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Synthesis of alpha,beta-unsaturated aryl esters via Heck reaction of unsymmetrical aryl tellurides

STEFANI, Helio A.; PENA, Jesus M.; GUEOGJIAN, Kemilla; PETRAGNANI, Nicola; VAZ, Boniek G.; EBERLIN, Marcos N.
Fonte: PERGAMON-ELSEVIER SCIENCE LTD Publicador: PERGAMON-ELSEVIER SCIENCE LTD
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
66.15%
A variety of alpha,beta-unsaturated aryl esters were prepared by the direct reaction of unsymmetrical aryltellurides and ethyl acrylate, catalyzed by PdCl(2) via a Heck cross-coupling reaction. (C) 2009 Elsevier Ltd. All rights reserved.; FAPESP[07/59404-2]; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); FAPESP[03/09931-5]; CNPq[300.613/2007-5]; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); CNPq[302.674/2005-5]; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Lipase-catalyzed kinetic resolution of beta-borylated carboxylic esters

Reis, Joel Savi dos; Andrade, Leandro Helgueira de
Fonte: PERGAMON-ELSEVIER SCIENCE LTD; OXFORD Publicador: PERGAMON-ELSEVIER SCIENCE LTD; OXFORD
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
66.2%
The kinetic resolution of chiral beta-borylated carboxylic esters via lipase-catalyzed hydrolysis and transesterification reactions was studied. The enantioselective hydrolysis catalyzed by CAL-B furnished the beta-borylated carboxylic acid with reasonable enantiomeric excess (62% ee), while both methyl and ethyl beta-borylated carboxylic esters were recovered with excellent ee (>99%). Meanwhile, the transesterification reaction of beta-borylated carboxylic esters and several alcohols, catalyzed by CAL-B, only indicated a high selectivity when ethanol and methyl-(beta-pinacolylboronate)-butanoate were used as substrates, which gave ethyl-(beta-pinacolylboronate)-butanoate with >99% ee. (C) 2012 Elsevier Ltd. All rights reserved.; FAPESP; FAPESP; CNPq; CNPq; CAPES; CAPES

Redução eletroquímica de 3,3' - (1,X - fenileno) - bis - (2 - propenoatos de etila); Electrochemical Reduction of Ethyl 3,3' - (1,X - phenylene) - bis - (2- propenoates)

Curilazo, Ricardo
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 12/04/2006 PT
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A redução eletroquímica de 3,3'-(1,3- e 1,4-fenileno)-bis-(2-propenoatos de etila), sistemas diolefínicos cujas duplas ligações estão separadas por um anel benzênico, foi investigada em N,N-dimetilformamida (DMF) e acetonitrila (MeCN) e metanol/acetonitrila (MeOH/MeCN) (7:3) (v/v). As eletrólises a potencial controlado em DMF e MeCN conduziram a hidrodímeros cíclicos derivados da ciclopentanona com elevada estereosseletividade, análogos aos produtos formados a partir de ésteres do ácido cinâmico nas mesmas condições experimentais. Ao lado dos hidrodímeros, quantidades variáveis de produtos de polimerização e de hidrogenação das duplas ligações dos grupos etoxicarbonilvinila eram formados. Foram examinados a influência do pH, concentração inicial dos substratos e presença de doadores de prótons (MeOH/MeCN) sobre o curso da redução eletroquímica. A maior complexidade dos produtos de eletrólise no substrato 1,4-substituído quando comparada as produtos do 1,3-substituído pode ser explicada, em parte, pela maior interação eletrônica dos grupos etoxicarbonilvinila através do anel aromático no primeiro.; The electrochemical reduction of ethyl 3,3' -(1,3 and 1,4-phenylene)-bis-(2-propenoates), diolefinic systems whose double bonds are separated by a benzene ring...

