Synthesis and in vitro antitumor activity of new butenolide-containing dithiocarbamates

Article abstract of DOI:10.1016/j.bmcl.2011.03.029

Three series of butenolide-containing dithiocarbamates were designed and synthesized. Their anti-tumor activity in vitro was evaluated. Among them compound I-14 exhibited broad spectrum anti-cancer activity against five human cancer cell lines with IC₅₀ <30 μM. Structure-activity relationship analysis showed that the introduction of dithiocarbamate side chains on the C-3 position of butenolide was crucial for anti-tumor activity.

Full text of DOI:10.1016/j.bmcl.2011.03.029

Bioorganic & Medicinal Chemistry Letters 21 (2011) 3074–3077
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Synthesis and in vitro antitumor activity of new butenolide-containing
dithiocarbamates
Xiao-Juan Wang a,b, Hai-Wei Xu a,c, Lin-Lin Guo a,c, Jia-Xin Zheng a,c, Bo Xu a,c, Xiao Guo a,c, Chen-Xin Zheng a,c
,
Hong-Min Liu a,b,c,
⇑
a New Drug Research & Development Center, Zhengzhou University, Zhengzhou 450001, PR China
b Department of Chemistry, Zhengzhou University, Zhengzhou 450052, PR China
c School of Pharmaceutical Sciences, Zhengzhou University, No. 100, Avenue Kexue, Zhengzhou 450001, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Three series of butenolide-containing dithiocarbamates were designed and synthesized. Their anti-tumor
Received 23 December 2010
Revised 22 February 2011
Accepted 9 March 2011
Available online 17 March 2011
activity in vitro was evaluated. Among them compound I-14 exhibited broad spectrum anti-cancer activ-
ity against five human cancer cell lines with IC50 <30 lM. Structure–activity relationship analysis showed
that the introduction of dithiocarbamate side chains on the C-3 position of butenolide was crucial for
anti-tumor activity.
Ó 2011 Elsevier Ltd. All rights reserved.
Keywords:
Butenolides
Dithiocarbamate
Anti-tumor activity
One of the main objectives of organic and medicinal chemistry
is the design, synthesis and production of molecules having value
as human therapeutic agents. During the past decade, number of
dithiocarbamates were synthesized and evaluated,1 by which some
privileged structures receiving special attention have been found
to possess excellent anti-tumor activity.2,3 For example, structure
modification of Brassinin (1)3 (Fig. 1), a dithiocarbamate isolated
from cruciferous plants, led to the design and synthesis of a poten-
tial cancer chemopreventive agent Sulforamate (2)4 (Fig. 1). Fur-
The butenolide derivatives I with dithiocarbamates side chain
at C-3 position were obtained by the reaction of 3-bromomethyl
butenolide (9) with CS2 and various amines in the presence of Na3-
PO4Á11H2O in acetone8 as shown in Scheme 1. 3-bromomethyl but-
enolide (9) was derived from
c-butyrolactone (4) by five-step
reaction according to the reported method.9 The synthesized deri-
vativies were summarized in Table 1.
The butenolide derivatives II with dithiocarbamate side chain at
C-4 position were obtained by the reaction of 4-bromomethyl but-
enolide (12) with CS2 and various amines. Compound 12 was pre-
pared by an intramolecular substitution reaction of compound 11
which could be obtained from starting material 10 with 70% yield
as shown in Scheme 2.11
Fortunately, a new scaffold of spirothiazolidine-2-thiones III
was obtained during the reaction of compound 12 with primary
amines. The compounds II and the novel spirothiazolidine-2-thi-
ones III were shown in Table 2.
