Synthesis and biological activity of 6-substituted 5-acetyl-4,7- dimethoxybenzofuran derivatives

Article abstract of DOI:10.1515/hc-2013-0081

In the search for new antimicrobial and anticancer agents, a series of (aryl/heteroaryl-piperazino-alkyl)-substituted derivatives of benzo[b]furans were prepared. All compounds were characterized by 1H NMR, 13C NMR, ESI-MS spectra and elemental analyses. Most of the investigated compounds had no antimicrobial activity (MIC > 512 mg/L) except for 2l, 2m and 2o, which showed activity against Candida albicans. None of the tested compounds showed significant anticancer activity in K562 and HeLa cells.

Full text of DOI:10.1515/hc-2013-0081

ꢁꢁꢁꢂ
ꢀHeterocycl. Commun. 2013; 19(4): 281–286
DOI 10.1515/hc-2013-0081ꢀ
Mariola Krawiecka*, Bożena Kuran, Jerzy Kossakowski, Marta Kierzkowska,
Grażyna Młynarczyk, Julia Kazmierczak-Barańska, Karolina Królewska and Marcin Cieślak
Synthesis and biological activity of 6-substituted
5-acetyl-4,7-dimethoxybenzofuran derivatives
Abstract: In the search for new antimicrobial and antican- results on the design and synthesis of new compounds
cer agents, a series of (aryl/heteroaryl-piperazino-alkyl)- with potential biological activity (Scheme 1).
substituted derivatives of benzo[b]furans were prepared.
1
All compounds were characterized by H NMR, 13C NMR,
ESI-MS spectra and elemental analyses. Most of the inves-
tigated compounds had no antimicrobial activity (MIC Results and discussion
ꢀ> ꢀ 512 mg/L) except for 2l, 2m and 2o, which showed activ-
ity against Candida albicans. None of the tested com-
Synthesis
pounds showed significant anticancer activity in K562 and
HeLa cells.
The synthesis of compounds 1a,b and 2a–p was accom-
plished as presented in Scheme 1. The starting compound
Keywords: antifungal activity; antimicrobial activity;
benzo[b]furans; cytotoxicity.
was 5-acetyl-6-hydroxy-4,7-dimethoxybenzofuran which
was alkylated with 1,2-dibromoethane or 1,3-dibromo-
propane to give the respective products 1a or 1b. The
*Corresponding author: Mariola Krawiecka, Department of Medical
Chemistry, Medical University of Warsaw, 3 Oczki Street, 02-007
Warsaw, Poland, e-mail: mariola.krawiecka@wum.edu.pl
Bożena Kuran and Jerzy Kossakowski: Department of Medical
Chemistry, Medical University of Warsaw, 3 Oczki Street, 02-007
Warsaw, Poland
Marta Kierzkowska and Grażyna Młynarczyk: Department
of Medical Microbiology, Medical University of Warsaw, 5
Chałubińskiego Street, 02-004 Warsaw, Poland
Julia Kazmierczak-Barańska, Karolina Królewska and Marcin
Cieślak: Department of Bioorganic Chemistry, Centre of Molecular
and Macromolecular Studies, Polish Academy of Sciences, 112
Sienkiewicza Street, 90-363 Łódź, Poland
final products 2a–p were prepared with good yields by
condensation of the intermediate product 1a or 1b with
the appropriate 1-aryl/heteroarylpiperazine in the pres-
ence of K2CO3 and KI in refluxing acetonitrile. The amino
derivatives were converted into their hydrochlorides.
1
All reported products showed H NMR, 13C NMR, ESI-MS
spectra and elemental analyses in agreement with the
assigned structures.
Antimicrobial activity
The obtained compounds 1a,b and 2a–p were tested
for their antimicrobial activity against aerobic bacteria:
Staphylococcus aureus, Escherichia coli, Stenotropho-
monas maltophilia and yeast strain Candida albicans and
Introduction
The benzofuran system, as an important pharmacophore, some (1a, 2a–e) against selected anaerobes Propionibac-
is present in numerous compounds isolated from natural terium acnes, Bacteroides thetaiotaomicron and Bacte-
sources as well as in synthetic products. These heterocy- roides fragilis.
clic compounds show a variety biological activity, includ-
Most of the investigated compounds showed no
ing antiarrhythmic, spazmolitic, antiviral, anticancer, antimicrobial activity and did not inhibit growth even
antifungal and anti-inflammatory properties [1–10]. The at the concentration of 512 mg/L. Some activity was
most recognized derivatives of the benzofurans are Khel- observed for compounds 2l, 2m and 2o. They were
linone and Visnaginone isolated from Ammi visnaga (Api- active against C. albicans. The compounds inhibited
aceae) [11].
the growth of yeast at a concentration of 512 mg/L.
Our research group obtained a large group of com- The highest activity was observed for compound 2o.
pounds which show antimicrobial, antiviral and cytotoxic For compounds 2l and 2m, the growth of fungi was
activities [12–15]. This article describes our latest research observed on the second day.
