Methyl 7-meth­oxy-9-oxo-9H-xanthene-2-carboxyl­ate

Paweł Niedziałkowski; Tadeusz Ossowski; Artur Sikorski

doi:10.1107/S1600536809003602

. 2009 Feb 6;65(Pt 3):o484–o485. doi: 10.1107/S1600536809003602

Methyl 7-methoxy-9-oxo-9H-xanthene-2-carboxylate

Paweł Niedziałkowski ^a, Tadeusz Ossowski ^a, Artur Sikorski ^a,^*

PMCID: PMC2968451 PMID: 21582153

Abstract

The crystal structure of the title compound, C₁₆H₁₂O₅, is stabilized by C—H⋯O hydrogen bonds and C=O⋯π interactions; π–π interactions are also present. With respective average deviations from planarity of 0.003 (2) and 0.002 (1) Å, the xanthone and ester fragments are oriented at an angle of 2.8 (2)° with respect to each other. The mean planes of the xanthone skeleton lie either parallel to each other or are inclined at an angle of 85.5 (2)° in the crystal structure.

Related literature

For general background and uses of xanthones, see: Chen et al. (1993 ▶); Denisova-Dyatlova & Glyzin (1982 ▶); Fukai et al. (2005 ▶); Gopalakrishnan et al. (1997 ▶); Ignatushchenko et al. (2000 ▶); Ito et al. (2003 ▶); Librowski et al. (2005 ▶); Pfister et al. (1972 ▶, 1980 ▶). For related structures, see: Evans et al. (2004 ▶); Shi et al. (2004 ▶); Macias et al. (2001 ▶). For synthesis, see: Geertsema et al. (2006 ▶). For background to the various types of intermolecular interactions, see: Bianchi et al. (2004 ▶); Steiner (1999 ▶) Santos-Contreras et al. (2007 ▶); Hunter & Sanders (1990 ▶). For analysis of intermolecular interactions, see: Spek (2003 ▶).

Experimental

Crystal data

C₁₆H₁₂O₅
M _r = 284.26
Monoclinic,
a = 4.7709 (4) Å
b = 10.5375 (8) Å
c = 26.7854 (19) Å
β = 93.266 (7)°
V = 1344.40 (18) Å³
Z = 4
Mo Kα radiation
μ = 0.11 mm⁻¹
T = 295 (2) K
0.20 × 0.04 × 0.04 mm

Data collection

Oxford Diffraction Ruby CCD diffractometer
Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2008 ▶) T _min = 0.994, T _max = 0.997
23842 measured reflections
2366 independent reflections
1051 reflections with I > 2σ(I)
R _int = 0.086

Refinement

R[F ² > 2σ(F ²)] = 0.038
wR(F ²) = 0.092
S = 0.81
2366 reflections
193 parameters
H-atom parameters constrained
Δρ_max = 0.13 e Å⁻³
Δρ_min = −0.14 e Å⁻³

Data collection: CrysAlis CCD (Oxford Diffraction, 2008 ▶); cell refinement: CrysAlis RED (Oxford Diffraction, 2008 ▶); data reduction: CrysAlis RED; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: ORTEPII (Johnson, 1976 ▶); software used to prepare material for publication: SHELXL97 and PLATON (Spek, 2003 ▶).

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536809003602/xu2476sup1.cif

e-65-0o484-sup1.cif^{(18.2KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809003602/xu2476Isup2.hkl

e-65-0o484-Isup2.hkl^{(116.3KB, 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
C3—H3⋯O16ⁱ	0.93	2.54	3.362 (3)	147
C20—H20A⋯O21ⁱⁱ	0.96	2.50	3.454 (3)	173

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

Table 2. π–π interactions (Å,°).

CgI	CgJ	Cg⋯Cg	Dihedral angle	Interplanar distance	Offset
A	Cⁱⁱⁱ	3.549 (1)	0.8	3.420 (1)	1.068 (1)
B	Aⁱⁱⁱ	3.583 (1)	0.1	3.454 (1)	0.953 (1)
B	Cⁱⁱⁱ	3.772 (1)	0.8	3.455 (1)	1.525 (1)

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Symmetry code: (iii) Inline graphic . CgA, CgB and CgC are the centroids of the C9/O10/C11–C14, C1–C4/C12/C11 and C5–C8/C13/C14 rings, respectively. The dihedral angle is that between the planes of the rings CgI and CgJ. The interplanar distance is the perpendicular distance of CgI from ring J. The offset is the perpendicular distance of ring I from ring J.

