(20S*,24S*)-25-Hy­droxy-20,24-ep­oxy-A-homo-4-oxadammaran-3-one (Chrysura) isolated from the leaves of Walsura chrysogyne

Ilya Iryani Mahmod; Huey Chong Kwong; Mohamed Ibrahim Mohamed Tahir; Intan Safinar Ismail

doi:10.1107/S1600536811047337

. 2011 Nov 12;67(Pt 12):o3296. doi: 10.1107/S1600536811047337

(20S,24S)-25-Hydroxy-20,24-epoxy-A-homo-4-oxadammaran-3-one (Chrysura) isolated from the leaves of Walsura chrysogyne

Ilya Iryani Mahmod ^a, Huey Chong Kwong ^a, Mohamed Ibrahim Mohamed Tahir ^a, Intan Safinar Ismail ^a,^*

PMCID: PMC3238949 PMID: 22199798

Abstract

The title dammarane triterpenoid, C₃₀H₅₀O₄, assigned the name chrysura, was isolated from an ethyl acetate extract of Walsura chrysogyne leaves (Meliaceae). It has 20S*,24S* relative stereochemistry and an oxepanone ring with two methyl groups at position 4. The two cyclohexane rings adopt chair conformations. The cyclopentane and tetrahydrofuran rings have envelope conformations; their mean planes make a dihedral angle of 13.1 (3)°, indicating that the rings are only slightly tilted with respect to each other. There is an intramolecular C—H⋯O hydrogen bond in the molecule, which forms S(6) and S(7) ring motifs. In the crystal, molecules are linked via O—H⋯O and C—H⋯O hydrogen bonds, forming chains propagating along [001] which stack along the b-axis direction.

Related literature

For related structures, see: Pan et al. (2010 ▶). For graph-set analysis, see: Bernstein et al. (1995 ▶). For the biological activity of related compounds, see: Burkill (1966 ▶); Hegnauer (1990 ▶); Fujiwara et al. (1982 ▶).

Experimental

Crystal data

C₃₀H₅₀O₄
M _r = 474.70
Orthorhombic,
a = 6.9881 (1) Å
b = 11.0108 (2) Å
c = 34.9733 (7) Å
V = 2691.01 (8) Å³
Z = 4
Cu Kα radiation
μ = 0.59 mm⁻¹
T = 100 K
0.40 × 0.08 × 0.07 mm

Data collection

Bruker APEXII CCD diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2009 ▶) T _min = 0.801, T _max = 0.960
48305 measured reflections
5058 independent reflections
5040 reflections with I > 2σ(I)
R _int = 0.045

Refinement

R[F ² > 2σ(F ²)] = 0.092
wR(F ²) = 0.233
S = 1.21
5058 reflections
316 parameters
H-atom parameters constrained
Δρ_max = 0.47 e Å⁻³
Δρ_min = −0.38 e Å⁻³

Data collection: APEX2 (Bruker, 2009 ▶); cell refinement: SAINT (Bruker, 2009 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: Mercury (Macrae et al., 2006 ▶); software used to prepare material for publication: SHELXL97.

Supplementary Material

Crystal structure: contains datablock(s) global, I. DOI: 10.1107/S1600536811047337/su2332sup1.cif

e-67-o3296-sup1.cif^{(28.4KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536811047337/su2332Isup2.hkl

e-67-o3296-Isup2.hkl^{(247.8KB, 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
C19—H19A⋯O32	0.96	2.44	3.082 (6)	124
O34—H34A⋯O32ⁱ	0.82	2.20	3.010 (5)	170
C26—H26A⋯O31ⁱ	0.96	2.53	3.392 (7)	150

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Symmetry code: (i) Inline graphic .

