- Product Control and Insight into Conversion of C6 Aldose Toward C2, C4 and C6 Alditols in One-Pot Retro-Aldol Condensation and Hydrogenation Processes
-
Alcohols have a wide range of applicability, and their functions vary with the carbon numbers. C6 and C4 alditols are alternative of sweetener, as well as significant pharmaceutical and chemical intermediates, which are mainly obtained through the fermentation of microorganism currently. Similarly, as a bulk chemical, C2 alditol plays a decisive role in chemical synthesis. However, among them, few works have been focused on the chemical production of C4 alditol yet due to its difficult accumulation. In this paper, under a static and semi-flowing procedure, we have achieved the product control during the conversion of C6 aldose toward C6 alditol, C4 alditol and C2 alditol, respectively. About C4 alditol yield of 20 % and C4 plus C6 alditols yield of 60 % are acquired in the one-pot conversion via a cascade retro-aldol condensation and hydrogenation process. Furthermore, in the semi-flowing condition, the yield of ethylene glycol is up to 73 % thanks to its low instantaneous concentration.
- Gao, Lou,Hou, Wenrong,Hui, Yingshuang,Tang, Yi,Zhan, Yulu,Zhang, Yahong
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p. 560 - 566
(2021/06/25)
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- Photocatalytic Conversion of Xylose to Xylitol over Copper Doped Zinc Oxide Catalyst
-
Abstract: In the present investigation, photocatalytic conversion of xylose by Copper (Cu) doped Zinc oxide (ZnO) was investigated under Ultraviolet Light emitting diode (UVA-LED) illumination. Photocatalysts were synthesized successfully by chemical prec
- Rohini,Hebbar, H. Umesh
-
p. 2583 - 2594
(2021/02/05)
-
- Hydrogenolysis of sorbitol into valuable C3-C2 alcohols at low H2 pressure promoted by the heterogeneous Pd/Fe3O4 catalyst
-
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)
-
- CYCLIC COMPOUND
-
The present invention provides compounds having a Toll-like receptor 4 (TLR4) signaling inhibitory action useful as preventive and therapeutic drugs of autoimmune disease and/or inflammatory disease or diseases such as chemotherapy-induced peripheral neuropathy (CIPN), chemotherapy-induced neuropathic pain (CINP), liver injury, ischemia-reperfusion injury (IRI) and the like. The present invention relates to a compound represented by formula (I) and a salt thereof: (wherein, each symbol is explained in greater detail in the specification).
- -
-
Paragraph 0321
(2018/04/13)
-
- Effect of tungsten surface density of WO3-ZrO2 on its catalytic performance in hydrogenolysis of cellulose to ethylene glycol
-
One-pot hydrogenolysis of cellulose to ethylene glycol (EG) was carried out on WO3-based catalysts combined with Ru/C. To probe the active catalytic site for breaking the C-C bond of cellulose, a series of WO3-ZrO2 (WZr) catalysts were synthesized and systematically characterized with XRD, Raman, UV-Vis, H2-TPR, DRIFS and XPS techniques and N2 physisorption experiment. It was found that the WO3 crystallites became more easily reduced to W5+-OH species with increasing crystallite size or tungsten surface density of the WZr catalyst owing to the decrease of their absorption edge energy (AEE) originating from weakening their interaction with ZrO2 support. This, as a result, gave higher EG yield at higher tungsten surface density. The structure-activity relationship of the WZr catalyst reveals that the active catalytic site for cleaving the C2-C3 bond of the glucose molecule is the W5+-OH species.
- Chai, Jiachun,Zhu, Shanhui,Cen, Youliang,Guo, Jing,Wang, Jianguo,Fan, Weibin
-
p. 8567 - 8574
(2017/02/10)
-
- CYCLIC COMPOUNDS
-
The present invention provides compounds having a Toll-like receptor 4 (TLR4) signaling inhibitory action useful as preventive and therapeutic drugs of inflammatory disease and/or central nervous system disease or diseases such as chemotherapy-induced peripheral neuropathy (CIPN), chemotherapy-induced neuropathic pain (CINP), liver injury, ischemia-reperfusion injury (IRI) and the like. The present invention relates to a compound represented by formula (I) and a salt thereof: (wherein, each symbol is explained in greater detail in the specification).
