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ISSN: 2056-9890

5,3′-Dihydr­­oxy-7,4′-di­meth­oxy­flavanone from Artemisia sphaerocephala Kraschen

aMedical College of Henan University, Henan University, Kaifeng 475004, People's Republic of China
*Correspondence e-mail: ysum@yahoo.cn

(Received 6 April 2008; accepted 6 April 2008; online 10 April 2008)

The title compound, C17H16O6, was isolated from the Chinese Tibetan medicinal plant Artemisia sphaerocephala Kraschen. The mol­ecular conformation is consolidated by two intra­molecular O—H⋯O hydrogen bonds. A further inter­molecular O—H⋯O hydrogen bond leads to chains along [010] in the crystal structure.

Related literature

For background, see: Zhao et al. (2007[Zhao, D. B., Li, L. X., Liu, X. H., Li, M. J. & Wang, W. L. (2007). Chin. Chem. Lett. 18, 551-557.]).

[Scheme 1]

Experimental

Crystal data
  • C17H16O6

  • Mr = 316.30

  • Monoclinic, P 21

  • a = 5.4234 (12) Å

  • b = 9.293 (2) Å

  • c = 14.940 (3) Å

  • β = 91.039 (2)°

  • V = 752.9 (3) Å3

  • Z = 2

  • Mo Kα radiation

  • μ = 0.11 mm−1

  • T = 296 (2) K

  • 0.22 × 0.18 × 0.12 mm

Data collection
  • Bruker SMART APEX CCD diffractometer

  • Absorption correction: multi-scan (SADABS; Bruker, 2001[Bruker (2001). SAINT-Plus (Version 6.45), SMART and SADABS. Bruker AXS, Inc., Madison, Wisconsin, USA.]) Tmin = 0.977, Tmax = 0.987

  • 7958 measured reflections

  • 1581 independent reflections

  • 1489 reflections with I > 2σ(I)

  • Rint = 0.019

Refinement
  • R[F2 > 2σ(F2)] = 0.028

  • wR(F2) = 0.077

  • S = 1.06

  • 1581 reflections

  • 212 parameters

  • 1 restraint

  • H-atom parameters constrained

  • Δρmax = 0.11 e Å−3

  • Δρmin = −0.14 e Å−3

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
O3—H3⋯O2 0.82 1.85 2.579 (2) 148
O6—H5⋯O5 0.82 2.18 2.640 (2) 116
O6—H5⋯O4i 0.82 2.29 2.892 (2) 130
Symmetry code: (i) [-x, y+{\script{1\over 2}}, -z].

Data collection: SMART (Bruker, 2001[Bruker (2001). SAINT-Plus (Version 6.45), SMART and SADABS. Bruker AXS, Inc., Madison, Wisconsin, USA.]); cell refinement: SAINT-Plus (Bruker, 2001[Bruker (2001). SAINT-Plus (Version 6.45), SMART and SADABS. Bruker AXS, Inc., Madison, Wisconsin, USA.]); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); molecular graphics: PLATON (Spek, 2003[Spek, A. L. (2003). J. Appl. Cryst. 36, 7-13.]); software used to prepare material for publication: PLATON.

Supporting information


Comment top

As part of the ongoing investigations of the Chinese Tibetan medicinal plant Artemisia sphaerocephala Kraschen (Zhao et al., 2007), we now report the isolation and structure of the flavone-related title compound, (I).

Compound (I) consists of three-ring system, including a phenyl ring and a benzopyrone fused ring (Fig.1). The C–O bond distances range from 1.239 (2) to 1.453 (2) Å, in which C4–O2 [1.239 (2) Å] is typical for a C=O double-bond. The S(6) ring of O1/C2/C3/C4/C9/C10 in (I) is nonplanar, charactrtized by a O1–C2–C3–C4 torsion angle of 52.9 (2) °. Atom C2 is chiral, but the absolute structure of (I) could not be established from the present experiment. The dihedral angle between the aromatic ring planes is 77.26 (9) °.

Two intramolecular O-H···O hydrogen bonds (Table 1) help to establish the molecular conformation, both constructing S(6) rings. In addition, an intermolecular O-H···O link leads to [010] chains in the crystal (Fig. 2).

Related literature top

For background, see: Zhao et al. (2007).

