organic compounds
1,2-Bis[(3,6,9-trimethyl-3,12-epoxy-3,4,5,5a,6,7,8,8a,9,10,12,12a-dodecahydropyrano[4,3-j][1,2]benzodioxepin-4-yl)oxy]ethane
aSchool of Pharmacy, Heilongjiang University of Chinese Medicine, Harbin 150040, People's Republic of China, bSchool of Chemistry and Materials Science, Heilongjiang University, Harbin 150080, People's Republic of China, and cHeilongjiang Environmental Monitoring Central Station, Harbin 150056, People's Republic of China
*Correspondence e-mail: wsjlw@yahoo.cn
The title compound, C32H50O10, prepared from a mixture of α- and β-dihydroartemisinin, has two β-arteether moieties linked via an –OCH2CH2O– bridge, so that the molecule is symmetric about the bridge. Each contains a β-arteether moiety and an –OCH2 group, which is only one-half of the molecule. The endo-peroxide bridges of the parent compounds have been retained in each half of the diol-bridged dimer. The rings exhibit chair and twist-boat conformations.
Related literature
For related literature and structures, see: Brossi et al. (1988); Dominguez Gerpe et al. (1988); Flack & Bernardinelli (2000); Flippen-Anderson et al. (1989); Haynes et al. (2002); Luo et al. (1984); Paik et al. (2006); Qinghaosu Research Group (1980); Venugopalan et al. (1995); Woerdenbag et al. (1993); Yue et al. (2006). For the synthesis, see: Posner et al. (1997). For puckering parameters, see: Cremer & Pople (1975).
Experimental
Crystal data
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Data collection: RAPID-AUTO (Rigaku, 1998); cell RAPID-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: ORTEPII (Johnson, 1976); software used to prepare material for publication: SHELXL97.
Supporting information
10.1107/S1600536812005089/jj2118sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536812005089/jj2118Isup2.hkl
Supporting information file. DOI: 10.1107/S1600536812005089/jj2118Isup3.cml
The title compound has been prepared according to a literature procedure (Posner et al., 1997). To a solution of dihydroartemisinin (297 mg, 1.05 mmol) in toluene (30 mL) at 293~298 K, glycol (0.029 mL, 0.53 mmol) was added followed by BF3Et2O (0.032 mL, 0.26 mmol). The reaction was stirred at the same temperature for 3 h. The mixture was then diluted with methylene chloride and was washed twice with water. The organic portions were collected, dried over (MgSO4) and concentrated. The crude product was purified by
