Synthesis and antimicrobial evaluation of new benzofuran derivatives

Article abstract of DOI:10.1016/j.ejmech.2011.04.053

Thirteen compounds, based on benzofuran skeleton bearing aryl substituents at its C-3 position through methanone linker, were synthesized and screened for their antibacterial and antifungal activities against four bacteria Escherichia coli, Staphylococcus aureus, Methicillin-resistant S. aureus, Bacillus subtilis, and a fungus Candida albicans. Four hydrophobic benzofuran analogs were found to exhibit favorable antibacterial activities (MIC₈₀ = 0.39-3.12 μg/mL), which were better than the control drugs.

Full text of DOI:10.1016/j.ejmech.2011.04.053

European Journal of Medicinal Chemistry 46 (2011) 3526e3530
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Short communication
Synthesis and antimicrobial evaluation of new benzofuran derivatives
1
1
*
Xizhen Jiang , Wenlu Liu , Wei Zhang, Faqin Jiang, Zhe Gao, Hao Zhuang, Lei Fu
School of Pharmacy, Shanghai Jiao Tong University, No. 800 Dongchuan Rd., Shanghai 200240, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Thirteen compounds, based on benzofuran skeleton bearing aryl substituents at its C-3 position through
methanone linker, were synthesized and screened for their antibacterial and antifungal activities against
four bacteria Escherichia coli, Staphylococcus aureus, Methicillin-resistant S. aureus, Bacillus subtilis, and
a fungus Candida albicans. Four hydrophobic benzofuran analogs were found to exhibit favorable anti-
Received 6 December 2010
Received in revised form
20 April 2011
Accepted 21 April 2011
Available online 28 April 2011
bacterial activities (MIC80 ¼ 0.39e3.12
m
g/mL), which were better than the control drugs.
Ó 2011 Elsevier Masson SAS. All rights reserved.
Keywords:
Benzofuran
Stilbenoid
Anti-microorganism
Synthesis
1. Introduction
of the benzofuran ring. In this report, we have purposely left
40-methoxyphenyl unit at the C-2 position to eliminate contribu-
tions from C-2 substitutions. In natural products, corsifuran C
analogs bearing the 4-methoxyphenyl substituent at the C-2 posi-
tion were reported to have no antimicrobial activity. We introduced
the carbonyl group between the aryl ring and benzofuran at the C-3
position, which is different from oligostilbenes, to evaluate the
effects of substituents at the C-3 position on antimicrobial activities
(Fig. 3).
Benzofuran derivatives are of special interest to natural product
researchers for their biological activities and potential applications
as pharmacological agents, e.g. corsifuran C (Fig. 1) [1e4]. Specifi-
cally, several benzofuran ring systems bearing various substituents
at C-2 and C-3 positions are widely distributed in nature, the stil-
benoids structural compounds, e.g. an oligostilbene derivative
viniferin (Fig. 1), are known to possess antimicrobial, antiviral,
antioxidant, antifungal, and antitumor activities [5e10].
Moreover, compounds containing methanone linker between
the aromatic rings and benzofuran at the C-3 position had been
investigated and reported as a uricosuricagent, a vasodilator, and
a selective estrogen receptor modulator, such as benzbromarone
and raloxifene (Fig. 2) [11e14]. In addition, phenyl(2-
phenylbenzofuran-3-yl)methanone derivatives, e.g. SKF-64346,
had been demonstrated to possess neuroprotective and anti-
tumor activities [15]. As for antimicrobial activities of benzofuran
families, researches have so far demonstrated that the antimicro-
bial activities of benzofuran families are a combination of substi-
tutions at C-2 and C-3 positions of the benzofuran ring [16e23].
In our effort to search for better antimicrobial agents resulting
from C-2 and C-3 substitutions, individually and collectively, we
have initiated a study focusing on substitutions at the C-3 position
2. Synthetic chemistry and biological evaluation
2.1. Synthetic chemistry
The benzofuran biphenyls described in this paper were
prepared according to the synthetic Scheme 1 [24,25]. In Scheme 1,
iodination of phenol 1 with NaI in the presence of NaOH and NaClO
at low temperature (0 ꢀC) gave the monoiodine-phenol 2, which
upon treatment with acetyl chloride produced intermediate 3.
Coupling of 3 with 1-ethynyl-4-methoxybenzene, using the Sono-
gashira protocol Pd(PPh3)2Cl2/CuI/Et3N, afforded diphenylethyne 4.
