7,8-Di­hydroxy-3-methyl-10-oxo-1H,10H-pyrano­[4,3-b]­chromene-9-carboxyl­ic acid

The structure of the title compound, an­hydro­fulvic acid, C₁₄H₁₀O₇, a yellow acidic metabolite isolated from Paecilomyces sp. was determined by X-ray analysis. The chromone ring system is essentially planar, with the carboxyl­ic acid group coplanar with the ring.

Key indicators

• Single-crystal X-ray study
• T = 296 K
• Mean [sigma](C-C) = 0.002 Å
• R factor = 0.037
• wR factor = 0.119
• Data-to-parameter ratio = 13.0

checkCIF/PLATON results

No syntax errors found



Alert level B
PLAT028_ALERT_3_B _diffrn_measured_fraction_theta_max  Low .....       0.95

Alert level C
PLAT066_ALERT_1_C Predicted and Reported Transmissions Identical          ?
PLAT147_ALERT_1_C su on Symmetry Constrained Cell Angle(s) .....          ?
PLAT230_ALERT_2_C Hirshfeld Test Diff for    O5     -   C14    =       6.06 su

   0 ALERT level A = In general: serious problem
   1 ALERT level B = Potentially serious problem
   3 ALERT level C = Check and explain
   0 ALERT level G = General alerts; check

   2 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   1 ALERT type 2 Indicator that the structure model may be wrong or deficient
   1 ALERT type 3 Indicator that the structure quality may be low
   0 ALERT type 4 Improvement, methodology, query or suggestion

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S1. Comment

The title compound, (I), had been prepared by dehydration of a natural product, fulvic acid [3,7,8-trihydroxy-3-methyl-10-oxo-4,10-dihydro-1H,3H-pyrano[4,3-b]chromene- 9-carboxylic acid, (II)], isolated from several fungi (Dean, 1957). In this study, (I) was isolated from the fermentation broth of Paecilomyces sp., an endophytic fungi of Cephalataxus fortunei, and its structure was determined by X-ray analysis.

The chromone ring system of (I) is essentially planar, with the hydroxyl and carboxylic acid groups coplanar with the ring. There is one intermolecular hydrogen bond and three intramolecular hydrogen bonds in the crystal structure (Table 2), which make the crystal very stable (m.p. 516–518 K).

S2. Experimental

The title compound, (I) was isolated from the organic extract of the liquid culture of the Paecilomyces sp. Recrystallization from ethyl acetate afforded green crystals suitable for X-ray analysis. The molecular formula of (I) was deduced from the high resolution ESI–MS spectrum as C₁₄H₁₀O₇, showing an accurate mass at m/z 291.0501 [M + H]⁺. The ¹³C NMR analysis revealed 14 carbons: δ (p.p.m.) = 20.0 (C13), 64.3(C12), 94.5 (C10), 101.3 (C4), 103.358 (C8), 113.0 (C6), 118.0 (C1), 143.5 (C2), 149.8 (C3), 152.0 (C5), 158.6 (C9), 167.6 (C11), 168.8 (C14) and 171.3 (C7).

S3. Refinement

Molecule (I) crystallized in the monoclinic, space group P2₁/c. H atoms on O atoms were located in difference Fourier syntheses and the C-bound H atoms were placed at calculated positions (C—H = 0.93, 0.96 or 0.97 Å) and were included in the refinement in the riding-model approximation. Their displacement parameters were set at 1.2 and or 1.5 times U_eq of the equivalent isotropic displacement parameters of the parent C or O atoms, respectively.

Computing details

Data collection: SMART (Bruker, 2001); cell refinement: SAINT (Bruker, 2001); data reduction: SAINT; program(s) used to solve structure: SIR97 (Altomare et al., 1998); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: SHELXL97.

Figures

Fig. 1. ORTEP-3 (Farrugia, 1997) plot of the structure of the title compound, with displacement ellipsoids drawn at the 50% probability level.

