Studies on Catalytic Enantioselective Total Synthesis of Caprazamycin B: Construction of the Western Zone

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• 作者：Purushothaman Gopinath ; Takumi Watanabe ; Masakatsu Shibasaki
• 刊名：The Journal of Organic Chemistry
• 出版年：2012
• 出版时间：October 19, 2012
• 年：2012
• 卷：77
• 期：20
• 页码：9260-9267
• 全文大小：404K
• 年卷期：v.77,no.20(October 19, 2012)
• ISSN：1520-6904

文摘

We describe a simple and convenient synthesis of the western zone of caprazamycin B using two catalytic asymmetric reactions as key elements of our approach. Desymmetrization of 3-methylglutaric anhydride with the (S)-Ni₂-(Schiff base) complex as a catalyst furnished the chiral hemiester, and a thioamide-aldol reaction with mesitylcopper, (R,R)-Ph-BPE, and 2,2,5,7,8-pentamethylchromanol as a catalyst furnished the 尾-hydroxy thioamide in good yield and enantioselectivity. On further transformation, the thioamide functionality was converted to the corresponding 尾-hydroxy ester. Finally, a convergent synthesis of the western zone of caprazamycin B was achieved by connecting the hemiester, the 尾-hydroxy ester, and the 2,3,4-tri-O-methyl-l-rhamnose fragments.