Discovery, bioactivity and docking simulation of Vorinostat analogues containing 1,2,4-oxadiazole moiety as potent histone deacetylase inhibitors and antitumor agents

Article abstract of DOI:10.1016/j.bmc.2015.04.028

Abstract In our study, three series of hydroxamate, 2-aminobenzamide, and trifluoromethyl ketone analogues have been designed and synthesized. The synthesized compounds were investigated for their in vitro antiproliferative activities using the MTT-based assay against three human cancer cell lines including A549, NCI-H661, and U937. Most analogues exhibited higher antiproliferative activities against human acute myeloid leukemia cell U937 than the other two human lung cancer cell lines. Furthermore, the compounds were examined against HDAC1, 2, and 8 isoforms. Docking study of compounds 6h, 9b, and 10a suggested that they might bind tightly to the binding pocket of HDAC2 and/or HDAC8. The results suggest that these compounds might have potential as lead compounds for the development of anti-tumor drugs with HDACs inhibitory activities.

Full text of DOI:10.1016/j.bmc.2015.04.028

Accepted Manuscript
Discovery, bioactivity and docking simulation of Vorinostat analogues contain-
ing 1,2,4-oxadiazole moiety as potent histone deacetylase inhibitors and anti-
tumor agents
Jin Cai, Hongtao Wei, Kwon Ho Hong, Xiaoqing Wu, Xi Zong, Meng Cao, Peng
wang, Lushen Li, Chunlong Sun, Bo Chen, Gaoxing Zhou, Junqing Chen, Min
Ji
PII:
S0968-0896(15)00326-0
DOI:
http://dx.doi.org/10.1016/j.bmc.2015.04.028
BMC 12240
Reference:
To appear in:
Bioorganic & Medicinal Chemistry
Received Date:
Revised Date:
Accepted Date:
15 February 2015
9 April 2015
10 April 2015
Please cite this article as: Cai, J., Wei, H., Hong, K.H., Wu, X., Zong, X., Cao, M., wang, P., Li, L., Sun, C., Chen,
B., Zhou, G., Chen, J., Ji, M., Discovery, bioactivity and docking simulation of Vorinostat analogues containing
1
,2,4-oxadiazole moiety as potent histone deacetylase inhibitors and antitumor agents, Bioorganic & Medicinal
Chemistry (2015), doi: http://dx.doi.org/10.1016/j.bmc.2015.04.028
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Discovery, bioactivity and docking simulation of Vorinostat analogues
containing 1,2,4-oxadiazole moiety as potent histone deacetylase
inhibitors and antitumor agents
a, †
Jin Cai , Hongtao Wei , Kwon Ho Hong , Xiaoqing Wu , Xi Zong , Meng Cao ,
b, †
c
d
a
e
e
e
a
e
e
Peng wang , Lushen Li , Chunlong Sun , Bo Chen , Gaoxing Zhou , Junqing Chen
a
a, e, f,
and Min Ji
*
a
School of Chemistry and Chemical Engineering, Institute of Pharmaceutical Engineering, Southeast
University, Nanjing, Jiangsu, 210096, P. R. China
b
College of Chemistry and Pharmaceutical Sciences, Qingdao Agricultural University, Qingdao
266109, P. R. China
c
Department of Medicinal Chemistry and the Institute for Therapeutics Discovery and
Development, University of Minnesota, Minneapolis, MN 55414, USA
d
Department of Molecular Biosciences, University of Kansas, Lawrence, KS 66045, USA
e
School of Biological Science & Medical Engineering, Southeast University, Nanjing 210096, P. R.
China
f
Suzhou Key Laboratory of Biomaterials and Technologies & Collaborative Innovation Center of
Suzhou Nano Science and Technology, Suzhou 215123, P. R. China
*Corresponding Authors:
Min Ji, Ph.D.
School of Chemistry and Chemical Engineering
Southeast University
8
7 Dingjiaqiao
Nanjing 210096, Jiangsu, China
Tel: 025-83272078
E-mail: jimin@seu.edu.cn
†
These authors contribute equally to this work.

Abstract
In our study, three series of hydroxamate, 2-aminobenzamide, and
trifluoromethyl ketone analogues have been designed and synthesized. The
synthesized compounds were investigated for their in vitro antiproliferative activities
using the MTT-based assay against three human cancer cell lines including A549,
NCI-H661, and U937. Most analogues exhibited higher antiproliferative activities
against human acute myeloid leukemia cell U937 than the other two human lung
cancer cell lines. Furthermore, the compounds were examined against HDAC1, 2, and 8
isoforms. Docking study of compounds 6h, 9b, and 10a suggested that they might bind
tightly to the binding pocket of HDAC2 and/or HDAC8. The results suggest that these
compounds might have potential as lead compounds for the development of
anti-tumor drugs with HDACs inhibitory activities.
Key words: histone deacetylases (HDAC), antiproliferative activity, hydroxamate,
2
-aminobenzamide, trifluoromethyl ketone, docking simulation
1
. Introduction
Pharmacological targeting of proteins that regulate epigenetics has emerged as a
1, 2
promising therapeutic area of study. Histone lysine acetylation and deacetylation
3
are crucial post-translational modifications in the epigenetic field. Histone deacetylase
(HDAC) proteins are responsible for governing the acetylation state of lysine residues
located on the amino-terminal tails of histone proteins for chromatin remodeling and
4
, 5
therefore the regulation of gene expression.
Overexpression of HDAC enzymes
results in hypoacetylation of the histone proteins and suppression of gene
transcriptional activities, and such hypoacetylation has been associated with
6
, 7
precancerous or malignant states.
Moreover, the aberrant recruitment of HDAC
enzymes by oncogene may alter gene expression in favor of unregulated proliferation
8
and/or arrested differentiation. Thus, inhibition of HDACs provides a potential
9
strategy for the development of synthetic anticancer drugs. HDAC inhibitors (HDACi)

mediate cancer cell death through several pathways, including apoptosis,
differentiation, cell cycle arrest, inhibition of DNA repair, downregulation of growth
1
0, 11
factors, autophagy, oxidative stress, and control of angiogenesis.
In human, 18 HDAC isoforms have been described and classified into four classes
1
2, 13
on the basis of their homologies to yeast HDACs.
Class I (HDACs 1, 2, 3 and 8) is
homologous to the yeast RPD3 protein, and detected generally in the nucleus and
ubiquitously expressed in various cell lines and tissues in human. Class II (HDACs 4, 5, 6,
7
, 9 and 10) shares homologies with the yeast HDA1 protein and shuttles between the
nucleus and the cytoplasm. Class III HDACs (SirT1-7) are homologues of the yeast
protein Sir2. Class IV (HDAC11) displays the characteristics of both class I and class II
1
4-17
2+
Class I, Class II, and Class IV HDACs are Zn dependent while Class III is
HDACs.
+
NAD dependent.
TM
The first HDAC inhibitor Vorinostat (SAHA, Zolinza ; Merck) (Fig. 1) was
approved by the FDA in October 2006 for the treatment of the advanced cutaneous
1
8
TM
T-cell lymphoma (CTCL). Moreover, Belinostat (PXD101, Beleodaq ) (Fig. 1) was
approved by the FDA in July 2014 for the treatment of patients with relapsed or
1
refractory peripheral T-cell lymphoma (PTCL). Many small molecular agents such as
9
20
Entinostat (MS-275) are under investigation inhuman clinical trials (Fig. 1). A close
2
+
view of these small molecule HDAC inhibitors indicated that two most common Zn
chelators found in these molecules were hydroxamates (Vorinostat and Belinostat)
and 2-aminobenzamides (Entinostat). Most hydroxamate HDAC inhibitors are pan
inhibitors, while 2-aminobenzamides exert some isoform selectivity: for instance,
2
1
Entinostat is relatively unique in inhibiting HDAC1, 2, and 3.
Besides hydroxamates
and 2-aminobenzamides, trifluoromethyl ketones were reported to functionality exert
2
+
22
potent inhibitory activity against all four subclasses of the Zn -dependent HDACs.
HKI 46F08 (Fig. 1), a novel trifluoromethyl ketone HDAC inhibitor, inhibits HDAC
activity in cell-free assays with IC50 of 0.6 µM and intracellular HDAC activity with IC50
2
3
of 1.8 µM.
Despite the variety of structural motifs, the HDAC inhibitors can be described by a
2
4
2+
common pharmacophore (Fig. 1), which can be segmented into four parts: 1) Zn

2
+
binding group (ZBG), chelating Zn at the bottom of the active binding site of HDACs; 2)
a hydrophobic linker occupying the long and narrow tube-like channel; 3) a surface
recognition group (cap), essential for recognizing and interacting with amino acid
residues on the rim of the HDACs active site; and 4) usually, a polar connection unit
(CU) linking “cap group” with the hydrophobic linker.
Consequently, on the basis of this common pharmacophore, we chose Vorinostat
as a lead compound for the development of the novel HDACs inhibitors. We designed
and synthesized a series of 1,2,4-oxadiazole–containing Vorinostat analogues (Fig. 2):
1
) we replaced the amide moiety of Vorinostat with 1,2,4-oxadiazole moiety as
heterocyclic amide and ester bioisostere to investigate the effects of changes at “CU”
in such analogues; 2) hydroxamate group is replaced by other chelating group,
2
-aminobenzamide group as in Entinostat, or trifluoromethyl ketone group as in HKI
6F08; 3) To optimize the lead compound Vorinostat further, we performed a SAR
4
study on the cap moiety by investigating the electronic effects of the aryl ring by
introducing phenyl rings or heterocycles with various electronics. This study aimed to
determine whether these compounds would manifest antiproliferative activities
against cancer cells and be highly potent in inhibiting HDAC enzymes.
2
. Chemistry
As summarized in Table 1-3, 32 target compounds (6a-6k, 9a-9k and 10a-10j) were
synthesized. The synthetic routes are illustrated in Scheme 1-4.
The syntheses of hydroxamate compounds (6a-6k) are depicted in Scheme 1.
The appropriately substituted nitriles 1a-1k were treated with hydroxylamine
hydrochloride in methanol at 65 °C, in the presence of triethylamine (TEA), to give
N’-hydroxybenzimidamide intermediates 2a-2k, respectively. Condensation of 2a-2k
with methyl 8-chloro-8-oxooctanoate 3 in dry pyridine at room temperature provided
the O-acyl intermediates, which were then cyclized in refluxing pyridine to obtain the
1
,2,4-oxadiazole compounds 4a-4k in satisfactory yields. Intermediates 4a-4k were
subsequently hydrolyzed by LiOH in tetrahydrofuran (THF) at room temperature to

generate 5a-5k in high yields. Compounds 5a-5k were condensed with ethyl
chlorocarbonate and then treated with hydroxylamine hydrochloride to produce the
target compounds 6a-6k. Intermediate 8-chloro-8-oxooctanoate 3 was prepared as
2 4
shown in Scheme 2. Using H SO as catalyst, carboxyl groups of octanedioic acid 11
were esterified with excessed methanol to produce 12 in satisfactory yield.
Saponification of methyl ester 12 in the presence of KOH at room temperature
followed by the chlorination with oxalyl chloride and pyridine in toluene afforded 3 in
2
5
high yield.
The syntheses of 2-aminobenzamide compounds (9a-9k) are shown in Scheme 3.
Compounds 5a-5k were treated with oxalyl chloride and condensed with tert-butyl
(2-aminophenyl)carbamate in dry THF with N-methylmorpholine as catalyst to
2
6
generate 8a-8k. 2-Aminobenzamide target compounds 9a-9k were finally obtained by
deprotection of 8a-8k with trifluoroacetic acid (TFA) in dichloromethane at room
temperature in high yields. As shown in Scheme 4, trifluoromethyl ketone compounds
(10a-10j) were achieved by the chlorination in the presence of oxalyl chloride and
pyridine in dry THF at room temperature followed by the treatment with excess
trifluoroacetic anhydride (TFAA) and anhydrous pyridine in dichloromethane.
3
. Results and discussion
3
.1. In vitro antiproliferative activities of the target compounds
2 newly synthesized hydroxamate compounds 6a-6k, 2-aminobenzamide
3
compounds 9a-9k and trifluoromethyl ketone compounds 10a-10j were investigated
for their antiproliferative activities employing the MTT-based assay using Vorinostat
and Entinostat as positive controls against three human cancer cell lines representing
different tumor types: human acute monocytic myeloid leukemia cell line (U937),
human lung adenocarcinoma epithelial cell line (A549) and human lung large cell
carcinoma cell line (NCI-H661). Their antiproliferative activities are indicated by IC50
values that were calculated by linear regression analysis of the concentration-response
curves obtained for each compound.
The results from the antiproliferation assay of the analogues 6a-6k are

