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Synthetic Studies Towards The Total Synthesis Of Lancifodilactone G
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Book Synopsis Synthetic Studies Towards the Total Synthesis of Lancifodilactone G. by : Sanil Sreekumar
Download or read book Synthetic Studies Towards the Total Synthesis of Lancifodilactone G. written by Sanil Sreekumar and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents our studies towards the first total synthesis of the novel anti- HIV agent lancifodilactone G, which has a highly unusual aliphatic enol. The first chapter provides a survey of architecturally diverse nortriterpenoids that were isolated from the Schisandraceae family. A proposed biosynthetic pathway for lancifodilactone G and closely related natural products provides a rationale for the formation of the consecutive 7/8/5 fused carbo cycles that are unique to Schisandra nortriterpenoids. Chapter 1 goes on to outline the reported strategies to access the core of lancifodilactone G and concludes with a retrosynthetic analysis proposed by the Evans group, which includes a biosynthetically inspired single-pot polycyclisation reaction. Chapter 2 describes the highly stereocontrolled synthesis of the eastern fragment (F-G rings) using transition metal-mediated Pauson-Khand reaction. This chapter also reviews the metal-mediated diastereoselective Pauson-Khand reaction directed by the stereogenic centre at C2, with the ample illustration to total synthesis. Attempted strategies for the assembly of the bicyclic cyclopentanone motif via a dienyl Pauson-Khand reaction of silicon- and oxygen- tethered diene-enes are presented. The failure of these strategies at different stages of the synthesis resulted in the exploration of a classical Pauson-Khand approach, which successfully furnished the eastern fragment. Finally, a second-generation synthesis is described which provided the fully functionalised eastern fragment with improved efficiency and overall yield. Chapter 3 discusses the successful synthesis of the western fragment (B-C rings) using a diastereoselective [4+3] cycloaddition strategy. Attempted strategies for the synthesis of the key 2,3-disubstituted furan derivative are presented, which was achieved via a hetero Pauson- Khand reaction. This chapter includes a brief account of the classical [4+3] cycloaddition reactions of furans using an in situ generated oxyallyl cation and also employing vinyl carbenoids in the metal-catalysed version. The review also highlights the application of the [4+ 3] cycloaddition reaction in the expeditious assembly of functionalised 7-membered rings that occur in a number of important biologically active natural products. The third chapter goes on to describe the application of these cycloaddition reactions in the synthesis of the fully functionalised western fragment of Lancifodilactone G. Chapter 4 describes a model study aimed at expediting the synthesis of the western fragment using a rhodium-catalysed allylic substitution reaction. A brief mechanistic discussion on unique aspects of the allylic alkylation reaction is illustrated. Chapter 4 concludes by outlining the coupling strategy for eastern and western fragments and the end game studies for the completion of the synthesis of lancifodilactone G.
Book Synopsis Synthetic Studies Towards the Total Synthesis of Altohyrtin A by : Stuart Edward Bradley
Download or read book Synthetic Studies Towards the Total Synthesis of Altohyrtin A written by Stuart Edward Bradley and published by . This book was released on 1998 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Studies on the Total Synthesis of Lancifodilactone G by : Ashley A. Katana
Download or read book Studies on the Total Synthesis of Lancifodilactone G written by Ashley A. Katana and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Lancifodilactone G is a member of a unique set of eight ring systems that expresses anti-HIV, anti-tumor, and anti-hepatitis activities. A pathway has been proposed to synthesize the two halves of this complicated molecule with the hope of joining them to make the natural product. The synthesis of the eastern sector of the molecule has been focused on the formation of a five-membered lactone 8. This will serve as the base of the D and H rings of the system. The rings will be formed by two separate fragments 9 and 11. Completion of the proposed synthesis will also lead to the discovery and characterization of new compounds. Fragment 9 has been nearly accomplished through seven steps of a nine step path, but the yield dropped with the hydrogenolysis to cleave a benzyl protecting group. Fragment 11 has progressed through two steps of a six step synthesis, as it proved difficult to work with the unstable 4-methoxybenzyl chloride to protect an alcohol. Concerning the western sector of the molecule, we have been working on a model study of the deoxygenation of a highly functionalized enone 46. The synthesis of this sector has advanced 22 steps along the pathway, but there is no current documentation on the removal of a carbonyl oxygen that is compatible with the acid sensitive acetal functionality present in our molecule. Completion of the western sector should follow the discovery of a new method. We have currently completed the first three optimized steps of a six step synthesis. The completed three steps have introduced unknown compounds high yields that have enlisted further characterization.
