Synthesis and evaluation of novel diphenylthiazole derivatives as potential anti-inflammatory agents

Article abstract of DOI:10.1007/s00044-015-1418-5

In the presented study, we synthesized a novel series of 18 diphenylthiazole derivatives and tested their anti-inflammatory properties. They showed significant anti-inflammatory properties in inflamed mice paws animal model. Docking-based analysis suggested that they act as COX enzyme inhibitors. The most potent compound 9e is significantly more active in reducing inflamed animal paws compared to diclofenac. Accordingly, we believe these compounds are good leads for further development into potent anti-inflammatory drugs.

Full text of DOI:10.1007/s00044-015-1418-5

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res
DOI 10.1007/s00044-015-1418-5
ORIGINAL RESEARCH
Synthesis and evaluation of novel diphenylthiazole derivatives
as potential anti-inflammatory agents
Ahmed H. Abdelazeem1 Maha Habash2 Ibrahim A. Maghrabi3 Mutasem O. Taha4
•
•
•
Received: 26 October 2014 / Accepted: 15 July 2015
Ó Springer Science+Business Media New York 2015
Abstract In the presented study, we synthesized a novel
series of 18 diphenylthiazole derivatives and tested their
anti-inflammatory properties. They showed significant anti-
inflammatory properties in inflamed mice paws animal
model. Docking-based analysis suggested that they act as
COX enzyme inhibitors. The most potent compound 9e is
significantly more active in reducing inflamed animal paws
compared to diclofenac. Accordingly, we believe these
compounds are good leads for further development into
potent anti-inflammatory drugs.
serious ailments such as Alzheimer’s disease, cancer,
heart vascular diseases (Fitzgerald, 2004; Grosser et al.,
2006). Nonsteroidal anti-inflammatory drugs (NSAIDs),
such as ketoprofen, ibuprofen and aceclofenac, which are
currently in clinical use for the treatment of inflammatory
disorders (Fitzgerald, 2004; Grosser et al., 2006), are
associated with major drawbacks related to gastrointesti-
nal disorders such as dyspepsia, gastric ulcers and so
forth. These side effects are due to the direct contact of
their free carboxylic groups with the gastric mucosa and
due to decreased production of prostaglandins in the GIT
(Fries and Grosser, 2005; Sauzem et al., 2008). In order
to overcome these drawbacks, there is an urgent need to
design and synthesize new anti-inflammatory agents with
excellent anti-inflammatory response and minimal side
effects.
Keywords Diphenylthiazole Á Anti-inflammatory Á
Docking Á Inflamed animal paws
Introduction
Various diphenylthiazole derivatives have been suc-
cessfully tested as anti-inflammatory agents (Carter et al.,
1999; Abdelazeem et al., 2015), anti-prion agents (Heal
et al., 2007; Thompson et al., 2010), monoamine trans-
porter inhibitors (Enyedy et al., 2002) and platelet
aggregation inhibitors (Rynbrandt et al., 1981). Accord-
ingly, in response to the existing need for potent anti-
inflammatory compounds devoid of the classical NSAIDs
side effects combined with the interesting biological
profiles of diphenylthiazole derivatives, we were
prompted to undertake the synthesis of novel
diphenylthiazole derivatives devoid of any carboxylic
substituents (or any related bioisostere, e.g., sulfonamides
(Carter et al., 1999)) hoping to get improved anti-in-
flammatory activity and fewer side effects. In doing so,
we have designed two scaffolds through tethering the
diphenylthiazole skeleton, as a known anti-COXs phar-
macophore, to various hydrophobic moieties using urea
or amide linkers.
Inflammation is a physiological reaction which involves
cellular and biochemical responses that cause symptoms
for common diseases and even an early phase for some
& Mutasem O. Taha
mutasem@ju.edu.jo
1
Department of Medicinal Chemistry, Faculty of Pharmacy,
Beni-Suef University, Beni-Suef 62514, Egypt
2
Department of Pharmacognosy, Faculty of Pharmacy,
Applied Science University, Amman, Jordan
3
Department of Clinical Pharmacy, College of Pharmacy, Taif
University, Taif 21974, Saudi Arabia
4
Drug Discovery Unit, Department of Pharmaceutical
Sciences, Faculty of Pharmacy, The University of Jordan,
Amman, Jordan
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Med Chem Res
1
k. All compounds were characterized by H-NMR, 13C-
NMR, ESI–MS and elemental analyses which were
agreement with the calculated values.
Results and discussion
Chemistry
In vivo anti-inflammatory activity and docking
studies
The synthesis of the novel diphenylthiazole derivatives was
accomplished as depicted in Scheme 1. The starting
material 8, 4,5-diphenylthiazol-2-amine, was easily pre-
pared by condensation of desyl chloride 7 with thiourea in
absolute ethanol according to the reported method (Ren
et al., 2008). Subsequently, the amine 8 was reacted with
N,N’-carbonyldiimidazole (CDI) in anhydrous tetrahydro-
furan in the presence of triethylamine followed by addition
of the appropriate amine, benzyl alcohol and benzo[d]thi-
azole-2-thiol and reflux for 6 h to afford the desired com-
pounds 9a–g. It should be mentioned that compounds 9b
and 9g were reported as acyl CoA: cholesterol O-acyl-
transferase (ACAT) inhibitors which were prepared with a
different procedure via reaction of the amine starting
material 8 with the appropriate isocyanate in toluene
(Romeo et al., 1999). The reaction of chloroacetyl chloride
with amine 8 in methylene chloride and triethylamine at
0 °C furnished the intermediate 10 which in turn was
coupled with equimolar amount of various amines, benzyl
alcohol and benzo[d]thiazole-2-thiol in DMF and potas-
sium carbonate to afford the targeted compounds 11a–
We tested the anti-inflammatory properties of the prepared
compounds employing carrageenan-induced paw edema
assay performed on male BALB/c mice. We recorded the
observed reduction in the size of the inflamed paws upon
administration of 60 mg/kg (body weight) oral dose of
tested compounds 1 h before inflammation induction.
Table 1 summarizes the in vivo anti-inflammatory results
of our newly synthesized compounds, while Fig. 1 shows
the anti-inflammatory results of two potent derivatives (9e
and 11k) compared to diclofenac-treated (oral dose of
60 mg/kg body weight) and untreated controls.
Careful evaluation of the structure–activity relationship
in Table 1 shows that the structural requirements for potent
anti-inflammatory bioactivities of urea-based analogs (9a–
g) differ from those observed for the amide-based analogs
(11a–k). For example, the urea derivative 9e showed
considerable anti-inflammatory reduction in inflamed mice
paws compared to weak anti-inflammatory action for the
Scheme 1 aReagents and reactions conditions: a SOCl2, pyridine, 1 h; b thiourea, EtOH, reflux, 2 h; c CDI, appropriate amine or thiol, TEA,
THF, reflux 6 h; d ClCH2COCl, TEA, CH2Cl2, 0 °C, 5 h; e appropriate amine, alcohol or thiol, K2CO3, DMF, 60 °C, 3 h
123

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130
120
110
100
90
**
**
*
*
80
70
Control.
Dichlofenac
9e
11k
60
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
Time (hours)
Fig. 1 Effects of 9e, 11k, diclofenac and untreated controls on paw
edema induced by carrageenan in mice. Each value is represented as
mean S.E.M. *P \ 0.05, **P \ 0.01 as compared to untreated
control (one-way ANOVA)
Fig. 2 Comparison between the docked pose of celecoxib (red) as
produced by docking simulation and the crystallographic structure of this
inhibitor within COX-1 (green, PDB code: 3KK6) (Color figure online)
corresponding amide-based analog 11f. Similar trends can
be seen by comparing the anti-inflammatory properties of
11d versus 9d, Table 1. These observations suggested that
there could be two binding modes assumed by these
compounds within the binding pocket(s) of certain
inflammatory promoting enzyme(s), e.g., COX-1.
