One pot synthesis of some novel coumarins containing 5-(substituted-2- hydroxybenzoyl) pyridine as a new class of antimicrobial and antituberculosis agents

Article abstract of DOI:10.1007/s00044-012-0437-8

A novel class of substituted pyridyl coumarin derivatives has been synthesized starting from 3-acetyl coumarin and chromone-3-carbaldehyde via one pot reaction and fully characterized by spectral and elemental analysis. All these derivatives 3a-l were screened in vitro for antimicrobial activity against a representative panel of pathogenic strains. Compounds demonstrated good to excellent antibacterial activity, while some compounds exhibited equipotent antifungal activity as compared to that of first line standard drug. As a part of investigation of new antitubercular agents, in vitro screening of synthesized compounds against Mycobacterium tuberculosis H₃₇Rv has been done. Among the designed molecules, three compounds showed relatively better activity. From the entire study, it has been revealed that compounds appear to be better antimicrobials but relatively poor antituberculars.

Full text of DOI:10.1007/s00044-012-0437-8

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res (2013) 22:4338–4346
DOI 10.1007/s00044-012-0437-8
ORIGINAL RESEARCH
One pot synthesis of some novel coumarins containing
5-(substituted-2-hydroxybenzoyl) pyridine as a new class
of antimicrobial and antituberculosis agents
•
•
•
Varun G. Bhila Chirag V. Patel Niraj H. Patel
Dinkar I. Brahmbhatt
Received: 29 May 2012 / Accepted: 18 December 2012 / Published online: 8 January 2013
Ó Springer Science+Business Media New York 2013
Abstract A novel class of substituted pyridyl coumarin
derivatives has been synthesized starting from 3-acetyl
coumarin and chromone-3-carbaldehyde via one pot reac-
tion and fully characterized by spectral and elemental
analysis. All these derivatives 3a–l were screened in vitro
for antimicrobial activity against a representative panel of
pathogenic strains. Compounds demonstrated good to
excellent antibacterial activity, while some compounds
exhibited equipotent antifungal activity as compared to that
of first line standard drug. As a part of investigation of new
antitubercular agents, in vitro screening of synthesized
compounds against Mycobacterium tuberculosis H37Rv has
been done. Among the designed molecules, three com-
pounds showed relatively better activity. From the entire
study, it has been revealed that compounds appear to be
better antimicrobials but relatively poor antituberculars.
concern is justified by a current report from the World
Health Organization, according to which there are 9.4 mil-
lion new cases of TB and 1.65 million deaths due to TB
every year. One-third of the human population is believed to
be infected by this pathogen (WHO, 2008). Among HIV-
infected people with weakened immune system, TB is a
leading killer epidemic. Every year about 2 million people
living with HIV die due to TB (Jain et al., 2003). A recent
estimation by WHO has revealed that within next 20 years,
approximately 30 million people will be infected with the
bacillus (OMS, 2003). The forging facts reveal that there is a
crucial need for the development of new drugs which are
synthetically feasible, lack side effects, and have shorter
duration of treatment.
The coumarins are of great importance to chemists as
well as biologists as it is one of the key building blocks for
many naturally occurring compounds (Murray et al., 1982;
Fylaktakidou et al., 2004; O’Kennedy and Thornes, 1997).
Among the various heterocyclic moieties of pharmacolog-
ical interest, coumarin is endowed with various activities
such as antituberculosis (Manvar et al., 2008), anti-
inflammatory (Kontogiorgis and Hadjipavlou-Litina, 2005),
anti cancer (Kamal et al., 2009), anti HIV (Kaye et al.,
2004), anti tumor (Suzuki et al., 2006), and anti coagulant
(Garazd et al., 2005). The incorporation of heterocyclic ring
in the coumarin nucleus can bring about an extensive
modification in the biological activities of the parent com-
pound. Among the heterocyclic substituted coumarins,
pyridyl coumarins have a special importance due to their
diverse physiological actions. A number of coumarin
derivatives having pyridine substituted mainly at 3- and
4-position of the coumarin possess CNS depressant
(Moffett, 1964), anti fungal (Garazd et al., 2005), antibac-
terial (Sreenivasulu et al., 1974), and moth proofing activity
(Moffett, 1965).
Keywords Coumarin ꢀ Chromone-3-carbaldehyde ꢀ
¨
Krohnke’s reaction ꢀ Antituberculosis ꢀ Antimicrobial
Introduction
Mankind is surrounded by many infectious diseases, and
tuberculosis is one of them. TB is a lung infection caused
mainly by Mycobacterium tuberculosis and is considered as
one of the most threatening diseases for public health. This
V. G. Bhila ꢀ C. V. Patel ꢀ D. I. Brahmbhatt (&)
Department of Chemistry, Sardar Patel University,
388120 Vallabh Vidyanagar, Gujarat, India
e-mail: drdib317@gmail.com
N. H. Patel
Oxygen Bioresearch Ltd, Pharmez, Ahmedabad, Gujarat, India
123

Med Chem Res (2013) 22:4338–4346
4339
Chromone-3-carbaldehyde has been extensively used in
the synthesis of various heterocyclic systems. The synthe-
sis and reactivity of this versatile compound has been
reviewed (Ghosh, 1997, 2004). Most of the synthetic util-
ities of this compound are derived from the reactivity of its
electron-deficient centers at C-2, C-4, and formyl group
(Sabitha, 1996). Chromone-3-carbaldehyde can give access
to compounds where the chromone ring is retained, or to
2-hydroxybenzoyl derivatives resulting from the opening
of the pyran-4-one ring.
cyclized to give the final product 3a–l in good to excellent
yields (Table 1). Reaction proceeds in a single step, and the
¨
mechanism follows Krohnke’s reaction pathway to afford
the target molecule (Krohnke and Zecher, 1961; Krohnke,
1976) (Scheme 2).
Pharmacology
The MICs of synthesized compounds were carried out by
broth micro dilution method according to the National
Committee for Clinical Laboratory Standards (NCCLS,
2002). All the newly synthesized target compounds were
evaluated for their in vitro antibacterial activity against
Staphylococcus aureus (MTCC 96) and Bacillus subtilis
(MTCC 441) as Gram positive bacterial strains while
against Escherichia coli (MTCC 443) and Salmonella typhi
(MTCC 98) as Gram negative bacterial strains. They were
also evaluated for their in vitro antifungal activity against
Candida albicans (MTCC 227) and Aspergillus niger
(MTCC 282) as fungal strains. For comparison, the stan-
dard drug used for antibacterial potency of the compounds
was ampicillin, a broad spectrum antibiotic, while the
drugs used for antifungal potency of the compounds were
griseofulvin and nystatin. Minimum inhibitory concentra-
tion (MIC) was measured as described in ‘‘In vitro evalu-
ation of antimicrobial activity’’. The screening results
(Table 2) indicated that all the tested compounds exhibited
different inhibitory effects against different test organisms.
