A regioselective facile synthesis of furo[3,4-b]carbazolones: application to the total synthesis of mafaicheenamine E and claulansine D.

1-Hydroxycarbazole-2,3-dicarboxylates have been shown to undergo chemoselective reductive cyclization to furo[3,4-b]carbazolones on reaction with LiAlH4. One of the furocarbazolones is utilized to accomplish the first total synthesis of claulansine D and mafaicheenamine E in 9 and 6 steps respectively. The other key steps of the syntheses are addition of an allylic indium reagent and CC double bond isomerization.