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Acta Cryst. (2008). E64, o395-o396    [ doi:10.1107/S1600536808000251 ]

7[beta]-Hydroxyartemisinin

P. B. Carvalho, B. Liu, Y. Wu, J. S. Williamson and M. A. Avery

Abstract top

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 crystal structure, together with intermolecular C-H...O hydrogen bonds.

Comment top

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).

Related literature top

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); Farrugia (1997); Klayman (1985); TDR (2007); Zhan, Guo et al. (2002). See also International Tables for Crystallography (1992). Vol. C, edited by A. J. C. Wilson. Dordrecht: Kluwer.

Experimental top

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 chromatography (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.

Refinement top

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).

Computing details top

Data collection: SMART (Bruker, 2002); cell refinement: 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).

Figures top
[Figure 1] Fig. 1. View of the molecular structure of (I) with displacement elipsoids drawn at the 50% probability level. Hydrogen atoms are omitted for clarity.
[Figure 2] Fig. 2. The formation of the title compound.
(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 top
Crystal data top
C15H22O6F000 = 640
Mr = 298.33Dx = 1.404 Mg m−3
Orthorhombic, P212121Cu Kα radiation
λ = 1.54178 Å
Hall symbol: P 2ac 2abCell parameters from 9907 reflections
a = 6.3047 (2) Åθ = 3.6–66.0º
b = 9.1266 (2) ŵ = 0.90 mm−1
c = 24.5309 (6) ÅT = 296 (2) K
V = 1411.52 (6) Å3Needle, colourless
Z = 40.23 × 0.15 × 0.12 mm
Data collection top
Bruker SMART CCD
diffractometer		2456 reflections with I > 2σ(I)
Monochromator: graphiteRint = 0.020
T = 100 Kθmax = 66.5º
ω scansθmin = 3.6º
Absorption correction: noneh = −7→7
12572 measured reflectionsk = −10→10
2464 independent reflectionsl = −28→29
Refinement top
Refinement on F2Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: fullH-atom parameters constrained
R[F2 > 2σ(F2)] = 0.028  w = 1/[σ2(Fo2) + (0.0408P)2 + 0.3857P]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.072(Δ/σ)max = 0.001
S = 1.08Δρmax = 0.24 e Å−3
2464 reflectionsΔρmin = −0.16 e Å−3
194 parametersExtinction correction: none
Primary atom site location: structure-invariant direct methodsAbsolute structure: Flack (1983), 990 Friedel pairs
Secondary atom site location: difference Fourier mapFlack parameter: 0.11 (14)
Crystal data top
C15H22O6V = 1411.52 (6) Å3
Mr = 298.33Z = 4
Orthorhombic, P212121Cu Kα
a = 6.3047 (2) ŵ = 0.90 mm−1
b = 9.1266 (2) ÅT = 296 (2) K
c = 24.5309 (6) Å0.23 × 0.15 × 0.12 mm
Data collection top
Bruker SMART CCD
diffractometer		2464 independent reflections
Absorption correction: none2456 reflections with I > 2σ(I)
12572 measured reflectionsRint = 0.020
Refinement top
R[F2 > 2σ(F2)] = 0.028H-atom parameters constrained
wR(F2) = 0.072Δρmax = 0.24 e Å−3
S = 1.08Δρmin = −0.16 e Å−3
2464 reflectionsAbsolute structure: Flack (1983), 990 Friedel pairs
194 parametersFlack parameter: 0.11 (14)
Special details top

