12-Acetyl-6-hy­droxy-3,3,9,9-tetra­methyl­furo[3,4-b]pyrano[3,2-h]xanthene-7,11(3H,9H)-dione

Gwendoline Cheng Lian Ee; Siow Hwa Teo; Huey Chong Kwong; Mohamed Ibrahim Mohamed Tahir; Sidik Silong

doi:10.1107/S1600536810048592

. 2010 Nov 27;66(Pt 12):o3331–o3332. doi: 10.1107/S1600536810048592

12-Acetyl-6-hydroxy-3,3,9,9-tetramethylfuro[3,4-b]pyrano[3,2-h]xanthene-7,11(3H,9H)-dione

Gwendoline Cheng Lian Ee ^a,^*, Siow Hwa Teo ^a, Huey Chong Kwong ^a, Mohamed Ibrahim Mohamed Tahir ^a, Sidik Silong ^a

PMCID: PMC3011782 PMID: 21589606

Abstract

The title compound, Artonol B, C₂₄H₂₀O₇, isolated from the stem bark of Artocarpus kemando, consists of four six-membered rings and one five-membered ring. The tricyclic xanthone ring system is almost planar [maximum deviation 0.115 (5) Å], whereas the pyranoid ring is in a distorted boat conformation·The furan ring is almost coplanar with the fused aromatic ring, making a dihedral angle of 3.76 (9)°. The phenol ring serves as a intramolecular hydrogen-bond donor to the adjacent carbonyl group and also acts as an intermolecular hydrogen-bond acceptor for the methyl groups of adjacent molecules, forming a three-dimensional network in the crystal.

Related literature

For bond-length data, see Allen et al. (1987 ▶). For related structures, see: Doriguetto et al. (2001 ▶); Marek et al. (2003 ▶); Boonnak et al. (2007 ▶). For the biological activity of flavonoids from Artocarpus kemando and other species of Artocarpus, see: Burkill (1935 ▶); Makmur et al. (1999 ▶); Wei et al. (2005 ▶); Toshio et al. (2003 ▶); Lin et al. (1996 ▶); Shimizu et al. (2000 ▶); Patil et al. (2002 ▶); Tati et al. (2001 ▶). For a description of the Cambridge Structural Database, see: Allen (2002 ▶).

Experimental

Crystal data

C₂₄H₂₀O₇
M _r = 420.42
Monoclinic,
a = 36.511 (2) Å
b = 5.3275 (2) Å
c = 20.0218 (8) Å
β = 96.318 (5)°
V = 3870.8 (3) Å³
Z = 8
Cu Kα radiation
μ = 0.89 mm⁻¹
T = 150 K
0.30 × 0.28 × 0.04 mm

Data collection

Oxford Diffraction Gemini E diffractometer
Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2006 ▶) T _min = 0.780, T _max = 0.965
17338 measured reflections
3813 independent reflections
3383 reflections with I > 2.0σ(I)
R _int = 0.018

Refinement

R[F ² > 2σ(F ²)] = 0.039
wR(F ²) = 0.110
S = 0.99
3813 reflections
280 parameters
H-atom parameters constrained
Δρ_max = 0.32 e Å⁻³
Δρ_min = −0.21 e Å⁻³

Data collection: CrysAlis CCD (Oxford Diffraction, 2006 ▶); cell refinement: CrysAlis CCD; data reduction: CrysAlis RED (Oxford Diffraction, 2006 ▶); program(s) used to solve structure: SIR92 (Altomare et al., 1994 ▶); program(s) used to refine structure: CRYSTALS (Betteridge et al., 2003 ▶); molecular graphics: Mercury (Macrae et al., 2006 ▶); software used to prepare material for publication: CRYSTALS.

