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Tesis sobre el tema "Alkaloids"

Autor: Grafiati
Publicado: 4 de junio de 2021
Última modificación: 30 de julio de 2024

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1

Witt, Anette. "Synthetic development towards benzodiazepine alkaloids : total synthesis of circumdatin F and C /". Stockholm, 2002. http://diss.kib.ki.se/2002/91-7349-077-6/.

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2

Callaghan, Owen. "Synthetic and mechanistic studies in free radical". Thesis, University of Strathclyde, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366957.

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3

Kalusa, Andrew. "Synthesis of marine alkaloids". Thesis, University of Oxford, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.275274.

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4

Goddard, Euan. "Asymmetric Synthesis of Alkaloids". Thesis, University of Oxford, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.489446.

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5

Smith, Catherine Janet. "Synthesis of histrionicotoxin alkaloids". Thesis, University of Cambridge, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.620245.

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6

Brock, Elizabeth Anne. "Alkaloids from transannular iodoaminations". Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:0feddc99-0fde-4dcd-b717-b0c6b0515615.

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This thesis is concerned with the development of transannular iodoamination methodology for the synthesis of pyrrolizidine, indolizidine and tropane alkaloids. Chapter 1 introduces the concept of a ‘transannular cyclisation’ and outlines the utility of such cyclisations in the synthesis of a range of [x.y.z]-azabicyclic alkaloids. Chapter 2 describes the development of a three step lithium amide conjugate addition, ring-closing metathesis and transannular iodoamination protocol for the preparation of the pyrrolizidine scaffold ([3.3.0]-azabicycle). Cyclisation of a hexahydroazocine occurs with concomitant N-debenzylation to give a single diastereoisomer of the corresponding C(7)-iodopyrrolizidine product, which is then elaborated to the known pyrrolizidine, (−)-7a-epi-hyacinthacine A1. Chapter 3 delineates an extension of the methodology described in Chapter 2, and an investigation into accessing alternate diastereoisomeric pyrrolizidine scaffolds via the transannular iodoamination process. These studies culminate in the synthesis of two pyrrolizidine alkaloids, (−)-hyacinthacine A1 and (−)-hyacinthacine A2. Chapter 4 details investigations into the further elaboration of the C(7)-iodopyrrolizidine scaffold synthesised in Chapter 2. A nucleophilic displacement reaction with azide leads to the synthesis of novel 7-deoxy-7-aminoalexine analogues, whilst radical-mediated substitution of the iodide by oxygen allows the synthesis and isolation of the pyrrolizidine alkaloid (−)-1-epi-alexine. Chapter 5 outlines the development of the transannular iodoamination reaction to facilitate the synthesis of the tropane architecture ([3.2.1]-azabicycle). A tandem lithium amide conjugate addition and aldol reaction sequence is followed by ring-closing metathesis to give the required aminocycloheptene. Subsequent treatment with iodine results in transannular cyclisation to give a single iodotropane product which, following elaboration culminates in the synthesis of (+)-pseudococaine. Chapter 6 contains full experimental procedures and characterisation data for all compounds synthesised in Chapters 2, 3, 4 and 5.
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7

Stanley, Paul. "Semisynthesis of jerantinine alkaloids". Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/47504/.

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This thesis details the synthetic studies undertaken on natural products with anti-cancer activity. The general aim was to explore the synthesis and find an efficient and effective method to generate compounds, which would be used to further examine novel biological action. The first half of this thesis details the synthetic studies on the jerantinine family of natural products. The approach utilised the complex alkaloid (-)-tabersonine as a starting material, which was isolated from an abundant and sustainable source. Ultimately the first synthesis of (-)-jerantinine A and first enantioselective synthesis of (-)-jerantinine E were achieved. The biological activity of the synthetic material proved to be identical to that isolated from natural sources. The final part of this work describes the synthesis of a series of compounds derived from piperlongumine, which is of the Piperaceae family of natural products. The synthesis was accomplished using a novel methodology, which enabled the generation of a focussed library of derivatives. The compounds were tested by collaborators and their anti-cancer activity assessed in a variety of cell lines, revealing features of the structure activity relationship.
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8

Choi, Joong-Kwon. "Synthesis of pyrrolizidine alkaloids /". The Ohio State University, 1985. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487259125219504.

