title: Synthetic studies on the icetexones: enantioselective formal syntheses of icetexone andepi-icetexone.
abstract: Two strategies for the synthesis of the icetexane diterpenoids icetexone andepi-icetexone that rely on Ga(III)-catalyzed cycloisomerization of alkynyl indene substrates to yield fused [6-7-6] tricycles have been explored. In the first approach, access to a tricycle bearing agem-dimethyl group paved the way for explorations of C-H functionalization of one of the methyl groups in close proximity to a hydroxyl-directing group. This approach was ultimately unsuccessful and led only to ring cleaved products. In the second approach, an alkynyl indene substrate bearing a cyano substituent was utilized, which was effective in providing a functional handle to access the icetexone subclass of diterpenoids. A key epoxide opening/diazene rearrangement sequence was utilized to complete a formal synthesis of icetexone andepi-icetexone, which is discussed in detail. Furthermore, the cyano-containing substrate has been prepared in enantioenriched form using a Rh-catalyzed conjugate addition reaction, which now provides a route to the enantioselective synthesis of these natural products.
authors.affiliation: Department of Chemistry, University of California, Berkeley, CA 94720, United States.
authors.forename: Felipe
authors.initials: F
authors.lastname: de Jesus Cortez
authors.forename: David
authors.initials: D
authors.lastname: Lapointe
authors.forename: Amy M
authors.initials: AM
authors.lastname: Hamlin
authors.forename: Eric M
authors.initials: EM
authors.lastname: Simmons
authors.forename: Richmond
authors.initials: R
authors.lastname: Sarpong
keywords: Cycloheptadienes; Diterpenes; Enantioselective conjugate addition; Ga(III) cycloisomerization; Icetexanes; Total synthesis