Synthesis, characterization, crystal structure and urease-inhibition activities of three 2-phenylthiazole derivatives

Article abstract of DOI:10.1016/j.molstruc.2018.06.096

Three 2-phenylthiazole derivatives were synthesized, characterized and evaluated as urease inhibitors. The structures of the 2-phenylthiazole derivatives were characterized by FT-IR, ¹H NMR and ¹³C NMR spectroscopy. Their crystal str

Full text of DOI:10.1016/j.molstruc.2018.06.096

Journal of Molecular Structure 1173 (2018) 81e91
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: http://www.elsevier.com/locate/molstruc
Synthesis, characterization, crystal structure and urease-inhibition
activities of three 2-phenylthiazole derivatives
, b, c,
Da-Hua Shi a
*, Xiao-Dong Ma b, Zong-Ming Tang b, Tong Dong b, Bao-Yun Xu b,
,
Yu-Wei Liu b c, Xiao-Kai Song b, Wei-Wei Liu b, Meng-Qiu Song b
a Key Laboratory of Marine Pharmaceutical Compound Screening, Huaihai Institute of Technology, Lianyungang, 222005, People's Republic of China
b Pharmacy School, Huaihai Institute of Technology, Lianyungang, 222005, People's Republic of China
c Co-Innovation Center of Jiangsu Marine Bio-industry Technology, Lianyungang, 222005, People's Republic of China
a r t i c l e i n f o
a b s t r a c t
Article history:
Three 2-phenylthiazole derivatives were synthesized, characterized and evaluated as urease inhibitors.
The structures of the 2-phenylthiazole derivatives were characterized by FT-IR, 1H NMR and 13C NMR
spectroscopy. Their crystal structures were also determined by single-crystal X-ray diffraction studies.
Hirshfeld surfaces analysis and their associated two dimensional fingerprint plots of compounds were
used as theoretical approach to assess driving force for crystal structure formation via the intermolecular
interactions in the crystal lattices of synthesized compounds. The study of X-ray single crystal diffraction
and Hirshfeld surfaces analysis of the prepared compounds shows NeH/O hydrogen bonds and CeH/O
intermolecular interactions among molecules of synthesized compounds. The urease-inhibition activities
of the synthesized compounds were tested by phenol red method. Among the three compounds, the
compound N-cyclohexyl-2-(4-methoxyphenyl)thiazole-4-carboxamide (5b) showed the best urease
Received 21 January 2018
Received in revised form
3 June 2018
Accepted 24 June 2018
Available online 26 June 2018
Keywords:
2-Phenylthiazole derivatives
Hirshfeld surface analyses
Crystal structure
Urease
inhibitory activity with the IC50 of 1.82 mM. The docking study performed demonstrated that compound
N-cyclohexyl-2-(4-methoxyphenyl)thiazole-4- carboxamide could interact with the catalytic active site
of urease.
© 2018 Elsevier B.V. All rights reserved.
1. Introduction
pivotal part in the inhibition of the harmful effects of urease
enzyme and substantially improve human health. Numerous ure-
Urease (urea amidohydrolase; E.C.3.5.1.5) is a nickel-containing
metalloenzyme that catalyzes the hydrolysis of urea to form
ammonia and carbon dioxide [1]. The enzyme is found in many
plants, selected fungi, and a wide variety of prokaryotes [2]. Activity
of urease has been shown to be an important virulence determi-
nant in the pathogenesis of many clinical conditions which are
detrimental for human and animal health as well as for agriculture
[3]. It is also known to be a major cause of pathologies induced by
Helicobacter pylori which allows the bacteria to survive at the low
pH of the stomach during colonization and therefore plays an
important role in the pathogenesis of gastric and peptic ulcers
which may lead to cancer [4]. Various strategies based on urease
inhibition were considered as treatment approaches for infections
caused by urease-producing bacteria [5]. Urease inhibitors play a
ase inhibitors such as hydroxamic corrosive subordinates, hy-
droxyurea, hydroxamic acids, phosphorodiamidates, imidazoles,
quinines, thiol derivatives, and phenols, Schiff base and thiourea
derivatives have been reported [6].
