Synthesis, anti-microbial activity and molecular docking studies on triazolylcoumarin derivatives

Article abstract of DOI:10.1007/s12039-015-0810-5

A series of triazolylcoumarins was synthesized by the cycloaddition of acetylenic derivatives to azide in the presence of Cu(I) catalyst at room temperature. All the synthesized compounds were evaluated for their anti-microbial activity against Gram-posit

Full text of DOI:10.1007/s12039-015-0810-5

c
J. Chem. Sci. Vol. 127, No. 3, March 2015, pp. 565–574. ꢀ Indian Academy of Sciences.
DOI 10.1007/s12039-015-0810-5
Synthesis, anti-microbial activity and molecular docking studies
on triazolylcoumarin derivatives
CHINNADURAI SATHEESHKUMARa,b, MAHALINGAM RAVIVARMAa,
PANDIAN ARJUNc, VAITHIYANATHAN SILAMBARASANd, NANJIAN RAAMANc,
DEVADASAN VELMURUGANd, CHANGSIK SONGb and PERUMAL RAJAKUMARa,∗
aDepartment of Organic Chemistry, University of Madras, Guindy Campus, Chennai 600 025,
Tamilnadu, India
bDepartment of Chemistry, Sungkyunkwan University, Suwon, Gyeonggi 440-746, Republic of Korea
cCentre for Advanced Studies in Botany, Fungal Biotechnology, Natural Products and Plant Tissue Culture
Lab, University of Madras, Guindy Campus, Chennai 600 025, Tamilnadu, India
dCenter of Advanced Study in Crystallography and Biophysics, University of Madras, Guindy Campus,
Chennai 600 025, Tamilnadu, India
e-mail: perumalrajakumar@gmail.com
MS received 5 April 2014; revised 22 August 2014; accepted 13 October 2014
Abstract. A series of triazolylcoumarins was synthesized by the cycloaddition of acetylenic derivatives to
azide in the presence of Cu(I) catalyst at room temperature. All the synthesized compounds were evaluated
for their anti-microbial activity against Gram-positive (B. subtilis and S. aureus), Gram-negative bacteria (K.
pneumonia and P. vulgaris) and human pathogenic fungi (C. tropicalis and C. krusei), with tetracycline and
fluconazole as standards for anti-microbial and anti-fungal activity. Triazolylcoumarins exhibit anti-microbial
activity against all the tested pathogens, which is further supported by molecular docking studies.
Keywords. Coumarin; 1,2,3-triazole; anti-microbial; molecular docking and ADMET.
1. Introduction
attention due to its wide range of biological activi-
ties13,14 as well as in material applications.15 Click reac-
tion is unique due to high yield and there is no need
for a protection or deprotection protocol. Further, 1,2,3-
triazole ring system is highly stable under hydrolytic
as well as under reductive and oxidative conditions.
Recent synthesis have focused on the design of triazole
based coumarin compounds using CuAAC reaction.16,17
In fact, compounds with the combination of
coumarin with triazole systems will be interesting
and such molecules may have better bioactivity than
coumarin itself. Hence, the aim of the present investi-
gation is to synthesize and characterize triazole-based
coumarin derivatives 1–8 (figure 1) and screen them for
their in vitro anti-microbial activity. Molecular docking
and Absorption, Distribution, Metabolism, Excretion
and Toxicity (ADMET) properties of the synthesized
coumarin derivatives have also been studied.
During the last decade, due to the increase in the num-
ber of immuno-compromised hosts, the incidence of
systemic microbial infection has been increasing dras-
tically. Further, most of the microorganisms develop
resistance over a period of time against available
drugs. Hence, the available anti-microbial medicines
are either less effective or ineffective. There is a need to
search for alternative antimicrobial agents. Coumarin,
known as 1,2-benzopyrone, occurs naturally in plants,
notably in high concentration in the tonka bean, vanilla
grass, sweet woodruff and mullein. Coumarin and its
derivatives attract great attention due to their wide
range of biological activities such as anti-cancer,1 anti-
microbial,2 anti-HIV,3 antioxidant,4 anti-viral,5 anti-
inflammatory,6 anti-coagulant7 and as inhibitors of
lipoxygenase8 and cyclooxygenase.9
Click chemistry10–12 has emerged as a reliable
approach for the stereo selective synthesis of 1,2,3-
triazole with desired properties. Cycloaddition of azide
to alkyne in the presence of copper sulphate and sodium
ascorbate to give 1,2,3-triazole has drawn considerable
2. Experimental
2.1 General
All melting points were determined using a Toshni-
wal melting point apparatus by the open capillary tube
∗For correspondence
565

566
Chinnadurai Satheeshkumar et al.
