organic compounds
7β-Hydroxyartemisinin
aDepartment of Medicinal Chemistry, University of Mississippi, 417 Faser Hall, University, MS 38677, USA, bNational Center for Natural Products Research, Research Institute of Pharmaceutical Sciences, School of Pharmacy, University of Mississippi, University, MS 38677, USA, and cDepartment of Chemistry and Biochemistry, University of Mississippi, University, MS 38677, USA
*Correspondence e-mail: mavery@olemiss.edu
Crystals of the title compound [systematic name: (3R,6R,7S,8aR,9R,12aR)-7-hydroxy-3,6,9-trimethyloctahydro-3,12-epoxy[1,2]dioxepino[4,3-i]isochromen-10(3H)-one], C15H22O6, were obtained from microbial transformation of artemisinin by a culture of Cunninghamella elegans. The stereochemistry of the compound is consistent with the spectroscopic findings in previously published works. A weak O—H⋯O hydrogen bond occurs in the together with intermolecular C—H⋯O hydrogen bonds.
Related literature
For related literature, see: Blasko & Cordell (1988); Chen & Yu (2001); Liu et al. (2006); Parshikov et al. (2004, 2005, 2006); Zhan, Zhang et al. (2002); CDC (2007); Klayman (1985); TDR (2007); Zhan, Guo et al. (2002).
Experimental
Crystal data
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Data collection
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Data collection: SMART (Bruker, 2002); cell SAINT (Bruker, 2002); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Bruker, 2002); software used to prepare material for publication: SHELXTL.
Supporting information
10.1107/S1600536808000251/hb2682sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536808000251/hb2682Isup2.hkl
7β-Hydroxyartemisinin was obtained following a method previously published by our group (Parshikov et al., 2004). Well developed fungal mycelia of Cunninghamella elegans ATCC 9245 were removed from the surface of agar slants, suspended in 100 ml of sterilized water, and used to inoculate 1 liter of medium (400 g Sabouraud-dextrose, 300 g sucrose, 200 g peptone, in 20 liters of deionized water) in 4 liter shake flasks. The pH was adjusted to 6.5 using 0.1 N NaOH. Cultures were grown for 48 h on a rotary shaker at 301 K with shaking at 180 rpm. The resulting biomass was used as inocula for 1,000 ml of medium contained in 4 liter shake flasks that were again incubated for 48 h. 10 g of Artemisinin (Mediplantex, Vietnam) were dissolved in 400 ml of methanol (MeOH), filter-sterilized, and 20 ml were added to each flask to make the final concentration 500 mg/l. The cultures were returned to the shaker incubators (180 rpm) for an additional 14 days at 301 K. The cultures were harvested and the broth and mycelia were separated using coarse filter paper in a Büchner funnel. The mycelia were washed with water and discarded. The culture broth was extracted with three equal volumes of ethyl acetate (EtOAc) and evaporated under vacuum. The residues were dissolved in MeOH for analysis.
Thin layer
(TLC) was performed on precoated silica gel G and GP Uniplates (Analtech, Newark, Del.) in EtOAc/hexanes (v/v 50:50). TLC plates were visualized with iodine, and p-anisaldehyde stain. Metabolites were purified by semi-preparative flash-chromatography carried out on silica gel 60 (SCI Adsorbents, Louisville, Ky.) using the EtOAc/hexanes solvent system in a gradient mode, eluting from 10–40% EtOAc, collecting 50 ml fractions with a flow rate of 30 ml/min.Colourless needles of (I) were grown by slow evaporation of a solution in absolute ethanol.
The hydrogen atoms were placed in idealized locations (C—H = 0.96–0.98 Å, O—H = 0.82 Å) and refined as riding with Uiso(H) = 1.2Ueq(C) or 1.5Ueq(methyl C, O).
