organic compounds
Redetermination of dihydroartemisinin at 103 (2) K
aDepartment of Chemistry, Keene State College, 229 Main Street, Keene, NH 03435-2001, USA, bDepartment of Chemistry, Howard University, 525 College Street NW, Washington DC 20059, USA, cDepartment of Studies in Chemistry, University of Mysore, Manasagangotri, Mysore 570006, India, and dDepartment of Studies in Chemistry, Mangalore University, Mangalagangotri 574199, India
*Correspondence e-mail: jjasinski@keene.edu
Tthe structure of the title compound, C15H24O5, has been redetermined at 103 (2) K, with much improved precision. The title compound was first reported by Luo, Yeh, Brossi, Flippen-Anderson & Gillardi [Helv. Chim. Acta (1984). 67, 1515–1522]. It is a derivative of the antimalaria compound artemisinin and consists primarily of three substituted ring systems fused together. A cyclohexane ring (with a distorted chair conformation), is fused to a tetrahydropyran group (also with a distorted chair conformation), and is adjacent to an oxacycloheptane unit containing an endoperoxide bridge. This gives the molecule a unique three-dimensional arrangement. The crystal packing is stabilized by intermolecular C–H⋯O and O–H⋯O interactions between an H atom from the cyclohexane ring and an O atom from the endoperoxide bridge, as well as between the hydroxyl H atom and an O atom from a tetrahydropyran ring.
Related literature
For crystal structures of similar compounds, see: Flippen-Anderson et al. (1989), Yue et al. (2006), Li et al. (2006); Karle & Lin (1995); Brossi et al. (1988). For the biological activity of artemisinin derivatives in vitro and in vivo, see: Li et al. (2001); Yang et al. (1997); Grace et al. (1998); Maggs et al. (2000). For endoperoxide sesquiterpene lactone derivatives, see: Venugopalan et al. (1995); Wu et al. (2001); Saxena et al. (2003). For the synthesis of artemisinin and its derivatives, see: Lui et al. (1979); Liu (1980); Robert et al. (2001). For related literature, see: Allen et al. (1987); Cremer & Pople (1975); Lisgarten et al. (1998); Qinghaosu Research Group (1980); Shen & Zhuang (1984); Wu & Li (1995); Luo et al. (1984).
Experimental
Crystal data
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Refinement
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Data collection: APEX2 (Bruker, 2006); cell APEX2; data reduction: SAINT (Bruker, 2006); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 2000); software used to prepare material for publication: SHELXTL.
Supporting information
https://doi.org/10.1107/S1600536807063180/fj2084sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536807063180/fj2084Isup2.hkl
The title compound (C15H24O5)was obtained in the pure form from Strides Arco Labs, Mangalore, India. X-ray diffraction quality crystals were grown from acetone-methylacetoacetate (1:1). (m.p.: 413 K).
All H atoms were initially located in a difference Fourier map. The methyl H atoms were then constrained to an ideal geometry with C—H distances of 0.98 Å and Uiso(H) = 1.5Ueq(C), but each group was allowed to rotate freely about its C—C bond. All other H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms with C—H distances in the range 0.98–1.00 Å and Uiso(H) = 1.17–1.22Ueq(C). The hydroxyl H was idealized with an O—H distance of 0.84Å and Uiso(H) = 1.21Ueq(O). Because no strong
atoms are present, the Friedel pairs were merged in the refinement.Artemisinin and its derivatives, dihydroartemisinin, artemether, arteether and artesunate are antimalarial drugs which possess bioactivity with less toxicity (Wu & Li, 1995). Artemisinin is isolated from the leaves of plant Artemisia annua (Qinghao). It is a sesquiterpene lactone with an endoperoxide linkage. Artemisinin derivatives are more potent than artemisinin and are active by virtue of the endoperoxide. Their activity against strains of the parasite that had become resistant to conventional chloroquine therapy and the ability due to its lipophilic structure, to cross the blood brain barrier, it was particularly effective for the deadly cerebral malaria (Shen & Zhuang, 1984). Because of their shorter life time and decreasing activity, they are used in combination with other antimalarial drugs. The notable activity of artemisinin derivatives in vitro and in vivo has been reported in literature (Li et al. 2001 & Yang et al. 1997). However, some derivatives of artimisinine showed moderate cytotoxicity in vitro. The α- and β-dihydroartemisinin (Yue et al. 2006) and that of 9,10-dehydrodeoxyartemisin is recently reported (Li et al. 2006). The synthesis of artemisinin and its derivatives are described (Lui et al. 1979; Lui, 1980; Robert et al. 2001). The synthesis and antimalarial properties of arteether have been reported (Brossi et al. 1988). β-Arteether (AE) is an endoperoxide sesquiterpene lactone derivative currently being developed for the treatment of severe, complicated malaria caused by multidrug-resistant Plasmodium falciparum (Grace et al. 1998). β-Artemether (AM), the O-methyl ether prodrug of dihydroartemisinin (DHA), is an endoperoxide antimalarial (Maggs et al. 2000). In view of the importance of the title compound, (I) C15H24O5, as n antimalarial drug, this paper reports a redetermination of the first reported by Luo et al. (1984).