(flash, 7–20% ethyl acetate/petro ether) to produce the title compound (50.7 mg, 0.085 mmol, yield 17%). Crystals were obtained from ether, diffused with hexane at room temperature.The methyl H atoms were constrained to an ideal geometry (C—H = 0.96 Å) with Uiso(H) = 1.5Ueq(C), but were allowed to rotate freely about the C—C bonds. All other H atoms were placed in geometrically idealized positions and constrained to ride on their parent C atoms at distances of 0.97 or 0.98 Å for methylene or methine groups, respectively, and with Uiso(H) = 1.2Ueq(C). As there are no significant anomalous scatterers in the molecule, attempts to confirm the
by of the (Flack & Bernardinelli, 2000) in the presence of 1614 sets of Friedel equivalents led to an inconclusive value for the parameter. Therefore, the Friedel pairs were merged before the final and the was assigned to correspond to that determined for artemisinin (Qinghaosu Research Group, 1980).Data collection: RAPID-AUTO (Rigaku, 1998); cell
RAPID-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: ORTEPII (Johnson, 1976); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).Fig. 1. View of the asymmetric unit showing with the atom-labeling and with displacement ellipsoids drawn at the 30% probability level. |
C32H50O10 | F(000) = 644 |
Mr = 594.72 | Dx = 1.276 Mg m−3 |
Monoclinic, C2 | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: C 2y | Cell parameters from 5507 reflections |
a = 18.033 (4) Å | θ = 3.7–26.0° |
b = 9.3127 (19) Å | µ = 0.09 mm−1 |
c = 11.061 (2) Å | T = 295 K |
β = 123.58 (3)° | Prism, colorless |
V = 1547.5 (8) Å3 | 0.42 × 0.38 × 0.31 mm |
Z = 2 |
Rigaku R-AXIS RAPID diffractometer | 1614 independent reflections |
Radiation source: fine-focus sealed tube | 1195 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.043 |
Detector resolution: 10.000 pixels mm-1 | θmax = 26.0°, θmin = 3.7° |
ω scans | h = −22→22 |
Absorption correction: multi-scan (ABSCOR; Higashi, 1995) | k = −11→9 |
Tmin = 0.962, Tmax = 0.972 | l = −13→13 |
6717 measured reflections |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.042 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.129 | H-atom parameters constrained |
S = 1.10 | w = 1/[σ2(Fo2) + (0.0715P)2 + 0.1671P] where P = (Fo2 + 2Fc2)/3 |
1614 reflections | (Δ/σ)max < 0.001 |
194 parameters | Δρmax = 0.20 e Å−3 |
1 restraint | Δρmin = −0.20 e Å−3 |
C32H50O10 | V = 1547.5 (8) Å3 |
Mr = 594.72 | Z = 2 |
Monoclinic, C2 | Mo Kα radiation |
a = 18.033 (4) Å | µ = 0.09 mm−1 |
b = 9.3127 (19) Å | T = 295 K |
c = 11.061 (2) Å | 0.42 × 0.38 × 0.31 mm |
β = 123.58 (3)° |
Rigaku R-AXIS RAPID diffractometer | 1614 independent reflections |
Absorption correction: multi-scan (ABSCOR; Higashi, 1995) | 1195 reflections with I > 2σ(I) |