OH
N
N
N
N
N
N
N
N
N
N
N
N
O
O
O
O
O
O
O
O
O
O
O
O
ortho - 1
para - 2
meta - 3
4
N
O
O
O
N
N
N
N
N
N
N
N
N
N
N
O
O
O
O
O
O
O
O
O
O
O
O
6
5
O
O
O
N
N
N
N
R
R
N
N
N
O
N
R
O
N
O
O
O
O
7 R = H
8 R = CH3
Figure 1. Molecular structures of triazolylcoumarins 1–8.
method and are uncorrected. H NMR and 13C NMR
spectra were recorded on a Bruker 300 MHz instrument.
The mass spectra (ESI-electron spray ionization) were
recorded on a Perkin Elmer Sciex mass spectropho-
tometer. Elemental analyses were carried out using a
Perkin Elmer CHNS 2400 instrument. Column chro-
matography was performed on silica gel (ACME, 100–
200 mesh). Routine monitoring of the reaction was
made using thin layer chromatography developed on
glass plates coated with silica gel-G (ACME) of 25 mm
thickness and visualized with iodine. All the reagents
and solvents employed were of the best grade available
and used without further purification.
1
2.2 General procedure for the synthesis of di and tri
azides from di and tri bromides (18–25)
To corresponding di or tri bromides (1 mmol) dissolved
in dry DMF (20 mL), sodium azide (1.5 mmol) was
added and stirring was continued at room temperature
for 12 h. The reaction mixture was poured into water
(30 mL) and extracted with CHCl3 (3 × 100 mL). The
organic layer was washed with water (100 mL) and sat-
urated NaCl (3 × 100 mL), dried (MgSO4). Solvent was
evaporated under reduced pressure to afford the crude
product, which was purified by column chromatogra-
phy (SiO2).

Synthesis, anti-microbial activity and molecular docking studies
567
2.2a 4,4ꢁꢁ-bis(azidomethyl)-1,1ꢁ:3ꢁ,1ꢁꢁ-terphenyl (22):
Yield 0.25 g (81%); M.p. 96–98◦C; 1H NMR:
(300 MHz, CDCl3)δ 2.32 (s, 4H), 7.12 (s, 1H), 7.14
(d, 2H), 7.16 (s, 4H), 7.29 (s, 4H), 7.31(s, 1H). 13C
NMR: (75 MHz, CDCl3)δ 54.5, 128.4, 128.5, 128.8,
129.2, 129.8, 137.2, 145.5, 148.1. HRMS m/z = 341.40
(M+1)+; Elemental Anal. Calcd. for C20H16N6: C,
70.57; H,4.74; N, 24.69; Found C, 70.27; H, 4.86; N,
24.31. Elemental Analysis: C, 70.57; H, 4.74; N, 24.69
Anal. Calcd. for C32H24N6O6: C, 65.30; H,4.11; N,
14.28; Found C, 65.28; H, 4.12; N, 14.31.
2.3c 4-((1-(3-((4-(((2-oxo-4a,8a-dihydro-2H-chromen-
4-yl)oxy)methyl)-1H-1,2,3-triazol-1-yl)methyl)benzyl)-
1H-1,2,3-triazol-4-yl)methoxy)-2H-chromen-2-one (3):
Yield 0.34 g (72%); M.p. 213–215◦C; 1H NMR
(300 MHz, DMSO-d6)δ 5.40 (s, 4H), 5.67 (s, 4H), 6.12
(s, 2H), 7.31–7.45 (m, 8H), 7.64 (t, 2H, J = 7.8 Hz),
7.72 (d, J = 7.8 Hz, 2H), 8.46 (s, 2H); 13C NMR
(75 MHz, DMSO-d6)δ 52.6, 62.7, 91.3, 114.9, 116.4,
122.8, 124.2, 125.4, 127.5, 127.9, 129.3, 132.8, 136.5,
141.2, 152.7, 161.5, 164.3; MALDI-TOF-MS m/z =
611.49 (M+Na)+, 627.49 (M+K)+; Elemental Anal.
