- 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
-
p. 560 - 566
(2021/06/25)
-
- Selective and Scalable Synthesis of Sugar Alcohols by Homogeneous Asymmetric Hydrogenation of Unprotected Ketoses
-
Sugar alcohols are of great importance for the food industry and are promising building blocks for bio-based polymers. Industrially, they are produced by heterogeneous hydrogenation of sugars with H2, usually with none to low stereoselectivities. Now, we present a homogeneous system based on commercially available components, which not only increases the overall yield, but also allows a wide range of unprotected ketoses to be diastereoselectively hydrogenated. Furthermore, the system is reliable on a multi-gram scale allowing sugar alcohols to be isolated in large quantities at high atom economy.
- Tindall, Daniel J.,Mader, Steffen,Kindler, Alois,Rominger, Frank,Hashmi, A. Stephen K.,Schaub, Thomas
-
supporting information
p. 721 - 725
(2020/10/19)
-
- Domino Hydroalkoxylation-[4+2]-Cycloaddition for Stereoselective Synthesis of 1,4-Heterocycle-Fused Chromenes: Rapid Access to the [6-6-7-6] Tetracyclic Core of Cytorhizhins B–D
-
A substrate dependent regio- and stereoselective domino hydroalkoxylation-formal-[4+2] cycloaddition is described for the facile synthesis of linear as well as spirocyclic 1,4-heterocycle-fused chromene ketals. Enantiospecific synthesis of oxazepino chromene derivatives was successfully carried out using chiral pool amino alkynols. The developed hydroalkoxylation cascade offered rapid access to the spirocyclic [6-6-7-6] tetracyclic core of cytorhizhins B–D with correct relative configuration.
- Fartade, Dipak J.,Gharpure, Santosh J.,Nanda, Santosh K.,Vishwakarma, Dharmendra S.
-
supporting information
p. 6892 - 6897
(2020/01/25)
-
- Practical Cleavage of Acetals by Using an Odorless Thiol Immobilized on Silica
-
A practical, efficient and general method was developed for the deprotection of a variety of aromatic and aliphatic acetals to their corresponding catechol or diol derivatives using thiol immobilized on silica gel. This is an application for the well-known commercial solid-supported thiol (SiliaMetS Thiol). The procedure is mild and amenable to scale-up. It does not require inert atmosphere and clean conversions were observed. This method is applicable to substituted 1,3-benzodioxole and aliphatic acetals with different functionalities. It offers the advantage of a general route with high yield, which can be undertaken at ambient temperature.
- de Léséleuc, Mylène,Kukor, Andrew,Abbott, Shaun D.,Zacharie, Boulos
-
p. 7389 - 7393
(2019/12/03)
-
- 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 0301
(2018/04/13)
-
- 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)
-
- Xylitol Hydrogenolysis over Ruthenium-Based Catalysts: Effect of Alkaline Promoters and Basic Oxide-Modified Catalysts
-
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
-
p. 2145 - 2159
(2017/06/28)
-
- 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).
- -
-
Paragraph 0701; 0702; 0703
(2016/11/24)
-
- 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)
-
- 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)
-
- Exploring the reaction conditions for Ru/C catalyzed selective hydrogenolysis of xylitol alkaline aqueous solutions to glycols in a trickle-bed reactor
-
The hydrogenolysis of an alkaline aqueous solution of xylitol to mainly ethylene- and propylene-glycols was studied over a Ru/C catalyst in a high pressure fixed-bed reactor run in the trickle-bed mode with co-current downflow of liquid feed and hydrogen. The effects of reaction parameters including H 2 pressure (40-80 bar), temperature (190-200 °C) and pH values (NaOH/xylitol molar ratio in the range 0.1-0.2, pH 9-12) and residence time have been explored to increase the selectivity of this reaction to the desired ethyleneglycol product. The activity and final products distribution were much influenced by the hydrogen pressure. An optimum to afford a high conversion and a high selectivity to ethyleneglycol at different space times was found at 60 bar. The effects observed are in agreement with the reaction pathways previously proposed and the relative reaction rates of the dehydrogenation/hydrogenation and base-catalyzed reactions of the intermediates are affected by the hydrogen pressure and the concentration of the alkaline promoter.
- Auneau, Florian,Berchu, Maeva,Aubert, Guillaume,Pinel, Catherine,Besson, Michèle,Todaro, Daniela,Bernardi, Marco,Ponsetti, Tiziano,Di Felice, Renzo
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p. 100 - 106
(2014/07/07)
-
- 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
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p. 116 - 124
(2013/02/26)
-
- 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
-
p. 1366 - 1375
(2013/11/19)
-
- 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
-
experimental part
p. 1565 - 1570
(2012/04/05)
-
- 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
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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)
-
- 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)
-
- 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)
-
- 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
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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
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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)
-
- 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
-
(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
-
p. 1757 - 1761
(2007/10/03)
-
- Process for the preparation of optically active alcohols
-
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
-
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.
- -
-
-
- Synthesis and application of (3R,4R)-3,4-bis(diphenylphosphino)tetrahydrofuran as ligand for asymmetric hydrogenation of acrylic acids
-
A new, chiral bisphosphine, (3R,4R)-3,4-bis(diphenylphosphino)tetrahydrofuran (4), is synthesized in three steps from (R,R)-tartaric acid esters. With rhodium(I) complexes of 4 enantiomeric excesses of 54 to 97% are obtained on catalytic hydrogenation of 2-(acetylamino)acrylic acid, 2-(acetylamino)cinnamic acids and itaconic acid. The applied substrate/catalyst ratios were between 250:1 and 11,000:1.
- Terfort
-
p. 951 - 953
(2007/10/02)
-
- Catalytic osmylation of conjugated dienes: A one-pot stereoselective synthesis of polyols
-
Conjugated dienes have been hydroxylated with catalytic amounts of osmium tetroxide. The reaction can be highly stereoselective depending on the nature of the terminal substituents, leading to polyols of predictable configurations.
- Park, Christine Y.,Kim, B. Moon,Sharpless, K. Barry
-
p. 1003 - 1006
(2007/10/02)
-
- Compression-moldet meso-erythritol products.
-
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
-
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
-
p. 637 - 644
(2007/10/02)
-
- Synthesis of cis- and trans-1,3,5,7-Tetranitro-1,3,5,7-tetraazadecalin
-
The synthesis and preliminary characterization of two new polynitramine compounds, cis- and trans-1,3,5,7-tetranitro-1,3,5,7-tetraazadecalin (1 and 2), is described.Also isolated and partially characterized were two byproducts of the synthesis of 1 and 2, (R*,R*)-1,1',3,3'-tetranitro-4,4'-biimidazolidine (3) and (R*,S)-1,1',3,3'-tetranitro-4,4'-biimidazolidine (4).
- Willer, Rodney L.
-
p. 5150 - 5154
(2007/10/02)
-
- 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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