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9

Saensuk, Pilan. "Phytochemistry of norditerpenoid alkaloids". Thesis, University of Bath, 2007. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.485128.

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Norditerpenoid alkaloids have important biological activities. Many of them are potent ligands and therefore promising leads for novel selective antagonists and/or agonists of subtypes of nicotinic acetylcholine receptors (nAChR) and voltage-gated sodium channels. Aconitum, Consolida, and Delphinium are important sources of norditerpenoid alkaloids. This thesis is focussed on the chemistry of norditerpenoid alkaloids from these three genera, starting with a review of those recently isolated from Aconitum, Consolida, and Delphinium with brief aspects of taxonomy, biological activities, and modes of action. Selected aspects of the uses in traditional medicine of Delphinium and Aconitum are presented, including data on both toxicity and detoxification. In this thesis, chemical constituents of the seeds of Delphinium cultivar Pacific Giant and the seeds ofAconitum lycoctonum were investigated. To extract the crude alkaloidal material, Soxblet extraction was used for Delphinium cv Pacific Giant seeds and room temperature extraction for A. lycoctonum seeds. The crude extracts were purified by repeated column chromatography (over silica and alumina gels), yielding five known norditerpenoid alkaloids from Delphinium cv Pacific Giant (delavaines A and B, delpheline, methyllycaconitine (MLA), and pacinine) and two from A. lycoctonum (lycaconitine and N-succinylanthranoyl lycoctonine) which were analysed by detailed spectroscopic methods. X-Ray crystallographic analysis of aconitine, mesaconitine, lycoctonine, and delpheline was also studied. Three compounds were obtained from semisynthesis starting with MLA: lycoctonine by basic hydrolysis, inuline by acidic hydrolysis and by esterification of lycoctonine, and elatine by methylenedioxy acetal fonnation. These known alkaloids were structurally elucidated by a variety of spectroscopic techniques. MLA is a selective competitive antagonist at 0.7 sub-type nAChR. From collaborative studies, the results of biological activity for methyl esters delavaines A and B (a 3:2 mixture), delpheline'iand pacinine (the B-ring C6-ketone of delpheline) are reported in this thesis. Their biological activities were detennined in competitive o.-bungarotoxin binding assays for 0.7 nAChR in rat brain membranes. Delavaines A and B were potent ligands (ICso = 50 nM, cfMLA ICso =-1-2 nM), whereas delpheline and pacinine displayed only modest activity at 0.7 nAChR (ICso = -1 JlM). After studying N-ethylpiperidine as a model alkaloid, the pKa (a key physico-chemical parameter) ofMLA was measured by IH NMR as 7.15. A brief comparison with pKa data reported in the literature IS made across closely related norditerpenoid alkaloids.
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10

Sedlock, Andrea B. "Ergot alkaloids and herbivory in model animals and variation in an ergot alkaloid biosynthesis gene". Morgantown, W. Va. : [West Virginia University Libraries], 2003. http://etd.wvu.edu/templates/showETD.cfm?recnum=3190.

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Thesis (M.S.)--West Virginia University, 2003.
Title from document title page. Document formatted into pages; contains viii, 62 p. : ill. (some col.) Vita. Includes abstract. Includes bibliographical reference.
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11

Antropow, Alyssa Hope. "Synthesis and anticancer evaluation of agelastatin alkaloid derivatives and enantioselective total synthesis of aspidosperma alkaloids". Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/118214.

