Synthesis and antiproliferative evaluation of novel N-arylquinolones

Article abstract of DOI:10.1007/s00706-019-02504-5

Abstract: Novel N-aryl-substituted quinolones were evaluated for antiproliferative activity. The chemical modifications were inspired by previously reported cytotoxic agents with structural similarities. Dimethylated anilines displayed the most potent effect in the renal cancer cell line Caki-1 and the breast cancer cell line MDA-MB-231, with GI₅₀ values down to 24 μM. Further evaluation in the NCI60 cell lines revealed growth inhibition up to 50%, with the strongest effect observed in renal and lung cancer cell lines. In silico ADMET evaluation indicated favorable characteristics for both gastrointestinal and CNS uptake. The potential toxic electrophilic α,β-unsaturated carbonyl functionalities were shown to be inert to ethanethiol. Graphic abstract: [Figure not available: see fulltext.]

Full text of DOI:10.1007/s00706-019-02504-5

Monatshefte für Chemie - Chemical Monthly
https://doi.org/10.1007/s00706-019-02504-5
ORIGINAL PAPER
Synthesis and antiproliferative evaluation of novel N‑arylquinolones
Vegard Torp Lien1 · Dag Erlend Olberg1,2 · Gunnar Hagelin1 · Jo Klaveness1
Received: 6 August 2019 / Accepted: 9 September 2019
© Springer-Verlag GmbH Austria, part of Springer Nature 2019
Abstract
Novel N-aryl-substituted quinolones were evaluated for antiproliferative activity. The chemical modifcations were inspired
by previously reported cytotoxic agents with structural similarities. Dimethylated anilines displayed the most potent efect
in the renal cancer cell line Caki-1 and the breast cancer cell line MDA-MB-231, with GI50 values down to 24 µM. Further
evaluation in the NCI60 cell lines revealed growth inhibition up to 50%, with the strongest efect observed in renal and lung
cancer cell lines. In silico ADMET evaluation indicated favorable characteristics for both gastrointestinal and CNS uptake.
The potential toxic electrophilic α,β-unsaturated carbonyl functionalities were shown to be inert to ethanethiol.
Graphic abstract
Keywords Antitumor agents · Cancer · Heterocycles · Structure–activity relationships · NCI60
Introduction
activity, an acid group is vital at the 3-position, and typically
an amino substituent is also present in the 7-position of the
quinolone scafold. Some biologically active N-aryl substi-
tuted quinolones with substituents at the 2- and/or 3-posi-
tion have been described. One such example is temafoxa-
cin, which is a potent broad-spectrum antibiotic [4], later
withdrawn from the market due to serious side efects [5].
However, only a few N-aryl-substituted quinolones without
substitution at the 2- and 3-position are known, and knowl-
edge about their antiproliferative activity is limited.
Quinolones are a well-studied class of antibiotics interfering
with bacterial DNA, and this general scafold is therefore
abundant in the medicinal chemistry literature [1]. Other
applications and efects have also been reported [2], includ-
ing antiproliferative efects [3]. For potent antimicrobial
Electronic supplementary material The online version of this
article (https://doi.org/10.1007/s00706-019-02504-5) contains
supplementary material, which is available to authorized users.
The reaction between quinoline 1 and 1-fluoro-4-ni-
trobenzene (2) shown in Scheme 1 produced the N-arylqui-
nolones 3 as side-products, in addition to the intended diaryl
ethers 4. The quinolones were formed in somewhat higher
yield than the diaryl ethers under the present conditions.
The formation of quinolones 3 was expected due to a high
ppm value observed in 13C NMR, rationalized to originate
* Vegard Torp Lien
v.t.lien@farmasi.uio.no
1
Department of Pharmacy, University of Oslo, Boks 1068,
Blindern, 0316 Oslo, Norway
2
Norwegian Medical Cyclotron Center, Sognsvannsveien 20,
0372 Oslo, Norway
Vol.:(0123456789)
1 3

V. T. Lien et al.
Scheme 1
from a carbonyl carbon. X-ray crystallography confrmed
the structure [6].
phenol derivative 13b was obtained due to loss of the benzyl
protection group under the acidic conditions. Dimethyla-
tion to the tertiary amines 14 was performed under Esch-
weiler–Clarke conditions.
A thorough literature search indicated that quinolones 3
have structural similarities with earlier published structures
with antiproliferative activity, and examples are shown in
Fig. 1a. The indoles 5 and 6 and the tetrahydroquinoline 7
were reported to be tubulin-interrupting agents [7–9], and
were active in cancer cell lines at nanomolar concentrations.
Carbazole 8 showed antiproliferative activity towards pan-
creatic cancer cells [10], while carbazole 9 did efciently
block mitosis [11]. The structurally simple tetrahydronaph-
thalene 10 showed afnity for the insulin-like growth factor
1 receptor (IGF-1R), and efcacy towards breast cancer cells
[12]. Quinolones 3 in Fig. 1b share structural characteristics
comparable with structures 5–10 in Fig. 1a. With the excep-
tion of 10, the common molecular scafold highlighted in
red consists of an N-aryl-substituted fused heterocycle. The
para-nitro group in both 3a and 3b, and the benzyl pro-
tecting group in 3b enables for chemical functionalizations.
Modifcations at these positions were sought to evaluate this
structural class as antiproliferative agents.
Further modifcations were performed as presented in
Scheme 3. Debenzylation of 12b furnished the 6-hydroxy
analogue 12d. This compound was further modifed to the
fuoroethyl analogue 12e employing fuoroethyl tosylate as
electrophile. Bromination of the aromatic ring ortho to the
acetamide group in 12b was attempted with NBS. Exclusive
α-bromination of the ketone was observed, similar to reac-
tions reported elsewhere [16, 17].
Antiproliferative efect
The quinolones were evaluated for their efcacy to inhibit
tumor cell growth. Initially, the compounds 3a, 11a, and 12a
were submitted for screening in the NCI60 program at the
National Cancer Institute. These compounds were selected
to assess the efects of electron withdrawing, electron donat-
ing and anilide substituents. In the NCI60 program, com-
pounds submitted are evaluated in cells derived from nine
diferent tumor types. Percentage inhibition of selected cell
lines at 10 µM concentration are reported in Table 1.
