3-Aryl-4-acyloxyethoxyfuran-2(5H)-ones as inhibitors of tyrosyl-tRNA synthetase: Synthesis, molecular docking and antibacterial evaluation

Article abstract of DOI:10.1016/j.bmc.2013.06.066

Thirty-eight 3-aryl-4-acyloxyethoxyfuran-2(5H)-ones were designed, prepared and tested for antibacterial activities. Some of them showed significant antibacterial activity against Gram-positive organism, Gram-negative organism and fungus. Out of these compounds, 4-(2-(3-chlorophenylformyloxy)ethoxy)-3-(4- chlorophenyl)furan-2(5H)-one (d40) showed the widest spectrum of activity with MIC₅₀ of 2.0 μg/mL against Staphylococcus aureus, 4.3 μg/mL against Escherichia coli, 1.5 μg/mL against Pseudomonas aeruginosa and 1.2 μg/mL against Candida albicans. Our data disclosed that MIC₅₀ values against whole cell bacteria are positive correlation with MIC ₅₀ values against tyrosyl-tRNA synthetase. Meanwhile, molecular docking of d40 into S. aureus tyrosyl-tRNA synthetase active site was also performed, and the inhibitor tightly fitting the active site might be an important reason why it has high antimicrobial activity.

Full text of DOI:10.1016/j.bmc.2013.06.066

Bioorganic & Medicinal Chemistry 21 (2013) 4914–4922
Contents lists available at SciVerse ScienceDirect
Bioorganic & Medicinal Chemistry
journal homepage: www.elsevier.com/locate/bmc
3-Aryl-4-acyloxyethoxyfuran-2(5H)-ones as inhibitors
of tyrosyl-tRNA synthetase: Synthesis, molecular docking
and antibacterial evaluation
Xu-Dong Wang a, Rui-Cheng Deng a, Jing-Jun Dong b, Zhi-Yun Peng a, Xiao-Ming Gao a, Shu-Ting Li a,
Wan-Qiang Lin a, Chun-Lei Lu a, Zhu-Ping Xiao a, , Hai-Liang Zhu a,b,
⇑
⇑
a College of Chemistry and Chemical Engineering, Key Laboratory of Hunan Forest Products and Chemical Industry Engineering, Jishou University, Jishou 416000, PR China
b State Key Laboratory of Pharmaceutical Biotechnology, Nanjing University, Nanjing 210093, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Thirty-eight 3-aryl-4-acyloxyethoxyfuran-2(5H)-ones were designed, prepared and tested for antibacte-
rial activities. Some of them showed significant antibacterial activity against Gram-positive organism,
Gram-negative organism and fungus. Out of these compounds, 4-(2-(3-chlorophenylformyloxy)eth-
oxy)-3-(4-chlorophenyl)furan-2(5H)-one (d40) showed the widest spectrum of activity with MIC50 of
Received 18 April 2013
Revised 26 June 2013
Accepted 28 June 2013
Available online 11 July 2013
2.0
l
g/mL against Staphylococcus aureus, 4.3
lg/mL against Escherichia coli, 1.5 lg/mL against Pseudomo-
nas aeruginosa and 1.2
l
g/mL against Candida albicans. Our data disclosed that MIC50 values against whole
Keywords:
cell bacteria are positive correlation with MIC50 values against tyrosyl-tRNA synthetase. Meanwhile,
molecular docking of d40 into S. aureus tyrosyl-tRNA synthetase active site was also performed, and
the inhibitor tightly fitting the active site might be an important reason why it has high antimicrobial
activity.
3-Aryl-4-acyloxyethoxyfuran-2(5H)-ones
Antibacterial
Molecular docking
Tyrosyl-tRNA synthetase
Structure–activity relationship
Ó 2013 Elsevier Ltd. All rights reserved.
1. Introduction
ven by Mupirocin (an inhibitor of isoleucyl-tRNA synthetase) and
AN-2690 (an inhibitor of leucyl-tRNA synthetase).13,14
The widely use of antimicrobial drugs as human and veterinary
medicine for the prevention and treatment of infectious diseases
has brought significant health benefits.1,2 However, the bacteria
which resist to conventional antibiotics have enabled major kill-
ers.3,4 For example, methicillin-resistant Staphylococcus aureus
leads to nearly 100,000 infections and 20,000 deaths in the United
States annually,5 and drug-resistant Mycobacterium tuberculosis
significantly undermine the major advances achieved in treat-
ment.6,7 With the resistance increasing, antibacterial research for
finding new antibacterial agents becomes more and more emer-
gency.8–10
In our group, some 3-aryl-4-aminofuran-2(5H)-ones were re-
ported as potent inhibitors of tyrosyl-tRNA synthetase (TyrRS)15,16
and several of them exhibit excellent growth inhibition activity
against bacteria. However, all of them show no activity against fun-
gi. TEA-0777, a derivative of clarithromycin (Scheme 1) by esterifi-
cation at C-3, has the potential as the next generation of macrolide
antibiotics, which shows not only good activity against erythromy-
cin-susceptible Gram-positive pathogens but also inducibly mac-
rolides–lincosamides–streptogramin B (MLSB)-resistant S. aureus
and efflux-resistant Streptococcus pneumoniae.17–19 Perhaps
The antibacterial mechanism of actions mainly includes altera-
tions of membrane permeability and interruptions of protein or
nucleic acid synthesis. Aminoacyl-tRNA synthetase (aaRS) is an en-
zyme which ligates specific amino acid to its cognate tRNA mole-
cule(s) and plays an important role in the production of
proteins.11,12 Therefore, more and more researchers are focusing
on the development of aaRS inhibitors as new antibacterial agents.
AaRSs as the leading targets of antimicrobial agents have been pro-
NMe2
O
NMe2
O
HO
OMe
HO
OMe
O
O
9
7
9
7
HO
HO
HO
HO
O
O
11
5
11
5
3
3
13
13
O
O
O
1
O
1
O
O
O
NO2
O
OH
⇑
OMe
Corresponding authors. Tel./fax: +86 743 8563911 (Z.-P.X.); tel.: +86 25
83592572; fax: +86 25 83592672 (H.-L.Z.).
E-mail addresses: xiaozhuping2005@163.com (Z.-P. Xiao), zhuhl@nju.edu.cn
(H.-L. Zhu).
TEA-0777
Clarithromycin
Scheme 1. Structure of clarithromycin and TEA-0777.
0968-0896/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.bmc.2013.06.066

X.-D. Wang et al. / Bioorg. Med. Chem. 21 (2013) 4914–4922
4915
because of introducing ester group, TEA-0777 becomes a potent
agent with a broad spectrum. Based on this finding, we therefore
introduced ester group to furan-2(5H)-ones, trying to endow them
with a broader spectrum. Thirty-eight esters of furan-2(5H)-one
were synthesized and evaluated for antimicrobial activity. The re-
sults displayed that some of the compounds show good antibacte-
rial and antifungal activity.
(30 mL) was added and the solution was extracted twice with ethyl
ether. The aqueous phase was cooled to 0 °C and then acidified
with concentrated hydrochloric acid to give a solid precipitate. Fil-
tration and washing with water furnished compound (b1 or b2)
(Scheme 2), which was used without further purification.
2.1.3. General procedure for preparation of compounds c1–c2
Compound (b1 or b2) (5 mmol) was dissolved in 35 mL of dry
acetone, followed by addition of 1,2-dibromoethane (4.3 mL,
50 mmol) and triethylamine (2.2 mL, 15 mmol). The resulted mix-
ture was refluxed for 3–5 h. After the solvent was removed, the res-
idue was partitioned between AcOEt and water. The organic layer
was then dried over MgSO4 and concentrated under reduced pres-
sure. Flash chromatography (AcOEt/petroleum ether, from 3:2 to
2:3) furnished compound (c1 or c2) (Scheme 2) in good yield.
