Design, synthesis and evaluation of small molecule imidazo[2,1-b][1,3,4]thiadiazoles as inhibitors of transforming growth factor-β type-I receptor kinase (ALK5)

Article abstract of DOI:10.1016/j.ejmech.2014.09.002

A new series of imidazo[2,1-b][1,3,4]thiadiazoles 5(a-g), 6(a-g), 9(a-i) and 12(a-h) were synthesized as transforming growth factor-β (TGF-β) type I receptor (also known as activin receptor-like kinase 5 or ALK5) inhibitors. These compounds were evaluated

Full text of DOI:10.1016/j.ejmech.2014.09.002

European Journal of Medicinal Chemistry xxx (2014) 1e15
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Design, synthesis and evaluation of small molecule imidazo[2,1-b]
[1,3,4]thiadiazoles as inhibitors of transforming growth factor-
b type-I
receptor kinase (ALK5)
Harun M. Patel a, Baljeet Sing b, Varun Bhardwaj c, Mahesh Palkar a,
Mahamadhanif S. Shaikh a, Rajesh Rane a, Wesam S. Alwan a, Andanappa K. Gadad d,
,
, **
Malleshappa N. Noolvi e *, Rajshekhar Karpoormath a
a Department of Pharmaceutical Chemistry, College of Health Sciences, University of KwaZulu-Natal (Westville Campus), Private Bag X54001, Durban 4000,
South Africa
b Department of Pharmaceutical Chemistry, ASBASJSM College of Pharmacy, Bela (Ropar) 140111, Punjab, India
c Department of Biotechnology, Bioinformatics and Pharmacy, Jaypee University of Information Technology, Waknaghat, Solan 173234, Himachal Pradesh,
India
d School Pharmacy, Faculty of Medical Sciences, EWMS Complex, Mt. Hope, The University of the West Indies, Trinidad and Tobago, West Indies
e Department of Pharmaceutical Chemistry, Shree Dhanvantary Pharmacy College, Kim (Surat) 3941110, Gujarat, India
a r t i c l e i n f o
a b s t r a c t
Article history:
A new series of imidazo[2,1-b][1,3,4]thiadiazoles 5(aeg), 6(aeg), 9(aei) and 12(aeh) were synthesized
Received 30 May 2014
Received in revised form
21 August 2014
Accepted 2 September 2014
Available online xxx
as transforming growth factor-
ALK5) inhibitors. These compounds were evaluated for their ALK5 inhibitory activity in an enzyme assay
and their TGF- -induced Smad2/3 phosphorylation inhibitory activity in a cell-based assay. Compound
6d, 2-(5-((2-cyclopropyl-6-(4-fluorophenyl) imidazo [2,1-b][1,3,4]thiadiazol-5-yl)methylene)-4-oxo-2-
thioxothiazolidin-3-yl) acetic acid, shows prominent ALK5 inhibition (IC50 ¼ 0.0012 M) and elective
inhibition (91%) against the P38 kinase at10 M. The binding mode of compound 6d by XP docking
b (TGF-b) type I receptor (also known as activin receptor-like kinase 5 or
b
m
a
m
Keywords:
studies shows that it fits well into the active site cavity of ALK5 by forming broad and tight interactions.
Lipinski's rule and in silico ADME pharmacokinetic parameters are within the acceptable range defined
for human use thereby indicating their potential as a drug-like molecules.
Synthesis imidazo [2,1-b][1,3,4]thiadiazole
ALK5
XP docking
Lipinski's rule
© 2014 Elsevier Masson SAS. All rights reserved.
1. Introduction
Smad3 proteins at the C-terminal SSXS-motif thereby causing
dissociation from the receptor and heteromeric complex formation
Transforming growth factor-beta (TGF-
kine that affects various biological processes such as regulation of
cell proliferation, immune responses, growth, differentiation,
b
) is a ubiquitous cyto-
with the Smad4 [3e5]. Smad complexes translocate to the nucleus,
assemble with specific DNA-binding co-factors and co-modulators
to finally activate transcription of an extracellular matrix compo-
nent, and inhibitors of matrix-degrading proteases [6]. Therefore, it
becomes evident that inhibition of ALK5 phosphorylation of
angiogenesis, and apoptosis of different cell types [1]. TGF-
transduces signals through two highly conserved single trans-
membrane serine/threonine kinases, the type I and type II TGF-
receptors (T R-I and T R-II, respectively) [2]. T R-II activates T R-I
b1
b
Smad2/Smad3 could reduce TGF-
tion of the extracellular matrix. Small molecules inhibitors of TGF-
R1 offer an attractive way to regulate the TGF- pathway and can
b1-induced excessive accumula-
b
b
b
b
upon formation of the ligandereceptor complex by hyper-
b
b
phosphorylating serine/threonine residues in the GS region of the
TbR-I or activin-like kinase (ALK5), which creates a binding site for
Smad proteins. The activated TbR-I in turn phosphorylates Smad2/
consequently find applications in the treatment of various diseases,
especially, cancer [7]. Our on-going interest in the design and
synthesis of novel anti-cancer agents [8e13], and recent reports by
Hoelzemann and collaborators [14] suggesting the imidazo[2,1-b]
[1,3,4]thiadiazoles scaffold as a template to the design of inhibitors
of ALK5; inspired us to synthesize and in vitro evaluated imidazo
[2,1-b][1,3,4]thiadiazoles 5(aeg), 6(aeg), 9(aei) and 12(aeh) for
* Corresponding author.
** Corresponding author.
E-mail
addresses:
mallesh7301@rediffmail.com,
mnoolvi@yahoo.co.uk
the ALK5 inhibitory activity in an enzyme assay and their TGF-
b
(M.N. Noolvi), karpoormath@ukzn.ac.za, rvk2006@gmail.com (R. Karpoormath).
http://dx.doi.org/10.1016/j.ejmech.2014.09.002
0223-5234/© 2014 Elsevier Masson SAS. All rights reserved.
Please cite this article in press as: H.M. Patel, et al., Design, synthesis and evaluation of small molecule imidazo[2,1-b][1,3,4]thiadiazoles as
inhibitors of transforming growth factor-b type-I receptor kinase (ALK5), European Journal of Medicinal Chemistry (2014), http://dx.doi.org/
10.1016/j.ejmech.2014.09.002

2
H.M. Patel et al. / European Journal of Medicinal Chemistry xxx (2014) 1e15
-induced Smad2/3 phosphorylation inhibitory activity in a cell-
based assay.
of water. The electronic and steric factors at 5th position of 2-
amino-5-substituted-1,3,4-thiadiazole are crucial in determining
the course of its reaction with substituted a-haloaryl ketones. The
strongly electronegative groups impart less nucleophilic character
to the nitrogen at 4th position of the 1,3,4-thiadiazole.
2. Chemistry
In the next step, imidazo[2,1-b][1,3,4]-thiadiazoles 4(aeg) were
subjected to VilsmeiereHack reaction to afford 2-cyclopropyl-6-
The synthetic route of the compound 5(aeg), 6(aeg), 9(aei) and
12(aeh) is outlined in Schemes 1e3 respectively. 2-amino-5-
substituted-1,3,4-thiadiazole 3, 8 and 11 was obtained by direct
cyclization of benzoic acid 1, substituted benzoic acid 7, 10, and
thiosemicarbazide 2 in the presence of phosphorus oxychloride,
substituted
phenylimidazo[2,1-b][1,3,4]thiadiazole-5-
carbaldehyde 5(aeg). The obtained imidazo[2,1-b][1,3,4]thiadia-
zoles-5-carbaldehydes 5(aeg) were subjected to Knoevenagel
condensation [16,17] using 2-(4-oxo-2-thioxothiazolidin-3-yl)ace-
tic acid (rhodanine acetic acid) in the presence of the catalytic
amount of piperidine acetate to afford the 2-(5-((2-cyclopropyl-6-
the latter refluxed with substituted
a-haloaryl ketones in dry
ethanol with drop of dimethyl formamide to yield the imidazo[2,1-
b][1,3,4]-thiadiazoles 4(aeg), 9(aei) and 12(aeh) in good yield as
per the procedure reported by Gadad et al. [15] It is well established
that this reaction proceeds via the intermediate iminothiadiazole
[15], which undergoes dehydrocyclisation to form the desired fused
heterocycle under reflux temperature spontaneously. The ring ni-
trogen of the imino form of thiadiazole is involved preferably on the
substituted
phenylimidazo[2,1-b][1,3,4]thiadiazol-5-yl)methy-
lene)-4-oxo-2-thioxothiazolidin-3-yl)acetic acid 6(aeg). The
physical and elemental data of all the synthesized compounds is
shown in Tables 1 and 2.
nucleophilic displacement of bromine of the
a
-bromoketones
3. Results and discussion
forming an intermediate. It undergoes further cyclodehydration on
heating with a suitable medium like ethanol, DMF to afford imi-
dazothiadiazoles in good yields. The cyclodehydration involves
intramolecular nucleophilic addition of the 2-amino group to
carbonyl functions of the intermediate followed by the elimination
To evaluate whether these compounds 5(aeg), 6(aeg), 9(aei)
and 12(aeh) could inhibit ALK5, an enzyme based kinase assay and
TGF-b-induced Smad2/3 phosphorylation inhibitory activity in a
cell-based assay was performed (Table 3). The ALK5 inhibitory
Scheme 1. Synthesis of title compounds 5(a-g) and 6(a-g).
Please cite this article in press as: H.M. Patel, et al., Design, synthesis and evaluation of small molecule imidazo[2,1-b][1,3,4]thiadiazoles as
inhibitors of transforming growth factor-b type-I receptor kinase (ALK5), European Journal of Medicinal Chemistry (2014), http://dx.doi.org/
10.1016/j.ejmech.2014.09.002

