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Strategies and Tactics in Organic Synthesis

Chapter 7. Total Syntheses of Hamigeran B

By: Michel Miesch,Tania Welsch,Vincent Rietsch,Laurence Miesch

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Strategies and Tactics in Organic Synthesis

Chapter 7. Total Syntheses of Hamigeran B

By: Michel Miesch,Tania Welsch,Vincent Rietsch,Laurence Miesch

This chapter describes various syntheses of hamigeran B. Different methodologies were developed, and for our part, we achieved a formal synthesis of (±)-hamigeran B involving an intramolecular alkynylogous Mukaiyama aldol reaction promoted by dual Lewis acid activation as a key step. This unexpected reaction was discovered by treating a ketone with TBSOTf/NEt3 in order to obtain the corresponding silyl enol ether, which, in fact, evolves toward a new type of intramolecular aldol reaction. Fortunately, the study of the scope and limitations of this reaction allowed us to set up an original synthetic route to hamigeran B. Our results indicated clearly that serendipity plays a key role in the development of original strategies in organic synthesis.

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34

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Elsevier Inc. Chapters

Published Date

ISBN 10

012805610X

ISBN 13

9780128056103

Studies in Natural Products Chemistry

Chapter 9. 14β-Hydroxypregnanes from Succulent Plants Belonging to Hoodia gordonii and Caralluma Genus: Extraction, Biological Activities, and Synthesis

By: Yatin J. Shukla,Ikhlas A. Khan,Philippe Geoffroy,Michel Miesch

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Studies in Natural Products Chemistry

Chapter 9. 14β-Hydroxypregnanes from Succulent Plants Belonging to Hoodia gordonii and Caralluma Genus: Extraction, Biological Activities, and Synthesis

By: Yatin J. Shukla,Ikhlas A. Khan,Philippe Geoffroy,Michel Miesch

Caralluma and Hoodia are genera of succulent plants belonging to the subfamily of Asclepiadoideae in the family of Apocynaceae. Caralluma is distributed in dry regions of tropical Asia and Africa, majority of species being indigenous to the Indian subcontinent and the Arabian Peninsula. The genus Hoodia is mainly found in the Kalahari desert regions in Southern Africa. We focus on Caralluma adscendens var. fimbriata and Hoodia gordonii due to their popularity and growing commercial interest during the past 20 years. Indeed, it was claimed that these succulent plants contain bioactive compounds, especially 14β-hydroxypregnane derivatives, which showed appetite-suppressant activity and weight loss properties. This chapter describes the isolation, biological properties, and synthesis of 14β-hydroxypregnane derivatives found in C. adscendens var. fimbriata and H. gordonii.

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31

Publisher

Elsevier Inc. Chapters

Published Date

ISBN 10

012808474X

ISBN 13

9780128084748