Synthesis of novel building blocks of benzosuberone bearing coumarin moieties and their evaluation as potential anticancer agents

Article abstract of DOI:10.1016/j.ejmech.2014.04.015

A series of novel benzosuberone bearing coumarin moieties 5a-c have been synthesized and their structures were determined by analytical and spectral (FT-IR, ¹H NMR, ¹³C NMR, HRMS) studies. The newly synthesized compounds were evaluated for their cytotoxicity against four human cancer cell lines, A549 (Human alveolar adenocarcinoma cell line), HeLa (Human cervical cancer cell line), MDA-MB-231 (Human breast adenocarcinoma cell line), MCF-7 (Human breast adenocarcinoma cell line) and normal cell line HEK293 (Human embryonic kidney cell line). Compound 5a exhibited promising cytotoxicity with IC₅₀ values ranging from 3.35 to 16.79 μM against all the cancer cell lines like A549, HeLa, MCF-7 and MDA-MB-231, while compound 5c showed significant cytotoxicity against HeLa and MDA-MB-231 with IC₅₀ values of 6.72 and 4.87, respectively.

Full text of DOI:10.1016/j.ejmech.2014.04.015

European Journal of Medicinal Chemistry 79 (2014) 260e265
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Synthesis of novel building blocks of benzosuberone bearing coumarin
moieties and their evaluation as potential anticancer agents
,
Bandi Yadagiri a, Uma Devi Holagunda a, Rajashaker Bantu a, Lingaiah Nagarapu a
*
,
C. Ganesh Kumar b, Sujitha Pombala b, B. Sridhar c
a Organic Chemistry Division II, CSIR-Indian Institute of Chemical Technology, Tarnaka, Hyderabad 500007, India
b Centre for Medicinal Chemistry & Pharmacology, CSIR-Indian Institute of Chemical Technology, Tarnaka, Hyderabad 500007, India
c Centre for X-ray Crystallography, CSIR-Indian Institute of Chemical Technology, Tarnaka, Hyderabad 500007, India
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of novel benzosuberone bearing coumarin moieties 5aec have been synthesized and their
structures were determined by analytical and spectral (FT-IR, 1H NMR, 13C NMR, HRMS) studies. The
newly synthesized compounds were evaluated for their cytotoxicity against four human cancer cell lines,
A549 (Human alveolar adenocarcinoma cell line), HeLa (Human cervical cancer cell line), MDA-MB-231
(Human breast adenocarcinoma cell line), MCF-7 (Human breast adenocarcinoma cell line) and normal
cell line HEK293 (Human embryonic kidney cell line). Compound 5a exhibited promising cytotoxicity
Received 3 December 2013
Received in revised form
19 March 2014
Accepted 4 April 2014
Available online 5 April 2014
with IC50 values ranging from 3.35 to 16.79 mM against all the cancer cell lines like A549, HeLa, MCF-7
and MDA-MB-231, while compound 5c showed significant cytotoxicity against HeLa and MDA-MB-231
with IC50 values of 6.72 and 4.87, respectively.
Keywords:
Benzosuberone
Vilsmeier HaackeArnold reaction
Cytotoxicity
Ó 2014 Elsevier Masson SAS. All rights reserved.
Cell lines
1. Introduction
isolated from microbial sources, e.g. novobiocin and coumermycin
from Streptomyces, and aflatoxins from Aspergillus species and
Colchicine, a major natural alkaloid derived from the plant
Colchicum autumnal, is a benzosuberone derivative exhibiting anti-
tumour activity, due to the binding of aromatic ring of colchicine
with hydrophobic domain of tubulin. Colchicine was the first drug
reported to function through a tubulin binding mechanism in the
late 1930s [1]. However, colchicine was eventually withdrawn from
clinical use for cancer treatment due to significant in vivo toxicity
[2]. Nonetheless, colchicine has been used in the treatment of gout
at very low doses since the late 1950s [3]. Recent investigations on
benzosuberone-containing moiety showed that chemokine recep-
tor CCR5, is expressed in prostate cancer specimens [4]. Benzosu-
berone derivatives also showed a wide range of biological activities
like antimicrobial [5], anti-inflammatory [6], anti-estrogenic [7],
anti-malarial [8] and anti-platelet aggregation [9] but their anti-
cancer effects have been reported to be more potent against a
majority of human cancer cell lines.
(þ)-Calanolide A, a natural product isolated from several tropical
plants of the genus Calophyllum as shown in Fig. 1. Pharmacologi-
cally, they belong to neoflavonoid class of compounds, which have
been found to exhibit a wide variety of biological activities, usually
associated with low toxicity and have raised considerable interest
because of their potential beneficial effects on human health. In the
recent years, they have attracted immense interest due to their
diverse pharmacological properties like anti-HIV [11] anti-
coagulant [12], anti-bacterial [13], and anti-malarial [14]. In addi-
tion, few coumarin derivatives have the special ability to show
potent anti-tumour activity against several human tumour cell
lines. The coumarins are extremely variable in structure, due to
various types of substitutions in their basic structure, which in turn
can influence their biological activity.