Compound 4 underwent an intra-molecular cyclization in potas-
sium carbonate to furnish benzofuran 5. Treatment of commercially
available benzoic acids with SOCl2 followed by the addition of 5 and
tin (IV) chloride, using the FriedeleCrafts procedure furnished
compounds 7 (7a-h). Acetylated compounds 7 were upon hydro-
lysis with KOH, resulting in their respective phenolic compounds
7ie7m (Table 1).
* Corresponding author. Tel.: þ86 21 34204791; fax: þ86 21 34204787.
E-mail address: leifu@sjtu.edu.cn (L. Fu).
1
Co-first authors.
0223-5234/$ e see front matter Ó 2011 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2011.04.053

X. Jiang et al. / European Journal of Medicinal Chemistry 46 (2011) 3526e3530
3527
Fig. 1. Aryl benzofuran derivatives and oligostilbene derivatives.
2.2. Biological evaluation
Fig. 3. Structure of synthesized compounds (7ae7m).
As one of the largest groups of secondary plant metabolites,
stilbenoids compounds were reported to be the defense response
to microbial infections. Therefore, it was meaningful to investigate
the antimicrobial activity for the synthesized compounds in vitro
against the Gram-positive bacteria Staphylococcus aureus (ATCC
29213), Bacillus subtilis (ATCC 33712), Methicillin-resistant S. aureus
(ATCC 700699), the Gram-negative bacteria Escherichia coli (ATCC
11303), and fungi Candida albicans (ATCC 6258), following the
procedure for the microtiter broth dilution method of the National
Committee for Clinical Laboratory Standards (NCCLS) for suscepti-
bility testing [26,27]. The minimal inhibitory concentration (MIC) is
defined as the amount of compound required for >80% inhibition of
bacterial growth, which made the visible clarity [8,28e30].
Resveratrol, Ceftazidime, Cefotaxime, Sodium penicillin, Micona-
zole nitrate, and Ketoconazole were used as control drugs. The
observed data on the antimicrobial activity of the compounds and
control drugs are given in Table 2.
3.12
group at C-30 position, compound 7k, also had similar activities
against all four bacteria as compound 7i (MIC80 ¼ 0.39e0.78 g/mL).
Unexpectedly, compound 7l, when the hydroxyl group appeared at
C-20 position, has no activity against the bacteria (MIC80 > 200
g/
mL). On the other hand, compounds with the methylation of the
hydroxyl group would reduce the solubility and decrease their
antimicrobial abilities, such as compounds 7a versus 7k and 7b
versus 7i. Much different from the natural products, compounds
7ee7h with the halogen atoms substituents showed no antibacte-
rial activity, whereas 7h had favorable activity against B. subtilis with
mg/mL against E. coli and B. subtilis. The presence of hydroxyl
m
m
MIC80 of 0.78 mg/mL. All of the tested compounds showed no activity
against C. albicans.
4. Conclusions
Thirteen new compounds with different substitutes at the C-3
position were prepared using reported methodologies. Surveying
the data presented in Table 2, we have demonstrated that
compounds with hydroxyl groups at C-30 or C-40 position had dis-
played antimicrobial activities similar to the findings with oligos-
tilbene derivatives. Our results also indicated that the methanone
linker makes no significant improvement from that of oligos-
tilbenes in terms of antibacterial activities studied [5]. In addition,
the hydroxyl groups on the aromatic ring enhanced the antimi-
crobial activity, whereas the methoxyl groups and halogen atoms
reduced the activities.
3. Results and discussion
In this present work, a series of thirteen new benzofuran
derivatives were synthesized starting from 2-(4-methoxyphenyl)-
5-methylbenzofuran (5) and benzoyl chloride (6) through the
FriedeleCrafts reaction. Their 1H NMR spectra suggested the pres-
ence of one characteristic ABX system [
7.12e7.19 (d, 1H, Hc), and 7.39e7.45 (d, 1H, Hd)], one methyl singlet
2.40e2.46 (s, 3H)], and two doublet signals of 1,4-substituted
benzene ring [ 6.75e6.86 (d, 2H) and 7.46e7.63 (d, 2H)] in each
case, which were consistent with those of 5. Furthermore, the
absence of the signal of Ha [ 6.84 (s, 1H)] revealed the substituent
d 7.26e7.51 (s, 1H, Hb),
[
d
d
d
5. Materials and methods
at the C-3 position, respectively.
