Synthesis, molecular docking study and in vitro thymidine phosphorylase inhibitory potential of oxadiazole derivatives

Article abstract of DOI:10.1016/j.bioorg.2018.02.020

We have synthesized oxadiazole derivatives (1–16), characterized by ¹H NMR, ¹³C NMR and HREI-MS and screened for thymidine phosphorylase inhibitory potential. All derivatives display varied degree of thymidine phosphorylase inhibitio

Full text of DOI:10.1016/j.bioorg.2018.02.020

Accepted Manuscript
Synthesis, Molecular docking study and in vitro Thymidine Phosphorylase In-
hibitory Potential of Oxadiazole Derivatives
Hayat Ullah, Fazal Rahim, Muhammad Taha, Imad Uddin, Abdul Wadood,
Syed Adnan Ali Shah, Rai Khalid Farooq, Mohsan Nawaz, Zainul Wahab,
Khalid Mohammed Khan
PII:
S0045-2068(17)30982-3
DOI:
https://doi.org/10.1016/j.bioorg.2018.02.020
YBIOO 2280
Reference:
To appear in:
Bioorganic Chemistry
Received Date:
Revised Date:
Accepted Date:
26 December 2017
18 February 2018
21 February 2018
Please cite this article as: H. Ullah, F. Rahim, M. Taha, I. Uddin, A. Wadood, S. Adnan Ali Shah, R. Khalid Farooq,
M. Nawaz, Z. Wahab, K. Mohammed Khan, Synthesis, Molecular docking study and in vitro Thymidine
Phosphorylase Inhibitory Potential of Oxadiazole Derivatives, Bioorganic Chemistry (2018), doi: https://doi.org/
1
0.1016/j.bioorg.2018.02.020
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Synthesis, Molecular docking study and in vitro Thymidine Phosphorylase Inhibitory
Potential of Oxadiazole Derivatives
a
a*,
b
a
c
Hayat Ullah , Fazal Rahim Muhammad Taha , Imad Uddin , Abdul Wadood , Syed Adnan
d,e
f
a
g
h
Ali Shah , Rai Khalid Farooq , Mohsan Nawaz , Zainul Wahab , Khalid Mohammed Khan
a
b
Department of Chemistry, Hazara University, Mansehra-21300, Pakistan; Department of
Clinical Pharmacy, Institute for Research and Medical Consultations (IRMC), Imam
c
Abdulrahman Bin Faisal University, P.O. Box 31441, Dammam, Saudi Arabia; Department of
d
Biochemistry, Abdul Wali Khan University Mardan, Mardan-23200, Pakistan. Atta-ur-Rahman
Institute for Natural Product Discovery, Universiti Teknologi MARA (UiTM), Puncak Alam
e
Campus, 42300 Bandar Puncak Alam, Selangor, Malaysia, Faculty of Pharmacy, Universiti
Teknologi MARA, Puncak Alam Campus, 42300 Bandar Puncak Alam, Selangor D.E., Malaysia.
f
Department of Neuroscience Research, Institute of Research and Medical Consultations, Imam
Abdulrahman Bin Faisal University, P.O. Box 1982 , Dammam 31441, Saudi Arabia;
g
h
Department of Conservation Sciences, Hazara University, Mansehra-21300, Pakistan; H. E. J.
Research Institute of Chemistry, International Center for Chemical and Biological Sciences,
University of Karachi, Karachi-75270, Pakistan.
…
……………………………………………………………………………………………………
Abstract:
1
13
We have synthesized oxadiazole derivatives (1-16), characterized by HNMR, CNMR and
HREI-MS and screened for thymidine phosphorylase inhibitory potential. All derivatives display
varied degree of thymidine phosphorylase inhibition in the range of 1.10 ± 0.05 to 49.60 ± 1.30
μM when compared with the standard inhibitor 7-Deazaxanthine having an IC50 value 38.68 ±
1
.12 μM. Structure activity relationships (SAR) has been established for all compounds to
explore the role of substitution and nature of functional group attached to the phenyl ring which
applies imperious effect on thymidine phosphorylase activity. Molecular docking study was
performed to understand the binding interaction of the most active derivatives with enzyme
active site.
Keywords: Synthesis, oxadiazole, thymidine phosphorylase, molecular docking, SAR.

Correspondence and reprints
E-mail: fazalstar@gmail.com, Tel.: 0092-335-9528343;
E-mail: E-mail: taha_hej@yahoo.com and mtaha@iau.edu.saTel: 00966502057370
1

1
.0. Introduction
Thymidine phosphorylase (TP) is a pro-angiogenic factor which catalyzes the reversible
phosphorolysis of thymidine into thymine and 2 ؘ- deoxy- -ribose 1-phosphate [1, 2]. The 2 ؘ-
deoxy- -ribose 1-phosphate undergoes further dephosphorylation to yield 2 ؘ- deoxy- -ribose
D
D
D
which motivates the discharge of vascular endothelial growth factor (VEGF). VEGF stimulates
a numeral of processes including endothelial cells for discharge of matrix metalloproteinases,
proliferation and migration of endothelial cells to tumor tissue. These movements result in fast
generation of new blood vessels and cancer metastasis [3]. Thymidine phosphorylase inhibitors
distract the production of 2 ؘ- deoxy- -ribose and in turn destroy tumor growth [4]. Consequently,
D
there is an urgent need to develop new and effective TP inhibitors which have the capability to
stop tumor growth [5]. A number of struggles have been described on the development of TP
inhibitors [6-8]. The pyrimidine analog 5-chloro-6-[1-(2-iminopyrrolidinyl)methyl] uracil
hydrochloride (TPI) is the most effective inhibitor of human TP known till date and 7-
deazaxanthine (7DX) is the first purine analog recognized as TP inhibitor (Fig-1) [9-11].
Furthermore, TPI is currently being evaluated in phase-II clinical trials for solid tumors.
Figure-1: Structure of known TP inhibitors- TPI and 7DX
1
,3,4-oxadiazole moiety is well known due to its number of biological properties such as anti-
cancer, anti-bacterial, anti-tumor, anti-trypanosomacruzi, anti-microbial, anti-HIV and anti-
inflammatory activities [12-20]. 1,3,4-oxadiazole analogs are also recognized as effective
inhibitors of dengue and West Nile Virus NS2B/NS3 proteases, immunosuppressive agents, anti-
hepatitis B virus compounds and also urease inhibitors [21-25].
Our research group has reported the α-glucosidase inhibitory activity of oxindole based
oxadiazole analogs [26], α-glucosidase inhibitory of 5-aryl-2-(6’-nitrobenzofuran-2’-yl)-1,3,4-
oxadiazoles [27], as well as also reported the novel sulfonamides having oxadiazole ring as
potential class of β-glucuronidase inhibitors [28] (Figure-2). Keeping in view the great biological
2