and bulk of the substituents that attached to the aryl group plays an insignificant role in cytotoxicity. The antimalarial activity and cytotoxicity of some has been reported in the literature (Venugopalan et al. 1995; Wu et al. 2001 and Saxena et al. 2003). The endoperoxide moiety present in these compounds plays an important role in antimalarial activity. Its 1,2,4 trioxane ring is unique in nature. After being opened in the plasmodium it liberates singlet oxygen and forms which inturn produces oxidative damage to the parasites membrane. Artemisinin is hydrophobic in nature and are partitioned into the membrane of the plasmodium. The structures of the antimalarials dihydroqinghaosu, artemether and artesunic acid derived from qinghaosu were elaborated by 1H-NMR spectroscopy, and supported with X-ray data have been reported (Luo et al. 1984). The of an ether dimer of deoxydihydroqinghaosu, a potential metabolite of the antimalarial arteether is reported (Flippen-Anderson et al. 1989). The correlation of the crystal structures of diastereomeric artemisinin derivatives with their proton NMR spectra in CDCl3 is reported (Karle & Lin, 1995). The of artemisinin is reported (Lisgarten et al. 1998). The of a dimer ofThe six-membered cyclohexane ring (A, C1—C6) is a slightly distorted chair, with Cremer & Pople (1975) puckering parameters Q, θ and φ of 0.553 (2) Å, 4.8 (2)° and 170 (3)°, respectively. The tetrahydropyran group (D, C1—C2—C12—C11—O2—C10) is also a slightly distorted chair configuration with puckering parameters Q, θ and φ of 0.539 (2) Å, 2.7 (2)° and 227 (4)°, respectively. For an ideal chair θ has a value of 0 or 180°. Similar conformations for rings A and D were found in 9,10-dehydrodeoxyartemisinin (Shu-Hui Li et al. 2006). The seven-membered ring B (C1/C6—C9/O1—C10) contains the important peroxy linkage [O3—O4 = 1.471 (2) Å]. The six-membered ring C (O1—C9—O3—O4—C1—C10) which contains both an oxygen bridge and a peroxy bridge is best described by a twist-boat conformation with puckering parameters Q, θ and φ of 0.750 (2) Å, 85.26 (15)° and 96.58 (11)°, respectively. For an ideal twist-boat conformation, θ and φ are 90° and (60n + 30)°, respectively. This conformation is consistent with both 9,10-dehydrodeoxyartemisinin (Li et al. (2006) and dihydroartemisinin (Qinghaosu Research Group, 1980).
For crystal structures of similar compounds, see: Flippen-Anderson et al. (1989), Yue et al. (2006), Li et al. (2006); Karle & Lin (1995); Brossi et al. (1988). For the biological activity of artemisinin derivatives in vitro and in vivo, see: Li et al. (2001); Yang et al. (1997); Grace et al. (1998); Maggs et al. (2000). For endoperoxide sesquiterpene lactone derivatives, see: Venugopalan et al. (1995); Wu et al. (2001); Saxena et al. (2003). For the synthesis of artemisinin and its derivatives, see: Lui et al. (1979); Liu (1980); Robert et al. (2001). For related literature, see: Allen et al. (1987); Cremer & Pople (1975); Lisgarten et al. (1998); Qinghaosu Research Group (1980); Shen & Zhuang (1984); Wu & Li (1995); Luo et al. (1984).