In continuation to our ongoing research program [15e21] to
discover and develop tumour growth inhibitors and apoptotic in-
ducers as potential new anti-cancer agents, we have designed and
synthesized novel benzosuberone-bearing coumarin moiety ana-
logues (using VilsmeiereHaack and Suzuki cross-coupling re-
actions) and evaluated their in vitro cytotoxicity against different
human cancer cell lines like A549, HeLa, MDA-MB-231 and MCF-7.
Significantly, the compound 5a showed promising cytotoxicity
against the HeLa and MCF-7 cancer cell lines with IC50 values of
Coumarins are an elite class of oxygen heterocycles, which occur
naturally in many food sources including citrus fruits, herbs and
vegetables [10]. Some important coumarin members have been
* Corresponding author.
E-mail address: lnagarapuiict@yahoo.com (L. Nagarapu).
http://dx.doi.org/10.1016/j.ejmech.2014.04.015
0223-5234/Ó 2014 Elsevier Masson SAS. All rights reserved.

B. Yadagiri et al. / European Journal of Medicinal Chemistry 79 (2014) 260e265
261
O
O
O
O
O
O
O
O
O
O
O
OH
N
H
O
OH
O
O
O
OH
NH2
O
OH
HN
O
Colchicine
Novabiocine
(+)- Calanolide A
Fig. 1. Structures of some previously isolated important natural alkaloids.
ꢀ
3.35 and 9.63
m
M, respectively, and compound 5c displayed the
radiation (
l
¼ 0.71073 A) with
u-scan method [23]. Preliminary
most potent selectivity against HeLa and MDA-MB-231 cell lines
with IC50 values of 6.72 and 9.63 mM, respectively.
lattice parameters and orientation matrices were obtained from
four sets of frames. Unit cell dimensions were determined using
5417 reflections in the range of 2.25 <
q
< 27.95ꢀ. Integration and
scaling of intensity data were accomplished using SAINT [24] pro-
gram. The structure was solved by Direct Methods using SHELXS97
[24] and refinement was carried out by full-matrix least-squares
technique using SHELXL97 [24]. All hydrogen atoms were posi-
tioned geometrically and were treated as riding on their parent
2. Results and discussion
2.1. Chemistry
The detailed reaction conditions for the synthesis of cross-
condensed coumarin moieties are illustrated in Scheme 1. The
synthesis of compounds 2aec was easily carried out from the
corresponding ketones by VilsmeiereHaackeArnold reaction [22].
The vinyl chlorides obtained above, were activated by the presence
of an electron-withdrawing group, which in turn allowed their
easy coupling with o-anicyl boronic acids in the presence of 2 mol
% of palladium (II) acetate, tetrabutylammonium bromide and
potassium carbonate, with water as the reaction medium at 45 ꢀC
for 3 h afforded compound 3aec in 79.1e90.7% yields. Oxidation of
aldehydes 3aec with sodium chlorite in the presence of 30% H2O2
in acetonitrile at room temperature allowed the formation of acids
4aec in 70.2e74.9% yields. Finally, the acids were converted to the
corresponding acyl chlorides, followed by cyclization with
aluminium chloride in dichloromethane at room temperature to
furnish the desired tetra cyclic systems 5aec in 81.5e88.7% yields.
All the new synthesized compounds were characterized using
NMR, IR and mass spectrometry (see supporting information).
Spectral data of all synthesized compounds were in good agree-
ment with the proposed structures. IR spectrum revealed the
presence of C]O bond in lactone (1712e1716 cmꢁ1) and CH
(2928e2934 cmꢁ1) functional groups in the synthesized com-
pounds. This was further confirmed by 1H NMR spectrum
(300 MHz) of 5aec recorded in CDCl3 displayed the disappearance
ꢀ
carbon atoms, with CeH distance of 0.93e0.98 A, with
U
iso(H) ¼ 1.2Ueq (C) or 1.5Ueq(C).
Crystal data for AI41: C20H17ClO2, M ¼ 324.79, colourless plate,
0.14 0 0.12 0 0.06 mm3, triclinic, space group P-1 (No. 2), a ¼ 9.8232
ꢀ
3
ꢀ
(11), b ¼ 9.9810 ꢀ(11), c ¼ 18.362 (2) A, a ¼ 84.591 (2), b ¼ 81.371 (2),
g ¼ 64.395 (2) , V ¼ 1604.2 (3) A , Z ¼ 4, Dc ¼ 1.345 g/cm3,
ꢀ
F000 ¼ 680, CCD Area Detector, MoKa radiation, l ¼ 0.71073 A,
T ¼ 294 (2)K, 2qmax ¼ 50.0ꢀ, 15,411 reflections collected, 5635
unique (Rint
¼
0.0156). Final GooF
¼
1.030, R1
¼
0.0370,
(I)
wR2 ¼ 0.1010, R indices based on 5037 reflections with I > 2
s
(refinement on F2), 418 parameters, 0 restraints, m ¼ 0.245 mmꢁ1
.
