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.
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