Download or read book 2 2 Photocycloaddition in Natural Product Synthesis written by Roel Klein Nijenhuis and published by . This book was released on 2018 with total page 229 pages. Available in PDF, EPUB and Kindle. Book excerpt: [2+2]-Photocycloaddition is a powerful method to synthesise highly strained, complex and multicyclic compounds. The research described in this thesis focusses on using this reaction to pursue the total synthesis of a number of complex natural products. The main project focusses on the synthesis of solanoeclepin A, an extremely potent hatching agent of the potato cyst nematode. To reach this goal, the molecule was divided in two parts, the left- and the right-hand substructure. With the left-hand substructure completed in previous research, the goal was now to synthesise the right-hand substructure, and to complete the total synthesis by connecting the two fragments. The key step is a [2+2]-photocycloaddition of 2-substituted 3-methyl-2-cyclohexenones, described in chapter 3. Using this reaction the highly strained bicyclo[2.1.1]cyclohexane core structure of the natural product was accessed from simple starting materials in a few steps. A racemic approach to the right-hand substructure of solanoeclepin A is described in chapter 2. Extensive research ultimately led to a short and efficient enantioselective formal synthesis of solanoeclepin A, as described in chapter 4. Finally, the efforts to combine both fragments are described in chapter 5. The final chapter describes the first total syntheses of aquatolide and wilfolide B. Aquatolide was prepared using the [2+2]-photocycloaddition of an allene-substituted pentenolide, ultimately leading to the natural product. Retro-ene type rearrangement of the cycloaddition product led to a different carbon skeleton, leading to the successful total synthesis of wilfolide B.
Download or read book Natural Product Synthesis I written by Johann H. Mulzer and published by Springer Science & Business Media. This book was released on 2005-01-12 with total page 258 pages. Available in PDF, EPUB and Kindle. Book excerpt: B. Basler, S. Brandes, A. Spiegel and T. Bach: Total Synthesis of Kalsoene and Preussin .- R. Bandichhor, B. Nosse and O. Reiser: Paraconic Acids- the Natural Products from Lichen Symbiont .- M. Hiersemann and H. Helmboldt: Recent Progress in the Total Synthesis of Dolabellane and Dolastane Diterpenes .- L. Wessjohann and E. Ruijter: Strategies for Total and Diversity- Oriented Synthesis of Natural Product (-Like) Macrolides .-M. Sefkow: Enantioselectice Synthesis of C(8)-Hydroxylated Lignans: Early Approaches and Recent Advances
Download or read book 2 2 Photocycloaddition Reactions in the Synthesis of Novel Scaffolds and Natural Products written by Bethan Donnelly and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A 2 2 Photocycloaddition Fragmentation Approach for Cis Fused Lycorine type Natural Product Synthesis written by Maike H. Wahl and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Retrosynthetic Analysis and Synthesis of Natural Products 1 written by Olivier Piva and published by John Wiley & Sons. This book was released on 2019-12-12 with total page 314 pages. Available in PDF, EPUB and Kindle. Book excerpt: For chemists, attempting to mimic nature by synthesizing complex natural products from raw material is a challenge that is fraught with pitfalls. To tackle this unique but potentially rewarding task, researchers can rely on well-established reactions and methods of practice, or apply their own synthesis methods to verify their potential. Whatever the goal and its complexity, there are multiple ways of achieving it. We must now establish a strategic and effective plan that requires the minimum number of steps, but lends itself to widespread use. This book is structured around the study of a dozen target products (butyrolactone, macrolide, indole compound, cyclobutanic terpene, spiro- and polycyclic derivatives, etc.). For each product, the different disconnections are presented and the associated syntheses are analyzed step by step. The key reactions are described explicitly, followed by diagrams showing the range of impact of certain transformations. This set of data alone is conducive to understanding syntheses and indulging in this difficult, but worthwhile activity.
