A Unified Strategy for the Stereocontrolled Construction of Structurally Unusual Sesquiterpene Lactones. Asymmetric Synthesis of Vulgarolide and Deoxocrispolide
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- 作者：Leo A. Paquette ; Claudio F. Sturino ; Xiaodong Wang ; Jeremy C. Prodger ; and Dongsoo Koh
- 刊名：Journal of the American Chemical Society
- 出版年：1996
- 出版时间：June 19, 1996
- 年：1996
- 卷：118
- 期：24
- 页码：5620 - 5633
- 全文大小：662K
- 年卷期：v.118,no.24(June 19, 1996)
- ISSN：1520-5126
文摘
The bicyclic ketone (+)-17b reacts withvinylmagnesium bromide from its exo face, thus enablingexploitation of the anionic oxy-Cope rearrangement and directalkylation of the enolate so formed with ethyl iodoacetateto provide 24 in an efficient, stereocontrolled manner.Tricyclic lactone 26b, readily produced from24, proved tobe a common precursor to both synthetic targets. The constructionof vulgarolide (9) proceeded by transformingtheSEM group in 26b into a mesylate for the purpose ofconversion to epoxy acid 39 in advance of oxidativecleavageof the double bond. This transformation resulted in directconversion to 9 and its epimer 42. Centralto the companionsynthesis of deoxocrispolide (4) was the ability of37 to undergo the Michael addition of methoxide ion and of54to experience regiocontrolled dehydration to bridgehead olefin55 in a protocol that involves the smoothtranslocationof bridgehead unsaturation with concomitant functionalization as anallylic alcohol.