Synthesis, evaluation of 6,8-dibromo-2-aryl-2,3-dihydroquinolin-4(1H)-ones in MCF-7 (breast cancer) cell lines and their docking studies

Article abstract of DOI:10.1007/s00044-011-9688-z

A series of novel 6,8-dibromo-2-aryl-2,3-dihydroquinolin-4(1H)-ones have been synthesized and evaluated in vitro (in MCF-7 breast cancer cell lines). Compounds 5a, 5d, 5e, and 5g exhibited potent GI₅₀ and TGI values compared with reference stan

Full text of DOI:10.1007/s00044-011-9688-z

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res (2012) 21:1741–1750
DOI 10.1007/s00044-011-9688-z
ORIGINAL RESEARCH
Synthesis, evaluation of 6,8-dibromo-2-aryl-2,3-dihydroquinolin-
4(1H)-ones in MCF-7 (breast cancer) cell lines and their docking
studies
•
Lakshmi Narayana Bheemanapalli Amandeep Kaur
•
•
•
•
Ramandish Arora Sangeeta Raghuram Rao Akkinepally
Narashima Murthy Javali
Received: 18 December 2010 / Accepted: 26 May 2011 / Published online: 14 June 2011
Ó Springer Science+Business Media, LLC 2011
Abstract A series of novel 6,8-dibromo-2-aryl-2,3-dihy-
droquinolin-4(1H)-ones have been synthesized and evalu-
ated in vitro (in MCF-7 breast cancer cell lines).
Compounds 5a, 5d, 5e, and 5g exhibited potent GI50 and
TGI values compared with reference standard and com-
pounds 5b and 5c showed moderate activity. The docking
studies (in silico) were conducted to recognize the hypo-
thetical binding motif of the title compounds within the
active site of aromatase enzyme employing GOLD docking
software. The binding mode and SAR of the title com-
pounds has been proposed based on the docking studies.
2010). Excluding cancers of skin, breast cancer is the most
frequently diagnosed cancer in women. The Indian Council
of Medical Research (ICMR) registry records an whooping
figure of 1,00,000 every year as new cases in Indian
women and 40% of them die either of late detection or
shyness of subjects to get examined (ICMR, 2008). In a
high percentage of cases, it proves to be hormone-depen-
dent because tumor progression is dependent on high levels
of circulating estrogens, which play a critical role in cancer
cell proliferation. Two pharmacological strategies have
been employed essentially to control or alleviate the dis-
tress due to the pathological events of estrogen (Murthy
et al., 2004). These include drugs which either act through
estrogen receptor (ER) antagonism (antiestrogens) or
interfere with the synthesis of steroidal hormones by
inhibiting the enzymes controlling the interconversion
from androgenic precursors, i.e., aromatase inhibitors
(AIs). The third generation AIs, such as letrozole, anas-
trozole, and exemestane are now considered a valid alter-
native to tamoxifen as first line treatment option for
advanced breast cancer (Needleman and Tobias, 2008).
Besides the development of synthetic compounds, the
potential of various classes of natural products to inhibit
aromatase was evaluated in order to discover novel thera-
peutic agents for breast cancer. As a result, several natu-
rally occurring and synthetic flavonoids that mediate a host
of biological activities were found to demonstrate inhibi-
tory effects on aromatase (Carlo et al., 1999; Jeong et al.,
1999; Kao et al., 1998). It has been demonstrated that
several flavonoid derivatives are potent AIs and effective
antiproliferative agents against MCF-7 breast cancer cell
lines (Le-Bail et al., 1998; Pouget et al., 2001). This sub-
stantiates our hypothesis that the flavonoidal scaffold could
churn out to be a milestone in developing the next gener-
ation of safer AIs (Rao and Murthy, 2009).
Keywords Dihydroquinolin-4(1H)-ones ꢀ
MCF-7 cell line ꢀ Nonsteroidal aromatase inhibitors ꢀ
Docking studies
Introduction
Breast cancer is one of the most common forms of female
cancers and currently considered as the leading cause of
death among women (accounting for 35% of all cancers
and 20% of all cancer deaths) worldwide (Bandi et al.,
L. N. Bheemanapalli ꢀ A. Kaur ꢀ R. Arora ꢀ Sangeeta ꢀ
R. R. Akkinepally (&)
Pharmaceutical Chemistry Division, University Institute
of Pharmaceutical Sciences and Centre of Advanced Study
in Pharmaceutical Sciences (UGC-CAS), Panjab University,
Chandigarh 160014, India
e-mail: rrakkinepally@pu.ac.in
N. M. Javali
Department of Pharmaceutics and Medicinal Chemistry,
Thomas J. Long School of Pharmacy & Health Sciences,
University of the Pacific, Stockton, CA 95211, USA
123

1742
Med Chem Res (2012) 21:1741–1750
Flavonoids, which are structurally similar to estrogens,
and synthesized with a view to develop as new AIs. In this
communication, we report the synthesis, in vitro biological
evaluation of a series of new 6,8-dibromo-2-aryl-2,3-di-
hydroquinolin-4(1H)-ones in MCF-7 breast cancer cell
lines. Further, we propose the molecular interactions and
the binding mode of the synthesized compounds using the
X-ray crystal structure of human placental microsomal
aromatase (PDB ID: 3EQM) (Ghosh et al., 2009) through
in silico docking studies.
are able to bind to the ER and possess antiestrogenic
activities. Based on the data obtained from site-directed
mutagenesis and ligand-docking studies into the aromatase
enzyme, a binding orientation was predicted in which the A
and C rings of the flavonoid mimic the D and C rings of the
androstendione, respectively, while the B ring is oriented in
a similar position to that of the androstendione ring A and
points toward the extrahydrophobic pocket within the
active site (Kao et al., 1998; Pelissero et al., 1996). This
analysis places the flavonoid 4-keto functionality in the
same position as the androstendione C-19 angular methyl
group which interacts with the heme iron of the aromatase
enzyme (Fig. 1).