Data collection: APEX2 (Bruker, 2006); cell
APEX2 (Bruker, 2006); data reduction: SAINT (Bruker, 2006); program(s) used to solve structure: SHELXS90 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 2000); software used to prepare material for publication: SHELXTL (Bruker, 2000).C15H24O5 | F(000) = 616 |
Mr = 284.34 | Dx = 1.271 Mg m−3 |
Orthorhombic, P212121 | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: P 2ac 2ab | Cell parameters from 4650 reflections |
a = 5.5910 (6) Å | θ = 2.6–29.6° |
b = 14.1309 (14) Å | µ = 0.09 mm−1 |
c = 18.8062 (19) Å | T = 103 K |
V = 1485.8 (3) Å3 | Needle, colorless |
Z = 4 | 0.67 × 0.11 × 0.09 mm |
Bruker APEXII CCD area-detector diffractometer | 2475 independent reflections |
Radiation source: fine-focus sealed tube | 2130 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.044 |
φ and ω scans | θmax = 30.5°, θmin = 1.8° |
Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | h = −5→7 |
Tmin = 0.940, Tmax = 0.992 | k = −19→19 |
16573 measured reflections | l = −26→26 |
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)] = 0.038 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.100 | H-atom parameters constrained |
S = 1.06 | w = 1/[σ2(Fo2) + (0.0434P)2 + 0.5149P] where P = (Fo2 + 2Fc2)/3 |
2475 reflections | (Δ/σ)max = 0.002 |
185 parameters | Δρmax = 0.37 e Å−3 |
0 restraints | Δρmin = −0.22 e Å−3 |
C15H24O5 | V = 1485.8 (3) Å3 |
Mr = 284.34 | Z = 4 |
Orthorhombic, P212121 | Mo Kα radiation |
a = 5.5910 (6) Å | µ = 0.09 mm−1 |
b = 14.1309 (14) Å | T = 103 K |
c = 18.8062 (19) Å | 0.67 × 0.11 × 0.09 mm |
Bruker APEXII CCD area-detector diffractometer | 2475 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | 2130 reflections with I > 2σ(I) |
Tmin = 0.940, Tmax = 0.992 | Rint = 0.044 |
16573 measured reflections |
R[F2 > 2σ(F2)] = 0.038 | 0 restraints |
wR(F2) = 0.100 | H-atom parameters constrained |
S = 1.06 | Δρmax = 0.37 e Å−3 |
2475 reflections | Δρmin = −0.22 e Å−3 |
185 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 | 0.2493 (3) | 0.35457 (10) | 0.85285 (7) | 0.0212 (3) | |
O2 | 0.1910 (3) | 0.31049 (9) | 0.96710 (6) | 0.0187 (3) | |
O3 | −0.1579 (3) | 0.36796 (11) | 0.87194 (7) | 0.0250 (3) | |
O4 | −0.1419 (3) | 0.45439 (10) | 0.91529 (7) | 0.0229 (3) | |
O5 | 0.4123 (3) | 0.34511 (9) | 1.06918 (7) | 0.0198 (3) | |
H5 | 0.4953 | 0.2959 | 1.0648 | 0.024* | |
C1 | 0.1042 (4) | 0.47570 (13) | 0.93520 (9) | 0.0178 (4) | |
C2 | 0.0886 (4) | 0.50052 (13) | 1.01511 (9) | 0.0195 (4) | |