All MTCC cultures were collected from Institute of
Microbial Technology, Chandigarh and tested against
above mentioned known drugs. Mueller–Hinton broth was
used as nutrient medium to grow and dilute the drug sus-
pension for the test. The size of the inoculum for the test
strain was adjusted to 108 colony forming unit (CFU) per
milliliter by comparing the turbidity. DMSO was used as a
diluent to get the desired concentration of compounds to
test upon standard bacterial strains.
Considering the importance of pyridyl-substituted cou-
marins, a variety of substituted coumarins were synthesized
from our laboratory (Brahmbhatt et al., 2004, 2005, 2007;
Patel et al., 2010a, b). In continuation of that work, we syn-
thesized 2-hydroxybenzoyl-substituted pyridines attached to
coumarins for the first time, which we found here to show
good antimicrobial activity.
A frightening rise in pathogenic resistance to existing
drugs is a serious problem with antimicrobial therapy and
necessitates continuing research into new class of antimi-
crobials (Woodford, 2003). No new drugs have been
developed specifically against mycobacteria since the
1960s, and within the last few years, only some promising
drug candidates emerged (Primm and Franzblau, 2007;
´
`
Medecins Sans Frontieres, 2009). So this is our sincere
effort in this direction to check activity of the synthesized
series of compounds against M. tuberculosis H37Rv.
Chemistry
The starting material 3-acetyl coumarins were prepared
from various salicylaldehydes by Knoevenagel condensa-
tion while chromone-3-carbaldehydes were prepared from
various o-hydroxy acetophenones by Vilsmeier Haack
reaction. The synthetic route employed to produce the
library of target compounds 3-(5-(2-hydroxybenzoyl)pyri-
din-2-yl)coumarins 3a–l is portrayed in Scheme 1.
In the presence of ammonium acetate in acetic acid,
chromone-3-carbaldehyde gets converted into enamine
derivative which upon reaction with 3-acetyl coumarin
results in a chalcone type intermediate which in situ gets
In vitro antituberculosis activity of all the synthesized
compounds against M. tuberculosis H37Rv strain was
determined using Lowenstein–Jensen medium (conven-
tional method) as described by (Rattan, 2000). The observed
Scheme 1 Synthetic pathway for target compounds 3a–l. Reagents and conditions (a) NH4OAc, AcOH, reflux 8 h
123

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Med Chem Res (2013) 22:4338–4346
Table 1 Physical parameters of 3-(5-(2-hydroxybenzoyl)pyridin-2-yl)coumarin derivatives 3a–l
Compd.
R1
R2
R3
R4
Formula (mw)
mp (°C)
Yield %
3a
3b
3c
3d
3e
3f
H
H
H
H
H
H
H
H
H
H
H
H
C21H13NO4 (343.33)
C22H15NO4 (357.36)
220
184
210
188
204
230
225
190
196
250
240
260
74
69
75
83
77
85
72
70
78
80
84
82
H
H
CH3
Cl
H
H
C21H12ClNO4 (377.78)
OCH3
OCH3
OCH3
H
H
H
C22H15NO5 (373.36)
C23H17NO5 (387.38)
C22H14ClNO5 (407.80)
H
CH3
Cl
H
3g
3h
3i
Br
H
C21H12BrNO4 (422.23)
H
Br
CH3
Cl
C22H14BrNO4 (436.25)
H
Br
C
21H11BrClNO4 (456.67)
25H15NO4 (393.39)
3j
H
Benzo
Benzo
Benzo
H
C
3k
3l
H
CH3
Cl
C26H17NO4 (407.42)
H
C25H14ClNO4 (427.84)
Scheme 2 Plausible
mechanistic pathway for the
synthesis of compounds 3a–l
R
R
O
O
O
O
O
O
c
NH4OA
CH3
CH2
AcOH
R1
R1
R2
R2
1a-d
R
R
O
O
O
O
O
O
HO
CH2
O
O
R1
R1
R2
R2
R3
OHC
R3
OHC
O
2a-c
NH4OAc
AcOH
R
R
O
O
O
O
R3
OH
HO
R1
R1
H
O
HN
O
R2
R2
R3
H2N
H
O
OH
OH
HO
(i) -
2H2O
(ii)
Aromatization
R
O
O
R3
R1
N
R2
3a-l
O
OH
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Med Chem Res (2013) 22:4338–4346
4341
Table 2 In vitro antimicrobial activity of various synthesized coumarin derivatives 3a–l. (MICs, lg/mL)
Compd.
Gram positive bacteria
Gram negative bacteria
Fungi
S.A.
MTCC 96
B.S.
MTCC 441
E.C.
MTCC 443
S.T.
MTCC 98
C.A.
MTCC 227
A.N.
MTCC 282
3a
200
100
250
500
250
200
200
500
62.5
100
125
100
250
nta
250
200
200
200
250
200
100
500
100
100
100
125
250
nta
100
250
250
200
100
125
50
125
200
250
250
100
200
125
100
100
250
250
250
100
nta
500
250
1000
1000
[1000
[1000
500
3b
3c
500
3d
1000
1000
[1000
200
3e
3f
[1000
[1000
500
3g
3h
100
62.5
200
200
250
100
nta
500
3i
100
[1000
500
3j
250
3k
500
1000
3l
1000
nta
100
nta
Ampi
Nyst
Grise
100
100
nta
nta
nta
nta
500
100
S.A. Staphylococcus aureus, B.S. Bacillus subtilis, E.C. Escherichia coli, S.T. Salmonella typhi, C.A. Candida albicans, A.N. Aspergillus niger,
MTCC Microbial Type Culture Collection, Ampi ampicillin, Nyst nystatin, Grise griseofulvin
a
nt not tested
0
results of their MICs are presented in Table 3 in lg/mL
compared with isoniazid, the standard antitubercular drug.
doublet (J = 8.4 Hz). The C6 –H of pyridine ring appears as
poorly resolved doublet at around 9.00 d in compounds 3g–l
while it merges with C4–H proton signal in compounds 3a–f.
The C4–H proton of coumarin ring appears in the downfield
region due to peri effect of nitrogen atom of pyridine ring.
The phenolic O–H proton appears as a sharp singlet between
11.69 and 11.91 d and gets exchanged by D2O. The 13C NMR
spectra are in good agreement with the structures assigned.