H.M. Patel et al. / European Journal of Medicinal Chemistry xxx (2014) 1e15
3
Scheme 2. Synthesis of title compounds 9(a-i).
Scheme 3. Synthesis of title compounds 12(a-h).
activity of imidazo[2,1-b][1,3,4]thiadiazoles having substitution at
2, 5 and 6 position was compared. In case of compound 5(aeg) and
6(aeg) having cyclopropyl substitution at C-2 position; it is seen
that the rhodanine acetic acid derivatives are more potent as
compared to formyl derivatives at C-5, it is obvious by comparing
and 6d (IC50 ¼ 0.0012
m
M) reveals that at C-6 position more than
one electron withdrawing group has diminishing effect on the ac-
tivity. Compound 5d, the most potent analogue, was evaluated for
electivity using a diverse kinase panel and it was found to be se-
lective toward the P 38
a kinase with significant percentage of in-
6d (IC50 ¼ 0.0012
m
M) and 5d (IC50 ¼ 0.019
m
M). Further structure
hibition (91%) at10 M as shown in Table 4.
m
activity relationship at C-6 position of imidazo[2,1-b][1,3,4]thia-
diazoles indicates that presence of electron withdrawing group on
phenyl ring is more crucial for ALK5 inhibition e.g. 5d
The docking studies in the X-ray crystal structure of ALK5 (PDB
code: 1RW8) have revealed that the central imidazo[2,1-b][1,3,4]
thiadiazole ring and its substituent form several interactions with
amino acid residues in the binding pocket, facilitating binding of
the ligand deep into the active site (Table 5). The sulfur atom of
(IC50 ¼ 0.019
m
M) and 6d (IC50 ¼ 0.0012
m
M). Comparison of 5b
(IC50 ¼ 0.064
mM) and 5d (IC50 ¼ 0.019 M); 6b (IC50 ¼ 0.03
m
mM)
Please cite this article in press as: H.M. Patel, et al., Design, synthesis and evaluation of small molecule imidazo[2,1-b][1,3,4]thiadiazoles as
inhibitors of transforming growth factor-b type-I receptor kinase (ALK5), European Journal of Medicinal Chemistry (2014), http://dx.doi.org/
10.1016/j.ejmech.2014.09.002

4
H.M. Patel et al. / European Journal of Medicinal Chemistry xxx (2014) 1e15
Table 1
Physicochemical properties of the synthesized compounds 5 (aeg), 6 (aeg), 9 (aei) and 12 (aeh).
Sr. No.
Compound
Molecular formula
Molecular weight
Yield %
Melting point (ꢀC)
Solvent system
B:A (9:1)
Rf (cm)
5a
C14H11N3OS
269.3216
70
112e115
0.68
5b
C14H9Cl2N3OS
338.2118
65
154e158
B:A (9:1)
0.71
5c
C14H10BrN3OS
C14H10FN3OS
348.2177
287.3121
69
68
159e162
124e126
B:A (9:1)
B:A (9:1)
0.79
0.71
5d
5e
5f
C14H10ClN3OS
C14H12N4OS
303.7667
284.3363
70
67
137e140
143e146
B:A (9:1)
B:A (9:1)
0.70
0.69
5g
6a
C14H11N3O3S
301.3204
442.5345
68
77
197e199
232e235
B:A (9:1)
0.75
0.64
C19H14N4O3S3
T:E:F (5:4:1)
6b
C19H12Cl2N4O3S3
511.4246
69
222e224
T:E:F (5:4:1)
0.66
6c
C19H13BrN4O3S3
521.4305
460.5249
78
76
213e215
209e212
T:E:F (5:4:1)
T:E:F (5:4:1)
0.59
0.61
6d
C19H13FN4O3S3
6e
6f
C19H13ClN4O3S3
476.9795
457.5491
76
68
190e192
168e171
T:E:F (5:4:1)
T:E:F (5:4:1)
0.63
0.76
C19H15N5O3S3
6g
C19H14N4O5S3
474.5333
58
156e159
T:E:F (5:4:1)
0.73
9a
9b
C17H13N3S
291.3702
360.2603
70
58
138e140
151e154
CHCl3:CH3OH (9:1)
CHCl3:CH3OH (9:1)
0.55
0.58
C17H11Cl2N3S
Please cite this article in press as: H.M. Patel, et al., Design, synthesis and evaluation of small molecule imidazo[2,1-b][1,3,4]thiadiazoles as
inhibitors of transforming growth factor-b type-I receptor kinase (ALK5), European Journal of Medicinal Chemistry (2014), http://dx.doi.org/
10.1016/j.ejmech.2014.09.002

H.M. Patel et al. / European Journal of Medicinal Chemistry xxx (2014) 1e15
5
Table 1 (continued )
Sr. No.
Compound
Molecular formula
Molecular weight
Yield %
Melting point (ꢀC)
Solvent system
Rf (cm)
9c
9d
9e
9f
C17H12BrN3S
C17H12ClN3S
C17H14N4S
370.2663
325.8153
306.3849
323.3690
321.3962
307.3696
306.3849
346.2338
68
69
78
69
65
64
67
70
170e173
146e149
156e159
134e137
112e115
122e124
148e151
172e174
CHCl3:CH3OH (9:1)
CHCl3:CH3OH (9:1)
CHCl3:CH3OH (9:1)
CHCl3:CH3OH (9:1)
CHCl3:CH3OH (9:1)
CHCl3:CH3OH (9:1)
CHCl3:CH3OH (9:1)
CHCl3:CH3OH (9:1)
0.67
0.61
0.54
0.67
0.51
0.60
0.59
0.55
C17H13N3O2S
C18H15N3OS
C17H13N3OS
C17H14N4S
9g
9h
9i
12a
C16H9Cl2N3S
12b
12c
12d
C16H7Cl4N3S
C16H8BrCl2N3S
C16H10Cl2N4S
415.1239
425.1298
361.2484
58
68
78
196e198
147e150
178e181
CHCl3:CH3OH (9:1)
CHCl3:CH3OH (9:1)
CHCl3:CH3OH (9:1)
0.54
0.62
0.58
12e
12f
12g
C16H9Cl2N3O2S
C17H11Cl2N3OS
C16H9Cl2N3OS
378.2326
376.2597
362.2332
69
65
64
170e172
152e154
162e164
CHCl3:CH3OH (9:1)
CHCl3:CH3OH (9:1)
CHCl3:CH3OH (9:1)
0.61
0.57
0.75
12h
C16H10Cl2N4S
361.2484
67
157e159
CHCl3:CH3OH (9:1)
0.63
B:A (Benzene:Acetone).
T:E:F (Toluene:Ethyl acetate:Formic acid).
CHCl3:CH3OH (Chloroform:Methanol).
imidazo[2,1-b][1,3,4]thiadiazole of 5 (aeg), 6 (aeg), 9 (aei) and 12
(aeh) forms hydrogen bonding via sulfur atom with His-283 in the
hinge region of the kinase respectively, originally a binding pocket
for the adenine ring of ATP, and it is major interaction of inhibitor
with the binding site [18,19]. The imidazo[2,1-b][1,3,4]thiadiazole
ring occupies the hydrophobic pocket containing Ser280, which is
critical for the selectivity of the ALK5 [20]. The fluorine atom of
compound 5d, 6d and N-3 of imidazo[2,1-b][1,3,4]thiadiazoles of
remaining compound forms water mediated hydrogen bond with
Asp-351 and Tyr-249 which is one of key interactions observed in
the X-ray structures of ALK5 complexed with other inhibitors as
shown in Fig. 1 [3]. It was reported that Asp351 is usually located
close to bound inhibitors in the inactivated conformation of ALK5
[18]. The H-bonding between imidazo[2,1-b][1,3,4]thiadiazoles
with Asp351 may contribute to hold the loop containing Asp351
and stabilize inactive conformation of ALK5. The present docking
model demonstrates a possible broad and tight interaction of 6d
with the ALK5 active site ranging from His-283, Asp351 and Tyr-
249, and this may be related to the excellent activity of com-
pound 6d. Conclusively, the binding mode of 6d generated by
docking studies supports the strong and selective activity of this
compound and provides the insights for further modification to
develop analogs with more desirable biological activity.
As a part of our study, the compliance of compounds to Lip-
inski's rule of five was evaluated. As discussed by Lipinski, molec-
ular properties are closely related to the oral bioavailability of a
drug. The QikProp 3.2 was used to analyze drug likeness (Lipinski's
Rule of Five) and in silico ADME evaluation; the results are given in
Table 6 and it was found that all the synthesized compounds
comply with these rules with the exception of 6b and 6c, which did
not comply for molecular weight and QPlogP O/W; showing
violation for Lipinski's Rule of Five. In addition, it is well known that
numerous drug candidates have failed during clinical tests because
of problems related to ADME (absorption, distribution, metabolism
and excretion) properties. The results for ADME prediction is
shown in Table 6. Human Intestinal Absorption (HIA) and Caco-2
(QPPCaco) permeability are good indicators of drug absorbance in
the intestine and Caco-2 monolayer penetration, respectively. Hu-
man Intestinal Absorption data are the sum of bioavailability and
absorption evaluated from the ratio of excretion or cumulative
excretion in urine, bile and feces [21]. The predicted percentages of
intestinal absorption are excellent for all of the compounds tested,
with values above 59e100% in all cases. The compounds present
Please cite this article in press as: H.M. Patel, et al., Design, synthesis and evaluation of small molecule imidazo[2,1-b][1,3,4]thiadiazoles as
inhibitors of transforming growth factor-b type-I receptor kinase (ALK5), European Journal of Medicinal Chemistry (2014), http://dx.doi.org/
10.1016/j.ejmech.2014.09.002