H2A | −0.0458 | 0.5467 | 1.0205 | 0.023* | |
C3 | 0.3158 (4) | 0.55071 (13) | 1.04118 (10) | 0.0238 (4) | |
H3A | 0.2942 | 0.5701 | 1.0914 | 0.029* | |
H3B | 0.4523 | 0.5062 | 1.0390 | 0.029* | |
C4 | 0.3716 (5) | 0.63737 (13) | 0.99635 (10) | 0.0269 (5) | |
H4A | 0.5198 | 0.6674 | 1.0142 | 0.032* | |
H4B | 0.2398 | 0.6837 | 1.0012 | 0.032* | |
C5 | 0.4035 (4) | 0.61214 (13) | 0.91802 (10) | 0.0225 (4) | |
H5A | 0.5412 | 0.5673 | 0.9140 | 0.027* | |
C6 | 0.1797 (4) | 0.56209 (13) | 0.88957 (9) | 0.0195 (4) | |
H6A | 0.0459 | 0.6089 | 0.8925 | 0.023* | |
C7 | 0.2078 (4) | 0.53662 (14) | 0.81060 (9) | 0.0245 (4) | |
H7A | 0.1986 | 0.5957 | 0.7825 | 0.029* | |
H7B | 0.3697 | 0.5098 | 0.8035 | 0.029* | |
C8 | 0.0260 (5) | 0.46691 (15) | 0.78064 (10) | 0.0269 (5) | |
H8A | 0.0621 | 0.4558 | 0.7298 | 0.032* | |
H8B | −0.1353 | 0.4955 | 0.7836 | 0.032* | |
C9 | 0.0230 (4) | 0.37149 (15) | 0.81945 (10) | 0.0247 (4) | |
C10 | 0.2609 (4) | 0.38836 (12) | 0.92316 (9) | 0.0163 (4) | |
H10A | 0.4306 | 0.4051 | 0.9343 | 0.020* | |
C11 | 0.1826 (4) | 0.32865 (13) | 1.04225 (9) | 0.0184 (4) | |
H11A | 0.1159 | 0.2713 | 1.0663 | 0.022* | |
C12 | 0.0176 (4) | 0.41122 (14) | 1.05737 (9) | 0.0200 (4) | |
H12A | −0.1444 | 0.3922 | 1.0400 | 0.024* | |
C13 | 0.4636 (5) | 0.70119 (16) | 0.87466 (12) | 0.0342 (6) | |
H13A | 0.6048 | 0.7321 | 0.8950 | 0.051* | |
H13B | 0.3278 | 0.7450 | 0.8760 | 0.051* | |
H13C | 0.4967 | 0.6833 | 0.8253 | 0.051* | |
C14 | −0.0293 (6) | 0.28799 (17) | 0.77187 (11) | 0.0364 (6) | |
H14A | −0.0491 | 0.2310 | 0.8010 | 0.055* | |
H14B | 0.1039 | 0.2788 | 0.7387 | 0.055* | |
H14C | −0.1765 | 0.2999 | 0.7451 | 0.055* | |
C15 | −0.0068 (5) | 0.42857 (16) | 1.13739 (10) | 0.0299 (5) | |
H15A | −0.0695 | 0.3715 | 1.1604 | 0.045* | |
H15B | −0.1169 | 0.4814 | 1.1456 | 0.045* | |
H15C | 0.1503 | 0.4439 | 1.1574 | 0.045* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.0215 (8) | 0.0257 (6) | 0.0163 (5) | −0.0011 (6) | 0.0014 (6) | −0.0038 (5) |
O2 | 0.0211 (7) | 0.0181 (6) | 0.0168 (6) | −0.0022 (6) | −0.0012 (6) | 0.0004 (5) |
O3 | 0.0209 (8) | 0.0333 (7) | 0.0208 (6) | −0.0074 (6) | −0.0017 (6) | 0.0001 (6) |
O4 | 0.0142 (7) | 0.0317 (7) | 0.0228 (6) | 0.0013 (6) | −0.0024 (5) | −0.0013 (6) |
O5 | 0.0172 (7) | 0.0190 (6) | 0.0232 (6) | 0.0012 (5) | −0.0047 (6) | 0.0003 (5) |
C1 | 0.0132 (9) | 0.0230 (8) | 0.0171 (8) | 0.0018 (7) | −0.0005 (7) | −0.0016 (7) |
C2 | 0.0197 (10) | 0.0210 (8) | 0.0180 (8) | 0.0061 (8) | 0.0005 (8) | −0.0014 (6) |
