Synthesis and anticancer activity of novel amide derivatives of non-acetal deoxoartemisinin

Article abstract of DOI:10.1016/j.bmcl.2009.09.093

Novel amide derivatives of C-12 non-acetal deoxoartemisinin were synthesized. Some of the derivatives had potent in vitro anticancer activity against major human cancer cell lines. The deoxoartemisinin amide trimer had potent in vivo antiangiogenic activi

Full text of DOI:10.1016/j.bmcl.2009.09.093

Bioorganic & Medicinal Chemistry Letters 19 (2009) 6303–6306
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Synthesis and anticancer activity of novel amide derivatives of non-acetal
deoxoartemisinin
a
b
a
c
c
Mankil Jung a, , Namsoo Park , Hyung-In Moon , Yongnam Lee , Won-Yoon Chung , Kwang-Kyun Park
*
a Department of Chemistry, Yonsei University, Seoul 120-749, Republic of Korea
b Department of Neuroscience and Inam Neuroscience Research Center, Sanbon Medical Center, Wonkwang University, Kyunggido 435-040, Republic of Korea
c Department of Oral Biology, College of Dentistry, Yonsei University, Seoul 120-752, Republic of Korea
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 22 July 2009
Revised 10 September 2009
Accepted 24 September 2009
Available online 27 September 2009
Novel amide derivatives of C-12 non-acetal deoxoartemisinin were synthesized. Some of the derivatives
had potent in vitro anticancer activity against major human cancer cell lines. The deoxoartemisinin
amide trimer had potent in vivo antiangiogenic activity, according to the mouse matrigel plug assay.
Ó 2009 Elsevier Ltd. All rights reserved.
Keywords:
Anticancer activity
Deoxoartemisinin
Non-acetal type
Antiangiogenesis
Artemisinin (1a), a sesquiterpene isolated from Artemisia annua
L.,1 and its derivatives have been used clinically to treat drug-resis-
tant malaria.2 The pharmacology and pharmacokinetics of artemis-
inin and its derivatives have been well studied.3 Artemisinin
contains an endoperoxide that reacts with an iron ion to form a
carbon-based free radical. When formed intracellularly, this free
radical could cause macromolecular damage, leading to cell death.
Since tumor cells uptake a large amount of iron compared to nor-
mal cells,3g they are more vulnerable to the cytotoxic effect of arte-
misinin. As we describe previously,4 a variety of researchers have
reported on the potential antitumor properties of artemisinin and
its derivatives.5 Of the derivatives, some dimeric chemical struc-
tures exhibited the high anticancer activity.4a Non-acetal 12b(C–
C)-type derivatives of artemisinin exhibited higher anticancer
activity,4a along with 20 times more acid stability in oral adminis-
tration, than acetal (C–O)-type derivatives of artemisinin.4b Re-
cently, artemisinin has also been reported to have antiangiogenic
activity.6 Chen et al. reported that artesunate exhibits antiangio-
genesis, as well as apoptic activity in human endothelial cells.6b
In this study, we report on the synthesis of novel amide deriv-
atives of non-acetal deoxoartemisinin. These derivatives exhibit
in vitro anticancer activity against major human cancer cell lines,
and further in vivo antiangiogenic activity.
temisinin (1b), deoxoartemisinin (1c), artemether (1d), and 11-a-
13-bromodeoxoartemisinin (2a), all shown in Figure 1. The various
other derivatives ( 6–7, 9), shown in Figure 2, were prepared
according to the procedure described by Jung et al.4a,7 12-Carboxy-
ethyl deoxoartemisinin (2b) was also prepared from artemisinin,
as previously presented by the same authors.8
New amide derivatives 3, 4, 5 and 8 were prepared by reacting
2b with various amines, in the presence of HOBt and EDC as cou-
pling agents, as outlined in Scheme 1. The new amide derivatives9
3–5 and 8 were obtained in 64–87% yield. The 1,4-propylpiperi-
dine-linked dimer 8 was synthesized with the same coupling con-
ditions as the other derivatives, with the exception that 2 equiv of
compound 2b were used. In amide coupling conditions, the endo-
peroxide functional group remains intact.
O
O
O
O
O
O
H
H
11
11
O
O
12
Br
13
13
R
R'
1a: R, R'= O
2a
We synthesized previously reported4a,7 artemisinin derivatives
for comparison with new amide derivatives, including dihydroar-
1b: R=H, R'=OH
1c: R= R'= H
1d: R=H, R'=OCH3
* Corresponding author. Tel.: +82 2 2123 2648; fax: +82 2 364 7050.
E-mail address: mjung@yonsei.ac.kr (M. Jung).
Figure 1. Structure of artemisinin (1a), dihydroartemisinin (1b), deoxoartemisinin
(1c), artemether (1d) and 11- -13-bromodeoxo-artemisinin (2a).
a
0960-894X/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2009.09.093

