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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Development of the 5-exo-dig/Prins Reaction and Efforts towards the Total Synthesis of (±)-Magellanine

Bétournay, Geneviève L. January 2012 (has links)
Gold catalysis has attracted much attention within the chemical community in recent years, and its importance as a synthetic tool has only started to be uncovered. This thesis describes the development of a gold(I) catalyzed transformation and its application to the synthesis of a structurally unique Lycopodium alkaloid, Magellanine. Although there have been a few reports on the synthesis of the magellanane core to date, the approach described herein would represent a new and efficient strategy to construct the angularly fused tetracyclic core. The 5 exo dig/Prins reaction that would be the key step of the synthesis was first developed and studied on a model substrate, enabling the verification of the hypothesis that this transformation could indeed form the A and B rings of Magellanine and be applied to its synthesis. This reaction formed the tricyclic products in good yields and in good exo:endo ratios. The synthesis of Magellanine was undertaken, but problems of isomerization prevented the synthesis of the desired 5 exo dig/Prins substrate, which contained the C and D rings of Magellanine with a cis relationship at the ring junction. However, an almost identical substrate, save for a trans configuration between the C and D rings instead of the cis configuration, was prepared and served in further establishing the applicability of this methodology to the synthesis of Magellanine by successfully undergoing the 5-exo-dig/Prins reaction and generating the tetracyclic products. Studies of the steps following the key transformation were performed on the model substrate, allowing for the evaluation of these steps prior to their use in the synthesis. The results of the studies indicate a possible need to revisit the order in which the steps should be carried out. Promising solutions to the different obstacle encountered during the work are presented, demonstrating how the synthesis of Magellanine through a route featuring the 5-exo-dig/Prins cyclization is attainable.
12

NFC-Spore Biocomposites : A study of flame retardancy, density, mechanical properties and production of films

Romson, Tomas, Goch, Victor January 2014 (has links)
Sporopollenin is considered a resistant material and might be applicable in flame retardant material. The use of renewable material in fields mainly dominated by toxic materials, such as bromides in flame retardant materials, could greatly improve the sustainability in those fields. A renewable porous film could be of interest in applications were cellophane is used today. The aim of this report is to investigate some basic properties of films made from nanofibrillated cellulose (NFC) and Lycopodium spores with a specific focus on flame retardant and mechanical properties. These properties were investigated using machines such as SEM, a universal electromechanical tester, TGA and vertical flame testing. During the production of the films an ultra turrax, rotavapor and rapid köthen was used. The films containing spores did not improved properties such as flame retardancy and mechanical properties when compared to the original NFC film. Density was lowered by almost half in some cases compared to the original NFC-film. Mechanical properties of the alkali-treated spores showed a significant increase compared to the untreated spores. An increased spore-ratio shows a decreased Young’s modulus. Further research on flame retardancy could be done using xyloglucan or another more flame retardant organic compound as a matrix. A foaming agent inside the sporopollenin could also contribute to flame retardancy. The mechanical properties could be compared to cellophane in order to see any future possibility of application. If possible pure sporopollenin should be used instead of whole spores. / Degree Project in Polymeric Materials, First Cycle
13

An Acyl Radical Cascade Model for the Total Synthesis of Lyconadin A

Grant, Seth W. 02 September 2005 (has links) (PDF)
Lyconadin A (1) is a structurally unique Lycopodium alkaloid with antitumor properties, isolated from the club moss Lycopodium complanatum. We are developing a synthetic route to 1 based on a novel 7-exo-trig/6-exo-trig acyl radical cascade cyclization. The synthesis of model acyl radical cascade precursor 23 will be presented. Key features of this synthesis include the suppression of competing elimination during the alkylation of a hindered phenethyl bromide and the use of a lactone as a precursor to a compound bearing two differentially protected primary alcohols. An account of our studies on the model acyl radical cascade cyclization (23 to 24 above) will also be given, including a stereochemical analysis of the product. Our findings have been applied to develop a more detailed stereoselective synthetic plan for Lyconadin A (1).
14

Approche biomimétique des manadomanzamines et préparation d’analogues de la pelletiérine pour la synthèse biomimétique d’alcaloïdes de lycopodes / Biomimetic approach to manadomanzamines and preparation of derivatives of pelletierine for biomimetic synthesis of Lycopodium alkaloids.

Yan, Lok-Hang 30 June 2011 (has links)
Au cours de ce travail, nous nous sommes intéressés dans une première partie à la synthèse biomimétique d’alcaloïdes de type manzamines et plus particulièrement, aux manadomanzamines. Une étude de la réactivité des deux intermédiaires clés de leur biogenèse, les glutaconaldéhydes et les aminopentadiènals, a été entreprise. Ces mêmes molécules ont ensuite été utilisées comme équivalents synthétiques dans une synthèse biomimétique du squelette pentacyclique de la manadomanzamine A. Une seconde partie est consacrée à la préparation d’analogues stables de la pelletiérine en vue d’une synthèse biomimétique d’alcaloïdes du genre Lycopodium. / This work is dedicated to the biomimetic synthesis of complex polycyclic alkaloids namely the manzamine alkaloids and especially to manadomanzamine. The biogenetic hypotheses postulated for these alkaloids are reported in a first introductory chapter. A few examples of manzamine alkaloids biogenesis are described and compared. The second chapter is focused on the reactivity of reactive units (considered as simplified models of two key biosynthetic intermediates, namely glutaconaldehydes and aminopentadienals) resulting from the ring-opening of pyridinium salts, and their implication in natural products synthesis. Particularly detailed are the investigations conducted on 5-dimethylamino-2-methylpenta-2,4-dienal and the condensation of potassium glutaconaldehyde onto a pyridinium salt. The chemistry of these reactive units has been exploited to design several model studies towards the synthesis of pentacyclic indole nucleus of manadomanzamine A, isolated from an Indonesian sponge Acanthostrongylophora sp.. These biomimetic models, elaborated from a biosynthetic intermediate postulated in our biosynthesis hypothesis have culminated in the synthesis of the central pentacyclic indole nucleus. The last chapter reports the preparation of more or less oxidized analogs of pelletierine, the well known alkaloid isolated from Punica granatum. Compounds such as phenyloxazolopelletierine have been prepared and their reactivity investigated in view of the biomimetic synthesis of Lycopodium alkaloids.

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