Enantioselective total synthesis of (-)-9-epi-Ambrox, a potent ambergris-type olfactory agent
摘要:
Addition of the cerium reagent derived from 5-lithio-2,3-dihydrofuran and anhydrous CeCl3 to bicyclic enone 5 (92% ee by lipase hydrolysis of its chloroacetate precursor) affords 6 selectively. Anionic oxy-Cope rearrangement of 6 in refluxing THF induces [3,3] sigmatropy and subsequent enolate ion equilibration. This tandem sequence of reactions allows for an efficient pathway to (-)-2.