potential of oxadiazole here in this study we decided to synthesize oxadiazole derivatives 1-16
and evaluation for their thymidine phosphorylase inhibition potential.
Figure-2: Rational of the current study
2
2
.0. Results and Discussion
.1. Chemistry
Methyl 4-cyanobenzoate was mixed with excess of hydrazine hydrate in methanol and refluxed
for 6 hrs to give us compound I. Compound I was then treated with methyl 4-formylbenzoate in
methanol in the presence of catalytic amount of acetic acid to afford hydrazone II, which was
then subjected through an oxidative cyclization using phenyliododiacetate (PhI(OAc) ) in
2
dichloromethane to form 1,3,4-oxadiazole III. The ester functional group of compound III was
further converted into hydrazide by treating with hydrazine hydrate to afford compound IV,
which was then reacted with various different substituted benzaldehyde in methanol to targeted
1
,3,4-oxadiazole analogs (1-16).
3

Scheme: Synthesis of oxadiazole derivatives (1-16)
Table-1: Different substituents of oxadiazole derivatives and their thymidine phosphorylase
activity (1-16)
S. No
1
R
IC50 values S. No
4.30 ± 0.10
R
IC50 values
29.20 ± 0.50
9
4

2
9.40 ± 0.20
10
8.10 ± 0.30
3
4
39.10 ± 0.80
28.60 ± 0.40
11
12
17.30 ± 0.40
4.60 ± 0.2
5
6
6.60 ± 0.20
13
14
1.10 ± 0.05
2.40 ± 0.10
16.10 ± 0.20
7
8
36.20 ± 0.90
15
16
17.50 ± 0.30
49.60 ± 1.30
N.A
7
-Deazaxanthine
38.68 ± 1.12 μM
2
.2. In vitro thymidine phosphorylase inhibitory potential:
In continuous effort on enzyme inhibition [29]; sixteen derivatives of oxadiazole (1-16) were
synthesized and screened against thymidine phosphorylase inhibitory potential. These derivatives
displayed variable degree of inhibition in the range of 1.10 ± 0.05 to 49.60 ± 1.30 μM when
compared with the standard inhibitor 7-Deazaxanthine having an IC50 value 38.68 ± 1.12 μM
(
Table-1). Derivatives 1, 2, 3, 4, 5, 6, 7, 9, 10, 11, 12, 13, 14, 15 showed excellent thymidine
5

phosphorylase inhibitory potentials with IC50 values 4.30 ± 0.10, 9.40 ± 0.20, 39.10 ± 0.80, 28.60
0.40, 6.60 ± 0.20, 16.10 ± 0.20, 36.20 ± 0.90, 29.20 ± 0.50, 8.10 ± 0.30, 17.30 ± 0.40, 4.60 ±
.2, 1.10 ± 0.05, 2.40 ± 0.10 and 17.50 ± 0.30μM respectively, which is many folds better than
±
0
the standard 7-Deazaxanthine. Derivative 16 showed good inhibitory potential while derivative 8
remain inactive among the series. If we compare the TP inhibition of our design compounds with
other oxadiazole analogs as reported by
[15, 16] our compounds are superior. The
SAR in previous study was mainly based on substitution pattern on phenyl ring. Here in this
study the structural activity relationship (SAR) was also mainly based upon by bring about
different substituents on phenyl ring.
The most active derivative among the series is compound 13 (IC50 = 1.10 ± 0.05 μM) having two
methoxy and one hydroxy substituents on the phenyl ring. The greater potential of this
compound is mainly seems to be due to the two methoxy groups which is electron donating
group.
If we compare derivative 12 (IC50 = 4.60 ± 0.2 µM) having one methoxy and one hydroxy
substituents with derivative 14 (IC50 = 2.40 ± 0.10 µM) also having one methoxy and one
hydroxy substituents on phenyl ring. In derivative 12 the methoxy group is present at 4-position
and hydroxy is present at 3-position and in derivative 13 the methoxy group is present at 3-
position and hydroxy at 4-position on phenyl ring. Both derivatives have the same methoxy and
hydroxy groups but the position of the hydroxy and methoxy groups are different on phenyl ring.
Compound 13 was found to be superior who showed that position of substituent also play role in
this inhibition.
Figure-3: Comparison of structure activity relationship between analogs 12 and 14
6

All those analogs having chloro group on phenyl ring like analog 1 and 2 showed greater
potential among the series. The analog 1, a 2,4-dichloro analog (IC50 = 4.30 ± 0.10 µM) show
greater potential as compare to 4-chloro analog 2 (IC50 = 9.40 ± 0.20 µM). This shows that
increasing the number of chloro group correspondingly increase the inhibitory potential of these
compounds.
Figure-4: Comparison of structure activity relationship between analogs 1 and 2
If we compare derivative 10 having IC50 value 8.10 ± 0.30 μM with derivative 11 having IC50
value 17.30 ± 0.40 μM, both the derivatives have hydroxy group on phenyl ring, but the
arrangement of hydroxy group is different in them which confirm that the difference in position
of substituents greatly affect the inhibitory potentials of the derivatives.
Figure-5: Comparison of structure activity relationship between analogs 10 and11
To understand the binding interaction of the most active analogs molecular docking study was
performed.
7

2
.3. Docking study
The docking results of the oxadiazole series with the thymidine phosphorylase enzyme have
given good information about the nature of the binding mode that was excellent correlated with
the experimental results. From the docking calculation study, it was observed that the top ranked
conformations of almost all compounds were well accommodated inside the active site of
thymidine phosphorylase enzyme and were involved in various type of interactions with the
active site residues of thymidine phosphorylase enzyme i.e., His 85, Arg 115, Thr 123, Tyr 168,
Arg 171, Ile 183, Ser 186, Lys 190 and Phe 210 etc. The detail of docking scores and interactions
for all compounds are listed in Table-2. The structural features observed in this group for the
active nature of compounds are the presence of electronegative groups like -OH, halogen and
Methoxy (MeO) groups. Among halogen Cl containing compounds were found superior than Br
supported by hydroxyl group. Figure-6 (a-d) displays the interaction modes of some most active
compounds among these docked conformations. The confirmations obtained after docking
showed good docking scores and demonstrated healthy in-silico inhibition of the thymidine
phosphorylase enzyme. Overall a good correlation was observed between the docking study and
biological evaluation of active compounds.
8