Experimental top

The air-dried whole plant (5.1 kg) was ground into powder and extracted three times with 95% EtOH for 3 h each time. The concentrated extract was dispersed in water and partitioned successively with petroleum ether, CHCl3, EtOAC and n-BuOH. The chloroform fraction (115 g) was subjected to silics gel with petroleum ether-acetone (9:1) to yield two fractions (Frs. 1–2). Fraction 2 (50 g) was subjected to silics gel with petroleum ether-EtOAC (50:1, 45:1, 40:1, 30:1) to yield six fractions. After a week, the crude title compound (20 mg) was crystallized from the fourth fraction. After recrystallization from petroleum ether-EtOAC, colourless blocks of (I) arose, with a melting point of 475 K. The molecular formula, C17H16O6, was established by ESIMS m/z:316(M+). Spectroscopic analysis, 1H NMR (400 MHz, DMSO-d6) δ: 12.15 (1H, s), 6.08 (1H, d, J=2.2 Hz), 6.05 (1H, d, J=2.2 Hz), 5.47 (1H, dd, J=12.6 Hz, 3.0 Hz), 3.20 (1H, dd, J=15.5 Hz, 12.6 Hz), 2.82 (1H, dd, J=15.5 Hz, 3.0 Hz); 13 C NMR (400 MHz, DMSO-d6) δ: 197.0 (C-4), 168.0 (C-7), 163.8 (C-5), 163.1 (C-9), 147.8 (C-4'), 146.7 (C-3'), 131.8 (C-1'), 117.9 (C-6'), 113.5 (C-5'), 111.3 (C-2'), 102.9 (C-10), 94.6 (C-6), 93.7 (C-8), 79.0 (C-2), 42.6 (C-3), 55.4 (4'-OCH3), 55.3 (7-OCH3).

Refinement top

Anomalous dispersion was negligible and Friedel pairs were merged before refinement.

The H atoms were geometrically placed (C-H = 0.93–0.98Å, O—H = 0.82 Å), and refined as riding with Uiso(H)=1.2Ueq(C) or Uiso(H)=1.5Ueq(O or methyl C).

Computing details top

Data collection: SMART (Bruker, 2001); cell refinement: SAINT (Bruker, 2001); data reduction: SAINT (Bruker, 2001); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2003); software used to prepare material for publication: PLATON (Spek, 2003).