Data collection: SMART (Bruker, 2002); cell
SMART (Bruker, 2002); data reduction: SAINT (Bruker, 2002); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Bruker, 2002); software used to prepare material for publication: SHELXTL (Bruker, 2002).Fig. 1. View of the molecular structure of (I) with displacement elipsoids drawn at the 50% probability level. Hydrogen atoms are omitted for clarity. | |
Fig. 2. The formation of the title compound. |
C15H22O6 | F(000) = 640 |
Mr = 298.33 | Dx = 1.404 Mg m−3 |
Orthorhombic, P212121 | Cu Kα radiation, λ = 1.54178 Å |
Hall symbol: P 2ac 2ab | Cell parameters from 9907 reflections |
a = 6.3047 (2) Å | θ = 3.6–66.0° |
b = 9.1266 (2) Å | µ = 0.90 mm−1 |
c = 24.5309 (6) Å | T = 296 K |
V = 1411.52 (6) Å3 | Needle, colourless |
Z = 4 | 0.23 × 0.15 × 0.12 mm |
Bruker SMART CCD diffractometer | 2456 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube, Siemens KFF Cu 2 K90 | Rint = 0.020 |
Graphite monochromator | θmax = 66.5°, θmin = 3.6° |
ω scans | h = −7→7 |
12572 measured reflections | k = −10→10 |
2464 independent reflections | l = −28→29 |
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)] = 0.028 | H-atom parameters constrained |
wR(F2) = 0.072 | w = 1/[σ2(Fo2) + (0.0408P)2 + 0.3857P] where P = (Fo2 + 2Fc2)/3 |
S = 1.08 | (Δ/σ)max = 0.001 |
2464 reflections | Δρmax = 0.24 e Å−3 |
194 parameters | Δρmin = −0.16 e Å−3 |
0 restraints | Absolute structure: Flack (1983), 990 Friedel pairs |
Primary atom site location: structure-invariant direct methods | Absolute structure parameter: 0.11 (14) |
C15H22O6 | V = 1411.52 (6) Å3 |
Mr = 298.33 | Z = 4 |
Orthorhombic, P212121 | Cu Kα radiation |
a = 6.3047 (2) Å | µ = 0.90 mm−1 |
b = 9.1266 (2) Å | T = 296 K |
c = 24.5309 (6) Å | 0.23 × 0.15 × 0.12 mm |
Bruker SMART CCD diffractometer | 2456 reflections with I > 2σ(I) |
12572 measured reflections | Rint = 0.020 |
2464 independent reflections |
R[F2 > 2σ(F2)] = 0.028 | H-atom parameters constrained |
wR(F2) = 0.072 | Δρmax = 0.24 e Å−3 |
S = 1.08 | Δρmin = −0.16 e Å−3 |
2464 reflections | Absolute structure: Flack (1983), 990 Friedel pairs |
194 parameters | Absolute structure parameter: 0.11 (14) |
0 restraints |
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 | 0.61177 (15) | 1.07519 (10) | 0.80390 (4) | 0.0180 (2) | |
O2 | 0.80303 (16) | 1.07108 (10) | 0.76947 (4) | 0.0196 (2) | |
O5 | 1.06564 (17) | 1.28606 (12) | 0.91615 (4) | 0.0257 (2) | |
O11 | 1.00751 (15) | 1.07562 (11) | 0.87615 (4) | 0.0202 (2) | |
O3 | 0.96938 (15) | 0.88540 (11) | 0.81679 (4) | 0.0179 (2) | |
O4 | 0.3981 (2) | 0.79291 (13) | 0.99868 (4) | 0.0312 (3) | |
H4 | 0.5183 | 0.7748 | 1.0095 | 0.047* | |
C10 | 0.9351 (2) | 1.20070 (15) | 0.90000 (5) | 0.0180 (3) | |