Acknowledgments

This research work was supported financially by the Research University Grant Scheme (RUGS: 05–01–09–0732RU) of Universiti Putra Malaysia, Malaysia.

supplementary crystallographic information

Comment

Meliaceae or Mahogany is a plant family, in the order of Sapindales, which consists of flowering plants of mostly trees, shrubs and a few herbaceous plants (Burkill, 1966). This family is noted for the wide range of compounds of different classes of which it is compossed, for example, terpenoids (triterpenoids, monoterpenes, sesquiterpenes, limonoids), saponins, alkaloids, polyphenols, quinines, fatty and hydroxyl acids (Hegnauer, 1990). Among these groups of constituents, some are responsible for biological activities such as antiviral, anthelmintic, antitumor, anti-inflammatory and anti-rheumatic, which have been scientifically proven (Fujiwara et al., 1982). Walsura chrysogyne is a Meliaceae species which is among the least explored of higher plants.

The title dammarane triterpenoid, namely chrysura (1), has been isolated for the first time from the ethyl acetate extract of the leaves of Walsura chrysogyne (Meliaceae). Recently, the same compound was reported to have been obtained from Aglaia foveolata, but in resin form (compound 5 in reference Pan et al., 2010). They determined its relative stereochemistry by Nuclear Magnetic Resonance (NMR) spectroscopy. Herein, we describe the crystal structure of the title compound, chrysura (1), whose relative configuration was also obtained by two-dimensional NMR spectroscopy. By a close comparison of the ¹³C NMR signals at C-20, C-21, C-22, C-23 and C-24 reported for compound 5 (δ 86.5, 27.2, 34.8, 26.3 and 86.4; Pan et al., 2010) and those obtained for the title compound, chrysura (1) (δ 86.5, 27.2, 35.0, 26.4 and 86.5), it was shown that these two compounds are identical. This is substantiated by the ¹H NMR signal at H-24 of chrysura (1), which is a doublet of doublet with J values of 10 and 5.5 Hz, comparable to the values observed for compound 5, that is 9.9 and 5.6 Hz. Hence, the relative configuration at C20 and C24 of chrysura (1), was determined by NMR to be the same as that of compound 5 [Pan et al., 2010].

The molecular structure of the title molecule, chrysura (1), is shown in Fig. 1. The two cyclohexane rings, B (C5-C10) and C (C8,C9,C11-C14), adopt chair conformations. The cyclopentane ring D (C13-C17) and the tetrahydrofuran ring E (O33,C20, C22-C24) have envelope conformations, with atoms C14 and C23 at the flap of rings D and E, respectively. The mean planes through rings D and E make a dihedral angle of 13.1 (3)°, indicating that they are only slightly twisted with respect to each other. As shown in Fig. 1, the structure of the molecule is stabilized by an intramolecular C—H···O hydrogen bond (Table 1), which forms S(6) and S(7) ring motifs (Bernstein et al., 1995).

In the crystal of chrysura (1), molecules are linked via intermolecular O—H···O and C—H···O hydrogen bonds (Table 1), forming chains propagating along [001]. These chains stack along the b-axis, as shown in Fig. 2.

Hence, in the title compound, chrysura (1), the relative configurations at C20 and C24 of the epoxy unit (ring E) have been confirmed to be S-methyl configurations.

Experimental

The air-dried ground leaves of Walsura chrysogyne (8.94 kg) collected at Pasir Raja, Terengganu, Malaysia, were macerated in methanol at room temperature (3 × 1000 ml). The crude extract (230 g) was partitioned into hexane (12.2 g), ethyl acetate (EtOAc; 16.6 g), and water (16.8 g). A portion (9.0 g) of the EtOAc extract was further fractionated by using vacuum column chromatography on silica gel normal phase (7.5 × 20 cm) eluted with CHCl₃, and CHCl₃—MeOH in 10% increasing amounts of MeOH. Fraction MeOH-CHCl₃ [9:1] (2.0 g) was subjected to another column chromatography on Sephadex LH-20 (2 × 30 cm) with CHCl₃–MeOH (9:1) to yield four fractions. The fraction obtained by hexane-EtOAc [7:3] (85.3 mg) was further purified on silica gel normal phase (1 × 20 cm) eluted with hexane-acetone (9:1) to afford the title compound (134.8 mg, 0.059%). Colourless needle-shaped crystals of the title compound, suitable for X-ray diffraction analysis, were recrystallized from ethyl aceate-acetone. The ¹H- and ¹³C-NMR spectral data were consistent with those reported by (Pan et al., 2010).