Dissertations / Theses: 'Cascade synthesis'

1

Amjad, Ê¿AliÌ„. "Cobalt-mediated cascade cyclisation reactions in synthesis." Thesis, University of Nottingham, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357981.

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Demircan, Aydin. "Cascade reactions involving a furan core." Thesis, University of Sussex, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297561.

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3

Double, Philip John. "Acyl radical cascade reactions : the synthesis of azasteroids." Thesis, University of Nottingham, 1998. http://eprints.nottingham.ac.uk/27769/.

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Our work has been concerned with the synthesis of azasteroid ring systems, utilising acyl radical cascade reactions. Chapter 1 comprises an overview of published work relevant to our studies: an analysis of steroid biosynthesis and synthesis; a review of the use of azasteroids, their biological activity and current synthetic techniques in azasteroid formation. This initial chapter also includes an introduction to published work in the area of nitrogen heterocycle synthesis using radical reactions and finally the use of acyl radicals in synthesis, particularly cascade reactions. Chapter 2 starts by describing the requirements of a reaction system for use in acyl radical cascades and then discusses the relevance of this to the synthesis of ring junction azasteroids. Our attempts to synthesise ring junction azasteroids and the problems that we encountered are then discussed. Subsequent sections describe the disconnection of azasteroids where nitrogen is part of the body of the ring and the synthetic work that we performed in this area. Using cyclohexenyl enamides as the terminal electrophore in cascade reactions we were able to synthesise a 12-aza-D-homosteroid in nine steps. The final step was a cascade reaction involving three consecutive 6-endo-trig cyclisations starting from an acyl radical and terminating on an cyclohexenyl enamide electrophore. An extensive, though unsuccessful, study attempting to use linear enamides in cascade reactions is described showing routes towards the synthesis of steroid models. Finally we reveal the work that was performed in the use of highly stabilised enamides as radical acceptors. This work resulted in the formation of a bicyclo[8.3.0]tridecene after a 10-endo-trig, 5-exo-trig cascade from a linear precursor designed to form a 7-azaandrostane skeleton.

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Boehm, Haydn M. "Tandem radical cascade cyclisation reactions in steroid synthesis." Thesis, University of Nottingham, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364673.

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5

Wallace, Stephen. "A cascade approach towards the gephyrotoxins." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:1f7b55ec-0346-498c-be03-81f3b9fde2f5.

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The aim of this project was to develop a cascade approach towards perhydropyrrolo-[1,2-a]-quinolines and to apply this to the asymmetric synthesis of the gephyrotoxin alkoids. Chapters Two and Three outline the development of a synthetic route towards a range of cascade precursors, whilst Chapter Four outlines investigations into the enamine-Michael cascade. Central to understanding the cascade process was the discovery that the major product of the enamine-Michael cascade was the unusual tricyclic hydroquinium salt. This can subsequently be engaged in a diastereoselective inter- or intramolecular reduction to afford either a trans-perhydro-[1,2-a]-quinoline or a tetracyclic aminal in high overall yield depending on the C1 oxygen substituent.

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6

Lingard, Hannah. "Cascade approaches to decahydroquinoline ring systems." Thesis, University of Oxford, 2010. http://ora.ox.ac.uk/objects/uuid:e0ff1123-eae7-47aa-b377-1a12346d2538.

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The aims of this project were to develop a cascade approach towards decahydroquinoline frameworks (Scheme I) and apply this to the synthesis of decahydroquinoline-containing natural products such as lycopodine, cermizine B and lepadin D (Scheme I). Scheme I. Several linear precursors were synthesized via a modular strategy. For example, lycopodine linear precursor i was synthesized in a total of 12 steps (Scheme II). Scheme II. Conditions for cyclization and hydrogenation were tested, with the diastereoselectivity examined in each system. For example, the lepadin linear precursor ii produced two decahydroquinolines iii and iv upon cyclization (Scheme III). Scheme III. It was found that the diastereoselectivity was dependent on the ring substituents and variation of the hydrogenation conditions could change the facial selectivity of enamine reduction.

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7

Zhong, Cheng. "Amine promoted asymmetric cascade synthesis of highly functionalized heterocycles." Morgantown, W. Va. : [West Virginia University Libraries], 2010. http://hdl.handle.net/10450/10986.

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Thesis (Ph. D.)--West Virginia University, 2010.
Title from document title page. Document formatted into pages; contains xvi, 498 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 75-82).

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Gauntlett, Carolyn. "Cascade strategies for chemical synthesis : towards a total synthesis of nakadomarin A." Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612075.

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9

Ulrich, Natalie Christine. "Cascade cyclizations in total synthesis: applications to the synthesis of cytotoxic natural products." Diss., University of Iowa, 2010. https://ir.uiowa.edu/etd/752.