C3 | 0.0315 (12) | 0.0206 (8) | 0.0194 (8) | −0.0016 (9) | −0.0056 (9) | 0.0010 (7) |
C4 | 0.0385 (13) | 0.0177 (8) | 0.0245 (9) | −0.0005 (9) | −0.0043 (9) | −0.0011 (7) |
C5 | 0.0267 (11) | 0.0185 (8) | 0.0223 (8) | −0.0003 (8) | −0.0016 (8) | 0.0033 (7) |
C6 | 0.0196 (10) | 0.0191 (8) | 0.0198 (8) | 0.0021 (7) | −0.0019 (8) | 0.0013 (7) |
C7 | 0.0299 (12) | 0.0257 (9) | 0.0179 (8) | −0.0017 (9) | 0.0000 (8) | 0.0036 (7) |
C8 | 0.0293 (13) | 0.0346 (11) | 0.0168 (8) | −0.0045 (10) | −0.0052 (8) | 0.0032 (8) |
C9 | 0.0245 (11) | 0.0323 (10) | 0.0175 (8) | −0.0066 (9) | −0.0010 (8) | −0.0005 (8) |
C10 | 0.0165 (9) | 0.0170 (7) | 0.0156 (7) | −0.0003 (7) | −0.0006 (7) | −0.0007 (6) |
C11 | 0.0160 (9) | 0.0230 (8) | 0.0161 (7) | −0.0023 (8) | −0.0016 (7) | 0.0020 (7) |
C12 | 0.0169 (10) | 0.0265 (9) | 0.0165 (8) | 0.0011 (8) | 0.0016 (7) | 0.0016 (7) |
C13 | 0.0446 (15) | 0.0275 (10) | 0.0304 (10) | −0.0116 (11) | −0.0032 (11) | 0.0058 (9) |
C14 | 0.0470 (17) | 0.0386 (12) | 0.0234 (10) | −0.0151 (12) | −0.0042 (11) | −0.0034 (9) |
C15 | 0.0351 (14) | 0.0370 (11) | 0.0177 (9) | 0.0037 (10) | 0.0051 (9) | −0.0001 (8) |
O1—C10 | 1.407 (2) | C6—C7 | 1.536 (3) |
O1—C9 | 1.432 (3) | C6—H6A | 1.0000 |
O2—C10 | 1.431 (2) | C7—C8 | 1.524 (3) |
O2—C11 | 1.437 (2) | C7—H7A | 0.9900 |
O3—C9 | 1.414 (3) | C7—H7B | 0.9900 |
O3—O4 | 1.471 (2) | C8—C9 | 1.533 (3) |
O4—C1 | 1.457 (2) | C8—H8A | 0.9900 |
O5—C11 | 1.400 (2) | C8—H8B | 0.9900 |
O5—H5 | 0.8400 | C9—C14 | 1.509 (3) |
C1—C10 | 1.531 (3) | C10—H10A | 1.0000 |
C1—C2 | 1.546 (2) | C11—C12 | 1.514 (3) |
C1—C6 | 1.551 (3) | C11—H11A | 1.0000 |
C2—C3 | 1.535 (3) | C12—C15 | 1.531 (3) |
C2—C12 | 1.543 (3) | C12—H12A | 1.0000 |
C2—H2A | 1.0000 | C13—H13A | 0.9800 |
C3—C4 | 1.519 (3) | C13—H13B | 0.9800 |
C3—H3A | 0.9900 | C13—H13C | 0.9800 |
C3—H3B | 0.9900 | C14—H14A | 0.9800 |
C4—C5 | 1.526 (3) | C14—H14B | 0.9800 |
C4—H4A | 0.9900 | C14—H14C | 0.9800 |
C4—H4B | 0.9900 | C15—H15A | 0.9800 |
C5—C6 | 1.533 (3) | C15—H15B | 0.9800 |
C5—C13 | 1.537 (3) | C15—H15C | 0.9800 |
C5—H5A | 1.0000 | ||
C10—O1—C9 | 113.35 (15) | C7—C8—H8A | 108.9 |
C10—O2—C11 | 116.08 (13) | C9—C8—H8A | 108.9 |
C9—O3—O4 | 108.29 (14) | C7—C8—H8B | 108.9 |
C1—O4—O3 | 111.82 (13) | C9—C8—H8B | 108.9 |
C11—O5—H5 | 109.5 | H8A—C8—H8B | 107.7 |
O4—C1—C10 | 109.63 (15) | O3—C9—O1 | 108.65 (14) |
O4—C1—C2 | 104.10 (15) | O3—C9—C14 | 104.33 (18) |
C10—C1—C2 | 111.04 (14) | O1—C9—C14 | 107.5 (2) |
O4—C1—C6 | 106.12 (15) | O3—C9—C8 | 111.78 (19) |