Figure-6: Docking conformations of compounds on thymidine phosphorylase enzyme. (a) 3D
binding mode of compound 13 as inhibitor of thymidine phosphorylase enzyme. (b) 3D binding
mode of compound 14. (c) 3Dbinding mode of compound 1. (d) 3D binding mode of compound
1
2 in binding cavity of thymidine phosphorylase enzyme. Ligands are shown green color.
Figure-7: Correlation graph for IC50 values and docking predicted activity.
Table-2: Docking scores and report of predicted interactions of docked conformations.
Compounds Docking
scores (S)
Interaction Report
Ligand Receptor
Interaction Distance E (kcal/mol)
1
-12.9432
N 28
N 31
OD1 TYR 168 (A)
H-donor
3.03
2.63
3.76
2.22
3.28
2.42
-0.2
-0.2
-0.2
-8.2
-0.7
-2.6
N ARG 115 (A)
N ARG 115 (A)
NZ LYS 190 (A)
NH2 ARG 171 (A)
NZ LYS 190 (A)
H-acceptor
pi-H
5
-ring
N 32
N 13
O 27
H-acceptor
H-acceptor
H-acceptor
2
-11.4997
9

N 45
-ring
N
MET 211 (A)
H-acceptor
3.55
3.59
3.04
3.41
2.91
4.26
3.89
4.80
4.60
4.09
2.78
3.61
4.14
3.91
4.79
4.33
4.22
4.51
4.05
4.36
4.53
3.75
3.57
3.40
2.67
3.36
3.92
-1.3
-0.0
-1.4
-0.3
-0.8
-0.1
-0.3
-0.1
-0.1
-0.7
-0.4
-0.1
-0.2
-0.4
-0.1
-0.4
-0.2
-0.3
-0.6
-0.1
-0.4
-0.2
-0.1
-0.1
-2.0
-0.1
-0.1
6
6-ring TYR 168 (A) pi-pi
3
-8.1102
C 1
OD2 ASP 92 (A) H-donor
C 24
N 28
N 30
N 59
O
O
ARG 115 (A) H-donor
LEU 117 (A) H-donor
CE1 PHE 210 (A) H-acceptor
SER 95 (A) H-acceptor
N
6
6
6
-ring
-ring
-ring
CA GLY 122 (A) pi-H
CB ALA 175 (A) pi-H
CZ PHE 210 (A) pi-H
OD2 ASP 172 (A) H-donor
CB LEU 117 (A) H-acceptor
CG MET 111 (A) H-acceptor
4
-8.8854
C 37
O 27
N 49
N 49
N
ILE 112 (A) H-acceptor
6
6
5
6
6
6
6
-ring
-ring
-ring
-ring
-ring
-ring
-ring
CA HIS 85
SER 86
(A) pi-H
(A) pi-H
(A) pi-H
(A) pi-H
N
CB SER 86
CB SER 86
CA SER 113 (A) pi-H
CB THR 120 (A) pi-H
CG2 VAL 177 (A) pi-H
5
-11.7449
C 34
C 36
CL 42
O 43
N 12
N 13
OD2 ASP 83 (A) H-donor
SD MET 111 (A) H-donor
OG1 THR 123 (A) H-donor
OG SER 95 (A) H-donor
CA LYS 165 (A) H-acceptor
NZ LYS 190 (A) H-acceptor
10

6
6
6
6
5
5
5
6
-ring
-ring
-ring
-ring
-ring
-ring
-ring
-ring
CA HIS 85 (A) pi-H
SER 86 (A) pi-H
4.23
3.74
4.43
3.88
4.16
4.24
3.41
3.12
3.81
2.71
2.69
3.87
4.32
4.20
3.32
3.14
3.28
3.20
3.87
4.47
-0.6
-0.5
-0.1
-0.1
-0.1
-0.5
-0.3
-0.1
-0.1
-3.3
-3.1
-0.1
-0.1
-0.8
-0.2
-0.4
-0.4
-0.1
-0.2
-0.1
N
CB SER 86 (A) pi-H
CA SER 113 (A) pi-H
CA LYS 165 (A) pi-H
CB TYR 168 (A) pi-H
CD2 TYR 168 (A) pi-H
CE LYS 190 (A) pi-H
6
-11.4853
C 36
N 12
N 53
C 34
O
N
N
TYR 168 (A) H-donor
THR 123 (A) H-acceptor
SER 95
(A) H-acceptor
6-ring TYR 168 (A) H-pi
OG SER 113 (A) pi-H
CD1 LEU 117 (A) pi-H
CA GLY 122 (A) pi-H
OD2 ASP 164 (A) H-donor
6
6
5
-ring
-ring
-ring
7
-8.2376
C 22
C 43
C 58
N 63
O
O
SER 86 (A) H-donor
SER 186 (A) H-donor
CD1 LEU 117 (A) H-acceptor
OH TYR 168 (A) pi-H
NA
6
-ring
8
9
NA
NA
-8.6509
C 43
N 52
N 52
O 49
OD2 ASP 172 (A) H-donor
CD LYS 191 (A) H-acceptor
NZ LYS 191 (A) H-acceptor
6-ring PHE 210 (A) H-pi
CD1 LEU 117 (A) pi-H
CA GLY 118 (A) pi-H
3.76
2.75
3.26
4.50
4.60
4.88
-0.2
-0.6
-3.0
-0.2
-0.1
-0.2
6
6
-ring
-ring
11