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
O10.61177 (15)1.07519 (10)0.80390 (4)0.0180 (2)
O20.80303 (16)1.07108 (10)0.76947 (4)0.0196 (2)
O51.06564 (17)1.28606 (12)0.91615 (4)0.0257 (2)
O111.00751 (15)1.07562 (11)0.87615 (4)0.0202 (2)
O30.96938 (15)0.88540 (11)0.81679 (4)0.0179 (2)
O40.3981 (2)0.79291 (13)0.99868 (4)0.0312 (3)
H40.51830.77481.00950.047*
C100.9351 (2)1.20070 (15)0.90000 (5)0.0180 (3)
C8A0.5644 (2)1.08876 (15)0.89973 (5)0.0164 (3)
H8A0.41851.11750.89100.020*
C150.6384 (2)1.33349 (16)0.94762 (6)0.0231 (3)
H15A0.68121.29170.98180.035*
H15B0.48771.34860.94770.035*
H15C0.70911.42560.94240.035*
C60.4729 (2)0.76793 (15)0.90164 (6)0.0196 (3)
H60.60860.72270.91140.024*
C70.4095 (2)0.87131 (16)0.94816 (6)0.0211 (3)
H70.26720.90860.94010.025*
C30.8719 (2)0.92375 (15)0.76551 (5)0.0189 (3)
C131.0455 (3)0.92467 (16)0.72317 (6)0.0244 (3)
H13A0.98500.94230.68790.037*
H13B1.11650.83160.72320.037*
H13C1.14561.00070.73150.037*
C50.5912 (2)0.74642 (15)0.80360 (6)0.0205 (3)
H5A0.69830.68460.82030.025*
H5B0.47630.68310.79190.025*
C90.6978 (2)1.22918 (15)0.90130 (6)0.0177 (3)
H90.66511.28170.86750.021*
C140.3095 (2)0.64461 (16)0.89482 (6)0.0241 (3)
H14A0.28100.60090.92960.036*
H14B0.36470.57160.87050.036*
H14C0.18060.68420.88010.036*
C40.6880 (2)0.81822 (16)0.75307 (6)0.0207 (3)
H4A0.57770.87170.73400.025*
H4B0.73890.74190.72890.025*
C12A0.6419 (2)0.98999 (15)0.85346 (6)0.0164 (3)
C120.8748 (2)0.95112 (15)0.86157 (6)0.0166 (3)
H120.88210.88100.89180.020*
C80.5571 (2)1.00298 (15)0.95338 (5)0.0185 (3)
H8B0.69870.96980.96270.022*
H8C0.50741.06650.98240.022*
C5A0.5049 (2)0.85116 (16)0.84744 (5)0.0171 (3)
H5A10.36440.88320.83520.021*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0161 (5)0.0194 (5)0.0185 (5)0.0033 (4)0.0003 (4)0.0022 (4)
O20.0198 (5)0.0179 (5)0.0212 (5)0.0016 (4)0.0043 (4)0.0019 (4)
O50.0209 (5)0.0243 (5)0.0318 (5)−0.0053 (5)−0.0020 (4)−0.0077 (4)
O110.0135 (5)0.0206 (5)0.0266 (5)−0.0006 (4)−0.0026 (4)−0.0048 (4)
O30.0156 (4)0.0185 (5)0.0196 (5)0.0031 (4)−0.0004 (4)−0.0017 (4)
O40.0419 (7)0.0276 (6)0.0240 (5)−0.0063 (5)0.0054 (5)0.0044 (5)
C100.0188 (7)0.0186 (7)0.0166 (6)−0.0016 (6)−0.0004 (5)−0.0003 (5)
C8A0.0130 (6)0.0155 (6)0.0208 (6)0.0007 (6)−0.0018 (5)−0.0004 (5)
C150.0225 (7)0.0183 (7)0.0283 (7)−0.0007 (6)0.0008 (6)−0.0034 (6)
C60.0174 (7)0.0171 (7)0.0244 (7)−0.0005 (6)−0.0004 (6)0.0021 (6)
C70.0194 (7)0.0214 (7)0.0225 (7)−0.0011 (6)0.0033 (6)0.0025 (6)
C30.0213 (7)0.0165 (7)0.0189 (6)0.0020 (6)−0.0004 (6)−0.0002 (5)
C130.0279 (8)0.0201 (7)0.0253 (7)0.0001 (6)0.0054 (6)−0.0001 (6)
C50.0205 (7)0.0174 (6)0.0234 (7)−0.0033 (6)−0.0011 (6)−0.0029 (6)
C90.0178 (7)0.0160 (7)0.0192 (6)0.0006 (6)−0.0018 (5)0.0000 (5)
C140.0235 (7)0.0193 (7)0.0295 (8)−0.0029 (7)0.0009 (6)0.0020 (6)
C40.0226 (7)0.0200 (7)0.0196 (6)0.0004 (6)−0.0024 (6)−0.0023 (5)
C12A0.0157 (7)0.0159 (6)0.0175 (6)0.0009 (6)−0.0024 (5)0.0018 (5)
C120.0146 (6)0.0154 (6)0.0198 (7)−0.0007 (5)−0.0002 (5)0.0003 (5)
C80.0189 (7)0.0184 (7)0.0181 (6)0.0012 (6)0.0009 (6)−0.0014 (5)
C5A0.0126 (6)0.0186 (7)0.0202 (6)−0.0006 (5)−0.0027 (5)−0.0004 (5)