Herein, we report synthesis and biological evaluation of
novel N-aryl quinolones as antiproliferative agents. In silico
ADMET evaluation and antimicrobial screening are also
disclosed.
Overall, the antiproliferative efect was low-to-moder-
ate for the selected compounds 3a, 11a, and 12a towards
the NCI60 cell lines. However, both the cell lines UO-31
and Caki-1 displayed a stable reduction in cell growth for
all three compounds. Overall, the most potent efect was
observed for the nitro compound 3a towards the renal cancer
cell line RXF 393, albeit the other compounds displayed
lower activity towards this cell line. In MDA-MB-231, an
increased efcacy was seen when moving from nitro com-
pound 3a to the aniline 11a and further on to the acetamide
12a. Due to this positive trend, MDA-MB-231 was selected
for the evaluation of the remaining analogues, together with
Caki-1, where a reduction in cell growth was seen for all
three compounds. In Table 2, percent inhibitions at 10 µM
and GI50 values are reported. The analogue 12a was included
Results and discussion
Chemistry
Structural modifications were performed as shown in
Scheme 2. The nitro groups in 3 were reduced to aford the
anilines 11 for further modifcations of the para-position.
The acetamides 12a and 12b and the trifuoroacetamide
12c were easily accessible from the corresponding anhy-
drides. The quinolines 13 were synthesized by a modifed
Skraup–Doebner–von Miller protocol [15], employing
acrolein diethyl acetal in strongly acidic environment. The
1 3

Synthesis and antiproliferative evaluation of novel N-arylquinolones
Fig. 1 a Examples of N-aryl-
substituted heterocycles earlier
investigated as antiproliferative
agents; b the N-aryl quinolone
scafold explored herein. Red
bonds are used to highlight the
common structural core
(a)
(b)
to ensure a correlation between the results in Tables 1 and
2, and staurosporine was included as a positive reference
compound.
The dimethylated analogues 14a and 14b were the most
efective against the evaluated cell lines shown in Table 2.
To determine how the structural modifcations of the qui-
nolones had afected the antiproliferative properties, the
NCI60 panel was again used for the evaluation of 14a. In
Table 3, the percent inhibitions of the most afected cell
lines are given.
For the acetamides 12, modifcations of the 6-position
did not result in large variations in activity amongst the
methyl, fuoroethyl and hydroxyl analogues. However, the
benzylated 12b displayed an increased efect, with 20% inhi-
bition of MDA-MB-231 cell growth. The trifuoroacetamide
12c was inactive towards Caki-1 cells, and less active than
12a against MDA-MB-231. For the quinolines 13, methyl
in the 6-position was advantageous over the hydrogen ana-
logue. Further on, the dimethylated analogues 14 displayed
a stronger inhibition of cell proliferation, especially in the
MDA-MB-231 cell line. The methyl analogue 14a showed
lower GI50 values than the benzylated 14b; however, the
percent inhibition at 10 µM was higher for 14b. Bromination
of the quinolone ring to the analogue 15 reduced the activity
compared to 12b.
The strongest efect was observed in the renal cancer cell
lines A498 and UO-31 and the lung cancer cell lines NCI-
H522 and HOP-92. Compared to the initial screening of 3a,
11a, and 12a reported in Table 1, the antiproliferative efect
with the dimethylated 14a was improved for some cell lines
(e.g. A498) while it was reduced for other cell lines (e.g.
PC-3). Overall, a somewhat increased average efect was
observed with 14a, with the strongest efect being towards
renal, lung and breast cancer cell lines.
1 3

V. T. Lien et al.
Scheme 2
Scheme 3
of 100 µg/cm3, the analogues were tested against the Gram
positive Staphylococcus aureus 1085 (MRSA strain), the
Gram negative Escherichia coli and the eukaryote yeast
Candida albicans. No antimicrobial efect was observed on
either of the microorganisms. The absence of an acid group
Antimicrobial efect
Due to the structural similarities between the quinolones
presented herein and known antibiotics, the compounds were
evaluated for their antimicrobial efect. At a concentration
1 3

Synthesis and antiproliferative evaluation of novel N-arylquinolones
Table 1 Percent inhibition for selected cell lines in the NCI60 panel at 10 µM concentration of 3a, 11a, and 12a
Compound
R1
R2
% inhibition at 10 µM
RXF 393
UO-31
Caki-1
MDA-
MB-231
3a
11a
12a
Me
Me
Me
NO2
NH2
NH(CO)Me
40
0
9
21
18
23
11
11
9
5
10
15
aComplete data are given in the supporting information
in the quinolone 3-position and N-alkyl group in 7-position
compared to known antimicrobial agents is a reasonable
explanation for the lack of activity.
with ethanethiol under various conditions to see if the addi-
tion product 16 shown in Scheme 4 was formed. The reac-
tion was monitored by LC–MS, but 16 was not observed
under the evaluated conditions. This indicates that the α,β-
unsaturated carbonyl is not sufciently electrophilic to react
with thiols at the evaluated conditions, and is therefore con-
ceivable to not pose a problem in vivo. Based on the above
fndings, this compound class can be expected to display
favorable ADMET characteristics.
ADMET evaluation
Initial in silico studies of fundamental drug properties as
logP, total polar surface area (TPSA) and bioavailability
were performed employing the SwissADME tool [18]. The
compounds 12a, 13a, 14a, and 14b were evaluated, and
showed clogP and TPSA in the intervals 2.41–4.07 and
43.70–69.56 Å2, respectively, and these measurements are
graphically presented in Fig. 2 with the BOILED-egg [19]
representation.
Conclusion
Novel N-aryl quinolones were synthesized and evaluated in
cancer cell lines to assess the antiproliferative efect. Despite
moderate potency, initial screening of three selected ana-
logues in the NCI60 program revealed cell lines that could
be used for evaluation of the remaining analogues. In the
Caki-1 and MDA-MB-231 cell lines, the dimethylated ana-
logues 14a and 14b were the most potent, with GI50 val-
ues down to 24 µM. Compound 14a was submitted to the
NCI60 program, and displayed overall, an increased efect,
with renal, lung and breast cancer cell lines being most sen-
sitive. Finally, an in silico ADMET evaluation suggested
favorable properties for gastrointestinal absorption and CNS
permeability. Importantly, the potential toxicity of the α,β-
unsaturated carbonyl functionalities was not observed using
This graphical method ranks the compounds after clogP
and TPSA, and those inside the elliptical or the circular area
are expected to have good gastrointestinal absorption or abil-
ity to cross the blood–brain barrier (BBB), respectively. All
four compounds were inside these boundaries, and were also
predicted to have good bioavailability and not to be substrate
of the P-glycoprotein efux transporter.