Met522, Trp387, Tyr385, Val349, Ala527 and Leu531.
On the other hand, the hydrophobic hexyl chain of 9d
seems to protrude outside the binding pocket forming
limited hydrophobic interactions with the aliphatic side
chain of Thr94 and Ser516.
This trend of interactions seems consistent among all urea-
based structures including compounds having cyclic (cyclo-
hexyl) and bicyclic (adamantane) hydrophobic aliphatic side
chains, e.g., 9a and 9b. However, urea-based compounds with
extended aliphatic side chains, i.e., 9f and 9e, apparently
exhibit superior anti-inflammatory properties, probably
because their hydrophobic character promotes their penetra-
tion across physiological membranes and binding into COX.
Interestingly, the urea derivatives 9g and 9c have med-
iocre anti-inflammatory properties. Apparently, the steric
size of the benzothiazole ring in 9c and 9g seems to cause
loss of the hydrogen bonding interaction connecting this
group with the imidazole N of His90. In both compounds,
weakened hydrogen bonding with His90 explains their
mediocre anti-inflammatory properties.
In an attempt to explain these observations, we docked
two representatives, i.e., for urea and amide-based analogs,
namely 9d and 11k, within the binding pocket of COX-1
enzyme (PDB code: 3KK6). We selected this particular
crystallographic structure for COX-1 (i.e., 3KK6) because
it includes celecoxib as co-crystallized ligand. Needless to
say that celecoxib is potent selective COX-1 inhibitor, and
should therefore appropriately imprint the binding pocket
of COX-1 (i.e., by induced fit) in such away that gives
better realistic docked poses for 9d and 11k.
We validated our docking settings by re-docking the co-
crystallized inhibitor celecoxib, i.e., after being extracted
from 3KK6, using the same docking settings intended for
9d and 11k. Figure 2 compares the docked pose of cele-
coxib with the corresponding experimental co-crystallized
structure. Clearly from the figure, our docking settings
closely reproduced the bound structure with RMSD value
On the other hand, amide-based analogs seem to assume
completely different poses within COX-1, as exemplified
by 11k shown in Fig. 3a, c. In these poses, the hydrophobic
tails of these compounds tend to be deeply embedded
inside a hydrophobic pocket comprised of Pro86, Leu93
and Ile89. Clearly from Fig. 3c, both the amidic and alpha
ether oxygen atoms of 11k are hydrogen bonded to the
guanidino side chain of Arg120. Analogous hydrogen
bonding interaction is expected with other isosteric
hydrogen bond acceptor groups (i.e., to the alpha ether in
11k) at the same position (e.g., amine groups in 11a and
11i). On the other hand, the thiazole nitrogen of 11k, and
other amide-based analogs, seems to be hydrogen bonded
to the phenolic hydroxy of Tyr355.
˚
of 0.99 A giving confidence in our docking experiment.
Figure 3 shows how 9d and 11k dock within COX-1.
Obviously from the figure, the two compounds assume
different binding modes within COX-1, which agrees with
our previous suggestion.
Apparently, urea-based compounds, e.g., 9d, assume a
binding mode, shown in Fig. 3, in which the urea system is
tightly hydrogen bonded to the side chains of Tyr355,
His90 and Gln192, while the diphenylthiazole groups are
hydrophobically stacked within a hydrophobic pouch
composed of the hydrophobic side chains of Phe518,
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Med Chem Res
Fig. 3 A overlay of docked
poses of 9d (green) and
11 k (red) within COX-1
(A)
enzyme (PDB code: 3KK6),
B and C are the separate docked
poses of 9d and 11 m,
respectively, D and E are the
chemical structures of 9d and
11k, respectively. Green lines in
B and C represent hydrogen
bonds (Color figure online)
(B)
(D)
O
S
N
N
H
N
H
(C)
(E)
N
S
O
N
H
O
Apparently, amide analogs with fairly large hydrophobic
tails (e.g., 11f) tend to sterically clash with the hydrophobic
side chains of Pro86, Leu93 and Ile89, which might
explain their inferior bioactivities. However, amide analogs
of larger hydrophobic chains (e.g., 11g and 11h) seem to
have comparably enhanced anti-inflammatory properties
because their hydrophobic character helps them to pene-
trate different physiological membranes and allow them to
reach inflammatory sites more efficiently.
causing the apparent weak anti-inflammatory potential of
11i, i.e., compared to 11a and 11k.
Finally, 11b and 11j exhibited moderate anti-inflam-
matory properties, which seem to be related to their ben-
zothiazole rings. The electron-withdrawing properties of
benzothiazoles in these compounds should significantly
reduce the electronic densities on the corresponding alpha
heteroatoms (NH in 11b and S in 11j), which should
undermine their hydrogen bond acceptor propensities with
the guanidino side chain of Arg120 leading to inferior
ligand COX-1 affinities and therefore reduced anti-in-
flammatory properties. Unsurprisingly, these effects are
On the contrary, the hydrophilicity 11i, which is related
to its piperidine ring, renders the compound too hydrophilic
and therefore less penetrant of inflammatory tissues
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from 95 % ethanol. The product 8 was obtained as yellow
crystals (75 %).
augmented in 11c. The absence of the aromatic electronic
density of the fused benzene ring in benzothiazole (i.e.,
11b and 11j) renders simple thiazole (11c) rings signifi-
cantly more electron withdrawing compared to benzothia-
zole, which should further reduce the hydrogen bonding
acceptor tendency of the respective alpha NH in 11c
leading to the observed inferior anti-inflammatory proper-
ties of 11c compared to 11b and 11j.
General procedure A Synthesis of compounds (9a–g) To
a suspension of compound 8 (2 mmol) in THF (40 mL)
was stirred at room temperature during addition of N,N0-
carbonyldiimidazole (CDI, 3 mmol). The mixture was
stirred for 2 h and treated with dropwise addition of vari-
ous amines, alcohols or thiols (2.1 mmol) in anhydrous
THF (10 mL). Then, the mixture was refluxed for more
6 h. The resulting reaction mixture was cooled to room
temperature and distilled under reduced pressure. Water
(50 mL) was added to remove excess CDI. The aqueous
layer was extracted with methylene chloride (3 9 30 mL).
The combined organic extract was washed with water
(30 mL) and brine (30 mL), respectively, and then dried
with anhydrous Na2SO4. The solvent was removed in
vacuo, and the residue was purified by flash column
chromatography (SiO2) using hexane/ethylacetate (8: 2) as
eluent to afford compounds 9a–g.
Experimental protocols: chemistry
Chemical reagents and solvents were obtained from com-
mercial sources. Solvents are dried by standard methods
when necessary. Melting points (m.p.) were uncorrected and
were carried out by open capillary tube method using IA
9100MK-Digital Melting Point Apparatus. Microanalyses
were measured at the Microanalytical Center, Faculty of
Science, Cairo University. The proton magnetic resonance
1H-NMR spectra were recorded on a Bruker APX400 spec-
trometer at 400 MHz in the specified solvent, chemical shifts
were reported on the d scale and were related to that of the
solvent, and J values are given in Hz. 13C NMR spectra were
obtained on a Bruker APX400 at 100 MHz at the Faculty of
Pharmacy, Beni-Suef University. Mass spectra were recor-
ded onShimadzu Qp-2010Plus, mass spectrometer, at 70 eV
(EI) at the Microanalytical Center, Faculty of Science, Cairo
University. Thin layer chromatography was done using
Macherey–Nagel Alugram Sil G/UV254 silica gel plates and
CH2Cl2:MeOH (9.5:0.5) as the eluting system.
