Cycloaddition Chemistry of Cyclic Oxyallic Cations

Michael Harmata教授对环氧基阳离子的环加成化学的研究得到了有机合成计划的支持。密苏里大学哥伦比亚分校化学系的Harmata博士正在研究（4+3）环加成反应，重点关注这类反应的几个新方面。含卤素取代基的底物的环加成反应提供的产物可以被加工成更复杂的结构，特别是通过准法沃斯基重排。使用手性碱来介导（4+3）环加成，特别是在设计允许手性碱在分子内传递的底物中，将赋予环加合物手性。通过氧基阳离子（4+3）环加成反应的合成路线，将制备环辛烷类天然产物的代表性成员，即dactylol和11-羟基茉莉酮。构成现代化学和制药科学基础的复杂分子的合成需要以高度选择性的方式形成碳-碳键。在“环加成”反应中，两个（或更多）反应分子相互加成形成环状产物，这是实现这种选择性键形成的一种特别有效的方式。Harmata博士研究环加成反应，这种反应会形成一个环中含有七个碳原子的化合物，并探索在这些反应中引入额外选择性和多功能性的方法。他将利用一种不寻常的环转化反应，使这些七元环化合物转化为含有八元环的产物。这些研究最终将合成几种特定的化合物，包括具有抗菌和抗真菌活性的11-羟基茉莉酮，并将为合成其他已知或潜在的生物或药物活性的八元环化合物提供一个通用平台。

Professor Michael Harmata's studies of the cycloaddition chemistry of cyclic oxyallylic cations are supported by the Organic Synthesis Program. Dr. Harmata, of the Department of Chemistry at the University of Missouri - Columbia, is studying (4+3) cycloaddition reactions, focusing on several novel aspects of this class of reactions. Cycloaddition reactions of substrates containing halogen substituents provide products which may be elaborated into more complex structures, particularly through quasi-Favorskii rearrangements. Use of chiral bases to mediate the (4+3) cycloadditions, particularly in substrates designed to permit intramolecular delivery of the chiral base, will impart chirality to the cycloadducts. Representative members of the cyclooctanoid class of natural products, dactylol and 11-hydroxyjasionone, will be prepared through synthetic routes highlighting the efficacy of the (4+3) cycloaddition reactions of oxyallylic cations. Synthesis of the often-complex molecules forming the basis of modern chemical and pharmaceutical science requires the formation of carbon-carbon bonds in a highly selective manner. `Cycloaddition` reactions, in which two (or more) reacting molecules add to one another to form a cyclic product, represent a particularly powerful way in which to achieve such selective bond formation. Dr. Harmata studies cycloaddition reactions which result in the formation of compounds containing seven carbon atoms in a ring, exploring ways to introduce additional selectivity and versatility into these reactions. He will exploit an unusual ring transformation reaction which allows the conversion of these seven-membered ring compounds into products containing eight-membered rings. These studies will culminate in the synthesis of several specific compounds, including 11-hydroxyjasionone, which displays antibacterial and antifungal activity, and will serve as a general platform for the synthesis of other eight-membered ring compounds of known or potential biological or medicinal activity.