One concern with the quinolone scafold presented herein
is the α,β-unsaturated carbonyl group present. Such groups
can be susceptible to nucleophilic attack, and theoreti-
cally pose a toxicity problem in vivo if nucleophilic cent-
ers of macromolecules (e.g. cysteines in proteins) react via
Michael addition to the drug. To evaluate this, 3b was stirred
1 3

V. T. Lien et al.
Table 2 Percent inhibition at 10 µM and GI50 values against the cell lines Caki-1 and MDA-MB-231
Compound
R1
R2
Caki-1
GI50
MDA-MB-231
GI50
% inhibition at
10 µM
% inhibition
at 10 µM
12a
Me
Bn
Me
H
CH2CH2F
Me
H
Me
Bn
–
NH(CO)Me
NH(CO)Me
NH(CO)CF3
NH(CO)Me
NH(CO)Me
–
> 100
> 100
> 100
> 100
> 100
> 100
> 100
70
6
17
0
7
5
11
2
8
17
4
92
> 100
> 100
> 100
> 100
> 100
> 100
> 100
24
14
20
9
7
9
24
5
27
39
12
93
12b
12c
12d
12e
13a
13b
–
14a
N(Me)2
N(Me)2
–
14b
> 100
> 50
0.0025
43
>50
0.0035
15
Staurosporine
aAverage of two parallels
bGI50: Concentration needed to achieve 50% reduced cell growth
Table 3 Percent inhibition
Experimental
Cell line
% inhibition
for selected cancer cell lines
in the NCI60 panel at 10 µM
concentration of 14a
at 10 µM
All chemicals were purchased from Sigma–Aldrich or
Fluorochem and used without further purifcation. Air
and/or moisture-sensitive reactions were performed
under argon atmosphere with dried solvents and reagents.
TLC was performed on Merck silica gel 60 F254 plates,
and visualized using UV light at 312 nm or 365 nm, a
phosphomolybdic acid solution (12 g phosphomolybdic
acid in 250 cm3 EtOH) or a potassium permanganate
(1.5 g KMnO4, 10 g K2CO3, 2.5 cm3 5 M NaOH/H2O,
200 cm3 H2O) solution for detection. Column chroma-
tography was performed with silica gel (pore size 60 Å,
A498
51
21
21
20
16
16
12
2
NCI-H522
HOP-92
UO-31
MDA-MB-231
ACHN
MCF7
Caki-1
aComplete data are given in the
supporting information
1
230–400 mesh particle size) purchased from Fluka. H
and 13C NMR spectra were obtained on a Bruker AVIII
(HD) 400 instrument (400/101 MHz) or Bruker AVII 600
(600/151 MHz). Chemical shifts (δ) are reported in parts
per million, and coupling constants are reported in Hertz
ethanethiol as a model nucleophile. The N-aryl quinolone
scafold may serve as a starting point for further structural
optimizations with regard to antiproliferative activity.
1
(Hz). The residual proton solvent resonance in H NMR
(CDCl3 at δ = 7.27 ppm, DMSO-d6 at 2.50 ppm) and the
residual carbon solvent resonance in 13C NMR (CDCl3 at
δ = 77.16 ppm and DMSO-d6 at 39.52 ppm) are used as
1 3

Synthesis and antiproliferative evaluation of novel N-arylquinolones
Fig. 2 The structures 12a, 13a,
14a, and 14b were evaluated
with the SwissADME tool,
graphically presented with
the BOILED-egg method.
Compounds in the white area
might have the property of oral
absorption, while the com-
pounds inside the yellow “yolk”
are predicted to pass the BBB
MeCN, and stirred for 15 min. 2 (101 mg, 0.716 mmol)
was added, and the reaction mixture was stirred for 20 h
at 55 °C. The reaction mixture was diluted with 15 cm3
EtOAc, washed with water (4×10 cm3) and 10 cm3 brine,
dried over MgSO4 and concentrated on a rotary evaporator.
The crude product was purifed by column chromatography
(Hep:EtOAc 4:1 → Hep:EtOAc:MeOH 10:10:1). The title
compounds were obtained as yellow solids.
Scheme 4
Yield of 3a: 40 mg (38%); 1H NMR (400 MHz, CDCl3):
δ=8.48 (d, 2H, J=8.8 Hz, H-11), 7.79 (s, 1H, H-5), 7.67
(d, 2H, J = 8.8 Hz, H-10), 7.48 (d, 1H, J = 7.8 Hz, H-2),
6.35 (d, 1H, J=7.7 Hz, H-3), 6.32 (s, 1H, H-8), 3.98 (s, 3H,
-OCH3), 3.72 (s, 3H, –OCH3) ppm; 13C NMR (101 MHz,
CDCl3): δ = 176.98 (C=O), 153.56 (C-6), 147.96 (C-12),
147.71 (C-7), 146.91 (C-9), 140.54 (C-2), 136.08 (C-4a),
128.64 (C-10), 125.92 (C-11), 120.99 (C-8a), 110.68 (C-3),
106.17 (C-5), 98.10 (C-8), 56.46 (–OCH3), 56.21 (–OCH3)
ppm; HRMS (ESI+): m/z calcd. for C17H15N2O5 ([M+H]+)
327.0975, found 327.0976.
reference. Accurate mass determination (HRMS) in posi-
tive or negative mode was performed on a Waters Prospec
Q instrument, ionized by electrospray (ESI). LC–MS was
performed on a Thermo Finnigan LCQ Deca XP Plus
using a gradient from 10% to 90% acetonitrile in water
over 10 min.
