Racemic total synthesis of dactyloidin and demethyldactyloidin through the dl-proline-catalyzed Knoevenagel condensation/[4 + 2] cycloaddition cascade

Abstract

An efficient approach towards the first racemic total synthesis of dactyloidin (2) and demethyldactyloidin (3) is described. Their oxygen-bridged tricyclic ketal systems were rapidly constructed by using a remarkable biomimetic Knoevenagel condensation/[4 + 2] cycloaddition cascade as the critical strategy and the 1,5-dicarbonyl segment was assembled by Grignard addition.