6
H.M. Patel et al. / European Journal of Medicinal Chemistry xxx (2014) 1e15
Table 2
Table 3
Elemental analysis of 5 (aeg), 6 (aeg), 9 (aei) and 12 (aeh).
Compound code Compound Elemental analysis (%)
Calculated Found
Inhibitory profile of 5 (aeg), 6 (aeg), 9 (aei) and 12 (aeh).
Compound code
Compound
IC50
(
mM)
ALK5a
Smad2/3a
0.529
C
H
N
C
H
N
5a
5b
5c
5d
5e
5f
5g
6a
6b
6c
C14H11N3OS
C14H9Cl2N3OS
C14H10BrN3OS
62.43 4.12 15.60 62.45 4.10 15.63
49.72 2.68 12.42 49.74 2.68 12.43
48.29 2.89 12.07 48.31 2.91 12.07
58.53 3.51 14.63 58.56 3.54 14.66
55.35 3.32 13.83 55.38 3.32 13.85
59.14 4.25 19.70 59.16 4.223 19.68
55.80 3.68 13.95 55.78 3.70 13.97
51.57 3.19 12.64 51.59 3.21 12.68
5a
5b
0.081
C
C
C
C
C
C
14H10FN3OS
14H10ClN3OS
14H12N4OS
14H11N3O3S
19H14N4O3S3
0.064
0.537
19H12Cl2N4O3S3 44.62 2.37 10.96 44.64 2.39 10.94
5c
0.03
0.223
0.268
C19H13BrN4O3S3 43.76 2.51 10.74 43.74 2.53 10.77
6d
6e
6f
6g
9a
9b
9c
9d
9e
9f
9g
C
C
C
C
C
C
19H13FN4O3S3
49.55 2.85 12.17 49.57 2.87 12.19
19H13ClN4O3S3 47.84; 2.75 11.75 47.84; 2.77 11.76
19H15N5O3S3
19H14N4O5S3
17H13N3S
49.88 3.30 15.31 49.90 3.32 15.33
48.09 2.97 11.81 48.11 2.95 11.79
70.08 4.50 14.42 70.06 4.50 14.44
56.68 3.08 11.66 56.70 3.06 11.68
55.14 3.27 11.35 55.16 3.29 11.37
62.67 3.71 12.90 62.69 3.73 12.93
66.64 4.61 18.29 66.66 4.63 18.31
63.14 4.05 12.99 63.16 4.07 12.99
67.27 4.70 13.07 67.29 4.73 13.05
66.43 4.26 13.67 66.45 4.29 13.65
66.64 4.61 18.29 66.66 4.63 18.31
55.50 2.62 12.14 55.53 2.65 12.17
46.29 1.70 10.12 46.32 1.67 10.15
5d
0.019
17H11Cl2N3S
5e
5f
0.025
0.112
0.693
0.486
C17H12BrN3S
C
C
C
C
C
C
C
C
C
C
C
C
C
C
17H12ClN3S
17H14N4S
17H13N3O2S
18H15N3OS
17H13N3OS
17H14N4S
16H9Cl2N3S
16H7Cl4N3S
16H8BrCl2N3S
16H10Cl2N4S
16H9Cl2N3O2S
17H11Cl2N3OS
16H9Cl2N3OS
16H10Cl2N4S
9h
9i
12a
12b
12c
12d
12e
12f
12g
12h
5g
6a
0.123
0.04
0.257
0.126
45.20 1.90 9.88 45.20 1.92
9.85
53.20 2.79 15.51 53.23 2.77 15.53
50.81 2.40 11.11 50.84 2.43 11.14
54.27 2.95 11.17 54.30 2.94 11.16
53.05 2.50 11.60 53.04 2.51 11.62
53.20 2.79 15.51 53.22 2.79 15.53
6b
0.03
0.133
good permeability values in Caco-2 (QPPCaco) cells, ranging from
57.285 to 4759.477. Hence, theoretically, all of these compounds
should present good passive oral absorption except compound 6f
and 6g. The partition coefficient (QPlogPo/w) and water solubility
(QPlogS), critical for estimation of absorption and distribution of
drugs within the body ranged between 1.416 and 5.145 and ꢁ3.79
to ꢁ6.229. Cell permeability (QPPCaco), a key factor governing drug
metabolism and its access to biological membranes, ranged from
57.285 to 4759.477. We similarly studied number of violations of
Jorgensen's rule of three. The three rules are: QPlogS > ꢁ5.7,
QPCaco > 22 nm/s, Primary Metabolites < 7. Compounds with fewer
(and preferably no) violations of these rules are more likely to be
orally available. All the compounds are following this rule except
6b, 6f and 6g; showing best candidate for oral bioavailability. All
these pharmacokinetic parameters are within the acceptable range
defined for human use (see Table 6 footnote), thereby indicating
their potential as a drug-like molecules.
6c
0.015
0.014
6d
0.0012
0.0209
6e
6f
0.018
0.042
0.093
0.358
4. Conclusion
In conclusion, a new series of imidazo[2,1-b][1,3,4]thiadiazoles
5(aeg), 6(aeg), 9(aei) and 12(aeh) were synthesized. To evaluate
the ALK5 inhibitory activity of imidazo[2,1-b][1,3,4]thiadiazoles an
6g
9a
0.047
0.214
0.104
1.691
enzyme based kinase assay and TGF-b-induced Smad2/3 phos-
phorylation inhibitory activity in a cell-based assay was performed.
Among them, compound 6d shows highest ALK5 inhibition
IC50 ¼ 0.0012
m
M and it was found to be selective toward the P 38
a
kinase with significant percentage of inhibition (91%) at10
mM. The
docking studies revealed that the sulfur atom of imidazo[2,1-b]
[1,3,4]thiadiazole of 5(aeg), 6(aeg), 9(aei) and 12(aeh) forms
hydrogen bonding via sulfur atom with His-283 in the hinge region
Please cite this article in press as: H.M. Patel, et al., Design, synthesis and evaluation of small molecule imidazo[2,1-b][1,3,4]thiadiazoles as
inhibitors of transforming growth factor-b type-I receptor kinase (ALK5), European Journal of Medicinal Chemistry (2014), http://dx.doi.org/
10.1016/j.ejmech.2014.09.002

