Design, synthesis and evaluation of 3-quinoline carboxylic acids as new inhibitors of protein kinase CK2

Article abstract of DOI:10.1080/14756366.2016.1222584

In this article, the derivatives of 3-quinoline carboxylic acid were studied as inhibitors of protein kinase CK2. Forty-three new compounds were synthesized. Among them 22 compounds inhibiting CK2 with IC₅₀ in the range from 0.65 to 18.2 μM were identified. The most active inhibitors were found among tetrazolo-quinoline-4-carboxylic acid and 2-aminoquinoline-3-carboxylic acid derivatives.

Full text of DOI:10.1080/14756366.2016.1222584

Journal of Enzyme Inhibition and Medicinal Chemistry
ISSN: 1475-6366 (Print) 1475-6374 (Online) Journal homepage: http://www.tandfonline.com/loi/ienz20
Design, synthesis and evaluation of 3-quinoline
carboxylic acids as new inhibitors of protein kinase
CK2
Anatolii R. Syniugin, Olga V. Ostrynska, Maksym O. Chekanov, Galyna P.
Volynets, Sergiy A. Starosyla, Volodymyr G. Bdzhola & Sergiy M. Yarmoluk
To cite this article: Anatolii R. Syniugin, Olga V. Ostrynska, Maksym O. Chekanov, Galyna
P. Volynets, Sergiy A. Starosyla, Volodymyr G. Bdzhola & Sergiy M. Yarmoluk (2016):
Design, synthesis and evaluation of 3-quinoline carboxylic acids as new inhibitors
of protein kinase CK2, Journal of Enzyme Inhibition and Medicinal Chemistry, DOI:
10.1080/14756366.2016.1222584
To link to this article: http://dx.doi.org/10.1080/14756366.2016.1222584
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ISSN: 1475-6366 (print), 1475-6374 (electronic)
J Enzyme Inhib Med Chem, Early Online: 1–10
2016 Informa UK Limited, trading as Taylor & Francis Group. DOI: 10.1080/14756366.2016.1222584
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RESEARCH ARTICLE
Design, synthesis and evaluation of 3-quinoline carboxylic acids as new
inhibitors of protein kinase CK2
Anatolii R. Syniugin, Olga V. Ostrynska, Maksym O. Chekanov, Galyna P. Volynets, Sergiy A. Starosyla, Volodymyr G.
Bdzhola, and Sergiy M. Yarmoluk
Department of Medicinal Chemistry, Institute of Molecular Biology and Genetics, NAS of Ukraine, Kyiv, Ukraine
Abstract
Keywords
In this article, the derivatives of 3-quinoline carboxylic acid were studied as inhibitors of protein
kinase CK2. Forty-three new compounds were synthesized. Among them 22 compounds
inhibiting CK2 with IC50 in the range from 0.65 to 18.2 mM were identified. The most active
inhibitors were found among tetrazolo-quinoline-4-carboxylic acid and 2-aminoquinoline-3-
carboxylic acid derivatives.
Inhibitor, protein kinase CK2, tetrazolo[1,5-
a]quinoline-4-carboxylic acid, 2-aminoqui-
noline-3-carboxylic acid, 2-chloroquinoline-
3-carboxylic acid, 2-oxo-1,2-dihydroquino-
line-3-carboxylic acid, 5-oxo-2,3-dihydro-
1H,5H-pyrido[3,2,1-ij]quinoline-6-carboxylic
acid
History
Received 1 June 2016
Revised 26 July 2016
Accepted 29 July 2016
Published online 26 August 2016
Introduction
by O. Meth-Cohn method12. The key intermediates are 2-chlor-
oquinoline-3-carboxylic acids 3, which were obtained by means
of oxidation with silver nitrate in alkaline medium13.
CK2 is a ubiquitous, highly pleiotropic, and constitutively active
Ser/Thr protein kinase with tetrameric structure (two catalytic ꢀ
and/or ꢀ0 and two regulatory ꢁ subunits). This enzyme has
approximately 400 physiological substrates including growth and
transcription factors, cell cycle, apoptosis, and stress response
regulators1–3. The overexpression of CK2 is associated with the
development of autoimmune and CNS diseases4, cardiac hyper-
trophy5, inflammation6, cancers7, etc. Also CK2 is known to be
used by many viruses for phosphorylation of their own proteins8.
The development of novel effective and selective CK2
inhibitors, which can be stable in physiological fluids and able
to penetrate cell membranes, requires a few steps of chemical
optimization. Among identified to date various CK2 inhibitors,
the only one compound CX-4945 (Silmitasertib)9 has entered the
second phase of clinical trials, as anticancer drug10,11. Thus,
development of new effective inhibitors of CK2 is still actual.
A series of 2-oxo-1,2-dihydroquinoline-3-carboxylic acids 4
were obtained after hydrolysis of chlorine in position 2 of
quinoline by treatment with boiling acetic acid with addition
of water. Alternatively, chlorine in position 2 was replaced with
amino group in aqueous ammonia at 150 ꢀC, 2-aminoquinoline-
3-carboxylic acids 5 were isolated with 30–50% yield after
fractional crystallization. A series of tetrazolo[1,5-a]quinoline-4-
carboxylic acids 6 were synthesized by reaction of intermediates
3 with sodium azide in dimethylformamide (DMF) at 100 ꢀC14.
The bromine in benzene ring of 2-oxo-1,2-dihydroquinoline-3-
carboxylic acid 4 and tetrazolo[1,5-a]quinoline-4-carboxylic acid
5 was replaced with phenylboronic acid residues by modificated
Suzuki reaction (Scheme 2).
Under reaction conditions, bromine atom in 6 and 7 positions
of 2-oxo-1,2-dihydroquinoline-3-carboxylic acid 4 and tetra-
zolo[1,5-a]quinoline-4-carboxylic acid 5 has been more replace-
able, and products of interaction of 8-bromo tetrazolo[1,5-
a]quinoline-4-carboxylic acid 6j (Table 3) with phenylboronic
acids were not formed. The 1-acetyl-1,2,3,4-tetrahydroquinoline 8
was a starting compound for the synthesis of 5-oxo-2,3-dihydro-
1H,5H-pyrido[3,2,1-ij]quinoline-6-carboxylic acid derivatives 11,
13, and 14 (Scheme 3). This compound was used in reaction with
Vilsmeier complex with obtaining 5-oxo-2,3-dihydro-1H,5H-
pyrido[3,2,1-ij]quinoline-6-carbaldehyde 9, which was treated
with hydroxylamine hydrochloride in phosphorus oxychloride at
100 ꢀC thus yielding 5-oxo-2,3-dihydro-1H,5H-pyrido[3,2,1-ij]
Experimental
Chemistry
The 2-chloroquinoline-3-carbaldehydes 2 were synthesized from
acetanilides 1 (Scheme 1) with the excess of Vilsmeier complex
Address for correspondence: Anatolii R. Syniugin, Department of
Medicinal Chemistry, Institute of Molecular Biology and Genetics,
NAS of Ukraine, 150 Zabolotny Str., Kyiv 03680, Ukraine. Tel: +380 97
310 5213. Fax: +380 44 526 3449. E-mail: asinugin@gmail.com

2
A. R. Syniugin et al.
J Enzyme Inhib Med Chem, Early Online: 1–10
O
O
H
N
AgNO
NaOH
POC1
DMF
3
3
H
OH
EtOH
O
N
Cl
N
Cl
R
R
R
2
3
1
DMF
NaN
NH
3
3
H O
2
AcOH
H O
2
O
O
O
O
OH
OH
OH
N
N
NH
2
N
N
H
R
R
R
N
6
N
5
4
Scheme 1. Synthesis of 3-quinoline carboxylic acids.
O
O
O
Pd(Ph P) Cl
2
OH
3
2
OH
EtOH
N
O
H
OH
B
N
R
2
H
Br
4.1
4
OH
O
O
R
Pd(Ph P) Cl
2
3
2
2
Br
OH
OH
EtOH
R
2
N
N
N
N
N
N
N
N
6.1
Scheme 2. Synthesis of phenyl substituted 3-quinoline carboxylic acids.
6
quinoline-6-carbonitrile 10 (Scheme 3). The last one was data were converted into PDBQT-format with Vega ZZ in
bromated to position 9 by N-bromosuccinimide action in DMF AUTODOCK force field. This format contains the coordinates
at room temperature. Obtained compounds 10 and 12 were of the atoms and partial charges. Hydrogen atoms were removed
hydrolyzed in process of prolonged boiling with ethanol solution from nonpolar atoms. The receptor was prepared using MGL
of sodium hydroxide. Obtained 9-bromo-5-oxo-2,3-dihydro- Tools and AutoGrid.
1H,5H-pyrido[3,2,1-ij]quinoline-6-carboxylic acid 14 was added
to the modificated Suzuki reaction with phenylboronic acids eters: translation step – 2 A, quaternion step – 50 , torsion step –
For docking calculation we have used the following param-
ꢀ
˚
generating 14‘ and 14b derivatives (Table 2).