Download or read book Part I Synthesis of Naturally Occurring Cyclobutanes Via Stereoselective Photocycloadditions Part II Development of Photocatalytic Net oxidative Transformations Using Copper II Salts as Terminal Oxidants written by Byung Joo Lee (Ph.D.) and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Among many unique transformations accessible using photochemical activation, the [2+2] photocycloaddition of olefins has had the largest impact on total synthesis. However, relatively few asymmetric total syntheses of natural products involving an enantioselective [2+2] photocycloaddition have been reported to date. This is due in part to the difficulty of conducting enantioselective [2+2] photocycloaddition reactions. Recent work in the Yoon lab has focused on developing enantioselective [2+2] photocycloadditions using a dual catalysis approach. The work presented herein will describe the use of chiral Lewis acid catalysts to enable highly enantioselective photocycloadditions and further application of this strategy toward natural product synthesis. Photoredox catalysis is a powerful strategy to generate radical and radical ion intermediates under exceptionally mild conditions. However, the development of photocatalytic oxidation reactions has been much more challenging compared to redox-neutral and net reductive transformations due to the lack of generally applicable terminal oxidants that are compatible with photoredox conditions. This thesis describes the use of copper(II) salts as terminal oxidants for robust photocatalytic oxidation reactions.
Download or read book Toward a Visible Light Mediated 2 2 Photocycloaddition cyclobutane Fragmentation Synthesis of Natural Products written by Jeffrey Rein and published by . This book was released on 2021 with total page 246 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Photocycloaddition of Conjugated Enynes and Its Application in Natural Products Synthesis written by Buddha Bahadur Khatri and published by . This book was released on 2016 with total page 450 pages. Available in PDF, EPUB and Kindle. Book excerpt: Aromatic 2-pyridones and 2-pyrones are known to undergo a facile [4+4] photocycloaddition with themselves and other conjugated molecules. The unifying objective of this work is to explore the potential of conjugated enynes as a photocycloaddition partner with a variety of unsaturated systems and establish it as a path for the synthesis of valuable natural products and molecular scaffolds. With a 1,3-enyne as a reactant, the immediate photocycloadduct, a highly strained cyclic allene, was stabilized and functionalized to give advanced intermediates in natural product synthesis. Participation of substituted benzenes in higher order photocycloaddition with 2-pyridones was also discovered. Intramolecular enyne-pyridone [4+4] photocycloaddition led to the formation of cyclic, strained allenic products that undergo rapid dimerization through various modes leading to complex mixtures. Such allene-allene dimerization was suppressed by introducing steric shielding. With reactive tethered functional group present, the intermediate allene can undergo a secondary cycloaddition with either the proximal or distal double bond, depending on the tether length. In the absence of such functional groups, the allene can isomerize to a 1,3-diene. Oxidation of the allene led to a cyclopropanone, a bicyclo-[5.1.0]-octane, which was transformed into pseudoguaiane-like 7-5 ring systems. Participation of enynes in the photocycloaddition of other unsaturated systems was also investigated. Anthracene, naphthalene derivatives and 2-pyrones were all found to undergo quantitative photocycloaddition with an enyne. During this investigation, a low temperature Cope rearrangement was also discovered. In addition, meta-substituted benzenes were reluctant partners in [4+4] photocycloaddition with enynes but underwent efficient [4+4] photocycloaddition with 2-pyridones. The synthetic utility of enyne photocycloaddition was applied in the synthesis of the cyclooctanoid containing natural product, (+)-dactylol. The intramolecular enyne - 2-pyrone [4+4] photocycloaddition-isomerization gave a lactone bridged-cyclooctanoid product which serves as an advanced intermediate for sesquiterpene synthesis.
Download or read book Modern Natural Product Synthesis written by Masahisa Nakada and published by Springer Nature. This book was released on with total page 518 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book New Strategies for 2 2 Photocycloadditions of Aliphatic Alkenes written by Christopher S. Gravatt and published by . This book was released on 2020 with total page 316 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cyclobutanes are important targets in synthetic chemistry, due to their prominence in a diverse range of biologically active molecules displaying meaningful therapeutic properites. Among many methods for the synthesis of these strained rings, the most well-developed involves [2+2] photocycloaddition reactions of alkenes. To date, neither photoredox nor photosensitization processes have proven applicable to the activation of simple, unconjugated aliphatic alkenes. My doctoral research focused on solutions to this synthetic limitation through a range of photochemical tactics. Building upon early work from Salomon and Kochi on copper (I) catalyzed [2+2] photocycloadditions a more robust catalyst system for these reactions has been discovered and subsequently employed in the total synthesis of cyclobutane natural product (+)- sulcatine G.