H.M. Patel et al. / European Journal of Medicinal Chemistry xxx (2014) 1e15
7
Table 3 (continued )
that further derivatization of such compounds will be of interest
with the hope to get more selective and potent ALK5 inhibitors.
Compound code
Compound
IC50
(m
M)
ALK5a
Smad2/3a
5. Experimental
All chemicals and solvents were supplied by Merck, S.D. Fine
Chemical Limited, Mumbai. All the solvents were distilled and dried
before use. The reactions were monitored with the help of thin-
layer chromatography using pre-coated aluminum sheets with
GF254 silica gel, 0.2 mm layer thickness (E. Merck). Melting points of
the synthesized compounds were recorded on the Veego (VMP-
MP) melting point apparatus. IR spectrum was acquired on a Shi-
madzu Infra Red Spectrometer, (model FTIR-8400S). Both 1H NMR
(DMSO) and 13C NMR (DMSO) spectra of the synthesized com-
pounds were performed with Bruker Avance-II 400 NMR Spec-
trometer operating at 400 MHz in SAIF, Punjab University
(Chandigarh). Chemical shifts were measured relative to internal
9b
9c
9d
9e
9f
0.452
7.82
0.539
0.519
>10
0.11
0.107
>10
>10
>10
standard TMS (d: 0). Chemical shifts are reported in d scale (ppm).
Mass spectra of the synthesized compounds were recorded at MAT
120 in SAIF, Punjab University.
9g
9h
9i
3.548
>10
3.98
1.25
1.778
>10
5.1. 5-Cyclopropyl-1,3,4-thiadiazol-2-amine (3)
6.67
It is synthesized as per the procedure reported [10].
12a
>10
5.2. 2-Cyclopropyl-6-substituted phenylimidazo[2,1-b][1,3,4]
thiadiazole 4(aeg)
12b
12c
0.04
0.050
0.118
It is synthesized as per the procedure reported [10].
0.019
5.3. General procedure for the synthesis of 2-cyclopropyl-6-
substituted phenylimidazo[2,1-b][1,3,4]thiadiazole-5-carbaldehyde
5(aeg)
12d
12e
1.023
1.17
5.98
The VilsmeireHaack reagent was prepared by adding phos-
phorus oxychloride (3 mL) to dimethyl-formamide (20 mL) at 0 ꢀC
with stirring. Then, compound 2-cyclopropyl-6-substituted phe-
nylimidazo[2,1-b][1,3,4]thiadiazole 4(aeg) (0.01 mol) was added to
the reagent and stirred at 0 ꢀC for 30 min. The mixture was further
stirred at room temperature for 2 h and then at 60 ꢀC for an addi-
tional 2 h. The reaction mixture was then poured onto sodium
carbonate solution and stirred at 90 ꢀC for 2 h. After cooling, the
mixture was diluted with water and extracted with chloroform. The
chloroform layer was washed with water, dried over anhydrous
sodium sulfate and the residue obtained after removal of the sol-
vent was crystallized from chloroform/methanol.
6.589
12f
0.38
0.268
0.429
12g
0.724
12h
0.823
>10
a
Values are the mean of two or more separate experiment.
of the kinase which is a major interaction for ALK5 inhibition. The
imidazo[2,1-b][1,3,4]thiadiazole ring occupies the hydrophobic
pocket containing Ser280, which is critical for the selectivity of the
ALK5. Lipinski's rule and in silico ADME pharmacokinetic param-
eters are within the acceptable range defined for human use
thereby indicating their potential as drug-like molecules. The
overall outcome of this model revealed that: (i) the imidazo[2,1-b]
[1,3,4]thiadiazole ring is a satisfactory backbone for ALK5 inhibi-
tion; (ii) presence of electron withdrawing group on phenyl ring at
C-6 of imidazo[2,1-b][1,3,4]thiadiazole is more crucial for ALK5
inhibition; (iii) rhodanine acetic acid derivatives at C-5 of imidazo
[2,1-b][1,3,4]thiadiazole are more potent as compared to the other
derivatives. Lipinski's rule and in silico ADME pharmacokinetic
parameters are within the acceptable range defined for human use
thereby indicating their potential as drug-like molecules. These
encouraging results of biological screening of the tested com-
pounds could offer an excellent framework in this field that may
lead to discovery of potent ALK5 inhibitors. Finally, it is conceivable
5.3.1. 2-Cyclopropyl-6-phenylimidazo[2,1-b][1,3,4]thiadiazole-5-
carbaldehyde (5a)
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢁ1): 3054.00 (Ar CeH stretch),
2939.21 (Ali. CeH stretch) and 1724.15 [(C]O) aldehyde]; 1H NMR
(DMSO-d6)
d
ppm): 10.00 (s, 1H, CHO), 7.26e7.84 (m, 5H, AreH),
ppm: 186.32,
1.51e2.42 (m, 5H, cyclopropyl); 13C NMR (DMSO-d6)
d
166.74,157.83, 143.53, 134.53, 133.62, 129.52, 128.63, 127.84,13.12,
10.84; HRMS (EI) m/z calcd for C14H11N3OS: 269.0623; found:
269.0628.
5.3.2. 2-Cyclopropyl-6-(2,4-dichlorophenyl)imidazo[2,1-b][1,3,4]
thiadiazole-5-carbaldehyde (5b)
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢁ1): 3059.50 (Ar CeH stretch),
2920.42 (Ali. CeH stretch), 1718.59 (C]O), 721 (CeCl); 1H NMR
(DMSO-d6)
d
ppm): 9.97 (s, 1H, CHO), 7.46e8.41 (m, 3H, AreH) and
ppm: 186.74,
1.13e2.50 (m, 5H, cycloproyl); 13C NMR (DMSO-d6)
d
Please cite this article in press as: H.M. Patel, et al., Design, synthesis and evaluation of small molecule imidazo[2,1-b][1,3,4]thiadiazoles as
inhibitors of transforming growth factor-b type-I receptor kinase (ALK5), European Journal of Medicinal Chemistry (2014), http://dx.doi.org/
10.1016/j.ejmech.2014.09.002

8
H.M. Patel et al. / European Journal of Medicinal Chemistry xxx (2014) 1e15
Table 4
Table 5
Selectivity of compound 6d against a panel of kinases.a
Glide docking results based on glide dock score, glide energy, glide emodel and
hydrogen bonding interaction of synthesized compounds 5(aeg), 6 (aeg), 9 (aei)
and 12 (aeh).
Compound
Sr.
No.
Compounds
Docking
score
Glide energy (kcal/ Glide
mol) emodel
AMPK
CDK2/A
CHK1
CK1
CK2
CSK
35%
29%
21%
37%
11%
32%
23%
24%
21%
36%
19%
24%
10%
16%
18%
42%
91%
41%
39%
35%
12%
48%
34%
21%
5a
5b
ꢁ7.311282 ꢁ42.178455
ꢁ7.626115 ꢁ44.974126
ꢁ60.375544
ꢁ63.757605
DYRK 1A
ERK2
GSK 3b
MKK 1A
MKK 1
MKK 2
MSK 1
NEK2A
NEK 6
KDR
5c
ꢁ7.308838 ꢁ45.354199
ꢁ7.50468 ꢁ42.650333
ꢁ63.704139
ꢁ60.342029
5d
P 38
P 38
a
b
2
P 38bg
P 38bd
PBK
PDK 1
PK A
5e
5f
ꢁ8.54196 ꢁ44.61315
ꢁ7.666718 ꢁ44.495791
ꢁ63.130529
ꢁ63.405014
PK B
a
Values are % inhibition at 10
m
M using 100 mM ATP.
5g
6a
ꢁ6.007193 ꢁ46.855993
ꢁ6.831427 ꢁ45.11235
ꢁ67.139747
ꢁ62.625068
166.42,157.83, 143.12, 134.64, 134.74, 132.12, 130.23, 129.64, 128.73,
126.12, 13.84, 10.63; HRMS (EI) m/z calcd for C14H9Cl2N3OS:
336.9843; found: 336.9847.
5.3.3. 6-(4-Bromophenyl)-2-cyclopropylimidazo[2,1-b][1,3,4]
thiadiazole-5-carbaldehyde (5c)
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢁ1): 3072.93 (Ar CeH stretch),
2920.97 (Ali. CeH stretch) 1722.74 [(C]O) aldehyde], 621 (CeBr);
6b
6c
ꢁ7.452996 ꢁ45.783689
ꢁ9.856962 ꢁ48.93824
ꢁ42.820554
ꢁ61.945298
1H NMR (DMSO-d6)
d
ppm): 9.97 (s, 1H, CHO), 7.55e7.85 (m, 4H,
AreH), 1.14e2.50 (m, 5H, cylopropyl); 13C NMR (DMSO-d6)
d
ppm:
186.24, 166.53,157.43, 143.84, 134.12, 132.12, 128.24, 126.34, 124.45,
13.12, 10.36; HRMS (EI) m/z calcd for C14H10BrN3OS: 346.9728;
found: 346.9732.
5.3.4. 2-Cyclopropyl-6-(4-fluorophenyl)imidazo[2,1-b][1,3,4]
thiadiazole-5-carbaldehyde (5d)
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢁ1): 3060.36 (Ar CeH stretch),
2924.12 (Ali. CeH stretch), 1720.52 [(C]O) aldehyde], 1210 (CeF);
6d
6e
ꢁ10.238062 ꢁ58.242453
ꢁ9.616341 ꢁ49.454991
ꢁ70.046054
ꢁ66.552017
1H NMR (DMSO-d6)
d
ppm): 10.02 (s, 1H, CHO), 7.16e7.92 (m, 4H,
AreH), 1.16e2.44 (m, 5H, cylopropyl); 13C NMR (DMSO-d6)
d
ppm:
186.12, 166.83, 160.82, 157.73, 143.62, 134.12, 129.62, 128.12, 121.82,
13.62, 10.34; HRMS (EI) m/z calcd for C14H10FN3OS: 287.0529;
found: 287.0533.
5.3.5. 6-(4-Chlorophenyl)-2-cyclopropylimidazo[2,1-b][1,3,4]
thiadiazole-5-carbaldehyde (5e)
6f
ꢁ6.571304 ꢁ48.061152
ꢁ6.913584 ꢁ52.962205
ꢁ61.449938
ꢁ75.295121
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢁ1): 3063.93 (Ar CeH stretch),
2920.77 (Ali. CeH stretch) and 1718.02 [(C]O) aldehyde], 731
(CeCl); 1H NMR (DMSO-d6)
d
ppm): 9.98 (s,1H, CHO), 7.46e7.79 (m,
4H, AreH), 1.13e2.54 (m, 5H, cylopropyl); 13C NMR (DMSO-d6)
ppm: 186.12, 166.83,157.82, 143.23, 134.74, 133.63, 131.83, 130.82,
6g
d
Please cite this article in press as: H.M. Patel, et al., Design, synthesis and evaluation of small molecule imidazo[2,1-b][1,3,4]thiadiazoles as
inhibitors of transforming growth factor-b type-I receptor kinase (ALK5), European Journal of Medicinal Chemistry (2014), http://dx.doi.org/
10.1016/j.ejmech.2014.09.002