50ꢀ. Torsional degrees of freedom and coefficient were 2 and
˚
0.274, respectively. Cluster tolerance – 2 A. External grid energy
– 1000, max initial energy – 0, max number of retries – 10 000.
Number of individuals in population – 300, maximum number of
Molecular docking
Software packages of Autodock 4.2.615 and Dock 4.016 were used energy evaluations – 850 000, maximum number of generations –
for flexible docking. The crystal structure of human protein 27 000, number of top individuals, which survived to the next
kinase CK2 was obtained from the Brookhaven Protein Data Bank generation – 1, rate of gene mutation – 0.02, rate of crossover –
(PDB ID: 3R0T)17–20
.
0.8, mode of crossover – arithmetic. Alpha parameter of Cauchy
distribution was 0, Beta parameter Cauchy distribution – 1. The
number of iterations of Lamarckian genetic algorithm was 50 for
each ligand.
AutoDock
Water molecules, ions, and ligand were removed from the PDB
file of receptor.
Dock
Ligands were prepared by Vega ZZ (command line)21 and
MGL Tools 1.5.615. To carry out calculation with the aid of The receptor molecule has been minimized in water with
Autodock program the incoming formats of receptor and ligands GROMACS molecular dynamics simulation package22

DOI: 10.1080/14756366.2016.1222584
Design, synthesis and evaluation of 3-quinoline carboxylic acid derivatives
3
O
O
N
DMF, POCl
NH OH HCl
3
2
NaOH
OH
H
POCl
3
EtOH
N
N
O
N
O
N
O
O
8
9
10
11
NBS
DMF
R
O
O
O
O
N
Br
Br
R-PhB(OH)
2
OH
OH
Pd (Ph P) Cl
NaOH
EtOH
3
2
2
N
N
N
O
EtOH
13
14a-b
12
Scheme 3. Synthesis of 5-oxo-2,3-dihydro-1H,5H-pyrido[3,2,1-ij]quinoline-6-carboxylic acid derivatives.
(GROMACS force field, steepest descent algorithm, 1000 steps, an equal volume of dimethyl sulfoxide (DMSO) was added to the
em_tolerance ¼ 100, em_step ¼ 0.001). Active site spheres were reaction mixture. Inhibition percentage was calculated as ratio of
calculated with DOCK sphgen software. The spheres with the substrate-incorporated radioactivity in the presence of inhibitor to
positions outside the ATP-binding site were deleted manually. the radioactivity incorporated in control reactions, i.e. in the
Connolly MS23 and Grid programs from DOCK package were absence of inhibitor. Serial dilutions of inhibitor stock solution
used to generate receptor Connolly surface and energy grids. were used to determine its IC50 concentration. The IC50 values
Surface and grid calculations were performed with parameter represent means of triplicate experiments with SEM never
settings as in24, except for grid spacing that was set to 0.3.
Calculations of ligand geometry were performed using YFF
force field developed by the authors25, partial atomic charges of
exceeding 15%.
Results and discussion
the ligands were calculated with Kirchhoff method26,27
.
Earlier, we found protein kinase CK2 inhibitors among the
derivatives of 3-carboxy-4(1H)-quinolone30. Recently, we have
identified hit compound among the derivatives of 3-carboxy
quinolin-2-one-7-bromo-2-oxo-1,2-dihydroquinoline-3-carboxylic
acid 93 (Figure 1) which decreased activity of CK2 on 22% at
concentration of 33 mM31,32. In this article, we have optimized the
structure of this compound with the aim of improvement of CK2
inhibitory activity.
Accordingly to the molecular docking results, the interaction
between ligand and ATP-binding pocket of CK2 occur due to
hydrophobic contacts with five amino acid residues of protein
kinase (Ile95, Phe113, Ile174, Val66, and Met163) and two
hydrogen bonds, which are formed between carboxylic group of
the compound and Lys68 and Asp175 amino acid residues. It
should be noted that the interaction with Lys68 is observed among
many low molecular weight inhibitors of human protein kinase
CK233. Taking into account the key interactions of compound 93
in CK2 active site, the several ways for structural optimization of
quinoline-3-carboxylic acid derivatives were proposed:
For receptor–ligand flexible docking the DOCK program has
been used. DOCK input parameters were set as in24 with some
exceptions to increase the calculations accuracy: the minimum of
heavy atoms in the anchor was set to 6, the maximum number of
orientations was set to 1000, and the ‘‘all atoms’’ model has been
chosen. DOCK employs an incremental reconstruction algorithm,
where rigid anchor fragments are identified first. At the next step,
the selected fragment is placed into the active site of the receptor
using a sphere-matching procedure. The complete ligand is
constructed by adding the remaining components step by step. At
each step of reconstruction a specified number of optimal partial
solutions are selected for the next extension step. Solutions are
scored using energy score (sum of van der Waals and electrostatic
components).
Visual analysis
For visual inspection of obtained with molecular docking protein
kinase–ligand complexes Discovery Studio Visualizer 4.028 was
used.
(1) To study the impact of substituents of benzene ring B
(Figure 1) on formation of hydrogen bonds and hydrophobic
interactions with CK2 active site, we have synthesized
derivatives with methoxy group and hydrophobic substituents
in position 5, 6, 7, and 8 of quinolin-2(1H)-one cycle.
Biology
Compounds were tested using in vitro kinase assay29. Each test
was carried out in triplicate in 30 mL reaction volume which (2) To determine the influence of carbonyl group on hydrogen
contains 6 mg of peptide substrate RRRDDDSDDD (New England
Biolabs); 10 units of recombinant human CK2 holoenzyme (New
bonds formation we have substituted it with chlorine atom or
amino group in position 2 of quinoline cycle A.
England Biolabs); 50 mM ATP and 0.05–0.1 mCi g-labeled 32P (3) To investigate influence of cyclic systems on compound
ATP with final specific activity of labeled ATP 3000 mCi/mmol;
CK2 buffer (20 mM Tris-HCl, pH 7.5; 50 mM KCl; 10 mM
MgCl2) and inhibitor in varying concentrations. Incubation time
was 20 min at 30 ꢀC. The reaction was stopped by adding an equal
activity via enhancing of hydrophobic effect, we have
synthesized derivatives with additional hydrophobic cycle
in position 5–6, 7–8 and aliphatic cycle in 1–8 position with
fixed amide bond of cycle A.
volume of 10% o-phosphoric acid and the reaction mixture was (4) Also, it was interesting to determine the influence of another
loaded onto 20-mm discs of phosphocellulose paper (Whatman).
Disks were washed three times with 1% o-phosphoric acid
solution, air-dried at room temperature, and counted by the
Cherenkov method in a beta-counter (LKB). As negative control
heterocycles in compounds structure on stabilization of
complex ‘‘inhibitor-CK2’’ via ꢂ–ꢂ stacking with Phe113.
Thus, the derivatives with condensed tetrazole cycle in 1 and
2 positions of quinoline cycle have been obtained.

4
A. R. Syniugin et al.
J Enzyme Inhib Med Chem, Early Online: 1–10
Table 2. Structure of 2-oxo-1,2-dihydroquinoline-3-carboxylic acid
derivatives and the data related to their in vitro screening.
O
O
R
5
R
R
4
OH
N
R
3
R
2
1
Compounds R1
R2
R3
R4
R5 IC50 (mM)
4a
4b
4c
4d
4k
4l
4.1.a
4.1.b
4.1.c
4.1.d
4.1.e
4.1.f
4.1.j
11
H
H
H
H
H
H
H
H
H
–OCH3
H
–OCH3
–OPh
H
H
H
H
H
H
430
430
430
430
6.8
–OCH3
–OCH3
H
H –CH ¼ CH–CH ¼ CH–
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
Ph
H
H
H
H
H
H
H
H
H
–CH ¼ CH–CH ¼ CH– 430
Ph
H
H
H
H
H
H
H
H
H
H
H
H
5.8
13.7
5.0
2.6
5.9
5.6
13
430
430
11.2
10
4-MeO-Ph-
3-MeO-Ph-
4-Cl-Ph-
3-Cl-Ph-
3-CF3-Ph-
H
Br
Ph
3-Cl-Ph-
Figure 1. Schematic representation of the complex of compound 93 with
active site of protein kinase CK2 (green line indicates amino acid residues
involved in hydrophobic contacts; dotted lines indicate hydrogen bonds).
–(CH2)3–
–(CH2)3–
–(CH2)3–
–(CH2)3–
13
14a
14b
Table 1. Structure of 2-chloro- and 2-aminoquinoline-3-carboxylic acid Table 3. Structure of tetrazolo[1,5-a]quinoline-4-carboxylic acid
derivatives and the data related to their in vitro screening. derivatives and the data related to their in vitro screening.