6
6
-ring
-ring
CA GLY 118 (A) pi-H
5-ring HIS 85 (A) pi-pi
4.12
3.68
3.66
3.10
3.60
3.53
4.04
3.71
3.19
3.43
3.88
3.97
2.85
4.83
4.12
2.79
2.21
3.26
3.43
4.40
2.15
3.52
2.01
2.01
1.91
2.01
2.17
-0.2
-0.0
-0.1
-0.1
-0.1
-0.1
-0.1
-0.3
-0.7
-0.2
-0.2
-0.1
-0.6
-0.3
-0.1
-1.4
-0.2
-4.2
-3.2
-0.7
-2.4
-0.2
-2.4
-0.2
-2.3
-2.3
-2.3
1
0
-9.4593
O 43
O 27
N 30
C 9
O
ARG 371 (A) H-donor
CB LEU 117 (A) H-acceptor
CD1 LEU 117 (A) H-acceptor
5-ring HIS 85 (A) H-pi
CB ILE 112 (A) pi-H
CA GLY 118 (A) pi-H
6
6
-ring
-ring
1
1
-9.6861
C 4
O
O
N
ILE 112 (A) H-donor
ARG 370 (A) H-donor
THR 123 (A) H-acceptor
O 43
N 12
O 27
N 46
CE1 PHE 210 (A) H-acceptor
CB LYS 84 (A) H-acceptor
CA HIS 85 (A) pi-H
6
6
-ring
-ring
CA GLY 118 (A) pi-H
1
1
2
3
-12.5698
N 33
N 9
NH1 ARG 171 (A) H-acceptor
NZ LYS 190 (A) H-acceptor
NZ LYS 190 (A) pi-cation
NE2 HIS 85 (A) H-acceptor
CG2 ILE 183 (A) pi-H
5
-ring
O 27
-ring
6
-14.2399
O 42
C 44
O 42
O 32
N 9
NH TYR 168 (A) H-donor
O
ILE 183 (A) H-donor
NH ARG 171 (A) H-donor
NH ARG 171 (A) H-donor
OG1 THR 123 (A) H-acceptor
NH THR 123 (A) H-acceptor
OG1 THR 123 (A) H-acceptor
N 9
N 13
12

O 27
N 54
C 1
NE2 HIS 85 (A) H-acceptor
CE1 PHE 210 (A) H-acceptor
6-ring PHE 210 (A) H-pi
5-ring HIS 85 (A) H-pi
CB TYR 168 (A) pi-H
OD1 ASP 178 (A) H-donor
1.93
4.27
4.66
4.46
4.79
3.50
3.16
2.10
2.06
2.51
3.01
2.81
3.53
4.78
3.87
3.83
4.12
3.75
4.27
3.19
2.67
3.13
2.53
3.23
4.58
3.72
4.30
-3.2
-0.1
-0.1
-0.1
-0.1
-0.2
-0.3
-6.1
-6.2
-6.2
-5.2
-0.1
-0.2
-0.5
-0.1
-0.1
-0.1
-0.7
-0.1
-0.5
-0.3
-0.1
-0.1
-0.3
-0.1
-0.1
-0.1
C 19
6
-ring
1
4
-13.9108
C 1
C 9
O
VAL 177 (A) H-donor
N 12
N 13
N 12
O 42
O 27
O 27
NH1 ARG 171 (A) H-acceptor
NH2 ARG 171 (A) H-acceptor
NH2 ARG 171 (A) H-acceptor
OH TYR 168 (A) H-acceptor
NE2 HIS 85 (A) H-acceptor
CE
NE2 HIS 85 (A) pi-H
ARG 115 (A) pi-H
LYS 190 (A) H-acceptor
6
6
6
5
5
6
-ring
-ring
-ring
-ring
-ring
-ring
N
CB ARG 115 (A) pi-H
CG1 ILE 183 (A) pi-H
CG2 ILE 183 (A) pi-H
CD1 ILE 183 (A) pi-H
1
5
-9.6860
C 4
O
ILE 112 (A) H-donor
OH TYR 168 (A) H-donor
LEU 117 (A) H-donor
C 19
C 22
C 24
C 34
O
OG1 THR 120 (A) H-donor
OD1 ASP 172 (A) H-donor
6
6
6
-ring
-ring
-ring
CB
CB
SER 86 (A) pi-H
LEU 117 (A) pi-H
CD1 LEU 117 (A) pi-H
13

5
-ring
CA GLY 122 (A) pi-H
ND1 HIS 85 (A) H-donor
OE1 GLU 194 (A) H-donor
4.06
2.80
2.80
2.93
2.74
2.49
3.07
4.70
3.18
2.61
3.28
3.16
4.64
-0.6
-0.2
-0.7
-0.1
-0.1
-0.1
-0.2
-0.1
-2.3
-0.4
-2.3
-4.0
-1.9
1
6
-6.7812
C 36
C 38
O 27
N 46
N 46
N 46
CB
GLN 156 (A) H-acceptor
CB GLN 156 (A) H-acceptor
CG GLN 156 (A) H-acceptor
CD LYS 190 (A) H-acceptor
CA SER 113 (A) pi-H
6
-ring
Standard
-8.0025
N 1
O 7
O 8
O 8
OG SER 186 (A) H-donor
NZ LYS 190 (A) H-acceptor
NH1 ARG 171 (A) H-acceptor
NH2 ARG 171 (A) H-acceptor
NE2 HIS 85 (A) pi-H
6
-ring
3
. Conclusion
In conclusion we have synthesized sixteen oxadiazole derivatives (1-16) and screened against
thymidine phosphorylase inhibitory potential. All derivatives exhibited a varied degree of
thymidine phosphorylase inhibition with IC50 values ranging between 1.10 ± 0.05 to 49.60 ± 1.30
μM when compared with standard drug 7-Deazaxanthine having an IC50 value38.68 ± 1.12 μM.
Our synthesized compounds are more active than the previously reported oxadiazole analogs for
the thymidine phosphorylase activity on the basis of IC50 values. The SAR was mainly based on
substitution pattern on phenyl ring which is in consistent with previous reported oxadiazole
analogs for the thymidine phosphorylase activity. Molecular docking study was performed to
understand the binding interaction of the most active derivatives with enzyme active site.
4
4
. Materials and Methods
.1. Synthetic procedure for 4-cyanobenzohydrazide (I)
Methyl 4-cyanobenzoate (20 mmol) was mixed with hydrazine hydrate (20 mL) in methanol (15
mL). The mixture was refluxed for 6 hrs. Methanol was then evaporated and the product formed
14

