Structure Revision of Anti-Inflammatory Indole Alkaloids with a 1,2-Benzisoxazole Ring
Ju Ryeong Lee1, Kyoung Jin Park2, Song Lim Ham1
1Department of Biopharmaceutical Convergence, Sungkyunkwan University, Suwon 16419, Republic of Korea.
Abstract:
(R)- and (S)-2-(benzo[d]isoxazol-3-yl)-2-ethylindolin-3-one [(±)-1] were previously isolated from NIRAM, a natural blue dye from Polygonum tinctorium, and their structures were initially proposed to possess a 1,2-benzisoxazole ring. In this study, the structures of (±)-1 were revised to have an indole-anthranilic acid fused tetracyclic ring rather than the 1,2-benzisoxazole ring by reanalysis of one-dimensional (1D) and two-dimensional (2D) NMR followed by density functional theory (DFT) chemical shift calculation, DP4+ technique, and ECD simulation.
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