R
O
R
O
5
4
1
R
R
R
R
4
3
OH
OH
N
R
N
N
N
N
1
3
2
R
R
2
Compounds R1
R2
R3
R4
R5 IC50 (mM)
Compounds
R1
R2
R3
R4 IC50 (mM)
3a
3b
3c
3d
3e
3k
3l
5a
5b
5c
5d
5e
5f
Cl
Cl
Cl
Cl
Cl
H
H
H
H
H
H
–OCH3
–OCH3
H
–OCH3
H
–OCH3
–OPh
–OCH3
H
H
H
H
H
H
H
430
6.1
430
430
430
1.5
6a
6b
6c
6d
6e
6f
6j
6k
6l
6.1a
6.1b
6.1c
H
H
H
H
H
H
H
H
–OCH3
H
–OCH3
–OPh
–OCH3
Br
H
H
H
H
H
H
H
H
430
0.8
–OCH3
–OCH3
H
Br
H
Br
430
430
430
430
4.2
Br
Cl –CH ¼ CH–CH ¼ CH–
Cl
H
H
H
H
H
H
H
H
H
–CH ¼ CH–CH ¼ CH– 430
H
H
NH2
NH2
NH2
NH2
NH2
NH2
–OCH3
H
H
H
H
H
H
H
H
430
1.2
0.7
430
430
18.2
0.65
–CH ¼ CH–CH ¼ CH–
1.0
–OCH3
Br
H
H
Br
H
H
H
H
H
H
H
H
–CH ¼ CH–CH ¼ CH–
430
15.1
13.2
2.5
H
Br
–OPh
–OCH3
H
Ph
3-MeO-Ph-
3-Cl-Ph-
H
H
H
5k
NH2 –CH ¼ CH-CH ¼ CH–
quinoline heterocycle forms hydrophobic contacts with amino
acid residues Val66, Ile95, Met163, and Ile174; stacking with
Phe113 is observed here as well. The substituent in position 2 of
quinoline heterocycle is located in ribose pocket of CK2 and
forms a series of hydrophobic contacts: compounds with tetrazole
cycle (6b, 6k, and 6j) have strong hydrophobic contacts with
amino acid residues Ile95, Phe113, and Ile174; compounds with
chlorine atom (3b, 3k) and oxygen atom (4b, 4k, and 93) do not
have hydrophobic interaction with Ile95. Besides ligands with
oxygen atom or tetrazole cycle form hydrogen bond with Asp175.
Thus, the most active inhibitor among above-mentioned com-
pounds is tetrazole derivative (compound 6b, IC50 ¼0.8 mM). It
can be explain by the fact that this ligand has more hydrophobic
contacts in ATP-binding site of CK2.
As a result of our modifications, 43 novel derivatives of 3-
quinoline carboxylic acid have been synthesized and tested in
vitro. Their chemical structures and inhibitory activity toward
CK2 (IC50 values) are shown in Tables 1–3.
Accordingly to the results of structure–activity relationship
(SAR) analysis, a series of regularities can be observed.
Inhibitors’ activity is greatly influenced by the replacement of
substituents in position 2 of quinoline heterocycle, which can be
shown by comparing groups of compounds 3b–4b–5b–6b, 3k–
4k–5k–6k, 5c–93 (see Figure 1) –6j. In order to explain this
relationship, we performed molecular docking of novel 3-
carboxyquinoline derivatives into ATP-binding pocket of human
CK2. Accordingly to computer modeling results, the ligands

DOI: 10.1080/14756366.2016.1222584
Design, synthesis and evaluation of 3-quinoline carboxylic acid derivatives
5
Figure 2. Compound 5k (violet) in ATP-binding site of CK2 (the
complex was obtained with molecular docking, hydrogen bonds are CK2 (the complex was obtained by molecular docking, hydrogen bonds
Figure 3. Compounds 6‘ (green) and 6b (blue) in ATP-binding site of
indicated by green dotted lines).
are indicated by green dotted lines).
For ligands with NH2- group 5a–5k, we were expecting the
same binding mode as described above, but both docking
programs AutoDock and Dock proposed reverse position
(Figure 2). The carboxylic and amino groups of these compounds
were oriented toward the CK2 hinge region (Figure 2). The
quinoline heterocycle of compounds 5b, 5k, and 5c has hydro-
phobic interactions with Val66, Ile95, Met163, Ile174, ꢂ–ꢂ
stacking with Phe113 and additional contact with Val53.
Carboxylic acid residue of ligands forms H-bond with Val116,
while -NH2 is involved in the formation of hydrogen bond with
Glu114. Opposite to this, the empirical data of inhibitory activity
for compounds 5b, 5k, and 5c confirmed substituent effects in the
ring B on compounds activity, as well as for 3b, 3k, and 6j. Also,
we have found that the introduction of –NH2 into the second
position of 3-carboxyquinolines, instead C¼O, leads to consid-
erable increase of CK2 inhibition activity (pair of compounds 4k–
5k, 93–5c, and 4b–5b).
Figure 4. Compounds 6b (blue) and 6p (purple) in ATP-binding site of
CK2 (the complex was obtained by molecular docking, hydrogen bonds
are indicated by green dotted lines).
Compounds with 7-methoxy substituent of quinoline are more
active than compounds with 6-methoxy or 6,7-dimethoxy sub-
stituents that can be shown by comparing the groups of
compounds 3a–3b–3c and 6a–6b–6c. This regularity can be
explained based on the complexes of pairs of compounds 6a–6b
(Figure 3) and 6b–6c (Figure 4). Carboxyl group of compounds is 6f–6j. It is interesting that compounds 4.1a and 4.1b, with bulk
located in the area with a positive electrostatic potential (near substituent (Ph) in position 6- and 7 of quinolone, show the
Lys68), which attracts negatively charged groups of compounds opposite regularity. This can be explained by the binding modes
and influences on position of ligands in the active site. In this of these compounds with CK2 active site. As we can see from the
area, the hydrogen bond is formed between oxygen atom of the Figure 5, substituent in position 6 of quinolone (compound 4.1a)
ligand’s carboxyl group and nitrogen atom of Lys68 side chain is located in hydrophobic region II while the Ph in position 7 of
and hydrogen bond occurs between tetrazole cycle and nitrogen quinolone (compound 4.1b) should be directed toward hinge
atom of Asp175 main chain.
region, but its size prevents it. As a result, 4.1b changes its
Oxygen atom of the methoxy group of compounds 6a and 6b location in active site that leads to weakening of hydrophobic
forms hydrogen bond with nitrogen atom of Val116. As both 6- contacts with Leu45 and Val66, and breakdown of ꢂ–ꢂ stacking
and 7-substituted quinolines have the same hydrogen bonds, with Phe113.
higher inhibitory activity of the last one can be explained by
Introduction of oxygen atom between phenyl substituent and
tighter hydrophobic interaction with Val66 (Figure 3). In its turn, 2-quinolone heterocycle negatively effects compounds activity, as
the absence of expected inhibitory activity of dimethoxy was shown by pair of compounds 4d–4.1a and 6d–6.1f. In this
substituted derivative 6p can be caused by the fact that the case, the compounds with phenoxy in position 6 lost their
introduction of the second methoxy group results in the repulsion inhibitory activity.
of methoxy group in position 6 of quinoline from Leu45,
The positive effect on inhibitory activity of compounds
whereupon compound is buried deeper into enzyme’s active site through increasing hydrophobicity of ligands can be seen in the
and loses the hydrogen bonds with CK2 hinge region (Figure 4). pair of compounds 6.1a–6.1b–6.1c. Thus, the introduction of
In a way similar to methoxy substituted quinoline derivatives, additional substituents into the phenyl cycle leads to increased
7-bromine substituted compounds exhibit better inhibitory activ- interactions with Leu45 and contributes to the formation of
ity toward CK2, compared to 6-bromine substituted: 5c–5d and additional hydrophobic contacts with imidazole cycle of His115.

6
A. R. Syniugin et al.
J Enzyme Inhib Med Chem, Early Online: 1–10
given as s (singlet), d (doublet), dd (double doublet), t (triplet), q
(quartet), or m (multiplet). High-performance liquid chromatog-
raphy-mass spectra (HPLC-MS) analysis was performed using the
Agilent 1100 LC/MSD SL (Agilent Technologies) separations
module and Mass Quad G1956B mass detector with electrospray
ionization (Agilent Technologies) (+ve or ꢁ ve ion mode as
indicated) and with HPLC performed using Zorbax SB-C18
(Agilent Technologies), Rapid Resolution HT Cartridge 4.6
30 mm 1.8-m (Agilent Technologies P/N:823975-902) i.d.
column, at 40 ꢀC with gradient elution of 0–100% CH3CN
(with 1 mL/L HCOOH): H2O (with 1 mL/L HCOOH) at a flow
rate of 3 mL/min and a run time of 2.8 min. Compounds were
detected at 215 nm using Diode Array G1315B detector. Melting
points were determined on a micro hot stage apparatus and are
uncorrected.
General procedure synthesis of 2-chloroquinoline-3-carboxylic
acids 3‘–l
Figure 5. Compounds 4.1‘ (yellow) and 4.1b (pale gray) in ATP-binding
site of CK2 (the complex was obtained by molecular docking, hydrogen
bonds are indicated by green dotted lines).