Thiazole derivatives have stable structures and aromatic prop-
erties and they have wide-ranging pharmacological activities such
as antimalarial, anticancer, antifungal, anti-inflammatory, neuro-
protective activity, etc [7]. Some thiazole derivatives were reported
to possess the urease-inhibitory activities [8].
In this study, three novel 2-phenylthiazole derivatives have
been synthesized and characterized by infrared and nuclear mag-
netic resonance spectroscopy. The roles of intermolecular in-
teractions of these compounds have been analyzed through single
crystal structure studies. Also, we report detailed analysis of
* Corresponding author. Key Laboratory of Marine Pharmaceutical Compound Screening, Huaihai Institute of Technology, Lianyungang, 222005, People's Republic of China.
E-mail address: shidahua@hhit.edu.cn (D.-H. Shi).
https://doi.org/10.1016/j.molstruc.2018.06.096
0022-2860/© 2018 Elsevier B.V. All rights reserved.

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D.-H. Shi et al. / Journal of Molecular Structure 1173 (2018) 81e91
intermolecular interactions by Hirshfeld surfaces analysis. The
urease-inhibition activities of the three compounds were tested
in vitro. To understand the mechanism of the anti-urease activities
of the synthesized compounds, the in silico approach was used by
performing molecular modeling and docking studies on the x-ray
crystal of jack bean urease (PDB ID:4H9M) using the MOE program.
diffractometer.
2.2. Synthesis of compound 5a-5c
The target compounds (5a-5c) were synthesized according to
Scheme 1. A mixture of para-hydroxythiobenzamide (1) (3.93 g,
25.67 mmol) and ethyl bromopyruvate (2) (5.00 g, 25.64 mmol)
were combined in ethanol (50 mL). The reaction mixture was
refluxed for 4 h, after which the reaction mixture was cooled and
distilled water (100 mL) was added to it. The precipitated solid was
filtered and washed with distilled water (50 mL), dried under
reduced pressure to obtain ethyl 2-(4-hydroxyphenyl)thiazole-4-
carboxylate (3) as a white solid. Compound 3 (1.00 g, 4.02 mmol)
was combined with methyl iodide (8.04 mmol), K2CO3 (1.11 g,
8.04 mmol) and DMF (8 mL). The reaction mixture was heat to 40 ꢀC
for 8 h. The reaction mixture was cooled and DMF was evaporated
under reduced pressure. The residue was extracted with ethyl ac-
etate (50 mL), filtered and evaporated under reduced pressure to
yield the crude product that was purified by column chromatog-
raphy using petroleum ether and ethyl acetate (4:1) as an eluent to
obtain 2-(4-methoxyphenyl)thiazole-4-carboxylate (4) as white
solid. KOH (0.83 g) was added in to the solution of compound 4 (1 g)
2. Experimental
2.1. General instrumentations and materials
All synthetic reagents with AR grade were purchased from
Aladdin Industrial Corporation and were used as received. Urease
was purchased from Sigma-Aldrich Inc. TLC was performed on the
glassbacked silica gel sheets (Silica Gel 60 GF254) and visualized in
UV light (254 nm). Melting points were determined on a Yanaco
melting point apparatus and are uncorrected. The NMR spectra
were recorded in CDCl3 solvent on a Bruker Avance 500 MHz in-
strument. Infrared Infrared (IR) spectra were recorded on a Thermo
Scientific Nicolet iS10 spectrometer in KBr. HRMS were acquired
using an Agilent 6200 Series TOF. The X-ray single crystal diffrac-
tion data were recorded on
a Bruker SMART APEX-II CCD
Scheme 1. Synthesis scheme of 2-phenylthiazole derivatives.

D.-H. Shi et al. / Journal of Molecular Structure 1173 (2018) 81e91
83
Table 1
Selected bond lengths (Å) and angles (o) for the compound 5a, 5b and 5c.
