2-(2-Amino-6-methylpyrimidin-4-yl)-4-arylmethylidene- 5-methyl-2,4-dihydro-3H-pyrazol-3-ones: Design, synthesis, structure, in vitro anti-tubercular activity, and molecular docking study

Article abstract of DOI:10.1016/j.molstruc.2021.130863

A series of 2-(2-amino-6-methylpyrimidin-4-yl)-4-arylmethylidene-2,4-dihydro-3H-pyrazol-3-ones 6a-f was in silico predicted to display moderate anti-tubercular activity. To obtain these compounds, the Knoevenagel condensation of the corresponding pyrazol-3-ol 10 with aromatic aldehydes was performed. It was found that arylidenepyrazolones 6b, 6d and 6e bearing 4-diethylamino (6b), 3,4-dimethoxy (6d) and 4-hydroxy-3-methoxy (6e) substituents on the arylidene pendant did possess activity against Mycobacterium tuberculosis H37Rv. Their minimal inhibitory concentrations (MICs = 0.07-0.14 mmol/L) were comparable with MIC value for isoniazid (0.01 mmol/L) used as the reference drug. In accordance with a molecular docking study, a plausible mode of action of arylidenepyrazolones 6b, 6d and 6e was the inhibition of UDP-galactopyranose mutase responsible for the biosynthesis of arabinogalactan, one of the important components of the mycobacterial cell wall. The above results indicated that compounds 6b, 6d and 6e might serve as promising hits in further search for anti-tubercular agents based thereon.

Full text of DOI:10.1016/j.molstruc.2021.130863

Journal of Molecular Structure 1243 (2021) 130863
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstr
2-(2-Amino-6-methylpyrimidin-4-yl)-4-arylmethylidene-
5-methyl-2,4-dihydro-3H-pyrazol-3-ones: Design, synthesis, structure,
in vitro anti-tubercular activity, and molecular docking study
a,∗
a
b,c
d
Andrei V. Erkin , Aleksandra V. Yurieva , Oleg S. Yuzikhin , Vladislav V. Gurzhiy ,
Viktor I. Krutikova
a
Department of Chemistry and Technology of Synthetic Biologically Active Compounds, Saint Petersburg State Institute of Technology (Technical University),
2
6 Moskovskiy avenue, 190013 Saint Petersburg, Russia
b
Laboratory of Microbiological Plant Protection, All-Russian Institute of Plant Protection, 3 Podbelʹskiy highway, 196608 Saint Petersburg, Pushkin-8, Russia
Laboratory of Rhizosphere Microflora, All-Russian Research Institute of Agricultural Microbiology, 3 Podbelʹskiy highway, 196608, Saint Petersburg,
c
Pushkin-8, Russia
d
Department of Crystallography, Institute of Earth Sciences, Saint Petersburg State University, 7-9 Universitetskaya embankment, 199034 Saint Petersburg,
Russia
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of 2-(2-amino-6-methylpyrimidin-4-yl)-4-arylmethylidene-2,4-dihydro-3H-pyrazol-3-ones 6a-f
was in silico predicted to display moderate anti-tubercular activity. To obtain these compounds, the Kno-
evenagel condensation of the corresponding pyrazol-3-ol 10 with aromatic aldehydes was performed.
It was found that arylidenepyrazolones 6b, 6d and 6e bearing 4-diethylamino (6b), 3,4-dimethoxy (6d)
and 4-hydroxy-3-methoxy (6e) substituents on the arylidene pendant did possess activity against My-
cobacterium tuberculosis H37Rv. Their minimal inhibitory concentrations (MICs = 0.07-0.14 mmol/L) were
comparable with MIC value for isoniazid (0.01 mmol/L) used as the reference drug. In accordance with
a molecular docking study, a plausible mode of action of arylidenepyrazolones 6b, 6d and 6e was the
inhibition of UDP-galactopyranose mutase responsible for the biosynthesis of arabinogalactan, one of the
important components of the mycobacterial cell wall. The above results indicated that compounds 6b, 6d
and 6e might serve as promising hits in further search for anti-tubercular agents based thereon.
Received 14 March 2021
Revised 8 May 2021
Accepted 8 June 2021
Available online 11 June 2021
Keywords:
2
H-Pyrazol-3-ols
Aromatic aldehydes
Knoevenagel condensation
Structure
Anti-tubercular activity
Molecular docking
©
2021 Elsevier B.V. All rights reserved.
1
. Introduction
molecular-weight hit against Staphylococcus aureus [11] and an in-
hibitor of human solute carrier protein SLC11A2 [12] have also
been found.
Pyrimidines bearing a pyrazole moiety at one of the even-
numbered positions of the ring represent N-pyrazolylpyrimidines
The mepirizole 2 precursor is tautomeric methylene ketone 3
[13], which, when reacting with aldehydes, gives the Knoevenagel
condensation products 4 [14–17] (Fig. 1). These compounds have
been prepared mainly as methine dyes, so there appears to be no
available data on their biological activity. Nevertheless, arylidene
derivatives 4 (R = Ar) were a priori asserted to be less toxic than
those of edaravone, 5-methyl-2-phenyl-2,4-dihydro-3H-pyrazol-3-
one [18]. As a continuation of our work in the field of synthesis
and biological screening of compounds 4 (R = Ar) [19], we have
fulfilled the present research1 on their analogues with modified
pyrimidine moiety.
1
, an important class of hybrid heterocycles with diverse bio-
logical properties. Compounds 1 possess anti-tubercular [1], anti-
inflammatory [2], and cytoprotective antiulcer [3] activities. More-
over, 3-methyl-5-methoxy-1-(6-methyl-4-methoxypyrimidin-2-yl)-
1
H-pyrazole (2), better known as mepirizole, is clinically used
as an oral non-steroidal anti-inflammatory drug for muscle and
joint pain [4] (Fig. 1). N-Pyrazolylpyrimidines 1 are of certain in-
terest as antioxidant and anti-inflammatory agents [5], inhibitors
of human dihydroorotate dehydrogenase [6], Syk kinase [7] and
cyclin-dependent kinase 2 [8], antibacterial and antimalarial agents
[
9], and pesticides [10]. Among compounds 1, a promising low-
∗
1
Corresponding author.
This research did not receive any specific grant from funding agencies in the
E-mail address: anerkin@yandex.ru (A.V. Erkin).
public, commercial, or not-for-profit sectors
https://doi.org/10.1016/j.molstruc.2021.130863
022-2860/© 2021 Elsevier B.V. All rights reserved.
0

A.V. Erkin, A.V. Yurieva, O.S. Yuzikhin et al.
