Crystal structure of tuguaconitine, a diterpene alkaloid from Aconitum sibiricum

Abstract

The three-dimensional structure of a natural product, tuguaconitine (C 23H35NO7) from Aconitum sibiricum was determined by single crystal X-ray diffraction analysis. The compound was recrystallized from a methanol solution into orthorhombic crystal system, with a=18.093(4), b=12.075(11), c=9.824(4) A, Dm = 1.35, D x = 1.354 g/cm3, space group P212 121, and Z=4. The structure was solved by direct method and refined by least-squares procedure to the final R value of 0.046 for 1495 observed reflections with I≥2σ(I). Aconitines are diterpene alkaloid composed of six rings. In the molecule, two 6-membered rings have stable chair conformation, but other two 6-membered rings have unstable boat conformation because of their bonding strain and hydrogen bonds. Based on the three-dimensional structure of tuguaconitine, we suggest another 2D-diagram for the compound which is far better in imagination of the spatial shape of the molecule than the ordinary one.