5a
Bond lengths
S(1)eC(8)
S(1)eC(10)
N(1)eC(8)
N(1)eC(9)
1.7353(17)
1.6971(19)
1.307(2)
1.375(2)
1.346(2)
N(2)eC(12)
N(2)eC(14)
O(1)eC(1)
O(1)eC(2)
O(2)eC(11)
1.460(2)
1.462(2)
1.426(3)
1.365(2)
1.231(2)
N(2)eC(11)
Bond angles
C(2)-O(1)-C(1)
C(8)-N(1)-C(9)
C(9)-C(10)-S(1)
C(10)-S(1)-C(8)
C(11)-N(2)-C(12)
C(11)-N(2)-C(14)
N(1)-C(8)-S(1)
5b
118.49(18)
111.27(14)
110.29(14)
89.91(8)
125.10(14)
118.11(14)
113.45(13)
N(1)-C(8)-C(5)
N(1)-C(9)-C(11)
N(2)-C(11)-C(9)
N(2)-C(12)-C(13)
O(1)-C(2)-C(3)
O(2)-C(11)-N(2)
O(2)-C(11)-C(9)
123.96(15)
122.45(14)
119.75(14)
113.49(15)
115.63(17)
121.62(16)
118.63(16)
Bond lengths
S(1)eC(8)
S(1)eC(10)
N(1)eC(8)
N(1)eC(9)
1.734(2)
1.693(3)
1.304(3)
1.372(3)
1.334(3)
N(2)eC(12)
O(1)eC(1)
O(1)eC(2)
O(2)eC(11)
1.448(3)
1.403(4)
1.365(3)
1.232(2)
N(2)eC(11)
Bond angles
C(2)-O(1)-C(1)
C(5)-C(8)-S(1)
C(8)-N(1)-C(9)
C(10)-S(1)-C(8)
C(10)-C(9)-N(1)
C(11)-N(2)-C(12)
N(1)-C(8)-S(1)
N(1)-C(8)-C(5)
5c
118.5(2)
121.9(2)
110.7(2)
89.37(14)
115.3(3)
122.9(2)
113.85(19)
124.2(2)
N(1)-C(9)-C(11)
N(2)-C(11)-C(9)
N(2)-C(12)-C(13)
N(2)-C(12)-C(17)
O(1)-C(2)-C(3)
121.4(2)
116.5(2)
111.4(2)
111.5(2)
124.9(3)
122.4(3)
121.0(2)
O(2)-C(11)-N(2)
O(2)-C(11)-C(9)
Bond lengths
S(1)eC(8)
S(1)eC(10)
N(1)eC(8)
N(1)eC(9)
1.740(3)
1.694(3)
1.306(4)
1.374(4)
1.340(4)
N(2)eC(12)
N(2)eC(16)
O(1)eC(1)
O(1)eC(2)
O(2)eC(11)
1.460(4)
1.478(4)
1.430(5)
1.372(4)
1.230(4)
N(2)eC(11)
Bond angles
C(2)-O(1)-C(1)
C(8)-N(1)-C(9)
C(10)-S(1)-C(8)
C(10)-C(9)-N(1)
C(11)-N(2)-C(12)
N(1)-C(8)-S(1)
N(1)-C(8)-C(5)
117.4(3)
110.9(2)
89.49(14)
115.3(3)
127.1(3)
113.7(2)
125.3(2)
N(1)-C(9)-C(11)
N(2)-C(11)-C(9)
N(2)-C(12)-C(13)
N(2)-C(16)-C(15)
O(1)-C(2)-C(3)
124.4(2)
119.7(3)
110.3(3)
111.2(3)
116.0(3)
118.1(3)
122.1(3)
O(2)-C(11)-C(9)
O(2)-C(11)-N(2)
in 15 mL anhydrous methanol and reflux for 9 h. After reaction, the
solution was neutralized to pH 5 and poured into cool water
(100 mL). The residue was filtered and dried to obtain the 2-(4-
methoxyphenyl)thiazole-4-carboxylic acid. Sulfoxide chloride
(0.45 mL) was added to the solution of 2-(4-methoxyphenyl)thia-
zole-4-carboxylic acid (0.4 g) in the dichloromethane (10 mL) and
reflux for 10 h. When the reaction was completed, solvent was
evaporated under reduced pressure. The residual mass was dis-
solved into dichloromethane (10 mL). Then the amine was added to
the solution and reflux for another 6 h. When the reaction was
finished, the solvent was evaporated under reduced pressure. The
cmꢁ1): 3072, 2987, 2972, 2931, 2851,1625,1611,1575,1519,1462; 1H
NMR (500 MHz, CDCl3)
d
7.89 (d, J ¼ 8.6 Hz, 2H), 7.82 (s, 1H), 6.96 (d,
J ¼ 8.6 Hz, 2H), 3.87 (s, 3H), 3.72 (d, J ¼ 6.4 Hz, 2H), 3.56 (d,
J ¼ 6.8 Hz, 2H), 1.33 (t, J ¼ 6.5 Hz, 3H), 1.27 (t, J ¼ 6.8 Hz, 3H); 13C
NMR (126 MHz, CDCl3)
d 166.8, 163.5, 161.3, 152.0, 128.1, 126.4,
122.7, 114.4, 55.5, 43.5, 41.1, 14.7, 12.9. HRMS (ESI) calcd. for
C
15H18N2O2S [MþNa]þ: m/z 313.0981; found: m/z 313.0995.
