Academic literature on the topic 'Hydrolysis-dehydration'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the lists of relevant articles, books, theses, conference reports, and other scholarly sources on the topic 'Hydrolysis-dehydration.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Journal articles on the topic "Hydrolysis-dehydration"
1
Wang, Bin, Chan-Juan Xia, Hong-Lin Fang, Wen-Jie Chen, Yong-Fan Zhang, and Xin Huang. "Mononuclear thorium halide clusters ThX4 (X = F, Cl): gas-phase hydrolysis reactions." Physical Chemistry Chemical Physics 20, no. 32 (2018): 21184–93. http://dx.doi.org/10.1039/c8cp03071e.
Full text
2
Manurung, R., H. Silalahi, O. Winda, and A. G. Siregar. "Synthesis of 5-Hydroxymethylfurfural from Cassava (Manihot utilissima pohl) Peels through Dehydration Reaction using Deep Eutectic Solvent Based on Choline Chloride/Citric Acid." Asian Journal of Chemistry 33, no. 5 (2021): 1115–19. http://dx.doi.org/10.14233/ajchem.2021.22374.
Full textAbstract:
The high cellulose content in cassava peel has an opportunity to produce bio-based chemical products in 5-hydroxymethylfurfural (5-HMF) form. This study aimed to determine the optimum conditions of glucose dehydration reaction as a result of hydrolysis of the best cassava peel cellulose. The variables observed in this study were H2SO4 catalyst concentrations in the hydrolysis reaction, temperature and amount of deep eutectic solvents based on choline chloride/citric acid. The optimum dehydration reaction conditions in this study was the glucose:deep eutectic solvents mass ratio of 1:6 at the reaction temperature of 80 ºC. The highest yield of 64.50% at an initial glucose concentration of 5.70% using a 1.5% H2SO4 catalyst during the hydrolysis of cassava peel cellulose. The results obtained in this study indicated that addition of choline chloride/citric acid as deep eutectic solvent can increase the yield of 5-HMF.
3
Ding, Qing, Xue Gang Luo, and Xiao Yan Lin. "Thermal Decomposition Characteristics of Mg (NO3)2·6H2O and MgCl2·6H2O Composite as Phase Change Material." Materials Science Forum 724 (June 2012): 425–28. http://dx.doi.org/10.4028/www.scientific.net/msf.724.425.
Full textAbstract:
The thermal decomposition characteristics of Mg (NO3)2·H2O and MgCl2·6H2O composite were studied by integrated thermal analysis. Results show that there are five steps during the thermal decomposition of phase change material (PCM): the starting temperature of each step is 35.5°C, 93°C, 196°C, 260°C and 318°C, respectively. PCM was calcined at different temperatures at each decomposition step. The composition and morphology of the calcined product was characterized by XRD and SEM. Two major reactions including dehydration and hydrolysis occur in the thermal decomposition progress. Dehydration is the main process below 196 °C, while hydrolysis is predominant process when the temperature is higher than 196 °C.
4
Morávek, Vladimír, and Miloš Kraus. "Kinetics of individual steps in reaction network ethanol-diethyl ether-ethylene-water on alumina." Collection of Czechoslovak Chemical Communications 51, no. 4 (1986): 763–73. http://dx.doi.org/10.1135/cccc19860763.
Full textAbstract:
The rates of single reactions have been measured at 250 °C in the complex reaction of ethanol dehydration to ethylene and to diethyl ether involving also hydrolysis of the ether, its disproportionation to ethanol and ethylene and its dehydration to ethylene. The found dependences of the initial reaction rates on partial pressures of the reactants were correlated by semiempirical Langmuir-Hinshelwood type rate equations.
5
Xiong, Xinni, Iris K. M. Yu, Season S. Chen, et al. "Sulfonated biochar as acid catalyst for sugar hydrolysis and dehydration." Catalysis Today 314 (September 2018): 52–61. http://dx.doi.org/10.1016/j.cattod.2018.02.034.
Full text
6
Deutsch, John C. "Spontaneous Hydrolysis and Dehydration of Dehydroascorbic Acid in Aqueous Solution." Analytical Biochemistry 260, no. 2 (1998): 223–29. http://dx.doi.org/10.1006/abio.1998.2700.
Full text
7
Taniguchi, Takuya, Miri Nakamura, Koichi Tsutao, Kohei Otogawa, Yoshiyuki Ogino, and Toru Asahi. "Reformation of Thalidomide from Its Hydrolysis Compound via Intramolecular Dehydration." Chemistry Letters 50, no. 7 (2021): 1388–91. http://dx.doi.org/10.1246/cl.210099.
Full text
8
Sharma, Neha, Lekha Charan Meher, Krishna Chandra, Mitesh Mittal, Sanjai Kumar Dwivedi, and Madhu Bala. "Synthesis of 2, 5 Dimethyl Furan from Renewable Lignocellulosic Biomass." Defence Life Science Journal 4, no. 2 (2019): 96–102. http://dx.doi.org/10.14429/dlsj.4.12641.