Tmin = 0.962, Tmax = 0.972 | Rint = 0.043 |
6717 measured reflections |
R[F2 > 2σ(F2)] = 0.042 | 1 restraint |
wR(F2) = 0.129 | H-atom parameters constrained |
S = 1.10 | Δρmax = 0.20 e Å−3 |
1614 reflections | Δρmin = −0.20 e Å−3 |
194 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 | ||
O1 | 0.85534 (15) | 0.7920 (3) | 0.4203 (3) | 0.0696 (7) | |
O2 | 0.81128 (13) | 0.6711 (3) | 0.4401 (2) | 0.0638 (7) | |
O3 | 0.76331 (14) | 0.7918 (3) | 0.1695 (2) | 0.0578 (6) | |
O4 | 0.68018 (14) | 0.8818 (2) | 0.2453 (3) | 0.0600 (6) | |
O5 | 0.52997 (15) | 0.8430 (3) | 0.1553 (3) | 0.0655 (7) | |
C1 | 0.8536 (2) | 0.7701 (5) | 0.2924 (4) | 0.0638 (9) | |
C2 | 0.8844 (2) | 0.6212 (5) | 0.2839 (5) | 0.0741 (11) | |
H2A | 0.9172 | 0.6284 | 0.2382 | 0.089* | |
H2B | 0.9251 | 0.5858 | 0.3818 | 0.089* | |
C3 | 0.8104 (2) | 0.5128 (4) | 0.2012 (5) | 0.0694 (10) | |
H3A | 0.8369 | 0.4211 | 0.2041 | 0.083* | |
H3B | 0.7740 | 0.5427 | 0.1005 | 0.083* | |
C4 | 0.7496 (2) | 0.4904 (4) | 0.2559 (4) | 0.0590 (8) | |
H4A | 0.7836 | 0.4307 | 0.3431 | 0.071* | |
C5 | 0.6668 (2) | 0.4016 (4) | 0.1475 (4) | 0.0652 (9) | |
H5 | 0.6336 | 0.4546 | 0.0557 | 0.078* | |
C6 | 0.6066 (2) | 0.3825 (4) | 0.2020 (4) | 0.0700 (10) | |
H6A | 0.5535 | 0.3308 | 0.1298 | 0.084* | |
H6B | 0.6371 | 0.3255 | 0.2901 | 0.084* | |
C7 | 0.5804 (2) | 0.5246 (4) | 0.2323 (4) | 0.0642 (9) | |
H7A | 0.5408 | 0.5085 | 0.2645 | 0.077* | |
H7B | 0.5485 | 0.5805 | 0.1435 | 0.077* | |
C8 | 0.6620 (2) | 0.6093 (4) | 0.3487 (4) | 0.0576 (8) | |
H8 | 0.6917 | 0.5495 | 0.4362 | 0.069* | |
C9 | 0.6407 (2) | 0.7511 (4) | 0.3906 (4) | 0.0634 (9) | |
H9 | 0.6964 | 0.7825 | 0.4786 | 0.076* | |
C10 | 0.6163 (2) | 0.8677 (4) | 0.2800 (4) | 0.0643 (9) | |
H10 | 0.6147 | 0.9586 | 0.3231 | 0.077* | |
C11 | 0.6992 (2) | 0.7533 (3) | 0.1973 (4) | 0.0505 (7) | |
H11 | 0.6452 | 0.7232 | 0.1059 | 0.061* | |
C12 | 0.72923 (18) | 0.6310 (4) | 0.3060 (3) | 0.0497 (7) | |
C13 | 0.9078 (3) | 0.8911 (6) | 0.2898 (5) | 0.0916 (15) | |
H13A | 0.8908 | 0.9796 | 0.3125 | 0.137* | |
H13B | 0.8974 | 0.8977 | 0.1950 | 0.137* | |
H13C | 0.9698 | 0.8732 | 0.3603 | 0.137* | |
C14 | 0.6926 (4) | 0.2560 (5) | 0.1183 (6) | 0.0950 (14) | |
H14A | 0.7275 | 0.2040 | 0.2078 | 0.143* | |
H14B | 0.7269 | 0.2700 | 0.0768 | 0.143* | |
H14C | 0.6398 | 0.2025 | 0.0520 | 0.143* | |
C15 | 0.5731 (3) | 0.7405 (6) | 0.4325 (5) | 0.0923 (15) | |
H15A | 0.5162 | 0.7137 | 0.3490 | 0.138* | |
H15B | 0.5684 | 0.8318 | 0.4680 | 0.138* | |
H15C | 0.5924 | 0.6693 | 0.5070 | 0.138* | |
C16 | 0.4917 (3) | 0.9620 (4) | 0.0595 (5) | 0.0737 (10) | |
H16A | 0.5156 | 1.0498 | 0.1152 | 0.088* | |