Crystallographic data has been deposited for compound AI41 with
the Cambridge Crystallographic Data Centre [CCDC No. 933434].
Copies of the data can be obtained free of charge at www.ccdc.cam.
ac.uk/conts/retrieving.html [or from the Cambridge Crystallo-
graphic Data Centre (CCDC), 12 Union Road, Cambridge CB2 1EZ,
UK; fax: þ44 (0) 1223 336 033; email: deposit@ccdc.cam.ac.uk].
2.3. Effects of the compounds on the viability of human cancer cells
The results of the assay are summarized in Table 1. To examine
the effects of the compounds on the viability of different human
cancer cell lines, the in vitro antitumour activity was evaluated
against A549, HeLa, MDA-MB-231 and MCF-7 by the standard MTT
assay method. The inhibitory activity was expressed in micromolar
concentrations of the compound, which caused 50% inhibition (IC50
value) under the assay conditions and Doxorubicin was used as a
reference drug. Data in Table 1 showed that the majority of the
synthesized compounds displayed antitumour activities against the
tested four human cancer cell lines, which could support the
rationale of the drug design. An attempt was made to draw some
considerations concerning the structureeactivity relationship
(SAR). Compound 5a with no substitution on the benzene ring A
(Scheme 1) exhibited promising antitumour effect against A549
of eOCH3 substituent at
pound indicating that the cyclization occurred in the final step.
Two additional triplets around 2.43e3.41 ppm and multiplet at
1.81e2.30 ppm in seven membered ring were observed. The
d 3.30e3.40 ppm in the starting com-
d
d
compound 5b was obtained as colourless crystal after recrystalli-
sation in ethanol and the structure was confirmed by X-ray crys-
tallography. The X-ray diffraction analysis of the single crystal of
5b (Fig. 1) proved the presence of chlorine substitution at ring D;
whereas the compounds 5a and 5c lack it; herein we studied the
amount of catalyst in different equivalents. The molecular formula
of all the synthesized compounds was confirmed by HRMS data
analysis (Fig. 2).
and MCF-7 cell lines with IC50 values of 3.35 and 9.63
respectively.
mM,
2.2. X-ray crystallography and spectral studies
Introduction of electron donating groups (eCH3, eOCH3) on
benzene ring A was associated with a noticeable increase in the
cytotoxic effect against all the four tested cell lines. On the contrary,
compound 5b with an electron-donating group (eCl) at benzene
ring D effected moderate anti-tumour activity against all the tested
2.2.1. X-ray crystal data for compound AI41 (5b)
Data were collected at room temperature using a Bruker Smart
Apex CCD diffractometer with graphite monochromated MoK
a

262
B. Yadagiri et al. / European Journal of Medicinal Chemistry 79 (2014) 260e265
Scheme 1. Synthesis of compounds 5aec.
significantly more active than compounds 5a and 5b. Further, these
compounds did not show any cytotoxicity against the normal
cancer cell line, HEK293. Compounds 5a, 5b, and 5c differed
structurally only at the ring A and ring D. This could suggest the
importance of the substituted benzene ring A of this molecular
modification for exhibiting the bioactivity. Finally, we conclude that
the substitutions on ring A played an important role in the exhib-
iting cytotoxicity due its conjugation effect on the coumarin moiety
(ring C) and were more favourable than having substitutions on
ring D.
3. Pharmacology
3.1. In vitro cytotoxicity assay
Cytotoxicity of all the synthesized compounds was determined
on the basis of measurement of in vitro growth inhibition of tumour
cell lines in 96 well plates by cell-mediated reduction of tetrazo-
lium salt to water insoluble formazan crystals using doxorubicin as
a standard. The cytotoxicity as assessed against a panel of four
different human tumour cell lines: A549 derived from human
alveolar adenocarcinoma epithelial cells (ATCC No. CCL-185), HeLa
derived from human cervical cancer cells (ATCC No. CCL-2), MDA-
MB-231 derived from human breast adenocarcinoma cells (ATCC
No. HTB26), MCF7 derived from human breast adenocarcinoma
cells (ATCC No. HTB22) and HEK293 (normal human embryonic
kidney cells) (ATCC No. CRL-1573) using the MTT assay [25]. The
IC50 values (50% inhibitory concentration) were calculated from the
plotted absorbance data for the doseeresponse curves. IC50 values
Fig. 2. The molecular structure of 5b, with the atom-numbering scheme. Displacement
ellipsoids are drawn at the 30% probability level. The asymmetric unit contains two
crystallographically independent molecules (labelled with suffix A and B) and for
clarity molecule B has been omitted.
cell lines as compared to the compounds 5a and 5c. Although,
compound 5c with a stronger electron-donating group (-OCH3) at
benzene ring A displayed promising anti-tumour activity as
compared to doxorubicin with IC50 values of 6.72 and 4.87
against HeLa and MDA-MB-231 cell lines, respectively, it was
m
M
(in
m
M) are indicated as means ꢂ SD of three independent
experiments.

