organic compounds
Cynaratriol, a sesquiterpene lactone from Centaurea musimomum
aInstituto de Bioorgánica "A. González", Universidad de La Laguna, Astrofísico Francisco Sánchez, 2, 38206 La Laguna, Tenerife, Spain, bInstituto de Productos Naturales y Agrobiología del CSIC, Instituto de Bioorgánica "A. González", Universidad de La Laguna, Astrofísico Francisco Sánchez, 2, 38206 La Laguna, Tenerife, Spain, cLaboratoire de Phytochemie et Analyses Physico-Chimiques et Biologiques, Equipe Associée à l'ANDRS, Université Mentouri, Route de Aïn El Bey, 25000 Constantine, Algeria, and dLaboratoire de Valorisation des Resources Naturelles et Synthèse de Substances, Bioactives, Equipe Associée à l'ANDRS, Université Mentouri, Route de Aïn El Bey, 25000 Constantine, Algeria
*Correspondence e-mail: malopez@ull.es
The title compound [systematic name: 3,8-dihydroxy-3-(hydroxymethyl)-9-methyl-6-methylenedecahydroazuleno[4,5-b]furan-2(3H)-one], C15H22O5, is a sesquiterpene lactone showing the typical tricyclic guaianolide skeleton which has been isolated, together with other related metabolites, from the plant Centaurea musimomum. The present study confirms the molecular structure, assigned by 1H NMR and MS spectroscopy, as well as the the 11β-hydroxymethyl, 3β-hydroxy and 4α-methyl stereochemistry. The is built through a network of O—H⋯O hydrogen bonds involving the three hydroxyl groups that are present in the molecular skeleton.
Related literature
For the ethyl acetate soluble extract of Centaurea musimomum, an endemic specie from Algeria, see: Quezel & Santa (1963). For the structures of several guaianolide type sesquiterpene isolated from the chloroform-soluble part of Centaurea musimomum, see: Medjroubi et al. (1997, 2003, 2005); González-Platas et al. (1999). Cynaratriol was previously isolated from Cynara species, see: von Heinz et al. (1979). For related structures, see: Oksuz et al. (1993); González-Platas et al. (1999).
Experimental
Crystal data
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Data collection
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Refinement
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Data collection: COLLECT (Nonius, 2000); cell SCALEPACK (Otwinowski & Minor, 1997); data reduction: SCALEPACK and DENZO (Otwinowski & Minor, 1997); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2009); software used to prepare material for publication: WinGX (Farrugia, 1999).
Supporting information
10.1107/S1600536809026701/bx2222sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536809026701/bx2222Isup2.hkl
The H-atoms of the hydroxyl groups were located on difference-Fourier map and freely refined. All other H atoms were positioned with idealized geometry: C—H = 0.98(CH3), 0.99(CH2), 1.00(CH) Å and included in the
in a riding-model approximation with Uiso(H) = 1.2Ueq(C) and Uiso(H) = 1.5Ueq for methyl. The lack of suitable anomalous scatters did not allow us to reliably determine the according to the Flack parameters: -10 (10) and, therefore, the Friedel pairs were merged prior to the final refinement.Data collection: COLLECT (Nonius, 2000); cell
