Biomimetic Synthesis of the Tetracyclic Core of Berkelic Acid

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• 作者：Jingye Zhou ; Barry B. Snider
• 刊名：Organic Letters
• 出版年：2007
• 出版时间：May 24, 2007
• 年：2007
• 卷：9
• 期：11
• 页码：2071 - 2074
• 全文大小：110K
• 年卷期：v.9,no.11(May 24, 2007)
• ISSN：1523-7052

文摘

Acid-catalyzed condensation of 2,6-dihydroxybenzoic acid 3 with ketal aldehyde 14 in methanol at 25 C, followed by CH₂N₂ esterification,gave a 4:1:4:1 mixture of diastereomers 15b-18b in 60% yield. Equilibration of this mixture with TFA in CDCl₃ provided tetracycle 15b (83%yield) with the complete skeleton of berkelic acid. A similar condensation at 0 C afforded 15b-18b and a reduction product 19b, which wasprobably formed by a 1,5-hydride shift.