organic compounds
Bostrycin
aState Key Laboratory for Rice Biology, Institute of Biotechnology, Zhejiang University, People's Republic of China, and bCollege of Pharmaceutical Sicence, Zhejiang University, People's Republic of China
*Correspondence e-mail: fuchenglin@zju.edu.cn
The title compound, C16H16O8, is a potent nonspecific phytotoxin. The is the average of two tautomers, 5,6,7,9,10-pentahydroxy-2-methoxy-7-methyl-1,4,5,6,7,8-hexahydroanthracene-1,4-dione and 1,4,5,6,7-pentahydroxy-2-methoxy-7-methyl-5,6,7,8,9,10-hexahydroanthracene-9,10-dione. The cyclohexene rings in both tautomers display a half-chair conformation. An extensive O—H⋯O hydrogen-bonding network is present in the crystal structure.
Related literature
For general background, see: Charudattan & Rao (1982); van Eijk (1975). For a related structure, see: Kelly & Saha (1985).
Experimental
Crystal data
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Refinement
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Data collection: PROCESS-AUTO (Rigaku, 1998); cell PROCESS-AUTO; data reduction: CrystalStructure (Rigaku/MSC, 2002); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).
Supporting information
10.1107/S1600536808032030/xu2453sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536808032030/xu2453Isup2.hkl
For morphological identification (Arthrinium sp. (CGMCC 2082), a fungi from Polygonum hydropiper L.) cultures were grown on OA, PDA, and SNA media for 7–14 days at room temperature (293 K) under ambient daylight. Microscopic observations and measurements were made from slides mounted in water. For metabolite production, the strains were inoculated onto PDA media and incubated for 10 days at 298 K in the dark. Selected strains were also cultivated in liquid media placed in a rotary shaker at 120 rpm for 7 days at 298 K in the dark. After cultivation, the bottles were stored at 253 K until extraction.
Liquid cultures were extracted with trichloromethane. The trichloromethane phase was filtered and evaporated in vacuo. Samples were then redissolved in trichloromethane, then filtered to remove solid. The trichloromethane solution was evaporated in vacuo. The single crystals were obtained from an ethanol solution.
Hydroxyl H atoms were located in a difference Fourier map and refined as riding in as-found relative positions with Uiso(H) = 1.5Ueq(O). Methyl H atoms were placed in calculated positions with C—H = 0.96 Å and torsion angles were refined to fit the electron density, Uiso(H) = 1.5Ueq(C). Other H atoms were placed in calculated positions with C—H = 0.93 (aromatic), 0.97 (methylene) or 0.98 Å (methine), and refined in riding mode with Uiso(H) = 1.2Ueq(C). In the absence of significant