was being washed with distilled water to remove excess of hydrazine hydrate. The product
formed was left to dry at room temperature.
4
.2. Synthetic procedure for methyl (E)-4-((2-(4-cyanobenzoyl) hydrazono) methyl)
benzoate (II)
Compound I (15 mmol) was reacted and refluxed with methyl 4-formylbenzoate (15 mmol) in
methanol (mL) in the presence of catalytic amount of acetic acid. The solvent was evaporated
and the residue (II) was washed with ether, filtered, dried and then crystallized from ethanol.
4
.3. Synthetic procedure for methyl 4-(5-(4-cyanophenyl)-1,3,4-oxadiazole-2-yl)benzoate
III)
A mixture of compound II (12 mmol) and equivalent amount of PhI(OAc)
(
2
was stirred in
dichloromethane (20 mL) at room temperature overnight. The solvent was evaporated and the
residue (III) was washed with ether, filtered, dried and then crystallized from ethanol.
4
.4. Synthetic procedure for 4-(5-(4-cyanophenyl)-1,3,4-oxadiazole-2-yl)benzohydrazide
IV)
Compound III (10 mmol) was mixed and refluxed with hydrazine hydrate (15 mL) in methanol
15 mL). Methanol was then evaporated and the product formed was washed with distilled water
(
(
to remove excess of hydrazine hydrate. The product formed (IV) was left to dry at room
temperature.
4
.5. General procedure for the synthesis of oxadiazole derivatives (1-16)
Compound IV (1 mmol) was treated and refluxed with different benzaldehyde (1 mmol) in
methanol (15 mL) to give us the resulting oxadiazole derivatives (1-16). The resulting solid was
filtered and recrystallized from methanol in good yields.
4
.5.1.
(E)-4-(5-(4-cyanophenyl)-1,3,4-thiadiazol-2-yl)-N'-(2,4-dichlorobenzylidene)
benzohydrazide (1)
1
Yield: 87%, H-NMR (500 MHz, DMSO-d6): δ 11.50 (s, 1H, NH), 8.93 (s, 1H, CH=N), 8.05 (d,
J = 7.9 Hz, 2H, Ar), 8.03 (d, J = 7.7 Hz, 1H, Ar), 7.91 (d, J = 7.5 Hz, 2H, Ar), 7.90 (d, J = 7.6
1
3
Hz, 2H, Ar), 7.80 (d, J = 7.3 Hz, 2H, Ar), 7.73 (s, 1H, Ar), 7.50 (d, J = 7.1 Hz, 1H, Ar), C-
NMR (125 MHz, DMSO-d ): δ 164.8, 164.1, 163.0, 138.4, 132.4, 132.2, 132.0, 131.7, 131.3,
6
15

1
1
4
30.2, 130.1, 130.0, 129.8, 124.1, 129.3, 128.9, 128.7, 128.4, 127.5, 127.3, 126.0, 118.1,
+
12.2.HREI-MS: m/z calcd for C23
.5.2.
H
13Cl
2
N
5
O
2
[M] 461.0446, Found 461.0442.
(E)-N'-((4-chlorocyclohexa-1,3-dien-1-yl)methylene)-4-(5-(4-cyanophenyl)-1,3,4-
oxadiazol-2-yl)benzohydrazide (2)
1
Yield: 82%, H-NMR (500 MHz, DMSO-d6): δ 10.70 (s, 1H, NH), 8.91 (s, 1H, CH=N), 8.11 (d,
J = 7.9 Hz, 2H, Ar), 7.91 (d, J = 7.5 Hz, 2H, Ar), 7.90 (d, J = 7.6 Hz, 2H, Ar), 7.80 (d, J = 7.3
13
Hz, 2H, Ar), 7.77 (d, J = 7.4 Hz, 2H, Ar), 7.44 (d, J = 7.3 Hz, 2H, Ar), C-NMR (125 MHz,
DMSO-d
6
): δ 164.2, 164.4, 163.1, 144.3, 137.4, 136.2, 133.4, 132.4, 132.1, 130.8, 130.3, 130.1,
1
29.6, 129.1, 128.0, 127.9, 127.7, 127.1, 122.2, 118.3, 112.2, 34.1, 19.3.HREI-MS: m/z calcd for
+
C
23
H16ClN
5
O
2
[M] 427.0836, Found 427.0831.
4
.5.3.
(E)-N'-(4-(benzyloxy)benzylidene)-4-(5-(4-cyanophenyl)-1,3,4-oxadiazol-2-
yl)benzohydrazide (3)
1
Yield: 90%, H-NMR (500 MHz, DMSO-d6): δ 11.70 (s, 1H, NH), 8.93 (s, 1H, CH=N), 8.03 (d,
J = 7.9 Hz, 2H, Ar), 7.91 (d, J = 7.5 Hz, 2H, Ar), 7.90 (d, J = 7.6 Hz, 2H, Ar), 7.83 (d, J = 7.6
Hz, 2H, Ar), 7.80 (d, J = 7.3 Hz, 2H, Ar), 7.45 (d, J = 7.1 Hz, 2H, Ar), 7.37 (m, 2H, Ar), 7.30
1
3
(
dd, J = 7.9, 3.5 Hz, 1H, Ar), 7.10 (d, J = 7.0 Hz, 2H, Ar), 5.13 (s, 2H, CH
2
), C-NMR (125
MHz, DMSO-d ): δ 164.2, 164.1, 163.4, 161.0, 146.3, 136.2, 133.8, 133.1, 132.4, 130.2, 130.0,
6
1
1
4
4
39.8, 139.6, 130.4, 129.2, 128.6, 128.4, 128.1, 127.9, 127.6, 127.4, 127.2, 126.9, 126.4,126.3,
+
18.4, 114.2, 114.0, 112.3, 70.3.HREI-MS: m/z calcd for C30
99.1639.
H
21
N
5
O
3
[M] 499.1644, Found
.5.4.
(E)-N'-(5-bromo-2-methoxybenzylidene)-4-(5-(4-cyanophenyl)-1,3,4-oxadiazol-2-
yl)benzohydrazide (4)
1
Yield: 85%, H-NMR (500 MHz, DMSO-d6): δ 11.70 (s, 1H, NH), 8.92 (s, 1H, CH=N), 8.09 (d,
J = 7.9 Hz, 2H, Ar), 7.91 (d, J = 7.5 Hz, 2H, Ar), 7.90 (d, J = 7.6 Hz, 2H, Ar), 7.90 (s, 1H, Ar),
7
3
1
1
4
.80 (d, J = 7.3 Hz, 2H, Ar), 7.56 (d, J = 7.3 Hz, 1H, Ar), 6.94 (d, J = 6.5 Hz, 1H, Ar), 3.80 (s,
1
3
H, CH
3
), C-NMR (125 MHz, DMSO-d ): δ 164.1, 164.0, 163.0, 156.4, 145.0, 134.7, 132.5,
6
32.3, 132.2, 131.4, 130.8, 130.4, 130.0, 129.3, 128.9, 128.7, 127.4, 127.2, 119.8, 118.4, 113.2,
+
12.3, 110.2, 55.7. HREI-MS: m/z calcd for C24
.5.5.
H16BrN
5
O
3
[M] 501.0437, Found 501.0431.
(E)-N'-(3-chloro-4-hydroxybenzylidene)-4-(5-(4-cyanophenyl)-1,3,4-oxadiazol-2-
yl)benzohydrazide (5)
16

