1α,6β,7β,14β,15β-Penta­hydr­oxy-7α,20-ep­oxy-ent-kaur-16-ene

Chuang Feng; Fu-Lin Yan; Xue-Mei Di; Peng-Li Sun

doi:10.1107/S1600536809052490

. 2009 Dec 12;66(Pt 1):o103. doi: 10.1107/S1600536809052490

1α,6β,7β,14β,15β-Pentahydroxy-7α,20-epoxy-ent-kaur-16-ene

Chuang Feng ^a, Fu-Lin Yan ^a,^*, Xue-Mei Di ^a, Peng-Li Sun ^a

PMCID: PMC2980239 PMID: 21579994

Abstract

The title compound, enmenol, C₂₀H₃₀O₆, a natural ent-kaurane diterpenoid, comprises five fused rings, four of which are six-membered. Cyclohexane ring A adopts a chair conformation, rings B and C adopt boat conformations, while ring D has an envelope conformation, and two intramolecular O—H⋯O interactions occur. In the crystal, intermolecular O—H⋯O hydrogen bonds generate a two dimensional network.

Related literature

For the genus Isodon and diterpenoids from this genus see: Sun et al. (2001 ▶); Mori et al. (1970 ▶); Wang et al. (1995 ▶); Yan et al. (2008 ▶). For bond-length data, see: Allen et al. (1987 ▶).

Experimental

Crystal data

C₂₀H₃₀O₆
M _r = 366.44
Orthorhombic,
a = 8.0007 (3) Å
b = 10.7161 (6) Å
c = 20.7759 (9) Å
V = 1781.25 (14) Å³
Z = 4
Mo Kα radiation
μ = 0.10 mm⁻¹
T = 93 K
0.43 × 0.37 × 0.23 mm

Data collection

Rigaku AFC10 Saturn724+ diffractometer
14459 measured reflections
2336 independent reflections
2263 reflections with I > 2σ(I)
R _int = 0.029

Refinement

R[F ² > 2σ(F ²)] = 0.031
wR(F ²) = 0.071
S = 1.01
2336 reflections
249 parameters
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.28 e Å⁻³
Δρ_min = −0.17 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/S1600536809052490/zs2022sup1.cif

e-66-0o103-sup1.cif^{(24.2KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809052490/zs2022Isup2.hkl

e-66-0o103-Isup2.hkl^{(114.8KB, 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
O3—H3O⋯O6ⁱ	0.80 (3)	2.00 (3)	2.7761 (18)	164 (3)
O4—H4O⋯O5	0.83 (3)	1.95 (3)	2.6806 (18)	146 (2)
O5—H5O⋯O2ⁱⁱ	0.86	1.90	2.7455 (18)	167
O6—H6O⋯O3	0.83 (2)	1.88 (2)	2.6642 (18)	157 (2)

Open in a new tab

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

Acknowledgments

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

supplementary crystallographic information

Comment

The title compound, 1α,6β,7β,14β,15β-pentahydroxy-7α,20- epoxy-ent-kaur-16-ene, C₂₀H₃₀O₆ (I) (enmenol) is a natural ent-kaurane diterpenoid isolated from the medicinal plant Isodon japonica var glaucocalyx (Maxim.) Hara. The leaves of this plant have been used for the treatment of colds, throat swelling and pain, tonsillitis, gastritis, hepatitis, mastitis and cancer. The title compound has also been isolated from Isodon trichocarpus (Mori et al., 1970) and Isodon macrocabyx (Wang et al.,1995), and its structure was postulated from spectroscopic methods (Mori et al., 1970; Wang et al., 1995). The X-ray crystallographic analysis of (I) confirms this proposed molecular structure (Fig. 1). In the structure there is a trans junction between ring A (C1—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). Ring A adopts a chair conformation with an average torsion angle of 51.8 (2)°. Rings B and C adopt a boat conformation because of the formation of the oxygen bridge between C7 and C20. Ring D shows an envelope conformation. In addition, the six-membered rings O1/C20/C10/C5—C7 and O1/C7—C10/C20 both adopt boat conformations. The five hydroxy groups at C1,C6,C7,C14 and C15 adopt α,β, β,β,β-orientations respectively. Bond lengths and angles are within expected ranges (Allen et al., 1987), with average values (Å): Csp³—Csp³ = 1.544 (2), Csp³—Csp² = 1.514 (2), Csp²—Csp² (CC) = 1.322 (2), Csp³—O = 1.441 (2).

The title compound has ten chiral centers at C1(S), C5(R), C6(S), C7(S), C8(R), C9(S), C10(S), C13(S) C14(R) and C15(R). Although the absolute configuration could not be reliably determined from anomalous dispersion effects, the negative optical rotation showed that this compound belongs to the ent-kaurane series as found in genus Isodon (Sun et al., 2001), rather than to the kaurane series, allowing us to assign the correct configuration. In the crystal structure, intermolecular O—H···O hydrogen bonds (Table 1) are effective in the stabilization of the structure and are responsible for the formation of a two-dimensional network (Fig. 2).

Experimental

The dried and crushed leaves of Isodon japonica var. glaucocalyx (21 kg), (collected from Huixian Prefecture, Henan Province, China) were extracted three times with Me₂CO/H₂O (7:3, v/v) at room temperature over a period of seven 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 Me₂CO/MeOH (10:1), giving 28 mg of compound (I) (m.p. 527–529 K; optical rotation: [α]_D²² -30° (c 0.15, MeOH). Crystals suitable for X-ray analysis were obtained by slow evaporation of a solution of the compound in MeOH at room temperature.