Total Synthesis by Asymmetric Catalytic Methods

描述（由申请人提供）：该计划的目标是通过创造性地应用不对称催化方法合成结构和生物学上有趣的天然产物。选择不同的结构和立体化学复杂性的目标来说明和挑战最近发现的对映选择性合成方法，并激发新的催化反应的发展。比平那丁I（1）是新近发现的西松膜二萜类化合物，是一种很有前途的细胞毒药物。该目标具有密集官能化的14元碳环结构，并为新的合成方法的应用提供了一个出色的平台。我们建议应用新的丁烯二酰亚胺方法和反需求杂狄尔斯桤木化学，沿着更成熟的不对称环氧化反应，以引入大多数的立体中心存在于1。合成的完成将依赖于底物导向的非对映选择性转化，以有效生成剩余的立体中心，包括关键的大环化事件。在抗癌剂peloruside A（2）的9个立体中心中，我们计划通过对映体纯末端环氧化物的创新开环引入4个。然后，通过将已知的催化、对映体选择性方法扩展到催化剂控制的非对映体选择性环境，建立除一个之外的所有剩余立体中心。Escherasin（3）和elisapterosin B是两个相邻的全碳立体异构中心的复杂四环海洋天然产物。我们提出了简洁的合成，通过应用不对称催化反应，发现专门为这些目标产生双环醌中间体，然后通过后期的分子内环加成反应。我们建议完成奎宁（4）的第一个不对称催化合成，利用最近发现的不对称迈克尔加成和环氧化方法，以简洁和选择性的方式接近这个经典的目标。

DESCRIPTION (provided by applicant): This program has as its goal the synthesis of structurally and biologically interesting natural products through creative application of asymmetric catalytic methodologies. Targets of varying structural and stereochemical complexity are selected to both illustrate and challenge recently discovered methods for enantioselective synthesis, and to inspire development of new catalytic reactions. Bipinnatin I (1) is a recently discovered member of the cembrane diterpenoids and a promising cytotoxic agent. This target has a densely functionalized 14-membered carbocyclic structure, and presents an outstanding platform for the application of new synthetic methodologies. We propose to apply novel butenolide methodology and inverse demand hetero-Diels Alder chemistry, along with more established asymmetric epoxidation reactions to introduce the majority of the stereocenters present in 1. Completion of the synthesis will rely on substrate-directed diastereoselective transformations for the efficient generation of the remaining stereocenters, including the key macrocyclization event. Of the nine stereocenters in the anti-cancer agent peloruside A (2), we plan to introduce four through innovative ring-openings of enantiopure terminal epoxides. All but one of the remaining stereocenters will then be established by extending known catalytic, enantioselective methods to catalyst-controlled diastereoselective contexts. Colombiasin (3) and elisapterosin B are complex tetracyclic marine natural products incorporating two contiguous all carbon-stereogenic centers. We propose concise syntheses through application of asymmetric catalytic reactions discovered specifically for these targets to generate bicyclic quinone intermediates, followed by late stage intramolecular cycloaddition reactions. We propose to accomplish the first asymmetric catalytic synthesis of quinine (4), taking advantage of recently discovered asymmetric Michael addition and epoxidation methodologies to access this classic target in a concise and selective manner.