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282ꢀ ꢀM. Krawiecka et al.: 6-Substituted 5-acetyl-4,7-dimethoxybenzofuran derivatives
OMe O
OMe O
OMe O
A
B
Me
OH
Me
O(CH2)nBr
Me
O
O
O
O(CH2)n
N
N R
OMe
OMe
OMe
2a-p
1a-b
1a
2e
2k
: n = 2
: n = 3
: R = 2-pyrimidinyl; n = 2
: R = 2-Cl-Ph; n = 3
2l: R = 2-pyridyl; n = 3
2m: R = 2-pyrim idinyl; n = 3
2n
1b
2a
2b
2c
2f: R = 3-OMe-Ph; n = 2
2g: R = 3-Cl-Ph; n = 2
: R = Ph; n = 2
: R = 2-OMe-Ph; n = 2
: R = 2-Cl-Ph; n = 2
2h
: R = 4-NO2-Ph; n = 2
: R = 3-OMe-Ph; n = 3
2o: R = 3-Cl-Ph; n = 3
2p
2i: R = Ph; n = 3
2j
2d: R = 2-pyridyl; n = 2
: R = 2-OMe-Ph; n = 3
: R = 4-NO2-Ph; n = 3
Scheme 1ꢀSynthesis of compounds 2a–p; (A) Br(CH2)2Br or Br(CH2)3Br, K2CO3, acetonitrile; (B) 1-aryl/heteroarylpiperazine, K2CO3, KI.
(0.01 mol) and 1,2-dibromoethane (0.03 mol) or 1,3-dibromopropane
Cytotoxic properties
(0.03 mol). The mixture was heated under reflux for 7–15 h, then fil-
tered and concentrated. The residue was purified by column chroma-
The selected derivatives 1b, 2i, 2j, 2m, 2o and 2p were
tested for their cytotoxic properties in K562 and HeLa cells.
tography eluting with chloroform.
On the basis of dose-response curves it was not possible
to calculate IC50 values, which indicates that none of the
tested compounds show significant anticancer activity.
5-Acetyl-6-(2-bromoethoxy)-4,7-dimethoxybenzofuran
(1a)ꢀThis compound was obtained in 84% yield as a colorless oil;1H
NMR (DCl3: δ 7.59 (d, 1H, C2-H, J ꢀ= ꢀ 2.1 Hz), 6.88 (d, 1H, C3-H, J ꢀ= ꢀ 2.1 Hz),
4.36 (t, 2H, C1′-H, J ꢀ= ꢀ 6.3 Hz), 4.09 (s, 3H, -OCH3), 3.99 (s, 3H, -OCH3),
3.58 (t, 2H, -C2′-H, J ꢀ= ꢀ 6.3 Hz), 2.55 (s, 3H, -COCH3); 13C NMR: δ 31.5,
32.6, 60.6, 61.0, 73.8, 105.4, 115.8, 123.3, 133.3, 143.0, 143.6, 145.8, 147.9,
200.4; ESI-MS: m/z 343.17 [M+]. Anal. Calcd for C14H15BrO5: C, 49.00; H,
4.41. Found: C, 48.98; H, 4.39.
Conclusion
In the present study, we obtained and tested for antimi-
crobial and anticancer activity new aryl/heteroaryl-piper-
azino-alkyl derivatives of benzo[b]furans. The results show
that this class of benzofurans possess low antimicrobial
activity and do not show significant anticancer activity.
5-Acetyl-6-(3-bromopropoxy)-4,7-dimethoxybenzofuran
(1b)ꢀThis compound was obtained in 80% yield as a colorless oil;1H
NMR: δ 7.57 (d, 1H, C2-H, J ꢀ= ꢀ 2.1 Hz), 6.87 (d, 1H, C3-H, J ꢀ= ꢀ 2.1 Hz), 4.22–
4.14 (m, 2H, C3′-H), 4.09 (s, 3H, -OCH3), 3.99 (s, 3H, -OCH3), 3.62–3.58
(m, 2H, C1′-H), 2.55 (s, 3H, -COCH3), 2.29–2.21 (m, 2H, C2′-H); 13C NMR:
δ 30.1, 30.5, 33.3, 33.8, 61.6, 73.0, 105.5, 117.0, 124.7, 134.8, 144.5, 144.6,
145.1, 149.1, 202.4; ESI-MS: m/z 380.9 [M+]. Anal. Calcd for C15H17BrO5:
C, 50.44; H, 4.80. Found: C, 50.30; H, 4.59.
Experimental
Melting points were determined by the capillary method using the
Electrothermal 9100 apparatus and were uncorrected. Unless stated
otherwise, nuclear magnetic resonance spectra were recorded in
DMSO (dimethyl sulfoxide)-d6 on a Bruker VMNRS300 operating at
300 MHz (1H NMR) and 75 MHz (13C NMR). Mass spectral (electrospray
ionization, ESI) measurements were carried out on a Mariner Perspec-
tive – Biosystem instrument with a TOF detector. The spectra were
obtained in the positive ion mode with a declustering potential of
140–300 V. Elemental analyses were recorded using a CHN model 2400
Perkin-Elmer analyzer. Chromatographic columns were filled with
Merck Kieselgel 0.05–0.2 mm (70–325 mesh ASTM) silica gel. Reac-
tions were monitored by thin layer chromatography (TLC) on silica gel
(plates with 254 nm fluorescent indicator, layer thickness 0.2 mm, Kie-
selgel G., Merck), eluting with 9.8:0.2 or 9.5:0.5 chloroform/methanol.