- -
-
Page/Page column 0669; 0670; 0671
(2016/11/24)
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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
-
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
-
-
- A facile synthesis of vicinal cis-diols from olefins catalyzed by in situ generated MnxOy nanoaggregates
-
A novel protocol for the practical and green synthesis of vicinal cis-diols from 10.0 mmol olefins by using 5.0 mmol KMnO4 as oxidant and 30.0 mmol H2O2 as co-oxidant is reported. The presented procedure is easy to carry out and enables the direct transformation of linear and cyclic alkenes to the corresponding vicinal cis-diols. The synthesis of vicinal cis-diols by dihydroxylation of olefins with a KMnO4/H2O2 system was catalyzed by in situ generated MnxOy nanoaggregates. The use of H2O2 as a co-oxidant is the key for the protocol to synthesize vicinal cis-diols in high yields, because it assists the oxidation of MnxOy nanoaggregates, which have an active role in the oxidation reaction medium.
- Dalmizrak, Di?dem,G?ksu, Haydar,Gültekin, Mehmet Serdar
-
p. 20751 - 20755
(2015/03/18)
-
- A method for producing isomaltooligo hydrogenolytic
-
PROBLEM TO BE SOLVED: To provide a method for producing a hydrogenolysis product of erythritol, with which the erythritol is efficiently subjected to hydrogenolysis in mild conditions to provide butane-mono, di or triol.SOLUTION: The method for producing the hydrogenolysis product of erythritol includes a process of reacting the erythritol and hydrogen in the presence of a catalyst to prepare at least one of compound selected from butane-mono, di and triol, wherein, as the catalyst, a catalyst prepared by depositing at least one of metal component selected from a group comprising iridium, platinum, rhodium, cobalt, palladium and nickel is used.
- -
-
Paragraph 0079-0081
(2017/01/02)
-
- Unravelling the Ru-Catalyzed Hydrogenolysis of Biomass-Based Polyols under Neutral and Acidic Conditions
-
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)
-
- Conversion of glucose and sorbitol in the presence of Ru/C and Pt/C catalysts
-
The conversion of glucose and sorbitol in the presence of Ru and Pt catalysts supported on carbon was carried out at different pressure and temperature conditions, using a batch and a semi-batch reactor. Attempts were made to improve the selectivity of glycols and alcohols (ethanol), introducing a promoter and inhibiter of the hydrogenolysis in the reactant mixture. On the basis of these results, which confirm the higher activity of Ru with respect to Pt, and the important role of an inhibitor like sulphur, the mechanism driving these reactions and the promising thermocatalytic conditions are clearer. This journal is
- Tronci, Stefania,Pittau, Barbara
-
p. 23086 - 23093
(2015/06/02)
-
- Acid-catalyzed reactions of epoxides for atmospheric nanoparticle growth
-
Although new particle formation accounts for about 50% of the global aerosol production in the troposphere, the chemical species and mechanism responsible for the growth of freshly nucleated nanoparticles remain largely uncertain. Here we show large size
- Xu, Wen,Gomez-Hernandez, Mario,Guo, Song,Secrest, Jeremiah,Marrero-Ortiz, Wilmarie,Zhang, Annie L.,Zhang, Renyi
-
supporting information
p. 15477 - 15480
(2015/02/18)
-
- Selective hydrogenolysis of biomass-derived xylitol to ethylene glycol and propylene glycol on Ni/C and basic oxide-promoted Ni/C catalysts
-
The selective hydrogenolysis of xylitol to ethylene glycol and propylene glycol was examined on Ni/C catalysts in the presence of solid bases, e.g. Ca(OH)2 and CeO2, physically mixed with or co-supported with Ni on C. Compared with Ru/C, the Ni/C catalysts were more selective to the two target glycols under identical conditions, apparently as a result of their lower hydrogenation activity and consequently favored the CC cleavage of xylose intermediate by the base catalyst over its competitive hydrogenation on the Ni particles. Noticeably, the presence of the solid bases rendered the Ni particles resistant to leaching and sintering, and thus stable in the xylitol hydrogenolysis. Supporting the solid bases, especially CeO2 and CaO, with the Ni particles on C led not only to a reduction in the amount of solid bases required, but also efficient formation of the two glycols with negligible lactic acid. For instance, on Ni-CaO/C (at a CaO/Ni molar ratio of 0.66), the combined selectivity to ethylene glycol and propylene glycol, together with glycerol, reached 69.5% at nearly 100% xylitol conversion at 473 K, 4.0 MPa H2. These features of the basic oxide-promoted Ni catalysts show their promising advantages over the noble Ru catalysts, upon optimization of their compositions and structures, and the reaction parameters, for the efficient hydrogenolysis of xylitol and other lignocellulose-derived polyols to produce the two target glycols.
