Synthetic Studies Towards The Synthesis Of Core Skeleton Of Buanmycin And Citreamicin

Buanmycin and Citreamicin are natural polycyclic xanthone(fully aromatized),which exhibit potent antibacterial and anticancer properties.Its basic structure includes a core skeleton of naphthaxanthone and an oxazolidinone ring.By analyzing the possible biosynthetic pathway,this paper proposes a structural correlation between these two natural products.In the course of our synthetic studies,the efficient synthesis of the BCD ring was achieved by the 6? electrocyclization reaction.The difference between the two BCD skeleton appeared in different oxidation state of the C ring.We originally employed Friedel-Crafts reaction to construct C-C bond of the E ring,but it was proven to be failed.Then we used the nucleophilic aromatic substitution reaction(SNAr reaction)or Ullmann reaction to form C-O bond of the E ring,followed by the intramolecular Friedel-Crafts reaction to furnish BCDEF rings.Finally the total synthesis should be achieved through the condensation of amino acids with the BCDEF rings.We finished the synthesis of core skeleton of buanmycin and citreamicin in a total of 15 steps,1.2%and 3.1%yield.