LITHIUM PERCHLORATE DIETHYL ETHER MEDIATED REACTIONS

是次拨款续期申请的主要焦点，是进一步探讨 几种有机反应在高密度下的反应性和选择性 极性介质，如3.0-5.0M高氯酸锂-二乙醚 应用于具有生物学意义的分子。这项建议是 鼎足而三。这项提案的第一部分集中在 离子Diels-Alder反应及其在全合成中的应用 烯二酸A，11-氧代类固醇和石松素。建议进行的所有研究 这一领域将具有根本性，以便界定界限和 这一潜在有用反应的范围。第二部分重点阐述了 阳离子[5，2]环加成反应 过去30年的关注，尽管它具有潜在的 从事天然和非天然产物合成的人员。我们有 发现使用3.0M可以显著提高产量 LiClO4-EtOAc在三甲基硅基三氟酸盐存在下。我们建议 考察一些分子间和分子内的阳离子[5 2]环加成反应 反应，以确定我们的研究结果的一般性。我们建议 将上述化学方法应用于新型非金属有机化合物的全合成 类固醇雌激素，米非司酮。此外，我们还计划准备一批 与紫杉醇相关的双环[5.3.1]系统。在最后一节中，我们 将专注于完成Tabersonine的合成和开发 牛至生物碱的一种新方法。

The major focus of this grant renewal application is to probe further the reactivity and selectivity of a number of organic reactions in highly polar media such as 3.0-5.0 M lithium perchlorate-diethyl ether with applications to molecules of biological interest. This proposal is divided into three parts. The first part of this proposal concentrates on ionic Diels-Alder reactions with applications to the total synthesis of endiandric acid A, 11-oxosteroids, and lycopodine. All studies proposed in this area will be of a fundamental nature in order to define limits and scope of this potentially useful reaction. The second part focuses on cationic [5+2] cycloaddition reactions which have received only scant attention during the past 30 years despite the potential it holds for those engaged in the synthesis of natural and unnatural products. We have found that the yields can be dramatically improved by employing 3.0 M LiClO4-EtOAc in the presence of trimethylsilyl triflate. We propose to examine a number of inter- and intramolecular cationic [5+2] cycloaddition reactions in order to determine the generality of our findings. We propose to apply the above chemistry to the total synthesis of the novel non- steroidal estrogen, miroestrol. In addition we plan to prepare a number of bicyclo [5.3.1] systems related to taxol. In the final section, we will focus on completion of a synthesis of tabersonine and development of a novel approach to iboga alkaloids.