C8A | 0.5644 (2) | 1.08876 (15) | 0.89973 (5) | 0.0164 (3) | |
H8A | 0.4185 | 1.1175 | 0.8910 | 0.020* | |
C15 | 0.6384 (2) | 1.33349 (16) | 0.94762 (6) | 0.0231 (3) | |
H15A | 0.6812 | 1.2917 | 0.9818 | 0.035* | |
H15B | 0.4877 | 1.3486 | 0.9477 | 0.035* | |
H15C | 0.7091 | 1.4256 | 0.9424 | 0.035* | |
C6 | 0.4729 (2) | 0.76793 (15) | 0.90164 (6) | 0.0196 (3) | |
H6 | 0.6086 | 0.7227 | 0.9114 | 0.024* | |
C7 | 0.4095 (2) | 0.87131 (16) | 0.94816 (6) | 0.0211 (3) | |
H7 | 0.2672 | 0.9086 | 0.9401 | 0.025* | |
C3 | 0.8719 (2) | 0.92375 (15) | 0.76551 (5) | 0.0189 (3) | |
C13 | 1.0455 (3) | 0.92467 (16) | 0.72317 (6) | 0.0244 (3) | |
H13A | 0.9850 | 0.9423 | 0.6879 | 0.037* | |
H13B | 1.1165 | 0.8316 | 0.7232 | 0.037* | |
H13C | 1.1456 | 1.0007 | 0.7315 | 0.037* | |
C5 | 0.5912 (2) | 0.74642 (15) | 0.80360 (6) | 0.0205 (3) | |
H5A | 0.6983 | 0.6846 | 0.8203 | 0.025* | |
H5B | 0.4763 | 0.6831 | 0.7919 | 0.025* | |
C9 | 0.6978 (2) | 1.22918 (15) | 0.90130 (6) | 0.0177 (3) | |
H9 | 0.6651 | 1.2817 | 0.8675 | 0.021* | |
C14 | 0.3095 (2) | 0.64461 (16) | 0.89482 (6) | 0.0241 (3) | |
H14A | 0.2810 | 0.6009 | 0.9296 | 0.036* | |
H14B | 0.3647 | 0.5716 | 0.8705 | 0.036* | |
H14C | 0.1806 | 0.6842 | 0.8801 | 0.036* | |
C4 | 0.6880 (2) | 0.81822 (16) | 0.75307 (6) | 0.0207 (3) | |
H4A | 0.5777 | 0.8717 | 0.7340 | 0.025* | |
H4B | 0.7389 | 0.7419 | 0.7289 | 0.025* | |
C12A | 0.6419 (2) | 0.98999 (15) | 0.85346 (6) | 0.0164 (3) | |
C12 | 0.8748 (2) | 0.95112 (15) | 0.86157 (6) | 0.0166 (3) | |
H12 | 0.8821 | 0.8810 | 0.8918 | 0.020* | |
C8 | 0.5571 (2) | 1.00298 (15) | 0.95338 (5) | 0.0185 (3) | |
H8B | 0.6987 | 0.9698 | 0.9627 | 0.022* | |
H8C | 0.5074 | 1.0665 | 0.9824 | 0.022* | |
C5A | 0.5049 (2) | 0.85116 (16) | 0.84744 (5) | 0.0171 (3) | |
H5A1 | 0.3644 | 0.8832 | 0.8352 | 0.021* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.0161 (5) | 0.0194 (5) | 0.0185 (5) | 0.0033 (4) | 0.0003 (4) | 0.0022 (4) |
O2 | 0.0198 (5) | 0.0179 (5) | 0.0212 (5) | 0.0016 (4) | 0.0043 (4) | 0.0019 (4) |
O5 | 0.0209 (5) | 0.0243 (5) | 0.0318 (5) | −0.0053 (5) | −0.0020 (4) | −0.0077 (4) |
O11 | 0.0135 (5) | 0.0206 (5) | 0.0266 (5) | −0.0006 (4) | −0.0026 (4) | −0.0048 (4) |
O3 | 0.0156 (4) | 0.0185 (5) | 0.0196 (5) | 0.0031 (4) | −0.0004 (4) | −0.0017 (4) |
O4 | 0.0419 (7) | 0.0276 (6) | 0.0240 (5) | −0.0063 (5) | 0.0054 (5) | 0.0044 (5) |
C10 | 0.0188 (7) | 0.0186 (7) | 0.0166 (6) | −0.0016 (6) | −0.0004 (5) | −0.0003 (5) |
C8A | 0.0130 (6) | 0.0155 (6) | 0.0208 (6) | 0.0007 (6) | −0.0018 (5) | −0.0004 (5) |
C15 | 0.0225 (7) | 0.0183 (7) | 0.0283 (7) | −0.0007 (6) | 0.0008 (6) | −0.0034 (6) |
C6 | 0.0174 (7) | 0.0171 (7) | 0.0244 (7) | −0.0005 (6) | −0.0004 (6) | 0.0021 (6) |
