Natural Products Inspired [3 + 2] Cycloaddition Enables Efficient Syntheses of Lignans

Mimicking biosynthetic pathways of hongkonoids led to the development of a new Cu(Ⅰ)-catalyzed [3 + 2] cycloaddition of α-hydroxyketone and β-keto enol ethers, affording chiral tetrahydrofuran acetals in a highly diastereoselective manner and 100% atom economy. Computational studies on the mechanism disclosed a concerted but asynchronous Michael addition/aldol reaction. Of the same importance, this methodology provides a practical biomimetic approach for one-step construction of the dibenzylbutyrolactol lignan backbone starting from two phenyl propane derivatives, opening up a powerful new approach for lignan synthesis, which is showcased by succinct total syntheses of two biologically important aryltetralin-type lignans, β-apopicropodophyllin and cycloolivil. Given the mild and operationally simple conditions, the developed chemistry might have a promising prospect in potential industrial applications