organic compounds
1-Bromo-2-(10β-dihydroartemisinoxy)ethane
aDepartment of Pharmaceutical Chemistry, North-West University, PO NWU 2520, Potchefstroom, South Africa, and bMolecular Sciences Institute, School of Chemistry, University of the Witwatersrand, PO Wits 2050, Johannesburg, South Africa
*Correspondence e-mail: 13014196@nwu.ac.za
The title compound, C17H27BrO5, DEB, is a derivative of artemisinin which is used in malara therapy. The OR-group at C12 is cis to the CH3-group at C11 and axially oriented on ring D which has a chair conformation. The crystal packing is stabilized by several weak intermolecular C—H⋯O interactions, which combine to form a C—H—O bonded network parallel to (001).
Related literature
For background to malaria, see: World Health Organisation (2008). For the effective of artemisinin analogs against malaria, see: Ploypradith (2004). For the of artemisinin, see: Kuhn & Wang (2008) and of dihydroartemisinin (DHA), see: Luo et al. (1984). Jasinski et al. (2008a) redetermined the structure of DHA as well as characterizing the second polymer of β-arteether (Jasinski et al., 2008b). For the reaction of DEB with see: Li et al. (2000). For the synthesis of artemisinin hybrids, see: Walsh et al. (2007); Basco et al. (2001); Grelepois et al. (2005); Gupta et al. (2002). For puckering analysis, see: Cremer & Pople (1975); Evans & Boeyens (1989).
Experimental
Crystal data
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Data collection: APEX2 (Bruker, 2005); cell SAINT (Bruker, 2005); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) and SCHAKAL99 (Keller, 1999); software used to prepare material for publication: WinGX (Farrugia, 1999) and PLATON (Spek, 2009).
Supporting information
https://doi.org/10.1107/S1600536810029090/jj2039sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536810029090/jj2039Isup2.hkl
The title compound was prepared as described by Li and co-workers (Li et al., 2000). The product was recrystallized from methanol using a slow evaporation technique at room temperature with a 71% yield of white needle-like crystals. IC50 (ng/ml) of the title compound (DEB): D10 = 41.39, Dd2 = 129.47 IC50 (ng/ml) of Dihydroartemisinin: D10 = 1.45, Dd2 = 0.59.
All H atoms were positioned geometrically, and allowed to ride on their parent atoms, with Atom—H bond lengths of 1.00 Å (CH), 0.99 Å (CH2), or 0.98 Å (CH3). Isotropic displacement parameters for these atoms were set to 1.2 times (CH and CH2) or 1.5 times (CH3) Ueq of the parent atom.
Malaria is one of the top three priority diseases of the WHO and is becoming a worldwide threat because of its wide spread resistance to current anti-malaria drugs (World Health Organization, 2008). Artemisinin and its derivatives currently represent the most effective group of compounds against multidrug-resistant malaria with a rapid onset of action and a short half life. However, when artemisinin analogs are used as monotherapy it results in significant recrudescence (Ploypradith, 2004). Therefore it is recommended by the WHO that all uncomplicated P. falciparum infections should be treated with an artemisinin-based combination therapy (ACT).
When DHA is prepared from artemisinin by reduction, it exists as a mixture of α- and β-isomers. Luo and co-workers (Luo et al. 1984) determined that these isomers can exist in two conformations of ring D, a half-chair form and a half-boat form. DEB was tested in vitro against Plasmodium falciparum sensitive (D10) and resistant (Dd2) strains, but did not show any improved activity with respect to the reference drug: dihydroartemisinin (DHA).
The title compound, C17H27BrO5 or 2-(10β-dihydroartemisinoxy)ethylbromide (DEB), is a derivative of artemisinin. DEB was synthesized from the reaction of DHA with bromoethanol. DHA was supplied as a mixture of With the formation of DEB the OR-group at C12 is positioned cis to the CH3-group at C11 and axially oriented on ring D. Therefore, DEB can be assigned to the β-chair series. The rings in the title compound have also been previously labeled as rings A, B, C and D (scheme). Ring A has a twist boat conformation with puckering parameters (Cremer & Pople, 1975) Q, θ and φ of 0.739 (2), 94.21 (15)° and 274.46 (16)°, respectively (Fig. 1). Ring B has a distorted boat conformation and ring C is in a slightly distorted chair conformation with puckering parameters Q, θ and φ of 0.539 (3), 8.6 (3)° and 195.6 (18)°. Ring D is in a chair conformation with puckering parameters Q, θ and φ of 0.532 (2), 178.2 (3)° and 73 (11)°. Crystal packing in DEB is stabilized by a several C—H···O weak intermolecular interactions (Table 1) some of which are shown in Fig 2. These combine to form a C—H—O bonded network parallel to (001).
