Design, practical synthesis, and biological evaluation of novel 6-(Pyrazolylmethyl)-4-quinoline-3-carboxylic acid derivatives as HIV-1 integrase inhibitors

Article abstract of DOI:10.3390/molecules170910652

A series of novel 6-(pyrazolylmethyl)-4-oxo-4H-quinoline-3-carboxylic acid derivatives bearing different substituents on the N-position of quinoline ring were designed and synthesized as potential HIV-1 integrase (IN) inhibitors, based on the structurally related GS-9137 scaffold. The structures of all new compounds were confirmed by ¹H-NMR, ¹³C-NMR and ESI (or HRMS) spectra. Detailed synthetic protocols and the anti-IN activity studies are also presented.

Full text of DOI:10.3390/molecules170910652

Molecules 2012, 17, 10652-10666; doi:10.3390/molecules170910652
OPEN ACCESS
molecules
ISSN 1420-3049
www.mdpi.com/journal/molecules
Article
Design, Practical Synthesis, and Biological Evaluation of Novel
6-(Pyrazolylmethyl)-4-quinoline-3-carboxylic Acid Derivatives
as HIV-1 Integrase Inhibitors
Liming Hu 1,*, Song Yan 1, Zaigang Luo 1,2, Xiao Han 1, Yujie Wang 1, Zhanyang Wang 1 and
Chengchu Zeng 1
1
College of Life Science and Bioengineering, Beijing University of Technology, Beijing 100124, China
2
College of Chemical Engineering, Anhui University of Science Technology, Huainan 232001, China
* Author to whom correspondence should be addressed; E-Mail: huliming@bjut.edu.cn;
Tel.: +86-10-6739-6211; Fax: +86-10-6739-2001.
Received: 6 July 2012; in revised form: 6 August 2012 / Accepted: 24 August 2012 /
Published: 6 September 2012
Abstract: A series of novel 6-(pyrazolylmethyl)-4-oxo-4H-quinoline-3-carboxylic acid
derivatives bearing different substituents on the N-position of quinoline ring were designed
and synthesized as potential HIV-1 integrase (IN) inhibitors, based on the structurally
related GS-9137 scaffold. The structures of all new compounds were confirmed by
1H-NMR, 13C-NMR and ESI (or HRMS) spectra. Detailed synthetic protocols and the
anti-IN activity studies are also presented.
Keywords: HIV-1; integrase inhibitors; quinolone-3-carboxylic acid derivatives
1. Introduction
Human immunodeficiency virus type 1 (HIV-1) encodes three enzymes reverse transcriptase,
protease, and integrase which have been identified as key targets to arrest the HIV life cycle. To date,
most of the currently used oral drugs for the treatment of HIV infection inhibit the first two of these
enzymes. Unfortunately, the infection has been difficult to cure because of drug resistance and immune
response [1]. The viral enzyme integrase (IN), which is essential for interrupting the viral replication
cycle and has no counterpart in mammalian cells, is a crucial target for the development of new HIV-1
inhibitors with high selectivity and low toxicity [2,3]. As a kind of HIV-1 inhibitors, quinolone
derivatives have great attractive to researcher because of their small extremely versatile molecules,

Molecules 2012, 17
10653
easily synthesized at low cost on a large scale and endowed with well-known biochemical properties [4,5].
Researchers at Japan Tobacco reported the quinoline-3-carboxylic acid GS-9137 (elvitegravir,
Figure 1), which has finished phase III trials [6].
Figure 1. Structure of GS-9137 and new 6-(pyrazolylmethyl)-4-oxo-4H-quinoline-3-
carboxylic acid derivatives as potential HIV in inhibitors.
F
O
N
OH
Me
O
OH
Cl
O
N
N
O
R1
O
N
Me
OH
R2
GS-9137
new designed compounds 11-16
Gilead submitted a marketing application to the U.S. FDA for elvitegravir on Jun 27, 2012.
Quinoline-3-carboxylic acid can be used as an alternative scaffold to diketo acids (DKA) in order to
obtain a novel class of IN inhibitors through modification of antibiotic quinolones [7]. High interest
were generated by this class of inhibitors to study their structure-activity relationships (SAR) [8–11].
The quinoline-3-carboxylic acid pharmacophore was developed utilizing a training set of compounds
including GS-9137 [8] (Figure 2).
Figure 2. (A) 3D arrangement of the four pharmacophoric features in the quinolone
3-carboxylic acid pharmacophore. (B) The clinically studied HIV-1 integrase inhibitor
(GS-9137) is mapped onto the quinolone 3-carboxylic acid pharmacophore. The
pharmacophore features depicted as H-bond acceptor (HBA) in green, negatively ionisable
(NI) feature in blue and hydrophobic features (HRA1-2) in cyan. Interfeature distances are
given in angstroms.

Molecules 2012, 17
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The pharmacophore models of these compounds have four distinct characteristics: a negatively
ionizable (NI) feature, an H-bond acceptor (HBA) feature and two hydrophobic aromatic (HRA)
features, mapping of the hypothesis onto the GS-9137 shows an excellent agreement between key
chemical features of the compound and the pharmacophoric features of the hypotheses [8]. When the
methylene at the C-6 position was replaced by ethylene, carbonyl, amide, inverse amide, and amino
group, the resulting compounds proved to be completely inactive (IC50 > 100 µM) or a loss of activity
in the strand transfer (ST) assay occurred with hydroxyalkyl chains of variable length at the N-1
position [9]. Even removal of spacer between the two aromatic rings, characterized by a phenyl or a
pyridyl group directly linked to C-6, proved to be completely inactive in inhibiting the enzyme
integrase, thus displaying the importance of a methylene spacer [9].
On the basis of the above information as well as on our interest in the development of new potential
anti-HIV agents [12], we decided to explore the effect of chemical structure modification on the
quinoline-3-carboxylic acid scaffold by decorating it at the N-1 and C-6 positions, with the aim of
gaining further SAR data for anti-IN activity. We prepared the final compounds 11–16 (Figure 1)
based on the following considerations: (1) A large number of compounds with important biological
and pharmaceutical activities contain pyrazoles as a key substructure [13,14] and its planar structure
may facilitate the π stacking interaction with target enzymes similar to a phenyl ring, so it is very
interesting to design novel biologically active compounds by bringing the pyrazole moieties into the
quinolone-3-carboxylic acid molecular framework with a view to study their additive effect on anti-IN
properties. We considered that the phenyl ring at C-6 could thus be replaced by a bioisosteric pyrazole
ring; meanwhile, halogen atoms were introduced at C-4′ on the pyrazole ring with two hydrophobic
methyl groups also at the C-3′ and C-5′ positions; (2) Variable substituent groups were introduced at
N-1 to study the effects of alkyl and aromatic spacer groups, respectively [7]; (3) The methoxy group
at C-7 was ignored, although this substituent group affects the pharmacokinetic and in vivo activity
features, it does not influence in vitro binding ability, which can be seen by comparing the strand
transfer inhibition IC50 values of GS-9137 and its 7-demethoxy derivative (7.2 nM and 8.2 nM,
respectively). In this paper, a series of 6-(pyrazolylmethyl)-4-oxo-4H-quinoline-3-carboxylic acid
derivatives bearing different substituents on the N-1 position were synthesized and characterized and
their anti-IN activities were also screened.
2. Results and Discussion
2.1. Synthesis of 6-(Pyrazolylmethyl)-4-oxo-4H-quinoline-3-carboxylic Acid Derivatives
The syntheses of the designed 6-(pyrazolylmethyl)-4-oxo-4H-quinoline-3-carboxylic acid
derivatives 11a–c–16a–c are carried out as shown in Schemes 1 and 2. Compounds 1b–c, 2a–c, 3a–c,
4a–c and 5a–c were prepared according to the corresponding literature procedures [15–19].
Compounds 5a–c were then alkylated using varied alkyl halides or benzyl bromides to provide
derivatives 6a–c–10a–c in moderate yields. After hydrolysis of 5–10 in 10% aq NaOH or HCl, the
corresponding 4-oxo-4H-quinoline-3-carboxylic acid derivatives 11a–c–16a–c were obtained in yields
ranging from 42% to 81%.