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Thesis: Ph. D. in Organic Chemistry, Massachusetts Institute of Technology, Department of Chemistry, 2018.
Cataloged from PDF version of thesis. Vita.
Includes bibliographical references.
I. Synthesis and Evaluation of Agelastatin Derivatives as Potent Modulators for Cancer Invasion and Metastasis The synthesis of new agelastatin alkaloid derivatives and their anticancer evaluation in the context of the breast cancer microenvironment is described. A variety of Ni -alkyl and C5-ether agelastatin derivatives were accessed via application of our strategy for convergent imidazolone synthesis. We have discovered that agelastatin alkaloids are potent modulators for cancer invasion and metastasis at non-cytotoxic doses. We discuss the increased potency of (-)-agelastatin E as compared to (-)-agelastatin A in this capacity, in addition to identification of new agelastatin derivatives with activity that is statistically equivalent to (-)-agelastatin E. II. Enantioselective Synthesis of (-)-Vallesine: Late-stage C17-Oxidation via Complex Indole Boronation The first enantioselective total synthesis of (-)-vallesine via a strategy that features a late-stage regioselective C17-oxidation followed by a highly stereoselective transannular cyclization is described. The versatility of this approach is highlighted by divergent synthesis of the archetypal alkaloid of this family, (+)-aspidospermidine, and an A-ring oxygenated derivative (+)- deacetylaspidospermine, the precursor to (-)-vallesine, from a common intermediate. III. Enantioselective Total Synthesis of (-)-Jerantinine A from (-)-Melodinine P via Bio-Inspired A-Ring Oxidation The first enantioselective synthesis of (-)-melodinine P and its direct conversion to related alkaloid (-)-jerantinine A is described. A key para-aza-quinone methide pentacyclic intermediate enables A-ring to C-ring oxidation state transfer. Our synthesis is streamlined through the development of two multi-step single-pot procedures which proceed with high efficiency. We further demonstrate the utility ofpara-aza-quinone methide intermediates in our strategy for CI6-methoxylation which provides entry to the (-)-jerantinine alkaloid family.
by Alyssa Hope Antropow.
Ph. D. in Organic Chemistry
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12

Coufal-Majewski, Stephanie. "Characterising the impact of ergot alkaloids on digestibility and growth performance of lambs". Thesis, The University of Sydney, 2017. http://hdl.handle.net/2123/17226.

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The negative impacts of ergot contamination of grain on the health of humans and animals were first documented during the fifth century AD. Although ergotism is now rare in humans, cleaning contaminated grain concentrates ergot bodies in screenings which are used as livestock feed. Ergot is found worldwide, with even low concentrations of alkaloids in the diet (<100 ppb total), reducing the growth efficiency of livestock. Extended periods of increased moisture and cold during flowering promote the development of ergot in cereal crops. Furthermore, the unpredictability of climate change may have detrimental impacts to important cereal crops, such as wheat, barley, and rye, favoring ergot production. Allowable limits for ergot in livestock feed are confusing as they may be determined by proportions of ergot bodies or by total levels of alkaloids, measurements that may differ widely in their estimation of toxicity. The proportion of individual alkaloids, including ergotamine, ergocristine, ergosine, ergocornine, and ergocryptine is extremely variable within ergot bodies and the relative toxicity of these alkaloids has yet to be determined. This raises concerns that current recommendations on safe levels of ergot in feeds may be unreliable. Furthermore, the total ergot alkaloid content is greatly dependent on the geographic region, harvest year, cereal species, variety and genotype and can vary greatly depending on the chosen analytical method. Considerable animal-to-animal variation in the ability of the liver to detoxify ergot alkaloids also exists and the impacts of factors, such as pelleting of feeds or use of binders to reduce bioavailability of alkaloids require study. Accordingly, unknowns greatly outnumber the knowns for cereal ergot and further study to help better define allowable limits for livestock would be welcome.
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13

Hesse, Ronny, Anne Jäger, Arndt W. Schmidt y Hans-Joachim Knölker. "Palladium(II)-catalysed total synthesis of naturally occurring pyrano[3,2-a]carbazole and pyrano[2,3-b]carbazole alkaloids". Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-149135.

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Seven naturally occurring pyranocarbazole alkaloids (pyrayafoline A–E, O-methylmurrayamine A and O-methylmahanine) have been obtained by total synthesis using a palladium(II)-catalysed oxidative cyclisation of a diarylamine to an orthogonally diprotected 2,7-dihydroxycarbazole as key step.
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14

Pereira, Tamara Nishanthi. "Cytotoxic effects of pyrrolizidine alkaloids /". [St. Lucia, Qld.], 2004. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe18303.pdf.