The signals observed at around 20.48 and 56.36 d can be
assigned to CH3 and OCH3, respectively. The signals
Results and discussion
Analytical results
A series of 3-(5-(2-hydroxybenzoyl)pyridin-2-yl)couma-
¨
rins 3a–l have been synthesized via Krohnkes pyridine
synthesis as exemplified in Scheme 1. The structures of all
the newly synthesized compounds were confirmed by ele-
mental analysis and FT-IR, 1H NMR, 13C NMR, and
DEPT-90 spectral analysis. A mass spectrum was recorded
for one representative compound 3a.
Table 3 In vitro antituberculosis activity of title compounds against
M. tuberculosis H37Rv (MICs, lg/mL) compared with isoniazid
(0.2 lg/mL)
Compd.
MIC (lg/mL)
The IR spectra of compounds 3a–l exhibited carbonyl
stretching band of ketone between 1,612 and 1,628 cm-1
and a characteristic d-lactone carbonyl stretching band
between 1,713 and 1,728 cm-1. C=N and C=C aromatic
stretching bands were observed in the range of
1,454–1,489 cm-1 and 1,566–1,597 cm-1, respectively.
The aromatic C–H stretching band was observed between
3,044 and 3,063 cm-1. A characteristic O–H stretching band
3a
3b
3c
3d
3e
3f
1,000
100
250
500
62.5
500
3g
3h
3i
250
100
1
was observed around 3,420 cm-1. In H NMR spectra of
1,000
250
compounds 3a–l, the aromatic protons resonate as multiplets
between 6.94 and 8.18 d (except pyridine ring protons).
3j
3k
3l
1,000
500
0
C4 –H of pyridine ring resonates at around 8.10 d as doublet
0
(J = 2, 8.4 Hz), while C3 –H resonates at around 8.70 d as a
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Med Chem Res (2013) 22:4338–4346
appearing between 116 and 160 d are for aromatic carbons.
The Carbonyl carbon of d-lactone ring of coumarin appears
around 163.40 d, while ketonic carbon appears in the most
downfield region at around 198.66 d. It is important to note
that in case of compounds 3a, 3d, 3e, and 3f, one carbon
signal in 13C NMR spectra is less than expected. This may be
due to identical chemical shifts of two carbon atoms which
may appear at the same position. The presence of tertiary
carbon atoms was ascertained by DEPT-90 spectra. The
selected mass spectrum of compound 3a showed M? peak at
m/z 343 along with other fragment peaks. The appearance of
molecular ion peak at 343 mass units supports the structure of
compound 3a.
(MIC = 100 lg/mL). Compounds 3g (MIC = 200 lg/mL)and
3b, 3j (MIC = 250 lg/mL) showed higher activity as compared
with griseofulvin (MIC = 500 lg/mL) against C. albicans.
The observation indicates that the compounds 3j, 3k, and
3l havingthe presence of fused benzene ring at 5,6positionof
the chromene ring show good activity against Gram positive
bacterial strain but poor activity against Gram negative
bacterial strain. The compounds 3g and 3h containing bro-
mine at 6th position of chromene ring are more potent toward
Gram negative bacterial strain as compared with Gram
positive bacterial strain, while compound 3i having bromine
at 6th position and chlorine in hydroxybenzoyl ring shows
excellent activity against all the four bacterial strains. It is
interesting to note that the values of MIC are considerably
increased with the presence of chlorine atom in the
hydroxybenzoyl ring in compounds 3c, 3f, 3i, and 3l. The
compounds having methoxyl group at 8th position in chro-
mene ring as well as compounds having no substitution in
chromene ring show good to moderate activity.
Biological results
In general, the compounds showed an improved antibac-
terial activity when compared to their antifungal activity.
The deduced patterns of antimicrobial activity of the syn-
thesized target compounds are in the following order:
Antibacterial activity [ antifungal activity.
A close investigation of the in vitro antibacterial and
antifungal activity profiles of the 3-(5-(2-hydroxya-
royl)pyridin-2-yl)coumarins gives a clear picture of the
structure activity relations (SAR) among the compounds
under study.
The encouraging results from the antimicrobial studies
prompted us to go for the screening of the title com-
pounds for their in vitro antituberculosis activity against
M. tuberculosis H37Rv. The results of the screening showed
relatively good anti-TB activity for compounds 3b and 3h
having R4 = CH3, as compared to the most potent activity
for compound 3e having R4 = CH3 and R1 = OCH3. The
rest of the compounds showed poor anti-TB activity.
Upon reviewing antimicrobial data, it has been observed
that compound 3i (MIC = 62.5 lg/mL) showed excellent
activity against gram positive bacteria S. aureus as com-
pared with ampicillin (MIC = 250 lg/mL). Compounds
3g (MIC = 50 lg/mL) and 3i (MIC = 62.5 lg/mL)
showed excellent activity against gram negative bacteria
E. coli as compared with ampicillin (MIC = 100 lg/mL).
Compounds 3b, 3j, 3l (MIC = 100 lg/mL), 3k (MIC =
125 lg/mL), and 3a, 3f, 3g (MIC = 200 lg/mL) were more
potent when compared with ampicillin (MIC = 250 lg/mL)
against S. aureus while 3c, 3e were equipotent compared
with ampicillin (MIC = 250 lg/mL) against S. aureus.
Compounds 3g, 3i, 3j, 3k (MIC = 100 lg/mL), 3l (MIC =
125 lg/mL), and 3b, 3c, 3d, 3f (MIC = 200 lg/mL) were
found to be more active while compounds 3a, 3e
(MIC = 250 lg/mL) were found to be equally active as
compared with ampicillin (MIC = 250 lg/mL) against
B. subtilis.
Conclusion
The present research study reports the successful synthesis,
antibacterial and antituberculosis studies of a new series of
the 3-(5-(2-hydroxyaroyl)pyridin-2-yl)coumarin deriva-
tives carrying biologically active heterocyclic entities. We
are reporting for the first time that coumarin containing
5-(substituted-2-hydroxybenzoyl)pyridines might be
a
suitable pharmacophore for developing novel antimicrobial
and antitubercular agents. Their screening results revealed
that all the compounds showed moderate to very good
antimicrobial activities against various pathogenic strains
and moderate to poor antituberculosis activity against
M. tuberculosis H37Rv strain. Compounds 3g and 3i
exhibited excellent antimicrobial activity and are said to be
the most proficient members of the series.