summarized in Table 1. Most hydroxamate analogues (6) manifested evident
antiproliferative activities against three tumor cell lines. They exhibited the most
significant inhibition against human acute monocytic myeloid leukemia cell line U937,
and especially 6h with nitro group at C4 of the phenyl group, 6j and 6k with
heterocycles substitution displayed higher antiproliferative activities (at
submicromolar concentrations) against U937 than Vorinostat and Entinostat. However,
hydroxamate analogues (6) displayed low inhibitory activities against both of two
human lung cancer cell lines. It is worth pointing out that these analogues
demonstrated slight diversities of inhibition between two different human lung cancer
cell lines, most compounds except for 6h displayed higher antiproliferative activities
against A549 than NCI-H661, which were different from Vorinostat and Entinostat. It
seemed that compound 6h with nitro group at C4 of the phenyl group demonstrated
higher antiproliferative activity than compound 6i with nitro group at C3 of the phenyl
group (IC50 values of 5.31, 3.09, and 0.29 µM versus 10.84, 16.12, and 1.16 µM).
As shown in Table 2 and 3, compared with hydroxamate analogues (6),
2
-aminobenzamide analogues (9) and trifluoromethyl ketone analogues (10) displayed
slightly lower antiproliferative activities. Similar to hydroxamate analogues (6),
analogues (9) and (10) demonstrated higher antiproliferative activities against human
acute myeloid leukemia cell U937 than both of two human lung cancer cell lines A549
2
7-29
and NCI-H661, which accorded with some previous reports
: although HDAC
inhibitors like Vorinostat have shown to be effective against a defined subset of
hematological tumors, less convincing results have been observed in the treatment of
solid tumors. Compounds 9d, 9h, and 10b showed poor inhibitory activities against
human lung cancer cell lines. Interestingly, contrary to hydroxamate analogues (6),
2
-aminobenzamides (9) and trifluoromethyl ketones (10) displayed higher
antiproliferative activities against NCI-H661 than A549. It is worth pointing out that
among analogues (9) the most significant inhibition was achieved for compound 9b
with IC50 values of 0.41 and 0.46 µM toward NCI-H661 and U937, respectively, which
were similar to or better than that of Vorinostat (IC50 = 0.13 and 2.83 µM, respectively).
Meanwhile, the compounds (10b-10i) with either electron-donating or
electron-withdrawing groups on the phenyl group exhibited decreased
antiproliferations compared to compounds 10a (IC50 = 7.68, 0.52, and 0.41 µM,

respectively) without any substitution at the corresponding phenyl group. Compound
0i with nitro group at C3 of the phenyl group demonstrated higher antiproliferative
activity than compound 10h with nitro group at C4 of the phenyl group; and compound
0g with chlorine at C2 of the phenyl displayed slightly higher antiproliferative activity
than compound 10f with chlorine at C4.
1
1
3
.2. HDAC enzyme inhibitory activities of the target compounds
In order to study the potency of the newly synthesized compounds, all
compounds were assayed for their inhibitory activities against HDAC1, 2, and 8
isoforms using Vorinostat and Entinostat as a reference compounds. As shown in
Table 1-3, hydroxamate analogues 6a-6k and 2-aminobenzamide analogues 9a-9k
manifested inhibitory activities against HDAC1 and 2 at submicromolar concentrations.
Most hydroxamate and 2-aminobezamide analogues (6 and 9) exhibited a higher
selectivity for HDAC1 over HDAC2. For example, compounds 6h, 6k, and 9b had lower
IC50 values (70 nM, 80 nM, and 140 nM, respectively) for HDAC1 than those for HDAC2
(230 nM, 390 nM, and 680 nM, respectively). Hydroxamate analogues (6) displayed
decreased inhibitory activities against HDAC8 compared to HDAC1 and 2. In addition,
2
-aminobenzamide analogues (9) were not active against HDAC8 like Entinostat, which
3
0, 31
accorded with the previous reports.
Interestingly, contrary to hydroxamate and
2
-aminobezamide analogues (6 and 9), trifluoromethyl ketone analogues (10)
demonstrated the most significant inhibitory activities against HDAC8. Moreover, most
trifluoromethyl ketones (10) exhibited a higher selectivity for HDAC2 over HDAC1, and
some compounds like 10b, 10e, 10f, and 10h were even inactive against HDAC 1. In
addition, the enzyme inhibitory activities of most target compounds were well
correlated with their antiproliferative activities. Compounds 6h, 6j, 6k, 9b, and 10a
with stronger antiproliferative activities also showed the higher inhibitory activities
against HDACs. Taken the biological data together, we could preliminarily arrive at the
conclusion that some target compounds might be potent HDAC enzyme inhibitors.
Thus they may be promising lead compounds for the development of novel anti-tumor
drugs that can alter the disease state potentially via inhibiting HDACs.

3
.3. Docking simulation study
To further investigate the interactions between these compounds and HDACs, we
performed docking simulations using Glide in Schrodinger Suite. Following ligand
preparation, the compounds were docked into the binding pockets in HDAC2 and
HDAC8 isoforms.
3
2
As shown in Fig. 3 A (PDB ID: 4LY1 ), docking simulations suggest that
hydroxamate compound 6h, 2-aminobenzamide compound 9b and trifluoromethyl
ketone compound 10a interact with the active site in a fashion similar to Vorinostat
3
observed in the reported crystal structure of HDAC2 (PDB ID: 4LXZ ). The docking pose
2
of 6h in complex with HDAC2 is shown in Fig. 3 B and C. The HDAC2 active site consists
2
+
of a long, narrow tunnel leading to a cavity that contains the catalytic Zn ion, which is
pentacoordinated with Asp181, His183, and Asp269 as well as the carbonyl and
hydroxyl oxygens of the hydroxamate of 6h. In addition to the bidentate chelate
2
+
formation with Zn , simultaneously, compound 6h forms hydrogen bonding
interactions with His145, His146, and Tyr308 through its hydroxamate moiety. The
linker region of 6h occupies in the lipophilic tube formed by Gly154, Phe155, His183,
Phe210, and Leu276. The “CU” 1,2,4-oxadiazole moiety here might play an important
role in increasing the binding affinity for HDAC2 since it is able to form water-mediated
hydrogen bonding interactions with His183, Tyr209, and Phe210. In addition, the nitro
group of the phenyl group forms a hydrogen bonding interaction with Glu208 at the
2
+
rim of the HDAC2 active site. As shown in Fig. 3 D, compound 9b chelates Zn ion
through its amino group of N-2-aminophenyl and the carbonyl oxygen of the
benzamide moiety, as well as hydrogen bonding interactions with His145, His146, and
Gly154. Moreover, 1,2,4-oxadiazole moiety forms a T-π interaction with Phe155, and
methyl phenyl group forms a π-π interaction with His33. The docking pose of 10a in
2
+
HDAC2 is shown in Fig. 3 E. In the Zn binding region, the ketone moiety of 10a
2
+
interacts with Zn ion, and also forms hydrogen bonding interactions with Gly306 and
Tyr308. Very similar to 6h in HDAC2, a water-mediated hydrogen bonding interaction
network has been observed between 1,2,4-oxadiazole moiety of 10a and residues

His183, Tyr209, Phe210. Simultaneously, 1,2,4-oxadiazole moiety forms a T-π
interaction with Phe210.
The selectivity of 2-aminobenzamide analogues (9) observed for HDAC2 over
HDAC8 can best be rationalized by the presence of the voluminous Trp141 of HDAC8
(Corresponding amino acid residue in HDAC2 is Leu144) at the bottom of the tunnel,
which would partially occludes the pocket into which the aniline ring of analogues (9)
are docked in HDAC8. The docking simulation result suggested that hydroxamate
analogues (6) and trifluoromethyl ketone analogues (10) might tightly bind to the
active binding site of HDAC8. The situation is similar to that observed for Vorinostat in
33
2+
complex with HDAC8. As shown in Fig. 4 A (PDB ID: 1VKG ), the catalytic Zn ion is
bound to carboxylate oxygens of Asp178 and Asp267, and to the nitrogen of His180.
Two other coordination sites are occupied by the carbonyl and hydroxyl oxygens of the
hydroxamate of 6h. Simultaneously, 6h forms hydrogen bonding interactions with
His142, His143, Asp178, Gly304, and Tyr306 through its hydroxamate moiety. In
addition to these hydrogen bonding interactions, the “CU” 1,2,4-oxadiazole moiety
forms a π-π interaction with Phe208. The nitro-phenyl group forms a T-π interaction
with Phe152 and positively charged nitrogen forms a cation-π interaction with Phe152,
meanwhile the nitro moiety forms a hydrogen bonding interaction with Ala149. The
2
+
docking pose of 10a in HDAC8 is shown in Fig. 4 B. Besides chelation to Zn ion, the
electrophilic ketone of 10a forms a hydrogen bonding interaction with Tyr306.
Moreover, abundant interactions were observed between 1,2,4-oxadiazole and amino
acid residues: 1,2,4-oxadiazole moiety forms a T-π interaction with Phe152 and π-π
interaction with Phe208, hydrogen bonding interactions with Gly151 and Phe152.
Therefore, these interactions seem to enhance the binding affinity of 10a for HDAC8.
4
. Conclusion
In our study, three series of compounds including hydroxamate,
2
-aminobenzamide, and trifluoromethyl ketone analogues have been designed and
synthesized. The synthesized compounds were investigated for their in vitro

antiproliferative activities using the MTT-based assay against three human cancer cell
lines including A549, NCI-H661, and U937 as well as their enzyme inhibitory activities
against HDAC1, 2, and 8. Most analogues demonstrated higher antiproliferative
activities against human acute myeloid leukemia cell U937 than both of the two human
lung cancer cell lines. 6h, 6j, and 6k exerted higher antiprolierative activities against
U937 than the lead compounds. 9b, 10a, and 10i exhibited an antiproliferative activity
against U937 similar to or higher than the lead compounds. Hydroxamate and
2
-aminobezamide analogues exhibited relatively lower inhibitory activities against
HDAC8 than HDAC1 and 2, while trifluoromethyl ketone analogues exerted relatively
higher affinity toward HDAC8 over HDAC1 and 2. The results from the enzyme
inhibition assays against HDAC1, 2, and 8 suggest that some target compounds might
be potent HDAC enzyme inhibitors, and these compounds manifest antiproliferative
activities via the inhibition of HDACs. Docking study with selected compounds 6h, 9b,
and 10a revealed that they might bind tightly to the binding pocket of HDAC2 and/or
HDAC8. The results suggest that they may be promising lead compounds for the
development of anti-tumor drugs that can affect the disease state as a consequence of
the inhibition of HDACs.
5
. Experimental protocols
5
.1. Synthesis
All reagents were purchased from commercial sources and used without further
purification. Melting points were measured on an RY-1 hot-stage microscope, and the
1
13
thermometer was uncorrected. H-NMR and C-NMR spectra were recorded in CDCl
3
on a Bruker-ACF 300/500 spectrometer; chemical shifts (δ) are reported in parts per
million (ppm) relative to tetramethylsilane (TMS), used as an internal standard. Mass
spectra (MS) were obtained from Agilent 1100LC/MS Spectrometry Services. IR spectra
were run on FI-IR Spectrometer (Perkin–Elmer). Elementary analyses were performed
on Elementar Vario EL III instrument. All compounds were routinely checked by TLC
with silica gel GF-254 glass plates and viewed under UV light at 254 nm.
5
.1.1. General Procedure for the Synthesis of N'-Hydroxybenzimidamides 2a-2k

A solution of the appropriate cyanophenyl 1a-1k (0.1 mol), hydroxylamine
hydrochloride (0.2 mol), and TEA (0.2 mol) in methanol was left under stirring at room
temperature for 1 h, then heated under reflux until the disappearance of the starting
materials (TLC analysis). After cooling, the solvent was evaporated to dryness under
reduced pressure to give the crude, which was dissolved in ethyl acetate (400 mL) and
2 4
washed with brine (3 × 100 mL) and dried with Na SO . The ethyl acetate was
evaporated under reduced pressure to yield the compounds 2a-2k.
Compounds 2a-2k were characterized as follows.
5
5
5
5
5
5
5
5
5
5
5
.1.2. N'-hydroxybenzimidamide (2a)
3
White solid, yield: 75%, mp: 74-75 °C (lit. 76°C ).
4
.1.3. N'-hydroxy-4-methylbenzimidamide (2b)
3
White flake solid, yield: 66%, mp: 148-149 °C (lit. 148-149 °C ).
5
.1.4. N'-hydroxy-4- methoxybenzimidamide (2c)
3
White solid, yield: 65%, mp: 121-122 °C (lit. 121 °C ).
4
.1.5. N'-hydroxy-4- (trifluoromethyl)benzimidamide (2d)
3
White solid, yield: 98%, mp: 127-129 °C (lit. mp: 127-129 °C ).
6
.1.6. 4- Fluoro -N'-hydroxybenzimidamide (2e)
3
White solid, yield: 71%, mp: 93-94 °C (lit. 93-95 °C ).
6
.1.7. 4-Chloro- N'-hydroxybenzimidamide (2f)
3
White solid, yield: 85%, mp: 133 °C (lit. 133-134 °C ).
4
.1.8. 2-Chloro- N'-hydroxybenzimidamide (2g)
3
7
White solid, yield: 85%, mp: 119-120 °C (lit. 119-121 °C ).
.1.9. N'-hydroxy-4- nitrobenzimidamide (2h)
3
8
Yellow solid, yield: 95%, mp: 180-181 °C (lit. 181 °C ).
.1.10. N'-hydroxy-3- nitrobenzimidamide (2i)
3
6
Yellow solid, yield: 93%, mp: 180-182 °C (lit. 180-182 °C ).
.1.11. N'-hydroxythiophene-2-carboximidamide (2j)
3
9
White solid, yield: 80%, mp: 88-90 °C (lit. 88-90 °C ).
.1.12. N'-hydroxynicotinimidamide (2k)
4
0
Light blue crystal, yield: 62%, mp: 133-134 °C (lit. 134-136 °C ).