C7 | 0.0194 (7) | 0.0214 (7) | 0.0225 (7) | −0.0011 (6) | 0.0033 (6) | 0.0025 (6) |
C3 | 0.0213 (7) | 0.0165 (7) | 0.0189 (6) | 0.0020 (6) | −0.0004 (6) | −0.0002 (5) |
C13 | 0.0279 (8) | 0.0201 (7) | 0.0253 (7) | 0.0001 (6) | 0.0054 (6) | −0.0001 (6) |
C5 | 0.0205 (7) | 0.0174 (6) | 0.0234 (7) | −0.0033 (6) | −0.0011 (6) | −0.0029 (6) |
C9 | 0.0178 (7) | 0.0160 (7) | 0.0192 (6) | 0.0006 (6) | −0.0018 (5) | 0.0000 (5) |
C14 | 0.0235 (7) | 0.0193 (7) | 0.0295 (8) | −0.0029 (7) | 0.0009 (6) | 0.0020 (6) |
C4 | 0.0226 (7) | 0.0200 (7) | 0.0196 (6) | 0.0004 (6) | −0.0024 (6) | −0.0023 (5) |
C12A | 0.0157 (7) | 0.0159 (6) | 0.0175 (6) | 0.0009 (6) | −0.0024 (5) | 0.0018 (5) |
C12 | 0.0146 (6) | 0.0154 (6) | 0.0198 (7) | −0.0007 (5) | −0.0002 (5) | 0.0003 (5) |
C8 | 0.0189 (7) | 0.0184 (7) | 0.0181 (6) | 0.0012 (6) | 0.0009 (6) | −0.0014 (5) |
C5A | 0.0126 (6) | 0.0186 (7) | 0.0202 (6) | −0.0006 (5) | −0.0027 (5) | −0.0004 (5) |
O1—C12A | 1.4556 (16) | C7—C8 | 1.525 (2) |
O1—O2 | 1.4727 (13) | C7—H7 | 0.9800 |
O2—C3 | 1.4164 (17) | C3—C13 | 1.509 (2) |
O5—C10 | 1.2003 (18) | C3—C4 | 1.538 (2) |
O11—C10 | 1.3615 (17) | C13—H13A | 0.9600 |
O11—C12 | 1.4558 (17) | C13—H13B | 0.9600 |
O3—C12 | 1.3866 (17) | C13—H13C | 0.9600 |
O3—C3 | 1.4429 (16) | C5—C4 | 1.529 (2) |
O4—C7 | 1.4328 (17) | C5—C5A | 1.5383 (19) |
O4—H4 | 0.8200 | C5—H5A | 0.9700 |
C10—C9 | 1.5193 (19) | C5—H5B | 0.9700 |
C8A—C12A | 1.5297 (18) | C9—H9 | 0.9800 |
C8A—C8 | 1.5320 (18) | C14—H14A | 0.9600 |
C8A—C9 | 1.5333 (19) | C14—H14B | 0.9600 |
C8A—H8A | 0.9800 | C14—H14C | 0.9600 |
C15—C9 | 1.5289 (19) | C4—H4A | 0.9700 |
C15—H15A | 0.9600 | C4—H4B | 0.9700 |
C15—H15B | 0.9600 | C12A—C12 | 1.5234 (19) |
C15—H15C | 0.9600 | C12A—C5A | 1.5405 (19) |
C6—C7 | 1.5336 (19) | C12—H12 | 0.9800 |
C6—C14 | 1.535 (2) | C8—H8B | 0.9700 |
C6—C5A | 1.5444 (18) | C8—H8C | 0.9700 |
C6—H6 | 0.9800 | C5A—H5A1 | 0.9800 |
C12A—O1—O2 | 111.00 (9) | C5A—C5—H5A | 108.2 |
C3—O2—O1 | 108.33 (9) | C4—C5—H5B | 108.2 |
C10—O11—C12 | 124.56 (11) | C5A—C5—H5B | 108.2 |
C12—O3—C3 | 113.74 (10) | H5A—C5—H5B | 107.4 |
C7—O4—H4 | 109.5 | C10—C9—C15 | 111.29 (12) |
O5—C10—O11 | 117.15 (13) | C10—C9—C8A | 113.38 (11) |
O5—C10—C9 | 123.87 (13) | C15—C9—C8A | 113.89 (11) |
O11—C10—C9 | 118.85 (12) | C10—C9—H9 | 105.8 |
C12A—C8A—C8 | 110.23 (11) | C15—C9—H9 | 105.8 |
C12A—C8A—C9 | 109.62 (11) | C8A—C9—H9 | 105.8 |
C8—C8A—C9 | 114.95 (11) | C6—C14—H14A | 109.5 |
C12A—C8A—H8A | 107.2 | C6—C14—H14B | 109.5 |
C8—C8A—H8A | 107.2 | H14A—C14—H14B | 109.5 |
C9—C8A—H8A | 107.2 | C6—C14—H14C | 109.5 |
C9—C15—H15A | 109.5 | H14A—C14—H14C | 109.5 |
C9—C15—H15B | 109.5 | H14B—C14—H14C | 109.5 |
H15A—C15—H15B | 109.5 | C5—C4—C3 | 114.09 (11) |