Estudos visando a síntese do alcaloide indolizidínico (+)-ipalbidina; Studies toward the synthesis of the indolizidine alkaloid (+)-ipalbidine

Prado, Viviana da Silva
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 02/02/2012 PT
Relevância na Pesquisa
36.13%
A ipalbidina é um alcaloide indolizidínico com propriedades analgésica e antirradicais livres. Este alcaloide possui como fonte natural a Ipomoea alba L., uma espécie de dama-da-noite, sendo isolado das suas sementes na forma de aglicona da ipalbina (ligada à D-glicose). A ipalbidina possui estrutura química relativamente simples, porém sua síntese na forma enantiomericamente pura se apresenta como um desafio sintético. Dentre as inúmeras rotas de síntese da ipalbidina, apenas quatro são enantiosseletivas. Neste trabalho de dissertação é apresentada uma nova estratégia sintética visando a preparação da S-(+)-ipalbidina. A estratégia tem como etapas chaves: uma reação de olefinação (Wittig e Horner-Wadsworth-Emmons); a preparação de uma diazocetona e de α-clorocetonas; e a conversão destas no esqueleto indolizidínico por uma reação de ciclização. Como material de partida para a reação de olefinação foi empregado o S-prolinal protegido (Boc e Cbz). Este aminoaldeído foi empregado como fonte do centro estereogênico e de um dos anéis presentes na estrutura final. A partir das reações de olefinação, foram obtidos compostos carbonílicos α, β-insaturados que, em seguida, sofreram redução da dupla ligação (28-94%). A partir dos produtos hidrogenados...

Chemoenzymatic Synthesis of alpha-Hydroxy-beta-methyl-gamma-hydroxy Esters: Role of the Keto-Enol Equilibrium To Control the Stereoselective Hydrogenation in a Key Step

Milagre, Cintia D. F.; Milagre, Humberto M. S.; Moran, Paulo J. S.; Rodrigues, J. Augusto R.
Fonte: Amer Chemical Soc Publicador: Amer Chemical Soc
Tipo: Artigo de Revista Científica Formato: 1410-1418
ENG
Relevância na Pesquisa
26.05%
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); alpha-Hydroxy-beta-methyl-gamma-hydroxy esters not only are found in many natural products and potent drugs but also are useful intermediates in organic synthesis due to their highly functionalized skeleton that can be further manipulated and applied in the synthesis of many compound with remarkable biological activities. This work was based on a chemoenzymatic approach to obtain these molecules with three contiguous stereogenic centers in a highly enantio- and diastereoselective way. Two distinct linear routes were proposed in which the key steps in both routes consisted of initial stereocontrolled ketoester bioreduction followed by unsaturated carbonyl bioreduction or reduction with Pd-C. Other key reactions in the synthesis include a Wasserman protocol for chain homologation and a Mannnich-type olefination with maintenance of enantiomeric excess for all intermediates during the sequence. Whereas route A gave exclusively the skeleton with 3R,4R,5S configuration (99% ee and 11.5% global yield after 7 steps), route B gave the skeleton with 3R...

Influence of the cultivation system in the aroma of the volatile compounds and total antioxidant activity of passion fruit

Janzantti, Natalia S.; Macoris, Mariana S.; Garruti, Deborah S.; Monteiro, Magali
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 511-518
ENG
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); The aim of this study was to investigate the influence of the cultivation system on the volatile composition of the passion fruit and to determine the odoriferous contribution of the compounds for the aroma of the organic and conventional fruit, besides to assess the total antioxidant activity. The volatile compounds were isolated from dynamic headspace, separated by high-resolution gas chromatography and the odoriferous contribution to the passion fruit aroma was evaluated using the OSME technique. Total antioxidant activity was determined using the ABTS radical reaction. The organic and conventional passion fruit showed similar volatile profile, although some differences occurred. Ethyl 2-propenoate, 2-methyl-1 -propanol, diethyl carbonate and ethyl hexanoate were threefold higher in the organic fruit while butyl acetate, hexanal, cis-3-hexenyl acetate and trans-3-hexenyl butanoate were threefold higher in the conventional fruit. Hexanoate and acetate esters, and saturated alcohols described as fruity, sweet, citrus and passion-fruit aroma showed the highest odorific intensity in the organic fruit. Furthermore, trans and cis-3-hexenyl acetate and alpha-copaene...