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Plant-derived natural products continue to be a valuable source of useful therapies for cancer as well as other diseases. As part of a continuing mission to obtain anticancer agents from natural sources, researchers at the National Cancer Institute (NCI) established the 60 human tumor cell line anticancer screen. The schweinfurthins are one family of unique natural products discovered through this screening process. Most of these natural compounds exhibit potent and differential activity in the 60-cell screen. Importantly, the pattern of activity displayed by the schweinfurthins shows no correlation to any clinically used anticancer drug, indicating that this family of natural products probably acts via a novel mechanism or at a novel target. Our group has conducted extensive structure-activity relationship studies in an effort to illuminate the mechanism of action of the schweinfurthins. In this thesis, the preparation and biological activity of a number of new schweinfurthin F analogues possessing variations in the D-ring alkyl chain and stilbene moiety will be discussed. These studies have clarified the importance of the D-ring to the schweinfurthins' pharmacophore. Based on the results obtained from the exploration of the structural requirements of these natural products, it was determi-ned that the right-half of the schweinfurthins would be an appropriate site for attachment of a molecular probe to be used in affinity experiments. The synthesis of these biotinylated probes will be examined in detail, and their use in pull-down assays will be summarized. The preparation of key schweinfurthin intermediates has involved the extensive use of Lewis acid-mediated cationic cascade cyclizations terminated by MOM-protected phenols. Those successes have inspired investigations of additional applications of these cyclizations. In particular, a variant of these cyclizations using "MOM-protected" enol ethers as reasonable substitutes for β-keto ester terminating moieties has been studied. These interrelated studies involving the synthesis of schweinfurthin analogues and the exploration of cascade cyclizations will be discussed in detail.

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Cordonnier, Marie-Caroline A. "Palladium-catalysed cascade cyclisation of alkynyl silanes and studies towards rubriflordilactone A." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:24302e85-de80-4562-a98e-ee0e6ba93862.

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In this work, a new methodology for the synthesis of a number of silylated bicyclic dienes has been reported. These bicyclic dienes allowed access to a variety of enones and phenols in 2 further steps. The stabilities and reactivities of different dialkylisopropoxy silanes have been evaluated,revealing relative instability of the dimethylisopropoxy silyl group towards chromatography. When using the analogous diethylisopropoxy silyl group instead, the products showed greater stability towards chromatography, however a higher temperature was necessary to oxidise the more sterically hindered silyl group to the desired hydroxyl moiety. A powerful cascade cyclisation for the synthesis of the CDE-core of rubriflordilactone A was then demonstrated and was successfully used for the synthesis of two systems, 284 and 333. The phenolic oxygen has been successfully installed by oxidation of a dialkylisopropoxy silane. The synthesis of these ring systems provides a solid foundation for the completion of the total synthesis of rubriflordilactone A. Finally the synthesis of suitable diynes 405 for the synthesis of the acyclic precursor of the cyclisation has been achieved. The stabilities of theses silanes towards a range of reaction have been demonstrated.

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11

Topczewski, Joseph John. "Cascade cyclizations & the schweinfurthins." Diss., University of Iowa, 2011. https://ir.uiowa.edu/etd/2780.

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Cancer is a serious family of disease that continues to cripple and claim those afflicted. For the last several decades, America has invested in a national program to alleviate cancer and cancer related suffering, ultimately seeking a cure. As part of this goal, the National Cancer Institute (NCI) has spent significant effort scouring the globe with the hope of finding naturally occurring compounds that can successfully combat cancer. Presently, this effort has uncovered many natural products with chemotherapeutic potential and many of the lead agents used in the fight against cancer are either natural products themselves or are compounds inspired by a natural product. This work describes one family of natural products uncovered by the NCI that is being explored for chemotherapeutic applications, namely the schweinfurthins. The schweinfurthins were isolated by the NCI; however the natural source, Macaranga schweinfurthii, did not provide these compounds in ample quantity to permit further study. The paucity of natural material indicated that a chemical synthesis of these compounds would be the most reliable method to provide meaningful amounts of schweinfurthins. The present work describes the chemical synthesis of four of the most potent schweinfurthins, describes the synthesis of numerous structural analogues, and details advances to the field of cascade cyclizations which makes their synthesis possible.

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Alkayar, Ziad Tariq Ibrahim. "Synthesis of iboga alkaloids using cascade cyclisation, nitrone cycloaddition." Thesis, University of Sheffield, 2017. http://etheses.whiterose.ac.uk/16898/.

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13

McKenna, Shane. "Molybdenum-containing oxidases and their application in cascade synthesis." Thesis, University of Liverpool, 2015. http://livrepository.liverpool.ac.uk/2045359/.

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Molybdenum-dependent xanthine oxidoreducatases (XOR) are a family of well characterized enzymes which are known to oxidise purines, imines and aldehydes in cellular metabolism. Despite significant studies relating to drug metabolism, application to chemical synthesis is relatively unexplored. Herein we report the first use of XORs in the cascade synthesis of carboxylic acids from activated and unactivated alcohols by the combination of the mutant alcohol oxidase GOaseM3-5 and XOR (E.coli XDH & PaoABC). Twenty five carboxylic acids were obtained in quantitative conversion and the methodology compares very well with state-of-the-art catalytic chemical oxidation methods. The reactions were performed in water at ambient temperature and pH using oxygen as the terminal oxidant with the only by-product being H2O2. The oxidation system was also applied to the synthesis of the biomass-derived platform chemical FDCA starting from HMF. The biocatalysts used were able to tolerate a substrate concentration of 100 mM, 20 times higher than previous reported methods with 74% isolated yield of FDCA. Although XORs exhibited a wide substrate scope, no chiral selectivity could be demonstrated. The application of XOR enzymes was also demonstrated in the synthesis of lactams from amino alcohols via an in situ generated imine intermediate. Although pyrrolidone was obtained in 85% yield from its corresponding amino alcohol, longer chain amino alcohols were not well tolerated with either poor or no conversion observed. Although currently limited in substrate scope, this novel biomimetic oxidative cyclisation represents an interesting synthetic approach to lactams, found in a wide variety of biologically interesting target molecules.