C9—C15—H15C | 109.5 | C5—C4—H4A | 108.7 |
H15A—C15—H15C | 109.5 | C3—C4—H4A | 108.7 |
H15B—C15—H15C | 109.5 | C5—C4—H4B | 108.7 |
C7—C6—C14 | 110.94 (12) | C3—C4—H4B | 108.7 |
C7—C6—C5A | 111.84 (11) | H4A—C4—H4B | 107.6 |
C14—C6—C5A | 110.77 (11) | O1—C12A—C12 | 111.07 (11) |
C7—C6—H6 | 107.7 | O1—C12A—C8A | 105.26 (10) |
C14—C6—H6 | 107.7 | C12—C12A—C8A | 110.38 (11) |
C5A—C6—H6 | 107.7 | O1—C12A—C5A | 106.63 (10) |
O4—C7—C8 | 110.58 (12) | C12—C12A—C5A | 111.18 (11) |
O4—C7—C6 | 110.46 (12) | C8A—C12A—C5A | 112.12 (11) |
C8—C7—C6 | 112.84 (12) | O3—C12—O11 | 106.56 (11) |
O4—C7—H7 | 107.6 | O3—C12—C12A | 114.31 (11) |
C8—C7—H7 | 107.6 | O11—C12—C12A | 113.85 (11) |
C6—C7—H7 | 107.6 | O3—C12—H12 | 107.2 |
O2—C3—O3 | 107.52 (10) | O11—C12—H12 | 107.2 |
O2—C3—C13 | 105.32 (11) | C12A—C12—H12 | 107.2 |
O3—C3—C13 | 107.01 (11) | C7—C8—C8A | 110.41 (11) |
O2—C3—C4 | 112.14 (12) | C7—C8—H8B | 109.6 |
O3—C3—C4 | 110.01 (11) | C8A—C8—H8B | 109.6 |
C13—C3—C4 | 114.44 (12) | C7—C8—H8C | 109.6 |
C3—C13—H13A | 109.5 | C8A—C8—H8C | 109.6 |
C3—C13—H13B | 109.5 | H8B—C8—H8C | 108.1 |
H13A—C13—H13B | 109.5 | C5—C5A—C12A | 112.32 (11) |
C3—C13—H13C | 109.5 | C5—C5A—C6 | 110.02 (11) |
H13A—C13—H13C | 109.5 | C12A—C5A—C6 | 113.30 (11) |
H13B—C13—H13C | 109.5 | C5—C5A—H5A1 | 106.9 |
C4—C5—C5A | 116.20 (12) | C12A—C5A—H5A1 | 106.9 |
C4—C5—H5A | 108.2 | C6—C5A—H5A1 | 106.9 |
D—H···A | D—H | H···A | D···A | D—H···A |
O4—H4···O4i | 0.82 | 2.48 | 3.2488 (18) | 156 |
C5A—H5A1···O3ii | 0.98 | 2.53 | 3.4731 (16) | 161 |
C5—H5B···O2iii | 0.97 | 2.53 | 3.4571 (17) | 159 |
C13—H13B···O2iv | 0.96 | 2.44 | 3.3703 (18) | 164 |
Symmetry codes: (i) x+1/2, −y+3/2, −z+2; (ii) x−1, y, z; (iii) −x+1, y−1/2, −z+3/2; (iv) −x+2, y−1/2, −z+3/2. |
Experimental details
Crystal data | |
Chemical formula | C15H22O6 |
Mr | 298.33 |
Crystal system, space group | Orthorhombic, P212121 |
Temperature (K) | 296 |
a, b, c (Å) | 6.3047 (2), 9.1266 (2), 24.5309 (6) |
V (Å3) | 1411.52 (6) |
Z | 4 |
Radiation type | Cu Kα |
µ (mm−1) | 0.90 |
Crystal size (mm) | 0.23 × 0.15 × 0.12 |
Data collection | |
Diffractometer | Bruker SMART CCD diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 12572, 2464, 2456 |
Rint | 0.020 |
(sin θ/λ)max (Å−1) | 0.595 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.028, 0.072, 1.08 |
No. of reflections | 2464 |
No. of parameters | 194 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.24, −0.16 |
Absolute structure | Flack (1983), 990 Friedel pairs |
Absolute structure parameter | 0.11 (14) |
Computer programs: SMART (Bruker, 2002), SAINT (Bruker, 2002), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Bruker, 2002).
D—H···A | D—H | H···A | D···A | D—H···A |
