Abstract
This paper describes a rare phenomenon of multi-conformers caused by conformational change of A-ring in the C18- and C19- N-dealkyl diterpenoid alkaloids. The possible reasons for the generation of multiple conformational isomers are complex, which could be affected by the substituents at C-1, C-3, C-13, C-14, and C-15, pH, solvents, the intramolecular hydrogen bond between 1α-OCH3/1α-OH and N-H groups, acid-base treatment, preparation methods, and work-up procedures.
Graphical Abstract
![](/cms/asset/a8ab85ef-d13f-4664-a52b-4136db725edd/ganp_a_2164711_uf0001_c.jpg)
Acknowledgements
We gratefully acknowledge Professor Ming Zhao (College of Pharmacy, Capital University, Beijing) for measuring 1H-15N HMBC spectra. We also thank Hao Yisheng Pharmaceutical Company for providing the sample of 3,14,15-triacetyl-N-deethylaconine (21a).
Disclosure statement
No potential conflict of interest was reported by the author(s).