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1
Wheatley, Joseph R. "Lactones in synthesis". Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337424.
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2
Shangula, Suha. "Effect of paraoxonase (PON1) on lactones and ROS induced DNA damage". Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/effect-of-paraoxonase-pon1-on-lactones-and-ros-induced-dna-damage(928ac761-7039-4f6f-9135-40a6f71b9465).html.
Testo completoAbstract (sommario):
Paraoxonase 1 (PON1) is an enzyme synthesised in the liver that is associated with High Density Lipoprotein (HDL) and increasingly with a number of human diseases, including cardiovascular disease and cancer. PON1 is (i) a lactonase, hydrolysing aliphatic and aromatic lactones, (ii) a phosphotriesterase, acting on certain organophosphates and (iii) a peroxidase that combats lipid oxidation. The aim of this study was to investigate the extent to which PON1 might impact on the levels of lactone-induced and oxidative DNA damage. Initially, the plasmid DNA (pDNA) nicking assay was used to show that of the 12 lactones and homocysteine (HC) examined, only alpha angelica lactone (AAL), Furanone (FUR) and HC caused DNA single strand breaks (SSB) under physiological conditions. Further studies indicated that AP sites were not involved suggesting that DNA-phosphotriesters were responsible. AAL-reacted pDNA bound the damage sensing protein, Atl1, and AAL, HC and HC thiolactone (HCTL) -reacted calf thymus DNA inhibited the activity of the DNA repair protein, MGMT, both indicating the presence of O6-alkylguanines in DNA, although this could not be confirmed using MALDI-ToF MS analyses of tryptic digests of MGMT incubated with lactone-reacted DNA. The inhibition of rPON1 by these lactones and HC was determined using paraoxon as a substrate and two groups were identified comprising lactones that caused reductions in PON1 activity of (i) ˃15% (e.g. HCTL, and AAL) and (ii) ˂10% (e.g. FUR, and HC). The pDNA nicking assay then showed that only AAL and FUR induced DNA single strand breaks. PON1 itself nicked pDNA, and bound to group 1 lactone-reacted pDNA by an unknown mechanism, both effects not previously reported, but, with the possible exception of AAL, did not increase the extent of plasmid nicking. The MTT, cell viability assay, indicated that all of the lactones with the exception of γ-BL (IC50 >12 mM) were to some degree toxic in HepG2 cells with AAL being the most toxic (IC50 1.0 ±0.03 mM). It was not possible to quantify PON1 activity in HepG2 cells and agents that are reported to change the expression levels of PON1 had no detectable impact on the toxicity of AAL, γ-VL, FUR or MBL, so any possible effect of PON1 could not be determined. The neutral Comet assay showed that AAL and HCTL generated the highest levels of DNA double strand breaks and DNA fragmentation in HepG2 cells, and that this effect was greatly enhanced for most of the lactones by the addition of rPON1. The impact of PON1 on oxidative stress was investigated using serum samples collected as part of a previous case-control study of lung cancer. Initially, an in-house developed ELISA assay to quantify 8-hydroxydeoxyguanosine (8-OHdG) levels had insufficient sensitivity and poor reproducibility. Hence 8OHdG levels were measured using kits along with PON1 levels and other serum parameters including HDL-C, LDL-C, TG and apoAI in serum from 112 patients with lung cancer and 249 patients without. No correlation was found between serum level of PON1 activity and level of 8-OHdG in patients with lung cancer, however a negative non-significant correlation was found between PON1 and 8-OHdG in control. The level of 8-OHdG was significantly higher in lung cancer patients than in controls and in the controls, the OGG1 wild type genotype correlated with reduced levels of 8-OHdG in serum. These studies showed that certain lactones, are toxic and DNA damaging and this can be increased by PON1, suggesting that any association between PON1 and human disease will be substrate dependent and may be PON1 genotype-dependent.
3
Arasa, Bertomeu Mª Mercè. "Nous termoestables epoxídics modificats amb gamma-lactones i bis-gamma-lactones condensades". Doctoral thesis, Universitat Rovira i Virgili, 2009. http://hdl.handle.net/10803/9033.
Testo completoAbstract (sommario):
Aquest treball s'emmarca en el camp dels materials termoestables amb aplicacions en recobriments o encapsulants per microelectrònica i pretén l'obtenció de materials amb millor durabilitat i que després del temps d'ús puguin ser degradats i permetin la recuperació del material electrònic, el que constitueix una gran avantatja des del punt de vista mediambiental. L'estratègia escollida ha estat la copolimerització de diglicidilèter de bisfenol A (DGEBA) amb mono--lactones i bis--lactones utilitzant diversos triflats de terres rares i el BF3·MEA com iniciadors catiònics i varies amines terciàries com iniciadors aniònics. Aquesta estratègia permet la introducció de grups ester, tèrmica i químicament làbils i alhora reduir l'encongiment que es produeix durant el curat. La incorporació de cadenes alifàtiques, provinents de les lactones, entre punts d'entrecreuament augmenta la flexibilitat de la xarxa polimèrica i disminueix la fragilitat del material. La millora de les propietats mecàniques també va ser estudiada addicionant montmorillonites laminars.This work focuses on the thermosetting materials area with applications in coatings or encapsulates for microelectronic devices and it seeks to obtain materials with better durability that after their working life, could be degraded and let the recuperation of the electronic material, which means a great advantage for the environment. The strategy followed has been the copolymerization of diglycidylether of bisphenol A (DGEBA) with mono--lactones and condensed bis--lactones using several rare earth triflates and BF3·MEA as cationic initiators and several tertiary amines as anionic iniciators. This strategy lets the introduction of ester linkages, thermal and chemically cleavable and at the same time the reduction of the shrinkage which is produced during the curing process. The incorporation of aliphatic chains, that come from lactones, between cross-linking points increases the flexibility of the polymeric network and decreases the fragility of the material. The improvement of the mechanical properties also was studied adding layered montmorillonites.
4
Fairbanks, Antony J. "Sugar lactones in synthesis". Thesis, University of Oxford, 1993. http://ora.ox.ac.uk/objects/uuid:44329487-5d08-4df4-8baf-fc682d4bc9cc.