Synthesis of 4-arylpiperazino derivatives
2a–p
A mixture of N-bromoalkyl derivative 1a or 1b (0.01 mol), a powdered
anhydrousK2CO3 (0.01mol),acatalyticamountofKIinacetone(30mL)
and a substituted piperazine (0.01 mol) was heated under reflux for
10–20 h, then filtered and concentrated. The residue was purified
by column chromatography eluting with chloroform or chloroform/
methanol, 50:0.2. All products were converted into their hydrochlo-
rides and the salts were crystallized from methanol/ether.
Hydrochloride of 5-acetyl-4,7-dimethoxy-6-[2-(4-phenylpiper-
azino)ethoxy]benzofuran (2a)ꢀThe hydrochloride salt was obtain-
ed in 60% yield as a colorless oil; 1H NMR: δ 10.92 (s, 1H, NH+), 8.08
(d, 1H, C2-H, J ꢀ= ꢀ 2.4 Hz), 7.30–7.24 (m, 3H, CH, C3-H), 7.04–7.01 (m, 2H,
CH), 6.87 (t, 1H, CH, J ꢀ= ꢀ 7.2 Hz), 4.40–4.37 (m, 2H, -CH2-piperazine),
4.06 (s, 3H, -OCH3), 4.00 (s, 3H, -OCH3), 3.90–3.86 (m, 2H, C1′-H),
3.68–3.65 (m, 2H, -CH2-piperazine), 3.58–3.50 (m, 5H, -COCH3, -CH2-
Synthesis of compounds 1a and 1b
A
solution of 5-acetyl-1-(6-hydroxy)-4,7-dimethoxybenzofuran piperazine), 3.30–3.13 (m, 4H, -CH2-piperazine); 13C NMR: δ 32.7, 45.3,
(0.01 mol) in acetonitrile (30 mL) was treated with anhydrous K2CO3 51.0, 54.9, 60.6, 61.1, 68.8, 105.5, 115.9, 116.2, 119.9, 123.0, 129.1, 133.4,
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M. Krawiecka et al.: 6-Substituted 5-acetyl-4,7-dimethoxybenzofuran derivativesꢀ
ꢀ283
142.6, 143.8, 146.2, 147.7, 149.5, 201.0; ESI-MS: m/z 425.2 [M+H+]. Anal. Hydrochloride of 5-acetyl-4,7-dimethoxy-6-[2-[4-(3-methoxy-
Calcd for C24H28N2O5‧HCl: C, 62.54; H, 6.34; N, 6.08. Found: C, 62.34; phenyl)piperazino]ethoxy]benzofuran (2f)ꢀThe hydrochloride
H, 6.14; N, 6.01.
salt was obtained in 76% yield as an oil;1H NMR: δ 10.94 (s, 1H, NH+),
8.08 (d, 1H, C2-H, J ꢀ= ꢀ 2.4 Hz), 7.25 (d, 1H, C3-H, J ꢀ= ꢀ 2.4 Hz), 7.16 (t,
1H, C-H, J ꢀ= ꢀ 8.2 Hz), 6.62–6.54 (m, 2H, C-H), 6.47–6.43 (m, 1H, C-H),
4.80–4.70 (m, 2H, -CH2-piperazine), 4.38 (t, 2H, -CH2-piperazine, J ꢀ= ꢀ
4.8 Hz), 4.06 (s, 3H, -OCH3), 4.00 (s, 3H, -OCH3), 3.90–3.86 (m, 2H,
-CH2-piperazine), 3.73 (s, 3H, -OCH3), 3.66–3.63 (m, 2H, C1′-H), 3.54–
3.53 (m, 2H, -CH2-piperazine), 3.28–3.21 (m, 2H, C2′-H), 2.50 (s, 3H,
-COCH3); 13C NMR: δ 32.6, 45.2, 50.9, 54.9, 54.9, 60.6, 61.1, 68.6, 102.1,
105.2, 105.5, 108.3, 116.2, 119.1, 123.0, 129.8, 133.4, 142.4, 143.9, 146.2,
147.7, 150.8, 160.2, 200.9; ESI-MS: m/z 455.3 [M+H+]. Anal. Calcd for
C25H30N2O6‧HCl: C, 61.16; H, 6.36; N, 5.71. Found: C, 61.20; H, 6.30; N,
5.68.
Hydrochloride of 5-acetyl-4,7-dimethoxy-6-[2-[4-(2-methoxy-
phenyl)piperazino]ethoxy]benzofuran (2b)ꢀThe hydrochloride
1
salt was obtained in 70% yield as a white powder; mp 174–176°C; H
NMR: δ 10.89 (s, 1H, NH+), 8.08 (d, 1H, C2-H, J ꢀ= ꢀ 2.4 Hz), 7.26 (d, 1H,
C-H, C3-H, J ꢀ= ꢀ 2.4 Hz), 7.06–6.88 (m, 4H, C-H), 4.39 (t, 2H, -CH2-piper-
azine, J ꢀ= ꢀ 4.8 Hz), 4.07 (s, 3H, -OCH3), 4.00 (s, 3H, -OCH3), 3.80 (s, 3H,
-OCH3), 3.65–3.62 (m, 2H, C1′-H), 3.56–3.53 (m, 4H, -CH2-piperazine,
C2′-H), 3.39–3.28 (m, 2H, -CH2-piperazine), 3.14–3.07 (m, 2H, -CH2-pi-
perazine), 2.50 (s, 3H, -COCH3); 13C NMR: δ 32.7, 46.8, 51.4, 54.9, 55.3,
60.6, 61.1, 68.6, 105.5, 111.9, 116.1, 118.3, 120.8, 123.0, 123.5, 133.3, 139.2,
142.5, 143.8, 146.2, 147.7, 151.8, 201.0; ESI-MS: m/z 455.2 [M+H+]. Anal.