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536810048592/kp2279sup1.cif

e-66-o3331-sup1.cif^{(19.6KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536810048592/kp2279Isup2.hkl

e-66-o3331-Isup2.hkl^{(191.1KB, 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
C16—H161⋯O15ⁱ	0.96	2.55	3.4062 (19)	148
C20—H202⋯O13ⁱ	0.97	2.53	3.4918 (19)	171
O22—H221⋯O5	0.88	1.78	2.5922 (19)	153
C31—H313⋯O22ⁱⁱ	0.97	2.57	3.5170 (19)	165
C27—H271⋯O5ⁱⁱⁱ	0.94	2.58	3.4923 (19)	163

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

Acknowledgments

The authors would like to acknowledge Ministry of Science, Technology and Innovation (MOSTI) for the e-science funding provided.

supplementary crystallographic information

Comment

Flavonoids are polyphenolic compounds which are important for human health. Previous studies on flavonoids from this plant and other species of Artocarpus have revealed their wide range of pharmacological activities (Wei, et al., 2005; Toshio, et al., 2003; Lin et al., 1996; Shimizu et al., 2000; Patil et al., 2002; Tati et al., 2001). Artocarpus kemando, a tree of the forests and swamps is distributed in Thailand, Peninsular Malaysia, Sumatra and Borneo island (Burkill, 1935). In our continuing search for anti-cancer hit compounds we decided to look at Artocarpus kemando. We found that the chloroform extract of the stem bark of Artocarpus kemando displayed significant growth inhibition activities towards HL-60 cell lines and obtained Artonol B (I).

The molecular structure of (I) (Fig. 1) with the xanthone skeleton (ring B, C and D) is nearly planar with the exception of the atom C8 with the deviation from planarity of 0.115 Å. Rings A, B, C and D are individually almost planar, including the O5, O15 abd O22 atoms that are linked to them. The largest deviations from the individiual least-squares planes are 0.030 Å, 0.023 Å, 0.037 Å and 0.019 Å for ring A, B, C and D, respectively. Rings A and B form a dihedral angle of 3.06°, those of B and C ring form an angle of 4.23° and rings C and D form an dihedral angle of 3.42°. The planes of rings B and D intersect on a line which is approximately through the middle of ring C and gives rise to a dihedral angle of 7.65°. The mean torsion angle of ring D is 16.26° and it adopts a conformation half way between an envolope and a half-boat. The major pucking is in ring D at C28, owing to the constraint of the double bond between C26 and C27.

Bond distances and angles in the titled compound are in normal range (Allen et al., 1987). The average value of C—O1 bond lengths in pyranoid ring C is 1.368 Å and the observed geometries of pyranoid ring C are comparable to other reported pyranoxanthone geometries (Doriguetto et al., 2001; Marek et al.,2003; Boonnak et al., 2007). The crystal structure is stabilised by intra- and intermolecular O—H···O and C—H···O hydrogen bonding. The titled molecules exhibit a moderate intramolecular hydrogen bond O22—H221···O5, with O···O = 2.5922 (19) Å. Meanwhile, the H atom of the C31 methyl group forms a hydrogen bond with O22 at (-x, -y + 2, -z) [the C···O distance is 3.5170 (19) Å]. The H atom at C27 forms a hydrogen bond with O5 at (x, -y + 1, z - 1/2)[the C···O distance is 3.4923 (19) Å](Table 1).

The cystallographic data of this crystal structure has been deposited at Cambridge Crystallographic Data Center with deposition number CCDC 796169 (Allen, 2002).

Experimental

The powdered stem bark (4.7 kg) of Artocarpus kemando were defatted with n-hexane and sequentially extracted using methanol at room temperature for more than 48 h. This resulted in 198.5 g of methanol extract. The methanol extract was dissolved in a water-acetone mixture (1: 3, 500 mL) and the soluble portion was partitioned using chloroform (CHCl₃) (3 × 400 mL) to afford a crude chloroform extract (20 g). Repeated silica gel column chromatographic separation on the chloroform extract (20 g) (hexane, hexane-chloroform, chloroform-ethyl acetate, ethyl acetate-methanol and methanol in order of increasing polarity) followed by radial chromatography yielded pure artonol B (I), fine yellow solid with melting point 462-467 K. Good single crystals for X-ray diffraction were prepared by slow evaporation and diffusion of diethyl ether into a solution of (I) in chloroform at room temperature.