On the basis of intensive interpretation of the 1H NMR spectroscopic data, the ring A conformation of aconine (1) was speculated as twist boat in CDCl3, and as chair or twist boat in acetone-d6 and pyridine-d5. The ring A of pseudaconine (2) adopts the chair conformation in CDCl3, acetone-d6, and pyridine-d5. Accordingly, the boat conformation of ring A in these two diterpenoid alkaloids in CDCl3 reported in the literature [1] should be revised. The difference in 13C NMR data for the same compound (1 or 2) in two different solvents (CDCl3, pyridine-d5) can be attributed to solvent effects.
PelletierS.W., ModyN.V., SawhneyR.S. (1979) 13C nuclear magnetic resonance spectra of some C19-diterpenoid alkaloids and their derivatives. Canadian Journal of Chemistry, 57, 1652–1655.
2.
JiH., ChenD.L., WangF.P. (2004) Two new C19-diterpenoid alkaloids from Aconitum nagarum var. lasiandrum. Heterocycles, 63, 2383–2370.
3.
JiangB.G., LinS., ZhuC.G., WangS.A., WangY.N., ChenM.H., ZhangJ.J., HuJ.F., ChenN.H., YangY.C., ShiJ.G. (2012) Diterpenoid alkaloids from the lateral root of Aconitum carmichaelii. Journal of Natural Products, 75, 1145–1159.
4.
ZhangZ.T., WangL., ChenQ.F., ChenQ.H., ChenD.L., LiuX.Y., WangF.P. (2013) Revision of the diterpenoid alkaloids reported in JNP paper (2012, 75, 1145–1159). Tetrahedron, 69, 5859–5866.
5.
LiangX.T.Nuclear magnetic resonances: Interpretation and application of high-resolution NMR. (in Chinese). Science Press, pp. 19, 7976.