1-(adamantan-2-yl)-3-(4,5-diphenylthiazol-2-yl)urea (9a)
White solid (EtOH): This compound was prepared from
4,5-diphenylthiazol-2-amine 8 (2 mmol) and adamantan-2-
amine (2.1 mmol) according to general Procedure A. The
product was obtained as a white solid. Yield 69 %, mp
1
209-210 °C. H NMR (400 MHz, DMSO-d6) d 1.53–1.59
(m, 2H), 1.70–1.85 (m, 10H), 1.06–2.09 (m, 2H),
3.81–3.92 (m, 1H), 7.15 (s, 1H, NH), 7.22–7.42 (m, 8H),
7.68–7.75 (m, 2H), 10.42 (s, 1H, NH). 13C NMR
(101 MHz, DMSO) d 166.55 (C, C = O), 158.23 (C, C-2
thiazole ring), 153.40 (C, C-4 thiazole ring), 143.90 (C,
C-5 thiazole ring), 136.75 (C, C-1 phenyl ring A), 129.63
(C, C-1 phenyl ring B), 129.39 (CH, C-2 and C-6 phenyl
ring A), 129.33 (CH, C-3 and C-5 phenyl ring A), 128.75
(CH, C-2 and C-6 phenyl ring B), 128.64 (CH, C-3 and C-5
phenyl ring B), 122.10 (CH, C-4 phenyl ring A), 117.61
(CH, C-4 phenyl ring B), 56.19 (CH, C-2 adamantyl),
53.71 (CH, C-1 and C-3 adamantyl), 37.49 (CH2, C-4
adamantyl), 37.17 (CH2, C-6 adamantyl), 32.36 (CH, C-5
and C-7 adamantyl), 31.38 (CH2, C-8 and C-10 ada-
mantyl), 27.15 (CH, C-9 adamantyl). MS (EI) m/z 431.00
(M?2). Anal. calcd for C26H27N3OS: C, 72.69; H, 6.34; N,
9.78. Found: C, 72.34; H, 6.21; N, 9.85.
2-chloro-1,2-diphenylethanone (7) (Ren et al., 2008) Color-
less crystals (EtOH): This compound was prepared from
heating a mixture of benzoin (10 g, 47 mmol) and pyridine
(5.7 ml) until a solution was obtained and then cooled in an
ice bath until solid. The mass obtained was coarsely
ground, and thionyl chloride (7.5 g, 63 mmol) was added
slowly with vigorous stirring and cooling in an ice bath.
After about an hour, water was added and the solid is
coarsely ground, filtered and washed several times with
water. The crude product was dried by suction and left
overnight over calcium chloride until full dryness. The
product was obtained as a white powder which was further
recrystallized from ethanol to give colorless crystals of
2-chloro-1,2-diphenylethanone 7 (79 %).
1-Cyclohexyl-3-(4,5-diphenylthiazol-2-yl)urea (9b) (Romeo
et al., 1999) White solid (EtOH): This compound was
obtained from 4,5-diphenylthiazol-2-amine 8 (2 mmol) and
cyclohexyl amine (2.1 mmol) according to general Proce-
dure A. The product was obtained as a white solid. Yield
4,5-diphenylthiazol-2-amine (8) (Ren et al., 2008) Yel-
low crystals (EtOH): This compound was prepared from
refluxing of a solution of 2-chloro-1,2-diphenylethanone, 7
(10 g, 41.5 mmol) in ethanol (40 ml) and thiourea (3.5 g,
45 mmol) for 2 h. The solvent was removed under vacuum,
and the solid product was soaked in 100 mL of 30 %
NaOH at 50 °C for 5 h. The crude product was filtered and
washed with water to neutrality and then was recrystallized
1
67 %, mp 213–215 °C. H NMR (400 MHz, DMSO-d6) d
1.17–1.52 (m, 5H), 1.64–1.83 (m, 5H), 3.33–3.56 (m, 1H),
6.52 (s, 1H, NH), 7.26–7.41 (m, 10H), 10.35 (s, 1H, NH).
13C NMR (101 MHz, DMSO) d 158.20 (C, C = O),
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Med Chem Res
153.47 (C, C-2 thiazole ring), 143.89 (C, C-4 thiazole
ring), 135.41 (C, C-5 thiazole ring), 132.73 (C, C-1 phenyl
ring A), 129.62 (C, C-1 phenyl ring B), 129.32 (CH, C-2
and C-6 phenyl ring A), 128.77 (CH, C-3 and C-5 phenyl
ring A), 128.63 (CH, C-2 and C-6 phenyl ring B), 128.11
(CH, C-3 and C-5 phenyl ring B), 127.95 (CH, C-4 phenyl
ring A), 124.42 (CH, C-4 phenyl ring B), 48.50 (CH, C-1
cyclohexyl), 33.08 (CH2, C-2 and C-6 cyclohexyl), 25.57
(CH2, C-3 and C-5 cyclohexyl), 24.64 (CH2, C-4 cyclo-
hexyl). MS (EI) m/z 377.00 (M?). Anal. calcd for C22
H23N3OS: C, 70.00; H, 6.14; N, 11.13. Found: C, 69.97; H,
6.32; N, 11.52.
14.32 (CH2, C-6 hexyl). MS (EI) m/z 379.00 (M?). Anal.
calcd for C22H25N3OS: C,69.62; H, 6.64; N, 11.07. Found:
C, 69.79; H, 6.75; N, 10.95.
1-Decyl-3-(4,5-diphenylthiazol-2-yl)urea (9e) Yellow semisolid
(MeOH): This compound was prepared from 4,5-
diphenylthiazol-2-amine 8 (2 mmol) and decan-1-amine
(2.1 mmol) according to general Procedure A. The product
was obtained as a yellow semisolid. Yield 68 %, mp 80–
82 °C. 1H NMR (400 MHz, DMSO-d6) d 0.79 (t,
J = 6.32 Hz, 3H, CH3), 1.18–1.51 (m, 16H), 3.12 (t,
J = 6.44 Hz, 2H), 6.77 (s, 1H, NH), 7.20–7.40 (m, 10H),
8.08 (s, 1H, NH). 13C NMR (101 MHz, DMSO) d 158.42
(C, C = O), 154.36 (C, C-2 thiazole ring), 143.86 (C, C-4
thiazole ring), 135.43 (C, C-5 thiazole ring), 132.80 (C,
C-1 phenyl ring A), 129.47 (C, C-1 phenyl ring B), 129.11
(CH, C-2 and C-6 phenyl ring A), 128.71 (CH, C-3 and C-5
phenyl ring A), 128.42 (CH, C-2 and C-6 phenyl ring B),
124.33 (CH, C-3 and C-5 phenyl ring B), 121.29 (CH, C-4
phenyl ring A), 116.88 (CH, C-4 phenyl ring B), 31.76
(CH2, C-1 decyl), 31.74 (CH2, C-2 decyl), 29.93 (CH2, C-3
decyl), 29.49 (CH2, C-4 decyl), 29.43 (CH2, C-5 decyl),
29.19 (CH2, C-6 decyl), 29.16 (CH2, C-7 decyl), 26.72
(CH2, C-8 decyl), 22.53 (CH2, C-9 decyl), 14.14 (CH2,
C-10 decyl). MS (EI) m/z 435.00 (M?). Anal. calcd for
C26H33N3OS: C, 71.69; H, 7.64; N, 9.65. Found: C, 71.84;
H, 7.57; N, 9.49.
1-(Benzo[d]thiazol-2-yl)-3-(4,5-diphenylthiazol-2-yl)urea
(9c) White solid (EtOH): This compound was prepared
8
from 4,5-diphenylthiazol-2-amine
(2 mmol) and
benzo[d]thiazol-2-amine (2.1 mmol) according to general
Procedure A. The product was obtained as a white solid.