All of these compounds were tested for anti-tumor activity
against five different human cancer cell lines in vitro by MTT [3-
(4,5-dimethylthiao-2-yl)-2, 5-diphenyl-tetrazolium bromide] cell
proliferation assay.14 The anti-tumor drug 5-fluorouracil was used
as positive control. The results are summarized in Tables 3 and 4
Analysis of the MTT assay results suggest that the position of
dithiocarbamate side chain is crucial for the activity. Butenolides
I with dithiocarbamate side chain on C-3 position were generally
more potent than series II with dithiocarbamate side chain on C-
4 position, compounds II had no or unconspicuous cytotoxic activ-
ity towards all these five cell lines. The bioassay results also sug-
gest that except compound III-3, the spirothiazolidine-2-thiones
thermore, the dithiocarbamate portion of the brassinin is
a
crucial moiety for the anti-tumor activity.3
Butenolides (3) (Fig. 1) are ubiquitous chemical moieties occur-
ring in a large number of natural products and known to be asso-
ciated with several biological activities.5 Many of the butenolide-
containing compounds can be considered as potential anti-cancer
agent, bactericides, fungicides, etc.6 There are also a wide variety
of pharmacologically active non-natural products bearing the het-
erocycle as the active site.7
In an effort to look for the possible anti-tumor agents, we were
interested in the incorporation of dithiocarbamate moiety with
butenolide. In addition, it is suspected that there is a close relation-
ship between the position of dithiocarbamates side chain on bute-
nolide and their biological activities. So three series of butenolide
containing dithiocarbamates were designed and synthesized in or-
der to investigate the structure–activity relationship and obtain
significant insight into the impact of activity on molecular.
⇑
Corresponding author. Tel./fax: +86 371 67781739.
E-mail address: liuhm@zzu.edu.cn (H.-M. Liu).
0960-894X/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2011.03.029

X.-J. Wang et al. / Bioorg. Med. Chem. Lett. 21 (2011) 3074–3077
3075
O
S
CH3
O
S
N
H
Z
X
O
S
S
dithiocarbamate moiety
CH3
Y
N
H
N
H
S
H3C
Common natural products subunit,
butenolide >13,000 examples
indole core
2
1
3
Figure 1. Structures of brassinin (1) sulforamate (2) and butenolides (3).
PhS
O
OH
SPh
O
Br
a
b
c
O
O
O
O
6
O
4
O
5
7
S
Br
OH
R1
N
S
R2
O
d
e
O
f
O
O
O
8
O
9
I-1-14
Scheme 1. The synthesis of butenolide derivatives I. Reagents and conditions: (a) Br2, P, 69%; (b) PhSNa, CH3OH, 88%; (c) CH3ONa, CH3OH, (CH2O)n, TMEDA, 95%; (d) (1)
mCPBA, CH2Cl2, 0 °C; (2) CaCO3, CCl4, reflux, 82% two steps; (e) PBr3, Et2O, 0 °C, 83%; (f) CS2, NHR1R2, Na3PO4Á11H2O, acetone, 0.5–1 h.
Table 1
The butenolide derivatives I with dithiocarbamate side chain at C-3 position
Productsa
–NR1R2
Yieldb (%)
Productsa
I-8
–NR1R2
Yieldb (%)
90
N
I-1
CH3NH–
83
Me
N
I-2
I-3
C2H5NH–
85
81
I-9
93
86
N
N
(CH3)2N–
(C2H5)2N–
I-10
O
H
I-4
I-5
I-6
77
80
87
I-11
I-12
I-13
N
75
77
81
H
N
(CH3)2CHNH–
Me
Cl
H
NH
N
H
N
N
I-7
86
I-1410
77
H
a
All the products were characterized by IR, NMR and mass spectral data.
Refer to isolated pure products.
b
S
S
R1
N
R2
Br
O
COOH
c
O
Br
Br
COOH
II-1-7
a
O
b
S
O
c
S
12
11
10
N
R3
O
O
III-1
-7
Scheme 2. Reagents and conditions: (a) 2.2 equiv NBS, Ph(CO)2O2, CCl4, reflux, 95%; (b) 5% aq NaOH, rt 12 h, 73%; (c) CS2, amines, Na3PO4Á11H2O, acetone, 0.5–1 h.

3076
X.-J. Wang et al. / Bioorg. Med. Chem. Lett. 21 (2011) 3074–3077
Table 2
The compounds II and the novel spirothiazolidine-2-thiones III
Productsa
II-112
–NR1R2
Yieldb (%)
81
Productsa
III-113
R3
Yieldb (%)
87
(CH3)2N–
II-2
(C2H5)2N–
77
I-2
88
II-3
II-4
((CH3)2CH)2N–
76
87
III-3
75
81
N
I-4
Me
Cl
Me
N
II-5
II-6
93
86
I-5
I-6
90
86
N
N
O
F
Me
N
II-7
80
I-7
75
OH
a
All the products were characterized by IR, NMR and mass spectral data;
Refer to isolated pure products.
b
Table 3
Inhibitory results of compounds I to 5 human cancer cell lines
No.