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Marcotte, Joel. "Formal Synthesis of (+/-) Morphine via an Oxy-cope/Claisen/Ene Reaction Cascade." Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/23560.

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For years now, opium alkaloids and morphinans have been attractive synthetic targets for numerous organic chemists due to their important biological activity and interesting molecular architecture. Morphine is one of the most potent analgesic drugs used to alleviate severe pain. Our research group maintains a longstanding interest in tandem pericyclic reactions such as the oxy-Cope/Claisen/ene reaction cascade and their application to the total synthesis of complex natural products. Herein we report the ventures towards the formal synthesis of (+/-)-morphine based on the novel tandem oxy- Cope/Claisen/ene reaction developed in our laboratory. These three highly stereoselective pericyclic reactions occurring in a domino fashion generate the morphinan core structure after only 7 steps from commercially available material. The formal synthesis culminated in the production of a formal intermediate after a total of 18 linear steps, with an overall yield of 1.0%, successfully intersecting two previous syntheses of the alkaloids, namely the ones of Taber (2002) and Magnus (2009).

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15

Lo, Kai-yip, and 羅啟業. "Synthesis of aza-bicyclic compounds via palladium-catalyzed cascade cyclization reactions." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B47849691.

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A palladium-catalyzed oxidative cascade cyclization reaction has been developed to prepare pyrrolizidine and indolizidine derivatives from simple aliphatic alkenyl amides 2.1ak in one step in moderate to good yields, using Pd(TFA)2 as the catalyst and molecular oxygen (1 atm) as a green oxidant. This cascade cyclization can also proceed for ring-containing unsaturated amides 2.1ln to afford azatricyclic systems. Palladium(II)-catalyzed dehydrohalogenation cascade cyclization reactions have been developed to synthesize polycyclic pyrrolizidine derivatives from iodoalkenylanilides 4.1ai in satisfactory to excellent yields under mild conditions. This reaction produces two stereocenters in one step and only one single diastereomer was obtained in the cyclization of 4.1. The reaction is proposed to proceed through an organopalladium(IV) species, formed by oxidative addition after the aminopalladation. This organopalladium(IV) species then undergoes reductive elimination to give the cyclized product. This cyclization is a fast and efficient way to construct natural alkaloids that contain pyrrolizidine or indolizidine cores.
published_or_final_version
Chemistry
Doctoral
Doctor of Philosophy

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16

Burrell, Adam James Musgrave. "Cyclisation-intramolecular dipolar cycloaddition cascade chemistry: Synthesis of tricyclic amines." Thesis, University of Sheffield, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.489129.

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17

Letort, Aurelien. "Ring-closing metathesis cascade toward a formal synthesis of taxol." Thesis, University of Glasgow, 2015. http://theses.gla.ac.uk/6677/.

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TaxolTM and its derivatives are the largest selling anticancer drugs of all time. Numerous synthetic works and total syntheses have been published since its discovery, but to date no high yielding synthesis with less than 37 steps has been achieved. In this thesis is presented our synthetic efforts toward such a robust and efficient synthesis of Taxol. The optimisation of the Shapiro coupling fragments syntheses were investigated to enhance the robustness of our strategy. Then the C7-deoxy model ABC tricycle ring-system of Taxol, which lacks the oxygenated substituent at C7, has been efficiently synthesised by a dienyne ring-closing metathesis cascade (RCDEYM). This cascade closed the AB 6/8 membered ring system in a single operation. Other dienyne ring-closing metathesis cascades with similar substrates were also performed, assessing the influence of ruthenium catalysts, C1-C2 diol protecting groups (R1, R2), and substitution of the alkene at C13. Synthetic efforts were also devoted to apply such a powerful method toward a formal synthesis of Taxol from an intermediate Holton and co-workers synthesised. During our studies, the C7-oxy group was found to be critical to access the ABC tricyclic core of Taxol by metathesis cascade. Understanding of the importance of this C7-oxy group was undertaken and led to the conception of a metathesis cascade prediction model. Once the metathesis cascade was optimised, differentiation of the three trisubstituted alkenes present on the ABC tricyclic ring system was studied and elaboration of a formal synthesis was endeavoured.

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18

Naoe, Saori. "Synthesis of Fused-Ring Compounds through Gold-Catalyzed Cascade Reactions." 京都大学 (Kyoto University), 2016. http://hdl.handle.net/2433/215495.

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19

Shah, Parin Ajay. "Synthesis of terpenoids using a tandem cationic cascade cyclization-electrophilic aromatic substitution reaction." Diss., University of Iowa, 2018. https://ir.uiowa.edu/etd/6639.

