Revision of structures of acridone alkaloids from natural sources

• Published in: Journal of the Chinese Chemical Society (Taipei) 2021-04, Vol.68 (4), p.669-677
• Main Authors: Chen, Hung‐Yi, Lam, Sio‐Hong, Yang, Mei‐Lin, Hung, Hsin‐Yi, Shieh, Po‐Chuen, Chen, Fu‐An, Kuo, Ping‐Chung, Wu, Tian‐Shung
• Format: Article
• Language: English
• Subjects: acridone alkaloid; Alkaloids; Functional groups; Glycosmis macrantha; NMR; Nuclear magnetic resonance; Pleiospermium alatum; Severinia buxifolia; Spectra
• ISSN: 0009-4536; 2192-6549
• DOI: 10.1002/jccs.202000345

The reported chemical structures of tricyclic acridone alkaloids (1–6) from Severinia buxifolia and Pleiospermium alatum were reinvestigated through a comparison of the nuclear magnetic resonance (NMR) spectral data of similar compounds and a comprehensive study of their two‐dimensional (2D) NMR spectra. The structures of 1–5 were further confirmed by a comparison of their spectral data with those of the authentic samples and standards. The different chemical shifts caused by substituted functional groups in the tricyclic acridones were summarized according to the results in the present study. Furthermore, the synthetic compound 10 (N‐methyl‐1,3‐dihydroxy‐4,5,6‐trimethoxyacridine‐9‐one) has not been reported from any natural sources in the previous literature. In addition, the chemical structures of macranthanine (21) and 7‐hydroxy‐noracronycine (22) from Glycosmis macrantha were also revised. The 1H and 13C NMR data of tricyclic (1–20) and two polycyclic acridone alkaloids (21 and 22) were reinvestigated. The different chemical shifts caused by substituted functional groups in the tricyclic acridones were summarized according to the results in the present study. These results are potentially useful for the determination of the acridone structures with multiple substitutions.