H.M. Patel et al. / European Journal of Medicinal Chemistry xxx (2014) 1e15
9
Table 5 (continued )
5.3.6. 6-(3-Aminophenyl)-2-cyclopropylimidazo[2,1-b][1,3,4]
thiadiazole-5-carbaldehyde (5f)
Sr.
Compounds
Docking
score
Glide energy (kcal/ Glide
mol) emodel
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢁ1): 3346.05, 3267.37 (NeH
stretch), 3105.15 (Ar CeH stretch), 2910.37 (Ali. CeH stretch),
No.
1711.81 [(C]O) aldehyde]; 1H NMR (DMSO-d6)
d
ppm): 9.97 (s, 1H,
CHO), 7.46e7.99 (m, 4H, AreH), 4.85 (s, 2H, NH2), 1.13e2.53 (m, 5H,
cylopropyl); 13C NMR (DMSO-d6)
ppm: 186.23, 166.73,157.12,
d
9a
9b
9c
9b
9b
9c
9d
ꢁ6.436358 ꢁ38.453996
ꢁ6.876485 ꢁ41.066372
ꢁ6.517072 ꢁ39.232817
ꢁ6.876485 ꢁ41.066372
ꢁ6.876485 ꢁ41.066372
ꢁ6.517072 ꢁ39.232817
ꢁ6.927513 ꢁ40.685597
ꢁ51.320462
ꢁ59.100521
ꢁ51.944223
ꢁ59.100521
ꢁ59.100521
ꢁ51.944223
ꢁ53.246391
146.63, 143.12, 134.63, 132.12, 129.32, 123.83, 120.62, 118.63, 12.53,
10.01; HRMS (EI) m/z calcd for C14H12N4OS: 284.0732; found:
284.0736.
5.3.7. 2-Cyclopropyl-6-(2,4-dihydroxyphenyl)imidazo[2,1-b][1,3,4]
thiadiazole-5-carbaldehyde (5g)
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢁ1): 3415.36 (OeH stretch),
3023.88 (Ar CeH stretch), 2902.81(Ali. CeH stretch), 1722.59 [(C]
O) aldehyde]; 1H NMR (DMSO-d6)
d
ppm): 10.19 (s, 1H, CHO),
7.24e7.80 (m, 3H, AreH), 5.49 (s, 1H, OH), 5.20 (s, 1H, OH) and
1.10e2.22 (m, 5H, cylopropyl); 13C NMR (DMSO-d6)
ppm: 186.12,
166.63, 158.73, 157.12, 156.73, 143.63, 134.23, 130.74, 121.23, 114.73,
d
110.73, 13.22, 10.12; HRMS (EI) m/z calcd for
C14H11N3O3S:
301.0521; found: 301.0526.
9e
9f
ꢁ7.159149 ꢁ40.847965
ꢁ7.163349 ꢁ43.078769
ꢁ6.038678 ꢁ42.56103
ꢁ6.588913 ꢁ45.4578
ꢁ6.249185 ꢁ37.768197
ꢁ6.299645 ꢁ43.771403
ꢁ56.083704
ꢁ67.151507
ꢁ56.704833
ꢁ57.506909
ꢁ51.745678
ꢁ54.995851
5.4. General procedure for the synthesis of 2-(5-((2-cyclopropyl-6-
substituted phenylimidazo[2,1-b][1,3,4]thiadiazol-5-yl)methylene)-
4-oxo-2 thioxothiazolidin-3-yl)acetic acid 6(aeg)
A mixture of 2-cyclopropyl-6-substituted imidazo[2,1-b][1,3,4]
thiadiazole-5-carbaldehyde 5(aeg) (0.001 mol), piperidine
(0.001 mol) and rhodanine acetic acid (0.001 mol) in toluene
(50 mL) was heated under reflux with azeotropic removal of water
for 16e30 h. The mixture was cooled to 5 ꢀC, filtration gave crude
compound 6(aeg), which was crystallized from ethanol.
9g
9h
9i
5.4.1. 2-(5-((2-cyclopropyl-6-phenylimidazo[2,1-b][1,3,4]
thiadiazol-5-yl)methylene)-4-oxo-2 thioxothiazolidin-3-yl)acetic
acid (6a)
12a
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢁ1): 3057.02 (Ar CeH stretch),
2893.10 (Ali. CeH stretch), 2510.10 [(OeH stretch) acid], 1720.46
12b
12c
12d
ꢁ6.723885 ꢁ44.609527
ꢁ7.051427 ꢁ42.216975
ꢁ7.18204 ꢁ45.93587
ꢁ60.087791
ꢁ58.205195
ꢁ60.077071
[(C]O) acid]; 1H NMR (DMSO-d6)
d
ppm): 9.06 (s, 1H, OH), 8.13 (s,
1H, CH), 7.46e7.66 (m, 5H, AreH), 4.64 (s, 2H, CH2), 1.34e1.62 (m,
5H, cyclopropyl); 13C NMR (DMSO-d6)
ppm: 192.71, 166.20,
d
164.73,144.62,134.73,132.23,131.43,130.34,129.78,128.24, 124.89,
120.23, 64.78, 44.23, 13.12, 10.73; HRMS (EI) m/z calcd for
C19H14N4O3S3: 442.0228; found: 442.0232.
12e
12f
12g
ꢁ7.248774 ꢁ45.32108
ꢁ5.352337 ꢁ43.902908
ꢁ5.274743 ꢁ44.391567
ꢁ61.212514
ꢁ59.632729
ꢁ62.866919
5.4.2. 2-(5-((2-cyclopropyl-6-(2,4-dichlorophenyl)imidazo[2,1-b]
[1,3,4]thiadiazol-5-yl)methylene)-4-oxo-2-thioxothiazolidin-3-yl)
acetic acid (6b)
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢁ1): 3063.95 (Ar CeH stretch),
2849.92 (Ali. CeH stretch), 2519.92 [(OeH stretch) acid], 1718.12
12h
ꢁ5.449304 ꢁ42.293621
ꢁ59.041235
[(C]O) acid], 701 (CeCl); 1H NMR (DMSO-d6)
d
ppm): 9.24 (s, 1H,
OH), 8.22 (s, 1H, CH), 7.24e7.89 (m, 3H, AreH), 4.49 (s, 2H, CH2),
1.10e2.22 (m, 5H, cylopropyl); 13C NMR (DMSO-d6)
ppm: 192.24,
d
128.91, 13.12, 10.01; HRMS (EI) m/z calcd for C14H10ClN3OS:
303.0233; found: 303.0237.
166.53, 165.74, 145.74, 138.34, 136.73, 134.21, 132.73, 130.56, 128.24,
127.89, 126.35, 122.67, 120.56, 65.89, 44.56, 13.72, 10.11; HRMS (EI)
m/z calcd for C19H12Cl2N4O3S3: 509.9449; found: 509.9454.
Please cite this article in press as: H.M. Patel, et al., Design, synthesis and evaluation of small molecule imidazo[2,1-b][1,3,4]thiadiazoles as
inhibitors of transforming growth factor-b type-I receptor kinase (ALK5), European Journal of Medicinal Chemistry (2014), http://dx.doi.org/
10.1016/j.ejmech.2014.09.002

10
H.M. Patel et al. / European Journal of Medicinal Chemistry xxx (2014) 1e15
Fig. 1. Binding mode of 6d in the X-ray crystal structure of ALK5 (PDB code: 1RW8). Compound 6d shows hydrogen bond interaction with sulfur atom of imidazo[2,1-b][1,3,4]
thiadiazoles hydrogen atom of amino acid backbone of Hie-283 and fluoro functional of imidazo[2,1-b][1,3,4]thiadiazoles with water-mediated hydrogen bond with the side chains
of Tyr-249 and backbone of Asp-351.
5.4.3. 2-(5-((6-(4-Bromophenyl)-2-cyclopropylimidazo[2,1-b]
[1,3,4]thiadiazol-5-yl)methylene)-4-oxo-2-thioxothiazolidin-3-yl)
acetic acid (6c)
125.89, 121.36, 66.78, 48.12, 13.78, 10.12; HRMS (EI) m/z calcd for
19H13ClN4O3S3: 475.9838; found: 475.9842.
C
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢁ1): 3065.95 (Ar CeH stretch),
2859.25 (Ali. CeH stretch), 2529.92 [(OeH stretch) acid], 1724.82
5.4.6. 2-(5-((6-(3-Aminophenyl)-2-cyclopropylimidazo[2,1-b]
[1,3,4]thiadiazol-5-yl)methylene)-4-oxo-2-thioxothiazolidin-3-yl)
acetic acid (6f)
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢁ1): 3268.12, 3234.27 (eNHe),
3065.95 (Ar CeH stretch), 2859.25 (Ali. CeH stretch), 2529.92
[(OeH stretch) acid], 1724.82 [(C]O) acid]; 1H NMR (DMSO-d6)
[(C]O) acid], 632 (CeBr); 1H NMR (DMSO-d6)
d
ppm): 8.96 (s, 1H,
OH), 8.19 (s, 1H, CH), 7.56e7.70 (m, 4H, AreH), 4.52 (s, 2H, CH2),
1.22e2.56 (m, 5H, cylopropyl); 13C NMR (DMSO-d6)
ppm: 193.63,
d
169.12, 167.63, 147.63, 138.73, 135.73, 133.83, 132.34, 128.78, 126.56,
124.34, 120.78, 64.67, 48.45, 13.34, 10.46; HRMS (EI) m/z calcd for
C
19H13BrN4O3S3: 519.9333; found: 519.9338.
d
ppm): 9.11 (s, 1H, OH), 8.18 (s, 1H, CH), 7.56e7.70 (m, 4H, AreH),
4.88 (s, 2H, NH2), 4.58 (s, 2H, CH2), 1.18e2.59 (m, 5H, cylopropyl);
13C NMR (DMSO-d6)
ppm: 195.12, 166.56, 164.34, 144.89, 142.34,
d
5.4.4. 2-(5-((6-(4-Bromophenyl)-2-cyclopropylimidazo[2,1-b]
[1,3,4]thiadiazol-5-yl)methylene)-4-oxo-2-thioxothiazolidin-3-yl)
acetic acid (6d)
138.78, 134.34, 130.12, 130.34, 128.92, 126.24, 121.45, 118.24, 116.89,
61.38, 42.71, 13.22, 10.12; HRMS (EI) m/z calcd for C19H15N5O3S3:
457.0337; found: 457.0342.
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢁ1): 3062.92 (Ar CeH stretch),
2962.33(Ali. CeH stretch), 2530.35 [(OeH stretch) acid], 1698.59
5.4.7. 2-(5-((2-cyclopropyl-6-(2,4-dihydroxyphenyl)imidazo[2,1-b]
[1,3,4]thiadiazol-5-yl)methylene)-4-oxo-2-thioxothiazolidin-3-yl)
acetic acid (6g)
[(C]O) acid], 1052 (CeF); 1H NMR (DMSO-d6)
d
ppm): 9.52 (s, 1H,
OH), 8.31 (s, 1H, CH), 7.16e7.92 (m, 4H, AreH), 4.45 (s, 2H, CH2), 1.
16e2.44 (m, 5H, cylopropyl); 13C NMR (DMSO-d6)
ppm: 193.12,
d
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢁ1): 3451.78 (OeH stretch),
3084.89 (Ar CeH stretch), 2953.89(Ali. CeH stretch), 1722.59 [(C]
169.63, 165.82, 160.12, 148.22, 138.73, 132.12, 130.32, 129.44, 122.45,
121.23, 118.12, 66.78, 49.12, 13.12, 10.23; HRMS (EI) m/z calcd for
C
19H13FN4O3S3: 460.0134; found: 460.0140.
O) acid]; 1H NMR (DMSO-d6)
d ppm): 10.28 (s, 1H, OH), 8.18 (s, 1H,
CH), 7.24e7.80 (m, 3H, AreH), 5.49 (s, 1H, OH), 5.36 (s, 1H, OH), 4.21
(s, 2H, CH2), 1.12e2.23 (m, 5H, cylopropyl); 13C NMR (DMSO-d6)
5.4.5. 2-(5-((6-(4-Chlorophenyl)-2-cyclopropylimidazo[2,1-b]
[1,3,4]thiadiazol-5-yl)methylene)-4-oxo-2-thioxothiazolidin-3-yl)
acetic acid (6e)
d
ppm: 193.34,169.88,164.56,160.34,154.23,148.68,135.99,132.78,
130.34, 128.67, 122.34, 116.89, 112.34, 110.56, 62.88, 42.71, 13.12,
10.76; HRMS (EI) m/z calcd for C19H14N4O5S3: 474.0126; found:
474.0130.
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢁ1): 3057.02 (Ar CeH stretch),
2893.10 (Ali. CeH stretch), 2667.36 [(OeH stretch) acid], 1714.91
[(C]O) acid], 692 (CeCl); 1H NMR (DMSO-d6)
d
ppm) 8.95 (s, 1H,
OH), 8.37 (s, 1H, CH), 7.35e7.81 (m, 4H,AreH), 4.42 (s, 2H, CH2),
1.11e1.69 (m, 5H, cylopropyl); 13C NMR (DMSO-d6)
ppm: 192.23,
169.73, 165.64, 148.24,135.78, 133.78, 132.83, 131.24, 130.78, 129.46,
5.5. 5-m-Tolyl-1,3,4-thiadiazol-2-amine (8)
d
It is synthesized as per the reported procedure [10].
Please cite this article in press as: H.M. Patel, et al., Design, synthesis and evaluation of small molecule imidazo[2,1-b][1,3,4]thiadiazoles as
inhibitors of transforming growth factor-b type-I receptor kinase (ALK5), European Journal of Medicinal Chemistry (2014), http://dx.doi.org/
10.1016/j.ejmech.2014.09.002