Molecules 2012, 17
Scheme 1. Synthesis of ethyl 6-(pyrazolylmethyl)-4-oxo-4H-quinoline-3-carboxylates 5.
10655
O
O
NH2
Me
Me
OEt
Me
NO2
R1
EtO
iii)
N
iv)
N
N
R1
N
N
N
NH
R1
Me
2a-c
Me
ii)
Me 3a-c
4a-c
ii)
v)
O
O
Me
Me
R1
Me
i)
N
N
OEt
R1
N
N
N
H
Me
N
H
N
H
Me
Me
5a-c
1b-c
1a
1
1
: R = H, : R = Cl, : R1 = Br
a
b
c
Reagents and conditions: (i) NCS or NBS, CCl4, rt, 2–5 h; (ii) 4-Nitrobenzyl bromide, K2CO3,
CH3CN, reflux, 2 h; (iii) SnCl2·2H2O, EtOAc, reflux, 3–5 h; (iv) EMME, 1,4-dioxane, reflux;
(v) Ph2O, reflux, 1 h.
Scheme 2. Synthesis of 6-(pyrazolylmethyl)-4-oxo-4H-quinoline-3-carboxylic acid derivatives 11–16.
Me
R1
O
O
O
O
O
N
O
Me
R1
Me
Me
R1
O
N
O
10% aq
N
N
N
N
N
N
OEt
OH NaOH
OEt
N
reflux
Me
Me
6a-c
OH
OH
OCH3
12a-c
7a-c
O
BrCH2CO2Me
Cl
O
10% aq NaOH
reflux
K2CO3 / DMF / 60°C
K2CO3 / DMF / 60°C
O
O
Me
O
O
O
Me
Me
N
10% aq
NaOH
N
N
N
N
OH
R1
OH
OEt
R1
R1
N
N
N
H
ref lux
N
H
Me
Me
OH
Me
5a-c
13a-c
11a-c
O
1
1
1
a
b
c
: R = H; : R = Cl; : R = Br
O
Br
Br
Cl
NO2
S
F
K2CO3/DMF / 60°C
K2CO3 / DMF / 60
°C
K2CO3 / DMF / 60°C
O
N
O
O
N
O
Me
N
Me
R1
Me
R1
Me
O
N
O
OEt
N
N
N
N
OEt
R1
N
OEt
Me
Me
O
8a-c
9a-c
S
10a-c
F
NO2
10% aq HCl
reflux
10% aq NaOH
reflux
10% aq HCl
reflux
Me
R1
Me
O
O
Me
R1
Me
O
O
O
Me
R1
Me
O
N
N
N
N
N
N
OH
OH
F
OH
N
N
N
16a-c
15a-c
14a-c
SH
NO2

Molecules 2012, 17
10656
1
The structures of new quinoline-3-carboxylic acid derivatives 11–16 were confirmed by H-NMR,
1
13C-NMR, and ESI-MS (or HRMS) spectra. In the H-NMR spectra, one sharp proton signal for the
COOH group was observed in the δ 14.68–15.29 range and the chemical shifts of the methylene group
protons at C-6 were around 5.50 ppm, two sharp proton signals of the methyl groups at C-3' and C-5'
appeared at low field (δ 2.08–2.27). E.g., the proton signals of the COOH group, methylene group at
C-6 and the two methyl group at C-5′ and C-3′ of compound 12c were located at 15.15 ppm,
5.51 ppm, 2.27 ppm and 2.19 ppm, respectively. The characterized protons signals at C-2, C-5, C-7
13
and C-8 of the 4-oxo-4H-quinoline ring were also clearly observed. In the C-NMR spectra of these
compounds one C=O peak at about 178 ppm and one around 166 ppm corresponded to the signals of
the 3-carboxylic acid and carbonyl groups in the quinoline rings. The corresponding signals of the Cl
and Br isotopes in these compounds were also observed in the mass spectra.
2.2. HIV Inhibitory Activity
A HIV-1 integrase strand transfer (ST) activity assay was carried out to test the inhibition
effectiveness of our compounds as described previously [20] with some minor modifications.
Compounds diluted in DMSO were pre-incubated with 800 ng integrase at 37.8 °C in the reaction
buffer in the absence of Mn2+ for 10 min. Subsequently, 1.5 pmol donor DNA and 9 pmol target DNA
were added and the reaction was initiated by the addition of 10 mmol/L Mn2+ into the final reaction
volume. The reactions were carried out at 37.8 °C for 1 h and subsequent detection procedure was
applied to detect the assay signals. Integrase inhibitor, S-1360, was used as the control compound
(positive control), whereas no compound but only DMSO in the reaction mixture was set as the
drug-free control (negative control). The inhibition effects of 6-(pyrazolylmethyl)-4-oxo-4H-quinoline-
3-carboxylic acids 11–16 were calculated based on the positive and negative controls (Table 1).
As shown in Table 1, the values of IC50 of these compounds are more than 100 μg/mL, which
means they have a low inhibitory activity towards HIV integrase. The low HIV inhibitory activity of
these designed 4-oxo-4H-quinolizine-3-carboxylic acid derivatives might be attributed to various
cofactors. Structurally, 3′,5′-dimethyl-1H-pyrazolyl moiety maybe shows a reduced hydrophobic
interaction ability with integrase comparable to the parent benzenyl moiety. In addition, an appropriate
substituent at N-1 position seems also essential to enhance potential anti-IN activity.
Table 1. Integrase inhibitory activity data of 4-oxo-4H-quinolizine-3-carboxylic acid derivatives a.
Sample
S-1360
11a
Initial concentration (µg/mL)
IC50 (µg/mL) b
7.8
100
100
100
100
100
100
100
100
100
0.55
-c
11b
-c
11c
-c
12a
-c
12b
12c
13a
-c
-c
-c
13b
-c
13c
-c