Preliminary anti-microorganism tests with thirteen compounds
(Table 2) have established some interesting structure-activity rela-
tionships. Compound 7i, with a hydroxyl group at C-40, displayed
the excellent antibacterial activities against S. aureus and MRSA with
5.1. Chemistry
The 1H NMR spectra were recorded at 300 MHz on a Varian EM-
360 spectrometer using TMS as an internal standard. Splitting
patterns are designated as follows: s, singlet; d, doublet; t, triplet;
m, multiplet. Chemical shift values are given in parts per million
and coupling constants (J) in Hertz. The mass spectra were recorded
MIC80 values of 0.39 and 0.78 mg/mL, respectively, as compared to
the positive control drugs. Its activities against E. coli and B. subtilis
(Table 2) are comparable to that of Sodium penicillin against E. coli
and that of Cefotaxime against B.subtilis, respectively. Compounds 7j
and 7m, with additional substituents at C-30 position, had shown
medium antimicrobial activities with MIC80 values from 0.78 to
c
a
b
d
e
Scheme 1. Reagents and conditions (a) NaI, NaOH, NaClO, H2O,
0
ꢀC; (b) Ac2O,
pyridine; (c) Pd(PPh3)2Cl2 (2%), CuI (4%) and 1.2 equiv. 1-ethynyl-4-methoxybenzene,
Et3N, DMF, 60 ꢀC; (d) K2CO3, methanol; (e) i) RCOCl, SnCl4, CH2Cl2, ii) KOH, EtOH,
H2O (for 7ie7m).
Fig. 2. Structure of benzbromarone, raloxifene and SKF-64346.

3528
X. Jiang et al. / European Journal of Medicinal Chemistry 46 (2011) 3526e3530
Table 1
palladium (II) (44 mg, 0.06 mmol), and copper iodide (24 mg,
0.13 mmol) in DMF. After the reaction vessel was sealed, trie-
thylamine (0.88 mL, 6.32 mmol) and 1-ethynyl-4-methoxy-
benzene (0.84 g, 6.32 mmol) in DMF were injected through the
septum. The reaction mixture was heated for 6 h at 60 ꢀC. Purifi-
cation was performed by flash chromatography, and an amor-
phous solid was obtained. Yield 80%; m.p. 58e60 ꢀC; EI-MS m/z
281.3; 1H NMR (300 MHz, CDCl3): 2.33 (s, 3H, COMe), 2.35 (s, 3H,
Me), 3.83 (s, 3H, OMe), 6.87 (d, 2H, ArH, J ¼ 8.7 Hz), 6.99 (d, 1H,
ArH, J ¼ 8.4 Hz), 7.13 (dd, 1H, ArH, J ¼ 9.0, 1.5 Hz), 7.36 (d, 1H, ArH,
J ¼ 0.6 Hz), 7.42 (d, 2H, ArH, J ¼ 9.0 Hz).
Structures of targeted compounds, and their respective MS, m.p. and yield values.
R
Modular
25H22O5
C24H20O4
C25H22O5
C26H24O6
M.S
m.p.(ꢀC) Yield (%)
7a 3,5-dimethoxyphenyl
7b 4-methoxyphenyl
7c 2,3-dimethoxyphenyl
7d 3,4,5-trimethoxyphenyl
7e 4-chlorophenyl
C
403.1
373.2
403.1
433.1
oil
oil
84e88
56e60
58e62
49%
64%
63%
63%
37%
C23H17ClO3 342.2
23H16Cl2O3 411.0
7f 3,5-dichlorophenyl
7g 2-bromo-4,5-difluorophenyl C23H15BrF2O3 457.0/459.0 92e94
C
102e106 70%
71%
C23H17BrO3 421.0/422.1 98e100 71%
7h 2-bromophenyl
7i 4-hydroxyphenyl
7j 4-hydroxy-3-methylphenyl C24H20O4
7k 3-hydroxy-5-methoxyphenyl C24H20O5
7l 2-hydroxy-3-methoxyphenyl C24H20O5
C23H18O4
359.1
373.1
389.1
389.3
485.0
166e170 48%
oil 65%
140e144 52%
oil 57%
170e172 35%
5.1.4. Synthesis of 2-(4-methoxyphenyl)-5-methylbenzofuran (5)
To a solution of compound 4 (0.6 g, 2.3 mmol) in methanol was
added potassium carbonate (0.79 g, 5.75 mmol). The reaction
mixture was heated to 60 ꢀC overnight, then being left to cool. The
reaction was poured onto EtOAc, washed with brine, and dried over
anhydrous sodium sulfate. Purification was performed by flash
chromatography, and an amorphous solid was obtained. Yield 90%;
m.p. 170e172 ꢀC; EI-MS m/z 239.2; 1H NMR (300 MHz, CDCl3): 2.47
(s, 3H, Me), 3.80 (s, 3H, OMe), 6.84 (s, 1H, ArH), 6.99 (d, 2H, ArH,
J ¼ 8.7 Hz), 7.08 (d, 1H, ArH, J ¼ 7.5 Hz), 7.36 (s, 1H, ArH), 7.40 (d, 1H,
ArH, J ¼ 8.4 Hz), 7.81 (d, 2H, ArH, J ¼ 8.7 Hz).