Compounds 3a, 3e, 3h (MIC = 100 lg/mL) were found
to be equipotent against gram negative bacteria E. coli as
compared with ampicillin (MIC = 100 lg/mL) while on
the other hand, compounds 3e, 3h, 3i (MIC = 100 lg/mL)
showed equipotent activity against gram negative bacteria
S. typhi as compared with ampicillin (MIC = 100 lg/mL).
Compounds 3i, 3l (MIC = 100 lg/mL) were the only can-
didates which showed equal activity against anti fungal strains
C. albicans and A. niger, respectively as compared with nystatin
Experimental
Chemistry
All reactions were performed with commercially available
reagents, and they were used without further purification.
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Med Chem Res (2013) 22:4338–4346
4343
3-(5-(2-Hydroxybenzoyl)pyridin-2-yl)coumarin (3a) IR
(KBr, mmax, cm-1): 1454 (C=N aromatic stretching), 1597
(C=C aromatic stretching), 1625 (C=O ketone stretching),
1722 (C=O d-lactone stretching), 3065 (C–H aromatic
stretching), 3421 (OH stretching); 1H NMR (400 MHz,
CDCl3, d): 6.95–7.75 (8H, m, Ar–H), 8.14 (1H, dd, J = 8.4
and 2.4 Hz, C4 –H), 8.69 (1H, d, J0= 8.4 Hz, C3 –H), 9.02
(2H, merged singlet, C4–H and C6 –H), 11.88 (1H, s, OH,
D2O-exchangeable); 13C NMR (100 MHz, CDCl3, d):
116.53 (CH), 118.80 (CH), 118.98 (C), 119.15 (CH),
119.29 (C), 123.44 (CH), 124.90 (C), 129.34 (CH), 132.96
(C), 133.04 (CH), 137.11 (CH), 137.85 (CH), 144.35 (CH),
149.10 (CH), 151.22 (C), 153.79 (C), 154.24 (C), 159.99
(C), 163.40 (d-lactone CO), 198.66 (CO); Anal. Calcd. for
C21H13NO4: C, 73.46; H, 3.82; N, 4.08 %. Found:
C, 73.61; H, 3.74; N, 4.16 %.
Organic solvents were purified by standard methods
(Furniss et al., 2004) and stored over molecular sieves. All
reactions were monitored by thin-layer chromatography
(TLC, on aluminum plates coated with silica gel 60 F254
,
0.25 mm thickness, Merck), and detection of the compo-
nents was made by exposure to UV light. Melting points
were determined in open capillaries and are uncorrected.
Infrared spectra were recorded on Shimadzu FTIR 8401
spectrophotometer using potassium bromide pellets in the
range 4,000–400 cm-1, and frequencies of only charac-
0
0
1
teristic peaks are expressed in cm-1. H and 13C Nuclear
Magnetic Resonance spectra were recorded in CDCl3 on a
Bruker Avance 400 (MHz) spectrometer (Bruker Scientific
Corporation Ltd., Switzerland) using TMS signal as an
internal standard at 400 and 100 MHz, respectively.
Chemical shifts are reported in parts per million (ppm).
The coupling constants (J) are given in Hertz (Hz). Mass
spectrum of compound 3a was scanned on a Shimadzu QP
2010 spectrometer (Shimadzu, Tokyo, Japan). The com-
pounds were purified by column chromatography using
silica gel (60–120 mesh). Reference drugs ampicillin,
griseofulvin, nystatin, and isoniazid were commercial.
Starting precursors 3-acetyl coumarins (Bischler, 1892;
Bui-Hoi et al., 1957; Murthi and Basak, 1993) 1a–d and
chromone-3-carbaldehydes (Zhao et al., 2007) 2a–c were
prepared using the reported procedures.
3-(5-(2-Hydroxy-5-methylbenzoyl)pyridin-2-yl)coumarin
(3b) IR (KBr, mmax
,
cm-1): 1489 (C=N aromatic
stretching), 1589 (C=C aromatic stretching), 1628 (C=O
ketone stretching), 1720 (C=O d-lactone stretching), 3063
(C–H aromatic stretching), 3420 (OH stretching); 1H NMR
(400 MHz, CDCl3, d): 2.31 (3H, s, CH3), 7.03–7.75 (7H,
0
m, Ar–H), 8.12 (1H, dd, J = 8.4 and 2 Hz, C4 –H), 8.67
0
(1H, d, J = 08.4 Hz, C3 –H), 9.00 (2H, merged singlet,
C4–H and C6 –H), 11.72 (1H, s, OH, D2O-exchangeable);
13C NMR (100 MHz, CDCl3, d): 20.48 (CH3), 116.53
(CH), 118.53 (CH), 118.73 (C), 119.34 (C), 123.26 (CH),
124.88 (CH), 128.38 (C), 129.25 (CH), 132.53 (CH),
132.91 (CH), 137.57 (CH), 138.16 (CH), 144.04 (CH),
144.79 (C), 149.29 (CH), 152.69 (C), 153.77 (C), 154.19
(C), 160.06 (C), 161.28 (d-lactone CO), 198.76 (CO); Anal.
Calcd. for C22H15NO4: C, 73.94; H, 4.23; N, 3.92 %.
Found: C, 74.06; H, 4.29; N, 3.87 %.
General procedure for the synthesis of 3-(5-(2-
hydroxybenzoyl)pyridin-2-yl)coumarins 3a–l
In a 100 mL three-necked flask equipped with a dropping
funnel, condenser, guard tube, and magnetic needle, an
appropriate chromone-3-carbaldehyde 2a–c (0.004 mol)
was taken in glacial acetic acid (15 mL). To this, ammo-
nium acetate (0.04 mol) was added with stirring at room
temperature. Then a solution of appropriate 3-acetyl cou-
marin 1a–d (0.004 mol) in glacial acetic acid (15 mL) was
added with stirring at room temperature. The reaction
mixture was further stirred for 45 min and then refluxed in
an oil bath at 140–150 °C for 8 h. It was then allowed to
come to room temperature and was poured into ice cold
water (100 mL). The solid product obtained was extracted
with chloroform (3 9 30 mL). The combined chloroform
extract was washed with 10 % sodium bicarbonate solution
(3 9 20 mL) and then with water (3 9 20 mL). It was
then dried over anhydrous sodium sulfate. The removal of
chloroform under vacuum gave a solid product which was
purified by column chromatography using silica gel and
chloroform–petroleum ether (60°–80°) (6:4) as an eluent.
Thus, 3-(5-(2-hydroxyaroyl)pyridin-2-yl)coumarins 3a–l
were obtained as a solid material, which were recrystal-
lized from chloroform–hexane.
