-2-pentulose (1) and D-threo-2-pentulose (2) and their 1-13C- and 2-13C-substituted derivatives were prepared by hydrogenating the corresponding isotopically normal and 13C-substituted D-pentos-2-uloses with a Pd-carbon catalyst. The threo isomer and its labeled derivatives were alternatively prepared from isotopically normal and 13C-substituted D-xyloses with immobilized D-xylose (D-glucose) isomerase (E.C.5.3.1.5). The equilibrium compositions of 1 and 2 (furanose anomers and acyclic keto forms) in 2H2O were determined from 13C-n.m.r. spectra (75 MHz) of the 2-13C-labeled derivatives. The conformational properties of the cyclic and acyclic forms in 2H2O were assessed with the use of 1H-1H, 13C-1H, and 13C-13C spin-coupling constants obtained from 1H-n.m.r. (620 MHz) and 13C-n.m.r. (75 MHz) spectra. Compared with the structurally related aldotetrofuranoses the 2-pentulofuranoses more strongly prefer conformations in which the anomeric hydroxyl group is oriented quasi-axially. The strongly dipolarized carbonyl group in the acyclic keto forms of 1 and 2 appears to stabilize chain conformations having O-1 and O-3 eclipsed with the carbonyl oxygen.
- Vuorinen,Serianni
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- (1-13C)alditols: elimination of magnetic equivalence in 1H- and 13C-n.m.r. spectra of symmetric compounds through (13C)-substitution.
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(1-13C)Glycerol, D-(1-13C)arabinitol, D-(1-13C)ribitol, D-(1-13C)xylitol, D-(1-13C)glucitol, D-(1-13C)mannitol, and D-(1-13C)talitol have been prepared by NaBH4 reduction of the corresponding (1-13C)aldoses. A comparison of the 1H- (300 and 620 MHz) and 13C (75 MHz) n.m.r. spectra of natural and (1-13C)-substituted dissymmetric alditols has permitted the unequivocal assignments of their hydroxymethyl proton and carbon signals and the measurement of several 13C-1H and 13C-13C spin-coupling constants. Similar spectra of (1-13C)-substituted symmetric alditols, however, are more difficult to interpret since they are composed of overlapping 13C-coupled and 13C-noncoupled subspectra. In some cases, 1H difference spectra and 1H-coupled 13C spectra may be used to extract the 13C-1H and 13C-13C spin couplings from the 13C-coupled component. These couplings have been examined in light of conformational models previously proposed, permitting a preliminary evaluation of standard 3JCH and 3JCC values for specific coupling pathways in these compounds.
- Garrett,Serianni
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- Analysis of Aldoses and Alditols by Capillary Gas Chromatography as Alditol Trifluoroacetates
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Analysis of aldoses and alditols by capillary gas chromatography as alditol trifluoroacetates was carried out by using a fused silica capillary column (cyanopropyl-bonded phase) and a hydrogen flame ionization detector.Seventeen alditols were completely resolved within 18 min.The detection limits were about 1-4 ng/injection which are one hundred times smaller than as those of a packed column.Special care was necessary in the use of internal standards for the simultaneous determination of multiple components, and good reproducibility was obtained by using double internal standards.Keywords- aldose; alditol; alditol trifluoroacetate; capillary gas chromatography
- Haga, Hidehiko,Nakajima, Terumi
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p. 1562 - 1564
(2007/10/02)
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- Stereoselective Synthesis of β,γ-Unsaturated- and β,γ-Epoxy Glycerol Derivatives starting with Glyceraldehyde and their Use in the Synthesis of Alditols
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Highly stereoselective addition of vinylcopper and vinylcuprate compounds to glyceraldehyde acetonide affords both syn- and anti-β,γ-unsaturated glycerol derivatives, respectively, which can readily be converted into all the possible steric isomers of the β,γ-epoxy glycerol derivatives, which are useful intermediates in the synthesis of alditols.
- Kusakabe, Masato,Sato, Fumie
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p. 989 - 991
(2007/10/02)
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- ON STEREOCHEMISTRY OF OSMIUM TETRAOXIDE OXIDATION OF ALLYLIC ALCOHOL SYSTEMS. EMPIRICAL RULE
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An empirical formulation is presented to predict the stereochemistry of major osmylation products of allylic alcohols and their derivatives.
- Cha, J. K.,Christ, W. J.,Kishi, Y.
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p. 2247 - 2256
(2007/10/02)
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- Cologne consisting of microcapsule suspension
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Described are hydro-alcohol compositions of matter including, but not limited to, colognes, after-shave lotions, after-bath preparations and splash lotions, which yield continuously high fragrance intensity release, evenly and uniformly over an extended period of time and which can be adapted to yield differing aromas from a qualitative and quantitative standpoint in a controllable manner containing a mixture of (i) a non-confined fragrance composition; (ii) one or more fragrance oils which are physically entrapped in one or more types of solid particles and (iii) a suspending agent such as hydroxypropyl cellulose, silica, xanthan gum, ethyl cellulose or combinations of the previously mentioned four substances; the non-confined fragrance substance, the entrapped fragrance oil and the suspension agent being premixed prior to the subsequent creation of the hydro-alcohol compositions of matter.
