Asymmetric Synthesis of Allylsilanes by the Borylation of Lithiated Carbamates: Formal Total Synthesis of (-)-Decarestrictine D
Asymmetric Synthesis of Allylsilanes by the Borylation of Lithiated Carbamates: Formal Total Synthesis of (-)-Decarestrictine D
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DOI：
10.1002/anie.201001223
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发表时间：
2010-01-01
影响因子：
16.6
通讯作者：
Aggarwal, Varinder K.
中科院分区：
文献类型：
--
作者：
Binanzer, Michael;Fang, Guang Yu;Aggarwal, Varinder K.
手性烯丙基硅烷是立体选择性有机合成中非常有价值的亲核试剂，因为它们可以进行大量的不对称转化。[1]例如，β-羟基烯丙基硅烷已被Panek和Paneh的团队广泛用于天然产物合成。近年来最有用的应用之一是[3+ 2]环化[2]和[4+ 2]环化[3]，因为它们允许容易地获得呋喃和吡喃。[4]然而，取代的β-羟基烯丙基硅烷的合成并不总是简单的，并且通常需要多个步骤。[5]β-羟基烯丙基硅烷广泛的合成用途促使我们开发更有效的合成路线以获得此类中间体。我们最近报道了一种新的方法，用于硼酸酯和硼烷的同系化[6]，该方法采用Hoppe等人报道的锂化氨基甲酸酯。[7]我们的方法涉及使用衍生自伯醇和仲醇的氨基甲酸酯，这导致在氧化后以高对映体比率形成仲醇和叔醇[8]。该反应可推广为一锅法、多步同系化反应，并可应用于（+）-阿魏醛的合成。[9]在进一步扩展这一方法的过程中，我们考虑了它在β-羟基烯丙基硅烷的立体控制一锅法合成中的应用。我们设想，锂化氨基甲酸酯与β甲硅烷基乙烯基硼烷3 [10]的反应将形成中间体烯丙基硼烷5 [11]，其可以与醛反应得到Z-构型的反烯丙基硅烷7（方案1）。[12]随后的环氧化和消除/开环可以提供立体控制的路线，得到2-烯-反-1，4-二醇9，天然产物中的常见基序（方案1）。在此，我们详细介绍了我们在开发这种方法及其在合成中的应用的成功。
Chiral allylsilanes are highly valuable nucleophiles in stereoselective organic synthesis because of the multitude of asymmetric transformations that they can undergo.[1] For example, β-hydroxy allylsilanes have been used extensively by the groups of both Panek and Roush in natural product synthesis. Amongst the most useful applications in recent years are the [3+ 2] annulation [2] and the [4+ 2] annulation [3] as they allow facile access to furans and pyrans.[4] However, the synthesis of substituted β-hydroxy allylsilanes is not always straightforward and usually requires multiple steps.[5] The broad synthetic utility of β-hydroxy allylsilanes motivated us to develop more efficient synthetic routes to such intermediates.We recently reported a new method for the homologation of boronic esters and boranes [6] by employing the lithiated carbamates reported by Hoppe et al.[7] Our method involved the use of carbamates derived from primary and secondary alcohols, which led to the formation of secondary and tertiary [8] alcohols in high enantiomeric ratios after oxidation. The reaction could be extended to a one-pot, multiple homologation process and its application in the synthesis of (+)-faranal was demonstrated.[9] In extending this methodology further, we considered its application in the stereocontrolled, one-pot synthesis of β-hydroxy allylsilanes. We envisioned that the reaction of a lithiated carbamate with βsilyl vinyl borane 3 [10] would form the intermediate allylborane 5 [11] which could react with an aldehyde to give an Z-configured anti-allylsilane 7 (Scheme 1).[12] Subsequent epoxidation and elimination/ring-opening could then provide a stereocontrolled route to 2-ene-anti-1, 4-diols 9, a common motif in natural products (Scheme 1). Herein we detail our success in developing this methodology and its application in synthesis.