Synthesis, structure, molecular docking, and structure-activity relationship analysis of enamines: 3-Aryl-4-alkylaminofuran-2(5H)-ones as potential antibacterials

Article abstract of DOI:10.1016/j.bmc.2011.01.051

Thirty-one 3-aryl-4-alkylaminofuran-2(5H)-ones were designed, prepared and tested for their antibacterial activity. Some of them showed significant antibacterial activity against Gram-positive organisms, especially against Staphylococcus aureus ATCC 25923, but all were inactive against Gram-negative organisms. Out of these compounds, 3-(4-bromophenyl)-4-(2-(4-nitrophenyl) hydrazinyl)furan-2(5H)-one (4a11) showed the most potent antibacterial activity against S. aureus ATCC 25923 with MIC₅₀ of 0.42 μg/mL. The enzyme assay revealed that the possible antibacterial mechanism of the synthetic compounds might be due to their inhibitory activity against tyrosyl-tRNA synthetase. Molecular dockings of 4a11 into S. aureus tyrosyl-tRNA synthetase active site were also performed. This inhibitor snugly fitting the active site might well explain its excellent inhibitory activity. Meanwhile, this modeling disclosed that a more suitable optimization strategy might be to modify the benzene ring at 3-position of furanone with hydrophilic groups.

Full text of DOI:10.1016/j.bmc.2011.01.051

Bioorganic & Medicinal Chemistry 19 (2011) 1571–1579
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry
journal homepage: www.elsevier.com/locate/bmc
Synthesis, structure, molecular docking, and structure–activity
relationship analysis of enamines: 3-Aryl-4-alkylaminofuran-2(5H)-ones
as potential antibacterials
Zhu-Ping Xiao a,b, , Xing-Bing He c, Zhi-Yun Peng a, Tao-Ju Xiong d, Juan Peng d, Li-Hua Chen a,
⇑
Hai-Liang Zhu a,b,
⇑
a College of Chemistry and Chemical Engineering, and 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
c College of Biology and Environmental Sciences, Jishou University, Jishou 416000, PR China
d Xiangxi Autonomous Prefecture People’s Hospital, Jishou 416000, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Thirty-one 3-aryl-4-alkylaminofuran-2(5H)-ones were designed, prepared and tested for their
antibacterial activity. Some of them showed significant antibacterial activity against Gram-positive
organisms, especially against Staphylococcus aureus ATCC 25923, but all were inactive against Gram-
negative organisms. Out of these compounds, 3-(4-bromophenyl)-4-(2-(4-nitrophenyl)hydrazi-
nyl)furan-2(5H)-one (4a11) showed the most potent antibacterial activity against S. aureus ATCC
Received 2 December 2010
Revised 24 January 2011
Accepted 25 January 2011
Available online 1 February 2011
25923 with MIC50 of 0.42 lg/mL. The enzyme assay revealed that the possible antibacterial mechanism
Keywords:
3-Aryl-4-alkylaminofuran-2(5H)-one
Antibacterial
Molecular docking
Tyrosyl-tRNA synthetase
Structure–activity relationship
of the synthetic compounds might be due to their inhibitory activity against tyrosyl-tRNA synthetase.
Molecular dockings of 4a11 into S. aureus tyrosyl-tRNA synthetase active site were also performed. This
inhibitor snugly fitting the active site might well explain its excellent inhibitory activity. Meanwhile, this
modeling disclosed that a more suitable optimization strategy might be to modify the benzene ring at
3-position of furanone with hydrophilic groups.
Ó 2011 Elsevier Ltd. All rights reserved.
1. Introduction
being the only possible isomer as a means of enhancing efficacy.
The strategy employed is to form a ring between the ester moiety
Bacterial resistance to the available drugs provides physicians
with a real challenge to the effective treatment of infectious dis-
eases and poses a serious threat to human health. Although a more
appropriate use of current antibacterial agents will result in a
reduction of the resistance phenomenon, the development of
new antibacterial agents appears to be the most attractive chal-
lenge to fight against the emergence of resistance.1 Modification
of known antibacterial scaffolds is becoming increasingly difficult
to deliver new leads. The focus of much antibacterial research
has, therefore, moved to the identification and development of
new structural classes of antibacterial agents.2
of (E)-ethyl 2-aryl-3-arylaminoacrylate (A) and the double bond,
resulting in compound B with a furan-2(5H)-one core (Scheme 1).
Furan-2(5H)-ones showed many biological activities, such as being
inhibitors of HIV-1 integrase5 as well as antibacterial,6 antioxi-
dant,7,8 anti-pyretic,9 anti-osteoporosis,10 and anti-inflammatory
agents.7,8 Herein, we reported furan-2(5H)-ones (B) with an ali-
phatic amino group as antibacterials and the compounds with an
aryl amino group will be reported elsewhere. The possible mecha-
nism of their antibacterial action was also discussed.
We recently found that 2-aryl-3-arylaminoacrylates have po-
tent antibacterial activity against Staphylococcus aureus with E-
configuration exhibiting much higher antibacterial activity than
the corresponding Z-isomer.3,4 Furthermore, E-isomers have a risk
of isomerization to Z-isomers at low pH. Therefore, we shifted our
focus to design and synthesis of an enamine with E-configuration
O
O
O
O
R1
R1
R3
NH
R2
R3 is a group attached the
furanone ring with N atom
⇑
Corresponding authors. Tel./fax: +86 743 8563911 (Z.-P.X.); tel.: +86 25 8359
2572; fax: +86 25 8359 2672 (H.-L.Z.).
A
B
E-mail addresses: xiaozhuping2005@163.com (Z.-P. Xiao), zhuhl@nju.edu.cn
(H.-L. Zhu).
Scheme 1.
0968-0896/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2011.01.051

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Z.-P. Xiao et al. / Bioorg. Med. Chem. 19 (2011) 1571–1579
Table 1
Crystal structure data for 4a9
2. Results and discussion
2.1. Chemistry
Compounds
Formula
4a9
C
12H12BrNO2
Thirty-one 3-aryl-4-alkylaminofuran-2(5H)-ones were designed
and synthesized by the routes outlined in Scheme 2. Synthesis of the
3-aryl-4-alkylaminofuran-2(5H)-ones (4a1–4a11, 4b1, 4c1, 4d1–
4d9, 4e1–4e8) required first the synthesis of chlorohydrocarbon 3
which was obtained by chloration of 2 with PCl3 in the presence of
N,N-dimethylformamide (DMF) in Et2O. Chlorohydrocarbon 3 was
then aminated in dry THF with an appropriated amine to give the
desired product 4 (Scheme 2). The intermediates 2 were synthesized
according to the previously reported method with some modifica-
tions.7 In brief, base-catalyzed esterification of an appropriately
substituted phenylacetic acid with ethyl bromoacetate yielded ester
1 using sodium ethoxide in ethanol. Furanone 2 was then obtained
by the Dieckmann ester condensation of 1 at the presence of sodium
hydride in dry THF. All 3-aryl-4-alkylaminofuran-2(5H)-ones were
first reported and were fully characterized by spectroscopic meth-
ods and elemental analysis together with a crystal structure (4a9).
