2,5-Di­phenyl-3,6-di­hydroxy-1,4-benzo­quinone (polyporic acid)

The title compound, C₁₈H₁₂O₄, is a naturally occurring product found in several genera of fungi and lichens. Its structure is composed of a 1,4-benzo­quinone moiety 2,5-disubstituted with phenyl rings and 3,6-disubstituted with hydroxyl groups. The angle between the planes of the phenyl rings and that of the benzo­quinone is 45.24 (8)°. Intermolecular hydrogen bonding produces infinite molecular chains. The mol­ecule has crystallographic inversion symmetry.

Key indicators

• Single-crystal X-ray study
• T = 296 K
• Mean [sigma](C-C) = 0.003 Å
• R factor = 0.035
• wR factor = 0.110
• Data-to-parameter ratio = 11.9

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry

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S1. Comment

Polyporic acid, (I), is currently the only known benzoquinone naturally occurring in lichens (Huneck & Yoshimura, 1996). While the sole published paper on the chemical identity of synthesized polyporic acid states that the MS and ¹H NMR data for (I) are in agreement with the expected structure, no mass spectral data or numerical proton shift values are actually provided in the publication (Dallacker & Ditgens, 1975). This study was undertaken to provide crystallographic data affording the definitive structural characterization of polyporic acid which, for almost 50 years, has been known in the scientific literature without any substantive information about its absolute structure.

The molecule, shown in Fig. 1, is composed of a benzoquinone moiety 2,5-disubstituted with phenyl rings and 3,6-disubstituted with hydroxyl groups. A center of symmetry, located at the center of the benzoquinone moiety, relates the two halves of the molecule. Only minor deviations from expected geometry were noted. There is minor distortion of the bond angles involving O1 and O2 as shown in Table 1, perhaps a result of the hydrogen bonding. The phenyl rings are rotated 45.24 (8)° with respect to the central ring, as would be expected, and all ring systems are essentially flat. A hydrogen bond involving the hydroxyl group and the carbonyl oxygen results in the linking of individual molecules into infinite one-dimensional chains which propagate in the [100] direction as shown in Fig. 2; Table 2 gives the hydrogen-bond geometry. The molecular packing is shown in Fig. 3 with the molecular chains normal to the plane of the paper; nine individual chains can be seen. The packing produces double-layers of phenyl rings which sandwich single-layers of benzoquinone rings. It is conceivable, given the packing arrangement and high electron density of the aromatic rings, that polyporic acid might be a strong conductor in the solid state.

S2. Experimental

Polyporic acid occurs naturally in several genera of higher fungi (Basidiomycetes) including Polyporus and Fomes (Murray, 1952; Huneck & Yoshimura, 1996; Huneck, 2001). In addition, it occurs in the tropical lichen species Pseudocyphellaria coronata. Polyporic acid was isolated as follows: 100 g of dried P. coronata (collected in Wakaito, New Zealand in July 2000) was continuously extracted with one liter of MeOH overnight. The red-brown extract was concentrated in vacuo to give a red solid. The red solid (12 g) was purified by column chromotography on Sephadex L-50 (eluent: 9:1 CH₂Cl₂—MeOH) to give fractions containing polyporic acid totaling 200 mg. This crude material was further purified by preparative TLC (eluent: 9:1 CH₂Cl₂–MeOH) to give 80 mg of pure polyporic acid (0.08% yield dry weight). This material was recrystallized from hot acetone to give purple prisms, m.p. 579–581 K, used in the X-ray study. The structure of polyporic acid so determined is in agreement with that suggested by its ¹H NMR (300 MHz) and ¹³C NMR (125 MHz) spectra, as well as EIMS low-resolution mass spectra. The EI mass spectrum shows a sharp peak at 292 mass units corresponding to the molecular weight for polyporic acid, while the ¹H NMR spectrum shows the presence of five aromatic protons, indicative of the two equivalent phenyl side-chains determined by the crystallographic study.

S3. Refinement

The location of the hydroxyl H atom was determined by the circular Fourier method available in SHELXL97 (Sheldrick, 1997). All H atoms are riding.

