An Expedient Formal Total Synthesis of (-)-Diazonamide A via a Powerful, Stereoselective O-Aryl to C-Aryl Migration To Form the C10 Quaternary Center

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• 作者：Chi-Ming Cheung ; Frederick W. Goldberg ; Philip Magnus ; Claire J. Russell ; Rachel Turnbull ; Vince Lynch
• 刊名：Journal of the American Chemical Society
• 出版年：2007
• 出版时间：October 10, 2007
• 年：2007
• 卷：129
• 期：40
• 页码：12320 - 12327
• 全文大小：267K
• 年卷期：v.129,no.40(October 10, 2007)
• ISSN：1520-5126

文摘

During the course of studies on the synthesis of diazonamide A 1, an unusual O-aryl into C-arylrearrangement was discovered that allows partial control of the absolute stereochemistry of the C-10quaternary stereogenic center. Treatment of 30 with TBAF/THF gave the O-tyrosine ethers 31 and 32(1:1), which on heating each separately in chloroform at reflux rearranged to 33 and 34 in ratios of 84:16and 56:44, respectively. This corresponds to a 70% yield of the correct C-10 stereoisomer 33 and a 30%yield of the wrong C-10 stereoisomer 34. Attempts to convert 34 into 33 by ipso-protonation and equilibrationwere unsuccessful. Confirmation of the stereochemical outcome of the rearrangement was obtained byconverting 33 into 37, an advanced intermediate in the first synthesis of diazonamide A by Nicolaou et al.It was also found that the success of the above rearrangement is sensitive to the protecting group on boththe tryptophan nitrogen atom and the tyrosine nitrogen atom.