Testo completoAbstract (sommario):
This thesis describes the synthesis of some novel carbohydrate lactones and their uses as starting materials in (a) the syntheses of various polyfunctionalised cyclopentanes, via intramolecular aldol condensations, (b) the synthesis of 1-epihydantocidin, in which the crucial synthetic step involves a novel transformation induced by tetra-n-propylammonium perruthenate, and (c) the syntheses of various tetrahydrofurans and tetrahydropyrans. The syntheses of 3,4-O-isopropylidene and cyclohexylidene altrono and allono-1,5-lactones via Kiliani ascension of protected forms of D-ribose are described. The stereochemistry of the major reaction product, which was identified as 2,3-O-isopropylidene-D-altrono-l,5-lactone was confirmed by X-ray diffraction. Introduction of azide and iodide at C-2 is achieved via silyl protection of C-6 and formation of the 2-O-triflates. Nucleophilic displacement with azide or iodide produces mixtures of C-2 epimers. Desilylation is readily achieved by treatment with acetic acid to yield azido and iodo alcohols. Attempted oxidation of C-6 to an aldehyde functionality, in an attempt to effect cyclopentane formation via intramolecular aldol condensation of C-2 onto C-6 failed. Treatment of altrono and allono azido alcohols with tetrapropylammonium perruthenate unexpectedly results in the formation of a [2.2.2.] bicyclic hemiaminal, whose structure was confirmed by X-ray diffraction. Conversion of the amine functionality to a urea is effected by treatment with potassium cyanate. Cyclisation of the urea functionality onto the lactone carbonyl and subsequent deprotection effects the synthesis of 1-epihydantocidin. Investigations into acid catalysed epimerisation of the spiro centre in both hydantocidin and 1-epihydantocidin are described. Potassium carbonate induced ring contraction of 6-O-silyl altrono- and allono- 1,5-lactone-2-O-triflates yields tetrahydrofurans, the stereochemistry of which is confirmed by conversion to symmetric materials. Intramolecular Mitsunobu cyclisation of OH-2 onto C-6 of altrono-1,5-lactones effects tetrahydropyran formation. Inversion of C-5 of the known 3,4:5,6-di-O-ispropylidene-D-glycero-D-galacto-heptono- 1,5-lactone is described. Confirmation of product stereochemistry is achieved by conversion to 2,3-O-isopropylidene-L-altrono-1,5-lactone. Introduction of iodide and azide at C-2 is achieved via the formation of the 2-O-triflate. Selective deprotection of the 5,6 isopropylidene and subsequent periodate cleavage yields aldehydo lactones which undergo potassium fluoride induced intramolecular aldol cyclisation, to yield bicyclic [2.2.1.] azido and iodo carbocycles. Sodium azide induced intramolecular aldol cyclisation of 5-azido-5-deoxy-3,4-O-isopropylidene-L-galacturono-2,6-lactone, which produces two [2.2.1.] bicyclic azido carbocycles, is described. The second azido carbocycle, which is found to be the major reaction product, readily undergoes a retro aldol reaction, resulting in the formation of a third azido carbocycle, the structure of which was confirmed by X-ray diffraction. Investigations into the equilibration of these three bicyclic [2.2.1.] azido carbocycles under the reaction conditions employed to effect their formation are described. Various ring opening reactions of the second and third materials, and their uses in the syntheses of a novel amino pentol, two novel tetrahydroxy cyclopentane spirohydantoins and two novel cyclopentane amino acids are described. The structure of the asymmetric amino acid was confirmed by X-ray diffraction. Under basic reaction conditions retro aldol equilibration is seen to compete effectively with ring opening.
5
Maughan, K. "Grignard reactions with lactones". Thesis, University of Nottingham, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356029.
Testo completo
6
Mitchell, Helen Joy. "Stereocontrol with diphenylphosphinoyl lactones". Thesis, University of Cambridge, 1995. https://www.repository.cam.ac.uk/handle/1810/271942.
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7
Rogers, Paul S. "Sugar lactones in organic synthesis". Thesis, University of Oxford, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.425897.
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8
Simone, Michela A. "Studies on branched sugar lactones". Thesis, University of Oxford, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.497098.
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9
Toczek, Judy. "Synthetic studies on terpenoid lactones". Thesis, Brunel University, 1985. http://bura.brunel.ac.uk/handle/2438/7401.
Testo completoAbstract (sommario):
A novel stereoselective route has been developed to a vernolepin intermediate in nine steps from 2-phenylthiocyclopentenone. During this research, a regiospecific method for the alkylation of the Δ5,6 - tetrahydroindanone system has been achieved. In addition, the synthetic route demonstrates a means of differentiating between two carboxylic acid functions via a selective lactonisation. The first total ynthesis of boonein has also been completed, in 3% yield from cyclopentadiene. This route uses a chlorine atom to direct the stereo- and regiochemical outcome of most of these reaction.
10
Dumeunier, Raphaël. "New methodologies towards lactones and methylene-lactones : application to the total synthesis of Polycavernoside A". Université catholique de Louvain, 2004. http://edoc.bib.ucl.ac.be:81/ETD-db/collection/available/BelnUcetd-05242004-130732/.
Testo completoAbstract (sommario):
Methylene-butyrolactones are readily accessed by two methodologies based on a particular ene reaction. Both methodologies have been applied to the synthesis of the northern fragment of Polycavernoside. A reverse Julia reaction was used as the key step of a new methodology towards triene frameworks ; a mechanistic study revealed the unexpected role of triflic acid in the field of metal triflates catalysed acylation of alcohols, and a new tandem Brook rearrangement-allylation sequence was developed in the viewpoint of an improved total synthesis of Polycavernoside A.
11
Fouque, Elie. "Synthèse itérative de lactones α, β-ethyléniques à cycle moyen : hydrolyse enzymatique de lactones saturées". Paris 11, 1989. http://www.theses.fr/1989PA112246.
Testo completoAbstract (sommario):
Dans ce mémoire de thèse, nous proposons une nouvelle voie d'accès aux lactones alpha, bêta-éthyléniques à cycle moyen par une méthode d'agrandissement de cycle, qui, utilisée de façon récurrente permet à chaque itération d'incorporer dans le squelette laconique un atome de carbone porteur ou non d'un substituant. Dans le premier chapitre, après un exposé concernant la préparation des éthers d'énols triméthylsilyliques de lactones, nous étudions la réaction de ces énoxysilanes avec trois chlorocarbénoïdes différents. Les adduits cyclopropaniques ainsi obtenus, conduisent thermiquement aux lactones alpha, bêta-éthyléniques d'agrandissement de cycle. A l'aide de cette méthode, nous avons préparé avec des rendements satisfaisants des lactones alpha, bêta éthyléniques non substituées, méthylées ou fluorées en alpha, de taille comprise entre 7 et 10 maillons. Dans le second chapitre, nous étudions les propriétés spectroscopiques ainsi que quelques propriétés chimiques de ces lactones insaturées à cycle moyen. Nous mettons en évidence les différences importantes existant entre les composés de stéréochimie E et Z. Par hydrogénation catalytique en phase hétérogène, nous préparons les lactones saturées correspondantes, réalisant ainsi la dernière étape de la séquence et rendant la méthode itérative. Dans le troisième chapitre, nous présentons une nouvelle méthode de préparation des lactones à cycle moyen optiquement actives méthylées en alpha de l'atome d'oxygène, par dédoublement cinétique catalysée par des hydrolases. En utilisant l'estérase de foie de porc (PLE) ou l'estérase de foie de cheval (HLE) sous forme de leur extrait acétonique, en milieu aqueux, l'hydrolyse de ces alkanolides procède de façon hautement énantiosélective. Ainsi le (S)-(+) octanolide-7, le (S)-(+)-nonanolide-8 et le (S)-(+)-décanolide-9 ((S)-(+)-phoracantholide I) ont été isolés avec un bon rendement et un excès énantiomérique supérieur à 95%In this thesis, we report a new method for the preparation of alpha,beta-ethylenic medium ring lactones involving a ring enlargement method which can be used in an iterative way allowing, at each iteration, the incorporation of a carbon atom, substituted or not, in the lactonic skeleton. In the first chapter, is reported the preparation of trimethylsilyl enol ethers of lactones, then the reaction of these enoxysilanes with three different chlorocarbenoids. The cyclopropane adducts so obtained, are thermally transformed into alpha, beta-ethylenic ring expanded lactones. By this way we have prepared in satisfactory yields alpha unsubstituted, alpha methylated or alpha fluorinated 7 to 10 membered alpha,beta-ethylenic lactones. In the second chapter, we study spectroscopic and chemical properties of these unsaturated medium ring lactones. We outline large differences between E and Z isomers. By catalytic heterogeneous hydrogenation we prepare the corresponding saturated compounds, allowing thus the last step of this iterative method. In the third chapter, we present a new method for the preparation of optically active medium ring lactones, methylated in the alpha position of the oxygen atom, by an hydrolase-catalyzed kinetic resolution. Using pig liver esterase (PLE) or horse liver esterase (HLE) (acetone powder), in aqueous phase the hydrolysis is performed with a high enantioselectivity. Thus, (S)-(+)-7- octanolide, (S)-(+)-8-nonanolide and (S)-(+)-9-decanolide ((S)-(+)-phoracantholide I) have been isolated in good yield and enantiomeric excess (over 95%)
12
Wilstermann, Michael. "Synthesis of conformationally restricted oligosaccharides". Lund : Dept. of Organic Chemistry 2, Lund University, 1997. http://catalog.hathitrust.org/api/volumes/oclc/39751534.html.