Results and discussion
Chemistry
With an objective of designing new and potent AIs
(Murthy et al., 2006; Rao and Murthy, 2009), we relied on
flavonoid nucleus as a structural scaffold and by bioisos-
teric modification on ring oxygen with nitrogen led to a
series of 6,8-dibromo-2-aryl-2,3-dihydroquinolin-4(1H)-
one derivatives. We took clue from the most active bromo
derivative YM511 (Okada et al., 1996) and introduced
bromo group in our compounds. In the patent (Rao and
Murthy, 2009), which was filed from our laboratories, the
human placental microsomal aromatase inhibition poten-
cies of the final compounds, i.e., imidazole and triazole
derivatives were reported. In continuation of our ongoing
research, we investigated the antiproliferative activity
against MCF-7 breast cancer cell lines and the aromatase
inhibitory activity of 2-aryl-2,3-dihydroquinolin-4(1H)-
ones to get the lead molecules (unpublished data from these
laboratories). A series of such analogs have been designed
As illustrated in Scheme 1, the title compounds were
synthesized from 2-aminoacetophenone (1). On bromina-
tion using bromine in dichloromethane at 0–5°C, a mixture
of 1-(2-amino-3,5-dibromophenyl)ethanone (2) and 1-(2-
amino-5-dibromophenyl)ethanone was obtained. It was
interesting to observe that maintaining the reaction tem-
perature at 0–5°C and increasing the time period of stirring
to 7 h were found to be crucial in the formation of com-
pound 2 as major product. In 1H NMR spectrum, the
presence of two doublet peaks at d 6.67 (J = 2.2 Hz) and d
7.79 (J = 2.2 Hz) confirmed the formation of compound 2.
It was characterized by comparing with the literature data
(Baker et al., 2001).
Compound 2 was subjected to Claisen–Schmidt con-
densation using different substituted aromatic aldehydes
(3a–j) in the presence of sodium hydroxide and absolute
ethanol keeping the temperature 0–5°C for 35–40 h results
in the formation of different chalcones (4a–j). The chem-
ical structures were confirmed through physical and spec-
tral data. The 1H NMR spectrum showed the presence of a
broad singlet at d 6.9 (–NH2), a signal at d 7.4 (J =
15.5 Hz) and d 7.6 (J = 15.5 Hz). The higher magnitude
of coupling constants (J value) for both protons indicate
trans configuration.
Chalcones (4a–j) were cyclized by using a mixture of
orthophosphoric acid and glacial acetic acid, where the
addition of glacial acetic acid was considered to increase
the acidity of the medium, thereby it readily donates the
proton to chalcone to undergo intramolecular cyclization,
resulting in the facile formation of title compounds (5a–j).
The compounds were purified by column (hexane, ethyl
acetate; 99:1). Formation of the title compounds was
confirmed by physical and spectral data. IR spectra of 5
exhibited sharp characteristic secondary amine peak at
3390.4 cm-1 (absence of primary amine double band
1
peak), while in the H NMR spectrum showed the disap-
pearance of vinyl and primary amine protons and the
Fig. 1 Comparison of the chemical features between the model
framework of androstenedione and flavonoids
presence of additional signals at d 2.8, at d 4.5 (–NH,
123

Med Chem Res (2012) 21:1741–1750
1743
CHO
O
O
R
O
Br
CH3
i
Br
R
CH3
3(a-j)
ii
NH2
NH2
NH2
Br
1
2
Br
4 (a-j)
iv
iii
R
a = 4-F
b = 4-Cl
c = 4-Br
d = 4-NO2
e = 4-CN
O
Br
f = 4-OCH3
g = 4-OH
h = 3-OH
i = 4-N(CH3)2
j = 3,4,5-tri-OCH3
N
H
R
Br
5 (a-j)
Scheme 1 Reaction conditions (i) Br2, DCM, 0–5°C, 7 h, (ii) absolute ethanol, NaOH, 0–5°C, 24 h, (iii) glacial acetic acid, orthophosphoric
acid, 100°C, 2–3 h, and (iv) 3a–j, L-proline, methanol, 55–60°C, 48 h
secondary amine) and at d 4.8, providing evidence for the
formation of the title compounds.
adriamycin (ADR) as standard at different (molar) con-
centrations. The results obtained from in vitro screening
expressed as molar concentration at three assay end points:
the 50% growth inhibitory power (GI50), the cytostatic
effect (TGI = total growth inhibition), and the cytotoxic
effect (LC50) Table 1.
Alternatively, a one pot synthesis of title compounds was
also attempted using 1-(2-amino-3,5-dibromophenyl)etha-
none (2) and different aromatic aldehydes (3a–j) in equi-
molar quantities in the presence of L-proline (30 mol%).
The reaction took place at 55–60°C, while stirring the
reaction mixture in methanol for 48 h. The workup of
reaction was conducted by treating the reaction mixture
with saturated ammonium chloride solution followed by
repeated extraction of the product with dichloromethane.
The combined organic layers were dried over anhydrous
sodium sulfate, and purified by column chromatography
(hexane, ethyl acetate; 99:1) gave the pure products (5a–j).
The percentage yields were found to be comparable to that
of synthesis via chalcones.
All the compounds 5a–j showed comparable growth
inhibitory potencies to that of the standard drug ADR at a
Table 1 In vitro screening in MCF-7 breast cancer cell lines, per-
centage growth as compared to control
S. no. Percentage growth as compared to control at lM concentrations
10-7
M
10-6
M
10-5
M M LC50 TGI GI50
10-4
5a
5b
5c
5d
5e
5f
30.1
60.2
69.7
50.5
43.1
168.1
3.7
9.2
-3.6
-48.1 [100 0.145 \0.1
-40.0 [100 2.87 0.146
61.7
69.7
34.5
12.5
-43.0 [100 2.6
0.151
In vitro screening using MCF-7 breast cancer cell lines
8.6
-4.4
-5.1
87.8
-52.3 [100 0.132 \0.1
-58.5 [100 0.126 \0.1
7.1 [100 [100 [100
-45.3 [100 0.151 \0.1
14.7 [100 [100 [100
43.0 [100 [100 [100
34.3 [100 [100 [100
8.2
The synthesized compounds were evaluated for their
inhibition potential on MCF-7 breast cancer cell lines
(ACTREC, Mumbai, India). The current research program
is the design and development of AIs and the objective is to
identify some lead molecules with potent MCF-7 inhibitory
activity. As a preliminary study only antiprolifirative
activity in MCF-7 cell lines is reported. The percentage
growth inhibitions of the compounds were compared with
140.5
9.6
5g
5h
5i
-2.0
25.6
117.7
164
107.8
143.8
110.5
-13.9
130.5
99.6
5j
129.5
ADR 53.5
-23.7
-33.5
35.5 0.183 \0.1
All the values derived from average of three (3) experiments
123

1744
Med Chem Res (2012) 21:1741–1750
˚
site of aromatase (2.62 A, Fig. 3e). In case of compound
˚
˚
5b (4.213 A, Fig. 3f) and compound 5c (4.241 A, Fig. 3g)
are showing the same binding mode (docking orientation),
these derivatives are forming week H-bonding with Ser 478
amino acid of the active site.