7,8-Dihydroxy-3-methyl-10-oxo-1H,10H-pyrano[4,3-b]chromene-9-carboxylic acid

Crystal data

C14H10O7	F(000) = 600
Mr = 290.22	Dx = 1.617 Mg m^−3
Monoclinic, P21/c	Melting point = 516–518 K
Hall symbol: -P 2ybc	Mo Kα radiation, λ = 0.71069 Å
a = 7.814 (5) Å	Cell parameters from 2225 reflections
b = 10.085 (5) Å	θ = 2.4–27.5°
c = 15.124 (5) Å	µ = 0.13 mm^−1
β = 90.178 (5)°	T = 296 K
V = 1191.8 (10) Å^3	Chunk, green
Z = 4	0.20 × 0.18 × 0.10 mm

Data collection

Bruker AXS area-detector diffractometer	2615 independent reflections
Radiation source: fine-focus sealed tube	2225 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.000
ϕ and ω scans	θmax = 27.5°, θmin = 2.4°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −10→10
Tmin = 0.974, Tmax = 0.987	k = 0→13
2615 measured reflections	l = −19→0

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.037	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.119	w = 1/[σ^2(Fo^2) + (0.0758P)^2 + 0.0975P] where P = (Fo^2 + 2Fc^2)/3
S = 1.09	(Δ/σ)max < 0.001
2615 reflections	Δρmax = 0.24 e Å^−3
201 parameters	Δρmin = −0.20 e Å^−3
0 restraints	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.013 (3)

Special details

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 (Ų)

	x	y	z	Uiso*/Ueq
O1	0.78838 (13)	0.14646 (9)	0.63238 (5)	0.0384 (2)
C1	0.84098 (14)	0.06547 (12)	0.39489 (7)	0.0310 (3)
O2	0.48841 (13)	−0.14163 (10)	0.73806 (6)	0.0446 (3)
C2	0.92692 (15)	0.18227 (13)	0.37272 (7)	0.0332 (3)
O3	0.64067 (14)	−0.16488 (10)	0.47837 (6)	0.0477 (3)
C3	0.96229 (16)	0.28357 (12)	0.43593 (8)	0.0363 (3)
O4	0.87828 (14)	−0.00461 (10)	0.24704 (6)	0.0486 (3)
C4	0.91286 (17)	0.26637 (13)	0.52140 (8)	0.0385 (3)
O5	0.73718 (16)	−0.14121 (11)	0.33084 (7)	0.0573 (3)
C5	0.82745 (16)	0.15028 (12)	0.54437 (7)	0.0321 (3)
O6	0.98542 (13)	0.21222 (10)	0.29248 (6)	0.0440 (3)
C6	0.78576 (14)	0.04765 (12)	0.48533 (7)	0.0297 (3)
O7	1.04580 (15)	0.39362 (10)	0.41172 (6)	0.0511 (3)
C7	0.69266 (15)	−0.06445 (12)	0.52273 (8)	0.0327 (3)
C8	0.65930 (15)	−0.06322 (12)	0.61391 (7)	0.0332 (3)
C9	0.70915 (16)	0.03979 (13)	0.66582 (8)	0.0340 (3)