Book Synopsis Synthetic Studies Towards the Total Synthesis of Phyllanthocin by : Andrew John King
Download or read book Synthetic Studies Towards the Total Synthesis of Phyllanthocin written by Andrew John King and published by . This book was released on 1990 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Synthetic Studies written by Qiang Han and published by . This book was released on 2005 with total page 286 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Synthetic Studies Toward the Total Synthesis of Magellanine by : Denis Robert St. Laurent
Download or read book Synthetic Studies Toward the Total Synthesis of Magellanine written by Denis Robert St. Laurent and published by . This book was released on 1988 with total page 294 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Studies Towards the Total Synthesis of 15G256upsilon by :
Download or read book Studies Towards the Total Synthesis of 15G256upsilon written by and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Part I. Total Synthesis and Structural Revision of (±)-Tricholomalides A and B. Part II. Synthetic Studies Towards (+)-Cortistatin A by : Zhang Wang
Download or read book Part I. Total Synthesis and Structural Revision of (±)-Tricholomalides A and B. Part II. Synthetic Studies Towards (+)-Cortistatin A written by Zhang Wang and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The first part describes the total synthesis and structural revision of (±)-tricholomalides A and B. The synthetic strategy started from a homo-Robinson annulation, followed by a ketene-olefin [2+2] cycloaddition to introduce the lactone ring. Then a Grignard-type reaction appended the isopropenyl moiety, and the synthesis of tricholomalides A and B was achieved. During the course of synthesis, the structures of tricholomalides A and B were revised. The second part describes the synthetic studies towards (+)-cortistatin A, especially the A ring functionalization. The C3 nitrogen was introduced by azide displacement, and C2 hydroxyl was built up by Luche reduction. The challenging C1 functionalization was achieved with bromine-induced methoxymethyl deprotection, and some interesting chemistry was found in this system. The synthetic endeavor set a promising stage for the total synthesis of cortistatin A.
Book Synopsis Protecting Group Free Total Synthesis of (-)-palmyrolide A and Synthetic Studies Towards the Syntheses of Taumycin A by : Tara Devi Newar
Download or read book Protecting Group Free Total Synthesis of (-)-palmyrolide A and Synthetic Studies Towards the Syntheses of Taumycin A written by Tara Devi Newar and published by . This book was released on 2016 with total page 244 pages. Available in PDF, EPUB and Kindle. Book excerpt: A full account of our synthetic work toward the first total synthesis of the neuroactive marine macrolide (-)-palmyrolide A is highlighted. Our first-generation approach aimed to unlock the unknown C(5)- C(7) stereochemical relationship via the synthesis of four diastereomers of palmyrolide A aldehyde, a known degradation product. When these efforts provided inconclusive results, recourse to synthesizing all possible stereocombinations of the 15-membered macrolide was undertaken. These studies were critical in confirming the absolute stereochemistry, yielding the first total synthesis of (+)-ent palmyrolide A. Subsequent to this work, the first protecting group-free total synthesis of natural (-)-palmyrolide A is also described. After the successful total synthesis, a small library of synthetic (-)-palmyrolide A diastereomers, analogues, and acyclic precursors have been synthesized and examined with respect to their interaction with voltage-gated sodium channels (VGSCs). A detailed NMR and computational analysis of four diastereomers revealed that none had the same combination of shape and electrostatic potential as exhibited by natural (-)-palmyrolide A. These data indicated that the relative configuration about the tert-butyl and methyl substituents and an intact macrolide is required a prerequisite for biological function. Synthetic work towards the total synthesis of the lipodesipeptides Taumycins A and B was investigated. Enantiomeric isoleucine residues and the unique side chain consisting of a methyl stereocenter imbedded between two trisubstituted E-olefins are key features of this structurally intriguing natural product. By first targeting the taumycin aldehyde, the relative configuration of the macrocycle was identified in 2014 by the Maio laboratory. With the known relative configuration in hand, A total synthesis campaign was initiated, making use of a stereoselective aldol union between a pseudo-symmetrical side chain with orthogonal protecting groups, as a means to access the two possible diastereomeric combinations of the desired natural product. Synthetic studies to synthesize the pseudosymmetric side chain exploring a variety of methods, including an sp3-sp2 Negishi cross coupling reaction, are described.