Conclusion
A series of novel 6,8-dibromo-2-aryl-2,3-dihydroquinolin-
4(1H)-ones (5a–j) was synthesized, characterized, and
evaluated for in vitro screening in MCF-7 breast cancer cell
lines. Compounds 5a, 5d, 5e, and 5g exhibited potent GI50
and TGI values compared with reference standard and
compounds 5b and 5c showed moderate activity. The
binding mode of the title compounds has been proposed
based on the docking studies. Further in silico docking
studies were undertaken to gain an insight into the
molecular interactions and binding mode of the target
compounds into aromatase enzyme. All the final com-
pounds were docked well into the active site and interacted
with the cyclic ketone group with the heme (Fe3?) of the
Fig. 2 Percentage growth control versus molar concentrations of
compounds
concentration of 10-4 M. Compounds 5a, 5d, 5e, and 5g
exhibited potent GI50 and TGI values compared with ref-
erence standard and compounds 5b and 5c showed mod-
erate GI50 and TGI values, whereas compounds 5f, 5h, 5i,
and 5j did not show significant GI50 and TGI values at
molar concentrations tested (Fig. 2).
The final compounds (5a–j) were evaluated in silico
(molecular docking) to recognize their hypothetical bind-
ing mode using the X-ray crystal structure of human pla-
cental microsomal aromatase and also to rationalize their
structure–activity relationships. To investigate the ability
of molecular docking to reproduce an experimentally
observed ligand-binding mode, the co-crystallized ligand
androstenedione has been used as reference ligand. It was
docked back into its binding site (Fig. 3a) of the crystal
structure of human placental microsomal aromatase using
GOLD molecular docking program. The top docked con-
formations (poses) closely resembled the co-crystallized
conformation with a root-mean-square deviation (RMSD)
˚
aromatase with a distance of 2.0–2.7 A. The most active
compounds 5a, 5d, 5e, and 5g are forming a H-bonding
with Ser 478 or Asp 309 amino acids of the active site,
which probably account for their better activity compared
to other analogs of the series. The docking results revealed
useful information to understand the interaction mode
between dihydroquinolin-4(1H)-ones and aromatase and
will facilitate the next cycle of drug design to explore the
newer lead molecules. Efforts are currently being taken up
to optimize the lead structure and the results of which will
be the basis of our future research endeavor.
˚
between 0.48 and 0.50 A of non-hydrogen atomic positions
of the ligand (androstenedione).
All the compounds were docked well into the active site
of aromatase enzyme. The cyclic ketone group interacts
with the heme (Fe3?) of the aromatase with a distance of
Experimental
Chemistry
˚
2.0–2.7 A. The potent compounds 5a, 5d, 5e, and 5g are
forming H-bonding with Ser 478 or Asp 309 amino acids of
the active site, which probably account for their better
activity, whereas this interaction is not possible with other
compounds. Fluoro derivative (5a) may form a H-bonding
Melting points were recorded in open capillaries on
LABINDIA melting point apparatus (MEPA MP08050204)
and were uncorrected. IR spectra were recorded on Perkin
Elmer FT-IR Spectrometer (Spectrum RX I) using KBr
1
pellet technique. H and 13C NMR spectra were recorded
˚
with Ser 478 (3.09 A, Fig. 3b) and nitro derivative (5d)
˚
may form a H-bonding with Ser 478 (2.65 A, Fig. 3c).
on Bruker Avance II 400 MHz spectrometer in CDCl3
using TMS as internal standard. Mass spectra (ESI) were
recorded on Waters Micromass Q-TOF Micro and ele-
mental analyses were performed using Thermo EA 2110
series elemental analyser. All chemicals used were of
analytical grade and commercially available from E.
Merck, Mumbai. Solvents were used without further puri-
fication. Silica gel (100–200 mesh; E. Merck, Mumbai)
Compound (5e) may form a H-bonding with Ser 478
˚
(3.68 A, Fig. 3d), unlike other derivatives H-bond forming
nitrogen atom is not directly attached to aromatic ring
which might here resulted in the docking orientation with a
˚
distance of 3.68 A between the nitrogen and HO-Ser 478
amino acid of the active site. Hydroxy derivative (5g) may
form a H-bonding with Asp 309 amino acid of the active
123

Med Chem Res (2012) 21:1741–1750
1745
Fig. 3 a Superposition of top
docked configurations of
androstenedione on crystal
structure within the active site
of aromatase, b Docking
orientation of 5a, c Docking
orientation of 5d, d Docking
orientation of 5e, e Docking
orientation of 5g, f Docking
orientation of 5b, and g Docking
orientation of 5c
Synthesis of 1-(2-amino-3,5-dibromophenyl)ethanone (2)
was used for column chromatography. All the reactions
were monitored by thin layer chromatography (TLC) on
precoated silica gel 60 F254 (mesh) (E. Merck, Mumbai)
and spots were visualized under UV light (254 nm).
Bromine (0.16 g, 1 mmol) dissolved in dichloromethane
(10 ml) was added dropwise to a solution containing
123

1746
Med Chem Res (2012) 21:1741–1750
1-(2-Amino-3,5-dibromophenyl)-3-(4-bromophenyl)prop-
2-en-1-one (4c)
2-aminoacetophenone (1) (0.135 g, 1 mmol) in dichloro-
methane (10 ml). The resulting mixture stirred for 7 h
at 0–5°C. The solid mass obtained was filtered and the
product was purified using column chromatography (hex-
ane, ethyl acetate; 95:5). The purified compound was
recrystallized from methanol (Baker et al., 2001; Leonard
and Boyd, 1946).
Yield, 68%; mp. 130–135°C; IR (KBr) cm-1: 3459.0,
3336.2 (–NH2), 1643.0 (C=O). 1H NMR (CDCl3,
400 MHz): d 6.90 (br s, 2H), 7.35 (d, J = 2.4 Hz, 1H),
7.51 (m, 5H), 7.68 (d, J = 15.6 Hz, 1H), 7.91 (d,
J = 2.4 Hz, 1H). Anal. Calcd for C15H10Br3NO: C, 39.17;
H, 2.19; N, 3.05. Found: C, 39.34; H, 2.10; N, 3.16.