Table 3. C—O⋯π interactions (Å,°).

X	I	J	I⋯J	X⋯J	X—I⋯J
C15	O16	CgBⁱⁱⁱ	3.564 (2)	3.689 (2)	86.4 (1)

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Symmetry code: (iii) Inline graphic . CgB is the centroid of the C1–C4/C12/C11 ring.

Acknowledgments

This work was supported by Funds for Science in 2008 as a Research Project (No. BW-8000-5-0453-8).

supplementary crystallographic information

Comment

Xanthones represent a structurally diverse group of natural products with a broad range of biological activities. The unsubstituted xanthones have not been discovered in nature but its numerous derivatives have been isolated from representatives of higher plants, lichens, and lower fungi (Denisova-Dyatlova & Glyzin, 1982). Many naturally occurring xanthones as well as their synthetic derivatives described in numerous scientific publications exploit wide spectrum of biological activities: anti-allergic (Pfister et al., 1972), anti-inflammatory (Librowski et al., 2005), antitumor (Ito et al., 2003), antimicrobial (Fukai et al., 2005), cardiovascular (Chen et al., 1993), antimalarial (Gopalakrishnan et al., 1997) and antifungal activity (Ignatushchenko et al., 2000). The biological activity and the features responsible for the activity of xanthones largely depends on their structures. It is know that the 7-substituted xanthone-2-carboxylic acids and their esters show anti-allergic activity, which depends on the substituted groups (Pfister et al., 1980).

In the molecule of the title compound (Fig. 1) the bond lengths and angles characterizing the geometry of the xanthone skeleton are typical for this group compounds (Evans et al., 2004; Shi et al., 2004; Macias et al., 2001).

With respective average deviations from planarity of 0.003 (2) and 0.002 (1) Å, the xanthone and ester fragment are oriented at 2.8 (2)° to each other. The methoxy group lies nearly in the mean plane of the xanthone skeleton; the dihedral angles between the mean planes xanthone skeleton and delineated by atoms C7/O19/C20 are equal 0.7 (2)°. The mean planes of the xanthone skeleton lie either parallel or are inclined at an angle of 85.5 (2)° in the lattice.

In the crystal structure, weak intermolecular C—H···O hydrogen bonds (Table 1, Fig. 2) link the molecules, forming layers. The central ring A and the lateral rings B and C are involved in multidirectional π–π interactions and link layers between themselves (Table 2, Fig. 3). The O16(carboxyl) atom is involved in weak C—O···π interactions directed toward the lateral aromatic ring (ring B) (Table 3, Fig. 3).

All the interactions demonstrated were found by PLATON (Spek, 2003). The C—H···O (Bianchi et al., 2004; Steiner, 1999) interactions exhibit a hydrogen-bond-type nature. The C—O(carbonyl)···π interactions (Santos-Contreras et al., 2007), and also π–π interactions (Hunter & Sanders, 1990) should be of an attractive nature.

Experimental

7-Methoxy-9-oxo-9H-xanthene-2-carboxylatic acid methyl ester was synthesized by three steps. First, in a nucleophilic substitution of 4-methoxyphenol and 4-bromoisophthalic acid, to yield 4-(4-methoxyphenoxy)isophthalic acid, by refluxing 45 min in N,N-dimethylformamide with potassium carbonate, sodium iodide and activated Cu-bronze. In the next reaction, called intramolecular Friedel–Crafts acylation was synthesized 7-methoxy-9-oxo-9H-xanthene-2-carboxylatic acid (Geertsema et al., 2006). In last step 7-methoxy-9-oxo-9H-xanthene-2-carboxylatic acid was esterified with methanol by refluxing in thionyl chloride in 45 min and then treated with mixture of methanol and triethylamine in room temperature by 12 h with catalytic amount of 4-dimethylaminopyridine (DMAP). The crude product was dissolved in small amount of anhydrous methanol to obtain single crystals suitable for X-ray analysis by slow evaporation of methanol solution at 298 K.