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Acta Cryst. (2009). E65, o484-o485    [ doi:10.1107/S1600536809003602 ]

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

P. Niedzialkowski, T. Ossowski and A. Sikorski

Abstract top

The crystal structure of the title compound, C16H12O5, is stabilized by C-H...O hydrogen bonds and C=O...[pi] interactions; [pi]-[pi] 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.

Comment top

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.

Related literature top

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). [Please check rephrasing]

Experimental top

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.

Refinement top

All H atoms were positioned geometrically and refined using a riding model, with C—H = 0.93 Å and Uiso(H) = 1.2Ueq(C) for aromatic, and with C—H = 0.96 Å and Uiso(H) = 1.5Ueq(C) for methyl groups.

Computing details top

Data collection: CrysAlis CCD (Oxford Diffraction, 2008); cell refinement: CrysAlis RED (Oxford Diffraction, 2008); data reduction: CrysAlis RED (Oxford Diffraction, 2008); 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 (Sheldrick, 2008) and PLATON (Spek, 2003).

Figures top
[Figure 1] Fig. 1. The molecular structure of the title compound showing the atom-labeling scheme. Displacement ellipsoids are drawn at the 25% probability level and H atoms are shown as small spheres of arbitrary radius. CgA, CgB and CgC denote the ring centroids.
[Figure 2] Fig. 2. The arrangement of the molecules in the crystal structure viewed approximately along a axis. The C—H···O interactions are represented by dashed lines. H atoms not involved in the interactions have been omitted. [Symmetry codes: (i) 2 - x, 1 - y, 1 - z; (ii) -1 - x, -1/2 + y, 1/2 - z.]
[Figure 3] Fig. 3. The arrangement of the molecules in the crystal structure viewed approximately along a axis. The C—H···O and C—O···π interactions are represented by dashed lines and the π–π interactions are represented by dotted lines. H atoms not involved in the interactions have been omitted. [Symmetry codes: (iii) 1 + x, y, z.]
Methyl 7-methoxy-9-oxo-9H-xanthene-2-carboxylate top
Crystal data top
C16H12O5F(000) = 592.0
Mr = 284.26Dx = 1.404 Mg m−3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 2126 reflections
a = 4.7709 (4) Åθ = 3.0–25.0°
b = 10.5375 (8) ŵ = 0.11 mm−1
c = 26.7854 (19) ÅT = 295 K
β = 93.266 (7)°Needle, white
V = 1344.40 (18) Å30.2 × 0.04 × 0.04 mm
Z = 4
Data collection top
Oxford Diffraction Ruby CCD
diffractometer		2366 independent reflections
Radiation source: Enhance (Mo) X-ray Source1051 reflections with I > 2σ(I)
graphiteRint = 0.086
Detector resolution: 10.4002 pixels mm-1θmax = 25.0°, θmin = 3.0°
ω scansh = −5→5
Absorption correction: multi-scan
(CrysAlis RED; Oxford Diffraction, 2008)		k = −12→12
Tmin = 0.994, Tmax = 0.997l = −31→31
23842 measured reflections
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.038Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.092H-atom parameters constrained
S = 0.81 w = 1/[σ2(Fo2) + (0.0471P)2]
where P = (Fo2 + 2Fc2)/3
2366 reflections(Δ/σ)max = 0.001
193 parametersΔρmax = 0.13 e Å−3
0 restraintsΔρmin = −0.13 e Å−3
Crystal data top
C16H12O5V = 1344.40 (18) Å3
Mr = 284.26Z = 4
Monoclinic, P21/cMo Kα radiation
a = 4.7709 (4) ŵ = 0.11 mm−1
b = 10.5375 (8) ÅT = 295 K
c = 26.7854 (19) Å0.2 × 0.04 × 0.04 mm
β = 93.266 (7)°
Data collection top
Oxford Diffraction Ruby CCD
diffractometer		2366 independent reflections
Absorption correction: multi-scan
(CrysAlis RED; Oxford Diffraction, 2008)		1051 reflections with I > 2σ(I)
Tmin = 0.994, Tmax = 0.997Rint = 0.086
23842 measured reflectionsθmax = 25.0°
Refinement top
R[F2 > 2σ(F2)] = 0.038H-atom parameters constrained
wR(F2) = 0.092Δρmax = 0.13 e Å−3
S = 0.81Δρmin = −0.13 e Å−3
2366 reflectionsAbsolute structure: ?
193 parametersFlack parameter: ?
0 restraintsRogers parameter: ?
Special details top

