An expedient formal total synthesis of (-)-diazonamide A via a powerful, stereoselective O-aryl to C-aryl migration to form the C10 quaternary center
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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DOI：
10.1021/ja0744448
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发表时间：
2007-10-10
影响因子：
15
通讯作者：
Lynch, Vince
中科院分区：
文献类型：
--
作者：
Cheung, Chi-Ming;Goldberg, Frederick W.;Lynch, Vince
在合成重氮酰胺A1的研究过程中，发现了一种不常见的O-芳基到C-芳基的重排，它允许部分控制C-10四元立体中心的绝对立体化学。用四氢呋喃/四氢呋喃处理30个样品，得到31个和32个邻位酪氨酸醚(1：1)，分别在回流氯仿中加热时，分别以84：16和56：44的比例重排到33和34。这相当于正确的C-10立体异构体33的产率为70%，错误的C-10立体异构体的产率为30%。通过质子化和平衡将34转化为33的尝试没有成功。重排的立体化学结果通过将33转化为37而得到确认，37是Nicolaou等人首次合成重氮酰胺A的高级中间体。研究还发现，上述重排的成功对色氨酸氮原子和酪氨酸氮原子上的保护基团都很敏感。
During the course of studies on the synthesis of diazonamide A1, an unusualO-aryl intoC-aryl rearrangement was discovered that allows partial control of the absolute stereochemistry of the C-10 quaternary stereogenic center. Treatment of30with TBAF/THF gave theO-tyrosine ethers31and32(1:1), which on heating each separately in chloroform at reflux rearranged to33and34in ratios of 84:16 and 56:44, respectively. This corresponds to a 70% yield of the correct C-10 stereoisomer33and a 30% yield of the wrong C-10 stereoisomer34. Attempts to convert34into33byipso-protonation and equilibration were unsuccessful. Confirmation of the stereochemical outcome of the rearrangement was obtained by converting33into37, 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 both the tryptophan nitrogen atom and the tyrosine nitrogen atom.