5
.1.13. Dimethyl octanedioate (12)
2 4
To a solution of octanedioic acid (100g, 0.58 mol) in methanol (450 mL), H SO (10
mL) was added and the mixture was heated to reflux for 12 h. After cooling to room
temperature, the solvent was removed under reduced pressure. The residue was
poured to ice water (200 mL) and extracted with ethyl ether (3 × 400 mL), the
combined organic phase was washed with 10% sodium bicarbonate (200 mL) and brine
4
(200 mL), dried with MgSO and concentrated under reduced pressure to give 12 (98 g,
1
5%) as colorless oil. H NMR (300MHz, CDCl
8
4
5
3
) δ: 1.24-1.39 (m, 4H, -CH
2
), 1.56-1.69 (m,
H, -CH
2
), 2.26-2.35 (m, 4H, 2CH
2
CO
2
), 3.67 (s, 6H, 2CO CH ).
2
3
.1.14. 8-Methoxy-8-oxooctanoic acid (13)
A mixture of compound 12 (82 g, 0.4 mol), KOH (22.4 g, 0.4 mol) and methanol
450 mL) was stirred at room temperature for 4 h. The solvent was removed under
(
reduced pressure and the residue was taken up with water (200 mL) and washed with
ethyl ether (100 mL). The pH of the aqueous phase adjusted to 3 with 10% HCl,
extracted with ethyl ether (3 × 200 mL). The combined organic phase was washed with
4
brine (100 mL), dried with MgSO and concentrated under reduced pressure to afford
1
3 (31 g, 41%) as colorless oil. H NMR (300MHz, CDCl
1
1
5
3
) δ: 1.25-1.44 (m, 4H, -CH
2
),
.56-1.72 (m, 4H, -CH ), 2.27-2.41 (m, 4H, 2CH CO ), 3.67 (s, 3H, CO
2
2
2
2
CH ).
3
.1.15. Methyl 8-chloro-8-oxooctanoate (3)
Compound 13 (5 g, 26.6 mmol) and DMF (2 drip) were dissolved in anhydrous
toluene (40 mL). To this mixture, oxalyl chloride was added by dripping at 5 °C for 0.5 h.
The solution was stirred at room temperature for 1 h, and the solvent was removed
under reduced pressure to give the crude. Reduced pressure distillation (bp:
9
5
5
8–101 °C/4.5 mmHg) afforded 3 (4.9 g, 90%) as colorless oil.
.1.16. General Procedure for the Synthesis of methyl 7-(3-aryl-1,2,4-oxadiazol-
-yl)heptanoate 4a-4k
To a solution of N'-Hydroxybenzimidamides 2a-2k (36 mmol) in dry pyridine (15
mL) was added methyl 8-chloro-8-oxooctanoate 3 (44 mmol) by dripping at room
temperature over a period of 0.5 h. Then the mixture was heated to reflux for 3-6 h.
After cooling to room temperature, the mixture was added ethyl acetate (100 mL) and

was partitioned once with water (50 mL). The organic layer was then washed with 2M
HCl solution (2 × 50 mL), saturated sodium bicarbonate (50 mL) and brine (50 mL),
2 4
dried over Na SO , and concentrated under reduced pressure to give the crude
products, which were chromatographed on silica gel using ethyl acetate/petroleum
ether as an eluent to afford the products 4a-4k.
Compounds 4a-4k were characterized as follows.
5
.1.17. Methyl 7-(3-phenyl-1,2,4-oxadiazol-5-yl)heptanoate (4a)
1
Colorless oil, yield: 65%. H NMR (CDCl
3
, 500 MHz) δ (ppm): 1.37-1.47 (m, 4H,
), 2.31 (t, J = 7.4 Hz, 2H,
-
CH
2
2
), 1.62-1.68 (m, 2H, -CH
2
), 1.85-1.91 (m, 2H, -CH
2
-CH
CO ), 2.94 (t, J = 7.5 Hz, 2H, -CH
2
2
), 3.66 (s, 3H, CO
2
CH
3
), 7.28-7.49 (m, 3H, ArH),
+
.06-8.08 (m, 2H, ArH); ESI-MS m/z: 289.1 [M+H] , 311.1 [M+Na] .
+
8
5
.1.18. Methyl 7-(3-(p-tolyl)-1,2,4-oxadiazol-5-yl)heptanoate (4b)
1
White solid, yield: 68%, mp: 52-54 °C. H NMR (CDCl
3
, 500 MHz) δ (ppm): 1.38-1.47
(
m, 4H, -CH
2
), 1.64-1.67 (m, 2H, -CH
2
), 1.86-1.89 (m, 2H, -CH
2
), 2.31 (t, J = 7.4 Hz, 2H,
-
CH CO ), 2.41(s, 3H, Ar-CH
2
2
3
), 2.94 (t, J = 7.5 Hz, 2H, -CH
2
), 3.66 (s, 3H, CO
2
CH
3
), 7.27 (d,
+
+
J = 7.7 Hz, 2H, ArH), 7.94-7.96 (m, 2H, ArH); ESI-MS m/z: 303.1 [M+H] , 325.1 [M+Na] .
5
.1.19. Methyl 7-(3-(4-methoxyphenyl)-1,2,4-oxadiazol-5-yl)heptanoate (4c)
1
White solid, yield: 69%, mp: 48-50 °C. H NMR (CDCl
3
, 500 MHz) δ (ppm): 1.38-1.47
(
-
(
m, 4H, -CH
2
), 1.64-1.68 (m, 2H, -CH
2
), 1.84-1.89 (m, 2H, -CH
2
), 2.31 (t, J = 7.4 Hz, 2H,
), 7.08
CH
2
CO
2
), 2.92 (t, J = 7.5 Hz, 2H, -CH
2
), 3.66 (s, 3H, CO CH ), 3.86 (s, 3H, Ar-OCH
2
3
3
dd, J
1
= 7.2 Hz, J
2
1 2
= 1.5 Hz, 2H, ArH), 8.00 (dd, J = 7.2 Hz, J = 1.5 Hz, 2H, ArH); ESI-MS
+
+
m/z: 319.1 [M+H] , 341.1 [M+Na] .
5
.1.20. Methyl 7-(3-(4-(trifluoromethyl)phenyl)-1,2,4-oxadiazol-5-yl)heptanoate (4d)
1
White solid, yield: 70%, mp: 69-71 °C. H NMR (CDCl
3
, 500 MHz) δ (ppm): 1.40-1.48
(
m, 4H, -CH
2
), 1.65-1.68 (m, 2H, -CH
2
), 1.88-1.90 (m, 2H, -CH
2
), 2.32 (t, J = 7.4 Hz, 2H,
-
CH CO ), 2.96 (t, J = 7.5 Hz, 2H, -CH
2
2
2
), 3.67 (s, 3H, CO
2
CH
3
), 7.74 (d, J = 8.1 Hz, 2H, ArH),
+
+
8
.20 (d, J = 8.1 Hz, 2H, ArH); ESI-MS m/z: 357.2 [M+H] , 379.2 [M+Na] .
5
.1.21. Methyl 7-(3-(4-fluorophenyl)-1,2,4-oxadiazol-5-yl)heptanoate (4e)
1
Colorless oil, yield: 58%. H NMR (CDCl
3
, 500 MHz) δ (ppm): 1.39-1.45 (m, 4H,

2 2 2 2 2
-CH ), 1.61-1.67 (m, 2H, -CH ), 1.88-1.91 (m, 2H, -CH ), 2.32 (t, J = 7.4 Hz, 2H, -CH CO ),
2
2
5
.97 (t, J = 7.6 Hz, 2H, -CH
2
), 3.66 (s, 3H, CO
2
CH
3
), 7.14-7.17 (m, 2H, ArH), 8.06-8.09 (m,
+
H, ArH); ESI-MS m/z: 307.1 [M+H] , 329.2 [M+Na] .
+
.1.22. Methyl 7-(3-(4-chlorophenyl)-1,2,4-oxadiazol-5-yl)heptanoate (4f)
1
White solid, yield: 68%, mp: 57-59 °C. H NMR (CDCl
3
, 500 MHz) δ (ppm): 1.39-1.45
(
m, 4H, -CH
2
), 1.61-1.67 (m, 2H, -CH
2
), 1.88-1.91 (m, 2H, -CH
2
), 2.32 (t, J = 7.4 Hz, 2H,
-
CH CO ), 2.97 (t, J = 7.6 Hz, 2H, -CH
2
2
2
), 3.66 (s, 3H, CO
2
CH
3
), 7.35-7.38 (m, 2H, ArH),
+
.17-8.19 (m, 2H, ArH); ESI-MS m/z: 323.1 [M+H] , 345.1 [M+Na] .
+
8
5
.1.23. Methyl 7-(3-(2-chlorophenyl)-1,2,4-oxadiazol-5-yl)heptanoate (4g)
1
Colorless oil, yield: 52%. H NMR (CDCl
3
, 500 MHz) δ (ppm): 1.39-1.45 (m, 4H,
), 2.30-2.33 (m, 2H, -CH CO ),
), 7.37-7.43 (m, 2H, ArH), 7.53 (dd, J = 8.0
= 7.6 Hz, J = 1.8 Hz, 1H, ArH); ESI-MS m/z: 323.1
-
CH
2
), 1.64-1.67 (m, 2H, -CH
.92-2.93 (m, 2H, -CH ), 3.66 (s, 3H, CO
= 1.2 Hz, 1H, ArH), 7.91 (dd, J
2
), 1.86-1.89 (m, 2H, -CH
2
2
2
2
2
2
CH
3
1
Hz, J
2
1
2
+
M+H] , 345.1 [M+Na] .
+
[
5
.1.24. Methyl 7-(3-(4-nitrophenyl)-1,2,4-oxadiazol-5-yl)heptanoate (4h)
1
Yellow solid, yield: 63%, mp: 62-64 °C. H NMR (CDCl
3
, 500 MHz) δ (ppm):
1
.39-1.49 (m, 4H, -CH
2
), 1.63-1.68 (m, 2H, -CH
2
), 1.88-1.92 (m, 2H, -CH
2
), 2.32 (t, J = 7.4
Hz, 2H, -CH
2
CO ), 2.97 (t, J = 7.6 Hz, 2H, -CH
2
2
), 3.66 (s, 3H, CO CH
2
3
), 7.27 (d, J = 8.6 Hz,
+
H, ArH), 8.33 (d, J = 8.6 Hz, 2H, ArH); ESI-MS m/z: 334.2 [M+H] , 356.1 [M+Na] .
+
2
5
.1.25. Methyl 7-(3-(3-nitrophenyl)-1,2,4-oxadiazol-5-yl)heptanoate (4i)
1
Light yellow oil, yield: 55%. H NMR (CDCl
3
, 500 MHz) δ (ppm): 1.41-1.47 (m, 4H,
-CH
2
), 1.64-1.68 (m, 2H, -CH
2
), 1.89-1.92 (m, 2H, -CH
2
), 2.32 (t, J = 7.4 Hz, 2H, -CH CO ),
2
2
2
1
.97 (t, J = 7.6 Hz, 2H, -CH
2 2 3
), 3.66 (s, 3H, CO CH ), 7.67-7.70 (m, 1H, ArH), 8.34-8.37 (m,
H, ArH), 8.40-8.42 (m, 1H, ArH), 8.93 (d, J = 2.0 Hz, 1H, ArH); ESI-MS m/z: 334.2
+
+
[
M+H] , 356.1 [M+Na] .
5
.1.26. Methyl 7-(3-(thiophen-2-yl)-1,2,4-oxadiazol-5-yl)heptanoate (4j)
1
Colorless oil, yield: 60%. H NMR (CDCl
3
, 500 MHz) δ (ppm): 1.41-1.47 (m, 4H,
), 2.32 (t, J = 7.4 Hz, 2H, -CH CO ),
), 7.24-7.27 (m, 1H, ArH), 7.77-7.79 (m,
-
CH
2
), 1.64-1.68 (m, 2H, -CH
2
), 1.89-1.92 (m, 2H, -CH
CH
2
2
2
2
.96 (t, J = 7.6 Hz, 2H, -CH ), 3.66 (s, 3H, CO
2
2
3