Computing details

Data collection: MSC/AFC Diffractometer Control Software (Molecular Structure Corporation, 1996); cell refinement: MSC/AFC Diffractometer Control Software (Molecular Structure Corporation, 1996); data reduction: PROCESS in TEXSAN (Molecular Structure Corporation, 1997); program(s) used to solve structure: SIR92 (Burla et al., 1989); program(s) used to refine structure: LS in TEXSAN and SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP (Johnson, 1965) in TEXSAN; software used to prepare material for publication: TEXSAN, SHELXL97 and PLATON (Spek, 2000).

Figures

	Fig. 1. The molecular structure and atom-numbering scheme for (I) with displacement ellipsoids at the 50% probablilty level. [Symmetry code: (i) -x + 1, -y + 1, -z + 1.]
	Fig. 2. The hydrogen bonding in (I) and the resultant infinite molecular chains propagating in the [100] direction.
	Fig. 3. The molecular packing in (I) as viewed down [100].

2,5-Diphenyl-3,6-dihydroxy-1,4-benzoquinone

Crystal data

C18H12O4	Dx = 1.425 Mg m^−3
Mr = 292.28	Melting point = 579–581 K
Orthorhombic, Pbca	Mo Kα radiation, λ = 0.71069 Å
a = 7.323 (3) Å	Cell parameters from 25 reflections
b = 26.980 (4) Å	θ = 20.8–24.3°
c = 6.897 (4) Å	µ = 0.10 mm^−1
V = 1362.7 (9) Å^3	T = 296 K
Z = 4	Prism, dark red
F(000) = 608	0.49 × 0.39 × 0.33 mm

Data collection

Rigaku AFC-5S diffractometer	Rint = 0
Radiation source: sealed tube	θmax = 25.0°, θmin = 3.0°
Graphite monochromator	h = 0→8
ω scans	k = 0→32
1201 measured reflections	l = 0→8
1201 independent reflections	3 standard reflections every 199 reflections
796 reflections with I > 2σ(I)	intensity decay: 0.3%

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.035	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.110	H-atom parameters constrained
S = 1.02	w = 1/[σ^2(Fo^2) + (0.0592P)^2 + 0.1614P] where P = (Fo^2 + 2Fc^2)/3
1201 reflections	(Δ/σ)max < 0.001
101 parameters	Δρmax = 0.14 e Å^−3
0 restraints	Δρmin = −0.24 e Å^−3

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
O1	0.20394 (16)	0.43886 (5)	0.5248 (2)	0.0407 (4)
O2	0.16424 (16)	0.53454 (5)	0.5013 (2)	0.0478 (4)
C1	0.6777 (3)	0.36869 (7)	0.3815 (3)	0.0407 (5)
C2	0.7063 (3)	0.31824 (7)	0.3823 (3)	0.0488 (6)
C3	0.6139 (3)	0.28848 (8)	0.5103 (3)	0.0483 (6)
C4	0.4931 (3)	0.30933 (7)	0.6379 (3)	0.0494 (6)
C5	0.4623 (2)	0.36002 (6)	0.6384 (3)	0.0403 (5)
C6	0.5547 (2)	0.39035 (6)	0.5094 (2)	0.0304 (4)
C7	0.5226 (2)	0.44474 (6)	0.5062 (2)	0.0286 (4)
C8	0.3558 (2)	0.46590 (7)	0.5134 (2)	0.0294 (4)
C9	0.3236 (2)	0.52103 (7)	0.5038 (2)	0.0304 (4)
H1	0.1147	0.4571	0.5179	0.061*
H1a	0.7414	0.3885	0.2943	0.049*
H2	0.7888	0.3043	0.2956	0.059*
H3	0.6333	0.2544	0.5104	0.058*
H4	0.4309	0.2892	0.7253	0.059*
H5	0.3795	0.3737	0.7255	0.048*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0181 (6)	0.0353 (7)	0.0687 (10)	−0.0016 (5)	0.0008 (6)	−0.0011 (6)
O2	0.0176 (6)	0.0415 (8)	0.0844 (11)	0.0034 (6)	−0.0008 (7)	0.0023 (7)
C1	0.0387 (10)	0.0418 (10)	0.0415 (11)	0.0046 (9)	0.0050 (9)	0.0013 (9)
C2	0.0514 (12)	0.0421 (12)	0.0528 (13)	0.0136 (10)	0.0036 (11)	−0.0079 (10)
C3	0.0490 (13)	0.0334 (10)	0.0625 (15)	0.0049 (9)	−0.0074 (11)	−0.0021 (10)
C4	0.0432 (11)	0.0383 (10)	0.0667 (14)	−0.0027 (9)	0.0038 (11)	0.0136 (10)
C5	0.0304 (9)	0.0408 (11)	0.0499 (12)	0.0025 (8)	0.0063 (9)	0.0023 (9)
C6	0.0205 (8)	0.0346 (9)	0.0361 (10)	0.0006 (7)	−0.0035 (8)	−0.0004 (8)
C7	0.0222 (9)	0.0318 (9)	0.0319 (9)	0.0014 (7)	0.0004 (7)	−0.0003 (7)
C8	0.0208 (8)	0.0326 (10)	0.0349 (10)	−0.0026 (7)	0.0004 (8)	−0.0014 (8)
C9	0.0203 (8)	0.0371 (10)	0.0339 (10)	0.0027 (7)	0.0008 (8)	−0.0014 (8)

