(1α,8β)-6β-Benzoyloxy-6-dehydroxyheteratisine from Aconitum zeravschanicum

The title compound, C29H37NO6, was isolated from Aconitum zeravschanicum and exhibits antiarhythmic activity. It is a derivative of the diterpenoid alkaloid heteratisine and as such the core framework of the molecule contains four six-membered, three seven-membered and one five-membered ring. The chair conformation of one of the methoxy-substituted six-membered rings is different from that observed in heteratisine hydrobromide monohydrate. In the latter case, this ring adopts a boat conformation due to a stabilizing intramolecular N—H⋯O hydrogen bond. In the crystal structure of the title compound, there is only one acidic H atom. This hydroxyl group forms an intermolecular O—H⋯O hydrogen bond that links molecules into infinite chains along the b axis.

The title compound, C 29 H 37 NO 6 , was isolated from Aconitum zeravschanicum and exhibits antiarhythmic activity. It is a derivative of the diterpenoid alkaloid heteratisine and as such the core framework of the molecule contains four sixmembered, three seven-membered and one five-membered ring. The chair conformation of one of the methoxysubstituted six-membered rings is different from that observed in heteratisine hydrobromide monohydrate. In the latter case, this ring adopts a boat conformation due to a stabilizing intramolecular N-HÁ Á ÁO hydrogen bond. In the crystal structure of the title compound, there is only one acidic H atom. This hydroxyl group forms an intermolecular O-HÁ Á ÁO hydrogen bond that links molecules into infinite chains along the b axis.
We thank the Academy of Sciences of Uzbekistan for supporting this study.
The molecular structure of the title compound is shown in Fig. 1. The heteratisine skeleton contains four six-membered rings, (A, C, D and F), one five-membered ring (B), and three seven-membered rings (e.g. E, others not labeled for clarity) ( Fig. 2). Ring B has an envelope and ring Ca more or less regular chair conformation. Ring F shows a significant distortion and rings D and E adopt a boat conformations. The chair conformation of ring A in the title molecule is different from that observed in heteratisine hydrobromide monohydrate (Przybylska, 1965). For the salt of the parent compound ring A adopts a boat conformation due to a stabilizing intramolecular N-H···O hydrogen bond between the protonated amine towards the oxygen atom, an interaction not present in the title compound.
The aromatic ring and the acyl-group are rotated against each other, the dihedral angle of their respective planes is 32.6 (9)°. There is only one acidic hydrogen atom in the crystal structure of the title compound. This hydroxyl group forms an intermolecular O-H···O hydrogen bond that links the molecules into infinite chains along the b-axis. (Table 1; Fig.3)

Experimental
The title compound was isolated from the chloroform fraction of the leaves of Aconitum zeravschanicum by a known method (Nigmatullaev et al., 2000). Crystals suitable for X-ray analysis were obtained by slow evaporation of an ethanol solution at room temperature (m.p. 485-487 K).

Refinement
The hydroxyl H atom was located in a difference Fourier map but was ultimately placed geometrically (with an O-H distance of 0.82 Å). The H atoms bonded to C atoms were placed geometrically (with C-H distances of 0.98 Å for CH; 0.97 Å for CH 2 ; 0.96 Å for CH 3 ; and 0.93 Å for C ar ) and included in the refinement in a riding motion approximation with  Fig. 1. The molecular structure of 6-benzoylheteratisine, showing the atomic numbering scheme and displacement ellipsoids drawn at the 30% probability level.  (1α,8β)-6β-Benzoyloxy-6-dehydroxyheteratisine