To stirring suspension of corresponding 2-chloroquinoline-3-
carbaldehyde 2a–l [9, 16] (0.01 mol) in 60 mL EtOH was added
warm AgNO3 solution 2.71 g (0.016 mol) in 30 mL EtOH.
Solution of NaOH 2 g (0.05 mol) in 30 mL 80% aqueous EtOH
was added dropwise with intensive stirring during 15 min at room
temperature. Reaction mixture was stirred 12 h and filtered
through CELIT pad. The solvent was removed by rotary
evaporation. Water was added to completely solved Na+ salt of
3, than acidified 15% aqueous HCl solution to pH 1. Solid
products 3a–l were filtered, washed with water (2 ꢂ 20 mL) and
then dried in a vacuum oven at 60 ꢀC.
Also, halogen bonds between oxygen atom of Asn118 and
halogen atoms of ligand are likely to occur.
Additional aliphatic cycle (–CH2–CH2–CH2–N–) decreases
the activity of compounds which was proved by pairs 4.1‘–14‘,
4.1f–14b. The quinolones with additional cycle have lost the
hydrogen bond with Asp175 due to inability to locate in the depth
of the active site. Also, their hydrophobic interaction with Phe113
was weakened.
The best inhibitory activity due to hydrophobic substituent is
shown by benzo[h]quinoline-3-carboxylic acid derivatives 3–6k.
At the same time, their benzo[f]quinoline-2-carboxylic acid
analogs (compounds 3 l, 4 l, and 6 l) are inactive at all. The lack
of activity can be explained by different position of compounds in
the CK2 active site. The complexes of compounds 3k, 4k, and 6k
with enzyme have shown that quinoline heterocycle is located in
the depth of active site and forms strong hydrophobic interaction
with Val53, Val66, Ile95, and Ile174. The presence of additional
cycle in position 5–6 prevents similar position of compounds 3 l,
4 l, and 6 l. These ligands are located closer to the exit from the
active site and consequently their hydrophobic contacts with
Val66 and Ile95 are weakened.
2-chloro-6-methoxyquinoline-3-carboxylic
acid
3‘.
Yield ¼ 89%. Mp. ¼ 259 ꢀC; white powder. LCMS m/z 238, 240
[M + H+], Rf ¼0.75 min. 1HNMR (DMSO-d6) d 3.91 (s, 3H,
–OCH3), 7.52–7.64 (m, 2H), 7.91 (d, 1M, CM, J ¼ 8.79 Hz), 8.79
(s, 1M, CM).
2-chloro-7-methoxyquinoline-3-carboxylic
acid
3b.
Yield ¼ 83%. Mp. ¼ 203 ꢀC; white powder. LCMS m/z 238, 240
[M + H+], Rf ¼0.77 min. 1HNMR (DMSO-d6) d 3.95 (s, 3H,
–OCH3), 7.29–7.45 (m, 2H), 8.07 (d, 1M, CM, J ¼ 8.79 Hz), 8.86
(s, 1M, CM), 13.55 (br. s., 1M, COOM).
2-chloro-6,7-dimethoxyquinoline-3-carboxylic acid 3c.
Yield ¼ 87%. Mp. ¼ 236 ꢀC; yellow powder. LCMS m/z 268,
1
270 [M + H+], Rf ¼0.81 min. HNMR (DMSO-d6) d 3.93 (s, 3H,
Thus, taking into account the results obtained by SAR analysis
and molecular modeling data, it is possible to conclude that the
key interactions, which cause the increase of inhibitory activity of
studied 3-quinoline carboxylic acid derivatives are hydrophobic
contacts.
–OCH3), 3.97 (s, 3H, –OCH3), 7.39 (s, 1H, CH), 7.53 (s, 1H, CH),
8.71 (s, 1M, CM).
2-chloro-6-phenoxyquinoline-3-carboxylic
acid
3d.
Yield ¼ 92%. Mp. ¼ 184 ꢀC; light-yellow powder. LCMS m/z
300, 302 [M + H+], Rf ¼0.88 min. 1HNMR (DMSO-d6) d 7.16 (d,
2M, C2M2, J ¼ 7.81 Hz), 7.24 (t, 1M, CM, J ¼ 7.08 Hz), 7.47 (t, 2M,
C2M2, J ¼ 6.84 Hz), 7.60 (s, 1H, CH), 7.66 (d, 1M, CM,
J ¼ 8.79 Hz), 8.03 (d, 1M, CM, J ¼ 8.30 Hz), 8.81 (s, 1H, CH),
13.77 (br. s., 1M, COOH).
Conclusion
Modifications of the 3-quinoline carboxylic acid moiety have led
to the identification of promising protein kinase CK2 inhibitors.
The most active compounds with IC50 in submicromolar range
were found among the tetrazolo-quinoline-4-carboxylic acid and
2-amino-quinoline-3-carboxylic acid derivatives. We suppose that
the last ones are the most perspective for further chemical
optimization and biological investigations.
7-bromo-2-chloro-6-methoxy-3-carboxylic
acid
3e.
Yield ¼ 94%. Mp. ¼ 264 ꢀC; yellow powder. LCMS m/z 321
[M + H+], Rf ¼0.93 min. 1HNMR (DMSO-d6) d 4.00 (s, 3H,
–OCH3), 7.71(s, 1H, CH), 8.28 (s, 1H, CH), 8.81 (s, 1H, CH),
13.75 (br. s., 1M, COOM).
2-chlorobenzo[h]quinoline-3-carboxylic
acid
3k.
Yield ¼ 83%. Mp. ¼ 228 ꢀC; beige powder. LCMS m/z 258, 260
[M + H+], Rf ¼0.89 min. 1HNMR (DMSO-d6) d 7.82 (m, 2 H,
C2M2), 8.04 (m, 3 H, C3M3), 8.95 (s, 1 H, CM), 9.00 (d,
J ¼ 7.32 Hz, 1 H, CM), 13.85 (s, 1 H, CONM).
Yield ¼ 89%. Mp. ¼ 233 ꢀC; white powder. LCMS m/z 258, 260
[M + H+], Rf ¼0.97 min. 1HNMR (DMSO-d6) d 7.75–7.85 (m,
2 H, C2M2), 7.89 (d, 1 H, CM, J ¼ 9.16 Hz), 8.11 (d, 1 H, CM,
Experimental section
Starting materials and solvents were purchased from commercial
suppliers and were used without further purification. 1HNMR
spectra were recorded on Varian VXR 400 spectrometer at
400 MHz (Agilent Technologies, Santa Clara, CA). Chemical
shifts are described as parts per million (d) downfield from an
internal standard of tetramethylsilane, and spin multiplicities are
3-chlormbenzo[f]quinoline-2-carboxylic
acid
3 l.

DOI: 10.1080/14756366.2016.1222584
Design, synthesis and evaluation of 3-quinoline carboxylic acid derivatives
7
J ¼ 7.32 Hz), 8.28 (d, 1 H, CM, J ¼ 9.16 Hz), 8.90 (d, 1 H, CM,
J ¼ 7.94 Hz), 9.59 (s, 1 H, CM).
2-amino-7-bromoquinoline-3-carboxylic
acid
5c.
Yield ¼ 27%. Mp. ¼ 286 ꢀC; yellow powder. LCMS m/z 267,
1
269 [M + H+], Rf ¼0.71 min. HNMR (DMSO-d6) d 7.34 (d, 1M,
General procedure synthesis of 2-oxo-1,2-dihydroquinoline-3-
carboxylic acids 4a–l
CM, J ¼ 7.33 Hz), 7.65 (s, 1H, CH), 7.79 (d, 1M, CM, J ¼ 7.33 Hz),
8.75 (s, 1H, CH).
2-amino-6-bromoquinoline-3-carboxylic
acid
5d.
Suspension of corresponding 2-chloroquinoline-3-carboxylic acid
3 (1 mmol) in glacial acetic acid (25 mL) and water (1.5 mL) was
boiled with stirring during 12–24 h. The reaction was monitored
by NMR. After cooling, water (100 mL) was added and solid
products 4a–l were filtered, washed with water (2 ꢂ 20 mL) and
then dried in a vacuum oven at 60 ꢀC.
Yield ¼ 41%. Mp. ¼ 245 ꢀC; yellow powder. LCMS m/z 267,
1
269 [M + H+], Rf ¼0.61 min. HNMR (DMSO-d6) d 7.43 (d, 1M,
CM, J ¼ 9.77 Hz), 7.69 (d, 1M, CM, J ¼ 9.28 Hz), 8.08 (s, 1M, CM),
8.72 (s, 1M, CM).
2-amino-6-phenoxyquinoline-3-carboxylic
acid
5e.
Yield ¼ 50%. Mp. ¼ 318 ꢀC; yellow powder. LCMS m/z 281
[M + H+], Rf ¼0.71 min. 1HNMR (DMSO-d6) d 7.02 (d, 2M,
C2M2, J ¼ 7.81 Hz), 7.13 (t, 1M, CM, J ¼ 7.32 Hz), 7.39 (t,
3M, C3M3, J ¼ 7.81 Hz), 7.49 (s, 1H, CH), 7.55 (d, 1M, CM,
J ¼ 9.28 Hz), 8.72 (s, 1M, CM).