effects, Friedel pairs were merged; the was not determined.Data collection: PROCESS-AUTO (Rigaku, 1998); cell
PROCESS-AUTO (Rigaku, 1998); data reduction: CrystalStructure (Rigaku/MSC, 2002); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).Fig. 1. The molecular structure of (I) with 50% probability displacement ellipsoids (arbitrary spheres for H atoms), dashed line indicates hydrogen bonding. | |
Fig. 2. The molecular structure of (II) with 50% probability displacement ellipsoids (arbitrary spheres for H atoms), dashed line indicates hydrogen bonding. |
C16H16O8 | F(000) = 352 |
Mr = 336.29 | Dx = 1.579 Mg m−3 |
Monoclinic, P21 | Mo Kα radiation, λ = 0.71069 Å |
Hall symbol: P 2yb | Cell parameters from 5814 reflections |
a = 8.280 (2) Å | θ = 6.1–54.9° |
b = 6.644 (2) Å | µ = 0.13 mm−1 |
c = 13.1535 (12) Å | T = 293 K |
β = 102.12 (2)° | Chunk, red |
V = 707.5 (3) Å3 | 0.30 × 0.20 × 0.08 mm |
Z = 2 |
Rigaku R-AXIS RAPID IP diffractometer | 1517 independent reflections |
Radiation source: fine-focus sealed tube | 1282 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.025 |
Detector resolution: 10 pixels mm-1 | θmax = 26.0°, θmin = 3.2° |
ω scans | h = −10→10 |
Absorption correction: multi-scan (ABSCOR; Higashi, 1995) | k = −8→8 |
Tmin = 0.953, Tmax = 0.990 | l = −16→16 |
6151 measured reflections |
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.035 | H-atom parameters constrained |
wR(F2) = 0.105 | w = 1/[σ2(Fo2) + (0.0667P)2 + 0.0817P] where P = (Fo2 + 2Fc2)/3 |
S = 1.08 | (Δ/σ)max = 0.001 |
1517 reflections | Δρmax = 0.24 e Å−3 |
220 parameters | Δρmin = −0.19 e Å−3 |
1 restraint | Extinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.009 (3) |
C16H16O8 | V = 707.5 (3) Å3 |
Mr = 336.29 | Z = 2 |
Monoclinic, P21 | Mo Kα radiation |
a = 8.280 (2) Å | µ = 0.13 mm−1 |
b = 6.644 (2) Å | T = 293 K |
c = 13.1535 (12) Å | 0.30 × 0.20 × 0.08 mm |
β = 102.12 (2)° |
Rigaku R-AXIS RAPID IP diffractometer | 1517 independent reflections |
Absorption correction: multi-scan (ABSCOR; Higashi, 1995) | 1282 reflections with I > 2σ(I) |
Tmin = 0.953, Tmax = 0.990 | Rint = 0.025 |
6151 measured reflections |
R[F2 > 2σ(F2)] = 0.035 | 1 restraint |
wR(F2) = 0.105 | H-atom parameters constrained |
S = 1.08 | Δρmax = 0.24 e Å−3 |
1517 reflections | Δρmin = −0.19 e Å−3 |
220 parameters |
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. |
x | y | z | Uiso*/Ueq | Occ. (<1) | |
O1 | 0.4354 (2) | 0.3424 (4) | 0.34450 (13) | 0.0399 (5) | |
