6β,15β-Diacet­oxy-1β,7β,13α-trihydr­oxy-7α,20-ep­oxy-ent-kaur-16-ene

Xue-Mei Di; Fu-Lin Yan; Chuang Feng; Jian-Min Cui

doi:10.1107/S1600536810001170

. 2010 Jan 16;66(Pt 2):o359. doi: 10.1107/S1600536810001170

6β,15β-Diacetoxy-1β,7β,13α-trihydroxy-7α,20-epoxy-ent-kaur-16-ene

Xue-Mei Di ^a, Fu-Lin Yan ^a,^*, Chuang Feng ^a, Jian-Min Cui ^b

PMCID: PMC2979703 PMID: 21579784

Abstract

The title compound, C₂₄H₃₄O₈, a natural ent-kaurane diterpenoid, is composed of four rings with the expected cis and trans junctions. The crystal structure is stabilized by intermolecular O—H⋯O hydrogen bonds. In addition, an intramolecular O—H⋯O hydrogen bond occurs.

Related literature

For the genus Isodon and diterpenoids, see: Sun et al. (2001 ▶); Jung et al. (1990 ▶); Li & Tian (2001 ▶); Yan et al. (2008 ▶); Han et al. (2005 ▶). For bond-length data, see: Allen et al. (1987 ▶)

Experimental

Crystal data

C₂₄H₃₄O₈
M _r = 450.51
Orthorhombic,
a = 10.295 (2) Å
b = 13.696 (3) Å
c = 15.802 (3) Å
V = 2228.1 (8) Å³
Z = 4
Mo Kα radiation
μ = 0.10 mm⁻¹
T = 93 K
0.33 × 0.33 × 0.30 mm

Data collection

Rigaku SPIDER diffractometer
18422 measured reflections
2878 independent reflections
2819 reflections with I > 2σ(I)
R _int = 0.034
Standard reflections: 0

Refinement

R[F ² > 2σ(F ²)] = 0.030
wR(F ²) = 0.073
S = 1.07
2878 reflections
306 parameters
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.21 e Å⁻³
Δρ_min = −0.15 e Å⁻³

Data collection: RAPID-AUTO (Rigaku, 2004 ▶); cell refinement: RAPID-AUTO; data reduction: RAPID-AUTO; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: ORTEP-3 (Farrugia, 1997 ▶) and DIAMOND (Brandenburg, 1998 ▶); software used to prepare material for publication: SHELXTL (Sheldrick, 2008 ▶).

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536810001170/lx2122sup1.cif

e-66-0o359-sup1.cif^{(26.4KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536810001170/lx2122Isup2.hkl

e-66-0o359-Isup2.hkl^{(141.3KB, 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
O2—H2O⋯O6ⁱ	0.85 (3)	1.96 (3)	2.7811 (17)	163 (3)
O5—H5O⋯O4	0.88 (3)	2.19 (3)	2.9373 (18)	142 (2)
O6—H6O⋯O8ⁱⁱ	0.94 (3)	1.83 (3)	2.7600 (17)	170 (2)

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

Acknowledgments

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

supplementary crystallographic information

Comment

The title compound (I), 6β, 15β-Diacetoxy-1β, 7β, 13α-trihydroxy-7α, 20-epoxy-ent-kaur-16-ene is a new natural ent-kaurane diterpenoid isolated from the medicinal plant Isodon japonica. The leaves of this plant has been used as an antibacterial, anti-inflammatory, stomachic, and anthelmintic agent in China, Korean and Japan by local people (Jung et al., 1990; Li & Tian, 2001). The structure of compound (I) was postulated from spectroscopic methods. In order to further confirm the structure and conformation of (I), a crystal structure analysis has been undertaken. The X-ray crystallographic analysis of (I) confirms the molecular structure of (I) proposed by spectroscopic methods.

Fig.1 shows its conformation: three hydroxyl groups adopt β, β, α-orientations at C1, C7 and C13, two acetoxyl groups adopt β-orientations at C6 and C15 respectively. There is a trans junction between ring A (C1–C5/C10) and ring B (C5–C10); cis junctions are present between ring B and ring C (C8/C9/C11–C14), and ring C and ring D (C8/C13–C16). The bond lengths and angles are within expected aranges (Allen et al., 1987). Conformation of ring can be seen according to the X-ray diffraction pattern (Fig.1). Ring A adopts chair conformation, with an average torsion angles of 51.43 (18) °. Rings B and C adopt boat conformation because of the formation of the oxygen bridge at C-7 and C-20. Ring D shows an evenlope conformation; the flap atom, C14, lies 0.693 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(R), C5(R), C6(S), C7(S), C8(S), C9(S), C10(S), 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 seuies as reported in genus Isodon (Sun et al.,2001), rather than in the kaurane series, and so allowed us to assign the correct configuration.

The molecular packing (Fig. 2) is stabilized by two different intermolecular O–H···O hydrogen bonds (Table 1; symmetry code as in Fig. 2). The crystal packing (Fig. 2) is further stabilized by an intramolecular O–H···O hydrogen bond (Table 1; symmetry code as in Fig. 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/CH₃OH(10:1), giving 70 mg of compound (I) (m.p. 505-507 K. Optical rotation: [α]_D²⁰ -79.6 ° (c 0.45, CH₃OH). Single crystals suitable for X-ray diffraction were obtained by slow evaporation of a solution of the title compound in methanol at room temperature.