POLYCYCLE SYNTHESIS VIA 4-PYRONE PHOTOCHEMISTRY

该提案详细介绍了新的合成方法的发展， 在通过以下方法捕获光化学产生的氧烯丙基两性离子时， 侧基亲核试剂或1，3-二烯。 初步结果表明 在内部亲核捕获反应中潜在的普遍性 使用碳或杂原子亲核试剂。 协调一致 [4+3]-环加成反应也已被证明是相互和 分子内的 虽然初步结果是积极的，但其范围和局限性 这些反应在这一点上是未知的。 有人建议， 通过碳亲核试剂和侧链二烯被系统地胺化。 该方法学在阿维菌素和 cardenolides介绍。此外，双环捕获产物 似乎可以进行Grob类型的分裂， 中环产品。 将这样的协议应用于八元 环醚类和环辛倍半萜类前槟榔二烯， 讨论 一个重要的问题，这将是解决不对称归纳 在zwitzerland形成期间。 探索可行性的几种方法 的不对称4-吡喃酮光化学。 的能力 获得光学纯形式的加合物非常重要， 关于拟议研究的生物医学意义。 许多 待研究的反应在理论上可以提供 与临床有用的药物相关的高级中间体的有效途径 毒品 这项研究的长期目标是开发这种新的 方法论到这样一个地步， 可以尝试活性天然产物。

This proposal details the development of new synthetic methodology based upon trapping of photochemically generated oxyallyl zwitterions by pendant nucleophiles or 1,3-dienes. Preliminary results indicated potential generality in the internal nucleophilic trapping reaction using either carbon or heteroatom nucleophiles. Concerted [4+3]-cycloadditions have also been demonstrated both inter- and intramolecularly. Although initial results have been positive, the scope and limitations of these reactions are unknown this point. It is proposed that trapping by carbon nucleophiles and pendant dienes be systematically amined. Potential application of this methodology to the avermectins and cardenolides is presented. In addition the bicyclic trapping products appear to be amenable to Grob-type fragmentation, providing access medium-ring products. Application of such a protocol to eight-membered cyclic ethers and the cyclooctanoid sesquiterpene precapnelladiene is discussed. An important issue which will be addressed is asymmetric induction during zwitterion formation. Several approaches to probe the viability of asymmetric 4-pyrone photochemistry have been proposed. The ability to obtain adducts in optically pure form is of great importance as regards the biomedical implications of the proposed research. Many of the reactions to be investigated can theoretically provide very efficient cess to advanced intermediates related to clinically useful drugs. The long-term goal of this research is to develop this new methodology to such a point that synthetic approaches to biologically active natural products can be attempted.