Yield 63 %, mp 331–333 °C. 1H NMR (400 MHz, DMSO-
d6) d 7.10 (s, 1H, NH), 7.17–7.45 (m, 12H), 7.63 (d,
J = 7.93 Hz, 1H), 7.90 (d, J = 8.16 Hz, 1H), 10.49 (s, 1H,
NH). 13C NMR (101 MHz, DMSO) d 174.36 (C, C = O),
172.06 (C, C-2 benzothiazole), 158.22 (C, C-2 thiazole
ring), 157.71 (C, C-4 thiazole ring), 149.89 (C, C-3d ben-
zothiazole), 140.49 (C, C-5 thiazole ring), 130.57 (C,
C-1d benzothiazole), 129.61 (C, C-1 phenyl ring A), 129.36
(C, C-1 phenyl ring B), 129.34 (CH, C-2 and C-6 phenyl
ring A), 129.20 (CH, C-3 and C-5 phenyl ring A), 129.18
(CH, C-2 and C-6 phenyl ring B), 128.89 (CH, C-3 and C-5
phenyl ring B), 128.54 (CH, C-4 phenyl ring A), 128.52
(CH, C-4 phenyl ring B), 127.34 (CH, C-4 benzothiazole),
125.92 (CH, C-7 benzothiazole), 121.33 (CH, C-5 ben-
zothiazole), 118.18 (CH, C-6 benzothiazole). MS (EI) m/z
428.00 (M?). Anal. calcd for C23H16N4OS2: C, 64.46; H,
3.76; N, 13.07. Found: C, 64.61; H, 3.64; N, 13.15.
1-(4,5-Diphenylthiazol-2-yl)-3-tetradecylurea (9f) Yellow
solid (MeOH): This compound was prepared from 4,5-
diphenylthiazol-2-amine 8 (2 mmol) and tetradecan-1-
amine (2.1 mmol) according to general Procedure A. The
product was obtained as a yellow solid. Yield 73 %, mp
64–65 °C. 1H NMR (400 MHz, DMSO-d6) d 0.84 (t,
J = 4.18 Hz, 3H, CH3), 1.12–1.35 (m, 24H), 2.94 (t,
J = 8.13 Hz, 2H), 6.52 (s, NH), 7.26–7.41 (m, 10H), 10.53
(s, 1H, NH). 13C NMR (101 MHz, DMSO) d 158.02 (C,
C = O), 154.39 (C, C-2 thiazole ring), 129.68 (C, C-4
thiazole ring), 129.59 (C, C-5 thiazole ring), 129.35 (C,
C-1 phenyl ring A), 129.29 (C, C-1 phenyl ring B), 128.90
(CH, C-2 and C-6 phenyl ring A), 128.77 (CH, C-3 and C-5
phenyl ring A), 128.65 (CH, C-2 and C-6 phenyl ring B),
128.60 (CH, C-3 and C-5 phenyl ring B), 128.35 (CH, C-4
phenyl ring A), 128.11 (CH, C-4 phenyl ring B), 31.76
(CH2, C-1 tetradecyl), 29.91 (CH2, C-2 tetradecyl), 29.51
(CH2, C-3 tetradecyl), 29.50 (CH2, C-4 tetradecyl), 29.48
(CH2, C-5 tetradecyl), 29.44 (CH2, C-6 tetradecyl), 29.17
(CH2, C-7 tetradecyl), 29.14 (CH2, C-8 tetradecyl), 29.11
(CH2, C-9 tetradecyl), 26.69 (CH2, C-10 tetradecyl), 22.55
(CH2, C-11 tetradecyl), 15.14 (CH2, C-12 tetradecyl),
14.81 (CH2, C-13 tetradecyl), 14.38 (CH2, C-14 tetrade-
cyl). MS (EI) m/z 491.00 (M?). Anal. calcd for C30H41
N3OS: C, 73.28; H, 8.40; N, 8.55. Found: C, 73.35; H,
8.34; N, 8.78.
1-(4,5-Diphenylthiazol-2-yl)-3-hexylurea
solid (MeOH): This compound was prepared from 4,5-
diphenylthiazol-2-amine (2 mmol) and hexylamine
(2.1 mmol) according to general Procedure A. The product
was obtained as white solid. Yield 72 %, mp
(9d) White
8
a
1
164–166 °C. H NMR (400 MHz, DMSO-d6) d 0.84 (t,
J = 6.36 Hz, 3H, CH3), 1.22–1.46 (m, 8H), 2.96 (t,
J = 4.12, 2H), 6.54 (s, 1H, NH), 7.05 – 7.41 (m, 10H),
10.56 (s, 1H, NH). 13C NMR (101 MHz, DMSO) d 158.59
(C, C = O), 154.28 (C, C-2 thiazole ring), 143.88 (C, C-4
thiazole ring), 135.44 (C, C-5 thiazole ring), 132.77 (C,
C-1 phenyl ring A), 129.58 (C, C-1 phenyl ring B), 129.27
(CH, C-2 and C-6 phenyl ring A), 128.76 (CH, C-3 and C-5
phenyl ring A), 128.58 (CH, C-2 and C-6 phenyl ring B),
128.04 (CH, C-3 and C-5 phenyl ring B), 127.90 (CH, C-4
phenyl ring A), 124.39 (CH, C-4 phenyl ring B), 51.50
(CH2, C-1 hexyl), 31.54 (CH2, C-2 hexyl), 30.50 (CH2, C-3
hexyl), 26.54 (CH2, C-4 hexyl), 22.57 (CH2, C-5 hexyl),
123

Med Chem Res
S-benzo[d]thiazol-2-yl
(4,5-diphenylthiazol-2-yl)car-
was obtained as a brown solid. Yield 85 %, mp 109–110 °C.
1H NMR (400 MHz, DMSO-d6) d 1.38–1.45 (m, 2H),
1.61–1.80 (m, 10H), 1.97–2.10 (m, 2H), 3.00–3.09 (t,
J = 6.74 Hz, 1H), 3.48 (s, 2H), 4.16 (s, 1H, NH), 7.10–7.63
(m, 10H), 7.95 (s, 1H, CONH). 13C NMR (101 MHz,
DMSO) d 171.82 (C, C = O), 156.01 (C, C-2 thiazole ring),
144.27 (C, C-4 thiazole ring), 135.13 (C, C-5 thiazole ring),
132.35 (C, C-1 phenyl ring A), 129.70 (C, C-1 phenyl ring
B), 129.37 (CH, C-2 and C-6 phenyl ring A), 128.90 (CH,
C-3 and C-5 phenyl ring A), 128.69 (CH, C-2 and C-6
phenyl ring B), 128.36 (CH, C-3 and C-5 phenyl ring B),
128.14 (CH, C-4 phenyl ring A), 125.85 (CH, C-4 phenyl
ring B), 61.41 (CH2, CH2NH), 49.86 (CH, C-2 adamantyl),
37.92 (CH, C-1 and C-3 adamantyl), 37.23 (CH2, C-4 ada-
mantyl), 31.96 (CH2, C-6 adamantyl), 31.20 (CH, C-5 and
C-7 adamantyl), 30.30 (CH2, C-8 and C-10 adamantyl),
27.61 (CH, C-9 adamantyl). MS (EI) m/z 443.00 (M?).
Anal. calcd for C27H29N3OS: C, 73.10; H, 6.59; N, 9.47.
Found: C, 73.46; H, 6.35; N, 9.78.
bamothioate (9g) Yellow crystals (EtOH): This com-
pound was prepared from 4,5-diphenylthiazol-2-amine 8
(2 mmol) and benzo[d]thiazole-2-thiol (2.1 mmol)
according to general Procedure A. The product was
obtained as a yellow crystal. Yield 71 %, mp 165–166 °C.