B. Yadagiri et al. / European Journal of Medicinal Chemistry 79 (2014) 260e265
263
Table 1
red liquid. The product was purified by column chromatography
using 60e120 mesh silica gel (hexane/EtOAc).
IC50 of the tested compounds against human cancer and normal cell lines.
Compounds IC50 ina
A549
mM
5.2.1. 5-Chloro-8,9-dihydro-7H-benzocycloheptene-6-
carbaldehyde(2a)
He La
MDA-MB-231 MCF-7
HEK293
5a
5b
5c
3.35 ꢂ 0.05 14.07 0.07 16.79 0.08 9.63 0.06 >200
10.77 0.04 12.69 0.06 13.28 0.07 15.76 ꢂ 0.06 >200
Brown liquid. Yield: 84.4% (5.4 g), IR (NEAT, v cmꢁ1): 2936, 2860,
1671, 1580, 1448, 1262, 919, 750, 1H NMR (300 MHz, CDCl3):
d 2.11e
>200
6.72 0.05 4.87 0.06 >200
0.51 0.02 0.91 0.02 1.07 0.03 >200
>200
Doxorubicinb 0.46 0.02
2.25 (m, 4H, 2CH2), 2.62 (t, J ¼ 6.4, 6.9 Hz, 2H, CH2), 2.60 (t, J ¼ 6.4,
6.6 Hz, 2H, CH2), 7.19e7.27 (m, 1H, AreH), 7.28e7.37 (m, 2H, AreH),
5.90e7.68 (m, 1H, AreH), 10.36 (s, 1H, CHO), 13C NMR (75 MHz,
a
Data presented is the mean value of three independent experiments.
Positive control.
b
CDCl3):
d 22.5, 32.0, 33.8, 96.2, 126.5, 126.7, 128.4, 128.8, 129.0,
130.5, 140.7, 189.3, ESI-MS: m/z ¼ 207 [M þ H]þ, 229 [M þ Na]þ.
4. Conclusion
In conclusion, we have reported a simple synthesis of novel
benzosuberone-bearing coumarin compounds using Vilsmeiere
Haack and Suzuki cross-coupling followed by cyclization and
evaluated there in vitro cytotoxicity against HeLa, A549, MCF-7,
MDA-MB-231 and normal HEK293 cell lines. All the synthesised
compounds indicated significant growth inhibitory effects. In
addition, the compounds 5a, 5b and 5c exhibited potent activity
against the four tested human cancer cell lines. Moreover, the
compound 5a was more potent against A549 and MCF-7 cell lines
and compound 5c was selectively potent against HeLa and MDA-
MB-231 cell lines. Introduction of substitution on ring A was
associated with a distinct tendency to increase the in vitro cytotoxic
potential. This study provides valuable information for further drug
design and in developing more promising anticancer agents.
5.2.2. 5-Chloro-2,3-dimethyl-8,9-dihydro-7H-benzocycloheptene-
6-carbaldehyde (2b)
Brown liquid. Yield: 67.6% (4.7 g): IR (KBr, v cmꢁ1): 2932, 1670,
1582, 1447, 1266, 749, 1H NMR (300 MHz, CDCl3):
d 2.07e2.12 (m,
2H, CH2), 2.21 (t, J ¼ 6.4, 3.5 Hz, 2H, CH2), 2.29 (s, 3H, CH3), 2.30 (s,
3H, CH3), 2.50 (t, J ¼ 6.6, 7.1 Hz, 2H, CH2), 6.69 (s, 1H, AreH), 7.38 (s,
1H, AreH),10.33 (s,1H, CHO), 13C NMR (75 MHz, CDCl3):
d 19.3,19.6,
22.6, 31.3, 33.7, 129.3, 130.2, 134.9, 135.0, 135.8, 138.5, 139.7, 147.8,
190.2, ESI-MS: m/z ¼ 235 [M þ Na]þ.
5.2.3. 5-Chloro-2,3-dimethoxy-8,9-dihydro-7H-
benzocycloheptene-6-carbaldehyde (2c)
Brown liquid. Yield:79.9% (3.5 g): IR (KBr, v cmꢁ1): 2929, 2854,
1658, 1512, 1457, 1267, 1214, 1121, 859, 768, 1H NMR (300 MHz,
CDCl3):
d
2.11e2.18 (m, 2H, CH2), 2.23 (t, J ¼ 6.7 Hz, 2H, CH2), 2.55 (t,
5. Experimental protocols
J ¼ 7.2, 6.7 Hz, 2H, CH2), 3.91 (s, 3H, OCH3), 3.92 (s, 3H, OCH3), 6.69 (s,
1H, AreH), 7.11 (s, 1H, AreH), 10.32 (s, 1H, CHO), 13C NMR (75 MHz,
5.1. General information
CDCl3): d 22.8, 31.8, 55.9, 56.0, 111.2, 111.6, 115.0, 129.4, 135.0, 135.8,
147.5,147.6,150.6,190.2, ESI-MS: m/z ¼ 267 [M þ H]þ, 289 [M þ Na]þ.