Calcd. for C32H24N6O6: C, 65.30; H,4.11; N, 14.28;
Found C, 65.35; H, 4.16; N, 14.29.
2.3 General procedure for the Cu(I)-catalyzed
Huisgen click reaction (1–8)
Acetylenic derivative (1.0 mmol) was added to azide
(0.5 mmol) in a mixture of THF and water (1:1)
solution. Sodium ascorbate (10 mol%) was added to
the reaction mixture, followed by the addition of
CuSO4.5H2O (5 mol%). The reaction mixture was
stirred overnight at room temperature and after comple-
tion of the reaction the solvent was evaporated under
reduced pressure and the crude product was dissolved
in ethyl acetate (100 mL), washed with water (100 mL),
brine solution (50 mL) and dried (Na2SO4). Evapo-
ration of the solvent afforded a residue which was
purified by column chromatography (silica gel) with
CHCl3/MeOH (9:1) as an eluent to give the correspond-
ing triazolylcoumarins.
2.3d 4,4ꢁ-(((1,1ꢁ-((5-hydroxy-1,3-phenylene)bis(methy-
lene))bis(1H-1,2,3-triazole-4,1-diyl))bis(methylene))bis
(oxy))bis(2H-chromen-2-one) (4): Yield 0.42 g (71%);
1
M.p. 237–239◦C; H NMR (300 MHz, DMSO-d6)δ
5.40 (s, 4H), 5.57 (s, 4H), 6.14 (s, 2H), 6.66 (s, 2H),
6.76 (s, 1H), 7.31–7.41 (m, 4H), 7.64 (t, 2H, J = 7.2
Hz), 7.73 (d, 2H, J = 7.5 Hz), 8.44 (s, 2H), 9.77 (s,
1H); 13C NMR (75 MHz, DMSO-d6)δ 52.6, 62.7, 91.2,
114.5, 114.9, 116.4, 117.8, 122.8, 124.2, 125.4, 132.8,
137.7, 141.2, 152.7, 157.9, 161.6, 164.3; MALDI-
TOF-MS m/z = 627.72 (M+Na)+, 643.71 (M+K)+;
Elemental Anal. Calcd. for C32H24N6O7: C, 63.57;
H,4.00; N, 13.90; Found C, 63.58; H, 4.00; N, 13.88.
2.3a 4-((1-(2-((4-(((2-oxo-4a,8a-dihydro-2H-chromen-
4-yl)oxy)methyl)-1H-1,2,3-triazol-1-yl)methyl)benzyl)-
1H-1,2,3-triazol-4-yl)methoxy)-2H-chromen-2-one (1):
Yield 0.33 g (70%); M.p. 234–236◦C; 1H NMR
(300 MHz, DMSO-d6)δ 5.43 (s, 4H), 5.91 (s, 4H), 6.15
(s, 2H), 7.19–7.22 (m, 2H), 7.30–7.41 (m, 6H), 7.64 (t,
2H, J = 7.8 Hz), 7.75 (d, 2H, J = 7.8 Hz), 8.44 (s,
2H); 13C NMR (75 MHz, DMSO-d6)δ 50.0, 62.7, 91.3,
115.0, 116.4, 122.9, 124.2, 125.6, 128.9, 129.3, 132.8,
134.1, 141.3, 152.7, 161.5, 164.3; MALDI-TOF-MS
m/z = 611.39 (M+Na)+, 627.39 (M+K)+; Elemental
Anal. Calcd. for C32H24N6O6: C, 65.30; H,4.11; N,
14.28; Found C, 65.26; H, 4.12; N, 14.34.