Testo completo
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Prata, Camila Barbieri [UNESP]. "Aspectos do controle de resíduos de avermectinas no abate de bovinos". Universidade Estadual Paulista (UNESP), 2014. http://hdl.handle.net/11449/122080.
Testo completoAbstract (sommario):
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000816587.pdf: 400325 bytes, checksum: fe57a4f95b8cfd93f1cdf6d5195f67d6 (MD5)As mudanças nos controles internacionais dos alimentos visando sua inocuidade se efetivaram com a mudança de século, tendo como base a Análise de Riscos e a Análise de Perigos e Pontos Críticos de Controle. Para os resíduos químicos, apesar de problema pré-existente, a situação só ganhou notoriedade a partir de 2010 com a detecção da presença de resíduos de avermectinas em produtos cárneos brasileiros exportados para os Estados Unidos e União Europeia. A partir de então, várias medidas de mitigação foram inseridas no conjunto rotineiro de autocontroles pelas empresas processadoras. Neste trabalho objetivou-se verificar a praticidade e eficácia dessas medidas para o controle efetivo dos processos, segregando animais abatidos que pudessem contribuir para níveis inaceitáveis do perigo, com base na monitoração de resíduos de avermectinas em duas matrizes amostrais, fígado e músculo de bovinos abatidos. Para a matriz músculo foram analisados 81.565 lotes de animais, com 1,41% desses ou 1.153 lotes que apresentaram resíduos de avermectinas superiores ao LMR de 10μg/kg durante os anos de 2010 e 2011. A partir de 2012 utilizou-se a matriz fígado, sendo analisadas 77.056 amostras. Dessas, 29.267 ou 37,98% apresentaram positividade para resíduos, sendo que 4.602 ou 5,97% foram superiores ao LMR de 100μg/kg. Os resultados analíticos demonstram, até agora, agravamento do problema no elo primário da produção de carne bovina brasileira
Changes in international food controls aiming their safety occurred with the change of the century, based on the Risk Analysis and Hazard Analysis and Critical Control Points. For chemical residues, although a pre-existing problem, the situation only gained notoriety after 2010, with the presence of avermectin residues in Brazilian meat products exported to the United States and European Union. Since then, several mitigation measures were incorporated in the routine set of self-controls the processing companies.This work aimed to verify the practicality and effectiveness of these measures for effective control of processes, segregating slaughtered animals that could contribute to unacceptable levels of risk, based on monitoring of avermectins residues in two sample matrices, liver and muscle of cattle slaughtered. For the muscle matrix were analyzed 81,565 batches of animals, with 1,153 or 1.41% batches whose residues were above the avermectin MRL (Maximum Residue Level) of 10μg/kg during the years 2010 and 2011. from 2012 was used the liver matrix , with 77,056 samples being analyzed. Of these, 29,267 or 37.98% were positive for residues, with 4,602 or 5.97% above the MRL of 100μg/kg. The analytical results shown so far, the aggravation of problems at the primary link of the production chain of Brazilian beef
14
Prata, Camila Barbieri. "Aspectos do controle de resíduos de avermectinas no abate de bovinos /". Jaboticabal, 2014. http://hdl.handle.net/11449/122080.
Testo completoAbstract (sommario):
Orientador: Adolorata Aparecida Bianco CarvalhoBanca: Ana Maria Centola Vidal Martins
Banca: Estevam Guilherme Lux Hoppe
Banca: Paulo Sérgio Jorge
Banca: Fabio Fernando Ribeiro Manhoso
Resumo: As mudanças nos controles internacionais dos alimentos visando sua inocuidade se efetivaram com a mudança de século, tendo como base a Análise de Riscos e a Análise de Perigos e Pontos Críticos de Controle. Para os resíduos químicos, apesar de problema pré-existente, a situação só ganhou notoriedade a partir de 2010 com a detecção da presença de resíduos de avermectinas em produtos cárneos brasileiros exportados para os Estados Unidos e União Europeia. A partir de então, várias medidas de mitigação foram inseridas no conjunto rotineiro de autocontroles pelas empresas processadoras. Neste trabalho objetivou-se verificar a praticidade e eficácia dessas medidas para o controle efetivo dos processos, segregando animais abatidos que pudessem contribuir para níveis inaceitáveis do perigo, com base na monitoração de resíduos de avermectinas em duas matrizes amostrais, fígado e músculo de bovinos abatidos. Para a matriz músculo foram analisados 81.565 lotes de animais, com 1,41% desses ou 1.153 lotes que apresentaram resíduos de avermectinas superiores ao LMR de 10μg/kg durante os anos de 2010 e 2011. A partir de 2012 utilizou-se a matriz fígado, sendo analisadas 77.056 amostras. Dessas, 29.267 ou 37,98% apresentaram positividade para resíduos, sendo que 4.602 ou 5,97% foram superiores ao LMR de 100μg/kg. Os resultados analíticos demonstram, até agora, agravamento do problema no elo primário da produção de carne bovina brasileira
Abstract: Changes in international food controls aiming their safety occurred with the change of the century, based on the Risk Analysis and Hazard Analysis and Critical Control Points. For chemical residues, although a pre-existing problem, the situation only gained notoriety after 2010, with the presence of avermectin residues in Brazilian meat products exported to the United States and European Union. Since then, several mitigation measures were incorporated in the routine set of self-controls the processing companies.This work aimed to verify the practicality and effectiveness of these measures for effective control of processes, segregating slaughtered animals that could contribute to unacceptable levels of risk, based on monitoring of avermectins residues in two sample matrices, liver and muscle of cattle slaughtered. For the muscle matrix were analyzed 81,565 batches of animals, with 1,153 or 1.41% batches whose residues were above the avermectin MRL (Maximum Residue Level) of 10μg/kg during the years 2010 and 2011. from 2012 was used the liver matrix , with 77,056 samples being analyzed. Of these, 29,267 or 37.98% were positive for residues, with 4,602 or 5.97% above the MRL of 100μg/kg. The analytical results shown so far, the aggravation of problems at the primary link of the production chain of Brazilian beef
Doutor
15
Serba, Christelle. "Nouvelles approches vers les lactones sesquiterpéniques". Thesis, Strasbourg, 2015. http://www.theses.fr/2015STRAF017/document.