Molecules 2012, 17
10657
Table 1. Cont.
Sample
Initial concentration (µg/mL)
IC50 (µg/mL) b
14a
14b
14c
15a
15b
15c
16a
16b
16c
100
100
100
100
100
100
100
100
100
-c
-c
-c
-c
-c
-c
-c
-c
-c
a
HIV-1 IN inhibitory activities were measured according to the procedure described [20].
b Inhibition of strand transfer. -c indicates that the HIV-IN inhibitory effect was less than 50% at
the initial concentration.
3. Experimental
3.1. General
All melting points (mp) were measured with a XT4A electrothermal apparatus equipped with a
1
microscope and are uncorrected. H-NMR and 13C-NMR spectra were recorded on an AV 400 M
Bruker spectrometer. Chemical shifts were measured in DMSO-d6 with TMS as internal reference. The
MS spectra (ESI) were recorded on a Bruker Esquire 6000 mass spectrometer. HRMS spectra were
recorded in the positive ion mode using APEX IV FT-ICRMS of Bruker Daltonics Inc. Purities of
target compounds 11a–c, 12a–c, 13a–c, 14a–c, 15a–c, 16a–c were determined by an Agilent 1260
HPLC system equipped with a Agilent Zorbax SB-C18 column (5 μm, 4.4 × 25mm), UV detector at
254 nm, mobile phase CH3OH/H2O (70%–100% or 80%) and flow rate of 1 mL/min. All solvents
were of commercial quality and were dried and purified by standard procedures.
3.2. General Procedure for the Synthesis of Ethyl 1-Substitued-6-(pyrazolylmethyl)-4-oxo-4H-quinoline-
3-carboxylates 6–10
A mixture of the appropriate quinolone derivative 5 (2 mmol), the appropriate alkyl halide or benzyl
bromide (5.6 mmol), and solid K2CO3 (772 mg, 5.6 mmol) in dry DMF (5 mL) was heated under Ar
atmosphere at 60 °C for 12 h and then poured into an ice-water mixture, extracted with DCM and
purified by flash chromatography on silica gel eluting with DCM/MeOH (40:1–20:1).
Ethyl 6-((3,5-Dimethyl-1H-pyrazol-1-yl)methyl)-1-(oxiran-2-ylmethyl)-4-ox-1,4-dihydroquinoline-3-
1
carboxylate (6a). Yield: 33%; mp: 162–165 °C; H-NMR (CDCl3, δ ppm) 1.43 (t, 3H, J = 7.2 Hz,
-CH2CH3), 2.16 (s, 3H, CH3-pyrazole), 2.24 (s, 3H, CH3-pyrazole), 2.59 (q, 1H, J = 4.4 Hz,
CH2OCHCH2-), 2.92 (t, 1H, J = 4.4 Hz, CH2OCHCH2-), 3.33–3.36 (m, 1H, CH2OCHCH2-), 4.20 (dd,
1H, J = 5.6 and 15.6 Hz, CH2OCHCH2-), 4.42 (q, 2H, J = 7.2 Hz, -CH2CH3), 4.55 (dd, 1H, J = 2.0 and
15.6 Hz, CH2OCHCH2-), 5.32 (s, 2H, -CH2-pyrazole), 5.86 (s, 1H, H-pyrazole), 7.44 (dd, 1H, J = 2.4
and 8.8 Hz, H7), 7.50 (d, 1H, J = 8.8 Hz, H8), 8.32 (d, 1H, J = 2.0 Hz, H5), 8.43 (s, 1H, H2).

Molecules 2012, 17
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Ethyl 6-((4-Chloro-3,5-dimethyl-1H-pyrazol-1-yl)methyl)-1-(oxiran-2-ylmethyl)-4-oxo-1,4-Dihydro-
1
quinoline-3-carboxylate (6b). Yield: 33%; mp: 200–202 °C; H-NMR (CDCl3, δ ppm) 1.42 (t, 3H,
J = 6.8 Hz, -CH2CH3), 2.15 (s, 3H, CH3-pyrazole), 2.23 (s, 3H, CH3-pyrazole), 2.59 (q, 1H, J = 4.8 Hz,
CH2OCHCH2-), 2.92 (t, 1H, J = 4.4 Hz, CH2OCHCH2-), 3.32–3.36 (m, 1H, CH2OCHCH2-), 4.19 (dd,
1H, J = 6.0 and 15.6 Hz, CH2OCHCH2-), 4.42 (q, 2H, J = 7.0 Hz, -CH2CH3), 4.56 (dd, 1H, J = 2.0 and
15.6 Hz, CH2OCHCH2-), 5.31 (s, 2H, -CH2-pyrazole), 7.44 (dd, 1H, J = 2.4 and 8.8 Hz, H7), 7.51
(d, 1H, J = 8.8 Hz, H8), 8.33 (d, 1H, J = 2.0 Hz, H5), 8.43 (s, 1H, H2).
Ethyl
6-((4-Bromo-3,5-dimethyl-1H-pyrazol-1-yl)methyl)-1-(oxiran-2-ylmethyl)-4-oxo-1,4-dihydro-
1
quinoline-3-carboxylate (6c). Yield: 47%; mp: 199–201 °C; H-NMR (CDCl3, δ ppm) 1.42 (t, 3H,
J = 7.2 Hz, -CH2CH3), 2.16 (s, 3H, CH3-pyrazole), 2.23 (s, 3H, CH3-pyrazole), 2.59 (q, 1H, J = 4.4 Hz,
CH2OCHCH2-), 2.92 (t, 1H, J = 4.4 Hz, CH2OCHCH2-), 3.33–3.36 (m, 1H, CH2OCHCH2-), 4.18 (dd,
1H, J = 6.0 and 15.6 Hz, CH2OCHCH2-), 4.41 (q, 2H, J = 7.2 Hz, -CH2CH3), 4.56 (dd, 1H, J = 2.4 and
15.6 Hz, CH2OCHCH2-), 5.33 (s, 2H, -CH2-pyrazole), 7.43 (dd, 1H, J = 2.0 and 8.8 Hz, H7), 7.50 (d,
13
1H, J = 8.8 Hz, H8), 8.31 (d, 1H, J = 2.0 Hz, H5), 8.42 (s, 1H, H2); C-NMR (CDCl3, 100 MHz, δ
ppm) 10.4, 12.3, 14.4, 45.2, 49.6, 53.1, 54.8, 60.9, 94.8, 111.6, 116.7, 125.9, 128.8, 131.5, 133.9,
137.4, 138.8, 146.6, 149.4, 165.4, 173.8; ESI-MS: m/z 459.9, 461.9 [M+H]+.
Ethyl 6-((3,5-Dimethyl-1H-pyrazol-1-yl)methyl)-1-(2-methoxy-2-oxoethyl)-4-oxo-1,4-dihydroquino-line-
1
3-carboxylate (7a). Yield: 53%; mp: 225–228 °C; H-NMR (CDCl3, δ ppm) 1.41 (t, 3H, J = 7.2 Hz,
-CH2CH3), 2.16 (s, 3H, CH3-pyrazole), 2.24 (s, 3H, CH3-pyrazole), 3.79 (s, 3H, -OCH3), 4.42 (q, 2H,
J = 7.0 Hz, -CH2CH3), 4.84 (s, 2H, -COCH2-), 5.31 (s, 2H, -CH2-pyrazole), 5.86 (s, 1H, H-pyrazole),
7.15 (d, 1H, J = 8.8 Hz, H8), 7.40 (dd, 1H, J = 2.0 and 8.4 Hz, H7), 8.28 (d, 1H, J = 2.0 Hz, H5), 8.39
(s, 1H, H2).
Ethyl 6-((4-Chloro-3,5-dimethyl-1H-pyrazol-1-yl)methyl)-1-(2-methoxy-2-oxoethyl)-4-oxo-1,4-dihydro
1
quinoline-3-carboxylate (7b). Yield: 43%; mp: 235–237 °C; H-NMR (CDCl3, δ ppm) 1.43 (t, 3H,
J = 7.2 Hz, -CH2CH3), 2.14 (s, 3H, CH3-pyrazole), 2.26 (s, 3H, CH3-pyrazole), 3.80 (s, 3H, -OCH3),
4.42 (q, 2H, J = 7.2 Hz, -CH2CH3), 4.84 (s, 2H, -COCH2-), 5.31 (s, 2H, -CH2-pyrazole), 7.16 (d, 1H,
J = 8.4 Hz, H8), 7.40 (dd, 1H, J = 2.4 and 8.8 Hz, H7), 8.32 (d, 1H, J = 2.0 Hz, H5), 8.39 (s, 1H, H2).
Ethyl 6-((4-Bromo-3,5-dimethyl-1H-pyrazol-1-yl)methyl)-1-(2-methoxy-2-oxoethyl)-4-oxo-1,4-dihydro
1
quinoline-3-carboxylate (7c). Yield: 55%; mp: 239–242 °C; H-NMR (CDCl3, δ ppm) 1.43 (t, 3H,
J = 7.2 Hz, -CH2CH3), 2.16 (s, 3H, CH3-pyrazole), 2.26 (s, 3H, CH3-pyrazole), 3.80 (s, 3H, -OCH3),
4.42 (q, 2H, J = 7.2 Hz, -CH2CH3), 4.84 (s, 2H, -COCH2-), 5.34 (s, 2H, -CH2-pyrazole), 7.17 (d, 1H,
J = 8.8 Hz, H8), 7.40 (dd, 1H, J = 2.0 and 8.4 Hz, H7), 8.33 (d, 1H, J = 2.0 Hz, H5), 8.41 (s, 1H, H2);
ESI-MS: m/z 476, 478 [M+H]+, 498, 500 [M+Na]+, 514, 516 [M+K]+.
Ethyl 1-(3-(Acetylthio)propyl)-6-((3,5-dimethyl-1H-pyrazol-1-yl)methyl)-4-oxo-1,4-dihydroquinoline-
1
3-carboxylate (8a). Yield: 49%; mp: 125–128 °C; H-NMR (CDCl3, δ ppm) 1.43 (t, 3H, J = 7.2 Hz,
-CH2CH3), 2.11-2.14 (m, 2H, -CH2CH2CH2S-), 2.16 (s, 3H, CH3-pyrazole), 2.24 (s, 3H, CH3-pyrazole),
2.38 (s, 3H, -COCH3), 2.95 (t, 2H, J = 6.4 Hz, -CH2CH2CH2S-), 4.22 (t, 2H, J = 7.6 Hz,
-CH2CH2CH2S-), 4.42 (q, 2H, J = 7.0 Hz, -CH2CH3), 5.31 (s, 2H, -CH2-pyrazole), 5.85 (s, 1H,