Calcd for C25H30N2O6‧HCl: C, 61.16; H, 6.36; N, 5.71. Found: C, 61.11; H,
6.12; N, 5.80.
Hydrochloride of 5-acetyl-4,7-dimethoxy-6-[2-[4-(3-chlorophe-
nyl)piperazino]ethoxy]benzofuran (2g)ꢀThe hydrochloride salt
was obtained in 76% yield as a white powder; mp 140–142°C;1H NMR:
δ 10.35 (s, 1H, NH+), 8.08 (d, 1H, C2-H, J ꢀ= ꢀ 2.1 Hz), 7.30–7.24 (m, 2H,
C-H), 7.11–7.08 (m, 1H, C3-H), 7.01–6.98 (m, 1H, C-H), 6.89–6.87 (m, 1H,
C-H), 4.36–4.30 (m, 2H, -CH2-piperazine), 4.06 (s, 3H, -OCH3), 4.00
(s, 3H, -OCH3), 3.69–3.65 (m, 2H, -CH2-piperazine) 3.58–3.54 (m, 2H,
C1′-H), 3.43–3.12 (m, 5H, -COCH3, -CH2-piperazine), 2.50–2.48 (m, 4H,
-CH2-piperazine, C2′-H); 13C NMR: δ 32.6, 44.7, 50.7, 54.8, 60.6, 61.1,
68.6, 105.5, 114.1, 115.2, 116.2, 119.1, 123.0, 130.6, 133.4, 133.9, 142.4,
143.8, 146.2, 147.7, 150.7, 200.9; ESI-MS: m/z 459.2 [M+H+]. Anal. Calcd
for C24H27ClN2O5‧HCl: C, 58.19; H, 5.70; N, 5.65. Found: C, 58.01; H, 5.71;
N, 5.69.
Hydrochloride of 5-acetyl-4,7-dimethoxy-6-[2-[4-(2-chlorophe-
nyl)piperazino]ethoxy]benzofuran (2c)ꢀThe hydrochloride salt
was obtained in 72% yield as a white powder; mp 154–155°C; 1H NMR:
δ 11.04 (s, 1H, NH+), 8.08 (d, 1H, C2-H, J ꢀ= ꢀ 2.4 Hz), 7.48–7.45 (m, 1H,
C-H), 7.37–7.32 (m, 1H, C-H), 7.26–7.22 (m, 2H, C-H, C3-H), 7.15–7.09 (m,
1H, C-H), 4.40–4.38 (m, 2H, -CH2-piperazine), 4.07 (s, 3H, -OCH3), 4.00
(s, 3H, -OCH3), 3.70–3.46 (m, 6H, -CH2-piperazine, C1′-H), 3.30–3.19
(m, 4H, -CH2-piperazine, C2′-H), 2.50 (s, 3H, -COCH3); 13C NMR: δ 32.6,
47.6, 51.5, 54.9, 60.6, 61.1, 68.6, 105.5, 116.2, 121.0, 123.0, 124.8, 127.5,
128.2, 130.4, 133.3, 142.5, 143.8, 146.2, 147.4, 147.7, 200.9; ESI-MS: m/z
459.1 [M+H+]. Anal. Calcd for C24H27ClN2O5‧HCl: C, 58.19; H, 5.70; N,
5.65. Found: C, 58.02; H, 5.80; N, 5.78.
Hydrochloride of 5-acetyl-4,7-dimethoxy-6-[2-[4-(4-nitrophenyl)
piperazino]ethoxy]benzofuran (2h)ꢀThe hydrochloride salt was
obtained in 54% yield as a white powder; mp 206–208°C; 1H NMR:
δ 11.14 (s, 1H, NH+), 8.14–8.10 (m, 2H, C-H), 8.08 (d, 1H, C2-H, J ꢀ= ꢀ 2.4
Hz), 7.26 (d, 1H, C3-H, J ꢀ= ꢀ 2.4 Hz), 7.17–7.14 (m, 2H, C-H), 4.39–4.36 (m,
2H, -CH2-piperazine), 4.28–4.24 (m, 2H, -CH2-piperazine), 4.06 (s, 3H,
-OCH3), 4.00 (s, 3H, -OCH3), 3.70–3.66 (m, 2H, -CH2-piperazine), 3.62–
3.50 (m, 2H, C1′-H), 3.47–3.40 (m, 4H, -CH2-piperazine, C2′-H), 3.28 (s,
3H, -COCH3); 13C NMR: δ 32.6, 43.5, 50.5, 54.8, 60.6, 61.1, 68.6, 105.5,
113.5, 116.2, 123.0, 125.6, 133.4, 138.0, 142.4, 143.9, 146.2, 147.7, 153.7,
200.9; ESI-MS: m/z 492.2 [M+Na+]. Anal. Calcd for C24H27N3O7‧HCl: C,
56.97; H, 5.58; N, 8.31. Found: C, 56.91; H, 5.70; N, 8.21.