Mr
282.14
Crystal size (mm3)
0.20 ꢁ 0.20 ꢁ 0.10
Monoclinic
P21/n
16.0128(9)
8.8528(5)
17.6007(10)
2353.6(2)
8
Crystal system
Space group
a (Å)
b (Å)
c (Å)
V (Å3)
Z
Dc (g/cmꢀ3
)
1.592
3.477
1136
l
(mmꢀ1
F(0 0 0)
)
Max. and min. trans.
h range (°)
0.7224 and 0.5431
2.10/28.26
ꢀ21/21, ꢀ11/11, ꢀ23/23
28164/5830
5830/0/293
0.0368
Index range (h, k, l)
Reflections collected/unique
Data/restraints/parameters
Rint
Goodness-of-fit on F2
R1, wR2 [I > 2
R1, wR2
1.052
r(I)]
0.0481/0.1175
0.0700/0.1307
—
0.429/ꢀ1.207
2.2. Description of the crystal structure
Extinction coefficient
max., (
(e (Å3))
(D
q
)
D
q)
min.
Compound 4a9 was determined by X-ray diffraction analysis.
The crystal data are presented in Table 1 and some important bond
lengths are given in Table 2. As shown in Fig. 1, 4a9 crystallized
with two chemically equivalent but crystallographically distinct
molecules per asymmetric unit. To simplify the description, we
represent them as units A (containing Br1) and B (containing
Br2), respectively. Within the A and B units, both bond lengths
and angles are almost identical, but the molecules run along differ-
ent directions which make an angle of 50.0(2)°. The bond C7–C10
(1.375(4) Å) was assigned as a double bond,11,12 and compound
4a9 was therefore identified as a furan-2(5H)-one not a furan-
2(3H)-one. 1H NMR spectrum of 4a9 provides another evidence
for this assignment. For the lactone moiety, the 1H NMR spectrum
displayed the two proton signals as singlet at about dH 5.06. Com-
paring 1H NMR spectra of 4a9 with those of other compounds, all
synthetic compounds were determined as 3-aryl-4-alkylaminofu-
ran-2(5H)-ones. C10–N1 (1.333(3) Å) bond has a shorter bond dis-
tance than the standard C–N single bond (1.46 Å),13 but longer
than C–N double bond (1.27 Å).14 This strongly indicates that the
Table 2
Important bond lengths (Å) of compound 4a9
Bond
Bond length
C1–C7
C7–C8
C7–C10
C9–C10
C10–N1
C11–N1
1.472(4)
1.437(4)
1.375(4)
1.502(4)
1.333(3)
1.456(4)
p orbital of N1 seems to be conjugated with the
p molecular orbital
of C7–C10 double bond, which is supported by the torsion angle of
C8–C7–C10–N1 (ꢀ172.8(3)°) being small deviation from 180°. The
C–C double bond attached by a nitrogen atom clearly indicates that
compound 4a9 is an enamine.
O
O
O
OEt
Br
EtO
R2
R1
R2
R1
O
NaH
O
OH
CO2H
O
EtONa
R1
R2
2a-2f
1a-1f
R1=Br, R2=H
R1=Cl, R2=H
R1=R2=OMe
b
d
f
R1=R2=H
a
c
e
R1=H, R2=Cl
R1=H, R2=Br
O
O
O
O
PCl3
DMF
amine
R3
Cl
R1
R3 is a group attached the furanone ring with N atom
4a1-4a11; 4b1 4c1 4d1-4d9; 4e1-4e8; 4f1
R1
R2
R2
3a-3f
;
;
(See Table 2 for details)
Scheme 2.

Z.-P. Xiao et al. / Bioorg. Med. Chem. 19 (2011) 1571–1579
1573
Figure 1. Molecular structure of compound 4a9 which crystallizes with two molecules per asymmetric unit, showing the atom-numbering scheme. Displacement ellipsoids
are drawn at the 30% probability level.
The stereochemistry of the double bond in furanone ring was
assigned as E-configuration based on X-ray crystallography of
product 4a9 (Fig. 1). This provides a basis for assigning the
E-configuration to all newly synthetic 3-aryl-4-alkylaminofuran-
2(5H)-ones.
2.4. Inhibitory activities of 3-aryl-4-aminofuran-2(5H)-ones
against tyrosyl-tRNA synthetase from S. aureus
To explore the possible antibacterial mechanism of the syn-
thetic compounds, many antibacterial agents with clear mecha-
nism were used to overlap with the most potent compound
(4a11) based on the energy-minimized conformation. It turns out
that conformation of 4a11 is very similar to SB-239629 (Scheme
3, Fig. 2), which leads to a conception that 3-aryl-4-aminofuran-
2(5H)-onewouldbe a noveltyrosyl-tRNAsynthetaseinhibitor. Com-
pound SB-239629,15 a semi-synthetic derivative16 of SB-219383
which is a naturally occurring antibiotic,17 shows significant inhibi-
tory activity against tyrosyl-tRNA synthetase (IC50 = 3 nM).15,16
Unfortunately, SB-239629exhibitedonlyweak antibacterialactivity
2.3. Antibacterial activity
All synthetic compounds were evaluated for their antimicrobial
activities against three Gram-positive organisms (Bacillus subtilis
ATCC 6633, S. aureus ATCC 25923, Candida albicans ATCC 10231)
and a Gram-negative organism (Escherichia coli ATCC 35218), and
the results are presented in Table 3. The first information obtained
in this study is that some of the tested compounds showed good
activities against Gram-positive organisms, and all of them were
inactive against Gram-negative organism (E. coli ATCC 35218).
The second is that, of the three Gram-positive strains, S. aureus
ATCC 25923 was the most sensitive to these compounds. The
structure–activity relationships were therefore established from
the antibacterial data against S. aureus ATCC 25923.
The first set of analogues that were prepared are 4-bromophe-
nyl derivatives (4a1–4a11), the aim which was to explore the role
of R3 (Scheme 2) on the antibacterial activity. Compound contain-
ing a 1-pyrrolidinyl (4a1), 4-morpholinyl (4a3), 1-piperazinyl
(4a4), cyclohexylamino (4a6) or benzylamino (4a10) group was
slightly less active than compound 4a2, while the propylamino
(4a7), butylamino (4a8) and N,N-dimethylamino (4a9) analogues
showed significant decreases in activity. This indicates that R3
(MIC over 64 l
g/mL against Streptococcus pneumoniae R616) due to
its highly polar nature, which leads to a poor penetration of bacterial
cells.17 It is well known that tyrosyl-tRNA synthetase is one of the
aminoacyl-tRNA synthetases which are responsible for maintaining
the fidelity of transfer of genetic information from DNA into protein
by producing charged tRNAs.18–20 These enzymes are essential for
cell viability, and they are potential targets for antibacterial agents.