2.3e 4,4ꢁ-(((1,1ꢁ-(1,1ꢁ:3ꢁ,1ꢁꢁ-terphenyl-4,4ꢁꢁ-diylbis(me-
thylene))bis(1H-1,2,3-triazole-4,1-diyl))bis(methylene))
bis(oxy))bis(2H-chromen-2-one) (5): Yield 0.50 g
(76%); M.p. 222–224◦C; 1H NMR (300 MHz, DMSO-
d6)δ 5.45 (s, 4H), 5.73 (s, 4H), 6.18 (s, 2H), 7.20–7.27
(m, 8H), 7.38–7.42 (m, 8H), 7.65 (d, 2H, J = 7.5
Hz), 7.76 (d, 2H, J = 7.8 Hz), 8.54 (s, 2H); 13C NMR
(75 MHz, DMSO-d6)δ 52.6, 62.8, 91.3, 115.0, 116.4,
122.9, 124.2, 125.5, 127.5, 128.5, 129.0, 129.6, 135.1,
136,7, 141.3, 142.2, 146.9, 152.7, 161.5, 164.3; HRMS
m/z = 741.59 (M+1)+; Elemental Anal. Calcd. for
C44H32N6O6: C, 71.34; H,4.35; N, 11.35; Found C,
71.35; H, 4.39; N, 11.31.
2.3b 4-((1-(4-((4-(((2-oxo-4a,8a-dihydro-2H-chromen-
4-yl)oxy)methyl)-1H-1,2,3-triazol-1-yl)methyl)benzyl)-
1H-1,2,3-triazol-4-yl)methoxy)-2H-chromen-2-one (2):
Yield 0.31 g (66%); M.p. 248–250◦C; 1H NMR
(300 MHz, DMSO-d6)δ 5.41 (s, 4H), 5.65 (s, 4H), 6.15 2.3f 4,4ꢁ-(((1,1ꢁ-(((oxybis(ethane-2,1-diyl))bis(oxy))bis
(s, 2H), 7.30–7.42 (m, 8H), 7.66 (t, 2H, J = 7.5 Hz), (ethane-2,1-diyl))bis(1H-1,2,3-triazole-4,1-diyl))bis(me-
7.73 (d, 2H, J = 7.8 Hz), 8.44 (s, 2H); 13C NMR thylene))bis(oxy))bis(2H-chromen-2-one) (6): Yield
1
(75 MHz, DMSO-d6)δ 52.5, 62.7, 91.3, 115.0, 116.4, 0.30 g (75%); M.p. 138–140◦C; H NMR (300 MHz,
122.8, 124.2, 125.3, 128.5, 132.8, 135.9, 141.3, 152.7, DMSO-d6)δ 3.39–3.45 (m, 4H), 3.48–3.50 (m, 4H),
161.5, 164.3; HRMS m/z = 591 (M+1)+; Elemental 3.83 (t, 4H, J = 4.8 Hz), 4.57 (t, 4H, J = 4.8 Hz),

568
Chinnadurai Satheeshkumar et al.
5.42 (s, 4H), 6.17 (s, 2H), 7.31 (t, 2H, J = 7.5 Hz), using a sterile cork (9 mm diam) borer, wells were cut
7.39 (d, 2H, J = 8.1 Hz), 7.64 (t, 2H, J = 7.5 Hz), from the MHA in the petri dishes. The compounds were
7.71 (d, 2H, J = 7.8 Hz), 8.35 (s, 2H); 13C NMR weighed (5 mg/mL) and dissolved in dimethyl sulfoxide
(75 MHz, DMSO-d6)δ 49.5, 62.7, 68.6, 69.5 (2C), (DMSO). Different volumes of 25 μL, 50 μL and
91.3, 115.0, 116.4, 122.7, 124.1, 125.6, 132.7, 140.8, 75 μL test solution were poured into the wells using a
152.7, 161.5, 164.3; MALDI-TOF-MS m/z = 667.52 sterile micropipette. The inoculated plates were initially
(M+Na)+, 683.52 (M+K)+; Elemental Anal. Calcd. incubated for 15 min at room temperature and then they
for C32H32N6O9: C, 59.62; H,5.00; N, 13.04; Found C, were incubated at 37◦C for 24 h. Turbidity was adjusted
59.60; H, 5.01; N, 13.00.
with a sterile broth so as to correspond to 0.5 McFar-
land standards. Inhibition zones were recorded as the
diameter of the growth free zones, including the diame-
ter of the well in mm at the end of the incubation period.
The percentage of inhibition was calculated by the for-
mula: % of inhibition = {I (Diameter of the inhibition
zone)/90 (Diameter of the petri-plate in mm)} × 100,
where I = Zone of inhibition.
