Construction of the isocopalane skeleton: application of a desulfinylative 1,7-hydrogen atom transfer strategy

Xiong Xiao; ZhongYu Xu; Qian-Ding Zeng; Xi-Bo Chen; Wen-Hao Ji; Ying Han; PeiYing Wu; Jiangmeng Ren; Bu-Bing Zeng

doi:10.1002/chem.201500794

Construction of the isocopalane skeleton: application of a desulfinylative 1,7-hydrogen atom transfer strategy

Chemistry. 2015 Jun 1;21(23):8351-4. doi: 10.1002/chem.201500794. Epub 2015 Apr 23.

Authors

Xiong Xiao¹, ZhongYu Xu¹, Qian-Ding Zeng², Xi-Bo Chen¹, Wen-Hao Ji¹, Ying Han², PeiYing Wu³, Jiangmeng Ren¹, Bu-Bing Zeng^{4

5}

Affiliations

¹ 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.
² College of Chemistry & Chemical Engineering, Yangzhou University, Yangzhou, 225002 (P. R. China).
³ School of Pharmacy, Shanghai University of Traditional Chinese Medicine, 1200 Cailun Road, Shanghai, 201203 (P. R. China).
⁴ 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.
⁵ 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.

PMID: 25907201
DOI: 10.1002/chem.201500794

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.

Keywords: hydrogen transfer; natural products; persulfates; synthons; terpenoids.

Publication types

Research Support, Non-U.S. Gov't