Enantioselective Total Synthesis of the Antitumor Alkaloid (+)-pancratistatin and Ring Opening Olefin Metathesis of Cyclobutenes PDF Download
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Author: Umar S. M. Maharoof
Publisher:
ISBN:
Category :
Languages : en
Pages : 330
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Author: Umar S. M. Maharoof
Publisher:
ISBN:
Category :
Languages : en
Pages : 330
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Author: Alyssa Hope Antropow
Publisher:
ISBN:
Category :
Languages : en
Pages : 231
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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.
Author: Karine Poullennec
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Marine natural products biogenetically derived from the pyrrole-imidazole oroidin (i) display fascinating structural diversity and exhibit a wide range of significant biological activities. Hence, they have attracted great interest from the synthetic community leading to the development of new synthetic methodologies and providing an admirable set of strategies and tactics to assemble the most complex representatives of this class of alkaloids. In this work, a synthesis of the potent antitumor dibromophakellstatin (ii) was devised featuring a highly diastereoselective acylation of the C2-symmetric prolyl-prolyl anhydride (iii), an intramolecular Mitsunobu reaction installing the C6 animal and a tandem Hofmann rearrangement/cyclization that delivered the targeted imidazolidinone of the phakellstatins. Both enantiomers of phakellstatin were prepared starting from either D- or L- proline. Building on several findings made in the course of the synthesis of phakellstatin, namely the differential reactivity of the aminal centers (C6 and C9) and the formation of an oxidized phakellstatin, a second generation approach towards these deceitfully simple alkaloids was initiated. The second generation synthetic strategy towards phakellstatin (iv) and phakellin (v) utilizes a novel variation of Du Bois' C-H insertion involving a urea or a guanidine. This approach appears more amenable to the annulation of the phakellin substructure for the final stages of the synthesis of the potent immunosuppressant palau'amine (vi).
Author: Vivek Badarinarayana
Publisher:
ISBN: 9780542722608
Category : Chemistry, Organic
Languages : en
Pages :
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This dissertation consists of two parts. The first part describes the enantioselective total synthesis of martinellic acid. The Martinella alkaloids have attracted considerable attention in the synthetic community over the past few years. This interest is due in large part to their unique structure and useful biological activity (bradykinin receptor antagonist). In model systems we have successfully used the [3+2] azomethine ylide-alkene cycloaddition to construct the heterocyclic core of these alkaloids. The enantioselective approach described herein also involves the azomethine ylide-alkene cycloaddition as a key step in the total synthesis. The pyrrolo[3,2-c]quinoline core of this alkaloid was constructed in an enantioselective fashion by the elaboration of an N-aryl pyrrolidinone, which was obtained via Pd-catalyzed aryl amination reaction using a non-racemic lactam. Pirkle's chiral solvating agent was successfully used to demonstrate the stereochemical integrity of not only the N-aryl lactam (obtained by Pd-catalyzed cross-coupling) but also the cycloaddition precursor and the cycloaddition product (tetracyclic pyrroloquinoline core). The tetracyclic compound obtained via the azomethine ylide-alkene cycloaddition was elaborated to ( - )-martinellic acid in 11 steps and 6% overall yield. The second part of this dissertation describes application of several novel organometallic complexes for carrying out various organic transformations. A fluorinated tris(pyrazolyl)borato silver(I) complex catalyzes the addition of ethyl diazoacetate to benzene rings, providing norcaradienes, which undergo electrocyclization to provide the corresponding cycloheptatriene (the Bu & huml;chner reaction). These reactions are surprisingly selective for addition to the aromatic moiety rather than C-H insertion. A copper complex containing a fluorinated triazapentadienyl ligand has been used to catalyze some carbene and nitrene addition and insertion chemistry. Nitrene addition occurs rapidly and with both aryl and alkyl substituted olefins providing the corresponding aziridine. The carbene transfer reactions that were attempted include C-H insertion, O-H insertion and N-H insertion, of which the latter two were very efficient.
Author: Sunkyu Han
Publisher:
ISBN:
Category :
Languages : en
Pages :
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I. Total Synthesis of the (-)-Agelastatin Alkaloids The pyrrole-imidazole family of marine alkaloids, derived from linear clathrodin-like precursors, constitutes a diverse array of structurally complex natural products. The bioactive agelastatins are members of this family that possess a tetracyclic molecular framework incorporating C4-C8 and C7-N12 bond connectivities. We provide a hypothesis for the formation of the unique agelastatin architecture that maximally exploits the intrinsic chemistry of plausible biosynthetic precursors. We report the concise enantioselective total syntheses of all known agelastatin alkaloids including the first total syntheses of agelastatins C, D, E, and F. Our gram-scale chemical synthesis of agelastatin A was inspired by our hypothesis for the biogenesis of the cyclopentane C-ring and required the development of new transformations including an imidazolone-forming annulation reaction and a carbohydroxylative trapping of imidazolones. II. Total Synthesis of the (-)-Trigonoliimine Alkaloids The concise and enantioselective total syntheses of (-)-trigonoliimines A, B, and C are described. Our unified strategy to all three natural products is based on asymmetric oxidation and reorganization of a single bistryptamine, a sequence of transformations with possible biogenetic relevance. We revise the absolute stereochemistry of (-)-trigonoliimines A, B, and C.
