pallavicinins和pallambins的手性全合成研究

当前，追求天然产物的高效全合成是有机化学的前沿研究领域。无保护基全合成也是实现理想合成的重要策略之一。二萜类天然产物pallavicinins和pallambins是一种具有新颖梯形结构的多环多手性中心复杂化合物，目前仅有一例消旋全合成报道，且路线较为冗长，并涉及大量保护基的使用。有鉴于此，本项目拟以钯催化的不对称脱羧烯丙基化反应、选择性氧化双键、及串联的选择性加成/迈克尔加成等作为关键步骤，高效完成天然产物pallavicinins和pallambins的首次不对称全合成，并力争不使用任何保护基。本课题的开展对丰富无保护基法天然产物全合成具有重要的学术意义。

Currently, the development of shorter synthetic sequences for the synthesis of complex natural products is currently pursued actively by organic chemists, because they offer the best ways to achieve overall efficiency. Protecting-group-free synthesis offer an attractive strategy for the ideal synthesis. Natually occurring diterpenoids pallavicinins and pallambins were isolated from Pallavicinia subciliata and Pallavicinia ambigua respectively, which consist of unprecedented ladder-shaped skeleton tetracyclic skeleton bearing several contiguous stereogenic centers. However, only one tediously long, racemic total synthesis is reported up to date. This project aims at achieving the enantioselective total syntheses of palavicinins and pallambins based on a novel synthetic strategy. The syntheses will feature an asymmetric palladium-catalyzed decarbolative allylation, chemoselective oxidation of olefin, and a tandem selective addition/Michael addition as well as in a protecting-group-free manner. The value of this research subject is that it enriches the chemistry of protecting-group-free synthesis of natural product.