7m 4-hydroxy-3-iodophenyl
C23H17IO4
on an Esquire-LC-00075 mass spectrometer (Bruker). All reactions
were followed by TLC (silica gel, aluminum sheets 60 F254).
5.1.1. Synthesis of 2-iodo-4-methylphenol (2)
To a solution of 4-methyphenol (2 g, 18.5 mmol), NaOH (0.74 g,
18.5 mmol), and NaI (2.77 g, 18.5 mmol) in methanol 50 mL, was
added dropwise 5% NaClO 30 mL over 30 min, taking care to keep
the mixture below 0 ꢀC. After being stirred overnight at room
temperature, the mixture was quenched by Na2S2O3, extracted
with Et2O (50 mL ꢁ 3). The organic layer was washed by brine and
dried over Na2SO4. The purification was carried out by flash chro-
matography, yielding pale yellow oil. Yield 17%; EI-MS m/z 234.6;
1H NMR (300 MHz, CDCl3): 2.42 (s, 3H, Me), 5.09 (brs, 1H, OH), 6.87
(d, 1H, ArH, J ¼ 8.1 Hz), 7.03 (d, 1H, ArH, J ¼ 8.1 Hz), 7.46 (s, 1H, ArH).
5.1.5. General procedures for benzoyl chloride (6ae6m)
The selected acid was refluxed in thionyl chloride for 2e3 h, and
then the solution was cooled to room temperature, and the
remaining thionyl chloride was evaporated to afford the acyl
chloride, which was used without further purification.
5.1.6. General procedure for (3,5-dimethoxyphenyl)(2-(4-methoxy-
phenyl)-5-methylbenzofuran-3-yl)methanone (7a)
5.1.2. Synthesis of 2-iodo-4-methylphenyl acetate (3)
An excess of acetic anhydride (0.5 mL) was added to a solution of
2 (0.74 g, 3.16 mmol) in pyridine. After being stirred for 2 h, the
reaction was poured onto EtOAc, washed with 2 N HCl, 5% NaHCO3
and brine. The organic layers was dried over anhydrous sodium
sulfate, filtered, and evaporated under pressure. The residue was
directly used for the next reaction without further purification.
SnCl4 (1.2 eq.) was added dropwise to a mixture of 5 (50 mg,
0.21 mmol) and the 3,5-dimethoxybenzoyl chloride (1.2 eq.) in dry
dichloromethane and the resulting solution was stirred at room
temperature overnight. The reaction was quenched with ice and
stirred for 1 h. The organic layer was separated and the aqueous
layer was extracted with dichloromethane. The combined organic
extracts were washed with brine, dried over sodium sulfate. Puri-
fication was performed by flash chromatography, and the yellow oil
was obtained. 1H NMR (300 MHz, CDCl3): 2.41 (s, 3H, Me), 3.69 (s,
6H, OMe), 3.80 (s, 3H, OMe), 6.57 (s, 1H, ArH), 6.81 (d, 2H, ArH,
J ¼ 9.0 Hz), 6.99 (s, 1H, ArH), 7.00 (s, 1H, ArH), 7.16 (d, 1H, ArH,
J ¼ 8.1 Hz), 7.43 (d, 1H, ArH, J ¼ 7.2 Hz), 7.42 (brs, 1H, ArH), 7.58 (d,
2H, ArH, J ¼ 8.7 Hz). 13C NMR (75 MHz, CDCl3): 191.5, 160.3, 160.2,
157.6,151.7,139.2,132.9,129.5,128.2,125.8,121.9,120.6,114.2,113.4,
110.0, 106.9, 105.7, 55.1, 54.9, 20.9. HRMS [ESI (þ) -MS]: C25H22O5
[M þ H]þ m/z, calc. 403.1545, found 403.1542.