Journal of Molecular Structure 1243 (2021) 130863
Fig. 1. Structures of N-pyrazolylpyrimidines 1-4.
2
. Materials and methods
algorithm and refined using the SHELX programs [21, 22] incor-
porated in the OLEX2 program package [23]. The final model in-
cluded coordinates and anisotropic displacement parameters for all
non-H atoms. Selected interatomic bonds and angles are listed in
Table S2. The carbon and nitrogen-bound H atoms were placed
in calculated positions and were included in the refinement in
the ‘riding’ model approximation, Uiso(H) set to 1.5Ueq(C) and C–
2
.1. Chemistry
All required chemicals and solvents were purchased from com-
mercial sources (Sigma-Aldrich, Fluka and Merck) and used with-
out further purification, except phosphorus oxychloride and ethyl
acetoacetate. Reaction progress was monitored by thin layer chro-
matography (TLC) using pre-coated aluminum sheets plates 60
˚
H 0.96 A for the CH3 groups, Uiso(H) set to 1.2Ueq(C) and C–H
˚
0.93 A for the CH groups, and Uiso(H) set to 1.2Ueq(N) and N–H
˚
F254 (Merck Corp., USA) in a n-BuOH/AcOH/H O (1:1:1, v/v/v) sol-
0.86 A for the NH2 group. The H atoms of H O molecules were
2
2
vent system. The spots were detected by exposure to a UV lamp at
localized from difference Fourier maps and were included in the
refinement with Uiso(H) set to 1.5Ueq(O) and O–H restrained to
2
54 nm.
Melting points were determined with PTP block (Khimlabpribor
Ltd, Russia). The 1H (400 MHz) and 13C (100 MHz) NMR spectra
˚
0.85 A. CCDC 2013983 contains the supplementary crystallographic
data for this paper. These data can be obtained free of charge via
http://www.ccdc.cam.ac.uk/conts/retrieving.html.
as well as 13C NMR DEPT-135, { H- C}HMQC and { H-13C}HMBC
spectra were registered on a Bruker Avance III HD 400 NanoBay
spectrometer (Bruker BioSpin, GmbH, Germany) in DMSO-d6 and
1
13
1
2.3. Synthesis
in CDCl , the signals of residual protons of the solvents served
3
as internal references. The chemical shifts are expressed in the
δ (ppm). The coupling constants (J) are given in Hertz (Hz). Spin
multiples are given as s (singlet), d (doublet), dd (doublets of dou-
blets), t (triplet), q (quartet), and bs (broad singlet). IR spectra were
recorded on a Shimadzu IR Tracer 100 spectrophotometer (Shi-
madzu Corp., Japan) from KBr pellets. LC-HRMS analysis was per-
formed using Waters BEH-C18 column (100 × 3.0 mm, 3.5 μm)
and a 6538 Q-TOF mass spectrometer equipped with an ESI in-
terface (Agilent Technologies, Santa Clara, CA, USA). LC: ambient
temperature, injection volume 1-5 μL, the rate flow 0.15 mL/min.
The mobile phases were water-acetonitrile 95:5 + 0.1% formic acid
2
2
2
.3.1. General procedure for the synthesis of
-(2-amino-6-methylpyrimidin-4-yl)-4-aryl-methylidene-5-methyl-
,4-dihydro-3H-pyrazol-3-ones
(
6a-f)
A mixture of pyrazol-3-ol 10 (0.5 g, 2.4 mmol) and 2.4 mmol of
appropriate aromatic aldehyde in acetic acid (10 mL) was heated at
0°C for 1 h. After cooling, compounds 6a, 6c-6f were isolated as
8
colored precipitates by filtration, compound 6b was isolated as a
colored solid upon evaporation of the solvent to dryness. Purifica-
tion of compounds 6a-f thus obtained was carried out as follows.
Compounds 6a and 6b were recrystallized from H O-AcOH (5:3,
2
(
A) and acetonitrile-water 90:10 + 0.1% formic acid (B). The gra-
v/v) and from EtOH-DMF (2:1, v/v), respectively; compounds 6d
dient was as follows: 0-1 min 0% B; 1-13 min 0% → 90% B; 13-
and 6f were recrystallized from H O-AcOH (1:2, v/v); compounds
2
2
0 min, 90% B; and 20-25 min, 90% → 0% B. HRMS (positive ion
6
c and 6e were briefly heated with EtOH (10 mL) and H O (10
2
mode): drying gas (N ) flow rate 7.0 L/min; drying gas tempera-
2
mL), respectively. After washing with a small amount of warm wa-
ture 350°C; nebulizer pressure 30 psig; fragmentor voltage 175 V;
capillary voltage 3500 V; octapoleRFPeak voltage 750 V, and skim-
mer voltage 65 V. All the acquisitions and analyses of data were
controlled by MassHunter software B.05.00 (Agilent Technologies).
ter, compounds 6a-f were dried at 70°C to a constant weight.
2
.3.2. Synthesis of
Z)-2-(2-amino-6-methylpyrimidin-4-yl)-4-[(4-dimethylaminophenyl)-
methylidene]-5-methyl-2,4-dihydro-3H-pyrazol-3-one
(
(
6a)
2
.2. Single crystal X-ray diffraction study
Yield : 45%; Mp: > 255°C (dec.). 1H NMR, δ (ppm) (DMSO-d ):
2
6
2
.27 (s, 6H, Me), 3.14 (s, 6H, MeN), 6.45 (s, 2H, NH ), 6.79 (t, 2H,
The single-crystal XRD analysis was performed on the Rigaku
2
ArH, 3J = 8.7 Hz), 7.24 [s, 1H, C(5)H], 7.45 (s, 1H, H ), 8.54 (d,
β
Oxford Diffraction XtaLAB HyPix-3000 diffractometer and the
diffraction data have been collected using monochromated micro-
focused CuKα radiation. Data were integrated and corrected for
background, Lorentz, and polarization effects. An empirical absorp-
tion correction based on spherical harmonics implemented in the
SCALE3 ABSPACK algorithm was applied in CrysAlisPro program
13
H, ArH, 3J = 6.5 Hz); C NMR, δ (ppm) (DMSO-d ): 13.71 (Me,
2
6
pyrazole ring), 24.31 (Me, pyrimidine ring), 39.97 (MeN), 97.36
ꢀ ꢀ ꢀ ꢀ
[
C(5)], 111.7 [C(3 ’)], 118.3 [C(4 )], 121.5 [C(1 ’)], 137.9 [C(2 ’)], 148.8
β
ꢀ
ꢀ
ꢀ
(
C ), 152.8 [C(5 )], 154.4 [C(4 ’)], 157.2, 163.7, 163.9 [C(3 )], 168.4
[
C(6)]. 13C NMR DEPT-135, δ (ppm) (DMSO-d ): 13.55, 24.32, ~ 40,
6
7.59, 111.9, 138.1, 148.8. IR, νmax (cm 1) (KBr): 1672 (ν
−
), 1623
9
[
20]. The unit-cell parameters ([P-1, a = 7.2765(4), b = 9.6556(5),
C=O
˚
c = 13.2376(5) A, α = 71.290(4), β = 75.740(5), γ = 85.101(5) °,
˚
3
2
V = 852.04(8) A , Z = 2, R = 7.9%], Table S1) were refined by the
1
The yield optimization is currently underway and results thereof will be pub-
least-squares techniques. The structure was solved by dual-space
lished elsewhere
2

A.V. Erkin, A.V. Yurieva, O.S. Yuzikhin et al.