1
H, ArH), 7.85-7.87 (m, 1H, ArH), 8.93 (d, J = 2.0 Hz, 1H, ArH); ESI-MS m/z: 295.1
+
M+H] .
[
5
.1.27. Methyl 7-(3-(pyridin-3-yl)-1,2,4-oxadiazol-5-yl)heptanoate (4k)
1
Light yellow oil, yield: 58%. H NMR (DMSO-d6, 300 MHz) δ (ppm): 1.41-1.47 (m,
4
H, -CH
2
), 1.64-1.68 (m, 2H, -CH
2
), 1.89-1.92 (m, 2H, -CH ), 2.32 (t, J = 7.4 Hz, 2H,
2
-CH
2
CO
2
), 2.97 (t, J = 7.6 Hz, 2H, -CH
2
), 3.66 (s, 3H, CO CH ), 7.41-7.44 (m, 1H, ArH),
2
3
8
2
.34-8.36 (m, 1H, ArH), 8.73-8.75 (m, 1H, ArH), 9.31 (d, J = 2.0 Hz, 1H, ArH); ESI-MS m/z:
+
90.1 [M+H] .
5
.1.28. General Procedure for the Synthesis of 7-(3-Aryl-1,2,4-oxadiazol-5-yl)hep
tanoic acid 5a-5k
To a solution of the compounds 4a-4k (15 mmol) in dry THF (30 mL) was added
LiOH solution (0.6 M, 30 mL), and the reaction was allowed to stir at room temperature
overnight. Then poured into ice water (150 mL), and extracted with ethyl acetate (2 ×
1
00 mL). Discard the organic layer, the pH of the water layer adjusted to 3 with 10% HCl.
Then the precipitates obtained were filtered, washed with water and dried to get the
corresponding carboxylic compounds 5a-5k.
Compounds 5a-5k were characterized as follows.
5
.1.29. 7-(3-Phenyl-1,2,4-oxadiazol-5-yl)heptanoic acid (5a)
White solid, yield: 85%, mp: 100-101 °C.
5
5
5
5
5
.1.30. 7-(3-(p-Tolyl)-1,2,4-oxadiazol-5-yl)heptanoic acid (5b)
White solid, yield: 88%, mp: 95-97 °C.
.1.31. 7-(3-(4-Methoxyphenyl)-1,2,4-oxadiazol-5-yl)heptanoic acid (5c)
White solid, yield: 91%, mp: 103-105 °C.
.1.32. 7-(3-(4-(Trifluoromethyl)phenyl)-1,2,4-oxadiazol-5-yl)heptanoic acid (5d)
White solid, yield: 83%, mp: 107-109 °C.
.1.33. 7-(3-(4-Fluorophenyl)-1,2,4-oxadiazol-5-yl)heptanoic acid (5e)
White solid, yield: 95%, mp: 79-81 °C.
.1.34. 7-(3-(4-Chlorophenyl)-1,2,4-oxadiazol-5-yl)heptanoic acid (5f)
White solid, yield: 91%, mp: 104-106 °C.

5
5
5
5
5
5
.1.35. 7-(3-(2-Chlorophenyl)-1,2,4-oxadiazol-5-yl)heptanoic acid (5g)
White solid, yield: 75%, mp: 60-62 °C.
.1.36. 7-(3-(4-Nitrophenyl)-1,2,4-oxadiazol-5-yl)heptanoic acid (5h)
Yellow solid, yield: 78%, mp: 129-130 °C.
.1.37. 7-(3-(3-Nitrophenyl)-1,2,4-oxadiazol-5-yl)heptanoic acid (5i)
Yellow solid, yield: 81%, mp: 77-79 °C.
.1.38. 7-(3-(Thiophen-2-yl)-1,2,4-oxadiazol-5-yl)heptanoic acid (5j)
Light yellow solid, yield: 70%, mp: 65-67 °C.
.1.39. 7-(3-(Pyridin-3-yl)-1,2,4-oxadiazol-5-yl)heptanoic acid (5k)
Light yellow solid, yield: 83%, mp: 140-141 °C.
.1.40. General Procedure for the Synthesis of the target compounds 6a-6k
A solution of hydroxylamine hydrochloride (1 g, 15 mmol) in methanol (30 mL)
was added dropwise to a solution of KOH (0.84 g, 15 mmol) in methanol (10 mL). Then
the mixture was left under stirring for 15 min, the precipitate KCl obtained was filtered
and discard, the hydroxylamine filtrate was kept for the following step.
To a stirred solution of the compounds 5a-5k (10 mmol) and N-methylmorpholine
(
13 mmol) in dry THF (50 mL) was added dropwise a solution of ethyl chlorocarbonate
12 mmol) in THF (10 mL) at 0 °C, and the reaction was allowed to stir for 0.5 h. The
(
resulting precipitate was filtered and the filtrate was added dropwise to the
above-mentioned hydroxylamine solution. Then the reaction was allowed to stir at
room temperature for another 0.5 h. Solvent was removed under reduced pressure to
afford the crudes, which were dissolved in ethyl acetate (50 mL) and were partitioned
once with saturated ammonium chloride solution (30 mL). The organic layer was then
4
washed with brine (2 × 20 mL), dried over MgSO , and concentrated under reduced
pressure to yield the target compounds 6a-6k.
The target compounds 6a-6k were characterized as follows.
5
.1.41. N-hydroxy-7-(3-phenyl-1,2,4-oxadiazol-5-yl)heptanamide (6a)
-1
White powder, yield: 80%, mp: 84-86 °C. IR (KBr, cm ): 3295.31, 3176.24, 2936.90,
2
7
853.45, 1704.50, 1662.16, 1615.93, 1569.77, 1444.98, 1357.42, 1104.34, 909.72,
1
17.20; H NMR (DMSO-d6, 300 MHz) δ (ppm): 1.30-1.37 (m, 4H, -CH
2
), 1.46-1.56 (m,

2
2 2 2
H, -CH ), 1.74-1.81 (m, 2H, -CH ), 1.96 (t, J = 7.2 Hz, 2H, -CH CO), 2.99 (t, J = 7.5 Hz, 2H,
-
-
CH ), 7.56-7.58 (m, 3H, ArH), 7.99-8.02 (m, 2H, ArH), 8.66 (s, 1H, -NH-), 10.36 (s, 1H,
2
1
OH); C-NMR (DMSO-d6, 75 Hz) δ (ppm): 24.81, 25.65, 25.74, 27.99, 32.11, 126.29,
3
+
26.89, 129.13, 131.35, 167.44, 169.01, 180.29; ESI-MS m/z: 290.2 [M+H] , 312.2
1
+
-
-
[
M+Na] , 288.3 [M-H] , 324.1[M+Cl] ; Anal. Calcd for C15
19 3 3
H N O (%): C, 62.27; H, 6.62;
N, 14.52. Found: C, 62.53; H, 6.50; N, 14.38.
5
.1.42. N-hydroxy-7-(3-(p-tolyl)-1,2,4-oxadiazol-5-yl)heptanamide (6b)
-1
White powder, yield: 82%, mp: 102-104 °C. IR (KBr, cm ): 3256.28, 2912.88,
1
859.65, 1708.23, 1663.56, 1616.28, 1543.25, 1423.15, 916.57, 719.32; H NMR
2
(DMSO-d6, 300 MHz) δ (ppm): 1.27-1.39 (m, 4H, -CH
2
), 1.47-1.53 (m, 2H, -CH
2
),
1
7
.74-1.80 (m, 2H, -CH ), 1.95 (t, J = 7.2 Hz, 2H, -CH CO), 2.38 (s, 3H, Ar-CH ), 2.97 (t, J =
2 2 3
.5 Hz, 2H, -CH ), 7.37 (d, J = 8.1 Hz, 2H, ArH), 7.89 (d, J = 8.1 Hz, 2H, ArH), 8.65 (s, 1H,
2
1
NH-), 10.33 (s, 1H, -OH); C-NMR (DMSO-d6, 75 Hz) δ (ppm): 24.81, 25.65, 25.70,
3
-
2
7.95, 27.99, 32.12, 125.15, 128.71, 129.33, 136.11, 166.67, 169.01, 180.57; ESI-MS
+
+
-
21 3 3
m/z: 304.2 [M+H] , 326.2 [M+Na] , 302.2 [M-H] ; Anal. Calcd for C16H N O (%): C,
6
3.35; H, 6.98; N, 13.85. Found: C, 63.21; H, 6.79; N, 13.69.
.1.43. N-hydroxy-7-(3-(4-methoxyphenyl)-1,2,4-oxadiazol-5-yl)heptanamide (6c)
5
-1
White powder, yield: 89%, mp: 121-122 °C. IR (KBr, cm ): 3251.83, 2952.17,
1
712.29, 1667.18, 1615.29, 1431.71, 1109.28, 912.29, 720.33; H NMR (DMSO-d6, 300
1
MHz) δ (ppm): 1.28-1.41 (m, 4H, -CH
.94 (t, J = 7.2 Hz, 2H, -CH CO), 2.96 (t, J = 7.5 Hz, 2H, -CH
dd, J = 9.6 Hz, J = 2.8 Hz, 2H, ArH), 7.93 (dd, J = 9.6 Hz, J
2
), 1.45-1.54 (m, 2H, -CH
), 3.83 (s, 3H, Ar-OCH
= 2.8 Hz, 2H, ArH), 8.65 (s,
2
), 1.71-1.81 (m, 2H, -CH
2
),
1
2
2
3
), 7.11
(
1
2
1
2
1
3
1
2
1
6
H, -NH-), 10.33 (s, 1H, -OH); C-NMR (DMSO-d6, 75 Hz) δ (ppm): 24.81, 25.64, 25.76,
5.79, 27.96, 27.99, 32.15, 55.35, 114.63, 118.69, 128.64, 161.67, 167.24, 169.01,
+
-
21 3 4
80.02; ESI-MS m/z: 342.2 [M+Na] , 318.2 [M-H] ; Anal. Calcd for C16H N O (%): C,
0.17; H, 6.63; N, 13.16. Found: C, 60.29; H, 6.75; N, 13.52.
5
.1.44. N-hydroxy-7-(3-(4-(trifluoromethyl)phenyl)-1,2,4-oxadiazol-5-yl)heptanamide
(
6d)
-1
White powder, yield: 85%, mp: 84-86 °C. IR (KBr, cm ): 3263.68, 2937.82, 1705.66,