Synthesis of alpha,beta-unsaturated aryl esters via Heck reaction of unsymmetrical aryl tellurides

STEFANI, Helio A.; PENA, Jesus M.; GUEOGJIAN, Kemilla; PETRAGNANI, Nicola; VAZ, Boniek G.; EBERLIN, Marcos N.
Fonte: PERGAMON-ELSEVIER SCIENCE LTD Publicador: PERGAMON-ELSEVIER SCIENCE LTD
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
66.15%
A variety of alpha,beta-unsaturated aryl esters were prepared by the direct reaction of unsymmetrical aryltellurides and ethyl acrylate, catalyzed by PdCl(2) via a Heck cross-coupling reaction. (C) 2009 Elsevier Ltd. All rights reserved.; Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Conjugate Reduction of a,b-Unsaturated Carbonyl Compounds. Selective Inhibition of Benzyl Ether Hydrogenolysis by NH4OH/MeOH

Dias,Luiz C.; Campano,Priscila L.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/02/1998 EN
Relevância na Pesquisa
55.99%
A series of a,b-unsaturated alkyl and aryl ketones, esters and N-methoxy-N-methyl-amides (Weinreb amides) containing an O-benzyl protecting group undergo conjugate reduction by H2/Pd/C in the presence of 2N NH4OH/MeOH at room temperature and ordinary pressure leaving the benzyl group intact

Substitution reaction between functionalized Z-vinylic tellurides and lower order cyanocuprates: synthesis of Z or E alpha,beta unsaturated esters using the same Z-vinylic telluride

Castelani,Priscila; Comasseto,João V.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/08/2004 EN
Relevância na Pesquisa
126.43%
The substitution reaction between lower order cyanocuprates and functionalized Z-vinylic tellurides was investigated. alpha,beta-Unsaturated carbonyl compounds were obtained in excellent yields. Changes in the reaction conditions afforded alpha,beta-unsaturated esters in high diastereoselectivity.

Clean and atom-economic synthesis of alpha-phenylselenoacrylonitriles and alpha-phenylseleno- alpha,beta-unsaturated esters by knoevenagel reaction under solvent-free conditions

Perin,Gelson; Jacob,Raquel G.; Botteselle,Giancarlo V.; Kublik,Emerson L.; Lenardão,Eder J.; Cella,Rodrigo; Santos,Paulo César Silva dos
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/08/2005 EN
Relevância na Pesquisa
86.22%
A simple, clean and efficient method has been developed for the synthesis of alpha-phenylselenoacrylonitriles and alpha-phenylseleno-alpha,beta-unsaturated esters by a one-pot reaction of aldehydes with phenylselenoacetonitrile or ethyl(phenylseleno)acetate respectively, in the presence of a solid supported catalyst (KF/Al2O3), without any solvent.

The solvent free preparation of beta-amino esters alpha,beta-unsaturated ketones and esters with domestic microwave oven

Braibante,Mara E. F.; Braibante,Hugo T. S.; Morel,Ademir F.; Costa,Carla C.; Lima,Marcelo G.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/02/2006 EN
Relevância na Pesquisa
76.39%
A series of beta-amino esters alpha,beta-unsaturated ketones and esters 4a-h and 6a-d derived from alpha-amino acids have been prepared starting from alpha-amino esters hydrochorides 2a-d with 1,3- dicarbonyl compounds 3a,b and 5 in presence of triethylamine. These compounds have been prepared under domestic microwave oven, under solvent free condition with and without solid support (K-10 or KSF).

Synthesis of beta-phenylchalcogeno-alpha, beta-unsaturated esters, ketones and nitriles using microwave and solvent-free conditions

Lenardão,Eder J.; Silva,Márcio S.; Mendes,Samuel R.; Azambuja,Francisco de; Jacob,Raquel G.; Santos,Paulo César Silva dos; Perin,Gelson
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2007 EN
Relevância na Pesquisa
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A simple, clean and efficient solvent-free protocol was developed for hydrochalcogenation of alkynes containing a Michael acceptor (ester, ketone and nitrile) with phenylchalcogenolate anions generated in situ from the respective diphenyl dichalcogenide (Se, Te, S), using alumina supported sodium borohydride. This efficient and improved method is general and furnishes the respective (Z)-beta-phenylchalcogeno-a,b-unsaturated esters, ketones and nitriles, in good yield and higher selectivity, compared with those that use organic solvent and inert atmosphere. The use of microwave (MW) irradiation facilitates the procedure and accelerates the reaction.

Glycerophospholipid synthesis: improved general method and new analogs containing photoactivable groups.