Journal of Molecular Structure 1243 (2021) 130863
+
(
ν
), 1549 (ν
). LC, rt (min): 13.63-13.73. HRMS (ESI ): m/z
4.14 (q, 2H, MeCH O, J = 6.9 Hz), 6.60 (s, 2H, NH ), 6.97 (d, 1H,
β
C=N
C=C
2
2
+
ArH, 3J = 8.4 Hz), 7.15 [s, 1H, C(5)H], 7.67 (s, 1H, H ), 8.03 (dd, 1H,
calc. (С18 H20N O) [M+H] 337.1771, found 337.1786.
6
ArH, 3J = 8.5 Hz, J = 1.8 Hz), 8.62 (d, 1H, ArH, J = 1.7 Hz), 10.53
4
4
2
.3.3. Synthesis of
Z)-2-(2-amino-6-methylpyrimidin-4-yl)-4-[(4-diethylaminophenyl)-
methylidene]-5-methyl-2,4-dihydro-3H-pyrazol-3-one
13
(
bs, 1H, OH). C NMR, δ (ppm) (DMSO-d ): 13.50, 15.12, 24.49,
6
(
β
6
4.29, 97.58, 116.1, 118.9, 122.0, 125.7, 131.5, 146.8, 149.6 (C ),
−1
1
52.9, 153.8, 157.0, 163.6, 163.7, 168.7. IR, νmax (cm ) (KBr): 1684
(
6b)
(
ν
), 1614 (ν
), 1563 (ν
). LC, rt (min): 13.84-14.04. HRMS
C=O
C=N
C=C
Yield: 61%; Mp: 246-248°С. 1H NMR, δ (ppm) (DMSO-d ): 1.17
+
+
6
(ESI ): m/z calc. (С18 H19 N O ) [M+H] 354.1561, found 354.1574.
5
3
(
t, 6H, MeCH N, J = 7.0 Hz), 2.25 (s, 3H, Me), 2.26 (s, 3H, Me),
2
3
.52 (q, 4H, MeCH N, J = 7.1 Hz), 6.53 (s, 2H, NH ), 6.83 (d, 2H,
β
2
2
2.3.8. Procedure for the synthesis of
ArH, 3J = 9.3 Hz), 7.25 [s, 1H, C(5)H], 7.52 (s, 1H, H ), 8.58 (d, 2H,
2-amino-4-chloro-6-methylpyrimidine (8)
13
ArH, 3J = 8.6 Hz). C NMR, δ (ppm) (DMSO-d ): 13.07, 13.59, 19.01,
6
A mixture of pyrimidinone 7 (10 g, 80 mmol) and freshly dis-
β
2
4.35, 44.64, 56.56, 97.33, 111.5, 118.1, 121.3, 138.5, 148.6 (C ),
tilled phosphorus oxychloride (50 mL) was heated to 115°C and
kept at this temperature until homogenization, which occurred
within 20 min. Afterwards, excess of phosphorus oxychloride was
distilled off under diminished pressure. The residue was cooled to
1
52.3, 152.8, 157.2, 163.6, 164.0, 168.5. IR, νmax (cm 1) (KBr): 1686
−
(
(
ν
), 1632 (ν
), 1555 (ν
). LC, rt (min): 15.05-15.86. HRMS
C=O
C=N
C=C
+
+
ESI ): m/z calc. (С 0H N O) [M+H] 365.2084, found 365.2103.
2
24
6
5
°C and mixed with crushed ice. Then, 25% aqueous ammonia was
2
.3.4. Synthesis of (Z)-2-(2-amino-6-methylpyrimidin-4-yl)-4-[(4-
added to this mixture until pH thereof achieved 8÷9. The suspen-
sion thus formed was filtered; the precipitate was washed with
water to remove most of inorganic salts, recrystallized from 50%
aqueous ethanol and dried at 70°C to a constant weight. Yield: 6.14
g (53%); Mp: 186-188°C (Ref [24] 176.5-181°C, Ref [25] 183-186°C,
Ref [26] 182°C).
methoxyphenyl)-methylidene]-5-methyl-2,4-dihydro-3H-pyrazol-3-one
(
6c)
Yield: 28%; Mp: 255-257°С. 1H NMR, δ (ppm) (DMSO-d ): 2.26
6
(
s, 3H, Me), 2.31 (s, 3H, Me), 3.90 (s, 3H, MeO), 6.60 (s, 2H, NH ),
2
7
.14 [s, 1H, C(5)H], 7.15 (d, 2H, ArH, 3J = 2.0 Hz), 7.76 (s, 1H,
β
3
13
H ), 8.65 (d, 2H, ArH, J = 9.0 Hz). C NMR, δ (ppm) (DMSO-
β
d ): 13.65, 24.34, 56.29, 97.46, 114.8, 123.5, 126.5, 137.3, 148.8 (C ),
6
2
2
.3.9. Procedure for the synthesis of
1
53.1, 157.0, 163.4, 163.7, 164.2, 168.7. IR, νmax (cm 1) (KBr): 1698
−
-amino-4-hydrazino-6-methylpyrimidine (9)
A mixture of chloropyrimidine 8 (2.0 g, 14 mmol) and hydrazine
(
(
ν
), 1629 (ν
), 1559 (ν
). LC, rt (min): 13.63-13.93. HRMS
C=O
C=N
C=N
+
+
ESI ): m/z calc. (С17 H17 N O ) [M+H] 324.1455, found 324.1458.
