ASYMMETRIC DIELS-ALDER REACTIONS OF VINYLOGOUS URETHANES

这项新提案目标是制定出若干总数 利用一种新的方法合成复杂碳环，即 使用手性二烯类化合物，最终来源于四硝酸和脯氨酸 在Diels-Alder(D-A)型反应中。D-A反应已经成为一种 乙烯基氨基甲酸酯内酯(VUL)烯醇型碳-碳键的延伸 队形反应。作为功能丰富的双烯，这些系统提供 相对于其他环加成反应的几个合成优势。 一个主要的好处是形成了双环缩酮，它可以发挥作用 作为后续合成操作的保护基团。这些 早期的非外消旋环加成物允许在 刚性氧杂-[2.2.1]-引入额外的不对称中心 双环庚基体系。的简易性和可访问性 廉价的原料使这些双烯适用于大批量生产 规模不对称综合。我们打算展示的是 这些新的双烯类化合物在几个短的对映选择性的背景下 生物活性化合物的合成，同时进行研究 他们的面部选择性的起源和扩展他们的 适用性。我们的意图是实现一个简短而有效的 抗肿瘤、抗微生物药物埃司帕米星的构建 苷元(24)和几种生物活性独特的假糖 (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.