2.2.2. N-cyclohexyl-2-(4-methoxyphenyl)thiazole-4-carboxamide
(5b)
White crystals, yield: 78.1%; mp: 141.2e142.5 ꢀC. IR (KBr ʋmax
residual
was
purified
using
column
chromatograph
cmꢁ1): 3291, 3006, 2938, 2853, 1641, 1605, 1541, 1521, 1483, 1460;
(CH2Cl2:CH3OH ¼ 15:1) to get 2-phenylthiazole derivatives 5a-c.
The forming compounds were grown at room temperature from
organic solvent (methanol and dichloromethane) for single crystals
of compounds 5a-5c, respectively.
1H NMR (500 MHz, CDCl3)
d
8.00 (s, 1H), 7.89 (d, J ¼ 8.5 Hz, 2H), 7.33
(d, J ¼ 8.0 Hz,1H), 6.97 (d, J ¼ 8.5 Hz, 2H), 4.05e3.92 (m, 1H), 3.88 (s,
3H), 2.04 (dd, J ¼ 12.2, 3.0 Hz, 2H), 1.84e1.72 (m, 2H), 1.52e1.38 (m,
2H), 1.38e1.16 (m, 4H); 13C NMR (126 MHz, CDCl3)
d 167.9, 161.5,
2.2.1. N,N-diethyl-2-(4-methoxyphenyl)thiazole-4-carboxamide
(5a)
160.3, 151.0, 128.2, 125.9, 121.8, 114.4, 55.5, 48.1, 33.2, 25.6, 24.9;
HRMS (ESI) calcd. for C17H20N2O2S [MþNa]þ: m/z 339.1138; found:
m/z 339.1148.
Yellow crystals, yield: 51.0%; mp: 69.2e71.5 ꢀC; IR (KBr ʋmax

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D.-H. Shi et al. / Journal of Molecular Structure 1173 (2018) 81e91
2.2.3. (3,5-dimethylpiperidin-1-yl)(2-(4-methoxyphenyl)thiazol-4-
yl)methanone (5c)
nickel-containing catalytic site) was obtained from the RCSB Pro-
tein Data Bank (www.rcsb.org/pdb). Docking simulations were
performed on the compound 5c with Molecular Operating Envi-
ronment (MOE) [16] using the CHARMm force field. Enzyme
structure of 3LA4 was checked for missing atoms, bonds and con-
tacts. Hydrogens and partial charges were added using the pro-
tonate 3D application in MOE. The compound 5c was drawn in MOE
then protonated using the protonate 3D protocol and energy was
minimized using the MMFF94 ꢂ force field in MOE. After the
enzyme and the ligand were ready for the docking study, com-
pound 5c was docked into the active site of the protein which was
determined by acetohydroxamic acid by the “Triangle Matcher”
method. The Dock scoring in MOE software was done using ASE
scoring function and forcefield was selected as the refinement
method. The best 10 poses of molecules were retained and scored.
After docking, the geometry of resulting complex was studied using
the MOE's pose viewer utility.
