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

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.National Science and Technology Major Projects of China [2014ZX10005002-005]; Foundation of Key Laboratory of Plant Resources Conservation and Sustainable Utilization (South China Botanical Garden, Chinese Academy of Sciences)SCI(E)EIARTICLEtanhaibo@scbg.ac.cn; sxqiu@scbg.ac.cn399977-99831