Thisconceptis provenby the successof the broad-spectrum antibac-
terial drug mupirocin, which targets bacterial isoleucyl-tRNA
synthetases.21
Based on the above mentioned, compounds with MIC50 <30
lg/mL were therefore evaluated for inhibitory activity against
tyrosyl-tRNA synthetase from S. aureus and the results are pre-
sented in Table 4. The results revealed that the potent antibacterial
agents (4a11, 4b1, and 4d6) also exhibited strong inhibition
against this enzyme, with 4a11 being the most active and achiev-
bearing
S. aureus. On the contrary, substitution at R3 position with a mor-
pholinylethylamino (4a5) or p-nitrophenylhydrazino (4a11)
a ring is favorable for antibacterial activity against
a
ing IC50 as low as 0.12 0.04 lM. An obvious correlation was found
group led to an over 2- or 50-fold increase in activities by compar-
between the IC50 values in the enzyme assay and the MIC50 values
ison with 4a2. Out of the compounds tested, 4a11 was the most
against whole cell.
active with MIC50 of 0.42
antibacterial activity than that of the commercial antibiotic,
kanamycin (MIC50 = 1.0
g/mL). Variation of R3 led to compounds
(4a1–4a11) with MIC50 values differed greatly, ranging from 0.42
to >100
g/mL. This indicates that R3 seems to be more suitable
lg/mL, displaying higher level of
2.5. Molecular docking
l
With in vitro activity against tyrosyl-tRNA synthetase from
S. aureus in hand, it is thought worth-while to do molecular dock-
ing studies to support the potency of inhibition. To this end, molec-
ular docking of the most potent inhibitor 4a11 into SB-239629
binding site of tyrosyl-tRNA synthetase was performed on the
binding model based on the tyrosyl-tRNA synthetase complex
structure (1jij.pdb).15 The interactions between compound 4a11
and the active site residues of tyrosyl-tRNA synthetase are shown
in Fig. 3.
In the binding model, 4a11 locates in the substrate binding site
of tyrosyl-tRNA synthetase, with its O atom in furanone ring
forming hydrogen-bonding interactions with the backbone amino
groups of Gly193 (1.939 Å), while the NH group attached to fura-
none ring forms another hydrogen-bond with the carbonyl group
of Gly38, having the Hꢂ ꢂ ꢂO bond length of 2.062 Å. Compound
4a11 interacts with the side chain of Thr75 via two O–Hꢂ ꢂ ꢂO
l
for further modification.
We next prepared several sets of analogues (Table 3) by modi-
fication of the benzene ring at C3 in furanone moiety. Both removal
and replacement of the 4-bromo group led to compounds with re-
duced activity (4a11 vs 4b1, 4a1 vs 4c1). However, shifting substi-
tuent atom from 4-position (4a9 or 4c1) to 3-position (4f1 or 4d1)
resulted in a significant increase in antibacterial activity, indicating
that the modification in position 3 would result in compounds with
improved activity. Compounds (4e1–4e8), which introduced meth-
oxy groups at 3,4-positions in benzene ring, showed a dramatic
loss in activity compared to the analogues bearing only one substi-
tuent (4a1–4a11, 4d1–4d9). Based on these results, further modi-
fication at position 3 in benzene fragment and at R3 position
(Scheme 2) is undergoing.

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Z.-P. Xiao et al. / Bioorg. Med. Chem. 19 (2011) 1571–1579
Table 3
Inhibitory activity (IC50) of the synthetic compounds against microbes
O
O
1
Structure
R
MIC50 (lg/mL)
Compounds
R2
R3
R1
Br
Br
R2
H
R3
A
B
C
D
4a1
4a2
4a3
4a4
50
37.1
21.8
49.8
74.4
>100
>100
N
H
N
N
N
>100
Br
Br
H
H
O
91.8
78.5
42.6
54.7
89.7
77.4
>100
>100
NH
O
N
4a5
4a6
Br
Br
H
H
24.7
86.7
9.7
3.5
>100
>100
N
H
27.8
62.8
N
H
H
4a7
4a8
Br
Br
H
H
>100
>100
87.2
>100
>100
>100
>100
N
H
N
>100
Me
Me
N
4a9
Br
Br
H
H
>100
>100
>100
57.6
>100
>100
>100
>100
H
N
4a10
NO2
NO2
H
N
4a11
4b1
Br
H
H
H
9.5
0.42
0.85
5.2
79.4
N
H
H
N
15.6
13.1
>100
N
H
4c1
4d1
4d2
Cl
H
H
H
>100
87.4
41.6
88.4
12.6
7.5
>100
71.2
33.1
>100
>100
>100
N
N
N
Cl
Cl
4d3
4d4
4d5
H
H
H
Cl
Cl
Cl
N
N
N
O
93.1
>100
>100
25.7
37.4
65.2
74.6
>100
>100
>100
>100
>100
NH
N
Me
O
N
4d6
H
Cl
27.9
3.2
21.3
>100
N
H
H
4d7
4d8
H
H
Cl
Cl
>100
>100
52.4
>100
9.08
>100
>100
N
H
N
>100
H
N
4d9
H
Cl
>100
25.3
83.9
>100
4e1
4e2
4e3
4e4
MeO
MeO
MeO
MeO
MeO
MeO
MeO
MeO
N
N
N
N
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
O
NH

Z.-P. Xiao et al. / Bioorg. Med. Chem. 19 (2011) 1571–1579
1575
Table 3 (continued)
O
O
1
Structure
R
MIC50 (lg/mL)
Compounds
R2
R3
R1
R2
R3
A
B
C
D
4e5
4e6
MeO
MeO
>100
>100
>100
>100
>100
N
H
O
N
MeO
MeO
>100
68.3
>100
N
H
H
4e7
4e8
MeO
MeO
MeO
MeO
>100
>100
>100
>100
>100
>100
>100
>100
N
H
N
Me
Me
N
4f1
H
Br
>100
61.4
>100
>100
Kanamycin
Penicillin
Ketoconazole
0.43
—
—
1.0
—
—
—
—
4.4
—
2.5
—
Note: (A) B. subtilis ATCC 6633; (B) S. aureus ATCC 25923; (C) C. albicans ATCC 10231; (D) E. coli ATCC 35218.
O
OH
OH
Table 4
In vitro inhibitory activity data of the synthesized
O
O
H
N
O
N
N
H
compounds
synthetase
against
S.
aureus
methionyl-tRNA
N
H
HO
NH2
O2N
HO
OH
Compound
IC50 (lM)
HO
OH
4a2
4a5
4a6
4a11
4b1
4d1
4d2
4d3
4d6
4d9
7.7 1.3
3.3 0.6
14.5 3.7
0.12 0.04
0.24 0.06
5.6 1.1
Br
4a11
SB-239629
Scheme 3.