3-(5-(5-Chloro-2-hydroxybenzoyl)pyridin-2-yl)coumarin
(3c) IR (KBr, mmax, cm-1): 1466 (C=N aromatic stretch-
ing), 1589 (C=C aromatic stretching), 1612 (C=O ketone
stretching), 1720 (C=O d-lactone stretching), 3063 (C–H
aromatic stretching), 3425 (OH stretching); 1H NMR
(400 MHz, CDCl3, d): 7.10–7.75 (7H, m, Ar–H), 8.14 (1H,
0
dd, J = 8.4 and 2 Hz, C4 -H), 8.72 (1H, d, J = 9.2 Hz,
0
0
C3 -H), 9.01 (2H, merged singlet, C4–H and C6 –H), 11.79
(1H, s, OH, D2O-exchangeable); 13C NMR (100 MHz,
CDCl3, d): 116.55 (CH), 119.32 (C), 119.63 (C), 120.44
(CH), 123.35 (CH), 123.93 (C), 124.06 (C), 124.89 (CH),
129.29 (CH), 131.74 (CH), 132.15 (C), 132.99 (CH), 136.90
(CH), 137.49 (CH), 144.21 (CH), 149.35 (CH), 154.25 (C),
154.40 (C), 160.02 (C), 161.77 (d-lactone CO), 198.01 (CO);
Anal. Calcd. for C21H12ClNO4: C, 66.77; H, 3.20; N, 3.71 %.
Found: C, 66.61; H, 3.11; N, 3.78 %.
123

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Med Chem Res (2013) 22:4338–4346
8-Methoxy-3-(5-(2-hydroxybenzoyl)pyridin-2-yl)coumarin
(3d) IR (KBr, mmax, cm-1): 1478 (C=N aromatic stretch-
ing), 1582 (C=C aromatic stretching), 1623 (C=O ketone
stretching), 1723 (C=O d-lactone stretching), 3056 (C–H
aromatic stretching), 3419 (OH stretching); 1H NMR
(400 MHz, CDCl3, d): 4.04 (3H, s, OCH3), 6.94–7.62 (7H,
6-Bromo-3-(5-(2-hydroxybenzoyl)pyridin-2-yl)coumarin
(3g) IR (KBr, mmax
,
cm-1): 1484 (C=N aromatic
stretching), 1589 (C=C aromatic stretching), 1622 (C=O
ketone stretching), 1723 (C=O d-lactone stretching), 3044
(C–H aromatic stretching), 3420 (OH stretching); 1H NMR
(400 MHz, CDCl3, d): 6.95–7.86 (7H, m, Ar–H), 8.13 (1H,
0
0
m, Ar–H), 8.14 (1H, dd, J = 8.4 and 2 Hz, C4 –H), 8.71
0
dd, J = 8.4 and 2 Hz, C4 –H), 8.66 (1H, d, J 0= 8.4 Hz,
0
(1H, d, J = 8.4 Hz, C3 –H), 9.01 (2H, merged singlet, C4–H
and C6 –H), 11.87 (1H, s, OH, D2O-exchangeable); 13C
C3 –H), 9.01 (1H, poorly resolved doublet, C6 –H), 8.91
(1H, s, C4–H), 11.88 (1H, s, OH, D2O-exchangeable); 13C
NMR (100 MHz, CDCl3, d): 117.45 (C), 118.25 (CH),
118.82 (CH), 119.15 (CH), 120.83 (C), 123.46 (CH),
125.10 (C), 131.34 (CH), 132.97 (CH), 133.89 (C), 135.61
(CH), 137.18 (CH), 137.76 (CH), 142.66 (CH), 149.33
(CH), 153.00 (C), 153.28 (C), 159.41 (C), 161.10 (C),
163.34 (d-lactone CO), 198.74 (CO); Anal. Calcd. for
C21H12BrNO4: C, 59.74; H, 2.86; N, 3.32 %. Found: C,
59.87; H, 2.78; N, 3.24 %.
0
NMR (100 MHz, CDCl3, d): 56.36 (OCH3), 114.73 (CH),
118.79 (CH), 118.99 (C), 119.17 (CH), 119.90 (C), 120.67
(CH), 123.57 (CH), 124.77 (CH), 132.95 (CH), 137.12
(CH), 138.00 (CH), 142.37 (C), 143.92 (C), 144.58 (CH),
147.04 (C), 148.92 (CH), 153.63 (C), 159.42 (C), 163.34
(d-lactone CO), 198.59 (CO); Anal. Calcd. for C22H15NO5:
C, 70.77; H, 4.05; N, 3.75 %. Found: C, 70.91; H, 3.98; N,
3.69 %.
8-Methoxy-3-(5-(2-hydroxy-5-methylbenzoyl)pyridin-2-yl)-
coumarin (3e) IR (KBr, mmax, cm-1): 1481 (C=N aro-
matic stretching), 1582 (C=C aromatic stretching), 1628
(C=O ketone stretching), 1720 (C=O d-lactone stretching),
6-Bromo-3-(5-(2-hydroxy-5-methylbenzoyl)pyridin-2-yl)-
coumarin (3h) IR (KBr, mmax, cm-1): 1474 (C=N aro-
matic stretching), 1582 (C=C aromatic stretching), 1628
(C=O ketone stretching), 1713 (C=O d-lactone stretching),
1
1
3060 (C–H aromatic stretching), 3422 (OH stretching); H
3047 (C–H aromatic stretching), 3422 (OH stretching); H
NMR (400 MHz, CDCl3, d): 2.30 (3H, s, CH3), 4.04 (3H,
s, OCH3), 7.03–7.41 (6H, m, Ar–H), 8.09 (1H, dd, J = 8.4
NMR (400 MHz, CDCl3, d): 2.30 (3H, s, CH3), 7.03–7.84
0
(6H, m, Ar–H), 8.11 (1H, dd, J = 8.4 and 2 Hz, C4 –H),
0
0
0
and 2.4 Hz, C4 –H), 8.68 (1H, d, J0= 8.4 Hz, C3 –H), 8.97
(2H, merged singlet, C4–H and C6 –H), 11.72 (1H, s, OH,
D2O-exchangeable); 13C NMR (100 MHz, CDCl3, d):
20.49 (CH3), 56.36 (OCH3), 114.83 (CH), 118.58 (C),
118.62 (C), 119.84 (CH), 120.74 (CH), 123.38 (C), 123.80
(C), 124.83 (CH), 128.50 (CH), 132.43 (CH), 133.20 (C),
138.31 (CH), 143.91 (CH), 144.83 (CH), 147.02 (CH),
148.56 (C), 153.28 (C), 159.36 (C), 161.29 (d-lactone CO),
198.22 (CO); Anal. Calcd. for C23H17NO5: C, 71.31; H,
4.42; N, 3.62 %. Found: C, 71.43; H, 4.49; N, 3.69 %.
