Kopsileuconines A−D: Bisindole Alkaloids with Cytotoxic Activity from Kopsia Hainanensis

Kopsileuconines A-D (1-4), 1- 4 ), four monoterpenoid bisindole alkaloids with unprecedented skeletons, along with their biosynthetically related precursors (5-8) 5- 8 ) were isolated from the roots of Kopsia hainanensis. . Compound 1 possessed an undescribed C-6- C-5 ' ' dimerization pattern of aspidofractinine-type alkaloids. Compounds 2- 4 were rhazinilam-kopsine (2) 2 ) and rhazinilam-aspidofractinine type (3 3 and 4 ) bisindole alkaloids with undescribed skeletons, respectively. Their structures with absolute configurations were fully accomplished by extensive spectroscopic analysis, quantum-chemical calculations, and X-ray crystallography. A plausible biosynthetic pathway for 1- 4 was proposed. Compound 2 exhibited a significant inhibitory effect against human lung cancer cell lines PC9 (EGFR mutant), with an IC50 50 value of 15.07 f 1.19 mu M.