3-O-Methyl-1-isomangostin

Nawong Boonnak; Suchada Chantrapromma; Hoong-Kun Fun

doi:10.1107/S1600536812023409

. 2012 May 31;68(Pt 6):o1950–o1951. doi: 10.1107/S1600536812023409

3-O-Methyl-1-isomangostin

Nawong Boonnak ^a, Suchada Chantrapromma ^a,^*,^‡, Hoong-Kun Fun ^b,^§

PMCID: PMC3379502 PMID: 22719700

Abstract

In the title xanthone derivative [systematic name: 9-hydroxy-5,10-dimethoxy-2,2-dimethyl-11-(3-methylbut-2-en-1-yl)-2,3,4,12-tetrahydro-1,7-dioxatetraphen-12-one], C₂₅H₂₈O₆, the xanthone ring system is roughly planar, with an r.m.s. deviation of 0.1038 (1) Å. The chromane ring is in a half-chair conformation and the 3-methylbut-2-enyl substituent is axially attached with an (+)-anticlinal conformation. Two weak intramolecular C—H⋯O interactions generate two S(6) ring motifs. In the crystal, molecules are linked into ribbons along the c axis by O—H⋯O and weak C—H⋯O hydrogen bonds. A π–π interaction, with a centroid–centroid distance of 3.5413 (8) Å, is also observed.

Related literature

For background to xanthones and their biological activity, see: Bennett & Lee (1989 ▶); Boonnak et al. (2010 ▶); Gopalakrishnan et al. (1997 ▶); Ho et al. (2002 ▶); Mahabusarakam et al. (1987 ▶); Obolskiy et al. (2009 ▶); Phongpaichit et al. (1994 ▶); Shankaranarayan et al. (1979 ▶); Yoshikawa et al. (1994 ▶). For related structures, see: Chantrapromma et al. (2005 ▶). For details of hydrogen-bond motifs, see: Bernstein et al. (1995 ▶). For ring conformations, see: Cremer & Pople (1975 ▶). For bond-length data, see: Allen et al. (1987 ▶). For the stability of the temperature controller used in the data collection, see Cosier & Glazer (1986 ▶). graphic file with name e-68-o1950-scheme1.jpg

Experimental

Crystal data

C₂₅H₂₈O₆
M _r = 424.47
Monoclinic,
a = 10.8635 (9) Å
b = 16.6117 (13) Å
c = 13.4146 (8) Å
β = 118.843 (5)°
V = 2120.5 (3) Å³
Z = 4
Mo Kα radiation
μ = 0.09 mm⁻¹
T = 100 K
0.33 × 0.23 × 0.17 mm

Data collection

Bruker APEX DUO CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2009 ▶) T _min = 0.970, T _max = 0.984
21681 measured reflections
5630 independent reflections
4344 reflections with I > 2σ(I)
R _int = 0.031

Refinement

R[F ² > 2σ(F ²)] = 0.046
wR(F ²) = 0.134
S = 1.05
5630 reflections
286 parameters
H-atom parameters constrained
Δρ_max = 0.42 e Å⁻³
Δρ_min = −0.22 e Å⁻³

Data collection: APEX2 (Bruker, 2009 ▶); cell refinement: SAINT (Bruker, 2009 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009 ▶).

Supplementary Material

Crystal structure: contains datablock(s) global, I. DOI: 10.1107/S1600536812023409/rz2760sup1.cif

e-68-o1950-sup1.cif^{(32KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536812023409/rz2760Isup2.hkl

e-68-o1950-Isup2.hkl^{(275.7KB, hkl)}

Supplementary material file. DOI: 10.1107/S1600536812023409/rz2760Isup3.cml

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—H1O5⋯O2ⁱ	0.90	1.77	2.6082 (17)	155
C15—H15A⋯O1ⁱⁱ	0.99	2.55	3.3820 (18)	141
C20—H20C⋯O5	0.98	2.57	3.104 (2)	115
C21—H21A⋯O2	0.99	2.29	2.807 (2)	111

