Download or read book Studies Toward the Total Synthesis of Palau amine written by Hongwang Du and published by . This book was released on 2004 with total page 884 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Studies Towards the Total Synthesis of Palau amine written by Daniel Rivalti and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "The pyrrole-imidazole alkaloids (PIAs) are a family of structurally related natural products isolated from several species of marine sponges. Palau'amine, a dimeric PIA, has been a target for total synthesis ever since its isolation in 1993 due to its significant biological activity and, more importantly, its complex molecular architecture. In 2007, the structure ofpalau'amine was revised to incorporate a highly strained trans-fused azabicyclo[3.3.0]octane bicyclic system.This thesis follows the progression of efforts that culminated in the development of a cyclization strategy for the formation of the strained trans-fused 5,5-bicyclic ring system. In our initial exploration, attempts to secure the trans-fused 5,5-ring system via previously established metal-mediated diamination protocols and amidyl radical cyclization were thwarted. Finally, the synthesis of the trans-fused core within a simple cyclic model systemwas enabled by the conjugate addition of a carbamate nitrogen to an ynoate which furnishes a trans-fused azabicyclo[3.3.0]octane bicyclic system containing an exocyclic [alpha],[beta]-unsaturated ester. The latter would act as a synthetic handle to construct the remaining right-hand side core of palau'amine.Two particular monomeric PIAs, phakellin and phakellstatin, greatly resemble palau'amine in that they share the same ABCD tetracyclic core. The application of our conjugate addition strategy afforded the pyrrolidine A-ring, containing an exocyclic [alpha],[beta]-unsaturated ester. To access the phakellstatin core, the elaboration of that synthetic handle to the vinyl urea was achieved via a Curtius rearrangement. A cyclofunctionalization reaction secured the pyrazinone B-ring affording the desired tricyclic carbinolamine precursor suitable for the synthesis of phakellstatin. To access the phakellin core, the exocyclic [alpha],[beta]-unsaturated ester was elaborated, via a Curtius rearrangement/aza-Wittig one-pot process, to an advancedintermediate containing the complete nitrogen and carbon framework of phakellin. The cyclofunctionalization reaction with the guanidine-containing intermediate secured the pyrazinone B-ring affording the desired tricyclic carbinolamine. Unfortunately, final attempts to close the guanidine C-ring and to complete the synthesis of the natural product werehowever unsuccessful." --
Download or read book Synthetic Studies Toward Palau amine and Enantioselective Total Synthesis of Biogenetically Related phakellin and monobromophakellin written by Shaohui Wang and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Oroidin alkaloids, also known as pyrrole-imidazole alkaloids, have become a hot area of chemical and biological research due to their diverse and intriguing structural features and biological activities. Palau'amine (i), one of the hexacyclic oroidin-derived secondary metabolites, contains a fully substituted chloro-cyclopentane ring, a piperazinone moiety and two cyclic guanidines. With the uniqueness and complexity of its structure, palau'amine has been a synthetic challenge and has not yet succumbed to total synthesis. The overall objective of this work was to explore synthetic pathways toward palau'amine and biogenetically related congeners. Most of the work was focused on developing a synthetic pathway for the palau'amine structure proposed in its isolation report dated back to 1993. Starting from a Diels-Alder adduct (iii), oxidation/chlorination followed by phakellin (ii) annulation afforded an advanced pentacyclic intermediate possessing all the carbon framework and all but one ring system of palau'amine. Recently, however, a series of reports questioned the originally proposed palau'amine structure and called for a revision of the stereochemistry of two carbon centers (iv). Now palau'amine has an identical chlorocyclopentane core with axinellamine (vi). With the target changed, we devised a new biomimetic pathway toward both natural products via a common intermediate (v), which was synthesized in 12 steps from the Diels-Alder adduct (iii).