5
2
hydrate (4.2 g, 84 mmol) was heated at 100°C for 30 min. After
cooling to room temperature, the mixture was diluted with water
2
.3.5. Synthesis of
(
15 mL), the solid was filtered off, washed with water and dried at
0°C to a constant weight. Yield: 1.75 g (90%); Mp: 234-236°C. An-
(
Z)-2-(2-amino-6-methylpyrimidin-4-yl)-4-[(3,4-dimethoxyphenyl)-
7
methylidene]-5-methyl-2,4-dihydro-3H-pyrazol-3-one
6d)3
alytical sample was prepared by recrystallization of a small amount
(
Yield: 24%; Mp: 240-242°С. 1H NMR, δ (ppm) (DMSO-d ): 1.91
s, 3H, Me, Ac), 2.26 (s, 3H, Me), 2.30 (s, 3H, Me), 3.87 (s, 3H,
of crude compound 9 from water. Mp: 236-238°C (Ref [27] 237-
6
2
38°C, Ref [28] 240°C).
(
MeO), 3.91 (s, 3H, MeO), 6.61 (s, 2H, NH ), 7.14 [s, 1H, C(5)H],
2
.18 (d, 1H, ArH, 3J = 8.6 Hz), 7.74 (s, 1H, H ), 8.11 (dd, 1H, ArH,
β
2.3.10. Procedure for the synthesis of
7
3
4
4
13
2-(2-amino-6-methylpyrimidin-4-yl)-5-methyl-2H-pyrazol-3-ol (10)
To a boiling solution of hydrazinopyrimidine 9 (1 g, 7.2 mmol)
in water (40 mL) freshly distilled ethyl acetoacetate (0.94 g, 7.2
mmol) was added at once. The mixture was refluxed for 1 h, and
then it was cooled to room temperature. The precipitate formed
J = 8.6 Hz, J = 1.8 Hz), 8.65 (d, 1H, ArH, J = 1.8 Hz). C NMR,
δ (ppm) (DMSO-d ): 13.68, 21.48, 24.32, 55.96, 56.32, 97.60, 111.8,
6
β
1
16.4, 123.2, 126.8, 131.2, 148.5 (C ), 149.4, 153.0, 154.3, 156.9,
63.6, 163.9, 168.8, 172.5. IR, νmax (cm 1) (KBr): 1682 (ν
−
1
), 1623
+
C=O
(
ν
), 1659 (ν
). LC, rt (min): 13.74-13.94. HRMS (ESI ): m/z
C=N
C=N
+
was filtered off, washed with water, recrystallized from H O-AcOH
calc. (С18 H19N O ) [M+H] 354.1561, found 354.1575.
2
5
3
(
12:1, v/v) and dried at 70°C to a constant weight. Yield: 1.75 g
(59%); Mp: 244-246°C. 1H NMR, δ (ppm) (CDCl3): 2.26 (s, 3Н, Me),
2.41 (s, 3Н, Me), 5.06 (s, 2H, NH2), 5.43 [s, 1H, C(4)H], 7.01 [s,
1H, C(5)H], 12.20 (bs, 1H, OH). 13C NMR, δ (ppm) (CDCl3): 14.72,
2
.3.6. Synthesis of
Z)-2-(2-amino-6-methylpyrimidin-4-yl)-4-[(4-hydroxy-3-methoxy-
phenyl)methylidene]-5-methyl-2,4-dihydro-3H-pyrazol-3-one
6e)
Yield: 41%; Mp: 285-288°С (dec.). 1H NMR, δ (ppm) (DMSO-
d6): 2.26 (s, 3H, Me), 2.29 (s, 3H, Me), 3.89 (s, 3H, MeO), 6.61
(
24.50, 88.84, 97.18, 151.3, 152.6, 153.1, 157.4, 159.9. IR, νmax (cm 1)
−
(
(KBr): 3446 (νOH, νNH2), 1633 (νC=N), 1583 (νC=C). LC, rt (min):
+
+
5.26-5.85. HRMS (ESI ): m/z calc. (С9H11 N5O) [M+H] 206.1036,
3
(
s, 2H, NH ), 6.96 (d, 1H, ArH, J = 8.4 Hz), 7.16 [s, 1H, C(5)H],
found 206.1030.
2
.69 (s, 1H, H ), 8.04 (dd, 1H, ArH, 3J = 8.4 Hz, J = 1.8 Hz), 8.66
β
4
7
d, 1H, ArH, 4J = 1.7 Hz), 10.65 (bs, 1H, OH). C NMR, δ (ppm)
13
(
(
2.4. Microbiological assay
DMSO-d ): 13.63, 24.18, 56.25, 97.70, 111.2, 115.9, 116.1, 117.7,
6
β
1
22.2, 125.6, 126.5, 129.1, 131.6, 147.8, 148.7 (C ), 149.6, 153.0,
The target compounds were screened in vitro for antimycobac-
terial activity against a standard strain, Mycobacterium tuberculo-
53.4, 156.9, 163.6, 168.7. IR, νmax (cm 1) (KBr): 1682 (ν
−
), 1644
+
1
C=O
(
ν
), 1562 (ν
). LC, rt (min): 13.33-13.43. HRMS (ESI ): m/z
sis H37R , grown on the Soton medium, which contained 10% of
C=N
C=C
3
V
+
calc. (С17 H17 N O ) [M+H] 340.1404, found 340.1415.
horse serum, and the density of microbial suspension when seed-
ing was 50•106 cell/L. Antimycobacterial effect was determined by
5
2
.3.7. Synthesis of
Z)-2-(2-amino-6-methylpyrimidin-4-yl)-4-[(4-hydroxy-3-ethoxy-
phenyl)methylidene]-5-methyl-2,4-dihydro-3H-pyrazol-3-one
the serial dilution method. Substances were dissolved in DMSO and
titrated in the medium N-1, so that the preparation was contained
in separate test tubes with the medium in concentration from 100
to 1.56 μg/mL. The concentrations of the substance in the medium
in adjacent test tubes differed by the factor of two. DMSO titrated
in the same way as the substrate was utilized for the control. The
results were considered after a 72 hours cultivation of the my-
cobacteria at 37°C.
(
(
6f)
Yield: 27%; Mp: > 280°С (dec.). 1H NMR, δ (ppm) (DMSO-d ):
6
1.41 (t, 3H, MeCH O, J = 6.9 Hz), 2.26 (s, 3H, Me), 2.29 (s, 3H, Me),
2
3
This compound was isolated as a 1:1 solvate with acetic acid
3

A.V. Erkin, A.V. Yurieva, O.S. Yuzikhin et al.
Journal of Molecular Structure 1243 (2021) 130863
Fig. 2. HIV-1 RT inhibitors 5a-c and their structural analogues 6a-f
(
common fragments are marked with red).
Table 1
2
.5. Computational studies
The following online services were used in this work: Chem-
The probabilities for compounds 6a-f to be active against
HIV (Pʹa) and TB (Pʺa).
