TOTAL SYNTHESIS OF QUASSINOIDS AND VIRGINIAMYCIN

高细胞毒性的五环二萜的全合成， Quasimarian是提出的。从D-(+)-葡萄糖开始，我们打算准备 单环α-亚甲基-3-氧基环戊酮，共含有 三个手性中心和一个远端的二烯基团。这个 这种单环物种的制备将利用一些羟醛化学 它是在我们的实验室里开发出来的。分子内[4+2] 这种单环物质的环加成反应预计发生在 外部模式--密切关注我们自己在 倍半萜、二次方以及别人的工作。这个 环加成反应共生成5个手性中心。 代表目标的环B、C和E的三环骨架 天然产物。尤其重要的是确保这三个方面的安全 在正确的立体化学排列中C环上的氧合位置。 此外，三环物质既包含官能团又包含分子 适合和有利于年轮精加工的几何形状 A和D存在于这种五环二萜中。一种新的反应序列 在形成环状A时会用到。 我们还提出了一种完全合成的生物学上非常有趣的 大环类抗生素，维吉尼亚霉素。我们已经将这种分子分解成 两个部分，并将它们命名为上半部分和下半部分。上面的片段 利用了一些新的非常有用的赤霉醇方法学，它的特点是 乙烯基氨基甲酸酯的羟醛-内酯化反应。方法论 应该允许非常简短和高效的鞋面建造 一半的维吉尼亚霉素。下面的片段将从谷氨酸中提取 酸，并利用一些基于硫的方法WE和其他， 是在一段时间前开发出来的。我们从来没有在严肃的 综合设置，并希望在我们的工作过程中这样做 有问题。

A total synthesis of the highly cytotoxic pentacyclic diterpene, quasimarian is proposed. Starting from D-(+)-glucose, we intend to prepare a monocyclic alpha-methylene-3-oxycyclopentanone which contains a total of three chiral centers together with a remote diene function. The preparation of this monocyclic species will utilize some aldol chemistry which has been developed in our laboratories. Intramolecular [4 + 2] cycloaddition of this monocyclic substance is expected to occur in the exo-mode--closely following the stereochemical outcome of our own work on the sesquiterpene, quadrone as well as the work of others. The cycloaddition reaction yields a total of five chiral centers contained in a tricyclic framework which represents rings B, C, and E of the target natural product. Of particular importance is the securement of all three sites of oxygenation in ring C in the correct stereochemical arrangement. Further, the tircyclic substance contains both functionality and molecular geometry suitable and conducive to the annulative elaboration of the rings A and D present in this pentacyclic diterpene. A new reaction sequence resulting in the formation of ring A will be used. We also propose a total synthesis of the biologically very interesting macrocyclic antibiotic, virginiamycin. We have divided this molecule into two portions and named them the upper and lower halves. The upper fragment utilizes some new and very useful erythro aldol methodology which features the aldol-lactonization reaction of a vinylogous urethane. The methodology should permit an extremely brief and efficient construction of the upper half of virginiamycin. The lower fragment will be prepared from glutamic acid and takes advantage of some sulfur based methodology we, and other, developed some time ago. We have never used this methodology in a serious synthetic setting and hope to do so during the course of our work on this problem.