All of the solvents and reagents were purchased from Sigmae
Aldrich. Melting points were determined in capillaries and are
uncorrected. Nuclear Magnetic Resonance (1H and 13C NMR)
spectra were recorded on Varian 300 MHz or Bruker WH 75 MHz
spectrometers, using tetramethylsilane (TMS) as the internal
standard. Chemical shifts were expressed in (ppm) down field from
TMS. IR spectra were recorded on PerkineElmer model 683 or 1310
spectrometers with sodium chloride optics or KBr pellets with neat.
ESI-MS was recorded on Thermo Finnigan LCQ ion trap mass
spectrometer equipped with electron spray ionization. High Reso-
lution Mass spectra were recorded on QSTAR mass spectrometer
(Applied BioSystems, USA) at 5 or 7 K resolution using polyethylene
glycol as an internal reference compound. Visualization of the spots
on TLC plates was achieved either by exposure to UV (254 nm) light,
iodine vapour and by dipping the plates in phosphomolybdic acid-
ceric (IV) sulphate-sulphuric acid solution (PMA solution) and
heating the plates at 120 ꢀC.Finally, we used 60e120 mesh silica gel
in column chromatography.
5.3. General procedures for the synthesis of compounds (3aec)
The compounds 2aee (0.6 g, 2.9 mmol), boronicacid (0.4 g,
3.2 mmol), tetrabutylammonium bromide (0.9 g, 2.2 mmol),
palladium acetate (2 mol%) and potassium carbonate (1.0 g,
7.2 mmol) were added to the round-bottom flask. Deionised H2O
(5 mL) was added, and the reaction mixture was stirred vigorously
for 3 h at 45 ꢀC. The reaction mixture turned dark and non-
homogenous. The mixture was diluted with 20 mL H2O, and the
product was extracted with EtOAc (3 ꢃ 20 mL). The organic prod-
ucts were stirred over charcoal for 30 min followed by drying over
sodium sulphate. Then the organic products were filtered and
concentrated. The product was purified by column chromatography
using 60e120 mesh silica gel (hexane/EtOAc).
5.3.1. 5-(2-Methoxy-phenyl)-8,9-dihydro-7H-benzocycloheptene-
6-carbaldehyde (3a)
Pale Yellow semi-solid. Yield: 86.2% (2.24 g): IR (KBr, v cmꢁ1):
5.2. General procedures for the synthesis of compounds (2aec)
2934, 2856, 1664, 1596, 1457, 1244, 753. 1H NMR (300 MHz, CDCl3):
d
2.58e2.26 (m, 2H, CH2), 2.49e2.6 (m, 1H, CH), 2.60e2.72 (m, 1H,
Phosphorus oxychloride (0.9 g, 8.1 mmol) was added to a flask
containing N, N-dimethylformamide (5 mL) in an ice bath and
stirred for 10 min. The ice bath was replaced with an ambient
temperature water bath and stirred for an additional 10e15 min.
The substituted benzosuberone (1.0 g, 6.2 mmol) was added and
stirred for 15 min. The reaction mixture was heated to 80 ꢀC and
stirred for an additional 3 h. The orange solution was diluted with
ice water and neutralised with 20% sodium acetate solution and
with diethyl ether (3 ꢃ 10e20 mL). The combined organic extracts
were washed with saturated aqueous sodium bicarbonate solution
(50 mL), brine 50 mL, and water (3 ꢃ 50 mL). The organic layer was
dried with sodium sulphate, and concentrated in vacuum to yield a
CH), 2.79 (t, J ¼ 8.0 Hz, 1H, CH), 3.60 (s, 3H, OCH3), 6.79e6.91 (m, 2H,
AreH), 6.94e7.02 (m, 1H, AreH), 7.06e7.23 (m, 4H, AreH), 7.31e7.42
(m,1H, AreH), 9.55 (s,1H, CHO),13C NMR(75 MHz, CDCl3):
d 21.4, 31.8,
34.5, 55.5, 109.8, 111.2, 120.0, 121.1, 125.8, 128.2, 128.6, 130.1, 132.4,
136.7, 138.6, 141.5, 156.3, 157.3, 192.7, ESI-MS: m/z ¼ 279 [M þ H]þ,
HRMS calcd for C19H19O2[M þ H]þ: calcd 279.1379, Found 279.1373.
