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5. Lin, A. J.; Miller, R. E. J. Med. Chem. 1995, 38, 764.
6. Genovese, R. F.; Newman, D. B.; Brewer, T. G. Pharmacol. Biochem. Behav. 2000,
67, 37.
Proliferation inhibition assay against various cancer cell lines
Growth inhibition concentration against cancer cells (GI50a,
lM)
DLD-1
U87
Hela
SiHa
A172
B16
7. Lee, S. Mini Rev. Med. Chem. 2007, 7, 411.
8. Oh, S.; Jeong, I. H.; Shin, W. S.; Lee, S. Bioorg. Med. Chem. Lett. 2003, 13, 3665.
9. Oh, S.; Jeong, I. H.; Ahn, C. M.; Shin, W. S.; Lee, S. Bioorg. Med. Chem. 2004, 12,
3783.
5
6
7
8a
9a
10a
10b
10c
10d
10e
10f
10g
10h
Taxol
>50
9.44
>50
11.23
1.97
1.06
2.86
0.23
0.43
0.11
0.34
0.16
0.83
0.08
1.22
0.14
0.02
>50
0.49
9.07
1.13
1.47
3.22
0.26
0.54
0.15
0.35
0.15
1.13
0.09
0.35
0.20
0.03
16.81
2.31
0.89
2.50
0.22
0.45
0.33
0.42
0.37
1.31
0.10
1.21
0.29
0.01
>50
>50
1.56
1.93
0.72
0.13
0.21
0.05
0.60
0.08
0.31
0.03
0.56
0.14
0.02
10. Torok, D.; Ziffer, H. Tetrahedron Lett. 1995, 36, 829.
29.67
0.52
12.10
0.08
0.14
14.22
23.01
0.03
6.68
22.92
0.01
8.78
0.30
1.25
0.24
0.43
0.06
1.32
0.08
0.90
0.16
0.01
11. Torok, D.; Ziffer, H.; Meshinick, S. R.; Pan, X.-Q. J. Med. Chem. 1995, 38, 5045.
12. Haynes, R. K.; Wong, H. N.; Lee, K. W.; Lung, C. M.; Shek, L. Y.; Williams, I. D.;
Croft, S. L.; Vivas, L.; Rattray, L.; Stewart, L.; Wong, V. K.; Ko, B. C.
ChemMedChem 2007, 51, 1852.
13. Haynes, R. K.; Fugmann, B.; Stetter, J.; Rieckmann, K.; Heilmann, H. D.; Chan, H.
W.; Cheung, M. K.; Lam, W. L.; Wong, H. N.; Croft, S. L.; Vivas, L.; Rattray, L.;
Stewart, L.; Peters, W.; Robinson, B. L.; Edstein, M. D.; Kotecka, B.; Kyle, D. E.;
Beckermann, B.; Gerisch, M.; Radtke, M.; Schmuck, G.; Steinke, W.; Wollborn,
U.; Schmeer, K.; Römer, A. Angew. Chem. Int. Ed. Engl. 2006, 45, 2082.
14. Huisgen, R.; Guenter, S.; Leander, M. Chem. Berl. 1967, 100, 2494.
15. Tron, G. C.; Pirali, T.; Billington, R. A.; Canonico, P. L.; Sorba, G.; Genazzani, A. A.
Med. Res. Rev. 2008, 28, 278.
a
GI50 values were calculated from nonlinear regression using GraphPad Prism
16. Kolb, H. C.; Sharpless, K. B. Drug Discov. Today 2003, 8, 1128.
17. Chittaboina, S.; Xie, F.; Wang, Q. Tetrahedron Lett. 2005, 46, 2331.
18. Wilkinson, B. L.; Bornaghi, L. F.; Poulsen, S.-A.; Houston, T. A. Tetrahedron 2006,
62, 8115.
software. (R2 > 0.95).
19. Chorki, F.; Crousse, B.; Bonnet-Deipon, D.; Bégué, J. P.; Brigaud, T.; Portella, C.
Tetrahedron Lett. 2001, 42, 1487.
20. Chorki, F.; Grellepois, F.; Crousse, B.; Ourévitch, M.; Bonnet-Deipon, D.; Bégué,
J. P. J. Org. Chem. 2001, 66, 7858.
In order to evaluate the cytotoxicity of the synthetic 10-substi-
tuted triazolylartemisinin library, we tested the cell proliferation
inhibitory activity of these derivatives against cancer cell lines
such as DLD-1, U-87, Hela, SiHa, A172, and B1627 using the MTT
colorimetric method.28 These results are summarized in Table 1.