1
665.93, 1618.09, 1563.29, 1430.08, 917.73, 716.52; H NMR (DMSO-d6, 300 MHz) δ
1
(
ppm): 1.26-1.43 (m, 4H, -CH ), 1.45-1.53 (m, 2H, -CH ), 1.71-1.78 (m, 2H, -CH ), 1.94 (t,
2
2
2
2 2
J = 7.2 Hz, 2H, -CH CO), 2.98 (t, J = 7.5 Hz, 2H, -CH ), 7.11 (d, J = 7.8 Hz, 2H, ArH), 8.18
1
3
(
d, J = 7.8 Hz, 2H, ArH), 8.65 (s, 1H, -NH-), 10.33 (s, 1H, -OH); C-NMR (DMSO-d6, 75 Hz)
δ (ppm): 24.76, 25.63, 27.90, 27.96, 32.09, 118.32, 121.93, 126.14, 127.73, 130.11,
+
61.67, 166.49, 168.97, 180.84; ESI-MS m/z: 358.2 [M+H] , 380.2 [M+Na] , 356.2
+
1
-
-
[
M-H] , 392.1[M+Cl] ; Anal. Calcd for C16
18 3 3 3
H F N O (%): C, 53.78; H, 5.08; N, 11.76.
Found: C, 53.52; H, 4.95; N, 11.63.
5
.1.45. 7-(3-(4-Fluorophenyl)-1,2,4-oxadiazol-5-yl)-N-hydroxyheptanamide (6e)
-1
White powder, yield: 73%, mp: 64-66 °C. IR (KBr, cm ): 3287.35, 3179.51,
1
2
861.32, 1708.49, 1665.23, 1618.96, 1436.29, 915.68, 719.15; H NMR (CDCl
3
, 300 MHz)
),
), 7.13-7.17 (m, 2H, ArH), 8.03-8.09
δ (ppm): 1.36-1.49 (m, 4H, -CH
2 2 2
), 1.62-1.69 (m, 2H, -CH ), 1.81-1.90 (m, 2H, -CH
2
.14-2.16 (m, 2H, -CH CO), 2.90-2.95 (m, 2H, -CH
2
2
1
m, 2H, ArH), 9.60 (s, 1H, -NH-); C-NMR (DMSO-d6, 75 Hz) δ (ppm): 23.77, 25.61,
3
(
2
5.83, 28.05, 32.36, 126.15, 126.71, 129.38, 132.51, 167.38, 169.29, 180.15; ESI-MS
+
+
-
3 3
m/z: 308.1 [M+H] , 330.2 [M+Na] , 306.2 [M-H] ; Anal. Calcd for C15H18FN O (%): C,
5
8.62; H, 5.90; N, 13.67. Found: C, 58.36; H, 6.12; N, 13.83.
.1.46. 7-(3-(4-Chlorophenyl)-1,2,4-oxadiazol-5-yl)-N-hydroxyheptanamide (6f)
5
-1
White powder, yield: 80%, mp: 101-102 °C. IR (KBr, cm ): 3253.26, 3173.67,
1
2
863.16, 1705.22, 1667.41, 1617.82, 1426.71, 905.73, 709.15; H NMR (DMSO-d6, 300
MHz) δ (ppm): 1.26-1.45 (m, 4H, -CH
2
2 2
), 1.46-1.55 (m, 2H, -CH ), 1.73-1.83 (m, 2H, -CH ),
1
8
7
1
.96 (t, J = 7.2 Hz, 2H, -CH
2
CO), 2.99 (t, J = 7.5 Hz, 2H, -CH ), 7.63 (d, J = 8.5 Hz, 2H, ArH),
2
1
3
.01 (d, J = 8.5 Hz, 2H, ArH), 8.66 (s, 1H, -NH-), 10.35 (s, 1H, -OH); C-NMR (DMSO-d6,
5 Hz) δ (ppm): 24.50, 25.68, 25.83, 28.17, 32.96, 127.19, 127.82, 129.25, 136.38,
+
+
-
67.51, 169.12, 180.33; ESI-MS m/z: 324.2 [M+H] , 346.1 [M+Na] , 322.1 [M-H] , 358.1
-
[
M+Cl] ; Anal. Calcd for C15
H18ClN
3
O
3
(%): C, 55.64; H, 5.60; N, 12.98. Found: C, 55.39; H,
5
.78; N, 13.19.
.1.47. 7-(3-(2-Chlorophenyl)-1,2,4-oxadiazol-5-yl)-N-hydroxyheptanamide (6g)
5
-
1
Light yellow Oil, yield: 65%. IR (KBr, cm ): 3281.26, 3165.63, 2851.55, 1665.38,

1
616.55, 1538.29, 1436.37, 915.67, 716.39; H NMR (DMSO-d6, 300 MHz) δ (ppm):
1
1
.28-1.39 (m, 4H, -CH ), 1.45-1.54 (m, 2H, -CH ), 1.72-1.82 (m, 2H, -CH ), 1.94 (t, J = 7.2
2
2
2
2 2
Hz, 2H, -CH CO), 3.00 (t, J = 7.5 Hz, 2H, -CH ), 7.50-7.62 (m, 2H, ArH), 7.67 (d, J = 7.7 Hz,
1
3
H, ArH), 7.89 (d, J = 7.4 Hz, 1H, ArH), 8.66 (s, 1H, -NH-), 10.33 (s, 1H, -OH); C-NMR
1
(DMSO-d6, 75 Hz) δ (ppm): 24.84, 25.64, 25.68, 25.73, 28.00, 32.13, 125.67, 127.62,
+
30.78, 131.66, 132.11, 132.44, 166.37, 169.08, 179.86; ESI-MS m/z: 324.1 [M+H] ,
1
3
+
-
-
3 3
46.1 [M+Na] , 322.1 [M-H] , 358.1 [M+Cl] ; Anal. Calcd for C15H18ClN O (%): C, 55.64;
H, 5.60; N, 12.98. Found: C, 55.25; H, 5.85; N, 13.03.
5
.1.48. N-hydroxy-7-(3-(4-nitrophenyl)-1,2,4-oxadiazol-5-yl)heptanamide (6h)
-1
Yellow powder, yield: 88%, mp: 92-94 °C. IR (KBr, cm ): 3248.35, 2936.57, 1628.72,
1
576.22, 1542.49, 1414.47, 1358.54, 1308.20, 865.82, 713.66; H NMR (DMSO-d6, 300
1
MHz) δ (ppm): 1.29-1.40 (m, 4H, -CH
2
2 2
), 1.43-1.55 (m, 2H, -CH ), 1.74-1.84 (m, 2H, -CH ),
1
8
7
1
.95 (t, J = 7.2 Hz, 2H, -CH
2
CO), 3.00 (t, J = 7.5 Hz, 2H, -CH ), 8.25 (d, J = 9.1 Hz, 2H, ArH),
2
1
.37 (d, J = 9.1 Hz, 2H, ArH), 8.65 (s, 1H, -NH-), 10.33 (s, 1H, -OH); C-NMR (DMSO-d6,
3
5 Hz) δ (ppm): 24.77, 25.63, 27.90, 27.97, 32.09, 124.35, 128.30, 132.06, 149.07,
+
+
-
66.18, 168.98, 181.12; ESI-MS m/z: 335.1 [M+H] , 357.1 [M+Na] , 333.2 [M-H] , 369.1
-
[
M+Cl] ; Anal. Calcd for C15
H
18
N
4
O
5
(%): C, 53.89; H, 5.43; N, 16.76. Found: C, 54.09; H,
5
.68; N, 16.38.
.1.49. N-hydroxy-7-(3-(3-nitrophenyl)-1,2,4-oxadiazol-5-yl)heptanamide (6i)
5
-1
Yellow powder, yield: 78%, mp: 68-70 °C. IR (KBr, cm ): 3256.92, 3152.33, 2859.89,
1
1
706.36, 1663.28, 1616.63, 1435.91, 908.25, 709.38; H NMR (DMSO-d6, 300 MHz) δ
(
ppm): 1.29-1.38 (m, 4H, -CH
2
), 1.46-1.55 (m, 2H, -CH
CO), 3.02 (t, J = 7.5 Hz, 2H, -CH ), 7.58-7.63 (m, 1H, ArH), 8.33-8.37
= 4.8 Hz, J = 1.6 Hz, 1H, ArH), 9.15 (d, J = 2.1 Hz, 1H, ArH),
2 2
), 1.74-1.84 (m, 2H, -CH ), 1.95 (t,
J = 7.2 Hz, 2H, -CH
2
2
(m, 1H, ArH), 8.78 (dd, J
1
2
1
3
8
2
1
.64 (s, 1H, -NH-), 10.33 (s, 1H, -OH); C-NMR (DMSO-d6, 75 Hz) δ (ppm): 24.80, 25.68,
7.94, 27.99, 32.11, 121.35, 125.89, 127.75, 131.08, 132.92, 148.16, 166.04, 168.99,
+
+
-
-
81.07; ESI-MS m/z: 335.1 [M+H] , 357.1 [M+Na] , 333.2 [M-H] , 369.1 [M+Cl] ; Anal.
(%): C, 53.89; H, 5.43; N, 16.76. Found: C, 53.65; H, 5.58; N, 16.52.
.1.50. N-hydroxy-7-(3-(thiophen-2-yl)-1,2,4-oxadiazol-5-yl)heptanamide (6j)
18 4 5
Calcd for C15H N O
5

-1
Light Yellow powder, yield: 80%, mp: 75-77 °C. IR (KBr, cm ): 3266.33, 3158.61,
1
816.73, 1705.53, 1666.29, 1617.86, 1421.65, 920.67, 716.36 H NMR (DMSO-d6, 300
2
MHz) δ (ppm): 1.28-1.40 (m, 4H, -CH
2
), 1.44-1.54 (m, 2H, -CH ), 1.73-1.80 (m, 2H, -CH
2
2
),
1
7
.94 (t, J = 7.2 Hz, 2H, -CH
2
CO), 2.96 (t, J = 7.5 Hz, 2H, -CH ), 7.24-7.27 (m, 1H, ArH),
2
.77-7.79 (m, 1H, ArH), 7.85-7.87 (m, 1H, ArH), 8.64 (s, 1H, -NH-), 10.32 (s, 1H, -OH);
C NMR (DMSO-d6, 75 Hz) δ (ppm): 24.56, 25.36, 27.12, 28.05, 31.16, 123.52, 125.20,
1
3
+
27.39, 147.16, 166.89, 168.83, 179.23; ESI-MS m/z: 296.1 [M+H] , 318.1 [M+Na] ,
+
1
2
-
-
17 3 3
94.1 [M-H] , 330.1 [M+Cl] ; Anal. Calcd for C13H N O S (%): C, 52.86; H, 5.80; N, 14.23.
Found: C, 53.11; H, 5.53; N, 14.33.
5
.1.51. N-hydroxy-7-(3-(pyridin-3-yl)-1,2,4-oxadiazol-5-yl)heptanamide (6k)
-
Light Yellow powder, yield: 75%, mp: 114-116 °C. IR (KBr, cm ): 3252.29, 3153.36,
1
1
916.26, 2855.16, 1706.26, 1663.35, 1617.05, 1423.68, 907.56, 715.23; H NMR
2
(
DMSO-d6, 300 MHz) δ (ppm): 1.28-1.37 (m, 4H, -CH
2
), 1.45-1.56 (m, 2H, -CH
2
2
),
),
1
7
2 2
.73-1.84 (m, 2H, -CH ), 1.95 (t, J = 7.2 Hz, 2H, -CH CO), 3.02 (t, J = 7.5 Hz, 2H, -CH
.83-7.88 (m, 1H, ArH), 8.38-8.43 (m, 2H, ArH), 8.65 (d, J = 1.9 Hz, 1H, ArH), 8.66 (s, 1H,
1
NH-), 10.32 (s, 1H, -OH); C-NMR (DMSO-d6, 75 Hz) δ (ppm): 24.76, 25.68, 27.90,
3
-
2
7.95, 32.09, 122.53, 124.20, 134.49, 147.59, 152.13, 165.72, 168.97, 180.76; ESI-MS
+
+
-
-
m/z: 291.2 [M+H] , 313.1 [M+Na] , 289.2 [M-H] , 325.1 [M+Cl] ; Anal. Calcd for
14 18 4 3
C H N O (%): C, 57.92; H, 6.25; N, 19.30. Found: C, 57.76; H, 5.98; N, 19.39.
5
.1.52. General Procedure for the Synthesis of the target compounds 9a-9k
Oxalyl chloride (0.42 mL, 4.8 mmol) and DMF (40 μL) were added dropwise to a
stirred solution of the carboxylic compounds 5a-5k (1.0 mmol) in dry THF (40 mL) at
°C, and the reaction was allowed to stir at room temperature for 1 h. Solvent was
0
then removed under reduced pressure to give the acyl chlorides 7a-7k, which were
dissolved in THF (10 mL) and added dropwise to a solution of tert-butyl
(2-aminophenyl)carbamate (1.1 mmol) and N-methylmorpholine (1.0 mmol) in THF (40
mL) at 0 °C. Then the reaction was allowed to stir at room temperature for 4 h. Solvent
was removed under reduced pressure to afford the crudes, which were dissolved in
ethyl acetate (100 mL) and were partitioned once with water (50 mL). The organic layer