C10	0.67352 (18)	0.04178 (14)	0.75777 (8)	0.0400 (3)
C11	0.56121 (17)	−0.04719 (13)	0.78941 (8)	0.0393 (3)
C12	0.57850 (18)	−0.17989 (13)	0.65946 (8)	0.0398 (3)
C13	0.4922 (2)	−0.04747 (16)	0.88069 (9)	0.0532 (4)
C14	0.81714 (17)	−0.03259 (14)	0.32080 (8)	0.0383 (3)
H4A	0.9357	0.3310	0.5637	0.046*
H5	0.687 (3)	−0.156 (2)	0.4038 (8)	0.086*
H6	0.952 (2)	0.138 (2)	0.2601 (12)	0.066*
H7	1.066 (3)	0.393 (2)	0.3574 (15)	0.077*
H10A	0.7263	0.1028	0.7950	0.048*
H12A	0.4994	−0.2229	0.6191	0.048*
H12B	0.6668	−0.2435	0.6749	0.048*
H13A	0.5534	0.0161	0.9159	0.080*
H13B	0.5055	−0.1342	0.9060	0.080*
H13C	0.3730	−0.0245	0.8792	0.080*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0535 (5)	0.0374 (5)	0.0244 (4)	−0.0101 (4)	0.0063 (3)	−0.0020 (3)
C1	0.0342 (6)	0.0337 (6)	0.0252 (5)	0.0058 (5)	0.0004 (4)	−0.0023 (4)
O2	0.0499 (5)	0.0407 (5)	0.0434 (5)	−0.0048 (4)	0.0141 (4)	0.0014 (4)
C2	0.0387 (6)	0.0363 (6)	0.0246 (5)	0.0065 (5)	0.0019 (4)	0.0022 (4)
O3	0.0620 (6)	0.0400 (5)	0.0410 (5)	−0.0149 (5)	0.0075 (4)	−0.0107 (4)
C3	0.0447 (7)	0.0332 (6)	0.0310 (6)	−0.0014 (5)	0.0039 (5)	0.0038 (4)
O4	0.0673 (7)	0.0490 (6)	0.0297 (4)	0.0057 (5)	0.0094 (4)	−0.0084 (4)
C4	0.0525 (7)	0.0346 (6)	0.0284 (6)	−0.0065 (6)	0.0041 (5)	−0.0031 (4)
O5	0.0764 (8)	0.0546 (7)	0.0409 (5)	−0.0211 (6)	0.0112 (5)	−0.0197 (4)
C5	0.0389 (6)	0.0339 (6)	0.0236 (5)	0.0003 (5)	0.0026 (4)	−0.0003 (4)
O6	0.0614 (6)	0.0441 (5)	0.0264 (4)	0.0013 (5)	0.0102 (4)	0.0026 (4)
C6	0.0316 (5)	0.0309 (6)	0.0266 (5)	0.0035 (5)	0.0004 (4)	−0.0004 (4)
O7	0.0794 (7)	0.0416 (5)	0.0324 (4)	−0.0169 (5)	0.0130 (5)	0.0021 (4)
C7	0.0337 (6)	0.0321 (6)	0.0322 (6)	0.0020 (5)	0.0006 (4)	−0.0024 (4)
C8	0.0354 (6)	0.0320 (6)	0.0323 (6)	0.0015 (5)	0.0029 (4)	0.0023 (4)
C9	0.0379 (6)	0.0343 (6)	0.0299 (5)	−0.0006 (5)	0.0035 (4)	0.0033 (4)
C10	0.0490 (7)	0.0436 (7)	0.0274 (6)	−0.0035 (6)	0.0039 (5)	0.0000 (5)
C11	0.0462 (7)	0.0381 (7)	0.0337 (6)	0.0062 (5)	0.0056 (5)	0.0059 (5)
C12	0.0466 (7)	0.0332 (6)	0.0396 (6)	−0.0006 (6)	0.0087 (5)	0.0017 (5)
C13	0.0703 (9)	0.0509 (8)	0.0387 (7)	0.0033 (7)	0.0180 (6)	0.0096 (6)
C14	0.0425 (6)	0.0426 (7)	0.0298 (6)	0.0072 (6)	0.0005 (5)	−0.0075 (5)