H16B | 0.4280 | 0.9619 | 0.0162 | 0.088* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.0611 (13) | 0.0951 (18) | 0.0531 (14) | −0.0343 (13) | 0.0319 (11) | −0.0154 (14) |
O2 | 0.0523 (11) | 0.0890 (17) | 0.0424 (12) | −0.0224 (12) | 0.0214 (9) | −0.0031 (12) |
O3 | 0.0544 (11) | 0.0700 (15) | 0.0532 (13) | −0.0115 (10) | 0.0324 (10) | 0.0023 (11) |
O4 | 0.0605 (13) | 0.0547 (13) | 0.0710 (16) | −0.0134 (11) | 0.0401 (12) | −0.0100 (12) |
O5 | 0.0583 (12) | 0.0607 (14) | 0.0762 (17) | −0.0088 (11) | 0.0364 (12) | −0.0090 (13) |
C1 | 0.0488 (17) | 0.091 (2) | 0.0528 (19) | −0.0159 (17) | 0.0287 (15) | −0.0025 (19) |
C2 | 0.0547 (19) | 0.098 (3) | 0.073 (3) | 0.002 (2) | 0.0372 (18) | 0.007 (2) |
C3 | 0.067 (2) | 0.078 (3) | 0.067 (2) | 0.0031 (18) | 0.0399 (19) | 0.002 (2) |
C4 | 0.0566 (17) | 0.061 (2) | 0.050 (2) | −0.0021 (15) | 0.0237 (15) | 0.0081 (16) |
C5 | 0.073 (2) | 0.056 (2) | 0.055 (2) | −0.0097 (17) | 0.0284 (18) | 0.0009 (17) |
C6 | 0.073 (2) | 0.060 (2) | 0.062 (2) | −0.0256 (18) | 0.0282 (18) | −0.0002 (19) |
C7 | 0.0589 (18) | 0.068 (2) | 0.065 (2) | −0.0213 (16) | 0.0337 (17) | −0.0048 (18) |
C8 | 0.0548 (17) | 0.071 (2) | 0.0455 (18) | −0.0178 (15) | 0.0267 (15) | −0.0040 (17) |
C9 | 0.0580 (18) | 0.086 (2) | 0.054 (2) | −0.0178 (17) | 0.0354 (16) | −0.0146 (19) |
C10 | 0.0571 (17) | 0.068 (2) | 0.074 (2) | −0.0143 (17) | 0.0399 (17) | −0.020 (2) |
C11 | 0.0509 (17) | 0.0509 (17) | 0.0500 (18) | −0.0146 (13) | 0.0281 (15) | −0.0052 (14) |
C12 | 0.0446 (14) | 0.0619 (19) | 0.0361 (15) | −0.0144 (13) | 0.0183 (12) | −0.0016 (14) |
C13 | 0.073 (2) | 0.129 (4) | 0.079 (3) | −0.044 (3) | 0.046 (2) | −0.013 (3) |
C14 | 0.116 (3) | 0.066 (3) | 0.100 (4) | −0.009 (2) | 0.057 (3) | −0.013 (3) |
C15 | 0.087 (3) | 0.129 (4) | 0.086 (3) | −0.030 (3) | 0.063 (3) | −0.024 (3) |
C16 | 0.071 (2) | 0.0533 (19) | 0.093 (3) | 0.0042 (17) | 0.043 (2) | −0.005 (2) |
O1—C1 | 1.412 (4) | C6—H6B | 0.9700 |
O1—O2 | 1.463 (3) | C7—C8 | 1.532 (4) |
O2—C12 | 1.450 (3) | C7—H7A | 0.9700 |
O3—C11 | 1.397 (3) | C7—H7B | 0.9700 |
O3—C1 | 1.446 (4) | C8—C9 | 1.518 (5) |
O4—C10 | 1.407 (4) | C8—C12 | 1.538 (4) |
O4—C11 | 1.426 (4) | C8—H8 | 0.9800 |
O5—C10 | 1.416 (4) | C9—C10 | 1.508 (5) |
O5—C16 | 1.421 (5) | C9—C15 | 1.528 (5) |
C1—C13 | 1.502 (5) | C9—H9 | 0.9800 |
C1—C2 | 1.516 (6) | C10—H10 | 0.9800 |
C2—C3 | 1.512 (6) | C11—C12 | 1.522 (4) |
C2—H2A | 0.9700 | C11—H11 | 0.9800 |
C2—H2B | 0.9700 | C13—H13A | 0.9600 |
C3—C4 | 1.532 (5) | C13—H13B | 0.9600 |
C3—H3A | 0.9700 | C13—H13C | 0.9600 |
C3—H3B | 0.9700 | C14—H14A | 0.9600 |
C4—C5 | 1.539 (5) | C14—H14B | 0.9600 |
