Approaches to the quaternary stereocentre and to the heterocyclic core in diazonamide A using the Heck reaction and related coupling reactions
Approaches to the quaternary stereocentre and to the heterocyclic core in diazonamide A using the Heck reaction and related coupling reactions
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DOI：
10.1039/b609604b
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发表时间：
2006-01-01
影响因子：
3.2
通讯作者：
Pattenden, Gerald
中科院分区：
文献类型：
--
作者：
Booker, James E. M.;Boto, Alicia;Pattenden, Gerald
在针对重氮酰胺 A 中心的四元中心（早期结构 2；修改后的结构 1）的模型研究中，在 Heck 反应条件下，烯烃取代的碘代芳基 4、13、18 和 23 的环化显示分别生成相应的苯并二氢呋喃 5、苯并呋喃酮 14 以及羟吲哚 19 和 24，产率分别为 50-80%产量。然后对苯并二氢呋喃 5 进行进一步操作，得到中间体 30、33 和 39，它们构成重氮酰胺 A 中恶唑-吲哚杂环核心的部分。尝试从由 44 和 45 制备的前体 46a 进行相应的 13-exo-trig Heck 环化，得到 47，但没有成功。在尝试从酯 57 和相关醚 59 进行 Heck 环化时获得了类似的结果。用 Pd(OAc)(2)、PPh3 和 Ag2CO3 处理色烯取代的碘代芳基 62 得到了结晶固体状的螺环 64。 X 射线晶体结构分析表明，64 中的四元中心具有与重氮酰胺 A (1) 中存在的相同构型。
In model studies towards the quaternary centre at the heart of diazonamide A (early structure 2; revised structure 1), cyclisations of the alkene-substituted iodoaryls 4, 13, 18 and 23, under Heck reaction conditions, were shown to lead to the corresponding benzodihydrofuran 5, benzofuranone 14 and the oxindoles 19 and 24 respectively, in 50-80% yield. Further manipulation of the benzodihydrofuran 5 then led to the intermediates 30, 33 and 39, which make up parts of the oxazole-indole heterocyclic core in diazonamide A. Attempts to perform a corresponding 13-exo-trig Heck cyclisation from the precursor 46a, prepared from 44 and 45, leading to 47 were not successful. A similar outcome was obtained during attempts to effect Heck cyclisations from the ester 57 and the related ether 59. Treatment of the chromene-substituted iodoaryl 62 with Pd(OAc)(2), PPh3 and Ag2CO3 led to the spirocycle 64 as a crystalline solid. X-Ray crystal structure analysis established that the quaternary centre in 64 had the same configuration as that present in diazonamide A (1).