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The terpene and terpenoid family of compounds is considered to be the largest group of natural products. These compounds not only display great diversity in their structural features but are also known to have a multitude of biological activities including but not limited to anti-bacterial, anti-cancer, anti-inflammatory, and anti-HIV properties. Remarkably, all the terpenoids formed in nature come from two molecules viz. isopentenyl pyrophosphate and its isomer, dimethylallyl pyrophosphate both consisting of just five carbons but assembled in many ways. Nature utilizes highly efficient, enzyme-mediated cascade reactions to transform simple linear molecules to more complex cyclic scaffolds. Cascade or domino reactions are organic chemistry’s most powerful tools that, if executed correctly, mimic the extreme complexity of reactions occurring in nature. Our group has successfully utilized cationic cascade cyclization reactions, to prepare a large library of natural products along with their analogues. It was during the synthesis of one such natural product that it was discovered that a methoxymethyl (MOM) “protecting group” had been transferred within the same molecule. The optimization of this process not only allowed the synthesis of the desired tricyclic framework but also resulted in the liberated MOM group doing an EAS reaction which gave a new C-C bond. This transferred MOM group was further elaborated to different functional groups. Use of the tandem reaction sequence in an attempt to prepare radulanin E has been described. Total syntheses of two chalcone-based analogous meroterpenoids have been successfully completed using the aforementioned sequence. An advanced intermediate for an entire new class of acridine-based schweinfurthins has been elaborated. The results will be discussed in detail.

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20

Richmond, Edward. "An asymmetric pericyclic cascade approach to oxindoles." Thesis, University of St Andrews, 2014. http://hdl.handle.net/10023/4459.

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The research in this thesis describes an asymmetric pericyclic cascade approach to the synthesis of a range of enantioenriched oxindoles using enantiopure oxazolidine derived nitrones and disubstituted ketenes. Chapter 1 aims to place this work in the context of the literature, describing other commonly employed or state-of-the-art asymmetric approaches to oxindoles and related compounds. Examples of where these approaches have been used successfully in the total synthesis of related indole alkaloids are also presented. The conception of this project within the group is also described alongside initial attempts to develop the first enantioselective variant of the same reaction using nitrone chiral auxiliaries. Chapter 2 details the optimisation of this asymmetric oxindole forming reaction by structural variation of the nitrone component, culminating in the preparation of an N-TIPBS nitrone based on an oxazolidine framework, which proved to be optimal for this process. Also detailed are attempts to gain insight towards the mechanism of this transformation and to understand the mode of chirality transfer. Chapter 3 details the use of the N-TIPBS nitrone scaffold as a transmitter of chiral information in the synthesis of 3-alkyl-3-aryloxindoles and spirocyclic oxindoles. Chapter 4 delineates the mechanism of this transformation as a pericyclic cascade process. The key stereo-determining features are discussed including the conformational preferences of such chiral oxazolidine derived nitrones and the influence of the N-protecting group on the stereochemical outcome. Synthetic endeavours to provide evidence as to the validity of this computational mechanistic rationale are also presented. Chapter 5 describes regioselectivity studies, and tolerance of both the racemic and asymmetric reactions to varying substitution on the nitrone N-aryl ring. Initial studies were undertaken using achiral nitrones before the interplay between regio- and stereoselectivity was explored, initially with enantiopure N-Boc Garner's aldehyde derived nitrones, and further with N-TIPBS nitrones. Chapter 6 initially describes attempts to transform this chiral auxiliary methodology into a catalytic asymmetric protocol, by investigating in situ ketene formation via various strategies including activation of carboxylic acids. Also described are investigations into related nitrone-ketenimine cycloadditions, and related [3+2] nitrone cycloadditions. Chapter 7 describes the application of this methodology toward the synthesis of compounds with biological relevance. The concise asymmetric synthesis of a Roche anti-cancer agent is outlined, as is the extension of this methodology to the synthesis of indole alkaloid-like species. Finally, the attempted application of this methodology toward the asymmetric synthesis of (+)-gliocladin C is outlined.

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21

Lanoix, Stéphanie. "Development of Radical Cascade via Gold(I) Photocatalysis and Application towards One-Pot Bromination/Carbocyclization." Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/32062.

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Radical chemistry is a crucial tool to organic chemists. Recent trends in the field have been directed towards the development of photocatalysts capable of generating a radical through a renewable source like sunlight using a single electron transfer mechanism. The use of Au2dppm2Cl2, having a stronger reducing potential, allows an expansion of the reactivity to those achieved by iridium and ruthenium catalysts.1 The focus of this thesis is axed on the development of Au2dppm2Cl2 as an efficient photoredox catalyst for a tandem one-pot catalysis and its application in a dual catalytic system. The use of Au2dppm2Cl2 in a dual catalysis for the synthesis of β-amino acids was undertaken. The problems encountered over the course of the investigation showed an insufficient oxidation potential of the photoredox catalyst in addition to the facile homolytic cleavage of the C-halogen bond under UV light. However, this shows great promise for the achievement of beta amino acids using solely organocatalysis. The development of a tandem one-pot radical cyclization for the synthesis of fused- carbocycles, which are frequently encountered scaffolds in diterpenoid natural products, is reported. The initial experiments were conducted on a model substrate, enabling the verification of the proposed hypothesis. The success of this methodology was then applied to various substrates affording the desired fused 5 membered rings in good yields. These reactions show tremendous potential in the field of total synthesis for the rapid access of complex molecular structures. (1) Revol, G.; McCallum, T.; Morin, M.; Gagosz, F.; Barriault, L. Angew. Chem. Int. Ed. 2013, 52, 13342.