White crystals, yield: 72.%; mp: 122.5e123.9 ꢀC; IR (KBr ʋmax
cmꢁ1): 3091, 2954, 2924, 2872, 2837, 1616, 1576, 1520, 1505, 1459;
1H NMR (500 MHz, CDCl3)
d
7.89 (d, J ¼ 8.5 Hz, 2H), 7.75 (s, 1H), 6.96
(d, J ¼ 8.6 Hz, 2H), 4.69 (d, J ¼ 12.1 Hz, 1H), 4.48 (d, J ¼ 12.7 Hz, 1H),
3.87 (s, 3H), 2.56 (t, J ¼ 12.2 Hz, 1H), 2.24 (t, J ¼ 12.0 Hz, 1H), 1.87 (t,
J ¼ 12.3 Hz, 1H), 1.78 (s, 1H), 1.68e1.58 (m, 1H), 1.33e1.18 (m, 1H),
0.96 (d, J ¼ 6.1 Hz, 3H), 0.87 (d, J ¼ 6.1 Hz, 3H); 13C NMR (126 MHz,
CDCl3)
d 167.0, 162.6, 161.4, 151.6, 128.1, 126.2, 122.45, 122.41, 114.4,
55.5, 54.4, 50.0, 42.6, 32.3, 31.2, 19.2, 19.0; HRMS (ESI) calcd. for
C
18H22N2O2S [MþNa]þ: m/z 353.1294; found: m/z 353.1309.
2.3. Single crystal XRD studies
Crystals of compound 5a-c were grown by slow evaporation of
methanol and dichloromethane at room temperature, respectively.
Diffraction intensities for the compounds were collected at 296(2)
K using a Bruker SMART APEX-II CCD area-detector with MoK
a
radiation (
l
¼ 0.71073 Å). The collected data were reduced with the
SAINT program [9,10], and multi-scan absorption corrections were
performed using the SADABS program [11]. Structures were solved
by direct methods and refined against F2 by full-matrix least-
squares methods using the SHELXTL package [12]. All of the non-
hydrogen atoms were refined anisotropically. Hydrogen atoms
were placed in calculated positions and constrained to ride on their
parent atoms. The Mercury programs [13] were used to describe the
molecular structures. The crystallographic data for the compounds
are summarized in Table 1 in the supporting information.
2.4. Hirshfeld surfaces analysis
Analysis of Hirshfeld surfaces and their associated two dimen-
sional fingerprint plots of compounds 5a, 5b and 5c were calculated
by using CrystalExplorer17 [14]. The Hirshfeld surfaces are mapped
with different properties dnorm, shape index, curvedness. The dnorm
is normalized contact distance, defined in terms of de, di and the
vdW radii of the atoms. The combination of de and di in the form of
a 2D fingerprint plot displays summary of intermolecular contacts
in the crystal.
2.5. In vitro urease activity assay
The measurement of urease inhibitory activities was carried out
according to the method reported by Tanaka [15]. Generally, the
assay mixture, containing 25
mL of jack bean urease (10 kU/L) and
25 L of the tested compounds of various concentrations (dissolved
m
in the solution of DMSO:H2O ¼ 1:1 (v/v)), was preincubated for
1 h at 37 ꢀC in a 96-well assay plate. Then 0.2 mL of 100 mM Hepes
[N-(2-hydroxyethyl)piperazine-N’-(2-ethanesulfonic acid)] buffer
at pH 6.8 containing 500 mM urea and 0.002% phenol red were
added and incubated at 37 ꢀC. The reaction time, which was
required to produce enough ammonium carbonate to raise the pH
of a Hepes buffer from 6.8 to 7.7, was measured by a micro-plate
reader (570 nm) with the end-point being determined by the co-
lor of phenol red indicator. The acetohydroxamic acid was used as
the standard reference. All the tests were carried out for three
times.
2.6. Molecular modeling evaluations
Fig. 1. The structures of the compounds 5a, 5b and 5c with thermal ellipsoids drawn at
50% probability.
The pdb structure of Jack bean urease (PDB code: 4H9M, a
complex co-crystallized with inhibitor acetohydroxamic acid at the

D.-H. Shi et al. / Journal of Molecular Structure 1173 (2018) 81e91
85
3. Results and discussion
3.1. Spectral characterization
The route for the synthesis of the desired compounds 5a-5c is
illustrated in Scheme 1. All crude products 5a-5c were purified by
silica gel column chromatography. Purity of the obtained com-
pounds was checked by the TLC. The compounds were character-
ized by FT-IR, NMR, HRMS techniques and X-ray crystallography. All
Fig. 2. Packing diagrams of the compounds 5a, 5b and 5c viewed along the b axis.
