SYNTHESIS VIA 4-PYRONES AND RELATED SYSTEMS

这笔赠款的最初目标是开发新的方法 在合成有机化学领域，基于新颖的 4-吡喃酮的光化学 这种化学反应可以让 复杂的多环结构的构建，对应于许多 案例到生物医学上重要的天然产物，从简单，容易 可用的前体。 在更新中，各种新的方向被提出，沿着 进一步探讨本次赠款所涉问题 期 本申请的一个重要焦点是开发 立体选择性的反应。多达五个新的 手性中心由非手性前体产生。 因此， 形成这些具有良好的绝对立体化学控制的中心是 这是充分利用这种化学物质的关键 特别是使用 刘易斯酸来控制Nazarov 将检查电环化反应。 已经制定或正在制定的方法将 应用于两个具有挑战性的天然产物目标的合成。 的 2-吡喃酮分子内交叉[4+4]-光环加成化学 将用于7，8-环氧-4-巴斯曼-6-酮的合成。 环化/片段化方法，使用4-吡喃酮 光化学或Nazarov反应，将应用于紫杉碱。 长期目标包括最终将该方法应用于 紫杉醇及其类似物。

The original goal of this grant was the development of new methodology in the area of synthetic organic chemistry, based upon novel photochemistry of 4-pyrones. This chemistry allows for the rapid construction of complex, polycyclic structures, corresponding in many cases to biomedically important natural products, from simple, readily available precursors. In the renewal, a variety of new directions are presented, along with further exploration of the issues covered during the current grant period. An important focus in this application is the development of stereoselective versions of the reactions at hand. As many as five new chiral centers are created from achiral precursors. Thus, methods for forming these centers with good control of absolute stereochemistry are critical to fully exploit this chemistry. In particular, the use of Lewis acids to control the torquoselectivity of the Nazarov electrocyclization reaction will be examined. Methodology already developed or under current development will be applied to the synthesis of two challenging natural product targets. The intramolecular crossed [4+4]-photocycloaddition chemistry of 2-pyrones will be used in a synthesis of 7,8-epoxy-4-basmen-6-one. Cyclization/fragmentation approaches, using either 4-pyrone photochemistry or the Nazarov reaction, will be applied to taxinine. Long term goals include the eventual application of this methodology to taxol and related analogues.