2. Materials and methods
2.1. Chemistry
All chemicals (reagent grade) used were purchased from Aldrich
(U.S.A.) and Sinopharm Chemical Reagent Co., Ltd (China). Separa-
tion of the compounds by column chromatography was carried out
with silica gel 60 (200–300 mesh ASTM, E. Merck). The quantity of
silica gel used was 30–70 times the weight charged on the column.
Then, the eluates were monitored using TLC. Melting points
(uncorrected) were determined on a XT4 MP apparatus (Taike
Corp., Beijing, China). ESI mass spectra were obtained on a Mariner
System 5304 mass spectrometer, and 1H NMR spectra were re-
corded on Bruker AV-300 spectrometer at 25 °C with TMS and sol-
vent signals allotted as internal standards. Chemical shifts were
reported in ppm (d). Elemental analyses were performed on a
CHN–O-Rapid instrument and were within 0.4% of the theoretical
values.
2.1.4. General procedure for preparation of 3-aryl-4-
acyloxyethoxyfuran-2(5H)-ones (d3–d40)
Appropriately substituted sodium carboxylate (1.0 mmol) was
added in a solution of compound (c1 or c2) (0.5 mmol) in dry
DMSO (15 mL). The mixture was then stirred for 8–12 h at room
temperature (monitored by TLC). After 30 mL of water was added,
the precipitate was collected, which was purified by column chro-
matography on silica gel, eluting with AcOEt/petroleum ether.
2.1.5. 4-(2-Butyryloxyethoxy)-3-phenylfuran-2(5H)-one (d3)
Yellow oily liquid, 68.0%; 1H NMR (CDCl3): 0.92–0.97(m, 3H,
CH3); 1.60–1.71 (m, 2H, CH2); 2.32 (t, J = 7.3 Hz, 2H, CH2); 4.29 (t,
J = 4.3 Hz, 2H, CH2); 4.39 (t, J = 4.0 Hz, 2H, CH2); 4.85 (s, 2H, CH2);
7.26–7.33 (m, 2H, ArH); 7.39 (t, J = 7.4 Hz, 1H, ArH); 7.81 (d,
J = 7.1 Hz, 2H, ArH); EIMS m/z 290 (M+). Anal. Calcd for C16H18O5:
C, 66.19; H, 6.25; O, 27.56; Found: C, 66.28; H, 6.16; O, 27.56.
2.1.1. General procedure for preparation of compounds a1–a2
An appropriately substituted phenylacetic acid (40 mmol) was
dissolved in 0.1 M NaOH with pH in the range of 9.0–10.0. Then,
the solvent was removed under reduced pressure to give the corre-
sponding sodium phenylacetate. To a solution of the resulted so-
dium phenylacetate (40 mmol) in DMSO (45 mL) was added
1.1 equiv of ethyl bromoacetate, which was stirred at 25 °C for
3–4 h. The mixture was then poured into ice-water (50 mL), and
extracted twice with 200 mL of AcOEt. The organic layer was dried
over MgSO4 followed by removal of the solvent under reduced
pressure. The residue was then purified by column chromatogra-
phy on silica gel to give a1–a2 (Scheme 2) in yields of 90–95%.
2.1.6. 4-(2-Hexanoyloxyethoxy)-3-phenylfuran-2(5H)-one (d4)
Red-brown oily liquid, 71.2%; 1H NMR (CDCl3): 0.88 (t,
J = 6.9 Hz, 3H, CH3); 1.27–1.31 (m, 4H, CH2); 1.57–1.65 (m, 2H,
CH2); 2.34 (m, 2H, CH2); 4.29–4.32 (m, 2H, CH2); 4.37–4.41 (m,
2H, CH2); 4.85 (s, 2H, CH2); 7.26–7.33 (m, 1H, ArH); 7.37–7.42
(m, 2H, ArH); 7.82 (dd, J = 7.1 Hz, J = 8.6 Hz, 2H, ArH); EIMS m/z
318 (M+). Anal. Calcd for C18H22O5: C, 67.91; H, 6.97; O, 25.13;
Found: C, 67.80; H, 6.95; O, 25.25.
2.1.2. General procedure for preparation of compounds b1–b2
A dropwise solution of compound (a1 or a2) (10 mmol) in dry
THF (10 mL) was added to a suspension of NaH (24 mmol) in dry
THF (20 mL) in an ice cold bath and the stirring was maintained
at room temperature for several hours (monitored by TLC). Water
2.1.7. 4-(2-Octanoyloxyethoxy)-3-phenylfuran-2(5H)-one (d5)
Pale yellow oily liquid, 67.5%; 1H NMR (CDCl3): 0.85–0.91 (m,
3H, CH3); 1.15–1.28 (m, 10H, CH2); 1.65–1.70 (m, 2H, CH2); 2.34
O
OEt
EtO
Br
O
COONa
O
CO2H NaOH
O
R1
R1
DMSO
R1
a1-a2
O
a1 R1=H
a2 R1=Cl
O
O
O
O
O
Br
sodium carboxylate
Br
Br
NaH
OH
O
O
O
O
R2
R1
R1
R1
c1-c2
d3-d40
(See Table1 for details)
b1-b2
Scheme 2. Synthetic route of 3-aryl-4-acyloxyethoxyfuran-2(5H)-ones.

4916
X.-D. Wang et al. / Bioorg. Med. Chem. 21 (2013) 4914–4922
(t, J = 7.5 Hz, 2H, CH2); 4.39 (t, J = 4.8 Hz, 2H, CH2); 4.85 (s, 2H,
CH2); 7.36–7.41 (m, 3H, ArH), 7.81 (d, J = 7.1 Hz, 2H, ArH); EIMS
m/z 346 (M+). Anal. Calcd for C20H26O5: C, 69.34; H, 7.56; O,
23.09; Found: C, 69.21; H, 7.66; O, 23.13.
ArH); 7.93–7.96 (m, 1H, ArH); EIMS m/z 369 (M+). Anal. Calcd for
C19H15NO7: C, 61.79; H, 4.09; N, 3.79; O, 30.32; Found: C, 61.81;
H, 4.14; N, 3.75; O, 30.30.
2.1.15. 4-(2-(2-hydroxyphenylformyloxyl)ethoxy)-3-
phenylfuran-2(5H)-one (d13)
2.1.8. 4-(2-Phenylacetyloxylethoxy)-3-phenylfuran-2(5H)-one
(d6)
White powder, 37.8%, mp 132–134 °C; 1H NMR (CDCl3): 4.43 (s,
2H, CH2); 4.66 (d, J = 4.2 Hz, 2H, CH2); 4.87 (s, 2H, CH2); 6.90 (t,
J = 7.6 Hz, 1H, ArH); 7.01 (d, J = 8.4 Hz, 1H, ArH); 7.30–7.40 (m,
3H, ArH); 7.50 (t, J = 7.8 Hz, 1H, ArH); 7.81 (t, J = 6.7 Hz, 3H, ArH);
10.50 (s, 1H, OH); EIMS m/z 340 (M+). Anal. Calcd for C19H16O6:
C, 67.05; H, 4.74; O, 28.21; Found: C, 67.17; H, 4.68; O, 28.15.
