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[5C+2C] cycloadditions in polycyclic natural product syntheses.

机译：多环天然产物合成中的[5C + 2C]环加成。

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摘要

Seven-membered rings are ubiquitous in a broad range of complex polycyclic natural products of remarkable biological and medicinal significance. Among the wide variety of strategies and methods that have been developed for addressing seven-membered ring synthesis, cycloadditions are particularly appealing, as these reactions provide quick and convergent access to molecular complexity in a single transformation and often from simple building blocks.; Two types of [5C+2C] cycloadditions to construct seven-membered rings, including the oxidopyrylium-alkene [5+2] cycloaddition and the transition-metal-catalyzed [5+2] cycloaddition of vinylcyclopropanes and various π-systems, will be briefly introduced in the first part of this thesis. This thesis is a result of our ongoing interest in defining the scope, limitations, and applications of these two remarkable processes.; In Chapter 2, the application of the transition-metal-catalyzed intramolecular [5+2] cycloaddition of an allene and a vinyl-[1,1,2]-trisubstituted vinylcyclopropane to the formal total synthesis of isovelleral will be discussed. This strategy represents a novel approach to the synthesis of marasmane sesquiterpenes, provides efficient access to isovelleral (14 steps), and serves to define further aspects of this new [5+2] cycloaddition.; Cyathane diterpenes such as erinacines and scabronines are potent inducers of nerve growth factor (NGF) synthesis. A concise asymmetric synthesis of the common tricyclic skeleton of cyathane diterpenes, based on the novel transition-metal-catalyzed intramolecular [5+2] cycloaddition of an alkynone and a vinylcyclopropane, will be described in Chapter 4 of this thesis. This strategy provides efficient access (14 steps and 9% overall yield) to potential analogues as well as precursors of cyathane diterpenes.; Chapter 5 will describe the recent progress towards the total synthesis of kirkinine, one of the most powerful small molecule neurotrophic agents. The general synthetic strategy employed in this approach involves the rapid and stereoselective construction of the BC-ring skeleton of kirkinine through a substrate-controlled intramolecular [5+2] cycloaddition of an oxidopyrylium ylide and an alkene. Subsequent palladium mediated A-ring annulation allows for the construction of the complete tricyclic skeleton. Further functional group manipulations afford a highly functionalized intermediate in 36 linear steps from commercially available D-ribose. Work is in progress to reach the target molecule in the Wender group.
机译：七元环在具有显着生物学和医学意义的各种复杂的多环天然产物中无处不在。在为解决七元环合成而开发的各种策略和方法中，环加成特别吸引人，因为这些反应可在单一转化中（通常是从简单的结构单元中）快速而收敛地获得分子的复杂性。构成七元环的两种类型的[5C + 2C]环加成，包括氧化op-烯烃[5 + 2]环加成和过渡金属催化的乙烯基环丙烷和各种π系统的[5 + 2]环加成。本文的第一部分对此进行了简要介绍。本文是我们对定义这两个非凡过程的范围，局限性和应用的持续关注的结果。在第二章中，将讨论过渡金属催化的烯丙基和乙烯基-[1,1,2]-三取代乙烯基环丙烷的分子内[5 + 2]环加成反应在异戊醛的正式全合成中的应用。该策略代表了合成Marasmane倍半萜烯的新颖方法，提供了高效进入异黄酮的途径（14个步骤），并用于定义这种新的[5 + 2]环加成反应的其他方面。鞘氨醇二萜例如erinacines和scabronines是神经生长因子（NGF）合成的有效诱导剂。本文的第四章将介绍基于炔烃和乙烯基环丙烷的新型过渡金属催化的分子内[5 + 2]环加成反应，简单地对称合成胱氨酸二萜三环骨架的简明方法。该策略为潜在的类似物以及胞嘧啶二萜的前体提供了有效的途径（14个步骤，总产率为9％）。第5章将描述全合成的激肽释放素的最新进展，该蛋白是最有力的小分子神经营养剂之一。该方法中采用的一般合成策略涉及通过氧化吡啶鎓叶立德和烯烃的底物控制的分子内[5 + 2]环加成反应，快速，立体选择性地构建基尔金的BC环骨架。随后的钯介导的A环环化可以构建完整的三环骨架。进一步的官能团操作可从市售的 D -核糖以36个线性步骤提供高度官能化的中间体。正在努力达到Wender组中的目标分子。

著录项

  • 作者

    Bi, Feng Christopher.;

  • 作者单位

    Stanford University.;

  • 授予单位 Stanford University.;
  • 学科 Chemistry Organic.
  • 学位 Ph.D.
  • 年度 2004
  • 页码 365 p.
  • 总页数 365
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 有机化学;
  • 关键词

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