IC50
PC-3d
(l
M)a
EC-9706b
HeLac
SPCA1e
MCF-7f
I-1
I-2
I-3
I-4
I-5
I-6
I-7
I-8
85.41 3.4
44.41 0.8
181.50 3.7
135.89 2.4
59.42 1.6
53.57 1.3
36.05 2.4
ndh
76.50 2.7
30.62 0.3
146.57 1.0
57.05 2.3
49.42 1.2
116.86 2.4
—
113.68 3.7
40.50 2.6
48.83 1.3
186.05 2.9
93.49 1.4
ndh
43.89 3.2
ndh
—
83.1 2.4
80.08 1.3
—
g
114.41 2.2
1.39 0.8
136.71 2.4
24.14 1.9
150.03 2.1
2.63 0.2
0.77 0.3
2.43 0.2
111.23 1.2
5.44 0.3
ndh
86.96 1.5
107.64 2.3
57.50 1.3
—
31.35 1.5
53.73 1.7
37.87 1.7
95.31 2.9
63.82 1.4
ndh
121.32 3.5
133.91 2.2
94.92 2.4
179.54 2.3
56.41 1.2
86.52 2.6
60.30 2.3
89.91 1.7
97.37 2.9
ndh
g
—
14.36 1.3
14.26 1.5
26.02 1.2
16.22 2.3
90.99 1.7
ndh
I-9
I-10
I-11
I-12
I-13
I-14
5-Fu
34.26 1.4
20.30 1.3
15.08 0.8
41.46 2.5
13.72 0.2
29.30 1.9
20.14 1.2
26.92 1.4
31.93 1.3
7.54 0.7
a
Inhibitory activity was assayed by exposure for 72 h to substances and expressed as concentration required to inhibit tumor cell proliferation by 50% (IC50). Data are
expressed as mean SE from the dose–response curves of at least three independent experiments. Differences between groups were examined for statistical significance
using one-way ANOVA analysis with SPSS 16.0 for WINDOWS. In all cases, P <0.05 was considered significant.
b
Human esophageal cancer cell line.
Human cervical carcinoma cell line.
Human prostate cancer cell line.
Human lung cancer cell line.
c
d
e
f
Human breast cancer cell line.
g
IC50 values greater than 50
No detection.
lg/mL were considered as inactive and omitted here.
h
showed weaker or no inhibition activity compared with chain
dithiocarbamates.
In series I, compound bearing benzylamino (I-14) showed broad
spectrum anti-cancer activity to five different cell lines with IC50
the ring size is very important for activating effect in vitro, com-
pound I-6 containing cyclopropylamino has stronger activities
than compound I-7 containing cyclohexylamino. Compounds I-1
to I-5 showed moderate cytotoxicity, and no matter secondary
amines or tertiary amines showed negligible affect to their
cytotoxicity.
In summary, a new family of butenolides-containing dithio-
carbamates were synthesized and evaluated for their antitumor
activity in vitro. Structure–activity relationship for the anti-
tumor effect of them showed that the introduction of dithiocar-
bamate side chains on the C-3 position of butenolide was crucial
for anti-tumor activity. Especially compound I-14 exhibited
broad spectrum anti-cancer activity in vitro. This result is valu-
<30
weaker activity towards most cell lines tested, except compound
I-11 with IC50 = 16.22 M to EC9706 cell line and compound I-12
with IC50 = 5.44 M to HeLa cell line. Compounds I-8–10 which
lM. While compounds I-11–13 containing anilinos, exhibited
l
l
possess heterocyclic amino groups showed selective and signifi-
cant cytotoxicity, particularly with respect to HeLa cell line, with
IC50 values less than 3 lM, better than that of the control com-
pound fluorouracil. Comparing compound I-6 with I-7, both of
them possess exocyclic amino groups, the result indicates that

X.-J. Wang et al. / Bioorg. Med. Chem. Lett. 21 (2011) 3074–3077
3077
Table 4
R. M.; Baldwin, J. E.; Marquez, R. J. Org. Chem. 2004, 69, 9100; (e) Lee, S. S.; Lin,
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Zhang, T. J.; Yan, L. L. Chin. Chem. Lett. 2007, 18, 1075.
