Synthetic Studies Towards The Synthesis Of Ent-rugulotrosin A And Parafungin A1

This dissertation is mainly focused on the synthetic studies toward ent-rugulotrosin A and parafungin A1 which belong to the tetrahydroxanthones.Tetrahydroxanthones were isolated from bacteria,fungi,plants,and lichens as secondary metabolites.According to the structural characteristics,tetrahydroxanthones can be divided into monomeric,dimeric,and polycyclic skeletons.Firstly,the feasibility of Knoevenagel condensation/6? electronegic cascade reaction in the synthesis of tetrahydroxanthones was explored by total synthesis of diversonol.It was found that the diastereoselectivity of tetrasubstituded carbon center was well-controlled in the reaction,and we obtained a tricyclic skeleton with methyl and hydroxyl groups in a cis configuration.Then,this cascade reaction was used for the total synthesis of ent-rugulotrosin A,a dimeric tetrahydroxanthone.The tricyclic skeleton with ester group and hydroxyl group in a cis configuration was followed by aromatization,iodination reaction and one-pot Suzuki-Miyaura coupling reaction,et cetera,which realized the total synthesis of ent-rugulotrosin A.Finally,we carried out the synthetic study towards parafungin A1,a polycyclic tetrahydraxanthone.We initially designed a strategy of C-H bond functionalization to construct the isoxazolidinone ring.We tried a model reaction at first,but the strategy didn't work due to the unstable isoxazolidinone ring.Then the simple SN2 reaction was applied.We introduced a hydroxyl group in the starting material,and a tricylic skeleton was acquired with similar strategies in the total synthesis of ent-rugulotrosin A.But latter,the application of Suzuki-Miyaura and Stille reaction was unsuccessful.This part of work is still going on.