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- Regioselective and Stereoselective Methods for the Synthesis of the Pentitols
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Several different approaches to the stereoselective synthesis of xylitol (1), as well as the other two pentitols, ribitol (2) and DL-arabinitol DL-(3), from the (Z)- and (E)-1-hydroxypentadienes (4) and (5) and the (Z)- and (E)-4,5-epoxypent-2-enals (6) and (7) are described.They rely upon either (a) epoxidations of allylic C=C double bonds followed by stereospecific (anti) and sometimes regioselective epoxide cleavages, or (b) syn-hydroxylations of allylic C=C double bonds.Employing approach (a), the (Z)-isomers (4) and (6) do not afford any ribitol (2) among the products and the (E)-isomers do not afford any xylitol (1).The consequences are reversed when approach (b) is adopted.The most convenient synthesis of xylitol (1) starts from the (Z)-isomer (6) of 4,5-epoxypent-2-enal.The formyl group in (6) is reduced, provided acidic work-up conditions are employed, to yield (Z)-(4RS)-4,5-epoxy-1-hydroxypent-2-ene (9), which is characterised as its acetate (10).Opening of the epoxide ring in (10) with acetate ion gives the triacetate (11), which is deacetylated to afford a key intermediate, (Z)-(4RS)-1,4,5-trihydroxypent-2-ene (12).Epoxidation of (12) with peracids (e.g. p-nitroperbenzoic acid) yields (t-butyl hydroperoxide with catalytically active Ti4+, V5+, and Mo6+ complexes fails) two epoxides (13) and (14), arbitrarily named isomers A (13) and B (14) subsequently shown to have the relative stereochemistries (2S,3R,4R) and (2R,3R,4R), respectively.Epoxide ring opening with acetate ion in acetic anhydride of the more abundant isomer B (14), obtained with 70percent diastereoselectivity, yields xylitol penta-acetate (16) as the major product (>80percent diastereoselectivity) along with small and trace amounts of the other two pentitol penta-acetates.Epoxide ring opening of isomer A with acetate ion in acetic anhydride is not a straightforward reaction for the most part and has been found to involve the intermediacy of an isolatable bicyclic orthoester (23) en route to some of the xylitol penta-acetate (16) formed as the principal stable product during this reaction.These variations of approach (a) constitute stereoselective syntheses of xylitol (1), which are claimed to be acceptable on a laboratory scale.They provide a slightly better route than an alternative one involving the transformations (4) -> (33) -> (34) -> (39) -> (16) -> (1), starting from (Z)-1-hydroxypenta-2,4-diene (4), principally because this particular precursor is less readily accessible than (Z)-4,5-epoxypent-2-enal (6).By contrast, the (E)-isomer (5) of 1-hydroxypenta-2,5-diene is obtainable in high yield from the reduction of vinyl acrylic acid and the analogous transformations (26) -> (27) -> (28) -> DL-(5) -> DL-(3)> provide a highly stereoselective (91percent) synthetic route to DL-arabinitol DL-(3).Osmium-catalysed syn-hydroxylation of (E)-(4RS)-triacetoxypent-2-ene (22), prepared from (E)-4,5-epoxypent-2-enal (7) in two steps (20) -> (22)>, provides yet another...
- Holland, David,Stoddart, J. Fraser
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p. 1553 - 1571
(2007/10/02)
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- ON STEREOCHEMISTRY OF OSMIUM TETROXIDE OXIDATION OF ALLYLIC ALCOHOL SYSTEMS: EMPIRICAL RULE
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An empirical formulation is presented to predict the stereochemistry of major osmylation products of allylic alcohols and their derivatives.
- Cha, J. K.,Christ, W. J.,Kishi, Y.
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p. 3943 - 3946
(2007/10/02)
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- Synthesis of Saccharides and Related Polyhydroxylated Natural Products. 1. Simple Alditols
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A new approach to sugar synthesis is demonstrated through syntheses of tetritols, pentitols, and hexitols; titanium-catalyzed asymmetric epoxidation and a new selective opening reaction of 2,3-epoxy alcohols play essential roles.
- Katsuki, T.,Lee, A. W. M.,Ma, P.,Martin, V. S.,Masamune, S.,et al.
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p. 1373 - 1378
(2007/10/02)
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- STEREOSELECTIVE EPOXIDATION OF DIVINYLMETHANOL: A SYNTHETIC APPROACH TO THE PENTITOLS
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Peroxy-acid epoxidation of divinylmethanol (9), followed by acetylation afforded the acetylated monoepoxides 1 and 2 having the erythro (53percent) and threo (47percent) configurations.Peroxy-acid epoxidation of 1 and 2 yielded the acetylated diepoxides 3 (erythro-erythro, 36percent) and 4 (erythro-threo, 64percent) (from 1), and 4 (erythro-threo, 47percent) and 5 (threo-threo, 53percent) (from 2).Relative configurational assignments were made to 1-5 on the basis of (a) (1)H-n.m.r. chemical-shift and coupling-constant data, (b) the observation that 1 gave only 3 and 4, and that 2 gave only 4 and 5 on epoxidation, and (c) the fact that 3-5 separately undergo epoxidering opening preferentially at their primary carbon atoms with acetate ion in acetic anhydride, to afford the penta-acetates of ribitol, DL-arabinitol, and xylitol, respectively, as major products.Epoxide-ring formation favours the erythro configuration when either peroxy acids or tert-butyl hydroperoxide with catalitically active Ti(4+), V(5+), or Mo(6+) complexes are employed as epoxidation reagents.However, the diastereoselectivities characterising the epoxidations and the regioselectivities governing the epoxide-ring openings are not sufficiently high to constitute an attractive synthesis of euther ribitol, DL-arabinitol, or xylitol from divinylmethanol.
- Holland, David,Stoddart, J. Fraser
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p. 207 - 220
(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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- THE 13C-N.M.R. SPECTRA OF ALDITOLS
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The 13C-n.m.r. signals of the pentitols and hexitols in aqueous solution, and of their acetates in chloroform solution, have been assigned by tthe use of specifically deuterium-substituted compounds.Qualitative correlations have been established between the chemical shifts and the configuration and preponderant conformation of each of the alditols.
- Angyal, Stephen J.,Fur, Ronan Le
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p. 201 - 210
(2007/10/02)
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