Geometric parameters (Å, °) top
O1—C12A1.4556 (16)C7—C81.525 (2)
O1—O21.4727 (13)C7—H70.9800
O2—C31.4164 (17)C3—C131.509 (2)
O5—C101.2003 (18)C3—C41.538 (2)
O11—C101.3615 (17)C13—H13A0.9600
O11—C121.4558 (17)C13—H13B0.9600
O3—C121.3866 (17)C13—H13C0.9600
O3—C31.4429 (16)C5—C41.529 (2)
O4—C71.4328 (17)C5—C5A1.5383 (19)
O4—H40.8200C5—H5A0.9700
C10—C91.5193 (19)C5—H5B0.9700
C8A—C12A1.5297 (18)C9—H90.9800
C8A—C81.5320 (18)C14—H14A0.9600
C8A—C91.5333 (19)C14—H14B0.9600
C8A—H8A0.9800C14—H14C0.9600
C15—C91.5289 (19)C4—H4A0.9700
C15—H15A0.9600C4—H4B0.9700
C15—H15B0.9600C12A—C121.5234 (19)
C15—H15C0.9600C12A—C5A1.5405 (19)
C6—C71.5336 (19)C12—H120.9800
C6—C141.535 (2)C8—H8B0.9700
C6—C5A1.5444 (18)C8—H8C0.9700
C6—H60.9800C5A—H5A10.9800
C12A—O1—O2111.00 (9)C5A—C5—H5A108.2
C3—O2—O1108.33 (9)C4—C5—H5B108.2
C10—O11—C12124.56 (11)C5A—C5—H5B108.2
C12—O3—C3113.74 (10)H5A—C5—H5B107.4
C7—O4—H4109.5C10—C9—C15111.29 (12)
O5—C10—O11117.15 (13)C10—C9—C8A113.38 (11)
O5—C10—C9123.87 (13)C15—C9—C8A113.89 (11)
O11—C10—C9118.85 (12)C10—C9—H9105.8
C12A—C8A—C8110.23 (11)C15—C9—H9105.8
C12A—C8A—C9109.62 (11)C8A—C9—H9105.8
C8—C8A—C9114.95 (11)C6—C14—H14A109.5
C12A—C8A—H8A107.2C6—C14—H14B109.5
C8—C8A—H8A107.2H14A—C14—H14B109.5
C9—C8A—H8A107.2C6—C14—H14C109.5
C9—C15—H15A109.5H14A—C14—H14C109.5
C9—C15—H15B109.5H14B—C14—H14C109.5
H15A—C15—H15B109.5C5—C4—C3114.09 (11)
C9—C15—H15C109.5C5—C4—H4A108.7
H15A—C15—H15C109.5C3—C4—H4A108.7
H15B—C15—H15C109.5C5—C4—H4B108.7
C7—C6—C14110.94 (12)C3—C4—H4B108.7
C7—C6—C5A111.84 (11)H4A—C4—H4B107.6
C14—C6—C5A110.77 (11)O1—C12A—C12111.07 (11)
C7—C6—H6107.7O1—C12A—C8A105.26 (10)
C14—C6—H6107.7C12—C12A—C8A110.38 (11)
C5A—C6—H6107.7O1—C12A—C5A106.63 (10)
O4—C7—C8110.58 (12)C12—C12A—C5A111.18 (11)
O4—C7—C6110.46 (12)C8A—C12A—C5A112.12 (11)
C8—C7—C6112.84 (12)O3—C12—O11106.56 (11)
O4—C7—H7107.6O3—C12—C12A114.31 (11)
C8—C7—H7107.6O11—C12—C12A113.85 (11)
C6—C7—H7107.6O3—C12—H12107.2
O2—C3—O3107.52 (10)O11—C12—H12107.2
O2—C3—C13105.32 (11)C12A—C12—H12107.2
O3—C3—C13107.01 (11)C7—C8—C8A110.41 (11)
O2—C3—C4112.14 (12)C7—C8—H8B109.6
O3—C3—C4110.01 (11)C8A—C8—H8B109.6
C13—C3—C4114.44 (12)C7—C8—H8C109.6
C3—C13—H13A109.5C8A—C8—H8C109.6
C3—C13—H13B109.5H8B—C8—H8C108.1
H13A—C13—H13B109.5C5—C5A—C12A112.32 (11)
C3—C13—H13C109.5C5—C5A—C6110.02 (11)
H13A—C13—H13C109.5C12A—C5A—C6113.30 (11)
H13B—C13—H13C109.5C5—C5A—H5A1106.9
C4—C5—C5A116.20 (12)C12A—C5A—H5A1106.9
C4—C5—H5A108.2C6—C5A—H5A1106.9
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
O4—H4···O4i0.822.483.2488 (18)156
C5A—H5A1···O3ii0.982.533.4731 (16)161
C5—H5B···O2iii0.972.533.4571 (17)159
C13—H13B···O2iv0.962.443.3703 (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.
Table 1
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
O4—H4···O4i0.822.483.2488 (18)156
C5A—H5A1···O3ii0.982.533.4731 (16)161
C5—H5B···O2iii0.972.533.4571 (17)159
C13—H13B···O2iv0.962.443.3703 (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 top

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.

references
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