Introduction of the (−)-Berkelic Acid Side Chain and Assignment of the C-22 Stereochemistry

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• 作者：Xiaoxing Wu ; Jingye Zhou ; Barry B. Snider
• 刊名：Journal of Organic Chemistry
• 出版年：2009
• 出版时间：August 21, 2009
• 年：2009
• 卷：74
• 期：16
• 页码：6245-6252
• 全文大小：1102K
• 年卷期：v.74,no.16(August 21, 2009)
• ISSN：1520-6904

文摘

A Kiyooka aldol condensation of an aldehyde with a trimethylsilyl ketene acetal and the oxazaborolidinone prepared from N-Ts-(S)-valine gives two of the four possible aldol adducts, which were oxidized and deprotected to complete the synthesis of (−)-berkelic acid and (−)-22-epi-berkelic acid. This synthesis establishes the absolute stereochemistry and assigns the stereochemistry at C-22. A biosynthetic pathway is proposed that is consistent with the known absolute stereochemistry at the quaternary carbon of spiciferone A, spicifernin, and berkelic acid and provides a simple explanation for the differing stereochemistry at C-18 and C-19 of spicifernin and berkelic acid.