- Sun, Jiying,Liu, Haichao
-
-
- Direct conversion of cellulose into acetol on bimetallic Ni-SnO x/Al2O3 catalysts
-
The direct conversion of cellulose into acetol was studied on SnO x-modified Ni/Al2O3 catalysts with different Sn/Ni atomic ratios in the range of 0-2.0. The selectivity to acetol strongly depended on the Sn/Ni ratios, which reached the highest value of 53.9% at the ratio of 0.5, compared at similar cellulose conversions (~20%). On Ni-SnOx/Al2O3 (Sn/Ni = 0.5), cellulose, glucose and fructose converted to acetol in high yields of approximately 35%, 53% and 73%, respectively, at 210 °C and 6 MPa H2. The effects of the Sn/Ni ratios on the acetol selectivity appear to be related to their effects on the hydrogenation activity of the Ni-SnOx/Al2O3 catalysts that decreased with increase of the Sn/Ni ratios, and to the relative rate between the hydrogenation of C6 sugar intermediates (e.g. glucose and fructose) and their degradation intermediates (e.g. glyceraldeyde and dihydroxyacetone) involved in the cellulose reaction on the Ni particles and the isomerization of glucose to fructose and their CC bond cleavage by retro-aldol condensation on the SnOx domains. Comparison of SnO x with CeOx, ZnOx and AlOx supported on Al2O3 with different basicity suggested that the larger concentration of stronger basic sites on SnOx facilitated the isomerizaiton of glucose to fructose and its subsequent CC bond cleavage. These results and their understanding provide guidance for improving the acetol production from cellulose by tuning the catalytic functions required for the involved reactions of hydrogenation on the metal surfaces, and isomerization and CC bond cleavage on the basic sites.
- Deng, Tianyin,Liu, Haichao
-
-
- Conversion of sugars to ethylene glycol with nickel tungsten carbide in a fed-batch reactor: High productivity and reaction network elucidation
-
Bifunctional nickel tungsten carbide catalysis was used for the conversion of aqueous sugar solutions into short-chain polyols such as ethylene glycol. It is shown that very concentrated sugar solutions, viz. up to 0.2 kg L -1, can be converted without loss of ethylene glycol selectivity by gradually feeding the sugar solution. Detailed investigation of the reaction network shows that, under the applied reaction conditions, glucose is converted via a retro-aldol reaction into glycol aldehyde, which is further transformed into ethylene glycol by hydrogenation. The main byproducts are sorbitol, erythritol, glycerol and 1,2-propanediol. They are formed through a series of unwanted side reactions including hydrogenation, isomerisation, hydrogenolysis and dehydration. Hydrogenolysis of sorbitol is only a minor source of ethylene glycol. To assess the relevance of the fed-batch system in biomass conversions, both the influence of the catalyst composition and the reactor setup parameters like temperature, pressure and glucose addition rate were optimized, culminating in ethylene glycol yields up to 66% and separately, volume productivities of nearly 300 gEG L-1 h-1.
- Ooms, Roselinde,Dusselier, Michiel,Geboers, Jan A.,Op De Beeck, Beau,Verhaeven, Rick,Gobechiya, Elena,Martens, Johan A.,Redl, Andreas,Sels, Bert F.
