Arch. Pharm. Chem. Life Sci. 2010, 343, 411–416
4-(2-Arylthiazol-4-yl)-4H-chromenes as Cytotoxic Agents
415
evaporated and diethyl ether was added. The mixture was fil-
tered through a packed layer of diatomaceous earth and concen-
trated under reduced pressure. The product was crystallized
from methanol/water to afford the corresponding aldehydes
9a–e.
Hz, H3 and H5 phenyl), 7.89 (d, 1H, J = 8.5 Hz, H5 chromene); MS
(m/z,%): 410 [M + 2] (25), 408 [M+] (60), 344 (92), 214 (100), 198 (10),
174 (65). Anal. calcd. for C21H17ClN4OS: C, 61.68; H, 4.19; N, 13.70.
Found: C, 61.68; H, 3.99; N, 13.81.
2-Amino-3-cyano-4-[2-(4-bromophenyl)thiazol-4-yl]-7-
(dimethylamino)-4H-chromene 4e
General procedure for the preparation of 2-amino-3-
cyano-7-(dimethylamino)-4-(2-arylthiazol-4-yl)-4H-
chromenes 4a–e
Piperidine (10 mmol) was added to a mixture of the appropriate
aldehyde 9a–e (5 mmol), malonitrile (10, 5 mmol), and 3-(dime-
thylamino)phenol (11, 5 mmol) in ethanol (20 mL). The reaction
mixture was stirred at 358C for 12 h. After cooling, the precipi-
tated solid was filtered, washed with cold ethanol, and crystal-
lized from the same solvent.
Yield: 81%; m.p.: 208–2108C; IR (KBr, cm–1) mmax: 3349, 3134,
2796, 2182, 1654, 1521, 1398, 1239, 1122, 1065, 999, 830, 697,
553; 1H-NMR (DMSO-d6) d: 2.96 (s, 6H, CH3), 4.88 (s, 2H, NH2), 5.25
(s, 1H, H4 chromene), 6.10 (d, 1H, J = 2.2 Hz, H8 chromene), 6.53
(dd, 1H, J = 8.0 and 2.2 Hz, H6 chromene), 7.06 (s, 1H, thiazole),
7.84 (d, 2H, J = 8.5 Hz, H3 and H5 phenyl), 7.43 (d, 2H, J = 8.5 Hz, H2
and H6 phenyl), 7.90 (d, 1H, J = 8.5 Hz, H5 chromene); MS (m/z,%):
454 [M + 2] (20), 452 [M+] (25), 286 (10), 255 (28), 214 (100). Anal.
calcd for C21H17BrN4OS: C, 55.64; H, 3.78; N, 12.36. Found: C,
55.93; H, 3.66; N, 12.11.
2-Amino-3-cyano-7-(dimethylamino)-4-(2-phenylthiazol-
4-yl)-4H-chromene 4a
Yield: 74%; m.p.: 201–2038C; IR (KBr, cm–1) mmax: 3375, 3134,
Biological activity
1
2847, 2187, 1654, 1562, 1516, 1403, 1244, 1106, 825, 768; H-
NMR (DMSO-d6) d: 2.95 (s, 6H, CH3), 5.02 (s, 2H, NH2), 5.17 (s, 1H,
H4 chromene), 6.59 (d, 1H, J = 2.4 Hz, H8 chromene), 6.58 (dd, 1H, J
= 8.0 and 2.4 Hz, H6 chromene), 7.01–7.55 (m, 6H, phenyl and
thiazole), 7.89 (d, 1H, J = 8.8 Hz, H5 chromene); MS (m/z,%): 374
[M+] (40), 214 (100), 198 (14). Anal. calcd. for C21H18N4OS: C, 67.36;
H, 4.85; N, 14.96. Found: C, 67.12; H, 4.96; N, 15.15.
Cell lines and cell culture
The synthesized compounds were tested against different
human cancer cell lines including MCF-7 (breast cancer), A549
(lung cancer), KB (nasopharyngeal epidermoid carcinoma), Hep-
G2 (liver carcinoma), SW-480 (colon adenocarcinoma), U87-MG
(glioblastoma), 1321N1 (astrocytoma), and DAOY (medulloblas-
toma). The cytotoxic activities of the target compounds were
also assessed against normal mouse fibroblast (NIH/3T3) cells.
The cell lines were purchased from the National Cell Bank of
Iran (NCBI). The cells were grown in Dulbecco's Modified Eagle
Medium (DMEM, Sigma-Aldrich) supplemented with 10% heat-
inactivated fetal calf serum (Biochrom, Berlin, Germany), 100
lg/mL streptomycin, and 100 U/mL penicillin, in a humidified
air atmosphere at 378C with 5% CO2.