Tested compound
Pʹa
Pʹʹa
Mine Tools (www.chemminetools.ucr.edu) for calculation of Tani-
moto similarity coefficients (TSCs) [29], Way2Drug Predictive Ser-
vices (www.way2drug.com) for estimation of biological activi-
ties [30], Molinspiration Cheminformatics (www.molinspiration.
com) for calculation of molecular properties, NMRShiftDB (www.
nmrshiftdb.nmr.uni-koeln.de) for 13C NMR spectra simulation [31],
Mcule drug discovery platform (www.mcule.com) for molecular
6a
6b
0.079
0.068
0.076
0.077
0.083
0.087
0.263
0.344
0.346
0.359
0.408
0.437
6
6
6
6
c
d
e
f
4
docking study [32] , LiteMol (www.litemol.org) [34], and Protein-
Ligand Interaction Profiler (PLIP) (www.projects.biotec.tu-dresden.
de) [35] for visualization of the docking study results.
On the one hand, the Pʺa values indicated that the chance to
confirm the predicted activity by in vitro experiments was alas not
high. On the other hand, these values might be considered as no
more than a measure of the structural similarities of compounds
3. Results and discussion
6a-f and anti-TB drugs known up to date [30]. Be it that way or an-
3
.1. Design strategy
other, even partial confirmation of the predicted activity may pro-
vide an impetus for in-depth study of arylidenepyrazolones 6a-f
as novel5 potential anti-TB drugs. Indeed, the fact that compounds
6a-f complied with Lipinski’s Rule of Five was a criterion to classify
them as drug-like molecules (Table S4).
During a literature survey we turned attention to the very
close structural similarity between the Knoevenagel condensation
products 4 and 2-R-5-(het)arylmethylidene-3-(4-methyl-pyrimidin-
2
-yl)-4,5-dihydro-1H-imidazol-4-ones (5), which emerged as
a
Some comments should probably be given with regard to the
scope of compounds 6a-f limited by six examples. At the anti-HIV
activity prediction step, we aimed to achieve acceptable structural
similarities of reference arylideneimidazolones 5a-c and the target
compounds. Later, during the synthesis of arylidenepyrazolones 6a-
f, we came to the conclusion that only electron-donating groups
at para-position of the aromatic ring facilitated their formation.
Besides, some compounds [e.g., halogenated derivatives of com-
pound 6e (R3 = Cl, Br)] were excluded from the current research
due to their poor solubility in DMSO. This property obviously pre-
vented both spectral characterizations and biological screening of
the mentioned derivatives.
new class of non-nucleoside type of HIV-1 RT inhibitors. Of
them, the compounds bearing a small hydrophobic substituent
R, such as methyl group, combined with a bulky aromatic moi-
ety, met with general requirements for the activity [36]. In
particular, arylideneimidazolones 5a-c (Fig. 2) exerted
a sig-
nificant inhibitory effect on the enzyme: when tested at 20
μg/mL, they showed 51-71% inhibition as compared to 100%
at the same concentration for nevirapine. In this regard, we
evaluated 2-(2-amino-6-methylpyrimidin-4-yl)-4-arylmethylidene-
5
-methyl-2,4-dihydro-3H-pyrazol-3-ones (6a-f) (Fig. 2) in silico for
their possible anti-HIV properties. This seemed quite reasonable in
view of that TSCs for the corresponding pairs of reference aryli-
deneimidazolones 5a-c and compounds 6a-f ranged from 0.46 to
3
.2. Synthesis
0
.52 (Table S3).
Unexpectedly, arylidenepyrazolones 6a-f demonstrated very low
Arylidenepyrazolones 6a-f were prepared in four-step synthesis
probabilities to be active (Pʹa < 0.09) against HIV; instead, they
proved to possess anti-tubercular (anti-TB) properties with proba-
bilities (Pʺa) varied from 0.263 to 0.437 (Table 1).
outlined in Scheme 1. Compound 10 and its Knoevenagel conden-
sation products 6a-f were synthesized for the first time.
5
In any case, there are no structural analogues of compounds 6a-f among
4
Along with other docking tools, such as AutoDOCK, GLIDE, GOLD, FlexX, Mcule
promising anti-TB pyrazoles and pyrazole-pyrimidine hybrids, which have recently
been reviewed [4, 37].
affords equally reliable and accurate results [33]
4

A.V. Erkin, A.V. Yurieva, O.S. Yuzikhin et al.
Journal of Molecular Structure 1243 (2021) 130863
lution mass spectra. In the 1H NMR spectra, the proton signals at δ
2.25-2.30 ppm corresponded to both methyl groups, at δ 6.45-6.61
ppm to NH2 groups, at δ 7.45-7.74 ppm to the ylidene fragment
(H ), and at δ 6.7-8.6 ppm to aromatic rings. The 13C NMR spec-
tra contained signals, some of which might be attributed to both
methyl groups (at δ 13.50-13.68, 24.31-24.49 ppm), C(5) atom (at δ
97.33-97.78 ppm) and aromatic carbons (starting at δ 111 ppm and
on).
Initially, we carried out the exchange chlorination of com-
mercially available 2-amino-6-methylpyrimidin-4(3H)-one (7) with
a large excess of phosphorus oxychloride to obtain 2-amino-4-
chloro-6-methylpyrimidine (8). This procedure was successfully
modified by replacing the prolonged refluxing of the reaction mix-
ture [24–26] with heating thereof at 115°C until homogeniza-
tion occurred. Next, chloropyrimidine 8 and 6-fold excess of hy-
drazine hydrate were kept at 100°C with occasional stirring to af-
ford 2-amino-4-hydrazino-6-methylpyrimidine (9). In contrast to
the older synthetic protocol [27], we found that the hydrazi-
nolysis of compound 8 required to use no anhydrous hydrazine
and could take much less than 2 h to be completed. At the
same time, we failed to prepare hydrazinopyrimidine 9 by re-
fluxing the reactants in ethanol as described earlier [28]. Then,
the condensation of compound 9 and ethyl acetoacetate in boil-
ing water was performed. The reaction was of remarkable inter-
est as it led to 2-(2-amino-6-methyl-pyrimidin-4-yl)-5-methyl-2H-
pyrazol-3-ol (10) directly, without isolation of the corresponding
intermediate ethyl acetoacetate (pyrimidin-4-yl)hydrazone. More-
over, it required no alkaline catalyst to make the above hydra-
zone undergo the pyrazole ring closure smoothly. Finally, we in-
troduced pyrazol-3-ol 10 into the reaction with aromatic aldehy-
des bearing electron-donating groups at para-position of the ring
in glacial acetic acid at 80°C to obtain Knoevenagel condensation
products 6a-f. While acetic acid and DMF allowed the reaction to
proceed under homogeneous conditions, other suitable [38] sol-
vents, such as ethanol, acetonitrile and benzene, did not. How-
ever, DMF was discarded as the reaction medium to avoid possi-
ble [39] aminomethylenation of pyrazol-3-ol 10. If the aldehydes
bore no electron-donating groups, no products of type 6a-f appear
to be formed. For example, the reaction of pyrazol-3-ol 10 with
unsubstituted benzaldehyde gave two compounds. Identification of
the first one was not possible by even 1H NMR spectroscopy due
to extremely poor solubility in common organic solvents, including
DMSO, both at room and higher temperatures. 1H NMR spectrum
of the second one allowed presuming that it was the crude product
β
For accurate assignment of the characteristic Cβ atom signal,
1
we performed a series of experiments, such as DEPT-135, { H-
13
C}HMQC and { H-13C}HMBC. For example, of the set of signals in
1
the 13C NMR DEPT-135 spectrum of arylidenepyrazolone 6a, only
four at δ 97.59, 111.9, 138.1, 148.8 ppm might correspond to sp2
hybridized carbon atoms. On the basis of a joint examination of
the complex of correlations in the mentioned heteronuclear spec-
tra (Fig. 3a,b), the latter signal could be unambiguously assigned to
Cβ atom.
