Academic literature on the topic '2,6,9-trisubstituted purine'
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Journal articles on the topic "2,6,9-trisubstituted purine"
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Franěk, František, Věra Siglerová, Libor Havlíček, Miroslav Strnad, Tomáš Eckschlager, and Evžen Weigl. "Effect of the Purine Derivative Myoseverin and of Its Analogues on Cultured Hybridoma Cells." Collection of Czechoslovak Chemical Communications 67, no. 2 (2002): 257–66. http://dx.doi.org/10.1135/cccc20020257.
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Two 2,6,9-trisubstituted purine derivatives, 9-isopropyl-2,6-bis[(4-methoxybenzyl)amino]-9H-purine (myoseverin, PMYO, 1) and 9-isopropyl-2,6-bis[(2-methoxybenzyl)amino]-9H-purine (OMYO, 2), and two 6,9-disubstituted derivatives, 9-isopropyl-6-[(4-methoxybenzyl)amino]-9H-purine (3) and 9-isopropyl-6-[(2-methoxybenzyl)amino]-9H-purine (4), were synthesized with the aim to examine their cell proliferation inhibiting activity, and possible additional effects in cultures of hybridoma cells producing monoclonal antibody. The substances were tested over a concentration range from 0.003 to 30 μmol l-1. The most active compound 1 caused a total loss of cell viability at 1 μmol l-1, while its isomer 2 showed the same effect at 10 μmol l-1 concentration. In the presence of compound 1, but not of compound 2, the character of the cell cycle phases profile changed dramatically, most cells being arrested in the G2/M phase. At intermediate concentrations of compound 2 a substantially higher viable cell concentration was observed, relative to control. These differences demonstrated the principal significance of the position of the methoxy groups on the benzene rings for the biological effect. The 6,9-disubstituted derivatives 3 and 4 were without significant effect in the whole range of concentrations tested. The enhancement of monoclonal antibody production, observed in certain concentration intervals of added substances, was of marginal character.
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Mazumdar, Pooja Anjali, Amit Kumar Das, Anne Kristin Bakkestuen, Lise-Lotte Gundersen, and Valerio Bertolasi. "9-(2-Phenylethyl)-6-(2-thienyl)-9H-purine." Acta Crystallographica Section E Structure Reports Online 57, no. 11 (October 13, 2001): o1052—o1054. http://dx.doi.org/10.1107/s1600536801016907.
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Wang, Ning-Yu, Mei Deng, Yong Xia, and Luo-Ting Yu. "6-Chloro-9-(2-nitrophenylsulfonyl)-9H-purine." Acta Crystallographica Section E Structure Reports Online 67, no. 3 (February 23, 2011): o687. http://dx.doi.org/10.1107/s1600536811003102.
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Belyakov, Sergey, Martins Ikaunieks, and Marina Madre. "9-(2-Acetoxyethoxymethyl)-2-formamido-6-(p-tolylsulfonyloxy)purine." Acta Crystallographica Section E Structure Reports Online 61, no. 10 (September 28, 2005): o3452—o3454. http://dx.doi.org/10.1107/s1600536805030175.
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Hřebabecký, Hubert, Milena Masojídková, and Antonín Holý. "Synthesis of Racemic 9-(6- and 2,6-Substituted 9H-Purin-9-yl)-5-oxatricyclo[4.2.1.03,7]nonane-3-methanols, Novel Conformationally Locked Carbocyclic Nucleosides." Collection of Czechoslovak Chemical Communications 70, no. 1 (2005): 103–23. http://dx.doi.org/10.1135/cccc20050103.
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(1R*,3R*,6R*,7S*,9S*)- and (1R*,3R*,6R*,7S*,9R*)-9-Amino-5-oxatricyclo[4.2.1.03,7]nonane-3-methanols (16aand17a) were prepared from 2-(hydroxymethyl)bicyclo[2.2.1]hept-5-ene-2-methanol (10) in five easy steps. The amines16aand17awere used to construct 6-chloro-9H-purine20and21, 2-amino-6-chloro-9H-purine30and31, and 6-chloro-8-methyl-9H-purine analogues34and35. Ammonolysis of these compounds led to 6-amino-9H-purine22aand23a, 2,6-diamino-9H-purine32and33, and 6-amino-8-methyl-9H-purine derivatives of 5-oxatricyclo[4.2.1.03,7]nonane-3-methanol36and37. (1R*,3R*,6R*,7S*,9S*)- and (1R*,3R*,6R*,7S*,9R*)-9-[6-(Dimethylamino)-9H-purin-9-yl]-5-oxatricyclo[4.2.1.03,7]nonane-3-methanols (22band23b), and (1R*,3R*,6R*,7S*,9S*)- and (1R*,3R*,6R*,7S*,9R*)-9-[6-(cyclopropylamino)-9H-purin-9-yl]-5-oxatricyclo[4.2.1.03,7]nonane-3-methanols (22cand23c) were prepared by aminolysis of20and21.
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Brændvang, Morten, and Lise-Lotte Gundersen. "2-Chloro-6-(2-furyl)-9-(4-methoxybenzyl)-9H-purine." Acta Crystallographica Section C Crystal Structure Communications 63, no. 5 (April 14, 2007): o274—o276. http://dx.doi.org/10.1107/s0108270107011596.
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Hocek, Michal, Milena Masojídková, Antonín Holý, Graciela Andrei, Robert Snoeck, Jan Balzarini, and Erik De Clercq. "Synthesis and Antiviral Activity of Acyclic Nucleotide Analogues Derived from 6-(Aminomethyl)purines and Purine-6-carboxamidines." Collection of Czechoslovak Chemical Communications 61, no. 10 (1996): 1525–37. http://dx.doi.org/10.1135/cccc19961525.
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The synthesis of a series of 9-(2-phosphonomethoxyalkyl) derivatives of 6-(aminomethyl)purine 11, 2-amino-6-(aminomethyl)purine 12 and purine-6-carboxamidine 14 is reported. The 6-cyanopurines 1 and 2 were selectively alkylated with 2-[bis(isopropyloxy)phosphonylmethoxy]alkyl synthons 3 and 4 at the 9-position. Catalytic hydrogenation of the obtained 9-{2-[bis(isopropyloxy)phosphonylmethoxy]alkyl}-6-cyanopurines 9 and 10 followed by treatment with bromotrimethylsilane afforded the title compounds 11 and 12. Analogous acyclic nucleotides derived from purine-6-carboxamidines 14 were prepared from the cyanopurines 9a and 10a by treatment with sodium methoxide and ammonium chloride followed by deprotection. Compounds 11 and 12 exhibited moderate activity (MIC50 = 3-50 μg/ml) against herpes simplex virus type 1, varicella-zoster virus and Moloney murine sarcoma virus in vitro.
