Synthesis and anti-breast cancer activities of substituted quinolines

Article abstract of DOI:10.1016/j.bmcl.2008.04.024

Promising anti-breast cancer agents derived from substituted quinolines were discovered. The quinolines were readily synthesized in a large scale from a sequence of reactions starting from 4-acetamidoanisole. The Michael addition product was isolated as the reaction intermediate in the ring closing reaction of 4-amino-5-nitro-2-(3-trifluoromethylphenyloxy)anisole with methyl vinyl ketone leading to 6-methoxy-4-methyl-8-nitro-5-(3-trifluoromethylphenyloxy)quinoline (14). The amino function of 8-amino-6-methoxy-4-methyl-5-(3-trifluoromethylphenyloxy)quinoline, prepared from 14, was connected to various side chains via alkylation with N-(3-iodopropyl)phthalimide, Michael addition with acrylonitrile, and reductive amination with various heterocycle carboxaldehydes, such as imidazole-4-carboxaldehyde, thiophene-2-carboxaldehyde, and 2-furaldehyde. Effects of the substituted quinolines on cell viability of T47D breast cancer cells using trypan blue exclusion assay were examined. The results showed that the IC₅₀ value of 6-methoxy-8-[(2-furanylmethyl)amino]-4-methyl-5-(3-trifluoromethylphenyl oxy)quinoline is 16 ± 3 nM, the lowest IC₅₀ out of all the quinolines tested. IC₅₀ values of three other quinolines are in the nanomolar range, a desirable range for pharmacological testing.

Full text of DOI:10.1016/j.bmcl.2008.04.024

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Bioorganic & Medicinal Chemistry Letters 18 (2008) 3364–3368
Synthesis and anti-breast cancer activities of substituted quinolinesq
Aibin Shi,a Thu A. Nguyen,b Srinivas K. Battina,a Sandeep Rana,a Dolores J. Takemoto,c
Peter K. Chiangd,e and Duy H. Huaa,*
aDepartment of Chemistry, Kansas State University, Manhattan, KS 66506, USA
bDiagnostic Medicine and Pathology, Kansas State University, Manhattan, KS 66506, USA
cDepartment of Biochemistry, Kansas State University, Manhattan, KS 66506, USA
dDepartment of Pathology and Sandler Center, QB3, University of California, San Francisco, CA 94143, USA
e
Pharmadyn Inc., 525 Del Rey Avenue, Sunnyvale, CA 94085, USA
Received 24 February 2008; revised 8 April 2008; accepted 10 April 2008
Available online 13 April 2008
Abstract—Promising anti-breast cancer agents derived from substituted quinolines were discovered. The quinolines were readily syn-
thesized in a large scale from a sequence of reactions starting from 4-acetamidoanisole. The Michael addition product was isolated as
the reaction intermediate in the ring closing reaction of 4-amino-5-nitro-2-(3-trifluoromethylphenyloxy)anisole with methyl vinyl
ketone leading to 6-methoxy-4-methyl-8-nitro-5-(3-trifluoromethylphenyloxy)quinoline (14). The amino function of 8-amino-6-meth-
oxy-4-methyl-5-(3-trifluoromethylphenyloxy)quinoline, prepared from 14, was connected to various side chains via alkylation with N-
(3-iodopropyl)phthalimide, Michael addition with acrylonitrile, and reductive amination with various heterocycle carboxaldehydes,
such as imidazole-4-carboxaldehyde, thiophene-2-carboxaldehyde, and 2-furaldehyde. Effects of the substituted quinolines on cell
viability of T47D breast cancer cells using trypan blue exclusion assay were examined. The results showed that the IC50 value of
6-methoxy-8-[(2-furanylmethyl)amino]-4-methyl-5-(3-trifluoromethylphenyloxy)quinoline is 16 3 nM, the lowest IC50 out of all
the quinolines tested. IC50 values of three other quinolines are in the nanomolar range, a desirable range for pharmacological testing.
Ó 2008 Elsevier Ltd. All rights reserved.
Quinolines are known for their anti-malarial,1–3 leish-
manicidal,4 antibacterial,5 and anticancer activities.6–9
Recently, quinolines were examined in ATP-binding
cassette drug transporter inhibition,6 targeting tumor
hypoxia,7 modulation of multidrug resistance,8 and
tyrosine kinase inhibition.9 Based on these literature re-
sults, we investigated the substituted quinolines in
search of novel anti-breast cancer compounds. After
our initial anticancer screening, we focused on the
substituted quinolines with a skeletal structure derived
synthetic substituted quinolines are summarized in
Figure 1.
F3C
O
CH3
N
MeO
from
8-amino-5-(aryloxy)-6-methoxy-4-methylquino-
NHR
line,1 by derivatizing its C8-amino side chain. We report
herein the syntheses of new quinolines possessing amine,
nitrile, imidate, amidine, and heterocyclic functionalities
in the C8-amino side chain, and their potent anti-breast
cancer activities against T47D breast cancer cells. The
H2C
6 : R =
1 : R = CH2CH2CH2NH2
2 : R = CH2CH2CN
S
3 : R = CH2CH2C(=NH)OCH2CH3
4 : R = CH2CH2C(=NH)NH2
7 : R = H2C
O
Keywords: Synthesis of substituted quinolines; Anti-breast-cancer agents;
T47D breast cancer cells.
q
This manuscript is dedicated to ProfessorE.J. Corey on the occasion
of his 80th birthday.
H2C
5 : R =
NH
N
*
Corresponding author. Tel.: +1 785 532 6699; fax: +1 785 532
6666; e-mail: duy@ksu.edu
Figure 1. Structural formulas of substituted quinolines.
0960-894X/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2008.04.024