For background to malaria, see: World Health Organisation (2008). For the effective of artemisinin analogs against malaria, see: Ploypradith (2004). For the β-arteether (Jasinski et al., 2008b). For the reaction of DEB with see: Li et al. (2000). For the synthesis of artemisinin hybrids, see: Walsh et al. (2007); Basco et al. (2001); Grelepois et al. (2005); Gupta et al. (2002). For puckering analysis, see: Cremer & Pople (1975); Evans & Boeyens (1989).
of artemisinin, see: Kuhn & Wang (2008) and of dihydroartemisinin (DHA), see: Luo et al. (1984). Jasinski et al. (2008a) redetermined the structure of DHA as well as characterizing the second polymer ofData collection: APEX2 (Bruker, 2005); cell
SAINT (Bruker, 2005); data reduction: SAINT (Bruker, 2005); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) and SCHAKAL99 (Keller, 1999); software used to prepare material for publication: WinGX (Farrugia, 1999) and PLATON (Spek, 2009).C17H27BrO5 | F(000) = 408 |
Mr = 391.30 | Dx = 1.492 Mg m−3 |
Monoclinic, P21 | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: P 2yb | Cell parameters from 6155 reflections |
a = 9.2836 (2) Å | θ = 2.9–28.2° |
b = 9.1103 (2) Å | µ = 2.38 mm−1 |
c = 10.2999 (2) Å | T = 173 K |
β = 90.395 (1)° | Plate, colourless |
V = 871.11 (3) Å3 | 0.44 × 0.41 × 0.08 mm |
Z = 2 |
Bruker APEXII CCD diffractometer | 4196 independent reflections |
Radiation source: fine-focus sealed tube | 3432 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.068 |
φ and ω scans | θmax = 28.0°, θmin = 2.0° |
Absorption correction: integration (XPREP; Bruker, 2005) | h = −12→12 |
Tmin = 0.420, Tmax = 0.832 | k = −12→12 |
13762 measured reflections | l = −13→13 |
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)] = 0.034 | H-atom parameters constrained |
wR(F2) = 0.078 | w = 1/[σ2(Fo2) + (0.0405P)2] where P = (Fo2 + 2Fc2)/3 |
S = 0.95 | (Δ/σ)max = 0.001 |
4196 reflections | Δρmax = 0.61 e Å−3 |
211 parameters | Δρmin = −0.35 e Å−3 |
1 restraint | Absolute structure: Flack (1983), 1966 Friedel pairs |
Primary atom site location: structure-invariant direct methods | Absolute structure parameter: −0.012 (7) |
C17H27BrO5 | V = 871.11 (3) Å3 |
Mr = 391.30 | Z = 2 |
Monoclinic, P21 | Mo Kα radiation |
a = 9.2836 (2) Å | µ = 2.38 mm−1 |
b = 9.1103 (2) Å | T = 173 K |
c = 10.2999 (2) Å | 0.44 × 0.41 × 0.08 mm |
β = 90.395 (1)° |
Bruker APEXII CCD diffractometer | 4196 independent reflections |
Absorption correction: integration (XPREP; Bruker, 2005) | 3432 reflections with I > 2σ(I) |
Tmin = 0.420, Tmax = 0.832 | Rint = 0.068 |
