International audienceAn efficient synthesis of deoxy-lambertellols was reported through a highly chemo- and diastereoselective intermolecular Diels-Alder cycloaddition between trans-1,2-disiloxybenzocyclobutenes and 2-methylproto- anemonine. Such transformation with d-substituted c- alkylidenebutenolides, to prepare new analogues of these tricyclic spirolactones, which would be very difficult to prepare by other ways, was also studied