1α,11α,15β-Triacet­oxy-7β-hydroxy-7α,20-ep­oxy-ent-kaur-16-en-6-one

Fu-Lin Yan; Xue-Mei Di; Chuang Feng; Rei-Jie Hou

doi:10.1107/S1600536809041828

. 2009 Oct 17;65(Pt 11):o2770. doi: 10.1107/S1600536809041828

1α,11α,15β-Triacetoxy-7β-hydroxy-7α,20-epoxy-ent-kaur-16-en-6-one

Fu-Lin Yan ^a,^*, Xue-Mei Di ^a, Chuang Feng ^a, Rei-Jie Hou ^a

PMCID: PMC2971301 PMID: 21578364

Abstract

The title compound, C₂₆H₃₄O₉, a natural ent-kaurane diterpenoid, is composed of four rings with the expected cis and trans junctions. In the crystal structure, the molecules stack along the a axis and are linked together by intermolecular O—H⋯O hydrogen bonds.

Related literature

For the genus Isodon and diterpenoids, see: Sun et al. (2001 ▶); Li et al. (2006 ▶); Yan et al. (2009 ▶). For hydorgen bonds, see: Nardelli (1995 ▶). For a description of the Cambridge Structural Database, see: Allen et al. (1987 ▶).

Experimental

Crystal data

C₂₆H₃₄O₉
M _r = 490.53
Orthorhombic,
a = 11.3317 (5) Å
b = 11.5061 (4) Å
c = 19.0663 (6) Å
V = 2485.93 (16) Å³
Z = 4
Mo Kα radiation
μ = 0.10 mm⁻¹
T = 93 K
0.43 × 0.37 × 0.33 mm

Data collection

Rigaku AFC10/Saturn724+ diffractometer
Absorption correction: none
16790 measured reflections
3165 independent reflections
3073 reflections with I > 2σ(I)
R _int = 0.029

Refinement

R[F ² > 2σ(F ²)] = 0.034
wR(F ²) = 0.085
S = 1.00
3165 reflections
325 parameters
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.21 e Å⁻³
Δρ_min = −0.18 e Å⁻³

Data collection: CrystalClear (Rigaku, 2008 ▶); cell refinement: CrystalClear; data reduction: CrystalClear; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: SHELXTL (Sheldrick, 2008 ▶); software used to prepare material for publication: SHELXTL.

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536809041828/jj2009sup1.cif

e-65-o2770-sup1.cif^{(26.9KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809041828/jj2009Isup2.hkl

e-65-o2770-Isup2.hkl^{(155.3KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O5—H5O⋯O3ⁱ	0.89 (3)	2.18 (3)	2.853 (2)	133 (3)

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Symmetry code: (i) Inline graphic .

Acknowledgments

This work was supported by the Henan Provincial Science and Technology Foundation of China (No. 611042600)

supplementary crystallographic information

Comment

The title compound, (I), C₂₆H₃₄O₉, is a natural ent-kaurane diterpenoid isolated from the medicinal plant Isodon Japonica. The leaves of this plant have been used as an antibacterial, anti-inflammatory and stomachic agent. The structure of compound (I), derived from Isodon Parvifolius, has been postulated from spectroscopic methods (Li et al., 2006). As a conformation of (I) the crystal structure analysis has been determined here and confirms the structure proposed above. One hydroxyl group adopts a β-orientation at C7, and three acetoxyl groups adopt α,α,β-orientations at C1,C11 and C15, respectively, Fig.1. A trans junction occurs between ring A (C1—C5/C10) and ring B (C5—C10) while cis junctions are present between rings B and C (C8/C9/C11—C14), and between rings C and D (C8/C13—C16). Bond lengths and angles are within expected ranges (Allen et al., 1987), with average values (Å): Csp³—Csp³ = 1.542 (3), Csp³—Csp² = 1.509 (3), Csp²—Csp² (CC) = 1.320 (3), CO = 1.207 (2), Csp³—O = 1.438 (2), and Csp²—O = 1.351 (2). Ring A adopts a chair conformation, with an average torsion angle of 51.5 (2) °. Rings B and C adopt a boat conformation because of the formation of an oxygen bridge at C-7 and C-20. Ring D shows an envelope conformation; the flap atom, C14, lies 0.7648 (0.0028) Å from the plane defined by atoms C8, C15, C16 and C13. In addition, the six-membered rings O1/C20/C10/C5—C7 and O1/C7—C10/C20 both adopt boat conformations. Compound (I) contains nine chiral centers at C1(S), C5(R), C7(S), C8(S), C9(S), C10(S), C11(R), C13(S) and C15(R). Although the absolute configuration could not be reliably determined from anomalous dispersion effects, the negative optical rotation showed this compound to be in the ent-kaurane series as reported in genus Isodon (Sun et al.,2001), rather than in the Kaurane series, which allowed us to assign the correct configuration. The title molecule is characterized by the formation of O–H···O hydrogen-bonds (Table 1, Nardelli, 1995). The strong hydrogen bond O–H···O interaction is responsible for crystal growth in [100] direction, Fig. 2. Indeed, in the substructure, atom O5 in the molecule at (x, y, z) acts as a hydrogen bond donor to the carbonyl O3 atom in the molecule at (-x +1/2, -y +1, z +1/2).

Experimental

The dried and crushed leaves of Isodon Japonica (17 kg, collected from Tongbai Prefecture, Henan Province, China) were extracted four times with Me₂CO/H₂O (7:3, v/v) at room temperature over a period of six days. The extract was filtered and the solvent was removed under reduced pressure. The residue was then partitioned between water and AcOEt. After removal of the solvent, the AcOEt residue was separated by repeated silica gel (200–300 mesh) column chromatography and recrystallization from CHCl₃/Me₂CO(10:1), giving 60 mg of compound (I) (m.p. 430–432 K. Optical rotation: [α]_D²² -74.6 ° (c 0.45, MeOH). Crystals suitable for X-ray analysis were obtained by slow evaporation of a solution of compound (I) in Me₂CO at room temperature.