Download or read book Application of Modern Pummerer Methodology in Model Studies Toward the Total Synthesis of Palau amine written by Jianfeng Li and published by . This book was released on 2009 with total page 83 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A New Asymmetric Synthesis of Pyrrolidinoindolines written by Audris Huang and published by . This book was released on 2006 with total page 670 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Pursuit of Palau amine written by Ian Bass Seiple and published by . This book was released on 2011 with total page 1460 pages. Available in PDF, EPUB and Kindle. Book excerpt: These total syntheses were enabled by a catalytic, enantioselective Diels-Alder reaction and by the invention of a chemoselective silver(II)-mediated oxidation, which inspired an investigation into unexplored domains of silver-mediated chemistry. The discovery that a silver(I)/persulfate system can effect the radical deborylation of aryl- and alkylboronic acids led to new practical methods for the C-H functionalization of heterocycles and quinones. This discovery further prompted the reinvestigation of other underutilized methods for radical functionalization, namely radical trifluoromethylation of heterocyles. This thesis will show how an endeavor in total synthesis, namely the pursuit of palau'amine, can lead to discoveries and inventions that transcend its original goals and lead to lasting lessons in science.
Download or read book Progress Toward the Synthesis of dibromophakellin and Congeners written by Francisco Miguel Franco-Torres and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The pyrrole-imidazole alkaloid family of natural products illustrates the diversity of topographically unique molecules with potent biological activities that can be found in the marine environment. Thus, great interest for this class of compounds has developed leading to new synthetic methodologies and tactics to build these complex secondary metabolites. The overall objectives of this research project include the total synthesis of the phakellins and phakellstatins. First, we revisited the strategy developed in our group for the total synthesis of (+)-dibromophakellstatin and utilized it for the synthesis of its naturally occurring enantiomer and congeners. Second, we proposed and studied a new and more concise approach to the phakellstatins and phakellins based on a key C-H insertion process developed by Du Bois. Attempts to streamline the first synthesis of (+)-dibromophakellstatin proved to be quite challenging. Shortcomings in the reproducibility of some parts of the original strategy precluded us from completing and making more efficient the synthesis of the natural enantiomer ( - )-dibromophakellstatin. Fortuitously, our second generation approach though it presented itself as an efficient route to the phakellins and phakellstatins produced the undesired anti diastereomer of the key guanidine intermediate which precluded our study of the pivotal C-H insertion reaction.
Download or read book Studies Directed Toward the Synthesis of Palau amine and Axinellamines A D written by Jeremy T. Starr and published by . This book was released on 2001 with total page 416 pages. Available in PDF, EPUB and Kindle. Book excerpt: The use of spiro [2.4]hepta-4,6-diene-1-methanol 7 as a general precursor for the synthesis of highly functionalized cyclopentyl rings is described. Diene 7 was converted to its silyl protected 4-nitrile derivative 24 in 46% overall yield. The cyclopropyl ring of 24 reacted with soft carbanionic nucleophiles to give ring opened homo-conjugate addition products 25a-h in 76-97% yield without loss of optical purity. The addition products could be further manipulated by selective mono-hydrogenation to give 1,2 substituted cyclopentenes 26a-e in 85-96% yield. Diene 7 was used as a starting material for studies directed toward the synthesis of the stereochemically dense chloro-cyclopentyl core of palau'amine 1. Two advanced intermediates 50 and 72 were synthesized. Attempts to effect intramolecular chlorine transfer with 50 were unsuccessful. Attempted intramolecular chlorine transfer with 72 led, instead, to an oxygenated species resulting from oxygen radical trapping. The enantioselective synthesis of the stereochemically dense chloro-cyclopenty l core of axinellamines A-D 2-5 starting from 7 is also described. The core is synthesized in 4.6% yield over 24 steps. Nakamura's radical dehalogenative hydroxylation is applied for the first time to a cyclopropyl carbonyl iodide to give the ring-opened product in 86% yield. Bolm's meso-anhydride desymmetrization is used to introduce asymmetry in a norbornene intermediate. The final step is a diastereoselective intermolecular chlorination using Barton's methodology to achieve chlorine transfer in 76% yield.