Hydrochloride of 5-acetyl-4,7-dimethoxy-6-[2-(4-(pyridin-2-yl)
piperazino)ethoxy]benzofuran (2d)ꢀThe hydrochloride salt was
1
obtained in 86% yield as a white powder, mp 156–157°C; H NMR:
δ 10.88 (s, 1H, NH+), 8.18–8.15 (m, 1H, C-H), 8.08 (d, 1H, C2-H, J ꢀ= ꢀ
2.4 Hz), 7.74–7.70 (m, 1H, C-H), 7.26 (d, 1H, C-H, C3-H, J ꢀ= ꢀ 2.4 Hz),
7.09–7.06 (m, 1H, C-H), 6.84–6.80 (m, 1H, C-H), 4.49–4.44 (m, 2H,
-CH2-piperazine), 4.38–4.35 (m, 2H, -CH2-piperazine), 4.06 (s, 3H,
-OCH3), 4.00 (s, 3H, -OCH3), 3.70–3.64 (m, 2H, C1′-H), 3.58–3.50 (m,
2H, -CH2-piperazine,) 3.41–3.34 (m, 2H, -CH2-piperazine), 3.23–3.16
(m, 2H, C2′-H), 2.50 (s, 3H, -COCH3); 13C NMR: δ 32.6, 42.3, 47.6, 50.5,
54.9, 60.6, 61.1, 68.6, 105.5, 109.6, 114.0, 116.2, 122.9, 130.4, 133.3,
140.3, 142.4, 143.8, 146.2, 147.7, 200.9; ESI-MS: m/z 426.2 [M+H+]. Anal.
Calcd for C23H27N3O4‧HCl: C, 59.80; H, 6.11; N, 9.10. Found: C, 59.67; H,
6.01; N, 9.12.
Hydrochloride of 5-acetyl-4,7-dimethoxy-6-[3-(4-phenylpiper-
azino)propoxy]benzofuran (2i)ꢀThe hydrochloride salt was ob-
tained in 60% yield as a white powder; mp 180–182°C (lit. mp 175°C
[16]); 1H NMR: δ 10.84 (s, 1H, NH+), 8.04 (d, 1H, C2-H, J ꢀ= ꢀ 2.1 Hz),
7.29–7.22 (m, 1H, C3-H), 7.02–7.00 (m, 2H, C-H), 6.89–6.84 (m, 1H, C-H),
4.06 (t, 2H, C3′-H, J ꢀ= ꢀ 8.1 Hz), 4.01 (s, 3H, -OCH3), 3.98 (s, 3H, -OCH3),
3.84–3.81 (m, 2H, -CH2-piperazine), 3.61–3.58 (m, 2H, C1′-H), 3.30–3.25
(m, 2H, -CH2-piperazine), 3.19–3.09 (m, 4H, -CH2-piperazine), 2.46 (s,
3H, -COCH3), 2.19–2.14 (m, 2H, C2′-H); 13C NMR: δ 24.0, 32.6, 45.4, 50.6,
52.9, 60.5, 60.9, 71.8, 105.4, 115.7, 115.9, 120.0, 123.2, 129.1, 133.4, 143.3,
143.6, 145.9, 147.9, 149.5, 200.8; ESI-MS: m/z 439.1 [M+H+]. Anal. Calcd
for C25H30N2O5‧HCl: C, 63.22; H, 6.58; N, 5.90. Found: C, 63.11; H, 6.56;
N, 5.89.
Hydrochloride of 5-acetyl-4,7-dimethoxy-6-[2-(4-(pyrimidin-
2-yl)piperazino)ethoxy]benzofuran (2e)ꢀThe hydrochloride
salt was obtained in 76% yield as a white powder; mp 189–190°C;
1H NMR: δ 10.49 (s, 1H, NH+), 8.46 (d, 2H, C-H, J ꢀ= ꢀ 4.8 Hz), 8.08 (d,
1H, C2-H, J ꢀ= ꢀ 2.4 Hz), 7.26 (d, 1H, C-H, C3-H, J ꢀ= ꢀ 2.4 Hz), 6.79–6.76 (m,
1H, C-H), 4.77–4.73 (m, 2H, -CH2-piperazine), 4.38–4.30 (m, 2H, -CH2-
piperazine), 4.05 (s, 3H, -OCH3), 4.00 (s, 3H, -OCH3), 3.68–3.64 (m,
2H, C1′-H), 3.56–3.48 (m, 2H, -CH2-piperazine), 3.40–3.36 (m, 2H, -CH2-
piperazine), 3.31 (s, 3H, -COCH3), 3.20–3.16 (m, 2H, C2′-H); 13C NMR:
δ 32.6, 47.6, 50.7, 55.0, 60.6, 61.0, 68.4, 105.5, 111.3, 116.1, 122.9, 133.3,
142.4, 143.8, 146.2, 147.7, 158.1, 160.7, 200.9; ESI-MS: m/z 427.2 [M+H+]. Hydrochloride of 5-acetyl-4,7-dimethoxy-6-[3-[4-(2-methoxy-
Anal. Calcd for C22H26N4O4‧HCl: C, 57.08; H, 5.88; N, 12.10. Found: C, phenyl)piperazino]propoxy]benzofuran (2j)ꢀThe hydrochloride
57.17; H, 6.00; N, 12.01.