Unfortunately, two signals at δ 157.2 and 163.7 ppm in the 13C
NMR spectrum of compound 6a could not be assigned as reliably
as the signal at δ 148.8 ppm even using { H-13C}HMBC technique.
They were supposed to be attributed to C(2) and C(4) atoms, or
vice versa, respectively. However, none showed a cross peak with
either the C(5) atom proton or an C(6)-methyl proton. This was
probably due to the fact that the corresponding coupling constants
2J(H,C) and 4J(H,C) were close to zero. Meanwhile, simulation of
the 13C NMR spectrum of arylidenepyrazolone 6а indicated that
more downshifted signal (δ 163.7 ppm) might be assigned to C(2)
atom.
1
In the IR spectra of compounds 6a-f, a strong absorption band
was observed at 1684–1698 cm–1 attributable to the stretching
vibrations of the C=O group conjugated to the exocyclic double
–
1
bond. Accordingly, less strong absorption bands at 1644-1614 cm
and at 1563-1555 cm–1 might correspond to the stretching vibra-
tions of the C=N and C=C groups, respectively. The high resolu-
+
tion mass spectra contained the peaks of monoprotonated [M+H]
molecules with the m/z values coinciding with the calculated ones.
of the tandem Knoevenagel-Michael condensation of pyrazol-3-ol
ꢀ
1
0 with benzaldehyde, 4,4 -(phenylmethanediyl)-bis[2-(2-amino-6-
3.4. Stereochemistry of arylidenepyrazolones 6a-f
methylpyrimidin-4-yl)-5-methyl-2H-pyrazol-3-ol] (11). Anyway, the
spectrum contained the proton signals, whose chemical shifts,
multiplets and integral intensities might correspond to the C-
methyl groups attached to the pyrazole and the pyrimidine rings,
and the exocyclic methine group (Figure S1).
In DMSO-d6 solution, compounds 6a-f were found to ex-
ist exclusively as (Z)-isomers. It clearly follows from compari-
ꢀ
son of the observed C(5 )-methyl proton signals (δ 2.27 ppm,
in average) with the reported ones for (Z)-4-(arylethylidene)-5-
To explain the formation of methanediylbispyrazol-3-ol 11, we
assumed that the nature of the substituent at para-position of the
aromatic aldehydes might play a crucial role in stabilization of re-
sulting heterocycles. If the position was occupied with an electron-
donating group (EDG) (pathway a), the formation of Knoevenagel
condensation products 6a-f took place via adduct A (R2 = EDG)
followed by its dehydration. When unsubstituted benzaldehyde
methyl-2-(pyrimidin-2-yl)-2,4-dihydro-3H-pyrazol-3-ones 15. Oth-
ꢀ
erwise, the C(5 )-methyl proton signals in arylidenepyrazolones
6a-f would probably be more shielded because of an anisotropic
effect of the aryl ring as it took place in the 1H NMR
spectra of 4-(diphenylmethylidene)-5-methyl-2-(pyrimidin-2-yl)-
2,4-dihydro-3H-pyrazol-3-ones 16 (Fig. 4) [41].
In favor of (Z)-configuration of compounds 6a-f, nuclear Over-
was used, structurally related adduct B (R1 = R = R = H) was
2
3
hauser effect (NOE) unequivocally testifies: for example, this effect
ꢀ
β
also formed apparently (pathway b), but on dehydration it afforded
was readily detected between a C(5 )-methyl proton and H atom
unstable intermediate C (R1 = R = R = H). For its stabiliza-
tion, nucleophilic addition of the second pyrazol-3-ol 10 molecule
occurred, giving tandem Knoevenagel-Michael reaction product 11
2
3
in the 2D-NOESY 1H NMR spectrum of arylidenepyrazolone 6a.
3
.5. Crystal structure of arylidenepyrazolone 6a
(
Scheme 2).
The crystal structure of compound 6a was determined using the
Noteworthy, a similar reaction course was observed in the
6
single crystal X-ray diffraction (XRD) analysis (Fig. 5) . The crystals
of arylidenepyrazolone 6a suitable for X-ray data collection were
obtained after slow evaporation of its DMF solution at room tem-
perature. The summaries of crystal data and refinement parameters
for compound 6a monohydrate are given in Table S1.
case of 2-[6-methyl-2-(methylsulfanyl)pyrimidin-4-yl]-5-methyl-
H-pyrazol-3-ol 12, which, depending on the nature of substituent
R2 in aromatic aldehyde, formed either arylidenepyrazolone 13 or
2
methanediylbispyrazol-3-ol 14 [40].
As it can be seen from Fig. 5, (Z)-configuration of compound
3
.3. Spectral characterizations of arylidenepyrazolones 6a-f
6a did not vary in going from DMSO-d6 solution to the crystalline
The structure of arylidenepyrazolones 6a-f was confirmed by a
combination of 1H and 13C NMR spectra, IR spectra, and high reso-
6
Note that crystal numbering does not obey the IUPAC numbering rules
5

A.V. Erkin, A.V. Yurieva, O.S. Yuzikhin et al.
Journal of Molecular Structure 1243 (2021) 130863
Fig. 3. Correlations and signal assignment in the HMQC (a) and HMBC (b) spectra of compound 6a
carbon atoms and their chemical shifts are marked with bold).
(
Fig. 4. Chemical shifts of the C(5)-methyl proton signals in compounds 6a, 15 and 16.
Fig. 5. Crystallographically non-equivalent moiety in the structure of compound 6a.
Thermal ellipsoids are shown at the 50% probability level.
