Stereocontrolled approach to the highly functionalized bicyclo[3.2.0] heptane core of bielschowskysin through intramolecular Cu(I)-catalyzed [2+2] photocycloaddition

A direct route for the synthesis of highly functionalized bicyclo[3.2.0]heptane core containing the bridged lactone with the functionalized C-12 substituent of bielschowskysin is reported. The key step involves a stereoselective Cu (I)-catalyzed [2+2] photocycloaddition of a 1,6-diene embedded in a sugar derivative.