Experimental. CrysAlis RED, Version 1.171.32.15 (Oxford Diffraction Ltd., 2008) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
C10.4869 (4)0.3741 (2)0.37390 (8)0.0507 (6)
H10.49500.40050.34090.061*
C20.6568 (4)0.4321 (2)0.41017 (8)0.0531 (6)
C30.6434 (5)0.3912 (2)0.45962 (9)0.0678 (7)
H30.75840.42890.48460.081*
C40.4634 (5)0.2964 (3)0.47187 (9)0.0735 (7)
H40.45480.27030.50490.088*
C5−0.2272 (5)−0.0083 (2)0.43087 (9)0.0742 (7)
H5−0.2221−0.02870.46470.089*
C6−0.4064 (5)−0.0705 (2)0.39752 (9)0.0723 (7)
H6−0.5229−0.13370.40890.087*
C7−0.4169 (4)−0.0408 (2)0.34712 (9)0.0570 (6)
C8−0.2448 (4)0.0520 (2)0.33022 (8)0.0506 (6)
H8−0.25140.07230.29640.061*
C90.1240 (4)0.2157 (2)0.34601 (8)0.0485 (5)
O100.1221 (3)0.14529 (15)0.44927 (5)0.0685 (5)
C110.3026 (4)0.2770 (2)0.38514 (7)0.0469 (5)
C120.2945 (4)0.2399 (2)0.43445 (8)0.0567 (6)
C13−0.0592 (4)0.1163 (2)0.36375 (7)0.0459 (5)
C14−0.0538 (4)0.0853 (2)0.41369 (8)0.0567 (6)
C150.8493 (5)0.5368 (2)0.39863 (10)0.0616 (6)
O160.9949 (4)0.59309 (17)0.42912 (7)0.0897 (6)
O170.8478 (3)0.56064 (15)0.34987 (6)0.0748 (5)
C181.0307 (5)0.6610 (2)0.33454 (10)0.0877 (8)
H18A0.99310.67830.29960.132*
H18B1.22280.63520.34030.132*
H18C0.99780.73620.35360.132*
O19−0.6050 (3)−0.10926 (15)0.31785 (6)0.0734 (5)
C20−0.6235 (5)−0.0814 (3)0.26581 (9)0.0837 (8)
H20A−0.7623−0.13510.24930.126*
H20B−0.4446−0.09620.25220.126*
H20C−0.67600.00580.26090.126*
O210.1291 (3)0.24526 (14)0.30176 (5)0.0657 (5)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
C10.0541 (13)0.0547 (16)0.0427 (13)0.0009 (12)−0.0024 (11)−0.0013 (11)
C20.0517 (13)0.0553 (16)0.0518 (15)−0.0049 (11)−0.0025 (11)−0.0058 (12)
C30.0741 (15)0.0794 (19)0.0481 (16)−0.0117 (14)−0.0139 (11)−0.0116 (14)
C40.0851 (17)0.087 (2)0.0471 (14)−0.0246 (16)−0.0071 (13)0.0017 (14)
C50.0855 (16)0.084 (2)0.0519 (15)−0.0292 (15)−0.0047 (13)0.0166 (14)
C60.0777 (16)0.0703 (19)0.0681 (19)−0.0229 (14)−0.0016 (14)0.0133 (15)
C70.0565 (13)0.0599 (16)0.0535 (15)−0.0049 (13)−0.0053 (11)0.0004 (13)
C80.0532 (12)0.0517 (15)0.0464 (13)−0.0031 (11)−0.0022 (11)−0.0001 (11)
C90.0491 (13)0.0508 (15)0.0449 (14)0.0006 (11)−0.0036 (11)0.0031 (12)
O100.0800 (10)0.0808 (13)0.0429 (9)−0.0254 (9)−0.0104 (8)0.0102 (8)