Figures top
[Figure 1] Fig. 1. The molecular structure of (I), with displacement ellipsoids for the non-hydrogen atoms drawn at the 40% probability level. Hydrogen bonds are shown as double dashed lines.
[Figure 2] Fig. 2. Fragment of the one-dimensional chain structure of (I) with hydrogen bonds shown as dashed lines.
5,3'-Dihydroxy-7,4'-dimethoxyflavanone top
Crystal data top
C17H16O6F(000) = 332
Mr = 316.30Dx = 1.395 Mg m3
Monoclinic, P21Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2y bCell parameters from 4047 reflections
a = 5.4234 (12) Åθ = 2.6–27.5°
b = 9.293 (2) ŵ = 0.11 mm1
c = 14.940 (3) ÅT = 296 K
β = 91.039 (2)°Block, colorless
V = 752.9 (3) Å30.22 × 0.18 × 0.12 mm
Z = 2
Data collection top
Bruker SMART APEX CCD
diffractometer
1581 independent reflections
Radiation source: fine-focus sealed tube1489 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.019
ϕ and ω scansθmax = 26.0°, θmin = 2.6°
Absorption correction: multi-scan
(SADABS; Bruker, 2001)
h = 66
Tmin = 0.977, Tmax = 0.987k = 1111
7958 measured reflectionsl = 1818
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.028Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.077H-atom parameters constrained
S = 1.06 w = 1/[σ2(Fo2) + (0.0485P)2 + 0.0531P]
where P = (Fo2 + 2Fc2)/3
1581 reflections(Δ/σ)max < 0.001
212 parametersΔρmax = 0.11 e Å3
1 restraintΔρmin = 0.14 e Å3
Crystal data top
C17H16O6V = 752.9 (3) Å3
Mr = 316.30Z = 2
Monoclinic, P21Mo Kα radiation
a = 5.4234 (12) ŵ = 0.11 mm1
b = 9.293 (2) ÅT = 296 K
c = 14.940 (3) Å0.22 × 0.18 × 0.12 mm
β = 91.039 (2)°
Data collection top
Bruker SMART APEX CCD
diffractometer
1581 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker, 2001)
1489 reflections with I > 2σ(I)
Tmin = 0.977, Tmax = 0.987Rint = 0.019
7958 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0281 restraint
wR(F2) = 0.077H-atom parameters constrained
S = 1.06Δρmax = 0.11 e Å3
1581 reflectionsΔρmin = 0.14 e Å3
212 parameters
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
O10.3993 (2)0.73089 (16)0.11833 (7)0.0443 (3)
O20.8292 (3)0.9824 (2)0.28305 (11)0.0697 (5)
O30.6055 (3)0.8761 (2)0.41875 (10)0.0703 (5)
H30.70860.92310.39190.105*
O40.0461 (3)0.54437 (19)0.35407 (9)0.0532 (4)
O50.5698 (3)0.79981 (18)0.28802 (9)0.0582 (4)
O60.2587 (3)0.94212 (19)0.18692 (9)0.0595 (4)
H50.27320.93770.24140.089*
C1'0.6333 (3)0.7757 (2)0.01135 (12)0.0396 (4)
C20.6447 (3)0.7700 (2)0.08935 (12)0.0407 (4)
H20.76050.69420.10790.049*
C2'0.8030 (4)0.7024 (2)0.06221 (12)0.0469 (5)
H2'0.92710.64940.03380.056*
C30.7244 (4)0.9111 (3)0.13314 (13)0.0509 (5)
H3A0.89460.93100.11850.061*
H3B0.62350.98890.10940.061*
C3'0.7904 (4)0.7070 (2)0.15510 (13)0.0508 (5)
H3'0.90560.65740.18860.061*
C40.7001 (4)0.9053 (2)0.23342 (13)0.0485 (5)
C4'0.6070 (4)0.7852 (2)0.19750 (12)0.0434 (4)
C50.4695 (4)0.7986 (2)0.35954 (12)0.0472 (5)
C5'0.4376 (3)0.8613 (2)0.14645 (12)0.0415 (4)
C60.2845 (4)0.7110 (3)0.39144 (12)0.0490 (5)
H60.25600.70470.45250.059*
C6'0.4503 (3)0.8559 (2)0.05446 (12)0.0439 (4)
H6'0.33590.90620.02100.053*
C70.1420 (3)0.6325 (2)0.33055 (12)0.0416 (4)
C7'0.7267 (6)0.7210 (3)0.34504 (14)0.0701 (7)
H7'A0.89430.75090.33500.105*
H7'B0.67980.73860.40630.105*
H7'C0.71200.62010.33240.105*
C80.1841 (3)0.6390 (2)0.23879 (12)0.0410 (4)
H80.08820.58520.19890.049*
C90.3691 (3)0.7260 (2)0.20815 (11)0.0373 (4)
C100.5161 (3)0.8091 (2)0.26731 (12)0.0413 (4)
C110.1037 (5)0.5297 (3)0.44657 (14)0.0660 (7)
H11A0.03530.48930.47840.099*
H11B0.24360.46730.45250.099*
H11C0.14130.62250.47100.099*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0462 (7)0.0580 (8)0.0285 (6)0.0111 (6)0.0003 (5)0.0007 (6)
O20.0826 (11)0.0731 (11)0.0531 (9)0.0365 (10)0.0075 (8)0.0084 (8)
O30.0893 (12)0.0821 (12)0.0389 (7)0.0298 (10)0.0109 (7)0.0116 (8)
O40.0558 (8)0.0709 (10)0.0330 (7)0.0121 (7)0.0052 (6)0.0056 (7)
O50.0790 (10)0.0625 (9)0.0332 (7)0.0170 (8)0.0059 (6)0.0006 (7)
O60.0639 (9)0.0755 (11)0.0391 (8)0.0270 (8)0.0006 (7)0.0045 (8)
C1'0.0429 (9)0.0412 (10)0.0346 (9)0.0019 (8)0.0026 (7)0.0034 (8)
C20.0407 (9)0.0457 (10)0.0357 (9)0.0013 (8)0.0004 (7)0.0048 (8)