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p. 695 - 707
(2014/02/14)
-
- Rabbit 3-hydroxyhexobarbital dehydrogenase is a NADPH-preferring reductase with broad substrate specificity for ketosteroids, prostaglandin D2, and other endogenous and xenobiotic carbonyl compounds
-
3-Hydroxyhexobarbital dehydrogenase (3HBD) catalyzes NAD(P) +-linked oxidation of 3-hydroxyhexobarbital into 3-oxohexobarbital. The enzyme has been thought to act as a dehydrogenase for xenobiotic alcohols and some hydroxysteroids, but its physiological function remains unknown. We have purified rabbit 3HBD, isolated its cDNA, and examined its specificity for coenzymes and substrates, reaction directionality and tissue distribution. 3HBD is a member (AKR1C29) of the aldo-keto reductase (AKR) superfamily, and exhibited high preference for NADP(H) over NAD(H) at a physiological pH of 7.4. In the NADPH-linked reduction, 3HBD showed broad substrate specificity for a variety of quinones, ketones and aldehydes, including 3-, 17- and 20-ketosteroids and prostaglandin D2, which were converted to 3α-, 17β- and 20α-hydroxysteroids and 9α,11β- prostaglandin F2, respectively. Especially, α-diketones (such as isatin and diacetyl) and lipid peroxidation-derived aldehydes (such as 4-oxo- and 4-hydroxy-2-nonenals) were excellent substrates showing low Km values (0.1-5.9 μM). In 3HBD-overexpressed cells, 3-oxohexobarbital and 5β-androstan-3α-ol-17-one were metabolized into 3-hydroxyhexobarbital and 5β-androstane-3α,17β-diol, respectively, but the reverse reactions did not proceed. The overexpression of the enzyme in the cells decreased the cytotoxicity of 4-oxo-2-nonenal. The mRNA for 3HBD was ubiquitously expressed in rabbit tissues. The results suggest that 3HBD is an NADPH-preferring reductase, and plays roles in the metabolisms of steroids, prostaglandin D2, carbohydrates and xenobiotics, as well as a defense system, protecting against reactive carbonyl compounds.
- Endo, Satoshi,Matsunaga, Toshiyuki,Matsumoto, Atsuko,Arai, Yuki,Ohno, Satoshi,El-Kabbani, Ossama,Tajima, Kazuo,Bunai, Yasuo,Yamano, Shigeru,Hara, Akira,Kitade, Yukio
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p. 1366 - 1375
(2013/11/19)
-
- Promoting effect of SnOx on selective conversion of cellulose to polyols over bimetallic Pt-SnOx/Al2O3 catalysts
-
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
-
p. 116 - 124
(2013/02/26)
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- Asymmetric organocatalytic formation of protected and unprotected tetroses under potentially prebiotic conditions
-
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
-
experimental part
p. 1565 - 1570
(2012/04/05)
-
- Probing the ruthenium-catalyzed higher polyol hydrogenolysis reaction through the use of stereoisomers
-
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)
-
- Efficient asymmetric organocatalytic formation of erythrose and threose under aqueous conditions
-
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)
-
- Properties and tissue distribution of a novel aldo-keto reductase encoding in a rat gene (Akr1b10)
-
A recent rat genomic sequencing predicts a gene Akr1b10 that encodes a protein with 83% sequence similarity to human aldo-keto reductase (AKR) 1B10. In this study, we isolated the cDNA for the rat AKR1B10 (R1B10) from rat brain, and examined the enzymatic properties of the recombinant protein. R1B10 utilized NADPH as the preferable coenzyme, and reduced various aldehydes (including cytotoxic 4-hydroxy-2-hexenal and 4-hydroxy- and 4-oxo-2-nonenals) and α-dicarbonyl compounds (such as methylglyoxal and 3-deoxyglucosone), showing low Km values of 0.8-6.1μM and 3.7-67μM, respectively. The enzyme also reduced glyceraldehyde and tetroses (Km=96-390μM), although hexoses and pentoses were inactive and poor substrates, respectively. Among the substrates, 4-oxo-2-nonenal was most efficiently reduced into 4-oxo-2-nonenol, and its cytotoxicity against bovine endothelial cells was decreased by the overexpression of R1B10. R1B10 showed low sensitivity to aldose reductase inhibitors, and was activated to approximately two folds by valproic acid, and alicyclic and aromatic carboxylic acids. The mRNA for R1B10 was expressed highly in rat brain and heart, and at low levels in other rat tissues and skin fibroblasts. The results suggest that R1B10 functions as a defense system against oxidative stress and glycation in rat tissues.