C110.0475 (12)0.0498 (15)0.0427 (13)−0.0023 (11)−0.0027 (10)0.0012 (11)
C120.0584 (13)0.0629 (17)0.0476 (14)−0.0139 (13)−0.0063 (11)0.0007 (12)
C130.0470 (12)0.0466 (14)0.0436 (14)0.0005 (11)−0.0022 (10)0.0020 (11)
C140.0617 (14)0.0596 (17)0.0473 (15)−0.0124 (12)−0.0087 (11)0.0037 (12)
C150.0620 (15)0.0620 (18)0.0598 (17)−0.0037 (13)−0.0044 (12)−0.0063 (15)
O160.1020 (13)0.0906 (14)0.0742 (12)−0.0367 (11)−0.0143 (10)−0.0106 (11)
O170.0865 (11)0.0729 (13)0.0641 (12)−0.0294 (10)−0.0039 (9)0.0052 (9)
C180.0935 (18)0.078 (2)0.092 (2)−0.0274 (16)0.0074 (15)0.0129 (16)
O190.0772 (10)0.0744 (12)0.0671 (12)−0.0265 (9)−0.0081 (8)−0.0049 (9)
C200.0931 (18)0.102 (2)0.0549 (17)−0.0282 (16)−0.0058 (13)−0.0135 (15)
O210.0744 (10)0.0781 (12)0.0432 (9)−0.0200 (8)−0.0084 (7)0.0105 (8)
Geometric parameters (Å, °) top
C1—C21.373 (3)C9—O211.227 (2)
C1—C111.394 (3)C9—C131.461 (3)
C1—H10.9300C9—C111.462 (3)
C2—C31.398 (3)O10—C121.366 (2)
C2—C151.480 (3)O10—C141.386 (2)
C3—C41.369 (3)C11—C121.380 (3)
C3—H30.9300C13—C141.376 (3)
C4—C121.384 (3)C15—O161.199 (2)
C4—H40.9300C15—O171.330 (3)
C5—C61.368 (3)O17—C181.446 (3)
C5—C141.383 (3)C18—H18A0.9600
C5—H50.9300C18—H18B0.9600
C6—C71.384 (3)C18—H18C0.9600
C6—H60.9300O19—C201.422 (3)
C7—O191.364 (2)C20—H20A0.9600
C7—C81.370 (3)C20—H20B0.9600
C8—C131.400 (3)C20—H20C0.9600
C8—H80.9300
C2—C1—C11121.9 (2)C12—C11—C9120.9 (2)
C2—C1—H1119.1C1—C11—C9121.22 (19)
C11—C1—H1119.1O10—C12—C11122.33 (19)
C1—C2—C3118.4 (2)O10—C12—C4116.0 (2)
C1—C2—C15122.2 (2)C11—C12—C4121.6 (2)
C3—C2—C15119.4 (2)C14—C13—C8119.0 (2)
C4—C3—C2121.0 (2)C14—C13—C9120.5 (2)
C4—C3—H3119.5C8—C13—C9120.44 (19)
C2—C3—H3119.5C13—C14—C5121.0 (2)
C3—C4—C12119.2 (2)C13—C14—O10122.5 (2)
C3—C4—H4120.4C5—C14—O10116.5 (2)
C12—C4—H4120.4O16—C15—O17123.1 (2)
C6—C5—C14119.2 (2)O16—C15—C2124.7 (2)
C6—C5—H5120.4O17—C15—C2112.2 (2)
C14—C5—H5120.4C15—O17—C18116.59 (19)
C5—C6—C7121.0 (2)O17—C18—H18A109.5
C5—C6—H6119.5O17—C18—H18B109.5
C7—C6—H6119.5H18A—C18—H18B109.5
O19—C7—C8125.1 (2)O17—C18—H18C109.5
O19—C7—C6115.3 (2)H18A—C18—H18C109.5
C8—C7—C6119.6 (2)H18B—C18—H18C109.5
C7—C8—C13120.2 (2)C7—O19—C20117.16 (17)
C7—C8—H8119.9O19—C20—H20A109.5
C13—C8—H8119.9O19—C20—H20B109.5