Testo completoAbstract (sommario):
Cette thèse développe de nouvelles séquences réactionnelles divergentes vers les lactones sesquiterpéniques, ainsi que leurs analogues. La réactivité multiple d’un substrat linéaire face à divers catalyseurs a tout d’abord permis d’obtenir différentes structures polycyliques dont la fonctionnalisation a permis d’isoler plusieurs produits naturels et des analogues. De nouvelles méthodologies ont été étudiées pour accéder aux gamma-butyrolactones, une fonctionnalité prépondérante dans les lactones sesquiterpéniques, ainsi qu’au noyau hydroazulène contenu dans les guaianes. Enfin, une synthèse divergente courte et performante a été mise au point pour accéder à divers analogues de la déoxyéléphantopine, un sesquiterpène aux propriétés anti-cancéreuses, afin de moduler et étudier son activité biologique. En parallèle de ces travaux sur les sesquiterpènes, une autre chimie a été explorée visant à réaliser la glycosylation de cystéines avec des carbohydrates non protégésThe main thread throughout this thesis is to develop reaction sequences that could provide facile access to the sesquiterpene lactones, or analogs thereof, using strategies that would be compatible with divergent reaction pathways. A first project harnessed the multiple reactivity mode of a linea rsubstrate to obtain different polycyclic frameworks found in sesquiterpenes whose functionalisation led to several natural products and their analogs. New methodologies were studied to access gamma-butyrolactones, a preponderant functionality in sesquiterpene lactones, and hydroazulene core, the bicyclic framework of guaianes. Finally, a short divergent pathway was designed to access diverse analogs of deoxyelephantopin, a sesquiterpene showing anti-cancer effects, so as to modulate and study its biological activity. In parallel to this work on sesquiterpenes, a different chemistry was explored aiming at performing glycosylation of cysteines with unprotected carbohydrates
16
Wright, Edward Andrew. "π-Allyltricarbonyliron lactones in asymmetric synthesis". Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621938.
Testo completo
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Ounsworth, James Paul. "Synthesis of [beta]-keto lactones and the synthetic consequences of the conformational preferences of 14-membered lactones". Thesis, University of British Columbia, 1985. http://hdl.handle.net/2429/25954.
Testo completoAbstract (sommario):
The preparation of the β-keto lactones 1̲9̲ via intramolecular alcoholysis of hydroxy Meldrum's acid derivatives was examined. Good yields of the 6- and 14-membered compounds were obtained, but the method was completely unsuccessful for medium-size rings.
An investigation was conducted on the conformational preference of substituted 14-merabered lactones with a view to understanding the stereochemical consequences of the reactions of these compounds. The conformational preferences of simple 14-membered cyclic compounds were first determined. These preferences are described in terms of steric and electronic interactions, with the support of computer-calculated steric energies.
A number of 14-membered lactones were prepared, beginning with the β-keto lactone 3-oxo-13-tetradecanolide (1̲3̲8̲). Hydride reduction of (1̲3̲8̲) gave the diastereomeric alcohols 1̲4̲6̲ and 1̲4̲7̲, which were then elaborated to give a series of derivatives. The stereochemistry and conformations of these compounds were determined by X-ray crystallography and/or nmr analysis. The preferred conformation was found to be Dale's [3434] diamond lattice model.
The relative rates of reaction were determined for several reactions of the alcohols 1̲4̲6̲ and 1̲4̲7̲ and for one reaction of the corresponding acetates. The conformational effects were found to be much smaller than those observed in 6-merabered rings. Explanations of this difference are given. The preparation of the ⍺, β-unsaturated lactones 1̲6̲3̲ and 1̲6̲4̲, the β-methyl-⍺, β-unsaturated lactones 1̲8̲5̲ and 1̲8̲̲6̲̲, the dimethyl lactones 1̲5̲4̲ and 1̲5̲5̲ and the epoxides 1̲9̲7̲ and 1̲9̲8̲ are described. The resulting geometry of double bonds and the stereochemistry of substituents are explained in terms of conformational preferences. [Formula Omitted]Science, Faculty of
Chemistry, Department of
Graduate
18
Mas, Quilez Cristina. "Modificació química de reïnes epoxi amb lactones". Doctoral thesis, Universitat Rovira i Virgili, 2004. http://hdl.handle.net/10803/8994.
Testo completoAbstract (sommario):
Les reïnes epoxi són monòmers àmpliament utilitzats degut a les bones propietats que s'obtenen una vegada que el material està curat. El procés d'entrecreuament d'aquests monòmers presenta alguns problemes. Durant el procés de curat té lloc una disminució del volum o contracció que dóna lloc a l'aparició de porus i esquerdes i per tant un empitjorament de les propietats mecàniques i de la capacitat de recobriment. Altres problemes associats a aquests materials és la fragilitat i la no degradabilitat, sent aquest últim un greu inconvenient des del punt de vista medioambiental.L'objectiu d'aquest treball ha estat disminuir la fragilitat i la contracció de materials termoestables i augmentar la seva degradabilitat. Per aconseguir-ho les reïnes epoxi s'han copolimeritzat amb lactones, ja que està descrit que la reacció entre epòxids i lactones dóna com a intermedis els espiroortoesters, que són compostos expandibles al polimeritzar, a la vegada que permeten augmentar la proporció de grups esters a la xarxa que poden ser degradats térmica o químicament.
S'han utilitzat com a catalitzadors catiònics els triflats de lantànid, ja que en un treball anterior van demostrar la seva capacitat de polimeritzar reïnes epoxi a temperatures moderades obtenint materials amb bones propietats mecàniques.
Els resultats més destacats de la tesi són:
- S'ha pogut, mitjançant FTIR/ATR, seguir l'evolució de les quatre reaccions que tenen lloc durant la polimerització de reïnes epoxi amb lactones de cinc membres: l'homopolimeritzacio de l'epòxid, la copolimerització de l'epòxid amb la lactona obtenit-se els espiroortoesters (SOE), la copolimerització de l'epòxid amb el SOE format i l'homopolimerització del SOE. A més, s'ha pogut confirmar que el procés d'iniciació té lloc a través de la formació de dues espècies actives.
- La copolimerització de reïnes epoxi amb lactones ha permès augmentar la degradabilitat d'aquests sistemes degut a un increment de grups esters a la xarxa.
- La copolimerització de DGEBA amb lactones ha permès reduir la contracció després de la gelificació i per tant s'ha disminuït la formació de porus i esquerdes.
- La utilització de diferents triflats de lantànid ha permès veure que a l'augmentar l'acidesa de Lewis del catió augmenta la constant de velocitat del procés global.
The curing of thermosetting materials is generally accompanied by shrinkage because covalent bonds form between chains and increase the density of the materials. This shrinkage leads to internal stress in the material, reduces adhesion to the substrate, and produces microvoids and microcracks, which reduce the durability of the material to worse the properties.