SCALEPACK (Otwinowski & Minor, 1997); data reduction: SCALEPACK and DENZO (Otwinowski & Minor, 1997); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2009); software used to prepare material for publication: WinGX (Farrugia, 1999).C15H22O5 | F(000) = 608 |
Mr = 282.33 | Dx = 1.307 Mg m−3 |
Orthorhombic, P212121 | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: P 2ac 2ab | Cell parameters from 7053 reflections |
a = 8.417 (4) Å | θ = 3.2–28.6° |
b = 9.919 (3) Å | µ = 0.10 mm−1 |
c = 17.187 (8) Å | T = 293 K |
V = 1434.9 (10) Å3 | Block, colourless |
Z = 4 | 0.40 × 0.30 × 0.25 mm |
Enraf–Nonius KappaCCD diffractometer | 1847 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.038 |
Graphite monochromator | θmax = 28.6°, θmin = 3.2° |
Detector resolution: 9 pixels mm-1 | h = −10→11 |
ϕ and ω scans | k = −12→12 |
8829 measured reflections | l = −22→23 |
2054 independent reflections |
Refinement on F2 | 0 restraints |
Least-squares matrix: full | H atoms treated by a mixture of independent and constrained refinement |
R[F2 > 2σ(F2)] = 0.042 | w = 1/[σ2(Fo2) + (0.0447P)2 + 0.2149P] where P = (Fo2 + 2Fc2)/3 |
wR(F2) = 0.101 | (Δ/σ)max = 0.01 |
S = 1.11 | Δρmax = 0.21 e Å−3 |
2054 reflections | Δρmin = −0.17 e Å−3 |
194 parameters |
C15H22O5 | V = 1434.9 (10) Å3 |
Mr = 282.33 | Z = 4 |
Orthorhombic, P212121 | Mo Kα radiation |
a = 8.417 (4) Å | µ = 0.10 mm−1 |
b = 9.919 (3) Å | T = 293 K |
c = 17.187 (8) Å | 0.40 × 0.30 × 0.25 mm |
Enraf–Nonius KappaCCD diffractometer | 1847 reflections with I > 2σ(I) |
8829 measured reflections | Rint = 0.038 |
2054 independent reflections |
R[F2 > 2σ(F2)] = 0.042 | 0 restraints |
wR(F2) = 0.101 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.11 | Δρmax = 0.21 e Å−3 |
2054 reflections | Δρmin = −0.17 e Å−3 |
194 parameters |
Experimental. Centaurea musimomum L.was collected in June 2002 in Didouche Mourad (Constantine) Algeria and authenticated by Professor Nadra Khalfallah (Quezel & Santa, 1963). A voucher specimen was deposited in the herbarium of the Department of Nature and Life Sciences, Mentouri University, Constantine. Air-dried leaves (339 g) and air-dried flowers (202 g) were separately macerated, three times for 24 h, at room temperature with a mixture of methanol-water (70:30). The filtrates were concentrated and successsively extracted with petrol, chloroform, ethyl acetate and n-butanol. The ethyl acetate phases yield, after drying and solvent evaporation 10.8 g and 4.9 g respectively. Analysis by TLC on silica-gel plates showed no significant differences between the leaves and the flowers extract and they were mixed. A part (13 g) of the combined extract was chromatographed on a 230–400 mesh silica gel (325 g) column with chloroform-acetone mixtures of increasing polarity as elution solvents to yield the title compound: cynaratriol together with other related sesquiterpene lactones. The molecular formula C~15~ H~22~ O~5~ was deduced from its high resolution MS spectrum which shows a molecular ion at m/z=280.1329. The ^13Ĉ and ^1ĤNMR data are very similar to those of 4β,15-Dihydro-3-dehydrosolstiatilin A (Medjroubi et al., 2003), the differences arises from the replacement of the oxo group at C3 by an hydroxyl group. |
Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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 > 2σ(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 | ||
O1 | −0.0496 (3) | 0.33998 (17) | 0.44392 (9) | 0.0577 (5) | |
H1O | −0.107 (5) | 0.379 (4) | 0.469 (2) | 0.108 (15)* | |
O2 | −0.14872 (16) | 0.42543 (15) | 0.15121 (8) | 0.0379 (3) | |
O3 | −0.30157 (18) | 0.45503 (19) | 0.04747 (9) | 0.0540 (4) | |
O4 | −0.0339 (3) | 0.60068 (15) | −0.01439 (9) | 0.0521 (5) | |
H4O | −0.020 (4) | 0.673 (3) | 0.0102 (18) | 0.070 (9)* | |
O5 | 0.0257 (3) | 0.25259 (15) | 0.02916 (9) | 0.0536 (5) | |
H5O | 0.074 (3) | 0.190 (3) | 0.0041 (15) | 0.052 (7)* | |
C1 | 0.2066 (2) | 0.4743 (2) | 0.28881 (12) | 0.0388 (5) | |
H1 | 0.2376 | 0.5613 | 0.3112 | 0.047* | |
C2 | 0.1768 (3) | 0.3797 (2) | 0.35773 (12) | 0.0472 (5) | |
H2A | 0.1727 | 0.2863 | 0.3412 | 0.057* | |
H2B | 0.258 | 0.3898 | 0.3973 | 0.057* | |
C3 | 0.0174 (3) | 0.4275 (2) | 0.38653 (11) | 0.0422 (5) | |
H3 | 0.0292 | 0.5179 | 0.4088 | 0.051* | |
C4 | −0.0815 (2) | 0.4369 (2) | 0.31246 (11) | 0.0358 (4) | |
H4 | −0.1096 | 0.3453 | 0.2962 | 0.043* | |
C5 | 0.0359 (2) | 0.49556 (18) | 0.25231 (10) | 0.0308 (4) | |
H5 | 0.0163 | 0.5926 | 0.2478 | 0.037* | |
C6 | 0.0215 (2) | 0.43313 (19) | 0.17180 (10) | 0.0289 (4) | |
H6 | 0.0675 | 0.3424 | 0.1721 | 0.035* | |
C7 | 0.0949 (2) | 0.51598 (19) | 0.10596 (10) | 0.0326 (4) | |
H7 | 0.0813 | 0.6111 | 0.12 | 0.039* | |
C8 | 0.2719 (3) | 0.4939 (3) | 0.09333 (13) | 0.0476 (5) | |
H8A | 0.3076 | 0.5493 | 0.0502 | 0.057* | |
H8B | 0.2906 | 0.4003 | 0.0798 | 0.057* | |
C9 | 0.3682 (3) | 0.5293 (3) | 0.16608 (14) | 0.0542 (6) | |
H9A | 0.4804 | 0.5268 | 0.1533 | 0.065* | |
H9B | 0.3425 | 0.6206 | 0.1819 | 0.065* | |
C10 | 0.3375 (2) | 0.4353 (2) | 0.23343 (13) | 0.0461 (5) | |
C11 | −0.0147 (2) | 0.48927 (19) | 0.03617 (10) | 0.0346 (4) | |
C12 | −0.1702 (2) | 0.4552 (2) | 0.07626 (11) | 0.0373 (4) | |
C13 | 0.0313 (3) | 0.37152 (19) | −0.01605 (12) | 0.0422 (5) | |
H13A | −0.042 | 0.3648 | −0.0594 | 0.051* | |
H13B | 0.1375 | 0.3848 | −0.0366 | 0.051* | |
C14 | 0.4258 (3) | 0.3269 (3) | 0.24326 (18) | 0.0706 (8) | |
H14A | 0.4085 | 0.2709 | 0.2858 | 0.085* | |
H14B | 0.5055 | 0.3065 | 0.2077 | 0.085* | |
C15 | −0.2339 (3) | 0.5172 (3) | 0.32204 (14) | 0.0529 (6) | |
H15B | −0.2088 | 0.6069 | 0.3391 | 0.079* | |
H15A | −0.3005 | 0.4742 | 0.36 | 0.079* | |
H15C | −0.2887 | 0.5213 | 0.2731 | 0.079* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.0988 (15) | 0.0417 (8) | 0.0325 (8) | 0.0184 (9) | 0.0167 (9) | 0.0085 (6) |