White powder, 64.3%, mp 134–136 °C; 1H NMR (CDCl3): 3.66 (s,
2H, CH2); 4.24 (t, J = 4.4 Hz, 2H, CH2); 4.41 (t, J = 4.5 Hz, 2H, CH2);
4.66 (s, 2H, CH2); 7.23 (m, 2H, ArH); 7.26–7.38 (m, 4H, ArH);
7.42 (t, J = 7.0 Hz, 2H, ArH); 7.77 (d, J = 7.1 Hz, 2H, ArH); EIMS m/
z 338 (M+). Anal. Calcd for C20H18O5: C, 70.99; H, 5.36; O, 23.64;
Found: C, 70.87; H, 5.53; O, 23.60.
2.1.16. 4-(2-(2-Methoxyphenylformyloxy)ethoxy)-3-
phenylfuran-2(5H)-one (d14)
2.1.9. 4-(2-(3-Pyridylformyloxy)ethoxy)-3-phenylfuran-2(5H)-
one (d7)
White powder, 63.8%, mp 90–91 °C; 1H NMR (CDCl3): 3.85 (s,
3H, CH3); 4.43 (t, J = 5.3 Hz, 2H, CH2); 4.61 (t, J = 5.3 Hz, 2H, CH2);
4.90 (s, 2H, CH2); 6.96–7.01 (m, 2H, ArH); 7.28–7.32 (m, 1H,
ArH); 7.35–7.41 (m, 2H, ArH); 7.47–7.53 (m, 1H, ArH); 7.77 (d,
J = 7.9 Hz, 1H, ArH); 7.86 (d, J = 8.6 Hz, 2H, ArH); EIMS m/z 354
(M+). Anal. Calcd for C20H18O6: C, 67.79; H, 5.12; O, 27.09; Found:
C, 67.81; H, 5.15; O, 27.04.
Orange powder, 52.7%, 111–113 °C; 1H NMR (CDCl3): 4.63 (t,
J = 4.6 Hz, 2H, CH2); 4.69 (t, J = 4.5 Hz, 2H, CH2); 4.87 (s, 2H, CH2);
7.30–7.39 (m, 3H, ArH); 7.46 (t, J = 7.9 Hz, 1H, ArH); 7.78 (d,
J = 7.2 Hz, 2H, ArH); 8.32 (d, J = 7.9 Hz, 1H, ArH); 8.82 (d,
J = 3.5 Hz, 1H, ArH); 9.25 (s, 1H, ArH); EIMS m/z 325 (M+). Anal.
Calcd for C18H15NO5: C, 66.46; H, 4.65; N, 4.31; O, 24.59; Found:
C, 66.38; H, 4.69; N, 4.30; O, 24.63.
2.1.17. 4-(2-(3-Nitrophenylformyloxy)ethoxy)-3-phenylfuran-
2(5H)-one (d15)
2.1.10. 4-(2-(Naphthalen-2-ylformyloxyl)ethoxy)-3-
phenylfuran-2(5H)-one (d8)
Colorless crystal, 61.2%, mp 151–152 °C; 1H NMR (CDCl3): 4.55–
4.60 (m, 4H, CH2); 5.17 (s, 2H, CH2); 6.85 (d, J = 8.8 Hz, 2H, ArH);
7.24–7.34 (m, 3H, ArH); 7.84–7.87 (m, 4H, ArH); EIMS m/z 369
(M+). Anal. Calcd for C19H15NO7: C, 61.79; H, 4.09; N, 3.79; O,
30.32; Found: C, 61.88; H, 4.15; N, 3.61; O, 30.36.
Colorless crystal, 79.2%, mp 194–196 °C; 1H NMR (CDCl3): 4.49
(t, J = 4.5 Hz, 2H, CH2); 4.74 (t, J = 4.5 Hz, 2H, CH2); 4.89 (s, 2H,
CH2); 7.30–7.40 (m, 3H, ArH); 7.47–7.57 (m, 3H, ArH); 7.85–7.92
(m, 3H, ArH); 8.06 (d, J = 8.2 Hz, 1H, ArH); 8.16 (d, J = 7.1 Hz, 1H,
ArH); 8.84 (d, J = 9.5 Hz, 1H, ArH); EIMS m/z 374 (M+). Anal. Calcd
for C23H18O5: C, 73.79; H, 4.85; O, 21.37; Found: C, 73.81; H, 4.80;
O, 21.39.
2.1.18. 4-(2-(3-Methylphenylformyloxy)ethoxy)-3-phenylfuran-
2(5H)-one (d16)
White solid, 52.9%, mp 134–136 °C; 1H NMR (CDCl3): 2.40 (s,
3H, CH3); 4.43 (t, J = 4.6 Hz, 2H, CH2), 4.63 (t, J = 4.6 Hz, 2H, CH2),
4.88 (s, 2H, CH2), 7.29–7.39 (m, 5H, ArH), 7.82–7.84 (m, 4H,
ArH); EIMS m/z 338 (M+). Anal. Calcd for C20H18O5: C, 70.99; H,
5.36; O, 23.64; Found: C, 70.85; H, 5.41; O, 23.74.
2.1.11. 4-(2-(6-Hydroxynaphthalen-2-ylformyloxyl)ethoxy)-3-
phenylfuran-2(5H)-one (d9)
Gray white powder, 77.1%, mp 202–204 °C; 1H NMR (CDCl3):
4.70 (t, J = 4.7 Hz, 4H, CH2); 5.20 (s, 2H, CH2); 7.16–7.24 (m, 3H,
ArH); 7.30 (t, J = 7.4 Hz, 2H, ArH); 7.79 (d, J = 8.8 Hz, 1H, ArH);
7.87–7.95 (m, 4H, ArH); 8.51 (s, 1H, ArH); 10.22 (s, 1H, ArH); EIMS
m/z 390 (M+). Anal. Calcd for C23H18O6: C, 70.76; H, 4.65; O, 24.59;
Found: C, 70.85; H, 4.72; O, 24.43.
2.1.19. 4-(2-(3-Trifluoromethylphenylformyoxyl)ethoxy)-3-
phenylfuran-2(5H)-one (d17)
White powder, 71.2%, mp 110–112 °C; 1H NMR (CDCl3): 4.44
(t, J = 4.4 Hz, 2H, CH2); 4.67 (t, J = 4.4 Hz, 2H, CH2); 4.87 (s, 2H,
CH2); 7.30–7.39 (m, 3H, ArH); 7.61 (t, J = 7.8 Hz, 1H, ArH);
7.79–7.87 (m, 3H, ArH); 8.21 (d, J = 7.9 Hz, 1H, ArH); 8.30 (s,
1H, ArH); EIMS m/z 392 (M+). Anal. Calcd for C20H15F3O5: C,
61.23; H, 3.85; F, 14.53; O, 20.39; Found: C, 61.32; H, 3.80; F,
14.54; O, 20.34.
2.1.12. 4-(2-(2-Methylphenylformyloxyl)ethoxy)-3-
phenylfuran-2(5H)-one (d10)
White powder, 68.1%, mp 121–123 °C; 1H NMR (CDCl3): 2.58 (s,
3H, CH3); 4.43 (t, J = 4.6 Hz, 2H, CH2); 4.63 (t, J = 4.6 Hz, 2H, CH2);
4.87 (s, 2H, CH2); 7.21–7.24 (m, 1H, ArH); 7.28–7.43 (m, 5H,
ArH); 7.82 (d, J = 7.1 Hz, 2H, ArH); 7.89 (d, J = 7.5 Hz, 1H, ArH);
EIMS m/z 338 (M+). Anal. Calcd for C20H18O5: C, 70.99; H, 5.36; O,
23.64; Found: C, 70.84; H, 5.31; O, 23.85.