C10—C1—C6 | 113.38 (16) | O1—C9—C8 | 110.25 (17) |
C2—C1—C6 | 112.01 (15) | C14—C9—C8 | 114.03 (16) |
C3—C2—C12 | 115.21 (16) | O1—C10—O2 | 105.60 (13) |
C3—C2—C1 | 111.63 (17) | O1—C10—C1 | 112.70 (14) |
C12—C2—C1 | 109.25 (15) | O2—C10—C1 | 112.21 (15) |
C3—C2—H2A | 106.8 | O1—C10—H10A | 108.7 |
C12—C2—H2A | 106.8 | O2—C10—H10A | 108.7 |
C1—C2—H2A | 106.8 | C1—C10—H10A | 108.7 |
C4—C3—C2 | 111.42 (17) | O5—C11—O2 | 110.82 (16) |
C4—C3—H3A | 109.3 | O5—C11—C12 | 111.27 (15) |
C2—C3—H3A | 109.3 | O2—C11—C12 | 110.01 (15) |
C4—C3—H3B | 109.3 | O5—C11—H11A | 108.2 |
C2—C3—H3B | 109.3 | O2—C11—H11A | 108.2 |
H3A—C3—H3B | 108.0 | C12—C11—H11A | 108.2 |
C3—C4—C5 | 111.80 (16) | C11—C12—C15 | 111.25 (16) |
C3—C4—H4A | 109.3 | C11—C12—C2 | 112.14 (16) |
C5—C4—H4A | 109.3 | C15—C12—C2 | 113.47 (17) |
C3—C4—H4B | 109.3 | C11—C12—H12A | 106.5 |
C5—C4—H4B | 109.3 | C15—C12—H12A | 106.5 |
H4A—C4—H4B | 107.9 | C2—C12—H12A | 106.5 |
C4—C5—C6 | 110.45 (18) | C5—C13—H13A | 109.5 |
C4—C5—C13 | 110.27 (16) | C5—C13—H13B | 109.5 |
C6—C5—C13 | 111.78 (17) | H13A—C13—H13B | 109.5 |
C4—C5—H5A | 108.1 | C5—C13—H13C | 109.5 |
C6—C5—H5A | 108.1 | H13A—C13—H13C | 109.5 |
C13—C5—H5A | 108.1 | H13B—C13—H13C | 109.5 |
C5—C6—C7 | 111.22 (18) | C9—C14—H14A | 109.5 |
C5—C6—C1 | 113.09 (15) | C9—C14—H14B | 109.5 |
C7—C6—C1 | 112.24 (15) | H14A—C14—H14B | 109.5 |
C5—C6—H6A | 106.6 | C9—C14—H14C | 109.5 |
C7—C6—H6A | 106.6 | H14A—C14—H14C | 109.5 |
C1—C6—H6A | 106.6 | H14B—C14—H14C | 109.5 |
C8—C7—C6 | 116.15 (18) | C12—C15—H15A | 109.5 |
C8—C7—H7A | 108.2 | C12—C15—H15B | 109.5 |
C6—C7—H7A | 108.2 | H15A—C15—H15B | 109.5 |
C8—C7—H7B | 108.2 | C12—C15—H15C | 109.5 |
C6—C7—H7B | 108.2 | H15A—C15—H15C | 109.5 |
H7A—C7—H7B | 107.4 | H15B—C15—H15C | 109.5 |
C7—C8—C9 | 113.55 (17) | ||
C9—O3—O4—C1 | −45.32 (18) | O4—O3—C9—C14 | −172.27 (16) |
O3—O4—C1—C10 | −15.82 (18) | O4—O3—C9—C8 | −48.58 (19) |
O3—O4—C1—C2 | −134.68 (13) | C10—O1—C9—O3 | −32.1 (2) |
O3—O4—C1—C6 | 106.97 (15) | C10—O1—C9—C14 | −144.41 (16) |
O4—C1—C2—C3 | −164.53 (15) | C10—O1—C9—C8 | 90.75 (18) |
C10—C1—C2—C3 | 77.58 (19) | C7—C8—C9—O3 | 96.3 (2) |
C6—C1—C2—C3 | −50.3 (2) | C7—C8—C9—O1 | −24.6 (2) |
O4—C1—C2—C12 | 66.88 (19) | C7—C8—C9—C14 | −145.6 (2) |
C10—C1—C2—C12 | −51.0 (2) | C9—O1—C10—O2 | 92.17 (17) |
C6—C1—C2—C12 | −178.90 (17) | C9—O1—C10—C1 | −30.7 (2) |
C12—C2—C3—C4 | 179.84 (17) | C11—O2—C10—O1 | −178.37 (16) |
C1—C2—C3—C4 | 54.5 (2) | C11—O2—C10—C1 | −55.2 (2) |