Yield, 80%; mp. 120–122°C [lit. 123–124°C (Leonard
and Boyd, 1946)]; IR (KBr) cm-1: 3449.4, 3315.1 (–NH2),
1
1674.5 (C=O). H NMR (CDCl3, 400 MHz): d 2.58 (s,
1-(2-Amino-3,5-dibromophenyl)-3-(4-nitrophenyl)prop-2-
en-1-one (4d)
3H), 6.90 (br s, 2H), 6.67 (d, J = 2.2 Hz, 1H), 7.79 (d,
J = 2.2 Hz, 1H). 13C NMR (CDCl3, 100 MHz): d 199.1,
147.2, 140.1, 134.1, 119.6, 112.1, 106.0, 31.5. ES? [m/z,
(% relative intensity)] 295.9 (M?, ?4, 14), 293.9 (M?, ?2,
27), 291.9 (M?, 15), 277.9 (50), 275.9 (100), 273.9 (51),
253.9 (7), 251.9 (14), 249.9 (8), 215.0(49), 213.0 (52),
197.0 (55), 195.0 (53).
Yield, 62%; mp. 142–146°C; IR (KBr) cm-1: 3459.4,
3346.6 (–NH2), 1603.4 (C=O). 1H NMR (CDCl3,
400 MHz): d 6.99 (br s, 2H), 7.39 (d, J = 2.4 Hz, H), 7.49
(d, J = 15.8 Hz, 1H), 7.53 (d, J = 8.8 Hz, 2H), 7.79 (d,
J = 15.8 Hz, 1H), 7.84 (d, J = 8.8 Hz, 2H), 7.91 (d, J =
2.4 Hz, 1H). Anal. Calcd for C15H10Br2N2O3: C, 42.29; H,
2.37; N, 6.57. Found: C, 41.98; H, 2.41; N, 6.77.
Synthesis of 1-(2-amino-3,5-dibromophenyl)-3-(4-
aryl)prop-2-en-1-ones (4a–j)
4-(3-(2-Amino-3,5-dibromophenyl)-3-oxoprop-1-
enyl)benzonitrile (4e)
General procedure 1-(2-Amino-3,5-dibromophenyl)eth-
anone (2) (0.294 g, 1 mmol) was stirred with absolute
ethanol (8 ml) and sodium hydroxide (750 mg) mixture at
room temperature. To the mixture different aromatic
aldehydes (3a–j) (1 mmol) were added and further stirred
for 35–40 h, the temperature being maintained at 0–5°C.
The solid products were separated by filtration and re-
crystallised from aqueous ethanol (Donnelly and Farrell,
1990b; Wattanasin and Murphy, 1980).
Yield, 72%; mp. 190–192°C; IR (KBr) cm-1: 3451.4,
3328.9 (–NH2), 2222.1(C:N), 1647.0 (C=O). H NMR
1
(CDCl3, 400 MHz): d 6.42 (br s, 2H), 7.36 (d, J = 2.2 Hz,
1H), 7.49 (d, J = 15.6 Hz, 1H), 7.58 (d, J = 15.6 Hz, 1H),
7.73 (m, 4H), 7.89 (d, J = 2.2 Hz, 1H). 13C NMR (CDCl3,
100 MHz): d 189.7, 150.0, 141.2, 139.3, 137.4, 132.9,
132.7, 128.7, 125.5, 119.7, 119.2, 118.5, 113.3, 106.9.
Anal. Calcd for C16H10Br2N2O: C, 47.32; H, 2.48; N, 6.90.
Found: C, 47.56; H, 2.24; N, 6.98.
1-(2-Amino-3,5-dibromophenyl)-3-(4-fluorophenyl)prop-2-
en-1-one (4a)
1-(2-Amino-3,5-dibromophenyl)-3-(4-methoxyphenyl)prop-
2-en-1-one (4f)
Yield, 62%; mp. 118–120°C; IR (KBr) cm-1: 3457.3,
3314.2 (–NH2), 1647.4 (C=O). 1H NMR (CDCl3,
400 MHz): d 6.89 (br s, 2H), 7.34 (d, J = 2.4 Hz, 1H),
7.39 (d, J = 6.4 Hz, 2H), 7.48 (d, J = 15.8 Hz, 1H), 7.56
(d, J = 6.4 Hz, 2H), 7.65 (d, J = 15.6 Hz, 1H), 7.91 (d,
J = 2.4 Hz, 1H). Anal. Calcd for C15H10Br2FNO: C,
45.15; H, 2.53; N, 3.51. Found: C, 44.92; H, 2.56; N, 3.44.
Yield, 82%; mp. 130–135°C; IR (KBr) cm-1: 3460.2,
3331.2 (–NH2), 1638.6 (C=O), 1259 (C–O–C assym str),
1024.7 (C–O–C symm str). 1H NMR (CDCl3, 400 MHz): d
3.82 (s, 3H), 6.89 (br s, 2H), 6.96 (d, J = 8.76 Hz, 2H),
7.31 (d, J = 15.4 Hz, 1H), 7.60 (d, J = 8.8 Hz, 2H), 7.72
(d, J = 2.12 Hz, 1H), 7.75 (d, J = 15.4 Hz, 1H), 7.91 (d,
J = 2.12 Hz, 1H). Anal. Calcd for C16H13Br2NO2: C,
46.75; H, 3.19; N, 3.41. Found: C, 46.71; H, 3.42; N, 3.49.
1-(2-Amino-3,5-dibromophenyl)-3-(4-chlorophenyl)prop-
2-en-1-one (4b)
Yield, 65%; mp. 124–128°C; IR (KBr) cm-1: 3458.3,
3313.2 (–NH2), 1645.4 (C=O). 1H NMR (CDCl3,
400 MHz): d 6.92 (br s, 2H), 7.35 (d, J = 2.4 Hz, 1H),
7.40 (d, J = 8.2 Hz, 2H), 7.49 (d, J = 15.6 Hz, 1H), 7.58
(d, J = 8.2 Hz, 2H) 7.69 (d, J = 15.6 Hz, 1H), 7.92 (d,
J = 2.4 Hz, 1H). Anal. Calcd for C15H10Br2ClNO: C,
43.36; H, 2.43; N, 3.37. Found: C, 43.18; H, 2.61; N, 3.18.