Full textAbstract:
Renewable biomass resources could reduce the dependency on the fossil fuels by conversion of its lignocellulose into bio-fuels and other valuable chemicals. Depolymerisation of lignocellulose, hydrolysis of cellulose to monomer glucose and its subsequent dehydration results 5-hydroxymethyl furfural (HMF). HMF is an important platform chemical for fuels and various other applications. The hydrogenation of HMF results 2, 5-dimethylfuran (DMF), which may be a biofuel with 40 per cent greater energy density than that of ethanol. The homogeneous catalytic method is preferred for lignocellulosic biomass conversion to cellulose, its hydrolysis and further dehydration to HMF. The Cu-Ru/C and related catalysts are preferred for hydrogenation of HMD to 2, 5-dimethylfuran. This review is an attempt to summarise the current research and developments in the field of lignocellulose derived HMF and further conversion to DMF as a potential biofuel.
9
Kristiani, Anis, Kiky Corneliasari Sembiring, Haznan Abimanyu, and Fauzan Aulia. "HIDROLISIS LIGNOSELULOSA PELEPAH DAN TANDAN KOSONG KELAPA SAWIT DENGAN KATALIS ZIRKONIA TERSULFATASI." Jurnal Kimia Terapan Indonesia 15, no. 2 (2013): 74–77. http://dx.doi.org/10.14203/jkti.v15i2.112.
Full textAbstract:
Lignocellulosic biomass which are frond and empty fruit bunches (EFB) is second generation raw material for ethanol production. Lignocellulose usage is expected to create a green process. Utilization of lignocellulose materials into ethanol involved four main processes, i.e pretreatment, hydrolysis/sacharification, fermentation, distillation and dehydration ethanol that was product. This research aims to optimize hydrolysis process of EFB and frond by using sulfated zirconia catalyst characterized its physical and chemical properties as a solid acid catalyst. Catalytic hydrolysis process conducted at 160 DCfor 3 hours gave the highest TRS (Total Reducing Sugar) which is 17,51 % for EFB while for frondfor 2 hours which is 19,23 % .Keyword: Hydrolysis, solid acid catalyst, lignocellulose, frond, EFB, sulfated zirconia
10
Xue, Shoufeng, Wenyuan Wu, Xue Bian, and Yongfu Wu. "Dehydration, hydrolysis and oxidation of cerium chloride heptahydrate in air atmosphere." Journal of Rare Earths 35, no. 11 (2017): 1156–63. http://dx.doi.org/10.1016/j.jre.2017.06.001.
Full textDissertations / Theses on the topic "Hydrolysis-dehydration"
1
Kanchanalai, Pakkapol. "New dehydration and pretreatment process for ethanol production from biomass." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/53559.
Full textAbstract:
The cost of pretreatment process for saccharification from biomass and the cost of dilute ethanol purification are significant components of the overall cost for fuel grade ethanol production through fermentation or other biological routes. This work focuses on developing optimal designs of dilute ethanol purification process and the new acid hydrolysis technology for the production of fermentable sugars from biomass where the overarching goal is to reduce the cost of ethanol production from biomass. In this thesis, the ethanol separation process with the reverse osmosis membrane pretreatment is developed to reduce separation cost and energy consumption especially when the feed is dilute. In addition, the new solid phase reactive separation system for biomass saccharification via acid hydrolysis is proposed. This new process is applied for both dilute and concentrated acid hydrolysis where the goal is to increase sugar yield and to reduce byproduct formation. The reaction kinetics of the concentrated acid hydrolysis is investigated through batch experiment. All of these use optimization approaches for seeking the best process designs and for parameter estimations.
2
Foo, Guo Shiou. "Surface interactions of biomass derived oxygenates with heterogeneous catalysts." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/54455.
Full textAbstract:
Energy demand is projected to increase by 56% before 2040 and this will lead to the fast depletion of fossil fuels. Currently, biomass is the only sustainable source of organic carbon and liquid fuels. One major method of converting biomass involves the utilization of heterogeneous catalysts. However, there is still a lack of understanding in the reaction mechanisms and surface interactions between biomass-derived oxygenates and catalysts. Specifically, three important reactions are investigated: i) dehydration of glycerol, ii) hydrolysis of cellulose and cellobiose, and iii) hydrodeoxygenation of bio-oil. Some important concepts are gathered and provide insight into the most attractive conversion strategies. These concepts include the role of Lewis and Brønsted acid sites, synergistic effect between defect sites and functional groups, the advantage of weak acid sites, steric effect imposed by aromatic substituents, and the evolution of surface species in catalyst deactivation. These studies show that a deep understanding of surface chemistry can help to elucidate elementary reaction steps, and there is great potential in using heterogeneous catalysts for the conversion of biomass into targeted fuels and chemicals.
3
Dias, Marina Oliveira de Souza. "Simulação do processo de produção de etanol a partir do açucar e do bagaço, visando a integração do processo e a maximização da produção de energia e excedentes do bagaço." [s.n.], 2008. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266223.
