Asymmetric Total Synthesis Of Andrographolide And Rostratone

This thesis aims at the asymmetric biomimetic total synthesis of two antipodal Labdane diterpenoids andrographolide and rostratone, which consists of the following three Chapters.Chapter 1:The application of the allylsilane functional group in the biomimetic polyene cyclization en route to natural products synthesis is reviewed, and the stereochemical controls of the cyclization product in some examples are briefly analyzed.Chapter 2:(1) General introduction on andrographolide, including the isolation, structural elucidation, biological activities, and synthetic studies, are summarized; (2) Typical synthetic approaches toward Labdanoids are briefly reviewed; (3) Details on the first enantioselective total synthesis of andrographolide by the biomimetic polyene cyclization strategy, is recorded, which involves the following three stages:(i) the assembling of the designated chiral epoxy allylsilane precursor via a practical protocol developed in our laboratory; (ii) the subsequent biomimetic bis-annulation mediated by Lewis acids; and (iii) the elaboration of the side-chain bearing a unique a-alkylidene y-butyrolactone unit and the completion of the total synthesis.Chapter 3:The isolation, structure, and racemic total synthesis of the antipodal Labdanoid rostratone are briefly summarized. The details of the first enantioselective biomimetic total synthesis of rostratone by an analogous approach from a diastereomeric chiral epoxy allylsilane precursor, is described.