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Yi, Xiu-Guang, Chong-Bo Liu, Zi-Sheng Wu, Jun-Hui Chen, and Hui-Liang Wen. "Dimethyl 2-[2-(2-amino-6-chloropurin-9-yl)ethyl]malonate." Acta Crystallographica Section E Structure Reports Online 63, no. 3 (February 7, 2007): o1113—o1114. http://dx.doi.org/10.1107/s1600536807004552.
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In the title compound, C12H14ClN5O4, the dihedral angles between the purine plane and two methoxycarbonyl planes are 15.806 (19) and 68.818 (18)°. Intermolecular N—H...O and N—H...N hydrogen bonds link molecules into bands along the b axis; they are further aggregated via C—H...O interactions into layers parallel to the ab plane.
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Kelley, James L., and Ed W. McLean. "Synthesis of 9-(2-fluorobenzyl)-6-methylamino-9H-purine." Journal of Heterocyclic Chemistry 23, no. 4 (July 1986): 1189–93. http://dx.doi.org/10.1002/jhet.5570230445.
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Adebambo, Kassim F., Nicola M. Howarth, and Georgina M. Rosair. "Benzyl 2-amino-6-chloro-9H-purine-9-carboxylate." Acta Crystallographica Section E Structure Reports Online 61, no. 2 (January 29, 2005): o486—o488. http://dx.doi.org/10.1107/s1600536805002047.
Full textDissertations / Theses on the topic "2,6,9-trisubstituted purine"
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McKeveney, Declan, and n/a. "The Solid-Phase Combinatorial Synthesis of 2,6,9- Trisubstituted Purines as Potential Adenosine A3 Receptor Antagonists." Griffith University. School of Science, 2005. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20050830.120105.
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Purines as a class of compounds have been implicated in many biological systems, including as adenosine receptor antagonists. A method of synthesising 2,6,9-trisubstituted purines would be useful to produce small libraries of compounds for probing adenosine receptor selectivity. A library of trisubstituted purines has been achieved using a solid-phase methodology. The electronic properties of the substrate were found to result in difficulties with the loading of substrate onto the resin. Theoretical calculations provided the basis for mono-substitution in order to activate the substrate. This modified substrate has loaded onto the resin in reproducible and high yields. Amine and thiol, on-resin, C-2 substitution was shown to proceed at room temperature. This represents significantly milder conditions than are generally seen in the literature. This is due to the activating effect of the carbamate linker chosen on the pyrimidine ring. This also results in a faster reaction rate than is seen in the corresponding solution-phase reaction. This study showed that the electronic profile of the loaded substrate was responsible for the low alkylation on the carbamate nitrogen of loaded dichloro- or C-6 substituted chloropyrimidines. This reaction was modified by activating the pyrimidine ring via C-2 substitution and has been shown to go to completion with three different alkyl groups to give a clean product direct from resin cleavage. On-resin nitro reduction had been planned. The resin bound product would then be carried on to the next step of resin cleavage and cyclisation of the imidazole ring to give the final purine products. On resin reduction could not be achieved, however, cleavage of the compound from the resin and reduction in solution was found to be efficient as the cyclisation reagents could be included in this step without interfering with yield or purity of products and so this represents a clear improvement upon the planned synthesis. Efforts to fully characterise the library brought up issues of purine NMR. Extremely broad signals were observed in the proton spectra of many of the compounds making assignments difficult. Broad 13C NMR signals have also been observed. Restricted rotation about the substituent N-C bond is responsible for these problems. Crystal structure data has confirmed the double bond character of this bond with one of the substituted pyrimidines. High temperature NMR experiments have demonstrated how this can be overcome and the fine structure of the spectra observed. HMBC and COSY correlations have been used alongside the 1H and 13C spectra to allow full characterisation of the compounds wherever possible. Receptor homology models were created and updated for all four adenosine receptor subtypes. Known adenosine agonists and antagonists were created and minimised for use in docking experiments. Receptor docking experimental data is reported. Binding assays are being carried out by a third party and will be submitted for publication at a later date. A small library of 2,6,9-trisubstituted purines has been synthesised, exemplifying an efficient and robust method to achieve pure compounds for biological evaluation. A good level of diversity has been achieved at each combinatorial position (two substitutions and an N-alkylation). Final compounds have been isolated in good yields with a high level of purity.
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Lespinasse, Anne-Dominique. "Voies d’accès à des dérives aminés du D-fructofuranose et du D-psicofuranose." Lyon, INSA, 1985. http://www.theses.fr/1985ISAL0057.
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Nos travaux s'inscrivent dans le domaine de la chimie des cétohexoses et en particulier de deux d'entre eux : le D-fructose et le D-psicose. En vue de l'évaluation des potentialités biologiques de ces oses, nous avons d'abord étudié les voies'd'accès à des nucléosides dérivés du D-fructofuranose puis la synthèse de composés aminés issus de cet ose et du D-psicofuranose. Cette approche nous a amené à mettre au point la préparation d'un dérivé du D-psicofuranose comportant une différenciation au niveau de ses deux hydroxyméthyles. Ce composé devrait permettre de résoudre certains problèmes synthétiques inhérents à la chimie des cétohexoses et qui n'avaient pas trouvé jusqu'ici de solution satisfaisante.
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Brun, Virginie. "Inhibiteurs de kinases dépendantes des cyclines : développement d'une nouvelle stratégie de synthèse de purines 2, 6, 9-trisubstituées sur support solide." Paris 11, 2002. http://www.theses.fr/2002PA112044.