Author: Dustin Scott Siegel
Publisher:
ISBN:
Category :
Languages : en
Pages : 285
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I. Enantioselective Total Synthesis of ( - )-Acylfulvene, and ( - )-Irofulven We report the enantioselective total synthesis of ( - )-acylfulvene and ( - )-irofulven, which features metathesis reactions for the rapid assembly of the molecular framework of these anti tumor agents. We discuss (1) the application of an Evans Cu-catalyzed aldol addition reaction using a strained cyclopropyl ketene thioacetal, (2) an efficient enyne ring-closing metathesis cascade reaction in a challenging setting, (3) the reagent, IPNBSH, for a late stage reductive allylic transposition reaction, and (4) the final ring-closing metathesis/dehydrogenation sequence for the formation of ( - )-acylfulvene and ( - )-irofulven. II. Total Synthesis of the ( - )-Agelastatin Alkaloids The pyrrole-imidazole super-family of marine alkaloids, derived from linear clathrodinlike precursors, constitutes a diverse array of structurally complex natural products. The bioactive agelastatins are members of this family that have a tetracyclic molecular framework incorporating C4-C8 and C7-N12 bond connectivities. We provide a hypothesis for the formation of the unique agelastatin architecture that maximally exploits the intrinsic chemistry of plausible biosynthetic precursors. We report the concise enantioselective total syntheses of the agelastatin alkaloids, including the first total syntheses of agelastatins C and E. Our gram-scale chemical synthesis of agelastatin A was inspired by our hypothesis for the biogenesis of the cyclopentane C-ring and required the development of new transformations including an imidazolone-forming annulation reaction and a carbohydroxylative trapping of imidazolones.
Author: Ernest I. Becker
Publisher: John Wiley & Sons
ISBN: 9780471061304
Category : Science
Languages : en
Pages : 470
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Author: G. Pattenden
Publisher: Elsevier
ISBN: 008091246X
Category : Science
Languages : en
Pages : 1209
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Volume 3 covers carbon-to-carbon single bond forming reactions involving sp3, sp2 and sp carbon centers, but only those which do not involve additions to C-X &pgr;-bonds. The volume first compares and contrasts the alkylation reactions of all types of sp3 carbon nucleophiles and also covers vinyl and alkynyl carbanions. Following on from Volume 2, a separate section covers Friedel-Crafts alkylation reactions, which is complemented by discussions of polyene cyclizations and electrophilic transannular cyclizations in synthesis. Coupling reactions leading to &agr;-bond formation, and involving all types of combinations ofsp3, sp2 and sp carbon centers are next covered, including those reactions based on pinacol, acyloin and phenol oxidative coupling reactions, and also the Kolbe reaction. Rearrangement reactions, leading to carbon-to-carbon &agr;-bond formation, are often used in a clever manner in synthesis. The volume includes all those rearrangement reactions based on intermediate carbonium ions and carbanions, and also includes the benzil-benzilic acid and the Wolff rearrangements. The volume closes with coverage of carbonylation reactions, and the use of carbene insertion reactions into the C-H bond in synthesis.
Author: Takahiko Akiyama
Publisher: John Wiley & Sons
ISBN: 1119736412
Category : Science
Languages : en
Pages : 798
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Book Description
Catalytic Asymmetric Synthesis Seminal text presenting detailed accounts of the most important catalytic asymmetric reactions known today This book covers the preparation of enantiomerically pure or enriched chemical compounds by use of chiral catalyst molecules. While reviewing the most important catalytic methods for asymmetric organic synthesis, this book highlights the most important and recent developments in catalytic asymmetric synthesis. Edited by two well-qualified experts, sample topics covered in the work include: Metal catalysis, organocatalysis, photoredox catalysis, enzyme catalysis C–H bond functionalization reactions Carbon–carbon bond formation reactions, carbon–halogen bond formation reactions, hydrogenations, polymerizations, flow reactions Axially chiral compounds Retaining the best of its predecessors but now thoroughly up to date with the important and recent developments in catalytic asymmetric synthesis, the 4th edition of Catalytic Asymmetric Synthesis serves as an excellent desktop reference and text for researchers and students, from upper-level undergraduates all the way to experienced professionals in industry or academia.
Author: Eric N. Jacobsen
Publisher: Springer Science & Business Media
ISBN: 9783540003335
Category : Science
Languages : en
Pages : 258
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Book Description
The first supplement to the three volume reference work "Comprehensive Asymmetric Catalysis" critically reviews new developments to the hottest topics in the field written by recognised experts. Eleven chapters which are already in the major reference work have been supplemented and additionally five new chapters have been included. Thus the state-of-the art in this area is now re-established. Together with the basic three volume book set this supplement is not only the principal reference source for synthetic organic chemists, but also for all scientific researchers who use chiral compounds in their work (for example, in biochemical investigations and molecular medicine) as well as for pharmaceutical chemists and other industrial researchers who prepare chiral compounds.