Yield: 89%, 1H NMR (500 MHz, DMSO-d6): δ 11.50 (s, 1H, NH), 8.45 (s, 1H, CH=N), 8.07
d, J = 7.9 Hz, 2H, Ar), 7.93 (d, J = 7.5 Hz, 2H, Ar), 7.93 (d, J = 7.6 Hz, 2H, Ar), 7.80 (d, J = 7.3
(
13
Hz, 2H, Ar), 7.72 (s, 1H, Ar), 7.52 (d, J = 7.3 Hz, 1H, Ar), 6.83 (d, J = 6.3 Hz, 1H, Ar), C-
NMR (125 MHz, DMSO-d
6
): δ 164.3, 164.1, 163.0, 155.5, 146.6, 132.6, 132.4, 132.2, 130.8,
1
1
4
30.6, 130.4, 130.1, 129.3, 128.5, 128.3, 128.0, 127.5, 127.4, 127.1, 124.1, 118.4, 117.2,
+
12.4.HREI-MS: m/z calcd for C23
H14ClN
5
O [M] 443.0785, Found 443.0782.
3
.5.6.
(E)-4-(5-(4-cyanophenyl)-1,3,4-oxadiazol-2-yl)-N'-(4-(dimethylamino)benzylidene)
benzohydrazide (6)
1
Yield: 80%, H-NMR (500 MHz, DMSO-d6): δ 11.45 (s, 1H, NH), 8.35 (s, 1H, CH=N), 8.05 (d,
J = 7.9 Hz, 2H, Ar), 7.93 (d, J = 7.5 Hz, 2H, Ar), 7.91 (d, J = 7.6 Hz, 2H, Ar), 7.80 (d, J = 7.3
1
3
Hz, 2H, Ar), 7.52 (d, J = 7.1 Hz, 2H, Ar), 6.80 (d, J = 6.3 Hz, 2H, Ar), 3.00 (s, 6H, CH
3
), C-
NMR (125 MHz, DMSO-d ): δ 164.2, 164.1, 163.0, 153.3, 146.4, 132.4, 132.2, 132.0, 130.8,
6
1
4
4
30.6, 130.2, 129.3, 128.8, 128.6, 128.2, 128.0, 127.4, 127.1, 123.0, 118.3, 112.3, 111.7, 111.4,
+
1.2, 41.0.HREI-MS: m/z calcd for C25
.5.7.
H
20
N
6
O
2
[M] 436.1648, Found 436.1643.
(E)-N'-(4-(benzyloxy)-3-methoxybenzylidene)-4-(5-(4-cyanophenyl)-1,3,4-oxadiazol-2-
yl)benzohydrazide (7)
1
Yield: 78%, H-NMR (500 MHz, DMSO-d6): δ 11.34 (s, 1H, NH), 8.45 (s, 1H, CH=N), 8.04 (d,
J = 7.9 Hz, 2H, Ar), 7.92 (d, J = 7.5 Hz, 2H, Ar), 7.90 (d, J = 7.6 Hz, 2H, Ar), 7.80 (d, J = 7.3
Hz, 2H, Ar), 7.54 (s, 1H, Ar), 7.44 (m, 2H, Ar), 7.41 (dd, J = 8.3, 3.3 Hz, 2H, Ar), 7.30 (m, 1H,
Ar), 7.23 (d, J = 7.1 Hz, 1H, Ar), 6.96 (d, J = 6.3 Hz, 1H, Ar), 5.14 (s, 2H, CH
2
), 3.82 (s, 3H,
): δ 164.3, 164.5, 163.0, 149.5, 148.4, 146.0, 136.4, 132.4,
32.2, 132.1, 130.4, 130.2, 130.0, 129.2, 129.0, 128.7, 128.5, 128.3, 128.0, 127.9, 127.6, 127.3,
1
3
CH
3
), C-NMR (125 MHz, DMSO-d
6
1
1
26.1, 126.0, 122.3, 118.3, 112.3, 111.3, 111.0, 71.3, 56.3.HREI-MS: m/z calcd for C31
H
23
N
5
O
4
+
[
M] 529.1750, Found 529.1744.
4
.5.8.
(E)-N'-(anthracen-9-ylmethylene)-4-(5-(4-cyanophenyl)-1,3,4-oxadiazol-2-yl)
benzohydrazide (8)
1
Yield: 73%, H-NMR (500 MHz, DMSO-d6): δ 11.00 (s, 1H, NH), 8.70 (s, 1H, Ar), 8.32 (s, 1H,
CH=N), 8.02 (d, J = 7.6 Hz, 2H, Ar), 8.02 (d, J = 7.9 Hz, 2H, Ar), 7.93 (d, J = 7.5 Hz, 2H, Ar),
7
4
1
.92 (d, J = 7.6 Hz, 2H, Ar), 7.86 (d, J = 7.5 Hz, 2H, Ar), 7.80 (d, J = 7.3 Hz, 2H, Ar), 7.47 (m,
1
3
H, Ar), C-NMR (125 MHz, DMSO-d
6
): δ 164.1, 164.0, 163.6, 143.0, 133.8, 132.2, 132.0,
31.9, 131.7, 130.5, 130.2, 130.0, 129.2, 129.0, 128.7, 128.5, 128.3, 128.0, 128.0, 127.9, 127.7,
17