2.1.20. 4-(2-(4-Nitrophenylformyloxyl)ethoxy)-3-phenylfuran-
2(5H)-one (d18)
Chartreuse powder, 56.0%, mp 147–149 °C; 1H NMR (DMSO-d6):
4.65 (d, J = 4.4 Hz, 2H, CH2); 4.76 (t, J = 4.0 Hz, 2H, CH2); 5.18 (s, 2H,
CH2); 7.25–7.30 (m, 3H, ArH); 7.86 (t, J = 4.3 Hz, 2H, ArH); 8.23 (d,
J = 8.8 Hz, 2H, ArH); 8.38 (d, J = 8.9 Hz, 2H, ArH); EIMS m/z 369
(M+). Anal. Calcd for C19H15NO7: C, 61.79; H, 4.09; N, 3.79; O,
30.32; Found: C, 61.83; H, 4.15; N, 3.56; O, 30.46.
2.1.13. 4-(2-(2-Chlorophenylformyloxyl)ethoxy)-3-
phenylfuran-2(5H)-one (d11)
White powder, 86.5%, mp 117–119 °C; 1H NMR (CDCl3): 4.43 (t,
J = 4.4 Hz, 2H, CH2); 4.65 (t, J = 4.2 Hz, 2H, CH2); 4.87 (s, 2H, CH2);
7.30–7.41 (m, 4H, ArH); 7.45–7.47 (m, 2H, ArH); 7.81 (t,
J = 7.4 Hz, 3H, ArH); EIMS m/z 358 (M+). Anal. Calcd for C19H15ClO5:
C, 63.61; H, 4.21; Cl, 9.88; O, 22.30; Found: C, 63.64; H, 4.27; Cl,
9.83; O, 22.26.
2.1.21. 4-(2-(4-Methylphenylformyloxyl)ethoxy)-3-
phenylfuran-2(5H)-one (d19)
White powder, 71.3%, mp 122–124 °C; 1H NMR (CDCl3): 2.42 (s,
3H, CH3); 4.42 (t, J = 4.8 Hz, 2H, CH2); 4.63 (t, J = 4.5 Hz, 2H, CH2);
4.87 (s, 2H, CH2); 7.24–7.32 (m, 3H, ArH); 7.37 (t, J = 7.3 Hz, 2H,
ArH); 7.83 (d, J = 8.3 Hz, 2H, ArH); 7.91 (d, J = 8.2 Hz, 2H, ArH);
EIMS m/z 338 (M+). Anal. Calcd for C20H18O5: C, 70.99; H, 5.36; O,
23.64; Found: C, 70.82; H, 5.38; O, 23.80.
2.1.14. 4-(2-(2-Nitrophenylformyloxyl)ethoxy)-3-phenylfuran-
2(5H)-one (d12)
White powder, 71.9%, mp 84–85 °C; 1H NMR (CDCl3): 4.36 (t,
J = 4.5, 2H, CH2); 4.65 (t, J = 4.4, 2H, CH2); 4.87 (s, 2H, CH2); 7.26–
7.41 (m, 3H, ArH); 7.64–7.76 (m, 3H, ArH); 7.77 (d, J = 7.0 Hz, 2H,

X.-D. Wang et al. / Bioorg. Med. Chem. 21 (2013) 4914–4922
4917
2.1.22. 4-(2-(4-fluorophenylformyloxyl)ethoxy)-3-phenylfuran-
2(5H)-one (d20)
9.86 (s, 1H, OH); EIMS m/z 356 (M+). Anal. Calcd for C19H16O7: C,
64.04; H, 4.53; O, 31.43; Found: C, 64.21; H, 4.48; O, 31.31.
White powder, 36.8%, mp 104–107 °C; 1H NMR (CDCl3): 4.42
(m, 2H, CH2); 4.65 (m, 2H, CH2); 4.87 (s, 2H, CH2); 7.30–7.48 (m,
5H, ArH); 7.70 (d, J = 8.8 Hz, 1H, ArH); 7.80 (d, J = 7.0 Hz, 3H,
ArH); EIMS m/z 342 (M+). Anal. Calcd for C19H15FO5: C, 66.66; H,
4.42; F, 5.55; O, 23.37; Found: C, 66.61; H, 4.42; F, 5.54; O, 23.43.
2.1.30. 4-(2-(3,5-Dihydroxyphenylformyloxyl)ethoxy)-3-
phenylfuran-2(5H)-one (d28)
White powder, 60.8%, mp 182–185 °C; 1H NMR (DMSO-d6): 4.60
(d, J = 5.3 Hz, 4H, CH2); 5.17 (s, 2H, CH2); 6.43–6.52 (m, 1H, ArH);
6.83–6.92 (m, 2H, ArH); 7.21–7.64 (m, 3H, ArH); 7.85 (d,
J = 7.1 Hz, 2H, ArH); 9.66 (s, 2H, OH); EIMS m/z 370 (M+). Anal.
Calcd for C19H16O7: C, 64.04; H, 4.53; O, 31.43; Found: C, 64.14;
H, 4.58; O, 31.48.
2.1.23. 4-(2-(4-Chlorophenylformyloxyl)ethoxy)-3-
phenylfuran-2(5H)-one (d21)
White powder, 76.1%, mp 155–157 °C; 1H NMR (CDCl3): 4.42 (d,
J = 4.4 Hz, 2H, CH2); 4.64 (s, 2H, CH2); 4.87 (s, 2H, CH2); 7.30–7.39
(m, 3H, ArH); 7.43 (d, J = 8.4 Hz, 2H, ArH); 7.81 (d, J = 7.3 Hz, 2H,
ArH); 7.95 (d, J = 8.4 Hz, 2H, ArH); EIMS m/z 358 (M+). Anal. Calcd
for C19H15ClO5: C, 63.61; H, 4.21; Cl, 9.88; O, 22.30; Found: C,
63.65; H, 4.23; Cl, 9.86; O, 22.26.
2.1.31. 4-(2-(3-Chlorophenylacetyloxyl)ethoxy)-3-phenylfuran-
2(5H)-one (d29)
White powder, 57.9%, mp 141–142 °C; 1H NMR (CDCl3): 3.63 (s,
2H, CH2); 4.26 (t, J = 4.5 Hz, 2H, CH2); 4.42 (t, J = 4.5 Hz, 2H, CH2);
4.73 (s, 2H, CH2); 7.11 (d, J = 7.1 Hz, 1H, ArH); 7.21–7.26 (m, 2H,
ArH); 7.31–7.41 (m, 3H, ArH); 7.72 (dd, J = 7.1 Hz, J = 8.6 Hz, 2H,
ArH); EIMS m/z 372 (M+). Anal. Calcd for C20H17ClO5: C, 64.44; H,
4.60; Cl, 9.51; O, 21.46; Found: C, 64.30; H, 4.81; Cl, 9.56; O, 21.33.
2.1.24. 4-(2-(4-Hydroxyphenylformyloxyl)ethoxy)-3-
phenylfuran-2(5H)-one (d22)
White powder, 49.5%, mp 160–162 °C; 1H NMR (CDCl3): 4.42 (d,
J = 4.4 Hz, 2H, CH2); 4.59 (d, J = 4.4 Hz, 2H, CH2); 4.87 (s, 2H, CH2);
6.97 (d, J = 6.8 Hz, 2H, ArH); 7.32–7.41 (m, 3H, ArH); 7.44 (d,
J = 8.3 Hz, 2H, ArH); 7.86 (d, J = 7.4 Hz, 2H, ArH); 10.45 (s, 1H,
OH); EIMS m/z 340 (M+). Anal. Calcd for C19H16O6: C, 67.05; H,
4.74; O, 28.21; Found: C, 67.21; H, 4.83; O, 27.96.