Molecules 2012, 17
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13
H-pyrazole), 7.37–7.44 (m, 2H, H7 H8), 8.32 (s, 1H, H5), 8.47 (d, 1H, J = 8.4 Hz, H2); C-NMR
(CDCl3, δ ppm) 11.1, 13.5, 14.4, 25.7, 28.9, 30.6, 51.9, 52.4, 60.9, 105.8, 111.4, 116.2, 126.1, 129.2,
131.5, 134.7, 138.1, 139.3, 147.9, 148.8, 165.7, 173.9, 194.9; ESI-MS: m/z 441.9 [M+H]+, 463.9
[M+Na]+, 479.8 [M+K]+.
Ethyl 1-(3-(Acetylthio)propyl)-6-((4-chloro-3,5-dimethyl-1H-pyrazol-1-yl)methyl)-4-oxo-1,4-dihydro-
1
quinoline-3-carboxylate (8b). Yield: 51%; mp: 122–125 °C; H-NMR (CDCl3, δ ppm) 1.43 (t, 3H,
J = 7.2 Hz, -CH2CH3), 2.13–2.17 (m, 2H, -CH2CH2CH2S-), 2.19 (s, 3H, CH3-pyrazole), 2.21 (s, 3H,
CH3-pyrazole), 2.32 (s, 3H, -COCH3), 2.96 (t, 2H, J = 6.8 Hz, -CH2CH2CH2S-), 4.22 (t, 2H, J = 7.6 Hz,
-CH2CH2CH2S-), 4.44 (q, 2H, J = 7.2 Hz, -CH2CH3), 5.32 (s, 2H, -CH2-pyrazole), 7.39–7.46 (m, 2H,
H7 H8), 8.35 (d, 1H, J = 2.0 Hz, H5), 8.45 (s, 1H, H2).
Ethyl 1-(3-(Acetylthio)propyl)-6-((4-bromo-3,5-dimethyl-1H-pyrazol-1-yl)methyl)-4-oxo-1,4-dihydro-
1
quinoline-3-carboxylate (8c). Yield: 46%; mp: 141–143 °C; H-NMR (CDCl3, δ ppm) 1.43 (t, 3H,
J = 7.2 Hz, -CH2CH3), 2.16 (s, 3H, CH3-pyrazole), 2.17–2.18 (m, 2H, -CH2CH2CH2S-), 2.24 (s, 3H,
CH3-pyrazole), 2.38 (s, 3H, -COCH3), 2.96 (t, 2H, J = 6.8 Hz, -CH2CH2CH2S-), 4.22 (t, 2H, J = 7.6 Hz,
-CH2CH2CH2S-), 4.43 (q, 2H, J = 7.2 Hz, -CH2CH3), 5.34 (s, 2H, -CH2-pyrazole), 7.38–7.42 (m, 2H,
H7 H8), 8.35 (d, 1H, J = 1.6 Hz, H5), 8.46 (s, 1H, H2).
Ethyl 6-((3,5-Dimethyl-1H-pyrazol-1-yl)methyl)-1-(4-fluorobenzyl)-4-oxo-1,4-dihydroquinoline-3-
1
carboxylate (9a). Yield: 50%; mp: 209–211 °C; H-NMR (CDCl3, δ ppm) 1.43 (t, 3H, J = 7.2 Hz,
-CH2CH3), 2.14 (s, 3H, CH3-pyrazole), 2.21 (s, 3H, CH3-pyrazole), 4.42 (q, 2H, J = 7.0 Hz, -CH2CH3),
5.28 (s, 2H, -CH2-pyrazole), 5.33 (s, 2H, -CH2-Ar), 5.83 (s, 1H, H-pyrazole), 7.05 (t, 2H, J = 6.4 Hz,
Ar-H), 7.13 (q, 2H, J = 8.8 Hz, Ar-H), 7.24 (d, 1H, J = 8.8 Hz, H8), 7.29 (dd, 1H, J = 2.0 and 8.8 Hz,
H7), 8.30 (d, 1H, J = 2.0 Hz, H5), 8.57 (s, 1H, H2); ESI-MS: m/z 433.9 [M+H]+, 455.9 [M+Na]+,
471.8 [M+K]+.
Ethyl 6-((4-Chloro-3,5-dimethyl-1H-pyrazol-1-yl)methyl)-1-(4-fluorobenzyl)-4-oxo-1,4-dihydroquinoline-
1
3-carboxylate (9b). Yield: 51%; mp: 226–228 °C; H-NMR (CDCl3, δ ppm) 1.44 (t, 3H, J = 7.2 Hz,
-CH2CH3), 2.13 (s, 3H, CH3-pyrazole), 2.20 (s, 3H, CH3-pyrazole), 4.42 (q, 2H, J = 7.2 Hz,
-CH2CH3), 5.28 (s, 2H, -CH2-pyrazole), 5.33 (s, 2H, -CH2-Ar), 7.05 (t, 2H, J = 6.8 Hz, Ar-H), 7.07 (q,
2H, J = 8.0 Hz, Ar-H), 7.27 (d, 1H, J = 8.8 Hz, H8), 7.30 (dd, 1H, J = 2.4 and 8.8 Hz, H7), 8.32 (d,
1H, J = 1.6 Hz, H5), 8.58 (s, 1H, H2); ESI-MS: m/z 467.9 [M+H]+.
Ethyl 6-((4-Bromo-3,5-dimethyl-1H-pyrazol-1-yl)methyl)-1-(4-fluorobenzyl)-4-oxo-1,4-dihydroquinoline-
1
3-carboxylate (9c). Yield: 55%; mp: 219–221 °C; H-NMR (CDCl3, δ ppm) 1.44 (t, 3H, J = 7.2 Hz,
-CH2CH3), 2.16 (s, 3H, CH3-pyrazole), 2.22 (s, 3H, CH3-pyrazole), 4.42 (q, 2H, J = 7.0 Hz, -CH2CH3),
5.32 (s, 2H, -CH2-pyrazole), 5.35 (s, 2H, -CH2-Ar), 7.06 (t, 2H, J = 8.4 Hz, Ar-H), 7.16 (q, 2H,
J = 9.2 Hz, Ar-H), 7.27 (d, 1H, J = 8.8 Hz, H8), 7.31 (dd, 1H, J = 2.0 and 8.8 Hz, H7), 8.30 (d, 1H,
J = 1.2 Hz, H5), 8.59 (s, 1H, H2); ESI-MS: m/z 521, 514 [M+H]+, 534, 536 [M+Na]+, 550, 552 [M+K]+.
Ethyl
6-((3,5-Dimethyl-1H-pyrazol-1-yl)methyl)-1-(4-nitrobenzyl)-4-oxo-1,4-dihydroquinoline-3-
1
carboxylate (10a). Yield: 49%; mp: 194–196 °C; H-NMR (CDCl3, δ ppm) 1.43 (t, 3H, J = 7.2 Hz,