O21—C9—C13122.78 (19)H20A—C20—H20B109.5
O21—C9—C11122.5 (2)O19—C20—H20C109.5
C13—C9—C11114.73 (19)H20A—C20—H20C109.5
C12—O10—C14118.97 (16)H20B—C20—H20C109.5
C12—C11—C1117.8 (2)
C11—C1—C2—C30.3 (3)C3—C4—C12—C11−0.1 (4)
C11—C1—C2—C15−178.91 (19)C7—C8—C13—C14−0.3 (3)
C1—C2—C3—C4−0.6 (3)C7—C8—C13—C9−179.76 (19)
C15—C2—C3—C4178.6 (2)O21—C9—C13—C14178.94 (19)
C2—C3—C4—C120.6 (4)C11—C9—C13—C14−0.7 (3)
C14—C5—C6—C7−0.2 (4)O21—C9—C13—C8−1.6 (3)
C5—C6—C7—O19−179.7 (2)C11—C9—C13—C8178.67 (18)
C5—C6—C7—C80.2 (4)C8—C13—C14—C50.3 (3)
O19—C7—C8—C13−179.99 (19)C9—C13—C14—C5179.7 (2)
C6—C7—C8—C130.1 (3)C8—C13—C14—O10−179.42 (18)
C2—C1—C11—C120.1 (3)C9—C13—C14—O100.0 (3)
C2—C1—C11—C9−179.66 (19)C6—C5—C14—C13−0.1 (4)
O21—C9—C11—C12−179.0 (2)C6—C5—C14—O10179.7 (2)
C13—C9—C11—C120.7 (3)C12—O10—C14—C130.8 (3)
O21—C9—C11—C10.8 (3)C12—O10—C14—C5−178.9 (2)
C13—C9—C11—C1−179.53 (17)C1—C2—C15—O16177.5 (2)
C14—O10—C12—C11−0.8 (3)C3—C2—C15—O16−1.7 (4)
C14—O10—C12—C4179.6 (2)C1—C2—C15—O17−3.8 (3)
C1—C11—C12—O10−179.70 (17)C3—C2—C15—O17177.05 (19)
C9—C11—C12—O100.1 (3)O16—C15—O17—C18−0.8 (3)
C1—C11—C12—C4−0.2 (3)C2—C15—O17—C18−179.59 (18)
C9—C11—C12—C4179.6 (2)C8—C7—O19—C20−0.2 (3)
C3—C4—C12—O10179.4 (2)C6—C7—O19—C20179.7 (2)
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
C3—H3···O16i0.932.543.362 (3)147
C20—H20A···O21ii0.962.503.454 (3)173
Symmetry codes: (i) −x+2, −y+1, −z+1; (ii) −x−1, y−1/2, −z+1/2.
Table 1
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
C3—H3···O16i0.932.543.362 (3)147
C20—H20A···O21ii0.962.503.454 (3)173
Symmetry codes: (i) −x+2, −y+1, −z+1; (ii) −x−1, y−1/2, −z+1/2.
Table 2
π–π interactions (Å,°). top
CgICgJCg···CgDihedral angleInterplanar distanceOffset
ACiii3.549 (1)0.83.420 (1)1.068 (1)
BAiii3.583 (1)0.13.454 (1)0.953 (1)
BCiii3.772 (1)0.83.455 (1)1.525 (1)
Symmetry code: (iii) 1 + x, y, z. 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,°) top
XIJI···JX···JX-I···J
C15O16CgBiii3.564 (2)3.689 (2)86.4 (1)
Symmetry codes: (iii) 1 + x, y, z.

Notes: CgB is the centroid of the C1–C4/C12/C11 ring.
Acknowledgements top

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

references
References top

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