6304
M. Jung et al. / Bioorg. Med. Chem. Lett. 19 (2009) 6303–6306
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
N
N
H
N
O
SH
5
3
4
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
NH
S
O
6
7
O
O
O
O
O
O
O
O
O
N
H
N
H
N
N
O
8
O
O
O
O
O
O
O
O
O
O
O
H
O
O
NH
H
H
N
N
O
O
9
Figure 2. Structure of amide and other derivatives of non-acetal type deoxoartemisinin.
To determine the in vitro anticancer activity of the amide deriv-
the mouse matrigel plug assay. Results are shown in Figures 3 and
atives and their dimers, a SRB (sulforhodamin B) assay was per-
4. Compound 2a and the amide trimer 9 showed excellent antian-
giogenic activity at 10 lM, with 95% and 80% inhibition, respec-
formed, as previously described.10
The results are listed in Table 1. The standard drug used for
comparison was doxorubicin. Although dihydroartemisinin 1b
exhibited high anticancer activity against all tested human cell
lines, its relative instability in acid, due to acetal formation at
C-12, rules it out as a potential anticancer drug candidate. Most
amide derivatives had high anticancer activity, although artemisi-
nin, 11-a-bromo-deoxoartemisinin 2a and amide trimer 9 showed
only moderate activity. Particularly, the low anticancer activity of
trimer 9 could be due to its low solubility.
In comparison, the sulfide dimer 7 showed anticancer activity
comparable to that of the amide derivatives. As shown in Table
1, dihydroartemisinin (1b), and the amide-linked dimer (8) had
high vitro anticancer activity. Furthermore, the HCl salt form of
the piperadine moiety on compound 8 increases its water solubil-
ity, making it suitable for injection.
tively, as shown in Figures 3 and 4. These results are comparable
to that of the (ꢀ)-thalidomide standard.
There is no direct correlation of the antiangiogenic and antican-
cer activities for this group of compounds. The results indicate
these high potent activities independently.
The proposed mechanism for the anticancer activity of artemis-
inin derivatives is alkylation to cellular proteins of carbon-centered
radical formed with homolytic cleavage of the endoperoxide bridge
catalyzed by Fe+2 ions, while that of the antiangiogenic activity is
unknown.
Therefore, we conclude that the trimer amide and 13-bromo-
deoxoartemisinin showed potent in vivo antiangiogenic activity,
although the in vitro anticancer activity was not as high as other
artemisinin derivatives.
In summary, non-acetal type amide derivatives of deoxoarte-
misinin and their novel derivatives were synthesized. Some of
the derivatives exhibited potent in vitro anticancer activity. Com-
pound 2a and the amide trimer 9 had very high in vivo antiangio-
Due to the potent ex vivo antiangiogenic activity (75–95%) of
11-
a-13-bromodeoxoartemisinin 2a, and the amide trimer 9, the
in vivo antiangiogenic activity of each derivative11 was tested with