Full textAbstract:
Orientadores: Rubens Maciel Filho, Carlos Eduardo Vaz Rossell<br>Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica<br>Made available in DSpace on 2018-08-11T20:59:18Z (GMT). No. of bitstreams: 1
Dias_MarinaOliveiradeSouza_M.pdf: 13614518 bytes, checksum: 8a7fafce0407822a32d8f9833a1d2d86 (MD5)
Previous issue date: 2008<br>Resumo: O objetivo desta dissertação é apresentar a descrição e a simulação de processos de produção de etanol a partir do caldo e do bagaço da cana-de-açúcar, visando o levantamento do consumo de energia destes processos. Foram consideradas melhor ias no processo convencional de produção de etanol a partir do caldo, tais como a realização de eficientes tratamento e esterilização do caldo, a condução da fermentação a temperaturas mais baixas (28°C) do que as utilizadas atuamente, o estudo de configuração de destilação duplo efeito e a otimização de processos de desidratação para produção de etanol anidro. O processo de produção de etanol a partir do bagaço da cana-de-açúcar é baseado em um processo de hidrólise do tipo Organosolv com ácido diluído em três etapas: pré-hidrólise da hemicelulose, deslignificação Organosolv e hidrólise da celulose. Considerando-se a utilização de 70 % do bagaço gerado nas moendas como matéria prima do processo de hidrólise estudado, seria possível aumentar a produção de etanol em cerca de 17 %, considerando somente a fermentação das hexoses obtidas a partir da celulose do bagaço. A realização do processo de hidrólise leva a um aumento do consumo de energia do processo, que pode ser compensado pela otimização do processo convencional de produção .de etanol a partir do caldo da cana-de-açúcar, do aproveitamento da palha e de subprodutos do processo de hidrólise como a lignina, e da integração térmica do processo integrado, que utiliza caldo e bagaço como matéria prima para produção de etanol. O equacionamento do consumo energético da produção integrada de etanol a partir da cana-de-açúcar e do bagaço de cana-de-açúcar constitui um obstáculo à viabilização técnica e econômica do processo de hidrólise. Este trabalho visa apresentar então colaborações no sentido de superar este obstáculo, considerando-se a produção de etanol a partir do bagaço de cana-de-açúcar por meio de um processo de hidrólise do tipo Organosolv com ácido diluído<br>Abstract: The main objective of this dissertation is to present the description and simulation of bioethanol production processes from sugarcane juice and bagasse, considering the evaluation of energy consumption. Some improvements were considered for the conventional bioethanol production process from sugarcane juice, such as efficient juice treatment, sterilization and concentration, lower fermentation temperatures (28°C) than the ones used nowadays in the industry, study of a double effect distillation sys tem and optimization of dehydration processes for anhydrous bioethanol production. The process considered for bioethanol production from sugarcane bagasse is based on an Organosolv process with dilute acid hydrolysis, carried on three non-simultaneous steps: prehydrolysis of hemicellulose, Organosolv delignification and cellulose hydrolysis. The use of 70 % of sugarcane bagasse generated on the mills as raw material for the hydrolysis process allows an increase in bioethanol production of 17 %, considering exclusively the fermentation of the hexose obtained from the cellulose fraction of sugarcane bagasse. An increase on energy consumption is observed when bagasse is used as raw material in the hydrolysis process, but it may become feasible considering the optimization of conventional bioetlJ.anol production process, the use of sugarcane trash and lignin as fuel in boilers and the thermal integration of the integrated process, which uses sugarcane juice and bagasse as raw materiaIs for bioethanol production. Evaluation of the energy consumption of the integrated production of ethanol from sugarcane and sugarcane bagasse constitutes an obstacle for the technical and economical feasibility of the hydrolysis processo This work aims to present contributions to help surpass this obstacle, considering the production of ethanol from sugarcane bagasse using an Organosolv process with dilute acid hydrolysis<br>Mestrado<br>Desenvolvimento de Processos Químicos<br>Mestre em Engenharia Química
4
Li, Xihao. "Characterization of Perphenazine and Scopolamine Aerosols Generated Using the Capillary Aerosol Generator." VCU Scholars Compass, 2006. http://scholarscompass.vcu.edu/etd/901.
Full textAbstract:
The characterization of perphenazine and scopolamine aerosols generated using the capillary aerosol generator (CAG) was reported. Variables including steady state power, the formulation vehicle, the drug concentration and the formulation flow rate were studied for their effects on the chemical stability and particle size of these drug aerosols.Stability-indicating HPLC and LC-MS assays were developed and validated for perphenazine and scopolamine, respectively. The chemical stability of each compound was investigated under a variety of stress conditions and the structure of degradation products was proposed.Perphenazine aerosols were generated from propylene glycol (PG) formulations with concentrations of 9, 48 and 90mM at formulation flow rates of 2.5 and 5.0µL/s at a series of steady state powers. At higher aerosolization powers, the low concentration formulation (9mM) degraded with dehalogenation being the major pathway. The size of perphenazine aerosols was between 0.4 to 0.6µm. Changing the solute concentration produced only small changes (~0.2µm) in perphenazine aerosol particle size. The formulation flow rate did not significantly affect the aerosol size.Scopolamine degraded significantly when aerosolized in PG formulations. It was possible to generate chemically stable scopolamine aerosols from ethanol formulations. Significant amounts of degradation products were formed only at or above 4.6W at 5.0µL/s. Hydrolysis and dehydration appeared to be the major degradation pathways at higher powers and low formulation flow rate. The MMAD of scopolamine aerosols was between 0.5 and 2.0µm from 8, 20 and 40mM formulations at 5.0 and 10.0µL/s. The size of scopolamine aerosols increased as a function of increasing the solute concentration. Increasing the formulation flow rate increased the linear velocity of the spray, thus the Reynolds number was increased and smaller particles were generated.