Shrinkage during curing could be reduced or eliminated using monomers that polymerize without contraction or even with expansion. Ring-opening polymerization leads to less shrinkage than that produced by polycondensation or polyaddition, because not only small molecules are not eliminated in the polymerization, but for every bond that changes from a van der Waals distance to a covalent distance there is another bond that changes front a covalent to a van der Waals distance. Thus, the ring-opening polymerization of bicyclic monomers [(spiroorthoesters (SOE)] is a good strategy for obtaining non-shrinkable resins that can be applied in adhesives, coatings or composites.
The classical synthetic procedure for obtaining SOEs is to react lactones with epoxides in the presence of a Lewis acid as a catalyst. In this way, cationic crosslinking of mixtures of epoxy resins with lactones could take place with little shrinkage because SOE groups are formed during this process.
The cationic catalysts were lanthanide triflates because in previous studies, we have demonstrated that lanthanide triflates are Lewis acid that can completely cure diglycidylic and cycloaliphatic epoxy resins.
The results of this study have been:
- Using FTIR/ATR, we have shown that there were four elemental reactive processes during the copolimerization of epoxy groups and lactones of five members: homopolymerization of epoxy groups, formation of SOE by reaction of epoxy groups and lactones, copolimerization of SOE and epoxy groups and homopolimerization of SOE. The initiation process takes place through two active species.
- The copolimerization of epoxy groups and lactones led to increase ester groups in the polymeric networks and this led to increase its degradability.
- The addition of lactones to the curing of epoxy groups reduced the contraction after gelation, and this led to lower internal stress.
- When Lewis acidity of lanthanide cation is increased, the catalyst becomes more active and the curing process accelerates.
19
Yu, Hongping. "Conformationally controlled reactions of 14-membered lactones". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0015/NQ56651.pdf.
Testo completo
20
Harrison, J. R. "Exploration of 8-membered lactones in synthesis". Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.603775.
Testo completoAbstract (sommario):
This dissertation details the synthesis of a range of 8-membered lacones via a Claisen rearrangement route and also efforts towards the synthesis of 8-membered lactones by a new radical cyclisation strategy. Chapter One reviews the effect of substituents on the rates and stereoselectivities of Claisen rearrangements. Chapter Two describes the synthesis of 8-membered lactones, such as 2.43d, 2.109 and 2.85 by Claisen rearrangement methodology. Potential application of this methodology to the synthesis of the immunosuppressant discodermolide is also discussed. (Fig. 3864A) Chapter Three reviews the use of radical cyclisation in the formation of medium- and large-ring lactones. Studies on a new method of 8-membered lactone preparation by the radical cyclisation of the allylstannane 4.47 are reported in Chapter Four (Fig. 3864B).
21
Dyke, H. J. "Synthetic studies towards Stemofoline and bicyclic lactones". Thesis, University of Southampton, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356689.
Testo completo
22
Rabiller, Christine. "Nouvelles voies de synthèse de lactones bioactives". Nancy 1, 1994. http://www.theses.fr/1994NAN10339.
Testo completoAbstract (sommario):
La synthèse enantiospécifique de lactones bioactives, inhibitrices d'une part de l'hmgcoa réductase, et d'autre part des lipases pancréatiques a été entreprise. Dans une première partie, l'accès facile et rapide à des composés de structure didesoxy-2-4-hexopyranose, chiron clé pour la synthèse d'inhibiteurs de la biosynthèse du cholestérol, a été réalisé par transformation stéréospécifique du 1,6-anhydro-beta-d-glucopyranose obtenu par pyrolyse dans de bonnes conditions qui ont été mises au point dans ce travail. Dans la deuxième partie, l'application des méthodes de création de liaison carbone-carbone en c-2 et en c-6 sur un dérivé du glucose, a permis d'ouvrir deux nouvelles voies pour la préparation d'intermédiaires clés de la synthèse de la valilactone, le tetrahydrolipstatine et la tetrahydroexterastine, composes d'intérêt pharmacologique pour le traitement de l'obésité
23
Gore, Sophie. "Transannular Claisen rearrangements of α-sulfonyl lactones". Thesis, Imperial College London, 2009. http://hdl.handle.net/10044/1/7827.
Testo completoAbstract (sommario):
This thesis is divided into three sections. Section one is a review of transannular pericyclic reactions. It covers the four main types of pericyclic reaction and major contributions in the field to date. Recent applications of these reactions to natural product synthesis are also included. Section two discusses the results of research efforts into transannular Claisen rearrangements of α-sulfonyl lactones. The background to the project is discussed along with initial investigations into the transannular Claisen and decarboxylative Claisen rearrangements (dCr) of the 7-membered ?-tosyl lactone to form vinyl cyclopropanes. Stereoselectivity from within the pericyclic array, by substitution at the lactone C7 position is examined. Efforts towards stereoinduction from outside of the pericyclic array are also detailed, along with aryl substitution at the lactone C5 position to form highly substituted vinyl cyclopropanes. Extension of this methodology to the unprecedented transannular Claisen rearrangement and dCr reaction of 8-membered ?-tosyl lactones to give vinyl cyclobutanes is reported. Finally, efforts towards a novel synthetic route to (?)-grandisol utilising the transannular Claisen rearrangement chemistry is described. Section three details the experimental procedures and spectroscopic data for the compounds described in section two.
24
Deshpande, N. R. "Studies in sequiterpenic lactones and related products". Thesis(Ph.D.), CSIR-National Chemical Laboratory, Poona, 2018. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/3897.
Testo completo
25
Metay, Estelle Nedelec Jean-Yves. "Méthodologie d'accès à des benzolactones de taille moyenne". Créteil : Université de Paris-Val-de-Marne, 2005. http://doxa.scd.univ-paris12.fr:80/theses/th0228183.pdf.
Testo completo
26
Schorr, Karin. "Smallanthus sonchifolius (Asteraceae): estudo fitoquímico, controle de qualidade e ensaios biológicos". Universidade de São Paulo, 2005. http://www.teses.usp.br/teses/disponiveis/59/59138/tde-22072005-102725/.