M. Jung et al. / Bioorg. Med. Chem. Lett. 19 (2009) 6303–6306
6305
P<0.01
0.6
0.5
0.4
0.3
0.2
0.1
0
O
O
O
O
RNH2
O
O
1a
*
O
O
HOBt, EDC
O
COOH
R
2b
3-5, 8
P<0.05
*
*
R :
*
N
N
N
H
O
O
SH
3
4
5
VEGF(100ng/ml)
+
+
+
+
(a)
(b)
(c)
(d)
µ
(
M)
O
O
O
Figure 4. Inhibition of VEGF-induced angiogenesis by deoxoartemisinin amide
trimer (9) with mouse matrigel plug assay: (a) control; (b) 9: 5 M; (c) 9: 10 M;
(d) (ꢀ)-thalidomide: 10 M.
O
O
l
l
l
N
N
H
H
N
N
genic activity. We conclude that non-acetal 12b(C–C)-type amide
derivatives of deoxoartemisinin deserve further evaluation as pos-
sible anticancer drug candidates, because of their high acid stabil-
ity and low toxicity, coupled with high in vitro and in vivo
anticancer activity.
8
Scheme 1. Synthesis of novel amide derivatives (3–5, and 8) of deoxoartemisinin.
Table 1
In vitro anticancer activity of nonacetal type amide derivatives of deoxoartemisinin
on human cancer cell lines
Acknowledgements
Compds
IC50 values (lM)
This study was supported by a Grant of the Disease Oriented
Translational Research (DOTR) Project (A084166), the Ministry of
Health & Welfare, Republic of Korea. N.P. and Y.L. received fellow-
ships from the BK21 program of the Ministry of Education and Hu-
man Resources Development, the Republic of Korea.
A549
SK-V3
SK-MEL-2
XF498
HCT15
1a
1b
1d
2a
3
4
5
6
15.2
0.63
8.54
11.2
5.13
3.12
1.35
7.63
5.63
0.85
13.5
0.075
14.3
0.85
8.03
15.4
4.75
2.35
1.65
4.36
4.86
0.63
12.4
0.046
12.9
0.75
7.24
14.2
8.36
3.15
1.25
9.94
7.56
0.45
18.2
0.028
16.2
0.54
9.10
16.4
3.46
2.66
1.95
5.76
5.44
0.46
11.6
.0.35
17.2
0.46
9.66
11.2
6.22
1.54
1.45
7.83
3.53
0.84
19.8
0.037
References and notes
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8
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system tumor, HCT15: colon adenocarcinoma.
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P<0.002
1.4
1.2
1
0.8
0.6
0.4
0.2
0
*
P<0.01
*
*
*
9. All new compounds exhibited physical and spectroscopic properties consistent
with their structure.Spectral data for compound 3: Rf 0.22 (n-hexane/
VEGF(100ng/ml)
EtOAc = 5:1 v/v); ½a D24
ꢁ
¼ þ91:6 (c 0.095, CHCl3); 1H NMR (250 MHz, CDCl3) d
+
(a)
+
+
+
µ
(b)
(c)
(d)
(
M)
7.30 (m, 5H, aromatic), 6.06 (br s, 1H), 5.28 (s, 1H, C-5), 4.44 (d, 2H), 4.05
(m, 1H, C-12), 2.72 (m, 1H, C-11), 2.48 (m, 1H), 2.34 (m, 2H), 1.37 (s, 3H, C-15),
0.96 (d, 3H, C-14), 0.88 (d, 3H, C-13); 13C NMR (63 MHz, CDCl3) d 172.9, 138.4,
128.7, 128.7, 128, 128, 127.5, 103.5, 88.8, 81.2, 76.1, 52.5, 44.5, 43.8, 37.4, 36.6,
Figure 3. Inhibition of VEGF-induced angiogenesis by 11-
misinin (2a) with mouse matrigel plug assay: (a) control; (b) 2a: 5
10 M.
M; (d) (ꢀ)-thalidomide: 10
a
-13-bromodeoxo arte-
lM; (c) 2a:
34.7, 34.5, 30.2, 26.2, 25, 24.9, 24.7, 20.3, 13.3; IR (KBr, cmꢀ1
) m max 3460, 2913,
l
l