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-CH2CH3), 2.15 (s, 3H, CH3-pyrazole), 2.19 (s, 3H, CH3-pyrazole), 4.42 (q, 2H, J = 7.2 Hz,
-CH2CH3), 5.27 (s, 2H, -CH2-pyrazole), 5.47 (s, 2H, -CH2-Ar), 5.83 (s, 1H, H-pyrazole), 7.10 (d, 1H,
J = 8.8 Hz, H8), 7.24 (dd, 1H, J = 2.4 and 8.8 Hz, H7), 7.31 (d, 2H, J = 8.8 Hz, Ar-H), 8.22 (d, 2H,
J = 6.0 Hz, Ar-H), 8.27 (d, 1H, J = 2.0 Hz, H5), 8.56 (s, 1H, H2).
Ethyl 6-((4-Chloro-3,5-dimethyl-1H-pyrazol-1-yl)methyl)-1-(4-nitrobenzyl)-4-oxo-1,4-dihydroquinoline-3-
1
carboxylate (10b). Yield: 39%; mp: 232–235 °C; H-NMR (CDCl3, δ ppm) 1.44 (t, 3H, J = 7.2 Hz,
-CH2CH3), 2.13 (s, 3H, CH3-pyrazole), 2.19 (s, 3H, CH3-pyrazole), 4.42 (q, 2H, J = 7.0 Hz, -CH2CH3),
5.27 (s, 2H, -CH2-pyrazole), 5.47 (s, 2H, -CH2-Ar), 7.12 (d, 1H, J = 8.4 Hz, H8), 7.28 (dd, 1H,
J = 2.0 and 8.4 Hz, H7), 7.32 (d, 2H, J = 8.8 Hz, Ar-H), 8.23 (d, 2H, J = 6.8 Hz, Ar-H), 8.33 (d, 1H,
J = 2.0 Hz, H5), 8.58 (s, 1H, H2); ESI-MS: m/z 516.8 [M+Na]+, 493.0 [M-H]−.
Ethyl 6-((4-Bromo-3,5-dimethyl-1H-pyrazol-1-yl)methyl)-1-(4-nitrobenzyl)-4-oxo-1,4-dihydroquinoline-3-
1
carboxylate (10c). Yield: 40%; mp: 240–242 °C; H-NMR (CDCl3, δ ppm) 1.43 (t, 3H, J = 7.2 Hz,
-CH2CH3), 2.15 (s, 3H, CH3-pyrazole), 2.19 (s, 3H, CH3-pyrazole), 4.42 (q, 2H, J = 7.0 Hz, -CH2CH3),
5.30 (s, 2H, -CH2-pyrazole), 5.47 (s, 2H, -CH2-Ar), 7.12 (d, 1H, J = 8.8 Hz, H8), 7.28 (dd, 1H, J = 2.0
and 8.8 Hz, H7), 7.32 (d, 2H, J = 8.8 Hz, Ar-H), 8.23 (d, 2H, J = 6.4 Hz, Ar-H), 8.33 (d, 1H, J = 1.6 Hz,
H5), 8.58 (s, 1H, H2).
3.3. General Procedure for the Synthesis of 1-Substitued-6-(pyrazolylmethyl)-4-oxo-4H-quinoline-3-
carboxylic Acids 11–16
A suspension of the appropriate ester 5–8 (0.5 mmol) in 10% aq. NaOH (10 mL) was refluxed
for 2 h. After cooling at room temperature, the reaction mixture was acidified using conc. HCl. The
resulting precipitate was filtered and washed with water and DCM to give the corresponding
4-quinolone-3-carboxylic acids 11–14. Alternatively, a suspension of the appropriate ester 9–10
(0.5 mmol) in 10% aq. HCl (10 mL) was refluxed for 2 h. After cooling at room temperature, the
resulting precipitate was filtered and washed with water and DCM to give the corresponding
4-quinolone-3-carboxylic acids 15–16.
6-((3,5-Dimethyl-1H-pyrazol-1-yl)methyl)-4-oxo-1,4-dihydroquinoline-3-carboxylic acid (11a). Yield:
1
63%; mp: 254–256 °C; H-NMR (DMSO-d6, δ ppm) 2.11 (s, 3H, CH3-pyrazole), 2.18 (s, 3H,
CH3-pyrazole), 5.38 (s, 2H, -CH2-pyrazole), 5.89 (s, 1H, H-pyrazole), 7.64 (dd, 1H, J = 2.0 and
8.8 Hz, H7), 7.81 (d, 1H, J = 8.4 Hz, H8), 7.99 (d, 1H, J = 1.6 Hz, H5), 8.84 (s, 1H, H2), 13.36 (s, 1H,
-NH-), 15.29 (s, 1H, -COOH); 13C-NMR (DMSO-d6, δ ppm) 11.1, 13.8, 51.5, 105.7, 108.2, 120.9,
123.2, 124.8, 133.2, 136.6, 139.4, 139.5, 145.8, 146.9, 166.9, 178.4; HRMS: m/z calcd for
C16H16N3O3: 298.1186; found: 298.1188; HPLC purity 98.36%.
6-((4-Chloro-3,5-dimethyl-1H-pyrazol-1-yl)methyl)-4-oxo-1,4-dihydroquinoline-3-carboxylic acid
(11b). Yield: 47%; mp: 263–265 °C; 1H-NMR (DMSO-d6, δ ppm) 2.09 (s, 3H, CH3-pyrazole), 2.19 (s,
3H, CH3-pyrazole), 5.45 (s, 2H, -CH2-pyrazole), 7.66 (dd, 1H, J = 2.0 and 8.4 Hz, H7), 7.82 (d, 1H,
J = 8.4 Hz, H8), 8.04 (d, 1H, J = 1.6 Hz, H5), 8.88 (s, 1H, H2), 13.51 (s, 1H, -NH-), 15.29 (s, 1H,
-COOH); 13C-NMR (DMSO-d6, δ ppm) 9.5, 11.5, 52.7, 107.0, 108.18, 120.9, 123.5, 124.8, 133.3,