2.8 0.7
10.8 1.8
0.86 0.09
8.9 1.4
Figure 2. Conformation overlap between SB-239629 (cyan) and
arylaminofuran-2(5H)-one (4a11, green).
a 3-aryl-4-
hydrogen bonds with Hꢂ ꢂ ꢂacceptor distances of 2.188 and 1.830 Å,
respectively. The modeling also suggested that there was a H–
p
interaction (3.422 Å) between the benzene ring of p-nitro-
phenylhydrazino moiety of 4a11 and amino group of Gln174. In
addition to the strong stabilizing H-bond interactions, the higher
affinity of 4a11 might also be accounted for by some hydrophobic
interactions. As an example, the spatially close residue Thr42 forms
a hydrophobic interaction with the bromine atom of 4a11. The
above mentioned interactions tightly anchoring 4a11 to the active
Figure 3. Binding mode of compound 4a11 with tyrosyl-tRNA synthetase from S.
aureus. For clarity, only interacting residues were labeled. Hydrogen-bonding
interactions are shown in dash. This figure was made using PyMol.
site of tyrosyl-tRNA synthetase might well explain its excellent
inhibitory activity. On the other hand, our modeling results also

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Z.-P. Xiao et al. / Bioorg. Med. Chem. 19 (2011) 1571–1579
revealed that the hydrophobic 4-bromophenyl group sat in a
hydrophilic pocket which is constructed by His47, His50, Lys84,
Arg88, Asp195, and Gln196. This indicates that introduction of
hydrophilic groups at this moiety may improve the antibacterial
potency. For a definite conclusion, some compounds bearing
hydrophilic groups as well as hydrophobic, electron withdrawing
or electron donating groups in benzene ring at 3-position of fura-
none would be synthesized for antibacterial evaluation.
37 °C in a mixture containing (final concentrations) 100 mM
Tris/Cl pH 7.9, 50 mM KC1, 16 mM MgCl2, 5 mM ATP, 3 mM DTT,
4 mg/mL E. coli MRE600 tRNA (Roche) and 10
(0.3
-[ring-3,5-3H] tyrosine (PerkinElmer, specific activity:
1.48–2.22 TBq/mmol), 10 M carrier). Tyrosyl-tRNA synthetase
lM L-tyrosine
lM L
l
(0.2 nM) was preincubated 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 experi-
ments 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 were presented in Table 4.
3. Conclusions
Thirty-one 3-aryl-4-alkylaminofuran-2(5H)-one derivatives
were prepared and tested for their antimicrobial activities. Some
of them showed good activities against Gram-positive organisms,
and all of them were inactive against Gram-negative bacterium
(E. coli ATCC 35218). Compound 4a11 showed the most potent
antibacterial activity with MIC50 of 0.42 lg/mL against S. aureus
4.3. Protocol of docking study
ATCC 25923. A positive correlation between the IC50 values in
the enzyme assay and the MIC50 values against whole cell indicates
that the possible action mechanism of the synthetic compounds
might be due to their inhibitory activities against tyrosyl-tRNA
synthetase. Molecular docking study revealed that various interac-
tions tightly anchored 4a11 to the active site, which could well ex-
plain its excellent enzyme inhibitory and antibacterial activity.
According to this modeling, a more suitable optimization strategy
might be to modify the benzene ring at 3-position of furanone with
hydrophilic groups and this work is undergoing.
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 46 ꢁ 58 ꢁ 48 Å size (x, y, 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 automated
docking studies were carried out to evaluate the binding free en-
ergy of the inhibitor within the macromolecules. The genetic algo-
rithm 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
4. Experiments
4.1. Antimicrobial activity
The antibacterial activities of the synthesized compounds was
tested against two Gram-positive bacterial strains (B. subtilis ATCC
6633, S. aureus ATCC 25923, kanamycin as positive control) and a
Gram-negative bacterial strain (E. coli ATCC 35218, penicillin as
positive control) using LB medium, The antifungal activities of
the compounds was tested against C. albicans ATCC 10231
(Gram-positive, ketoconazole as positive control) using RPMI-
1640 medium. The MIC50s of the test compounds were determined
by a colorimetric method using the dye MTT.22 A stock solution of
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
the results of the most favorable free energy of binding were se-
lected as the resultant complex structures.
4.4. Crystallographic studies
the synthesized compound (1000 lg/mL) in DMSO was prepared
X-ray single-crystal diffraction data for compound 4a9 was col-
lected on a Bruker SMART APEX CCD diffractometer at 296(2) K
using MoKa radiation (k = 0.71073 Å) by the x scan mode. The pro-
gram SAINT was used for integration of the diffraction profiles. The
and graded quantities of the test compounds were incorporated
in specified quantity of sterilized liquid medium (50% (v/v) of
DMSO in PBS). A specified quantity of the medium containing the
test compound was poured into 96-well plates. Suspension of the
microorganism was prepared to contain approximate 105 cfu/mL
and applied to 96-well plates with serially diluted compounds to
be tested and incubated at 37 °C for 24 h. In the case of fungi, plates
were incubated at 27 °C for 48 h. Fifty microliters of PBS containing
2 mg of MTT/mL was added to each well. Incubation was continued
at room temperature for 4–5 h. The content of each well was re-
structure was solved by direct methods using the SHELXS program
of the SHELXTL package and refined by full-matrix least-squares
23
methods with SHELXL
.
All non-hydrogen atoms of compound 4a9
were refined with anisotropic thermal parameters. All hydrogen
atoms were generated theoretically onto the parent atoms and re-
fined isotropically with fixed thermal factors.
moved, and 100 lL of 10% sodium dodecyl sulfate containing 5%
4.5. Chemistry
isopropanol and 1 mol/L HCl was added to extract the dye. After
12 h of incubation at room temperature, the optical density (OD)
was measured with a microplate reader at 550 nm. The observed
MIC50s were presented in Table 3.
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 a Bruker DPX400 or DPX300 spectrometer at 25 °C with
TMS and solvent signals allotted as internal standards. Chemical
4.2. Preparation of the tyrosyl-tRNA synthetase and enzyme
assay
S. aureus tyrosyl-tRNA synthetase was over-expressed in E. coli
and purified to near homogeneity (ꢃ98% as judged by SDS–PAGE)
using standard purification procedures.17 Tyrosyl-tRNA synthetase
activity was measured by aminoacylation using modifications to
previously described methods.16 The assays were performed at

Z.-P. Xiao et al. / Bioorg. Med. Chem. 19 (2011) 1571–1579
1577
shifts were reported in ppm (d). Elemental analyses were per-
formed on a CHN-O-Rapid instrument and were within 0.4% of
the theoretical values.
C, 51.87; H, 4.35; Br, 24.65; N, 4.32. Found: C, 51.95; H, 4.34; Br,
24.60; N, 4.31.
4.5.4.4. 3-(4-Bromophenyl)-4-(piperazin-1-yl)furan-2(5H)-one
(4a4). Colorless crystal, 64%, mp 166–168 °C, 1H NMR (DMSO-
d6): 2.66 (t, J = 5.3 Hz, 4H); 3.07 (t, J = 5.0 Hz, 4H); 4.90 (s, 2H);
7.81 (d, J = 8.0 Hz, 2H); 7.54 (d, J = 8.0 Hz, 2H); EIMS m/z 322
(M+). Anal. Calcd for C14H15BrN2O2: C, 52.03; H, 4.68; Br, 24.72;
N, 8.67. Found: C, 52.14; H, 4.69; Br, 24.66; N, 8.65.