6-methoxy-2-oxo-1,2-dihydroquinoline-3-carboxylic
acid
4‘. Yield ¼ 89%. Mp. ¼ 289 ꢀC; yellow powder. LCMS m/z 220
[M + H+], Rf ¼0.67 min. 1HNMR (DMSO-d6) d 3.84 (s, 3H,
–OCH3), 7.41–7.53 (m, 2H, C2H2), 7.59 (s, 1M, CM), 8.92 (s, 1M,
CM), 13.08 (br. s., 1M, NM), 14.94 (br. s., 1M, COOM).
2-amino-7-bromo-6-methoxyquinoline-3-carboxylic acid 5f.
Yield ¼ 32%. Mp. ¼ 285 ꢀC; yellow powder. LCMS m/z 297,
299 [M + H+], Rf ¼0.62 min. 1HNMR (DMSO-d6) d 3.90 (s,
3H, –OCH3), 7.45 (s, 1H, CH), 7.74 (s, 1H, CH), 8.69 (s, 1H,
CH).
7-methoxy-2-oxo-1,2-dihydroquinoline-3-carboxylic
acid
4b. Yield ¼ 73%. Mp. ¼ 293 ꢀC; beige powder. LCMS m/z 220
[M + H+], Rf ¼0.69 min. 1HNMR (DMSO-d6) d 3.90 (s, 3H,
–OCH3), 6.97 (s, 1M, CM), 7.03 (d, 1M, CM, J ¼ 8.3 Hz), 7.96 (d,
1M, CM, J ¼ 8.79 Hz), 8.87 (s, 1M, CM), 12.93 (br. s., 1M, NM),
14.59 (br. s., 1M, COOM).
2-aminobenzo[h]quinoline-3-carboxylic acid 5k. Yield 41%.
Mp. ¼ 254 ꢀC; yellow powder. LCMS m/z 239 [M + H+],
6,7-dimethoxy-2-oxo-1,2-dihydroquinoline-3-carboxylic
1
Rf ¼0.69 min. HNMR (DMSO-d6) d 7.71–7.85 (m, 3H, C3H3),
acid 4p. Yield ¼ 92%. Mp. ¼ 287 ꢀC; yellow powder. LCMS m/z
7.91 (d, 1H, CH, J ¼ 7.32 Hz), 8.05 (d, 1H, CH, J ¼ 7.32 Hz), 9.06
(s, 1H, CH), 9.16 (d, 1H, CH, J ¼ 7.94 Hz).
1
250 [M + H+], Rf ¼0.72 min. HNMR (DMSO-d6) d 3.84 (s, 3H,
–OCH3), 3.91 (s, 3H, –OCH3), 7.00 (s, 1H, CH), 7.53 (s, 1M, CM),
8.81 (s, 1M, CM), 12.93 (br. s., 1M, NM), 14.85 (br. s., 1M, COOM).
General procedure synthesis of tetrazolo[1,5-a]quinoline-4-car-
boxylic acids 6a–l
2-oxo-6-phenoxy-1,2-dihydroquinoline-3-carboxylic
acid
4d. Yield ¼ 97%. Mp. ¼ 272 ꢀC; yellow powder. LCMS m/z 282
[M + H+], Rf ¼0.76 min. 1HNMR (DMSO-d6) d 7.04 (d, 2M, Suspension of corresponding 2-chloroquinoline-3-carboxylic acid
C2M2, J ¼ 7.32 Hz), 7.17 (t, 1M, CM, J ¼ 7.08 Hz), 7.41 (t, 2M, 3 (1 mmol) and sodium azide (0.15 g, 2.3 mmol) in DMF (5 mL)
C2M2, J ¼ 7.08 Hz), 7.50–7.60 (m, 2H, C2H2), 7.71 (s, 1M, CM), stirred at 100 ꢀC during 12 h. After cooling, water (30 mL) was
8.92 (s, 1M, CM), 13.47 (br. s., 1M, NH), 14.08 (br. s., 1M, COOH). added than mixture acidified by 15% aqueous HCl solution to pH
2-oxo-1,2-dihydrobenzo[h]quinoline-3-carboxylic acid 4k. 1. Solid products 6a–l were filtered, washed with water
Yield ¼ 65%. Mp. ¼ 228 ꢀC; yellow powder. LCMS m/z 240 (2 ꢂ 20 mL) and then dried in a vacuum oven at 60 ꢀC.
[M + H+], Rf ¼0.82 min. 1HNMR (DMSO-d6) d 7.77 (m, 3 H,
7-methoxytetrazolo[1,5–a]quinoline-4-carboxylic acid 6‘.
C3M3), 7.94 (d, J ¼ 9.16 Hz, 1 H, CM), 8.05 (d, J ¼ 7.94 Hz, 1 H, Yield ¼ 79%. Mp. ¼ 255 ꢀC; beige powder. LCMS m/z 245
CM), 9.00 (d, J ¼ 7.94 Hz, 1 H, CM), 9.03 (s, 1 H, CM), 13.49 [M + H+], Rf ¼0.71 min. 1HNMR (DMSO-d6) d 3.95 (s, 3H,
(s, 1 H, NM).
–OCH3), 7.65 (d, 1M, CM, J ¼ 7.32 Hz), 7.92 (s, 1H, CH), 8.54 (d,
3-oxo-3,4-dihydrobenzo[f]quinoline-2-carboxylic acid 4 l. 1M, CM, J ¼ 8.79 Hz), 8.83 (s, 1M, CM), 13.62 (br. s., 1M, COOH).
Yield ¼ 74%. Mp. ¼ 228 ꢀC; yellow powder. LCMS m/z 240
8-methoxytetrazolo[1,5–a]quinoline-4-carboxylic acid 6b.
[M + H+], Rf ¼0.79 min. 1HNMR (DMSO-d6) d 7.65 (m, 2 H, Yield ¼ 71%. Mp. ¼ 260 ꢀC; white powder. LCMS m/z 245
C2M2), 7.78 (t, J ¼ 7.63 Hz, 1 H, CM), 8.04 (d, J ¼ 8.55 Hz, [M + H+], Rf ¼0.69 min. 1HNMR (DMSO-d6) d 4.08 (s, 3H,
1 H, CM), 8.28 (d, J ¼ 9.16 Hz, 1 H, CM), 8.67 (d, J ¼ 8.55 Hz, -OCH3), 7.47 (d, 1M, CM, J ¼ 8.30 Hz), 8.04 (s, 1H, CH), 8.34 (d,
1 H, CM), 9.57 (s, 1 H, CM).
1M, CM, J ¼ 8.79 Hz), 8.88 (s, 1M, CM).
7,8-dimethoxytetrazolo[1,5-a]quinoline-4-carboxylic acid
6c. Yield ¼ 95%. Mp. ¼ 286 ꢀC; beige powder. LCMS m/z 275
[M + H+], Rf ¼0.79 min. 1HNMR (DMSO-d6) d 3.96 (s, 3H,
–OCH3), 4.11 (s, 3H, –OCH3), 7.92 (s, 1H, CH), 8.03 (s, 1H, CH),
8.83 (s, 1H, CH), 13.48 (br. s., 1M, COOH).
General procedure synthesis of 2-aminoquinoline-3-carboxylic
acids 5‘–5 l
Suspension of corresponding 2-chloroquinoline-3-carboxylic
acids 3 (1 mmol) in 26% aqueous NH3 (5 mL) was heated in
stainless steel autoclave at 150 ꢀC during 4 h. After reaction
mixture cooling, clear solution was acidified by 5% aqueous HCl
solution to pH-4. Solid products 5a–l were filtered and
recrystallized from IPA–DMF mixture.
7-phenoxytetrazolo[1,5-a]quinoline-4-carboxylic acid 6d.
Yield ¼ 97%. Mp. ¼ 254 ꢀC; beige powder. LCMS m/z 307
[M + H+], Rf ¼0.82 min. 1HNMR (DMSO-d6) d 7.17 (d, 2M,
C2M2, J ¼ 7.81 Hz), 7.26 (t, 1M, CM, J ¼ 7.08 Hz), 7.48 (t,
2M, C2M2, J ¼ 7.08 Hz), 7.74 (d, 1M, CM, J ¼ 8.79 Hz), 8.02 (s,
1H, CH), 8.66 (d, 1M, CM, J ¼ 8.79 Hz), 8.89 (s, 1M, CM), 13.78
(br. s., 1M, COOH).
8-bromo-7-methoxytetrazolo[1,5-a]quinoline-4-carboxylic
acid 6e. Yield ¼ 86%. Mp. ¼ 291 ꢀC; white powder. LCMS m/z
323, 325 [M + H+], Rf ¼0.81 min. 1HNMR (DMSO-d6) d 4.04 (s,
3H, –OCH3), 8.08 (s, 1H, CH), 8.79 (s, 1H, CH), 8.82 (s, 1H,
CH).
2-amino-6-methoxyquinoline-3-carboxylic
acid
5‘.