was then washed with diluted hydrochloric acid (1 M, 2 × 50 mL), NaOH solution (1M, 2
50 mL), brine (2 × 50 mL), dried over MgSO , and concentrated under reduced
pressure to give the intermediates 8a-8k.
×
4
A solution of 8a-8k and TFA (1.5 mL) in dichloromethane (10 mL) was left under
stirring at room temperature until the disappearance of the starting materials (TLC
analysis). Saturated potassium carbonate solution was added to the reaction until no
bubble released. Then the mixture was extracted with dichloromethane (3 × 30 mL),
the combined organic layer was washed with NaOH solution (1M, 2 × 20 mL), brine (2 ×
2
4
0 mL) and dried with MgSO . The solvent was evaporated under reduced pressure to
yield the target compounds 9a-9k.
The target compounds 9a-9k were characterized as follows.
5
.1.53. N-(2-aminophenyl)-7-(3-phenyl-1,2,4-oxadiazol-5-yl)heptanamide (9a)
-1
White powder, yield: 83%, mp: 115-117 °C. IR (KBr, cm ): 3398.21, 3325.38,
1
7
655.23, 1643.37, 1593.16, 1529.15, 1461.36, 1413.01, 1355.43, 782.16, 745.59,
1
01.28; H NMR (CDCl
3
, 300 MHz) δ (ppm): 1.47-1.49 (m, 4H, -CH
2
), 1.76-1.79 (m, 2H,
-
CH
2
2
), 1.87-1.92 (m, 2H, -CH
2 2
), 2.40 (t, J = 7.4 Hz, 2H, -CH CO), 2.96 (t, J = 7.5 Hz, 2H,
-CH
), 3.86 (br, 2H, -NH ), 6.78-6.81 (m, 2H, ArH), 7.03-7.07 (m, 1H, ArH), 7.17 (d, J =
2
1
.6 Hz, 1H, ArH), 7.22 (br, 1H, -NH-), 7.45-7.51 (m, 3H, ArH), 8.05-8.09 (m, 2H, ArH); C
3
7
NMR (CDCl
3
, 75 Hz) δ (ppm): 24.40, 25.46, 26.40, 26.49, 28.62, 32.03, 36.76, 113.88,
1
1
3
6
14.23, 118.34, 119.71, 124.44, 125.23, 125.62, 126.90, 127.19, 127.39, 128.83, 129.30,
+
+
-
31.0, 168.27, 171.71, 179.87; ESI-MS m/z: 365.2 [M+H] , 387.2 [M+Na] , 363.2 [M-H] ,
-
99.1 [M+Cl] ; Anal. Calcd for C21
24 4 2
H N O (%): C, 69.21; H, 6.64; N, 15.37. Found: C,
9.52; H, 6.39; N, 15.55.
5
.1.54. N-(2-aminophenyl)-7-(3-(p-tolyl)-1,2,4-oxadiazol-5-yl)heptanamide (9b)
-1
White powder, yield: 81%, mp: 122-123 °C. IR (KBr, cm ): 3400.16, 3327.08,
1
7
655.41, 1642.42, 1592.82, 1527.71, 1460.21, 1412.83, 1355.08, 783.69, 746.37,
1
03.35; H NMR (CDCl
3
, 300 MHz) δ (ppm): 1.47-1.48 (m, 4H, -CH
), 2.38 (t, J = 7.4 Hz, 2H, -CH CO), 2.41 (s, 3H, -CH
), 3.86 (br, 2H, -NH ), 6.76-6.80 (m, 2H, ArH), 7.02-7.07 (m, 1H, ArH),
2
), 1.73-1.78 (m, 2H,
-CH
2
), 1.87-1.91 (m, 2H, -CH
2
2
3
), 2.94 (t,
J = 7.5 Hz, 2H, -CH
2
2

7
8
3
1
.15 (d, J = 7.7 Hz, 1H, ArH), 7.26 (br, 1H, -NH-), 7.27 (d, J = 8.1 Hz, 2H, ArH), 7.95 (d, J =
1
.1 Hz, 2H, ArH); C NMR (CDCl
3
3
, 75 Hz) δ (ppm): 21.51, 25.43, 26.38, 26.46, 29.66,
6.72, 118.20, 119.50, 124.04, 124.34, 125.20, 127.13, 127.28, 129.26, 129.52, 140.79,
+
41.38, 168.24, 171.62, 179.67; ESI-MS m/z: 379.2 [M+H] , 401.2 [M+Na] , 377.2
+
-
-
[
M-H] , 413.3 [M+Cl] ; Anal. Calcd for C22
26 4 2
H N O (%): C, 69.82; H, 6.92; N, 14.80. Found:
C, 69.63; H, 6.78; N, 14.71.
5
.1.55. N-(2-aminophenyl)-7-(3-(4-methoxyphenyl)-1,2,4-oxadiazol-5-yl)heptanamide
(
9c)
-1
White powder, yield: 85%, mp: 130-131 °C. IR (KBr, cm ): 3401.41, 3321.15,
1
1
1
654.60, 1615.21, 1592.55, 1527.03, 1461.82, 1414.35, 1362.51, 1256.33, 1176.13,
1
030.11, 842.48, 753.83; H NMR (CDCl
3
, 300 MHz) δ (ppm): 1.47-1.49 (m, 4H, -CH
), 1.87-1.91 (m, 2H, -CH ), 2.40 (t, J = 7.4 Hz, 2H, -CH CO), 2.94 (t,
), 3.85 (s, 3H, -OCH ), 6.77-6.80 (m, 2H, ArH),
2
),
.73-1.78 (m, 2H, -CH
2
2
2
J = 7.5 Hz, 2H, -CH
2
), 3.82 (br, 2H, -NH
2
3
6
1
2
1
.98 (d, J = 8.8 Hz, 2H, ArH), 7.04-7.07 (m, 1H, ArH), 7.16-7.18 (m, 1H, ArH), 7.26 (br,
1
H, -NH-), 8.00 (d, J = 8.8 Hz, 2H, ArH); C NMR (CDCl
3
3
, 75 Hz) δ (ppm): 24.38, 25.45,
6.38, 26.46, 28.60, 36.79, 55.35, 114,24, 118.27, 119.58, 127.14, 128.98, 158.80,
+
61.87, 167.97, 171.55, 179.55; ESI-MS m/z: 395.2 [M+H] , 417.2 [M+Na] , 393.2
+
-
-
[
M-H] , 429.2 [M+Cl] ; Anal. Calcd for C22
26 4 3
H N O (%): C, 66.99; H, 6.64; N, 14.20. Found:
C, 67.15; H, 6.81; N, 14.33.
5
.1.56. N-(2-aminophenyl)-7-(3-(4-(trifluoromethyl)phenyl)-1,2,4-oxadiazol-5-yl)hept
anamide (9d)
-1
White powder, yield: 88%, mp: 178-180 °C. IR (KBr, cm ): 3400.95, 3322.19,
1
8
1
655.23, 1615.20, 1595.63, 1527.29, 1463.11, 1361.85, 1253.39, 1175.53, 1031.16,
1
43.35, 752.96; H NMR (DMSO-d6, 300 MHz) δ (ppm): 1.36-1.38 (m, 4H, -CH
2
),
.61-1.88 (m, 4H, -CH
2
), 2.29-2.34 (m, 4H, -CH
2
), 4.79 (br, 2H, -NH
2
), 6.50-6.56 (m, 2H,
ArH), 6.71 (d, J = 7.9 Hz, 2H, ArH), 6.86-6.91 (m, 2H, ArH), 7.15 (d, J = 7.0 Hz, 2H, ArH),
1
3
9
2
1
.07 (br, 1H, -NH-); C NMR (DMSO-d6, 75 Hz) δ (ppm): 24.37, 25.47, 26.39, 26.46,
8.59, 36.82, 114.63, 118.69, 119.58, 127.14, 128.64, 158.80, 161.67, 167.24, 169.01,
+
80.02; ESI-MS m/z: 433.2 [M+H] ; Anal. Calcd for C22
H
23
F
3
N
4
O
2
(%): C, 61.10; H, 5.36;

N, 12.26. Found: C, 61.28; H, 5.59; N, 12.35.
5
.1.57. N-(2-aminophenyl)-7-(3-(4-fluorophenyl)-1,2,4-oxadiazol-5-yl)heptanamide
(
9e)
-1
White powder, yield: 85%, mp: 128-129 °C. IR (KBr, cm ): 3400.26, 3319.38,
1
8
656.83, 1616.09, 1595.71, 1526.36, 1463.05, 1361.91, 1253.68, 1176.85, 1031.52,
1
43.69, 752.43; H NMR (CDCl
3
, 300 MHz) δ (ppm): 1.45-1.46 (m, 4H, -CH
), 1.85-1.90 (m, 2H, -CH ), 2.36 (t, J = 7.4 Hz, 2H, -CH CO), 2.93 (t, J = 7.5 Hz,
), 6.74-6.79 (m, 2H, ArH), 7.02-7.07 (m, 1H, ArH), 7.13-7.18
2
), 1.71-1.75
(m, 2H, -CH
2
2
2
2
H, -CH
2
), 3.84 (br, 2H, -NH
2
1
3
(
m, 3H, ArH), 7.26 (br, 1H, -NH-), 8.04-8.09 (m, 2H, ArH); C NMR (CDCl
ppm): 25.41, 26.33, 26.42, 28.59, 29.70, 36.63, 115.82, 116.11, 118.13, 119.43, 125.25,
27.12, 129.43, 140.82, 162.80, 166.13, 167.42, 171.69, 179.96; ESI-MS m/z: 383.2
3
, 75 Hz) δ
(
1
+
+
-
-
[
4 2
M+H] , 405.2 [M+Na] , 381.2 [M-H] , 427.2 [M+Cl] ; Anal. Calcd for C21H23FN O (%): C,
6
5.95; H, 6.06; N, 14.65. Found: C, 65.86; H, 6.32; N, 14.59.
.1.58. N-(2-aminophenyl)-7-(3-(4-chlorophenyl)-1,2,4-oxadiazol-5-yl)heptanamide
5
(
9f)
-1
White powder, yield: 94%, mp: 125-127 °C. IR (KBr, cm ): 3401.53, 3319.26,
1
1
1
655.79, 1616.41, 1589.35, 1526.18, 1461.82, 1415.37, 1363.69, 1258.63, 1175.28,
1
031.71, 843.21, 753.66; H NMR (CDCl
3
, 300 MHz) δ (ppm): 1.47-1.48 (m, 4H, -CH
), 1.87-1.91 (m, 2H, -CH ), 2.39 (t, J = 7.4 Hz, 2H, -CH CO), 2.94 (t,
), 6.76-6.80 (m, 2H, ArH), 7.02-7.07 (m, 1H, ArH),
2
),
.73-1.78 (m, 2H, -CH
2
2
2
J = 7.5 Hz, 2H, -CH
2
), 3.85 (br, 2H, -NH
2
7
8
1
1
.15 (d, J = 7.7 Hz, 1H, ArH), 7.26 (br, 1H, -NH-), 7.45 (d, J = 8.5 Hz, 2H, ArH), 8.01 (d, J =
1
3
.5 Hz, 2H, ArH); C NMR (CDCl
3
, 75 Hz) δ (ppm): 25.43, 26.36, 26.49, 29.68, 36.73,
18.24, 119.54, 124.34, 125.17, 125.39, 127.15, 128.68, 129.13, 137.23, 140.75, 167.46,
+
+
-
71.58, 180.07; ESI-MS m/z: 399.2 [M+H] , 421.2 [M+Na] , 397.2 [M-H] ; Anal. Calcd
4 2
for C21H23ClN O
(%): C, 63.23; H, 5.81; N, 14.05. Found: C, 63.10; H, 5.73; N, 14.31.
5
.1.59. N-(2-aminophenyl)-7-(3-(2-chlorophenyl)-1,2,4-oxadiazol-5-yl)heptanamide
(
9g)
-1
White powder, yield: 76%, mp: 80-82 °C. IR (KBr, cm ): 3398.25, 3318.43, 1655.87,
1
615.63, 1587.15, 1525.56, 1461.03, 1415.93, 1361.18, 1256.69, 1175.58, 1031.73,