Geometric parameters (Å, º)

O1—C9	1.3410 (16)	C7—C8	1.4044 (16)
O1—C5	1.3671 (14)	C8—C9	1.3585 (18)
C1—C2	1.3972 (18)	C8—C12	1.5034 (18)
C1—C6	1.4468 (15)	C9—C10	1.4192 (16)
C1—C14	1.5057 (16)	C10—C11	1.344 (2)
O2—C11	1.3531 (18)	C11—C13	1.4838 (17)
O2—C12	1.4362 (16)	O3—H5	1.189 (10)
C2—O6	1.3329 (14)	C4—H4A	0.9300
C2—C3	1.4257 (18)	O5—H5	1.182 (9)
O3—C7	1.2802 (15)	O6—H6	0.93 (2)
C3—O7	1.3391 (16)	O7—H7	0.84 (2)
C3—C4	1.3613 (16)	C10—H10A	0.9300
O4—C14	1.2473 (16)	C12—H12A	0.9700
C4—C5	1.3922 (18)	C12—H12B	0.9700
O5—C14	1.2704 (18)	C13—H13A	0.9600
C5—C6	1.4046 (16)	C13—H13B	0.9600
C6—C7	1.4594 (17)	C13—H13C	0.9600
C9—O1—C5	119.65 (9)	C11—C10—C9	118.01 (12)
C2—C1—C6	118.46 (10)	C10—C11—O2	122.64 (11)
O6—C2—C1	125.17 (11)	C10—C11—C13	124.90 (13)
O6—C2—C3	112.45 (11)	O2—C11—C13	112.29 (12)
C1—C2—C3	122.38 (10)	O2—C12—C8	112.12 (11)
O7—C3—C4	120.34 (11)	O4—C14—O5	119.47 (11)
O7—C3—C2	120.28 (11)	O4—C14—C1	118.04 (13)
C4—C3—C2	119.37 (11)	O5—C14—C1	122.49 (11)
C3—C4—C5	118.80 (11)	C3—C4—H4A	120.6
O1—C5—C4	112.05 (10)	C5—C4—H4A	120.6
O1—C5—C6	123.10 (10)	C7—O3—H5	109.9 (11)
C4—C5—C6	124.85 (10)	C14—O5—H5	112.6 (11)
C5—C6—C1	116.12 (11)	C2—O6—H6	101.6 (12)
C5—C6—C7	116.07 (10)	C3—O7—H7	111.2 (16)
C1—C6—C7	127.81 (10)	C11—C10—H10A	121.0
O3—C7—C8	117.51 (11)	C9—C10—H10A	121.0
O3—C7—C6	124.58 (11)	O2—C12—H12A	109.2
C8—C7—C6	117.90 (10)	C8—C12—H12A	109.2
C9—C8—C7	121.37 (11)	O2—C12—H12B	109.2
C9—C8—C12	116.98 (11)	C8—C12—H12B	109.2
C7—C8—C12	121.50 (11)	H12A—C12—H12B	107.9
O1—C9—C8	121.83 (11)	C11—C13—H13A	109.5
O1—C9—C10	116.77 (11)	C11—C13—H13B	109.5
C8—C9—C10	121.35 (11)	H13A—C13—H13B	109.5
C2—C1—C14	115.70 (10)	C11—C13—H13C	109.5
C6—C1—C14	125.84 (11)	H13A—C13—H13C	109.5
C11—O2—C12	117.25 (10)	H13B—C13—H13C	109.5
C6—C1—C2—O6	179.85 (11)	C1—C6—C7—C8	177.05 (11)
C14—C1—C2—O6	0.86 (18)	O3—C7—C8—C9	−179.64 (11)
C6—C1—C2—C3	0.23 (18)	C6—C7—C8—C9	1.11 (18)
C14—C1—C2—C3	−178.77 (11)	O3—C7—C8—C12	4.87 (18)
O6—C2—C3—O7	0.01 (18)	C6—C7—C8—C12	−174.38 (10)
C1—C2—C3—O7	179.68 (11)	C5—O1—C9—C8	−2.91 (18)
O6—C2—C3—C4	−178.92 (11)	C5—O1—C9—C10	179.52 (11)
C1—C2—C3—C4	0.75 (19)	C7—C8—C9—O1	1.74 (19)
O7—C3—C4—C5	−179.51 (12)	C12—C8—C9—O1	177.42 (11)
C2—C3—C4—C5	−0.58 (19)	C7—C8—C9—C10	179.19 (12)
C9—O1—C5—C4	−178.53 (11)	C12—C8—C9—C10	−5.12 (18)
C9—O1—C5—C6	1.19 (18)	O1—C9—C10—C11	164.87 (12)
C3—C4—C5—O1	179.12 (11)	C8—C9—C10—C11	−12.7 (2)
C3—C4—C5—C6	−0.6 (2)	C9—C10—C11—O2	3.4 (2)
O1—C5—C6—C1	−178.16 (10)	C9—C10—C11—C13	−171.42 (13)
C4—C5—C6—C1	1.53 (18)	C12—O2—C11—C10	23.91 (18)
O1—C5—C6—C7	1.56 (17)	C12—O2—C11—C13	−160.72 (12)
C4—C5—C6—C7	−178.76 (12)	C11—O2—C12—C8	−39.37 (15)
C2—C1—C6—C5	−1.28 (16)	C9—C8—C12—O2	30.09 (16)
C14—C1—C6—C5	177.60 (11)	C7—C8—C12—O2	−154.23 (12)
C2—C1—C6—C7	179.04 (11)	C2—C1—C14—O4	1.73 (17)
C14—C1—C6—C7	−2.1 (2)	C6—C1—C14—O4	−177.18 (11)
C5—C6—C7—O3	178.19 (11)	C2—C1—C14—O5	−177.98 (12)
C1—C6—C7—O3	−2.1 (2)	C6—C1—C14—O5	3.1 (2)
C5—C6—C7—C8	−2.62 (16)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O5—H5···O3	1.18 (1)	1.19 (1)	2.3696 (15)	177 (2)
O6—H6···O4	0.93 (2)	1.56 (2)	2.4395 (18)	155.4 (18)
O7—H7···O6	0.84 (2)	2.17 (2)	2.6108 (16)	113.0 (19)
O7—H7···O4^i	0.84 (2)	1.94 (2)	2.6794 (15)	147 (2)

Symmetry code: (i) −x+2, y+1/2, −z+1/2.