5.3.2. 2,3-Di methyl-5-(2-methoxy-phenyl)-8,9-dihydro-7H-
benzocycloheptene-carbaldehyde (3b)
Pale yellow semi-solid. Yield: 90.7% (1.5 g) IR (KBr, v cmꢁ1):
3420, 2929, 2858, 1657, 1453, 1241, 1021, 758, 1H NMR (300 MHz,
CDCl3): d 1.99e2.10 (m, 2H, CH2), 2.11 (s, 3H, CH3), 2.24 (s, 3H, CH3),

264
B. Yadagiri et al. / European Journal of Medicinal Chemistry 79 (2014) 260e265
2.45e2.64 (m, 2H, CH2), 2.65e2.77 (m, 2H, CH2), 3.63 (s, 3H, OCH3),
6.53 (s, 1H, AreH), 6.88 (d, J ¼ 8.3 Hz, 1H, AreH), 6.92e7.01 (m, 3H,
d
1.97e2.09 (m, 1H, CH), 2.20 (t, J ¼ 6.6 Hz, 2H, CH2), 2.32 (d,
J ¼ 6.4 Hz, 1H, CH), 2.68 (t, J ¼ 6.4, 6.2 Hz, 2H, CH2), 3.60 (s, 3H,
OCH3), 3.64 (s, 3H, OCH3), 3.89 (s, 3H, OCH3), 6.28 (s, 1H, AreH),
6.78e6.99 (m, 3H, AreH), 7.21 (d, J ¼ 6.6 Hz, 1H, AreH), 13C NMR
AreH), 7.09 (dd, J ¼ 1.5 Hz, 1H, AreH), 7.30e7.39 (m, 1H, AreH), 13
C
NMR (75 MHz, CDCl3):
d 13.6, 19.1, 19.7, 21.6, 24.1, 31.3, 34.5, 55.5,
111.1, 120.2, 129.4, 130.0, 129.9, 132.3, 133.8, 137.3, 138.3, 139.0,
156.6, 157.3, 192.7, ESI-MS: m/z ¼ 307[M þ H]þ, 329[M þ Na]þ,
HRMS calcd for C21H23O2[M þ H]þ: calcd 307.1692, Found 307.1686.
(75 MHz, CDCl3): d 19.1, 27.4, 31.4, 35.4, 55.4, 55.7, 55.8, 111.3, 112.3,
120.2, 128.7, 128.9, 129.7, 130.3, 130.0, 130.8, 133.2, 135.0, 147.8,
148.5, 156.6, ESI-MS: m/z ¼ 355[M þ H]þ,377[M þ Na]þ, HRMS
calcd for C21H22O5Na [M þ Na]þ: calcd 377.1354, Found 377.1350.
5.3.3. 2,3-Dimethoxy-5-(2-methoxy-phenyl)-8,9-dihydro-7H-
benzocycloheptene-6-carbaldehyde (3c)
5.5. General procedures for the synthesis of the compounds (5aec)
Pale yellow semi solid. Yield: 79.1% (1.55 g): IR (KBr, v cmꢁ1):
2926, 2837, 1667, 1256, 1211, 1110, 1029, 870, 758, 1H NMR
To a solution of acid as a starting material (0.1 g, 0.34 mmol) in
DCM (5 mL), SOCl2 (1 mL) was added and the mixture was stirred at
reflux conditions for 3 h. After formation of the corresponding acid
chloride reaction as shown by the TLC, the excess SOCl2 was
distilled out, then DCM (5 mL) and AlCl3 (0.09 g, 0.68 mmol) were
added and the mixture was stirred at room temperature conditions
for half an hour. The reaction mixture was then diluted with H2O
(5 mL) and extracted with DCM (3 ꢃ 10 mL). The combined DCM
extracts were washed with H2O (2 ꢃ 10 mL), the organic phase
dried over Na2SO4 and filtered. The solvent was then evaporated
under reduced pressure and the residue purified by column chro-
matography using 60e120 mesh silica gel (hexane/EtOAc).
(300 MHz, CDCl3): d 2.11e2.25 (m,1H, CH2), 2.24e2.62 (m, 2H, CH2),
2.65e2.78 (m, 2H, CH2), 3.62 (s, 3H, OCH3), 3.64 (s, 3H, OCH3), 3.91
(s, 3H, OCH3), 6.29 (s, 1H, AreH), 6.74 (s, 1H, AreH), 6.89 (d,
J ¼ 8.3 Hz,1H, AreH), 6.97 (t, J ¼ 7.3 Hz,1H, AreH), 7.11 (d, J ¼ 7.3 Hz,
1H, AreH), 7.34 (t, J ¼ 8.3, 9.6 Hz, 1H, AreH), 13C NMR (75 MHz,
CDCl3):
d 21.7, 31.7, 34.9, 55.4, 55.6, 55.7, 111.0, 111.8, 111.8, 120.0,
126.8, 130.0, 132.2, 132.7, 135.2, 138.2, 148.9, 156.3, 157.2, 192.4, ESI-
MS: m/z ¼ 339[M þ H]þ, 361[M þ Na]þ. HRMS calcd for C21H23O4
[M þ H]þ: calcd 339.1590, Found 339.1586.
