Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 43 for “"polyene"”.
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Adventures in polyene chemistry
This thesis focuses on the development of new and efficient ways to synthesise diverse families of compounds containing different numbers of alkenes in conjugation. These new approaches involve sequences of cross-coupling reactions. Explorations into the chemical reactivity of these compounds have …
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Adventures in polyene chemistry
This thesis focuses on the development of new and efficient ways to synthesise diverse families of compounds containing different numbers of alkenes in conjugation. These new approaches involve sequences of cross-coupling reactions. Explorations into the chemical reactivity of these compounds have …
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Analysis and Engineering of Polyene Biosynthesis in Actinomycetes
… concerns the pathway to the giant linear polyol-polyene clethramycin from Streptomyces malaysiensis DSM4137, a rare sulfonated natural product. Gene deletion was used to identify the essential sulfotransferase involved. In Chapter 4, a novel genetic engineering approach dubbed "accelerated …
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Synthesis and function of the conserved motif of mycosamine-containing polyene macrolides
Mycosamine-containing polyene macrolides represent a large family of natural products with antifungal activity, of which amphotericin B (AmB) is an important member. Several of these clinically vital but toxic agents have been proposed to exert their biological activity through ion channel …
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Mechanisms underlying polyene macrolide mediated rescue of growth in ion channel deficient yeast
… ion pumps and transporters. AmB and other polyene macrolide ion channels are unregulated, unrectified, unselective, and passive. However, we hypothesized that through working together with H+-ATPases (drivers) and transporters (correctors) that imperfect small molecule ion channels are …
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Discrete polyene oligomer synthesis and related polymer characterization : (Appendix I: Reduced tungsten dimeric compounds)
Molybdenum complexes ... were used to synthesize polyene oligomeric compounds with up to 15 conjugated double bonds by reaction with aldehyde compounds in a Wittig-like fashion. The optical properties of highly nr-conjugated systems are investigated due to potential application in photooptical …
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Enantioselective, Lewis base-catalyzed transformations: I. Polyene sulfenocyclization (preparative and mechanistic aspects) II. Sulfenofunctionalization of alkenyl boronates enabled by 1,2-boronate migration
… enantioselective sulfenocyclization of polyenes (Chapter 2). Sulfenyl group transfer from a highly reactive, cationic, Lewis acid-base adduct to an unactivated alkene generates a cyclic thiiranium ion, which serves as the initiating event for a highly stereoselective polyene cyclization …
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Reagents and Strategies for the Total Synthesis of Halogenated Natural Products
… particular, the development of halonium-induced polyene cyclization, asymmetric halogenation, and medium-ring haloether formation would facilitate access to hundreds of halogenated natural products, but these reactions have traditionally proven challenging. Chapter 2. The Discovery of BDSB and …
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Lewis Base Catalyzed Aldol Additions of Chiral Silyl Enol Ethers and Total Synthesis of Rk-397
… studies were applied in the total synthesis of polyene macrolide antibiotic RK-397. The synthesis features the highly site- and enantioselective vinylogous aldol addition using a chiral bisphosphoramide which allowed efficient construction of the key building block. The polyene fragment was …
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Total synthesis and study of the antilipoperoxidant peridinin, synthesis of versatile MIDA boronate building blocks, and a general strategy for the synthesis of polyenes
… for how this can be achieved, we have identified polyene natural products as an excellent opportunity for testing this concept. We identified a collection of just 12 bifunctional haloalkenyl MIDA boronate building blocks would be required to prepare the polyene motifs found in >75% of all polyene …
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Ultrafast reaction dynamics of polyatomic molecules probed by ionization
… which is a substituted cyclic polyene, answers the crucial question to what extent an ultrafast reaction can be slowed down by the influence of a steric factor.
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Studies toward the synthesis of celastrol and the late-stage hydroxylation of arenes mediated by 4,5-dichlorophthaloyl peroxide
… to the incompatibility of biologically inspired polyene cyclization strategies to assemble friedelin triterpenoids. As a result of these problems residing at the interface of chemistry and biology, a purely synthesis-based strategy for polyene cyclizations to rapidly construct the pentacyclic …
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Oxidative Heck Reactions with Terminal Olefins
… to generate linear E-arylated olefins. Polyenes are prevalent motiefs in natural products and pharmaceuticals. Polyene functionality often requires mild and selective synthetic methods. The Heck vinylation uses orthogonally reactive C-H bonds and these bonds are often easy to carry …
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Synthesis and Biosynthesis of Polyketide Natural Products
… linear chain containing an abnormally dehydrated polyene system. We synthesized a putative advanced polyketide intermediate and tested its viability to undergo a mild chemical transformation to spiculoic acid A. In addition, we applied a synthetic and biochemical approach to elucidate the …
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The Synthesis, Characterisation and Electro-Optical Properties of Polypentenylene-Block-Co-Acetylene
… to effect control over block length of the polyene blocks. The length of the blocks of polypentenylene were reduced by the incorporation of a linear alkene during the ring opening metathesis polymerisation step of the synthesis. A simple electro-optical technique was developed for the …
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Singlet Fission in Pechmann Dyes and Molecular Oligomers
… tailor singlet fission dynamics by engineering polyene side chains. Finally, we address the challenge of decoupling singlet fission triplets by employing methods to improve their lifetimes. Utilizing DPH molecular dimers and TIPS trimers dispersed in polystyrene matrices at varying …
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THE PHOTOCHEMISTRY OF POLYENYL RADICALS AND ITS APPLICATION TO UHMWPE FOR USE IN ARTIFICIAL CARTILAGE
… wherein alkyl radicals migrate to stable polyene unsaturations and polyenyl radicals thereby increasing their order, as previously suggested. The valid mechanism appears to be the direct photoconversion of diene unsaturations to dienyl radicals and lower order polyenyl radicals to higher …
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Studies Towards the Total Synthesis of the Chivosazoles
… rapidly installed the requisite stereodefined polyene motifs within chivosazole F. Optimised Still-Gennari-type HWE olefination conditions were applied to install the (2Z,4E)-dienoate in D. MnO2-mediated double oxidation of D turned the terminal alcohol into an aldehyde and the oxazoline into …
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Comparative Study of Semisynthetic Derivative of Natamycin and the Parent Antibiotic on the Spoilage of Shredded Cheddar Cheese
The polyene macrolide antibiotic natamycin (Antibiotic A-5283) is commonly used to retard the growth of surface molds on various cheese varieties. Natamycin is commonly applied to the surface of cheese by dipping or spraying, using an aqueous dispersion containing 200 to 300 ppm of the additive. …
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Slow-release cross-coupling and an advanced method for β-glycosylation: methods stimulated by amphotericin B
… encountered in the construction of the AmB polyene, a new cross-coupling protocol was developed whereby N-methyliminodiacetic acid (MIDA) boronates can be used directly in Suzuki-Miyaura cross-coupling (SMC) reactions, enabling air-stable MIDA boronates to act as surrogates for boronic …
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