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22

Mistry, Kamlesh M. "The synthesis of 12-oxoPDA and the OPC cascade of compounds." Thesis, University of Nottingham, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293669.

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23

Poon, Hon-suen. "Michael initiated cascade reaction sequences and their application in target synthesis." Thesis, University of Southampton, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.246237.

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24

Davies, Paul William. "Palladium-catalysed cyclisation-carbonylation cascade processes and their application in synthesis." Thesis, University of Bristol, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268498.

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25

Jones, Daniel Ross. "Cascade cyclisation reactions and their application toward the synthesis of lactonamycin." Thesis, Imperial College London, 2018. http://hdl.handle.net/10044/1/59356.

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The lactonamycins represent a class of natural products which possess significant biological activity with high potencies in cancer cell lines and against multi-drug resistant strains of bacterial infections. Here, a cascade cyclisation, developed in the Parsons group, has been used in the synthesis of the pentacyclic core of lactonamycin. The thermal cyclisation of an ene-diyne allows for a transition metal free synthesis of five of the six rings of lactonamycin in ten synthetic steps. Studies on the functionalisation of the pentacyclic core of lactonamycin have also been undertaken. A proposed strategy for the completion of the total synthesis has also been outlined. In addition, a novel method for the synthesis of highly substituted aromatic rings has been discovered in the Parsons group. This reaction involves the thermal opening of a furan ring which is induced by the ring closing reaction of a diyne / Diels-Alder cascade. This provides penta- and hexa-substituted aromatic rings with potential pharmaceutical applications as templates for drug design. Some palladium-mediated cascade cyclisation methodology of similar, alkenyl bromide analogues is also discussed.

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Wzorek, Jr Joseph Stanley. "Macrocyclic Stereocontrol in Organic Synthesis: I. Efforts toward the Synthesis of (-)-Tetracycline II. Analysis of the Peripheral Attack Model." Thesis, Harvard University, 2012. http://dissertations.umi.com/gsas.harvard:10579.

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I. Efforts Toward the Synthesis of (–)-Tetracycline. A macrocyclic approach toward (–)-tetracycline is described. Traditional approaches towards the synthesis of tetracycline antibiotics employ the linear construction of the core structure starting with either the A- or D-rings. In contrast to this iterative annulation-based strategy, we have sought to employ a chiral macrocycle in our approach. Key to the success of our synthesis endeavor is the execution of two key steps: (1) a transannular Michael addition, which forms the A-ring and sets the C4a-stereogenic center; and (2) an isoxazole substitution reaction, which effects a ring contraction to produce both the B- and C-rings. This work describes our implementation of the strategy and focuses on the stereochemical interplay between the C4-, C4a-, C6-, and C12a-stereocenters within the context of the key steps. II. Analysis of the Peripheral Attack Model. The application of the peripheral attack model to 34 literature examples of intermolecular macrocyclic stereocontrol is described. While the peripheral attack model has been broadly applied in complex molecule synthesis, the validity of the model has not been subjected to analysis since being proposed in the early 1980’s. In order to assess the value of the model to organic chemists, we have developed a systematic method for probing the conformational profile of macrocycles. Using this tool, we then analyzed each of the 34 literature substrates and concluded whether the peripheral attack model predicts the correct stereochemical outcome in both a binary- and magnitude-based capacity. Analysis of both the bulk dataset and subsets of the dataset is included.
Chemistry and Chemical Biology

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27

Listén, Hedlin Embla. "Enzymatic cascade for dynamic kinetic resolution of amines." Thesis, KTH, Skolan för bioteknologi (BIO), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-215018.

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28

Schwantje, Travis R. "Towards a Formal Total Synthesis of Triptolide Via a Gold-catalyzed Cyclization Cascade." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/23712.

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This thesis discusses the progress made towards a formal total synthesis of triptolide, a naturally occurring diterpenoid triepoxide molecule. Isolated from a Chinese vine, triptolide features some interesting structural characteristics and has demonstrated a broad range of interesting medicinal effects. It has demonstrated remarkable cytotoxicity against a number of cancer cell lines, immunosuppressive activity, and reversible male sterility. This biological activity has made it a target of a number of total syntheses spanning from 1980 to 2010. Gold-catalyzed transformations are an emerging field in synthetic organic chemistry, but their efficacy and potential uses are gaining much recognition among the synthetic organic community. Our research group is extremely interested in the applications of such gold-catalyzed organic transformations in natural product synthesis. Here, we discuss our investigations towards accessing the tetracyclic core of triptolide using a gold-catalyzed cyclization cascade reaction. We explored a number of synthetic routes towards a common linear precursor, and our successes and failures are discussed herein. We also report numerous unsuccessful efforts towards an oxidative gold-catalyzed cyclization cascade to form the tetracyclic core of triptolide. Finally, we investigated the use of a photocatalytic radical cyclization cascade to access the desired core. We report some promising preliminary results, and this study is ongoing in the Barriault group.

