o-Quinone methide based approach to isoflavans:: application to the total syntheses of equol, 3′-hydroxyequol and vestitol

A concise strategy is developed for the synthesis of isoflavans employing a Diels-Alder reaction between o-quinone methides and aryl-substituted enol ethers followed by reductive cleavage of the acetal group. The method is extended towards the total syntheses of equol, 3'-hydroxyequol and vestitol. (C) 2008 Elsevier Ltd. All rights reserved.