C2—C3—C4—C5 | −58.2 (3) | O4—C1—C10—O1 | 56.06 (19) |
C3—C4—C5—C6 | 56.9 (2) | C2—C1—C10—O1 | 170.53 (16) |
C3—C4—C5—C13 | −179.1 (2) | C6—C1—C10—O1 | −62.3 (2) |
C4—C5—C6—C7 | 179.67 (16) | O4—C1—C10—O2 | −63.01 (18) |
C13—C5—C6—C7 | 56.5 (2) | C2—C1—C10—O2 | 51.5 (2) |
C4—C5—C6—C1 | −53.0 (2) | C6—C1—C10—O2 | 178.61 (14) |
C13—C5—C6—C1 | −176.14 (18) | C10—O2—C11—O5 | −67.1 (2) |
O4—C1—C6—C5 | 163.26 (15) | C10—O2—C11—C12 | 56.3 (2) |
C10—C1—C6—C5 | −76.35 (19) | O5—C11—C12—C15 | −60.2 (2) |
C2—C1—C6—C5 | 50.3 (2) | O2—C11—C12—C15 | 176.61 (17) |
O4—C1—C6—C7 | −69.9 (2) | O5—C11—C12—C2 | 68.1 (2) |
C10—C1—C6—C7 | 50.5 (2) | O2—C11—C12—C2 | −55.1 (2) |
C2—C1—C6—C7 | 177.11 (18) | C3—C2—C12—C11 | −72.8 (2) |
C5—C6—C7—C8 | 166.05 (18) | C1—C2—C12—C11 | 53.8 (2) |
C1—C6—C7—C8 | 38.2 (3) | C3—C2—C12—C15 | 54.3 (2) |
C6—C7—C8—C9 | −58.4 (3) | C1—C2—C12—C15 | −179.07 (18) |
O4—O3—C9—O1 | 73.30 (18) |
D—H···A | D—H | H···A | D···A | D—H···A |
O5—H5···O2i | 0.84 | 1.95 | 2.7799 (19) | 168 |
C5—H5A···O4ii | 1.00 | 2.38 | 3.381 (3) | 175 |
Symmetry codes: (i) x+1/2, −y+1/2, −z+2; (ii) x+1, y, z. |
Experimental details
Crystal data | |
Chemical formula | C15H24O5 |
Mr | 284.34 |
Crystal system, space group | Orthorhombic, P212121 |
Temperature (K) | 103 |
a, b, c (Å) | 5.5910 (6), 14.1309 (14), 18.8062 (19) |
V (Å3) | 1485.8 (3) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.09 |
Crystal size (mm) | 0.67 × 0.11 × 0.09 |
Data collection | |
Diffractometer | Bruker APEXII CCD area-detector |
Absorption correction | Multi-scan (SADABS; Sheldrick, 1996) |
Tmin, Tmax | 0.940, 0.992 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 16573, 2475, 2130 |
Rint | 0.044 |
(sin θ/λ)max (Å−1) | 0.714 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.038, 0.100, 1.06 |
No. of reflections | 2475 |
No. of parameters | 185 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.37, −0.22 |
Computer programs: APEX2 (Bruker, 2006), SAINT (Bruker, 2006), SHELXS90 (Sheldrick, 1990), SHELXL97 (Sheldrick, 1997), SHELXTL (Bruker, 2000).
D—H···A | D—H | H···A | D···A | D—H···A |
O5—H5···O2i | 0.84 | 1.95 | 2.7799 (19) | 168 |
C5—H5A···O4ii | 1.00 | 2.38 | 3.381 (3) | 175 |
Symmetry codes: (i) x+1/2, −y+1/2, −z+2; (ii) x+1, y, z. |
Acknowledgements
RJB acknowledges the Laboratory for the Structure of Matter at the Naval Research Laboratory, Washington DC, USA, for access to their diffractometers. BN thanks Strides Arco Labs, Mangalore, India, for a gift sample of the title compound.