2.3g 4,4ꢁ,4ꢁꢁ-(((1,1ꢁ,1ꢁꢁ-(benzene-1,3,5-triyltris(methy-
lene))tris(1H-1,2,3-triazole-4,1-diyl))tris(methylene))tris
(oxy))tris(2H-chromen-2-one) (7): Yield 0.51 g (74%);
1
M.p. 232–234◦C; H NMR (300 MHz, DMSO-d6)δ
5.37 (s, 6H), 5.67 (s, 6H), 6.08 (s, 3H), 7.29–7.38 (m,
9H), 7.62 (t, 3H, J = 7.8 Hz), 7.72 (d, 2H, J = 7.8
Hz), 8.46 (s, 3H); 13C NMR (75 MHz, DMSO-d6)δ
52.4, 62.7, 91.2, 114.9, 116.4, 122.9, 124.1, 125.4,
127.4, 132.7, 137.2, 141.2, 152.7, 161.5, 164.2; HRMS
m/z = 845.3 (M+1)+; Elemental Anal. Calcd. for
C45H33N9O9: C, 64.05; H,3.94; N, 14.94; Found C,
64.07; H, 3.89; N, 14.98.
2.5 Anti-fungal activity
Anti-fungal activity of compounds 1–8 was determi-
ned,19 Sabouraud Dextrose Agar (SDA) medium was
used for the preparation of plates. The anti-fungal activ-
ities of compounds 1–8 were tested against two human
pathogenic fungi Candida tropicalis and Candida kru-
sei. The medium was poured into sterile petriplates of
90 mm diameter. The agar was allowed to set at ambi-
ent temperature. Fresh fungal culture inoculated into
the Sabouraud Dextrose Broth (SDB) was spread on the
surface of the SDA plate with the swab. After incuba-
tion, the SDA plates were allowed pre-incubation for
10 min, after that using the cork borer (9 mm diameter)
well was cut on the agar plate. The compounds were
weighed (5 mg/mL) and dissolved in dimethyl sulfox-
ide (DMSO). The solution was poured (25 μL, 50 μL
and 75 μL) using a sterile micropipette. The inocu-
lated plates were initially incubated for 15 min at room
temperature and then they were incubated at 37◦C for
24 h. Then, the plates were examined for the growth
inhibition zone. Inhibition zones were measured as the
diameter of the growth free zones in mm including the
diameter of the well at the end of the incubation period.
The percentage of inhibition was calculated by the
formula: % of inhibition = {I (Diameter of the inhibi-
tion zone)/90 (Diameter of the petri-plate in mm)} ×
100, where I = Zone of inhibition.
2.3h 4,4ꢁ,4ꢁꢁ-(((1,1ꢁ,1ꢁꢁ-((2,4,6-trimethylbenzene-1,3,5-
triyl)tris(methylene))tris(1H-1,2,3-triazole-4,1-diyl))tris
(methylene))tris(oxy))tris(2H-chromen-2-one) (8): Yield
0.26 g (70%); M.p. 102–104◦C; H NMR (300 MHz,
1
CDCl3)δ 2.39 (s, 9H), 5.28 (s, 6H), 5.66 (s, 6H), 5.82
(s, 3H); 7.25–7.28 (m, 6H), 7.48–7.55 (m, 6H), 7.73 (d,
3H, J = 7.8 Hz); 13C NMR (75 MHz, CDCl3)δ 20.1,
48.8, 62.5, 91.1, 115.4, 116.7, 122.9, 123.9, 129.2,
131.8, 139.5, 141.3, 153.3, 164.9; HRMS m/z = 886.7
(M+1)+; Elemental Anal. Calcd. for C48H39N9O9: C,
65.08; H,4.44; N, 14.23; Found C, 65.10; H, 4.41; N,
14.25.
2.4 Anti-bacterial activity
The in vitro antibacterial activity of the triazole-based
coumarin derivatives 1–8 was determined by the well
diffusion method.18 The Muller Hinton Agar (MHA)
medium was used for the preparation of the plates.