8.64 (1H, d,0 J = 8.4 Hz, C3 –H), 8.89 (1H, poorly resolved
doublet, C6 –H), 8.97 (1H, s, C4–H), 11.69 (1H, s, OH,
D2O-exchangeable); 13C NMR (100 MHz, CDCl3, d):
20.49 (CH3), 117.42 (C), 118.23 (CH), 118.56 (CH),
118.68 (C), 120.83 (C), 123.37 (CH), 125.18 (C), 128.39
(C), 131.29 (CH), 132.48 (CH), 133.29 (C), 135.53 (CH),
137.58 (CH), 138.22 (CH), 142.47 (CH), 149.35 (CH),
152.94 (C), 153.16 (C), 159.38 (C), 161.30 (d-lactone CO),
198.65 (CO); Anal. Calcd. for C22H14BrNO4: C, 60.57; H,
3.23; N, 3.21 %. Found: C, 60.73; H, 3.16; N, 3.28 %.
8-Methoxy-3-(5-(5-chloro-2-hydroxybenzoyl)pyridin-2-yl)-
coumarin (3f) IR (KBr, mmax, cm-1): 1472 (C=N aro-
matic stretching), 1589 (C=C aromatic stretching), 1628
(C=O ketone stretching), 1728 (C=O d-lactone stretching),
6-Bromo-3-(5-(5-chloro-2-hydroxybenzoyl)pyridin-2-yl)-
coumarin (3i) IR (KBr, mmax, cm-1): 1466 (C=N aro-
matic stretching), 1582 (C=C aromatic stretching), 1628
(C=O ketone stretching), 1713 (C=O d-lactone stretching),
1
1
3056 (C–H aromatic stretching), 3421 (OH stretching); H
3047 (C–H aromatic stretching), 3420 (OH stretching); H
NMR (400 MHz, CDCl3, d): 4.05 (3H, s, OCH3),
7.09–7.58 (6H, m, Ar–H), 8.15 (1H, dd, J = 8.4 and 2 Hz,
NMR (400 MHz, CDCl3, d): 7.09–7.86 (6H, m, Ar–H),
0
8.12 (1H, dd, J = 8.4 and 2 Hz, C4 –H), 8.69 (1H, d,
0
0
0
C4 –H), 8.76 (1H, d, J = 8.4 Hz, C3 –H), 9.03 (2H, merged
J = 8.4 Hz, C3 –H), 8.91 (1H, poorly resolved doublet,
0
0
singlet, C4–H and C6 –H), 11.75 (1H, s, OH, D2O-
C6 –H), 9.00 (1H, s, C4–H), 11.77 (1H, s, OH, D2O-
exchangeable); 13C NMR (100 MHz, CDCl3, d): 56.37
(OCH3), 114.77 (CH), 119.58 (C), 119.89 (C), 120.46
(CH), 120.70 (CH), 123.65 (CH), 123.78 (C), 123.98 (C),
124.78 (CH), 131.71 (CH), 132.25 (C), 136.96 (CH),
137.86 (CH), 143.95 (C), 144.72 (CH), 147.05 (C), 148.98
(CH), 154.15 (C), 159.41 (C), 161.76 (d-lactone CO),
197.76 (CO); Anal. Calcd. for C22H14ClNO5: C, 64.79; H,
3.46; N, 3.43 %. Found: C, 64.94; H, 3.40; N, 3.50 %.
exchangeable); 13C NMR (100 MHz, CDCl3, d): 117.44
(C), 118.26 (CH), 119.60 (C), 120.47 (CH), 120.82 (C),
123.47 (CH), 123.93 (C), 125.11 (C), 131.33 (CH), 131.69
(CH), 132.44 (C), 135.64 (CH), 136.94 (CH), 137.53 (CH),
142.66 (CH), 149.42 (CH), 153.01 (C), 153.79 (C), 159.36
(C), 161.82 (d-lactone CO), 197.92 (CO); Anal. Calcd. for
C21H11BrClNO4: C, 55.23; H, 2.43; N, 3.07 %. Found: C,
55.11; H, 2.34; N, 3.13 %.
123

Med Chem Res (2013) 22:4338–4346
4345
3-(5-(2-Hydroxybenzoyl)pyridin-2-yl)-3H-benzo[f]couma-
rin (3j) IR (KBr, mmax, cm-1): 1481 (C=N aromatic
stretching), 1587 (C=C aromatic stretching), 1624 (C=O
ketone stretching), 1727 (C=O d-lactone stretching), 3056
(C–H aromatic stretching), 3419 (OH stretching); 1H NMR
(400 MHz, CDCl3, d): 6.96–8.12 (9H, m, Ar–H), 8.16 (1H,
(CH), 137.61 (CH), 139.98 (CH), 149.40 (CH), 153.21 (C),
154.43 (C), 154.63 (C), 160.15 (C), 161.78 (d-lactone CO),
198.01 (CO); Anal. Calcd. for C25H14ClNO4: C, 70.18; H,
3.30; N, 3.27 %. Found: C, 70.02; H, 3.22; N, 3.34 %.
Biological assay
0
dd, J = 8 and 2 Hz, C4 –H), 8.57 (1H, d, J = 8.4 Hz,
0
C5–H), 8.80 (1H, d,0J = 8.4 Hz, C3 –H), 9.07 (1H, poorly
In vitro evaluation of antimicrobial activity
resolved doublet, C6 –H), 9.88 (1H, s, C4–H), 11.91 (1H, s,
OH, D2O-exchangeable); 13C NMR (100 MHz, CDCl3, d):
113.80 (C), 116.52 (CH), 118.81 (CH), 119.04 (C), 119.17
(CH), 122.14 (CH), 123.33 (CH), 126.47 (CH), 128.81
(CH), 129.11 (CH), 129.71 (C), 130.45 (C), 132.98 (CH),
133.52 (C), 133.87 (C), 134.79 (CH), 137.09 (CH), 138.05
(CH), 140.15 (CH), 149.04 (CH), 153.88 (C), 154.47 (C),
160.02 (C), 163.38 (d-lactone CO), 198.49 (CO); Anal.
Calcd. for C25H15NO4 C, 76.33; H, 3.84; N, 3.56 %.
Found: C, 76.47; H, 3.90; N, 3.51 %.
The newly prepared compounds were screened for their
MICs by broth micro dilution method. DMSO was used as
a diluent to get desired concentration of compounds to test
upon standard bacterial strains. Serial dilutions were pre-
pared in primary and secondary screening. The control tube
containing no antibiotic was immediately subcultured
(before inoculation) by spreading a loopful evenly over a
quarter of plate of medium suitable for the growth of the
test organism and put for incubation at 37 °C overnight.