- Endo, Satoshi,Matsunaga, Toshiyuki,Kuragano, Tsukasa,Ohno, Satoshi,Kitade, Yukio,Tajima, Kazuo,El-Kabbani, Ossama,Hara, Akira
-
experimental part
p. 230 - 237
(2011/10/30)
-
- Hot water-promoted ring-opening of epoxides and aziridines by water and other nucleopliles
-
Effective hydrolysis of epoxides and aziridines was conducted by heating them in water at 60 or 100 °C. Other types of nucleophile such as amines, sodium azide, and thiophenol could also efficiently open epoxides and aziridines in hot water. It was proposed that hot water acted as a modest acid catalyst, reactant, and solvent in the hydrolysis reactions.
- Wang, Zhi,Cui, Yong-Tao,Xu, Zhao-Bing,Qu, Jin
-
p. 2270 - 2274
(2008/09/19)
-
- Preparation of 2,3,4-trihydroxybutylarsonic acid: A starting compound for novel arsonolipids
-
Possible routes for the preparation of 2,3,4-trihydroxybutylarsonic acid, a key compound for the synthesis of novel arsonolipids, were experimentally evaluated. The best substrate was found to be 3,4-epoxybutane-1,2-diol. Its reaction with alkaline sodium arsenite, "Na3AsO3," gave the arsonic acid in 50% yield, as two pairs of diastereoisomers, each pair being a racemic mixture. Copyright Taylor & Francis Group, LLC.
- Lala, Maria A.,Tsivgoulis, Gerasimos M.,Ioannou, Panayiotis V.
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p. 2747 - 2760
(2008/12/22)
-
- Methods for the electrolytic production of erythrose or erythritol
-
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.
- -
-
Page/Page column 8-9
(2008/06/13)
-
- Rhodium-catalyzed decarbonylation of aldoses
-
(Chemical Equation Presented) A catalytic procedure is described for decarbonylation of unprotected aldoses to afford alditols with one less carbon atom. The reaction is performed with the rhodium complex Rh(dppp)2Cl in a refluxing diglyme-DMA solution. A slightly improved catalyst turnover is observed when a catalytic amount of pyridine is added. Under these conditions most hexoses and pentoses undergo decarbonylation into the corresponding pentitols and tetrols in isolated yields around 70%. The reaction has been applied as the key transformation in a five-step synthesis of L-threose from D-glucose.
- Monrad, Rune Nygaard,Madsen, Robert
-
p. 9782 - 9785
(2008/03/17)
-
- Amino acid catalyzed neogenesis of carbohydrates: A plausible ancient transformation
-
Hexose sugars play a fundamental role in vital biochemical processes and their biosynthesis is achieved through enzyme-catalyzed pathways. Herein we disclose the ability of amino acids to catalyze the asymmetric neogenesis of carbohydrates by sequential cross-aldol reactions. The amino acids mediate the asymmetric de novo synthesis of natural L- and D-hexoses and their analogues with excellent stereoselectivity in organic solvents. In some cases, the four new stereocenters are assembled with almost absolute stereocontrol. The unique feature of these results is that, when an amino acid is employed as the catalyst, a single reaction sequence can convert a protected glycol aldehyde into a hexose in one step. For example, proline and its derivatives catalyze the asymmetric neogenesis of allose with > 99% ee in one chemical manipulation. Furthermore, all amino acids tested catalyzed the asymmetric formation of natural sugars under prebiotic conditions, with alanine being the smallest catalyst. The inherent simplicity of this catalytic process suggests that a catalytic prebiotic "gluconeogenesis" may occur, in which amino acids transfer their stereochemical information to sugars. In addition, the amino acid catalyzed stereoselective sequential cross-aldol reactions were performed as a two-step procedure with different aldehydes as acceptors and nucleophiles. The employment of two different amino acids as catalysts for the iterative direct aldol reactions enabled the asymmetric synthesis of deoxysugars with > 99% ee. In addition, the direct amino acid catalyzed C2+C 2+C2 methodology is a new entry for the short, highly enantioselective de novo synthesis of carbohydrate derivatives, isotope-labeled sugars, and polyketide natural products. The one-pot asymmetric de novo syntheses of deoxy and polyketide carbohydrates involved a novel dynamic kinetic asymmetric transformation (DYKAT) mediated by an amino acid.