1
27.4, 127.2, 126.6, 125.2, 125.0, 124.6, 124.2, 123.6, 118.2, 112.1.HREI-MS: m/z calcd for
+
C
31
H
19
N
5
O
2
[M] 493.1539, Found 493.1535.
4
.5.9.
(E)-4-(5-(4-cyanophenyl)-1,3,4-oxadiazol-2-yl)-N'-((2-hydroxynaphthalen-1-
yl)methylene)benzohydrazide (9)
1
Yield: 81%, H-NMR (500 MHz, DMSO-d6): δ 11.90 (s, 1H, NH), 9.00 (s, 1H, CH=N), 8.17 (d,
J = 8.3 Hz, 1H, Ar), 8.02 (d, J = 7.9 Hz, 2H, Ar), 7.93 (d, J = 7.5 Hz, 2H, Ar), 7.92 (d, J = 7.6
Hz, 2H, Ar), 7.81 (d, J = 7.3 Hz, 1H, Ar), 7.80 (d, J = 7.3 Hz, 2H, Ar), 7.80 (d, J = 7.5 Hz, 1H,
1
3
Ar), 7.50 (dd, J = 8.6, 3.4 Hz, 1H, Ar), 7.34 (m, 1H, Ar), 7.15 (d, J = 7.1 Hz, 1H, Ar), C-NMR
(
125 MHz, DMSO-d
6
): δ 171.3, 164.1, 164.0, 163.0, 143.0, 133.8, 133.4, 132.5, 132.3, 132.0,
1
1
4
30.9, 130.7, 130.5, 129.3, 129.0, 128.9, 128.7, 128.5, 127.3, 127.1, 126.5, 123.4, 120.1, 118.4,
+
18.0, 112.1, 108.1.HREI-MS: m/z calcd for C27
H
17
N
5
O [M] 459.1331, Found 459.1325.
3
.5.10.
(E)-4-(5-(4-cyanophenyl)-1,3,4-oxadiazol-2-yl)-N'-(4-hydroxybenzylidene)
benzohydrazide (10)
1
Yield: 71%, H-NMR (500 MHz, DMSO-d6): δ 11.10 (s, 1H, NH), 8.34 (s, 1H, CH=N), 8.03 (d,
J = 7.9 Hz, 2H, Ar), 7.93 (d, J = 7.5 Hz, 2H, Ar), 7.91 (d, J = 7.6 Hz, 2H, Ar), 7.80 (d, J = 7.3
13
Hz, 2H, Ar), 7.62 (d, J = 7.3 Hz, 2H, Ar), 6.81 (d, J = 6.4 Hz, 2H, Ar), C-NMR (125 MHz,
DMSO-d6):δ 164.1, 164.0, 163.5, 160.4, 146.4, 133.8, 132.4, 132.1, 131.6, 130.8, 130.6, 130.4,
1
29.8, 129.1, 128.8, 128.6, 127.4, 127.1, 126.1, 118.4, 116.8, 116.4, 112.1.HREI-MS: m/z calcd
+
for C23
H
15
N
5
O
3
[M] 409.1175, Found 409.1171.
4
.5.11.(E)-4-(5-(4-cyanophenyl)-1,3,4-oxadiazol-2-yl)-N'-(3-hydroxybenzylidene)benzohydrazide
(11)
1
Yield: 84%, H-NMR (500 MHz, DMSO-d6): δ 11.14 (s, 1H, NH), 8.43 (s, 1H, CH=N), 8.04 (d,
J = 7.9 Hz, 2H, Ar), 7.91 (d, J = 7.5 Hz, 2H, Ar), 7.90 (d, J = 7.6 Hz, 2H, Ar), 7.80 (d, J = 7.3
Hz, 2H, Ar), 7.30 (d, J = 7.0 Hz, 1H, Ar), 7.22 (s, 1H, Ar), 7.12 (dd, J = 8.1, 3.5 Hz, 1H, Ar),
1
3
6
1
1
4
4
.90 (d, J = 6.4 Hz, 2H, Ar), C-NMR (125 MHz, DMSO-d6):δ 165.0, 164.2, 163.0, 158.3,
46.5, 138.2, 132.4, 132.5, 132.4, 130.9, 130.7, 130.5, 130.1, 129.2, 128.6, 128.4, 127.3, 127.0,
+
21.6, 118.2, 118.0, 114.7, 112.4.HREI-MS: m/z calcd for C23
09.1171.
H
15
N
5
O
3
[M] 409.1175, Found
.5.12.
(E)-4-(5-(4-cyanophenyl)-1,3,4-oxadiazol-2-yl)-N'-(3-hydroxy-4-methoxybenzylidene)
benzohydrazide (12)
18

1
Yield: 80%, H-NMR (500 MHz, DMSO-d6): δ 11.40 (s, 1H, NH), 8.44 (s, 1H, CH=N), 8.05 (d,
J = 7.9 Hz, 2H, Ar), 7.93 (d, J = 7.5 Hz, 2H, Ar), 7.90 (d, J = 7.6 Hz, 2H, Ar), 7.80 (d, J = 7.3
Hz, 2H, Ar), 7.41 (s, 1H, Ar), 7.08 (d, J = 7.0 Hz, 1H, Ar), 7.02 (d, J = 7.0 Hz, 1H, Ar), 3.82 (s,
1
3
3
1
1
4
H, CH ), C-NMR (125 MHz, DMSO-d6):δ 164.2, 164.1, 163.0, 152.1, 147.0, 146.4, 132.2,
3
32.5, 132.3, 131.5, 130.2, 130.0, 130.0, 129.2, 128.8, 128.6, 127.4, 127.2, 122.4, 118.3, 115.6,
+
12.2, 112.1, 56.5.HREI-MS: m/z calcd for C24
.5.13.
H N
17 5
O
4
[M] 439.1281, Found 439.1276.
(E)-4-(5-(4-cyanophenyl)-1,3,4-oxadiazol-2-yl)-N'-(4-hydroxy-3,5-dimethoxy
benzylidene)benzohydrazide (13)
1
Yield: 83%, H-NMR (500 MHz, DMSO-d6): δ 11.49 (s, 1H, NH), 8.43 (s, 1H, CH=N), 8.05 (d,
J = 7.9 Hz, 2H, Ar), 7.93 (d, J = 7.5 Hz, 2H, Ar), 7.91 (d, J = 7.6 Hz, 2H, Ar), 7.80 (d, J = 7.3
1
3
Hz, 2H, Ar), 7.02 (s, 2H, Ar), 3.81 (s, 6H, CH
3
), C-NMR (125 MHz, DMSO-d6):δ 164.3,
1
1
64.1, 163.5, 148.0, 148.6, 146.4, 139.3, 132.4, 132.1, 132.0, 130.2, 130.0, 129.4, 129.0, 128.8,
28.6, 128.2, 127.3, 127.2, 118.2 , 112.6, 104.1, 104.0, 56.4, 56.0.HREI-MS: m/z calcd for
+
C
25
H
19
N
5
O
5
[M] 469.1386, Found 469.1380.
4
.5.14.
(E)-4-(5-(4-cyanophenyl)-1,3,4-oxadiazol-2-yl)-N'-(4-hydroxy-3-methoxybenzylidene)
benzohydrazide (14)
1
Yield: 89%, H-NMR (500 MHz, DMSO-d6): δ 11.33 (s, 1H, NH), 8.43 (s, 1H, CH=N), 8.02 (d,
J = 7.9 Hz, 2H, Ar), 7.92 (d, J = 7.5 Hz, 2H, Ar), 7.90 (d, J = 7.6 Hz, 2H, Ar), 7.80 (d, J = 7.3
Hz, 2H, Ar), 7.34 (s, 1H, Ar), 7.31 (d, J = 7.1 Hz, 1H, Ar), 6.83 (d, J = 7.1 Hz, 1H, Ar), 3.80 (s,
1
3
3
1
1
4
H, CH ), C-NMR (125 MHz, DMSO-d6):δ 164.8, 164.2, 163.6, 152.2, 147.1, 146.5, 132.4,
3
32.2, 132.1, 131.4, 130.0, 130.0, 129.2, 129.0, 128.5, 128.1, 127.8, 127.4, 122.4, 118.2, 115.7,
+
12.4, 112.0, 56.3.HREI-MS: m/z calcd for C24
H N
17 5
O
4
[M] 439.1281, Found 439.1276.
.5.15. (E)-4-(5-(4-cyanophenyl)-1,3,4-oxadiazol-2-yl)-N'-(2-nitrobenzylidene)benzohydrazide
(15)
1
Yield: 93%, H-NMR (500 MHz, DMSO-d6): δ 11.30 (s, 1H, NH), 8.53 (s, 1H, CH=N), 8.03 (d,
J = 7.9 Hz, 1H, Ar), 8.01 (d, J = 7.9 Hz, 2H, Ar), 7.91 (d, J = 7.5 Hz, 2H, Ar), 7.90 (d, J = 7.6
Hz, 2H, Ar), 7.90 (d, J = 7.7 Hz, 1H, Ar), 7.80 (d, J = 7.3 Hz, 2H, Ar), 7.67 (dd, J = 8.1, 2.7 Hz,
1
3
1
1
1
4
H, Ar), 7.55 (dd, J = 8.1, 2.6 Hz, 1H, Ar), C-NMR (125 MHz, DMSO-d6):δ 164.8, 164.4,
63.5, 147.6, 143.0, 134.6, 132.8, 132.6, 132.4, 131.7, 130.9, 130.6, 130.3, 130.0, 129.1, 128.9,
+
28.6, 128.4, 127.4, 127.1, 124.4, 118.8, 112.2.HREI-MS: m/z calcd for C23
38.1077, Found 438.1070.
H
14
N
6
4
O [M]
19