Table 6
Lipinski's rule of five for drug likeliness and in silico ADME properties of synthesized compounds 5 (aeg), 6 (aeg), 9 (aei) and 12 (aeh) by QikProp.
Criteria
Lipinski's rule of five (drug likeliness)
In silico ADME by QikProp, Schordinger 9.0
Sr.
No.
Compounds
Molecular
weight
QPlogP O/ H-bond
H-bond
acceptor
Violation of Lipinski's
rule
QPlogSb QPlogHERGc QPPCacod QPMDCKe QPlogKhsaf % Human oral
absorptiong
Violation of rule of
three
Wa
donor
5a
5b
269.32
2.515
0
4.5
4.5
0
0
ꢁ3.79 ꢁ5.048
ꢁ5.196 ꢁ4.888
1079.516
930.248 ꢁ0.093
95.959
0
0
338.211
3.484
0
1104.443 4874.467 0.16
1079.604 2469.754 0.061
100
5c
348.216
287.311
3.1
0
0
4.5
4.5
0
0
ꢁ4.679 ꢁ5.019
ꢁ4.166 ꢁ4.933
100
100
0
0
5d
2.755
1079.63
1683.594 ꢁ0.046
5e
5f
303.765
284.335
3.021
1.844
0
4.5
5.5
0
0
ꢁ4.558 ꢁ4.985
ꢁ4.033 ꢁ4.923
1079.567 2296.875 0.035
100
0
0
1.5
288.321
137.021
223.274 ꢁ0.055
99.914 ꢁ0.148
81.769
5g
6a
301.319
442.525
1.416
4.271
2
1
6
7
0
0
ꢁ3.852 ꢁ4.828
ꢁ5.505 ꢁ4.167
73.478
84.047
0
0
62.11
161.587 0.284
6b
511.415
5.145
1
7
2
ꢁ7.654 ꢁ3.814
61.245
753.14
0.501
63.138
1
0
6c
521.421
460.515
4.775
4.537
1
1
7
7
1
0
ꢁ5.167 ꢁ3.94
ꢁ5.644 ꢁ3.949
57.285
65.409
368.913 0.416
312.627 0.335
73.41
6d
86.009
0
(continued on next page)

Table 6 (continued)
Criteria
Lipinski's rule of five (drug likeliness)
In silico ADME by QikProp, Schordinger 9.0
Sr.
No.
Compounds
Molecular
weight
QPlogP O/ H-bond
H-bond
acceptor
Violation of Lipinski's
rule
QPlogSb QPlogHERGc QPPCacod QPMDCKe QPlogKhsaf % Human oral
absorptiong
Violation of rule of
three
Wa
donor
6e
6f
476.97
4.794
3.412
1
7
8
0
0
ꢁ5.211 ꢁ3.978
ꢁ6.229 ꢁ3.934
65.771
17.497
428.269 0.408
87.555
69.17
0
2
457.539
2.5
41.41
0.117
6g
474.523
2.937
3
8.5
0
ꢁ6.078 ꢁ3.936
7.517
16.756 0.002
59.824
2
9a
9b
9c
9d
9e
9f
291.37
4.673
4.675
4.273
4.194
3.787
3.34
0
2.5
2.5
2.5
2.5
3.5
4
0
0
0
0
0
0
0
0
0
0
ꢁ5.316 ꢁ6.216
ꢁ5.701 ꢁ6.101
ꢁ5.287 ꢁ6.173
ꢁ5.045 ꢁ6.14
ꢁ5.563 ꢁ6.086
ꢁ5.294 ꢁ6.003
ꢁ5.623 ꢁ6.121
ꢁ5.621 ꢁ6.128
ꢁ5.564 ꢁ6.085
ꢁ5.535 ꢁ6.147
4409.718 4228.445 0.724
100
0
0
0
0
0
0
0
0
0
0
360.26
0
4759.477 10,000
4409.407 10,000
4409.216 10,000
0.974
0.878
0.852
100
100
100
100
370.266
325.815
306.384
323.369
321.396
307.369
306.384
346.233
0
0
1.5
2
1175.906 1013.259 0.537
595.04
485.343 0.407
96.161
9g
9h
9i
4.746
4.109
3.786
4.956
0
3.25
3.25
3.5
2.5
4408.952 4227.273 0.699
100
100
100
100
1
1964.13
1764.445 0.596
1.5
0
1171.015 1008.692 0.538
12a
4114.758 10,000
4435.807 10,000
0.802
1.052
12b
415.123
4.958
0
2.5
0
ꢁ5.078 ꢁ6.03
100
0