1-(2-Amino-3,5-dibromophenyl)-3-(4-hydroxyphenyl)prop-
2-en-1-one (4g)
Yield, 60%; mp. 120–124°C; IR (KBr) cm-1: 3520 (–OH),
3458.6, 3334.5 (–NH2), 1637.2 (C=O). H NMR (CDCl3,
1
400 MHz): d 6.86 (br s, 2H), 6.95 (d, J = 8.72 Hz, 2H),
7.35 (d, J = 15.6 Hz, 1H), 7.62 (d, J = 8.8 Hz, 2H), 7.71
123

Med Chem Res (2012) 21:1741–1750
1747
6,8-Dibromo-2-(4-fluorophenyl)-2,3-dihydroquinolin-
4(1H)-one (5a)
(d, J = 2.16 Hz, 1H), 7.76 (d, J = 15.4 Hz, 1H), 7.90 (d,
J = 2.12 Hz, 1H), 7.97 (s, 1H). Anal. Calcd for
C15H11Br2NO2: C, 45.37; H, 2.79; N, 3.53. Found: C,
45.22; H, 2.53; N, 3.41.
Yield, 62%; mp. 135°C; IR (KBr) cm-1: 3353.2 (–NH),
1
1654.4 (C=O). H NMR (CDCl3, 400 MHz): d 2.81 (m,
2H), 4.55 (br s, 1H), 4.79 (m, 1H), 7.29 (m, 4H), 7.44 (d,
J = 2.6 Hz, 1H), 7.95 (d, J = 2.6 Hz, 1H). Anal. Calcd for
C15H10Br2FNO: C, 45.15; H, 2.53; N, 3.51. Found: C,
45.19; H, 2.46; N, 3.37.
1-(2-Amino-3,5-dibromophenyl)-3-(3-hydroxyphenyl)prop-
2-en-1-one (4h)
Yield, 58%; mp. 112–114°C; IR (KBr) cm-1: 3518 (–OH),
3459.6, 3335.5 (–NH2), 1637.2 (C=O). H NMR (CDCl3,
1
6,8-Dibromo-2-(4-chlorophenyl)-2,3-dihydroquinolin-
4(1H)-one (5b)
400 MHz): d 6.82 (br s, 2H), 7.12 (m, 4H), 7.34 (d,
J = 15.6 Hz, 1H), 7.72 (d, J = 2.16 Hz, 1H), 7.77 (d,
J = 15.4 Hz, 1H), 7.92 (d, J = 2.12 Hz, 1H), 7.95 (s, 1H).
Anal. Calcd for C15H11Br2NO2: C, 45.37; H, 2.79; N, 3.53.
Found: C, 45.28; H, 2.59; N, 3.44.
Yield, 58%; mp. 138–140°C; IR (KBr) cm-1: 3384.5
(–NH), 1656.7 (C=O). 1H NMR (CDCl3, 400 MHz): d 2.75
(m, 2H), 4.50 (br s, 1H), 4.72 (dd, J = 4.8, 12.8 Hz, 1H),
7.38 (m, 4H), 7.41 (d, J = 2.4 Hz, 1H), 7.97 (d,
J = 2.4 Hz, 1H). Anal. Calcd for C15H10Br2ClNO: C,
43.36; H, 2.43; N, 3.37. Found: C, 42.98; H, 2.66; N, 3.52.
1-(2-Amino-3,5-dibromophenyl)-3-(4-
(dimethylamino)phenyl)prop-2-en-1-one (4i)
Yield, 45%; mp. 146–148°C; IR (KBr) cm-1: 3462.1
(–NH2), 1606.6 (C=O). H NMR (CDCl3, 400 MHz): d
6,8-Dibromo-2-(4-bromophenyl)-2,3-dihydroquinolin-
4(1H)-one (5c)
1
3.05 (s, 6H), 6.83 (br s, 2H), 6.71 (d, J = 8.88 Hz, 2H),
7.20 (d, J = 15.68 Hz, 1H), 7.6 (d, J = 2.16 Hz, 1H), 7.50
(d, J = 8.88 Hz, 2H), 7.77 (d, J = 15.24 Hz, 1H), 7.91(d,
J = 2.16 Hz, 1H). Anal. Calcd for C17H16Br2N2O: C,
48.14; H, 3.80; N, 6.60. Found: C, 47.96; H, 4.10; N, 6.85.
Yield, 67%; mp. 146–148°C; IR (KBr) cm-1: 3391.5
(–NH), 1674.3 (C=O). 1H NMR (CDCl3, 400 MHz): d 2.79
(m, 2H), 4.52 (br s, 1H), 4.70 (dd, J = 4.8, 12.4 Hz, 1H),
7.32 (d, J = 8.8 Hz, 2H), 7.40 (d, J = 2.4 Hz, 1H), 7.52
(d, J = 8.8 Hz, 2H), 7.97 (d, J = 2.4 Hz, 1H). Anal. Calcd
for C15H10Br3NO: C, 39.17; H, 2.19; N, 3.05. Found: C,
40.06; H, 2.47; N, 3.18.
1-(2-amino-3,5-dibromophenyl)-3-(3,4,5-
trimethoxyphenyl)prop-2-en-1-one (4j)
6,8-Dibromo-2-(4-nitrophenyl)-2,3-dihydroquinolin-
4(1H)-one (5d)
Yield, 55%; mp. 128–130°C; IR (KBr) cm-1: 3458.2
(–NH2), 1645 (–C=O), 1248 (C–O–C asym str), 1113
(C–O–C symm str). 1H NMR (CDCl3, 400 MHz): d 3.90 (s,
9H), 6.91 (br s, 2H), 6.86 (s, 2H) 7.3 (d, J = 15.4 Hz, 1H),
7.6 (d, J = 15.4 Hz, 1H), 7.71 (d, J = 2.16 Hz, 1H), 7.91
(d, J = 2.2 Hz, 1H). Anal. Calcd for C18H17Br2NO4: C,
45.89; H, 3.64; N, 2.97. Found: C, 45.93; H, 3.42; N, 3.18.
Yield, 58%; mp. 144–148°C; IR (KBr) cm-1: 3384.5
(–NH), 1656.7 (C=O). 1H NMR (CDCl3, 400 MHz): d 2.81
(m, 2H), 4.56 (br s, 1H), 4.81 (m, 1H), 7.44 (d, J = 2.2 Hz,
1H), 7.72 (d, J = 8.24 Hz, 2H), 7.58 (d, J = 8.24 Hz, 2H),
7.96 (d, J = 2.2 Hz, 1H). Anal. Calcd for C15H10Br2N2O3:
C, 42.29; H, 2.37; N, 6.57. Found: C, 42.11; H, 2.39; N,
6.42.
Synthesis of 6,8-dibromo-2-aryl-2,3-dihydroquinolin-
4(1H)-one (5a–j)
4-(6,8-Dibromo-4-oxo-1,2,3,4-tetrahydroquinolin-2-
yl)benzonitrile (5e)
General procedure 1-(2-Amino-3,5-dibromophenyl)-3-
(4-aryl)prop-2-en-1-ones (4a–j) (3 mmol) were heated
with orthophosphoric acid (12 ml) and acetic acid (12 ml)
at 100°C for 2–3 h. The reaction was monitored by TLC.
