ent-Rosane and abietane diterpenoids as cancer chemopreventive agents

► First instance of isolation of ent-rosane diterpenoids from species of the Celastraceae. ► Determination of absolute configuration by application of Riguera ester procedure. ► Diterpenes as potent anti-tumour-promoter agents. ► Carnosol showed effectiveness in an in vivo two-stage carcinogenesis model.