Testo completoAbstract (sommario):
Esta tese de doutorado aborda alguns aspectos do estudo de plantas medicinais e de princípios ativos naturais. Os procedimentos experimentais incluíram o estudo fitoquímico de uma planta medicinal da família Asteraceae, o desenvolvimento de um método analítico com validação das análises empregadas e o estudo de atividades biológicas relativas ao processo inflamatório. A primeira etapa compreendeu o estudo fitoquímico da planta medicinal Smallanthus sonchifolius (Asteraceae), envolvendo o isolamento de metabólitos secundários da classe dos terpenóides. Do extrato de lavagem foliar foram isoladas as seguintes lactonas sesquiterpênicas (LSTs): enidrina, uvedalina, sonchifolina, fluctuanina, polimatina B, (1Z,4E)-8β-metacriloilóxi-9α-acetoilóxi-germacra-1(10),4,11(13)-trien-6α,12-olido-14-oato de metila, (1Z,4E)-8β-angeloilóxi-14-oxo-germacra-1(10),4,11(13)-trien-6α,12-olido, (1Z,4E)-8β-metacriloilóxi-germacra-1(10),4,11(13)-trien-6α,12-olido-14-oato de metila, ácido (1Z,4E)-8β-angeloilóxi-germacra-1(10),4,11(13)-trien-6α,12-olido-14-óico e (1Z)-3α,4β-epóxi-8β-[(1Z,4E)-(2S,3R)-2-hidróxi-3-óxi-(8β-angeloilóxi-germacra-1(10),4,11(13)-trien-6α,12-olido)]-9α-acetoilóxi-germacra-1(10),11(13)-dien-6α,12-olido-14-oato de metila. A segunda etapa tratou do desenvolvimento de método e validação das análises para controle de qualidade químico de S. sonchifolius em cromatografia líquida de alta eficiência (CLAE). Além disso, foi realizada a quantificação do principal metabólito secundário isolado nos extratos glandulares e de lavagem foliar, a LST enidrina. Esta substância compõe 0,97 % do peso seco das folhas de S. sonchifolius. A terceira etapa refere-se às atividades biológicas, as quais foram avaliadas empregando-se diversos ensaios. Também foi realizada a otimização de método para avaliação da secreção de elastase por neutrófilos humanos e o estudo da estimulação basal de neutrófilos. Ainda foram investigados os efeitos de produtos fitoterápicos, como gel de Arnica montana e extrato de Harpagophytum procumbens, e de metabólitos secundários, como LSTs e alcalóides, na atividade enzimática de elastase, na secreção de elastase por neutrófilos, na ativação do fator de transcrição NF-κB via EMSA, na produção de luciferase por meio de reporter gen assay e de interleucina-8 via ELISA. Com exceção de dois alcalóides, todas as substâncias e produtos testados apresentaram atividades de inibição dos processos inflamatórios investigados.This Ph.D. thesis deals with some aspects of the study of medicinal plants and their biologically active natural compounds. The experimental procedures comprised the phytochemical study of a plant from the family Asteraceae, the development of an analytical method with validation of the employed analysis and the study of the biological activities related to the inflammatory process. The first step comprised the phytochemical study of the medicinal plant Smallanthus sonchifolius (Asteraceae) and the isolation of secondary metabolites. From the leaf rinse extract were isolated the sesquiterpene lactones (STLs) enhydrin, uvedalin, sonchifolin, fluctuanin, polymatin B, methyl (1Z,4E)-8β-metacryloyloxy-9α-acetoyloxy-germacra-1(10),4,11(13)-trien-6α,12-olide-14-ate, (1Z,4E)-8β-angeloyloxy-14-oxo-germacra-1(10),4,11(13)-trien-6α,12-olide, methyl (1Z,4E)-8β-metacryloyloxy-germacra-1(10),4,11(13)-trien-6α,12-olide-14-ate, (1Z,4E)-8β-angeloyloxy-germacra-1(10),4,11(13)-trien-6α,12-olide-14-oic acid, methyl (1Z)-3α,4β-epoxy-8β-[(1Z,4E)-(2S,3R)-2-hydroxy-3-oxy-(8β-angeloyloxy-germacra-1(10),4,11(13)-trien-6α,12-olide)]-9α-acetoyloxy-germacra-1(10),11(13)-dien-6α,12-olide-14-ate. The second part was related to the development and validation of a chromatographic method for the chemical quality control of S. sonchifolius using high performance liquid chromatography (HPLC). Furthermore, the quantification of the main secondary metabolite, the STL enhydrin on glandular and leaf rinse extracts was also performed. This compound comprises 0,97 % of dried leaves weight of the plant. The third part deals with biological activities, which were investigated through different assays. One method for the study of the elastase release from human neutrophils was evaluated and the basal stimulation of neutrophils was studied. The effects of phytoterapeutic agents, like Arnica montana gel and Harpagophytum procumbens extract, and of the secondary metabolites, like LSTs and alkaloids, on the enzymatic activity of elastase, on elastase release from neutrophils, on the activation of the transcription factor NF-κB through EMSA, on luciferase production through reporter gene assay and on interleucina-8 production through ELISA were also carried out. Both phytoterapeutic agents as well as the great majority of the tested compounds showed some inhibitory activity over the investigated inflammatory processes.
27
Haudecoeur, Elise. "Signalisation quorum-sensing au cours de l'interaction Agrobacterium tumefaciens C58-plante hôte : régulation et fonctions des lactonases AttM et AiiB". Paris 11, 2008. http://www.theses.fr/2008PA112369.
Testo completoAbstract (sommario):
La bactérie phytopathogène Agrobacterium tumefaciens est l'agent responsable de la galle du collet, maladie touchant de nombreuses plantes d'intérêt agronomique. Tout au long du cycle de pathogénie, des échanges de signaux entre les deux partenaires ont des conséquences directes sur les processus de régulation génique et d'apparition des tumeurs chez les végétaux, ainsi que sur ceux de régulation génique et de dynamique des populations, chez les bactéries. La réplication et la dissémination du plasmide Ti, élément génétique associé au pouvoir pathogène d'A. Tumefaciens, sont sous le contrôle d'un mécanisme de régulation dépendant de la densité de population bactérienne, connu sous le nom de quorum sensing (QS). Ce mécanisme, activé par les opines issues des cellules végétales transformées, implique la synthèse par la bactérie, d'une molécule signal de type acyl-homoserine lactone (AHL). A. Tumefaciens C58 possède également deux lactonases, AiiB et AttM, lui conférant la capacité de dégrader ces AHLs et d'interrompre ou de perturber la communication QS. L'expression de la lactonase AttM est induite en présence d'acide gamma-aminobutyrique (GABA), molécule d'origine végétale, accumulée au site de blessure de la plante puis dans la tumeur. Dans ce travail, la construction de fusions transcriptionnelles nous a permis de définir les conditions physiologiques permettant l'expression de la lactonase AiiB mais aussi de préciser la voie de signalisation GABA impliquée dans le contrôle de la lactonase AttM. Ainsi, nous avons montré le rôle de composés accumulés au niveau de la tumeur végétale, dans la régulation des lactonases AiiB et AttM et leurs conséquences sur la virulence d'A. Tumefaciens C58. La connaissance des mécanismes de régulation de AiiB et AttM ajoutée à l'étude des mutants déficients pour la synthèse de l'une ou des deux lactonases nous ont permis de proposer des fonctions biologiques pour AiiB et AttM dans l'écologie d'A. Tumefaciens C58 et sa virulence sur plante. Enfin, nous avons identifié les caractéristiques génétiques d'une souche particulière d'A. Tumefaciens, dégradant les AHLs de manière rapide et constitutive et avons mesuré l'efficacité d'une telle souche comme agent biocontrôle, dans le cadre de l'infection de plants de pomme de terre par la bactérie Pectobacterium atrosepticum.
28
Reather, James Andrew. "Late steps in the biosynthesis of macrocyclic lactones". Thesis, University of Cambridge, 2000. https://www.repository.cam.ac.uk/handle/1810/251730.
Testo completo
29
Leslie, Ray. "Synthesis and reactions of unsaturated 14-membered lactones". Thesis, University of British Columbia, 1991. http://hdl.handle.net/2429/30016.
