title: Convergent Assembly of the Tetracyclic Meroterpenoid (-)-Cyclosmenospongine by a Non-Biomimetic Polyene Cyclization.
abstract: The cationic cyclization of polyenes constitutes a powerful and elegant transformation, which has been utilized by nature's biosynthetic machinery for the construction of complex polycyclic terpenoids. Previous studies by chemists to mimic this cyclization in the laboratory were limited to different modes of activation using biosynthetic-like precursors, which accommodate only simple methyl-derived substituents. Here we describe the development of an unprecedented and highly efficient polyene cyclization of an aryl enol ether containing substrate. The cyclization was shown to proceed in a stepwise manner to generate three rings and three consecutive stereocenters, two of which are tetrasubstituted, in a single flask. The developed transformation is of great synthetic value and has enabled the convergent assembly of the tetracyclic meroterpenoid (-)-cyclosmenospongine.
authors.affiliation: Department of Chemistry and Pharmacy, Ludwig Maximilians 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 Maximilians University Munich, Butenandtstrasse 5-13, 81377, Munich, Germany.
authors.forename: Raphael
authors.initials: R
authors.lastname: Wildermuth
authors.affiliation: Department of Chemistry and Pharmacy, Ludwig Maximilians University Munich, Butenandtstrasse 5-13, 81377, Munich, Germany. thomas.magauer@lmu.de.
authors.forename: Thomas
authors.initials: T
authors.lastname: Magauer
keywords: cations; cyclization; natural products; terpenoids; total synthesis