H1A | 0.5153 | 0.3341 | 0.3968 | 0.060* | 0.50 |
O2 | 0.1814 (2) | 0.3555 (4) | 0.19361 (12) | 0.0414 (5) | |
O3 | −0.1725 (2) | 0.3863 (4) | 0.43528 (13) | 0.0384 (5) | |
H3A | −0.1659 | 0.3844 | 0.4995 | 0.058* | 0.50 |
O4 | −0.0420 (2) | 0.3933 (4) | 0.63061 (13) | 0.0370 (5) | |
H4A | −0.1226 | 0.4012 | 0.5725 | 0.055* | 0.50 |
O5 | 0.1000 (3) | 0.2810 (5) | 0.82507 (17) | 0.0571 (7) | |
H5A | 0.0233 | 0.2963 | 0.7644 | 0.086* | |
O6 | 0.3619 (2) | 0.4004 (4) | 0.97960 (12) | 0.0417 (5) | |
H6A | 0.4364 | 0.3205 | 1.0303 | 0.063* | |
O7 | 0.5068 (2) | 0.6526 (3) | 0.84879 (13) | 0.0336 (5) | |
H7A | 0.5511 | 0.7105 | 0.7990 | 0.050* | |
O8 | 0.5671 (2) | 0.3429 (4) | 0.54013 (13) | 0.0401 (6) | |
H8A | 0.5559 | 0.3636 | 0.4666 | 0.060* | 0.50 |
C1 | 0.2943 (3) | 0.3552 (4) | 0.37142 (18) | 0.0302 (6) | |
C2 | 0.1464 (3) | 0.3632 (4) | 0.28875 (18) | 0.0303 (6) | |
C3 | −0.0063 (3) | 0.3742 (5) | 0.31216 (18) | 0.0314 (6) | |
H3 | −0.0996 | 0.3781 | 0.2587 | 0.038* | |
C4 | −0.0247 (3) | 0.3798 (4) | 0.41735 (18) | 0.0284 (5) | |
C5 | 0.1177 (3) | 0.3742 (4) | 0.50050 (17) | 0.0263 (5) | |
C6 | 0.1023 (3) | 0.3820 (4) | 0.60602 (17) | 0.0268 (5) | |
C7 | 0.2492 (3) | 0.3761 (5) | 0.68900 (17) | 0.0291 (6) | |
C8 | 0.2301 (3) | 0.3980 (5) | 0.80142 (17) | 0.0311 (6) | |
H8 | 0.2063 | 0.5396 | 0.8130 | 0.037* | |
C9 | 0.3863 (3) | 0.3403 (4) | 0.87974 (18) | 0.0323 (6) | |
H9 | 0.3996 | 0.1938 | 0.8790 | 0.039* | |
C10 | 0.5382 (3) | 0.4387 (4) | 0.85300 (17) | 0.0309 (6) | |
C11 | 0.5585 (3) | 0.3595 (5) | 0.74721 (17) | 0.0319 (6) | |
H11A | 0.6425 | 0.4383 | 0.7240 | 0.038* | |
H11B | 0.5970 | 0.2213 | 0.7552 | 0.038* | |
C12 | 0.4022 (3) | 0.3671 (4) | 0.66537 (17) | 0.0294 (6) | |
C13 | 0.4195 (3) | 0.3563 (4) | 0.55826 (18) | 0.0296 (6) | |
C14 | 0.2770 (3) | 0.3626 (4) | 0.47627 (17) | 0.0262 (5) | |
C15 | 0.0456 (3) | 0.3549 (6) | 0.10420 (18) | 0.0435 (8) | |
H15A | −0.0220 | 0.2384 | 0.1068 | 0.065* | |
H15B | 0.0881 | 0.3517 | 0.0417 | 0.065* | |
H15C | −0.0196 | 0.4743 | 0.1048 | 0.065* | |
C16 | 0.6936 (3) | 0.3933 (6) | 0.93488 (19) | 0.0408 (7) | |
H16A | 0.7885 | 0.4434 | 0.9117 | 0.061* | |
H16B | 0.7039 | 0.2505 | 0.9453 | 0.061* | |
H16C | 0.6861 | 0.4575 | 0.9991 | 0.061* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.0294 (10) | 0.0644 (15) | 0.0268 (8) | 0.0039 (10) | 0.0076 (7) | −0.0058 (10) |
O2 | 0.0318 (10) | 0.0719 (15) | 0.0203 (7) | 0.0052 (11) | 0.0050 (7) | −0.0025 (10) |
O3 | 0.0233 (9) | 0.0584 (13) | 0.0343 (9) | 0.0031 (10) | 0.0082 (7) | 0.0005 (10) |
O4 | 0.0279 (10) | 0.0541 (12) | 0.0311 (8) | −0.0002 (10) | 0.0112 (7) | −0.0016 (10) |