1H NMR (400 MHz, DMSO-d6) d 7.28–7.73 (m, 14H),
7.95 (s, 1H, NH). 13C NMR (101 MHz, DMSO) d 167.74
(C, C = O), 163.70 (C, C-2 benzothiazole), 153.88 (C, C-2
thiazole ring), 132.06 (C, C-4 thiazole ring), 130.80 (C,
C-3d benzothiazole), 130.77 (C, C-5 thiazole ring), 130.48
(C, C-1d benzothiazole), 130.15 (C, C-1 phenyl ring A),
129.95 (C, C-1 phenyl ring B), 129.83 (CH, C-2 and C-6
phenyl ring A), 129.74 (CH, C-3 and C-5 phenyl ring A),
129.66 (CH, C-2 and C-6 phenyl ring B), 129.51 (CH, C-3
and C-5 phenyl ring B), 129.29 (CH, C-4 phenyl ring A),
129.12 (CH, C-4 phenyl ring B), 126.69 (CH, C-4 ben-
zothiazole), 122.11 (CH, C-7 benzothiazole), 122.09 (CH,
C-5 benzothiazole), 118.94 (CH, C-6 benzothiazole). MS
(EI) m/z 447.00 (M?2). Anal. calcd for C23H15N3OS3: C,
62.00; H, 3.39; N, 9.43. Found: C, 62.32; H, 3.15; N, 9.64.
2-(Benzo[d]thiazol-2-ylamino)-N-(4,5-diphenylthiazol-2-yl)
acetamide (11b) Brown solid: This compound was pre-
2-chloro-N-(4,5-diphenylthiazol-2-yl)ac-
2-Chloro-N-(4,5-diphenylthiazol-2-yl)acetamide (10) Brown
solid: This compound was synthesized from adding
chloroacetyl chloride (2.9 g, 25.7 mmol) slowly to a
solution of compound 8 (5 g, 19.8 mmol) and triethy-
lamine (6 g, 59.5 mmol) in CH2Cl2 at 0 °C. The reaction
mixture was stirred for 1 h at 0 °C and then for 5 h at room
temperature. The organic layer was then separated and
evaporated in vacuo. The residue obtained was purified by
flash column chromatography (SiO2) using dichlor-
omethane/methanol (9.5: 0.5) as eluent. The product 10
was obtained as brown solid. Yield 81 %. 1H NMR
(400 MHz, DMSO-d6) d 5.17 (s, 2H, CH2), 7.28–7.46 (m,
10H), 12.09 (s, 1H, NH). MS (EI) m/z 328.05 (M?).
pared
from
etamide 10 (1 g, 3.3 mmol) and benzo[d]thiazol-2-amine
(3.3 mmol) according to general Procedure B. The product
was obtained as a brown solid. Yield 68 %, mp
1
273–275 °C. H NMR (400 MHz, DMSO-d6) d 3.89 (s,
2H, CH2), 4.25 (s, 1H, NH), 6.98–7.65 (m, 10H), 7.95 (s,
1H, NHCO). 13C NMR (101 MHz, DMSO) d 166.96 (C,
C = O), 166.89 (C, C-2 benzothiazole), 162.92 (C, C-2
thiazole ring), 153.11 (C, C-4 thiazole ring), 131.28 (C,
C-3d benzothiazole), 130.03 (C, C-5 thiazole ring), 129.99
(C, C-1d benzothiazole), 129.70 (C, C-1 phenyl ring A),
129.38 (C, C-1 phenyl ring B), 129.18 (CH, C-2 and C-6
phenyl ring A), 129.05 (CH, C-3 and C-5 phenyl ring A),
128.97 (CH, C-2 and C-6 phenyl ring B), 128.89 (CH, C-3
and C-5 phenyl ring B), 128.80 (CH, C-4 phenyl ring A),
128.74 (CH, C-4 phenyl ring B), 128.52 (CH, C-4 ben-
zothiazole), 125.92 (CH, C-7 benzothiazole), 121.31 (CH,
C-5 benzothiazole), 118.17 (CH, C-6 benzothiazole), 53.37
(CH2, CH2NH). MS (EI) m/z 442.00 (M?). Anal. calcd for
C24H18N4OS2: C, 65.13; H, 4.10; N, 12.66. Found: C,
65.36; H, 4.40; N, 12.46.
General procedure B Synthesis of compounds (11a–k)
Appropriate amine (3.3 mmol) and K2CO3 (9.9 mmol)
were added, under mechanical stirring, to a solution of
2-chloro-N-(4,5-diphenylthiazol-2-yl)acetamide 10 (1 g,
3.3 mmol) in DMF (30 mL). The reaction mixture was
heated at 60 °C for 3 h. After cooling, the mixture was
poured onto H2O (100 mL), extracted with ethyl acetate
(3 9 50 mL), washed with brine and dried. The solvent
was removed in vacuo, and the residue was chro-
matographed on a silica gel column using methylene
chloride/methanol (9.5:0.5) as eluent to give the final
compounds (11a–k).
N-(4,5-diphenylthiazol-2-yl)-2-(thiazol-2-ylamino)acetamide
(11c) Light brown solid: This compound was prepared
from 2-chloro-N-(4,5-diphenylthiazol-2-yl)acetamide 10
(1 g, 3.3 mmol) and thiazol-2-amine (3.3 mmol) according
to general Procedure B. The product was obtained as a light
brown solid. Yield 63 %, mp 289–290 °C. 1H NMR
(400 MHz, DMSO-d6) d 3.87 (s, 2H, CH2), 4.72 (s, 1H,
NH), 7.20–7.42 (m, 12H), 7.92 (s, 1H, NHCO). 13C NMR
(101 MHz, DMSO) d 168.31 (C, C = O), 164.27 (C, C-2
thiazol-2-ylamino), 163.89 (C, C-2 thiazole ring), 154.45
2-(adamantan-2-ylamino)-N-(4,5-diphenylthiazol-2-yl)
acetamide (11a) Brown solid: This compound was pre-
pared from 2-chloro-N-(4,5-diphenylthiazol-2-yl)acetamide
10 (1 g, 3.3 mmol) and adamantan-2-amine (0.5 g,
3.3 mmol) according to general Procedure B. The product
123

Med Chem Res
(C, C-4 thiazole ring), 132.63 (C, C-4 thiazol-2-ylamino),
131.05 (C, C-5 thiazole ring), 130.72 (C, C-5 thiazol-2-
ylamino), 130.31 (C, C-1 phenyl ring A), 130.23 (C, C-1
phenyl ring B), 130.08 (CH, C-2 and C-6 phenyl ring A),
129.86 (CH, C-3 and C-5 phenyl ring A), 129.69 (CH, C-2
and C-6 phenyl ring B), 127.26 (CH, C-3 and C-5 phenyl
ring B), 122.68 (CH, C-4 phenyl ring A), 122.66 (CH, C-4
phenyl ring B), 54.71 (CH2, CH2NH). MS (EI) m/z 393.00
(M?). Anal. calcd for C20H16N4OS2: C, 61.20; H, 4.11; N,
14.27 Found: C, 61.37; H, 4.18; N, 14.04
octyl), 26.81 (CH2, C-6 octyl), 22.54 (CH2, C-7 octyl),
14.31 (CH2, C-8 octyl). MS (EI) m/z 421.00 (M?). Anal.