Download or read book Natural Product Synthesis Via Photochemical Cycloadditions written by George Forrest Martin and published by . This book was released on 1984 with total page 256 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Supramolecular Photochemistry written by V. Ramamurthy and published by John Wiley & Sons. This book was released on 2011-07-07 with total page 511 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is the most updated, comprehensive collection of monographs on all aspects of photochemistry and photophysics related to natural and synthetic, inorganic, organic, and biological supramolecular systems. Supramolecular Photochemistry: Controlling Photochemical Processes addresses reactions in crystals, organized assemblies, monolayers, zeolites, clays, silica, micelles, polymers, dendrimers, organic hosts, supramolecular structures, organic glass, proteins and DNA, and applications of photosystems in confined media. This landmark publication describes the past, present, and future of this growing interdisciplinary area.
Download or read book The Patern B chi Reaction written by Maurizio D’Auria and published by Cambridge Scholars Publishing. This book was released on 2019-07-29 with total page 613 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book represents the most complete description of the scientific results obtained on a photochemical experiment described 110 years ago by the Italian scientist Emanuele Paternò. This detailed that the photochemical reaction between a carbonyl compound and an alkene gives a corresponding oxetane. This oxetane ring is present in several naturally occurring compounds and bioactive compounds, and can be obtained with high regio- and stereoselectivity.
Download or read book The Total Synthesis of Natural Products written by Michael C. Pirrung and published by John Wiley & Sons. This book was released on 2009-09-22 with total page 480 pages. Available in PDF, EPUB and Kindle. Book excerpt: The past two decades have seen an explosion in research on the synthesis of sesquiterpenes, an important class of hydrocarbons commonly found in oils, resins, and balsams. Volume Eleven in The Total Synthesis of Natural Products series continues to review this dynamic area of chemistry. It features systematic, A-to-Z coverage of sesquiterpenes synthesized between 1979-1994-a sesquidecade. Focusing on bicyclic and tricyclic compounds in sesquiterpene synthesis, this authoritative work complements Volume Ten's coverage of acyclic and monocyclic sesquiterpenes. The authors comb through the hundreds of sesquiterpene syntheses already developed, consolidating the multitude of research papers, and providing extensive references as well as author and subject indexes. To keep the presentation manageable, they emphasize literature where natural products were prepared, leaving out natural ring systems or compounds whose structures were misassigned. This volume presents multiple syntheses of the same compound in chronological order, making the various steps of the synthetic strategy easily accessible. In addition, it addresses one of the most important developments in sesquiterpene research, namely the increase in compound targets prepared in an optically active form. And while syntheses of racemates are not specifically marked, legends for synthesis schemes producing optically active compounds include their absolute configurations, signs of optical rotation, or both. An important resource for organic chemists, pharmaceutical and medicinal chemists, natural prod-ucts chemists, and biochemists, The Total Synthesis of Natural Products offers valuable insight into the structure and makeup of sesquiterpenes while serving as a practical tool for locating any of the major classes of sesquiterpene compounds. An invaluable guide for the chemist interested in natural products. Providing a fascinating, comprehensive look at sesquiterpene synthesis, Volume Eleven of The Total Synthesis of Natural Products reviews sesquiterpenes synthesized in the period 1979-1994, continuing the coverage begun with Volume Ten in the series (see below). This authoritative work: Focuses on bicyclic and tricyclic sesquiterpenes. Explains the structure and makeup of this important class of hydrocarbons. Serves as a useful, practical tool for researchers interested in locating any of the major classes of sesquiterpene compounds. Provides multiple syntheses of the same compound chronologically, clearly showing the evolution of the synthetic strategy. Also available . . .THE TOTAL SYNTHESIS OF NATURAL PRODUCTS Volume Ten, Edited by David Goldsmith. A complement to this work, Volume Ten examines compounds with acyclic and monocyclic ring structures in sesquiterpene synthesis. 1997 (0-471-59679-5) 173 pp.