5
Gromov, Nikolay. "Transformation catalytique de la cellulose en milieu aqueux pour la production de molécules plateformes." Thesis, Bordeaux, 2016. http://www.theses.fr/2016BORD0156/document.
Full textAbstract:
Ce projet de thèse a concerné la recherche et le développement de catalyseurs multifonctionnels efficaces et de procédés catalytiques en une étape (hydrolyse-déshydratation, hydrolyse-oxydation) pour la transformation de la cellulose en produits chimiques à valeur ajoutée (glucose, 5-HMF, acide formique). Ces produits sont également connus sous le nom de molécules plateformes et ils présentent un intérêt dans une large gamme d'applications, par exemple, pour les industries alimentaires et chimiques et pour la production de carburants. Dans ce projet, des recherches systématiques sur la synthèse de l'acide formique en présence de catalyseurs HPA contenant du vanadium ont d'abord été conduites. En particulier, l'influence de la composition du catalyseur et des paramètres du procédé sur le rendement en produit cible a été étudiée. Le rendement en AF obtenu (66%) est supérieur à tous les résultats rapportés dans la littérature à ce jour. Les catalyseurs NbOx / ZrO2 ont été évalués pour la première fois sur la réaction d'hydrolyse-déshydratation de la cellulose microcristalline activée en milieu aqueux. Des rendements élevés en glucose et en 5-HMF (22 et 16%, respectivement) ont été observés. Des catalyseurs carbonés à base du matériau Sibunit modifié ont été utilisés pour la première fois pour l'hydrolyse-déshydratation de la cellulose. Les rendements en glucose (jusqu'à 74% dans un réacteur en continu) et en 5-HMF (jusqu'à 21% dans un réacteur statique) ont été obtenus en présence de Sibunit modifié par sulfonation et / ou oxydation. Ces résultats sont également supérieurs à ceux reportés à ce jour sur les systèmes catalytiques carbonés. La relation entre l'activité sur les réactions d’hydrolyse-déshydratation et la méthode d'activation du carbone a été étudiée en profondeur. L'étude du mécanisme et de la cinétique de la réaction d'hydrolyse-déshydratation de la cellulose en présence de catalyseurs acides solides a également été réalisée<br>The PhD project was devoted to search for and to develop effective multifunctional catalysts and catalytic one-stage processes (hydrolysis-dehydration, hydrolysis-oxidation) for transformation of cellulose to valuable chemicals (glucose, 5-HMF, formic acid). These products are also known as platform molecules and they seem to be promising for a wide range of application in food and chemical industries and for fuel production. In this project, systematic investigations of the formic acid synthesis in the presence of vanadium-containing HPA catalysts was first conducted; the influence of the catalyst composition and process parameters on the yield of the target product was studied. The obtained FA yield (66 %) was superior to all the results reported in literature. The NbOx/ZrO2 catalysts were applied for the first time for hydrolysis-dehydration of activated microcrystalline cellulose in pure water. High yields of glucose and 5-HMF (22 and 16 %, respectively) were observed. Carbon catalysts based on modified Sibunit material was used for the first time for cellulose hydrolysis-dehydration. The yields of glucose (up to 74 % in a flow reactor) and 5-HMF (up to 21 % in a static reactor) were obtained in the presence of Sibunit modified by sulfation and/or oxidation; these are much superior to the results on carbon catalytic systems reported in literature. The relation between the activity to hydrolysis-dehydration and the method of the carbon activation was thoroughly studied. Investigations of the mechanism and kinetics of cellulose hydrolysis-dehydration in the presence of solid acid catalysts were also carried out
6
Karaki, Mariam. "Matériaux à porosité contrôlée sulfonés : Synthèse, Caractérisation, Etude des propriétés catalytiques." Phd thesis, Université de Haute Alsace - Mulhouse, 2013. http://tel.archives-ouvertes.fr/tel-01064374.
Full textAbstract:
La catalyse solide acide a été pendant longtemps l'objet d'activité de recherche intense, en particulier pour l'industrie pétrochimique. Aujourd'hui, les catalyseurs solides acides sont de plus en plus étudiés dans d'autres domaines et en particulier dans celles liées à la "chimie verte" et à la valorisation des bioressources, telles que la synthèse de biodiesel et la transformation des polysaccharides. L'objectif de la thèse est d'étudier le potentiel des matériaux poreux sulfonés ayant une porosité contrôlée dans des réactions catalysées par un acide en condition eau surchauffé telle que l'hydrolyse de la cellobiose. Dans une première partie, nous décrivons la préparation et la caractérisation des organosilicates mésoporeux périodiques sulfonés de type SBA-15, SBA-1 et KIT-6 par co-condensation de 1,4-bis (triéthoxysilyl) benzène (BTEB). Les matériaux ont été acidifiés suivant des voies différentes à l'aide de 3-mercaptopropyltriméthoxysilane (MPTMS)/H2O2 ou d'acide chlorosulfonique (ClSO3H). Leur propriété acide a été étudiée par adsorption d'NH3 suivie par calorimétrie et par la réaction de déshydratation d'isopropanol (IPA) comme réaction modèle en phase gazeuse. Contrairement à notre attente, l'adsorption d'NH3 suivie par calorimétrie a mis en évidence l'hétérogénéité de la force des sites suggérant la présence de sites distincts de la sulfonation. Les solides sulfonés avec l'acide chlorosulfonique ont une activité équivalente à celle de la résine sulfonée, Amberlyst 15, mais ils sont moins stables en raison de la libération des espèces de soufre. Les catalyseurs préparés en utilisant un groupement mercapto-propyle suivie d'une oxydation sont moins acides et ils ont donné des niveaux d'activité plus basse dans la réaction de déshydratation d'IPA. Pour l'hydrolyse de la cellobiose, de bonnes performances ont été obtenues à 150°C, mais, ces matériaux se sont montrés instables dans des conditions hydrothermales avec une lixiviation totale de soufre réalisant alors la réaction en phase homogène. Un lavage dans l'eau surchauffée des matériaux contenant des groupements propyles-SO3H conduit à une diminution de leur efficacité dans l'hydrolyse de la cellobiose, mais un gain de stabilité a été obtenu, permettant le recyclage de ces matériaux. Dans une deuxième partie, des répliques carbonées sulfonées par l'acide chlorosulfonique ou l'acide sulfurique ont été synthétisé. La sulfonation par l'acide sulfurique suivi par un lavage dans l'eau bouillante puis un prétraitement thermique à 300°C sous azote, de ces matériaux aboutissent au meilleur catalyseur en termes d'activité/stabilité.