6,7‑Dimethoxy‑1‑(4‑nitrophenyl)quinolin‑4(1H)‑one (3a,
C17H14N2O5) and 6,7‑dimethoxy‑4‑(4‑nitrophenoxy)qui‑
noline (4a) Cs2CO3 (212 mg, 0.65 mmol) and 67 mg 1a
(0.326 mmol) were dissolved in 3 cm3 DMF and 1 cm3
1 3

V. T. Lien et al.
Yield of 4a: 28 mg (26%); 1H NMR (400 MHz, CDCl3):
δ=8.61 (d, 1H, J=5.3 Hz), 8.32 (d, 2H, J=9.2 Hz), 7.49
(s, 1H), 7.37 (s, 1H), 7.27 (d, 2H, J=9.2 Hz), 6.68 (d, 1H,
J=5.3 Hz), 4.06 (s, 3H), 4.00 (s, 3H) ppm. The NMR analy-
sis was in accordance with earlier published data [13].
washed with EtOH and DCM (1:1, 20 cm3). The organic
phase was washed with water (2×10 cm3) and 10 cm3 brine,
dried over MgSO4 and reduced on a rotary evaporator. The
product was obtained as a white solid (123 mg, 81%) with-
out any further purifcation. 1H NMR (400 MHz, CDCl3):
δ = 7.81 (s, 1H, H-5), 7.52 (d, 1H, J = 7.6 Hz, H-2), 7.14
(d, 2H, J=8.64 Hz, H-10), 6.82 (d, 2H, J=8.64 Hz, H-11),
6.41 (s, 1H, H-8), 6.37 (d, 1H, J = 7.6 Hz, H-3), 4.00 (s,
3H, OCH3), 3.72 (s, 3H, OCH3) ppm; 13C NMR (400 MHz,
CDCl3): δ = 176.84 (C=O), 153.17 (C-6), 147.48 (C-9),
147.23 (C-7), 142.16 (C-2), 137.68 (C-4a), 131.96 (C-12),
128.27 (C-11), 120.67 (C-8a), 115.72 (C-10), 109.15 (C-3),
105.49 (C-5), 98.83 (C-8), 56.31 (–OCH3), 55.95 (–OCH3)
ppm; HRMS (ESI+): m/z calcd. for C17H17N2O3 ([M+H]+)
297.1234, found 297.1234.
6‑(Benzyloxy)‑7‑methoxy‑1‑(4‑nitrophenyl)quino‑
lin‑4(1H)‑one (3b, C23H18N2O5) and 6‑(benzyloxy)‑7‑meth‑
oxy‑4‑(4‑nitrophenoxy)quinoline (4b, C23H18N2O5) Cs2CO3
(39.1 g, 120 mmol) and 16.9 g 1b (60.2 mmol) were dis-
solved in 200 cm3 DMF and 150 cm3 MeCN, and stirred
for 15 min. 2 (21.67 g, 153.6 mmol) was added, and the
mixture was stirred at 55 °C for 24 h. The reaction mixture
was diluted with 200 cm3 EtOAc and washed with water
(4 × 100 cm3) and 100 cm3 brine, dried over MgSO4 and
concentrated on a rotary evaporator. The crude product
was purifed by column chromatography (heptane:EtOAc
4:1 → heptane:EtOAc:MeOH 5:5:2), and the title com-
pounds were obtained as yellow solids.
1‑(4‑Aminophenyl)‑6‑(benzyloxy)‑7‑methoxyquino‑
lin‑4(1H)‑one (11b, C23H20N2O3) Iron (340 mg, 6.1 mmol),
564 mg NH4Cl (10.2 mmol), and 378 mg 3b (0.939 mmol)
were dissolved in 8 cm3 water and 10 cm3 EtOH. The reac-
tion mixture was stirred for 3 h at 70 °C, fltered through
Celite and the Celite washed with 20 cm3 EtOAc. The
organic fltrate was washed with water (2 × 15 cm3) and
15 cm3 brine, dried over MgSO4 and reduced on a rotary
evaporator. The crude product was purifed by column chro-
matography (heptane:EtOAc 1:1, heptane:EtOAc:MeOH
5:5:2), and the title compound was obtained as a white
solid (129 mg, 37%). 1H NMR (400 MHz, CDCl3): δ=7.91
(s, 1H, H-5), 7.51 (d, 1H, J = 7.6 Hz, H-2), 7.48 (d, 2H,
J = 7.2, H-2′), 7.37 (t, 2H, J = 7.04 Hz, H-3′), 7.34-7.28
(m, 1H, H-4′), 7.13 (d, 2H, J = 8.56 Hz, H-10), 6.81 (d,
2H, J = 8.56 Hz, H-11), 6.43 (s, 1H, H-8), 6.38 (d, 1H,
J=7.52 Hz, H-3), 5.24 (s, 2H, O–CH2–), 3.71 (s, 3H, OCH3)
ppm; 13C NMR (400 MHz, CDCl3): δ = 176.70 (C=O),
153.75 (C-6), 147.52 (C-9), 146.50 (C-7), 142.25 (C-2),
137.87 (C-4a), 136.39 (C-1′), 131.89 (C-12), 128.57 (C-3′),
128.24 (C-11), 128.04 (C-4′), 127.66 (C-2′), 120.48 (C-8a),
115.72 (C-10), 109.04 (C-3), 107.16 (C-5), 99.12 (C-8),
70.90 (O–CH2–), 56.00 (–OCH3) ppm; HRMS (ESI +):
m/z calcd. for C23H20N2NaO3 ([M+Na]+) 395.1366, found
395.1366.
Yield of 3b: 8.15 g (34%); 1H NMR (400 MHz, CDCl3):
δ=8.49 (d, 2H, J=8.89, H-11), 7.91 (s, 1H, H-5), 7.67 (d,
2H, J=8.89 Hz, H-10), 7.51-7-46 (m, 3H, H-2, H-2′), 7.41-
7.35 (m, 2H, H-3′), 7.34-7.29 (m, 1H, H-4′), 6.44 (d, 1H,
J=7.72 Hz, H-3), 6.34 (s, 1H, H-8), 5.25 (s, 2H, O–CH2–),
3.72 (s, 3H, –OCH3) ppm; 13C NMR (400 MHz, CDCl3):
δ = 176.77 (C=O), 154.30 (C-6), 148.08 (C-12), 147.09
(C-9), 146.78 (C-7), 140.77 (C-2), 136.77 (C-1′), 136.21
(C-4a), 128.78 (C-3′), 128.66 (C-10), 128.33 (C-4′), 127.82
(C-2′), 125.99 (C-11), 120.65 (C-8a), 110.48 (C-3), 107.72
(C-5), 98.34 (C-8), 71.10 (O–CH2–, 56.30 (O–CH3) ppm;
HRMS (ESI+): m/z calcd. for C23H18N2NaO5 ([M+Na]+)
425.1108, found 425.1108.
