Crystal structure of sepaconitine, a C19-diterpenoid alkaloid from the roots of Aconitum sinomontanum Nakai

Xin-Wei Shi; Qiang-Qiang Lu; Jun-Hui Zhou; Xin-Ai Cui

doi:10.1107/S205698901501258X

. 2015 Jul 8;71(Pt 8):o550–o551. doi: 10.1107/S205698901501258X

Crystal structure of sepaconitine, a C₁₉-diterpenoid alkaloid from the roots of Aconitum sinomontanum Nakai

Xin-Wei Shi ^a,^*, Qiang-Qiang Lu ^a, Jun-Hui Zhou ^a, Xin-Ai Cui ^a

PMCID: PMC4571391 PMID: 26396791

Abstract

The title compound [systematic name: [(1α,14α,16β)-20-ethyl-8,9,10-trihydroxy-1,14,16-trimethoxyaconitan-4-yl 2-aminobenzoate], C₃₀H₄₂N₂O₈, a natural C₁₉-diterpenoid alkaloid, possesses an aconitane carbon skeleton with four six-membered rings and two five-membered rings. The fused ring system contains two chair, one boat, one twist-boat and two envelope conformations. Intramolecular N—H⋯O hydrogen bonds are observed between the amino and carbonyl groups. The molecules are linked together via O—H⋯O hydrogen bonds, forming a three-dimensional framework.

Keywords: crystal structure, C₁₉-diterpenoid alkaloid, hydrogen bonding

Related literature

For the synthesis of the title compound, see: Wei et al. (1996 ▸). The absolute configuration of the title compound has been assigned to be the same as that reported for typical natural C₁₉-diterpenoid alkaloids, see: Wang et al. (2007 ▸); He et al. (2008 ▸). The six-ring rigid-frame structure of the title compound is identical to that of lappaconitine and mesaconitine (Wang et al., 2007 ▸; He et al., 2008 ▸). graphic file with name e-71-0o550-scheme1.jpg

Experimental

Crystal data

C₃₀H₄₂N₂O₈
M _r = 558.66
Orthorhombic,
a = 9.6917 (5) Å
b = 16.0510 (7) Å
c = 18.3549 (7) Å
V = 2855.3 (2) Å³
Z = 4
Cu Kα radiation
μ = 0.77 mm⁻¹
T = 173 K
0.32 × 0.32 × 0.28 mm

Data collection

Bruker SMART CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2002 ▸) T _min = 0.791, T _max = 0.813
8125 measured reflections
4528 independent reflections
3831 reflections with I > 2σ(I)
R _int = 0.029

Refinement

R[F ² > 2σ(F ²)] = 0.046
wR(F ²) = 0.126
S = 1.05
4528 reflections
388 parameters
60 restraints
H-atom parameters constrained
Δρ_max = 0.46 e Å⁻³
Δρ_min = −0.19 e Å⁻³

Data collection: SMART (Bruker, 2002 ▸); cell refinement: SAINT (Bruker, 2002 ▸); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ▸); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Supplementary Material

Crystal structure: contains datablock(s) I, New_Global_Publ_Block. DOI: 10.1107/S205698901501258X/hg5447sup1.cif

e-71-0o550-sup1.cif^{(43.1KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S205698901501258X/hg5447Isup2.hkl

e-71-0o550-Isup2.hkl^{(221.9KB, hkl)}

Click here for additional data file.^{(8.1KB, cdx)}

Supporting information file. DOI: 10.1107/S205698901501258X/hg5447Isup4.cdx

Click here for additional data file.^{(1.8MB, tif)}

ORTEPII . DOI: 10.1107/S205698901501258X/hg5447fig1.tif

ORTEPII drawing of sepaconitine (I) with the atomic numbering scheme. Displacement ellipsoids are plotted at the 50% probability level.

Click here for additional data file.^{(2.4MB, tif)}

c . DOI: 10.1107/S205698901501258X/hg5447fig2.tif

The packing of molecules in the crystal structure of sepaconitine (I), viewed along the c direction (Hydrogen bonds are shown as dashed lines).

CCDC reference: 1409635

Additional supporting information: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (, ).

DHA	DH	HA	D A	DHA
O5H5AO6	0.84	2.34	2.909(3)	126
O4H4O5	0.84	2.27	2.684(3)	111
O4H4O3ⁱ	0.84	1.94	2.713(3)	153
O3H3O4	0.84	1.99	2.524(3)	121
N1H1BO1	0.88	2.00	2.666(4)	131
N1H1AO8ⁱⁱ	0.88	2.19	2.999(3)	152

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Symmetry codes: (i) Inline graphic ; (ii) .

Acknowledgments

This project was supported by the Science and Technology Research and Development Projects of Shaanxi Province (grant No. 2013KJXX-74), the National Natural Science Foundation of China (grant No. 31200257) and the Science and Technology Program of Shaanxi Academy of Sciences (grant No. 2012k-04).

supplementary crystallographic information

S1. Comment

The title compound was isolated from the roots of Aconitum sinomontanum Nakai, collected in Taibai mountain of the Qinling area, Shaanxi province, People's Republic of China. the crystal structure determination of sepaconitine was carried out and the result reported here.

The molecular structure is shown in Fig. 1. The molecule has a rigid structure consisting of six main rings (A—F), which is identical with that of lappaconitine and mesaconitine (Wang et al., 2007; He et al., 2008). The six-membered rings A (C1/C2/C3/C4/C5/C11) and N-containing heterocyclic ring E (C4/C5/C11/C17/N2/C18) adopt chair conformations; The six-membered ring D (C8/C9/C14/C13/C16/C15) displays a boat conformation, but B (C7/C8/C9/C10/C11/C17) adopts a twist-boat conformation; the five-membered rings C (C9/C10/C12/C13/C14) and F (C5/C6/C7/C17/C11) adopt C14- and C 17-envelope conformations, respectively. Two cis-fused ring junctions involve rings A/E and also B/C. Two trans-fused ring junctions are observed between rings A/B and between E/F. Ring E is slightly flattened at C5 due to the presence of an ethyl-substituted N atom in the ring. The benzoate moiety attached to C4 is almost planar. The OCH₃ group attached to C16 is disordered into two positions with site occupancies Factor of 0.5.

The crystal structure has an intra-molecular N—H···O hydrogen bond between the amino group and carbonyl O atom (Table 1). Inter-molecular N—H···O hydrogen bonds are observed in the crystal. The molecules are linked together via O—H```O hydrogen bonds in the c direction (Table 1, Fig. 2).

S2. Experimental

The title compound was isolated from the roots of Aconitum sinomontanum, using a method described previously (Wei et al., 1996). Colourless crystals were grown from methanol at room temperature by slow evaporation.

S3. Refinement

The hydrogen atoms were placed in calculated positions and refined as riding with U_iso(H) = 1.2 Ueq (C) or 1.5Ueq(C, O). The positions of methyl and hydroxy hydrogens were rotationally optimized. The absolute configuration of the title compound, sepaconitine, has been assigned to be the same as that reported for typical natural C₁₉-diterpenoid alkaloids (Wang et al., 2007; He et al., 2008).