To begin with, we found that the inhibitory effects of 5, 6, and 7
(at micromolar concentrations) differed with the type of cancer cell
line, but their antiproliferation effects against cancer cells in-
creased far when considering that the anticancer activity of arte-
misinin and dihydroartemisinin is quite weak.29,30 Although the
mechanism underlying the antiproliferative effect was not clear,
we could improve their biological properties by introducing a
nitrogen atom at the C-10 position. As expected, via the Huisgen
1,3-dipolar cylcoaddition reaction, we could successfully synthe-
size 10-substituted triazolylartemisinins with an additional bind-
ing group at C-10 and remarkably improved cytotoxicity. The
21. Lee, S.; Oh, S. Tetrahedron Lett. 2002, 43, 2891.
22. Spectral data for 5: 1H NMR(300 MHz, CDCl3) d 5.51(1H, s, H-12), 5.30(1H, d,
J = 7.6 Hz, H-10), 2.31(1H, m), 2.03(1H, td, J = 14.6, 4.0 Hz), 2.05(1H, m),
1.44(3H, s, 3-CH3), 0.96(3H, d, J = 6.2 Hz, 9-CH3), 0.90(3H, d, J = 6.4 Hz, 6-
CH3)ppm; 13C NMR(75 MHz, CDCl3) d 103.0, 90.3, 89.9, 81.8, 51.5, 46.6, 40.6,
37.3, 36.4, 34.1, 31.5, 25.8, 24.7, 19.9, 19.3 ppm; for 6: 1H NMR(300 MHz,
CDCl3) d 5.54(1H, s, H-12), 5.37(1H, d, J = 4.0 Hz, H-10), 2.72(1H, m), 2.37(1H,
td, J = 14.6, 4.1 Hz), 1.92(1H, m), 1.43(3H, s, 3-CH3), 1.16(3H, d, J = 7.1 Hz, 9-
CH3), 0.96(3H, d, J = 5.8 Hz, 6-CH3)ppm; 13C NMR(75 MHz, CDCl3) d 104.5, 91.8,
88.6, 80.7, 52.5, 44.1, 37.3, 36.3, 34.5, 30.2, 26.0, 24.6, 23.5, 20.3, 13.2 ppm; for
7: 1H NMR(300 MHz, CDCl3) d 5.39(1H, s, H-12), 4.61(1H, d, J = 10.2 Hz, H-10),
2.42(1H, m), 2.37(1H, m), 2.04(1H, m), 1.45(3H, s, 3-CH3), 0.97(3H, d, J = 5.9 Hz,
9-CH3), 0.92(3H, d, J = 7.1 Hz, 6-CH3)ppm; 13C NMR(75 MHz, CDCl3) d 104.5,
91.7, 87.7, 80.0, 51.6, 45.2, 37.3, 36.1, 34.0, 32.5, 25.9, 24.7, 21.7, 20.2,
12.9 ppm.
23. Sivakumar, K.; Xie, F.; Cash, B. M.; Long, S.; Barnhill, H. N.; Wang, Q. Org. Lett.
2004, 6, 4603.
24. Lee, B.-Y.; Park, S. R.; Jeon, H. B.; Kim, K. S. Tetrahedron Lett. 2006, 47, 5105.
25. Spectral data for 10a: 1H NMR(300 MHz, CDCl3) d 8.10(1H, s, triazol), 7.88(2H,
d, J = 7.0 Hz, phenyl), 7.44(2H, t, J = 7.1 Hz, phenyl), 7.34(H, t, J = 7.3 Hz,
phenyl), 5.95(1H, d, J = 10.7 Hz, H-10), 5.58(1H, s, H-12), 2.87(1H, m),
2.44(1H, td, J = 14.5, 3.8 Hz), 2.08(1H, m), 1.66(3H, s, 3-CH3), 1.01(3H, d,
J = 5.9 Hz, 9-CH3), 0.70(3H, d, J = 7.1 Hz, 6-CH3)ppm; 13C NMR(75 MHz, CDCl3) d
148.4, 130.5, 128.8, 128.2, 125.8, 117.1, 104.8, 92.1, 85.9, 78.0, 51.5, 45.5, 37.3,
36.1, 33.9, 33.8, 25.8, 24.6, 21.5, 20.1, 12.3 ppm; 10b: 1H NMR(300 MHz, CDCl3)
d 8.05(1H, s, triazol), 7.77(2H, d, J = 8.1 Hz, phenyl), 7.24(2H, d, J = 7.9 Hz,
phenyl), 5.93(1H, d, J = 10.7 Hz, H-10), 5.58(1H, s, H-12), 2.87(1H, m), 2.44(1H,
td, J = 14.4, 3.8 Hz), 2.38(3H, s, toluyl), 2.10(1H, m), 1.60(3H, s, 3-CH3), 1.01(3H,
d, J = 5.9 Hz, 9-CH3), 0.71(3H, d, J = 7.1 Hz, 6-CH3)ppm; 13C NMR(75 MHz,
CDCl3) d 138.0, 129.5, 127.8, 125.7, 116.8, 104.8, 92.1, 85.9, 78.0, 51.5, 45.5,
37.4, 36.1, 34.0, 33.9, 25.8, 24.6, 21.6, 21.3, 20.1, 12.3 ppm; 10c: 1H
NMR(300 MHz, CDCl3) d 8.06(1H, s, triazol), 7.85(2H, m, phenyl), 7.13(2H, t,
J = 8.8 Hz, phenyl), 5.94(1H, d, J = 10.7 Hz, H-10), 5.58(1H, s, H-12), 2.86(1H, m),