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Pour mettre en évidence de nouveaux inhibiteurs puissants et spécifiques de certaines CDK, nous avons développé une nouvelle stratégie de synthèse sur support solide afin de construire une banque originale de purines 2,6,9-trisubstituées. La stratégie de synthèse doit permettre l'introduction séquentielle des éléments de diversité dans les trois positions du noyau purine. Notre approche met en jeu une purine substituée en C6 par un groupement soufré et immobilisée sur la résine via cet atome de soufre. La faible réactivité et la stabilité de la liaison C6-S par rapport à la liaison C6-Cl, nous donne la possibilité d'introduire une grande variété de fonctions en N9 et en C2 avant la réaction en C6. L'activation ultérieure du soufre par oxydation permet dans le même temps l'introduction d'un substituant nucléophile en C6 ainsi que le décrochage de la purine trisubstituée du polymère et sa récupération en solution. .In order to find more potent and specific inhibitors of CDKs, we have developed a new solid phase synthesis strategy for the construction of 2,6,9-trisubstituted purine libraries. The objective of the approach is to permit the sequential introduction of functionality onto all three crucial positions of the purine ring. Our strategy is based upon the reactivity of a 6-thio substituted purine scaffold connected to the resin support via the sulfur atom. The low reactivity of the purine C6-S bond relative to C6-Cl provides the possibility to introduce a wide variety of functionality at the N9 and C2 position prior to reaction at C6. Subsequent activation of the sulfur atom (oxidation) then opens the way to concomitant introduction of a substituent (nucleophile) at C6 and cleavage of the trisubstituted purine product from the resin. It was necessary to first validate the synthetic plan in solution. The condensation of the 2-iodo-6-chloropurine with benzylthiol was achieved in high yield (this key transformation served to mimic the attachment of the purine scaffold to a resin support). .
Book chapters on the topic "2,6,9-trisubstituted purine"
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Yahyazadeh, Asieh. "Synthesis and Characterization of 6-Carbamoyl-2-Alkyl-9-(Phenyl or Benzyl)-9H-Purines." In Chemistry: The Key to our Sustainable Future, 141–46. Dordrecht: Springer Netherlands, 2013. http://dx.doi.org/10.1007/978-94-007-7389-9_10.
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Taber, Douglass. "Total Synthesis by Alkene Metathesis: Amphidinolide X (Urpí/Vilarrasa), Dactylolide (Jennings), Cytotrienin A (Hayashi), Lepadin B (Charette), Blumiolide C (Altmann)." In Organic Synthesis. Oxford University Press, 2011. http://dx.doi.org/10.1093/oso/9780199764549.003.0031.
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To assemble the framework of the cytotoxic macrolide Amphidinolide X 3, Fèlix Urpí and Jaume Vilarrasa of the Universitat de Barcelona devised (Organic Lett. 2008, 10, 5191) the ring-closing metathesis of the alkenyl silane 1. No Ru catalyst was effective, but the Schrock Mo catalyst worked well. In the course of a synthesis of (-)-Dactylolide 6, Michael P. Jennings of the University of Alabama offered (J. Org. Chem. 2008, 73, 5965) a timely reminder of the particular reactivity of allylic alcohols in ring-closing metathesis. The cyclization of 4 to 5 proceeded smoothly, but attempted ring closing of the corresponding bis silyl ether failed. Polyenes such as ( + )-Cytotrienin A 8 are notoriously unstable. It is remarkable that Yujiro Hayashi of the Tokyo University of Science could (Angew. Chem. Int. Ed. 2008, 47, 6657) assemble the triene of 8 by the ring-closing metathesis of the highly functionalized precursor 7. Bicyclo [2.2.2] structures such as 9 are readily available by the addition of, in this case, methyl acrylate to an enantiomerically-pure 2-methylated dihydropyridine. André B. Charette of the Université de Montréal found (J. Am. Chem. Soc. 2008, 130, 13873) that 9 responded well to ring-opening/ring-closing metathesis, to give the octahydroquinoline 10. Functional group manipulation converted 10 into the Clavelina alkaloid ( + )-Lepadin B 11. The construction of trisubstituted alkenes by ring-closing metathesis can be difficult, and medium rings with their transannular strain are notoriously challenging to form. Nevertheless, Karl-Heinz Altmann of the ETH Zürich was able (Angew. Chem. Int. Ed. 2008, 47, 10081), using the H2 catalyst, to cyclize 12 to cyclononene 13, the precursor to the Xenia lactone ( + )-Blumiolide C 14. It is noteworthy that these fi ve syntheses used four different metathesis catalysts in the key alkene forming step. For the cyclization of 7, the use of the Grubbs first generation catalyst G1, that couples terminal alkenes but tends not to interact with internal alkenes, was probably critical to success.
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Taber, Douglass. "Adventures in Alkaloid Synthesis: ( + )-α-Kainic Acid (Jung), 223AB (Ma), Pumiliotoxin 251F (Jamison), Spirotryprostatin B (Trost), (-)-Drupacine (Stoltz)." In Organic Synthesis. Oxford University Press, 2011. http://dx.doi.org/10.1093/oso/9780199764549.003.0058.
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Enantiomerically-pure natural amino acids can serve as starting materials for alkaloid synthesis. In his synthesis (J. Org. Chem. 2007, 72, 10114) of (-)-α-kainic acid 3, Kyung Woon Jung of the University of Southern California prepared the diazo sulfone 1 from (L)-glutamic acid. Rh-mediated intramolecular C-H insertion proceeded with the predicted high diastereoselectivity, to give the lactam 2, containing seven of the ten carbon atoms and two of the three stereogenic centers of (-)-α-kainic acid 3. The absolute configuration of the nitrogen ring system(s) can also be established by chiral catalysis. Dawei Ma of the Shanghai Institute of Organic Chemistry has developed (J. Am. Chem. Soc. 2007, 129, 9300) a chiral Cu catalyst that mediated the addition of alkynyl esters and ketones to the prochiral acylated pyridine 4 in high enantiomeric excess. The dihydro-pyridines (e.g. 5) so produced will be versatile starting materials both for alkaloid synthesis, as illustrated by the preparation of the Dendrobatid alkaloid 223AB 6, and for the production of pharmaceuticals. In his synthesis of the Dentrobatid alkaloid pumiliotoxin 251D 9, Timothy F. Jamison took (J. Org. Chem. 2007, 72, 7451) as his starting material another amino acid, proline. Ni-mediated cyclization of the epoxide 8 proceeded with high geometric and regiocontrol, to give 9. The chemistry to convert 7 into 8 with high diastereocontrol and without racemization is a substantial contribution that will have many other applications. In his synthesis (Organic Lett. 2007, 9, 2763) of spirotryprostatin B 12, Barry M. Trost of Stanford University also started with proline, which was readily elaborated to the oxindole 10. The question was, could the Pd-catalyzed decarboxylation of 10 be induced to provide specifically 11? Counting geometric isomers of the trisubstituted alkene, and allylic regioisomers, as well as diastereomers, there were sixteen possible products from this prenylation. Using chiral Pd control, the rearrangement proceeded with 14:1 regiocontrol, and 16:1 diasterocontrol. Oxidative cyclization of 11 then delivered spirotryprostatin B 12. The Cephalotaxus alkaloid (-)-drupacine 19 has five stereogenic centers, including four of the five positions on the cyclopentane ring.
