Gelsecorydines A–E, Five Gelsedine–Corynanthe-Type Bisindole Alkaloids from the Fruits of Gelsemium elegans

• DOI: 10.1021/acs.joc.8b00736
• Publication Date: 2018-05-03T06:45:37Z
• Authors: Ni-Ping Li; Miao Liu; Xiao-Jun Huang; Xue-Ying Gong; Wei Zhang; Min-Jing Cheng; Wen-Cai Ye; Lei Wang
• Keywords: Models, Molecular; Indoles; Dose-Response Relationship, Drug; Circular Dichroism; Macrophages; Molecular Conformation; Crystallography, X-Ray; Nitric Oxide; 01 natural sciences; Gelsemium; 0104 chemical sciences; Mice; Structure-Activity Relationship; Alkaloids; RAW 264.7 Cells; Fruit; Animals; Quantum Theory

Five monoterpenoid bisindole alkaloids with new carbon skeletons, gelsecorydines A-E (1-5), together with their biogenetic precursors were isolated from the fruits of Gelsemium elegans. Compounds 1-5 represent the first examples of heterodimeric frameworks composed of a gelsedine-type alkaloid and a modified corynanthe-type one. Notably, compound 2 featured an unprecedented caged skeleton with a 6/5/7/6/5/6 heterohexacyclic ring system, which possessed a pyridine ring that linked the two monomers. Their structures and absolute configurations were elucidated by spectroscopic analysis, X-ray diffraction, and electronic circular dichroism (ECD) calculation. A plausible biosynthetic pathway for compounds 1-5 is proposed. Compounds 1, 3, 4, and 5 exhibited a significant inhibitory effect against nitric oxide (NO) production in macrophages.