Gupta, C M; Radhakrishnan, R; Khorana, H G
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /10/1977 EN
Relevância na Pesquisa
35.83%
Current methods for phospholipid synthesis involving acylation of sn-glycero-3-phosphorylcholine, lysolecithins, and related glycerophosphate esters are not satisfactory. With N,N-dimethyl-4-aminopyridine as a catalyst and moderate amounts of fatty acid anhydrides (1.2-1.5 mol equiv per OH group), diacyl or 1,2-mixed diacylphosphatidylcholines, N-protected phosphatidylethanolamines, and phosphatide acids now can be conveniently prepared in high yields (75-90%). New phospholipids containing photoactivable groups, such as trifluorodiazopropionyl, diazirinophenoxy, 2-nitro-4-azidophenoxy, m-azidophenoxy, and alpha, beta-unsaturated keto groups, in the fatty acyl chains have been prepared. These phospholipids are of interest in studies of lipid-lipid and lipid-protein interactions in biological membranes.

Inhibition of steroid 5 alpha-reductase by specific aliphatic unsaturated fatty acids.

Liang, T; Liao, S
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 15/07/1992 EN
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26.21%
Human or rat microsomal 5 alpha-reductase activity, as measured by enzymic conversion of testosterone into 5 alpha-dihydrotestosterone or by binding of a competitive inhibitor, [3H]17 beta-NN-diethulcarbamoyl-4-methyl-4-aza-5 alpha-androstan-3-one ([3H]4-MA) to the reductase, is inhibited by low concentrations (less than 10 microM) of certain polyunsaturated fatty acids. The relative inhibitory potencies of unsaturated fatty acids are, in decreasing order: gamma-linolenic acid greater than cis-4,7,10,13,16,19-docosahexaenoic acid = cis-6,9,12,15-octatetraenoic acid = arachidonic acid = alpha-linolenic acid greater than linoleic acid greater than palmitoleic acid greater than oleic acid greater than myristoleic acid. Other unsaturated fatty acids such as undecylenic acid, erucic acid and nervonic acid, are inactive. The methyl esters and alcohol analogues of these compounds, glycerols, phospholipids, saturated fatty acids, retinoids and carotenes were inactive even at 0.2 mM. The results of the binding assay and the enzymic assay correlated well except for elaidic acid and linolelaidic acid, the trans isomers of oleic acid and linoleic acid respectively, which were much less active than their cis isomers in the binding assay but were as potent in the enzymic assay. gamma-Linolenic acid had no effect on the activities of two other rat liver microsomal enzymes: NADH:menadione reductase and glucuronosyl transferase. gamma-Linolenic acid...

Copper-catalyzed conjugate reduction

Jurkauskas, Valdas, 1966-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 91 p.; 2872472 bytes; 2872275 bytes; application/pdf; application/pdf
ENG
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Chapter 1. A highly enantioselective catalyst for the asymmetric conjugate reduction of a,- unsaturated cyclic ketones was generated upon combination of catalytic amounts of CuCl, NaOt-Bu, and a chiral bis-phosphine with poly(methylhydrosiloxane) (PMHS) as the stoichiometric reductant. In this process, chiral 3-alkylcyclopentanones were isolated in high enantiomeric excess (ee =/> 92%) and in moderate to excellent yields (42-91%). Chapter 2. Kinetic resolution, with good selectivity factors (25-52), was achieved by conjugate reduction with catalytic CuCl/NaOt-Bu/(S)-p-tol-BINAP and stoichiometric quantities of PMHS. When stoichiometric amounts of NaOt-Bu and t-BuOH were included in the reaction mixture, rapid racemization of the starting material occurred allowing for the dynamic kinetic resolution of the cyclopentenone substrates. In this process, chiral 2,4-dialkylcyclopentanones were isolated with high stereoselectivity (ee =/> 91%, dr=/>90:10) and in high yield (=/> 89%). Chapter 3. An N-heterocyclic carbene-copper chloride complex was prepared and used to catalyze the conjugate reduction of [alpha], [beta]-unsaturated carbonyl compounds. The combination of catalytic amounts of N-heterocyclic carbene-copper chloride complex and NaOt-Bu with PMHS as the stoichiometric reductant generates an active catalyst for the 1...