H.M. Patel et al. / European Journal of Medicinal Chemistry xxx (2014) 1e15
13
5.6. General procedure for the synthesis of 6-substituted phenyl-2-
m-tolylimidazo[2,1-b][1,3,4]thiadiazole 9(aei)
A mixture of equimolar quantities of 5-m-tolyl-1,3,4-thiadiazol-
2-amine 8 (0.01 mol) and substituted phenacyl bromides (0.01 mol)
was refluxed in dry ethanol (50 mL) for 24 h. The excess of solvent
was distilled off and the solid hydrobromide salt that separated out
was collected by filtration, suspended in water and neutralized by
sodium carbonate to get free base 9(aei). The product was filtered,
washed with water, dried and crystallized from carbon
tetrachloride.
5.6.1. 5 6-Phenyl-2-m-tolylimidazo[2,1-b][1,3,4]thiadiazole (9a)
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢁ1): 3063.52 (Ar CeH stretch),
2924.25 (Ali. CeH stretch); 1H NMR (DMSO-d6)
d
ppm): 8.25 (s, 1H,
C-5-H, imidazoles), 7.24e7.81 (m, 9H, AreH), 2.37 (s, 3H, CH3); 13
NMR (DMSO-d6) ppm: 145.21, 142.34, 140.23, 138.57, 133.85,
C
d
133.72, 131.45, 130.23, 130.01, 129.24, 128.12, 127.78, 126.12, 124.78,
23.66; HRMS (EI) m/z calcd for C17H13N3S: 291.0830; found:
291.0834.
5.6.2. 6 6-(2,4-Dichlorophenyl)-2-m-tolylimidazo[2,1-b][1,3,4]
thiadiazole (9b)
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢁ1): 3021.87 (Ar CeH stretch),
2945.94 (Ali. CeH stretch), 734.78 (CeCl); 1H NMR (DMSO-d6)
d
ppm): 8.41 (s, 1H, C-5-H, imidazoles), 6.88e8.36 (m, 7H, AreH),
2.28 (s, 3H, CH3); 13C NMR (DMSO-d6)
d
ppm: 145.56, 143.89,
140.33, 138.67, 137.56, 134.78, 132.46, 131.23, 130.12, 130.01, 129.24,
129.00, 128.01, 127.42, 126.12, 122.34, 23.86; HRMS (EI) m/z calcd
for C17H11Cl2N3S: 359.0051; found: 359.0055.
5.6.3. 6-(4-Bromophenyl)-2-m-tolylimidazo[2,1-b][1,3,4]
thiadiazole (9c)
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢁ1): 3032.85 (Ar CeH stretch),
2987.24 (Ali. CeH stretch), 623.23 (CeBr); 1H NMR (DMSO-d6)
d
ppm): 8.41 (s, 1H, C-5-H, imidazoles), 7.20e7.84 (m, 8H, AreH),
2.36 (s, 3H, CH3); 13C NMR (DMSO-d6)
d
ppm: 145.45, 142.68,
140.12, 138.28, 136.94, 132.81, 131.20, 130.24, 129.91, 129.12, 128.23,
126.12, 124.78, 122.34, 24.34; HRMS (EI) m/z calcd for C17H12BrN3S:
368.9935; found: 368.9939.
5.6.4. 6-(4-Chlorophenyl)-2-m-tolylimidazo[2,1-b][1,3,4]
thiadiazole (9d)
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢁ1): 3057.78 (Ar CeH stretch),
2956.78 (Ali. CeH stretch), 714.68 (CeCl); 1H NMR (DMSO-d6)
d
ppm): 8.33 (s, 1H, C-5-H, imidazoles), 7.35e8.08 (m, 8H, AreH),
2.41 (s, 3H, CH3); 13C NMR (DMSO-d6)
d
ppm: 145.46,142.68,141.42,
138.24, 136.78, 135.12, 132.24, 131.14, 130.23, 129.13, 129.12, 128.12,
126.92, 124.13, 23.34,; HRMS (EI) m/z calcd for C17H12ClN3S:
325.0440; found: 325.0444.
5.6.5. 3-(2-m-Tolylimidazo[2,1-b][1,3,4]thiadiazol-6-yl)aniline (9e)
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢁ1): 3334.42 and 3312.43 (NH-
stretch), 3083.37 (Ar CeH stretch), 2932.89 (Ali. CeH stretch); 1H
NMR (DMSO-d6)
(m, 8H, AreH), 4.54 (s, 2H,NH2), 2.33 (s, 3H, CH3); 13C NMR (DMSO-
d6) ppm: 149.46, 146.32, 142.12, 140.82, 138.42, 136.82, 134.46,
d ppm): 8.03 (s, 1H, C-5-H, imidazoles), 6.56e7.72
d
132.21, 131.46, 130.23, 129.12, 128.24, 126.68, 124.12, 121.78, 118.36,
23.28; HRMS (EI) m/z calcd for C17H14N4S: 306.0939; found:
306.0935.
Please cite this article in press as: H.M. Patel, et al., Design, synthesis and evaluation of small molecule imidazo[2,1-b][1,3,4]thiadiazoles as
inhibitors of transforming growth factor-b type-I receptor kinase (ALK5), European Journal of Medicinal Chemistry (2014), http://dx.doi.org/
10.1016/j.ejmech.2014.09.002

14
H.M. Patel et al. / European Journal of Medicinal Chemistry xxx (2014) 1e15
5.6.6. 4-(2-m-Tolylimidazo[2,1-b][1,3,4]thiadiazol-6-yl)benzene-
1,3-diol (9f)
8.62 (s, 1H, C-5-H, imidazoles), 7.24e8.57 (m, 8H, AreH); 13C NMR
(DMSO-d6) ppm: 172.24, 144.73,138.27, 136.26, 136.10, 132.56,
d
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢁ1): 3577.32 (OH stretch),
3067.45 (Ar CeH stretch), 2923.76 (Ali. CeH stretch); 1H NMR
131.60, 130.91, 130.67, 129.24, 128.37, 127.55, 126.24, 124.63; HRMS
(EI) m/z calcd for C16H9Cl2N3S: 344.9894; found: 344.9899.
(DMSO-d6)
C-5-H, imidazoles), 6.22e8.35 (m, 7H, AreH), 2.14 (s, 3H, CH3); 13
NMR (DMSO-d6) ppm: 156.46, 154.88, 148.12, 142.10, 140.98,
138.52, 134.84, 132.37, 130.43, 129.18, 128.00, 126.79, 124.83, 118.31,
115.60, 112.66, 23.46; HRMS (EI) m/z calcd for C17H13N3O2S:
323.0728; found: 323.0724.
d
ppm): 13.02 (s, 1H, OH), 12.45 (s, 1H, OH), 8.41 (s, 1H,
5.8.2. 6-(4-Bromophenyl)-2-(2,4-dichlorophenyl)imidazo[2,1-b]
[1,3,4]thiadiazole (12b)
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢁ1): 3032.12 (Ar CeH stretch),
2946.78 (CeH stretch), 756.83 (CeCl), 631.48 (CeBr); 1H NMR
C
d
(DMSO-d6)
d
ppm): 8.41 (s, 1H, C-5-H, imidazoles), 7.24e8.57 (m,
ppm: 172.81, 142.78, 138.56,
7H, AreH); 13C NMR (DMSO-d6)
d
5.6.7. 6-(4-Methoxyphenyl)-2-m-tolylimidazo[2,1-b][1,3,4]
thiadiazole (9g)
136.48, 134.88, 133.36, 132.28, 132.10, 130.88, 129.56, 128.44, 127.24,
124.78, 122.66; HRMS (EI) m/z calcd for C16H8BrCl2N3S: 422.8999;
found: 422.8994.
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢁ1): 3023.54 (Ar CeH stretch),
2945.83 (Ali. CeH stretch); 1H NMR (DMSO-d6)
d
ppm): 8.41 (s, 1H,
C-5-H, imidazoles), 7.61e8.36 (m, 8H, AreH), 3.82 (s, 3H, OCH3),
2.31 (s, 3H, CH3); 13C NMR (DMSO-d6)
ppm: 158.58, 148.32,
5.8.3. 3-(2-(2,4-Dichlorophenyl)imidazo[2,1-b][1,3,4]thiadiazol-6-
yl)aniline (12c)
d
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢁ1): 3334.12 and 3301.46 (NH-
stretch), 3021.42 (Ar CeH stretch), 2954.23 (CeH stretch), 743.54
142.24, 138.68, 136.24, 133.68, 131.42, 130.56, 129.34, 128.85, 127.19,
126.38, 122.56, 120.88, 55.28, 23.46; HRMS (EI) m/z calcd for
C
18H15N3OS: 321.0936; found: 321.0940.
(CeCl); 1H NMR (DMSO-d6)
d
ppm): 8.45 (s, 1H, C-5-H, imidazoles),
7.23e8.16 (m, 7H, AreH), 4.85 (s, 2H, NH2); 13C NMR (DMSO-d6)
d ppm: 172.68, 150.24, 143.14, 138.46, 136.78, 134.34, 132.12, 131.56,
5.6.8. 2-(2-m-Tolylimidazo[2,1-b][1,3,4]thiadiazol-6-yl)phenol (9h)
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢁ1): 3578.92 (OeH stretch),
3039.38 (Ar CeH stretch), 28,235.82 (Ali. CeH stretch),; 1H NMR
130.24, 130.12, 129.34, 128.24, 126.64, 124.68, 120.24, 118.42; HRMS
(EI) m/z calcd for C16H10Cl2N4S: 360.0003; found: 360.0007.
(DMSO-d6)
oles), 7.20e8.23 (m, 8H, AreH), 2.34 (s, 3H, CH3); 13C NMR (DMSO-
d6) ppm: 156.88, 148.34, 142.56, 140.56, 138.34, 134.78, 131.34,
130.78, 130.56, 129.67, 129.56, 127.56, 122.45, 121.46, 120.68, 118.44,
23.68; HRMS (EI) m/z calcd for C17H13N3OS: 307.0779; found:
307.0775.
d
ppm): 10.72 (s, 1H, OH), 8.43 (s, 1H, C-5-H, imidaz-
5.8.4. 4-(2-(2,4-Dichlorophenyl)imidazo[2,1-b][1,3,4]thiadiazol-6-
yl)benzene-1,3-diol (12d)
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢁ1): 3523.42 (OH stretch),
3067.54 (Ar CeH stretch), 2945.89 (CeH stretch), 723.23 (CeCl); 1H
d
NMR (DMSO-d6)
1H, C-5-H, imidazoles), 6.93e8.35 (m, 6H, AreH); 13C NMR (DMSO-
d6) ppm: 172.64, 158.68, 156.24, 142.24, 138.84, 136.22, 134.78,
d ppm): 12.02 (s, 1H, OH), 11.12 (s, 1H, OH), 8.41 (s,
5.6.9. 4-(2-m-Tolylimidazo[2,1-b][1,3,4]thiadiazol-6-yl)aniline (9i)
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢁ1): 3283.34 and 3241.56 (NH-
stretch), 3034.75 (Ar CeH stretch), 2923.78 (Ali. CeH stretch); 1H
d
132.56, 131.86,130.46, 129.24,128.23, 126.23, 122.56, 118.34,112.78;
HRMS (EI) m/z calcd for C16H9Cl2N3O2S: 376.9793; found: 376.9798.
NMR (DMSO-d6)
(m, 8H, AreH), 4.42 (s, 2H,NH2), 2.31 (s, 3H, CH3); 13C NMR (DMSO-
d6) ppm: 151.45, 146.89, 142.34, 140.89, 138.22, 134.84, 130.64,
129.18, 129.01, 128.34, 127.92, 126.12, 124.34, 120.22, 23.78; HRMS
(EI) m/z calcd for C17H14N4S: 306.0939; found: 306.0934.
d
ppm): 8.03 (s, 1H, C-5-H, imidazoles), 6.55e7.71
5.8.5. 2-(2,4-Dichlorophenyl)-6-(4-methoxyphenyl)imidazo[2,1-b]
[1,3,4]thiadiazole (12e)
d
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢁ1): 3042.54 (Ar CeH stretch),
2978.93 (CeH stretch), 724.23 (CeCl); 1H NMR (DMSO-d6)
d
ppm):
8.41 (s, 1H, C-5-H, imidazoles), 7.61e8.36 (m, 7H, AreH), 3.82 (s, 3H,
OCH3); 13C NMR (DMSO-d6)
ppm: 171.78, 162.66, 142.78, 138.56,
5.7. 5-(2,4-dichlorophenyl)-1,3,4-thiadiazol-2-amine (11)
d
136.42, 134.78, 132.16, 131.29, 130.13, 128.45, 126.14, 124.53, 122.63,
120.68, 55.34; HRMS (EI) m/z calcd for C17H11Cl2N3OS: 375.0000;
found: 375.0005.
It is synthesized as per the reported procedure [10].
5.8. General procedure for the synthesis of 2-(2,4-dichlorophenyl)-
6substituted phenylimidazo[2,1-b][1,3,4]thiadiazole 12(aeg)
5.8.6. 2-(2-(2,4-Dichlorophenyl)imidazo[2,1-b][1,3,4]thiadiazol-6-
yl)phenol (12f)
A mixture of equimolar quantities of 5-(2,4-dichlorophenyl)-
1,3,4-thiadiazol-2-amine 11 (0.01 mol) and substituted phenacyl
bromides (0.01 mol) was refluxed in dry ethanol (50 mL) for 24 h.
The excess of solvent was distilled off and the solid hydrobromide
salt that separated out was collected by filtration, suspended in
water and neutralized by sodium carbonate to get free base
12(aeg). The product was filtered, washed with water, dried and
crystallized from carbon tetrachloride.
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢁ1): 3512.12 (OH-stretch),
3076.23 (Ar CeH stretch), 2965.21 (CeH stretch), 721.54 (CeCl); 1H
NMR (DMSO-d6)
d
ppm): 10.52 (s, 1H, OH), 8.43 (s, 1H, C-5-H, im-
ppm:
idazoles), 7.20e8.23 (m, 7H, AreH); 13C NMR (DMSO-d6)
d
172.45, 158.56, 144.68, 140.24, 138.68, 136.34, 134.24, 132.11, 130.23,
129.78,128.68,126.66,124.34,122.12,120.78,118.48; HRMS (EI) m/z
calcd for C16H9Cl2N3OS: 360.9843; found: 360.9847.
5.8.1. 2-(2,4-dichlorophenyl)-6-phenylimidazo[2,1-b][1,3,4]
thiadiazole (12a)
5.8.7. 4-(2-(2,4-Dichlorophenyl)imidazo[2,1-b][1,3,4]thiadiazol-6-
yl)aniline (12g)
This compound was prepared and purified as per the above
This compound was prepared and purified as per the above
mentioned procedure: IR (KBr, cmꢁ1): 3054.00 (Ar CeH stretch),
mentioned procedure: IR (KBr, cmꢁ1): 3087.83 (Ar CeH stretch),
2939.21 (CeH stretch), 776.12 (CeCl); 1H NMR (DMSO-d6)
d
ppm):
2939.93 (CeH stretch), 724.12 (CeCl); 1H NMR (DMSO-d6)
d ppm):
Please cite this article in press as: H.M. Patel, et al., Design, synthesis and evaluation of small molecule imidazo[2,1-b][1,3,4]thiadiazoles as
inhibitors of transforming growth factor-b type-I receptor kinase (ALK5), European Journal of Medicinal Chemistry (2014), http://dx.doi.org/
10.1016/j.ejmech.2014.09.002