4.5.1. General procedure for preparation of compounds 1a–1f
An appropriately substituted phenylacetic acid (50 mmol) was
added to a solution of sodium ethoxide (60 mmol) in ethanol
(70 mL) and the mixture was stirred at 25 °C for 10 min. Ethyl bro-
moacetate (55 mmol) was added and the stirred mixture was
heated under reflux temperature for 4–6 h. The precipitated salt
was filtered off and the filtrate concentrated under reduced pres-
sure. The resulted oil was dissolved in EtOAc and washed with
water and brine. Then the solution was dried over MgSO4 and con-
centrated under reduced pressure. The oily residue was then puri-
fied by column chromatography on silica gel to give 1a–1e in yields
of 75–88%.
4.5.4.5. 3-(4-Bromophenyl)-4-(2-morpholinoethylamino)furan-
2(5H)-one (4a5). White powder, 71%, mp 132–134 °C, 1H NMR
(CDCl3): 2.51 (t, J = 4.6 Hz, 4H); 2.63 (t, J = 6.0 Hz, 2H); 3.24 (dt,
J = 6.4 Hz, J = 5.3 Hz, 2H); 3.74 (t, J = 4.6 Hz, 4H); 4.78 (s, 2H);
7.16 (d, J = 8.2 Hz, 2H); 7.47 (d, J = 8.0 Hz, 2H); EIMS m/z 366
(M+). Anal. Calcd for C16H19BrN2O3: C, 52.33; H, 5.21; Br, 21.76;
N, 7.63. Found: C, 52.38; H, 5.22; Br, 21.71; N, 7.62.
4.5.2. General procedure for preparation of compounds 2a–2f
A dropwise solution of compound 1 (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
(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 compounds 2. This
material was used without further purification.
4.5.4.6.
3-(4-Bromophenyl)-4-(cyclohexylamino)furan-2(5H)-
one (4a6). White powder, 75%, mp 166–167 °C, 1H NMR (CDCl3):
1.20–1.35 (m, 6H); 1.70–1.82 (m, 2H); 1.92–1.98 (m, 2H); 3.02–
3.11 (m, 1H); 4.81 (s, 2H); 5.15 (br s, 1H); 7.34 (d, J = 7.6 Hz, 2H);
7.53 (d, J = 6.9 Hz, 2H); EIMS m/z 335 (M+). Anal. Calcd for
C16H18BrNO2: C, 57.16; H, 5.40; Br, 23.77; N, 4.17. Found: C,
57.24; H, 5.41; Br, 23.74; N, 4.16.
4.5.4.7.
3-(4-Bromophenyl)-4-(propylamino)furan-2(5H)-one
(4a7). Colorless crystal, 69%, mp 138–140 °C, 1H NMR (CDCl3):
0.98 (t, J = 7.3 Hz, 3H); 1.58–1.70 (m, 2H); 3.15 (q, J = 6.8 Hz, 2H);
4.78 (s, 2H); 5.32 (br s, 1H); 7.30 (d, J = 7.8 Hz, 2H); 7.49 (d,
J = 7.4 Hz, 2H); EIMS m/z 295 (M+). Anal. Calcd for C13H14BrNO2:
C, 52.72; H, 4.76; Br, 26.98; N, 4.73. Found: C, 52.79; H, 4.75; Br,
26.94; N, 4.72.
4.5.3. General procedure for preparation of compounds 3a–3f
Two milliliters of PCl3 was added to 20 mL of DMF at 0 °C, after
stirring for 10 min, followed by addition of 12 mL of dry ether. The
mixture was stirred for further 10 min. Compound 2 (3 mmol) was
then added and the mixture was stirred for 1–6 h at 5–10 °C. Thirty
milliliters of saturated NaHCO3 was dropwise added to quench the
reaction and the solution was extracted thrice with EtOAc. Re-
moval of solvent under reduced pressure gave a yellow solid which
was used without further purification.
4.5.4.8.
3-(4-Bromophenyl)-4-(butylamino)furan-2(5H)-one
(4a8). Colorless crystal, 63%, mp 98–100 °C, 1H NMR (CDCl3):
0.99 (t, J = 7.3 Hz, 3H); 1.33–1.47 (m, 2H); 1.56–1.67 (m, 2H);
3.15 (q, J = 7.2 Hz, 2H); 4.78 (s, 2H); 5.33 (br s, 1H); 7.27 (d,
J = 7.6 Hz, 2H); 7.46 (d, J = 7.2 Hz, 2H); EIMS m/z 309 (M+). Anal.
Calcd for C14H16BrNO2: C, 54.21; H, 5.20; Br, 25.76; N, 4.52. Found:
C, 54.14; H, 5.21; Br, 25.73; N, 4.53.
4.5.4. General procedure for preparation of 3-aryl-4-
aminofuran-2(5H)-ones (4)
An appropriately substituted amine (0.6 mmol) was partially
added to a solution of 3 (0.3 mmol) in dry THF (4 mL) at a temper-
ature range of 0–10 °C. The reaction was quenched by addition of
10 mL water, and the solution was extracted thrice with EtOAc.
After the solvent was removed under reduced pressure, the residue
was purified by column chromatography on silica gel, eluting with
EtOAc/petroleum ether (1:4–2:1, v/v).
4.5.4.9. 3-(4-Bromophenyl)-4-(dimethylamino)furan-2(5H)-one
(4a9). Colorless crystal, 71%, mp 139–140 °C, 1H NMR (CDCl3):
3.27 (s, 6H); 4.78 (s, 2H); 7.28 (d, J = 7.8 Hz, 2H); 7.45 (d,
J = 7.4 Hz, 2H); EIMS m/z 281 (M+). Anal. Calcd for C12H12BrNO2:
C, 51.09; H, 4.29; Br, 28.32; N, 4.96. Found: C, 51.15; H, 4.28; Br,
28.35; N, 4.97.
4.5.4.1. 3-(4-Bromophenyl)-4-(pyrrolidin-1-yl)furan-2(5H)-one
(4a1). Colorless crystal, 87%, mp 197–198 °C, 1H NMR (CDCl3):
1.81–1.99 (m, 4H); 3.15–3.26 (m, 4H); 4.74 (s, 2H); 7.16 (d,
J = 7.0 Hz, 2H); 7.46 (d, J = 7.2 Hz, 2H); EIMS m/z 307 (M+). Anal.
Calcd for C14H14BrNO2: C, 54.56; H, 4.58; Br, 25.93; N, 4.55. Found:
C, 54.63; H, 4.57; Br, 25.87; N, 4.55.
4.5.4.10. 4-(Benzylamino)-3-(4-bromophenyl)furan-2(5H)-one
(4a10). Colorless crystal, 89%, mp 220–221 °C, 1H NMR (DMSO-
d6): 4.34 (d, J = 6.4 Hz, 2H); 4.81 (s, 2H); 7.24–7.39 (m, 5H); 7.43
(d, J = 8.4 Hz, 2H); 7.55 (d, J = 8.6 Hz, 2H); 8.16 (t, J = 6.4 Hz, 1H);
EIMS m/z 343 (M+). Anal. Calcd for C17H14BrNO2: C, 59.32; H,
4.10; Br, 23.21; N, 4.07. Found: C, 59.25; H, 4.11; Br, 23.24; N, 4.06.