calcd for C25H31N3OS: C, 71.22; H, 7.10; N, 9.97. Found:
C, 71.45; H, 7.19; N, 10.16
2-(Decylamino)-N-(4,5-diphenylthiazol-2-yl)acetamide
(11f) Yellow solid: This compound was prepared from
2-chloro-N-(4,5-diphenylthiazol-2-yl)acetamide 10 (1 g,
3.3 mmol) and decylamine (3.3 mmol) according to gen-
eral Procedure B. The product was obtained as a yellow
solid. Yield 69 %, mp 165–167 °C. 1H NMR (400 MHz,
DMSO-d6) d 0.84 (t, J = 4.35 Hz, 3H, CH3), 1.13–1.41
(m, 16H), 3.06 (t, J = 6.53 Hz, 2H), 3.36 (s, 2H), 3.45 (s,
1H, NH), 7.14–7.43 (m, 10H), 7.98 (s, 1H, CONH). 13C
NMR (101 MHz, DMSO) d 161.29 (C, C = O), 149.68 (C,
C-2 thiazole ring), 140.07 (C, C-4 thiazole ring), 130.36
(C, C-5 thiazole ring), 129.71 (C, C-1 phenyl ring A),
129.38 (C, C-1 phenyl ring B), 129.15 (CH, C-2 and C-6
phenyl ring A), 128.90 (CH, C-3 and C-5 phenyl ring A),
128.72 (CH, C-2 and C-6 phenyl ring B), 128.49 (CH, C-3
and C-5 phenyl ring B), 127.47 (CH, C-4 phenyl ring A),
113.02 (CH, C-4 phenyl ring B), 62.30 (CH2, CH2NH),
50.18 (CH2, C-1 decyl), 35.06 (CH2, C-2 decyl), 31.77
(CH2, C-3 decyl), 29.47 (CH2, C-4 decyl), 29.42 (CH2, C-5
decyl), 29.20 (CH2, C-6 decyl), 29.19 (CH2, C-7 decyl),
26.81 (CH2, C-8 decyl), 22.57 (CH2, C-9 decyl), 14.43
(CH2, C-10 decyl). MS (EI) m/z 449.00 (M?). Anal. calcd
for C27H35N3OS: C, 72.12; H, 7.85; N, 9.35. Found: C,
72.32; H, 7.57; N, 9.14.
N-(4,5-diphenylthiazol-2-yl)-2-(hexylamino)acetamide (11d)
Brown solid: This compound was prepared from 2-chloro-
N-(4,5-diphenylthiazol-2-yl)acetamide 10 (1 g, 3.3 mmol)
and hexylamine (3.3 mmol) according to general Proce-
dure B. The product was obtained as a brown solid. Yield
1
58 %, mp 113–114 °C. H NMR (400 MHz, DMSO-d6) d
0.61 (t, J = 6.53 Hz, 3H, CH3), 0.95–1.06 (m, 6H),
1.13–1.18 (m, 2H), 2.28 (s, 1H, NH), 2.65 (s, 2H), 2.85 (t,
J = 12.86 Hz, 2H), 6.90–7.21 (m, 10H), 7.77 (s, 1H,
CONH). 13C NMR (101 MHz, DMSO) d 164.80 (C,
C = O), 162.67 (C, C-2 thiazole ring), 135.82 (C, C-4
thiazole ring), 132.71 (C, C-5 thiazole ring), 129.92 (C,
C-1 phenyl ring A), 129.81 (C, C-1 phenyl ring B), 129.64
(CH, C-2 and C-6 phenyl ring A), 129.30 (CH, C-3 and C-5
phenyl ring A), 128.88 (CH, C-2 and C-6 phenyl ring B),
128.57 (CH, C-3 and C-5 phenyl ring B), 128.32 (CH, C-4
phenyl ring A), 119.53 (CH, C-4 phenyl ring B), 37.53
(CH2, CH2NH), 36.13 (CH2, C-1 hexyl), 31.41 (CH2, C-2
hexyl), 29.44 (CH2, C-3 hexyl), 26.50 (CH2, C-4 hexyl),
22.51 (CH2, C-5 hexyl), 14.21 (CH2, C-6 hexyl). MS (EI)
m/z 393.00 (M?). Anal. calcd for C23H27N3OS: C, 70.19;
H,6.92; N, 10.68. Found: C, 70.3; H,6.74; N, 10.71
N-(4,5-diphenylthiazol-2-yl)-2-(tetradecylamino)acetamide
(11g) Brown solid: This compound was prepared from
2-chloro-N-(4,5-diphenylthiazol-2-yl)acetamide 10 (1 g,
3.3 mmol) and tetradecylamine (3.3 mmol) according to
general Procedure B. The product was obtained as a brown
N-(4,5-diphenylthiazol-2-yl)-2-(octylamino)acetamide (11e)
Brown solid: This compound was prepared from 2-chloro-
N-(4,5-diphenylthiazol-2-yl)acetamide 10 (1 g, 3.3 mmol)
and octylamine (3.3 mmol) according to general Procedure
B. The product was obtained as a brown solid. Yield 65 %,
mp 107–108 °C. 1H NMR (400 MHz, DMSO-d6) d 0.84 (t,
J = 6.46 Hz, 3H), 1.23–1.39 (m, 12H), 2.50 (t,
J = 4.51 Hz, 2H), 3.05 (d, J = 8.32 Hz, 2H), 3.50 (br s,
1H, NH), 7.24–7.39 (m, 10H), 10.32 (s, 1H, CONH). 13C
NMR (101 MHz, DMSO) d 168.07 (C, C = O), 163.34 (C,
C-2 thiazole ring), 144.30 (C, C-4 thiazole ring), 135.82
(C, C-5 thiazole ring), 133.14 (C, C-1 phenyl ring A),
130.03 (C, C-1 phenyl ring B), 129.73 (CH, C-2 and C-6
phenyl ring A), 129.18 (CH, C-3 and C-5 phenyl ring A),
129.04 (CH, C-2 and C-6 phenyl ring B), 128.51 (CH, C-3
and C-5 phenyl ring B), 128.36 (CH, C-4 phenyl ring A),
124.82 (CH, C-4 phenyl ring B), 37.50 (CH2, CH2NH),
36.18 (CH2, C-1 octyl), 31.69 (CH2, C-2 octyl), 31.15
(CH2, C-3 octyl), 29.44 (CH2, C-4 octyl), 29.11 (CH2, C-5
1
solid. Yield 73 %, mp 149–150 °C. H NMR (400 MHz,
DMSO-d6) d 0.83 (t, J = 7.59 Hz, 3H), 1.04–1.41 (m,
26H), 3.44 (s, 2H, CH2), 3.88 (s, 1H, NH), 7.13–7.43 (m,
10H), 7.98 (s, 1H, CONH). 13C NMR (101 MHz, DMSO) d
166.55 (C, C = O), 161.85 (C, C-2 thiazole ring), 147.15
(C, C-4 thiazole ring), 129.70 (C, C-5 thiazole ring),
129.38 (C, C-1 phenyl ring A), 129.25 (C, C-1 phenyl ring
B), 129.14 (CH, C-2 and C-6 phenyl ring A), 128.91 (CH,
C-3 and C-5 phenyl ring A), 128.87 (CH, C-2 and C-6
phenyl ring B), 128.75 (CH, C-3 and C-5 phenyl ring B),
124.32 (CH, C-4 phenyl ring A), 117.31 (CH, C-4 phenyl
ring B), 62.76 (CH2, CH2NH), 55.11 (CH2, C-1 tetradecyl),
31.76 (CH2, C-1 tetradecyl), 29.52 (CH2, C-2 tetradecyl),
29.50 (CH2, C-3 tetradecyl), 29.47 (CH2, C-4 tetradecyl),
29.42 (CH2, C-5 tetradecyl), 29.40 (CH2, C-6 tetradecyl),
29.38 (CH2, C-7 tetradecyl), 29.18 (CH2, C-8 tetradecyl),
29.16 (CH2, C-9 tetradecyl), 29.15 (CH2, C-10 tetradecyl)
(CH2, C-11 tetradecyl), 29.13 (CH2, C-12 tetradecyl),
123

Med Chem Res
22.56 (CH2, C-13 tetradecyl), 14.40 (CH2, C-14 tetrade-
cyl). MS (EI) m/z 505.00 (M?). Anal. calcd for C31H43
N3OS: C, 73.62; H, 8.57; N, 8.31. Found: C, 73.48; H,
8.63; N, 8.69
2-(Benzo[d]thiazol-2-ylthio)-N-(4,5-diphenylthiazol-2-yl)
acetamide (11j) Light brown solid: This compound was
prepared from 2-chloro-N-(4,5-diphenylthiazol-2-yl)ac-
etamide 10 (1 g, 3.3 mmol) and benzo[d]thiazole-2-thiol
(3.3 mmol) according to general Procedure B. The product
was obtained as a light brown solid. Yield 63 %, mp
99-100 °C. 1H NMR (400 MHz, DMSO-d6) d 4.48 (s, 2H),
7.27 – 7.47 (m, 10H), 7.81 (d, J = 8.10 Hz, 2H), 7.93 (s,
1H, NH), 8.00 (d, J = 7.99 Hz, 2H). 13C NMR (101 MHz,
DMSO) d 166.77 (C, C = O), 166.19 (C, C-2 benzothia-
zole), 152.89 (C, C-2 thiazole ring), 144.38 (C, C-4 thia-
zole ring), 135.23 (C, C-3d benzothiazole), 135.06 (C, C-5
thiazole ring), 132.21 (C, C-1d benzothiazole), 129.69 (C,
C-1 phenyl ring A), 129.41 (C, C-1 phenyl ring B), 128.89
(CH, C-2 and C-6 phenyl ring A), 128.77 (CH, C-3 and C-5
phenyl ring A), 128.45 (CH, C-2 and C-6 phenyl ring B),
128.25 (CH, C-3 and C-5 phenyl ring B), 126.94 (CH, C-4
phenyl ring A), 126.07 (CH, C-4 phenyl ring B), 125.10
(CH, C-4 benzothiazole), 122.34 (CH, C-7 benzothiazole),
121.61 (CH, C-5 benzothiazole), 116.07 (CH, C-6 ben-
zothiazole), 36.82 (CH2, CH2S). MS (EI) m/z 460.00 (M?).
