Synthesis of ()-Madindoline A and ()-Madindoline B.

The allene ether version of the Nazarov cyclization was used to construct the cyclopentane dione portion of madindolines A and B. The racemic cyclopentane dione from the Nazarov cyclization was converted to an enol ether that was combined with the chiral, nonracemic hydroxyfuroindoline in a Mannich reaction. Deprotection and oxidation led to ()-madindoline A and ()-madindoline B. [ABSTRACT FROM AUTHOR]