1. Construction of the Isocopalane Skeleton: Application of a Desulfinylative 1,7-Hydrogen Atom Transfer Strategy.
- Author
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Xiao, Xiong, Xu, ZhongYu, Zeng, Qian-Ding, Chen, Xi-Bo, Ji, Wen-Hao, Han, Ying, Wu, PeiYing, Ren, Jiangmeng, and Zeng, Bu-Bing
- Subjects
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ALDEHYDES , *HYDROGEN atom , *NUCLEAR magnetic resonance spectroscopy , *X-ray diffraction , *DEUTERIUM , *HYDROGEN - 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 K2S2O8-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. [ABSTRACT FROM AUTHOR]
- Published
- 2015
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