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15

Bosch, Caroline. "Total Synthesis of Phlegmarine Alkaloids". Doctoral thesis, Universitat de Barcelona, 2016. http://hdl.handle.net/10803/399380.

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This doctoral thesis consists in two main parts. The first part focus in the study of methodology development in order to bring modularity and diversification to compounds studied within the research group. It consists first in the development of an easy procedure to access enantiopure substituted octahydroindoles relevant for natural products synthesis, then in the diversification of a common building block used for the total synthesis of phlegmarine alkaloids allowing access to unprecedented heterocyclic tetrahydrocarbazoles compounds, but most importantly in the achievement of a methodology allowing access to any phlegmarine alkaloids from a simple common precursor i.e. using a unified methodology. A stereodivergent hydrogenation route is reported in each phlegmarine alkaloid series, allowing modulation of the diastereoselectivity in key intermediates of the synthetic approach. The second part focuses on synthetic applications of the methodology developed to allow to perform the first total synthesis of various phlegmarine alkaloids and also shed light on missassigned structures. These structure reassignments gave birth to a revised classification of the phlegmarine alkaloids and were confirmed by total synthesis using the unified methodology developed in the first part. All of the analytical data obtained during this project led us to the establishment of general rules to determine easily the stereochemistry of any phlegmarine type alkaloids. In summary, the first total syntheses of (+)-serratezomine E, (-)-serralongamine, (-)-huperzine K, huperzine M and (-)-huperzine N have been achieved and the usefulness of the tandem intermolecular Michael reaction/intramolecular aldol reaction and in-situ intramolecular aza-Michael process has been extended to other series of azabicyclic compounds in enantiopure form.
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16

Chiba, Hiroaki. "Total Synthesis of Tetrahydroisoquinoline Alkaloids". 京都大学 (Kyoto University), 2013. http://hdl.handle.net/2433/174544.

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17

Shabrawy, Abdel-Rahman Omar El. "Alkaloids of selected medicinal plants /". Ann Arbor : Univ. Microfilms Intenational, 1985. http://www.gbv.de/dms/bs/toc/016435753.pdf.

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18

Swain, D. J. "Stereoselective synthesis of indole alkaloids". Thesis, University of Oxford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.238115.

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19

Bell, Andrew A. "Synthesis of pentahydroxylated bicyclic alkaloids". Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364022.

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20

Black, Gregory Philip. "Synthetic studies towards guanidine alkaloids". Thesis, Bangor University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263304.

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21

Montgomery, David J. "Synthetic approaches to pulmiliotoxin alkaloids". Thesis, Queen's University Belfast, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333820.

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22

Nelson, A. "Synthesis of bioactive indolizidine alkaloids". Thesis, Queen's University Belfast, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.421009.

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23

Barr, Stephen Alexander. "Quinoline alkaloids : synthesis and stereochemistry". Thesis, Queen's University Belfast, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333796.

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24

Ozturk, Turan. "Synthetic studies on cytotoxic alkaloids". Thesis, University of East Anglia, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292160.

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25

Rutherford, M. J. "Dimeric indole and quinolinone alkaloids". Thesis, University of Ulster, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378774.

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26

Williams, David Alan John. "Radical approaches toward polycyclic alkaloids". Thesis, University of York, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323499.

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27

Mohamad, Shaza Eva. "Biotransformation of the morphinan alkaloids". Thesis, University of York, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.445460.

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28

Hollinshead, S. P. "Enantiospecific approaches to indole alkaloids". Thesis, University of York, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379030.

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29

Coates, Galle. "Asymmentric synthesis of pyrrolidine alkaloids". Thesis, King's College London (University of London), 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.404336.

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30

Jenkinson, Julian John. "Tandem cyclisations towards indole alkaloids". Thesis, University of Southampton, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359241.

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31

West, Robert Ian. "Synthetic approaches to Strychnos alkaloids". Thesis, University of Southampton, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315007.