The medium was poured onto sterile petri dishes
of 90 mm diameter. The agar was allowed to set at
ambient temperature. Fresh human pathogenic bacte-
rial cultures inoculated into the Muller Hinton Broth
(MHB) of two Gram-positive bacteria, Bacillus subtilis
2.6 Docking studies
(MTCC-441) and Staphylococcus aureus (MTCC-98) The protein in complex with simocyclinone (PDB ID:
and two Gram-negative bacteria, Klebsiella pneumo- 2Y3P) was used as the template for molecular docking
niae (MTCC-109) and Proteus vulgaris (MTCC-742) studies. GLIDE 9.5 and IFD script from Schrödinger,
were spread on the surface of the MHA plate with LLC (New York) was employed as our primary docking
swabs. They were allowed to incubate; after incubation, engine.20 A hierarchical search protocol was utilized by

Synthesis, anti-microbial activity and molecular docking studies
569
(scheme 2). Compound 7 in 1H NMR spectrum
displayed two singlets at δ 5.37 and δ 5.67 for N-
methylene and O-methylene protons, respectively in
addition to aromatic proton signals. The 13C NMR spec-
trum showed the carbon signals at δ 52.4 and δ 62.7 for
N-methylene and O-methylene carbons, respectively
along with the signals for aromatic carbons. Similarly,
the structure of the compound 8 was also confirmed
from spectral and analytical data.
The synthesized compounds 1–8 were evaluated for
in vitro anti-bacterial and anti-fungal activity against
two Gram-positive bacteria, B. subtilis and S. aureus,
two Gram-negative bacteria, K. pneumoniae and P. vul-
garis and two fungal pathogens, C. tropicalis and C.
krusei using the well diffusion method. Standard anti-
bacterial and anti-fungal drugs, viz., tetracycline and
fluconazole were also screened for comparison. The
inhibition percentages of the various microbial strains
are shown in table 1. All the triazole based coumarin
derivatives showed various levels of inhibitory effects
against human pathogenic bacteria and fungi. The
anti-microbial activities of these compounds were
dose dependent and found to be significant at 75 μL
addition.
The synthesized triazolylcoumarins; compound 1 to
8 were screened for anti-bacterial and anti-fungal activ-
ity against human pathogens. Compound 1 showed anti-
bacterial activity against Gram-positive bacterium; S.
aureus, Gram-negative bacteria, K. pneumonia, P. vul-
garis, anti-fungal activity against C. tropicalis and C.
krusei. Compound 1 didn’t show any activity against
Gram-positive bacterium; B. subtilis. Compounds 2 and
3 showed activity against K. pneumonia, P. vulgaris,
C. tropicalis and C. krusei but didn’t show any activity
against B. subtilis and S. aureus. Compound 5 showed
activity against B. subtilis, S. aureus, P. vulgaris, C.
tropicalis and C. krusei, but didn’t show activity against
the docking algorithm of the GLIDE program. The scor-
ing function, called the GLIDE score, for computing the
binding affinity based Chem-Score function20 is used.
OPLS is the molecular mechanism whose potential
energy function was used throughout the calculations.
The extra precision mode of GLIDE, which has higher
penalties for unfavourable and unphysical interactions,
was used for docking. Computations were carried out
on a Linux system with CentOS-5 computer platform.
The pictures were generated using LIGPLOT.21
3. Results and Discussion
The reaction of di and tri bromides 10–17 with sodium
azide at room temperature afforded di and tri azides22
18–25 in good yields respectively (scheme 1).
The reaction of propargyloxy coumarin 9 with 0.5
equivalents of azides 18–23 under the click reaction
conditions of CuSO4.5H2O (5 mol%) and sodium ascor-
bate (10 mol%), in a mixture of water-THF (1:1) at
room temperature gave the triazolylcoumarin 1–6 in
good yield (scheme 2).
The 1H NMR spectrum of compound 1 displayed two
singlets at δ 5.43 and δ 5.91 for N-methylene and O-
methylene protons, respectively in addition to aromatic
proton signals. The 13C NMR spectrum of compound 1
displayed singlets at δ 50.0 and δ 62.7 for N-methylene
and O-methylene carbons, respectively, along with aro-
matic carbon signals. The appearance of a molecular
ion peak at m/z 611.39 confirmed the structure of the
triazolylcoumarin 1. Similarly, the structure of the com-
pounds 2–6 was also confirmed from the spectral and
analytical data.
