A powerful, novel approach to meroterpenes conicol, epiconicol and didehydroconicol has been achieved via a key step Diels–Alder reaction of (E)-3-methyl-1-(2′,5′-dimethoxyphenyl)buta-1,3-diene as diene with methyl vinyl ketone, methyl acrylate or methyl propiolate as dienophiles. Activation by high pressure (9 kbar) or by the use of Lewis acid catalysts, allows the Diels–Alder reaction to proceed in excellent yield and diastereoselectively to form cyclohexenyl-benzene cycloadducts, which are useful precursors for conicols. The successful total syntheses of conicol, epiconicol and didehydroconicol, are described.