Yield of 4b: 5.0 g (21%); 1H NMR (400 MHz, CDCl3):
δ = 8.62 (d, 1H, J = 4.8 Hz, H-2), 8.28 (d, 2H, J= 9.2 Hz,
H-11), 7.55 (s, 1H, H-5), 7.42 (d, 2H, J=5.6 Hz, H-1′), 7.37
(s, 1H, H-8), 7.35-7.28 (m, 3H, H-2′, H-3′), 7.18 (d, 2H,
J=9.2 Hz, H-10), 6.72 (d, 1H, J=5.6 Hz, H-3), 5.25 (s, 2H,
O–CH2–), 4.07 (s, 3H, OCH3) ppm; 13C NMR (101 MHz,
CDCl3): δ = 160.6 (C-9), 158.7 (C-4), 154.4 (C-7), 149.7
(C-6), 148.0 (C-2), 144.5 (C-12), 136.0 (C-1′), 128.8 (C-3′),
128.3 (C-4′), 127.5(C-2′), 126.4 (C-11), 119.6 (C-10),
116.7 (C-4a), 107.6 (C-5), 106.5 (C-3), 101.2 (C-8), 71.1
(O–CH2–), 56.5 (O–CH3) ppm; HRMS (ESI+): m/z calcd.
for C23H19N2O5 ([M+H]+) 403.1288, found 403.1287.
N‑[4‑(6,7‑Dimethoxy‑4‑oxoquinolin‑1(4H)‑yl)phenyl]aceta‑
mide (12a, C19H18N2O4) 11a (116 mg, 0.39 mmol) dissolved
in 10 cm3 DCM was added 0.15 cm3 acetic anhydride
(1.58 mmol) and stirred for 15 h at ambient temperature.
The reaction mixture was washed with water (2×10 cm3)
and 10 cm3 brine, dried over MgSO4 and reduced on a rotary
evaporator. The crude product was purifed by column chro-
matography (DCM:MeOH 10:1), and the title compound
was obtained as an of-white solid (115 mg, 87%). 1H NMR
(400 MHz, DMSO-d6): δ = 10.25 (s, 1H, –NH–), 7.86-
7.79 (m, 3H, H-11, H-2), 7.57 (s, 1H, H-5), 7.47 (d, 2H,
1‑(4‑Aminophenyl)‑6,7‑dimethoxyquinolin‑4(1H)‑one (11a,
C17H16N2O3) 3a (167 mg, 0.512 mmol) was dissolved in
9 cm3 dry EtOH under argon, and 97 mg Pd/C (10% loading,
50% water content, 0.046 mmol Pd) was added. The atmos-
phere was replaced with hydrogen gas, and pressurized with
a hydrogen flled balloon. The reaction was stirred for 15 h at
ambient temperature, fltered through Celite and the Celite
1 3

Synthesis and antiproliferative evaluation of novel N-arylquinolones
J=8.8 Hz, H-10), 6.39 (s, 1H, H-8), 6.08 (d, 1H, J=7.6 Hz,
H-3), 3.85 (s, 3H, OCH3), 3.60 (s, 3H, OCH3), 2.10 (s,
3H, (C=O)CH3) ppm; 13C NMR (101 MHz, DMSO-d6):
δ=175.22 (C=O), 168.68 (–NHC=O), 152.58 (C-6), 146.68
(C-7), 142.63 (C-2), 139.94 (C-12), 136.56(C-4a), 135.55
(C-9), 127.80 (C-10), 120.01 (C-8a), 119.88 (C-11), 108.50
(C-3), 104.97 (C-5), 98.85 (C-8), 55.58 (–OCH3), 55.44 (–
OCH3), 24.07 (C=O)CH3) ppm; HRMS (ESI+): m/z calcd.
for C19H19N2O4 ([M+H]+) 339.1339, found 339.1341.
(C-3), 105.05 (C-5), 98.85 (C-8), 55.65 (–OCH3), 55.53 (–
OCH3) ppm; HRMS (ESI+): m/z calcd. for C19H16F3N2O4
([M+H]+) 393.1057, found 393.1056.
N‑[4‑(6‑Hydroxy‑7‑methoxy‑4‑oxoquinolin‑1(4H)‑yl)phenyl]‑
acetamide (12d, C18H16N2O4) 12b (141 mg, 0.340 mmol)
was dissolved in 15 cm3 dry DMA under argon, and 95 mg
Pd/C (10% loading, 50% water content, 0.045 mmol Pd)
was added. The atmosphere was replaced with hydrogen
gas, and pressurized with a hydrogen flled balloon. The
reaction was stirred for 15 h at ambient temperature, fl-
tered through Celite and the Celite washed with DMF and
EtOAc (1:1, 20 cm3). The organic phase was washed with
water (4×10 cm3) and 10 cm3 brine, dried over MgSO4 and
reduced on a rotary evaporator. The crude product was puri-
fed by column chromatography (DCM:MeOH 10:1), and the
title compound was obtained as an of-white solid (91 mg,
N‑[4‑[6‑(Benzyloxy)‑7‑methoxy‑4‑oxoquinolin‑1(4H)‑yl]‑
phenyl]acetamide (12b, C25H22N2O4) 11b (337 mg,
0.905 mmol) dissolved in 30 cm3 DCM was added 0.15 cm3
acetic anhydride (1.58 mmol) and stirred for 15 h at ambi-
ent temperature. The reaction mixture was washed with
water (2 × 15 cm3) and 15 cm3 brine, dried over MgSO4
and reduced on a rotary evaporator. The crude product
was purifed by column chromatography (heptane:EtOAc
1:1), and the title compound was obtained as an of-white
1
83%). H NMR (400 MHz, DMSO-d6): δ = 10.24 (s, 1H,
–NH–), 9.61 (s, 1H, –OH), 7.83 (d, 2H, J=8.8 Hz, H-11),
7.75 (d, 1H, J=7.6 Hz, H-2), 7.52 (s, 1H, H-5), 7.46 (d, 2H,
J=8.8 Hz, H-10), 6.36 (s, 1H, H-8), 6.01 (d, 1H, J=7.6 Hz,
H-3), 3.60 (s, 3H, OCH3), 2.10 (s, 3H, (C=O)CH3) ppm;
13C NMR (101 MHz, DMSO-d6): δ = 175.34 (C=O),
168.71 (-NHC=O), 152.09 (C-6), 144.51 (C-7), 142.40
(C-2), 139.87 (C-12), 135.74 (C-4a), 135.72 (C-9), 127.83
(C-10), 120.53 (C-8a), 119.89 (C-11), 108.71 (C-5), 108.04
(C-3), 98.96 (C-8), 55.40 (–OCH3), 24.08 (C=O)CH3) ppm;
HRMS (ESI+): m/z calcd. for C18H16N2NaO4 ([M+Na]+)
347.1002, found 347.1002.
