Formal Total Synthesis of (±)-Merrilactone A and Studies Towards Anislactones A PDF Download
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Author: Naim Nazef
Publisher:
ISBN:
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Languages : en
Pages :
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Book Description
Merrilactone A (1) and the epimeric anislactones A (2) and B (3) are sesquiterpene natural products that were first isolated from the dried pericarps of Illicium merrillianum (Fukuyama in 2000) and Illicium anisatum (Kouno in 1990), respectively. Merrilactone A (1) was identified as a potent nonpeptidal neurotrophic factor that strongly promotes neurite outgrowth in the culture of foetal rat cortical neurons and is a potential small molecule lead for the treatment of neurodegenerative disorders. Merrilactone A (1) together with 2 and 3, are highly complex cage-like structures that have established themselves as challenging and attractive targets in natural product synthesis. Presented in this research is a regiodivergent approach to both sets of natural products via the first known application of the defining transformation, an intramolecular tandem cyano-aldol cyclisation. We demonstrated an efficient route to the cyano-aldol product 303, which acted as the common intermediate to either natural product by orthogonal lactonisation sequences. This culminated in the successful synthesis of known intermediate 320, which represents the formal total synthesis of 1, and advanced tetracyclic intermediate 309, that is the full carbon skeleton of 2 and 3.
Author: Naim Nazef
Publisher:
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Category :
Languages : en
Pages :
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Book Description
Merrilactone A (1) and the epimeric anislactones A (2) and B (3) are sesquiterpene natural products that were first isolated from the dried pericarps of Illicium merrillianum (Fukuyama in 2000) and Illicium anisatum (Kouno in 1990), respectively. Merrilactone A (1) was identified as a potent nonpeptidal neurotrophic factor that strongly promotes neurite outgrowth in the culture of foetal rat cortical neurons and is a potential small molecule lead for the treatment of neurodegenerative disorders. Merrilactone A (1) together with 2 and 3, are highly complex cage-like structures that have established themselves as challenging and attractive targets in natural product synthesis. Presented in this research is a regiodivergent approach to both sets of natural products via the first known application of the defining transformation, an intramolecular tandem cyano-aldol cyclisation. We demonstrated an efficient route to the cyano-aldol product 303, which acted as the common intermediate to either natural product by orthogonal lactonisation sequences. This culminated in the successful synthesis of known intermediate 320, which represents the formal total synthesis of 1, and advanced tetracyclic intermediate 309, that is the full carbon skeleton of 2 and 3.
Author: Lei Shi
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Merrilactone A (1) was isolated in only 0.004% yield from the methanol extracts of the pericarps of Illicium merrillianum. Structural elucidation of Merrilactone A revealed a compact, cage-like pentacyclic architecture of high molecular complexity, featuring seven stereocentres, five of which as contiguous fully substituted carbon atoms, two [gamma]-lactones and a central oxetane ring. Merrilactone A also exhibits an important neurotrophic activity, significantly promoting neurite outgrowth in the primary cultures of foetal rat cortical neurons at very low concentrations. Structurally, merrilactone A is related to anislactones A and B, a pair of epimeric sesquiterpene dilactones discovered ten years earlier by Kouno and co-workers from the related Illicium anisatum plant. Fukuyama has shown that anislactone B can be converted into merrilactone A using a simple three step sequence, suggesting that the anislactones may be biogenetic precursors to merrilactone A. Described in this thesis are our research efforts directed towards developing a conceptually novel synthetic route enabling regiodivergent total synthesis of both anislactone A / B and merrilactone A. Our synthetic route (around 22 steps) features several key reactions, which include a [2+2] photo-cycloaddition reaction, Tiffeneau-Demjanov ring expansion and titanium(III) mediated radical cyclization.