Yield ¼ 36%. Mp. ¼ 283 ꢀC; yellow powder. LCMS m/z 219
[M + H+], Rf ¼0.56 min. 1HNMR (DMSO-d6) d 3.83 (s, 3H,
–OCH3), 7.47 (m, 2H, C2H2), 7.61 (s, 1H, CH), 8.93 (s, 1H, CH),
15.01 (br. s., 1M, COOM).
2-amino-7-methoxyquinoline-3-carboxylic
acid
5b.
Yield ¼ 49%. Mp. ¼ 269 ꢀC; white powder. LCMS m/z 219
[M + H+], Rf ¼0.58 min. 1HNMR (DMSO-d6) d 3.86 (s, 3H,
–OCH3), 6.85 (d, 2H, C2H2, J ¼ 6.1 Hz), 6.89 (s, 1H, CH), 7.69
(d, 2H, C2H2, J ¼ 6.1 Hz), 8.61 (s, 1H, CH).
7-bromotetrazolo[1, 5-a]quinoline-4-carboxylic acid 6f.
Yield ¼ 91%. Mp. ¼ 274 ꢀC; beige powder. LCMS m/z 293, 295
[M + H+], Rf ¼0.78 min. 1HNMR (DMSO-d6) d 8.21 (d, 1M, CM,

8
A. R. Syniugin et al.
J Enzyme Inhib Med Chem, Early Online: 1–10
J ¼ 8.2 Hz), 8.58 (d, 1M, CM, J ¼ 8.79 Hz), 8.71 (s, 1M, CM), 8.89 (m, 2H, C2H2), 7.38–7.47 (m, 1H, CH), 7.60 (d, 1M, CM,
(s, 1H, CH).
J ¼ 8.30 Hz), 8.12 (d, 1M, CM, J ¼ 8.79 Hz), 8.40 (s, 1H, CH),
8-bromotetrazolo[1,5-a]quinoline-4-carboxylic acid 6j. 9.03 (s, 1H, CH), 13.20 (br. s., 1M, NM), 14.69 (br. s., 1M, COOH).
6-(4-chlorophenyl)-2-oxo-1,2-dihydroquinoline-3-car-
Yield ¼ 89%. Mp. ¼ 265 ꢀC; beige powder. LCMS m/z 293, 295
1
[M + H+], Rf ¼0.8 min. HNMR (DMSO-d6) d 8.04 (d, 1M, CM, boxylic acid 4.1e. Yield ¼ 86%, Mp. ¼ 314 ꢀC; light-yellow
1
J ¼ 8.71 Hz), 8.34 (d, 1M, CM, J ¼ 8.30 Hz), 8.81 (d, 2M, C2M2, powder. LCMS m/z 300, 302 [M + H+], Rf ¼1.01 min. HNMR
J ¼ 6.35 Hz).benzo[h]tetrazolo[1,5-a]quinoline-4-carboxylic
(DMSO-d6) d 7.58 (t, 3M, C3M3, J ¼ 7.81 Hz), 7.77 (d, 2M, C2M2,
acid 6k. Yield ¼ 83%. Mp. ¼ 228 ꢀC; white powder. LCMS m/z J ¼ 8.30 Hz), 8.12 (d, 1M, CM, J ¼ 9.28 Hz), 8.41 (s, 1H, CH),
265 [M + H+], Rf ¼0.88 min. 1HNMR (DMSO-d6) d 8.02 (m, 2 H, 9.02 (s, 1H, CH), 13.25 (br. s., 1M, NM), 14.69 (br. s., 1M, COOM).
C2M2), 8.36 (m, 3 H, C3M3), 9.12 (s, 1 H, CM), 10.19 (d, 1 H, CM,
J ¼ 8.55 Hz).benzo[f]tetrazolo[1,5-a]quinoline-12-carboxylic
6-(3-chlorophenyl)-2-oxo-1,2-dihydroquinoline-3-car-
boxylic acid 4.1f. Yield ¼ 87%, Mp. ¼ 271 ꢀC; white powder.
acid 6 l. Yield ¼ 86%. Mp. ¼ 228 ꢀC; white powder. LCMS m/z LCMS m/z 300, 302 [M + H+], Rf ¼0.94 min. HNMR (DMSO-
265 [M + H+], Rf ¼0.83 min. 1HNMR (DMSO-d6) d 7.82 (s, 1 H, d6) d 7.46 (d, 1M, CM, J ¼ 6.84 Hz), 7.54 (t, 1M, CM, J ¼ 7.57 Hz),
CM), 7.90 (s, 1 H, CM), 8.25 (d, J ¼ 7.94 Hz, 1 H, CM), 8.57 (d, 7.60 (d, 1M, CM, J ¼ 6.84 Hz), 7.72 (d, 1M, CM, J ¼ 6.84 Hz), 7.81
J ¼ 9.16 Hz, 1 H, CM), 8.71 (d, J ¼9.16 Hz, 1 H, CM), 8.96 (d, (s, 1H, CH), 8.13 (d, 1M, CM, J ¼ 7.81 Hz), 8.43 (s, 1H, CH), 9.00
1
J ¼7.94 Hz, 1 H, CM), 9.56 (s, 1 H, CM).
(s, 1H, CH), 13.16 (br. s., 1M, NM), 14.60 (br. s., 1M, COOH).
2-oxo-6-[3-(trifluoromethyl)phenyl]-1,2-dihydroquinoline-
3-carboxylic acid 4.1j. Yield ¼ 74%, Mp. ¼ 295 ꢀC; gray powder.
General procedure synthesis of 6- and 7-phenyl-2-oxo-1,2-
dihydroquinoline-3-carboxylic acids 4.1a-g and 7-phenyltetra-
zolo[1,5-a]quinoline-4-carboxylic acids 6.1a-c, modification of
Suzuki reaction
1
LCMS m/z 334 [M + H+], Rf ¼1.02 min. HNMR (DMSO-d6) d
7.62 (d, 1M, CM, J ¼ 8.30 Hz), 7.77 (m, 2H, C2H2), 8.08 (m, 2H,
C2H2), 8.18 (d, 1M, CM, J ¼ 8.30 Hz), 8.50 (s, 1H, CH), 9.00 (s,
1H, CH).
Synthesis of starting 6- and 7-bromo-2-oxo-1,2-dihydroquinoline-
3-carboxylic acids was carried out by general procedure, previ-
ously described for 4a–l, physical and analytical data which we
described earlier24.
7-phenyltetrazolo[1,5-a]quinoline-4-carboxylic acid 6.1a.
Yield ¼ 89%, Mp. ¼ 288 ꢀC; yellow powder. LCMS m/z 291
1
[M + H+], Rf ¼0.96 min. HNMR (DMSO-d6) d 7.49 (t, 1M, CM,
Mixture of corresponding bromide (0.75 mmol) with corres-
ponding phenylboronic acid (0.76 mmol) in ethanol (20 mL) was
ventilated by argon three times, then mixture or Na2CO3 (0.4 g,
3.75 mmol) with (Ph3P)2PdCl2 (0.052 g, 0.075 mmol) was added
in one portion with stirring and reaction vessel ventilated again.
Reaction mixture was boiled with stirring under argon during
12 h. The solvent was removed by rotary evaporation. The formed
solid residue was transferred to a stirred 10% aqueous HCl
solution (50 mL). Crude precipitate of product was filtered,
washed with water (2 ꢂ 10 mL) and hexane: DCM mixture 1:1
(5 ꢂ 10 mL) to get rid of Ph3PO. After drying crude precipitate
was dissolved in DMF and filtered through CELIT pad, to get rid
of Pd. Filtrate was concentrated by rotary evaporation and residue
treated by cold water. The formed solid of product was filtered,
washed with water (2 ꢂ 10 mL) and then dried in a vacuum oven
at 70 ꢀC. Typically the products were sufficiently pure, but if
necessary, they could be recrystallized from an IPA–DMF
mixture.
J ¼ 6.84 Hz), 7.59 (d, 2M, C2M2, J ¼ 7.57 Hz), 7.88 (d, 2M, C2M2,
J ¼ 7.32 Hz), 8.41 (d, 1M, CM, J ¼ 9.28 Hz), 8.72 (d, 1M, CM,
J ¼ 8.79 Hz), 8.78–8.81 (m, 1H, CH), 9.02 (s, 1H, CH).
7-(3-methoxyphenyl)tetrazolo[1,5-a]quinoline-4-carboxylic
acid 6.1b. Yield ¼ 68%, Mp. ¼ 269 ꢀC; yellow powder. LCMS m/z
1
321 [M + H+], Rf ¼0.98 min. HNMR (DMSO-d6) d 3.88 (s, 3H,
–OCH3), 7.04 (d, 1M, CM, J ¼ 6.35 Hz), 7.42 (d, 2M, C2M2,
J ¼ 13.18 Hz), 7.47 (d, 1M, CM, J ¼ 8.30 Hz), 8.41 (d, 1M, CM,
J ¼ 6.84 Hz), 8.70 (d, 1M, CM, J ¼ 8.79 Hz), 8.80 (s, 1H, CH),
9.01 (s, 1H, CH).