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29

Grant, Seth W. "An Acyl Radical Cascade Model for the Total Synthesis of Lyconadin A." BYU ScholarsArchive, 2005. https://scholarsarchive.byu.edu/etd/759.

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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).

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30

Carpenter, Lon E. "Cascade analysis and synthesis of transfer functions of infinite dimensional linear systems." Diss., Virginia Tech, 1992. http://hdl.handle.net/10919/38950.

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31

Hirano, Kimio. "Direct Synthesis of Fused Indoles by Gold-Catalyzed Intramolecular Alkyne Cycloisomerization Cascade." 京都大学 (Kyoto University), 2012. http://hdl.handle.net/2433/159419.

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32

Pilkington, Christopher John. "The synthesis and synthetic application of resin- supported TosMIC isonitriles in radical cascade reactions and studies towards the synthesis of the antifungal viridiofungins." Thesis, Imperial College London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368701.

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33

Li, Baojian, and 李保健. "Studies toward the total synthesis of pseudolaric acid B via an improved carbene cyclization cycloaddition cascade strategy." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/202371.

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34

Schmidt, Sandy [Verfasser]. "An artificial enzyme cascade for the biocatalytic synthesis of polymer building / Sandy Schmidt." Greifswald : Universitätsbibliothek Greifswald, 2015. http://d-nb.info/1078125511/34.

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35

Zhu, Kaicheng. "Total synthesis of (+)-SCH 351448 and rhodium catalyzed stereoselective nitrene/alkyne cycloaddition cascade." Thesis, Boston University, 2013. https://hdl.handle.net/2144/12900.

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Thesis (Ph.D.)--Boston University PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you.
SCH-351448 is a 28-membered C2-symmetric macrocyclic metabolite isolated from the fermentation broth of a Micromonospora microorganism. This macrodiolide selectively activates transcription of the low-density lipoprotein receptor (LDL-R) promoter, which is important in the treatment of people with high cholesterol levels. The biological potential as well as the intriguing structure of this natural product prompted us to initiate synthetic studies towards its preparation. A convergent, enantioselective total synthesis of (+)-SCH 351448 was achieved. The tetrahydropyran ring systems in both fragments were constructed through our organosilane-based [4+2]-annulation methodology. Olefin cross metathesis was utilized in the union of two advanced fragments to generate the monomeric subunit. A metal-template directed macrodimerization strategy was examined but proved unsuccessful. Thus, the macrodiolide was assembled through a two-step sequence involving dioxinone ring-opening with concomitant esterification followed by DMC/DMAP mediated macrolactonization. Due to the prevalence of nitrogen-containing heterocycles in many natural products and pharmaceutical agents, the development of efficient methods for N-incorporation has remained at the forefront of synthetic research. Transition metal-catalyzed nitrene chemistry, an effective method to incorporate N-containing functionality into simple organic substrates, has become an attractive field for direct carbon-nitrogen bond formation. Of particular interest in this area is the metallonitrene/alkyne cycloaddition cascade reaction, a process in which nitrenes formed from sulfamate esters undergo addition to alkynes. In light of this, homopropargylic ethers, derived from chiral allenylsilanes in high yields and levels of diastereoselectivity , were converted into sulfamate esters bearing an internal alkyne. The generated sulfamate esters then underwent a metallonitrene cycloaddition and a subsequent highly stereoselective dearomative cyclopropanation, which resulted in unique tetracyclic norcaradiene-like products with two contiguous quaternary stereocenters. After subsequent opening of the sulfamate ester ring, the norcaradiene scaffold rearranged via a 6π electrocyclic ring opening process to form a fused tricyclic cycloheptatriene.

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36

Guerrand, Helene. "Cyclisation-dipolar cycloaddition : cascade chemistry for the synthesis of pyrazolidines and bridged amines." Thesis, University of Sheffield, 2012. http://etheses.whiterose.ac.uk/2755/.

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37

Campbell, Natalie E. "Towards a total synthesis of (–)-amphidinolide K : development of new radical cascade methods." Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/50308.

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(–)-Amphidinolide K, a novel 19-membered macrolide isolated by Kobayashi and coworkers, possesses cytotoxic activity against L1210 and KB cells in vitro. I have utilized our radical relay cyclization methodology to access the tetrahydrofuran ring in high diastereoselectivity from a readily accessible precursor. N-alkoxyphthalimides, when subjected to radical conditions, are able to generate oxygen radicals, which may undergo a 1,5-hydrogen atom transfer, and subsequently cyclize onto a nearby radical acceptor. I also extended this radical methodology towards the synthesis of a number of 5-membered carbo- and heterocycles. The 1,3-dimethyl stereocenters of our target natural product were accessed by utilizing the inherent C₂ symmetry of a simple diol precursor. Several methods to rapidly access a diene fragment of our target have been explored. A tandem ring-closing metathesis/cycloreversion strategy was originally sought, with a number of approaches towards the synthesis of the requisite sulfur-containing precursors. While this strategy was ultimately unsuccessful, it was the model inspiration for a tandem one-electron/pericyclic cascade approach. Commencing with simple alkyl aldehydes, we are now about to effect the synthesis of substituted 1,3-butadienes in a single step with high yields and diastereoselectivities. Details of this work and progress towards the total synthesis of (–)-amphidinolide K will be discussed herein.
Science, Faculty of
Chemistry, Department of
Graduate

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38

Du, Wei, and 杜玮. "Palladium-catalyzed oxidative cascade cyclizations via C-N/C-C formation for synthesis of nitrogen heterocycles." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/206320.