Inhibitory results of compounds II and III to 5 human cancer cell lines
No.
IC50 (lM)
6. a WIPO Patent Application WO/ 1999 /052888; .; (b) Lattmann, E.; Ayuko, W.
O.; Kinchinaton, D.; Langley, C. A.; Singh, H.; Karimi, L.; Tisdale, M. J. J. Pharm.
Pharmacol. 2003, 55, 129; (c) Braun, M.; Hohmann, A.; Rahematpura, J.; Bühne,
C.; Grimme, S. Chem. Eur. J. 2004, 10, 4584; (d) Xavier, N. M.; Rauter, A. P.
Carbohydr. Res. 2008, 343, 1523; (e) Pimentel-Elardo, S. M.; Kozytska, S.; Bugni,
T. S.; Ireland, C. M.; Moll, H.; Hentschel, U. Mar. Drugs 2010, 8, 373.
7. (a) Kupchan, S. M.; Fessler, D. C.; Eakin, M. A.; Giacobbe, T. J. Science 1970, 168,
37; (b) Kupchan, S. M.; Eakin, M. A.; Thomas, A. M. J. Med. Chem. 1971, 14, 1147;
(c) Bourguignon, J. J.; Schoenfelder, A.; Schmitt, M.; Wermuth, C. G.; Hechler, V.;
Charlier, B.; Maitre, M. J. Med. Chem. 1988, 31, 893.
EC-9706
HeLa
PC-3
SPCA1
MCF-7
II-1
II-2
II-3
II-4
II-5
II-6
II-7
III-1
III-2
7.55 0.7
—
—
—
—
—
—
—
—
—
—
—
—
159.29 3.5
—
—
a
—
21.01 1.7
28.51 0.4
—
—
—
—
57.05 2.7
—
60.03 1.1
—
49.25 0.3
105.74 1.4
35.83 1.6
—
—
—
—
168.77 0.5
—
—
—
—
—
—
—
—
8. Cao, S. L.; Feng, Y. P.; Jiang, Y. Y.; Liu, S. Y.; Ding, G. Y.; Li, R. T. Bioorg. Med. Chem.
Lett. 2005, 15, 1915. General procedure for the synthesis of analogues I: CS2
(5 equiv) was added dropwise to the solution of amine (1 equiv) and
Na3PO4Á11H2O (0.6 equiv) in acetone, The reaction mixture was stirred at
28.73 0.9
—
III-3 128.33 2.4 18.03 0.5
III-4
III-5 32.61 1.2
III-6
III-7
100.70 2.3 134.21 2.4
—
—
—
—
—
98.08 2.4
—
—
—
—
—
—
—
—
room temperature for 0.5 h. Then
a,b-unsaturated ketones or esters (1 equiv)
—
—
—
was added to the mixture, the reaction mixture was stirred at room
temperature for 0.5 h (monitored by TLC). Upon completion, the reaction
mixture was filtered and the filter liquor concentrated under reduced pressure,
extracted with CHCl3 (3 Â 15 mL), dried over sodium sulfate, and concentrated
under reduced pressure. The residue was purified by flash column
chromatography on silica gel or recrystallized (in CHCl3/CH3OH 1/1) to afford
the product..
—
—
a
IC50 values greater than 50
here.
lg/mL were considered as inactive and omitted
9. (a) Morgan, B.; Dolphin, D.; Jones, R. H.; Jones, T.; Einstein, F. W. B. J. Org. Chem.
1987, 52, 4631; (b) Yang, H. S.; Qiao, X. X.; Cui, Q.; Xu, X. H. Chin. Chem. Lett.
