Studies On Novel Approach Toward Total Synthesis Of Agarofuran Sesquiterpenoids

Agarofuran sesquiterpenoids are an important class of natural products,which have attracted extensive attention from synthetic chemists because of their novel structure,complex stereochemistry and prominent biological activity.The thesis has been divided into two parts:Chapter 1 briefly summarized the distribution,chemical structure,classification and physiological activity of agarofuran sesquiterpenoids,and then systematically summarized the recent progress toward total synthesis of agarofuran.Chapter 2 described the novel strategy and experimental study for the synthesis of agarofuran skeleton.The first part summarized the biosynthetic pathway of agarofuran sesquiterpenoids,Simmons-Smith cyclopropanylation reaction and the novel reductive oxyNazarov electrocyclization reaction developed by our own group applied in the total synthesis.In the second part,the retrosynthetic analysis of agarofuran(Scheme 1)was designed base on the reductive oxy-Nazarov electrocyclization reaction.Lastly,we systematically discussed the total synthesis of the agarofuran skeleton by using the oxy-Nazarov electrocyclization reaction,Simmons-Smith cyclopropanylation reaction and intramolecular ring expanding-cyclization reaction.Starting from(-)-carvone,a novel reductive oxy-Nazarov electrocyclization reaction was used to synthesize the key intermediate compound 2-14,then Simmons-Smith cyclopropanylation reaction was applied to construct the cyclopropane 2-24.Finally,the asymmetric synthesis of the agarofuran skeleton was achieved by the cyclopropane expanding and cyclization reaction.