Development of transitional metal-catalyzed reactions for organic synthesis

Rainka, Matthew P. (Matthew Paul)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 130 leaves; 5428815 bytes; 5435258 bytes; application/pdf; application/pdf
ENG
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Chapter 1. A general catalyst system for the synthesis of tetra-ortho-substituted biaryls via the Suzuki-Miyaura cross-coupling reaction is described. It was found that the most efficient catalyst system is based on a phenanthrene-substituted biaryl phosphine ligand. Utilizing this ligand, a number of tetra-ortho-substituted biaryls were synthesized in good to excellent yields. Chapter 2. A procedure for the arylation of methyl and cyclic ketone enolates with o-halonitroarenes was developed. An unusual additive effect of phenols on the outcome of the reaction was observed and explored. This process has provided for the regioselective synthesis of a wide variety of substituted indoles from commercially available materials. Chapter 3. The first method for the asymmetric copper-catalyzed conjugate reduction of [alpha] ,[beta] unsaturated esters containing [beta]-heteroatoms was developed. We found that this system tolerated the presence of both lactams as well as azaheterocycles in the [beta]-position of various enoates. This has led to the asymmetric synthesis of a number of interesting [5- amino acid derivatives. Chapter 4. A copper-catalyzed conjugate reduction reaction that allows for a variety of [gamma]-aryl containing [alpha], [beta]-unsaturated butenolides to be reduced in both high enantiomeric and diastereomeric excess was developed. While a number of catalysts based on chiral bisphosphines were found to successfully perform this transformation...

Synthèse totale du méthyl ester de la zincophorine et étude DFT du transfert d’hydrogène diastéréosélectif impliquant des intermédiaires radicalaires vicinaux à un ester

Godin, François
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
FR
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46.1%
Cet ouvrage traite d’une méthodologie pour l’induction de centres stéréogènes au sein des motifs propionates par la chimie des radicaux et de son application à la synthèse totale du méthyl ester de la zincophorine. Cet ionophore, aux propriétés biologiques intéressantes, présente plusieurs défis synthétiques dont une séquence de type polypropionate anti, anti, anti, anti difficilement accessible ainsi qu’un tétrahydropyrane trans trisubstitué. Récemment, l’intérêt renouvelé pour ces composés polyéthers, en tant qu’agents anticancéreux, accentue l’importance de stratégies versatiles permettant l’accès à ces structures ainsi qu’à leurs analogues. Depuis quelques années, notre groupe s’intéresse à la synthèse d’unités propionates acycliques par une séquence réactionnelle contrôlée uniquement par le substrat. La première étape découle d’une aldolisation de Mukaiyama entre un aldéhyde alpha-chiral et un énoxysilane tétrasubstitué portant une liaison carbone-halogène, et où l’issue stéréochimique dépend de la nature monodentate ou bidentate de l’acide de Lewis employé. La seconde réaction-clé implique la formation d’un radical tertiaire, vicinal à un ester, pouvant être réduit diastéréosélectivement en présence d’hydrure d’étain. La première section décrit l’élaboration de motifs tétrahydropyranes trisubstitués et l’induction des centres stéréogènes vicinaux par une réduction radicalaire. Nous avons révélé que l’issue diastéréosélective de la réaction de cyclisation par une iodoéthérification était dictée par le groupement gamma-méthyle des esters alpha...

Kombinatorische Elektrosynthese in ionischen Flüssigkeiten; Combinatorial electrosynthesis in ionic liquids

Schwarz, Markus
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Masterarbeit
DE_DE
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46.05%
Anhand einer Modellreaktion, der Addition von alpha, beta-ungesättigten Estern und Allylhalogeniden durch kathodische Reduktion, wurde die computergesteuerte kombinatorische Elektrosynthese in einer ionischen Flüssigkeit erprobt. Zunächst wurde die ionische Flüssigkeit Buthylmethylimidazoliumtetrafluoroborat ([BMIM]BF4) synthetisiert, gereinigt und auf ihre elektrochemischen Eigenschaften hin untersucht. In einem zweiten Schritt wurde die Modellreaktion mit Diethylfumarat und Allylbromid im mg-Maßstab in einem klassischen Lösungsmittel (DMF) nachvollzogen. Anschließend wurde die Elektrolyse bei verringertem Reaktionsvolumen in der ionischen Flüssigkeit mit Diethylfumarat, Methylcrotonat, Allylbromid und 3,3-Dimethylallylbromid durchgeführt, wobei drei der vier erwarteten Produkte nachgewiesen werden konnten. Schließlich wurden in den Wells einer Mikrotiterplatte acht verschiedene Ester mit sechs verschiedenen Allylhalogeniden kombiniert. Als Elektrolyt diente wiederum [BMIM]BF4. Mit Hilfe einer SECM-Anordnung wurde ein Mikroelektrodenbündel in die Wells bewegt, in denen die jeweiligen Elektrolysen stattfanden. In 17 Wells konnte das erwartete Produkt mittels GC-MS nachgewiesen werden. In den anderen Fällen konnte anhand des Reaktionsmechanismus die verringerte oder ausbleibende Reaktivität erklärt werden und dadurch die Annahme für den Mechanismus selbst bestätigt werden. Die hier verwendete SECM-Anordnung im Zusammenspiel mit ionischen Flüssigkeiten eignet sich sehr gut zum kombinatorischen Screening von Elektrosynthesereaktionen.; On the basis of a model reaction (electrochemical addition of alpha...