A. Shi et al. / Bioorg. Med. Chem. Lett. 18 (2008) 3364–3368
3365
We utilized a similar synthetic method leading to 5-
(aryloxy)-4-methylprimaquine1,10 by starting with 4-ace-
tamidoanisole (8) via sequential C2 and C5 functional-
izations followed by a ring closing reaction. Hence, 2-
bromo-4-acetamido-5-nitroanisole (10)10 was prepared
from the bromination of compound 8 at C2 followed
by nitration at C5. Displacement of bromide 6 with
potassium 3-trifluoromethylphenoxide (11) in N,N-
dimethylformamide (DMF) at 120 °C gave 4-acetam-
ido-5-nitro-2-(3-trifluoromethylphenyloxy)anisole (12).
Removal of the acetyl protecting group of 12 with
hydrochloric acid in ethanol afforded 4-amino-5-nitro-
2-(3-trifluoromethylphenyloxy)anisole (13) (see Scheme
1).
Various reaction conditions were studied to maximize
the yield of the construction of the quinoline ring
from compound 13 with methyl vinyl ketone.2 Treat-
ment of 13 with vinyl methyl ketone, arsenic acid,
and 85% phosphoric acid at 100 °C after 20 min,8
a
mixture of desired quinoline 14 and 1,4-adduct 15
along with starting material 13 was obtained in a ratio
Br
Br
MeO
HNO3, Ac2O
AcOH
MeO
MeO
Br2, AcOH
(69% yield)
(82% yield)
NHCOCH3
NHCOCH3
NHCOCH3
NO2
8
9
10
O
CF3
O
CF3
KO
CF3
HCl. EtOH
(95% yield)
MeO
11
MeO
DMF, 120oC
(79% yield)
NHCOCH3
NH2
NO2
NO2
12
13
Scheme 1. Preparation of 4-amino-5-nitro-2-(3-trifluromethylphenyloxy)anisole (13).
methyl vinyl ketone
H3AsO4
85% H3PO4
O
Me
F3C
O
F3C
MeO
MeO
13
+
120oC, 20 min.
N
N
H
O
NO2
14
NO2
15
(7% yield)
(52% yield)
H3AsO4,
85% H3PO4
14
+
13
15
100oC, 20 min.
3-butyn-2-one
H3AsO4
85% H3PO4
14
13
100oC (24% yield)
Scheme 2. Preparation of quinoline 14.

