POLYCYCLE SYNTHESIS VIA 4-PYRONE PHOTOCHEMISTRY

该提案详细说明了基于以下内容的新综合方法学的开发 在捕获光化学生成的氧烯丙基两性离子时 侧链亲核剂或1，3-二烯。初步结果显示 内部亲核捕获反应中的势能共性 使用碳或杂原子亲核试剂。协调一致 [4 3]-环加成反应也已在相互间和 分子内。 尽管初步结果是积极的，但范围和局限性 这些反应中的哪一种目前尚不清楚。有人建议，诱捕 通过碳亲核试剂和侧链二烯被系统地胺化。 这一方法在阿维菌素和阿维菌素中的潜在应用 并对其化学成分进行了研究。此外，双环捕集产物 似乎服从Grob类型的碎片化，提供访问 中环产品。这样的议定书适用于八名成员 环醚和环辛烷倍半萜前碳二烯是 讨论过。 将解决的一个重要问题是不对称诱导 在两性离子形成过程中。探索生存能力的几种途径 提出了不对称4-吡喃酮的光化学合成方法。一种能力 获得光学纯形式的加合物非常重要，因为 关于拟议研究的生物医学影响。许多. 将被研究的反应在理论上可以提供非常 高效获取与临床有用相关的高级中间体 毒品。这项研究的长期目标是开发这一新的 方法论到了这样一个点：从生物学上讲，综合方法 可以尝试活性天然产品。

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.