7-(3-chlorophenyl)tetrazolo[1,5-a]quinoline-4-carboxylic
acid 6.1c. Yield ¼ 81%, Mp. ¼ 267 ꢀC; white powder. LCMS m/z
325, 327 [M + H+], Rf ¼0.94 min. 1HNMR (DMSO-d6) d 7.59 (d,
1M, CM, J ¼ 7.32 Hz), 7.65 (t, 1M, CM, J ¼ 7.08 Hz), 7.90 (d, 1M,
CM, J ¼ 6.84 Hz), 8.00 (s, 1H, CH), 8.48 (d, 1M, CM, J ¼ 8.30 Hz),
8.76 (d, 1M, CM, J ¼ 7.81 Hz), 8.87 (s, 1H, CH), 9.03 (s, 1H, CH).
Synthesis of 5-oxo-2,3-dihydro-1H,5H-pyrido[3,2,1-ij]quinoline-
6-carboxaldehyde 9
2-oxo-6-phenyl-1,2-dihydroquinoline-3-carboxylic
acid
4.1‘. Yield ¼ 74%. Mp. ¼ 285 ꢀC; yellow powder. LCMS m/z
To cooled (5 ꢀC) POCl3 (107.3 g, 0.7 mol) was added DMF
dropwise (11.6 mL, 0.15 mol) for 30 min (a strong exothermic
effect was observed, and the temperature should be kept within
5–15 ꢀC), and the reaction mixture was crystallized. After 15 min,
the 1-acetyl-1,2,3,4-tetrahydroquinoline (17.5 g, 0.1 mol) was
added in one portion and the reaction mixture temperature
slowly increased to 75–80 ꢀC for 2 h, then heated to 80 ꢀC for 12 h.
After cooling, the reaction mixture was slowly poured with
stirring into cold water (200 mL) with crushed ice (300 g).
Product 9 was filtered, washed with water (2 ꢂ 100 mL), saturated
NaHCO3 (2 ꢂ 50 mL), and water (50 mL), then dried in a vacuum
oven at 60 ꢀC. Yield 15.6 g, 73%. Mp. ¼ 186 ꢀC; white powder. 1H
NMR (DMSO-d6) d 2.03–2.09 (m, 2 H, CM2), 2.94–2.99 (m, 2 H,
CM2), 4.08–4.13 (m, 2 H, CM2), 7.24 (t, 1 H, J ¼ 7.57 Hz, CM),
7.55 (d, J ¼ 6.84 Hz, 1 H, CM), 7.82 (d, J ¼ 7.32 Hz, 1 H, CM),
8.48 (s, 1 H, CM) 10.3 (s, 1 H, OCH).
1
266 [M + H+], Rf ¼0.85 min. HNMR (DMSO-d6) d 7.43 (d, 1M,
CM, J ¼ 6.84 Hz), 7.53 (t, 2M, C2M2, J ¼ 7.32 Hz), 7.63 (d, 1M,
CM, J ¼ 8.30 Hz), 7.76 (d, 2M, C2M2, J ¼ 7.81 Hz), 8.13 (d, 1M,
CM, J ¼ 8.79 Hz), 8.39 (s, 1M, CM), 9.05 (s, 1M, CM), 13.18 (br. s.,
1M, NM), 14.68 (br. s., 1M, COOH).
2-oxo-7-phenyl-1,2-dihydroquinoline-3-carboxylic
acid
4.1b. Yield ¼ 53%. Mp. ¼ 318 ꢀC; gray powder. LCMS m/z 266
[M + H+], Rf ¼0.87 min. 1HNMR (DMSO-d6) d 7.48 (s, 1H, CH),
7.54 (m, 2H, C2H2), 7.72 (m, 4H, C4H4), 8.10 (s, 1H, CH), 8.97 (s,
1H, CH), 13.16 (br. s., 1M, NM), 14.64 (br. s., 1M, COOH).
6-(4-methoxyphenyl)-2-oxo-1,2-dihydroquinoline-3-car-
boxylic acid 4.1p. Yield ¼ 66%, Mp. ¼ 225 ꢀC; yellow powder.
1
LCMS m/z 296 [M + H+], Rf ¼0.87 min. HNMR (DMSO-d6) d
3.82 (s, 3H, –OCH3), 7.08 (d, 2M, C2M2, J ¼ 7.81 Hz), 7.58 (d, 1M,
CM, J ¼ 9.28 Hz), 7.69 (d, 2M, C2M2, J ¼ 7.81 Hz), 8.08 (d, 1M,
CM, J ¼ 9.28 Hz), 8.31 (s, 1M, CM), 9.02 (s, 1M, CM), 13.16 (br. s.,
1M, NM), 14.72 (br. s., 1M, COOM).
Synthesis of 5-oxo-2,3-dihydro-1H,5H-pyrido[3,2,1-ij]quinoline-
6-carbonitrile 10
6-(3-methoxyphenyl)-2-oxo-1,2-dihydroquinoline-3-car-
boxylic acid 4.1d. Yield ¼ 84%, Mp. ¼ 233 ꢀC; yellow powder.
1
LCMS m/z 296 [M + H+], Rf ¼0.88 min. HNMR (DMSO-d6) d
To the suspension of aldehyde 9 (15 g, 0.07 mol) in POCl3
(60 mL) was added NH2OH hydrochloride (9.78 g, 0.14 mol) in
3.85 (s, 3H, –OCH3), 6.98 (d, 1M, CM, J ¼ 7.32 Hz), 7.25–7.37

DOI: 10.1080/14756366.2016.1222584
Design, synthesis and evaluation of 3-quinoline carboxylic acid derivatives
9
one portion. Reaction mixture heated with stirrer 100 ꢀC for 3 h. CM), 8.04 (s, 1M, CM), 8.32 (s, 1M, CM), 8.98 (s, 1M, CM), 14.70
After cooling, the reaction mixture was slowly poured with (br. s., 1M, COOM).
stirring into cold water (200 mL) with crushed ice (300 g).
Product 9 was filtered, washed with water (2 ꢂ 100 mL), saturated
Acknowledgements
NaHCO3 (2 ꢂ 50 mL) and water (50 mL), then dried in a vacuum
1
oven at 60 ꢀC. Yield 13 g, 88%. Mp. ¼ 267 ꢀC; white powder. H
We thank Otava Ltd. Company for material and finance support.
NMR (DMSO-d6) d 2.01–2.08 (m, 2 H, CM2), 2.92–2.98 (m, 2 H,
CM2), 4.06–4.11 (m, 2 H, CM2), 7.28 (t, 1 H, J ¼ 7.57 Hz, CM),
7.58 (d, J ¼ 6.84 Hz, 1 H, CM), 7.67 (d, J ¼ 7.32 Hz, 1 H, CM), Declaration of interest
8.76 (s, 1 H, CM).
The authors report no conflicts of interest. The authors alone are
responsible for the content and writing of this article.
Synthesis of 5-oxo-2,3-dihydro-1H,5H-pyrido[3,2,1-ij]quinoline-
6-carboxylic acid 11
References
Solution of nitrile 10 (5 g, 0.24 mol) in EtOH (100 mL), contain-
ing 40% aqueous NaOH solution (20 mL) was boiled with stirrer
1. Pinna LA. Casein kinase 2: an ‘eminence grise’ in cellular
regulation? Biochim Biophys Acta 1990;1054:267–84.
48 h. The reaction was monitored by NMR. The solvent was
removed by rotary evaporation. The formed solid residue was
2. Faust M, Montenarh M. Subcellular localization of protein
kinase CK2. A key to its function? Cell Tissue Res 2000;301:
transferred to a stirred 10% aqueous HCl solution (100 mL) and
329–40.
formed solid of product 11 was filtered, washed with
water (2 ꢂ 10 mL) and then dried in a vacuum oven at 70 ꢀC.
Yield 5.1 g, 95%. Mp. ¼ 251 ꢀC; white powder. LCMS m/z
3. Piazza F, Manni S, Ruzzene M, et al. Protein kinase CK2 in
hematologic malignancies: reliance on a pivotal cell survival
regulator by oncogenic signaling pathways. Leukemia 2012;26:
1174–9.
4. Sarno S, Pinna LA. Protein kinase CK2 as a druggable target. Mol
BioSyst 2008;4:889–94.
5. Murtaza I, Wang HX, Feng X, et al. Down-regulation of catalase
and oxidative modification of protein kinase CK2 lead to the
failure of apoptosis repressor with caspase recruitment domain to
1
230 [M + H+], Rf ¼0.82 min. HNMR (DMSO-d6) d 2.07–2.12
(m, 2H, CH2), 2.97–3.01 (m, 2M, CM2,), 4.17–4.22 (m, 2M, CM2),
7.38 (t, J ¼ 7.32 Hz, 1M, CM), 7.64 (d, J ¼ 7.32 Hz, 1M, CM), 7.92
(s, J ¼ 7.81 Hz, 1M, CM), 8.93 (s, 1M, CM), 14.70 (br. s., 1M,
COOM).
inhibit cardiomyocyte hypertrophy.