4
.5.16. (E)-N'-(2-cyanobenzylidene)-4-(5-(4-cyanophenyl)-1,3,4-oxadiazol-2-yl) benzohydrazide
(16)
1
Yield: 88%, H-NMR (500 MHz, DMSO-d6): δ 11.09 (s, 1H, NH), 8.32 (s, 1H, CH=N), 8.07 (d,
J = 7.9 Hz, 2H, Ar), 7.96 (d, J = 7.7 Hz, 1H, Ar), 7.92 (d, J = 7.5 Hz, 2H, Ar), 7.91 (d, J = 7.6
Hz, 2H, Ar), 7.80 (d, J = 7.3 Hz, 2H, Ar), 7.76 (dd, J = 8.1, 2.7 Hz, 1H, Ar), 7.64 (dd, J = 8.1,
1
3
2
1
1
4
4
.6 Hz, 1H, Ar), 7.52 (d, J = 7.1 Hz, 1H, Ar). C-NMR (125 MHz, DMSO-d6):δ 164.7, 164.2,
63.0, 143.0, 134.3, 133.4, 133.1, 132.9, 132.6, 132.4, 131.1, 130.6, 130.3, 130.0, 129.7, 129.2,
+
28.5, 128.1, 127.3, 127.2, 118.2, 115.3, 112.2, 111.5.HREI-MS: m/z calcd for C24
18.1178, Found 418.1173.
H
14
N
6
2
O [M]
.6. Molecular docking
The docking is a significant tool to explore the interactions between an inhibitor and the target
30]. To find the binding interactions of these compounds in the active sites of the thymidine
[
phosphorylase, the MOE-Dock program (www.chemcomp.com) was used to perform molecular
docking. The 3D crystal structure of the thymidine phosphorylase (4EAD) was retrieved from
the Protein Databank (PDB). The synthesized compounds were docked into the active site of the
target enzyme in MOE (www.chemcomp.com) by the default parameters i-e Placement: Triangle
Matcher, Rescoring 1: London dG, Refinement: Force field, Rescoring 2: London dG. For each
ligand ten conformations were generated and the top ranked conformation based on docking
score was selected for further studies in molecular docking. After the molecular docking, we
analyzed the best poses having polar, H-pi and pi-H interactions by Pymol software.
.7. Assay Protocol of Thymidine phosphorylase
4
Thymidine phosphorylase/PD-ECGF (human and E. coli) activity was determined by measuring
the absorbance at 290 nm spectrophotometrically. The original method described by Krenitsky
and Bush by (1979) was modified [31, 32]. In brief, total reaction mixture of 200 µL contained
1
45 µL of potassium phosphate buffer (pH 7.4, 50 mM), 30 µL of enzyme (human and E. coli) at
concentration 0.05 and 0.002 U, respectively, were incubated with 5 µL of test materials
0.5 mM) for10 min at 25 °C in microplate reader. After incubation, pre-read at 290 nm was
(
taken to deduce the absorbance of substrate particles. Substrate “Thymidine” (20 µL, 1.5 mM),
was dissolved in potassium phosphate buffer, was immediately added to plate and continuously
read after 10, 20, and 30 min in microplate reader (spectra max, molecular devices, CA, USA).
7
-Deazaxanthine was used as positive control. All assays were performed in triplicate.
20

Source/ Supplier of the enzymes used
Thymidine phosphorylase enzyme (from E. coli, EC Number 2.4.2.4), thymidine, and
potassium phosphate monobasic were purchased from Sigma Aldrich, USA.
Acknowledgment:
Authors would like to acknowledge Higher Education Commission of Pakistan for providing a
research grant under National Research Program for Universities under project No. 5721.
References:
1
2
3
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Highlights:
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Synthesis of oxadiazole derivatives (1-16)
In vitro thymidine phosphorylase inhibitory potential
Identification of a new class of thymidine phosphorylase inhibitor
Structure activity relationship established
Molecular docking
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Graphical abstract
25