salt was obtained in 80% yield as a white powder; mp 181–184°C (lit.:
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284ꢀ ꢀM. Krawiecka et al.: 6-Substituted 5-acetyl-4,7-dimethoxybenzofuran derivatives
an oil for the free base [17]); 1H NMR: δ 10.81 (s, 1H, NH+), 8.04 (d, 1H,
C2-H, J ꢀ= ꢀ 2.4 Hz), 7.22 (d, 1H, C3-H, J ꢀ= ꢀ 2.4 Hz), 7.06–6.89 (m, 4H, C-H),
4.06 (t, 2H, C3′-H, J ꢀ= ꢀ 6 Hz), 4.01 (s, 3H, -OCH3), 3.98 (s, 3H, -OCH3),
3.80 (s, 3H, -OCH3), 3.60–3.49 (m, 4H, -CH2-piperazine), 3.30–3.23 (m,
2H, C1′-H), 3.19–3.03 (m, 4H, -CH2-piperazine), 2.47 (s, 3H, -COCH3),
2.21–2.11 (m, 2H, C2′-H); 13C NMR: δ 24.1, 32.6, 46.8, 51.1, 53.0, 55.3,
60.5, 60.9, 71.8, 105.5, 111.9, 115.7, 118.2, 120.8, 123.2, 123.5, 133.4, 139.3,
143.3, 143.6, 145.9, 147.9, 151.8, 200.9; ESI-MS: m/z 469.2 [M+H+]. Anal.
Calcd for C26H32N2O6‧HCl: C, 61.84; H, 6.59; N, 5.55. Found: C, 61.80;
H, 6.57; N, 5.61.
(m, 2H, C-H), 6.47–6.43 (m, 1H, C-H), 4.06–4.08 (m, 2H, C3′-H), 4.00
(s, 3H, -OCH3), 3.98 (s, 3H, -OCH3), 3.86–3.82 (m, 2H, -CH2-piperazine),
3.73 (s, 3H, -OCH3), 3.60–3.57 (m, 2H, -CH2-piperazine), 3.18–3.04 (m,
6H, C1′-H, -CH2-piperazine), 2.46 (s, 3H, -COCH3), 2.20–2.10 (m, 2H,
C2′-H); 13C NMR: δ 24.0, 32.6, 45.3, 50.6, 52.9, 54.9, 60.5, 60.9, 71.8,
102.1, 105.2, 105.4, 108.3, 115.7, 123.2, 129.8, 133.4, 143.3, 143.6, 145.9,
147.9, 150.9, 160.2, 200.8; ESI-MS: m/z 469.2 [M+H+]. Anal. Calcd for
C26H32N2O6‧HCl: C, 61.84; H, 6.59; N, 5.55. Found: C, 61.80; H, 6.57; N,
5.59.
Hydrochloride of 5-acetyl-4,7-dimethoxy-6-[3-[4-(3-chlorophe-
nyl)piperazino]propoxy]-1-benzofuran (2o)ꢀThe hydrochloride
salt was obtained in 70% yield as a white powder; mp 189–192°C; 1H
NMR: δ 10.52 (s, 1H, NH+), 8.04 (d, 1H, C2-H, J ꢀ= ꢀ 2.1 Hz), 7.28–7.26 (m,
1H, C-H), 7.24–7.22 (m, 1H, C3-H), 7.08–7.05 (m, 1H, C-H), 6.99–6.95 (m,
1H, C-H), 6.89–6.86 (m, 1H, C-H), 4.07–4.05 (m, 2H, C3′-H), 4.00 (s, 3H,
-OCH3), 3.98 (s, 3H, -OCH3), 3.92–3.89 (m, 2H, -CH2-piperazine), 3.62–
3.56 (m, 2H, C1′-H), 3.30–3.25 (m, 2H, -CH2-piperazine), 3.16–3.13 (m,
4H, -CH2-piperazine), 2.46 (s, 3H, -COCH3), 2.20–2.10 (m, 2H, C2′-H);
13C NMR: δ 24.0, 32.6, 44.8, 50.4, 52.9, 60.5, 60.9, 71.8, 105.4, 114.1, 115.2,
115.7, 119.1, 123.2, 130.6, 133.4, 133.9, 143.3, 143.6, 145.9, 147.9, 150.8,
200.8; ESI-MS: m/z 473.2 [M+H+]. Anal. Calcd for C25H29ClN2O5‧HCl: C,
58.94; H, 5.94; N, 5.50. Found: C, 58.96; H, 5.95; N, 5.49.
Hydrochloride of 5-acetyl-4,7-dimethoxy-6-[3-[4-(2-chlorophe-
nyl)piperazino]propoxy]-1-benzofuran (2k)ꢀThe hydrochloride
salt was obtained in 70% yield as a white powder; mp 206–207°C;
1H NMR: δ 10.44 (s, 1H, NH+), 8.04 (d, 1H, C2-H, J ꢀ= ꢀ 2.1 Hz), 7.48–7.44
(m, 1H, C-H), 7.38–7.32 (m, 1H, C-H), 7.23–7.21 (m, 2H, C3-H), 7.14–7.09
(m, 1H, C-H), 4.07 (t, 2H, C3′-H, J ꢀ= ꢀ 6 Hz), 4.01 (s, 3H, -OCH3), 3.98
(s, 3H, -OCH3), 3.65–3.61 (m, 2H, -CH2-piperazine), 3.47–3.43 (m, 2H,
-CH2-piperazine), 3.34–3.30 (m, 2H, C1′-H), 3.24–3.09 (m, 4H, -CH2-
piperazine), 2.47 (s, 3H, -COCH3), 2.17–2.12 (m, 2H, C2′-H); 13C NMR: δ
24.1, 32.6, 47.6, 51.2, 53.0, 60.5, 60.9, 71.8, 105.4, 115.7, 120.9, 123.2, 124.7,
127.5, 128.2, 130.4, 133.4, 143.3, 143.6, 145.9, 147.3, 147.9, 200.8; ESI-MS:
m/z 473.2 [M+H+]. Anal. Calcd for C25H29ClN2O5‧HCl: C, 58.94; H, 5.94;
N, 5.50. Found: C, 58.80; H, 5.91; N, 5.59.