O2 | 0.0299 (6) | 0.0527 (8) | 0.0313 (7) | −0.0041 (6) | −0.0031 (6) | −0.0017 (6) |
O3 | 0.0408 (8) | 0.0734 (11) | 0.0476 (9) | 0.0025 (8) | −0.0155 (7) | −0.0084 (8) |
O4 | 0.0908 (13) | 0.0333 (7) | 0.0323 (8) | −0.0003 (8) | −0.0162 (9) | 0.0022 (6) |
O5 | 0.0823 (13) | 0.0323 (7) | 0.0462 (9) | 0.0082 (8) | 0.0134 (9) | −0.0018 (7) |
C1 | 0.0402 (10) | 0.0410 (10) | 0.0353 (10) | −0.0029 (8) | −0.0124 (8) | −0.0052 (8) |
C2 | 0.0600 (13) | 0.0485 (11) | 0.0330 (11) | 0.0082 (11) | −0.0148 (10) | −0.0014 (9) |
C3 | 0.0679 (14) | 0.0321 (9) | 0.0268 (9) | 0.0063 (10) | −0.0025 (10) | −0.0004 (7) |
C4 | 0.0454 (10) | 0.0334 (9) | 0.0286 (9) | −0.0013 (9) | 0.0015 (8) | 0.0000 (7) |
C5 | 0.0344 (9) | 0.0299 (8) | 0.0280 (8) | 0.0005 (7) | −0.0039 (7) | −0.0003 (7) |
C6 | 0.0264 (8) | 0.0318 (8) | 0.0286 (9) | 0.0000 (7) | −0.0024 (7) | −0.0003 (7) |
C7 | 0.0358 (9) | 0.0345 (9) | 0.0276 (9) | −0.0040 (8) | −0.0006 (8) | −0.0009 (7) |
C8 | 0.0375 (11) | 0.0649 (14) | 0.0403 (11) | −0.0067 (11) | 0.0058 (9) | −0.0016 (11) |
C9 | 0.0317 (10) | 0.0745 (16) | 0.0563 (14) | −0.0137 (11) | 0.0001 (10) | −0.0048 (12) |
C10 | 0.0295 (9) | 0.0611 (12) | 0.0476 (12) | −0.0039 (10) | −0.0109 (9) | −0.0071 (10) |
C11 | 0.0464 (10) | 0.0300 (8) | 0.0272 (9) | 0.0007 (8) | −0.0045 (8) | −0.0004 (7) |
C12 | 0.0395 (10) | 0.0387 (10) | 0.0338 (10) | 0.0014 (9) | −0.0068 (8) | −0.0092 (8) |
C13 | 0.0572 (13) | 0.0373 (10) | 0.0320 (10) | 0.0021 (10) | 0.0015 (10) | −0.0045 (8) |
C14 | 0.0441 (13) | 0.088 (2) | 0.0794 (19) | 0.0196 (15) | −0.0051 (14) | −0.0036 (16) |
C15 | 0.0459 (12) | 0.0723 (15) | 0.0405 (12) | 0.0069 (12) | 0.0112 (10) | 0.0035 (11) |
O1—C3 | 1.430 (3) | C5—H5 | 0.98 |
O1—H1O | 0.76 (4) | C6—C7 | 1.529 (3) |
O2—C12 | 1.334 (2) | C6—H6 | 0.98 |
O2—C6 | 1.477 (2) | C7—C8 | 1.522 (3) |
O3—C12 | 1.211 (2) | C7—C11 | 1.536 (3) |
O4—C11 | 1.415 (2) | C7—H7 | 0.98 |
O4—H4O | 0.84 (3) | C8—C9 | 1.531 (3) |
O5—C13 | 1.413 (3) | C8—H8A | 0.97 |
O5—H5O | 0.86 (3) | C8—H8B | 0.97 |
C1—C10 | 1.507 (3) | C9—C10 | 1.509 (3) |
C1—C2 | 1.531 (3) | C9—H9A | 0.97 |
C1—C5 | 1.582 (3) | C9—H9B | 0.97 |
C1—H1 | 0.98 | C10—C14 | 1.317 (4) |
C2—C3 | 1.507 (3) | C11—C12 | 1.517 (3) |
C2—H2A | 0.97 | C11—C13 | 1.523 (3) |
C2—H2B | 0.97 | C13—H13A | 0.97 |
C3—C4 | 1.524 (3) | C13—H13B | 0.97 |
C3—H3 | 0.98 | C14—H14A | 0.93 |
C4—C15 | 1.519 (3) | C14—H14B | 0.93 |
C4—C5 | 1.544 (3) | C15—H15B | 0.96 |
C4—H4 | 0.98 | C15—H15A | 0.96 |
C5—C6 | 1.521 (2) | C15—H15C | 0.96 |
C3—O1—H1O | 110 (3) | C8—C7—H7 | 106.7 |
C12—O2—C6 | 110.58 (15) | C6—C7—H7 | 106.7 |
C11—O4—H4O | 110 (2) | C11—C7—H7 | 106.7 |
C13—O5—H5O | 108.2 (17) | C7—C8—C9 | 111.64 (18) |
C10—C1—C2 | 116.82 (18) | C7—C8—H8A | 109.3 |
C10—C1—C5 | 116.63 (16) | C9—C8—H8A | 109.3 |
C2—C1—C5 | 103.87 (16) | C7—C8—H8B | 109.3 |
C10—C1—H1 | 106.2 | C9—C8—H8B | 109.3 |
C2—C1—H1 | 106.2 | H8A—C8—H8B | 108 |
C5—C1—H1 | 106.2 | C10—C9—C8 | 113.23 (19) |
C3—C2—C1 | 101.96 (17) | C10—C9—H9A | 108.9 |