13762 measured reflections |
R[F2 > 2σ(F2)] = 0.034 | H-atom parameters constrained |
wR(F2) = 0.078 | Δρmax = 0.61 e Å−3 |
S = 0.95 | Δρmin = −0.35 e Å−3 |
4196 reflections | Absolute structure: Flack (1983), 1966 Friedel pairs |
211 parameters | Absolute structure parameter: −0.012 (7) |
1 restraint |
Experimental. 1H NMR (600.17 MHz; CDCl3; Me4Si): δH 5.46 (s, 1H, H-5), 4.82 (d, J = 3.4 Hz, 1H, H-12), 4.09 (ddd, J = 11.8, 6.6, 5.5 Hz, 1H, H-16α), 3.79 – 3.73 (m, 1H, H-16β), 3.51 – 3.47 (m, 2H, H-17), 2.66 – 2.59 (m, 1H, H-11), 2.39 – 2.30 (m, 1H, H-3α), 2.01 (ddd, J = 14.6, 4.7, 3.1 Hz, 1H, H-3β), 1.92 – 1.81 (m, 2H, H-2α; H-8α), 1.73 (ddd, J = 14.2, 7.7, 3.6 Hz, 1H, H-8β), 1.62 (dq, J = 13.2, 3.3 Hz, 1H, H-9β), 1.47 (qdd, J = 12.0, 8.9, 4.1 Hz, 2H, H-2α; H-7), 1.41 (s, 3H, H-15), 1.36 – 1.28 (m, 1H, H-10), 1.22 (td, J = 11.5, 6.6 Hz, 1H, H-1), 0.93 (d, J = 6.4 Hz, 3H, H-13), 0.91 (d, J = 7.4 Hz, 3H, H-14), 0.87 (dd, J = 13.3, 3.6 Hz, 3H, H-9α). 13C NMR (150.913 MHz; CDCl3; Me4Si): δC 104.10 (C-4), 102.02 (C-12), 88.12 (C-5), 81.07 (C-6), 68.14 (C-16), 52.54 (C-1), 44.33 (C-7), 37.36 (C-10), 36.37 (C-3), 34.63 (C-11), 31.41 (C-17), 30.86 (C-11), 26.12 (C-15), 24.62 (C-2), 24.33 (C-8), 20.34 (C-14), 12.95 (C-13). |
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 | ||
C1 | 0.4624 (2) | 0.8858 (2) | 0.7096 (2) | 0.0219 (6) | |
H1 | 0.4971 | 0.9825 | 0.6759 | 0.026* | |
C2 | 0.5821 (3) | 0.8288 (3) | 0.8003 (2) | 0.0240 (5) | |
H2A | 0.5667 | 0.7224 | 0.8142 | 0.029* | |
H2B | 0.6756 | 0.8404 | 0.7558 | 0.029* | |
C3 | 0.5930 (2) | 0.9028 (3) | 0.9323 (2) | 0.0254 (5) | |
H3A | 0.6188 | 1.0072 | 0.9196 | 0.030* | |
H3B | 0.6717 | 0.8561 | 0.9828 | 0.030* | |
C4 | 0.4535 (2) | 0.8946 (3) | 1.0112 (2) | 0.0236 (6) | |
C5 | 0.2721 (2) | 0.7966 (3) | 0.8734 (2) | 0.0193 (5) | |
H5 | 0.2584 | 0.7047 | 0.8217 | 0.023* | |
C6 | 0.3193 (2) | 0.9184 (3) | 0.7817 (2) | 0.0199 (4) | |
C7 | 0.1958 (2) | 0.9600 (3) | 0.6879 (2) | 0.0221 (5) | |
H7 | 0.2231 | 1.0558 | 0.6476 | 0.027* | |
C8 | 0.1822 (3) | 0.8494 (3) | 0.5770 (2) | 0.0293 (6) | |
H8A | 0.1553 | 0.7523 | 0.6126 | 0.035* | |
H8B | 0.1046 | 0.8812 | 0.5168 | 0.035* | |
C9 | 0.3227 (3) | 0.8356 (3) | 0.5027 (2) | 0.0286 (6) | |
H9A | 0.3101 | 0.7640 | 0.4312 | 0.034* | |
H9B | 0.3472 | 0.9317 | 0.4638 | 0.034* | |
C10 | 0.4453 (3) | 0.7860 (3) | 0.5903 (2) | 0.0268 (6) | |
H10 | 0.4230 | 0.6847 | 0.6215 | 0.032* | |
C11 | 0.0559 (3) | 0.9877 (3) | 0.7641 (2) | 0.0246 (5) | |
H11 | 0.0758 | 1.0741 | 0.8214 | 0.030* | |