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Taber, Douglass F. "The Fukuyama Synthesis of Gelsemoxonine." In Organic Synthesis. Oxford University Press, 2015. http://dx.doi.org/10.1093/oso/9780190200794.003.0091.
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The compact and highly functionalized Gelsemium alkaloids, exemplified by gelsemine (OHL20060403) and gelsemoxonine 3, offer a substantial challenge. The cytotoxicity of closely related alkaloids adds to the interest in this class. Tohru Fukuyama of the University of Tokyo envisioned (J. Am. Chem. Soc. 2011, 133, 17634) that cyclopropane-accelerated Cope rearrangement of 1 could deliver 2, ready for further functionalization to 3. The starting material for the synthesis was the enantiomerically pure acetate 4, for which a practical synthetic route was developed. Conjugate addition of 5 then proceeded away from the acetoxy group to give, after intramolecular alkylation, the cyclopropane 6. Selective protection of the derived triol 7 led to a monopivalate that was oxidized to the keto aldehyde 8. Condensation with the oxindole 9 followed by silylation then completed the assembly of 1. The trisubstituted alkene of 1 was established as a single geometric isomer. It followed that in the product 2, the oxindole and the bridging ether had the appropriate relative stereochemical arrangement. The product silyl enol ether was deprotected with fluoride to liberate the ketone 2. With 2 in hand, the next challenge was the kinetic installation of the less stable secondary aminated stereogenic center. To this end, the aldehyde 10 was exposed to TMS-CN and DBU. Under the reaction conditions, the alkene of the intermediate β,γ-unsaturated silylated cyanohydrin was brought into conjugation. Kinetic quench with allyl alcohol gave 11 with a 4:1 preference for the desired endo diastereomer 11. Inversion of the carboxyl then led to the protected amine 12. The ketone 12 was formylated under modified Vilsmeier-Haack conditions, first with Bredereck’s reagent 13 and then with oxalyl chloride, leading to the chloro aldehyde 14. The chlorine was removed by selective Pd-catalyzed reduction, and the product aldehyde was exposed to ethyl magnesium bromide followed by IBX to give the ethyl ketone 15. Epoxidation of the α,β-unsaturated ketone proceeded across the expected exo face leading to 16. The deprotected amine then opened the epoxide to establish the aminated quaternary center and complete the synthesis of gelsemoxonine 3.
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Taber, Douglass F. "The Fürstner Synthesis of Amphidinolide F." In Organic Synthesis. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780190646165.003.0090.
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The amphidinolides, having zero, one, or (as exemplified by amphidinolide F 3) two tetrahydrofuran rings, have shown interesting antineoplastic activity. It is a tribute to his development of robust Mo catalysts for alkyne metathesis that Alois Fürstner of the Max-Planck-Institut für Kohlenforschung Mülheim could with confidence design (Angew. Chem. Int. Ed. 2013, 52, 9534) a route to 3 that relied on the ring-closing metathesis of 1 to 2 very late in the synthesis. Three components were prepared for the assembly of 1. Julia had already reported (J. Organomet. Chem. 1989, 379, 201) the preparation of the E bromodiene 5 from the sulfone 4. The alcohol 7 was available by the opening of the enantiomerically-pure epoxide 6 with propynyl lithium, followed by oxidation following the Pagenkopf protocol. Amino alcohol-directed addition of the organozinc derived from 5 to the aldehyde from oxidation of 7 completed the assembly of 8. Addition of the enantiomer 10 of the Marshall butynyl reagent to 9 followed by protection, oxidation to 11, and addition of, conveniently, the other Marshall enantiomer 12 led to the protected diol 13. Silylcupration–methylation of the free alkyne set the stage for selective desilylation and methylation of the other alkyne. Iodination then completed the trisubstituted alkene of 14. Methylation of the crystalline lactone 15, readily prepared from D-glutamic acid, led to a mixture of diastereomers. Deprotonation of that product followed by an aqueous quench delivered 16. Reduction followed by reaction with the phosphorane 17 gave the unsaturated ester, that cyclized with TBAF to the crystalline 18. The last stereogenic center of 22 was established by proline-mediated aldol condensation of the aldehyde 19 with the ketone 20. To assemble the three fragments, the ketone of 21 was converted to the enol triflate and thence to the alkenyl stannane. Saponification gave the free acid 22, that was activated, then esterified with the alcohol 18. Coupling of the stannane with the iodide 14 followed by removal of the TES group led to the desired diyne 1. It is noteworthy that the Mo metathesis catalyst is stable enough to tolerate the free alcohol of 1 in the cyclization to 2.
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Taber, Douglass F. "C–O Ring Construction: (+)-Varitriol (Liu), (+)-Isatisine A (Panek), (+)-Herboxidiene/GEX1A (Ghosh), (–)-Englerin A (Chain), Platensimycin (Lear/Wright)." In Organic Synthesis. Oxford University Press, 2015. http://dx.doi.org/10.1093/oso/9780190200794.003.0050.