7
Helm, Richard Frederick. "The reversion and dehydration reaction of glucose during the dilute sulfuric acid hydrolysis of cellulose." 1987. http://catalog.hathitrust.org/api/volumes/oclc/17156244.html.
Full textBook chapters on the topic "Hydrolysis-dehydration"
1
"Chapter 11. Reactions involving water: hydration, dehydration, etherification, hydrolysis, and esterification." In Chemical Reaction Technology. De Gruyter, 2015. http://dx.doi.org/10.1515/9783110336443-013.
Full text
2
"Miscellaneous Reactions of Hydration and Dehydration." In Hydrolysis in Drug and Prodrug Metabolism. Verlag Helvetica Chimica Acta, 2006. http://dx.doi.org/10.1002/9783906390444.ch11.
Full text
3
Taber, Douglass. "The Paquette Synthesis of Fomannosin." In Organic Synthesis. Oxford University Press, 2011. http://dx.doi.org/10.1093/oso/9780199764549.003.0096.
Full textAbstract:
The compact sesquiterpene ( + )-fomannosin 3, isolated from the pathogenic fungus Fomes annonsus, presents an interesting set of challenges for the organic synthesis chemist, ranging from the strained cyclobutene to the easily epimerized cyclopentanone. In the synthesis of 3 developed (J. Org. Chem . 2008, 73, 4548) by Leo A. Paquette of Ohio State University, the cyclopentane was constructed by ring-closing metathesis of 1. The real challenge of the synthesis was the enantiospecific preparation of 1 from D-glucose. The starting point for the preparation of 1 was the glucose derivative 4. Selective acetonide hydrolysis followed by oxidative cleavage gave the ester 5, which on base treatment followed by hydrogenation delivered the endo ester 6. Condensation of the enolate of 6 with formaldehyde proceeded with high diastereoselectivity, to give, after protection, the ester 7. Conversion of the ester to the vinyl group, exposure to methanolic acid and ether formation completed the preparation of 9. The construction of the cyclobutane of 1 was effected by an interesting application of the Negishi reagent (Cp2ZrCl2/2 x BuLi). Complexation of Cp2Zr with the alkene followed by elimination generated an allylic organometallic 11, which added to the released aldehyde to give the cyclobutanes 12 and 13 in a 2.4:1 diastereomeric ratio. Homologation of the aldehyde 13 and subsequent oxidation were straightforward, but subsequent methylenation of the hindered carbonyl was not. At last, it was found that Peterson olefination worked well. Metathesis then delivered the cyclopentene 2. The last carbons of the skeleton were added by intramolecular aldol cyclization of the thioester 16. The seemingly simple task of converting the alkene of 17 into a ketone proved challenging. Eventually, dihydroxylation followed by oxidation, and then SmI2 reduction, completed the transformation. This still left the challenge of controlling the cyclopentane stereogenic center. Remarkably, dehydration and epimerization led to (+)-Fomannosin 3 as a single dominant diastereomer.
4
Taber, Douglass F. "The Tanino/Miyashita Synthesis of Solanoeclepin A." In Organic Synthesis. Oxford University Press, 2013. http://dx.doi.org/10.1093/oso/9780199965724.003.0104.