- Cordova, Armando,Ibrahem, Ismail,Casas, Jesus,Sunden, Henrik,Engqvist, Magnus,Reyes, Efraim
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p. 4772 - 4784
(2007/10/03)
-
- NaIO4/LiBr-mediated diastereoselective dihydroxylation of olefins: A catalytic approach to the prevost-woodward reaction
-
(Chemical Equation Presented) LiBr catalyzes efficiently the dihydroxylation of alkenes to afford syn and anti diols with excellent diastereoselectivity depending upon the use of NaIO4 (30 mol %) or PhI(OAc)2 (1 equiv), respectively, as the oxidants. The oxidation of non-benzylic halides has been achieved for the first time to afford the corresponding diols in excellent yields.
- Emmanuvel, Lourdusamy,Ali Shaikh, Tanveer Mahammad,Sudalai, Arumugam
-
p. 5071 - 5074
(2007/10/03)
-
- Mild and efficient method for the cleavage of benzylidene acetals by using erbium (III) triflate
-
Er(OTf)3 is proposed as new efficient Lewis acid catalyst in a mild deprotection protocol of benzylidene derivatives. In a modified procedure, where acetic anhydride is used as the reaction solvent, the simultaneous cleavage of the benzylidene acetal and the peracetylation of the substrates is obtained in quantitative yields and very short reaction times. The Royal Society of Chemistry 2005.
- Procopio, Antonio,Dalpozzo, Renato,De Nino, Antonio,Maiuolo, Loredana,Nardi, Monica,Romeo, Giovanni
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p. 4129 - 4133
(2007/10/03)
-
- Prebiotic carbohydrate synthesis: Zinc-proline catalyzes direct aqueous aldol reactions of α-hydroxy aldehydes and ketones
-
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)
-
- Unexpected remarkable stability of primary ozonides derived from alkenyl stannanes. One-pot synthesis of 1,2-diols from alkynes
-
(Matrix Presented) Primary ozonides derived from alkenyl stannanes display an unusual stability and can be transformed into 1,2-diols by treatment with dimethyl sulfide and borane-methyl sulfide complex. This observation has been incorporated into the development of a novel one-pot strategy for the conversion of alkynes into 1,2-diols.
- Gomez, Ana M.,Company, Maria D.,Valverde, Serafin,Lopez, J. Cristobal
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p. 383 - 386
(2007/10/03)
-
- Transformations of 4,5-substituted (4S,5S)-2,2-dimethyl-1,3-dioxolanes
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(4S,5S)-4,5-Bis(hydroxymethyl)-2,2-dimethyl-1,3-dioxolane treated with trifluoromethanesulfonyl chloride in pyridine undergoes tandem substitution of one hydroxy group by a triflate group, and the other by pyridinium moiety. In neutral solvents the (4S,5S)-4,5-bis(hydroxymethyl)-2,2-dimethyl-1,3-dioxolane dilithium salt reacts with trifluoromethanesulfonyl chloride affording both triflates and chlorides and also suffers a cleavage of the dioxolane ring followed by transformations of acyclic products. A triflate cationic complex rhodium cyclooctadiene (4S,5S)-2,3-dihydroxy-1,4-bis(dimemylamino)-2,3-O-isopropylidenebutane was prepared and used as catalyst for hydrogenation of α-acetamidocinnamic and itaconic acids.
- Shainyan,Ustinov,Nindakova
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p. 1757 - 1761
(2007/10/03)
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- Alkylation of partially protected xylofuranoses and tetritols with (2,2,3,3,4,4,5,5,6,6,7,7,7-tridecafluoroheptyl)-oxirane and the stability of protecting acetal groups towards Lewis acid-type catalyst
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1,2-O-Isopropylidene-3-O-methyl-α-D-xylofuranose (2), 1,2-O-isopropylidene-α-D-xylofuranose (3), 2,4-O-ethylidene-D-erythritol (4) and 1,3-O-ethylidene-D-threitol (5) were alkylated with racemic (2,2,3,3,4,4,5,5,6,6,7,7,7-tridecafluoroheptyl)oxirane (1) using boron trifluoride diethyl etherate as a catalyst. The desired mono- or disubstituted polyfluoroalkyl derivatives 6-11 were isolated only in low to medium yields. The fluoroalkylation was accompanied with disproportional distributions of the protecting acetal/ketal groups and polymerization of saccharides. Therefore the stability of 3, 4, 5, 5-O-acetyl-1,2-O-isopropylidene-α-D-xylofuranose (14) and 1,2-O-isopropylidene-α-D-glucofuranose (15) in the presence of a catalytic amount of boron trifluoride diethyl etherate was investigated in various solvents. A mechanism explaining the effect of the catalyst has been proposed.
