ASYMMETRIC DIELS-ALDER REACTIONS OF VINYLOGOUS URETHANES

这项新建议的目的是设计一系列 利用新方法合成复杂的碳环， 使用最终衍生自特窗酸和脯氨酸的手性二烯 Diels-Alder（D-A）反应 D-A反应已经成为 乙烯基氨基甲酸酯内酯烯醇化物碳-碳键的延伸 形成反应。 作为功能丰富的二烯，这些系统提供 相对于其他环加成反应的几个合成优点。 一个主要的好处是形成双环缩酮，其可以发挥作用， 作为后续合成操作的保护基。 这些 初始的非外消旋环加合物允许在 在刚性氧杂[2.2.1]中引入额外的不对称中心， 双环庚基体系。 合成的容易性和可获得性， 廉价的起始材料使得这些二烯适用于大规模的 规模不对称合成 我们打算展示 这些新的二烯在几个短的对映选择性的背景下， 生物活性化合物的合成，同时研究 它们的面部选择性的起源， 适用性 我们的目的是实现一个简短而有效的 抗肿瘤和抗微生物的构建，埃斯波霉素作为 糖苷配基（24）和几种生物活性和不同的假糖 (50 34、43）使用这种方法。

The objective of this new proposal is to devise a number of total syntheses of complex carbocycles exploiting a novel methodology, that employs chiral dienes ultimately derived from tetronic acids and proline in Diels-Alder (D-A) type reactions. The D-A reaction has become an extension of vinylogous urethane lactone (VUL) enolate carbon-carbon bond formation reactions. As functionally opulent dienes, these systems offer several synthetic advantages relative to other cycloaddition reactions. A major benefit is the formation of a bicyclic ketal, which can function as a protecting group for subsequent synthetic manipulations. These incipient nonracemic cycloadducts permit facile control in the introduction of additional asymmetric centers to the rigid oxa-[2.2.1]- bicyclic heptyl system. The ease of synthesis and accessibility of inexpensive starting materials makes these dienes applicable to large scale asymmetric synthesis. We intend to demonstrate the versatility of these novel dienes within the context of several short enantioselective syntheses of biologically active compounds, while concomitantly studying the origins of their p facial selectivity and expanding their applicability. It is our intent to effect a brief and efficient construction of the antitumor and antimicrobial, esperamicin as the aglycone (24) and several biologically active and distinct pseudo-sugars (50, 34, 43) using this methodology.