4.5.4.2. 3-(4-Bromophenyl)-4-(piperidin-1-yl)furan-2(5H)-one
(4a2). Colorless crystal, 93%, mp 145–147 °C, 1H NMR (CDCl3):
1.57–1.64 (m, 6H); 3.14 (t, J = 5.2 Hz, 4H); 4.75 (s, 2H); 7.17 (d,
J = 8.4 Hz, 2H); 7.47 (d, J = 8.1 Hz, 2H); EIMS m/z 321 (M+). Anal.
Calcd for C15H16BrNO2: C, 55.92; H, 5.01; Br, 24.80; N, 4.35. Found:
C, 55.84; H, 5.01; Br, 24.86; N, 4.34.
4.5.4.11.
3-(4-Bromophenyl)-4-(2-(4-nitrophenyl)hydrazinyl)
furan-2(5H)-one (4a11). Yellow crystal, 59%, mp 220–223 °C,
1H NMR (DMSO-d6): 3.55 (s, 2H); 6.72 (d, J = 9.1 Hz, 2H); 7.29 (d,
J = 8.4 Hz, 2H); 7.54 (d, J = 8.4 Hz, 2H); 8.04 (d, J = 9.2 Hz, 2H);
9.06 (s, 1H); 10.20 (s, 1H); EIMS m/z 389 (M+). Anal. Calcd for
C16H12BrN3O4: C, 49.25; H, 3.10; Br, 20.48; N, 10.77. Found: C,
4.5.4.3. 3-(4-Bromophenyl)-4-morpholinofuran-2(5H)-one (4a3).
Colorless crystal, 86%, mp 160–161 °C, 1H NMR (CDCl3): 3.18 (s,
4H); 3.67 (s, 4H); 4.77 (s, 2H); 7.17 (d, J = 8.4 Hz, 2H); 7.49 (d,
J = 8.0 Hz, 2H); EIMS m/z 323 (M+). Anal. Calcd for C14H14BrNO3:
49.18; H, 3.11; Br, 20.52; N, 10.75.
4.5.4.12. 4-(2-(4-Nitrophenyl)hydrazinyl)-3-phenylfuran-2(5H)-
one (4b1). Red crystal, 63%, mp 203–205 °C, 1H NMR (CDCl3):

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Z.-P. Xiao et al. / Bioorg. Med. Chem. 19 (2011) 1571–1579
3.32 (s, 2H); 4.91 (s, 1H); 5.40 (d, J = 8.9 Hz, 2H); 5.53 (s, 1H); 5.80
(t, J = 6.8 Hz, 1H); 5.93 (t, J = 7.5 Hz, 2H); 6.00 (d, J = 7.5 Hz, 2H);
6.64 (d, J = 9.0 Hz, 2H); EIMS m/z 311 (M+). Anal. Calcd for
4.5.4.21.
4-(Butylamino)-3-(3-chlorophenyl)furan-2(5H)-one
(4d8). White powder, 74%, mp 90–94 °C, 1H NMR (CDCl3): 0.97
(t, J = 7.3 Hz, 3H); 1.33–1.46 (m, 2H); 1.55–1.65 (m, 2H); 3.16 (q,
J = 7.2 Hz, 2H); 4.79 (s, 2H); 5.32 (br s, 1H); 7.20–7.24 (m, 1H);
7.32–7.37 (m, 2H); 7.44–7.47 (m, 1H); EIMS m/z 265 (M+). Anal.
Calcd for C14H16ClNO2: C, 63.28; H, 6.07; Cl, 13.34; N, 5.27. Found:
C, 63.35; H, 6.06; Cl, 13.32; N, 5.28.
C16H13N3O4: C, 61.73; H, 4.21; N, 13.50. Found: C, 61.61; H, 4.21;
N, 13.52.
4.5.4.13.
3-(4-Chlorophenyl)-4-(pyrrolidin-1-yl)furan-2(5H)-
one (4c1). Colorless crystal, 77%, mp 182–184 °C, 1H NMR
(CDCl3): 1.81–1.98 (m, 4H); 3.13–3.24 (m, 4H); 4.74 (s, 2H); 7.20
(d, J = 7.1 Hz, 2H); 7.47 (d, J = 7.4 Hz, 2H); EIMS m/z 263 (M+). Anal.
Calcd for C14H14ClNO2: C, 63.76; H, 5.35; Cl, 13.44; N, 5.31. Found:
C, 63.85; H, 5.35; Cl, 13.42; N, 5.30.
4.5.4.22. 4-(Benzylamino)-3-(3-chlorophenyl)furan-2(5H)-one
(4d9). Colorless crystal, 89%, mp 120–122 °C, 1H NMR (CDCl3):
4.39 (d, J = 6.2 Hz, 2H); 4.78 (s, 2H); 5.70 (br s, 1H); 7.20–7.24
(m, 1H); 7.26–7.30 (m, 2H); 7.31–7.44 (m, 5H); 9.48–7.51 (m,
1H); EIMS m/z 299 (M+). Anal. Calcd for C17H14ClNO2: C, 68.12; H,
4.71; Cl, 11.83; N, 4.67. Found: C, 68.23; H, 4.71; Cl, 11.81; N, 4.66.
4.5.4.14.
3-(3-Chlorophenyl)-4-(pyrrolidin-1-yl)furan-2(5H)-
one (4d1). Colorless crystal, 96%, mp 128–130 °C, 1H NMR
(CDCl3): 1.85–1.97 (m, 4H); 3.11–3.30 (m, 4H); 4.74 (s, 2H);
7.17–7.28 (m, 4H); EIMS m/z 263 (M+). Anal. Calcd for
4.5.4.23.
3-(3,4-Dimethoxyphenyl)-4-(pyrrolidin-1-yl)furan-
2(5H)-one (4e1). Colorless crystal, 94%, mp 147–149 °C, 1H NMR
(CDCl3): 1.84–1.92 (m, 4H); 3.88 (s, 6H); 4.72 (s, 2H); 6.77–6.86
(m, 3H); EIMS m/z 289 (M+). Anal. Calcd for C16H19NO4: C, 66.42;
H, 6.62; N, 4.84. Found: C, 66.34; H, 6.63; N, 4.84.
C14H14ClNO2: C, 63.76; H, 5.35; Cl, 13.44; N, 5.31. Found: C,
63.87; H, 5.34; Cl, 13.42; N, 5.31.
4.5.4.15. 3-(3-Chlorophenyl)-4-(piperidin-1-yl)furan-2(5H)-one
(4d2). White powder, 72%, mp 138–139 °C, 1H NMR (CDCl3):
1.56–1.63 (m, 6H); 3.15 (t, J = 5.7 Hz, 4H); 4.75 (s, 2H); 7.18–7.23
(m, 1H); 7.24–7.27 (m, 2H); 7.28–7.32 (m, 1H); EIMS m/z 277
(M+). Anal. Calcd for C15H16ClNO2: C, 64.87; H, 5.81; Cl, 12.76; N,
5.04. Found: C, 64.79; H, 5.82; Cl, 12.74; N, 5.05.
4.5.4.24.