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39

Saint-Dizier, Alexandre Christian Claude. "Samarium diiodide mediated cascade radical cyclisations of methylenecyclopropane derivatives : synthesis of bicyclo-[3.2.1]-octanes." Thesis, University of Southampton, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.395912.

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40

Lewis, Shane E. "Development of a Three Step Cascade Synthesis of 2,4-Dihydro-1H-benzo[f]isochromenes." W&M ScholarWorks, 2015. https://scholarworks.wm.edu/etd/1539626965.

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41

Iwata, Akira. "Development of Novel Methods for Synthesis of Fused Indole-Type Compounds." Kyoto University, 2018. http://hdl.handle.net/2433/232328.

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42

Tokimizu, Yusuke. "Synthesis of Heterocyclic Scaffolds through Transition-Metal-CatalyzedCascade Reactions of Alkynes." 京都大学 (Kyoto University), 2015. http://hdl.handle.net/2433/199500.

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43

Liu, Xiaoling. "Polymeric Multicompartmentalized Systems Mimicking Artificial Cells for Controllable Multiple Enzymatic Cascade Reactions." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-230515.

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Engineering artificial cells is currently an emerging area of research that involves constructing mimics of biological cells. These biomimetic cellular systems hold tremendous promise for the different biomedical applications (diagnostics, therapy, tissue engineering, gene transfection, bioactive coatings) as well as aspects of synthetic biology. A key architectural principle of the cell is a multicompartmentalized assembly, which is one of the features of biological cells that enable the performance of multiple complex biochemical reactions within confined environments. For this purpose, this study demonstrates novel artificial cells, not only presenting organelle mimics but also incorporating various stimuli for regulating enzymatic cascade reactions within the artificial cell and for controlled simultaneous and/or subsequent release of the encapsulated (therapeutic) molecules. To successfully fabricate the multifunctional polymeric multicompartmentalized systems as artificial cells aimed for, in the first step a hollow capsule as biomimetic cellular membrane was developed to simulate a key characteristic of functional artificial cells for the selective uptake and release of (bio)molecules and particles for intra- and intercellular signaling processes. Herein using LbL technique which involved alternate deposition of oppositely charged polyelectrolytes on silica template via electrostatic interaction, the pH and temperature dual-responsive and photo-crosslinked hollow capsule was fabricated and they can be used for the subsequent post-encapsulation process of protein-like macromolecules (≤ 11 nm) and their controllable release triggered by external stimuli for mimicking the controllable bio-inspired functions of cell membranes. The reversible temperature and pH dual-response ability of the hollow capsules has been analyzed. The uptake and release properties of the resulting hollow capsules with different degree of photo-crosslinking for cargos have been further investigated at various temperatures (25, 37 or 45°C) and pH (5.5 or 7.4) of the solution. Next, the design of the polymersomal subcompartmens as organelle mimics, which divide the interior of the multicompartmentalized systems into subcompartments and can stably encapsulate fragile hydrophobic and hydrophilic cargo, e.g., enzymes in order to conduct encapsulated catalysis-resembling cell organelles, was also an important subject. The fabrication of these subcompartments was starting with the synthesis of suitably end-group block copolymers to realize the enzyme-loaded, multifunctional, pH-responsive, photo-crosslinked and post-labelled polymersomes decorated with adamantane groups. The pH sensitivity and various enzymatic reactions of the established multifunctional Ada-polymersomes have been investigated. Based on the above concepts, a bottom-up approach was developed to assemble a structural and functional eukaryotic cell mimics, including “membrane-associated” multicompartmentalized system (MS1) and “free-floating” multicompartmentalized system (MS2), by loading pH-sensitive Ada-polymersomes inside the multifunctional cell membrane. The creation of these multicompartmentalized systems was based on the assembly of enzyme-loaded Ada-polymersomes as organelle mimics onto sacrificial particle templates by host-guest interaction, followed by the LbL deposition of temperature-responsive and photo-crosslinkable PMA(β-CD)/[PAH/PNMD]3 multilayers and outer protective capping PAH/PMA(PEG) bilayer as biomimetic cellular membrane. Upon photo-crosslinking the polymer biomimetic membrane and dissolution of the particle templates, multicompartmentalized systems were obtained. Spatial position of the subcompartments can be controlled using non-covalent host-guest concept, which yielded multicompartmentalized systems containing “membrane-associated” and “free-floating” subunits. Moreover, the metabolism mimicry of multicompartmentalized systems by performing multiple successive two-enzyme cascade reactions in the cells and the multiple parallel reactions by using a third enzyme for deactivating the reaction product and interfering the cascade reaction have been investigated. In conclusion, these multicompartmentalized systems, combining the advantages of both pH-responsive Ada-polymersomes as organelle mimics and multifunctional hollow capsule as biomimetic cellular membrane, present new opportunities for the development of functional cell mimics. The presented studies highlight crucial aspects for the successful applications of such cell mimics for diagnostics, tissue engineering, as nanoreactors, as carriers for multiple drug delivery with controlled release profiles, or as therapeutic artificial cells.

