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Applications of samarium(II) iodide-...

George, Kelly M.

Applications of samarium(II) iodide-promoted 8-membered ring cyclization reactions in natural product total synthesis: I. The total synthesis of (+)-isoschizandrin. II. Progress toward the total synthesis of variecolin.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Applications of samarium(II) iodide-promoted 8-membered ring cyclization reactions in natural product total synthesis: I. The total synthesis of (+)-isoschizandrin. II. Progress toward the total synthesis of variecolin.
Author:	George, Kelly M.
Description:	344 p.
Notes:	Source: Dissertation Abstracts International, Volume: 66-06, Section: B, page: 3134.
Notes:	Supervisor: Gary A. Molander.
Contained By:	Dissertation Abstracts International66-06B.
Subject:	Chemistry, Organic.
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3179736
ISBN:	0542198797

Applications of samarium(II) iodide-promoted 8-membered ring cyclization reactions in natural product total synthesis: I. The total synthesis of (+)-isoschizandrin. II. Progress toward the total synthesis of variecolin.
George, Kelly M.

Applications of samarium(II) iodide-promoted 8-membered ring cyclization reactions in natural product total synthesis: I. The total synthesis of (+)-isoschizandrin. II. Progress toward the total synthesis of variecolin. - 344 p.

Source: Dissertation Abstracts International, Volume: 66-06, Section: B, page: 3134.

Thesis (Ph.D.)--University of Pennsylvania, 2005.

(+)-Isoschizandrin is one of nearly forty dibenzocyclooctadiene lignans isolated from the fruit of Schizandra chinensis. The extract from this lignan-rich plant finds use in traditional medicine as an antitussive and also displays anti-ulcer activity in rats. Synthesis of the eight-membered ring of (+)-isoschizandrin, possessing the attendant functionality and stereochemistry, provides a significant synthetic challenge. The 13-step synthesis of (+)-isoschizandrin reported herein features a novel samarium(II) iodide-promoted 8-endo ketyl-olefin coupling to assemble the eight-membered ring present in the target concomitantly with the required functionality and stereochemistry.

ISBN: 0542198797Subjects--Topical Terms:

193634
Chemistry, Organic.

Applications of samarium(II) iodide-promoted 8-membered ring cyclization reactions in natural product total synthesis: I. The total synthesis of (+)-isoschizandrin. II. Progress toward the total synthesis of variecolin.
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245 1 0 $a Applications of samarium(II) iodide-promoted 8-membered ring cyclization reactions in natural product total synthesis: I. The total synthesis of (+)-isoschizandrin. II. Progress toward the total synthesis of variecolin.
300 $a 344 p.
500 $a Source: Dissertation Abstracts International, Volume: 66-06, Section: B, page: 3134.
500 $a Supervisor: Gary A. Molander.
502 $a Thesis (Ph.D.)--University of Pennsylvania, 2005.
520 # $a (+)-Isoschizandrin is one of nearly forty dibenzocyclooctadiene lignans isolated from the fruit of Schizandra chinensis. The extract from this lignan-rich plant finds use in traditional medicine as an antitussive and also displays anti-ulcer activity in rats. Synthesis of the eight-membered ring of (+)-isoschizandrin, possessing the attendant functionality and stereochemistry, provides a significant synthetic challenge. The 13-step synthesis of (+)-isoschizandrin reported herein features a novel samarium(II) iodide-promoted 8-endo ketyl-olefin coupling to assemble the eight-membered ring present in the target concomitantly with the required functionality and stereochemistry.
520 # $a Over the last 25 years, samarium(II) iodide has been employed as a versatile reagent to effect a wide array of functional group transformations. Consequently, SmI2 has been applied in a large number of total synthetic efforts with great success. The construction of a variety of different ring systems can be achieved by exploiting the mild and selective nature of SmI2. Specifically, SmI2 is capable of effecting medium-membered ring cyclizations, which have posed a significant challenge to chemists in the past. The results reported herein highlight the power of samarium(II) iodide to assemble the eight-membered rings present in the natural products (+)-isoschizandrin and variecolin.
520 # $a The goal of our research is to utilize a samarium(II) iodide-promoted annulation procedure for the construction of the cyclooctanyl core. Synthesis of the key hemiketal has been obtained in a model system. The success of this key reaction further demonstrates the utility of samarium(II) iodide to generate medium-sized rings in complex systems.
520 # $a The sesterterpenoid variecolin was first isolated by Hensens in 1991 from the fermentation of the fungus Aspergillus variecolor. Variecolin is an antagonist of the angiotensin-II AT1 receptor and has been shown to be a potent immunosuppressant. Despite such interesting properties, variecolin has received little synthetic attention, and so it is an active target for total synthesis in our laboratories.
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773 0 # $g 66-06B. $t Dissertation Abstracts International
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790 1 0 $a Molander, Gary A., $e advisor
791 $a Ph.D.
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