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En route to (+)-varitriol 4, Xue-Wei Liu of Nanyang Technological University coupled (Org. Lett. 2011, 13, 42) the glycosyl fluoride derived from 1 with the alkynyl fluoroborate salt 2 to give 3. James S. Panek of Boston University condensed (Org. Lett. 2011, 13, 502) the enantiomerically pure allyl silane 6 with the aldehyde 5 to give the tetrahydrofuran 7. Further elaboration led to (+)-isatisine A 8, the only alkaloid so far isolated from the roots and leaves of the traditional Asian folk medicine Isatis indigotica. Arun K. Ghosh of Purdue University effected (Org. Lett. 2011, 13, 66) oxidative ring expansion of the enantiomerically pure furan 9 to give, after reduction, the enone 10. This established the tetrahydropyran of (+)-herboxidiene 11, also known as GEXIA. William J. Chain of the University of Hawaii observed (J. Am. Chem. Soc. 2011, 133, 6553) unusual diastereoselectivity in the conjugate addition of the enone 12 to the enantiomerically pure aldehyde 13. Although eight diastereomers could have been formed, the reaction mixture was 2/3 the diastereomer 14. Reductive cyclization (SmI2) of 14 then led to (–)-englerin A 15. Martin J. Lear of the National University of Singapore cyclized (Org. Lett. 2010, 12, 5510) the enantiomerically pure lactol 16 to 17 with catalytic Bi(OTf)3. Dennis L. Wright of the University of Connecticut prepared (Org. Lett. 2011, 13, 2263) 21 by dipolar cycloaddition of 20 to 19. Both 17 and 21 were carried on via intramolecular alkylation toward platensimycin 18.
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Taber, Douglass. "The Johnson Synthesis of Zaragozic Acid C." In Organic Synthesis. Oxford University Press, 2011. http://dx.doi.org/10.1093/oso/9780199764549.003.0100.
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The zaragozic acids, exemplified by Zaragozic Acid C 3, are picomolar inhibitors of cholesterol biosynthesis. Jeffrey S. Johnson of the University of North Carolina developed (J. Am. Chem. Soc. 2008, 130, 17281) an audacious silyl glyoxylate cascade approach to the oxygenated backbone fragment 1. Intramolecular aldol cyclization converted 1 to 2, setting the stage for the construction of 3. The lactone 2 includes five stereogenic centers, two of which are quaternary. The authors were pleased to observe that exposure of 4 to vinyl magnesium bromide 5 led, via condensation, silyl transfer, condensation, and again silyl transfer, to a species that was trapped with t-butyl glyoxylate 6 to give 7 as a single diastereomer. This one step assembled three of the stereogenic centers of 2, including both of the quaternary centers. The alcohol 7 so prepared was racemic, so the wrong enantiomer was separated by selective oxidation. Intramolecular aldol condensation of the derived α-benzyloxy acetate 1 then completed the construction of 2. Addition of the alkyl lithium 8, again as a single enantiomerically-pure diasteromer, to 2 gave the hemiketal 9. Exposure of 9 to acid initially gave a mixture of products, but this could be induced to converge to the tricyclic ester 10. To convert 10 to 11 , the diastereomer that was needed for the synthesis, two of the stereogenic centers had to be inverted. This was accomplished by exposure to t-BuOK/t-amyl alcohol, followed by re-esterification. The inversion of the secondary hydroxyl group was thought to proceed by retro-aldol/re-aldol condensation. Debenzylation of 11 followed by acetylation delivered 12, an intermediate in the Carreira synthesis of the zaragozic acids. Following that precedent, the ring acetates of 12 were selectively removed, leaving the acetate on the side chain. Boc protection was selective for the endo ring secondary hydroxyl, leaving the exo ring secondary hydroxyl available for condensation with the enantiomerically-pure acid 13. Global deprotection then completed the synthesis of Zaragozic Acid C 3. The key to the success of this synthesis of the complex spiroketal 3 was the assembly of 7 in one step as a single diastereomer from the readily-available building blocks 4, 5, and 6.
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Taber, Douglass F. "The Williams Synthesis of (–)-Khayasin." In Organic Synthesis. Oxford University Press, 2015. http://dx.doi.org/10.1093/oso/9780190200794.003.0101.
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The tetranortriterpenoid (–)-khayasin 3 recently emerged as a potent and selective insecticide against the Coconut leaf beetle Brontispa longissima. In considering a synthetic route to 3, Craig M. Williams of the University of Queensland envisioned (J. Org. Chem. 2012, 77, 8913) the convergent preparation of the allyl vinyl ether 1 and subsequent Claisen rearrangement to the enone 2. To pursue this strategy, the ketone 8 and the allylic alcohol 15 had to be prepared in enantiomerically pure form. To this end, the DIP-Cl-derived enolate of the ketone 7 was added to the aldehyde 6 to give a secondary alcohol, exposure of which to KH led to the enone 8 in high ee. Methyl triflate converted the enone into the enol ether 9. The α-pinene used in the preparation of DIP-Cl was 83% ee. The authors have optimized (Adv. Synth. Catal. 2009, 351, 1148) the Morita-Baylis-Hillman addition of cyclohexenone 10 to formaldehyde to give, after silylation, the enone 11. Methylation followed by DIP-mediated aldol condensation with 13 led to the alcohol 14. Exposure of the derived acetate to lithium diisopropylamide induced cyclization and dehydration. Deprotection completed the preparation (Tetrahedron 2006, 62, 7355) of 15. Fortunately, the enantiomers of 15 could be separated chromatographically. Material having >99% ee was taken onto the next step. Warming of 9 and 15 in the presence of acid delivered the coupled ketone 2 accompanied by the ether 1. Further heating of 1 converted it (Chem. Commun. 2011, 47, 2258) to 2. To form the last ring, the enone 2 was epoxidized to give 16. The reduction of 16 with aluminum amalgam gave preparatively useful amounts of 17. Esterification completed the synthesis of 3. Most total syntheses yield only the target natural product. In this biomimetic project, intermediates 15, 2, and 17 were themselves natural products, and oxidation of 17 delivered an additional natural product, 18. The preparation of 14 and of 8 underscores the importance of the asymmetric transformation of prochiral starting materials, cyclic and acyclic. Although DIP-Cl is used in stoichiometric amounts in both cases, it is not expensive. The preparation of 8, in particular, offers a potentially general approach to high ee-substituted cyclohexenones.
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Taber, Douglass. "Stereocontrolled Carbocyclic Construction: The Trauner Synthesis of the Shimalactones." In Organic Synthesis. Oxford University Press, 2011. http://dx.doi.org/10.1093/oso/9780199764549.003.0080.