5.1.3. Synthesis of 2-((4-methoxyphenyl)ethynyl)-4-methylphenyl
acetate (4)
Into a round-bottomed flask, stirred magnetically, were placed
3
(0.78 g, 3.16 mmol), dichloro-bis-(triphenylphosphine)-
Table 2
In vitro antimicrobial activity of compounds (7ae7m).
Compounds
Minimum inhibitory concentration (mg/mL)
E. coli
S. aureus
MRSA
B. subtilis
C. albicans
7a
7b
7c
7d
7e
7f
7g
7h
7i
7j
7k
7l
>200
>200
>200
>200
>200
>200
>200
>200
0.78
0.78
0.78
>200
3.12
>200
>200
0.78
25
>200
>200
>200
>200
>200
>200
>200
>200
<0.39
0.78
<0.39
>200
0.78
0.78
3.12
3.12
25
>200
>200
>200
>200
>200
>200
>200
>200
0.78
0.78
0.78
>200
0.78
12.5
3.12
3.12
25
>200
>200
>200
>200
>200
>200
>200
0.78
0.78
1.56
0.78
>200
1.56
6.25
0.78
<0.39
25
>200
>200
>200
>200
>200
>200
>200
>200
>200
>200
>200
>200
>200
e
5.1.6.1. (4-Methoxyphenyl)(2-(4-methoxyphenyl)-5-methylbenzofuran-
3-yl)methanone (7b). The title compound was obtained by the
treatment of 5 and 4-methoxybenzoyl chloride as described for 7a.
1H NMR (300 MHz, CDCl3): 2.41 (s, 3H, Me), 3.80 (s, 3H, OMe), 3.89
(s, 3H, OMe), 6.76 (d, 2H, ArH, J ¼ 8.7 Hz), 6.81 (d, 2H, ArH,
J ¼ 8.7 Hz), 7.12 (d, 1H, ArH, J ¼ 7.2 Hz), 7.29 (s, 1H, ArH), 7.42 (d, 1H,
ArH, J ¼ 8.1 Hz), 7.61 (d, 2H, ArH, J ¼ 9.3 Hz), 7.79 (d, 2H, ArH,
J ¼ 8.7 Hz). HRMS [ESI (þ) -MS]: C24H20O4 [M þ H]þ m/z, calc.
373.1440, found 373.1438.
7m
Ceftazidime
Cefotaxime
Sodium penicillin
Resveratrol
Ketoconazole
Miconazole nitrate
5.1.6.2. (2,3-Dimethoxyphenyl)(2-(4-methoxyphenyl)-5-methyl-
benzofuran-3-yl)methanone (7c). The title compound was obtai-
ned by the treatment of 5 and 2,3-dimethoxybenzoyl chloride as
described for 7a. 1H NMR (300 MHz, CDCl3): 2.41 (s, 3H, Me), 3.77 (s,
3H, OMe), 3.78 (s, 3H, OMe), 3.82 (s, 3H, OMe), 6.76 (d, 2H, ArH,
J ¼ 8.7 Hz), 6.89 (m, 3H, ArH), 7.13 (d, 1H, ArH, J ¼ 8.1 Hz), 7.39 (d,1H,
e
e
>200
<0.39
<0.39
e
e
e
e
e
e
e
e
(e) means not used in experiment.

X. Jiang et al. / European Journal of Medicinal Chemistry 46 (2011) 3526e3530
3529
ArH, J ¼ 8.1 Hz), 7.51 (s, 1H, ArH), 7.58 (d, 2H, ArH, J ¼ 8.7 Hz). HRMS
[ESI (þ) -MS]: C25H22O5 [M þ H]þ m/z, calc. 403.1545, found 403.1544.