Anal. calcd for C24H17N3OS3: C, 62.72; H, 3.73; N, 9.14.
Found: C, 62.50; H, 3.91; N, 9.44.
N-(4,5-diphenylthiazol-2-yl)-2-((2-(naphthalen-1-ylamino)
ethyl)amino)acetamide (11h) Brown solid: This com-
pound was prepared from 2-chloro-N-(4,5-diphenylthiazol-
2-yl)acetamide 10 (1 g, 3.3 mmol) and N1-(naphthalen-1-
yl)ethane-1,2-diamine (3.3 mmol) according to general
Procedure B. The product was obtained as a brown solid.
Yield 66 %, mp 100–101 °C. 1H NMR (400 MHz, DMSO-
d6) d 1.21 (s, 1H, NH), 2.94 (t, J = 6.09 Hz, 2H), 3.31 (t,
J = 7.61 Hz, 2H), 4.51 (s, 2H), 4.73 (s, 1H, NH),
7.08–7.12 (m, 3H), 7.19–7.42 (m, 14H), 8.14 (s, 1H,
CONH). 13C NMR (101 MHz, DMSO) d 171.52 (C,
C = O), 166.59 (C, C-2 thiazole ring), 162.77 (C, C-4
thiazole ring), 156.03 (C, C-5 thiazole ring), 144.62 (C,
C-1 naphthyl), 144.28 (CH, C-2 naphthyl), 135.14 (C,
C-8a naphthyl), 134.50 (C, C-1 phenyl ring A), 132.36 (C,
C-1 phenyl ring B), 129.74 (CH, C-2 and C-6 phenyl ring
A), 129.39 (CH, C-3 and C-5 phenyl ring A), 128.92 (CH,
C-2 and C-6 phenyl ring B), 128.71 (CH, C-3 and C-5
phenyl ring B), 128.49 (CH, C-4 phenyl ring A), 128.41 (C,
C-3 naphthyl), 127.29 (C, C-4a naphthyl), 126.04 (C, C-4
naphthyl), 124.39 (C, C-5 naphthyl), 123.56 (C, C-8
naphthyl), 122.03 (C, C-7 naphthyl), 115.93 (C, C-6
naphthyl), 103.47 (CH, C-4 phenyl ring B), 52.04 (CH2,
NHCH2CO), 47.87 (CH2, Ar-NHCH2CH2NH), 43.65
(CH2, Ar-NHCH2CH2NH). MS (EI) m/z 479.00 (M?).
Anal. calcd for C29H26N4OS: C, 72.78; H, 5.48; N, 11.71.
Found: C, 72.58; H, 5.64; N, 11.90
2-(Benzyloxy)-N-(4,5-diphenylthiazol-2-yl)acetamide (11k)
Brown solid: This compound was prepared from 2-chloro-
N-(4,5-diphenylthiazol-2-yl)acetamide 10 (1 g, 3.3 mmol)
and benzyl alcohol (3.3 mmol) according to general Pro-
cedure B. The product was obtained as a brown solid. Yield
1
57 %, mp 278–280 °C. H NMR (400 MHz, DMSO-d6) d
4.20 (s, 2H), 5.17 (s, 2H), 7.21–7.43 (m, 15H), 7.95 (s, 1H,
CONH). 13C NMR (101 MHz, DMSO) d 169.41 (C,
C = O), 162.77 (C, C-2 thiazole ring), 149.03 (C, C-4
thiazole ring), 145.04 (C, C-5 thiazole ring), 139.65 (C,
C-1 benzyloxy), 129.74 (C, C-1 phenyl ring A), 129.45 (C,
C-1 phenyl ring B), 129.41 (CH, C-2 and C-6 phenyl ring
A), 129.23 (CH, C-3 and C-5 phenyl ring A), 128.98 (CH,
C-2 and C-6 phenyl ring B), 128.90 (CH, C-3 and C-5
phenyl ring B), 128.52 (CH, C-2 and C-6 benzyloxy),
128.48 (CH, C-3 and C-5 benzyloxy), 127.05 (CH, C-4
phenyl ring A), 126.86 (CH, C-4 phenyl ring B), 123.66
(CH, C-4 benzyloxy), 63.32 (CH2, COCH2), 56.20 (CH2,
OCH2). MS (EI) m/z 401.00 (M?). Anal. calcd for C24
H20N2O2S: C, 71.98; H, 5.03; N, 6.99. Found: C, 72.12; H,
5.15; N, 7.20.
N-(4,5-diphenylthiazol-2-yl)-2-(piperidin-1-yl)acetamide
(11i) Light brown solid: This compound was prepared
from 2-chloro-N-(4,5-diphenylthiazol-2-yl)acetamide 10
(1 g, 3.3 mmol) and piperidine (3.3 mmol) according to
general Procedure B. The product was obtained as a light
brown solid. Yield 61 %, mp 118–120 °C. 1H NMR
(400 MHz, DMSO-d6) d 1.41–1.57 (m, 6H), 2.55 (s, 4H),
3.29 (s, 2H), 7.32–7.45 (m, 10H), 7.98 (S, 1H, NH). 13C
NMR (101 MHz, DMSO) d 169.56 (C, C = O), 162.86
(C, C-2 thiazole ring), 155.80 (C, C-4 thiazole ring),
135.07 (C, C-5 thiazole ring), 132.26 (C, C-1 phenyl ring
A), 129.71 (C, C-1 phenyl ring B), 129.40 (CH, C-2 and
C-6 phenyl ring A), 128.89 (CH, C-3 and C-5 phenyl ring
A), 128.72 (CH, C-2 and C-6 phenyl ring B), 128.43 (CH,
C-3 and C-5 phenyl ring B), 128.20 (CH, C-4 phenyl ring
A), 125.93 (CH, C-4 phenyl ring B), 61.44 (CH2, CH2
NH), 54.26 (CH2, C-1 and C-5 piperidine), 25.93 (CH2,
C-2 and C-4 piperidine), 23.95 (CH2, C-3 piperidine). MS
(EI) m/z 377.00 (M?). Anal. calcd for C22H23N3OS: C,
70.00; H, 6.14; N, 11.13. Found: C, 70.32; H, 6.50; N,
11.35.