After cooling, the reaction mixture was added to 100 ml of
ice cold water and the resultant precipitate was filtered.
Crude product was purified by column chromatography
(hexane, ethyl acetate; 99:1) (Donnelly and Farrell, 1990a;
Tokes et al., 1992).
Yield, 72%; mp. 242–246°C; IR (KBr) cm-1: 3352.7
1
(–NH), 2225.2 (C:N), 1671.7 (C=O). H NMR (CDCl3,
400 MHz): d 2.82 (m, 2H), 4.58 (br s, 1H), 4.82 (m, 1H),
7.43 (d, J = 2.2 Hz, 1H), 7.59 (d, J = 8.24 Hz, 2H), 7.71
(d, J = 8.24 Hz, 2H), 7.97 (d, J = 2.2 Hz, 1H). 13C NMR
(CDCl3, 100 MHz): d 190.8, 149.7, 145.8, 138.2, 132.9,
130.0, 127.4, 120.3, 118.3, 117.9, 112.6, 111.5, 57.9, 45.6.
123

1748
Med Chem Res (2012) 21:1741–1750
Anal. Calcd for C16H10Br2N2O: C, 47.32; H, 2.48; N, 6.90.
Found: C, 47.12; H, 2.44; N, 6.56.
13.16 Hz, 1H), 6.67 (s, 2H), 7.71 (d, J = 2.24 Hz, 1H),
7.90 (d, J = 2.08 Hz, 1H). Anal. Calcd for C18H17Br2NO4:
C, 45.89; H, 3.64; N, 2.97. Found: C, 46.12; H, 3.84; N,
2.91.
6,8-Dibromo-2-(4-methoxyphenyl)-2,3-dihydroquinolin-
4(1H)-one (5f)
L-Proline catalyzed cyclization of 1-(2-amino-3,5-
dibromophenyl)ethanone (2)
Yield, 68%; mp. 162–166°C; IR (KBr) cm-1: 3376.4
(–NH), 1665.8 (C=O), 1247.9 (C–O–C assym str), 1029.2
1
(C–O–C symm str). H NMR (CDCl3, 400 MHz): d 2.81
1-(2-Amino-3,5-dibromophenyl)ethanone (2) and aromatic
aldehydes (3a–j) in equimolar quantities were stirred in the
presence of L-proline (30 mol%) in methanol for 48 h, the
temperature being maintained at 55–60°C (Chandrasekhar
et al., 2007). After completion of reaction (monitored by
TLC), reaction mixture was treated with saturated ammo-
nium chloride solution and extracted with dichlorometh-
ane. The combined organic layers were dried over
anhydrous sodium sulfate, concentrated under reduced
pressure and purified by column chromatography (hexane,
ethyl acetate; 95:5). The percentage yields were found to
be comparable to that of synthesis via chalcones.
(m, 2H), 3.82 (s, 3H), 4.57 (br s, 1H), 4.72 (dd, J = 3.8,
13.36 Hz, 1H), 6.96 (d, J = 6.72 Hz, 2H), 7.39 (d,
J = 6.72 Hz, 2H), 7.71 (d, J = 2.8 Hz, 1H), 7.92 (d,
J = 2.28 Hz, 1H). Anal. Calcd for C16H13Br2NO2: C,
46.75; H, 3.19; N, 3.41. Found: C, 46.52; H, 3.47; N, 3.21.
6,8-Dibromo-2-(4-hydroxyphenyl)-2,3-dihydroquinolin-
4(1H)-one (5g)
Yield, 58%; mp. 122–125°C; IR (KBr) cm-1: 3375.2
(–NH), 3596 (–OH), 1661.8 (C=O). 1H NMR (CDCl3,
400 MHz): d 2.75 (m, 2H), 4.68 (br s, 1H), 4.81 (m, 1H),
7.19 (m, 4H), 7.69 (d, J = 2.6 Hz, 1H), 7.89 (d, J =
2.6 Hz, 1H), 7.97 (s, 1H). Anal. Calcd for C15H11Br2NO2:
C, 45.37; H, 2.79; N, 3.53. Found: C, 45.21; H, 2.86; N,
3.33.
In vitro screening using MCF-7 breast cancer cell lines
The cell lines were grown in RPMI 1640 medium con-
taining 10% fetal bovine serum and 2 mM L-glutamine. For
present screening experiment, cells were inoculated into 96-
well microtiter plates in 100 ll at plating densities as shown
in the study details above, depending on the doubling time
of individual cell lines. After cell inoculation, the microtiter
plates were inoculated at 37°C, 5% CO2, 95% air and 100%
relative humidity for 24 h prior to addition of test com-
pounds (Vanicha and Kanyawim, 2006).
After 24 h, one 96-well plate containing 5 9 103 cells/
well was fixed in situ with TCA, to represent a measure-
ment of the cell population at the time of drug addition
(Tz). Test compounds were initially solubilized in dimethyl
sulfoxide at 1 mg/ml and stored frozen prior to use. At the
time of drug addition, an aliquot of frozen concentrate
(1 mg/ml) was thawed and diluted to 100, 200, 400, and
800 lg/ml with complete medium containing test article.
Aliquots of 10 ll of these different drug dilutions were
added to the appropriate microtiter wells already contain-
ing 90 ll of medium, resulting in the required final drug
concentrations (10, 20, 40, and 80 lg/ml) (Skehn et al.,
1990).
6,8-Dibromo-2-(3-hydroxyphenyl)-2,3-dihydroquinolin-
4(1H)-one (5h)
Yield, 55%; mp. 125–128°C; IR (KBr) cm-1: 3350 (–NH),
1
3245 (–OH), 1661 (C=O). H NMR (CDCl3, 400 MHz): d
2.81 (m, 2H), 4.53 (br s, 1H), 5.01 (m, 1H), 7.42 (m, 4H),
7.73 (d, J = 2.24 Hz, 1H), 7.91 (d, J = 2.36 Hz, 1H), 8.01
(s, 1H). Anal. Calcd for C15H11Br2NO2: C, 45.37; H, 2.79;
N, 3.53. Found: C, 45.52; H, 2.54; N, 3.50.