2.1.32. 4-(2-(4-Fluorophenylacetyloxyl)ethoxy)-3-phenylfuran-
2(5H)-one (d30)
White powder, 75.2%, mp 119–120 °C; 1H NMR (CDCl3): 3.62 (s,
2H, CH2); 4.26 (t, J = 4.7 Hz, 2H, CH2); 4.41 (t, J = 4.5 Hz, 2H, CH2);
4.75 (s, 2H, CH2); 6.97 (t, J = 8.7 Hz, 2H, ArH); 7.19 (t, J = 8.6 Hz,
2H, ArH); 7.31–7.42 (m, 3H, ArH); 7.79 (d, J = 8.4 Hz, 2H, ArH);
EIMS m/z 356 (M+). Anal. Calcd for C20H17FO5: C, 67.41; H, 4.81;
F, 5.33; O, 22.45; Found: C, 67.35; H, 4.75; F, 5.43; O, 22.47.
2.1.25. 4-(2-(2,4-Dichlorophenylformyloxy)ethoxy)-3-
phenylfuran-2(5H)-one (d23)
White powder, 61.2%, mp 150–151 °C; 1H NMR (CDCl3): 4.41 (t,
J = 4.5 Hz, 2H, CH2); 4.65 (t, J = 4.5 Hz, 2H, CH2); 4.68 (s, 2H, CH2);
7.29–7.33 (m, 4H, ArH); 7.49 (s, 1H, ArH); 7.75–7.82 (m, 3H,
ArH); EIMS m/z 392 (M+). Anal. Calcd for C19H14Cl2O5: C, 58.03;
H, 3.59; Cl, 18.03; O, 20.34; Found: C, 58.13; H, 3.76; Cl, 18.10;
O, 20.01.
2.1.33. 4-(2-(4-Bromophenylacetyloxyl)ethoxy)-3-phenylfuran-
2(5H)-one (d31)
Yellow oily liquid, 65.6%, mp 101–103 °C; 1H NMR (CDCl3): 3.60
(s, 2H, CH2); 4.26 (t, J = 4.4 Hz, 2H, CH2); 4.41 (t, J = 4.5 Hz, 2H,
CH2); 4.76 (s, 2H, CH2); 7.09 (d, J = 8.4 Hz, 2H, ArH); 7.29–7.42
(m, 5H, ArH); 7.79 (dd, J = 7.0 Hz, J = 8.4 Hz, 2H, ArH); EIMS m/z
416 (M+). Anal. Calcd for C20H17BrO5: C, 57.57; H, 4.11; Br, 19.15;
O, 19.17; Found: C, 57.64; H, 4.18; Br, 19.16; O, 19.02.
2.1.26. 4-(2-(2,5-Dichlorophenylformyloxy)ethoxy)-3-
phenylfuran-2(5H)-one (d24)
White powder, 68.6%, mp 118–120 °C; 1H NMR (CDCl3): 4.45 (t,
J = 4.3 Hz, 2H, CH2); 4.60 (t, J = 4.3 Hz, 2H, CH2); 4.81 (s, 2H, CH2);
7.20–7.42 (m, 6H, ArH); 7.70–7.79 (m, 2H, ArH); EIMS m/z 392
(M+). Anal. Calcd for C19H14Cl2O5: C, 58.03; H, 3.59; Cl, 18.03; O,
20.34; Found: C, 58.10; H, 3.74; Cl, 18.11; O, 20.05.
2.1.34. 4-(2-(4-Hydroxyphenylacetyloxyl)ethoxy)-3-
phenylfuran-2(5H)-one (d32)
White powder, 49.7%, mp 149–151 °C; 1H NMR (DMSO-d6): 3.45
(s, 2H, CH2); 4.28–4.33 (m, 4H, CH2); 4.77 (s, 2H, CH2); 6.65 (t,
J = 8.4 Hz, 2H, ArH); 6.94 (d, J = 8.4 Hz, 2H, ArH); 7.19–7.30 (m,
3H, ArH); 7.72 (d, J = 7.3 Hz, 2H, ArH); EIMS m/z 354 (M+). Anal.
Calcd for C20H18O6: C, 67.79; H, 5.12; O, 27.09; Found: C, 67.92;
H, 5.05; O, 27.03.
2.1.27. 4-(2-(3,4-Dichlorophenylformyloxyl)ethoxy)-3-
phenylfuran-2(5H)-one (d25)
Gray white powder, 57.0%, mp 127–128 °C; 1H NMR (CDCl3):
4.34–4.42 (m, 2H, CH2); 4.64 (t, J = 4.2 Hz, 2H, CH2); 4.87 (s, 2H,
CH2); 7.30–7.40 (m, 3H, ArH); 7.54 (d, J = 8.4 Hz, 1H, ArH); 7.78–
7.86 (m, 3H, ArH); 8.10 (s, 1H, ArH); EIMS m/z 392 (M+). Anal. Calcd
for C19H14Cl2O5: C, 58.03; H, 3.59; Cl, 18.03; O, 20.34; Found: C,
58.13; H, 3.57; Cl, 18.08; O, 20.22.
2.1.35. 4-(2-(3,4-Dimethoxyphenylacetyloxyl)ethoxy)-3-
phenylfuran-2(5H)-one (d33)
Red-brown oily liquid, 77.0%; 1H NMR (CDCl3): 3.59 (s, 2H,
CH2); 3.85 (s, 6H,OCH3); 4.26 (t, J = 4.5 Hz, 2H, CH2); 4.41 (t,
J = 4.5 Hz, 2H, CH2); 4.71 (s, 2H, CH2); 6.70–6.76 (m, 3H, ArH);
7.30–7.41 (m, 3H, ArH); 7.80 (t, J = 7.1 Hz, 2H, ArH); EIMS m/z
398 (M+). Anal. Calcd for C22H22O7: C, 66.32; H, 5.57; O, 28.11;
Found: C, 66.40; H, 5.51; O, 28.09.
2.1.28. 4-(2-(2,4-Dihydroxyphenylformyloxyl)ethoxy)-3-
phenylfuran-2(5H)-one (d26)
White powder, 48.5%, mp 200–203 °C; 1H NMR (DMSO-d6): 4.66
(t, J = 4.7 Hz, 4H, CH2); 5.17 (s, 2H, CH2); 6.31–6.39 (m, 2H, ArH);
7.24–7.34 (m, 3H, ArH); 7.68 (d, J = 8.6 Hz, 1H, ArH); 7.85 (d,
J = 7.1 Hz, 2H, ArH); 10.50 (s, 1H, OH); 10.62 (s, 1H, OH); EIMS m/
z 356 (M+). Anal. Calcd for C19H16O7: C, 64.04; H, 4.53; O, 31.43;
Found: C, 64.08; H, 4.59; O, 31.33.
2.1.36. 4-(2-(3-Chlorophenylacetyloxy)ethoxy)-3-(4-
chlorophenyl)furan-2(5H)-one (d34)
White powder, 57.4%, mp 99–100 °C; 1H NMR (DMSO-d6): 3.62
(s, 2H, CH2); 4.27–4.30 (m, 2H, CH2); 4.40 (t, J = 4.2 Hz, 2H, CH2);
4.73 (s, 2H, CH2); 7.09 (d, J = 7.3 Hz, 1H, ArH); 7.18 (d, J = 8.5 Hz,
1H, ArH); 7.23–7.25 (m, 2H, ArH); 7.32–7.36 (m, 2H, ArH); 7.75–
7.79 (m, 2H, ArH); EIMS m/z 406 (M+). Anal. Calcd for C20H16Cl2O5:
C, 58.99; H, 3.96; Cl, 17.41; O, 19.64; Found: C, 58.95; H, 3.93; Cl,
17.40; O, 19.72.