1
8
43.90, 753.87; H NMR (CDCl
3
, 300 MHz) δ (ppm): 1.46-1.49 (m, 4H, -CH
), 1.87-1.90 (m, 2H, -CH ), 2.38 (t, J = 7.5 Hz, 2H, -CH CO), 2.95 (t, J = 7.5 Hz,
), 6.75-6.81 (m, 2H, ArH), 7.28 (br, 1H, -NH-), 7.51-7.61 (m,
2
), 1.75-1.80
(m, 2H, -CH
2
2
2
2
2
2
1
1
H, -CH
2
), 3.83 (br, 2H, -NH
2
H, ArH), 7.66 (d, J = 7.5 Hz, 1H, ArH), 7.89 (d, J = 7.5 Hz, 1H, ArH), 8.02 (d, J = 8.5 Hz,
1
3
3
H, ArH); C NMR (CDCl , 75 Hz) δ (ppm): 25.23, 26.51, 26.63, 30.09, 36.95, 118.71,
19.63, 124.56, 125.88, 125.93, 127.28, 128.91, 129.33, 137.50, 140.87, 167.73, 171.96,
+
79.89; ESI-MS m/z: 399.2 [M+H] ; Anal. Calcd for C21
H23ClN
4
O
2
(%): C, 63.23; H, 5.81;
N, 14.05. Found: C, 63.05; H, 5.96; N, 14.33.
5
.1.60.
N-(2-aminophenyl)-7-(3-(4-nitrophenyl)-1,2,4-oxadiazol-5-yl)heptanamide
(
9h)
-
Yellow powder, yield: 78%, mp: 151-153 °C. IR (KBr, cm ): 3400.53, 3320.63,
1
1
647.73, 1529.32 , 1347.63, 1256.21, 1029.58, 841.92, 752.36; H NMR (CDCl
1
3
, 300
MHz) δ (ppm): 1.48-1.51 (m, 4H, -CH
2
), 1.76-1.81 (m, 2H, -CH
2
), 1.90-1.95 (m, 2H, -CH
2
),
),
2
6
1
.41 (t, J = 7.4 Hz, 2H, -CH
2
CO), 2.97 (t, J = 7.5 Hz, 2H, -CH ), 3.85 (br, 2H, -NH
2
2
.77-6.81 (m, 2H, ArH), 7.03-7.08 (m, 1H, ArH), 7.15 (d, J = 7.7 Hz, 1H, ArH), 7.26 (br,
1
3
3
H, -NH-), 8.25 (d, J = 8.9 Hz, 2H, ArH), 8.34 (d, J = 8.9 Hz, 2H, ArH); C NMR (CDCl , 75
Hz) δ (ppm): 25.45, 26.35, 26.51, 28.68, 29.71, 36.81, 118.36, 119.66, 124.10, 124.40,
25.12, 127.22, 128.39, 129.37, 132.86, 140.72, 149.43, 166.80, 171.50, 180.78;
1
+
+
-
ESI-MS m/z: 410.2 [M+H] , 432.2 [M+Na] , 408.2 [M-H] ; Anal. Calcd for C21
23 5 4
H N O (%):
C, 61.60; H, 5.66; N, 17.10. Found: C, 61.35; H, 5.82; N, 17.39.
5
.1.61. N-(2-aminophenyl)-7-(3-(3-nitrophenyl)-1,2,4-oxadiazol-5-yl)heptanamide (9i)
-
1
Yellow powder, yield: 75%, mp: 126-128 °C. IR (KBr, cm ): 3401.41, 3321.15,
1
7
648.66, 1595.69, 1527.03, 1533.62, 1515.83, 1461.80, 1369.06, 1349.24, 757.29,
1
18.58; H NMR (CDCl
3
, 300 MHz) δ (ppm): 1.46-1.50 (m, 4H, -CH
2
), 1.75-1.81 (m, 2H,
-
CH
2
2
), 1.89-1.95 (m, 2H, -CH
2 2
), 2.40 (t, J = 7.4 Hz, 2H, -CH CO), 2.98 (t, J = 7.5 Hz, 2H,
-CH
), 3.84 (br, 2H, -NH ), 6.77-6.80 (m, 2H, ArH), 7.03-7.07 (m, 1H, ArH), 7.15-7.22 (m,
2
1
H, ArH), 7.26 (br, 1H, -NH-), 7.65-7.70 (m, 1H, ArH), 8.34-8.42 (m, 2H, ArH), 8.93 (s, 1H,
1
3
ArH); C NMR (CDCl
3
, 75 Hz) δ (ppm): 25.46, 26.37, 26.52, 28.69, 29.70, 36.78, 118.30,
1
19.60, 122.56, 124.40, 125.18, 125.61, 127.18, 128.79, 129.32, 130.02, 140.77, 148.64,

+
+
-
1
66.72, 171.59, 180.75; ESI-MS m/z: 410.2 [M+H] , 432.2 [M+Na] , 408.2 [M-H] ; Anal.
Calcd for C21 (%): C, 61.60; H, 5.66; N, 17.10. Found: C, 61.70; H, 5.73; N, 17.28.
.1.62. N-(2-aminophenyl)-7-(3-(thiophen-2-yl)-1,2,4-oxadiazol-5-yl)heptanamide (9j)
23 5 4
H N O
5
-1
Yellow powder, yield: 83%, mp: 85-87 °C. IR (KBr, cm ): 3398.31, 3315.97,
1
643.29, 1590.68, 1520.18, 1535.89, 1515.36, 1459.76, 1355.09, 760.59, 716.85; H
1
3 2 2
NMR (CDCl , 300 MHz) δ (ppm): 1.48-1.51 (m, 4H, -CH ), 1.66-1.88 (m, 4H, -CH ),
2
2 2 2
.34-2.40 (m, 2H, -CH ), 2.89-2.95 (m, 2H, -CH ), 3.84 (br, 2H, -NH ), 6.77-6.79 (m, 2H,
ArH), 7.03-7.07 (m, 1H, ArH), 7.15-7.20 (m, 1H, ArH), 7.26 (br, 1H, -NH-), 7.46-7.52 (m,
1
3
2
2
1
3
H, ArH), 7.75-7.80 (m, 1H, ArH); C NMR (CDCl , 75 Hz) δ (ppm): 25.41, 26.32, 26.37,
8.69, 33.87, 36.70, 114.53, 118.21, 118.59, 119.55, 122.40, 124.37, 125.23, 127.14,
27.93, 128.84, 129.36, 130.02, 140.71, 164.29, 171.69, 179.86; ESI-MS m/z: 371.2
+
+
-
-
[
22 4 2
M+H] , 393.2 [M+Na] , 369.2 [M-H] , 405.1 [M+Cl] ; Anal. Calcd for C19H N O S (%): C,
6
1.60; H, 5.99; N, 15.12. Found: C, 61.23; H, 5.81; N, 15.39.
.1.63. N-(2-aminophenyl)-7-(3-(pyridin-3-yl)-1,2,4-oxadiazol-5-yl)heptanamide (9k)
5
-1
Yellow powder, yield: 71%, mp: 85-87 °C. IR (KBr, cm ): 3400.39, 3318.68,
1
646.58, 1590.19, 1523.71, 1535.61, 1515.26, 1459.95, 1356.65, 759.83, 716.55; H
1
NMR (CDCl
3
, 300 MHz) δ (ppm): 1.47-1.48 (m, 4H, -CH
.89-1.92 (m, 2H, -CH ), 2.39 (t, J = 7.4 Hz, 2H, -CH CO), 2.96 (t, J = 7.5 Hz, 2H, -CH
.84 (br, 2H, -NH
H, ArH), 7.26 (br, 1H, -NH-), 7.39-7.43 (m, 2H, ArH), 8.33 (d, J = 7.9 Hz, 1H, ArH),
2
), 1.75-1.78 (m, 2H, -CH
2
),
1
3
1
8
2
1
3
2
2
2
),
2
), 6.76-6.79 (m, 2H, ArH), 7.03-7.06 (m, 1H, ArH), 7.16 (d, J = 7.7 Hz,
1
3
.72-8.74 (m, 1H, ArH); C NMR (CDCl
3
, 75 Hz) δ (ppm): 25.44, 26.33, 26.45, 28.64,
9.70, 36.69, 118.18, 119.46, 123.25, 123.64, 124.39, 125.23, 127.12, 134.67, 140.82,
+
+
48.57, 151.89, 166.33, 171.66, 180.42; ESI-MS m/z: 366.2 [M+H] , 388.2 [M+Na] ,
-
-
23 5 2
64.2 [M-H] , 400.2 [M+Cl] ; Anal. Calcd for C20H N O (%): C, 65.73; H, 6.34; N, 19.16.
Found: C, 65.56; H, 6.69; N, 19.38.
5
.1.64. General Procedure for the Synthesis of the target compounds 10a-10j
Oxalyl chloride (0.42 mL, 4.8 mmol) and DMF (40 μL) were added dropwise to a
stirred solution of the carboxylic compounds 5a-5j (1.0 mmol) in dry THF (40 mL) at
°C, and the reaction was allowed to stir at room temperature for 1 h. Solvent was
then removed under reduced pressure to give the acyl chlorides 7a-7j, which were
0

dissolved in THF (10 mL). To this THF solution was added TFAA (0.84 mL, 6.0 mmol) and
anhydrous pyridine (0.62 mL, 8.0 mmol) dropwise at 0 °C. Then the reaction was
allowed to stir for 30 min at 0 °C and 2 h at room temperature. Water (2 mL) was added
to the mixture to quench the reaction and then stirred for 2 h at 45 °C. After cooling to
room temperature, the mixture was added dichloromethane (100 mL) and was
partitioned once with water (100 mL). The organic layer was then washed with 1M HCl
4
solution (2 × 50 mL) and brine (50 mL), dried over MgSO , and concentrated under
reduced pressure to give the crude products, which were chromatographed on silica
gel using ethyl acetate/petroleum ether (1:2) as an eluent to afford the products
1
0a-10j.
The target compounds 10a-10j were characterized as follows.
5
.1.65. 1,1,1-Trifluoro-8-(3-phenyl-1,2,4-oxadiazol-5-yl)octan-2-one (10a)
1
Colorless oil, yield: 55%. H NMR (CDCl
3
, 300 MHz) δ (ppm): 1.41-1.49 (m, 4H,
), 2.72 (t, J = 7.2 Hz, 2H, -CH CO),
), 7.46-7.50 (m, 3H, ArH), 8.06-8.08 (m, 2H, ArH); C-NMR
, 75 Hz) δ (ppm): 22.13, 26.30, 26.46, 28.55, 36.18, 126.92, 127.39, 127.65,
28.82, 131.08, 158.81, 168.30, 179.70; HRMS (ESI) m/z calculated for C16
-
CH
2
), 1.68-1.74 (m, 2H, -CH
2
), 1.86-1.93 (m, 2H, -CH
2
2
1
3
2
.95 (t, J = 7.5 Hz, 2H, -CH
2
(
CDCl
3
1
3
H
17
F
3
N
2
O
2
-
+
-
+
25.1164 [M-H] , 349.1140 [M+Na] . Found 325.1169 [M-H] , 349.1134 [M+Na] ; Anal.
(%): C, 58.89; H, 5.25; N, 8.58. Found: C, 58.68; H, 5.52; N, 8.36.
.1.66. 1,1,1-Trifluoro-8-(3-(p-tolyl)-1,2,4-oxadiazol-5-yl)octan-2-one (10b)
17 3 2 2
Calcd for C16H F N O
5
1
White powder, yield: 58%, mp: 50-51 °C. H NMR (CDCl
.38-1.49 (m, 4H, -CH ), 1.68-1.72 (m, 2H, -CH ), 1.83-1.91 (m, 2H, -CH
), 2.72 (t, J = 7.2 Hz, 2H, -CH CO), 2.94 (t, J = 7.5 Hz, 2H, -CH ), 7.28 (d, J = 7.8 Hz,
H, ArH), 7.95 (d, J = 8.2 Hz, 2H, ArH); C-NMR (CDCl , 75 Hz) δ (ppm): 21.26, 22.07,
3
, 300 MHz) δ (ppm):
1
2
2
2
), 2.41 (s, 3H,
-CH
3
2
2
1
3
2
2
1
3
6.26, 26.40, 28.16, 28.51, 36.13, 115.53, 124.01, 127.27, 129.49, 141.39, 168.22,
-
79.52, 191.03; HRMS (ESI) m/z calculated for C17
H
19
F
3
N
2
O
2
339.1321 [M-H] , 363.1296
+
-
+
[
M+Na] . Found 339.1326 [M-H] , 363.1291 [M+Na] ; Anal. Calcd for C17
H
19
F
3
N
2
O
2
(%):
C, 59.99; H, 5.63; N, 8.23. Found: C, 59.75; H, 5.76; N, 8.45.
.1.67. 1,1,1-Trifluoro-8-(3-(4-methoxyphenyl)-1,2,4-oxadiazol-5-yl)octan-2-one (10c)
5