6,8-Dibromo-2-(4-(dimethylamino)phenyl)-2,3-
dihydroquinolin-4(1H)-one (5i)
Yield, 66%; mp. 138–140°C; IR (KBr) cm-1: 3363.0
(–NH), 1681.8 (C=O). 1H NMR (CDCl3, 400 MHz): d 2.80
(m, 2H), 4.52 (br s, 1H), 4.74 (dd, J = 3.68, 13.76 Hz,
1H), 6.73(d, J = 8.6 Hz, 2H), 7.31 (d, J = 8.76 Hz, 2H),
7.69 (d, J = 2.28 Hz, 1H), 7.89 (d, J = 2.22 Hz, 1H).
Anal. Calcd for C17H16Br2N2O: C, 48.14; H, 3.80; N, 6.60.
Found: C, 48.42; H, 3.65; N, 6.79.
End point measurement
6,8-Dibromo-2-(3,4,5-trimethoxyphenyl)-2,3-
dihydroquinolin-4(1H)-one (5j)
After the sample addition, plates were incubated at stan-
dard condition for 48 h and assay was terminated by the
addition of cold TCA. Cells were fixed in situ by the gentle
addition of 50 ll of cold 30% (w/v) TCA (final concen-
tration, 10% TCA) and incubated for 60 min at 40°C. The
Yield, 60%; mp. 152–154°C; IR (KBr) cm-1: 3390.4
(–NH), 1676.3 (C=O). 1H NMR (CDCl3, 400 MHz): d 2.89
(m, 2H), 3.91(s, 9H), 4.55 (br s, 1H), 4.69 (dd, J = 4.08,
123

Med Chem Res (2012) 21:1741–1750
1749
supernatant was discarded; the plates were washed five
times with tap water and air dried. Sulforhodamine B
(SRB) solution (50 ll) at 0.4% (w/v) in 1% acetic acid was
added to each of the wells, and plates were incubated for
20 min at room temperature. After staining, unbound dye
was recovered and the residual dye was removed by
washing five times with 1% acetic acid. The plates were air
dried. Bound stain was subsequently eluted with 10 mM
trizma base, and the absorbance was read on a plate reader
at a wavelength of 540 nm with 690 nm reference wave-
length. Percent growth was calculated on a plate-by-plate
basis for test wells relative to control wells. Percent growth
was expressed as the ratio of average absorbance of the test
well to the average absorbance of the control wells 9 100.
Using the six absorbance measurements [time zero (Tz),
control growth (C), and test growth in the presence of drug
at the four concentration levels (Ti)], the percentage growth
was calculated at each of the drug concentration levels.
Percent growth inhibition was calculated as:
Quodro FX 4500 graphics card. Genetic optimization for
ligand docking (GOLD v4.0) molecular docking program
used in this study, which was obtained from Cambridge
Crystallographic Data Centre (CCDC), Cambridge (GOLD,
2008).
Protein preparation
The crystal structure of human placental microsomal aro-
matase with its bound natural substrate androstenedione was
taken from the Protein Data Bank (PDB ID: 3EQM) (Ghosh
et al., 2009) for protein preparation using Schrodinger pro-
tein preparation wizard tool (PPrep) (Protein preparation
(PPrep) Wizard, 2009). This performs the following steps:
assigning of bond orders, addition of hydrogens, and opti-
mization of hydrogen bonds by flipping amino side chains,
correction of charges, and minimization of the protein
complex. All the bound water molecules, ligands, and
cofactors were removed (preprocess) from the proteins
which were taken in ‘.mae’ format. The tool neutralized the
side chains that are not close to the binding cavity and do not
participate in salt bridges. This step is then followed by
restrained minimization of co-crystallized complex, which
reorients side chain hydroxyl groups and alleviates potential
steric clashes. The complex obtained was minimized using
OPLS_2005 force field with Polack-Ribiere Conjugate
Gradient (PRCG) algorithm. The minimization was termi-
nated either by completion of 5,000 steps or till the energy
gradient converged below 0.05 kcal/mol.
½ðTi ꢁ TzÞ=ðC ꢁ TzÞꢂ ꢃ 100
for concentrations for which Ti ꢄ Tz ðTi ꢁ TzÞ
positive or zero
½ðTi ꢁ TzÞ=Tzꢂ ꢃ 100
for concentrations for which Ti\TzðTi ꢁ TzÞ negative
The dose–response parameters were calculated for each
test article. Growth inhibition of 50% (GI50) was calculated
from ½ðTi ꢁ TzÞ=ðC ꢁ TzÞꢂ ꢃ 100 ¼ 50; which is the test
compound concentration resulting in a 50% reduction in
the net protein increase (as measured by SRB staining) in
control cells during the test compound incubation. The
drug concentration resulting in TGI was calculated from
Ti = Tz. The LC50 (concentration of test compound
resulting in a 50% reduction in the measured protein at
the end of the test compound treatment as compared to that
at the beginning) indicating a net loss of cells following
treatment is calculated from
Ligand preparation
Structures of the ligands were sketched using built panel of
Maestro and taken in ‘.mae’ format. LigPrep was used for
final preparation of ligands, LigPrep is a utility of Schro-
dinger software suit that combines tools for generating 3D
structures from 1D (Smiles) and 2D (SDF) representation,
searching for tautomers, steric isomers and perform a
geometry minimization of the ligands. The ligands were
minimized by means of molecular mechanics force fields
(OPLS_2005) with default setting.
½ðTi ꢁ TzÞ=Tzꢂ ꢃ 100 ¼ ꢁ50:
Values were calculated for each of these three
parameters if the level of activity was reached; however,
if the effect was not reached or was exceeded, the values
for that parameter were expressed as greater or less than the
maximum or minimum concentration tested.