2.1.29. 4-(2-(3,4-Dihydroxyphenylformyloxyl)ethoxy)-3-
phenylfuran-2(5H)-one (d27)
White powder, 50.4%, mp 175–177 °C; 1H NMR (DMSO-d6): 4.58
(s, 4H, CH2); 5.16 (s, 2H, CH2); 6.82 (d, J = 8.4 Hz, 1H, ArH); 7.23–
7.41 (m, 5H, ArH); 7.86 (d, J = 7.7 Hz, 2H, ArH); 9.37 (s, 1H, OH);

4918
X.-D. Wang et al. / Bioorg. Med. Chem. 21 (2013) 4914–4922
2.1.37. 4-(2-(3-Bromophenylacetyloxy)ethoxy)-3-(4-
chlorophenyl)furan-2(5H)-one (d35)
16 mM MgCl2, 5 mM ATP, 3 mM DTT, 4 mg/ml E. coli MRE600 tRNA
(Roche) and 10 -tyrosine (0.3
-[ring-3,5-3H] tyrosine
(PerkinElmer, Specific activity: 1.48–2.22 TBq/mmol), 10 M car-
lM
L
lM L
White powder, 64.4%, mp 79–81 °C; 1H NMR (DMSO-d6): 3.62
(s, 2H, CH2); 4.27–4.30 (m, 2H, CH2); 4.44–4.47 (m, 2H, CH2);
4.73 (s, 2H, CH2); 7.13–7.15 (m, 2H, ArH); 7.32–7.37 (m, 2H,
ArH); 7.38–7.41 (m, 2H, ArH); 7.76–7.80 (m, 2H, ArH); EIMS m/z
449 (M+). Anal. Calcd for C20H16BrClO5: C, 53.18; H, 3.57; Br,
17.69; Cl, 7.85; O, 17.71; Found: C, 53.25; H, 3.60; Br, 17.75; Cl,
7.45; O, 17.95.
l
rier). TyrRS (0.2 nM) was pre-incubated with a range of inhibitor
concentrations for 10 min at room temperature followed by the
addition of pre-warmed mixture at 37 °C. After specific intervals,
the reaction was terminated by adding aliquots of the reaction
mix into ice-cold 7% trichloroacetic acid and harvesting onto
0.45 mm hydrophilic Durapore filters (Millipore Multiscreen 96-
well plates) and counted by liquid scintillation. The rate of reaction
in the experiments was linear with respect to protein and time
with less than 50% total tRNA acylation. IC50s correspond to the
concentration at which half of the enzyme activity is inhibited by
the compound. The results are presented in Table 1.
2.1.38. 4-(2-(4-Hydroxyphenylacetyloxy)ethoxy)-3-(4-
chlorophenyl)furan-2(5H)-one (d36)
White powder, 56.6%, mp 110–112 °C; 1H NMR (DMSO-d6): 3.57
(s, 2H, CH2); 4.25 (t, J = 4.40 Hz, 2H, CH2); 4.42 (t, J = 4.3 Hz, 2H,
CH2); 4.55 (s, 2H, CH2); 5.65 (s, 1H, OH); 6.73 (d, J = 8.6 Hz, 2H,
ArH); 7.05 (d, J = 8.4 Hz, 2H, ArH); 7.35 (d, J = 8.6 Hz, 2H, ArH);
7.78 (d, J = 8.6 Hz, 2H, ArH); EIMS m/z 388 (M+). Anal. Calcd for C20-
H17ClO6: C, 61.78; H, 4.41; Cl, 9.12; O, 24.69; Found: C, 61.70; H,
4.45; Cl, 9.11; O, 24.74.
2.3. Antimicrobial activity
The antibacterial activities of the synthesized compounds were
tested against Gram-positive bacterial strain (S. aureus ATCC
25923, kanamycin as positive control) and two Gram-negative bac-
terial strains (E. coli ATCC 35218, kanamycin as positive control
and P. aeruginosa ATCC 27853, norfloxacin as positive control)
using LB medium. The antifungal activities of the compounds were
tested against C. albican ATCC 10231 (ketoconazol as positive con-
trol) using LB medium. The MTT proliferation assay was used to
measure the MIC50s of the test compounds by determining the
absorbance of the cells in culture.22 A stock solution of the synthe-
2.1.39. 4-(2-(4-Fluorophenylacetyloxy)ethoxy)-3-(4-
chlorophenyl)furan-2(5H)-one (d37)
White powder, 62.6%, mp 110–112 °C; 1H NMR (DMSO-d6): 3.62
(s, 2H, CH2); 4.30 (t, J = 4.4 Hz, 2H, CH2); 4.45 (t, J = 4.5 Hz, 2H,
CH2); 4.75 (s, 2H, CH2); 6.95–7.00 (m, 2H, ArH); 7.19 (d,
J = 8.6 Hz, 2H, ArH); 7.34 (d, J = 8.6 Hz, 2H, ArH); 7.80 (d,
J = 8.8 Hz, 2H, ArH); EIMS m/z 390 (M+). Anal. Calcd for C20H16-
ClFO5: C, 61.47; H, 4.13; Cl, 9.07; F, 4.86; O, 20.47; Found: C,
61.29; H, 4.10; Cl, 9.12; F, 4.75; O, 20.74.
sized compound (1000 lg/ml) in DMSO was prepared with differ-
ent concentrations using sterilized liquid medium (50% (v/v) of
DMSO in PBS). A specified quantity of the medium containing the
test compound was added into 96-well plates, which was replaced
by the sterilized liquid medium as blank control. Suspension of the
microorganism was prepared to contain approximate 105 cfu/mL
and applied to 96-well plates with serially diluted compounds
(or blank control) to be tested and incubated at 37 °C. In the case
of fungi, plates were incubated at 28 °C. Fifty microliter of PBS con-
taining 3 mg of MTT/mL was added to each well. Incubation was
continued at room temperature for 4–5 h. The content of each well
2.1.40. 4-(2-(4-Chlorophenylacetyloxy)ethoxy)-3-(4-
chlorophenyl)furan-2(5H)-one (d38)
White powder, 39.2%, mp 138–139 °C; 1H NMR (DMSO-d6): 3.65
(s, 2H, CH2); 4.29 (t, J = 4.5 Hz, 2H, CH2); 4.45 (t, J = 4.5 Hz, 2H,
CH2); 4.76 (s, 2H, CH2); 7.15 (d, J = 8.6 Hz, 2H); 7.25–7.36 (m, 4H,
ArH); 7.80 (d, J = 8.8 Hz, 2H, ArH); EIMS m/z 406 (M+). Anal. Calcd
for C20H16Cl2O5: C, 58.99; H, 3.96; Cl, 17.41; O, 19.64; Found: C,
58.90; H, 3.93; Cl, 17.47; O, 19.70.
was removed, and 100 lL of 10% sodium dodecyl sulfate contain-
2.1.41. 4-(2-(4-Bromophenylacetyloxy)ethoxy)-3-(4-
chlorophenyl)furan-2(5H)-one (d39)
ing 5% isopropanol and 10 mol/mL HCl was added to extract the
dye. After 8–10 h of incubation at room temperature, the control
OD value (at 570 nm) should be controlled under 1.0–2.0 to
achieve reliable results. The observed MIC50s were presented in
Table 2.
White powder, 60.0%, mp 137–139 °C; 1H NMR (DMSO-d6): 3.60
(s, 2H, CH2); 4.29 (t, J = 4.2 Hz, 2H, CH2); 4.44 (t, J = 4.2 Hz, 2H,
CH2); 4.77 (s, 2H, CH2); 7.09 (d, J = 8.4 Hz, 2H, ArH); 7.35 (t,
J = 2.0 Hz, 2H, ArH); 7.41 (d, J = 8.4 Hz, 2H, ArH); 7.80 (d,
J = 8.7 Hz, 2H, ArH); EIMS m/z 449 (M+). Anal. Calcd for C20H16-
BrClO5: C, 53.18; H, 3.57; Br, 17.69; Cl, 7.85; O, 17.71; Found: C,
53.20; H, 3.51; Br, 17.81; Cl, 7.65; O, 17.83.
