Total Synthesis Of(+)-Iresin And (+)-Aphidicolin

This thesis aims at the asymmetric total synthesis of sesquiterpene lactone (+)-Iresin and tetracyclic diterpenoid (+)-Aphidicolin and consists of the following three chapters:Chapter 1 summarized the structure, reactivity and synthetic methods of allylsianes, and their applications in natural product synthesis using biomimetic polyene cyclizations as key step. A brief introduction on the novel synthetic method of homoiodo allylsilanes previously developed in our research group was also given.Chapter 2 described the structure of the natural product (+)-Iresin which has a ent-Drimane skeleton and studied on the synthesis of the analogs of (+)-Iresin. We reported in detail the first asymmetric total synthesis of (+)-Iresin via the key oxidation intermediate 2-32 from the bicyclic aldehyde 1-116, which was a key intermediate in our previous total synthesis of andrographolde.Chapter 3 described the structure, bioactivity, biomimmetic synthetic pathway and previously reported synthetic strategy for the tetracyclic diterpenoid (+)-Aphidicolin. A brief comparative account on the previous total synthetic methods was given. We employed three three components as building blocks for construction of the functionalized tetrasubstituted homoiodo allylsilane 3-130 based on our previous synthetic method,3-130 was cyclized effectively under the action of Lewis acid to give tricyclic products 3-136 and 3-137. The asymmetric synthesis of the known Corey-Tius intermediate was achieved via a series of functional group transformations from spiro-cyclic intermediates 3-136 or 3-137, leading to a formal total synthesis of (+)-Aphidicolin according to Holton’s previous synthesis (1987). The unusual formation of an intramolecular cyclopropanated ring system 3-167 was disclosed with full structural characterization.