O5 | 0.0513 (14) | 0.0811 (19) | 0.0421 (11) | −0.0192 (13) | 0.0170 (10) | 0.0069 (12) |
O6 | 0.0528 (12) | 0.0518 (12) | 0.0226 (8) | 0.0093 (11) | 0.0126 (8) | 0.0056 (10) |
O7 | 0.0444 (11) | 0.0318 (10) | 0.0262 (8) | −0.0028 (9) | 0.0112 (7) | 0.0001 (8) |
O8 | 0.0223 (9) | 0.0710 (16) | 0.0279 (8) | 0.0015 (10) | 0.0073 (7) | −0.0065 (11) |
C1 | 0.0294 (13) | 0.0370 (15) | 0.0262 (11) | 0.0026 (13) | 0.0101 (9) | −0.0003 (12) |
C2 | 0.0326 (14) | 0.0360 (15) | 0.0233 (11) | 0.0014 (14) | 0.0079 (9) | −0.0003 (12) |
C3 | 0.0298 (13) | 0.0360 (14) | 0.0274 (11) | 0.0032 (13) | 0.0035 (9) | 0.0003 (12) |
C4 | 0.0249 (13) | 0.0297 (13) | 0.0307 (11) | 0.0012 (12) | 0.0064 (9) | 0.0003 (12) |
C5 | 0.0274 (13) | 0.0282 (12) | 0.0249 (11) | 0.0006 (12) | 0.0089 (9) | 0.0005 (12) |
C6 | 0.0267 (12) | 0.0279 (12) | 0.0278 (11) | −0.0006 (12) | 0.0103 (9) | −0.0021 (12) |
C7 | 0.0317 (13) | 0.0334 (13) | 0.0245 (11) | −0.0020 (13) | 0.0108 (9) | −0.0003 (12) |
C8 | 0.0335 (14) | 0.0369 (14) | 0.0261 (11) | −0.0011 (12) | 0.0137 (10) | 0.0017 (12) |
C9 | 0.0411 (15) | 0.0348 (14) | 0.0232 (10) | 0.0016 (13) | 0.0117 (10) | 0.0021 (11) |
C10 | 0.0363 (15) | 0.0338 (15) | 0.0224 (12) | 0.0012 (12) | 0.0055 (10) | 0.0004 (11) |
C11 | 0.0283 (13) | 0.0429 (16) | 0.0251 (11) | 0.0016 (13) | 0.0067 (9) | −0.0028 (12) |
C12 | 0.0304 (13) | 0.0340 (14) | 0.0248 (11) | 0.0024 (13) | 0.0079 (9) | −0.0028 (12) |
C13 | 0.0270 (13) | 0.0370 (15) | 0.0262 (11) | 0.0028 (12) | 0.0087 (9) | −0.0019 (11) |
C14 | 0.0250 (12) | 0.0309 (13) | 0.0230 (10) | 0.0014 (12) | 0.0059 (9) | −0.0019 (12) |
C15 | 0.0381 (15) | 0.068 (2) | 0.0225 (11) | 0.0052 (17) | 0.0028 (10) | −0.0018 (15) |
C16 | 0.0368 (15) | 0.0555 (17) | 0.0279 (12) | 0.0023 (15) | 0.0019 (10) | −0.0011 (14) |
O1—C1 | 1.293 (3) | C5—C6 | 1.421 (3) |
O1—H1A | 0.8501 | C5—C14 | 1.423 (3) |
O2—C2 | 1.344 (3) | C6—C7 | 1.454 (3) |
O2—C15 | 1.447 (3) | C7—C12 | 1.368 (4) |
O3—C4 | 1.294 (3) | C7—C8 | 1.527 (3) |
O3—H3A | 0.8350 | C8—C9 | 1.524 (4) |
O4—C6 | 1.304 (3) | C8—H8 | 0.9800 |
O4—H4A | 0.9046 | C9—C10 | 1.523 (4) |
O5—C8 | 1.415 (4) | C9—H9 | 0.9800 |
O5—H5A | 0.9154 | C10—C16 | 1.525 (3) |
O6—C9 | 1.427 (3) | C10—C11 | 1.530 (3) |
O6—H6A | 0.9667 | C11—C12 | 1.501 (3) |
O7—C10 | 1.444 (3) | C11—H11A | 0.9700 |
O7—H7A | 0.9012 | C11—H11B | 0.9700 |
O8—C13 | 1.296 (3) | C12—C13 | 1.448 (3) |
O8—H8A | 0.9624 | C13—C14 | 1.422 (3) |
C1—C14 | 1.417 (3) | C15—H15A | 0.9600 |
C1—C2 | 1.458 (3) | C15—H15B | 0.9600 |
C2—C3 | 1.364 (4) | C15—H15C | 0.9600 |
C3—C4 | 1.424 (3) | C16—H16A | 0.9600 |