- Kefurt, Karel,Moravcova, Jitka,Bambasova, Sarka,Buchalova, Katerina,Vymetalikova, Barbora,Kefurtova, Zdenka,Stanek, Jan,Paleta, Oldrich
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p. 1665 - 1681
(2007/10/03)
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- Process for the preparation of optically active alcohols
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Optically active alcohols are prepared by reducing optically active carboxylic acids with hydrogen in the presence of ruthenium catalysts.
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- Optically active phenoxypropionic esters
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Optically active compounds of the formula I STR1 where R is C1 -C12 -alkyl or -perfluoroalkyl in which one or two non-adjacent CH2 or CF2 groups can also be replaced by --O-- and/or --CO-- and/or --CO--O-- and/or --CH=CH-- and/or --CH-halogen-- and/or --CHCN-- and/or --0--CO--CH-halogen-- and/or --O--CO--CHCN--, or is C1 -C12 -alkyl which can have a terminal chemically reactive group and in which a CH2 group can be replaced by --O--, A1 and A2 are each, independently of one another, 1,4-phenylene which is unsubstituted or substituted by one or two F and/or Cl and/or Br atoms and/or CH3 groups and/or CN groups and in which one or two CH groups can also be replaced by N, 1,4-cyclohexylene in which one or two non-adjacent CH2 groups can also be replaced by --O-- and/or --S--, 1,4-piperidinediyl, 1,4-bicyclo[2.2.2]octylene, 2,6-naphthalenediyl, decahydro-2,6-naphthalenediyl or 1,2,3,4-tetrahydro-2,6-naphthalenediyl, A3 is unsubstituted or substituted phenyl, Z is --CO--O--, --O--CO--, --CH2 CH2 --, --OCH2 --, --CH2 O--, --C C-- or a single bond and m is 0, 1, 2 or 3.
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- Compression-moldet meso-erythritol products.
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A surface-modified meso-erythritol preparation in the same form as the commercially available sucrose preparations is disclosed. The preparation is less hygroscopic than sucrose preparations, exhibits a beautiful appearance of crystals, or is not solidified under pressurized conditions.
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- Chiral Lactols, VIII - A Way for the Asymmetric Induction in the Formation of Sugars
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The substituted glycol aldehyde 4 which bears an enantiomerically pure acetal-type protective group exhibiting the configuration of an α-L-sugar at the acetal centre is subjected to aldolization under basic conditions.The resulting products are reduced and characterized by comparison with reference compounds of known absolute configuration.L-Sugars are formed preferentially with L-erythrose being the main product.
- Noe, Christian R.,Knollmueller, Max,Ettmayer, Peter
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p. 637 - 644
(2007/10/02)
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- Decarbonylation of Unprotected Aldose Sugars by Chlorotris(triphenylphosphine)rhodium(I). A New Descent of Series Approach to Alditols, Deoxyalditols, and Glycosylalditols
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Unprotected Cn aldose sugars are cleanly decarbonylated by 1 equiv of chlorotris(triphenylphosphine)rhodium(I) in 1-24 h at 130 deg C in N-methyl-2-pyrrolidinone solution to give the corresponding Cn-1 alditol in about 75-95percent yields.This technique represents a useful variation on traditional carbohydrate "descent of series" reactions.The procedure is quite general and also works on a number of aldose derivatives, such as deoxy sugars, N-acetylated amino sugars, and disaccharides, providing convenient small-scale syntheses of deoxyalditols, (acetylamino)deoxyalditols, and glycosylalditols, respectively.The reactions proceed with complete retention of stereochemistry, the only side products observed being a few percent of the Cn lactones and the Cn-2 alditol.Attempts to make the reactions catalytic have not yet been very successful.
- Andrews, Mark A.,Gould, George L.,Klaeren, Stephen A.
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p. 5257 - 5264
(2007/10/02)
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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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- 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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