Table 2
Table 3
Intramolecular H-bonds in arylidenepyrazolone 6a.
Intermolecular H-bonds in arylidenepyrazolone 6a.
BondD–H•••A
Bond lengths ( A˚ ) and angles (°)
Bond D–H•••A
Bond lengths ( A˚ ) and angles (°)
D–H
H•••A
D•••A
D–H•••A
D–H
H•••A
D•••A
D–H•••A
C(6)–H(6)•••O(1)
C(12)– H(12)•••O(1)
0.93
0.93
2.22
2.15
2.828(3)
2.980(3)
122.6
148.6
N(5)–H(5)A•••O(2)
N(5)–H(5)B•••N(3)
O(2)–H(2)A•••N(4)
O(2)-H(2)B•••O(1)
C(17)-H(17)A•••N(1)
0.86
0.86
0.85
0.85
0.96
2.63
2.16
2.03
2.16
2.69
3.335(3)
2.998(3)
2.864(3)
2.977(3)
3.540(4)
139.8
166.0
167.6
161.1
147.9
state. The observed structural feature of arylidenepyrazolone 6a is
the formation of two weak intramolecular H-bonds between the H
atoms riding on C(6) and C(12), and O(1) atom (Table 2).
are linked through a branchy system of strong and weak hydrogen
In the crystal, arylidenepyrazolone 6a molecules are arranged in
bonds (Fig. 7, Table 3), involving two H O molecules, which include
2
the pseudo-layered complexes (Fig. 6) parallel to (210). Two H O
N(5)H•••O(2), N(5)H•••N(3), O(2)H•••N(4), and van der Waals in-
2
molecules are also arranged in the layer, between the compound
teractions. Layers are interlinked via fewer amounts of less strong
6a molecules. Within the layers, arylidenepyrazolone 6a molecules
H-bonds, which include O(2)H•••O(1), C(17)H•••N(1), and paral-
6

A.V. Erkin, A.V. Yurieva, O.S. Yuzikhin et al.
Journal of Molecular Structure 1243 (2021) 130863
Fig. 6. Packing of compound 6a molecules (view along the [001] and the pseudo-layered complexes). Legend: C atoms = grey, H = white, N = blue, O = red, H-bonds = thin
dashed lines.
Fig. 7. Arrangement of compound 6a molecules and the H-bonding system within the pseudo-layered complex (the molecule from the neighbor layer is shown as a wire-
frame). Legend: see Fig. 6.
Table 4
lel displaced π-stacking forces between pyrazole [C(1)-N(2)] and
Docking score of compounds 6b, 6d and 6e.
aryl [C(11)-C(16)] rings: plane-to-plane normal distance is 3.391(2)
˚
˚
A, plane-to-plane shift is 1.238(5) A, and plane-to-plane angle is
.4(1)°.
Enzyme
PDB ID
DSs of tested compounds
1
6b
6d
6e
ENR
UGMa
2B35
1V0J
2VG3
2IYV
1EYE
1GSI
- 8.9
- 9.3
- 7.6
- 6.9
- 6.8
- 7.8
- 8.0
- 10.0
- 8.9
- 7.2
-7.3
- 8.0
-10.1
- 9.1
- 7.9
-7.1
3
.6. Anti-tubercular activity of arylidenepyrazolones 6a-f
ALD
SK
In vitro biological screening of arylidenepyrazolones 6a-f
DHPS1
TK
showed that some of them possessed an inhibitory effect on My-
cobacterium tuberculosis H37RV (MTub) growth. This effect was
quantified by means of minimal inhibitory concentration (MIC)
values. Of all the compounds tested, arylidenepyrazolones 6b, 6d
and 6e were active against this strain with MIC = 25 (0.068), 50
- 8.8
- 7.7
a
For comparison, DSs for in vitro inactive com-
pounds 6a, 6c and 6f were equal - 9.7, -10.1 and -
9
.1, respectively
(
0.142) and 25 (0.074) μg/mL (mmol/L), respectively. The MIC val-
ues expressed in mmol/L were comparable with the MIC value es-
timated for first-line anti-TB drug isoniazid (INH) (0.01 mmol/L).
Other compounds 6a, 6c and 6f possessed no inhibitory effect on
MTub, when tested at concentrations up to 100 μg/mL.
mainly enoyl-[acyl-carrier-protein] reductase (ENR) [43], one of the
most important enzymes participating in the biosynthesis of my-
colic acids. Apart from ENR enzyme, UDP-galactopyranose mutase
(UGM) and alanine dehydrogenase (ALD) were also taken into con-
sideration since they play a prominent role in arabinogalactan and
peptidoglycan biosyntheses, respectively [44]. In accordance with
modern conception [45], these three biopolymers, mycolic acids,
arabinogalactan and peptidoglycan, are the major components of
MTub cell wall.
3
.7. Molecular docking study of arylidenepyrazolones 6b, 6d and 6e
To clarify a plausible mechanism of anti-TB action of aryli-
denepyrazolones 6b, 6d and 6e, a molecular docking study was
performed. Of a great variety of potential targets in MTub [42], we
focused our attention primarily on the enzymes involved in cell
wall construction. This was caused by the fact that INH targets
As docking scores (DSs) showed, all arylidenepyrazolones 6b, 6d
and 6e demonstrated the highest binding affinities (DSs ≥ 9.3) to
UGM enzyme (Table 4).
7

A.V. Erkin, A.V. Yurieva, O.S. Yuzikhin et al.
Journal of Molecular Structure 1243 (2021) 130863
Fig. 8. Docking pose of compound 6e
inside UGM enzyme (general view).
Fig. 9. Interactions of compound 6e
with amino acid residues in UGM enzyme (hydrophobic binding interactions are shown with grey dotted, H-bond interactions with dark blue and a salt bridge with yellow
dotted).
Table 5
Inside the enzyme, arylidenepyrazolones 6b, 6d and 6e were
Hydrophobic interactions of compound 6e.
retained mainly by both hydrophobic and H-bond interactions. In
particular, the docking pose of compound 6e (Fig. 8) revealed7
a
Index
Amino acid residue
Distance ( A˚ )
Ligand atom
Protein atom
number of hydrophobic interactions with Phe A14, Phe A15, Arg
A36 and Arg A353 (Fig. 9, Table 5). In addition to these, a network
of H-bond interactions with Arg A36, Asn A43, Thr A237, Arg A353
and Met A362 was observed (Fig. 9, Table 6). Lastly, a salt bridge
between guanidine moiety and negative ionizable Glu A318 center
1
2
3
4
5
Phe A14
Phe A14
Phe A15
Arg A36
Arg A353
3.88
3.71
3.34
3.97
3.93
С(21)
C(22)
C(14)
C(8)
С(1) (arom.)
