Synthetic studies toward penitrem E: enantiocontrolled construction of B–E rings

Abstract

Enantiocontrolled construction of B–E rings of penitrem E was accomplished from 4-iodoindole in 13 steps with an overall yield of 1.7%. Diastereoselective Tf₂NH-catalyzed (2+2)-cycloaddition between silyl enol ether and methyl acrylate furnished a tetracyclic product possessing the characteristic cyclobutane ring bearing a hydroxyl group.