Full textAbstract:
Building on the Tanino synthesis of glycinoeclepin (Organic Highlights, January 3, 2011), the hatch-stimulating substance for the soybean cyst nematode, Keiji Tanino of Hokkaido University and Masaaki Miyashita, now at Kogakuin University, described (Nat. Chem. 2011, 3, 484) a convergent synthesis of solanoeclepin A 3, the hatch-stimulating substance for the potato cyst nematode. A key step in the synthesis was the diastereoselective Diels-Alder cyclization of 1 to 2. The starting point for the synthesis was the conjugate addition of 5 to 3-methyl cyclohexenone 4, followed by aldol condensation. The secondary acetate corresponding to 6 was readily resolved by lipase hydrolysis. The next challenge was the installation of the angular vinyl group. Enone transposition gave 7, to which vinyl Grignard added with high diastereocontrol, leading to the diol 8. TMSOTf-mediated epoxide rearrangement with concomitant 1,2 vinyl shift then delivered 9. Epoxidation followed by Stork cyclization completed the construction of the cyclobutane 10. The allylic alcohol 12 was enantiomerically pure, so the relative configuration of the sidechain cyclopropane could be set by the Charette protocol. Grieco dehydration of 14 then gave 16, a latent form of the cyclobutanone of 3. Condensation of the ketone 17 with 18 delivered the expected keto enamine, which rearranged nicely on exposure to Tf2O to the aldehyde 19. Diastereoselective addition of the furyl lithium 20 followed by Pd-catalyzed coupling with 21 then completed the assembly of the Diels-Alder substrate 1. The Me2AlCl-mediated intramolecular Diels-Alder cyclization of 1 led to 2 with remarkable diastereocontrol. Oxidation gave 22, that was further oxidized to the protected enol 23. Reduction, alkene cleavage, and protecting group manipulation then set the stage for the final oxidation of 24 to solanoeclepin A 3.
5
Morrow, Gary W. "The Shikimate Pathway: Biosynthesis of Phenolic Products from Shikimic Acid." In Bioorganic Synthesis. Oxford University Press, 2016. http://dx.doi.org/10.1093/oso/9780199860531.003.0009.
Full textAbstract:
Like other amino acids, the aromatic amino acids phenylalanine, tyrosine, and tryptophan are vitally important for protein synthesis in all organisms. However, while animals can synthesize tyrosine via oxidation of phenylalanine, they can synthesize neither phenylalanine itself nor tryptophan and so these essential amino acids must be obtained in the diet, usually from plant material. Though many other investigators made significant contributions in this area over the years, it was Bernhard Davis in the early 1950s whose use of mutant stains of Escherichia coli led to a full understanding of the so-called shikimic acid pathway that is used by plants and also by some microorganisms for the biosynthesis of these essential amino acids. The pathway is almost completely devoted to their synthesis for protein production in bacteria, while in plants the pathway extends their use to the construction of a wide array of secondary metabolites, many of which are valuable medicinal agents. These secondary metabolites range from simple and familiar compounds such as vanillin (vanilla flavor and fragrance) and eugenol (oil of clove, a useful dental anesthetic) to more complex structures such as pinoresinol, a common plant biochemical, and podophyllotoxin, a powerful cancer chemotherapy agent. Earlier in Chapter 3, we encountered two important intermediates, erythrose-4-phosphate and phosphoenolpyruvate (PEP), each of which was derived from a different pathway utilized in carbohydrate metabolism. Erythrose-4-P was an intermediate in one of the steps of the pentose phosphate pathway while hydrolysis of PEP to pyruvic acid was the final step in glycolysis. These two simple intermediates provide the seven carbon atoms required for construction of shikimic acid itself. The two are linked to one another via a sequence of enzyme-mediated aldol-type reactions, the first being a bimolecular reaction and the second an intramolecular variant that ultimately leads to a cyclic precursor of shikimic acid known as 3-dehydroquinic acid as shown in Fig. 6.3. Subsequent dehydration of 3-dehydroquinic acid leads to 3-dehydroshikimic acid which then leads directly to shikimic acid via NADPH reduction.
6
Taber, Douglass F. "The Corey Synthesis of (+)-Lupeol." In Organic Synthesis. Oxford University Press, 2013. http://dx.doi.org/10.1093/oso/9780199965724.003.0086.
Full textAbstract:
The total synthesis of lupeol was one of the crowning achievements of the Robinson annulation/ reductive alkylation approach to stereocontrolled polycarbocyclic construction developed by Gilbert Stork (J. Am. Chem. Soc. 1971, 93, 4945). It is a measure of the progress of organic synthesis since that time that E. J. Corey of Harvard University could devise (J. Am. Chem. Soc. 2009, 131, 13928) an enantioselective synthesis of (+)-lupeol 3 that could be carried out by a single colleague. The key step in the synthesis was the Lewis acid–mediated cyclization of 1 to 2. The preparation of 1 began with the enantioselective epoxidation of farnesol acetate 4. To this end, asymmetric dihydroxylation delivered the diol 5. Selective mesylation followed by exposure to dilute methoxide effected ring closure to the epoxide, but also removed the acetate, so this had to be reapplied. The synthesis of the aromatic portion of 1 started with the phenol 7. Protection as the very bulky triisopropylsilyl ether was important for the success of the subsequent cyclization, perhaps because it discouraged complexation of the Lewis acid with the aryl ether. Metalation followed by formylation delivered the aldehyde 8, which was reduced and carried on to the bromide 9. The derived Grignard reagent coupled smoothly with 6 under Li2CuCl4 catalysis. The cyclization of 1 to 2 proceeded with remarkable efficiency (43%!), for a reaction in which three new C-C bonds, four rings, and five new stereogenic centers were established. It is particularly noteworthy that the cyclization cleanly set the trans, anti, trans, anti tetra-cyclic backbone of (+)-lupeol 3. To complete the synthesis of 3, the less substituted alkene of 2 was selectively hydrogenated, then CH3 Li was added to give 10. Hydrolysis and dehydration yielded 11, which was reduced and equilibrated to 12. On brief exposure to MsCl/Et3 N, 13 cyclized to (+)-lupeol 3. It is a measure of the remarkable effi ciency of this synthesis of (+)-lupeol 3 that it provided suffi cient material to enable studies of the rearrangement of 3 under acidic conditions to other pentacyclic triterpenes, including, inter alia, germanicol, α -amyrin, δ -amyrin, and taraxasterol 14 .
