Three new C20-diterpenoid alkaloids with a sulfonic acid unit,named aconicarmisulfonines B and C (1 and 2) and chuanfusulfonine A (3),respectively,were isolated from the Aconitum carmichaelii lateral roots (“fu zi” in Chinese).Structures of 1-3 were determined by spectroscopic data analysis.Intriguing chemical properties and reactions were observed for the C2o-diterpenoid alkaloids: (a) specific selective nucleophilic addition of the carbonyl (C-12) in 1 with CD3OD;(b) interconversion between 1 and 2 in D2O;(c) stereo-and/or regioselective deuterations of H-11 α in 1-3 and both H-11 α and H-11 β in aconicarmisulfonine A (4);(d) TMSP-2,2,3,3-d4 promoted cleavage of the C-12-C-13 bond of 4 in D2O;(e) dehydrogenation of 4 in pyridine-d5,and (f) Na2SO3-assisted dehydrogenation and N-deethylation of songorine (5,a putative precursor of 1-4).Biogenetically,1 and 2 are correlated with 4,for which the same novel carbon skeleton is proposed to be derived from semipinacol rearrangements via migrations of C-13-C-16 and C-15-C-16 bonds of the napelline-type skeleton,respectively.Meanwhile,3 is a highly possible precursor or a concurrent product in the biosynthetic pathways of 1,2,and 4.In the acetic acid-induced mice writhing assay,at 1.0 mg/kg (i.p.),compounds 1,2,5,5a,and 5b exhibited analgesic effects against mice writhing.