5.4. General procedures for the synthesis of the compounds (4aec)
Reactions were carried out by addition of aqueous NaClO2 (0.7 g,
7.92 mmol) to a solution of aldehyde 3aee (1.5 g, 4.5 mmol) and
(0.16 g, 4.6 mmol) equiv of 34% H2O2 in aqueous acetonitrile, at 0 ꢀC,
buffered with KH2PO4 at pH 4.3. The reaction mixture was stirred
overnight. After complete reaction, a small amount of the Na2SO3
(w0.5 g) was added to destroy the unreacted HOCl and H2O2.
Acidification with 10% HCl, the mixture was diluted with H2O (10e
20 mL). The compound was extracted with Et2O (10 mL). The
organic layer was separated and extracted with water and brine
and then dried over sodium sulphate and concentrated. The
product was purified by column chromatography using 60e120
mesh silica gel (hexane/EtOAc).
5.5.1. 8,9-Dihydro-7H-5-oxa-benzo [6,7] cyclohepta [1,2-a]
naphthalen-6-one (5a)
Pale yellow solid. Yield: 83.4% (1.4 g): mp 130 ꢀC: IR (KBr,
v cmꢁ1): 3447, 2929, 2858, 1716, 1603, 1159, 757, 1H NMR (300 MHz,
CDCl3):
(m, 2H, CH2), 3.09 (dd, J ¼ 4.5, 5.2 Hz,1H, CH), 7.13e7.55 (m, 8H, Are
H), 13C NMR (75 MHz, CDCl3):
23.5, 23.7, 31.0, 32.8, 116.9, 118.4,
d 1.83e1.96 (m, 1H, CH), 2.16e2.36 (m, 2H, CH2), 2.48e2.71
d
123.0, 125.8, 126.2, 126.5, 128.6, 128.8, 129.2, 129.4, 129.7, 130.5,
141.1, ESI-MS: m/z ¼ 263[M þ H]þ, 285[M þ Na]þ, HRMS calcd for
C
18H14O2Na [M þ Na]þ: calcd 285.0900. Found 285.0910.
5.5.2. 2-Chloro-11, 12-di methyl-8,9-dihydro-7H-5-oxa-benzo [6,7]
cyclohepta [1,2-a] naphthalen-6-one (5b)
5.4.1. 5-(2-Methoxy-phenyl)-8,9-dihydro-7H-benzocycloheptene-
6-carboxylicacid (4a)
Colourless solid. Yield: 88.7% (78 g): mp 151 ꢀC: IR (KBr, v cmꢁ1):
2928, 2858, 1712, 1446, 1069, 755, 1H NMR (300 MHz, CDCl3):
Yellow solid. Yield: 71.3% (1.2 g): mp 179 ꢀC: IR (KBr, v cmꢁ1):
d 1.82e1.96 (m, 1H, CH), 2.1e2.29 (m, 2H, CH2), 2.24e2.26 (m, 2H,
2927, 2860,1657, 1422,1021, 752, 1H NMR (300 MHz, CDCl3):
d
2.18e
CH2), 3.06 (dd, J ¼ 5.2, 5.4 Hz, 1H, CH), 2.34 (s, 6H, 2CH3), 7.07e7.21
2.26 (m, 2H, CH2), 2.32 (d, J ¼ 6.3, 2H, CH2), 2.76 (t, J ¼ 6.3 Hz, 2H,
CH2), 3.60 (s, 3H, OCH3), 6.72 (d, J ¼ 8.4 Hz,1H, AreH), 6.78e6.84 (m,
5H, AreH), 6.87 (t, J ¼ 7.3 Hz, 1H, AreH), 6.96 (t, J ¼ 7.3 Hz, 1H, Are
(m, 2H, AreH), 7.28e7.57 (m, 3H, AreH), 13C NMR (75 MHz, CDCl3):
d
19.4, 19.6, 23.8, 23.9, 29.6, 30.6, 32.7, 116.9, 118.3, 123.8, 126.0,
129.6, 130.0, 130.4, 130.5, 130.7, 134.0, 138.1, 138.6, 153.4, ESI-MS: m/
z ¼ 325[M þ H]þ, 347[M þ Na]þ, HRMS calcd for C20H18O2Cl
[M þ H]þ: calcd 325.0981, Found 325.0995.
H), 13C NMR (75 MHz, CDCl3):
d 27.1, 31.4, 34.8, 55.4, 111.0, 112.1,
120.2,125.9,128.0,128.2,128.4,128.7,128.8,128.9,130.1,130.3,141.4,
147.8,174.0. ESI-MS: m/z ¼ 295 [M þ H]þ, 317[M þ Na]þ, HRMS calcd
for C19H19O3 [M þ H]þ: calcd 295.1328, Found 295.1324.