C(3) (CH2)
C(3) (CH2)
C(4) (CH2)
C(4) (CH2)
C(18)
˚
at the distance of 4.81 A was detected.
With regard to other enzymes, such as shikimate kinase (SK),
dihydropteroate synthase 1 (DHPS1), and thymidylate kinase (TK)
essential for the biosyntheses of some aromatic amino acids
pounds 6b, 6d and 6e showed lower binding affinities (DSs ≤ 8.8)
(Table 4).
(
Phe, Tyr, Trp), 7,8-dihydropteroate, and DNA, respectively, com-
In most cases, the binding affinities of all arylidenepyrazolones
6a-f to UGM enzyme were higher than to any other enzyme
listed in Table 4. Despite the fact, we believe that only DSs for
in vitro active compounds appear to be of practical interest. In-
cidentally, these were noticed to decrease in the same direction
7
See footnote 6
8

A.V. Erkin, A.V. Yurieva, O.S. Yuzikhin et al.
Journal of Molecular Structure 1243 (2021) 130863
Scheme 1. Synthetic sequence for the preparation of compounds 6a-f Reagents and conditions: i – POCl3, 115°C, 20 min; ii – (H2N)2·H2O, 80°C, 30 min; iii – AcCH2COOEt,
1
2
3
H2O, reflux, 1h; iv – 3-R -4-R -5-R C6H2CHO, AcOH, 80°C, 1 h.
Scheme 2. Proposed mechanism for the formation of arylidenepyrazolones 6a-f, 13 and methylenebispyrazol-3-ols 11, 14 10, Pyr = 2-amino-6-methylpyrimidin-4-yl 11,
R1
=
R2
=
R
3
=
H, Pyr
=
2-amino-6-methylpyrimidin-4-yl 12, Pyr
=
6-methyl-2-(methylsulfanyl)pyrimidin-4-yl 13,
R
1
=
R
3
=
H,
R
2
=
Me2N, Pyr
=
6-methyl-2-
1
3
2
(
methylsulfanyl)pyrimidin-4-yl 14, R = R = H, R = NO2, Pyr = 6-methyl-2-(methylsulfanyl)pyrimidin-4-yl.
Table 6
taken into account in the forthcoming structural optimization of
the mentioned compounds.
H-bond interactions of compound 6e.
Amino
Donor
acid
Distance (A)
˚
Acceptor
atom
Index
atom
H-A
D-A
4
. Conclusions
residue
Arg A36
+
1
2
3
4
5
6
7
8
HN
N(1)
N(1)
O(15)
3.31
2.86
1.93
3.28
2.72
3.44
2.11
3.38
3.79
3.40
2.92
3.82
3.63
3.75
3.09
3.80
+
Arg A36
Asn A43
Asn A43
Asn A43
Thr A237
Arg A353
Met A362
H2N
In summary,
2-(2-amino-6-methylpyrimidin-4-yl)-4-
H2N [C(2)]
arylmethylidene-2,4-dihydro-3H-pyrazol-3-ones 6a-f were de-
signed as novel potential anti-tubercular agents. For their
synthesis, the Knoevenagel condensation of the corresponding
pyrazol-3-ol 10 with aromatic aldehydes was performed. However,
this reaction was observed to give the desired products only when
the aldehydes with electron-donating groups at para-position
of the ring were used. All compounds 6a-f were established to
exist exclusively as (Z)-isomers in DMSO-d6 solution. In addition,
one of them, arylidenepyrazolone 6a, was shown to retain (Z)-
configuration in going from the solution to the crystalline state. Of
the products synthesized, compounds 6b, 6d and 6e were found
to exhibit anti-tubercular activity level similar to that of isoniazid.
H2N [C(4)]
H2N [N(7)] a
N(7)
O [C(4)]b
HO [C(3)]
+
N(9)
N(7)
O(24)
HN
H2N [C(2)]
a
Pyrimidine amino group.
b
Asn carboxamide group oxygen atom
as both lipophilicities (LogPs) and molecular weights (MWs) of
arylidenepyrazolones 6b, 6d and 6e did (Table S4). Therefore, all
these three parameters, DSs, LogPs, and MWs, should certainly be
9

A.V. Erkin, A.V. Yurieva, O.S. Yuzikhin et al.
Journal of Molecular Structure 1243 (2021) 130863
A plausible mode of action of arylidenepyrazolones 6b, 6d and
[12] M. Poirier, J. Pujol-Gimenez, C. Manatschal, S. Bühlmann, A. Embaby, S. Javor,
M.A. Hediger, J.-L. Reymond, Pyrazolyl-pyrimidones inhibit the function of hu-
man solute carrier protein SLC11A2 (hDMT1) by metal chelation, RSC Med.
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6e was based on their capability to act as potential inhibitors
of UDP-galactopyranose mutase involved in the biosynthesis of
arabinogalactan, a building block for the mycobacterial cell wall.
[13] T. Hirayama, K. Nakagawa, Mepirizole. Ger. Offen. 2,237,632, Feb 15, 1973,
Chem. Abstr. 78 (1973) 111350.
[14] I. Cristea, Condensation des pyrimidinyl-1-pyrazolones-5 avec des aldehydes
aromatiques, Stud. Univ. Babes-Bolyai, Chem. 33 (1988) 61–64.
Declaration of Competing Interest
[
15] I. Cristea, I. Panea, Synthesis and stereochemistry of some 4-aryli-
dene-1-pyrimidinyl-2-pyrazolin-5-ones. Part VII, Stud. Univ. Babes-Bolyai,
Chem. 40 (1995) 171–175.
The authors declare no conflict of interest.
[
[
[
16] I. Panea, I. Cristea, 1H-NMR study of condensation products of
1
-(2-pyrimidinyl)-3-methylpyrazolin-5-ones with heterocyclic aldehydes,
CRediT authorship contribution statement
Stud. Univ. Babes-Bolyai, Chem. 41 (1996) 9–12.
17] T. Lovasz, C. Paizs, I. Cristea, F.D. Irimie, Synthesis and stereochemistry of some
4
-furylidene-1-pyrimidinyl-2-pyrazolin-5-ones, Stud. Univ. Babes-Bolyai, Chem.
3 (1998) 145-148, Chem. Abstr. 137 (2002) 247640.
Andrei V. Erkin: Conceptualization, Investigation, Formal anal-
ysis, Writing – original draft. Aleksandra V. Yurieva: Investiga-
tion. Oleg S. Yuzikhin: Investigation, Formal analysis. Vladislav V.
Gurzhiy: Investigation, Formal analysis, Writing – original draft.
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