C12 | 0.0223 (3) | 0.8610 (3) | 0.8544 (2) | 0.0230 (5) | |
H12 | −0.0616 | 0.8898 | 0.9092 | 0.028* | |
C13 | −0.0724 (3) | 1.0314 (3) | 0.6780 (3) | 0.0347 (6) | |
H13A | −0.1037 | 0.9465 | 0.6266 | 0.052* | |
H13B | −0.0436 | 1.1110 | 0.6196 | 0.052* | |
H13C | −0.1520 | 1.0647 | 0.7327 | 0.052* | |
C14 | 0.5866 (3) | 0.7794 (4) | 0.5130 (3) | 0.0378 (7) | |
H14A | 0.5710 | 0.7232 | 0.4331 | 0.057* | |
H14B | 0.6613 | 0.7317 | 0.5658 | 0.057* | |
H14C | 0.6173 | 0.8792 | 0.4911 | 0.057* | |
C15 | 0.4802 (3) | 0.8852 (3) | 1.1564 (2) | 0.0318 (7) | |
H15A | 0.5460 | 0.9638 | 1.1832 | 0.048* | |
H15B | 0.5231 | 0.7898 | 1.1776 | 0.048* | |
H15C | 0.3886 | 0.8959 | 1.2022 | 0.048* | |
C16 | −0.0657 (3) | 0.6166 (3) | 0.8603 (2) | 0.0281 (6) | |
H16A | −0.1615 | 0.6395 | 0.8966 | 0.034* | |
H16B | 0.0026 | 0.6017 | 0.9333 | 0.034* | |
C17 | −0.0743 (3) | 0.4798 (3) | 0.7792 (3) | 0.0290 (6) | |
H17A | −0.1326 | 0.4995 | 0.7003 | 0.035* | |
H17B | −0.1227 | 0.4014 | 0.8292 | 0.035* | |
Br1 | 0.11699 (3) | 0.41341 (4) | 0.72890 (3) | 0.04547 (10) | |
O1 | 0.37137 (18) | 0.76784 (19) | 0.97365 (16) | 0.0221 (4) | |
O2 | 0.34641 (18) | 1.05261 (18) | 0.85662 (16) | 0.0241 (4) | |
O3 | 0.3660 (2) | 1.02082 (18) | 0.99572 (17) | 0.0234 (4) | |
O4 | 0.13965 (17) | 0.82985 (18) | 0.93755 (15) | 0.0225 (4) | |
O5 | −0.01788 (17) | 0.73579 (18) | 0.78053 (15) | 0.0235 (4) |
U11 | U22 | U33 | U12 | U13 | U23 | |
C1 | 0.0195 (11) | 0.0211 (16) | 0.0252 (11) | −0.0027 (9) | 0.0061 (9) | 0.0001 (10) |
C2 | 0.0186 (12) | 0.0237 (12) | 0.0298 (13) | 0.0011 (10) | 0.0059 (10) | −0.0033 (11) |
C3 | 0.0193 (10) | 0.0246 (12) | 0.0322 (12) | −0.0011 (13) | 0.0004 (9) | −0.0026 (14) |
C4 | 0.0208 (11) | 0.0207 (15) | 0.0292 (12) | 0.0039 (11) | −0.0004 (9) | −0.0050 (11) |
C5 | 0.0199 (12) | 0.0195 (12) | 0.0185 (12) | −0.0010 (10) | −0.0003 (10) | 0.0001 (10) |
C6 | 0.0187 (9) | 0.0162 (9) | 0.0250 (11) | −0.0016 (13) | 0.0032 (8) | −0.0007 (13) |
C7 | 0.0211 (11) | 0.0202 (12) | 0.0250 (13) | −0.0024 (9) | 0.0015 (10) | 0.0066 (10) |
C8 | 0.0266 (14) | 0.0357 (13) | 0.0255 (13) | −0.0069 (11) | 0.0003 (11) | 0.0059 (12) |
C9 | 0.0343 (15) | 0.0308 (14) | 0.0206 (13) | −0.0052 (11) | 0.0046 (11) | 0.0010 (11) |
C10 | 0.0322 (14) | 0.0241 (12) | 0.0243 (13) | −0.0034 (11) | 0.0078 (11) | −0.0021 (11) |
C11 | 0.0199 (12) | 0.0233 (12) | 0.0307 (14) | −0.0003 (10) | −0.0024 (11) | 0.0005 (11) |
C12 | 0.0174 (11) | 0.0239 (11) | 0.0277 (13) | −0.0015 (9) | 0.0029 (10) | −0.0020 (10) |
C13 | 0.0219 (13) | 0.0359 (16) | 0.0463 (17) | 0.0016 (11) | −0.0030 (12) | 0.0072 (14) |