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Benjamin List of the Max Planck Institute, Mülheim devised (J. Am. Chem. Soc. 2008, 130, 6070) a chiral primary amine salt that catalyzed the enantioselective epoxidation of cyclohexenone 1 . Larger ring and alkyl-substituted enones are also epoxidized with high ee. Three- and four-membered rings are versatile intermediates for further transformation. Tsutomu Katsuki of Kyushu University developed (Angew. Chem. Int. Ed. 2008, 47, 2450) an elegant Al(salalen) catalyst for the enantioselective Simmons-Smith cyclopropanation of allylic alcohols such as 3. Kazuaki Ishihara of Nagoya University found (J. Am. Chem. Soc. 2007, 129, 8930) chiral amine salts that effected enantioselective 2+2 cycloaddition of α-acyloxyacroleins such as 5 to alkenes to give the cyclobutane 7 with high enantio- and diastereocontrol. Gideon Grogan of the University of York overexpressed (Adv. Synth. Cat. 2008, 349, 916) the enzyme 6-oxocamphor hydrolase in E. coli . The 6-OCH so prepared converted prochiral diketones such as 8 to the cyclopentane 9 in high ee. Richard P. Hsung of the University of Wisconsin found (Organic Lett. 2008, 10, 661) that the carbene produced by oxidation of the ynamide 10 cyclized to 11 with high de. Teck-Peng Loh of Nanyang Technological University extended (J. Am. Chem. Soc. 2008, 130, 7194) butane-2,3-diol directed cyclization to the preparation of the cyclopentane 15. Note that sidechain relative configuration is also controlled. We established (J. Org. Chem. 2008, 73, 3467) that the thermal ene reaction of 17 delivered the tetrasubstituted cyclopentane 18 as a single diastereomer. Tony K. M. Shing of the Chinese University of Hong Kong devised (J. Org. Chem. 2007, 72, 6610) a simple protocol for the conversion of carbohydrate-derived lactones such as 19 to the highly-substituted, enantiomerically-pure cyclohexenone 21. Hiromichi Fujioka and Yasuyuki Kita of Osaka University established (Organic Lett. 2007, 9, 5605) a chiral diol-mediated conversion of the cyclohexadiene 22 to the diastereomerically pure cyclohexenone 24. Dirk Trauner, now of the University of Munich, reported (Organic Lett. 2008, 10, 149) an elegant assembly of the neuritogenic polyketide shimalactone A 28.
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Taber, Douglass. "The Burke Synthesis of ( + )-Didemniserinolipid B." In Organic Synthesis. Oxford University Press, 2011. http://dx.doi.org/10.1093/oso/9780199764549.003.0088.
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The sulfate ( + )-didemniserinolipid B 3, isolated from the tunicate Didemnum sp, has an intriguing spiroether core. A key step in the synthesis of 3 reported (Organic Lett. 2007, 9, 5357) by Steven D. Burke of the University of Wisconsin was the selective ring-closing metathesis of 1 to 2. The diol 6 that was used to prepare the ketal 1 was readily prepared from the inexpensive D-mannitol 4. Many other applications can be envisioned for the enantiomerically-pure diol 6 and for the monoacetate and bis acetate that are precursors to it. To set up the metathesis, the β, γ-unsaturated ketone 10 was needed. To this end, the keto phosphonate derived from the addition of the phosphonate anion 8 to the lactone 7 was condensed with phenyl acetaldehyde 9. The derived enone 10 was a 5:1 mixture of β, γ- and α, β-regioisomers. The diol 6 is C2 -symmetrical, but formation of the ketal 1 dissolved the symmetry, with one terminal vinyl group directed toward the styrene double bond, and the other directed away from it. On exposure to the first generation Grubbs catalyst, ring formation proceeded efficiently, to give 2. Williamson coupling with the serine-derived alcohol 11 then gave 12. To establish the secondary alcohol of 13 and so of 3, the more electron rich alkene of 12 was selectively epoxidized, from the more open face. Diaxial opening with hydride then gave 13. With 13 in hand, another challenge of selectivity emerged. The plan had been to attach the ester-bearing sidechain to 13 using alkene metathesis, then hydrogenate. As the side-chain of 3 contained an additional alkene, this had to be present in masked form. To this end, the α-phenylselenyl ester 14 was prepared. Alkene metathesis with 13 proceeded smoothly, this time using the second generation Grubbs catalyst. The unwanted alkene was then removed by reduction with diimide, and the selenide was oxidized to deliver the α, β-unsaturated ester.
Conference papers on the topic "2,6,9-trisubstituted purine"
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Šišuļins, Andrejs, Irina Novosjolova, Māris Turks, and Ērika Bizdēna. "Synthesis of new fluorescent 9-alkyl-6-amino-2-triazolyl purines." In XVIth Symposium on Chemistry of Nucleic Acid Components. Prague: Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, 2014. http://dx.doi.org/10.1135/css201414231.
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Wang, Suh-Miin, Lee Muei Chng, Montha Meepripruk, and Pek-Lan Toh. "Vibrational frequencies and electronic structures of 2-amino-1, 9-dihydro-9-[(2-hydroxuethoxy) methyl]-6H-purin-6-one using density functional theory method." In INTERNATIONAL SYMPOSIUM ON GREEN AND SUSTAINABLE TECHNOLOGY (ISGST2019). AIP Publishing, 2019. http://dx.doi.org/10.1063/1.5126545.
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Solomon, Alvin A., Sean M. McDeavitt, V. Chandramouli, S. Anthonysamy, S. Kuchibhotla, and T. J. Downar. "Thoria-Based Cermet Nuclear Fuel: Sintered Microsphere Fabrication by Spray Drying." In 10th International Conference on Nuclear Engineering. ASMEDC, 2002. http://dx.doi.org/10.1115/icone10-22445.