Geometric parameters (Å, º)

O1—C8	1.332 (2)	C7—C8	1.349 (2)
O2—C9	1.223 (2)	C7—C9^i	1.458 (2)
C1—C2	1.377 (2)	C8—C9	1.507 (3)
C1—C6	1.390 (2)	O1—H1	0.820
C2—C3	1.372 (3)	C1—H1A	0.930
C3—C4	1.369 (3)	C2—H2	0.930
C4—C5	1.386 (2)	C3—H3	0.930
C5—C6	1.386 (2)	C4—H4	0.930
C6—C7	1.486 (2)	C5—H5	0.930
O1—C8—C7	121.74 (16)	C8—C7—C6	124.10 (15)
O1—C8—C9	114.36 (15)	C9^i—C7—C6	120.24 (15)
O2—C9—C8	116.35 (16)	C7^i—C9—C8	120.42 (15)
O2—C9—C7^i	123.22 (17)	C8—O1—H1	109.5
C8—C7—C9^i	115.66 (16)	C2—C1—H1A	119.6
C7—C8—C9	123.88 (16)	C6—C1—H1A	119.6
C2—C1—C6	120.77 (18)	C3—C2—H2	119.8
C3—C2—C1	120.42 (19)	C1—C2—H2	119.8
C4—C3—C2	119.45 (19)	C4—C3—H3	120.3
C3—C4—C5	120.8 (2)	C2—C3—H3	120.3
C4—C5—C6	120.09 (18)	C3—C4—H4	119.6
C5—C6—C1	118.42 (16)	C5—C4—H4	119.6
C5—C6—C7	121.02 (16)	C4—C5—H5	120.0
C1—C6—C7	120.56 (15)	C6—C5—H5	120.0
C6—C1—C2—C3	−0.2 (3)	C5—C6—C7—C9^i	134.85 (18)
C1—C2—C3—C4	−0.2 (3)	C1—C6—C7—C9^i	−45.6 (2)
C2—C3—C4—C5	0.4 (3)	C9^i—C7—C8—O1	−179.31 (16)
C3—C4—C5—C6	−0.3 (3)	C6—C7—C8—O1	0.2 (3)
C4—C5—C6—C1	−0.1 (3)	C9^i—C7—C8—C9	2.5 (3)
C4—C5—C6—C7	179.43 (17)	C6—C7—C8—C9	−177.99 (15)
C2—C1—C6—C5	0.3 (3)	O1—C8—C9—O2	−2.2 (2)
C2—C1—C6—C7	−179.21 (18)	C7—C8—C9—O2	176.10 (17)
C5—C6—C7—C8	−44.6 (3)	O1—C8—C9—C7^i	179.07 (15)
C1—C6—C7—C8	134.88 (19)	C7—C8—C9—C7^i	−2.6 (3)

Symmetry code: (i) −x+1, −y+1, −z+1.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···O2^ii	0.82	2.06	2.796 (2)	149

Symmetry code: (ii) −x, −y+1, −z+1.