5996–6004.
J Biol Chem 2008;283:
Synthesis of 9-bromo-5-oxo-2,3-dihydro-1H,5H-pyrido[3,2,1-ij]
quinoline-6-carbonitrile 12
6. Singh NN, Ramji DP. Protein kinase CK2, an important regulator of
the inflammatory response? J Mol Med (Berl) 2008;86:887–97.
7. Trembley JH, Chen Z, Unger G, et al. Emergence of protein
kinase CK2 as a key target in cancer therapy. Biofactors 2010;36:
187–95.
8. Meggio F, Pinna LA. One-thousand-and-one substrates of protein
kinase CK2? FASEB J 2003;17:349–68.
9. Siddiqui-Jain A, Drygin D, Streiner N, et al. CX-4945, an orally
bioavailable selective inhibitor of protein kinase CK2, inhibits
prosurvival and angiogenic signaling and exhibits antitumor effi-
cacy. Cancer Res 2010;70:10288–98.
10. Pierre F, Chua PC, O’Brien SE, et al. Discovery and SAR of 5-(3-
chlorophenylamino)benzo[c] [2,6]naphthyridine-8-carboxylic Acid
(CX-4945), the first clinical stage inhibitor of protein kinase CK2 for
the treatment of cancer. J Med Chem 2011;54:635–54.
11. ClinicalTrials.gov Identifier: NCT02128282.
To the stirring solution of nitrile 10 (5 g, 0.024 mol) in DMF
(75 mL) was added in 10 portions NBS (4.49 g, 0.0252 mol)
during 2 h. The reaction mixture was stirred at room temperature
12 h and poured in water (500 mL), containing sodium thiosulfate
(1.5 g). The formed solid of product was filtered, washed
with water (2 ꢂ 10 mL), and then dried in a vacuum oven at
70 ꢀC. Yield 6.5 g, 95%. Mp. ¼ 281 ꢀC; light-yellow powder.
1HNMR (DMSO-d6) d 2.01–2.05 (m., 2H, CH2), 2.94–3.00
(m, 2M, CM2), 4.04–4.10 (m, 2M, CM2), 7.4 (t, J ¼ 7.3 Hz, 1H,
CM), 7.6 (d, J ¼ 7.3 Hz, 1H, CM), 7.9 (d, J ¼ 7.8 Hz, 1 H, CM), 8.9
(s, 1 H, CM).
9-bromo-5-oxo-2,3-dihydro-1H,5H-pyrido[3,2,1-ij]quin-
oline-6-carboxylic acid 13 was synthesized as 12 from nitrile
11. Yield ¼ 92%. Mp. ¼ 268 ꢀC; beige powder. LCMS m/z
308, 310 [M + H+], Rf ¼0.87 min. 1HNMR (DMSO-d6) d
2.03–209 (m, 2H, CH2), 2.97–3.04 (m, 2M, CM2), 4.16–4.21
(m, 2M, CM2), 7.83 (s, 1M, CM), 8.20 (s, 1M, CM), 8.90 (s,
1M, CM).
12. Meth-Cohn O, Narine B. A versatile new synthesis of quinolines and
related fused pyridines. Tet Lett 1978;23:2045–8.
13. Rao KR, Bhanumathi N, Sattur PB. Synthesis of novel quino[2,3-
b][1,5]benzodiazepin-12-ones. J Het Chem 1991;28:1339–40.
14. Patent; Rigel Pharmaceuticals, Inc.; WO2005/30774 2005; A1.
15. Morris GM, Huey R, Lindstrom W, et al. Autodock4 and
AutoDockTools4: automated docking with selective receptor flexi-
bility. J Comp Chem 2009;16:2785–91.
5-oxo-9-phenyl-2,3-dihydro-1H,5H-pyrido[3,2,1-ij]quin-
oline-6-carboxylic acid 14a was synthesized by General
procedure described above for 4.1 from bromide 13 and
phenylboronic acid. Yield ¼ 72%. Mp. ¼ 229 ꢀC; light-gray
powder. LCMS m/z 300, 302 [M + H+], Rf ¼1.01 min.1HNMR
(DMSO-d6) d 2.09–2.13 (m, 2M, CM2), 3.03–3.10 (m, 2M, CM2),
4.16–4.19 (m, 2M, CM2), 7.39 (t, 1M, CM, J ¼ 6.59 Hz), 7.50 (t,
2M, C2M2, J ¼ 7.57 Hz), 7.76 (t, 2M, C2M2, J ¼ 6.84 Hz), 7.88 (s,
1M, CM), 8.12 (s, 1M, CM), 8.64 (s, 1M, CM).
16. Shoichet BK, Stroud RM, Santi DV, et al. Structure-based
discovery of inhibitors of thymidylate synthase. Science 1993;259:
1445–50.
17. Bodian DL, Yamasaki RB, Buswell RL, et al. Inhibition of the
fusion-inducing conformational change of influenza hemagglutinin
by benzoquinones and hydroquinones. Biochemistry 1993;32:
2967–78.
18. Ring CS, Sun E, McKerrow JH, et al. Structure-based inhibitor
design by using protein models for the development of antiparasitic
agents. Proc Natl Acad Sci USA 1993;90:3583–7.
9-(3-chlorophenyl)-5-oxo-2,3-dihydro-1H,5H-pyrido[3,2,1-
ij]quinoline-6-carboxylic acid 14b was synthesized by General
procedure described above for 4.1 from bromide 13 and 3-
chlorophenylboronic acid. Yield ¼ 54%. Mp. ¼ 302 ꢀC; yellow
19. Ewing TJ, Makino S, Skillman AG, Kuntz ID. DOCK 4.0: search
strategies for automated molecular docking of flexible molecule
databases. J Comput Aided Mol Des 2001;15:411–28.
20. Battistutta R, Cozza G, Pierre F, et al. Unprecedented selectivity and
structural determinants of a new class of protein kinase CK2
inhibitors in clinical trials for the treatment of cancer. Biochemistry
2011;50:8478–88.
1
powder. LCMS m/z 340, 342 [M + H+], Rf ¼1.21 min. HNMR
(DMSO-d6) d 2.10–2.14 (m, 2M, CM2), 3.03–3.09 (m, 2M, CM2),
4.19–4.25 (m, 2M, CM2), 7.46 (d, 1M, CM, J ¼ 7.81 Hz), 7.54 (d,
1M, CM, J ¼ 7.81 Hz), 7.75 (d, 1M, CM, J ¼ 7.81 Hz), 7.85 (s, 1M,
21. Pedretti A, Villa L, Vistoli G. VEGA – an open platform to
develop chemobioinformatics applications, using plug-in

10 A. R. Syniugin et al.
J Enzyme Inhib Med Chem, Early Online: 1–10
architecture and script programming. J Comput Aided Mol Des 28. http://accelrys.com.
2004;18:167–73.
29. Hastie CJ, McLauchlan HJ, Cohen P. Assay of protein
a
22. Lindahl E, Hess B, van der Spoel D. GROMACS 3.0: a package for
molecular simulation and trajectory analysis. J Mol Mod 2001;7:
306–17.
23. http://www.net-sci.org/Science/Compchem/featurel4.html.
24. Bursulaya BD, Totrov M, Abagyan R, Brooks III CL. Comparative
kinases using radiolabeled ATP:
2006;1:968–71.
protocol. Nat Protoc
30. Golub AG, Yakovenko OY, Bdzhola VG, et al. Evaluation of 3-
Carboxy-4(1H)-quinolones as Inhibitors of Human Protein Kinase
CK2. J Med Chem 2006;49:6443–50.
study of several algorithms for flexible ligand docking. J Comput 31. Synyugin AR, Chekanov MO, Nyporko OY, et al. New 2-
Aided Mol Des 2003;17:755.
quinolinone derivatives: synthesis and CK2 inhibitor activity. Ukr
Bioorg Acta 2012;1:51–60.
32. Synyugin AR, Chekanov MO, Lukashov SS, Yarmoluk SM.
Synthesis of 3-(quinoline-2-on-3-yl)propanoic acids. Ukr Bioorg
Acta 2010;2:58–62.
33. Suzuki Y, Oishi S, Takei Y, et al. Design and synthesis of a novel
class of CK2 inhibitors: application of copper- and gold-catalysed
cascade reactions for fused nitrogen heterocycles. Org Biomol Chem
2012;10:4907–15.
25. Yakovenko OY, Oliferenko AA, Golub AG, et al. Rational design of
protein kinase inhibitors. Ukr Bioorg Acta 2007;1:52.
26. Yakovenko OY, Li YY, Oliferenko AA, et al. Ab initio parameter-
ization of YFF1, a universal force field for drug-design applications.
J Mol Model 2012;18:663.
27. Yakovenko O, Oliferenko AA, Bdzhola VG, et al. Kirchhoff atomic
charges fitted to multipole moments: implementation for a virtual
screening system. J Comput Chem 2008;29:1332.