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Spray drying is a physical process of granulating fine powders that is used widely in the chemical, pharmaceutical, ceramic, and food industries. It is generally used to produce flowable fine powders for mechanized processing. Occasionally it is used to fabricate sintered bodies like cemented carbides, and has been used to produce sintered fuel and actinide microspheres [1]. As a physical process, it can be adapted to many powder types and mixtures and thus, has appeal for dispersion nuclear fuels, and waste forms of various compositions. It also permits easy recycling of unused powders, and generates minimal chemical waste streams that can arise in chemical sol/gel processing. On the other hand, the containment of the radioactive powders, present safety challenges that need to be addressed [2]. Detailed formal procedures and methods for characterizing and processing UO2/ThO2 mixtures have been established and approved by the Purdue Radiological Control Committee for (1) ball-milling, (2) viscosity and rheology measurements on slurries, (3) sintering, (4) co-precipitation, (5) particle size analysis using laser scattering, (6) surface area analysis using the BET technique, (7) X-ray diffraction, (8) stoichiometry measurement, (9) zeta potential measurements and (10) ceramographic preparation. The spray drying procedures represented a particular challenge since they deal with the handling of loose powders. Studies were carried out to formulate suitable stable, dense and homogeneous aqueous slurries of urania and thoria powders for the production of urania-thoria microspheres by the spray drying method. The studies included (a) particle size distribution after ball-milling, (b) viscosity, (c) zeta potential, (d) slurry flowability, stability and cleanability, (e) microsphere green strength, and f) effects of organic dispersants on the above properties. After formulating the slurry, U,ThO2 microspheres were produced using a commercial, laboratory-scale spray dryer modified for handling these radioactive materials. The microspheres thus obtained were dried at 473 K for 4 hours, presintered at 1173 K for 2 hours and sintered at 1923 K for 10 hours.
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Sammak, Majed, Marcus Thern, and Magnus Genrup. "Performance of a Semi-Closed Oxy-Fuel Combustion Combined Cycle (SCOC-CC) With an Air Separation Unit (ASU)." In ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/gt2018-76218.
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The objective of this paper is to evaluate the performance of a semi-closed oxy-fuel combustion combined cycle (SCOC-CC) and its power penalties. The power penalties are associated with CO2 compression and high-pressure oxygen production in the air separation unit (ASU). The paper discusses three different methods for high pressure oxygen (O2) production. Method 1 is producing O2 directly at high pressure by compressing the air before the air separation takes place. Method 2 is producing O2 at low pressure and then compressing the separated O2 to the desired pressure with a compressor. Method 3 is alike the second method, except that the separated liquid O2 is pressurized with a liquid oxygen pump to the desired pressure. The studied SCOC-CC is a dual-pressure level steam cycle due to its comparable efficiency with three pressure level steam cycle and less complexity. The SCOC-CC, ASU and CO2 compression train are modeled with the commercial heat and mass balance software IPSEpro. The paper analyzed the SCOC-CC performance at different combustion outlet temperatures and pressure ratios. The combustion outlet temperature (COT) varied from 1200 °C to 1550 °C and the pressure ratio varied from 25 to 45. The study is concerned with mid-sized SCOC-CC with a net power output 100 MW. The calculations were performed at the selected design point which was at 1400°C and pressure ratio at 37. The calculated power consumption of the O2 separation at a purity of 95 % was 719 kJ/kgO2. The power consumption for pressurizing the separated O2 (method 2) was 345 kJ/kgO2 whereas it was 4.4 kJ/kgO2 for pumping liquid O2 to the required pressure (method 3). The calculated power consumption for pressurizing and pumping the CO2-enriched stream was 323 kJ/kgCO2. The SCOC-CC gross efficiency was 57.6 %. The SCOC-CC net efficiency at method 2 for air separation was 46.7 %. The gross efficiency was reduced by 9 % due to ASU and other 2 % due to CO2 compression. The SCOC-CC net efficiency at method 3 of the air separation was 49.6 %. The ASU reduced the gross efficiency by 6 % and additional 2 % by CO2 compression. Using method 3 for air separation gave a 3 % gain in cycle efficiency.
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Pronske, Keith, Larry Trowsdale, Scott Macadam, Fermin Viteri, Frank Bevc, and Dennis Horazak. "An Overview of Turbine and Combustor Development for Coal-Based Oxy-Syngas Systems." In ASME Turbo Expo 2006: Power for Land, Sea, and Air. ASMEDC, 2006. http://dx.doi.org/10.1115/gt2006-90816.
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Coal combustion technology is required that is capable of: (1) co-producing electricity and hydrogen from coal while; (2) achieving high efficiency, low capital cost, low operating cost, and near-zero atmospheric emissions; and (3) producing a sequestration-ready carbon dioxide stream. Clean Energy Systems, Inc. (CES) and Siemens Power Generation, Inc., are developing this technology that would lead to a 300 to 600 MW, design for a zero emissions coal syngas plant, targeted for the year 2015, CES and Siemens received awards on September 30, 2005 from the U.S. Department of Energy’s; Office of Fossil Energy Turbine Technology R&D Program. These awards are designed to advance turbines and turbine subsystems for integrated gasification combined cycle (IGCC) power plants. Studies have shown [1–4] that replacing air with nearly pure oxygen and steam in a turbine’s combustion chamber is a promising approach to designing coal based power plants with high efficiency and near-zero emissions. Siemens will combine current steam and gas turbine technologies to design an optimized turbine that uses oxygen with coal derived hydrogen fuels in the combustion process under a DOE Turbine Development Project [5]. CES will develop and demonstrate a new combustor technology powered by coal syngas and oxygen under a DOE Combustor Development Project [6]. The proposed programs build upon twelve years of prior technical work and government-sponsored research to develop and demonstrate zero-emission fossil fuel power generation. The planned system studies build upon previous work conducted by private, public, and foreign organizations, including CES [7–9], DOE’s National Energy Technology Laboratory (NETL) [10–12], Air Liquide (AL) [1,13], Lawrence Livermore National Laboratory (LLNL) [2], Fern Engineering, Inc. [14], and Japanese investigators [15, 16]. Other pertinent data related to coal gasification, advanced air separation unit (ASU), plant integration and plant systems optimization, etc., can be found in references [17–23].
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Clukey, Edward C., Charles P. Aubeny, and J. Don Murff. "Comparison of Analytical and Centrifuge Model Tests for Suction Caissons Subjected to Combined Loads." In ASME 2003 22nd International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2003. http://dx.doi.org/10.1115/omae2003-37503.