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Artemisinin and its derivatives, dihydroartemisinin, artemether, arteether and artesunate are antimalarial drugs which possess bioactivity with less toxicity (Wu & Li, 1995). Artemisinin is isolated from the leaves of plant Artemisia annua (Qinghao). It is a sesquiterpene lactone with an endoperoxide linkage. Artemisinin derivatives are more potent than artemisinin and are active by virtue of the endoperoxide. Their activity against strains of the parasite that had become resistant to conventional chloroquine therapy and the ability due to its lipophilic structure, to cross the blood brain barrier, it was particularly effective for the deadly cerebral malaria (Shen & Zhuang, 1984). Because of their shorter life time and decreasing activity, they are used in combination with other antimalarial drugs. The notable activity of artemisinin derivatives in vitro and in vivo has been reported in literature (Li et al. 2001 & Yang et al. 1997). However, some derivatives of artimisinine showed moderate cytotoxicity in vitro. The electronegativity and bulk of the substituents that attached to the aryl group plays an insignificant role in cytotoxicity. The antimalarial activity and cytotoxicity of some sesquiterpenoids has been reported in the literature (Venugopalan et al. 1995; Wu et al. 2001 and Saxena et al. 2003). The endoperoxide moiety present in these compounds plays an important role in antimalarial activity. Its 1,2,4 trioxane ring is unique in nature. After being opened in the plasmodium it liberates singlet oxygen and forms free radical which inturn produces oxidative damage to the parasites membrane. Artemisinin is hydrophobic in nature and are partitioned into the membrane of the plasmodium. The structures of the antimalarials dihydroqinghaosu, artemether and artesunic acid derived from qinghaosu were elaborated by 1H-NMR spectroscopy, and supported with X-ray data have been reported (Luo et al. 1984). The crystal structure of an ether dimer of deoxydihydroqinghaosu, a potential metabolite of the antimalarial arteether is reported (Flippen-Anderson et al. 1989). The correlation of the crystal structures of diastereomeric artemisinin derivatives with their proton NMR spectra in CDCl3 is reported (Karle & Lin, 1995). The crystal structure of artemisinin is reported (Lisgarten et al. 1998). The crystal structure of a dimer of α- and β-dihydroartemisinin (Yue et al. 2006) and that of 9,10-dehydrodeoxyartemisin is recently reported (Li et al. 2006). The synthesis of artemisinin and its derivatives are described (Lui et al. 1979; Lui, 1980; Robert et al. 2001). The synthesis and antimalarial properties of arteether have been reported (Brossi et al. 1988). β-Arteether (AE) is an endoperoxide sesquiterpene lactone derivative currently being developed for the treatment of severe, complicated malaria caused by multidrug-resistant Plasmodium falciparum (Grace et al. 1998). β-Artemether (AM), the O-methyl ether prodrug of dihydroartemisinin (DHA), is an endoperoxide antimalarial (Maggs et al. 2000). In view of the importance of the title compound, (I) C15H24O5, as n antimalarial drug, this paper reports a redetermination of the crystal structure first reported by Luo et al. (1984).
The six-membered cyclohexane ring (A, C1—C6) is a slightly distorted chair, with Cremer & Pople (1975) puckering parameters Q, θ and φ of 0.553 (2) Å, 4.8 (2)° and 170 (3)°, respectively. The tetrahydropyran group (D, C1—C2—C12—C11—O2—C10) is also a slightly distorted chair configuration with puckering parameters Q, θ and φ of 0.539 (2) Å, 2.7 (2)° and 227 (4)°, respectively. For an ideal chair θ has a value of 0 or 180°. Similar conformations for rings A and D were found in 9,10-dehydrodeoxyartemisinin (Shu-Hui Li et al. 2006). The seven-membered ring B (C1/C6—C9/O1—C10) contains the important peroxy linkage [O3—O4 = 1.471 (2) Å]. The six-membered ring C (O1—C9—O3—O4—C1—C10) which contains both an oxygen bridge and a peroxy bridge is best described by a twist-boat conformation with puckering parameters Q, θ and φ of 0.750 (2) Å, 85.26 (15)° and 96.58 (11)°, respectively. For an ideal twist-boat conformation, θ and φ are 90° and (60n + 30)°, respectively. This conformation is consistent with both 9,10-dehydrodeoxyartemisinin (Li et al. (2006) and dihydroartemisinin (Qinghaosu Research Group, 1980).