2-Amino-3-cyano-4-[2-(2-chlorophenyl)thiazol-4-yl]-7-
(dimethylamino)-4H-chromene 4b
Yield: 64%; m.p.: 186–1888C; IR (KBr, cm–1) mmax: 3441, 3329,
3196, 2806, 2192, 1644, 1521, 1408, 1270, 1111, 1055, 825, 753,
589; 1H-NMR (DMSO-d6) d: 2.92 (s, 6H, CH3), 4.67 (s, 2H, NH2), 5.04
(s, 1H, H4 chromene), 6.30 (d, 1H, J = 2.4 Hz, H8 chromene), 6.60
(dd, 1H, J = 8.0 and 2.4 Hz, H6 chromene), 7.10–7.56 (m, 5H, phe-
nyl and thiazole), 7.90 (d, 1H, J = 8.8 Hz, H5 chromene); MS
(m/z,%): 410 [M + 2] (26), 408 [M+] (45), 344 (15), 271 (10), 214 (100),
198 (12), 174 (12). Anal. calcd. for C21H17ClN4OS: C, 61.68; H, 4.19;
N, 13.70. Found: C, 61.92; H, 4.41; N, 13.82.
Cytotoxicity assay
The in-vitro cytotoxic activity of each synthesized chromene
derivative 4a–e was assessed in monolayer cultures using MTT
colorimetric assay [17]. Briefly, each cell line in log-phase of
growth was harvested by trypsinization, resuspended in com-
plete growth medium to give a total cell count of 256103 cells/
mL. 100 lL of the cell suspension was seeded into the wells of 96-
well plates (Nunc, Denmark). The plates were incubated over-
night in a humidified air atmosphere at 378C with 5% CO2. Then,
50 lL of the media containing various concentrations of the
compound was added per well in triplicate. The plates were incu-
bated for further three days. The final concentration of DMSO in
the highest concentration of the applied compounds was 0.1%.
Etoposide was used as positive control for cytotoxicity while
three wells containing tumor cells cultured in 150 lL of com-
plete medium were used as controls for cell viability. After incu-
bation, 30 lL of a 2.5 mg/mL solution of MTT (Sigma-Aldrich) was
added to each well and the plates were incubated for another 1
h. The culture medium was then replaced with 100 lL of DMSO
and the absorbance of each well was measured by using a micro-
plate reader at 570 nm. Each set of experiments was independ-
ently performed three times. For each compound, the concentra-
tion causing 50% cell growth inhibition (IC50) compared with
the control was calculated from concentration-response curves
by regression analysis.
2-Amino-3-cyano-4-[2-(3-chlorophenyl)thiazol-4-yl]-7-
(dimethylamino)-4H-chromene 4c
Yield: 78%; m.p.: 200–2028C; IR (KBr, cm–1) mmax: 3482, 3313,
3201, 2847, 2192, 1659, 1521, 1398, 1234, 1106, 891, 814, 758,
671; 1H-NMR (DMSO-d6) d: 2.97 (s, 6H, CH3), 5.01 (s, 2H, NH2), 5.16
(s, 1H, H4 chromene), 6.10 (d, 1H, J = 2.3 Hz, H8 chromene), 6.52
(dd, 1H, J = 8.0 and 2.3 Hz, H6 chromene), 7.03–7.50 (m, 5H, phe-
nyl and thiazole), 7.91 (d, 1H, J = 8.5 Hz, H5 chromene); MS
(m/z,%): 410 [M + 2] (20), 408 [M+] (24), 344 (8), 214 (100), 198 (12),
174 (8). Anal. calcd. for C21H17ClN4OS: C, 61.68; H, 4.19; N, 13.70.
Found: C, 61.50; H, 4.12; N, 13.45.
2-Amino-3-cyano-4-[2-(4-chlorophenyl)thiazol-4-yl]-7-
(dimethylamino)-4H-chromene 4d
Yield: 79%; m. p.: 232–2358C; IR (KBr, cm–1) mmax: 3353, 3303,
3144, 2858, 2796, 2192, 1669, 1516, 1398, 1239, 1111, 1004, 825,
722, 558; 1H-NMR (DMSO-d6) d: 2.92 (s, 6H, CH3), 4.90 (s, 2H, NH2),
5.28 (s, 1H, H4 chromene), 6.05 (d, 1H, J = 2.2 Hz, H8 chromene),
6.50 (dd, 1H, J = 8.1 and 2.3 Hz, H6 chromene), 7.05 (s, 1H, thia-
zole), 7.81 (d, 2H, J = 8.7 Hz, H2 and H6 phenyl), 7.42 (d, 2H, J = 8.7
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