2.4. Protocol of docking study
The automated docking studies were carried out using Auto-
Dock version 4.2. First, AutoGrid component of the program pre-
calculates a three-dimensional grid of interaction energies based
on the macromolecular target using the AMBER force field. A grid
box of 60 ꢁ 60 ꢁ 60 Å size (x, y and z) with a spacing of 0.375 Å
and grid maps were created representing the catalytic active target
site region where the native ligand was embedded. Then auto-
mated docking studies were carried out to evaluate the binding
free energy of the inhibitor within the macromolecules. The genet-
ic algorithm with local search (GA-LS) was chosen to search for the
best conformers. The parameters were set using the software ADT
(AutoDockTools package, version 1.5.4) on PC which is associated
with AutoDock 4.2. Default settings were used with an initial pop-
ulation of 50 randomly placed individuals, a maximum number of
7.5 ꢁ 106 energy evaluations, and a maximum number of 2.7 ꢁ 104
2.1.42. 4-(2-(3-Chlorophenylformyloxy)ethoxy)-3-(4-
chlorophenyl)furan-2(5H)-one (d40)
White powder, 53.0%, mp 108–110 °C; 1H NMR (DMSO-d6): 4.55
(t, J = 4.4 Hz, 2H, CH2); 4.75 (t, J = 4.0 Hz, 2H, CH2); 4.76 (s, 2H,
CH2); 7.11–7.19 (m, 2H, ArH); 7.29 (t, J = 2.0 Hz, 2H, ArH); 7.37–
7.42 (m, 2H, ArH); 7.75–7.81 (m, 2H, ArH); EIMS m/z 393 (M+).
Anal. Calcd for C19H14Cl2O5: C, 58.03; H, 3.59; Cl, 18.03; O, 20.34;
Found: C, 57.95; H, 3.62; Cl, 17.99; O, 20.44.
2.2. Preparation of the TyrRS and enzyme assay
S. aureus TyrRS was over-expressed in Escherichia coli and puri-
fied to near homogeneity (ꢀ98% as judged by SDS–PAGE) using
standard purification procedures.20 TyrRS activity was measured
by aminoacylation using modifications to previously described
methods.21 The assays were performed at 37 °C in a mixture con-
taining (final concentrations) 100 mM Tris/Cl pH 7.9, 50 mM KCl,
generations. A mutation rate of 0.02 and a crossover rate of 0.8
0
were chosen. Results differing by less than 0.5 ÅA in positional
root-mean-square deviation (RMSD) were clustered together and

X.-D. Wang et al. / Bioorg. Med. Chem. 21 (2013) 4914–4922
4919
Table 1
In vitro inhibitory activity data of the synthesized compounds against S. aureus TyrRS
O
O
O
O
O
R2
R1
Compound
R2
IC50
(
l
M)
Compound
R2
IC50 (lM)
Entry
R1
H
Entry
R1
H
CH3
d3
84.6 2.7
47.8 3.2
d22
11.2 0.3
16.5 1.5
OH
Cl
CH3
Cl
Cl
Cl
d4
d5
H
H
d23
d24
H
H
CH3
41.0 2.6
5.2 0.3
Cl
Cl
d6
d7
d8
d9
H
H
H
H
12.8 1.1
26.0 0.9
17.7 0.7
16.8 0.7
d25
d26
d27
d28
H
H
H
H
33.4 3.1
50.2 3.7
75.3 4.7
6.7 0.5
OH
N
OH
OH
OH
OH
OH
OH
Cl
d10
d11
d12
d13
H
H
H
H
>100
d29
d30
d31
d32
H
H
H
H
>100
H3C
56.8 1.2
18.2 0.6
41.4 0.5
93.6 5.5
48.1 0.9
>100
Cl
F
Br
NO2
OH
HO
OCH3
d14
H
64.7 6.5
d33
H
83.8 1.4
MeO
OCH3
Cl
NO2
d15
d16
d17
H
H
H
>100
d34
d35
d36
Cl
Cl
Cl
1.1 0.1
3.5 0.2
7.9 0.3
CH3
CF3
Br
8.1 0.5
4.3 0.3
OH
F
d18
H
5.2 0.2
d37
Cl
5.7 0.4
NO2
(continued on next page)

4920
X.-D. Wang et al. / Bioorg. Med. Chem. 21 (2013) 4914–4922
Table 1 (continued)
Compound
R2
IC50
(
l
M)
Compound
R2
IC50 (lM)
Entry
R1
H
Entry
R1
Cl
d19
17.8 0.9
7.5 0.2
8.8 0.7
d38
9.3 0.7
16.7 1.5
0.9 0.05
CH3
Cl
Br
d20
d21
H
H
d39
d40
Cl
Cl
F
Cl
Cl
Table 2
were prepared by esterification of the corresponding sodium phen-
ylacetate with 2-bromoacetate, which greatly improved the yield
comparing with the previously reported method,15 and the inter-
mediates (b1–b2 and c1–c2) were prepared according to previ-
ously method.14,23 Subsequently, esterification of compounds
(c1–c2) with appropriately substituted sodium carboxylate in
DMSO gave 3-aryl-4-acyloxyethoxyfuran-2(5H)-ones (d3–d40),
which were first reported and fully characterized by elementary
analyses, EIMS and 1H NMR.
Inhibitory activity (IC50) of the synthetic compounds against microbes
Compound
IC50 (lg/ml)
A
B
C
D
d3
d4
d5
d6
d7
d8
d9
>100
>100
48.8
>100
18.6
>100
>100
19.3
17.9
17.5
15.7
>100
9.4
>100
23.3
5.0
>100
>100
>100
19.5
12.8
13.9
2.9
>100
>100
>100
>100
>100
78.7
53.6
>100
7.6
16.6
>100
>100
45.6
14.3
4.3
41.3
43.0
98.1
60.8
56.8
13.4
44.8
18.1
15.8
90.2
52.7
35.5
47.8
73.6
>100
16.7
2.4
11.4
37.7
13.8
14.5
21.3
21.3
2.9
88.7
21.4
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
2.7
23.4
18.1
78.4
23.0
22.9
>100
95.4
>100
>100
>100
>100
>100
>100
>100
92.3
2.5
>100
17.8
22.8
21.9
16.1
>100
72.9
24.3
24.9
>100
>100
15.8
17.5
24.5
18.3
8.2
3.2. Inhibitory activities of 3-aryl-4-acyloxyethoxyfuran-2(5H)-
ones against TyrRS from S. aureus
d10
d11
d12
d13
d14
d15
d16
d17
d18
d19
d20
d21
d22
d23
d24
d25
d26
d27
d28
d29
d30
d31
d32
d33
d34
d35
d36
d37
d38
d39
d40
Kanamycin
Norfloxacin
Ketoconazole
All synthesized compounds (d3–d40) were tested for inhibitory
activity against TyrRS from S. aureus. The IC50s of these compounds
are presented in Table 1. Compounds d3–d33 were prepared to
study the structure–activity relationship profiles of the acyloxy
moiety (R2). The compounds (d3–d5) with R2 being an aliphatic
group which show weak activity against TyrRS and the activities
increase as carbon chain increase. Compound containing a 3-piper-
idyl (d7) or 3-naphthy (d8) group is slightly less active than com-
pound with phenyl group (d6). In comparison with d6,
introduction of any substituent at the 2-position of aryl ring
(d10–d14) leads to a small reduction in potency. Compound con-
taining a 3-trifluoromethyl group (d17) is more active than com-
pounds with methyl group (d16) or nitro group (d15).