Hydrochloride of 5-acetyl-4,7-dimethoxy-6-[3-[4-(4-nitrophe-
nyl)piperazino]propan-1-oxy]benzofuran (2p)ꢀThe hydrochlori-
de salt was obtained in 80% yield as a white powder; mp 177–179°C;
1H NMR: δ 10.86 (s, 1H, NH+), 8.11–8.09 (m, 2H, C-H), 8.03 (d, 1H, C2-H,
J ꢀ= ꢀ 2.1 Hz), 7.22 (d, 1H, C3-H, J ꢀ= ꢀ 2.1 Hz), 7.16–7.10 (m, 2H, C-H), 4.08–
4.04 (m, 2H, C3′-H), 4.00 (s, 3H, -OCH3), 3.97 (s, 3H, -OCH3), 3.70–3.60
(m, 2H, -CH2-piperazine), 3.50–3.40 (m, 2H, C1′-H), 3.34–3.28 (m,
4H, -CH2-piperazine), 3.18–3.16 (m, 2H, -CH2-piperazine), 2.45 (s, 3H,
-COCH3), 2.22–2.00 (m, 2H, C2′-H); 13C NMR: δ 24.1, 32.6, 43.6, 50.3,
53.0, 60.5, 60.9, 71.8, 105.4, 113.4, 115.7, 123.2, 125.6, 133.4, 137.9, 143.4,
143.6, 145.9, 147.9, 153.8, 200.8; ESI-MS: m/z 484.3 [M+H+]. Anal. Calcd
for C25H29N3O7‧HCl: C, 57.75; H, 5.82; N, 8.08. Found: C, 57.81; H, 5.83;
N, 8.06.
Hydrochloride of 5-acetyl-4,7-dimethoxy-6-[3-(4-(pyridin-2-yl)
piperazino)propoxy]benzofuran (2l)ꢀThe hydrochloride salt was
obtained in 75% yield as a white powder; mp 188–189°C; 1H NMR: δ
10.67 (s, 1H, NH+), 8.17–8.15 (m, 1H, C-H), 8.03 (d, 1H, C2-H, J ꢀ= ꢀ 2.4
Hz), 7.76–7.71 (m, 1H, C-H), 7.22 (d, 1H, C3-H, J ꢀ= ꢀ 2.4 Hz), 7.10–7.07 (m,
1H, C-H), 6.85–6.81 (m, 1H, C-H), 4.50–4.40 (m, 2H, -CH2-piperazine),
4.08–4.06 (m, 2H, C3′-H), 4.00 (s, 3H, -OCH3), 3.98 (s, 3H, -OCH3),
3.64–3.60 (m, 2H, -CH2-piperazine), 3.34–3.24 (m, 4H, -CH2-piperazi-
ne, C1′-H), 3.16–3.11 (m, 2H, -CH2-piperazine), 2.46 (s, 3H, -COCH3),
2.17–2.12 (m, 2H, C2′-H); 13C NMR: δ 24.0, 32.6, 42.7, 50.0, 53.0, 54.9,
60.5, 60.9, 71.8, 105.4, 110.6, 113.9, 115.7, 123.2, 129.8, 133.4, 141.4, 143.3,
143.6, 145.9, 147.9, 200.8; ESI-MS: m/z 440.2 [M+H+]. Anal. Calcd for
C24H29N3O5‧HCl: C, 60.56; H, 6.35; N, 8.83. Found: C, 60.51; H, 6.50;
N, 8.81.
Microbiology
Hydrochloride of 5-acetyl-4,7-dimethoxy-6-[3-(4-(pyrimidin-2-
yl)piperazino)propoxy]benzofuran (2m)ꢀThe hydrochloride salt
was obtained in 70% yield as a white powder; mp 172–173°C; 1H NMR:
δ 11.09 (s, 1H, NH+), 8.45 (d, 2H, Harom., J ꢀ= ꢀ 4.8 Hz), 8.04 (d, 1H, C2-H,
J ꢀ= ꢀ 2.4 Hz), 7.23 (d, 1H, C3-H, J ꢀ= ꢀ 2.4 Hz), 6.78–6.75 (m, 1H, C-H), 4.73–
4.69 (m, 2H, -CH2-piperazine), 4.07–4.04 (m, 2H, C3′-H), 4.00 (s, 3H,
-OCH3), 3.97 (s, 3H, -OCH3), 3.60–3.57 (m, 2H, -CH2-piperazine), 3.42–
3.38 (m, 2H, C1′-H), 3.25–3.21 (m, 2H, -CH2-piperazine), 3.09–3.05 (m,
2H, -CH2-piperazine), 2.45 (s, 3H, -COCH3), 2.19–2.15 (m, 2H, C2′-H);
13C NMR: δ 24.1, 32.6, 47.6, 50.4, 53.1, 60.5, 60.9, 71.7, 105.4, 111.3, 115.7,
123.2, 133.4, 143.3, 143.6, 145.9, 147.9, 158.1, 160.6, 200.8; ESI-MS: m/z
441.3 [M+H+]. Anal. Calcd for C23H28N4O5‧HCl: C, 57.92; H, 6.13; N, 11.75.
