Enantioselective Total Synthesis of Shahamin K and Enantioselective Total Synthesis of Quadrigemine C, and Psycholeine PDF Download
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Author: Alec Donald Lebsack
Publisher:
ISBN:
Category : Alkaloids
Languages : en
Pages : 622
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Author: Alec Donald Lebsack
Publisher:
ISBN:
Category : Alkaloids
Languages : en
Pages : 622
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Author: Leonard Sung
Publisher:
ISBN: 9780549716709
Category :
Languages : en
Pages : 38
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Book Description
Synthetic efforts toward the [3+1] quadrigemine alkaloids are described in this dissertation. Chapter 1 reviews the quadrigemine alkaloids from a historical perspective and discusses methods for the construction of their highly congested vicinal and diaryl all-carbon quaternary stereocenters. The application of these methods is featured in the presentation of the enantioselective syntheses of hodgkinsine and quadrigemine C.
Author: Cheng Bi
Publisher:
ISBN:
Category : Guanidine
Languages : en
Pages : 0
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Author: Elias J. Corey
Publisher: Elsevier
ISBN: 0128001518
Category : Science
Languages : en
Pages : 334
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Book Description
Written by world-renowned and best-selling experts, Nobel Laureate E. J. Corey and Laszlo Kurti, Enantioselective Chemical Synthesis offers an authoritative and comprehensive overview of the field's progress; the processes and tools for key formations; future development for complex, stereocontrolled (enantiomeric or diastereoisomeric) molecules; and valuable examples of multi-step syntheses. Utilizing a color-coded scheme to illustrate chemical transformations, Enantioselective Chemical Synthesis provides clear explanation and guidance through vital asymmetrical syntheses and insight into the next steps for the field. Researchers, professionals, and academics will benefit from this valuable, thorough, and unique resource. - In Part I, the authors present clearly, comprehensively and concisely the most useful enantioselective processes available to synthetic chemists. - Part II provides an extensive discussion of the most logical ways to apply these new enantioselective methods to the planning of syntheses of stereochemically complex molecules. This hitherto neglected area is essential for the advancement of enantioselective synthesis to a more rational and powerful level. - Part III describes in detail many reaction sequences which have been used successfully for the construction of a wide variety of complex target molecules - Clearly explains stereochemical synthesis in theory and practice - Provides a handy tool box for scientists wishing to understand and apply chiral chemical synthesis - Describes almost 50 real life examples of asymmetric synthesis in practice and examines how the chiral centers were introduced at key synthetic stages
Author: Paul Allan Renhowe
Publisher:
ISBN:
Category :
Languages : en
Pages : 296
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Author: 賽思
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Theodore Mark Kamenecka
Publisher:
ISBN:
Category :
Languages : en
Pages : 336
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Author: Petra Lindovská
Publisher:
ISBN:
Category :
Languages : en
Pages : 339
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Book Description
I. Total Synthesis of (-)-Hodgkinsine, (-)-Calycosidine, (-)-Hodgkinsine B, (-)-Quadrigemine C and (-)-Psycholeine The enantioselective total synthesis of (-)-hodgkinsine, (-)-calycosidine, (-)-hodgkinsine B, (-)- quadrigemine C, and (-)-psycholeine through a diazene-directed assembly of cyclotryptamine fragments is described. Our synthetic strategy enables multiple and directed assembly of intact cyclotryptamine subunits for convergent synthesis of highly complex bis- and tris-diazene intermediates. Photoextrusion of dinitrogen from these intermediates enables completely stereoselective formation of all C3a-C3a' and C3a-C7' carbon-carbon bonds and all the associated quaternary stereogenic centers. The synthesis of these complex diazenes was made possible through a new methodology for synthesis of aryl-alkyl diazenes using electronically attenuated hydrazine-nucleophiles in a silver-promoted addition to C3a-bromocyclotryptamines. The application of Rh- and Ir-catalyzed C-H amination reactions in complex settings were used to gain rapid access to C3a- and C7-functionalized cyclotryptamine monomers, respectively, used for diazene synthesis. II. Total Synthesis of (-)-Naseseazine C and Identification of its Biosynthetic Pathway The biogenesis of unsymmetrical dimeric diketopiperazines is investigated, in collaboration with the Sherman group at the University of Michigan. Sequencing and mining the genome of Streptomyces sp. CB MQ-030, known to produce unsymmetrical diketopiperazine dimers, allowed the identification of NasB, a cytochrome P450 responsible for catalyzing late-stage oxidative dimerization of brevianamide F into (-)-naseseazine C. The relative and absolute stereochemical assignment was confirmed via its total synthesis using highly convergent late-stage fragment union of complex diketopiperazines.