2009, 20, 1023. Compound 8, red liquid, yield 83%. 1H NMR (CDCl3, 400 MHz) d:
4.11 (dd, J = 1.5 Hz, J = 3.0 Hz, 2H), 4.86 (dd, J = 1.6 Hz, J = 3.3 Hz, 2H), 7.52 (td,
J = 1.3 Hz, J = 2.8 Hz, 1H)..
able for the construction of compound libraries and the screen-
ing of lead compound. Further investigation of the synthesis of
compound I-14 derivatives and in vivo anti-tumor activity are
in progress.
10. Compound I-14: yellow solid (77%), mp = 84.8–85.3 °C. IR (KBr, cmÀ1
)
m
: 3231,
2918, 1736, 1529, 1427, 1367, 1205, 1088, 1040, 929, 827, 739, 694; 1H NMR
(400 MHz, CDCl3)
d 7.65–7.31 (m, 6H), 4.92 (d, J = 5.1 Hz, 2H), 4.84 (d,
Acknowledgments
J = 1.4 Hz, 2H), 4.18 (s, 2H), 1.62 (s, 1H); 13C NMR (101 MHz, CDCl3) d 196.09,
173.33, 148.07, 135.71, 130.08, 128.95, 128.29, 128.02, 70.22, 51.26, 29.01.
HRMS (ESI) Calcd for C13H13NO2S2Na [M+Na]+: 302.0388. Found: 302.0387.
11. (a) Robert, K. I.; Boeckman, J.; Soo, S. K. J. Am. Chem. Soc. 1982, 104, 1033; (b)
Wang, E. S.; Choy, Y. M.; Henry, N. C. W. Tetrahedron 1996, 52, 12137.
We are grateful for the financial support from the National Nat-
ural Science Foundation of China (Project No. 20902086), as well as
support from China Postdoctoral Science Foundation funded pro-
ject (Project No. 20080430864).
12. Compound II-1: white solid (82%). Mp = 141.2–141.8 °C. IR (KBr, cmÀ1
) m: 3079,
2926, 1744, 1634, 1377, 1254, 1176, 1021, 986, 886, 718; 1H NMR (400 MHz,
CDCl3) d 6.04 (s, 1H), 4.87 (s, 2H), 4.43 (s, 2H), 3.57 (s, 2H), 3.41(s, 3H); 13C NMR
(101 MHz, CDCl3) d 194.43, 173.22, 165.59, 117.86, 72.60, 46.08, 41.56, 30.94.
HRMS (ESI) Calcd for C8H11NO2S2Na [M+ Na]+: 240.0129. Found: 240.0130.
References and notes
13. Compound III-1: yellow solid (87%). Mp = 88.2–89.2 °C. IR (KBr, cmÀ1
) m: 2990,
2923, 1773, 1397, 1337, 1265, 1224, 986, 839, 697; 1H NMR (400 MHz, CDCl3) d
4.52 (dd, J = 25.0, 10.1 Hz, 2H), 3.51–2.37 (m, 3H), 2.77 (d, J = 17.8 Hz, 1H),
2.56–2.37 (m, 1H), 1.21–1.00 (m, 3H), 0.97–0.81 (m, 1H); 13C NMR (101 MHz,
CDCl3) d 200.12, 173.13, 76.11, 72.53, 38.47, 37.76, 27.89, 9.01, 8.32. HRMS
(ESI) Calcd for C10H15NO3S2Na [M+Na+CH3OH]+: 284.0391. Found: 284.1132.
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another 72 h. Afterwards, 10 lL of MTT solution (5 mg/mL in phosphate
buffered solution) was added to all wells and incubated for 4 h at 37 °C.
Pipetted out the spent media along with suspension of cultured cells and
unconverted MTT, 150 lL of dimethyl sulfoxide (DMSO) was added to each
well and shaked the plates to dissolve the dark blue crystals (formazan); their
absorbance was measured using a spectrophotometric microplate reader at a
wavelength of 490 nm. Each concentration was analyzed in triplicate and the
experiment was repeated three times. The average 50% inhibitory
5. For examples: (a) Ishikawa, T.; Nishigaya, K.; Uchikoshi, H.; Chen, I. S. J. Nat.
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concentration (IC50
) was determined from the dose-response curves
according to the inhibition ratio for each concentration..