The tubes were then incubated overnight. The MIC of the
control organism was read to check the accuracy of the
compound concentrations. The lowest concentration
(highest dilution) required to arrest the growth of bacteria
was regarded as minimum inhibitory concentration (MIC).
All the tubes showing no visible growth (same as control
tube) were subcultured and incubated overnight at 37 °C.
The amount of growth from the control tube before incu-
bation (which represents the original inoculum) was com-
pared. Subcultures might show (i) similar number of
colonies indicating bacteriostatic (ii) a reduced number of
colonies indicating a partial or slow bactericidal activity
(iii) no growth if the whole inoculum has been killed. The
test must include a second set of the same dilutions inoc-
ulated with an organism of known sensitivity. Each syn-
thesized compound was diluted obtaining 2,000 lg/mL
concentration as a stock solution. In primary screening,
500, 250, and 200 lg/mL concentrations of the synthesized
compounds were taken. The compounds which were found
active in this primary screening were further tested in a
second set of dilution using 100, 62.5, 50, and 25 lg/mL
concentrations against all microorganisms. The highest
dilution showing at least 99 % inhibition is taken as MIC.
3-(5-(2-Hydroxy-5-methylbenzoyl)pyridin-2-yl)-3H-benzo-
[f]coumarin (3k) IR (KBr, mmax, cm-1): 1474 (C=N
aromatic stretching), 1566 (C=C aromatic stretching), 1628
(C=O ketone stretching), 1728 (C=O d-lactone stretching),
1
3063 (C–H aromatic stretching), 3421 (OH stretching); H
NMR (400 MHz, CDCl3, d): 2.32 (3H, s, CH3), 7.04–8.10
0
(8H, m, Ar–H), 8.13 (1H, dd, J = 8.4 and 2.4 Hz, C4 –H),
8.54 (1H, d, J = 8.4 Hz, C5–H), 8.77 (1H, d, J = 8.4 Hz,
0
0
C3 –H), 9.05 (1H, poorly resolved doublet, C6 –H),
9.83(1H, s, C4–H), 11.74 (1H, s, OH, D2O-exchangeable);
13C NMR (100 MHz, CDCl3, d): 20.51 (CH3), 113.78 (C),
116.52 (CH), 118.54 (CH), 118.75 (C), 122.09 (CH),
122.36 (C), 123.23 (CH), 126.43 (CH), 128.40 (C), 128.74
(CH), 129.11 (CH), 129.64 (C), 130.41 (C), 132.54 (CH),
132.89 (C), 134.63 (CH), 137.82 (CH), 138.16 (CH),
139.91 (CH), 149.17 (CH), 153.87 (C), 154.38 (C), 160.11
(C), 161.29 (d-lactone CO), 198.67 (CO); Anal. Calcd. for
C26H17NO4: C, 76.65; H, 4.21; N, 3.44 %. Found:
C, 76.78; H, 4.28; N, 3.50 %.
3-(5-(5-Chloro-2-hydroxybenzoyl)pyridin-2-yl)-3H-benzo-
[f]coumarin (3l) IR (KBr, mmax, cm-1): 1466 (C=N aro-
matic stretching), 1566 (C=C aromatic stretching), 1628
(C=O ketone stretching), 1720 (C=O d-lactone stretching),
In vitro evaluation of antituberculosis activity
1
3063 (C–H aromatic stretching), 3418 (OH stretching); H
NMR (400 MHz, CDCl3, d): 7.10–8.13(8H, m, Ar–H),
All the compounds were tested for in vitro antituberculosis
activity against M. tuberculosis H37Rv by Lowensteine–
Jensen method, and then media was sterilized by inspissa-
tion method. A culture of M. tuberculosis H37Rv growing on
Lowensteine–Jensen medium was harvested in 0.85 % sal-
ine in bijou bottle. Each compound was tested using DMSO
as a diluent at a concentration range of 1,000–62.5 lg/mL,
and results are presented as the minimal inhibitory con-
centration (MIC) (Table 3) with respect to the standard drug
0
8.15 (1H, dd, J = 8.4 and 2 Hz, C4 –H), 8.56 (1H, d,
0
J = 8.4 Hz, C5–H), 8.82 (1H, d, 0J = 8.4 Hz, C3 –H), 9.06
(1H, poorly resolved doublet, C6 –H), 9.87 (1H, s, C4–H),
11.82 (1H, s, OH, D2O-exchangeable); 13C NMR
(100 MHz, CDCl3, d): 116.57 (CH), 119.68 (C), 120.45
(CH), 122.06 (CH), 122.57 (C), 123.26 (CH), 123.92 (C),
126.42 (CH), 128.75 (CH), 129.13 (CH), 129.67 (C),
130.43 (C), 131.76 (CH), 132.04 (C), 134.62 (CH), 136.87
123

4346
Med Chem Res (2013) 22:4338–4346
potential anticancer and antimicrobial agents. Lett Drug Des
Discovery 6:201–209
Kaye PT, Musa MA, Nichinda AT, Nocanda XW (2004) Novel
heterocyclic analogues of the HIV-1 protease inhibitor, ritonavir.
Synth Commun 34:2575–2589
Kontogiorgis CA, Hadjipavlou-Litina DJ (2005) Synthesis and
antiinflammatory activity of coumarin derivatives. J Med Chem
48:6400–6408
Krohnke F (1976) The specific synthesis of pyridines and oligopyri-
dines. Synthesis 1:1–24
Krohnke F, Zecher W (1961) Eine neue Synthese substituierter
Pyridine. I. Grundzu¨ge der Synthese. Chem Ber 94:690–697
Manvar A, Malde A, Verma J, Virsodia V, Mishra A, Upadhyay K,
Acharya H, Coutinho E, Shah A (2008) Synthesis, anti-tubercular
activity and 3D-QSAR study of coumarin-4-acetic acid benzyl-
idene hydrazides. Eur J Med Chem 43:2395–2403
isoniazid. These tubes were then incubated at 37 °C for 24 h
followed by streaking of M. tuberculosis H37Rv (5 9 104
bacilli per tube). The growth of bacilli was seen after
28 days of incubation. The tubes having the compounds
were compared with control tubes where medium alone was
incubated with M. tuberculosis H37Rv. The MIC can be
defined as the lowest concentration effecting the reduction
in fluorescence of 90 % relative to controls or the concen-
tration at which no development of colonies occurred or\20
colonies occurred, i.e., MIC can be determined either by
fluorescence or colony formation method. The colony for-
mation method was utilized to determine the MIC of the
compounds 3a–l. The compound 3e (R1 = OCH3 and
R4 = CH3) shows relatively good antituberculosis activity
with MIC value 62.5 lg/mL, while the compounds 3b
(R1 = H and R4 = CH3) and 3h (R2 = Br and R4 = CH3)
show a moderate activity with MIC value 100 lg/mL.