In vivo anti-inflammatory assay: measurement
of paw edema
1. Animals
Male BALB/c mice (28–30 g) were housed in a con-
trolled environment and provided with standard rodent
chow and water. Six mice including three males and
123

Med Chem Res
three females were used to test each compound, as a
control or for diclofenac as positive control.
that have docking energies below certain user-defined
threshold are subsequently clustered according to their
RMS similarities. Representative conformers/poses are
then selected, further energy-minimized within the
binding site, and saved for subsequent scoring.
2. Carrageenan-induced paw edema assay
Animal groups (n = 6 per particular treatment)
received orally 60 mg/kg (body weight) dose of the
tested compounds, diclofenac or vehicle (untreated
controls). One hour later, test animals received 30 ll
of carrageenan (1 % W/V in saline) s.c. on the plantar
surface of the left hind paw. The development of paw
edema was assessed by measuring paw-thickness
changes at 0 (immediately), 1, 2, 3 and 4 h after
carrageenan injection using electronic digital caliper
(Moilanen et al., 2012; Posadas et al., 2004). The right
hind paw served as a reference of non-inflamed paw
for qualitative comparison. Results are expressed as
paw thickness (mm) and percent thickness reduction
compared to control (Inhibition percent) as in Table 1.
In first case, all synthesized compounds in their union-
ized forms were docked into the binding site in the pres-
ence of explicit water molecules. The following docking
configurations were employed:
•
•
•
Monte Carlo search parameters were number of
trials = 30,000 and search step for torsions with polar
hydrogens = 30.0°.
The RMS threshold for ligand-to-binding site shape
˚
match was set to 2.0 A employing a maximum of 2.0
binding site partitions.
Interaction energy parameters: The interaction energies
were assessed employing CFF force field (version 1.02)
˚
with a non-bonded cutoff distance of 10.0 A and
Docking studies
distance dependent dielectric. An energy grid extending
˚
3.0 A from the binding site was implemented. The
Preparation of COX-1 crystal structure: The 3D coordi-
nates of COX-1 were retrieved from the Protein Data Bank
˚
(COX-1 PDB code: 3KK6, resolution: 2.75 A). Hydrogen
interaction energy was estimated by a trilinear interpo-
lation value using soft potential energy approximations
(Discovery Studio version 2.5 (DS 2.5) User Manual;
Accelrys Inc: San Diego, CA, 2009.; Venkatachalam
et al., 2003).
atoms were added to the protein utilizing DS 2.0 templates
for protein residues. Gasteiger–Marsili charges were
assigned to the protein atoms as implemented within DS
2.0 (Gasteiger and Marsili, 1980).
•
Rigid-body ligand minimization parameters: 40 steps
of steepest descend followed by 80 BFGS minimiza-
tion iterations were applied to every orientation of the
docked ligand. High-ranking docked conformers/poses
were scored using six scoring functions: Jain (Jain,
1996; Krammer et al., 2005; Venkatachalam et al.,
2003), LigScore1, LigScore2 (Krammer et al., 2005;
Venkatachalam et al., 2003), PLP1 (Gehlhaar et al.,
1995), PLP2 and PMF (Muegge, 2001; Muegge and
Martin, 1999). LigScore1 and LigScore2 scores were
calculated employing CFF force field (version 1.02)
and using grid-based energies with a grid extension of
The protein structure was utilized in subsequent docking
experiments without energy minimization. Docking
experiment was conducted employing LigandFit docking
engine. There are two steps implemented in the LigandFit
process (Taha and AlDamen, 2005).
1. Defining the location(s) of potential binding site
(Discovery Studio version 2.5 (DS 2.5) User Manual;
Accelrys Inc: San Diego, CA, 2009; Gehlhaar et al.,
1995; Venkatachalam et al., 2003). In the current
docking experiments, the binding site was generated
from the cocrystallized ligand (PDB codes: 3KK6)
within the targeted protein.
˚
7.5 A across the binding site. PMF scores were
˚
calculated employing cutoff distances of 12.0 A for
2. Docking the ligands in the binding site (Discovery
Studio version 2.5 (DS 2.5) User Manual; Accelrys
Inc: San Diego, CA, 2009.; Gehlhaar et al., 1995;
Venkatachalam et al., 2003). In LigandFit, docking is
composed of few substeps: (1) conformational search
of flexible ligands employing Monte Carlo randomized
process. (2) Pose/conformation selection based on
shape similarity with the binding site. (3) Candidate
conformers/poses exhibiting low shape discrepancy are
further enrolled in calculation of the dock energies. (4)
Each docked conformation/pose is further fitted into
the binding pocket through a number of rigid-body
minimization iterations. (5) Docked conformers/poses
carbon–carbon interactions and other atomic interac-
tions, while PMF04 scores were calculated employing
˚
cutoff values of 6.0 and 9.0 A for carbon–carbon
interactions
respectively.
and
other
atomic
interactions,
Conclusions
In the presented study, we synthesized several
diphenylthiazole derivatives linked to hydrophobic frag-
ments via amide or urea tethers. Our compounds showed
significant anti-inflammatory properties in inflamed mice
123

Med Chem Res
diphenyloxazoles as potential novel prion disease therapeutics.
J Med Chem 50:1347–1353
Jain AN (1996) Scoring noncovalent protein-ligand interactions: a
continuous differentiable function tuned to compute binding
affinities. J Comput Aided Mol Des 10:427–440
Krammer A, Kirchhoff PD, Jiang X, Venkatachalam CM, Waldman
M (2005) LigScore: a novel scoring function for predicting
binding affinities. J Mol Graph Model 23:395–407
Moilanen LJ et al (2012) TRPA1 contributes to the acute inflamma-
tory response and mediates carrageenan-induced paw edema in
the mouse. Sci Rep 2:380
paws animal model, docking-based analysis suggests they
primarily inhibit COX. The most potent compound (9e)
exhibited superior anti-inflammatory properties compared
to diclofenac. These results need further investigations to
study the mechanism of action in vitro, and we are plan-
ning to publish the full biological results in a future
communication.
Compliance with ethical standards
Muegge I (2001) Effect of ligand volume correction on PMF scoring.
J Comput Chem 22:418–425
Muegge I, Martin YC (1999) A general and fast scoring function for
protein-ligand interactions: a simplified potential approach.
J Med Chem 42:791–804
Conflict of interest None of the authors of the above manuscript
has declared any conflict of interest.
Posadas I, Bucci M, Roviezzo F, Rossi A, Parente L, Sautebin L, Cirino
G (2004) Carrageenan-induced mouse paw oedema is biphasic,
age-weight dependent and displays differential nitric oxide
cyclooxygenase-2 expression. Br J Pharmacol 142:331–338
Ren J, Wang S-M, Wu L-F, Xu Z-X, Dong B-H (2008) Synthesis and
properties of novel Y-shaped NLO molecules containing thiazole
and imidazole chromophores. Dyes Pigmemts 76:310–314
Romeo G, Salerno L, Milla P, Siracusa M, Cattel L, Russo F (1999)
Synthesis of novel 4,5 diphenyl thiazole derivatives as potential
acyl-CoA: cholesterol O-acyltransferase inhibitors. Pharmazie
54:19–23
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