title: Construction of the isocopalane skeleton: application of a desulfinylative 1,7-hydrogen atom transfer strategy.
abstract: Two attractive chirons, aldehyde 6 and chloride 7, exhibiting functionalized ent-spongiane-type tricyclic skeletons (ABC ring system), have been constructed and their absolute configurations have been studied by NMR spectroscopy and confirmed by single-crystal X-ray diffraction. Both of these chirons are derived from commercially available andrographolide in good yield. Aldehyde 6 is obtained through a novel K2 S2 O8 -catalyzed aquatic ring-closing reaction of allylic sodium sulfonate and intramolecular 1,7-hydrogen atom transfer process. Further mechanistic investigations demonstrate that the 1,7-hydrogen atom transfer is a free-radical process, whereby hydrogen migrates from C18 to C17, as evidenced by double-18- deuterium-labeled isotope experiments. Prospective applications of these two chiral sources are also discussed.
authors.affiliation: Shanghai Key Laboratory of New Drug Design, School of Pharmacy, East China University of Science and Technology, 130 Meilong Road, Shanghai, 200237 (P. R. China), Fax: (+86) 21-64253689.
authors.forename: Xiong
authors.initials: X
authors.lastname: Xiao
authors.affiliation: Shanghai Key Laboratory of New Drug Design, School of Pharmacy, East China University of Science and Technology, 130 Meilong Road, Shanghai, 200237 (P. R. China), Fax: (+86) 21-64253689.
authors.forename: ZhongYu
authors.initials: Z
authors.lastname: Xu
authors.affiliation: College of Chemistry & Chemical Engineering, Yangzhou University, Yangzhou, 225002 (P. R. China).
authors.forename: Qian-Ding
authors.initials: QD
authors.lastname: Zeng
authors.affiliation: Shanghai Key Laboratory of New Drug Design, School of Pharmacy, East China University of Science and Technology, 130 Meilong Road, Shanghai, 200237 (P. R. China), Fax: (+86) 21-64253689.
authors.forename: Xi-Bo
authors.initials: XB
authors.lastname: Chen
authors.affiliation: Shanghai Key Laboratory of New Drug Design, School of Pharmacy, East China University of Science and Technology, 130 Meilong Road, Shanghai, 200237 (P. R. China), Fax: (+86) 21-64253689.
authors.forename: Wen-Hao
authors.initials: WH
authors.lastname: Ji
authors.affiliation: College of Chemistry & Chemical Engineering, Yangzhou University, Yangzhou, 225002 (P. R. China).
authors.forename: Ying
authors.initials: Y
authors.lastname: Han
authors.affiliation: School of Pharmacy, Shanghai University of Traditional Chinese Medicine, 1200 Cailun Road, Shanghai, 201203 (P. R. China).
authors.forename: PeiYing
authors.initials: P
authors.lastname: Wu
authors.affiliation: Shanghai Key Laboratory of New Drug Design, School of Pharmacy, East China University of Science and Technology, 130 Meilong Road, Shanghai, 200237 (P. R. China), Fax: (+86) 21-64253689.
authors.forename: Jiangmeng
authors.initials: J
authors.lastname: Ren
authors.affiliation: Shanghai Key Laboratory of New Drug Design, School of Pharmacy, East China University of Science and Technology, 130 Meilong Road, Shanghai, 200237 (P. R. China), Fax: (+86) 21-64253689. zengbb@ecust.edu.cn.|Key Laboratory of Synthetic Chemistry of Natural Substances, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Road, Shanghai, 200032 (P. R. China). zengbb@ecust.edu.cn.
authors.forename: Bu-Bing
authors.initials: BB
authors.lastname: Zeng
keywords: hydrogen transfer; natural products; persulfates; synthons; terpenoids