6306
M. Jung et al. / Bioorg. Med. Chem. Lett. 19 (2009) 6303–6306
2046, 1740, 1650, 1540, 1450, 1376, 1258, 1094, 1053, 1017, 874, 698, 526,
45.7, 44.7, 43.1, 42.1, 38.4, 37.4, 36.6, 34.5, 32.6, 31.9, 31.4, 30.2, 26.3, 24.9,
24.7, 24.5, 20.4, 13.5; IR (KBr, cmꢀ1
max 3293, 2917, 2843, 2651, 1985, 1732,
457; MALDI-TOF MS: found 430.2171 [(M+H)+]. For compound 4: Rf 0.37
) m
(n-hexane/EtOAc = 1:1 v/v); ½a D24
ꢁ
¼ þ100 (c 0.03, CHCl3); 1H NMR (250 MHz,
1638, 1450, 1376, 1258, 1094, 1049, 1012, 910, 878, 767, 632, 481; MALDI-TOF
CDCl3) d 7.30 (m, 5H, aromatic), 6.29 (d, 1H), 5.29 (s. 1H, C-5), 4.80 (m, 1H), 4.05
(m, 1H, C-12), 3.74 (s, 3H), 3.71 (s, 2H), 2.97 (d, 2H), 1.40 (s, 3H, C-15), 0.95 (d,
3H, C-14), 0.89 (d, 3H, C-13); 13C NMR (63 MHz, CDCl3) d 172.8, 171.5, 137.8,
129, 129, 128.7, 128.7, 127.4, 103.5, 88.7, 81.2, 76.2, 55.1, 52.7, 52.5, 51.6, 44.6,
MS: found 498.2810 [(M+H)+]. For compound 8: Rf 0.42 (only MeOH v/v);
½
a 2D4
ꢁ
¼ þ204 (c 0.025, CHCl3); 1H NMR (250 MHz, CDCl3) d 6.89 (br s, 1H), 5.29
(s, 1H, C-5), 4.04 (m, 1H, C-12), 3.27 (m, 2H), 2.75 (m, 1H, C-11), 1.47 (s, 3H,
C-15), 0.96 (d, 3H, C-14), 0.86 (d, 3H, C-13); 13C NMR (63 MHz, CDCl3) d 172.8,
103.4, 100.1, 88.7, 81.3, 76.3, 57.3, 53.4, 52.5, 44.6, 39.3, 37.4, 36.6, 34.9, 34.5,
37.4, 36.7, 36, 34.5, 33.5, 30.2, 29.8, 26.2, 25, 24.8, 20.3, 13.3; IR (KBr, cmꢀ1
) m
max 3476, 2925, 2843, 2471, 2353, 2304, 1732, 1650, 1450, 1380, 1217, 1017,
30.2, 26.3, 25.8, 24.9, 24.7, 20.3, 13.4; IR (KBr, cmꢀ1
) m max 3444, 2913, 2843,
874, 763, 665, 498; MALDI-TOF MS: found 548.2216 [(M+H)+]. For compound
1732, 1646, 1384, 1249, 1021, 874, 767, 620, 477; MALDI-TOF MS: found
5: Rf 0.39 (n-hexane/EtOAc = 1:1 v/v); ½a D24
ꢁ
¼ þ45:5 (c 0.055, CHCl3); 1H NMR
845.5177 [(M+H)+].
(250 MHz, CDCl3) d 7.29–7.03 (m, 5H, aromatic), 5.30 (s, 1H, C-5), 4.62 (d, 1H),
4.04 (m, 1H, C-12), 3.91 (d, 1H), 2.91 (m, 1H, C-11), 2.76 (m, 1H), 2.53 (m, 2H),
2.31 (m, 2H), 1.42 (s, 3H, C-15), 0.95 (d, 3H, C-14), 0.91 (d, 3H, C-13); 13C NMR
(63 MHz, CDCl3) d 171.2, 140.1, 129.2, 128.4, 126.1, 103.6, 88.6, 81.3, 76.6, 52.6,
10. Nishino, H.; Nishino, A.; Takajasu, J.; Hasegawa, T.; Iwashima, A.; Hirabayashi,
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