C4—C12 | 1.544 (5) | C14—H14C | 0.9600 |
C4—H4A | 0.9800 | C15—H15A | 0.9600 |
C5—C6 | 1.515 (5) | C15—H15B | 0.9600 |
C5—C14 | 1.525 (6) | C15—H15C | 0.9600 |
C5—H5 | 0.9800 | C16—C16i | 1.504 (9) |
C6—C7 | 1.504 (5) | C16—H16A | 0.9700 |
C6—H6A | 0.9700 | C16—H16B | 0.9700 |
C1—O1—O2 | 109.0 (2) | C7—C8—H8 | 106.5 |
C12—O2—O1 | 112.1 (2) | C12—C8—H8 | 106.5 |
C11—O3—C1 | 113.3 (2) | C10—C9—C8 | 112.8 (3) |
C10—O4—C11 | 115.2 (2) | C10—C9—C15 | 111.6 (3) |
C10—O5—C16 | 114.8 (3) | C8—C9—C15 | 114.6 (3) |
O1—C1—O3 | 108.1 (3) | C10—C9—H9 | 105.6 |
O1—C1—C13 | 104.9 (3) | C8—C9—H9 | 105.6 |
O3—C1—C13 | 106.5 (3) | C15—C9—H9 | 105.6 |
O1—C1—C2 | 112.8 (3) | O4—C10—O5 | 112.0 (3) |
O3—C1—C2 | 109.3 (3) | O4—C10—C9 | 111.9 (3) |
C13—C1—C2 | 114.8 (3) | O5—C10—C9 | 110.1 (3) |
C3—C2—C1 | 114.7 (3) | O4—C10—H10 | 107.6 |
C3—C2—H2A | 108.6 | O5—C10—H10 | 107.6 |
C1—C2—H2A | 108.6 | C9—C10—H10 | 107.6 |
C3—C2—H2B | 108.6 | O3—C11—O4 | 105.4 (2) |
C1—C2—H2B | 108.6 | O3—C11—C12 | 113.0 (2) |
H2A—C2—H2B | 107.6 | O4—C11—C12 | 112.8 (2) |
C2—C3—C4 | 115.9 (3) | O3—C11—H11 | 108.5 |
C2—C3—H3A | 108.3 | O4—C11—H11 | 108.5 |
C4—C3—H3A | 108.3 | C12—C11—H11 | 108.5 |
C2—C3—H3B | 108.3 | O2—C12—C11 | 109.4 (2) |
C4—C3—H3B | 108.3 | O2—C12—C8 | 104.6 (2) |
H3A—C3—H3B | 107.4 | C11—C12—C8 | 110.1 (2) |
C3—C4—C5 | 111.3 (3) | O2—C12—C4 | 106.0 (2) |
C3—C4—C12 | 113.0 (3) | C11—C12—C4 | 113.7 (2) |
C5—C4—C12 | 114.5 (3) | C8—C12—C4 | 112.5 (2) |
C3—C4—H4A | 105.7 | C1—C13—H13A | 109.5 |
C5—C4—H4A | 105.7 | C1—C13—H13B | 109.5 |
C12—C4—H4A | 105.7 | H13A—C13—H13B | 109.5 |
C6—C5—C14 | 110.4 (3) | C1—C13—H13C | 109.5 |
C6—C5—C4 | 110.7 (3) | H13A—C13—H13C | 109.5 |
C14—C5—C4 | 111.3 (3) | H13B—C13—H13C | 109.5 |
C6—C5—H5 | 108.1 | C5—C14—H14A | 109.5 |
C14—C5—H5 | 108.1 | C5—C14—H14B | 109.5 |
C4—C5—H5 | 108.1 | H14A—C14—H14B | 109.5 |
C7—C6—C5 | 111.5 (3) | C5—C14—H14C | 109.5 |
C7—C6—H6A | 109.3 | H14A—C14—H14C | 109.5 |
C5—C6—H6A | 109.3 | H14B—C14—H14C | 109.5 |
C7—C6—H6B | 109.3 | C9—C15—H15A | 109.5 |
C5—C6—H6B | 109.3 | C9—C15—H15B | 109.5 |
H6A—C6—H6B | 108.0 | H15A—C15—H15B | 109.5 |
C6—C7—C8 | 111.5 (3) | C9—C15—H15C | 109.5 |
C6—C7—H7A | 109.3 | H15A—C15—H15C | 109.5 |
C8—C7—H7A | 109.3 | H15B—C15—H15C | 109.5 |
C6—C7—H7B | 109.3 | O5—C16—C16i | 113.8 (3) |
C8—C7—H7B | 109.3 | O5—C16—H16A | 108.8 |
H7A—C7—H7B | 108.0 | C16i—C16—H16A | 108.8 |
C9—C8—C7 | 114.6 (3) | O5—C16—H16B | 108.8 |
C9—C8—C12 | 110.8 (3) | C16i—C16—H16B | 108.8 |
C7—C8—C12 | 111.3 (3) | H16A—C16—H16B | 107.7 |
C9—C8—H8 | 106.5 | ||
C1—O1—O2—C12 | −44.0 (3) | C8—C9—C10—O4 | −51.6 (4) |