2.44(1H, td, J = 14.5, 3.8 Hz), 2.08(1H, m), 1.45(3H, s, 3-CH3), 1.01(3H, d,
J = 5.9Hz, 9-CH3), 0.71(3H, d, J = 7.1 Hz, 6-CH3)ppm; 13C NMR(75 MHz, CDCl3) d
161.1, 147.5, 127.6, 127.5, 116.9, 115.9, 115.6, 104.8, 92.1, 85.9, 79.9, 51.5,
45.4, 37.3, 36.1, 33.9, 29.7, 25.7, 24.6, 21.5, 20.1, 12.3 ppm; 10d: 1H
NMR(300MHz, CDCl3) d 8.11(1H, s, triazol), 7.89(1H, t, J = 1.7 Hz, phenyl),
7.77(1H, dt, J = 7.4, 1.5Hz, phenyl), 7.37(1H, t, J = 7.9 Hz, phenyl), 7.31(1H, t,
J = 1.5 Hz, phenyl), 5.95(1H, d, J = 10.8 Hz, H-10), 5.58(1H, s, H-12), 2.86(1H, m),
2.44(1H, td, J = 14.5, 3.8 Hz), 2.08(1H, m), 1.45(3H, s, 3-CH3), 1.01(3H, d,
J = 5.9 Hz, 9-CH3), 0.70(3H, d, J = 7.1 Hz, 6-CH3)ppm; 13C NMR(75 MHz, CDCl3) d
147.1, 134.8, 132.3, 130.1, 128.2, 125.9, 123.9, 117.6, 104.9, 92.2, 86.0, 79.9,
51.5, 45.6, 37.3, 36.1, 34.0, 33.9, 25.8, 24.6, 21.5, 20.2, 12.3 ppm; 10e: 1H
NMR(300 MHz, CDCl3) d 7.80(1H, s, triazol), 5.90(1H, d, J = 10.7 Hz, H-10),
5.77(1H, broad s, vinyl), 5.56(1H, s, H-12), 5.12(1H, broad s, vinyl), 2.82(1H, m),
2.43(1H, td, J = 14.6, 3.8 Hz), 2.16(3H, s, triazol-CH3), 2.04(1H, m), 1.44(3H, s, 3-
CH3), 1.01(3H, d, J = 5.9 Hz, 9-CH3), 0.67(3H, d, J = 7.1 Hz, 6-CH3)ppm; 13C
NMR(75 MHz, CDCl3) d 133.5, 112.8, 104.8, 92.1, 85.8, 80.0, 51.5, 45.5, 37.4,
36.1, 34.0, 33.8, 29.7, 25.8, 24.6, 21.6, 20.7, 20.2, 12.3 ppm; 10f: 1H
NMR(300 MHz, CDCl3) d 8.05(1H, s, triazol), 7.78(2H, d, J = 8.3 Hz, phenyl),
7.26(2H, d, J = 8.4 Hz, phenyl), 5.93(1H, d, J = 10.6 Hz, H-10), 5.58(1H, s, H-12),
2.86(1H, m), 2.63(2H, t, J = 7.5 Hz, benzyl), 2.44(1H, td, J = 13.2, 3.7 Hz),
2.10(1H, m), 1.48(3H, s, 3-CH3), 1.01(3H, d, J = 5.9 Hz, 9-CH3), 0.69(3H, d,
J = 7.1 Hz, 6-CH3)ppm; 13C NMR(75 MHz, CDCl3) d 148.5, 143.1, 128.9, 127.9,
125.7, 116.7, 104.8, 100.5, 92.1, 85.6, 79.9, 51.5, 45.5, 37.3, 36.1, 35.7, 33.9,
majority of the 10a-substituted triazolylartemisinins (10a–h) syn-
thesized in this study exhibited a strong growth inhibition effect
on cancer cell growth even at submicromolar concentrations. In
particular, the cytotoxicity of 10f, which has a pentylbenzene
group, was found to be comparable to that of taxol, positive control
drug. We could not confirm the structure–activity relationship
from the results of this study because we were unable establish a
complete library containing every possible diastereomer set of
the derivatives obtained from 5, 6, and 7; nevertheless, we can
state that triazolyl artemisinins will be promising candidates for
anticancer agents.
In conclusion, in vitro screening of 10-substituted triazolylar-
temisinins (synthesized by the Huisgen 1,3-dipolar cylcoaddition
of diastereomeric 10-azidoartemisinin with various acetylenes)
for their proliferation inhibitory effect revealed the strong antican-
cer activity of some of these derivatives. Further research is cur-
rently underway for establishing a complete library that includes
all possible diastereomers synthesized from 5 and 6.
Acknowledgment
This research was supported by a grant from the Marine
Biotechnology Program funded by the Ministry of Land, Transport
and Maritime Affairs, Republic of Korea.
References and notes
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