Studien zur enantioselektiven Synthese des marinen Makrolactons (–)-Dictyostatin; Studies towards the enantioselective synthesis of the marine macrolactone (–)-dictyostatin

Röhm, Hartmut
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
DE_DE
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36.09%
Heute handelt es sich bei mehr als der Hälfte aller zugelassenen Arzneimittel um Naturstoffe, Naturstoffderivate oder Naturstoffanaloga. Die Suche nach neuen Leitstrukturen beschränkt sich nicht mehr nur auf terrestrische Pflanzen und Mikroorganismen, sondern vermehrt auf marine Organismen. Dabei sind vor allem fest am Meeresboden verwachsene Schwämme und Korallen sehr interessant, da sie sich nur durch Anpassung ihres Metabolitprofiles, das heißt die Biosynthese geeigneter Toxine, vor Feinden schützen können. So wurde auch das marine 22-gliedrige Makrolacton (–)-Dictyostatin erstmals 1988 bei der systematischen Suche nach neuen Leitstrukturen von G. R. Pettit aus Spongia sp. isoliert. Durch zellbiologische Studien von A. E. Wright wurde der Taxol-ähnliche Wirkmechanismus, welcher durch Stabilisierung der Mikrotubuli zum Zellzyklusarrest zwischen der G2/M-Phase führt, aufgeklärt und im Jahr 2003 veröffentlicht. Im darauf folgenden Jahr gelang der Beweis des von I. Paterson publizierten vollständigen Strukturvorschlages durch zwei voneinander unabhängige Totalsynthesen. Neben der Etablierung der drei Stereokaskaden (C6-C9, C12-C16, C19-C22) stellen bei der Synthese von (–)-Dictyostatin vor allem die C2:C3-(Z)- und die C10:C11-(Z)-Doppelbindung eine Herausforderung dar...

Synthesis of rearranged unsaturated drimane derivatives

Miranda,Domingos S. de; Conceição,Gelson J. A. da; Zukerman-Schpector,Julio; Guerrero,Mário C.; Schuchardt,Ulf; Pinto,Angelo C.; Rezende,Claudia M.; Marsaioli,Anita J.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2001 EN
Relevância na Pesquisa
55.93%
A full account to the preparation and application of three appropriately substituted vinylcyclohexenes (2,2-dimethyl-3-vinylcyclohex-3-en-1-ol, 2,2-dimethyl-3-vinylcyclohex-3-en-1-one and 3,3-dimethyl-2-vinylcyclohexene) in thermal Diels-Alder reactions with alpha,beta-unsaturated esters (methyl tiglate and methyl angelate) is given. This approach delivered the racemic synthesis of ten octalin derivatives bearing a rearranged drimane skeleton (4 diastereomers of 1-methoxycarbonyl-6-hydroxy-1,2,5,5-tetramethyl-1,2,3,5,6,7, 8,8a-octahydronaphthalene; 1-methoxycarbonyl-6-oxo-1,2,5,5-tetramethyl-1,2,3,4,5,6,7,8-octahydronaphthalene; 2-methoxycarbonyl-6-oxo-1,2,5,5-tetramethyl-1,2,3,5,6,7,8,8a-octahydronaphthalene; 3 diastereomers of 1-methoxycarbonyl-1,2,5,5-tetramethyl-1,2,3,5,6,7,8,8a-octahydronaphthalene and 2-methoxycarbonyl-1,2,5,5-tetramethyl-1,2,3,5,6,7,8,8a-octahydronaphthalene) . Central synthetic features included preparation of enoltriflates by Stang's protocol and the successful palladium-catalyzed cross-coupling reaction (Stille reaction) of the triflate with the tri-n-butylvinylstannane. The octalins relative stereochemistry was unequivocally ascertained by spectroscopic methods and/or X-ray crystallography and these data now stand as useful tools to support the correct assignment of related natural products usually isolated in minute amounts.