title: Total Synthesis of d,l-Isospongiadiol: An Intramolecular Radical Cascade Approach to Furanoditerpenes.
abstract: A stereoselective oxidative free-radical cyclization of beta-keto ester polyenes 7 and 19 has been accomplished as a one-step entry to the tricarbocyclic synthons 8and 21 which contain five and six stereogenic centers, respectively. These key synthons possessing an axial carboethoxy group at C-4 were ultimately converted to the spongian skeleton (8--> 14 and 21 --> 25 -->14). The synthesis of d,l-isospongiadiol (3) from the common intermediate 14 was realized after introduction of the 2alpha-hydroxy group in the spongian A-ring via epoxidation of silyl enol ether 28 and subsequent desilylation.
authors.affiliation: Duke NMR Spectroscopy Center, Department of Radiology, Duke University Medical Center, Durham, North Carolina 27710.
authors.forename: Phillip A.
authors.initials: PA
authors.lastname: Zoretic
authors.forename: Ming
authors.initials: M
authors.lastname: Wang
authors.forename: Yongzheng
authors.initials: Y
authors.lastname: Zhang
authors.forename: Zhongqi
authors.initials: Z
authors.lastname: Shen
authors.forename: Anthony A.
authors.initials: AA
authors.lastname: Ribeiro