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A. Shi et al. / Bioorg. Med. Chem. Lett. 18 (2008) 3364–3368
of 1:2:1. When the reaction was carried out at 120 °C
for 20 min, a 7:1:1 ratio of compounds 14:15:13 was
achieved (Scheme 2). The crude products were sepa-
rated by silica gel column chromatography to give a
52% yield of compound 14, 7% yield of compound
15, and 7% recovery of 13. A longer reaction time re-
sulted in the decomposition of the products and yields
were not improved. The use of excess of vinyl methyl
ketone did not improve the yield either. The 1,4-ad-
duct, 15, can be treated with arsenic acid and phos-
phoric acid under similar reaction conditions as that
mentioned above to give quinoline 14 and amine 13
along with starting material 15 in a ratio of ꢀ7:1:1.
Hence, uses of a large excess of arsenic acid and
85% phosphoric acid may minimize the formation of
intermediate 15. The results suggest that adduct 15
is the reaction intermediate leading to quinoline 14,
but it also underwent reversed Michael addition reac-
tion to provide amine 13 and vinyl methyl ketone.
Since conjugated alkynones had been used in the con-
struction of quinolines from aromatic amines,4,11
amine 13 was treated with 3-butyn-2-one and arsenic
acid and phosphoric acid at 100 °C. Desired product
14 was isolated in a 24% yield along with 28% of
recovery of starting material 13. The 1,4-adduct was
not detected, and various unidentifiable oligomers
were obtained. The lower yield may contribute to
the ease of polymerization of the terminal alkynone
or the decomposition of the intermediate 1,4-adduct.
of the nitro function of 14 with iron powder in acetic
acid–water under reflux gave a 96% yield of amino quin-
oline 16 (Scheme 3). Alkylation of 16 with iodide 1712
and sodium bicarbonate in DMF produced compound
18 which upon treatment with hydrazine in refluxing
ethanol afforded quinoline 1.
Quinolines 2–4 were synthesized through a Michael
addition reaction of arylamine 16 with acrylonitrile
in phenol13 at 100 °C in a sealed tube and gave adduct
2 (61% yield). No reaction was found when 16 was
treated with acrylonitrile in refluxing ethanol.14 Ethan-
olysis of quinoline 2 with HCl (gas) in ethanol15 pro-
duced ethyl imidate 3, which upon treatment with
NH3 (gas) in ethanol16 at 50 °C for 6 h afforded ami-
dine 4 (57% yield) along with 13% of recovered start-
ing material 3.
Quinolines 5–7 were synthesized via a reductive amina-
tion of amine 16 and aldehydes (Scheme 4). Treatment
of amine 16 with aldehyde 19 in methanol–acetic acid
followed by sodium cyanoborohydride17 furnished quin-
oline 5. Similar treatment of amine 16 with aldehydes 20
and 21 separately afforded quinolines 6 and 7, respec-
tively. Aldehyde 19 was prepared from the oxidation
of 4-hydroxymethylimidazole with manganese dioxide
in methanol (99% yield).18
The effects of quinolines 1–7 on cell viability of T47D
breast cancer cells using trypan blue exclusion assay
were examined. The trypan blue exclusion assay pro-
vides a rapid and effective means in screening multiple
drugs.19 Assays for each compound were conducted in
Quinoline 14 was converted to compound 16,2 which
serves as the precursor to produce various substituted
quinolines depicted in Figure 1. Hence, the reduction
O
N
(CH2)3
I
O
Me
F3C
Fe, H2O
AcOH
O
Me
F3C
O
MeO
(17)
MeO
14
(96% yield)
O
NaHCO3, DMF
(72% yield)
N
N
N
HN
NH2
O
16
18
H2NNH2, EtOH
1
(80% yield)
Phenol
1. EtOH, HCl
(69% yield)
O
Me
F3C
O
Me
100oC, 48 h
F3C
16
MeO
MeO
2. NH3, EtOH
(57% yield)
CN
61% yield)
N
N
HN
HN
CN
R
2
3 : R = C(=NH)OCH2CH3
4 : R = C(=NH)NH2
Scheme 3. Synthesis of substituted quinolines 1– 4.

A. Shi et al. / Bioorg. Med. Chem. Lett. 18 (2008) 3364–3368
3367
O
Me
N
F3C
NaBH3CN
MeOH
O
H
Y
16
+
MeO
AcOH
X
19 : X = NH, Y = N
20 : X = S, Y = CH
21 : X = O, Y = CH
Y
HN
X
5 : X = NH, Y = N (79% yield)
6 : X = S, Y = CH (47% yield)
7 : X = O, Y = CH (52% yield)
Scheme 4. Synthesis of substituted quinolines 5 – 7.
Table 1. Cell viability using trypan blue exclusion
Compound
1
2
3
4
5
6
7
IC50 value (nM)
119 21
378 79
1974 404
519 102
1276 246
3732 696
15.6 3.0
T47D breast cancer cells were treated with various concentrations of 1–7 for 2 days. A cell suspension was mixed with trypan blue dye and then
visually examined to determine whether cells take up or exclude dye. The number of live cells (excluded dye) was quantified and IC50 value for each
compound was determined.
triplicate and the statistical significances are shown
along with the IC50 values in Table 1. The results
Supplementary data
showed that the IC50 value of quinoline
7
is
Synthetic procedure, analysis data, cell line and cell cul-
ture, and protocols for cell-viability assay. Supplemen-
tary data associated with this article can be found, in
the online version, at doi:10.1016/j.bmcl.2008.04.024.
16 3 nM, the lowest IC50 out of all the quinolines
tested. The weak inhibition of quinoline 6 may due to
the oxidation of sulfur of the thiophene moiety during
the 2-day incubation with the T47D breast cancer cells.
IC50 values of 1, 2, and 4 are in the nanomolar range, a
desirable range for pharmacological testing. Compound
1620 did not inhibit T47D cell viability even at 10 lM
concentration.
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Acknowledgments
We gratefully acknowledge financial support by
EYRO113421 to D.J.T., NIH R01AG025500, NSF
CHE-0555341 and American Heart Association
0750115Z to D.H.H., and NIH P20RR017686 to
T.A.N.

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