A unified strategy for the synthesis of three conicol marine natural products

A powerful, novel approach to meroterpenes conicol, epiconicol and didehydroconicol has been achieved via a key step DielseAlder 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 DielseAlder 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.