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135.7, 136.1, 139.4, 144.0, 145.7, 166.8, 178.5; HRMS: m/z calcd for C16H15ClN3O3: 332.0796; found:
332.0799; HPLC purity 99.40%.
6-((4-Bromo-3,5-dimethyl-1H-pyrazol-1-yl)methyl)-4-oxo-1,4-dihydroquinoline-3-carboxylic
acid
(11c). Yield: 81%; mp: 253–256 °C; 1H-NMR (DMSO-d6, δ ppm) 2.09 (s, 3H, CH3-pyrazole), 2.17 (s,
3H, CH3-pyrazole), 5.44 (s, 2H, -CH2-pyrazole), 7.64 (dd, 1H, J = 2.0 and 8.4 Hz, H7), 7.79 (d, 1H,
J = 8.4 Hz, H8), 8.01 (d, 1H, J = 1.6 Hz, H5), 8.84 (s, 1H, H2), 13.36 (s, 1H, -NH-), 15.20 (s, 1H,
-COOH); 13C-NMR (DMSO-d6, δ ppm) 10.4, 12.5, 52.8, 93.8, 108.2, 120.8, 123.6, 124.8, 133.4,
135.8, 137.8, 139.3, 145.5, 145.6, 166.7, 178.5; HRMS: m/z calcd for C16H15BrN3O3: 376.0291,
378.0276; found: 376.0296, 378.0278; HPLC purity 97.17%.
1-(2,3-Dihydroxypropyl)-6-((3,5-dimethyl-1H-pyrazol-1-yl)methyl)-4-oxo-1,4-dihydroquinoline-3-
1
carboxylic acid (12a). Yield: 52%; mp: 187–189 °C; H-NMR (DMSO-d6, δ ppm) 2.19 (s, 3H,
CH3-pyrazole), 2.27 (s, 3H, CH3-pyrazole), 3.40–3.55 (m, 2H, HOCH2CHOHCH2-), 3.81–3.83 (m,
1H, HOCH2CHOHCH2-), 4.28 (q, 1H, J = 14.4 Hz, HOCH2CHOHCH2-), 4.82 (dd, 1H, J = 2.4 and
10.4 Hz, HOCH2CHOHCH2-), 5.53 (s, 2H, -CH2-pyrazole), 6.08 (s, 1H, H-pyrazole), 6.31 (br, 2H,
HOCH2CHOHCH2-), 7.75 (dd, 1H, J = 2.0 and 9.2 Hz, H7), 8.02 (d, 1H, J = 9.2 Hz, H8), 8.12 (d, 1H,
13
J = 2.0 Hz, H5), 8.86 (s, 1H, H2), 15.01 (s, 1H, -COOH); C-NMR (DMSO-d6, δ ppm) 11.1, 13.2,
51.1, 57.4, 63.7, 69.5, 106.5, 107.7, 119.3, 124.3, 125.9, 133.4, 135.6, 139.5, 141.3, 146.8, 151.0,
166.5, 177.9; HRMS: m/z calcd for C19H22N3O5: 372.1554; found: 372.1556; HPLC purity 98.10%.
1-(2,3-Dihydroxypropyl)-6-((4-chloro-3,5-dimethyl-1H-pyrazol-1-yl)methyl)-4-oxo-1,4-dihydro-
quinoline-3-carboxylic acid (12b). Yield: 63%; mp: 278–280 °C; 1H-NMR (DMSO-d6, δ ppm) 2.12 (s,
3H, CH3-pyrazole), 2.20 (s, 3H, CH3-pyrazole), 3.39–3.55 (m, 2H, HOCH2CHOHCH2-), 3.82 (m, 1H,
HOCH2CHOHCH2-), 4.27 (q, 1H, J = 14.4 Hz, HOCH2CHOHCH2-), 4.80 (dd, 1H, J = 2.0 and
14.4 Hz, HOCH2CHOHCH2-), 4.96 (t, 1H, J = 5.6 Hz, HOCH2CHOHCH2-), 5.22 (d, 1H, J = 5.6 Hz,
HOCH2CHOHCH2-), 5.48 (s, 2H, -CH2-pyrazole), 7.73 (dd, 1H, J = 2.0 and 8.8 Hz, H7), 8.00 (d, 1H,
13
J = 9.2 Hz, H8), 8.13 (d, 1H, J = 1.6 Hz, H5), 8.86 (s, 1H, H2), 15.13 (s, 1H, -COOH); C-NMR
(DMSO-d6, δ ppm) 9.5, 11.5, 52.4, 57.5, 63.8, 69.4, 107.5, 107.7, 119.2, 124.4, 125.9, 133.4, 135.8,
136.1, 139.5, 144.1, 151.0, 166.5, 178.0; HRMS: m/z calcd for C19H21ClN3O5: 406.1164; found:
406.1167; HPLC purity 97.%.
1-(2,3-Dihydroxypropyl)-6-((4-bromo-3,5-dimethyl-1H-pyrazol-1-yl)methyl)-4-oxo-1,4-dihydroquino-
1
line-3-carboxylic acid (12c). Yield: 62%; mp: 267–269 °C; H-NMR (DMSO-d6, δ ppm) 2.19 (s, 3H,
CH3-pyrazole), 2.27 (s, 3H, CH3-pyrazole), 3.39–3.53 (m, 2H, HOCH2CHOHCH2-), 3.81 (m, 1H,
HOCH2CHOHCH2-), 4.27 (q, 1H, J = 10.8 Hz, HOCH2CHOHCH2-), 4.80 (d, 1H, J = 12.8 Hz,
HOCH2CHOHCH2-), 4.98 (t, 1H, J = 5.6 Hz, HOCH2CHOHCH2-), 5.22 (d, 1H, J = 5.6 Hz,
HOCH2CHOHCH2-), 5.51 (s, 2H, -CH2-pyrazole), 7.73 (dd, 1H, J = 1.6 and 8.8 Hz, H7), 8.00 (d, 1H,
J = 4.8 Hz, H8), 8.13 (s, 1H, H5), 8.86 (s, 1H, H2), 15.15 (s, 1H, -COOH); 13C-NMR (DMSO-d6,
δ ppm) 10.4, 12.5, 52.5, 57.4, 63.7, 69.4, 93.8, 107.7, 119.2, 124.4, 125.9, 133.4, 135.8, 137.8, 139.5,
145.6, 151.0, 166.5, 178.0; HRMS: m/z calcd for C19H21BrN3O5: 450.0659, 452.0644; found:
450.0664, 452.0651; HPLC purity 97.73%.