1
White powder, yield: 63%, mp: 39-41 °C. H NMR (CDCl
.36-1.45 (m, 4H, -CH ), 1.66-1.75 (m, 2H, -CH ), 1.83-1.93 (m, 2H, -CH
Hz, 2H, -CH CO), 2.93 (t, J = 7.5 Hz, 2H, -CH ), 3.86 (s, 3H, -OCH ), 6.95-7.01 (m, 2H,
ArH), 7.98-8.03 (m, 2H, ArH); C-NMR (CDCl , 75 Hz) δ (ppm): 22.09, 26.28, 26.42,
8.18, 28.53, 36.15, 55.32, 114.20, 119.33, 128.95, 161.85, 167.94, 179.40; HRMS (ESI)
3
, 300 MHz) δ (ppm):
1
2
2
2
), 2.73 (t, J = 7.2
2
2
3
1
3
3
2
-
355.1270 [M-H] , 379.1245 [M+Na] . Found 355.1275
+
m/z calculated for C17
H
19
F
3
N
2
O
3
-
+
[
M-H] , 379.1240 [M+Na] ; Anal. Calcd for C17
H
19
F
3
N
2
O
3
(%): C, 57.30; H, 5.37; N, 7.86.
Found: C, 57.43; H, 5.25; N, 8.01.
5
.1.68. 1,1,1-Trifluoro-8-(3-(4-(trifluoromethyl)phenyl)-1,2,4-oxadiazol-5-yl)octan-2-
one (10d)
1
White powder, yield: 43%, mp: 25-26 °C. H NMR (CDCl
.36-1.45 (m, 4H, -CH ), 1.66-1.75 (m, 2H, -CH ), 1.83-1.93 (m, 2H, -CH
Hz, 2H, -CH CO), 2.98 (t, J = 7.5 Hz, 2H, -CH ), 7.74 (d, J = 8.2 Hz, 2H, ArH), 8.20 (d, J =
3
, 300 MHz) δ (ppm):
1
2
2
2
), 2.73 (t, J = 7.2
2
2
1
.2 Hz, 2H, ArH); C-NMR (CDCl
3
8
3
3
, 75 Hz) δ (ppm): 22.13, 26.26, 26.46, 28.21, 28.56,
6.17, 121.98, 125.59, 125.76, 125.81, 125.86, 125.91, 127.77, 167.33, 180.27; HRMS
-
393.1038 [M-H] , 395.1194 [M+H] . Found
+
(ESI) m/z calculated for C17
H
16
F
6
N
2
O
2
-
+
3
93.1043 [M-H] , 395.1189 [M+H] ; Anal. Calcd for C17 (%): C, 51.78; H, 4.09;
16 6 2 2
H F N O
N, 7.10. Found: C, 51.53; H, 4.36; N, 7.28.
5
.1.69. 1,1,1-Trifluoro-8-(3-(4-fluorophenyl)-1,2,4-oxadiazol-5-yl)octan-2-one (10e)
1
Colorless oil, yield: 51%. H NMR (CDCl
3
, 300 MHz) δ (ppm): 1.35-1.47 (m, 4H,
), 2.72 (t, J = 7.2 Hz, 2H, -CH CO),
), 7.13-7.18 (m, 2H, ArH), 8.05-8.10 (m, 2H, ArH); C-NMR
-
CH
2
), 1.65-1.76 (m, 2H, -CH
2
), 1.82-1.91 (m, 2H, -CH
2
2
1
3
2
.94 (t, J = 7.5 Hz, 2H, -CH
2
(CDCl
3
, 75 Hz) δ (ppm): 22.15, 26.30, 26.47, 28.24, 28.58, 36.22, 113.65, 115.89, 116.18,
1
C
23.21, 129.51, 129.62, 162.90, 166.23, 167.52, 179.86; HRMS (ESI) m/z calculated for
-
+
-
16
H
16
F
4
N
2
O
2
343.1070 [M-H] , 345.1226 [M+H] . Found 343.1073 [M-H] , 345.1228
+
[
M+H] ; Anal. Calcd for C16
H
16
F
4
N
2
O
2
(%): C, 55.81; H, 4.68; N, 8.14. Found: C, 55.63; H,
4
.37; N, 8.29.
5
.1.70. 8-(3-(4-Chlorophenyl)-1,2,4-oxadiazol-5-yl)-1,1,1-trifluorooctan-2-one (10f)
1
Colorless oil, yield: 65%. H NMR (CDCl
3
, 300 MHz) δ (ppm): 1.36-1.45 (m, 4H,

-
CH
.95 (t, J = 7.5 Hz, 2H, -CH
CDCl , 75 Hz) δ (ppm): 22.12, 26.26, 26.43, 28.21, 28.55, 36.17, 125.42, 128.70, 129.15,
37.26, 139.31, 167.51, 179.94; HRMS (ESI) m/z calculated for C16 359.0774
M-H] , 361.0931 [M+H] . Found 359.0780 [M-H] , 361.0925 [M+H] ; Anal. Calcd for
2
), 1.66-1.75 (m, 2H, -CH
2 2 2
), 1.83-1.93 (m, 2H, -CH ), 2.73 (t, J = 7.2 Hz, 2H, -CH CO),
1
3
2
2
), 7.43-7.47 (m, 2H, ArH), 7.98-8.05 (m, 2H, ArH); C-NMR
(
3
1
3 2 2
H16ClF N O
-
+
-
+
[
16 3 2 2
C H16ClF N O (%): C, 53.27; H, 4.47; N, 7.77. Found: C, 53.52; H, 4.33; N, 7.95.
5
.1.71. 8-(3-(2-chlorophenyl)-1,2,4-oxadiazol-5-yl)-1,1,1-trifluorooctan-2-one (10g)
1
Colorless oil, yield: 55%. H NMR (CDCl
3
, 500 MHz) δ (ppm): 1.39-1.45 (m, 4H,
-CH
2
), 1.64-1.67 (m, 2H, -CH
2
), 1.86-1.89 (m, 2H, -CH
2
), 2.30-2.33 (m, 2H, -CH
2
CO), 2.93
(t, J = 7.5 Hz, 2H, -CH
2
), 7.37-7.43 (m, 2H, ArH), 7.53 (dd, J
1
= 8.0 Hz, J = 1.2 Hz, 1H,
2
1
3
ArH), 7.91 (dd, J
1
2 3
= 7.6 Hz, J = 1.8 Hz, 1H, ArH); C-NMR (CDCl , 125 Hz) δ (ppm): 21.23,
2
1
3
C
2.53, 26.76, 26.35, 28.19, 28.83, 36.16, 115.65, 123.87, 127.81, 129.59, 141.36,
-
359.0774 [M-H] ,
68.29, 180.29; HRMS (ESI) m/z calculated for C16
H16ClF
3
N
2
O
2
+
61.0931 [M+H] . Found 359.0780 [M-H] , 361.0925 [M+H] ; Anal. Calcd for
-
+
16 3 2 2
H16ClF N O
(%): C, 53.27; H, 4.47; N, 7.77. Found: C, 53.45; H, 4.53; N, 7.82.
5
.1.72. 1,1,1-Trifluoro-8-(3-(4-nitrophenyl)-1,2,4-oxadiazol-5-yl)octan-2-one (10h)
1
Light yellow oil, yield: 58%. H NMR (CDCl
3
, 500 MHz) δ (ppm): 1.39-1.49 (m, 4H,
), 2.32 (t, J = 7.4 Hz, 2H, -CH CO),
), 7.27 (d, J = 8.6 Hz, 2H, ArH), 8.33 (d, J = 8.6 Hz, 2H, ArH);
, 125 Hz) δ (ppm): 21.89, 22.56, 26.73, 26.98, 28.33, 28.79, 36.38,
15.76, 124.35, 128.30, 132.06, 149.07, 168.15, 179.86; HRMS (ESI) m/z calculated for
-
CH
2
), 1.63-1.68 (m, 2H, -CH
2
), 1.88-1.92 (m, 2H, -CH
2
2
2
.97 (t, J = 7.6 Hz, 2H, -CH
2
1
3
C-NMR (CDCl
3
1
C
-
+
-
16
H
16
F
3
N
3
O
4
370.1015 [M-H] , 372.1171 [M+H] . Found 370.1020 [M-H] , 372.1166
+
[
M+H] ; Anal. Calcd for C16
H
16
F
3
N
3
O
4
(%): C, 51.75; H, 4.34; N, 11.32. Found: C, 51.67; H,
4
.59; N, 11.18.
5
.1.73. 1,1,1-Trifluoro-8-(3-(3-nitrophenyl)-1,2,4-oxadiazol-5-yl)octan-2-one (10i)
1
Light yellow oil, yield: 53%. H NMR (CDCl
3
, 300 MHz) δ (ppm): 1.38-1.53 (m, 4H,
), 2.74 (t, J = 7.2 Hz, 2H, -CH CO),
), 7.67-7.71 (m, 1H, ArH), 8.34-8.43 (m, 2H, ArH), 8.92-8.95
, 75 Hz) δ (ppm): 22.11, 26.22, 26.45, 28.20, 28.55, 36.17,
-
CH
2
), 1.68-1.77 (m, 2H, -CH
2
), 1.87-1.96 (m, 2H, -CH
2
2
2
.99 (t, J = 7.5 Hz, 2H, -CH
2
13
(
m, 1H, ArH); C-NMR (CDCl
3

1
15.55, 125.54, 128.77, 129.99, 132.95, 148.67, 166.73, 180.59, 191.58; HRMS (ESI)
-
370.1015 [M-H] , 372.1171 [M+H] . Found 370.1020
+
m/z calculated for C16
H
16
F
3
N
3
O
4
-
+
[
M-H] , 372.1166 [M+H] ; Anal. Calcd for C16
H
16
F
N
3 3
O
4
(%): C, 51.75; H, 4.34; N, 11.32.
Found: C, 51.58; H, 4.51; N, 11.29.
5
.1.74. 1,1,1-Trifluoro-8-(3-(thiophen-2-yl)-1,2,4-oxadiazol-5-yl)octan-2-one (10j)
1
Light yellow oil, yield: 40%. H NMR (DMSO-d6, 300 MHz) δ (ppm): 1.41-1.47 (m,
4
H, -CH
2
), 1.64-1.68 (m, 2H, -CH
2
2
), 1.89-1.92 (m, 2H, -CH ), 2.32 (t, J = 7.4 Hz, 2H,
-CH
2
CO), 2.96 (t, J = 7.5 Hz, 2H, -CH
2
), 7.24-7.27 (m, 1H, ArH), 7.77-7.79 (m, 1H, ArH),
1
3
.85-7.87 (m, 1H, ArH); C-NMR (DMSO-d6, 75 Hz) δ (ppm): 21.31, 22.38, 26.55, 26.71,
7
2
1
8.15, 28.83, 36.29, 115.95, 121.35, 125.89, 127.75, 131.08, 132.92, 147.89, 168.51,
+
S 371.0443 [M+K] . Found 371.0449
79.76; HRMS (ESI) m/z calculated for C14
H
15
F
3
N O
2 2
+
[
M+K] ; Anal. Calcd for C14
H
15
F
3
N
2
O
2
S (%): C, 50.60; H, 4.55; N, 8.43. Found: C, 50.79; H,
4
5
5
.69; N, 8.66.
.2. Biological evaluation
.2.1. In vitro antiproliferative activity against 3 human cancer cell lines
The entire target compounds were evaluated against human acute monocytic
myeloid leukemia cell line (U937), human lung cancer cell lines (A549 and NCI-H661) as
4
1-43
previous described.
The cell viability was determined employing the MTT-based
assay using WST-8 reagent, a reagent solution prepared as an aqueous solution
containing 5 mM WST-8 (Sigma), 0.2 mM 1-methoxyphenazinium salt (Sigma) and 150
4
4
mM NaCl. Briefly, the tumor cell lines in RPMI1640 medium with 10% fetal bovine
serum were plated in 96-well microtiter plates (5.0×103 cells/well), and allowed to
2
adhere at 37 °C with 5% CO for 4 h. The test compound was then added, and the cells
were incubated at 37 °C with 5% CO
was removed, and WST-8 was added to each well for another incubation of 1.5 h at
7 °C. Absorbance was finally measured with a plate reader at 650 nm. The results
2
for 72 h later. Subsequently, cell growth medium
3
were expressed as the percentage of absorbance of treated wells versus that of the
vehicle control. IC50, the drug concentration causing 50% growth inhibition, was
calculated via sigmoid curve fitting using GraphPad Prism 5.0.