Testo completoAbstract (sommario):
Via a lactonization of the open chain hydroxy acid, the 14-membered unsaturated lactones 14 and 15 were synthesised. Treatment of these two lactones with borane dimethylsulphide, disiamyl borane and 9BBN led to formationof hydroxy lactones 30, 31, 32 and 33. The structures of 31 and 32 were determined by comparison with known compounds whereas structures 30 and 33 were deduced by considering the transition structures of the hydroboration reaction. Although both the regio and the stereoselectivity of the reactions were poor the π-face selectivity was high. Product distributions were estimated by the conformational control induced by the ring, using Houk's parameters for the hydroboration transition structures, in an MM2 force field, to calculate their relative strain energies.
[ formulas omitted]Science, Faculty of
Chemistry, Department of
Graduate
30
Maurice, Joseph Roger Luc. "Synthesis and reactivity of 14-membered keto lactones". Thesis, University of British Columbia, 1991. http://hdl.handle.net/2429/31129.
Testo completoAbstract (sommario):
A convergent synthesis using dithiane alkylations to produce a long chain hydroxy acid, and subsequent macrolactonization of the latter, yielded the 14-membered macrolides 47 and 58.
[ Formulas omitted ]
Alkylation of 47 with methyl iodide gave a diastereomeric product mixture of α-methylated lactones with the major product having the 2R*,13S* stereochemistry (71). The product ratio was explained by using low energy starting material conformations combined with MM2 calculations. Alkylation of 58 in the same manner also yielded a mixture with the major product having the 2R*,13S* stereochemistry (77a).
[ Formulas omitted ]
Hydrolysis of the dithiane ring on 47 and 58 gave the keto lactones 28 and 29 respectively. Reduction of the ketone in 28 yielded a mixture of diastereomeric hydroxy lactones of which the major product had the 5S*,13S* stereochemistry (61); this stereochemistry was confirmed by the X-ray crystallographic structure of the p-bromobenzene sulfonate derivative. Reduction of the ketone in 29 also yielded a diastereomeric mixture of hydroxy lactones; the 7S*,13S* stereochemistry of the major product 67 was suggested by MM2 calculations.
[ Formulas omitted ]
Treatment of both 28 and 29 with trimethylsilyl trifluoromethanesulfonate and tert-butyldimethylsilyl trifluoromethanesulfonate in the presence of triethylamine gave rise to mixtures of isomeric enol ethers; the product distribution could be partly explained by MM2 calculations based on product conformations.Science, Faculty of
Chemistry, Department of
Graduate
31
Edwards, M. I. "Asymmetric synthesis of lignan lactones from meso compounds". Thesis, Swansea University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636768.
Testo completoAbstract (sommario):
The purpose of this research was to form (2S, 3R)-2,3bis(3,4-dimethoxybenzyl) butyrolactone. A brief review of the main classes of lignans, their biosynthesis, biological activity and clinical utility is given in the first chapter. The main chemical synthesis routes to such compounds are also provided covering the six most commonly used routes including the Stobbe condensation. An overview of the use of meso compounds for the production of chiral synthons and use of the 'meso trick' to enhance yields during chiral induction to meso substrates are discussed in chapter two. Construction of the basic C18 lignan skeleton in chapter three is achieved via a double Stobbe condensation with preferential formation of the E-isomer at each stage. In the first step the Stobbe product is reduced to give the maleic anhydride. This resisted further reduction but reduction of the dimethyl maleate successfully gave the meso succinic anhydride with no d/l isomer formation. The formation of the target compound is described in chapter four. Reaction of the meso substrate with (+)-α-methylbenzylamine proceeded with chiral induction in 81% d.e. The use of chiral alcohols including 1-methol, 1-α phenyl ethylalcohol and S-(+)-methyl mandelate has also been examined showing widely varying diastereoselectivities. Conversion of (2S, 3R, αR)-N-(α-phenylethyl)- 2,3-bis(3,4-dimethoxybenzyl)butanedioic acid monoamide to the target dibenzyl butyrolactone has been readily achieved by reduction to the corresponding alcohol prior to lactonisation. Racemisation of (2S, 3R)-2,3-bis(3,4-dimethoxybenzyl) butyrolactone under basic conditions and comparison of the optical rotation values obtained with those in the literature allowed the absolute stereochemistry to be assigned. The attempted formation of picrostegane type lignans by non phenolic oxidative coupling is also described.
32
Murphy, Alison. "Lactones en route to altohyrtin A and tetrahydrolipstatin". Thesis, University of Liverpool, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243211.
Testo completo
33
Sandey, Helen Jane. "Biotransformations of bicyclic ketones to lactones by microorganisms". Thesis, University of Exeter, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293978.
Testo completo
34
Tang, Andrew. "Synthetic methodology towards the synthesis of sesquiterpene lactones". Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612321.
Testo completo
35
O'Sullivan, Paul Thomas. "Natural product systems from eight-membered ring lactones". Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621632.
Testo completo
36
Lakhrissi, Mohammed. "Dichloromethylenation de lactones et d'esters : synthèse et réactivité". Nancy 1, 1993. http://www.theses.fr/1993NAN10176.
Testo completoAbstract (sommario):
La dichloromethylenation des lactones et d'esters a été mise au point par l'utilisation d'un nouveau système de réactifs: triphenylphosphine-tetrachlorure de carbone. Ce système permet de transformer les lactones en présence des groupements o-benzyl, o-methylmethylether et d'esters encombres comme les pivaloyles et 4-phenylbenzoyles. Les nouvelles conditions que nous avons mises au point permettent la transformation des lactones -1,4; 1,5 et des acétates. Le motif dichloromethylene se prête bien à des transformations chimiques telles que la réduction, la chloration, la coupure oxydante ainsi que la cyclopropanation
37
Harmange, Jean-Christophe. "Synthèse totale énantiosélective d'acétogénines d'Annonacées (gamma-lactones monotétrahydroguraniques)". Paris 11, 1992. http://www.theses.fr/1992PA114840.
Testo completo
38
Parmar, Dixit. "Reductive cyclisations of lactones using SmI2 and H2O". Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/reductive-cyclisations-of-lactones-using-smi2-and-h2o(533c0430-fd14-4a24-93f2-18a7fb27232f).html.
Testo completoAbstract (sommario):
Carbonyl reduction is a fundamental transformation that underpins synthetic chemistry. The re-routing of carbonyl reduction through less-conventional intermediates allows new selectivity and reactivity to be found in the resulting reaction space. We have shown for the first time that the unusual radical anions formed by electron transfer to the ester carbonyl group can be exploited in additions to alkenes. We have demonstrated that the reductive cyclisations of lactones, triggered by electron-transfer from SmI2-H2O, allow for highly decorated cyclopentane and cycloheptane ring systems to be constructed. Futhermore, the reductive cyclisations of lactones can be exploited in cyclisation cascades. The cascade sequences involve the generation and trapping of unusual radical anions formed from the ester carbonyl followed by the trapping of more conventional radical anions from the carbonyl groups of ketone intermediates.
39
Martinez, Sandra Ainsua. "Oxidative radical cyclisations for the synthesis of lactones". Thesis, University of Oxford, 2017. http://ora.ox.ac.uk/objects/uuid:4a8185e5-41fb-409c-9856-88f51b71912c.