3-(3,4-Dimethoxyphenyl)-4-(piperidin-1-yl)furan-
2(5H)-one (4e2). Colorless crystal, 97%, mp 153–154 °C, 1H NMR
(DMSO-d6): 1.43–1.49 (m, 4H); 1.51–1.56 (m, 2H); 3.13 (t,
J = 5.0 Hz, 4H); 3.73 (s, 3H); 3.75 (s, 3H); 4.85 (s, 2H); 6.74 (dd,
J = 8.5 Hz, J = 2.0 Hz, 1H); 6.76 (d, J = 2.0 Hz, 1H); 6.92 (d,
J = 8.0 Hz, 1H); EIMS m/z 303 (M+). Anal. Calcd for C17H21NO4: C,
67.31; H, 6.98; N, 4.62. Found: C, 67.23; H, 6.99; N, 4.62.
4.5.4.16.
3-(3-Chlorophenyl)-4-morpholinofuran-2(5H)-one
(4d3). Light yellow crystal, 97%, mp 177–178 °C, 1H NMR (CDCl3):
3.19 (t, J = 5.1 Hz, 4H); 3.68 (t, J = 4.8 Hz, 4H); 4.78 (s, 2H); 7.17–
7.21 (m, 1H); 7.27–7.31 (m, 3H); EIMS m/z 279 (M+). Anal. Calcd
for C14H14ClNO3: C, 60.11; H, 5.04; Cl, 12.67; N, 5.01. Found: C,
60.24; H, 5.03; Cl, 12.64; N, 5.02.
4.5.4.25. 3-(3,4-Dimethoxyphenyl)-4-morpholinofuran-2(5H)-
one (4e3). Colorless crystal, 67%, mp 175–177 °C, 1H NMR
(DMSO-d6): 3.15 (t, J = 5.0 Hz, 4H); 3.57 (t, J = 5.0 Hz, 4H); 3.73 (s,
3H); 3.75 (s, 3H); 4.88 (s, 2H); 6.75 (dd, J = 8.5 Hz, J = 2.0 Hz, 1H);
6.77 (d, J = 2.0 Hz, 1H); 6.93 (d, J = 8.0 Hz, 1H); EIMS m/z 305
(M+). Anal. Calcd for C16H19NO5: C, 62.94; H, 6.27; N, 4.59. Found:
C, 62.89; H, 6.27; N, 4.60.
4.5.4.17. 3-(3-Chlorophenyl)-4-(piperazin-1-yl)furan-2(5H)-one
(4d4). White powder, 66%, mp 182–184 °C, 1H NMR (DMSO-d6):
2.67 (t, J = 5.2 Hz, 4H); 3.09 (t, J = 5.4 Hz, 4H); 4.92 (s, 2H); 7.18–
7.22 (m, 1H); 7.26–7.30 (m, 3H); EIMS m/z 278 (M+). Anal. Calcd
for C14H15ClN2O2: C, 60.33; H, 5.42; Cl, 12.72; N, 10.05. Found: C,
60.42; H, 5.43; Cl, 12.70; N, 10.03.
4.5.4.26.
3-(3,4-Dimethoxyphenyl)-4-(piperazin-1-yl)furan-
2(5H)-one (4e4). White powder, 61%, mp 122–124 °C, 1H NMR
(DMSO-d6): 2.66 (t, J = 5.2 Hz, 4H); 3.07 (t, J = 5.4 Hz, 4H); 3.72 (s,
3H); 3.75 (s, 3H); 4.93 (s, 2H); 6.74 (dd, J = 8.4 Hz, J = 2.1 Hz, 1H);
6.76 (d, J = 2.0 Hz, 1H); 6.94 (d, J = 8.4 Hz, 1H); EIMS m/z 304
(M+). Anal. Calcd for C16H20N2O4: C, 63.14; H, 6.62; N, 9.20. Found:
C, 63.22; H, 6.61; N, 9.18.
4.5.4.18. 3-(3-Chlorophenyl)-4-(4-methylpiperazin-1-yl)furan-
2(5H)-one (4d5). Colorless crystal, 68%, mp 118–121 °C, 1H
NMR (CDCl3): 2.31 (s, 3H); 2.41 (t, J = 5.1 Hz, 4H); 3.22 (t,
J = 4.9 Hz, 4H); 4.76 (s, 2H); 7.16–7.21 (m, 1H); 7.23–7.32 (m,
3H); EIMS m/z 292 (M+). Anal. Calcd for C15H17ClN2O2: C, 61.54;
H, 5.85; Cl, 12.11; N, 9.57. Found: C, 61.41; H, 5.86; Cl, 12.13; N,
9.58.
4.5.4.27. 4-(Cyclohexylamino)-3-(3,4-dimethoxyphenyl)furan-
2(5H)-one (4e5). Colorless crystal, 73%, mp 124–125 °C, 1H NMR
(CDCl3): 1.15–1.41 (m, 6H); 1.73–1.84 (m, 2H); 1.91–1.99 (m,
2H); 3.01–3.12 (m, 1H); 3.89 (s, 3H); 3.90 (s, 3H); 4.81 (s, 2H);
5.17 (d, J = 9.1 Hz, 1H); 6.91 (s, 2H); 7.10 (s, 1H); EIMS m/z 317
(M+). Anal. Calcd for C18H23NO4: C, 68.12; H, 7.30; N, 4.41. Found:
C, 68.20; H, 7.29; N, 4.42.
4.5.4.19.
3-(3-Chlorophenyl)-4-(2-morpholinoethylamino)
furan-2(5H)-one (4d6). Light yellow crystal, 82%, mp 124–
127 °C, 1H NMR (CDCl3): 2.51 (t, J = 4.6 Hz, 4H); 2.63 (t, J = 6.0 Hz,
2H); 3.24 (dt, J = 6.4 Hz, J = 5.3 Hz, 2H); 3.74 (t, J = 4.6 Hz, 4H);
4.78 (s, 2H); 6.41 (br s, 1H); 7.19–7.25 (m, 1H); 7.36 (t, J = 7.9 Hz,
1H); 7.40–7.52 (m, 2H); EIMS m/z 322 (M+). Anal. Calcd for
4.5.4.28. 3-(3,4-Dimethoxyphenyl)-4-(2-morpholinoethylami-
no)furan-2(5H)-one (4e6). White powder, 78%, mp 143–145 °C,
1H NMR (CDCl3): 2.52 (t, J = 4.6 Hz, 4H); 2.66 (t, J = 6.0 Hz, 2H);
3.26 (dt, J = 6.4 Hz, J = 5.3 Hz, 2H); 3.75 (t, J = 4.6 Hz, 4H); 3.89 (s,
3H); 3.91 (s, 3H); 4.79 (s, 2H); 6.43 (br s, 1H); 6.76–6.84 (m, 3H);
EIMS m/z 348 (M+). Anal. Calcd for C18H24N2O5: C, 62.05; H, 6.94;
N, 8.04. Found: C, 62.13; H, 6.93; N, 8.02.
C16H19ClN2O3: C, 59.54; H, 5.93; Cl, 10.98; N, 8.68. Found: C,
59.46; H, 5.94; Cl, 11.00; N, 8.69.