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1-(Carboxymethyl)-6-((3,5-dimethyl-1H-pyrazol-1-yl)methyl)-4-oxo-1,4-dihydroquinoline-3-carboxylic
1
acid (13a). Yield: 78%; mp > 300 °C; H-NMR (DMSO-d6, δ ppm) 2.09 (s, 3H, CH3-pyrazole), 2.17
(s, 3H, CH3-pyrazole), 5.38 (s, 2H, -CH2-pyrazole), 5.42 (s, 2H, -CH2COOH), 5.88 (s, 1H, H-pyrazole),
7.68 (dd, 1H, J = 2.0 and 8.8 Hz, H7), 7.79 (d, 1H, J = 8.8 Hz, H8), 8.05 (d, 1H, J = 1.6 Hz, H5), 9.02
(s, 1H, H2), 13.63 (s, 1H, -NH-), 14.97 (s, 1H, -COOH); 13C-NMR (DMSO-d6, δ ppm) 11.1, 13.8,
51.2, 54.7, 105.7, 108.3, 118.8, 124.0, 125.5, 133.6, 136.9, 139.4, 139.7, 147.0, 151.1, 166.2, 169.2,
178.2; HRMS: m/z calcd for C18H18N3O5: 356.1241; found: 356.1242; HPLC purity 97.80%.
1-(Carboxymethyl)-6-((4-chloro-3,5-dimethyl-1H-pyrazol-1-yl)methyl)-4-oxo-1,4-dihydroquinoline-3-
1
carboxylic acid (13b). Yield: 58%; mp: 292–295 °C; H-NMR (DMSO-d6, δ ppm) 2.12 (s, 3H,
CH3-pyrazole), 2.20 (s, 3H, CH3-pyrazole), 5.35 (s, 2H, -CH2-pyrazole), 5.46 (s, 2H, -CH2COOH),
7.71 (dd, 1H, J = 2.0 and 8.8 Hz, H7), 7.79 (d, 1H, J = 9.2 Hz, H8), 8.12 (d, 1H, J = 1.6 Hz, H5), 9.07
13
(s, 1H, H2), 15.01 (s, 1H, -COOH); C-NMR (DMSO-d6, δ ppm) 9.5, 11.5, 52.3, 55.4, 107.0, 108.2,
119.1, 124.2, 125.5, 133.7, 135.9, 136.2, 139.9, 144.1, 151.1, 166.3, 169.1, 178.1; HRMS: m/z calcd
for C18H17ClN3O5: 390.0851; found: 390.0855; HPLC purity 99.15%.
1-(Carboxymethyl)-6-((4-bromo-3,5-dimethyl-1H-pyrazol-1-yl)methyl)-4-oxo-1,4-dihydro-quinoline-3-
1
carboxylic acid (13c). Yield: 72%; mp: 278–280 °C; H-NMR (DMSO-d6, δ ppm) 2.12 (s, 3H,
CH3-pyrazole), 2.21 (s, 3H, CH3-pyrazole), 5.36 (s, 2H, -CH2-pyrazole), 5.48 (s, 2H, -CH2COOH),
7.71 (dd, 1H, J = 2.0 and 9.2 Hz, H7), 7.79 (d, 1H, J = 9.2 Hz, H8), 8.12 (d, 1H, J = 2.0 Hz, H5), 9.07
13
(s, 1H, H2), 14.99 (s, 1H, -COOH); C-NMR (DMSO-d6, δ ppm) 10.4, 12.5, 52.5, 55.3, 93.8, 108.3,
119.0, 124.3, 125.6, 133.7, 135.9, 137.8, 139.9, 145.6, 151.1, 166.2, 169.1, 178.2; HRMS: m/z calcd
for C18H17BrN3O5: 434.0346, 436.0331; found: 434.0350, 436.0329; HPLC purity 99.23%.
1-(3-Mercaptopropyl)-6-((3,5-dimethyl-1H-pyrazol-1-yl)methyl)-4-oxo-1,4-dihydroquinoline-3-carboxylic
acid (14a). Yield: 65%; mp: 225–226 °C; 1H-NMR (DMSO-d6, δ ppm) 2.08 (m, 2H,
-CH2CH2CH2SH), 2.12 (s, 3H, CH3-pyrazole), 2.19 (s, 3H, CH3-pyrazole), 2.54–2.58 (m, 2H,
-CH2CH2CH2SH), 4.62 (t, 2H, J = 7.2 Hz, -CH2CH2CH2SH), 5.41 (s, 2H, -CH2-pyrazole), 5.89 (s, 1H,
H-pyrazole), 7.71 (dd, 1H, J = 2.0 and 8.8 Hz, H7), 8.05 (d, 1H, J = 8.8 Hz, H8), 8.08 (d, 1H,
J = 2.0 Hz, H5), 9.02 (s, 1H, H2), 15.13 (s, 1H, -COOH); 13C-NMR (DMSO-d6, 100 MHz, δ ppm) 11.1,
13.8, 21.1, 28.5, 34.3, 51.2, 105.7, 108.2, 118.9, 124.2, 126.1, 133.5, 136.8, 138.9, 139.5, 147.0, 149.9,
166.5, 178.0; HRMS: m/z calcd for C19H22N3O3S: 372.1376; found: 372.1380; HPLC purity 97.50%.
1-(3-Mercaptopropyl)-6-((4-chloro-3,5-dimethyl-1H-pyrazol-1-yl)methyl)-4-oxo-1,4-dihydro-quinoline-
1
3-carboxylic acid (14b). Yield: 54%; mp: 238–240 °C; H-NMR (DMSO-d6, δ ppm) 2.08–2.09 (m,
2H, -CH2CH2CH2SH), 2.11 (s, 3H, CH3-pyrazole), 2.20 (s, 3H, CH3-pyrazole), 2.56–2.58 (m, 2H,
-CH2CH2CH2SH), 4.62 (t, 2H, J = 7.2 Hz, -CH2CH2CH2SH), 5.45 (s, 2H, -CH2-pyrazole), 7.73 (dd,
1H, J = 2.0 and 8.8 Hz, H7), 8.06 (d, 1H, J = 8.4 Hz, H8), 8.14 (d, 1H, J = 2.0 Hz, H5), 9.03 (s, 1H,
H2), 15.09 (s, 1H, -COOH); 13C-NMR (DMSO-d6, δ ppm) 9.5, 11.5, 21.1, 28.6, 34.3, 52.4, 107.1,
108.3, 119.0, 124.5, 126.1, 133.6, 135.9, 136.1, 139.1, 144.1, 149.9, 166.4, 178.0; HRMS: m/z calcd
for C19H21ClN3O3S: 406.0986; found: 406.0989; HPLC purity 96.68%.

