title: Evolution of a Polyene Cyclization Cascade for the Total Synthesis of (-)-Cyclosmenospongine.
abstract: We report a full account on the development of a unique cationic polyene cyclization for the total synthesis of the tetracyclic meroterpenoid (-)-cyclosmenospongine. A highly convergent three-component coupling strategy enabled rapid access to individual cyclization precursors that were tested for their reactivity. The successful transformation generates three rings and sets four consecutive stereocenters in a single operation proceeding in a highly efficient manner to give exclusively the trans-decalin framework. In addition, we found that the enol ether geometry and the relative configuration of C3 and C8 are crucial for the success of the polyene cyclization.
authors.affiliation: Department of Chemistry and Pharmacy, Ludwig Maximillians University Munich, Butenandtstrasse 5-13, 81377, Munich, Germany.
authors.forename: Klaus
authors.initials: K
authors.lastname: Speck
authors.affiliation: Department of Chemistry and Pharmacy, Ludwig Maximillians University Munich, Butenandtstrasse 5-13, 81377, Munich, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Magauer
mesh_terms: D018360:Crystallography, X-Ray; D003500:Cyclization; D008968:Molecular Conformation; D011090:Polyenes / Q000737:chemistry*; D011809:Quinones / Q000138:chemical synthesis* / Q000737:chemistry; D012717:Sesquiterpenes / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism; D013729:Terpenes / Q000138:chemical synthesis / Q000737:chemistry
chemical_list: D011090:Polyenes; D011809:Quinones; D012717:Sesquiterpenes; D013729:Terpenes; C482168:cyclosmenospongine
keywords: cyclization; high-pressure chemistry; natural products; terpenoids; total synthesis