C3—H3 | 0.9300 | C16—H16B | 0.9600 |
C4—C5 | 1.431 (3) | C16—H16C | 0.9600 |
C1—O1—H1A | 112.1 | C10—C9—C8 | 111.2 (2) |
C2—O2—C15 | 118.3 (2) | O6—C9—H9 | 108.9 |
C4—O3—H3A | 108.7 | C10—C9—H9 | 108.9 |
C6—O4—H4A | 110.2 | C8—C9—H9 | 108.9 |
C8—O5—H5A | 99.7 | O7—C10—C9 | 106.3 (2) |
C9—O6—H6A | 106.8 | O7—C10—C16 | 109.9 (2) |
C10—O7—H7A | 110.5 | C9—C10—C16 | 111.6 (2) |
C13—O8—H8A | 106.3 | O7—C10—C11 | 110.9 (2) |
O1—C1—C14 | 123.4 (2) | C9—C10—C11 | 108.4 (2) |
O1—C1—C2 | 117.6 (2) | C16—C10—C11 | 109.7 (2) |
C14—C1—C2 | 119.0 (2) | C12—C11—C10 | 113.5 (2) |
O2—C2—C3 | 127.1 (2) | C12—C11—H11A | 108.9 |
O2—C2—C1 | 112.4 (2) | C10—C11—H11A | 108.9 |
C3—C2—C1 | 120.4 (2) | C12—C11—H11B | 108.9 |
C2—C3—C4 | 120.9 (2) | C10—C11—H11B | 108.9 |
C2—C3—H3 | 119.5 | H11A—C11—H11B | 107.7 |
C4—C3—H3 | 119.5 | C7—C12—C13 | 120.6 (2) |
O3—C4—C3 | 118.4 (2) | C7—C12—C11 | 122.6 (2) |
O3—C4—C5 | 121.4 (2) | C13—C12—C11 | 116.7 (2) |
C3—C4—C5 | 120.2 (2) | O8—C13—C14 | 121.8 (2) |
C6—C5—C14 | 119.9 (2) | O8—C13—C12 | 118.2 (2) |
C6—C5—C4 | 121.1 (2) | C14—C13—C12 | 120.1 (2) |
C14—C5—C4 | 119.0 (2) | C1—C14—C13 | 120.0 (2) |
O4—C6—C5 | 121.3 (2) | C1—C14—C5 | 120.5 (2) |
O4—C6—C7 | 118.7 (2) | C13—C14—C5 | 119.5 (2) |
C5—C6—C7 | 120.0 (2) | O2—C15—H15A | 109.5 |
C12—C7—C6 | 119.9 (2) | O2—C15—H15B | 109.5 |
C12—C7—C8 | 120.9 (2) | H15A—C15—H15B | 109.5 |
C6—C7—C8 | 119.0 (2) | O2—C15—H15C | 109.5 |
O5—C8—C9 | 106.9 (2) | H15A—C15—H15C | 109.5 |
O5—C8—C7 | 113.5 (2) | H15B—C15—H15C | 109.5 |
C9—C8—C7 | 112.6 (2) | C10—C16—H16A | 109.5 |
O5—C8—H8 | 107.8 | C10—C16—H16B | 109.5 |
C9—C8—H8 | 107.8 | H16A—C16—H16B | 109.5 |
C7—C8—H8 | 107.8 | C10—C16—H16C | 109.5 |
O6—C9—C10 | 112.1 (2) | H16A—C16—H16C | 109.5 |
O6—C9—C8 | 106.7 (2) | H16B—C16—H16C | 109.5 |
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1A···O3i | 0.85 | 2.55 | 3.229 (3) | 137 |
O3—H3A···O8ii | 0.84 | 2.40 | 2.808 (3) | 111 |
O4—H4A···O8ii | 0.90 | 2.54 | 3.223 (3) | 132 |
O5—H5A···O4 | 0.92 | 1.85 | 2.687 (3) | 152 |
O6—H6A···O7iii | 0.97 | 1.92 | 2.821 (3) | 154 |
O7—H7A···O1iv | 0.90 | 2.11 | 2.966 (3) | 159 |
O7—H7A···O2iv | 0.90 | 2.40 | 3.066 (3) | 131 |
Symmetry codes: (i) x+1, y, z; (ii) x−1, y, z; (iii) −x+1, y−1/2, −z+2; (iv) −x+1, y+1/2, −z+1. |
Experimental details
Crystal data | |
Chemical formula | C16H16O8 |
Mr | 336.29 |
Crystal system, space group | Monoclinic, P21 |
Temperature (K) | 293 |
a, b, c (Å) | 8.280 (2), 6.644 (2), 13.1535 (12) |
β (°) | 102.12 (2) |
V (Å3) | 707.5 (3) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 0.13 |
Crystal size (mm) | 0.30 × 0.20 × 0.08 |
