Download or read book Progress Towards the Total Synthesis of Azaspiracids written by Jianyan Xu and published by . This book was released on 2006 with total page 458 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Synthetic Studies on Total Synthesis of Azaspiracid 3 written by Yong Chen and published by . This book was released on 2013 with total page 216 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Azaspiracid, a structurally complex marine toxin isolated from the mussel Mytilus edulis in Killary Harbor, Ireland, represents a new class of marine toxin unrelated to any previous known agent of shellfish poisoning. Due to the interesting biological activities and challenging structures, these natural products have drawn considerable attention among organic chemists. This thesis details the study towards the total synthesis of azaspiracid-3.

Download or read book Toward Total Synthesis of Azaspiracid 3 and Azaspiracid 34 written by Antony Akura Okumu and published by . This book was released on 2016 with total page 201 pages. Available in PDF, EPUB and Kindle. Book excerpt: Azaspiracids are a class of marine natural products that accumulate in shellfish. Azaspiracid 1 was first reported in 1995 in the Netherlands after a poisoning incident and this led to its isolation and structure elucidation in 1998. Biological activities of azaspiracids are not fully known and further studies are necessary. They occur in scarce quantities in nature and therefore synthesis in the laboratory would facilitate these studies. There is need to examine their molecular pharmacology and to develop better means of their detection. The C1-C21 (ABCD) and C22-C40 (FGHI) fragments have been synthesized in our lab. The key reactions toward these synthesis were Nozaki-Hiyama-Kishi reaction, the Chelation controlled Mukaiyama aldol reaction, and trioxadispiroketalization under thermodynamic conditions. Earlier work in the group also involved gold-catalyzed trioxadispiroketalization. Syntheses of analogs of azaspiracids are necessary for toxicological studies, and to enable better environmental regulation. The highlight of the synthesis of the ABCD fragment of azaspiracid 34 was a Wittig olefination, selective conjugate reduction that was carried out at different stages of synthesis, and NHK coupling.

Download or read book Studies Toward the Total Synthesis of Azaspiracid 1 written by Damien L. Kuiper and published by . This book was released on 2010 with total page 474 pages. Available in PDF, EPUB and Kindle. Book excerpt: Azaspiracid has generated an enormous amount of scientific interest in the fourteen years since its initial discovery. The structure contains a 6,5,6 bis-spiroketal, a [3.3.1] bicyclic ketal and a 6,5-spiroaminal linkage as key moieties. With 9 rings, 20 stereocenters and three alkenes, the azaspiracid immediately attracted the interest of the synthetic community. To date, two syntheses have been reported by the Nicolaou and Evans laboratories. An initial route to the C13-C19 aldehyde was plagued by a problematic 1,2 silyl migration. An improved route to the C13-C19 aldehyde was developed based on a modified protecting group strategy utilizing a PMP ketal. The improvements in the synthesis led to facile production of 250 mg of the key transoidal ABC ring bisspiroketal. This second generation route dramatically improved the efficiency of our synthesis, with the overall yield for the C13-C19 aldehyde increasing from 2% to 15%, which allowed the synthesis of over 250 mg the bisspiroketal. An optimized route to the FGHI spiroaminal was developed. A unique equilibration method for the construction of the anomerically-stabilized spiroaminal was discovered. After cleavage of the Cbz carbamate, an in situ tautomerization provided the desired doubly anomeric FGHI spiroaminal subunit. This transformed a total synthesis of FGHI spiroaminal into a process which could easily produce gram quantities of advanced intermediates requisite for the synthesis of azaspiracid. With an optimized synthesis of the FGHI ring system complete, a host of routes were investigated for the coupling of the C26-C40 fragment and C20-C25 fragment was developed. The C25-C26 bond was formed via an aldol condensation between FGHI methyl ester and the C20-C26 aldehyde. A novel TAS-F-mediated elimination was developed to provide the C26-C44 olefin. The Horner-Wadsworth-Emmons coupling of the C4-C19 lactol and C20-C40 ketophosphonate furnished the contiguous C4-C45 framework of azaspiracid-1. Davis oxidation of C20 provided the requisite oxidation state. The only challenges remaining are desilylation at C25 and cross metathesis at C4 to complete a formal synthesis of azaspiracid.

Download or read book Studies Toward the Total Synthesis of Azaspiracid 1 written by Brian Kenneth Raymer and published by . This book was released on 2004 with total page 312 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Part I Total Synthesis of Azaspiracid 3 written by Eriketi Loizidou and published by . This book was released on 2006 with total page 430 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Towards the Total Synthesis of Azaspiracid 3 written by Ding Yue and published by . This book was released on 2010 with total page 127 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: A novel tert-butyl lithium mediated ring closure strategy was described in the synthesis of the carbon skeleton of azaspiracid-3. This novel strategy disconnected the compound into two fragments. The synthesis of both fragments was described. Because of reactivity issues, some protecting group must be altered before the coupling could be achieved. After coupling, the key ring closure proceeded as expected. Some purification techniques were needed in order to achieve the total synthesis of azaspiracid-3.