4.5.4.20. 3-(3-Chlorophenyl)-4-(propylamino)furan-2(5H)-one
(4d7). Colorless crystal, 74%, mp 134–136 °C, 1H NMR (CDCl3):
1.00 (t, J = 7.3 Hz, 3H); 1.59–1.71 (m, 2H); 3.14 (q, J = 6.8 Hz, 2H);
4.79 (s, 2H); 5.33 (br s, 1H); 7.20–7.24 (m, 1H); 7.30–7.36 (m,
2H); 7.44–7.47 (m, 1H); EIMS m/z 251 (M+). Anal. Calcd for
4.5.4.29. 4-(Butylamino)-3-(3,4-dimethoxyphenyl)furan-2(5H)-
one (4e7). White powder, 92%, mp 70–72 °C, 1H NMR (CDCl3):
0.96 (t, J = 7.3 Hz, 3H); 1.32–1.45 (m, 2H); 1.52–1.63 (m, 2H);
3.14 (q, J = 6.8 Hz, 2H); 3.88 (s, 3H); 3.90 (s, 3H); 4.78 (s, 2H);
5.21 (br s, 1H); 6.90 (s, 2H); 7.10 (s, 1H); EIMS m/z 291 (M+). Anal.
C13H14ClNO2: C, 62.03; H, 5.61; Cl, 14.08; N, 5.56. Found: C,
61.96; H, 5.62; Cl, 14.10; N, 5.56.

Z.-P. Xiao et al. / Bioorg. Med. Chem. 19 (2011) 1571–1579
1579
3. Xiao, Z.-P.; Xue, J.-Y.; Tan, S.-H.; Li, H.-Q.; Zhu, H.-L. Bioorg. Med. Chem. 2007, 15,
4212.
4. Xiao, Z.-P.; Fang, R.-Q.; Li, H.-Q.; Xue, J.-Y.; Zheng, Y.; Zhu, H.-L. Eur. J. Med.
Chem. 2008, 43, 1828.
Calcd for C16H21NO4: C, 65.96; H, 7.27; N, 4.81. Found: C, 65.85; H,
7.28; N, 4.81.
5. Cotelle, P.; Cotelle, N.; Teissier, E.; Vezin, H. Bioorg. Med. Chem. 2003, 11, 1087.
6. Lattmann, E.; Dunn, S.; Niamsanit, S.; Sattayasai, N. Bioorg. Med. Chem. Lett.
2005, 15, 919.
7. Weber, V.; Rubat, C.; Duroux, E.; Lartigue, C.; Madesclaire, M.; Coudert, P.
Bioorg. Med. Chem. 2005, 13, 4552.
8. Weber, V.; Coudert, P.; Rubat, C.; Duroux, E.; Vallee-Goyet, D.; Gardette, D.;
Bria, M.; Albuisson, E.; Leal, F.; Gramain, J. C.; Couquelet, J.; Madesclaire, M.
Bioorg. Med. Chem. 2002, 10, 1647.
9. Campbell, A. C.; Maidment, M. S.; Pick, J. H.; Stevenson, D. F. M. J. Chem. Soc.,
Perkin Trans. 1 1985, 1567.
4.5.4.30.
4-(Benzylamino)-3-(3,4-dimethoxyphenyl)furan-
2(5H)-one (4e8). Colorless crystal, 87%, mp 193–195 °C, 1H NMR
(CDCl3): 3.87 (s, 3H); 3.88 (s, 3H); 4.36 (d, J = 6.2 Hz, 2H); 4.78 (s,
2H); 5.60 (t, J = 6.0 Hz, 1H); 6.90 (d, J = 8.2 Hz, 1H); 6.94 (dd,
J = 8.2 Hz, J = 1.8 Hz, 1H); 7.12 (d, J = 1.7 Hz, 1H); 7.25–7.44 (m,
5H); EIMS m/z 325 (M+). Anal. Calcd for C19H19NO4: C, 70.14; H,
5.89; N, 4.31. Found: C, 70.01; H, 5.90; N, 4.32.
10. Verniest, G.; De Kimpe, N. Synlett 2005, 0947.
11. Harrison, W. T. A.; Kumar, C. S. C.; Yathirajan, H. S.; Ashalathac, B. V.; Narayana,
B. Acta Crystallogr., Sect. E 2010, 66, o2477.
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2010, 66, o2531.
13. Guzei, I. A.; Langenhan, J. M.; Chung, Y. J. Acta Crystallogr., Sect. E 2002, 58, o65.
14. Burkhardt, A.; Eriksson, L.; Widmalm, G.; Cumpstey, I. Acta Crystallogr., Sect. E
2009, 65, o633.
15. Qiu, X.; Janson, C. A.; Smith, W. W.; Green, S. M.; McDevitt, P.; Johanson, K.;
Carter, P.; Hibbs, M.; Lewis, C.; Chalker, A.; Fosberry, A.; Lalonde, J.; Berge, J.;
Brown, P.; Houge-Frydrych, C. S.; Jarvest, R. L. Protein Sci. 2001, 10, 2008.
16. Berge, J. M.; Broom, N. J. P.; Houge-Frydrych, C. S. V.; Jarvest, R. L.; Mensah, L.;
Mcnair, D. J.; O’hanlon, P. J.; Pope, A. J.; Rittenhouse, S. J. Antibiot. 2000, 53,
1282.
17. Stefanska, A. L.; Coates, N. J.; Mensah, L. M.; Pope, A. J.; Ready, S. J.; Warr, S. R. J.
Antibiot. 2000, 53, 345.
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2009, 44, 239.
4.5.4.31.
3-(3-Bromophenyl)-4-(dimethylamino)furan-2(5H)-
one (4f1). White powder, 84%, mp 127–129 °C, 1H NMR (CDCl3):
3.28 (s, 6H); 4.81 (s, 2H); 7.23 (t, J = 8.4 Hz, 1H); 7.33 (d,
J = 8.4 Hz, 1H); 7.38 (d, J = 8.2 Hz, 1H); 7.43 (s, 1H); EIMS m/z 281
(M+). Anal. Calcd for C12H12BrNO2: C, 51.09; H, 4.29; Br, 28.32; N,
4.96. Found: C, 51.13; H, 4.29; Br, 28.33; N, 4.95.
Acknowledgments
The work was financed by Scientific Research Fund of Hunan
Provincial Education Department (Project 09B083) of China, by a
Grant (Project JSDXKYZZ0801) from Jishou University for talent
introduction, China and by aid program for Science and Technology
Innovative Research Team (Chemicals of Forestry Resources and
Development of Forest Products) in Higher Educational Institutions
of Hunan Province.
20. Jarvest, R. L.; Berge, J. M.; Berry, V.; Boyd, H. F.; Brown, M. J.; Elder, J. S.; Forrest,
A. K.; Fosberry, A. P.; Gentry, D. R.; Hibbs, M. J.; Jaworski, D. D.; O’Hanlon, P. J.;
Pope, A. J.; Rittenhouse, S.; Sheppard, R. J.; Slater-Radosti, C.; Worby, A. J. Med.
Chem. 2002, 45, 1959.
21. Hudson, I. R. J. Hosp. Infect. 1994, 27, 81.
22. Chiou, C. C.; Mavrogiorgos, N.; Tillem, E.; Hector, R.; Walsh, T. J. Antimicrob.
Agents Chemother. 2001, 45, 3310.
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