C14 | 0.0356 (16) | 0.0446 (17) | 0.0331 (15) | 0.0036 (13) | 0.0099 (13) | −0.0098 (13) |
C15 | 0.0280 (12) | 0.0380 (19) | 0.0294 (13) | 0.0083 (11) | −0.0025 (10) | −0.0077 (12) |
C16 | 0.0265 (13) | 0.0291 (14) | 0.0287 (14) | −0.0081 (10) | 0.0059 (11) | 0.0050 (11) |
C17 | 0.0243 (12) | 0.0301 (13) | 0.0326 (14) | −0.0061 (11) | 0.0003 (11) | 0.0075 (11) |
Br1 | 0.03348 (15) | 0.03086 (14) | 0.0721 (2) | 0.00014 (15) | 0.00489 (12) | −0.00932 (17) |
O1 | 0.0188 (9) | 0.0213 (9) | 0.0262 (10) | 0.0004 (7) | −0.0008 (7) | 0.0009 (8) |
O2 | 0.0249 (9) | 0.0177 (8) | 0.0296 (10) | −0.0009 (7) | −0.0010 (8) | −0.0022 (7) |
O3 | 0.0239 (9) | 0.0236 (10) | 0.0228 (9) | 0.0051 (7) | 0.0001 (7) | −0.0055 (8) |
O4 | 0.0188 (8) | 0.0270 (9) | 0.0219 (8) | −0.0001 (7) | 0.0026 (7) | 0.0006 (7) |
O5 | 0.0195 (8) | 0.0254 (9) | 0.0255 (9) | −0.0045 (7) | 0.0014 (7) | 0.0030 (7) |
C1—C10 | 1.536 (3) | C9—H9B | 0.9900 |
C1—C2 | 1.538 (3) | C10—C14 | 1.539 (3) |
C1—C6 | 1.556 (3) | C10—H10 | 1.0000 |
C1—H1 | 1.0000 | C11—C12 | 1.515 (3) |
C2—C3 | 1.520 (3) | C11—C13 | 1.533 (4) |
C2—H2A | 0.9900 | C11—H11 | 1.0000 |
C2—H2B | 0.9900 | C12—O4 | 1.410 (3) |
C3—C4 | 1.535 (3) | C12—O5 | 1.420 (3) |
C3—H3A | 0.9900 | C12—H12 | 1.0000 |
C3—H3B | 0.9900 | C13—H13A | 0.9800 |
C4—O3 | 1.416 (3) | C13—H13B | 0.9800 |
C4—O1 | 1.435 (3) | C13—H13C | 0.9800 |
C4—C15 | 1.517 (3) | C14—H14A | 0.9800 |
C5—O1 | 1.404 (3) | C14—H14B | 0.9800 |
C5—O4 | 1.433 (3) | C14—H14C | 0.9800 |
C5—C6 | 1.523 (3) | C15—H15A | 0.9800 |
C5—H5 | 1.0000 | C15—H15B | 0.9800 |
C6—O2 | 1.467 (3) | C15—H15C | 0.9800 |
C6—C7 | 1.541 (3) | C16—O5 | 1.434 (3) |
C7—C8 | 1.528 (4) | C16—C17 | 1.502 (4) |
C7—C11 | 1.543 (4) | C16—H16A | 0.9900 |
C7—H7 | 1.0000 | C16—H16B | 0.9900 |
C8—C9 | 1.522 (4) | C17—Br1 | 1.949 (3) |
C8—H8A | 0.9900 | C17—H17A | 0.9900 |
C8—H8B | 0.9900 | C17—H17B | 0.9900 |
C9—C10 | 1.517 (4) | O2—O3 | 1.472 (2) |
C9—H9A | 0.9900 | ||
C10—C1—C2 | 110.89 (19) | C9—C10—C1 | 111.9 (2) |
C10—C1—C6 | 114.27 (19) | C9—C10—C14 | 110.0 (2) |
C2—C1—C6 | 112.98 (18) | C1—C10—C14 | 110.7 (2) |
C10—C1—H1 | 106.0 | C9—C10—H10 | 108.0 |
C2—C1—H1 | 106.0 | C1—C10—H10 | 108.0 |
C6—C1—H1 | 106.0 | C14—C10—H10 | 108.0 |
C3—C2—C1 | 115.91 (19) | C12—C11—C13 | 113.0 (2) |
C3—C2—H2A | 108.3 | C12—C11—C7 | 111.41 (19) |
C1—C2—H2A | 108.3 | C13—C11—C7 | 113.7 (2) |
C3—C2—H2B | 108.3 | C12—C11—H11 | 106.0 |
C1—C2—H2B | 108.3 | C13—C11—H11 | 106.0 |
H2A—C2—H2B | 107.4 | C7—C11—H11 | 106.0 |
C2—C3—C4 | 113.6 (2) | O4—C12—O5 | 111.26 (19) |