Download or read book Total Synthesis of Pseudo dimeric Cyclobutane Natural Products Via Br nsted Acid catalyzed Asymmetric 2 2 Photocycloadditions written by Matthew James Genzink and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Pseudo-dimeric cyclobutanes constitute a large class of natural products. Though a [2+2] cycloaddition would be the most direct way to access these molecules, its use in total synthesis has been limited due to selectivity challenges in the cycloaddition. The work in this dissertation details the development of a new platform for enantioselective [2+2] photocycloadditions based on chiral Brønsted acid catalysis and its application to the total synthesis of (pseudo)-dimeric cyclobutane natural products. Initial mechanistic investigations revealed that the reaction proceeds via a chromophore activation mechanism in which coordination of the catalyst to the substrate engenders a red-shifted substrate absorption. This insight enabled the development of (hetero)dimerization reactions, the products of which could be transformed into enantioenriched natural products.
Download or read book PYRIDONE PHOTOCYCLOADDITION IN SYNTHESIS OF DIVERSE NATURAL AND UNNATURAL PRODUCTS written by Svitlana Kulyk and published by . This book was released on 2014 with total page 620 pages. Available in PDF, EPUB and Kindle. Book excerpt: 2-Pyridones are known to undergo a facile [4+4] photocycloaddition with themselves and other conjugated molecules. These transformations provide an access to complex molecular structures such as highly substituted cyclooctanoid derivatives, which normally represent a significant synthetic challenge. Moreover, the 2-pyridone photoadducts can be further elaborated into various biologically relevant products. The work presented here broadens the horizons of the [4+4] photocycloaddition in two distinct directions: 1) by utilizing [4+4] photocycloaddition in a total synthesis of crinipellin natural products possessing antibiotic and antitumor activity and 2) by developing a novel type of [4+4] photocycloaddition that employs a conjugated enyne as a partner of 2- pyridone. Our approach to the tetraquinane core of the crinipellins features intramolecular [4+4] photocycloaddition of a tethered furan-pyridone molecule followed by a four-step transannular ring closure. The sequence allows for a rapid assembly of a molecular framework by installing 19 of the 20 required carbon atoms and all but two stereogenic centers. The described synthesis represents an interesting new approach to these polycyclic molecules and a way to access crinipellin analogues. The enyne-pyridone [4+4] photocycloaddition led to formation of intriguing 1,2,5-cyclooctatriene-based products. Presence of the allene functionality was used as a lever in exploring the possibilities for derivatization of these photoadducts. Our investigations of enyne-pyridone photocycloaddition have come a long way: from the first proof-of-concept intermolecular trials producing complex mixtures, through the initial investigations of the intramolecular variant that taught us how to direct the reaction to the necessary mode ([2+2] vs. [4+4] photocycloaddition), and eventually to the controlled formation of stable allenic photoadducts and their further transformation into a diverse set of functionalized molecular scaffolds. We found that the inherent kinetic instability of 1,2,5-cyclooctatrienes facilitates several pathways of strain relief: allene-allene [2+2] dimerization, photooxidative decarbonylation when the irradiation is conducted in presence of air, isomerization of the 1,2-diene fragment into a 1,3-diene and the acid-promoted Cope rearrangement. Additionally, enyne-pyridone photoadducts can undergo transannular ring closure when treated with bromine and also be transformed into valuable bicyclo [5.1.0] octane structures that incorporate a rare example of a stable cyclopropanone by a fast and selective epoxidation-rearrangement process. Several important goals were achieved in the described research study. First, strategic incorporation of [4+4] photocycloaddition as one of the key steps in targeted synthesis of natural products has demonstrated the potential of this powerful reaction. Second, an efficient new approach to a tetraquinane skeleton was developed and successfully executed. Third, the fundamental basis for the novel photochemical transformation (enyne-pyridone cycloaddition) was set and major trends for this reaction were established resulting in obtaining stable allenic photoadducts. Finally, chemical properties and reactivity of stabilized amide-bridged 1,2,5-cyclooctatriene photoproducts were investigated breaking the ground for future involvement of these intermediates in synthetic strategies towards biologically active natural products and their analogues.
Download or read book Metathesis in Natural Product Synthesis written by Janine Cossy and published by John Wiley & Sons. This book was released on 2011-09-22 with total page 413 pages. Available in PDF, EPUB and Kindle. Book excerpt: Emphasizing the impact of metathesis in natural product synthesis through the different types of key reactions, this is a comprehensive view of a hot topic. Written by top international authors, this ready reference is clearly structured and packed with important information, including representative experimental procedures for practical applications. A real must-have for anyone working in natural product synthesis.