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The holding capacity of suction caissons increases significantly when the mooring line is attached below the mudline. In addition to the position of the attachment point, the soil profile, caisson geometry and the loading angle at the attachment point (padeye) will also influence the holding capacity. Various combinations of these parameters will control the failure mechanism that determines the holding capacity. The failure capacity can be dominated by the vertical or horizontal failure mechanisms — or a combination of the two. When the combination controls, the caisson response is referred to as being in the ‘interaction’ region’. If the suction caisson response is in the interaction region, methods of analyses required to predict the ultimate holding capacity are more complex than for pure vertical or horizontal failure mechanisms. This paper considers the response of suction caissons for all three failure mechanisms. The various failure mechanisms were primarily investigated through comparisons of an upper bound plasticity model and centrifuge model tests. Finite element results were also obtained and compared to the plasticity model solutions. The general foundation conditions investigated are considered fairly typical of suction caissons currently being used to anchor deepwater facilities in normally consolidated soils. The caisson scaled diameters investigated were slightly less than 5.36 m. with embedment (L) to diameter (D) ratios (L/D) slightly less than 5 for comparisons between the plasticity and centrifuge models. Comparisons were made between the finite element and plasticity models for an L/D ratio of 6. The padeye attachment point was about 2L/3 below the mudline for the plasticity and centrifuge comparisons and 0 (mudline) and L/2 for the finite element and plasticity model comparisons. The finite element estimates were slightly less than the plasticity model estimates (3 to 9%) with the largest differences in the interaction region. Both the plasticity and centrifuge models indicated that the transition from a vertical mechanism to an interaction failure mechanism occurs at a load angle of 40 to 45° from the horizontal. In the interaction region the centrifuge results were generally less than the plasticity model predictions. Centrifuge tests with a bevel at the caisson tip were inconclusive in terms of establishing the effectiveness of the bevel for displacing more soil to the outside of the caisson and thereby increasing the external skin friction.
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Kang, Ki Moon, Hyo-Won Kim, Il-Wun Shim, and Ho-Young Kwak. "Syntheses of Specialty Nanomaterials at the Multibubble Sonoluminescence Condition." In ASME 2008 International Mechanical Engineering Congress and Exposition. ASMEDC, 2008. http://dx.doi.org/10.1115/imece2008-68320.
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In recent years, a large number of nano-size semiconductors have been investigated for their potential applications in photovoltaic cells, optical sensor devices, and photocatalysts [1, 2, 3]. Nano-size semiconductor particles have many interesting properties due mainly to their size-dependent electronic and optical properties. Appropriately, many speciality of nanomaterials such as CdS and ZnS semiconductor particles, and other metal oxides such as ZnO and lithium-titanate oxide (LTO) have been prepared. However, most of them were prepared with toxic reactants and/or complex multistep reaction processes. Particularly, it is quite difficult to produce LTO nanoparticles, since it typically requires wearisome conditions such as very high temperature over 1000 °C, long producing times, and so on. To overcome such problems, various core/shell type nanocrystals were prepared through different methods such as the hydrothermal synthetic method, microwave, and sonochemistry. Also many coating methods on inorganic oxide nanoparticles were tried for the preparations of various core-shell type nanocrystals. Sonoluminescence (SL) is a light emission phenomenon associated with the catastrophic collapse of a gas bubble oscillating under an ultrasonic field [4]. Light emission of single bubble sonoluminescence (SBSL) is characterized by picosecond flashes of the broad band spectrum extending to the ultraviolet [5, 6]. The bubble wall acceleration has been found to exceed 1011 g at the moment of bubble collapse. Recently observed results of the peak temperature and pressure from the sonoluminescing gas bubble in sulfuric acid solutions [9] were accurately predicted by the hydrodynamic theory for sonoluminescence phenomena [7, 10, 11, 12], which provides a clue for understanding sonochemical reactions inside the bubble and liquid layer adjacent to the bubble wall. Sonochemistry involves an application of sonoluminescence. The intense local heating and high pressure inside the bubbles and liquid adjacent bubble wall from such collapse can give rise to unusual effects in chemical reactions. The estimated temperature and pressure in the liquid zone around the collapsing bubble with equilibrium radius 5 μm, an average radius of bubbles generated in a sonochemical reactor at a driving frequency of 20 kHz with an input power of 179 W, is about 1000 °C and 500 atm, respectively. At the proper condition, a lot of transient bubbles are generated and collapse synchronistically to emit blue light when high power ultrasound is applied to liquid, and it is called multibubble sonoluminescence (MBSL). Figure 1 shows an experimental apparatus for MBSL with a cylindrical quartz cell, into which a 5 mm diameter titanium horn (Misonix XL2020, USA) is inserted [13]. The MBSL facilitates the transient supercritical state [14].in the liquid layer where rapid chemical reactions can take place. In fact, methylene blue (MB), which is one of a number of typical textile dyestuffs, was degraded very fast at the MBSL condition while MB does not degrade under simple ultrasonic irradiation [13]. MBSL has been proven to be a useful technique to make novel materials with unusual properties. In our study, various metal oxides such as ZnO powder [15], used as a primary reinforcing filler for elastomer, homogeneous Li4Ti5O12 nanoparticles [16], used for electrode materials, and core/shell nanoparticles such as CdS coating on TiO2 nanoparticles [17] and ZnS coating on TiO2 nanoparticles [18], which are very likely to be useful for the development of inorganic dye-sensitized solar cells, were synthesized through a one pot reaction under the MBSL condition. Figure 2 shows the XRD pattern of ZnO nanoparticles synthesized from zinc acetate dehydrate (Zn(CH3CO2)2 · 2H2O, 99.999%, Aldrich) in various alcohol solutions with sodium hydroxide (NaOH, 99.99%, Aldrich) at the MBSL condition. The XRD patterns of all powers indicate hexagonal zincite. The XRD pattern for the ZnO nanoparticles synthesized is similar to the ZnO powder produced by a modified sol-gel process and subsequent heat treatment at about 600 °C [19] as shown in Fig.3. The average particle diameter of ZnO powder is about 7 nm. A simple sonochemical method for producing homogeneous LTO nanoparticles, as shown schematically in Fig. 4. First, LiOH and TiO2 nanoparticles were used to prepare LiOH-coated TiO2 nanoparticles as shown in Fig.5. Second, the resulting nanoparticles were thermally treated at 500 °C for 1 hour to prepare LTO nanoparticles. Figure 6 shows a high resolution transmission electron microscope image of LTO nanoparticles having an average grain size of 30–40 nm. All the nanoparticle synthesized are very pure in phase and quite homogeneous in their size and shape. Recently we succeeded in synthesizing a supported nickel catalyst such as Ni/Al2sO3, MgO/Al2O3 and LaAlO3, which turned out to be effective for methane decomposition [20]. Sonochemistry may provide a new way to more rapidly synthesize many specialty nanoparticles with less waste [21]. This clean technology enables the preparation of new materials such as colloids, amorphous particles [22], and various alloys.