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烟云听雨

铁杆木虫 (正式写手)

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Stemona alkaloids 1–3 have been the targets of successful synthetic campaigns by this (24–26) and other groups (2737),although the synthesis of neotuberostemonine 4 has yet to be realized.Our own interest in this class of natural products was driven initially by the challenges presented by these alkaloids in such a total synthesis context. To that end, we carried out a first-generation
formal synthesis of stenine (26). In the course of this work,we discovered that it was possible to streamline the synthesis by combining two Lewis acid-promoted reactions, a Diels–Alder and an intramolecular Schmidt reaction, into a tandem reaction sequence (Scheme 1). Realizing the general value of this process for heterocyclic synthesis, this methodology was further developed into a general intermolecular variant (38) that was in turn reapplied to the problem of Stemona alkaloid synthesis. This methodology enabled efficient and practical total syntheses of both stenine (25) and neostenine (24) that yielded ample quantities for biological study (9 and 13 steps from commercially available starting materials, respectively). This Diels–Alder/Schmidt reaction sequence also provided straightforward access to Stemona alkaloid-like scaffolds for the parallel synthesis of a diverse compound collection (39).
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zuodg

铁杆木虫 (正式写手)

有为青年

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sltmac(金币+1): 多谢交流~~ 2011-06-06 18:18:22
烟云听雨(金币+15, 翻译EPI+1): 谢谢 2011-06-06 18:44:27
百部生物碱1-3是(24-26)及其他研究组(2737)成功实现化学合成的范例,然而neotuberostemonine 4还没有取得成功。该类生物碱化学全合成是摆在我们面前的一个挑战,这也是我们对该类天然产物的兴趣所在。为此,我们首先合成了stenine (26).在该项工作中,我们发现通过2个Lewis酸促进反应,1个Diels-Alder反应和一个分子间Schmidt反应组合起来,形成连续反应,可以精简反应流程(流程图1)。在意识到异环合成的价值之后,该方法的进一步发展形成了分子间变异(38),该方法反过来应用于Stemona生物碱合成。该方法能够高效切实的合成大量的stenine(25)与neostenine(24),可用于生物学研究(商业起始原料分别需要9部和13部反应)。Diels–Alder/Schmidt reaction的反应顺序也提供了直接合成stemona生物碱类似结构单元的捷径,合成了多种化合物集合。
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2楼2011-06-06 17:22:05
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