SYNTHESIS VIA 4-PYRONES AND RELATED SYSTEMS

这笔赠款的最初目标是开发新的方法论。 在合成有机化学领域，基于小说 4-吡喃的光化学。这种化学反应允许快速 构建复杂的多环结构，对应于许多 从简单、容易的案例到具有重要生物医学意义的天然产品 可用的前驱物质。 在更新中，提出了各种新的方向，以及 进一步探讨在当前赠款期间涉及的问题 句号。此应用程序的一个重要关注点是开发 手头反应的立体选择版本。多达五个新的 手性中心是由非手性前体形成的。因此，用于 形成这些中心，并很好地控制绝对立体化学是 对充分利用这种化学反应至关重要。尤其是，使用 刘易斯酸控制纳扎罗夫的扭矩选择性 将考察电环化反应。 已经开发或正在开发的方法将是 应用于两个具有挑战性的天然产物目标的合成。这个 2-吡喃的分子内交叉[4+4]-光环加成化学 将用于合成7，8-环氧基-4-碱基-6-酮。 环化/裂解方法，使用4-吡喃酮 光化学或纳扎罗夫反应将应用于紫杉碱。 长期目标包括最终将这一方法应用于 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.