C2'0.0465 (10)0.0504 (11)0.0438 (10)0.0109 (9)0.0036 (8)0.0073 (9)
C30.0557 (11)0.0530 (12)0.0440 (11)0.0138 (10)0.0009 (9)0.0023 (9)
C3'0.0552 (11)0.0531 (12)0.0446 (11)0.0140 (10)0.0117 (9)0.0014 (10)
C40.0525 (11)0.0484 (11)0.0443 (10)0.0106 (10)0.0054 (9)0.0026 (9)
C4'0.0561 (10)0.0409 (10)0.0334 (9)0.0030 (9)0.0069 (8)0.0024 (8)
C50.0568 (11)0.0521 (12)0.0326 (9)0.0008 (10)0.0075 (8)0.0051 (8)
C5'0.0443 (9)0.0430 (10)0.0372 (9)0.0055 (8)0.0010 (8)0.0040 (8)
C60.0597 (11)0.0605 (12)0.0267 (8)0.0003 (10)0.0001 (8)0.0005 (9)
C6'0.0465 (10)0.0484 (10)0.0370 (9)0.0089 (9)0.0075 (8)0.0013 (8)
C70.0422 (10)0.0491 (11)0.0335 (9)0.0010 (8)0.0014 (7)0.0047 (8)
C7'0.1016 (19)0.0707 (16)0.0385 (11)0.0154 (15)0.0164 (11)0.0066 (12)
C80.0409 (9)0.0494 (10)0.0326 (9)0.0038 (8)0.0039 (7)0.0016 (8)
C90.0405 (9)0.0424 (10)0.0290 (8)0.0004 (8)0.0028 (7)0.0007 (8)
C100.0450 (9)0.0443 (10)0.0346 (9)0.0016 (8)0.0031 (7)0.0011 (8)
C110.0706 (15)0.0886 (18)0.0393 (11)0.0062 (14)0.0133 (10)0.0150 (12)
Geometric parameters (Å, º) top
O1—C91.3555 (19)C3'—C4'1.377 (3)
O1—C21.453 (2)C3'—H3'0.9300
O2—C41.239 (2)C4—C101.439 (3)
O3—C51.350 (2)C4'—C5'1.397 (3)
O3—H30.8200C5—C61.383 (3)
O4—C71.359 (2)C5—C101.409 (3)
O4—C111.429 (2)C5'—C6'1.376 (2)
O5—C4'1.370 (2)C6—C71.390 (3)
O5—C7'1.419 (3)C6—H60.9300
O6—C5'1.360 (2)C6'—H6'0.9300
O6—H50.8200C7—C81.395 (2)
C1'—C2'1.383 (3)C7'—H7'A0.9600
C1'—C6'1.390 (3)C7'—H7'B0.9600
C1'—C21.506 (2)C7'—H7'C0.9600
C2—C31.525 (3)C8—C91.373 (3)
C2—H20.9800C8—H80.9300
C2'—C3'1.389 (3)C9—C101.409 (2)
C2'—H2'0.9300C11—H11A0.9600
C3—C41.507 (3)C11—H11B0.9600
C3—H3A0.9700C11—H11C0.9600
C3—H3B0.9700
C9—O1—C2115.53 (13)C6—C5—C10121.46 (17)
C5—O3—H3109.5O6—C5'—C6'119.12 (16)
C7—O4—C11119.06 (17)O6—C5'—C4'120.52 (16)
C4'—O5—C7'117.54 (18)C6'—C5'—C4'120.37 (17)
C5'—O6—H5109.5C5—C6—C7118.79 (17)
C2'—C1'—C6'119.09 (16)C5—C6—H6120.6
C2'—C1'—C2121.06 (16)C7—C6—H6120.6
C6'—C1'—C2119.86 (16)C5'—C6'—C1'120.31 (17)
O1—C2—C1'106.57 (13)C5'—C6'—H6'119.8
O1—C2—C3109.97 (16)C1'—C6'—H6'119.8
C1'—C2—C3113.88 (16)O4—C7—C6123.92 (16)
O1—C2—H2108.8O4—C7—C8114.67 (16)
C1'—C2—H2108.8C6—C7—C8121.40 (17)
C3—C2—H2108.8O5—C7'—H7'A109.5
C1'—C2'—C3'120.83 (17)O5—C7'—H7'B109.5
C1'—C2'—H2'119.6H7'A—C7'—H7'B109.5
C3'—C2'—H2'119.6O5—C7'—H7'C109.5
C4—C3—C2111.48 (16)H7'A—C7'—H7'C109.5
C4—C3—H3A109.3H7'B—C7'—H7'C109.5
C2—C3—H3A109.3C9—C8—C7119.13 (17)
C4—C3—H3B109.3C9—C8—H8120.4
C2—C3—H3B109.3C7—C8—H8120.4
H3A—C3—H3B108.0O1—C9—C8116.84 (16)
C4'—C3'—C2'119.86 (17)O1—C9—C10121.70 (16)
C4'—C3'—H3'120.1C8—C9—C10121.44 (15)
C2'—C3'—H3'120.1C5—C10—C9117.77 (17)
O2—C4—C10122.49 (18)C5—C10—C4121.68 (17)
O2—C4—C3121.02 (19)C9—C10—C4120.51 (16)
C10—C4—C3116.47 (17)O4—C11—H11A109.5
O5—C4'—C3'126.74 (17)O4—C11—H11B109.5
O5—C4'—C5'113.72 (17)H11A—C11—H11B109.5
C3'—C4'—C5'119.53 (16)O4—C11—H11C109.5
O3—C5—C6118.64 (17)H11A—C11—H11C109.5
O3—C5—C10119.90 (18)H11B—C11—H11C109.5
C9—O1—C2—C1'177.36 (16)C2'—C1'—C6'—C5'0.5 (3)
C9—O1—C2—C353.5 (2)C2—C1'—C6'—C5'179.73 (18)
C2'—C1'—C2—O1128.91 (19)C11—O4—C7—C60.2 (3)
C6'—C1'—C2—O151.3 (2)C11—O4—C7—C8179.76 (19)
C2'—C1'—C2—C3109.7 (2)C5—C6—C7—O4179.2 (2)
C6'—C1'—C2—C370.1 (2)C5—C6—C7—C80.8 (3)
C6'—C1'—C2'—C3'0.8 (3)O4—C7—C8—C9179.50 (18)
C2—C1'—C2'—C3'179.46 (18)C6—C7—C8—C90.6 (3)
O1—C2—C3—C452.9 (2)C2—O1—C9—C8155.13 (17)
C1'—C2—C3—C4172.44 (16)C2—O1—C9—C1026.5 (3)
C1'—C2'—C3'—C4'0.0 (3)C7—C8—C9—O1178.69 (17)
C2—C3—C4—O2154.3 (2)C7—C8—C9—C100.3 (3)
C2—C3—C4—C1027.3 (3)O3—C5—C10—C9180.00 (19)
C7'—O5—C4'—C3'3.6 (3)C6—C5—C10—C90.6 (3)
C7'—O5—C4'—C5'177.3 (2)O3—C5—C10—C42.5 (3)
C2'—C3'—C4'—O5179.8 (2)C6—C5—C10—C4176.9 (2)
C2'—C3'—C4'—C5'1.1 (3)O1—C9—C10—C5179.19 (17)
O5—C4'—C5'—O60.8 (3)C8—C9—C10—C50.9 (3)
C3'—C4'—C5'—O6178.4 (2)O1—C9—C10—C41.6 (3)
O5—C4'—C5'—C6'179.39 (18)C8—C9—C10—C4176.67 (19)
C3'—C4'—C5'—C6'1.4 (3)O2—C4—C10—C50.9 (3)
O3—C5—C6—C7179.2 (2)C3—C4—C10—C5177.44 (19)
C10—C5—C6—C70.2 (3)O2—C4—C10—C9178.4 (2)
O6—C5'—C6'—C1'179.19 (19)C3—C4—C10—C90.0 (3)
C4'—C5'—C6'—C1'0.6 (3)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O3—H3···O20.821.852.579 (2)148
O6—H5···O50.822.182.640 (2)116
O6—H5···O4i0.822.292.892 (2)130
Symmetry code: (i) x, y+1/2, z.