5.1.6.9. (4-Hydroxy-3-methylphenyl)(2-(4-methoxyphenyl)-5-meth-
ylbenzofuran-3-yl)methanone (7j). The title compound was ob-
tained by the treatment of
5
and 4-(chlorocarbonyl)-2-
5.1.6.3. (3,4,5-Trimethoxyphenyl)(2-(4-methoxyphenyl)-5-methyl-
benzofuran-3-yl)methanone (7d). The title compound was obtai-
ned by the treatment of 5 and 3,4,5-trimethoxybenzoyl chloride as
described for 7a. 1H NMR (300 MHz, CDCl3): 2.43 (s, 3H, Me), 3.71
(s, 6H, OMe), 3.80 (s, 3H, OMe), 3.88 (s, 3H, OMe), 6.82 (d, 2H, ArH,
J ¼ 9.0 Hz), 7.14 (brs, 2H, ArH), 7.17 (d, 1H, ArH, J ¼ 9.0 Hz), 7.45 (d,
1H, ArH, J ¼ 9.0 Hz), 7.51 (brs, 1H, ArH), 7.56 (d, 2H, ArH, J ¼ 8.7 Hz).
HRMS [ESI (þ) -MS]: C26H24O6 [M þ H]þ m/z, calc. 433.1651, found
433.1649.
methylphenyl acetate as described for 7i. 1H NMR (300 MHz,
CDCl3): 2.28 (s, 3H, Me), 2.42 (s, 3H, Me), 3.80 (s, 3H, OMe), 5.38
(brs, 1H, OH), 6.83 (d, 2H, ArH, J ¼ 8.7 Hz), 7.03 (d, 1H, ArH,
J ¼ 7.5 Hz), 7.15 (d, 1H, ArH, J ¼ 9.0 Hz), 7.28 (s, 1H, ArH), 7.34 (s, 1H,
ArH), 7.44 (d, 1H, ArH, J ¼ 8.7 Hz), 7.55 (s, 1H, ArH), 7.63 (d, 2H, ArH,
J ¼ 9.0 Hz). HRMS [ESI (þ) -MS]: C24H20O4 [M þ H]þ m/z, calc.
373.1440, found 373.1437.
5.1.6.10. (3-Hydroxy-5-methoxyphenyl)(2-(4-methoxyphenyl)-5-
methylbenzofuran-3-yl)methanone (7k). The title compound was
obtained by the treatment of 5 and 3-(chlorocarbonyl)-5-methox-
yphenyl acetate as described for 7i. 1H NMR (300 MHz, CDCl3): 2.41
(s, 3H, Me), 3.66 (s, 3H, OMe), 3.80 (s, 3H, OMe), 5.34 (brs, 1H, OH),
6.53 (t, 1H, ArH, J ¼ 2.3 Hz), 6.82 (d, 2H, ArH, J ¼ 9.0 Hz), 6.93 (brs,
2H, ArH), 7.14 (d, 1H, ArH, J ¼ 7.4 Hz), 7.39 (s, 1H, ArH), 7.42 (d, 1H,
ArH, J ¼ 8.7 Hz), 7.59 (d, 2H, ArH, J ¼ 9.0 Hz). HRMS [ESI (þ) -MS]:
C24H20O5 [M þ H]þ m/z, calc. 389.1389, found 389.1392.
5.1.6.4. (4-Chlorophenyl)(2-(4-methoxyphenyl)-5-methylbenzofuran-
3-yl)methanone (7e). The title compound was obtained by the
treatment of 5 and 4-chlorobenzoyl chloride as described for 7a. 1H
NMR (300 MHz, CDCl3): 2.41 (s, 3H, Me), 3.80 (s, 3H, OMe), 6.81 (d,
2H, ArH, J ¼ 8.4 Hz), 7.15 (d, 1H, ArH, J ¼ 8.4 Hz), 7.29 (d, 2H, ArH,
J ¼ 8.7 Hz), 7.36 (s, 1H, ArH), 7.43 (d, 1H, ArH, J ¼ 7.8 Hz), 7.56 (d, 2H,
ArH, J ¼ 9.6 Hz), 7.76 (d, 2H, ArH, J ¼ 8.7 Hz). HRMS [ESI (þ) -MS]:
C23H17ClO3 [M þ H]þ m/z, calc. 377.0944, found 377.0950.