´
`
Medecins Sans Frontieres (2009). http://www.msf.ch/fileadmin/user_
upload/uploads/rapports/2006_10_30_tb/TBPipeline.pdf. Acces-
sed 3 Sep 2009
Moffett RB (1964) Central nervous system depressants. VII. Pyridyl
coumarins. J Med Chem 7:446–449
Moffett RB (1965) US Patent 3,201,406
Murray RD, Mendez J, Brown SA (1982) The natural coumarins:
occurrence, chemistry and biochemistry. John Wiley, New York
Murthi GSS, Basak M (1993) Synthesis and reactions of some
3-substituted[5,6]benzocoumarins. Indian Chem Soc 70:170
NCCLS (National Committee for Clinical Laboratory Standards)
(2002) 940, West Valley Road, Suite 1400, Wayne, Pennsylva-
nia 19087–1898, USA. Performance Standards for Antimicrobial
Susceptibility Testing; Twelfth Informational Supplement (ISBN
1-56238-454-6), M100–S12 (M7)
Acknowledgments The authors are thankful to UGC for meritori-
ous research fellowship under RFSMS. The authors are also thankful
to the Department of Chemistry, Sardar Patel University for providing
research facilities.
References
O’Kennedy R, Thornes RD (1997) Coumarins: biology, applications
and mode of action. Wiley, Chichester, p 348
Bischler A (1892) Ueber die entstehung einiger substituirter indole.
Chem Ber 25:2860–2879
OMS (2003) WHO annual report on global TB control summary.
Wekl Epidemiol Rec 78:121–128
Patel AK, Patel NH, Patel MA, Brahmbhatt DI (2010a) Synthesis,
characterization and antimicrobial activity of some 4-aryl-2,6-
di(coumarin-3-yl)pyridines. Arkivoc 11:28–38
Patel NH, Patel AK, Patel CV, Patel AA, Brahmbhatt DI (2010b)
Synthesis of some 3-(1-aryl-9,10-dihydro-4-azaphenanthren-3-
yl)coumarins. Arkivoc 2:283–291
Primm TD, Franzblau SG (2007) Recent advances in methodologies
for the discovery of antimycobacterial drugs. Curr Bioact Compd
3:1–8
Brahmbhatt DI, Patel CN, Pandya VP, Patel MA (2004) Synthesis of
some 3-phenyl-4-methyl-6-(6-arylpyridin-2-yl)- and 3-phenyl-4-
methyl-6-(4,6-diarylpyridin-2-yl)coumarins. Indian J Chem 43B:
2228–2230
Brahmbhatt DI, Patel CN, Pandya VP, Patel MA (2005) Synthesis of
some 3-phenyl-4-methyl-6-(6-styryl-4-arylpyridin-2-yl)-, 6-(4-
styryl-6-arylpyridin-2-yl)- and 6-(4-aryl-8-aryledine-5,6,7,8-tet-
rahydroquinolin-2-yl)coumarins. Indian J Chem 44B:1863–1867
Brahmbhatt DI, Gajera JM, Pandya VP, Patel MA (2007) Synthesis of
3-(6-aryl-pyridin-2-yl)- and 8-(6-aryl-pyridin-2-yl)coumarins.
Indian J Chem 46B:869–871
Rattan A (2000) Antimicrobials in laboratory medicine. B I Churchill
Livingstone Pvt Ltd, Livingstone
Bui-Hoi NP, Loc TB, Xoung ND (1957) New 3-acyl coumarins. Bull
Soc Chim Fr 561:12895e; Chem. Abstr. 51
Sabitha G (1996) 3-Formyl chromone as a versatile synthon in
heterocyclic chemistry. Aldrichimica Acta 29:15–25
Sreenivasulu B, Sundaramurthy V, Subba Rao NV (1974) Search for
physiologically active compounds. Part XXIII. Synthesis of 3-(3-
pyridyl) and 3-(3-pyridyl)-4-methyl coumarins. Proc Indian
Acad Sci A 79:41–48
Suzuki M, Nakagawa-Goto K, Nakamura S, Tokuda H, Morris-
Natschke SL, Kozuka M, Nishino H, Lee KH (2006) Cancer
preventive agents. Part 5. anti-tumor-promoting effects of
coumarins and related compounds on Epstein-Barr virus activa-
tion and two-stage mouse skin carcinogenesis. Pharm Biol 44:
178–182
Woodford N (2003) Novel agents for the treatment of resistant Gram-
positive infections. Expert Opin Investig Drugs 12:117–137
World Health Organization (WHO) (2008) Global tuberculosis
control; surveillance, planning, financing. http://www.who.int/tb/
publications/global_report/en/index.html. Accessed Feb 2009
Zhao P, Li J, Yang G (2007) Synthesis and insecticidal activity of
chromanone and chromone analogues of diacylhydrazines. Bio
Med Chem 15:1888–1895
Furniss BS, Hannaford AJ, Smith PWG, Tatchell AR (2004) Vogel’s
textbook of practical organic chemistry, 5th edn. Longman,
Harlow
Fylaktakidou KC, Hadjipavlou-Litina DJ, Litinas KE, Nicolaides DN
(2004) Natural and synthetic coumarin derivatives with anti-
inflammatory/antioxidant activities. Curr Pharm Des 10:3813–
3833
Garazd YL, Kornienko EM, Maloshtan LN, Garazd MM, Khilya VP
(2005) Modified coumarins. 17. Synthesis and anticoagulant
activity of 3,4-cycloannelated coumarin D-glycopyranosides.
Chem Nat Prod 41:508–512
Ghosh CK (1997) Cycloaddition reaction of 1-benzopyran-4-ones.
Indian J Chem 36B:968–980
Ghosh CK (2004) Heterocycles directly linked to 3-position of
1-benzopyran-4-ones. Heterocycles 63:2875–2898
Jain R, Vaitilingam B, Nayyar A, Palde PB (2003) Substituted
4-methylquinolines as a new class of anti-tuberculosis agents.
Bioorg Med Chem Lett 13:1051–1054
Kamal A, Adil SF, Tamboli JR, Siddardha B, Murthy USN (2009)
Synthesis of coumarin linked naphthalimide conjugates as
123