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32

Gibbs, Gary. "Synthetic strategies towards hydroxylated alkaloids". Thesis, University of Bristol, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387484.

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33

Sharpe, David Anthony. "Synthetic studies towards ergot alkaloids". Thesis, Sheffield Hallam University, 1989. http://shura.shu.ac.uk/20353/.

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Some of the background to the biosynthesis, synthesis and uses of ergot alkaloids has been reviewed. A novel synthesis of the indole system has been used in an attempt to synthesise a derivative of the tricyclic Uhles ketone. A variation on this method has been carried out using 3-indole propionic acid as the starting material. The novel synthesis of the indole ring system has been developed into a synthesis of a 4-substituted indole. A number of literature methods for the synthesis of 4-substituted indoles have been investigated, and their usefulness in the laboratory assessed. A modified Reissert synthesis has been carried out, along with a Batcho-Leimgruber synthesis. Also the use of a thallium based method and palladium catalysed carbon-carbon bond formation have been investigated. A novel synthesis of p-benzoquinones has been discovered, by oxidation of aromatic sulphonamides. This method has not been optimised but low to moderate yields of quinones have been achieved. This method was used in an attempt to synthesise o-benzoquinones, but was found to be unsuitable. A novel synthesis of aromatic thiol esters has been developed starting from simple substituted benzaldehydes esters and methylmethylthiomethylsulphoxide. The resulting ketene thioacetal monosulphoxide was treated under the same conditions as those used in the novel indole synthesis. High yields of thiolesters were obtained.
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34

French, Christopher E. "Biotransformations of the morphine alkaloids". Thesis, University of Cambridge, 1994. https://www.repository.cam.ac.uk/handle/1810/272997.

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35

Rudge, Andrew John. "The synthesis of polyhydroxylated alkaloids". Thesis, University of Cambridge, 1994. https://www.repository.cam.ac.uk/handle/1810/272797.

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36

Kim, Hea-Young. "Molecular Toxicology of Pyrrolizidine Alkaloids". DigitalCommons@USU, 1994. https://digitalcommons.usu.edu/etd/3910.

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Pyrrolizidine alkaloids are cytotoxic, carcinogenic, and anti-carcinogenic in vivo and in vitro, and they produce many hazardous effects in humans and animals. Pyrrolizidine alkaloids (PAs) also cross-link with DNA and/or protein. However, whether such cross-linking is important to the toxic action of PAs is not known. In addition, the exact mechanism underlying these DNA cross-links or cytotoxicity is also not clear. In three separate studies, I characterized the nature of PA-induced DNA cross-links and the relationships between PA structures and cross-linking potency. In the first study (Chapter II), I found that cross-linking potency of PA congeners coincided with their abilities to cause cytopathologic effects. Macrocyclic a,p-unsaturated diesters PAs and their pyrrolic metabolites were the most potent inhibitors of colony formation, and inducers of cytopathologic changes and megalocyte formation. The macrocyclic α, β-saturated diester PA and open diesters PAs slightly inhibited colony formation, and slightly changed cell morphology. Retronecine and indicine N-oxide were completely inactive. In the next study (Chapter Ill), I found that pyrrolic macrocyclic metabolites were more potent DNA cross-linkers than their parent compounds as determined by alkaline elution. The pyrroles of the macrocyclic diester PAs were potent DNADNA (inter- and/or intra) cross-linkers in BstEll-digested λ-phage DNA or pBR322 plasmid DNA but dehydroretronecine and indicine N-oxide were not. I also examined which DNA sequences were more susceptible to PA-induced cross-links by using a series of restriction endonucleases to determine sequence specificity. The most favorable cross-linking site for PAs appeared to be 5'd(GG) and 5'-d(GA) although other sites, 5'-d(CC) or 5'-d(CG), might be also preferable cross-linking targets. In the next study (Chapter IV), I characterized the nature of DNA-protein interactions induced by PAs, because I found in previous studies that PA-induced cross-links are largely protein associated. In PA or pyrrolic PA exposed cells, cross-linked proteins with molecular weights 40 - 60 kD were detected. Two-dimensional electrophoretic analysis revealed that these proteins were probably acidic in nature. In an in vitro system utilizing pBR322 or Bst Ell-digested λ-phage DNA. dehydrosenecionine induced DNAprotein cross-links with BSA, indicating that such interactions might be related to amino acid composition of protein. These results confirmed that PA-induced DNA cross-links (DNA-DNA, DNA-protein cross-links) are influenced by three structural features: the C1 ,2 unsaturation of pyrrolizidine ring, α, β-unsaturation, and size of the macrocyclic diester ring. The ability to form cross-links was closely related to the known toxic potencies of these PAs. From this research, I also conclude that DNA crosslinking is the most critical event leading to PA-related diseases and that crosslinking is due to pyrrolic metabolites of PAs, not via a common metabolite as was once thought.
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37