Found: C, 57.89; H, 6.16; N, 11.78.
Organisms
Standard strains of S. aureus ATCC 25923, E. coli ATCC 25922, C. albi-
cans ATCC 14053, P. acnes ATCC 6919, B. thetaiotaomicron ATCC 29741,
B. fragilis ATCC 25285 and one clinical isolate S. maltophilia CO 2275
were used.
Screening for antimicrobial activity
Compounds were tested for bacteriostatic activity at high concen-
trations (512 mg/L) and if the bacteriostatic effect was observed, the
concentration was reduced. A method according to CLSI (Clinical
and Laboratory Standards Institute) [18] directives was applied. The
tested substances were dissolved in DMSO and then the solutions
were added to brain heart infusion broth (BHI-B) medium to a final
concentration of 512 mg/L. The aerobic bacteria were cultured on
Hydrochloride of 5-acetyl-4,7-dimethoxy-6-[3-[4-(3-methoxy-
phenyl)piperazino]propoxy]benzofuran (2n)ꢀThe hydrochlori-
de salt was obtained in 70% yield as a white powder; mp 172–174°C;
1H NMR: δ 10.42 (s, 1H, NH+), 8.04 (d, 1H, C2-H, J ꢀ= ꢀ 2.1 Hz), 7.23
(d, 1H, C3-H, J ꢀ= ꢀ 2.1 Hz), 7.16 (t, 1H, Harom., J ꢀ= ꢀ 8.1 Hz), 6.60–6.57
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M. Krawiecka et al.: 6-Substituted 5-acetyl-4,7-dimethoxybenzofuran derivativesꢀ
ꢀ285
plates with BHI agar (BHI-A) medium supplemented with 7% horse compounds were freshly prepared in DMSO. The final concentrations
blood, at temperature 35–37°C, in an aerobic atmosphere, for 18–24 h. of the compounds tested in the cell cultures were: 1 mm, 1 ꢀ× ꢀ 10–2 mm,
Anaerobes were cultured in Schaedler agar with 5% of sheep blood 1 ꢀ× ꢀ 10–4 mm and 1 ꢀ× ꢀ 10–6 mm. The concentration of DMSO in the cell
at 35–37°C for 48 h, in anaerobic atmosphere. The fungal strain was culture medium was 1%.
cultured in the Sabouraud agar (SA), at the same temperature and
The values of IC50 (the concentrations of test compound required
atmosphere, but for at least 24 h. The cultures which were in mid-log- to reduce the cell survival fraction to 50% of the control) were calcu-
arithmic phase of growth were suspended in 0.9% NaCl to obtain 0.5 lated from dose-response curves and used as a measure of cellular
MacFarland’s optical density and in the case of anaerobes 1.0 in the sensitivity to a given treatment.
same scale. Cells (1.0–9.0 ꢀ× ꢀ 105, 0.1 mL of the prepared suspension)
The cytotoxicity of all compounds was determined by the MTT
were added to sample tubes with 2 mL of BHI-B medium containing [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide; Sig-
the tested substances. For anaerobes, all media were pre-reduced. ma, St. Louis, MO, USA] assay as previously described [19]. Briefly,
Samples were incubated at temperature 35–37°C for 24–48 h and in
the case of anaerobes for 48–60 h. If afer 48 h (60 h for anaerobes),
afer 24 h or 48 h of incubation with drugs, the cells were treated with
the MTT reagent and incubation was continued for 2 h. The MTT-
growth was absent, the substance was noted as potentially possess- formazan crystals were dissolved in 20% SDS and 50% DMF at pH
ing antimicrobial activity. In all experiments, strain vitality controls 4.7 and absorbance was read at 570 and 650 nm on an ELISA-PLATE
and a DMSO antimicrobial activity control were performed at the READER (FLUOstar Omega). Cells grown in the presence of vehicle
used concentrations.
(1% DMSO) only were used as a control (100% viability).
Acknowledgments: The cytotoxicity studies were per-
formed in the Screening Laboratory, Department of Bioor-
ganic Chemistry, Centre of Molecular and Macromolecular
Studies of the Polish Academy of Sciences and financially
supported by the Ministry of Science and Higher Educa-
tion, project PBZ-MNiSW-07/I/2007 (2008–2010).
Anticancer activity
The HeLa (human cervix carcinoma) and K562 (leukemia) cells were
culturedinRPMI1640mediumsupplementedwithantibioticsand10%
fetal calf serum, in a 5% CO2–95% air atmosphere. The cells (7 ꢀ× ꢀ 103)
were seeded on each well on a 96-well plate (Nunc). Afer 48 h cells
were exposed to the test compounds. Stock solutions (100 mm) of test
Received May 22, 2013; accepted May 29, 2013
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