Studies Directed Towards an Enantioselective Total Synthesis of the Marine Alkaloid Haouamine A PDF Download
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Author: Douglas R. Murken
Publisher:
ISBN:
Category :
Languages : en
Pages : 112
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Author: Douglas R. Murken
Publisher:
ISBN:
Category :
Languages : en
Pages : 112
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Author:
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ISBN:
Category :
Languages : en
Pages :
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Author: Cheryl Faye Lichti
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ISBN:
Category : Alkaloids
Languages : en
Pages : 186
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Author: William L. Brown
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ISBN:
Category : Alkaloids
Languages : en
Pages : 436
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Author: Jin Li
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ISBN:
Category : Alkaloids
Languages : en
Pages : 534
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Author: Vivek Badarinarayana
Publisher:
ISBN: 9780542722608
Category : Chemistry, Organic
Languages : en
Pages :
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This dissertation consists of two parts. The first part describes the enantioselective total synthesis of martinellic acid. The Martinella alkaloids have attracted considerable attention in the synthetic community over the past few years. This interest is due in large part to their unique structure and useful biological activity (bradykinin receptor antagonist). In model systems we have successfully used the [3+2] azomethine ylide-alkene cycloaddition to construct the heterocyclic core of these alkaloids. The enantioselective approach described herein also involves the azomethine ylide-alkene cycloaddition as a key step in the total synthesis. The pyrrolo[3,2-c]quinoline core of this alkaloid was constructed in an enantioselective fashion by the elaboration of an N-aryl pyrrolidinone, which was obtained via Pd-catalyzed aryl amination reaction using a non-racemic lactam. Pirkle's chiral solvating agent was successfully used to demonstrate the stereochemical integrity of not only the N-aryl lactam (obtained by Pd-catalyzed cross-coupling) but also the cycloaddition precursor and the cycloaddition product (tetracyclic pyrroloquinoline core). The tetracyclic compound obtained via the azomethine ylide-alkene cycloaddition was elaborated to ( - )-martinellic acid in 11 steps and 6% overall yield. The second part of this dissertation describes application of several novel organometallic complexes for carrying out various organic transformations. A fluorinated tris(pyrazolyl)borato silver(I) complex catalyzes the addition of ethyl diazoacetate to benzene rings, providing norcaradienes, which undergo electrocyclization to provide the corresponding cycloheptatriene (the Bu & huml;chner reaction). These reactions are surprisingly selective for addition to the aromatic moiety rather than C-H insertion. A copper complex containing a fluorinated triazapentadienyl ligand has been used to catalyze some carbene and nitrene addition and insertion chemistry. Nitrene addition occurs rapidly and with both aryl and alkyl substituted olefins providing the corresponding aziridine. The carbene transfer reactions that were attempted include C-H insertion, O-H insertion and N-H insertion, of which the latter two were very efficient.
Author: Noah Z. Burns
Publisher:
ISBN:
Category : Antineoplastic agents
Languages : en
Pages : 538
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In 2003, Zubia and coworkers elucidated the structures of haouamines A and B that were isolated from a marine tunicate species (Aplidium haouarianum) collected off the coast of southern Spain. Haouamine A was reported to have high activity against HT-29 human colon cancer cells (0.1 [mug/mL), while haouamine B exhibited only mild cytotoxic activity. The unprecedented structure of these polyphenolic alkaloids is the result of an indeno-tetrahydropyridine core containing an all-carbon quaternary center onto which is fused the hallmark structural feature of these natural products: a 3-aza-[7]-paracyclophane macrocycle. A significant amount of strain is present within this macrocyclic system resulting in the bending of the cyclophane arene out of planarity into a boat-like conformation. These molecules were found to exist in solution as two rapidly interconverting isomers, and this was originally proposed by the isolation chemists to be a result of either atropisomerism of the cyclophane arene or slowed pyramidal inversion at nitrogen. Chapter 1 describes a first-generation racemic total synthesis of haouamine A that was enabled by the development of a cascade annulation sequence to build the indeno-tetrahydropyridine in one step from a readily available allyl oxime and the application of a pyrone/alkyne Diels-Alder reaction to access the paracyclophane. Chapter 2 describes synthetic investigations into the biosynthesis of these natural products. These resulted in the discovery of a mild, abnormal Chichibabin pyridine synthesis and the development of an enantioselective total synthesis of haouamine A. Furthermore, this led to a revised phenylalanine-based biosynthetic hypothesis. Chapter 3 describes a second-generation total synthesis of haouamine A that allowed for the production of large amounts (>0.5g) of the natural product. This approach involves the transfer of point-chirality to planar-chirality in a programmed synthesis of haouamine A and its atropisomer, proving through synthesis that the isomeric nature of these natural products is not due to atropisomerism. Biological testing of these compounds as well as a number of analogs has also been accomplished in PC3 human prostate cancer cells.
Author: Mark L. Boys
Publisher:
ISBN:
Category : Asymetric analysis
Languages : en
Pages : 254
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Author: Theodore Mark Kamenecka
Publisher:
ISBN:
Category :
Languages : en
Pages : 336
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Author: Jeffrey Thomas North
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ISBN:
Category : Alkaloids
Languages : en
Pages : 502
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