Book Synopsis Synthetic Studies Toward the Total Synthesis of Lomaiviticin A and B by : Virginia Heather Sharron Grant
Download or read book Synthetic Studies Toward the Total Synthesis of Lomaiviticin A and B written by Virginia Heather Sharron Grant and published by . This book was released on 2006 with total page 192 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Synthetic Studies Toward the Total Synthesis (±)-ajmaline and the Development Of, Investigation Into, and Application of a Phosphine-catalyzed [4+1] Annulation by : Brian Richard Blank
Download or read book Synthetic Studies Toward the Total Synthesis (±)-ajmaline and the Development Of, Investigation Into, and Application of a Phosphine-catalyzed [4+1] Annulation written by Brian Richard Blank and published by . This book was released on 2014 with total page 325 pages. Available in PDF, EPUB and Kindle. Book excerpt: Several synthetic routes toward the synthesis of the indole alkaloid (±)-ajmaline have been explored. The retrosynthetic plan was devised around two key transformations, one being a tandem aza-Michael-Michael reaction, and the other a phosphine-catalyzed [4+2] annulation. While these approaches have not allowed for the completion of ajmaline, they have provided a great deal of insight into the chemistry of many intermediates. For example, it was discovered that following installation of the D-ring, functionalization of the tricyclic scaffold to deliver a precursor for the aza-Michael-Michael sequence was a futile undertaking. As such, the necessary functionality had to be installed prior to the [4+2] annulation. For this purpose, ethyl 3-allyl-1H-indole-2-carboxylate was prepared by way of a stepwise Japp-Klingemann reaction, and a subsequent Fischer indolization. Successful conversion of this compound into the N-sulfonyl imine required the employment of 2,6-lutidine to impede isomerization of the allyl moiety. This imine was converted into the tetrahydropyridine through a phosphine-catalyzed [4+2] annulation with ethyl 2-methyl-2,3-butadienoate. Cross-metathesis with methyl acrylate provided the first precursor to the desired aza-Michael-Michael reaction sequence. Unfortunately, only mono-Michael addition was observed when this substrate was employed in the reaction, providing a tetracyclic structure instead of the desired pentacyclic scaffold. As a result, we are currently pursuing tricyclic derivatives that feature either alternative Michael donors or an increased strength of the second Michael acceptor. A phosphine-catalyzed [4+1] annulative rearrangement has been developed to prepare 3-pyrrolines from allenylic carbamates through phosphonium diene intermediates. This methodology was employed to synthesize an array of 1,3-disubstituted- and 1,2,3-trisubstituted-3-pyrrolines, including the often difficult to prepare 2-alkyl variants. A mechanistic investigation employing allenylic acetates and mononucleophiles unexpectedly unveiled that a phosphine-catalyzed [4+1] reaction previously reported by Tong might not occur through a phosphonium diene as was proposed, but rather involves multiple mechanisms working in concert to construct cyclopentene products. Consequentially, our phosphine-catalyzed rearrangement is most likely the first reaction that unequivocally forms a phosphonium diene intermediate along the reaction pathway. Concise formal syntheses of pyrrolizidine alkaloids (±)-trachelanthamidine and (±)-supinidine were completed, demonstrating the synthetic utility of this newly developed reaction.
Book Synopsis Model Studies Towards the Total Synthesis of Lyconadin A Via an Acyl Radical Cascade Reaction by : Koudi Zhu
Download or read book Model Studies Towards the Total Synthesis of Lyconadin A Via an Acyl Radical Cascade Reaction written by Koudi Zhu and published by . This book was released on 2006 with total page 74 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lyconadin A is an alkaloid possessing a unique structure and antitumor activity. The total synthesis of Lyconadin A was proposed via an acyl radical cascade reaction. To investigate the possibility and stereoselectivity of the cascade cyclization, phenyl selenoester 16 was chosen as a model substrate to study the 7-exo-5-exo radical cyclization. A synthetic route to phenyl selenoester 16 was developed. The 7-exo-5-exo radical cyclization was found to occur with a high yield and excellent stereoselectivty. Attempts were also tried to synthesize another radical precursor 14 albeit with less success. A synthetic pathway to the synthesis of 14 as well as its potential use in the context of the synthesis of Lyconadin A was proposed.
Book Synopsis Studies Towards the Total Synthesis of Merrilactone A by : Jone Iriondo-Alberdi
Download or read book Studies Towards the Total Synthesis of Merrilactone A written by Jone Iriondo-Alberdi and published by . This book was released on 2007 with total page 232 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Total Synthesis of Epicolactone and Synthetic Studies on Mutanobactins A and C by : Alberto Kravina
Download or read book Total Synthesis of Epicolactone and Synthetic Studies on Mutanobactins A and C written by Alberto Kravina and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Model Studies Toward the Total Synthesis of Lycolucine and the Development of Various Synthetic Methods by :
Download or read book Model Studies Toward the Total Synthesis of Lycolucine and the Development of Various Synthetic Methods written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A study directed at the total synthesis of lycolucine was carried out and discussed within. Various synthetic routes were attempted toward this end. The synthetic schemes all revolve around utilization of the well-established N-acylpyridinium salt chemistry as the foundational method of synthesis. One approach employs metathesis chemistry to attempt the construction of a key carbon-carbon bond. The development of a one-pot alkene homologation was discovered. This investigation reveals the ability to homologate terminal alkenes by one carbon utilizing the 2nd generation Grubbs catalyst. Various aromatic and non-aromatic substrates were used to demonstrate the scope of the reaction, with yields ranging from 65% to 86%. This work reveals the first example of a one-pot one carbon alkene homologation from an existing terminal alkene. A few synthetic methods, such as the formation of indolizidine scaffolds and amino alcohols, are also discussed. Various compounds were realized that could potentially lead to the development of more complex structures.
Download or read book Part I written by Ustun Bekir Sunay and published by . This book was released on 1984 with total page 388 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Synthetic Studies Toward the Total Synthesis of Amphidinolide B1 by : Wei Zhang
Download or read book Synthetic Studies Toward the Total Synthesis of Amphidinolide B1 written by Wei Zhang and published by . This book was released on 2006 with total page 660 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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