1
solid (346 mg, 92%). H NMR (400 MHz, DMSO-d6):
δ = 10.26 (s, 1H, –NH–), 7.85–7–79 (m, 3H, H-11, H-2),
7.68 (s, 1H, H-5), 7.50-7.46 (m, 4H, H-10, H-2′), 7.41 (t,
2H, J = 7.48 Hz, H-3′), 7.35 (d, 1H, J = 7.16 Hz, H-4′),
6.42 (s, 1H, H-8′), 6.08 (d, 1H, J = 7.64 Hz, H-3′), 5.20
(s, 1H, O–CH2–), 3.62 (s, 1H, OCH3), 2.11 (s, 1H, (C=O)
CH3) ppm; 13C NMR (101 MHz, DMSO-d6): δ = 175.22
(C=O), 168.69 (-NHC=O), 152.85 (C-6), 145.60 (C-7),
142.70 (C-2), 139.92 (C-12), 136.70 (C-4a), 136.67 (C-1′),
135.52 (C-9), 128.39 (C-3′), 127.87(C-4′), 127.79 (C-10),
127.73 (C-2′), 119.93 (C-8), 119.89 (C-11), 108.50 (C-3),
106.66 (C-5), 99.04 (C-8), 69.87 (O–CH2–), 55.50 (-OCH3),
24.05 (C=O)CH3) ppm; HRMS (ESI +): m/z calcd. for
C25H23N2O4 ([M+H]+) 415.1652, found 415.1652.
N‑[4‑[6‑(2‑Fluoroethoxy)‑7‑methoxy‑4‑oxoquinolin‑1(4H)‑yl]‑
phenyl]acetamide (12e, C20H19FN2O4) 12d (28 mg,
0.0863 mmol) and 26 mg K2CO2 (0.188 mmol) in 2 cm3
DMF were added 38 mg 2-fuoroethyl 4-methylbenzene-
sulfonate (0.173 mmol). The reaction mixture was stirred
at 50 °C for 15 h, washed with water (4 × 5 cm3), 5 cm3
brine, dried over MgSO4 and reduced on a rotary evaporator.
The crude product was purifed by column chromatography
(DCM:MeOH 95:5), and the title compound was obtained
as a white solid (25 mg, 78%). 1H NMR (400 MHz, DMSO-
d6): δ=10.28 (s, 1H, –NH–), 7.86-7.83 (m, 3H, H-11, H-2),
7.61 (s, 1H, H-5), 7.48 (d, 2H, J=8.5 Hz, H-10), 6.42 (s, 1H,
H-8), 6.13 (d, 1H, J=7.6 Hz, H-3), 4.78 (d, 2H, J=48.1 Hz,
-CH2F), 4.32 (d, 2H, J=30.1 Hz, –OCH2CH3), 3.63 (s, 3H,
OCH3), 2.11 (s, 3H, (C=O)CH3) ppm; 13C NMR (101 MHz,
DMSO-d6): δ=174.96 (C=O), 168.73 (–NHC=O), 152.84
(C-6), 145.64 (C-7), 142.98 (C-2), 140.03 (C-12), 136.90
(C-4a), 135.47 (C-9), 127.81 (C-10), 119.91 (C-11), 119.75
(C-8a), 108.41 (C-3), 106.21 (C-5), 99.09 (C-8), 81.99 (d,
J=167 Hz, –CH2F), 67.92 (d, J=18.94 Hz, –OCH2CH3),
55.51 (–OCH3), 24.10 (C=O)CH3) ppm; HRMS (ESI +):
m/z calcd. for C20H19FN2NaO4 ([M+Na]+) 393.1221, found
393.1220.
N‑ [ 4 ‑ ( 6 , 7 ‑ D i m e t h ox y ‑ 4 ‑ oxo q u i n o l i n ‑ 1 ( 4 H) ‑ y l ) ‑
phenyl]‑2,2,2‑trifluoroacetamide (12c, C19H15F3N2O4)
11a (22 mg, 0.0742 mmol) dissolved in 8 cm3 DCM was
added 0.050 cm3 trifuoroacetic anhydride (0.360 mmol)
and stirred for 15 h at ambient temperature. The reaction
mixture was washed with water (2 × 10 cm3) and 10 cm3
brine, dried over MgSO4 and reduced on a rotary evapo-
rator. The crude product was purifed by column chroma-
tography (DCM:MeOH 10:1), and the title compound was
1
obtained as a light yellow solid (25 mg, 94%). H NMR
(400 MHz, DMSO-d6): δ = 11.58 (s, 1H, -NH-), 7.95 (d,
2H, J=8.84 Hz, H-11), 7.85 (d, 1H, J=7.68 Hz, H-2), 7.63
(d, 2H, J=8.84 Hz, H-10), 7.59 (s, 1H, H-5), 6.41 (s, 1H,
H-8), 6.12 (d, 1H, J = 7.68 Hz, H-3), 3.87 (s, 3H, OCH3),
3.62 (s, 3H, OCH3) ppm; 13C NMR (101 MHz, DMSO-
d6): δ=175.38 (C=O), 154.76 (d, J=37.4 Hz, –NHC=O),
152.72 (C-6), 146.82 (C-7), 142.59 (C-2), 137.94 (C-9),
137.01 (C-12), 136.38 (C-4a), 128.23 (C-10), 122.26 (C-11),
120.03 (C-8a), 115.73 (d, J = 289.7 Hz, -CF3), 108.71
1 3