GOLD docking
GOLD is a ligand-docking application that utilizes a genetic
algorithm (GA) to explore ligand conformation flexibility
and orientation with partial flexibility of the protein, and
satisfy ligand-binding requirements. One advantage of
GOLD over many other docking algorithms is that it allows
for both unconstrained ligand flexibility and partial flexi-
bility of the binding pocket thus affording a more realistic
environment for ligand–receptor associations. For each of
the 10 independent GA runs, a maximum number of 100
Docking
Computational details
Molecular modeling investigations were carried out using
Dell Precision work station T3400 running Intel Core2 Duo
Processor, 4 GB RAM, 250 GB hard disk, and NVidia
123

1750
Med Chem Res (2012) 21:1741–1750
Donnelly JA, Farrell DF (1990a) Chalcone derivatives as precursors
of 1, 2, 3, 4-tetrahydro-4-quinolones. Tetrahedron 46:885–894
Donnelly JA, Farrell DF (1990b) The chemistry of 20-amino
anologues of 20-hydoxychalcone and its derivatives. J Org Chem
55:1757–1761
GA operations were performed. The standard set parame-
ters were used in all the calculations. User defined default
operator weights were used for crossover, mutation, and
migration of 95, 95, and 10, respectively. Default cutoff
˚
˚
Ghosh D, Griswold J, Erman M, Pangborn W (2009) Structural basis
for androgen specificity and oestrogen synthesis in human
aromatase. Nature 457:219–224
values of 2.5 A (for hydrogen bonds) and 4.0 A (for vdW)
were employed. Pop. Size = 100; max ops = 100,000;
niche size = 2 were also employed. To further speed up the
calculation, the GA docking was terminated when the top
ICMR (2008) Consolidated report of the population based cancer
registries 2008. National Cancer Registry Programme, New Delhi
Jeong HJ, Shin YG, Kim IH, Pezzuto JM (1999) Inhibition of
aromatase activity by flavonoids. Arch Pharm Res 22:309–312
Kao YC, Zhou C, Sherman M, Laughton CA, Chen S (1998)
Molecular basis of the inhibition of human aromatase (estrogen
synthetase) by flavone and isoflavone phytoestrogens: a site-
directed mutagenesis study. Environ Health Perspect 106:85–92
Le-Bail JC, Laroche T, Marre-Fournier F, Habrioux G (1998)
Aromatase and 17b-hydroxysteroid dehydrogenase inhibition
by flavonoids. Cancer Lett 133:101–106
Leonard NJ, Boyd SN (1946) Cinnolines: synthesis of aminoace-
tophenones and aminopropiophenones. J Org Chem 11:405–418
Mooij WTM, Verdonk ML (2005) General and targeted statistical
potentials for protein–ligand interactions. Proteins Struct Funct
Bioinf 61:272–287
Murthy N, Rao AR, Sastry GN (2004) Aromatase inhibitors: a new
paradigm in breast cancer treatment. Curr Med Chem Anticancer
Agents 4:523–534
Murthy JN, Nagaraju M, Sastry GM, Rao AR, Sastry GN (2006)
Active site acidic residues and structural analysis of medelled
human aromatase: a potential drug target for breast cancer.
J Comput Aided Mol Des 19:857–870
˚
three solutions were within 1.5 A RMSD of each other.
Astex statistical potential (ASP) score recorded on each
binding mode using a fitness function that accounts for the
frequency of interactions between ligand and receptor
atoms (heme) (Mooij and Verdonk, 2005). ASP score is the
atom–atom potential derived from a database of protein–
ligand complexes. Traditional scoring functions are based
on force field or on regression, where parameters are
derived from a set of experimental binding affinities and
structures. ASP score uses a different approach; information
about the frequency of interaction between ligand and
receptor atoms (heme) is gathered by analyzing existing
ligand–protein structures in the PDB and this information is
used to generate statistical potentials. The empirical
parameters used in the scoring function are hydrogen bond
energies, atom radii, polarisabilities, torsion potentials, and
hydrogen bond directionalities. The top 10 ranked solutions
of the ligands were taken for further observation of binding
orientation and H-bond interactions.
Needleman SJ, Tobias JS (2008) Aromatase inhibitors in early
hormone receptor-positive breast cancer: what is the optimal
initiation time for the maximum benefit? Drugs 68:1–15
Okada M, Yoden T, Kawaminami E, Shimada Y, Kudoh M, Isomura
Acknowledgments The authors thank the Chairman, University
Institute of Pharmaceutical Sciences, Panjab University (PU), Chan-
digarh for providing the facilities and BLN thanks the University
Grants Commission (UGC), New Delhi for granting a fellowship
[Research Fellowship in Science for Meritorious Students, F.4-3/
2006(BSR)/5-94/2007(BSR)] and AK, RA, and RS thank the UGC for
providing JRF. We gratefully acknowledge Mrs. Lauren Thomas,
CCDC, Cambridge, UK for providing the GOLD software. We thank
Dr R. S. Varma (M/s Senative Therapeutics (P) Ltd.), Hyderabad for
financial support.
Y, Shikama H, Fujikura
T (1996) Studies on aromatase
inhibitors. I. Synthesis and biological evaluation of 4-amino-
4H-1, 2, 4-triazole derivatives. Chem Pharm Bull 44:1871–1879
Pelissero C, Lenczowski MJ, Chinzi D, Cuisset DB, Sumpter JP,
Fostier A (1996) Effects of flavonoids on aromatase activity, an
in vitro study. J Steroid Biochem Mol Biol 57:215–223
Pouget C, Lauthier F, Simon AA (2001) Flavonoids: structural
requirements for antiproliferative activity on breast cancer cells.
Bioorg Med Chem Lett 11:3095–3097
Protein preparation (PPrep) Wizard (2009) Schrodinger LLC,
New York
Rao AR, Murthy JN (2009) Novel tetrahydroquinolines as aromatase
inhibitors. WO 2009087684A2
Skehn P, Storeng R, Scudiero A, Monks J, Mcmohan D, Vistica D,
Jonathan TW, Bokesch H, Kenney S, Boyd MR (1990) New
colorimetric cytotoxicity assay for anticancer drug screening.
J Natl Cancer Inst 82:1107–1117
Tokes AL, Litkei G, Szilagyi LN (1992) Heterocycles by cyclization
20-NHR chalcones, 20-NHR chalcone dibromides and 20-NHR
azidochalcones. Synth Commun 22:2433–2445
Vanicha V, Kanyawim K (2006) Sulforhodamine B colorimetric
assay for cytotoxicity screening. Nat Protoc 1:1112–1116
Wattanasin S, Murphy WS (1980) An improved procedure for the
preparation of chalcones and related enones. Synth Commun
647:650
References
GOLD v4.0.1 (2008) Cambridge Crystallographic Data Centre,
Cambridge, UK
Baker LJ, Copp BR, Rickard CEF (2001) 20-Amino-30, 50-dibromo-
acetophenone. Acta Cryst E57:538–539
Bandi P, Boone M, Brinton L, Buchert S (2010) Breast cancer facts &
figures 2009–2010. American Cancer Society, Atlanta
Carlo DG, Mascolo N, Capasso F (1999) Flavonoids, old and new
aspects of a class of natural therapeutic drugs. Life Sci 49:337–353
Chandrasekhar S, Vijeender K, Sridhar C (2007) L-Proline-catalyzed
one-pot synthesis of 2-aryl-2, 3- dihydroquinolin-4(1H)-ones.
Tetrahedron Lett 48:4935–4937
123