Testo completoAbstract (sommario):
The object of study of this thesis lies on the optimisation of the oxidative radical cyclisation methodology for the preferential formation of gamma-lactones from unsaturated alkyl malonate derivatives. Chapter 1 introduces the concept of free-radical cyclisation; more extensive explanations are given for the intramolecular oxidative radical cyclisation using manganese(III) and copper(II) salts as oxidants. An overview of the contribution of the Burton group in the field is given, in which both the applicability and the limitations of the transformation are showcased. Chapter 2 is concerned with the synthesis of the ethisolide family of natural products and one non-natural analogue, in which the oxidative radical cyclisation is key for the construction of the bis-gamme-lactone moiety present in such natural products. The initial limitations of the methodology allowed for the discovery of new conditions for the formation of chloro monocyclic systems and for the development of copper-free oxidative cyclisation conditions for gamma-lactone formation. Chapter 3 reports the developments on the metal-free oxidative radical cyclisation. Bicyclic gamma-lactones were synthesised from all-carbon alkyl malonate derivatives through anodic oxidation via constant current electrolysis. The development of a novel ionic oxidative cyclisation is also discussed. Chapter 4 describes our efforts towards the formation of both fused and spiro gamma-lactam-beta-lactone molecules, as potential analogues to proteasome inhibitors, from either gamma-lactam-gamma-lactones or exo-gamma-lactams precursors, previously synthesised through oxidative radical cyclisation. Full experimental details, NMR spectra for the natural products and for the non-natural analogue, and a comparison between the obtained and the previously reported NMR data are also provided.
40
Gokhale, N. J. "Synthesis of some bioactive lactones and acetylenic alcohols". Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 1997. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/3375.
Testo completo
41
Bouaziz, Zouhair. "Synthèse et étude par impact électronique de dérivés de l'hydroxy-5 naphtalène carbolactone-1,8 : relations structure-activité entre les paramètres électroniques et l'activité cytotoxique". Lyon 1, 1989. http://www.theses.fr/1989LYO1T087.
Testo completo
42
Sabie, Rafa. "Synthèse et étude structurale d'α-acétyl-α'-naphtols et de dihydronaphtoxazines dérivés de la 5-hydroxynaphtalène-1,8 carbolactone : recherche de l'activité cytotoxique in vitro". Lyon 1, 1990. http://www.theses.fr/1990LYO1T148.
Testo completo
43
Cao, Shuyong. "Characterization of macrolactonization catalyzed by the excised thioesterase domain of biosurfactant lichenysin D synthetase /". View abstract or full-text, 2005. http://library.ust.hk/cgi/db/thesis.pl?CHEM%202005%20CAO.
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Skead, Benjamin M. "Research in carbohydrate chemistry". Thesis, University of Oxford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358724.
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Rubinger, Mayura Marques Magalhaes. "A new approach to the pseudoguaianolides". Thesis, University of Reading, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259501.
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Falentin-Daudre, Céline. "Synthèse directe de monothioéthers, d'aminoacides polyhydroxylés et de lactames N-alkylés à partir de D-pentono-1,4-lactones". Amiens, 2009. http://www.theses.fr/2009AMIE0107.
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Garzino, Frédéric. "Synthèse radicalaire asymétrique de y-lactones et de2,3-dihydrofuranes induite par Mn(OAc)3 : Accès des lignanes enantiométriquement purs". Aix-Marseille 2, 2001. http://www.theses.fr/2001AIX22064.
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Mondal, S. "Organocatalytic enantioselective synthesis of functionalized cyclopentenes, beta-lactones and spirocyclohexenols". Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 2017. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/4527.
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Cervezan, Thalita Cristina Marques [UNESP]. "Avaliação fitoquímica e microbiológica da espécie Artemisia annua L., submetida a tratamentos de armazenamento e condições de ambiente". Universidade Estadual Paulista (UNESP), 2013. http://hdl.handle.net/11449/90610.
Testo completoAbstract (sommario):
Made available in DSpace on 2014-06-11T19:24:42Z (GMT). No. of bitstreams: 0
Previous issue date: 2013-02-25Bitstream added on 2014-06-13T19:11:19Z : No. of bitstreams: 1
cervezan_tcm_me_botfca.pdf: 497237 bytes, checksum: d6694ebd7c9403db49840bbd8579a450 (MD5)A espécie Artemisia annua, Asteraceae, nativa da China, tem a artemisinina como seu principal componente ativo, é considerado um potente antimalárico. Com o aumento do valor dos princípios ativos naturais, estudos relacionados à pós-colheita e armazenamento de material vegetal tornam-se importantes para melhor conservação de suas propriedades fitoterápicas. O presente estudo teve como objetivo definir as melhores condições de armazenamento para preservar a qualidade da droga vegetal. Folhas de A. annua secas foram armazenadas por seis meses em sacos de polietileno envolto por papel Kraft e acondicionadas em quatro tratamentos: em condição ambiente e refrigerada a 4º±2C, em embalagem normal e em embalagem sob vácuo. No tempo zero e nos períodos de 30, 90, 120 e 180 dias foram realizados as análises microbiológicas e avaliação do teor de artemisinina. Os resultados dos ensaios microbiológicos não demonstraram contaminação significante, assim como o teor de umidade do material armazenado, que permanecem entre 5% a 10%, mantendo-se dentro do parâmetro aceitável. O tratamento sem vácuo ambiente (SVA) foi o que melhor manteve estabilidade de armazenamento durante os 180 dias, no entanto, foi o sem vácuo refrigerado (SVR) que apresentou maior eficiência para a conservação do teor de artemisinina
Artemisia annua is an Asteracea native to China, its principal active component, artemisinin, is considered a potent antimalarial drug. With the increased interest in natural active principles, studies related to post-harvest and storage of vegetable material become important for better conservation of its phytotherapic properties. Therefore, the present study had as objective define best storage conditions to preserve and keep the quality of phytotherapic Leaves of A. annua dried were stored for six months in polyethylene bags wrapped in Kraft paper and packed in four treatments: at ambient condition, at ambient condition with vacuum packing in refrigerated conditions at 4° ± 2C normal and vacuum packing. At time zero, and the periods of 30, 90, 120 and 180 days were performed microbiological analyzes and evaluation of the level of artemisinin. The results of microbiological tests showed no significant contamination, as well as the moisture content of stored (biological) material, which remain between 5% and 10%, keeping within acceptable parameters. The vacuum environment without treatment (SVA) was the best storage stability maintained during 180 days, however, no vacuum was refrigerated (SVR) showed that greater efficiency to conserve the content of artemisinin, compared to the others
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Fatima, Angelo de. "Goniotalamina, epoxigoniotalamina, argentilactona e derivados : sinteses totais e atividades antiproliferativas contra celulas tumorais humanas". [s.n.], 2005. http://repositorio.unicamp.br/jspui/handle/REPOSIP/249281.
Testo completoAbstract (sommario):
Orientador: Ronaldo Aloise PilliTese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica
Made available in DSpace on 2018-08-04T13:47:35Z (GMT). No. of bitstreams: 1 Fatima_Angelode_D.pdf: 6353488 bytes, checksum: a8d593bc18e70b70bdac0ab5c7789f96 (MD5) Previous issue date: 2005
Doutorado
Quimica Organica
Doutor em Quimica