C3—C2—H2A | 111.4 | C8—C9—H9A | 108.9 |
C1—C2—H2A | 111.4 | C10—C9—H9B | 108.9 |
C3—C2—H2B | 111.4 | C8—C9—H9B | 108.9 |
C1—C2—H2B | 111.4 | H9A—C9—H9B | 107.7 |
H2A—C2—H2B | 109.2 | C14—C10—C1 | 122.8 (2) |
O1—C3—C2 | 112.74 (18) | C14—C10—C9 | 120.4 (2) |
O1—C3—C4 | 113.45 (19) | C1—C10—C9 | 116.8 (2) |
C2—C3—C4 | 103.36 (16) | O4—C11—C12 | 110.76 (17) |
O1—C3—H3 | 109 | O4—C11—C13 | 105.43 (15) |
C2—C3—H3 | 109 | C12—C11—C13 | 108.42 (17) |
C4—C3—H3 | 109 | O4—C11—C7 | 114.41 (16) |
C15—C4—C3 | 113.75 (17) | C12—C11—C7 | 101.65 (15) |
C15—C4—C5 | 114.55 (17) | C13—C11—C7 | 116.10 (17) |
C3—C4—C5 | 103.48 (16) | O3—C12—O2 | 121.20 (19) |
C15—C4—H4 | 108.3 | O3—C12—C11 | 127.03 (18) |
C3—C4—H4 | 108.3 | O2—C12—C11 | 111.76 (16) |
C5—C4—H4 | 108.3 | O5—C13—C11 | 107.92 (16) |
C6—C5—C4 | 113.89 (15) | O5—C13—H13A | 110.1 |
C6—C5—C1 | 112.26 (15) | C11—C13—H13A | 110.1 |
C4—C5—C1 | 105.39 (15) | O5—C13—H13B | 110.1 |
C6—C5—H5 | 108.4 | C11—C13—H13B | 110.1 |
C4—C5—H5 | 108.4 | H13A—C13—H13B | 108.4 |
C1—C5—H5 | 108.4 | C10—C14—H14A | 120 |
O2—C6—C5 | 108.44 (14) | C10—C14—H14B | 120 |
O2—C6—C7 | 104.02 (14) | H14A—C14—H14B | 120 |
C5—C6—C7 | 114.98 (15) | C4—C15—H15B | 109.5 |
O2—C6—H6 | 109.7 | C4—C15—H15A | 109.5 |
C5—C6—H6 | 109.7 | H15B—C15—H15A | 109.5 |
C7—C6—H6 | 109.7 | C4—C15—H15C | 109.5 |
C8—C7—C6 | 115.08 (17) | H15B—C15—H15C | 109.5 |
C8—C7—C11 | 116.86 (17) | H15A—C15—H15C | 109.5 |
C6—C7—C11 | 104.04 (15) | ||
C10—C1—C2—C3 | −165.75 (17) | C6—C7—C8—C9 | −59.8 (3) |
C5—C1—C2—C3 | −35.80 (18) | C11—C7—C8—C9 | 177.73 (18) |
C1—C2—C3—O1 | 170.47 (17) | C7—C8—C9—C10 | 67.0 (3) |
C1—C2—C3—C4 | 47.57 (19) | C2—C1—C10—C14 | −1.2 (3) |
O1—C3—C4—C15 | 72.7 (2) | C5—C1—C10—C14 | −124.9 (2) |
C2—C3—C4—C15 | −164.87 (18) | C2—C1—C10—C9 | −179.27 (18) |
O1—C3—C4—C5 | −162.39 (16) | C5—C1—C10—C9 | 57.1 (2) |
C2—C3—C4—C5 | −39.96 (19) | C8—C9—C10—C14 | 91.2 (3) |
C15—C4—C5—C6 | −95.3 (2) | C8—C9—C10—C1 | −90.7 (2) |
C3—C4—C5—C6 | 140.34 (15) | C8—C7—C11—O4 | −86.5 (2) |
C15—C4—C5—C1 | 141.25 (19) | C6—C7—C11—O4 | 145.49 (17) |
C3—C4—C5—C1 | 16.86 (18) | C8—C7—C11—C12 | 154.14 (18) |
C10—C1—C5—C6 | 17.1 (2) | C6—C7—C11—C12 | 26.08 (18) |
C2—C1—C5—C6 | −112.97 (17) | C8—C7—C11—C13 | 36.7 (3) |
C10—C1—C5—C4 | 141.60 (18) | C6—C7—C11—C13 | −91.3 (2) |
C2—C1—C5—C4 | 11.53 (19) | C6—O2—C12—O3 | −179.83 (19) |
C12—O2—C6—C5 | 140.81 (16) | C6—O2—C12—C11 | −0.8 (2) |
C12—O2—C6—C7 | 18.0 (2) | O4—C11—C12—O3 | 40.5 (3) |
C4—C5—C6—O2 | 45.5 (2) | C13—C11—C12—O3 | −74.7 (3) |
C1—C5—C6—O2 | 165.20 (15) | C7—C11—C12—O3 | 162.5 (2) |
C4—C5—C6—C7 | 161.46 (16) | O4—C11—C12—O2 | −138.44 (16) |
C1—C5—C6—C7 | −78.87 (19) | C13—C11—C12—O2 | 106.34 (18) |
O2—C6—C7—C8 | −156.38 (16) | C7—C11—C12—O2 | −16.5 (2) |
C5—C6—C7—C8 | 85.2 (2) | O4—C11—C13—O5 | −170.20 (19) |
O2—C6—C7—C11 | −27.24 (18) | C12—C11—C13—O5 | −51.6 (2) |
C5—C6—C7—C11 | −145.67 (15) | C7—C11—C13—O5 | 62.0 (2) |
D—H···A | D—H | H···A | D···A | D—H···A |
O4—H4O···O1i | 0.84 (3) | 1.93 (3) | 2.756 (2) | 169 (3) |
