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首页> 外文学位 >Total synthesis of cyanthiwigin natural products via double asymmetric catalytic alkylation, and, Investigations into the nature of double asymmetric processes.
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Total synthesis of cyanthiwigin natural products via double asymmetric catalytic alkylation, and, Investigations into the nature of double asymmetric processes.

机译：通过双不对称催化烷基化完全合成氰硫代木素天然产物，以及对双不对称过程性质的研究。

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摘要

Since the initial isolation of the cyathane molecules in 1970, considerable synthetic interest has been invested into the preparation of these diterpenoid natural products. Owing to the biological activity and intriguing molecular architecture of these compounds, the members of the cyathane family of natural products have emerged as appealing targets for total synthesis. After a brief summary of the isolation and bioactivity properties of these diterpene compounds, previous synthetic efforts toward these molecules are reviewed.;A concise and versatile approach toward the preparation of the cyanthiwigin family of cyathane natural products is described. By leveraging a unique double asymmetric catalytic alkylation procedure it is possible to quickly establish two of the most critical stereocenters of the cyanthiwigin framework with high levels of selectivity and expediency. The synthesis additionally employs a tandem ring-opening and cross-metathesis reaction, and an aldehyde-olefin radical cyclization process, to rapidly arrive at the tricyclic cyathane core of the cyanthiwigin molecules. From this unifying intermediate, the preparation of cyanthiwigins B, F, and G are attained swiftly and without the need for protecting groups.;The nature of double asymmetric transformations is investigated from a historical, mathematical, and experimental perspective. The initial findings of Langenbeck and Horeau concerning the enantioenriching effects of scalemic duplication are described, with a specific focus on the impact of this phenomenon on total synthesis. A thorough mathematical examination, based on the work of Kagan, is then presented for situations involving double asymmetric transformations of prochiral starting materials. Expressions relating the final quantities of the stereoisomeric products to the intermediary selectivity of each stereoselective process are presented based on these formulae.;Finally, experiments designed to probe the selectivity of each stage of stereoselective bond construction in a double asymmetric process are presented. The compiled results are scrutinized in keeping with the previously derived equations, and these findings are analyzed to understand the nature of the double asymmetric processes in question.
机译：自1970年首次分离出胞嘧啶分子以来，对这些二萜类天然产物的制备已投入了可观的合​​成兴趣。由于这些化合物的生物活性和引人入胜的分子结构，天然产物鞘烷家族的成员已成为全合成的诱人靶标。在对这些二萜化合物的分离和生物活性特性进行了简要总结之后，对先前对这些分子的合成研究进行了综述。；描述了一种简单而通用的方法来制备胞嘧啶环糊精的天然产物氰硫黄素家族。通过利用独特的双不对称催化烷基化方法，可以快速建立氰硫木素骨架的两个最关键的立体中心，同时具有很高的选择性和便利性。该合成另外采用串联开环和交叉复分解反应，以及醛-烯烃自由基环化过程，以快速到达氰基硫胺素分子的三环胞烷核心。从这种统一的中间体中，不需要任何保护基团就可以快速制备氰基维他命B，F和G。从历史，数学和实验的角度研究了双不对称转化的性质。描述了Langenbeck和Horeau关于规模复制的对映体富集作用的初步发现，特别关注此现象对全合成的影响。然后，针对涉及前手性原料的双重不对称转变的情况，提出了基于Kagan的工作的全面数学检查。基于这些公式，给出了将立体异构产物的最终量与每个立体选择性过程的中间选择性相关的表达式。最后，提出了旨在探究双不对称过程中立体选择性键结构各阶段选择性的实验。按照与先前得出的方程式一样仔细检查编译结果，并对这些发现进行分析以了解所讨论的双重不对称过程的性质。

著录项

  • 作者

    Enquist, John Andrew, Jr.;

  • 作者单位

    California Institute of Technology.;

  • 授予单位 California Institute of Technology.;
  • 学科 Organic chemistry.
  • 学位 Ph.D.
  • 年度 2011
  • 页码 329 p.
  • 总页数 329
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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