Download or read book Effort Toward the Total Synthesis of Azaspiracid 3 written by Zhigao Zhang and published by . This book was released on 2013 with total page 210 pages. Available in PDF, EPUB and Kindle. Book excerpt: A NHK reaction to couple the C1-C21 and C22-C40 domains has also been proposed. The revised C22-C40 domain was achieved with a similar synthetic route.

Download or read book Progress in Total Synthesis written by Sarah Danishefsky and published by Springer. This book was released on 2014-05-14 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This series stemmed from a group of weekly seminars in our research group aimed at keeping its members abreast of recent developments in organic synthesis. The seminars tended to consist of several syntheses of natural products or related systems with particular emphasis on the general strategy inherent in the effort, new and interesting reactions which were utilized in the work, and specificity (or the lack of it) in arranging the relative stereochemistry of asymmetric centers and the geometry of double bonds. We found that natural products offered an attractive setting in which the larger science of organic chemistry could be put to crucial tests. A truly elegant synthesis is a major advance in that it epitomizes how an imaginative mastery of the course of organic reactions can achieve a sophisticated objective by an economy of operations. Indeed any successful synthesis of a reasonably complex product, however cumbersome and graceless, is an important event for those who delight in the problem-solving dimension of science.

Download or read book More Dead Ends and Detours written by Miguel A. Sierra and published by John Wiley & Sons. This book was released on 2013-07-11 with total page 297 pages. Available in PDF, EPUB and Kindle. Book excerpt: Success comes in many forms and in synthesis it can be a failure that results in their ultimate successful solutions. This long-awaited sequel to "Dead Ends and Detours" retains the proven concept while featuring over 20 new case studies of failed strategies and their (successful) solutions in natural product total synthesis. Additionally, computational models are used to discuss the problem in much more detail and to provide readers with additional information not found in the primary literature. The topics range from classic synthetic reactions (e.g. Diels Alder reaction), metal-mediated coupling reactions, metathesis, and asymmetric catalysis to the importance of protecting and activating groups. This book will benefit not only graduate students in organic chemistry but also advanced researchers as they gain knowledge derived from the step-by-step analysis of mistakes made in the past and, thus be able to improve their own chemical reaction planning. With its coverage of the most commonly applied reaction types, the book perfectly complements its predecessor, which focuses on general aspects, such as reactivity and selectivity.

Download or read book Total Synthesis of Azaspiracid 3 C20 epi azaspiracid 3 and Structural Definition of the Azaspiracids written by Nathaniel T. Kenton and published by . This book was released on 2018 with total page 179 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the work described here, the previously-accepted structure of azaspiracid-3 was synthesized for the first time and shown to be non-identical to the natural product. A series of experiments, culminating in a total synthesis of the true structure, identified the C20 stereochemistry of the natural product as being epimeric to the expected structure. Because 1H-NMR data for the C19 and C20 methine protons among all known azaspiracids are very similar, a general stereochemical correction at C20 for this family of molecules is necessary. 5.5 mg of purified, natural azaspiracid-3 was produced.

Download or read book Progress in Total Synthesis written by Sarah Danishefsky and published by . This book was released on 2014-08-15 with total page 280 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Progress in Total Synthesis written by Sarah Etheredge Danishefsky and published by . This book was released on 1971 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Synthesis of the ABCD Domain of the Azaspiracids written by Feng Zhou and published by . This book was released on 2010 with total page 139 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: This thesis describes synthetic efforts toward the total synthesis of the azaspiracid marine toxins. The investigation here focuses on the synthesis of the ABCD bis-spiroketal domain. Several different approaches have been developed. One features a gold catalyzed spiroketalization, which used a triple bond as an oxidation-state equivalent of a ketone to establish a spiroketal structure. In the D-ring synthesis, a Co(modp)2 (modp: 1-mophorlinocarbamoyl-4,4-dimethyl-1,3-pentadione) catalyzed oxyetherification was applied. In the recently revised synthetic route, the D-ring was constructed through a tandem asymmetric epoxidation and epoxide opening process.

Download or read book I Progress Towards the Asymmetric Synthesis of methylasparagine II Progress Towards the Total Synthesis of Diazonamide A written by Todd Ritsema and published by . This book was released on 1999 with total page 84 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Progress in Total Synthesis V 1 written by Sarah Etheredge Danishefsky and published by . This book was released on 1971 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Progress in Heterocyclic Chemistry written by G.W. Gribble and published by Elsevier. This book was released on 2002-10-14 with total page 478 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent progress in the chemistry of sulphur-containing indoles. Electrophile-induced 5-Endo cyclizations. Three-membered ring systems. Four-membered ring systems. Five-membered ring systems. Six-membered ring systems. Eight membered and larger rings.