O5—H5O···O3ii | 0.86 (3) | 1.99 (3) | 2.844 (2) | 176 (3) |
O1—H1O···O3iii | 0.76 (4) | 2.26 (4) | 2.978 (3) | 159 (4) |
Symmetry codes: (i) −x, y+1/2, −z+1/2; (ii) x+1/2, −y+1/2, −z; (iii) −x−1/2, −y+1, z+1/2. |
Experimental details
Crystal data | |
Chemical formula | C15H22O5 |
Mr | 282.33 |
Crystal system, space group | Orthorhombic, P212121 |
Temperature (K) | 293 |
a, b, c (Å) | 8.417 (4), 9.919 (3), 17.187 (8) |
V (Å3) | 1434.9 (10) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.10 |
Crystal size (mm) | 0.40 × 0.30 × 0.25 |
Data collection | |
Diffractometer | Enraf–Nonius KappaCCD diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 8829, 2054, 1847 |
Rint | 0.038 |
(sin θ/λ)max (Å−1) | 0.674 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.042, 0.101, 1.11 |
No. of reflections | 2054 |
No. of parameters | 194 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.21, −0.17 |
Computer programs: COLLECT (Nonius, 2000), SCALEPACK (Otwinowski & Minor, 1997), SCALEPACK and DENZO (Otwinowski & Minor, 1997), SIR97 (Altomare et al., 1999), SHELXL97 (Sheldrick, 2008), PLATON (Spek, 2009), WinGX (Farrugia, 1999).
D—H···A | D—H | H···A | D···A | D—H···A |
O4—H4O···O1i | 0.84 (3) | 1.93 (3) | 2.756 (2) | 169 (3) |
O5—H5O···O3ii | 0.86 (3) | 1.99 (3) | 2.844 (2) | 176 (3) |
O1—H1O···O3iii | 0.76 (4) | 2.26 (4) | 2.978 (3) | 159 (4) |
Symmetry codes: (i) −x, y+1/2, −z+1/2; (ii) x+1/2, −y+1/2, −z; (iii) −x−1/2, −y+1, z+1/2. |
Acknowledgements
The authors wish to thank Professor N. Khalfallah of the Nature and Life Sciences Department, Mentorui University of Constantine, Algerie, for the identification of the plant material.
References
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This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.
The Centaurea genus plants are a natural source of various type of sesquiterpenic lactones, many of which have been shown to be biologically active: Medjroubi, Benayache & Bermejo. In connection with a systematic study of this genus, we have investigated the ethyl acetate soluble extract of Centaurea musimomum, an endemic specie from Algeria: Quezel & Santa, (1963). Our previous phytochemical study of the chloroform soluble part led to the isolation an molecular structure determination of several guaianolide type sesquiterpene lactones: Medjroubi et al., 1997; González-Platas et al. 1999; Medjroubi et al., 2003. Cynaratriol was previously isolated from Cynara species (Heinz, Thiele & Pretsch, 1979). In this work we report the isolation and the molecular and crystal structure determination of the title compound, which it is described for the first time as a metabolite for the Centaurea genus. The lack of suitable anomalous scatters did not allow us to reliably determine the absolute structure and that shown was chosen to be the same as that the, close related, 4β,15-Dihydro-3-dehydrosolstiatilin A (González-Platas et al., 1999) and its acetate (Oksuz, Clark & Herz, 1993).