5.1.6.11. (2-Hydroxy-3-methoxyphenyl)(2-(4-methoxyphenyl)-5-
methylbenzofuran-3-yl)methanone (7l). The title compound was
obtained by the treatment of 5 and 2-(chlorocarbonyl)-6-methox-
yphenyl acetate as described for 7i. 1H NMR (300 MHz, CDCl3): 2.40
(s, 3H, Me), 3.81 (s, 3H, OMe), 3.95 (s, 3H, OMe), 6.61 (t, 1H, ArH,
J ¼ 8.1 Hz), 6.86 (d, 2H, ArH, J ¼ 8.7 Hz), 7.03 (d, 1H, ArH, J ¼ 8.1 Hz),
7.13 (dd, 1H, ArH, J ¼ 7.8, 1.2 Hz), 7.15 (d, 1H, ArH, J ¼ 6.9 Hz), 7.27 (s,
1H, ArH,), 7.43 (d, 1H, ArH, J ¼ 8.7 Hz), 7.63 (d, 2H, ArH, J ¼ 8.7 Hz),
12.58 (s, 1H, OH). HRMS [ESI (þ) -MS]: C24H20O5 [M þ H]þ m/z, calc.
389.1389, found 389.1394.
5.1.6.5. (3,5-Dichlorophenyl)(2-(4-methoxyphenyl)-5-methylbenzo-
furan-3-yl)methanone (7f). The title compound was obtained by
the treatment of 5 and 3,5-dichlorobenzoyl chloride as described
for 7a. 1H NMR (300 MHz, CDCl3): 2.45 (s, 3H, Me), 3.80 (s, 3H,
OMe), 6.77 (d, 2H, ArH, J ¼ 9.0 Hz), 7.05e7.09 (m, 1H, ArH), 7.18
(d, 1H, ArH, J ¼ 9.0 Hz), 7.26 (s, 2H, ArH), 7.42 (d, 1H, ArH,
J ¼ 8.7 Hz), 7.46 (d, 2H, ArH, J ¼ 8.4 Hz), 7.67 (s, 1H, ArH,). HRMS
[ESI (þ) -MS]: C23H16Cl2O3 [M þ H]þ m/z, calc. 411.0554, found
411.0559.
5.1.6.6. (2-Bromo-4,5-difluorophenyl)(2-(4-methoxyphenyl)-5-meth-
ylbenzofuran-3-yl)methanone (7g). The title compound was obt-
ained by the treatment of 5 and 2-bromo-4,5-difluorobenzoyl
chloride as described for 7a. 1H NMR (300 MHz, CDCl3): 2.46 (s, 3H,
Me), 3.81 (s, 3H, OMe), 6.79 (d, 2H, ArH, J ¼ 8.7 Hz), 7.13 (dd, 1H,
ArH, J ¼ 10.3, 8.4 Hz), 7.19 (d, 1H, ArH, J ¼ 8.4 Hz), 7.30 (dd, 1H, ArH,
J ¼ 8.1, 6.9 Hz), 7.43 (d, 1H, ArH, J ¼ 8.4 Hz), 7.48 (d, 2H, ArH,
J ¼ 9.0 Hz), 7.68 (t, 1H, ArH, J ¼ 5.6 Hz). HRMS [ESI (þ) -MS]:
C23H15BrF2O3 [M þ H]þ m/z, calc. 457.0251, found 457.0260.
5.1.6.12. (4-Hydroxy-3-iodophenyl)(2-(4-methoxyphenyl)-5-methyl-
benzofuran-3-yl)methanone (7m). The title compound was ob-
tained by the treatment of 5 and 4-(chlorocarbonyl)-2-iodophenyl
acetate as described for 7i. 1H NMR (300 MHz, CDCl3): 2.42 (s, 3H,
Me), 3.83 (s, 3H, OMe), 6.86 (d, 2H, ArH, J ¼ 8.7 Hz), 6.88 (d, 1H, ArH,
J ¼ 7.5 Hz), 7.16 (d, 1H, ArH, J ¼ 9.0 Hz), 7.36 (brs, 1H, ArH), 7.44 (s,
1H, ArH), 7.45 (d, 1H, ArH, J ¼ 6.6 Hz), 7.62 (d, 2H, ArH, J ¼ 9.6 Hz),
7.71 (dd, 1H, ArH, J ¼ 8.1, 2.1 Hz), 8.28 (brs, 1H, OH). HRMS [ESI (þ)
-MS]: C23H17IO4 [M þ H]þ m/z, calc. 485.0250, found 485.0261.