Fig. 3. Hirshfeld surface mapped with dnorm for the compounds 5a, 5b and 5c.

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D.-H. Shi et al. / Journal of Molecular Structure 1173 (2018) 81e91
Fig. 4. The 2D fingerprint plots of the compounds 5a.
the result substantiates the structures proposed.
for compounds 5a, 5b and 5c respectively. The carbons of thiazole
rings are observed at 121.8 ppme167.9 ppm for the three com-
pounds. The HRMS spectrum of compound 5a-5c show [MþH]þ
peak at m/z: 313.0995, 339.1148, and 353.1309 corresponding to
The FT-IR spectrum of the prepared compounds are showed by a
strong broad absorption at the range of 1616e1641 cmꢁ1 which can
be assigned to the
in the range of 2837e2987 cmꢁ1 are corresponding to the
of the alkane chain for compounds 5a, 5b and 5c. The mode of
y
(C]O) stretches. The absorption bands falling
y
(CeH)
C15H18N2NaO2S
[MþH]þ,
C17H20N2NaO2S
[MþH]þ
and
y
C
18H22N2NaO2S [MþH]þ for compounds 5a, 5b and 5c respectively.
(CeH) appears at the range of 3006e3091 cmꢁ1 suggests the
presence of the aromatic benzene rings of the three compounds.
The band located at 3291 cmꢁ1 of the IR of compound 5b reveals the
existence of the stretching vibration of NeH in this compound. In
the 1H NMR spectrum of the prepared compounds, displayed the
protons of thiazole ring at 7.82 ppm, 8.00 ppm, and 7.75 ppm
respectively as singlets for compound 5a, 5b and 5c. The protons of
1,4-disubstituted benzene ring are observed as two 2H doublets at
7.89 ppm and 6.96 ppm (6.97 ppm for compound 5b) respectively.
Furthermore, amide- NH proton appears as a doublet at 7.33 ppm
for the compound 5b. The appeared signals of all the protons of the
compound 5a-5c were found as to be in their expected region. In
the 13C NMR spectra the characteristic phenyl signals are observed
at 114.4 ppme161.4 ppm for compounds 5a, 5b and 5c. The signals
of the carbonyl are found at 163.5 ppm, 161.5 ppm and 162.6 ppm
3.2. Crystal structure of the 2-phenylthiazole derivatives
The structures of compounds 5a, 5b and 5c were demonstrated
by X-ray diffraction analysis. The crystal data were presented in
Table 1 in supporting information, Figs. 1 and 2. The three com-
pounds possessed the similar structures. The compound 5a and
compound 5c had the same crystal system of triclinic and the same
space group of P-1. But the compound 5b had the different crystal
system (monoclinic) and space group (P2(1)/c). The selected bond
lengths and angles of the three 2-phenylthiazole derivatives were
listed in Table 1. All of the three compounds consist of one aromatic
phenyl ring (C5 phenyl) and one thiazole ring. The thiazole rings
(S1/C8/N1/C10) make dihedral angles of 4.49(0.09)o, 7.18(0.16)o and
6.15(0.22)o with phenyl rings (C2/C3/C4/C5/C6/C7) for compounds

D.-H. Shi et al. / Journal of Molecular Structure 1173 (2018) 81e91
87
Fig. 5. The 2D fingerprint plots of the compounds 5b.