Author: Bob Lui
Publisher: Open Dissertation Press
ISBN: 9781361418536
Category :
Languages : en
Pages :
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This dissertation, "Enantioselective Total Synthesis of (-)-16-hydroxytriptolide" by Bob, Lui, 呂思奇, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled ENANTIOSELECTIVE TOTAL SYNTHESIS OF (-)-16-HYDROXYTRIPTOLIDE Submitted by Lui Bob for the degree of Doctor of Philosophy at The University of Hong Kong in August 2005 (-)-16-Hydroxytriptolide, a natural product isolated from the Chinese medicinal plant Tripterygium wilfordii Hook F (Lei Gong Teng), shows potent immunosuppressive, antileukemic, and antineuropathic activities. The goal of this project is to develop an enantioselective total synthesis of (-)-16-hydroxytriptolide. The results are summarized as follows. (1) A convergent and efficient synthetic scheme towards ()-16-hydroxytriptolide ()-3.19a has been developed using 2-methylanisole as the starting material. This route involves 21 steps in a 1.8% total yield. The key steps include (i) radical cyclization of ()-3.1 mediated by Mn(OAc) -2HO, (ii) 3 2 α,β-unsaturated γ-lactone construction of ()-3.3, (iii) side-chain installation by Sonogashira coupling from ()-Q5, and (iv) triepoxide construction from ()-3.12. (2) Following a similar synthetic scheme as that of ()-16-hydroxytriptolide, the enantioselective synthesis of (-)-16-hydroxytriptolide has been accomplished. This route involves 21 steps in a 2.4% total yield. The chirality of the trans-ring juncture of the tricyclic core was established by diastereoselective radical cyclization using (+)-8-phenylmenthol as the chiral auxiliary (73% yield, 34:1 dr). The chiral induction of side chain at C-15 was achieved by asymmetric hydrogenation (90% yield, 5.3:1 dr). (3) α-Halogenation reactions of 1,3-dicarbonyl compounds have been investigated to improve the synthetic efficiency of ()-16-hydroxytriptolide. The effect of Lewis acids was examined. In the absence of Lewis acid, the α-bromination of 1,3-dicarbonyl compounds 4.1f afforded both di-brominated 4.4f and mono-brominated products 4.3f in poor yield and selectivity (45%, 4.3f:4.4f = 1.5:1). However, when the α-bromination reaction was carried out in the presence of 0.3 equiv of Mg(ClO ) at room temperature, both the yield and the selectivity of 4 2 α-monobromination improved significantly (85%, 4.3f:4.4f = 14.8:1). (4) In connection to the asymmetric radical cyclization of 5.1 using (+)-8-phenylmenthol as the chiral auxiliary, a one-pot synthesis of its precursor, (S)-(-)-pulegone, has been developed. The reaction of LiClO (0.1 equiv), IBX (3 equiv), and (S)-(-)-citronellol in EtOAc under reflux for 17 h followed by basic treatment, led to a high chemical yield (90%) of (S)-(-)-pulegone. This provides an efficient and economical means to afford (+)-8-phenylmenthol for our (-)-16-hydroxytriptolide synthesis. OMe OMe O OMe H H Cl CO Me CO Me 2 (-)-3.3 (-)-Q5 O (-)-3.1 OH OMe O HO HO C H O O H O O (-)-3.19a (-)-3.12 O O O O O O Ph OEt Ph OEt Ph OEt Br Br Br 4.3f 4.4f 4.1f DOI: 10.5353/th_b3636945 Subjects: Terpenes Organic compounds - Synthesis Medicinal plants - Analysis
Author: Tse-Lok Ho
Publisher: Wiley-Interscience
ISBN:
Category : Science
Languages : en
Pages : 340
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Book Description
In recent years the intense activities of enantioselective synthesis have been reflected in the burgeoning and ingenious applications of such natural substances as carbohydrates, -amino acids and terpenes. A comprehensive summary of terpene-based synthesis is offered, focusing on synthetic efforts using transformed chiral synthons. The author provides analysis of synthetic strategies and discusses the intricacies of reaction courses. Along with the number and variety of natural products derived from chiral terpenes, numerous flow-charts aid in clearly delineating synthetic pathways.
