Application of chiral tethers to intramolecular [2+2] photocycloadditions: synthetic approach to (−)-italicene and (+)-isoitalicene

A synthetic approach to (−)-italicene and (+)-isoitalicene, sesquiterpenes which possess the rare tricyclo[5.4.0.01,5] undecane skeleton has been developed using as key step a highly regio- and diastereoselective [2+2] photocycloaddition. (S)-Lactic acid plays the role of a chiral removable tether group during the building of the cyclobutane ring.