5a, 5b and 5c respectively. The cyclohexyl ring of compound 5b
adopts chair conformation as expected and all other bond param-
eters are normal. The 3,5-dimethylpiperidin ring of compound 5c
adopts chair conformation too. The three compounds possessed the
similar bond lengths with S1eC8 of 1.734e1.1.740 Å, S1eC10 of
1.693e1.697 Å and N1eC8 of 1.307e1.306 Å. The bond length of
C1eO1 for compound 5a and 5c were 1.426 Å and 1.430 Å respec-
tively. While, the bond length of C1eO1 for compound 5b was
1.403 Å. The packing diagrams of the compounds 5a, 5b and 5c
viewed along the b axis are showed in Fig. 2. The crystal packing
diagrams of three compounds are different. In compound 5b,
strong intermolecular NeH/O hydrogen bond (N2eH18...O2j,
intermolecular interactions and packing modes. The dnorm mapped
on Hirshfeld surface and selected 2D finger print plots of different
interaction of all the three compounds are shown in Figs. 3e6. For
the compound 5a, 5b and 5c, the red regions mainly indicate O/H
interaction. The dnorm map of compound 5a shows two pairs of
adjacent deep-red regions. One pairs of the deep-red regions
demonstrate the strong CeH/O intermolecular interactions be-
tween the thiazole group and the amide group. The other pairs of
the deep-red regions demonstrate the CeH/O intermolecular in-
teractions between the methoxy and the amide group. The dnorm
map of compound 5b shows two deep-red regions which demon-
strate the strong NeH/O hydrogen bonds forming corresponding
crystal packing pattern. The dnorm map of compound 5c shows a
pair of adjacent deep-red regions which demonstrate the CeH/O
intermolecular interactions forming dimers in the corresponding
crystal packing patterns.
j
2.924(3) Å, x,-yþ3/2,zþ1/2) occur between the oxygen atom of
amide group and the NeH of the amide group of another molecule.
There is no hydrogen bond for compound 5a and 5c.
3.3. Hirshfeld surface analysis
Their 2D fingerprint plots of the main intermolecular contacts
for compounds 5a, 5b and 5c are depicted in Figs. 4e6. H/H
intermolecular contacts with contribution of 53.6%, 56.9% and
52.9% of the overall contacts for compounds 5a, 5b and 5c
Hirshfeld surfaces and finger print plots were generated for all
the three compounds, analyzed in order to understand the different

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D.-H. Shi et al. / Journal of Molecular Structure 1173 (2018) 81e91
Fig. 6. The 2D fingerprint plots of the compounds 5c.
Table 2
The percentages of the various interactions contributions to the total Hirshfeld surface area of the compounds 5a, 5b and 5c.
Interactions
Percentage (%)
Compound 5a
Compound 5b
Compound 5c
H/H
C/H
O/H
N/H
S /H
C/C
C/O
C/N
C/S
N/S
O/S
S/S
53.6
15.0
14.6
3.3
7.5
2.9
0.1
0.3
2.8
0.0
56.9
13.5
12.6
2.8
6.0
3.3
0.8
0.9
2.0
1.2
52.9
21.0
13.6
3.7
6.8
0.4
0.4
0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.2
0.9

D.-H. Shi et al. / Journal of Molecular Structure 1173 (2018) 81e91
89
Table 3
compound 5b could inhibit the urease at the concentration of
100 g/mL. The compound 5b which had a N-cyclohexyl substitu-
ent possessed the best inhibitory activity of urease (IC50 ¼ 1.52 M).
The urease-inhibition activity of compound 5b was better than the
M). The compound
inhibited urease with a dose-dependent relationship (Fig. 7). The
urease inhibitory activities reported here were comparable to that
of the hybrid benzothiazole analogs reported by Taha et al. which
The urease-inhibition activities of 2-phenylthiazole derivatives.
m
IC50 (m
M)a
m
Comp.
Structure
5a
e
stand compound thiourea (IC50 ¼ 18.14
m
inhibited urease with IC50 varying from 1.4 to 34.43
mM [8]. The
urease inhibitory activity of compound 5b was better than that of
5b
1.82 0.12
compound
6-(4-methoxyphenyl)
g/mL) and N-(6-(p-tolyl)benzo[d]thiazol-2-yl)acet-
g/mL) which synthesized by Gull et al. [17] [18].
benzo[d]thiazole-2-amine
(IC50 ¼ 26.35
m
amide (IC50 ¼ 16.5
m
A series of iminothiazoline-sulfonamide hybrids with potent urease
inhibitory activities were reported by Saeed et al. The compound
(Z)eN-(3-(4-aminosulfonylphenyl)-4-methylthiazol-2(3H)-yli-
dene)-2-chloro-4- nitrobenzamide could inhibited urease with IC50
5c
e
of 0.058 mM [19].