H.M. Patel et al. / European Journal of Medicinal Chemistry xxx (2014) 1e15
15
[4] K. Miyazawa, M. Shinozaki, T. Hara, T. Furuya, K. Miyazono, Genes. Cells 7
(2002) 1191e1204.
[5] J. Massague, Ann. Rev. Biochem. 67 (1998) 773e791.
[6] M. Lutz, P. Knaus, Cell. Signal 14 (2002) 977e988.
8.46 (s,1H, C-5-H, imidazoles), 7.23e7.96 (m, 7H, AreH), 4.09 (s, 2H,
NH2); 13C NMR (DMSO-d6)
ppm: 170.34, 148.78, 146.71, 140.46,
138.65, 136.24, 132.78, 130.29, 128.34, 127.43, 126.68, 124.34,
122.88, 120.56; HRMS (EI) m/z calcd for C16H10Cl2N4S: 360.0003;
found: 360.0008.
d
[7] M. Lahn, S. Klocker, B.S. Berry, Expert. Opin. Invest. Drugs 14 (2005) 629e643.
[8] M.N. Noolvi, H.M. Patel, Eur. J. Med. Chem. 46 (2011) 2327e2346.
[9] M.N. Noolvi, H.M. Patel, Eur. J. Med. Chem. 46 (2011) 4411e4418.
[10] M.N. Noolvi, H.M. Patel, S. Kamboj, A. Kaur, V. Mann, Eur. J. Med. Chem. 56
(2012) 56e69.
[11] M.N. Noolvi, H.M. Patel, M. Kaur, Eur. J. Med. Chem. 54 (2012) 447e462.
[12] M.N. Noolvi, H.M. Patel, V. Bhardwaj, Med. Chem. 7 (2011) 2002e2012.
[13] M.N. Noolvi, H.M. Patel, Lett. Drug. Desi. Disc. 7 (2010) 556e586.
[14] G. Hoelzemann, H. Greiner, E. Rossignol, D. Swinnen, WO 2010/012345 A1,
2010.
Acknowledgment
The authors would like to thank General Advisor and Member
Secretary, Gujarat Council on Science and Technology, Gandhinagar
(Grant No. GUJCOST/MRP/12-13/65/1332), National Research
Foundation, South Africa and College of Health Sciences, University
of KwaZulu-Natal, South Africa for funding this project.
[15] A.K. Gadad, M.N. Noolvi, R.V. Karpoormath, Bioorg. Med. Chem. 12 (2004)
5651.
[16] B.C.C. Cantello, M.A. Cawthorne, G.P. Cottam, P.T. Duff, D. Haigh, R.M. Hindley,
C.A. Lister, S.A. Smith, P.L. Thurlby, J. Med. Chem. 37 (1994) 3977.
[17] M. Sortino, P. Delgado, S. Juarez, J. Quiroga, R. Abonia, B. Insuasty, L. Nogueras,
F.M. Garibotto, R.D. Enriz, S.A. Zacchino, Bioorg. Med. Chem. 15 (2007)
484e494.
Appendix A. Supplementary data
[18] F. Gellibert, J. Woolven, M.H. Fouchet, N. Mathews, H. Goodland, V. Lovegrove,
A. Laroze, V.L. Nguyen, S. Sautet, R. Wang, C. Janson, W. Smith, G. Krysa,
V. Boullay, A.C. deGouville, S. Huet, D. Hartley, J. Med. Chem. 47 (2004) 4494.
[19] F. Gellibert, A.C. deGouville, J. Woolven, N. Mathews, V.L. Nguyen, C. Bertho-
Ruault, A. Patikis, E.T. Grygielko, N.J. Laping, S. Huet, J. Med. Chem. 49 (2006)
2210e2221.
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.ejmech.2014.09.002.
References
[20] D.K. Kim, Y. Jang, H.S. Lee, H.J. Park, J. Yoo, J. Med. Chem. 50 (2007) 3143.
[21] Y.H. Zhao, J. Le, M.H. Abraham, A. Hersey, P.J. Eddershaw, C.N. Luscombe,
D. Butina, G. Beck, B. Sherborne, I. Cooper, J.A. Platts, J. Pharm. Sci. 90 (2001)
749e784.
[1] D. Bonafoux, C. Chuaqui, P.A.P. Ann Boriack-Sjodin, C. Fitch, G. Hankins,
S. Josiah, B. Black, G. Hetu, L. Ling, W. Lee, Bioorg. Med. Chem. Lett. 19 (2009)
912e916.
[2] D. Kim, J. Kim, H. Park, Bioorg. Med. Chem. Lett. 14 (2004) 2401e2405.
[3] M. Huse, T.W. Muir, L. Xu, Y. Chen, J. Kuriyan, J. Mol. Cell. 8 (2001) 671e682.
Please cite this article in press as: H.M. Patel, et al., Design, synthesis and evaluation of small molecule imidazo[2,1-b][1,3,4]thiadiazoles as
inhibitors of transforming growth factor-b type-I receptor kinase (ALK5), European Journal of Medicinal Chemistry (2014), http://dx.doi.org/
10.1016/j.ejmech.2014.09.002