Romeril, Stuart P. "Synthesis and structural elucidation of the Bis-3-alkylpyridine alkaloid pyrinodemin A and other monomeric alkaloids". Thesis, University of Oxford, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288526.

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38

Tang, Minyan. "The asymmetric synthesis of polyhydroxylated pyrrolizidine alkaloids". Department of Chemistry - Faculty of Science, 2004. http://ro.uow.edu.au/theses/233.

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Chapter 1 of this thesis is a review of the literature on the structure, biological activities and synthesis of polyhydroxylated 3-hydroxymethylpyrrolizidine alkaloids. This Chapter also outlines he aims of this project, which were to develop a flexible synthesis of the 1,2,7-trihydroxy-3-hydroxymethylpyrroizidine alkaloid australine, and its epimers. Chapter 2 describes model synthetic chemical studies on the synthesis of the pyrrolizidine core structure. The key synthetic steps, the aminolysis reaction of vinyl expoxides with ally1 amine, the ring-closing metathesis of the resulting diene, syndihydroxylation of the 2,5-dihydropyrrole product and finally ring closure to give the pyrrolizidine nucleus were successfully developed. Chapter 3 describes the application of the chemistry developed in Chapter 2 to the diastereoselective synthesis of the 3-hydroxymethy1-2,3,5,6,7,7 a-hexahydro-1H-pyrrolizine-1,2,7-triol structure, characteristic of several pyrrolizidine natural products. Two unnatural pyrrolizidine alkaloids, (-)-7-espiaustraline and (+)-1,7-diepiaustraline were successfully synthesized. The oxazolidinone group was found to be a useful protecting group in the RCM reaction and, as part of a pyrrolo[1,2-c]oxazol-3-one ring system, functioned as a stereo- and regio-directing group, in a key diastereoselective syn-dihydroxylation reaction and a regioselective nucleophilic ring-opening of a S,S-dioxo-dioxathiole. Chapter 4 describes the asymmetric synthesis of the pyrrolizidine alkaloid, (+)-1-epiaustraline. Attempts to extend this methodology to the synthesis of australine were not successful since the final pyrrolidine ring closure to produce the desired pyrrolizine was not productive.
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39

Gassner, Cemena, Ronny Hesse, Arndt W. Schmidt y Hans-Joachim Knölker. "Total synthesis of the cyclic monoterpenoid pyrano[3,2-a]carbazole alkaloids derived from 2-hydroxy-6-methylcarbazole". Royal Society of Chemistry, 2014. https://tud.qucosa.de/id/qucosa%3A28532.

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40

Williams, Benjamin [Verfasser] y Dirk [Akademischer Betreuer] Trauner. "Chiral pool approaches to lycopodium alkaloids, orchidaceae alkaloids and photoswitchable ceramides / Benjamin Williams ; Betreuer: Dirk Trauner". München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2018. http://d-nb.info/118820002X/34.

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41

Mihali, Troco Kaan Biotechnology &amp Biomolecular Sciences Faculty of Science UNSW. "Biosynthesis of toxic alkaloids in cyanobacteria". Publisher:University of New South Wales. Biotechnology & Biomolecular Sciences, 2008. http://handle.unsw.edu.au/1959.4/41485.

