Napelline-type C_(20)-diterpenoid alkaloid iminiums from an aqueous extract of ‘‘fu zi'': Solvent-/base-/acid-dependent transformation and equilibration between alcohol iminium and aza acetal forms  

作　　者：Xian-Hua Meng Zhi-Bo Jiang Cheng-Gen Zhu Qing-Lan Guo Cheng-Bo Xu Jian-Gong Shi 

机构地区：[1]State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College

出　　处：《Chinese Chemical Letters》2016年第7期993-1003,共11页中国化学快报（英文版）

基　　金：Financial support from the National Natural Science Foundation of China (NNSFC; Nos. 21132009, 30825044);the National Science and Technology Project of China (Nos. 2012ZX09301002002, 2011ZX0 9307-002-01)

摘　　要：Three new napelline-type C20-diterpenoid alkaloids,named aconicarmichinium A and B trifluoroacetates（1 and 2） and aconicarmichinium C chloride（3）,were isolated from an aqueous extract of ＂fu zi＂,the lateral roots of Aconitum carmichaelii.Their structures were elucidated by extensive spectroscopic data analysis.Compounds 1-3 represent the first examples of napelline-type C20 diterpenoid alkaloid alcohol iminiums,of which the structures were fully characterized.In addition,transformation and equilibration between the alcohol iminiums（1-3） and the aza acetals la-3a were investigated by measurements of the NMR spectra in protic and aprotic deuterium solvents including alkali pyridine-d5,along with evaporation under reduced pressure and gradual additions of TFA,AcOH,and HC1.The results demonstrated that the transformation and equilibration were solvent-,base-,and acid-dependent.Especially,in aqueous biological fluid,these C20-diterpenoid alkaloids would more likely exist as the alcohol iminiums accompanied by anion counterparts in biosystems to increase their solubility, bioavailability, transportations, and functions.The absolute configurations of 1-3 were confirmed by X-ray crystallographic analysis of 2a.Three new napelline-type C20-diterpenoid alkaloids,named aconicarmichinium A and B trifluoroacetates（1 and 2） and aconicarmichinium C chloride（3）,were isolated from an aqueous extract of ＂fu zi＂,the lateral roots of Aconitum carmichaelii.Their structures were elucidated by extensive spectroscopic data analysis.Compounds 1-3 represent the first examples of napelline-type C20 diterpenoid alkaloid alcohol iminiums,of which the structures were fully characterized.In addition,transformation and equilibration between the alcohol iminiums（1-3） and the aza acetals la-3a were investigated by measurements of the NMR spectra in protic and aprotic deuterium solvents including alkali pyridine-d5,along with evaporation under reduced pressure and gradual additions of TFA,AcOH,and HC1.The results demonstrated that the transformation and equilibration were solvent-,base-,and acid-dependent.Especially,in aqueous biological fluid,these C20-diterpenoid alkaloids would more likely exist as the alcohol iminiums accompanied by anion counterparts in biosystems to increase their solubility, bioavailability, transportations, and functions.The absolute configurations of 1-3 were confirmed by X-ray crystallographic analysis of 2a.

关 键 词：Aconitum carmichaelii Ranunculaceae Napelline-type C20-diterpenoid alkaloid Aconicarmichiniums A–C Alcohol iminium and aza acetal forms of the diterpenoid alkaloid Transformation and equilibration 

分 类 号：O629.3[理学—有机化学]