C2—C3—H3A | 108.8 | O4—C12—C11 | 111.38 (19) |
C4—C3—H3A | 108.8 | O5—C12—C11 | 109.76 (19) |
C2—C3—H3B | 108.8 | O4—C12—H12 | 108.1 |
C4—C3—H3B | 108.8 | O5—C12—H12 | 108.1 |
H3A—C3—H3B | 107.7 | C11—C12—H12 | 108.1 |
O3—C4—O1 | 108.64 (17) | C11—C13—H13A | 109.5 |
O3—C4—C15 | 104.26 (19) | C11—C13—H13B | 109.5 |
O1—C4—C15 | 107.6 (2) | H13A—C13—H13B | 109.5 |
O3—C4—C3 | 112.7 (2) | C11—C13—H13C | 109.5 |
O1—C4—C3 | 110.2 (2) | H13A—C13—H13C | 109.5 |
C15—C4—C3 | 113.08 (19) | H13B—C13—H13C | 109.5 |
O1—C5—O4 | 105.13 (17) | C10—C14—H14A | 109.5 |
O1—C5—C6 | 113.71 (18) | C10—C14—H14B | 109.5 |
O4—C5—C6 | 112.52 (18) | H14A—C14—H14B | 109.5 |
O1—C5—H5 | 108.4 | C10—C14—H14C | 109.5 |
O4—C5—H5 | 108.4 | H14A—C14—H14C | 109.5 |
C6—C5—H5 | 108.4 | H14B—C14—H14C | 109.5 |
O2—C6—C5 | 109.27 (16) | C4—C15—H15A | 109.5 |
O2—C6—C7 | 104.4 (2) | C4—C15—H15B | 109.5 |
C5—C6—C7 | 110.62 (18) | H15A—C15—H15B | 109.5 |
O2—C6—C1 | 105.43 (17) | C4—C15—H15C | 109.5 |
C5—C6—C1 | 114.0 (2) | H15A—C15—H15C | 109.5 |
C7—C6—C1 | 112.44 (17) | H15B—C15—H15C | 109.5 |
C8—C7—C6 | 111.4 (2) | O5—C16—C17 | 109.00 (18) |
C8—C7—C11 | 115.0 (2) | O5—C16—H16A | 109.9 |
C6—C7—C11 | 110.25 (19) | C17—C16—H16A | 109.9 |
C8—C7—H7 | 106.6 | O5—C16—H16B | 109.9 |
C6—C7—H7 | 106.6 | C17—C16—H16B | 109.9 |
C11—C7—H7 | 106.6 | H16A—C16—H16B | 108.3 |
C9—C8—C7 | 111.3 (2) | C16—C17—Br1 | 111.10 (18) |
C9—C8—H8A | 109.4 | C16—C17—H17A | 109.4 |
C7—C8—H8A | 109.4 | Br1—C17—H17A | 109.4 |
C9—C8—H8B | 109.4 | C16—C17—H17B | 109.4 |
C7—C8—H8B | 109.4 | Br1—C17—H17B | 109.4 |
H8A—C8—H8B | 108.0 | H17A—C17—H17B | 108.0 |
C10—C9—C8 | 111.6 (2) | C5—O1—C4 | 113.13 (18) |
C10—C9—H9A | 109.3 | C6—O2—O3 | 111.59 (16) |
C8—C9—H9A | 109.3 | C4—O3—O2 | 109.64 (16) |
C10—C9—H9B | 109.3 | C12—O4—C5 | 115.10 (17) |
C8—C9—H9B | 109.3 | C12—O5—C16 | 112.52 (17) |
H9A—C9—H9B | 108.0 | ||
C10—C1—C2—C3 | −170.2 (2) | C2—C1—C10—C14 | −59.8 (3) |
C6—C1—C2—C3 | −40.4 (3) | C6—C1—C10—C14 | 171.1 (2) |
C1—C2—C3—C4 | 57.3 (3) | C8—C7—C11—C12 | 75.3 (3) |
C2—C3—C4—O3 | −94.8 (3) | C6—C7—C11—C12 | −51.6 (3) |
C2—C3—C4—O1 | 26.8 (3) | C8—C7—C11—C13 | −53.7 (3) |
C2—C3—C4—C15 | 147.3 (2) | C6—C7—C11—C13 | 179.4 (2) |
O1—C5—C6—O2 | −56.7 (2) | C13—C11—C12—O4 | −176.3 (2) |
O4—C5—C6—O2 | 62.7 (2) | C7—C11—C12—O4 | 54.3 (3) |
O1—C5—C6—C7 | −171.20 (19) | C13—C11—C12—O5 | 60.0 (3) |
O4—C5—C6—C7 | −51.8 (3) | C7—C11—C12—O5 | −69.4 (2) |
O1—C5—C6—C1 | 60.9 (2) | O5—C16—C17—Br1 | 68.7 (2) |
O4—C5—C6—C1 | −179.69 (19) | O4—C5—O1—C4 | −93.8 (2) |
C10—C1—C6—O2 | −159.21 (19) | C6—C5—O1—C4 | 29.7 (3) |