V. T. Lien et al.
6,7‑Dimethoxy‑4H‑[1,6′‑biquinolin]‑4‑one (13a, C20H16N2O3)
11a (51 mg, 0.172 mmol) dissolved in 12 cm3 HCl (1 M)
was added 64 mm3 acrolein diethyl acetal (0.420 mmol) and
stirred at refux for 20 h. The reaction mixture was cooled,
neutralized with solid Na2CO3 and extracted with DCM
(3×10 cm3). The combined organic extracts were washed
with 15 cm3 water, 15 cm3 brine, dried over MgSO4 and
reduced on a rotary evaporator. The crude product was puri-
fed by column chromatography (DCM:MeOH 95:5), and the
title compound was obtained as a white solid (7 mg, 12%).
1H NMR (400 MHz, DMSO-d6): δ=9.05 (dd, 1H, J=4.2,
1.6 Hz, H-10), 8.50 (dd, 1H, J=8.3, 1.3 Hz, H-12), 8.29 (d,
1H, J=2.3 Hz, H-13), 8.24 (d, 1H, J=8.9 Hz, H-16), 8.00
(d, 1H, J=7.6 Hz, H-2), 7.93 (dd, 1H, J=8.9, 2.3 Hz, H-15),
7.68 (dd, 1H, J=8.3, 4.2 Hz, H-11), 7.62 (s, 1H, H-5), 6.47
(s, 1H, H-8), 6.16 (d, 1H, J = 7.6 Hz, H-3), 3.88 (s, 3H,
OCH3), 3.56 (s, 3H, OCH3) ppm; 13C NMR (151 MHz,
DMSO-d6): δ=175.36 (C=O), 152.73 (C-10), 151.90 (C-6),
147.10 (C-16a), 146.84 (C-7), 142.75 (C-2), 138.81 (C-14),
136.52 (C-12), 136.29 (C-4a), 131.02 (C-15), 128.71 (C-13),
128.46 (C-12a), 126.67 (C-16), 122.48 (C-11), 120.03
(C-8a), 108.84 (C-3), 105.07 (C-5), 98.98 (C-8), 55.63 (–
OCH3), 55.55 (–OCH3) ppm; HRMS (ESI+): m/z calcd. for
C20H17N2O3 ([M+H]+) 333.1234, found 333.1233.
was added 1 cm3 water and 0.1 cm3 formic acid (2.65 mmol,
98%) and cooled to 0 °C. Formaldehyde (0.40 cm3,
0.506 mmol, 35% aqueous solution) was added and the reac-
tion mixture was stirred at 70 °C for 15 h. The reaction mix-
ture was cooled, neutralized with 1 M NaOH, and extracted
with DCM (3×8 cm3). The combined organic extracts were
washed with 10 cm3 water, 10 cm3 brine, dried over MgSO4
and reduced on a rotary evaporator. The crude product was
purifed by column chromatography (DCM:MeOH 95:5),
and the title compound was obtained as a white solid (20 mg,
1
70%). H NMR (400 MHz, DMSO-d6): δ = 7.80 (d, 1H,
J=7.6 Hz, H-2), 7.58 (s, 1H, H-5), 7.31 (d, 2H, J=8.9 Hz,
H-11), 6.87 (d, 2H, J=8.9 Hz, H-10), 6.44 (s, 1H, H-8), 6.12
(d, 1H, J=7.6 Hz, H-3), 3.86 (s, 3H, OCH3), 3.61 (s, 3H,
OCH3), 3.0 (s, 6H, –N(CH3)2) ppm; 13C NMR (101 MHz,
DMSO-d6): δ=174.76 (C=O), 152.68 (C-6), 150.32 (C-12),
146.78 (C-7), 143.32 (C-2), 137.18 (C-4a), 129.41 (C-9),
127.69 (C-10), 119.82 (C-8a), 112.52 (C-11), 108.10 (C-3),
104.78 (C-5), 99.05 (C-8), 55.62 (–OCH3), 55.49 (–OCH3)
ppm; HRMS (ESI+): m/z calcd. for C19H21N2O3 ([M+H]+)
325.1547, found 325.1547.
6‑(Benzyloxy)‑1‑[4‑(dimethylamino)phenyl]‑7‑methoxyqui‑
nolin‑4(1H)‑one (14b, C25H24N2O3) 11b (39 mg, 0.105 mmol)
was added 1 cm3 water and 0.1 cm3 formic acid (2.65 mmol,
98%) and cooled to 0 °C. Formaldehyde (0.32 cm3,
0.402 mmol, 35% aqueous solution) was added, and the reac-
tion mixture was stirred at 70 °C for 15 h. The reaction mix-
ture was cooled, neutralized with 1 M NaOH, and extracted
with DCM (3×8 cm3). The combined organic extracts were
washed with 10 cm3 water, 10 cm3 brine, dried over MgSO4
and reduced on a rotary evaporator. The crude product was
purifed by column chromatography (DCM:MeOH 95:5),
and the title compound was obtained as a white solid (28 mg,
6‑Hydroxy‑7‑methoxy‑4H‑[1,6′‑biquinolin]‑4‑one (13b,
C19H14N2O3) 11b (519 mg, 1.39 mmol) dissolved in
100 cm3 HCl (1 M) was added 0.53 cm3 acrolein diethyl
acetal (3.49 mmol) and stirred at refux for 20 h. The reac-
tion mixture was cooled, neutralized with solid Na2CO3, and
extracted with DCM (3 × 80 cm3). The combined organic
extracts were washed with 100 cm3 water, 100 cm3 brine,
dried over MgSO4 and reduced on a rotary evaporator. The
crude product was purified by column chromatography
(DCM:MeOH 95:5), and the title compound was obtained as
a white solid (54 mg, 10%). 1H NMR (400 MHz, DMSO-d6):
δ=9.66 (s, 1H, -OH), 9.06 (dd, 1H, J=4.2, 1.6 Hz, H-10),
8.51 (dd, 1H, J=8.5, 1.3 Hz, H-12), 8.29 (d, 1H, J=2.3 Hz,
H-13), 8.25 (d, 1H, J = 8.9 Hz, H-16), 7.95 (d, 1H,
J=7.6 Hz, H-2), 7.93 (dd, 1H, J=8.9, 2.3 Hz, H-15), 7.69
(dd, 1H, J=8.5, 4.2 Hz, H-11), 7.57 (s, 1H. H-5), 6.44 (s,
1H, H-8), 6.09 (d, 1H, J=7.7 Hz, H-3), 3.57 (s, 3H, OCH3)
ppm; 13C NMR (101 MHz, DMSO-d6): δ=175.40 (C=O),
152.17 (C-10), 151.81 (C-6), 147.05 (C-16a), 144.65 (C-7),
142.45 (C-2), 138.93 (C-14), 136.46 (C-12), 135.40 (C-4a),
130.93 (C-15), 128.74 (C-13), 128.43 (C-12a), 126.58
(C-16), 122.42 (C-11), 120.52 (C-8a), 108.79 (C-3), 108.36
(C-5), 99.05 (C-8), 55.45 (-OCH3) ppm; HRMS (ESI +):
m/z calcd. for C19H14N2NaO3 ([M+Na]+) 341.0897, found
341.0897.