O4—H4···O4i | 0.82 | 2.48 | 3.2488 (18) | 156 |
C5A—H5A1···O3ii | 0.98 | 2.53 | 3.4731 (16) | 161 |
C5—H5B···O2iii | 0.97 | 2.53 | 3.4571 (17) | 159 |
C13—H13B···O2iv | 0.96 | 2.44 | 3.3703 (18) | 164 |
Symmetry codes: (i) x+1/2, −y+3/2, −z+2; (ii) x−1, y, z; (iii) −x+1, y−1/2, −z+3/2; (iv) −x+2, y−1/2, −z+3/2. |
Acknowledgements
The authors thank Dr K. Hardcastle for his helpful advice. The authors also thank the Center for Disease Control and Prevention, USA, for providing financial assistance (CDC cooperative agreements 1UO1 CI000211-03 and 1UO1 CI000362-01). This investigation was conducted in a facility constructed with support from Research Facilities Improvement Program grant No. C06 Rr-14503-01 from the National Center for Research Resources, National Institutes of Health.
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The natural occurring sesquiterpene lactone endoperoxide artemisinin has been the subject of extensive research for its effective therapeutic action against multidrug-resistant Plasmodium falciparum strains (Klayman, 1985). Some of the reasons for this are the increasing number of people under risk of contracting malaria, the alarming spread of drug-resistant parasites (TDR, 2007) and the relatively complicated treatment protocols, with so many variables and no effective cure for the several strains of Plasmodium causing the disease (CDC, 2007).
One of the strategies used for increasing the bioavailability of artemisinin is its semi-synthetic transformation through microorganisms (Chen & Yu, 2001; Zhan, Guo et al., 2002; Zhan, Zhang et al., 2002; Liu et al., 2006). The metabolites resulting from the action of several enzymes in selected strains of fungi can be further transformed in dimers or attached to other moieties for selective action and/or delivery.
Our group has been studying the microbial transformation of artemisinin for some years (Parshikov et al., 2005; 2006) and we follow the numbering system of Blasko & Cordell (1988), and the CA Index Name. Some authors follow a different numbering system and call the title compound, (I), 9β-hydroxyartemisinin, rather than 7β-hydroxyartemisinin. Several well established methods of one-dimensional and two-dimensional NMR have already determined the configuration of artemisinin and most of its derivatives. The crystallographic data confirm the assignment of the chiral centers proposed in a previously published paper (Parshikov et al., 2004). The configuration of the chiral centers in (I) are: C3 R, C5A S, C6 S, C7 S, C8A S, C9 R, C12 S, C12A R.
In the crystal of (I), a weak intermolecular O—H···O hydrogen bond links the molecules into chains and some short C—H···O contacts occur (Table 1).