Compounds with an electron-donating group at 4-position of aryl
ring are less active than those with an electron-withdrawing
group. As for compounds with two substituents in the aryl ring,
compounds with no substituent at 4-position (d24 and d28) show
2 to 12-fold more potent than others, indicating that these substit-
uents may cause a steric clash with the protein. Substituting a ben-
zyl group for the phenyl group (d30 vs d20, d32 vs d22, d34 vs
d40) obviously reduced the inhibitory activity.
17.2
23.3
18.2
24.8
19.9
15.3
19.9
2.2
22.7
36.7
>100
14.4
83.1
>100
22.0
68.1
>100
2.5
>100
16.5
15.4
22.5
>100
5.2
13.6
27.4
14.9
13.3
13.0
2.0
1.5
—
—
4.6
4.2
15.5
13.2
17.7
20.6
1.5
—
2.1
—
>100
15.6
>100
13.1
1.2
—
—
3.8
Introduction of a chlorine atom at 4-position in the 3-phenyl
group led to a significant increase in potency with respect to the
corresponding unsubstituted compound (d29 vs d34, d30 vs d37,
d31 vs d39). Out of these compounds, compound d40 was proved
3.5
—
—
as the most potent, having IC50 of 0.9 0.05 lM.
(A) E. coli ATCC 35218; (B) S. aureus ATCC 25923; (C) P. aeruginosa ATCC 27853; (D)
C. albicans ATCC 10231.
3.3. Antibacterial activity
the results of the most favorable free energy of binding were
selected as the resultant complex structures.
All compounds were tested against representative Gram-posi-
tive organism (S. aureus ATCC 25923), two Gram-negative organ-
isms (E. coli ATCC 35218; P. aeruginosa ATCC 27853) and a
fungus (C. albican ATCC 10231), and the results are presented in Ta-
ble 2. The results revealed that the compounds with strong inhibi-
tion against TyrRS also exhibit good antibacterial activities,
especially against P. aeruginosa ATCC 27853. By compared to other
compounds, d34 and d40 display good activity against Gram-posi-
tive organism, Gram-negative organism and fungus, and d40 is the
3. Results and discussion
3.1. Chemistry
Thirty-eight 3-aryl-4-acyloxyethoxyfuran-2(5H)-ones were
synthesized by the routes outlined in Scheme 2. Esters (a1–a2)

X.-D. Wang et al. / Bioorg. Med. Chem. 21 (2013) 4914–4922
4921
Figure 1. Binding mode of compound d40 with TyrRS. The enzyme is shown as
surface; while d40 docked structures are shown as sticks. This figure was made
using PyMol.
Figure 3. Binding mode of compound d29, d34, d40 with TyrRS. The enzyme is
shown as surface; while d29, d34, d40 docked structures are shown as sticks. This
figure was made using PyMol.
Table 3
Binding energy and
D
G of the synthetic compounds
Compound
d29
d34
d40
D
G
ꢃ4.06
ꢃ5.06
ꢃ5.80
Binding energy
4.06
5.06
5.80
moiety as acceptor receives a weak hydrogen-bonding interaction
from the CH2 group of Trp241 residue at a distance of 3.605 Å. The
unsaturated oxygen in 3-chlorophenylacetate moiety interacts
with the backbone amino groups of Arg88 (3.825 Å), while the sat-
urated oxygen in 3-chlorophenylacetate moiety forms another
hydrogen-bond with NH groups of His50 residue having the
Hꢂ ꢂ ꢂO bond length of 1.966 Å. The two CH2 groups in carbon chain
as donors, forming three hydrogen bonds, the CH2 group which
closes to 3-chlorophenylacetate moiety interacts with Asp80 and
Asp40 residues through hydrogen bonds at distances of 3.778
and 3.806 Å. The other CH2 group interacts with Gly38 at adistance
of 3.289 Å. The furanone-ring moiety interacts with Gly193 residue
through a hydrogen bond which is observed between the NH group
of residue Gly193 and saturated oxygen with Hꢂ ꢂ ꢂO bond length of
2.401 Å (Fig. 2). The 4-chlorobenzene-ring moiety which is used as
an acceptor, forming O–Hꢂ ꢂ ꢂCl hydrogen bonding interaction with
Thr75 residue is located at the bottom of the active site cavity
(Fig. 1).
Our modeling results revealed that the chlorine atom in 4-chlo-
robenzene-ring and the position of 3-chlorobenzene-ring had an
important influence on the interactions of the protein–ligand com-
plex and were crucial to the potency of TyrRS inhibitory activity
(Fig. 3). The compound d34, substituting a benzyl group for the
phenyl group of d40, located at a different position of the active
site due to space steric hindrance effects. This may be causes that
the enzyme inhibitory activity of d34 is weaker than d40. Removal
of the chlorine atom of 4-chlorobenzene-ring (d34 vs d29) leads to
a decrease in binding energy (Table 3), which is evidenced by a sig-
nificant decrease in enzyme inhibitory activity.
Figure 2. Binding mode of compound d40 with TyrRS from S. aureus. For clarity,
only interacting residues were labeled. Hydrogen bonding interactions are shown in
dash. This figure was made using PyMol.
most potent compound, which is close to or slightly over that of
marketed antibiotics. Out of the synthetic compounds, compound
d28 shows good activity against Gram-positive organism and com-
pound d17 shows good activity against Gram-negative organism
especially against P. aeruginosa with IC50 value of 2.4 lg/mL.
3.4. Molecular docking
To explain the structure–activity relationships observed in 3-
aryl-4-acyloxyethoxy-furan-2(5H)-ones, the compounds d29, d34
and d40 were selected to dock into the binding site of TyrRS which
were performed on the binding model based on the TyrRS complex
structure (1jij.pdb).20 The results showed that the most active
compound d40 is held to the active pocket tightly by several
hydrogen-bonding interactions and hydrophobic contacts. In the
binding model, 3-chlorobenzene-ring moiety of d40 is oriented to-
wards the entrance cavity (Fig. 1), which hydrophobically interacts
with Ile103, Trp241 and Ala43 residues. The benzene ring of 3-
chlorobenzene-ring moiety group as hydrogen bond acceptor ishy-
drogen-bonded with CH3 group of Thr42 and CH2 group of His50
(3.676 and 3.904 Å). The chlorine atom in 3-chlorobenzene-ring
4. Conclusions
In this study, thirty-eight 3-aryl-4-acyloxyethoxyfuran-2(5H)-
ones were synthesized and characterized by elementary analyses,
EIMS and 1H NMR, and their biological activities were also
evaluated as antimicrobial agents. Compound d40, 4-(2-(3-
chlorophenylformyloxy)ethoxy)-3-(4-chlorophenyl)furan-2(5H)-
one, displays good inhibitory activity against TyrRS and has a broad

4922
X.-D. Wang et al. / Bioorg. Med. Chem. 21 (2013) 4914–4922
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Acknowledgments
The work was financed by Grants from National Natural Science
Foundation (Grant No. 21262013) of China, by a Project supported
by Hunan Provincial Natural Science Foundation of China (Grant
Nos. 11JJ3113 and 13JJ2030), by Graduate Innovation Fund of Jis-
hou University (JGY201228), and by aid program for Science and
Technology Innovative Research Team (Chemicals of Forestry Re-
sources and Development of Forest Products) in Higher Educa-
tional Institutions of Hunan Province.
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