Studies On The Asymmetric Synthesis Of Nature Product Lachnone C

In this thesis, we mainly aim at the synthesis of nature products of benzopyran derivatives. We study on the methods of constructing benzopyran skeleton systemically. We attempt several routes toward the total synthesis of Lachnone C which has a novel structure of benzopyran. It consists of the following two parts:Chapter 1. Review on the synthesis of the nature product of benzopyran derivatives.Many natural products have a benzopyran skeleton, and most natural products have extraordinary biological activities. So benzopyran skeleton is an important intermediate for synthesizing of a series of natural products. This chapter introduces the methods of constructing benzopyran ring, summarizes the synthesis approach of benzopyran derivates, and focuses on building the benzopyran rings containing chiral centers.Chapter 2. Studies on the asymmetric synthesis of Lachnone CThis chapter is based on nature products Lachnone C, explores the asymmetric total synthesis of the target compound. On the basis of the summary and the previous work we explore a new synthetic strategy. The route is using 3,5-dihydroxybenzoic acid which is simple and easy to get as the starting material, the Key intermediate 28 is obtained through Vinylogous aldol reaction, Birch reduction, Sharpless asymmetric epoxidation as key steps, we get the key intermediate 28. Through the Sharpless asymmetric epoxidation we can construct the chiral centers. We can obtain lactone ring by opening the epoxy compounds 31 with diethyl malonate. Finally, after a series of functional group conversion we obtain the benzyl derivatives 38 of the target compound Lachnone C. This work is still ongoing. After 20 steps we get the benzyl derivatives 38 of the target compound Lachnone C in the total yield of 2%.