7
Taber, Douglass F. "The Funk Synthesis of (-)-Nakadomarin A." In Organic Synthesis. Oxford University Press, 2013. http://dx.doi.org/10.1093/oso/9780199965724.003.0101.
Full textAbstract:
The Z alkene of nakadomarin A 3 suggested to Raymond L. Funk an approach (Org. Lett. 2010, 12, 4912) based on ring-closing alkyne metathesis. The efficient assembly of 3 he reported illustrates the power of convergent design in target-directed synthesis. A practical limit on applications of alkyne metathesis is the requirement for internal alkynes, necessitating methyl capping of a terminal alkyne. In an alternative approach, Professor Funk took advantage of the long-known ( J. Chem. Soc. 1954 , 3201) equilibration of a terminal alkyne 4 to the internal alkyne 5. Homologation of 5 with the phosphonate 6, followed by condensation with the ketone 7, then delivered the furan 8. The assembly of the other half of 1 began with the commercial alcohol derived by reduction of D -pyroglutamic acid. Protection gave 9, which on hydride addition and dehydration was converted to 10. One-carbon homologation with the Vilsmeier-Haack reagent proceeded with the expected regiocontrol. This set the stage for the triply convergent assembly of 14 , first reductive amination of the aldehyde 11 with 12 , then acylation of the resulting secondary amine with 13. The nucleophilic 14 was condensed with the aldehyde 8 to give an enone (not illustrated). Exposure of the enone to InCl 3 initiated an elegant cascade cyclization, first of the enamide in a conjugate sense to the enone, then Friedel-Crafts addition of the resulting N-stabilized carbocation to the furan, to deliver 15. The pendant silyloxymethyl group exerted the hoped-for diastereocontrol, allowing the direct construction of the central tetracycle of 3. Hydrolysis and decarboxylation completed the assembly of the diyne 1. Initially, it was found that exposure of 1 to a molybdenum catalyst delivered 2 in only modest yield. As an alternative, they employed the technically more challenging tungsten-based Schrock catalyst. Later, they found that the recently developed Fürstner Mo protocol also worked well. The amide 2 could readily be carried on to the triene 18. With the first-generation Grubbs catalyst G1, kinetic ring-closing metathesis of 18, to complete the assembly of (-)-nakadomarin 3, could be effected without jeopardizing the existing Z alkene.
8
Taber, Douglass F. "The Kan Synthesis of the Streptomyces Alkaloid SB-203207." In Organic Synthesis. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780190646165.003.0092.
Full textAbstract:
The alkaloid SB-203207 3, isolated from a Streptomyces species by a SmithKline Beecham group, was shown to inhibit isoleucyl tRNA synthetase with an IC50 of less than 2 nM. Toshiyuki Kan of the University of Shizuoka envisioned (Org. Lett. 2014, 16, 1646) that the carbocyclic core of 3 could be assembled by the Rh-mediated cyclization of 1 to 2. The authors had already demonstrated (Org. Lett. 2008, 10, 169) the cyclization of 1 to 2. For the assembly of 3, they needed to scale up the preparation of 1. To this end, they required the mandelamide 5 and the aldehyde 8. To prepare 5, they devised a new preparation of diazoacetates, condensation with bromoacetyl bromide followed by exposure to the bis sulfonamide. The aldehyde 8 was prepared from the acid 6 (commercial, or Org. Synth. 2004, Coll. Vol. 10, 228). The preparation of the third component of 3, the acid 9, had been described earlier by Banwell and Easton (Bioorg. Med. Chem. 2003, 11, 2687). The cyclization of 1 proceeded smoothly with 0.1% loading of the Rh catalyst, to give 2 in 72% de (85:15 ratio of enantiomers of the carbocyclic core). The enantiomeric excess could be upgraded by recrystallization of a later intermediate. The ester 2 was exchanged with allyl alcohol to give 10, presumably with recovery of the liberated chiral auxiliary 4. Formaldehyde added to the β-keto ester 10 from the more open face. Hydride addition from that same face then delivered the diol 11. The allyl ester was removed, and the free acid was activated with SOCl2 then condensed with ammonia to give the primary amide. Ozonolysis followed by acidic methanol led to cyclization onto the amide, allowing ready differentiation of the two ends of the alkene. Reduction completed the preparation of the lactam 12. The nitrogen was sulfonylated, then the activated lactam was opened with assistance from the liberated primary alcohol. After acetal hydrolysis, the sulfonamide added to the aldehyde to give, after dehydration, the enamide 13. Inversion of the carboxyl converted the hydroxy acid to the urethane, that was formylated with the modified Vilsmeier reagent. Protection and deprotection followed by methylation then delivered the vinylogous amide 14.
9
Taber, Douglass F. "The Deslongchamps Synthesis of (+)-Cassaine." In Organic Synthesis. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780190646165.003.0091.