O2—O1—C1—O3 | 72.2 (3) | C15—C9—C10—O4 | 177.6 (3) |
O2—O1—C1—C13 | −174.5 (3) | C8—C9—C10—O5 | 73.6 (3) |
O2—O1—C1—C2 | −48.8 (3) | C15—C9—C10—O5 | −57.2 (4) |
C11—O3—C1—O1 | −31.6 (4) | C1—O3—C11—O4 | 92.6 (3) |
C11—O3—C1—C13 | −143.8 (3) | C1—O3—C11—C12 | −31.0 (4) |
C11—O3—C1—C2 | 91.6 (3) | C10—O4—C11—O3 | −180.0 (3) |
O1—C1—C2—C3 | 94.4 (4) | C10—O4—C11—C12 | −56.3 (3) |
O3—C1—C2—C3 | −25.9 (4) | O1—O2—C12—C11 | −17.4 (3) |
C13—C1—C2—C3 | −145.5 (4) | O1—O2—C12—C8 | −135.4 (2) |
C1—C2—C3—C4 | −56.7 (5) | O1—O2—C12—C4 | 105.6 (3) |
C2—C3—C4—C5 | 168.8 (3) | O3—C11—C12—O2 | 57.2 (3) |
C2—C3—C4—C12 | 38.4 (4) | O4—C11—C12—O2 | −62.2 (3) |
C3—C4—C5—C6 | −179.1 (3) | O3—C11—C12—C8 | 171.6 (3) |
C12—C4—C5—C6 | −49.4 (4) | O4—C11—C12—C8 | 52.2 (3) |
C3—C4—C5—C14 | 57.7 (4) | O3—C11—C12—C4 | −61.0 (3) |
C12—C4—C5—C14 | −172.7 (3) | O4—C11—C12—C4 | 179.6 (2) |
C14—C5—C6—C7 | 179.8 (3) | C9—C8—C12—O2 | 68.0 (3) |
C4—C5—C6—C7 | 56.0 (4) | C7—C8—C12—O2 | −163.2 (3) |
C5—C6—C7—C8 | −60.4 (4) | C9—C8—C12—C11 | −49.4 (3) |
C6—C7—C8—C9 | −177.2 (3) | C7—C8—C12—C11 | 79.4 (3) |
C6—C7—C8—C12 | 56.1 (4) | C9—C8—C12—C4 | −177.4 (3) |
C7—C8—C9—C10 | −77.1 (3) | C7—C8—C12—C4 | −48.6 (4) |
C12—C8—C9—C10 | 49.9 (4) | C3—C4—C12—O2 | −71.1 (3) |
C7—C8—C9—C15 | 52.1 (4) | C5—C4—C12—O2 | 160.1 (3) |
C12—C8—C9—C15 | 179.1 (3) | C3—C4—C12—C11 | 49.1 (4) |
C11—O4—C10—O5 | −69.3 (4) | C5—C4—C12—C11 | −79.8 (3) |
C11—O4—C10—C9 | 54.9 (4) | C3—C4—C12—C8 | 175.2 (3) |
C16—O5—C10—O4 | −69.2 (4) | C5—C4—C12—C8 | 46.4 (4) |
C16—O5—C10—C9 | 165.7 (3) | C10—O5—C16—C16i | 92.8 (4) |
Symmetry code: (i) −x+1, y, −z. |
Experimental details
Crystal data | |
Chemical formula | C32H50O10 |
Mr | 594.72 |
Crystal system, space group | Monoclinic, C2 |
Temperature (K) | 295 |
a, b, c (Å) | 18.033 (4), 9.3127 (19), 11.061 (2) |
β (°) | 123.58 (3) |
V (Å3) | 1547.5 (8) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 0.09 |
Crystal size (mm) | 0.42 × 0.38 × 0.31 |
Data collection | |
Diffractometer | Rigaku R-AXIS RAPID diffractometer |
Absorption correction | Multi-scan (ABSCOR; Higashi, 1995) |
Tmin, Tmax | 0.962, 0.972 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 6717, 1614, 1195 |
Rint | 0.043 |
(sin θ/λ)max (Å−1) | 0.617 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.042, 0.129, 1.10 |
No. of reflections | 1614 |
No. of parameters | 194 |
No. of restraints | 1 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.20, −0.20 |
Computer programs: RAPID-AUTO (Rigaku, 1998), CrystalStructure (Rigaku/MSC, 2002), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), ORTEPII (Johnson, 1976).