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Zhu, Koudi. "Model Studies Towards the Total Synthesis of Lyconadin A via An Acyl Radical Cascade Reaction." Diss., CLICK HERE for online access, 2006. http://contentdm.lib.byu.edu/ETD/image/etd1364.pdf.

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45

Bao, Guanglin. "Studies toward the synthesis of the kempane diterpene ring system, and some cascade radical cyclizations." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0029/NQ63947.pdf.

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46

Zhou, Hao, and 周浩. "An efficient algorithm for face sketch synthesis using Markov weight fields and cascade decomposition method." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B49618052.

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Great progress has been made in face sketch synthesis in recent years. State-of-the-art methods commonly apply a Markov Random Fields (MRF) model to select local sketch patches from a set of training data. Such methods, however, have two major drawbacks. Firstly, the MRF model used cannot synthesize new sketch patches. Secondly, the optimization problem in solving the MRF is NP-hard. In this thesis, a novel Markov Weight Fields (MWF) model is proposed. By applying linear combination of candidate patches, MWF is capable of synthesizing new sketch patches. The MWF model can be formulated into a convex quadratic programming (QP) problem to which the optimal solution is guaranteed. Based on the Markov property of MWF model, a cascade decomposition method (CDM) is further proposed for solving such a large scale QP problem efficiently. Experiments show that the proposed CDM is very efficient, and only takes about 2:4 seconds. To deal with illumination changes of input photos, five special shading patches are included as candidate patches in addition to the patches selected from the training data. These patches help keeping structure of the face under different illumination conditions as well as synthesize shadows similar to the input photos. Extensive experiments on the CUHK face sketch database, AR database and Chinese celebrity photos show that the proposed model outperforms the common MRF model used in other state-of-the-art methods and is robust to illumination changes.
published_or_final_version
Computer Science
Master
Master of Philosophy

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47

Levick, Matthew Thomas. "Connective-Pummerer cyclisations and SmI2-mediated cascade reactions for the synthesis of nitrogen-containing heteroacenes." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/connectivepummerer-cyclisations-and-smi2mediated-cascade-reactions-for-the-synthesis-of-nitrogencontaining-heteroacenes(762eea6e-0dc0-4397-8af0-07413517db63).html.

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This thesis describes work towards a range of novel nitrogen containing polyaromatic heterocycles for use as organic semiconductors. A route to benzo[b]carbazole end-capped oligothiophenes has been developed; relying on two key steps; namely a connective-Pummerer cyclisation and a SmI2-mediated cleavage–cyclisation cascade. A route to extended dibenzoindolo[3,2-b]carbazole-based aza-heptacenes has also been developed, by employing the same key steps in a two-directional manner. The physical and electronic properties of the resulting materials has been assessed, and the utility of the materials in OFET devices has been demonstrated.

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48

Gao, Ming. "Ketone synthesis via rhodium-catalyzed traceless chelation-controlled hydroacylation reactions." Thesis, University of Oxford, 2018. http://ora.ox.ac.uk/objects/uuid:487b65f9-d1f7-4fee-b2bb-358837866ca2.

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This thesis documents the development of rhodium-catalyzed traceless chelation-controlled hydroacylation reactions for the synthesis of a variety of ketone products. Chapter 1 provides an overview of rhodium-catalyzed hydroacylation chemistry, focusing on the origin of chelation-controlled strategies and the benefits thereof. Chapter 2 describes a sequential reaction involving alkene hydroacylation, sulfide elimination and boronic acid conjugate addition, which affords products with the initial sulfide coordinating group replaced by a stereochemically defined aryl group. Chapter 3 demonstrates a sequential process involving alkyne hydroacylation, boronic acid conjugate addition and sulfide elimination, which provides enantioenriched β'-arylα,β-unsaturated ketones in a highly efficient and selective manner. Chapter 4 illustrates a versatile chelating group, triazene, for hydroacylation reactions. Subsequent functionalization of aromatic C-H bonds, promoted by the same chelating unit, offers highly substituted phenyl ketone products. Chapter 5 documents experimental procedures and data.

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Matsuoka, Junpei. "Total Synthesis of Indole Alkaloids Based on Direct Construction of Pyrrolocarbazaole Scaffolds via Gold-Catalyzed Cascade Cyclizations." Doctoral thesis, Kyoto University, 2020. http://hdl.handle.net/2433/253241.

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京都大学
0048
新制・課程博士
博士(薬学)
甲第22405号
薬博第843号
新制||薬||241(附属図書館)
京都大学大学院薬学研究科薬学専攻
(主査)教授大野浩章, 教授高須清誠, 教授竹本佳司
学位規則第4条第1項該当
Doctor of Pharmaceutical Sciences
Kyoto University
DFAM

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50

Klaus, Tobias [Verfasser], and Bernhard [Akademischer Betreuer] Hauer. "Novel route to vanillin - an enzyme-catalyzed multi-step cascade synthesis / Tobias Klaus ; Betreuer: Bernhard Hauer." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2016. http://d-nb.info/1132134455/34.

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Dissertations / Theses on the topic 'Cascade synthesis'

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