Data collection | |
Diffractometer | Rigaku R-AXIS RAPID IP diffractometer |
Absorption correction | Multi-scan (ABSCOR; Higashi, 1995) |
Tmin, Tmax | 0.953, 0.990 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 6151, 1517, 1282 |
Rint | 0.025 |
(sin θ/λ)max (Å−1) | 0.617 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.035, 0.105, 1.08 |
No. of reflections | 1517 |
No. of parameters | 220 |
No. of restraints | 1 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.24, −0.19 |
Computer programs: PROCESS-AUTO (Rigaku, 1998), CrystalStructure (Rigaku/MSC, 2002), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), ORTEP-3 (Farrugia, 1997), WinGX (Farrugia, 1999).
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1A···O3i | 0.85 | 2.55 | 3.229 (3) | 137 |
O3—H3A···O8ii | 0.84 | 2.40 | 2.808 (3) | 111 |
O4—H4A···O8ii | 0.90 | 2.54 | 3.223 (3) | 132 |
O5—H5A···O4 | 0.92 | 1.85 | 2.687 (3) | 152 |
O6—H6A···O7iii | 0.97 | 1.92 | 2.821 (3) | 154 |
O7—H7A···O1iv | 0.90 | 2.11 | 2.966 (3) | 159 |
O7—H7A···O2iv | 0.90 | 2.40 | 3.066 (3) | 131 |
Symmetry codes: (i) x+1, y, z; (ii) x−1, y, z; (iii) −x+1, y−1/2, −z+2; (iv) −x+1, y+1/2, −z+1. |
Acknowledgements
The work was supported by the Science and Technology Project of Zhejiang Province (grant Nos. 2004 C22008 and 2006 C12088) and the National Natural Science Foundation of China (grant No. 30600002).
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Bostrycin, a nonspecific phytotoxin, was identified as a metabolite of the fungus Arthrinium phaeospermum in 1975 (van Eijk, 1975; Charudattan & Rao, 1982). It is active against Bacillus subtilis but inactive against the fungus Geotrichum candidum (Charudattan & Rao, 1982). We report here the crystal structure of the title compound.
The crystal structure of the title compound is the average structure of two tautomers, 5,6,7,9,10-pentahydroxy-2-methoxy-7-methyl-1,4,5,6,7,8-hexahydroanthracene- 1,4-dione (I) and 1,4,5,6,7-pentahydroxy-2-methoxy-7-methyl-5,6,7,8,9,10-hexahydroanthracene- 9,10-dione (II). The molecular structures of the two tautomers are shown in Fig. 1 and Fig. 2, respectively. Both of tautomer molecules contains three six-membered rings, among which the C9-containing ring displays a half-chair conformation. Within the molecule the carbonyl group is hydrogen bonded to the neighboring hydroxyl group(s). The bond distances and angles agree with those found in a derivative of bostrycin, bostrycin acetonide (Kelly & Saha, 1985). The extensive O—H···O hydrogen bonding network helps to stabilize the crystal structure (Table 1).