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Freshwater cyanobacteria produce a wealth of biologically active metabolites, which can adversely affect human and animal health, and cause great economic damage to the fishing, tourism and water-management industries on a global scale. We describe the molecular genetics and biochemistry of biosynthesis for the cyanobacterial toxic alkaloids cylindrospennopsin, paralytic shellfish toxins (PST) and anatoxin-a. Characterisation of the 43 kb cylindrospennopsin biosynthesis gene cluster (cyr), in Cylindrospermopsis raciborskii AWT205 is described. Biosynthesis is initiated via an amidinotransfer onto glycine followed by five polyketide extensions. Rings are formed via Michael additions, while the uracil ring is formed by a novel mechanism. Tailoring reactions, including sulfation and hydroxylation complete the biosynthesis. We describe the characterisation of PST biosynthesis gene clusters in Anabaena circinalis, Aphanizomenon sp. and Lyngbya wollei. These gene clusters span between 28 and 36 kb and contain genes coding for the biosynthesis and export of PSTs. The Lyngbya wollei PST gene cluster represents a 'natural combinatorial biosynthesis' event, explaining its unique toxin profile. A biosynthetic pathway leading to the formation of saxitoxin and its analogues in these organisms is proposed, and a putative insertion/excision site of the PST gene cluster in Anabaena circinalis 310F was identified. Interestingly, PSTs are produced by distantly related organisms via this unique biosynthesis pathway. We Investigated the phylogenetics of PST biosynthesis genes from four different genera of cyanobacteria. The results suggested that PST biosynthesis in cyanobacteria is an ancient trait, whereby the sporadic distribution of PST production in extant isolates of Anabaena circinalis and Aphanizomenon sp. is a result of the repeated loss of the biosynthetic gene cluster. Horizontal gene ransfer also appears to have had a critical influence on PST biosynthesis in Lyngbya wollei. We additionally propose a hypothetical, mixed non-ribosomal peptide synthetase (NRPS)/polyketide synthase (PKS) biosynthesis scheme for anatoxin-a. Degenerate PCR primers were developed, for the specific amplification of mixed NRPSIPKS hybrid ketosynthase (KS) domains. Gene-walking distally to a novel hybrid KS domain in the anatoxin-a producer Planktothrix rubescens, revealed an orphan gene cluster, denoted pro, which spans 24 kb and codes for a mixed NRPS/PKS system, putatively producing an acetylated and sulphated dipeptide.
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42

Wu, Tao. "Synthetic studies on polycyclic indole alkaloids". [Ames, Iowa : Iowa State University], 2006.

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43

Hager, Dominik. "From nucleosides to alkaloids and polyketides". Diss., Ludwig-Maximilians-Universität München, 2012. http://nbn-resolving.de/urn:nbn:de:bvb:19-153975.

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This dissertation describes the synthetic work on several natural products including nucleosides, alkaloids, and polyketides. The first and main part of this thesis focuses on the total synthesis of the nucleoside antibiotics herbicidin C and its hydrolysis product aureonuclemycin. Due to their diverse biological activity, the herbicidins are considered as promising herbicides for agricultural application. In cooperation with Bayer CropScience AG, a flexible and efficient access to the herbicidins was developed and the challenges and successes of this synthesis are described in detail. More specifically, the route to the undecose moiety integrates a stereoselective C-glycosylation with several reagent-controlled stereoselective transformations. The nucleobase was introduced by a surprisingly facile and highly diastereoselective late-stage N-glycosylation. In addition to that, natural herbicidin A was transformed into promising derivatives and all compounds, including the intermediates of the total synthesis, were provided to Bayer CropScience AG for a structure activity relationship study (SAR). A list of all provided derivatives is given at the end of the thesis. The progress toward the synthesis of stephadiamine is described in the second chapter of this thesis. The natural product is the first example of a C-norhasubanan alkaloid natural product and despite its structural beauty, no total synthesis of stephadiamine has been reported to date. The proposed racemic retrosynthetic analysis of stephadiamine makes use of a Curtius rearrangement and a late lactonization. The propellane skeleton of this alkaloid was envisioned to be made by means of a homoconjugated addition/Mannich cascade of the key enamine in an extremely efficient manner. An alternative strategy is proposed for future work, which includes a Tsuji-Trost allylation arising the potential for an enantioselective synthesis of stephadiamine. In chapter III, the progress toward the divergolides C and D is presented. Attention was focused on the large scale preparation of the volatile side chain, and its unusual isolation method is pointed out in detail. In addition, the assembly of the three main building blocks is discussed. The preparation of Legionella autoinducer 1 (LAI-1) is described in chapter IV. The bacterial signaling molecule LAI-1 belongs to the class of alpha-hydroxyketones (AHKs). Given the effects of LAI-1 on virulence and motility of the bacteria L. pneumophila, this signaling molecule has the potential for clinical or technical applications. For a deeper understanding of the signaling circuit in L. pneumophila and in order to gain more insight in the mechanism of cell-cell communication, synthetic LAI-1 was prepared and provided to the research group of H. Hilbi, who investigates the gene regulation by AHK-mediated signaling. Chapter V includes the experimental procedures for the preparation of all compounds, backed up by full analytical characterization. In addition, 1H- and 13C-NMR spectra as well as crystallographic details are given.
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44