C2—C1—C6—O2 | 72.8 (2) | O3—C4—O1—C5 | 32.8 (2) |
C10—C1—C6—C5 | 80.9 (2) | C15—C4—O1—C5 | 145.10 (19) |
C2—C1—C6—C5 | −47.1 (3) | C3—C4—O1—C5 | −91.2 (2) |
C10—C1—C6—C7 | −46.0 (3) | C5—C6—O2—O3 | 18.1 (2) |
C2—C1—C6—C7 | −174.0 (2) | C7—C6—O2—O3 | 136.50 (16) |
O2—C6—C7—C8 | 163.64 (17) | C1—C6—O2—O3 | −104.81 (18) |
C5—C6—C7—C8 | −78.9 (2) | O1—C4—O3—O2 | −72.2 (2) |
C1—C6—C7—C8 | 49.8 (3) | C15—C4—O3—O2 | 173.27 (17) |
O2—C6—C7—C11 | −67.5 (2) | C3—C4—O3—O2 | 50.3 (2) |
C5—C6—C7—C11 | 50.0 (3) | C6—O2—O3—C4 | 42.6 (2) |
C1—C6—C7—C11 | 178.7 (2) | O5—C12—O4—C5 | 65.7 (2) |
C6—C7—C8—C9 | −56.9 (3) | C11—C12—O4—C5 | −57.1 (2) |
C11—C7—C8—C9 | 176.8 (2) | O1—C5—O4—C12 | −179.24 (18) |
C7—C8—C9—C10 | 59.5 (3) | C6—C5—O4—C12 | 56.5 (2) |
C8—C9—C10—C1 | −54.3 (3) | O4—C12—O5—C16 | 62.4 (2) |
C8—C9—C10—C14 | −177.7 (2) | C11—C12—O5—C16 | −173.86 (19) |
C2—C1—C10—C9 | 177.06 (19) | C17—C16—O5—C12 | −167.5 (2) |
C6—C1—C10—C9 | 48.0 (3) |
D—H···A | D—H | H···A | D···A | D—H···A |
C15—H15B···O2i | 0.98 | 2.50 | 3.434 (3) | 159 |
C16—H16A···O3ii | 0.99 | 2.46 | 3.285 (3) | 141 |
C17—H17B···O4ii | 0.99 | 2.50 | 3.282 (3) | 136 |
Symmetry codes: (i) −x+1, y−1/2, −z+2; (ii) −x, y−1/2, −z+2. |
Experimental details
Crystal data | |
Chemical formula | C17H27BrO5 |
Mr | 391.30 |
Crystal system, space group | Monoclinic, P21 |
Temperature (K) | 173 |
a, b, c (Å) | 9.2836 (2), 9.1103 (2), 10.2999 (2) |
β (°) | 90.395 (1) |
V (Å3) | 871.11 (3) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 2.38 |
Crystal size (mm) | 0.44 × 0.41 × 0.08 |
Data collection | |
Diffractometer | Bruker APEXII CCD |
Absorption correction | Integration (XPREP; Bruker, 2005) |
Tmin, Tmax | 0.420, 0.832 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 13762, 4196, 3432 |
Rint | 0.068 |
(sin θ/λ)max (Å−1) | 0.661 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.034, 0.078, 0.95 |
No. of reflections | 4196 |
No. of parameters | 211 |
No. of restraints | 1 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.61, −0.35 |
Absolute structure | Flack (1983), 1966 Friedel pairs |
Absolute structure parameter | −0.012 (7) |
Computer programs: APEX2 (Bruker, 2005), SAINT (Bruker, 2005), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), ORTEP-3 for Windows (Farrugia, 1997) and SCHAKAL99 (Keller, 1999), WinGX (Farrugia, 1999) and PLATON (Spek, 2009).
D—H···A | D—H | H···A | D···A | D—H···A |
C15—H15B···O2i | 0.98 | 2.50 | 3.434 (3) | 159 |
C16—H16A···O3ii | 0.99 | 2.46 | 3.285 (3) | 141 |
C17—H17B···O4ii | 0.99 | 2.50 | 3.282 (3) | 136 |