Download or read book Studies Towards the Total Synthesis of Laulimalide and Neolaulimalide written by Adrian Longstaff and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Studies Towards the Total Synthesis of Galanthamine and the Total Synthesis of 2 Benzoyl 9 azabicyclo 4 2 1 non 2 ene written by Ravi Leckman Sumoreeah and published by . This book was released on 2002 with total page 436 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book From Biosynthesis to Total Synthesis written by Alexandros L. Zografos and published by John Wiley & Sons. This book was released on 2016-03-17 with total page 584 pages. Available in PDF, EPUB and Kindle. Book excerpt: Focusing on biosynthesis, this book provides readers with approaches and methodologies for modern organic synthesis. By discussing major biosynthetic pathways and their chemical reactions, transformations, and natural products applications; it links biosynthetic mechanisms and more efficient total synthesis. • Describes four major biosynthetic pathways (acetate, mevalonate, shikimic acid, and mixed pathways and alkaloids) and their related mechanisms • Covers reactions, tactics, and strategies for chemical transformations, linking biosynthetic processes and total synthesis • Includes strategies for optimal synthetic plans and introduces a modern molecular approach to natural product synthesis and applications • Acts as a key reference for industry and academic readers looking to advance knowledge in classical total synthesis, organic synthesis, and future directions in the field
Download or read book Part I Studies Towards a Total Synthesis of Laulimalide written by Upinder Singh and published by . This book was released on 1994 with total page 432 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Studies Toward the Enantioselective Synthesis of an Epidithiapiperazinedione Ring and Pummerer Reaction Chemistry written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Studies Towards the Total Synthesis of Canataxpropellane written by Konstantin Samarin and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Studies Towards the Total Synthesis of Neolaulimalide and Laulimalide and Synthesis of Novel Laulimalide Analogues written by J. K. Hutchinson and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Molecular Rearrangements in Organic Synthesis written by Christian M. Rojas and published by John Wiley & Sons. This book was released on 2015-09-25 with total page 528 pages. Available in PDF, EPUB and Kindle. Book excerpt: Designed for practitioners of organic synthesis, this book helps chemists understand and take advantage of rearrangement reactions to enhance the synthesis of useful chemical compounds. Provides ready access to the genesis, mechanisms, and synthetic utility of rearrangement reactions Emphasizes strategic synthetic planning and implementation Covers 20 different rearrangement reactions Includes applications for synthesizing compounds useful as natural products, medicinal compounds, functional materials, and physical organic chemistry
Download or read book Kinetic Control in Synthesis and Self Assembly written by Munenori Numata and published by Academic Press. This book was released on 2018-11-23 with total page 324 pages. Available in PDF, EPUB and Kindle. Book excerpt: Kinetic Control in Synthesis and Self-Assembly provides a unique overview of the fundamental principles, novel methods and practical applications for researchers across organic synthesis, supramolecular chemistry and materials sciences. The book examines naturally occurring molecular systems in which kinetic processes are more ubiquitous than thermodynamic processes, also exploring the control of reactions and molecular self-assemblies, through kinetic processes, in artificial systems. These methods currently play a crucial role for tuning materials functions. From organic synthesis, to supramolecular assemblies, and from restricted spaces, to material synthesis for hierarchical structures, the book offers valuable coverage for researchers across disciplines. Interesting topics include how to regulate kinetic pathways more precisely, essential molecular design for kinetic traps, and how molecular environments surrounding molecules (i.e., solvent, temperature, and pressure effects) influence kinetic control in reactions and self-assemblies. Describes the nature and potential applications of kinetic processes compared to thermodynamic processes Presents information useful to researchers active in molecular synthesis and self-assembly toward materials Collates coverage of kinetic control for synthesis and self-assembly, treated separately in literature