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.
Dihydroartemisinin is reported to be more therapeutically active than the parent compound. Some trioxane dimers have been found to possess high antimalarial activities (Venugopalan et al., 1995) and moderate antitumor activities. (Woerdenbag et al., 1993). The dihydroartemisinin triethylene glycol dimers, have strong in vitro growth-inhibitory activity. The dimer with β-stereochemistry at both of the lactol acetal positions is very active and highly antiproliferative (Posner et al., 1997). We conclude, therefore, that the stereochemistry of the diol linkage is an important determinant for cytotoxicity. We chose the simplified analogue, the title compound, whose structure and activity have not been reported, to find out the relationship between the activity and stereo-structure. Hence, knowledge of the structure of the title compound is of interest and is reported here.
The X-ray structures of artemisinin and artemisinin derivatives have been reported, including dihydroartemisinin, artemether, artesunic acid (Luo et al., 1984), both cis-deoxyarteether (Brossi et al., 1988) and trans-deoxyarteether (Dominguez Gerpe et al., 1988), α-artesunate, β-artesunate (Haynes et al., 2002), the symmetric form of the ether dimer of deoxydihydroartemisinin (Flippen-Anderson et al.,1989), the asymmetric form of the ether dimer of dihydroartemisinin (Yue et al., 2006), and the phthalate dimer (Paik et al. 2006). Although the endoperoxide group is an important determinant for cytotoxicity, no crystal structure of a diol dimer of dihydroartemisinin with a peroxy unit has been reported previously. We report here the crystal structure of a diol dimer of dihydroartemisinin, the title compound, which is a diol dimer of dihydroartemisinin with a unique 1,2,4-trioxane peroxy bridge.
The title molecule is symmetrical. Each moiety of the dimer is totally the same, hence we describe only the asymmetric unit here.
The seven-membered ring A(C1/C2/C3/C4/C12/O2/O1) includes key peroxy linkages [O1—O2 = 1.463 (3) Å]. The length of peroxy linkages is very close to that of the ether dimer of dihydroartemisinin (1.467 (4) Å and 1.461 (3) Å respectively) (Yue et al.,2006). The six-membered ring B(C4/C5/C6/C7/C8/C12) has a distorted chair conformation, with Cremer & Pople (1975) puckering parameters Q, θ and ϕ of 0.5422 (42) Å, 8.33 (43)° and 150 (3)°. For an ideal chair, θ has a value of 0 or 180°. The six-membered ring C(O4/C10/C9/C8/C12/C11) also has a distorted chair conformation, with puckering parameters Q, θ and ϕ of 0.5157 (39) Å, 179.09 (44)°, 93 (20)°. Similar conformations were found in the corresponding six-membered rings of dihydroartemisinin(Luo et al., 1984). The six-membered ring involving the endoperoxide bridges D(C1/O1/O2/C12/C11/O3), is best described by a twist-boat conformation, for which the puckering parameters Q, θ and ϕ are 0.7463 (38) Å, 85.77 (27)°, 335.6 (3)°. For an ideal twist-boat conformation, θ and ϕ are 90 and (60n + 30)° respectively. In contrast, the six-membered ring formed by the endoperoxide bridge in dihydroartemisinin has a distorted boat conformation.