Author: Atta-ur Rahman
Publisher: Elsevier
ISBN: 044464069X
Category : Science
Languages : en
Pages : 472
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Book Description
Studies in Natural Products Chemistry, Volume 55 covers rapid developments in spectroscopic techniques, also presenting advances in high-throughput screening techniques, including the new potential to isolate and determine the structures and biological activity of natural products and their applications in the field of new drug development. This ongoing series covers the synthesis, testing and recording of the medicinal properties of natural products, providing cutting-edge accounts of fascinating developments in the isolation, structure elucidation, synthesis, biosynthesis and pharmacology of a diverse array of bioactive natural products. - Focuses on the chemistry of bioactive natural products - Contains contributions by leading authorities in the field - Presents sources of new pharmacophores
Author: Jone Iriondo-Alberdi
Publisher:
ISBN:
Category :
Languages : en
Pages : 232
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Author: Michael Harmata
Publisher: Academic Press
ISBN: 0124058558
Category : Science
Languages : en
Pages : 345
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A classic in the area of organic synthesis, Strategies and Tactics in Organic Synthesis provides a forum for investigators to discuss their approach to the science and art of organic synthesis. Rather than a simple presentation of data or a secondhand analysis, we are given stories that vividly demonstrate the power of the human endeavor known as organic synthesis and the creativity and tenacity of its practitioners. Firsthand accounts of each project tell of the excitement of conception, the frustration of failure and the joy experienced when either rational thought or good fortune gives rise to the successful completion of a project. This book series shows how synthesis is really done, and we are educated, challenged and inspired by these accounts, which portray the idea that triumphs do not come without challenges. We also learn that we can meet challenges to further advance the science and art of organic synthesis, driving it forward to meet the demands of society, in discovering new reactions, creating new designs and building molecules with atom and step economies that provide solutions through function to create a better world. - Presents state-of-the-art developments in organic synthesis - Provides insight and offers new perspective to problem-solving - Written by leading experts in the field
Author: Lei Shi (Ph.D.)
Publisher:
ISBN:
Category :
Languages : en
Pages : 162
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Author: Karsten Meyer
Publisher:
ISBN:
Category :
Languages : en
Pages : 210
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Author: Michael F. Greaney
Publisher: Elsevier Inc. Chapters
ISBN: 012805607X
Category : Science
Languages : en
Pages : 58
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Book Description
This chapter describes the synthesis of two related sesquiterpenes, anislactone A and merrilactone A. We initially accessed a tetracyclic oxetane in the merrilactone series using a Paternò–Büchi reaction but found the compound to be too underfunctionalized to advance further. We then developed an approach based on reductive epoxide ring opening, whereby a fully elaborated C-ring epoxy-cyclopentane, containing five stereocenters, could undergo reductive epoxide cleavage when treated with Ti(III). The resulting tertiary radical then participates in a 5-exo-dig cyclization onto a pendant alkyne to afford the complete carbon skeleton of both natural products. From this point, orthogonal functionalization routes enabled the synthesis of both anislactone A and merrilactone A. A second-generation merrilactone A synthesis is then described, growing out of discoveries made over the course of the first route in the area of cyclopentannulation. An iodo-aldol method was used to develop an approach to the anislactone skeleton and succeeded in producing the BC bicycle with good stereocontrol and functional group tolerance. Further functionalization, however, did not prove possible due to excessive steric hindrance around the incorporated iodo group preventing any productive transformation. This problem was solved by switching the nucleophile in the tandem-aldol process to cyanide. The resulting domino cyanide-addition aldol cyclization was then successfully employed in the formal synthesis of merrilactone A, using a late-stage [2+2] photocycloaddition to access the D-ring.
Author: Zhaoyang Meng
Publisher:
ISBN:
Category :
Languages : en
Pages : 268
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Author: Michael Harmata
Publisher: John Wiley & Sons
ISBN: 1118057864
Category : Science
Languages : en
Pages : 395
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Book Description
The first authoritative book on using silver cations in organic chemistry—for catalysis and more! With more sophisticated catalytic methodologies fueling a resurgence in the study of cation-based chemistry, gold and platinum have stepped to the fore as the unique agents used to create new chemical reactions. Although these metals have become a primary focus of researchers in the field, another coinage metal that is often overlooked—but is as powerful as the others—is silver, a far less costly alternative to gold and platinum in aiding the development of new reactions. Making a strong case for the use of silver as a catalyst and structural element in organometal constructs, this authoritative book is the first to explore the benefits of using silver in organic chemistry by taking a close look at silver’s unique reactivity and structural characteristics for the development of new methods and materials. Silver in Organic Chemistry is: The first book to address catalysis using silver, whose use in organic chemistry is on the verge of exploding A resource for researchers wishing to do chemistry with silver cations, an area that stands in the shadow of gold chemistry, but still glistens, demonstrating that all that glitters is not gold—sometimes it’s silver! A guide for “first attempts” in working with silver cations Edited by a very well-respected, highly visible authority in this field Silver in Organic Chemistry promotes further scientific discussion by offering important new ways to examine the future possibilities of an emerging field. By elevating the importance of silver chemistry, this thought-provoking guide illustrates how this versatile metal can become an increasingly significant player in opening the door to new catalytic organic reactions and new organometal materials.