Experimental details

Crystal data
Chemical formulaC17H16O6
Mr316.30
Crystal system, space groupMonoclinic, P21
Temperature (K)296
a, b, c (Å)5.4234 (12), 9.293 (2), 14.940 (3)
β (°) 91.039 (2)
V3)752.9 (3)
Z2
Radiation typeMo Kα
µ (mm1)0.11
Crystal size (mm)0.22 × 0.18 × 0.12
Data collection
DiffractometerBruker SMART APEX CCD
diffractometer
Absorption correctionMulti-scan
(SADABS; Bruker, 2001)
Tmin, Tmax0.977, 0.987
No. of measured, independent and
observed [I > 2σ(I)] reflections
7958, 1581, 1489
Rint0.019
(sin θ/λ)max1)0.617
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.028, 0.077, 1.06
No. of reflections1581
No. of parameters212
No. of restraints1
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.11, 0.14

Computer programs: SMART (Bruker, 2001), SAINT (Bruker, 2001), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), PLATON (Spek, 2003).

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O3—H3···O20.821.852.579 (2)148
O6—H5···O50.822.182.640 (2)116
O6—H5···O4i0.822.292.892 (2)130
Symmetry code: (i) x, y+1/2, z.
 

References

First citationBruker (2001). SAINT-Plus (Version 6.45), SMART and SADABS. Bruker AXS, Inc., Madison, Wisconsin, USA.  Google Scholar
First citationSheldrick, G. M. (2008). Acta Cryst. A64, 112–122.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationSpek, A. L. (2003). J. Appl. Cryst. 36, 7–13.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationZhao, D. B., Li, L. X., Liu, X. H., Li, M. J. & Wang, W. L. (2007). Chin. Chem. Lett. 18, 551–557.  Web of Science CrossRef CAS Google Scholar

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