3.5. Molecular modeling study
To understand the binding mode of the compound 5b with the
urease, the compound was docked with urease from jack bean (PDB
code: 4H9M) with MOE program. The jack bean urease structure
was selected for the molecular modeling study because the bio-
logical assay was based on the enzyme. The molecule docking of the
compound 5b with urease showed that the compound 5b could
interact with the catalytic active site of urease as acetohydroxamic
acid (Fig. 8) [13]. When compound 5b was docked with urease, the
compound could interact with the active site of the enzyme. The
proton on the amide group could interact with ALA 636 via the
hydrogen bonds. The oxygen atom of the methoxy group of this
compound could interacted with HIS 519 and HIS 545 near the Ni
atom of urease via the hydrogen bonds. Acetohydroxamic acid also
could interacted with HIS 519 via hydrogen bond. While, compound
5a and 5c which possessed poor urease-inhibition activities
showed weak interaction with urease, with only one hydrogen
bond with urease respectively (Fig. 1 and 0.2 in the Electronic
Supplementary Information file). According to the results of
Hirshfeld surface analysis, only compound 5b possessed the inter-
molecular NeH/O hydrogen bonds. It seems that compound 5b
which possessed the intermolecular hydrogen bonds has better
urease-inhibition activity than other two compounds. The proton
on the amide group of compound 5b can be hydrogen bond donor
and interact with ALA 636 of urease via the hydrogen bonds. While,
there is no proton on the amide group of compound 5a and 5c. This
maybe the reason that why compound 5b possessed better urease-
inhibition activity than compound 5a and 5c.
Thiourea
18.14 0.16
a
The results were expressed as mean SD. n ¼ 3.
Fig. 7. Dose-dependent inhibition of compound 5b against urease. Values are
means SD, n ¼ 3.
4. Conclusion
respectively are the major contributor to the Hirshfeld surface. The
O/H intermolecular contacts being one of the strong contacts due
to the presence of CeH/O intermolecular interactions (compound
5a and 5c) and NeH/O hydrogen bonds (compound 5b) contrib-
utes to the Hirshfeld surface by 14.6%, 12.6% and 12.6% of the overall
contacts for compounds 5a, 5b and 5c respectively. Besides the
contacts mentioned above, the presence of C/H, N/H, S/H and
other interactions are summarized in Table 2.
In this study, three 2-phenylthiazole derivatives were synthe-
sized with simple ways and high yields. The structures of the three
compounds were determined by IR, NMR, HRMS and X-ray Crys-
tallography. Only compound 5b showed the intermolecular
hydrogen bond based on the crystallographic studies. Also, we
report detailed analysis of intermolecular interaction of all com-
pounds by Hirshfeld surface analysis and associated fingerprint
plots. Hirshfeld surface analysis and associated fingerprint plots
showed that H/H intermolecular contacts are the major contrib-
utor to the Hirshfeld surface. The O/H intermolecular contacts
being one of the strong contacts due to the presence of CeH/O
intermolecular interactions and NeH/O hydrogen bonds in com-
pounds 5a, 5b and 5c. The urease inhibitory activities of the 5-
benzyl-1,3,4-thiadiazole derivatives were evaluated in vitro. The
3.4. In vitro inhibition studies of urease
To determine urease inhibitory activities, the compounds were
measured in vitro using phenol red method [11]. Acetohydroxamic
acid was measured as a standard for the comparative purpose. The
results were summarized in Table 3. The results showed only

90
D.-H. Shi et al. / Journal of Molecular Structure 1173 (2018) 81e91
Fig. 8. The urease active site cavity (A) and interaction map (B) displaying the binding and interactions of compound 5b with urease (The green compound was acetohydroxamic
acid). (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)

D.-H. Shi et al. / Journal of Molecular Structure 1173 (2018) 81e91
91
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Acknowledgements
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We gratefully acknowledge financial supports of Natural Science
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Jiangsu key laboratory of marine pharmaceutical compound
screening (2015HYB07, HY201603), research and innovation pro-
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(XKYCXX2017-13) and project funded by the priority academic
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Supplementary data related to this article can be found at
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