Full textAbstract:
Although the Na+-K+-ATPase inhibitor (+)-cassaine 4 was isolated from the bark of Erythrophleum guineense in 1935, the structure was not established until 1959. Intriguing features of 4 include the unsaturated amide and the axial secondary methyl group, both pendant to the C ring. Pierre Deslongchamps, now at Université Laval, envisioned (Org. Lett. 2013, 15, 6270) that the relative stereochemistry of the secondary methyl could be established kinetically by intramolecular Michael addition of the enolate formed by the addition of the anion of 2 to the enone 1 to give 3. The sulfoxide 2 was readily prepared by the addition (Tetrahedron Lett. 1990, 31, 3969) of the anion derived from methyl phenyl sulfoxide to methyl crotonate. The enone 1 was prepared from commercial dihydrocarvone 5. Robinson annulation with ethyl vinyl ketone 6 (Tetrahedron 2000, 56, 3409) led to 7, that was reductively methylated, reduced further, and protected to give 8. Oxidative cleavage of the pendant isopropenyl group followed by Baeyer–Villiger oxidation, hydrolysis, and further oxidation gave the ketone 9, that was methoxycarbonylated, then oxidized further to 1. The addition of the anion derived from 2 to 1 presumably gave initially the axial adduct. Subsequent intramolecular Michael addition then proceeded selectively to one face of the residual enone to give, after elimination of the sulfoxide, the enone 3. The anionic cascade annulation that formed the C ring having been accomplished, the ester of 3 was removed by exposure to ethoxide to give 10, having the alkene conjugated with the B-ring ketone. Selective reduction followed by protection gave 11. In the course of the hydrogenolytic deprotection of the A-ring alcohol, selective hydrogenation of the tetrasubstituted alkene was also observed. Increasing the H2 pressure and extending the reaction time gave complete conversion to the desired 12, the relative configuration of which was established by X-ray crystallography. A series of protection, reduction, and oxidation steps led to the C-ring ketone, that was methoxycarbonylated to give 14. Reduction followed by dehydration gave the unsaturated ester, that was reduced to the saturated ester with Mg in methanol. Reduction followed by oxidation then delivered the aldehyde 15. After some investigation, it was found that the aldehyde could be converted to the desired enol triflate by exposure to KHMDS and the Comins reagent.
Conference papers on the topic "Hydrolysis-dehydration"
1
Anderson, W. H., M. Quibrera, W. K. O'Neal, et al. "Accelerated ATP Hydrolysis in Airway Surface Liquid (ASL) Provides a Mechanism for Mucus Dehydration in Chronic Bronchitis." In American Thoracic Society 2019 International Conference, May 17-22, 2019 - Dallas, TX. American Thoracic Society, 2019. http://dx.doi.org/10.1164/ajrccm-conference.2019.199.1_meetingabstracts.a3847.
Full text
2
Mathew, Anil, Mitch Crook, Keith Chaney, and Andrea Humphries. "Bioethanol Production From Canola Straw Using a Continuous Flow Immobilized Cell System." In ASME 2012 6th International Conference on Energy Sustainability collocated with the ASME 2012 10th International Conference on Fuel Cell Science, Engineering and Technology. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/es2012-91061.
Full textAbstract:
Global cultivation of canola increased by approximately 22% between 2000 and 2009, due to increased demand for canola oil for biodiesel production and as an edible oil. In 2009 over 290,000 km2 of canola was cultivated globally. In contrast to oilseed, the commercial market for canola straw is minimal and it is generally ploughed back into the field. The high carbohydrate content (greater than 50 % by dry weight) of canola straw suggests it would be a good feedstock for second-generation bioethanol production. There are four major steps involved in bioethanol production from lignocellulosic materials: (i) pretreatment, (ii) hydrolysis, (iii) fermentation, and (iv) further purification to fuel grade bioethanol through distillation and dehydration. Previous research demonstrated a glucose yield of (440.6 ± 14.9) g kg−1 when canola straw was treated using alkaline pretreatment followed by enzymatic hydrolysis. Whilst bioethanol can be produced using cells free in solution, cell immobilization provides the opportunity to reduce bioethanol production costs by minimizing the extent to which down-stream processing is required, and increasing cellular stability against shear forces. Furthermore, the immobilization process can reduce substrate and product inhibition, which enhances the yield and volumetric productivity of bioethanol production during fermentation, improves operational stability and increases cell viability ensuring cells can be used for several cycles of operation. Previous research used cells of Saccharomyces cerevisiae immobilized in Lentikat® discs to convert glucose extracted from canola straw to bioethanol. In batch mode a yield of (165.1 ± 0.1) g bioethanol kg−1 canola straw was achieved. Continuous fermentation is advantageous in comparison to batch fermentation. The amount of unproductive time (e.g. due to filling, emptying and cleaning) is reduced leading to increased volumetric productivity. The higher volumetric productivity of continuous fermentation means that smaller reactor vessels can be used to produce the same amount of product. This reduces the capital costs associated with a fermentation plant. Research demonstrated a higher bioethanol yield was attained (224.7 g bioethanol kg−1 canola straw) when glucose was converted to bioethanol using immobilized cells in packed-bed continuous flow columns. On an energy generation basis, conversion of 1 kg of canola straw to bioethanol resulted in an energy generation of 6 MJ, representing approximately 35% energy recovery from canola straw. The amount of energy recovered from canola straw could be improved by increasing the amount of energy recovered as bioethanol and by utilising the process by-products in a biorefinery concept.