Smith, Adrian L. "The nitrone route to dentrobatid alkaloids". Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316802.

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Lunn, R. J. "Enantiospecific syntheses of alkaloids from carbohydrates". Thesis, University of Oxford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376938.

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Potts, Deirdre Ann. "Synthesis of Piclavine and Martinelline alkaloids". Thesis, Queen's University Belfast, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.484265.

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47

Evans, Daniel Mackenzie. "Synthetic steps towards the cylindrospermopsin alkaloids". Thesis, Bangor University, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.590643.

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Detailed herein is the tethered Biginelli condensation between irninium ion 201 and beta keto ester 206 leading to a model tricyclic ring system representative of the guanidinium core of cylindrospennopsin alkaloids. This was achieved in a biosynthetically-inspired manner in 12 steps and 8.3% overall yield from simple, commercially available 1,5-pentanediol 172. Also discussed is the adaption of this methodology to allow for the highly efficient stereoselective synthesis of all 3 of the cylindrospermopsin alkaloids and the preparation of the advanced synthetic intermediate nitro-alcohol 223.
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48

Gardiner, John Michael. "New synthetic strategies towards cephalotaxus alkaloids". Thesis, Durham University, 1988. http://etheses.dur.ac.uk/6438/.

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Michael alkylation, with methyl acrylate, of nitrocyclohexenes bearing functionalized aromatic substituents at the 2-position, was found to be highly stereo selective. Subsequent dissolving metal reductive cyclization was highly efficient, and these two steps thus provided a stereo specific entry to a substituted 1-azaspirocyclic system, related to the cephalotaxine skeleton. Application of this methodology to trans-4-(3,4-dimethoxy-6-carbo- methoxyraethylphenyl)-5-nitrocyclohexene afforded spirolactam ester 6-(3,4-dimethoxy-6-carboraethoxymethylphenyl)-2-oxo-l-azaspiro[4.5]dec-8-ene. On reduction with DIBAL-H at -78ºC, this cyclized in high yield, with high stereoselectivity to the corresponding 3-benzazepine-2-ol system.Similar methodology with trans-4-(3,4-methylenedioxy-6-nitrophenyl) -5-nitrocyclohexene, allowed for a formaldehyde insertion reaction to provide a 1,3-benzodiazepine analogue. Preliminary studies hold promise for allowing modification of the cyclohexene ring to known pre-targets of cephalotaxine. These findings bring the synthetic strategy towards providing a competitive route to (±) cephalotaxine, and also a range of analogues, including the unknown 11-aza and 10-hydroxy-8-oxo systems.
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49

Ross, Frances I. "Efficient synthetic routes to indole alkaloids". Thesis, Heriot-Watt University, 1999. http://hdl.handle.net/10399/588.

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Cochrane, Philip. "Short synthetic routes to indole alkaloids". Thesis, Heriot-Watt University, 2000. http://hdl.handle.net/10399/529.

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