Petrosaspongiolide M (PM, 1), a marine sesterterpene metabolite bearing the γ- hydroxybutenolide scaffold and displaying a potent inhibitory activity toward PLA2 enzyme, was selected by us as an attractive target in order to explore its mechanism of action at molecular level. In the course of our investigations we decided to synthetically modify the parent compound to clarify the structural determinants responsible for the activity; in fact, ...