5.5.3. 11,12-Dimethoxy-8,9-dihydro-7H-5-oxa-benzo [6,7]
cyclohepta [1,2-a] naphthalen-6-one (5c)
5.4.2. 2,3-Di methyl-5-(2-methoxy-phenyl)-8,9-dihydro-7H-
benzocycloheptene-6-carboxylic acid (4b)
Pale yellow solid. Yield:81.5% (1.7 g): mp 200 ꢀC: IR (KBr,
v cmꢁ1): 3394, 2934, 1708, 1510, 1215, 773, 1H NMR (300 MHz,
Yellow solid. Yield: 74.9% (1.7 g): mp 209 ꢀC: IR (KBr, v cmꢁ1):
CDCl3): d 1.86e1.98 (m, 1H, CH), 2.1e2.23 (m, 2H, CH2), 2.45e2.60
2931, 2856, 1669, 1245, 751, 1H NMR (300 MHz, CDCl3):
d
2.10 (s, 3H,
(m, 2H,eCH2), 2.19e3.15 (dd, J ¼ 3.7, 3.9 Hz, 1H, CH), 3.86 (s, 3H,
OCH3), 3.90 (s, 3H, OCH3), 6.82 (s, 1H, AreH), 6.91 (s, 1H, AreH), 7.18
(t, J ¼ 6.9, 1H, AreH), 7.38 (d, J ¼ 7.3 Hz, 1H, AreH), 7.48 (t, J ¼ 6.9,
1H, AreH), 7.57 (d, J ¼ 7.9 Hz, 1H, AreH), 13C NMR (75 MHz, CDCl3):
CH3), 2.10e2.20 (m, 2H, CH2), 2.20 (s, 3H, CH3), 2.23 (t, J ¼ 6.6, 6.4 Hz,
2H, CH2), 2.65 (t, J ¼ 6.2, 6.6 Hz, 2H, CH2), 3.63 (s, 3H, OCH3), 6.52 (s,
1H, AreH), 6.70e6.96 (m, 4H, AreH), 7.15e7.24 (m, 1H, AreH), 13
C
NMR (75 MHz, CDCl3):
d
19.2, 19.5, 27.1, 27.2, 30.9, 34.8, 55.4, 55.8,
d 23.8, 30.8, 33.3, 55.1, 56.1, 112.1, 112.2, 117.0, 119.1, 123.8, 124.7,
111.0, 112.1, 120.2, 128.7, 129.6, 129.9, 130.3, 130.9, 133.7, 136.5, 138.9,
156.6,174.1, ESI-MS: m/z ¼ 323[M þ H]þ, 345[M þ Na]þ, HRMS calcd
for C21H22O3Na [M þ Na]þ: calcd 345.1461, Found 345.1454.
125.3, 126.3, 130.5, 134.6, 146.8, 149.1, 149.5, 153.3, 161.7, ESI-MS: m/
z ¼ 323[M þ H], 345[M þ Na]þ, HRMS calcd for C20H19O4 [M þ H]þ:
calcd 323.1270, Found 323.1283.
5.4.3. 2,3-Dimethoxy-5-(2-methoxy-phenyl)-8,9-dihydro-7H-
benzocycloheptene-6-carboxylic acid (4c)
Acknowledgements
Yellow solid. Yield of 70.2%, mp 173 ꢀC: IR (KBr, v cmꢁ1): 2937,
2857, 1658, 1437, 1258, 1210, 1021, 755, 1H NMR (300 MHz, CDCl3):
The authors are gratefully acknowledge DST-SERB/EMEQ-078/
2013 for the financial support and the Council of Scientific and

B. Yadagiri et al. / European Journal of Medicinal Chemistry 79 (2014) 260e265
265
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[12] A.G. Kidane, H.A. Salacinski, K.R. Tiwari, A.M. Bruckdorfer, Biomolecules 5
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Industrial Research (CSIR), New Delhi for the award of fellowship
to BY.
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Appendix A. Supplementary data
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.ejmech.2014.04.015.
[16] L. Nagarapu, J. Mateti, H.K. Gaikwad, R. Bantu, M. Shibarani, N.J.P. Shubhasini,
Bioorganic & Medicinal Chemistry Letters 21 (2011) 4138.
[17] L. Nagarapu, H.K. Gaikwad, R. Bantu, S.R. Manikonda, European Journal of
Medicinal Chemistry 46 (2011) 2152.
[18] L. Nagarapu, V. Paparaju, A. Satyenar, Bioorganic & Medicinal Chemistry Let-
ters 18 (2008) 2351.
[19] L. Nagarapu, A. Satyendar, B. Rajashaker, K. Srinivas, P. Ruparani, K. Rahika,
G. Shubhashini, Bioorganic & Medicinal Chemistry Letters 18 (2008) 1167.
[20] L. Nagarapu, S. Vanaparthi, R. Bantu, C.G. Kumar, European Journal of Me-
dicinal Chemistry 69 (2013) 817.
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