Symmetry codes: (i) −x+1, y−1/2, −z+2; (ii) −x, y−1/2, −z+2. |
Acknowledgements
This work was supported by the National Research Foundation, North-West University and the University of the Witwatersrand.
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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.
Malaria is one of the top three priority diseases of the WHO and is becoming a worldwide threat because of its wide spread resistance to current anti-malaria drugs (World Health Organization, 2008). Artemisinin and its derivatives currently represent the most effective group of compounds against multidrug-resistant malaria with a rapid onset of action and a short half life. However, when artemisinin analogs are used as monotherapy it results in significant recrudescence (Ploypradith, 2004). Therefore it is recommended by the WHO that all uncomplicated P. falciparum infections should be treated with an artemisinin-based combination therapy (ACT).
When DHA is prepared from artemisinin by reduction, it exists as a mixture of α- and β-isomers. Luo and co-workers (Luo et al. 1984) determined that these isomers can exist in two conformations of ring D, a half-chair form and a half-boat form. DEB was tested in vitro against Plasmodium falciparum sensitive (D10) and resistant (Dd2) strains, but did not show any improved activity with respect to the reference drug: dihydroartemisinin (DHA).
The title compound, C17H27BrO5 or 2-(10β-dihydroartemisinoxy)ethylbromide (DEB), is a derivative of artemisinin. DEB was synthesized from the reaction of DHA with bromoethanol. DHA was supplied as a mixture of anomers. With the formation of DEB the OR-group at C12 is positioned cis to the CH3-group at C11 and axially oriented on ring D. Therefore, DEB can be assigned to the β-chair series. The rings in the title compound have also been previously labeled as rings A, B, C and D (scheme). Ring A has a twist boat conformation with puckering parameters (Cremer & Pople, 1975) Q, θ and φ of 0.739 (2), 94.21 (15)° and 274.46 (16)°, respectively (Fig. 1). Ring B has a distorted boat conformation and ring C is in a slightly distorted chair conformation with puckering parameters Q, θ and φ of 0.539 (3), 8.6 (3)° and 195.6 (18)°. Ring D is in a chair conformation with puckering parameters Q, θ and φ of 0.532 (2), 178.2 (3)° and 73 (11)°. Crystal packing in DEB is stabilized by a several C—H···O weak intermolecular interactions (Table 1) some of which are shown in Fig 2. These combine to form a C—H—O bonded network parallel to (001).