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6-((4-Bromo-3,5-dimethyl-1H-pyrazol-1-yl)methyl)-1-(3-mercaptopropyl)-4-oxo-1,4-dihydroquinoline-
1
3-carboxylic acid (14c). Yield: 42%; mp: 231–233 °C; H-NMR (DMSO-d6, δ ppm) 2.08–2.11 (m,
2H, -CH2CH2CH2SH), 2.12 (s, 3H, CH3-pyrazole), 2.21 (s, 3H, CH3-pyrazole), 2.55–2.58 (m, 2H,
-CH2CH2CH2SH), 4.62 (t, 2H, J = 7.2 Hz, -CH2CH2CH2SH), 5.51 (s, 2H, -CH2-pyrazole), 7.73 (dd,
1H, J = 2.0 and 8.8 Hz, H7), 8.06 (d, 1H, J = 8.8 Hz, H8), 8.14 (d, 1H, J = 2.0 Hz, H5), 9.03 (s, 1H,
H2), 15.09 (s, 1H, -COOH); 13C-NMR (DMSO-d6, δ ppm) 10.4, 12.5, 21.1, 28.4, 34.3, 52.5, 93.9,
108.3, 119.1, 124.5, 126.1, 133.6, 135.9, 137.8, 139.0, 145.6, 149.9, 166.4, 178.0; HRMS: m/z calcd
for C19H21BrN3O3S: 450.0481, 452.0466; found: 450.0489, 452.0467; HPLC purity 96.90%.
1-(4-Fluorobenzyl)-6-((3,5-dimethyl-1H-pyrazol-1-yl)methyl)-4-oxo-1,4-dihydro-quinoline-3-carboxylic
1
acid (15a). Yield: 63%; mp: 271–273 °C; H-NMR (DMSO-d6, δ ppm) 2.09 (s, 3H, CH3-pyrazole),
2.16 (s, 3H, CH3-pyrazole), 5.36 (s, 2H, -CH2-pyrazole), 5.82 (s, 2H, -CH2-Ar), 5.87 (s, 1H,
H-pyrazole), 7.19 (t, 2H, J = 8.8 Hz, Ar-H), 7.37 (q, 2H, J = 8.4 Hz, Ar-H), 7.60 (dd, 1H, J = 2.0 and
9.2 Hz, H7), 7.87 (d, 1H, J = 8.8 Hz, H8), 8.05 (d, 1H, J = 1.6 Hz, H5), 9.26 (s, 1H, H2), 15.06 (s, 1H,
-COOH); 13C-NMR (DMSO-d6, δ ppm) 11.1, 13.8, 51.1, 56.2, 105.7, 108.5, 116.1, 116.4, 119.5,
124.1, 126.2, 129.5, 129.5, 133.4, 136.9, 139.1, 139.4, 147.0, 150.5, 166.4, 178.2; HRMS: m/z calcd
for C23H21FN3O3: 406.1561; found: 406.1569; HPLC purity 99.70%.
1-(4-Fluorobenzyl)-6-((4-chloro-3,5-dimethyl-1H-pyrazol-1-yl)methyl)-4-oxo-1,4-dihydro-quinoline-3-
1
carboxylic acid (15b). Yield: 75%; mp: 239–241 °C; H-NMR (DMSO-d6, δ ppm) 2.17 (s, 3H,
CH3-pyrazole), 2.22 (s, 3H, CH3-pyrazole), 5.34 (s, 2H, -CH2-pyrazole), 5.49 (s, 2H, -CH2-Ar), 7.10 (t,
2H, J = 8.0 Hz, Ar-H), 7.14–7.18 (m, 2H, Ar-H), 7.42–7.49 (m, 2H, H7 H8), 8.35 (s, 1H, H5), 8.89 (s,
1H, H2), 14.68 (s, 1H, -COOH); 13C-NMR (DMSO-d6, 100 MHz, δ ppm) 9.5, 11.4, 52.7, 57.6, 108.7,
109.4, 116.6, 116.8, 118.1, 125.1, 126.7, 128.0, 128.1, 132.8, 135.4, 135.6, 139.0, 145.4, 149.1, 166.6,
178.3; HRMS: m/z calcd for C23H20ClFN3O3: 440.1171; found: 440.1169; HPLC purity 99.55%.
1-(4-Fluorobenzyl)-6-((4-bromo-3,5-dimethyl-1H-pyrazol-1-yl)methyl)-4-oxo-1,4-dihydro-quinoline-3-
1
carboxylic acid (15c). Yield: 73%; mp: 255–257 °C; H-NMR (DMSO-d6, δ ppm) 2.17 (s, 3H,
CH3-pyrazole), 2.21 (s, 3H, CH3-pyrazole), 5.35 (s, 2H, -CH2-pyrazole), 5.48 (s, 2H, -CH2-Ar), 7.08
(t, 2H, J = 7.6 Hz, Ar-H), 7.14 (s, 2H, Ar-H), 7.43 (s, 2H, H7 H8), 8.35 (s, 1H, H5), 8.88 (s, 1H, H2),
15.06 (s, 1H, -COOH); 13C-NMR (DMSO-d6, δ ppm) 10.4, 12.31, 52.8, 57.6, 109.4, 116.6, 116.8,
118.0, 125.2, 126.7, 128.0, 128.1, 132.8, 135.4, 137.4, 139.1, 139.0, 146.9, 149.1, 166.5, 178.3;
HRMS: m/z calcd for C23H20BrFN3O3: 484.0666, 486.0651; found: 484.0665, 486.0646; HPLC purity
99.57%.
1-(4-Nitrobenzyl)-6-((3,5-dimethyl-1H-pyrazol-1-yl)methyl)-4-oxo-1,4-dihydro-quinoline-3-carboxylic
1
acid (16a). Yield: 56%; mp: 274–276 °C; H-NMR (DMSO-d6, δ ppm) 2.08 (s, 3H, CH3-pyrazole),
2.16 (s, 3H, CH3-pyrazole), 5.36 (s, 2H, -CH2-pyrazole), 5.87 (s, 1H, H-pyrazole), 6.01 (s, 2H,
-CH2-Ar), 7.52 (d, 2H, J = 8.8 Hz, Ar-H), 7.58 (dd, 1H, J = 2.0 and 8.8 Hz, H7), 7.75 (d, 1H, J = 8.8 Hz,
H8), 8.07 (d, 1H, J = 2.0 Hz, H5), 8.18 (d, 2H, J = 8.8 Hz, Ar-H), 9.32 (s, 1H, H2), 15.01 (s, 1H,
-COOH); 13C-NMR (DMSO-d6, δ ppm) 11.1, 13.8, 51.1, 56.3, 105.7, 108.8, 119.3, 124.2, 124.4,
126.2, 128.3, 133.6, 137.1, 139.0, 139.4, 143.5, 147.0, 147.6, 150.9, 166.3, 178.4; HRMS: m/z calcd
for C23H21N4O5: 433.1506; found: 433.1508; HPLC purity 99.80%.

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1-(4-Nitrobenzyl)-6-((4-chloro-3,5-dimethyl-1H-pyrazol-1-yl)methyl)-4-oxo-1,4-dihydroquinoline-3-
1
carboxylic acid (16b). Yield: 55%; mp: 282–284 °C; H-NMR (DMSO-d6, δ ppm) 2.09 (s, 3H,
CH3-pyrazole), 2.17 (s, 3H, CH3-pyrazole), 5.42 (s, 2H, -CH2-pyrazole), 6.01 (s, 2H, -CH2-Ar), 7.53
(d, 2H, J = 8.8 Hz, Ar-H), 7.60 (dd, 1H, J = 2.0 and 8.8 Hz, H7), 7.75 (d, 1H, J = 6.8 Hz, H8), 8.13
(d, 1H, J = 2.0 Hz, H5), 8.19 (d, 2H, J = 8.8 Hz, Ar-H), 9.33 (s, 1H, H2), 14.98 (s, 1H, -COOH);
13C-NMR (DMSO-d6, δ ppm) 9.5, 11.5, 52.2, 56.3, 107.7, 108.8, 119.5, 124.4, 124.5, 126.2, 128.3,
133.7, 136.2, 139.2, 143.5, 144.1, 147.6, 151.0, 166.3, 178.3; HRMS: m/z calcd for C23H20ClN4O5:
467.1116; found: 467.1124; HPLC purity 97.32%.
1-(4-Nitrobenzyl)-6-((4-bromo-3,5-dimethyl-1H-pyrazol-1-yl)methyl)-4-oxo-1,4dihydroquinoline-3-
1
carboxylic acid (16c). Yield: 69%; mp: 266–268 °C; H-NMR (DMSO-d6, δ ppm) 2.09 (s, 3H,
CH3-pyrazole), 2.18 (s, 3H, CH3-pyrazole), 5.45 (s, 2H, -CH2-pyrazole), 6.01 (s, 2H, -CH2-Ar), 7.53
(d, 2H, J = 8.8 Hz, Ar-H), 7.60 (dd, 1H, J = 2.0 and 8.8 Hz, H7), 7.75 (d, 1H, J = 8.8 Hz, H8), 8.13 (d,
1H, J = 1.6 Hz, H5), 8.19 (d, 2H, J = 8.8 Hz, Ar-H), 9.33 (s, 1H, H2), 14.99 (s, 1H, -COOH);
13C-NMR (DMSO-d6, δ ppm) 10.4, 12.5, 52.3, 56.4, 93.8, 108.8, 119.5, 124.4, 124.5, 126.6, 128.3,
133.7, 136.2, 137.9, 139.2, 143.5, 145.7, 147.6, 150.9, 166.3, 178.3; HRMS: m/z calcd for
C23H20BrN4O5: 511.0611, 513.0596; found: 511.0616, 513.0599; HPLC purity 97.64%.
4. Conclusions
A series of 6-(pyrazolylmethyl)-4-oxo-4H-quinoline-3-carboxylic acid derivatives were synthesized
to rationalize the influence on the anti-IN activity of the 4-oxo-4H-quinolizine-3-carboxylic acid
scaffold of different substituents at N-1 and replacement of the phenyl group by a pyrazole ring at C-6,
which allowed us to highlight new SAR aspects of quinoline IN inhibitors. However, the HIV-1
integrase strand transfer (ST) activity assay results showed no obvious inhibitory activities for
compounds 11–16. Therefore, the replacement of the benzene ring at C-6 by another bioisosteric
moiety and an appropriate substituent at N-1 position are essential to enhance the structure-activity
relationships study for new quinoline derivatives with potential anti-IN activity.
Acknowledgements
The authors gratefully thank the financial supports from the National Key Basic Research
Program of China (No.2009CB930200), Beijing Natural Science Foundation (No.7102009) and
Platform of Innovation of Science and Technology of Beijing Municipal Education Committee
(PXM 2012_014204_00_000152).
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Sample Availability: Samples of the compounds 11–16 are available from the authors.
© 2012 by the authors; licensee MDPI, Basel, Switzerland. This article is an open access article
distributed under the terms and conditions of the Creative Commons Attribution license
(http://creativecommons.org/licenses/by/3.0/).