5.1.6.7. (2-Bromophenyl)(2-(4-methoxyphenyl)-5-methylbenzofuran-
3-yl)methanone (7h). The title compound was obtained by the
treatment of 5 and 2-bromobenzoyl chloride as described for 7a. 1H
NMR (300 MHz, CDCl3): 2.42 (s, 3H, Me), 3.78 (s, 3H, OMe), 6.75 (d,
2H, ArH, J ¼ 9.0 Hz), 7.13e7.18 (m, 3H, ArH), 7.27e7.30 (m, 1H, ArH),
7.41 (d, 1H, ArH, J ¼ 8.7 Hz), 7.46e7.49 (m, 1H, ArH), 7.51 (d, 2H, ArH,
J ¼ 9.0 Hz), 7.53e7.56 (m, 1H, ArH). HRMS [ESI (þ) -MS]: C23H17BrO3
[M þ H]þ m/z, calc. 421.0439, found 421.0442.
5.2. Antimicrobial activities
The antimicrobial activities of the synthesized compounds were
determined by the minimum inhibitory concentration (MIC) in
accordance with NCCLS guideline M7-A6 and M38-P [26,27].
Pre-cultures of the tested bacteria were made by inoculating
10 mL of Luria-Bertani (LB) and incubating for 24 h at 37 ꢀC. The
tested fungus, C. albicans, was made by grown on Potato dextrose
agar (PDA) for more than three days at 28 ꢀC. The colonies were
harvested, suspended in sterile saline, and adjusted to a concen-
tration that yielded an absorbance similar to that of a 0.5 McFarland
standard in a spectrophotometer, bacteria at 625 nm or fungi at
530 nm, the equivalence of 1e2 ꢁ 108 cfu/mL. Then the samples
were further diluted 1:10,000 in LB or PDA to 1 ꢁ 104 cfu/mL.
For the test, from a stock solution of the compounds of 4 mg/mL
5.1.6.8. (4-Hydroxyphenyl)(2-(4-methoxyphenyl)-5-methylbenzofuran-
3-yl)methanone (7i). The title compound was obtained by the
treatment of 5 and 4-(chlorocarbonyl)phenyl acetate as described
for 7a. The ester was dissolved in aqueous ethanol solution with
KOH and stirred overnight. The solution was partially concentrated,
dispersed in dichloromethane and the organic phase was washed
with 1 N HCl, and brine; the organic phase was dried over sodium
sulfate and concentrated to yield pure compound. 1H NMR
(300 MHz, CDCl3): 2.41 (s, 3H, Me), 3.80 (s, 3H, OMe), 6.76 (d, 2H,
ArH, J ¼ 8.7 Hz), 6.81 (d, 2H, ArH, J ¼ 8.7 Hz), 7.12 (d, 1H, ArH,
J ¼ 7.2 Hz), 7.29 (s, 1H, ArH), 7.42 (d, 1H, ArH, J ¼ 8.1 Hz), 7.61 (d, 2H,
ArH, J ¼ 9.3 Hz), 7.79 (d, 2H, ArH, J ¼ 8.7 Hz), 8.10 (t, 1H, OH,
J ¼ 8.4 Hz). HRMS [ESI (þ) -MS]: C23H18O4 [M þ H]þ m/z, calc.
359.1283, found 359.1288.
in DMSO, 10
2 in 96-well plate. Using the multipipettes, 100
microorganisms were dispensed into wells from column 3 to
column 11. Another 200 L broth bacteria dilution was dispensed
into column 2, then being mixed up and down 6e8 times. With-
draw 100 L mixtures from column 2 and add this to column 3. This
made column 3 a two-fold dilution of column 2. Repeat the
procedure down to column 11. Discard 100 L from column 11
mL tested solution was pipette into the wells in column
m
L medium with
m
m
m

3530
X. Jiang et al. / European Journal of Medicinal Chemistry 46 (2011) 3526e3530
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rather than putting them in column 12. The compounds were
diluted two fold concentration from 200 g/mL to 0.39 g/mL, from
column 2 to column 11. Pipette 100 L of sterile medium into
column 1, and medium with microorganisms into column 12 as
control groups. After incubating another 24 h for bacteria or 48 h
for fungi, the lowest concentration of compounds that inhibited the
m
m
m
visible growth of the organism was considered as MIC80
.
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Acknowledgments
We thanked the National Comprehensive Technology Platforms
for Innovative Drug R&D, 2009ZX09301-007 for the financial
support. We also thanked Zhao’s Laboratory for the supplies about
the MIC80 test.
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