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

Acknowledgments

NB thanks Prince of Songkla University for a postdoctoral fellowship. Financial support from Prince of Songkla University is gratefully acknowledged. The authors also thank Universiti Sains Malaysia for the Research University Grant No. 1001/PFIZIK/811160.

supplementary crystallographic information

Comment

Garcinia genus plants are commonly known as a good providing source of bioactive xanthones (Bennett & Lee, 1989). The α-, β- and γ-mangostins are well known bioactive xanthones that were isolated from G. mangostana as major constituents (Mahabusarakam et al., 1987) and they exhibit various biological and pharmacological properties (Obolskiy et al., 2009; Phongpaichit et al., 1994) such as antibacterial (Boonnak et al., 2010), antifungal (Gopalakrishnan et al., 1997), anti-inflammatory (Shankaranarayan et al., 1979), antioxidant (Yoshikawa et al., 1994) and anti-cancer (Ho et al., 2002) activities. These interesting biological properties of xanthones have led us to synthesize the title compound (I) by modification of an isoprenyl side chain of β-mangostin to the chromane ring via acid catalysis (Gopalakrishnan et al., 1997) with the hope to enhance its bioactivity. However our antibacterial testing has found that (I) is less active than its precusor (β-mangostin). Herein the crystal structure of (I) is reported.

Compound (I) has a xanthone nucleus with a fused angular fashion chromane ring (Fig. 1). The three-ring system [C1–C13/O1] of the xanthone nucleus is roughly planar with an r.m.s. deviation of 0.1038 (1) Å from the plane through all the fourteen non-hydrogen atoms (maximum deviation of -0.192 (1) Å for atom O19). The chromane ring (C1–C2/C14–C16/O3) is in a half-chair conformation with puckering parameter Q = 0.4631 (17) Å, θ = 49.7 (2)° and φ = 272.7 (2)° (Cremer & Pople, 1975), with the puckered C14 and C15 atoms having deviations of -0.306 (1) and 0.293 (2) Å, respectively. The hydroxyl group is planarly attached at atom C8. The two methoxy groups have different orientations in which one methoxy group at atom C3 lies close to the plane of its bound benzene ring with the torsion angle C19–O4–C3–C4 = 1.79 (19)° whereas the other is axially attached at atom C9 with the torsion angle C20–O6–C9–C8 = 80.63 (15)°, indicating an (+)-anti-clinal conformation. The 3-methyl-2-butenyl substituent is attached at atom C10 with the torsion angle C9–C10–C21–C22 = 87.47 (16) °, indicating an (+)-anti-clinal conformation (Fig. 1). Intramolecular C20—H20C···O5 and C21—H21A···O2 weak interactions (Table 1) generate two S(6) ring motifs (Bernstein et al., 1995). The bond distances in (I) are within normal ranges (Allen et al., 1987) and comparable to those found in a related structure (Chantrapromma et al., 2005).

In the crystal packing, the molecules are linked into ribbons along [0 0 1] by O—H···O hydrogen bonds and the adjacent ribbons are further linked by weak C—H···O interactions (Fig. 2 and Table 1). A π–π interaction with the distance of Cg₂···Cg₂ⁱⁱ = 3.5413 (8) Å is observed; Cg₂ is the centroid of C1–C5/C13 ring; symmetry code: (ii) 1-x, 2-y, 2-z.

Experimental

A solution of β-mangostin (30 mg, 0.707 mmol) and p-toluenesulfonic acid (75 mg, 0.436 mmol) in dry acetic acid (1.30 ml) was stirred at room temperature for 24 h. The mixture was extracted with ethylacetate. The combined ethylacetate extract was further washed with a saturated aqueous NaHCO₃ solution and dried over anhydrous MgSO₄. The solvent was evaporated under reduced pressure to give a yellow residue, which was further purified by column chromatography (hexane/ethylacetate, 9:1 v/v) to yield the title compound (I). Yellow block-shaped single crystals of the title compound suitable for X-ray structure determination were recrystallized from a solution of CHCl₃/CH₃OH (9:1 v)/v by slow evaporation of the solvent at room temperature after several days.