1
67%). H NMR (400 MHz, DMSO-d6): δ = 7.83 (d, 1H,
J=7.6 Hz, H-2), 7.68 (s, 1H, H-5), 7.47 (m, 2H, H-2′), 7.41
(m, 2H, H-3′), 7.35 (m, 1H, H-4′), 7.32 (d, 2H, J=9.0 Hz,
H-11)), 6.88 (d, 2H, J = 9.0 Hz, H-10), 6.48 (s, 1H, H-8),
6.14 (d, 1H, J=7.6 Hz, H-3), 5.21 (s, 2H, O–CH2–), 3.63 (s,
3H, OCH3), 3.0 (s, 6H) ppm; 13C NMR (101 MHz, DMSO-
d6): δ=174.53 (C=O), 153.04 (C-6), 150.35 (C-12), 145.80
(C-7), 143.50 (C-2), 137.35 (C-4a), 136.66 (C-1′), 129.36
(C-9), 128.41 (C-3′), 127.89 (C-4′), 127.75 (C-2′), 127.68
(C-10), 119.64 (C-8a), 112.53(C-11), 108.02 (C-3), 106.38
(C-5), 99.25 (C-8), 69.92 (O-CH2-), 55.60 (–OCH3) ppm;
HRMS (ESI+): m/z calcd. for C25H24N2NaO3 ([M+Na]+)
423.1676, found 423.1679.
N‑ [ 4 ‑ [ 6 ‑ ( B e n z y l o x y ) ‑ 7 ‑ m e t h o x y ‑ 4 ‑ o x o q u i n o ‑
lin‑1(4H)‑yl]‑2‑bromophenyl]acetamide (15, C25H20BrN2O4)
12b (19 mg, 0.0458 mmol) dissolved in 2 cm3 DMA was
added 14 mg NBS (0.079 mmol) and stirred at ambient tem-
perature for 15 h. The reaction mixture was diluted with
1‑[4‑(Dimethylamino)phenyl]‑6,7‑dimethoxyquino‑
lin‑4(1H)‑one (14a, C19H20N2O3) 11a (26 mg, 0.088 mmol)
1 3

Synthesis and antiproliferative evaluation of novel N-arylquinolones
10 cm3 EtOH, washed with water (4×5 cm3), 5 cm3 brine,
dried over MgSO4 and reduced on a rotary evaporator. The
crude product was purified by column chromatography
(DCM:MeOH 95:5), and the title compound was obtained
as a white solid (18 mg, 80%). 1H NMR (400 MHz, DMSO-
d6): δ=10.28 (s, 1H, –NH–), 8.38 (s, 1H, H-2), 7.84 (d, 2H,
J=8.8 Hz, H-11), 7.71 (s, 1H, H-5), 7.53 (d, 2H, J=8.8 Hz,
H-10), 7.48 (m, 2H, H-2′), 7.41 (m, 2H, H-3′), 7.35 (m,
1H, H-4′), 6.40 (s, 1H, H-8), 5.23 (s, 2H, O-CH2-), 3.63
(s, 3H, OCH3), 2.11 (s, 3H, (C=O)CH3) ppm; 13C NMR
(101 MHz, CDCl3): δ=171.40 (C=O), 169.18 (–NHC=O),
154.34 (C-6), 147.34 (C-7), 142.05 (C-2), 140.19 (C-12),
136.96 (C-4a), 136.20 (C-1′), 135.88 (C-9), 128.78 (C-3′),
128.33 (C-4′), 127.94 (C-10), 127.84 (C-2′), 121.17 (C-11),
119.14 (C-8a), 107.83 (C-3), 105.14 (C-5), 98.89 (C-8),
71.19 (O-CH2-), 56.32 (–OCH3), 29.84 (C=O)CH3) ppm;
HRMS (ESI +): m/z calcd. for C25H21BrN2O4 ([M + H]+)
493.0757, found 493.0758.
antimicrobial activity, a difusion method in surface-inocu-
lated agar was applied. Wells (10 mm) were punched out in
the agar, flled with test solution and incubated at 37 °C for
20 h. Antimicrobial activity was disclosed as growth inhi-
bition zones. C. albicans were grown on Saboraud’s agar
medium and S. aureus and E. coli was grown on TSA agar
(tryptic soya agar).
Acknowledgements The National Cancer Institute is acknowledged
for the performed cell line studies. The authors are grateful for support
received from the Norwegian Medical Cyclotron Center.
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Antimicrobial activity
Test organisms were the Gram-positive Staphylococcus
aureus 1085 (a MRSA strain), the Gram-negative Escheri-
chia coli and the eukaryote yeast Candida albicans. Test
solutions were prepared from 1000 µg/cm3 DMSO stock
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water to a fnal concentration of 100 µg/cm3. To test for
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1 3