Further, the reaction of propargyloxy coumarin 9
with 0.33 equivalents of azides 24 and 25 under Cu
(I) catalyzed click reaction conditions, offered the com-
pound 7 and 8 in 74% and 70% yields, respectively
i
Br
R Br
N3
R
N3
OH
OH
H2C
CH2
R =
H2C
CH2
H2C
CH2
H2C
CH2
,
R =
,
H2C
CH2
H2C
CH2
,
,
,
,
21
22
18 ortho
19 meta
20 para
10 ortho
11 meta
12 para
14
13
Y
Y
H2C
CH2
Y
H2C
CH2
Y
Y
Y
3
3
,
H2C
CH2
O
,
H2C
CH2
O
CH2
CH2
16 (Y = H)
17 (Y = CH3)
15
24 (Y = H)
25 (Y = CH3)
23
Scheme 1. i)NaN3, DMF, rt., 12 h, 18 (84%), 19 (82%), 20 (81%), 21 (80%), 22 (81%), 23 (89%), 24
(87%) and 25 (89%).

570
Chinnadurai Satheeshkumar et al.
Scheme 2. i) CuSO4.5H2O (5 mol%), sodium ascorbate (10 mol%), H2O-
THF (1:1, v/v), rt., 10 h, 1 (70%), 2 (66%), 3 (72%), 4 (71%), 5 (76%), 6 (75%),
7 (74%) and 8 (70%).
Table 1. Anti-microbial activity of triazolylcoumarins 1–8 (values given are mean values with triplicate (n=3).
Well diffusion method (Zone of inhibition (dia. in mm)
Standarda
Microbial strains Ib I%c
1
2
3
4
5
6
7
8
I
I%
I
I%
I
I%
I
I%
I
I%
I
I%
I
I%
I
I%
B. subtilis
S. aureus
25 26.66 NI NI NI NI NI NI 12 13.33 12 13.33 11 12.22 15 16.66 14 15.55
22 23.33 12 13.33 NI NI NI NI 12 13.33 12 13.33 12 13.33 NI NI NI NI
K. pneumoniae NId NI 14 15.55 15 16.66 13 14.44 19 20 NI NI 16 17.77 17 18.88 17 18.88
P. mirabilis
C. krusei
C. tropical
20 21.11 14 15.55 12 13.33 NI NI 13 14.44 12 13.33 12 13.33 12 13.33 13 14.44
NI
NI
NI 15 16.66 15 16.66 14 15.55 15 16.66 14 15.55 15 16.66 12 13.33 13 14.44
NI 15 16.66 15 16.66 14 15.55 19 20 12 13.33 15 16.66 16 17.77 14 15.55
aStandard: antibacterial drug-Tetracycline; anti-fungal drug-Fluconacole are used
bZone of inhibition
cPercentage of zone of inhibition
dNo Inhibition
K. pneumonia. Compounds 7 and 8 showed activity against all the tested human pathogens. All the cou-
against B. subtilis, K. pneumonia, P. vulgaris, C. trop- marin triazole derivatives 1–8 showed excellent anti-
icalis and C. krusei, but didn’t show activity against fungal activity against C. tropicalis and C. krusei at
S. aureus. Tetracycline and fluconazole were used as a volume of 75 μL which is comparable to that
internal standard for anti-bacterial activity and fungal of standard viz., fluconazole. Within 6 h, fluconazole
activity, respectively.
showed activity against fungal pathogens, after 12 h
Compounds 4 and 6 showed anti-bacterial activity fluconazole’s activity was reduced against fungal
against B. subtilis, S. aureus, K. pneumonia, P. vulgaris pathogens. Triazolylcoumarins 4 and 6 exhibit good
and anti-fungal activity against C. tropicalis and C. krusei. activity among the synthesized compounds due to the
Compared to all the compounds 1 to 8, compound 4 combined effect of coumarin and triazole, with phenolic
and 6 exhibited anti-bacterial and anti-fungal activity and tetraethyleneglycol units, respectively.

Synthesis, anti-microbial activity and molecular docking studies
571
The structures of the compounds 1–8 were employed respectively and it has be seen that for each compound,
for docking studies with the target DNA gyrase B (PDB the binding sites and their hydrogen bonding inter-
ID: 2Y3P).23 The ligands maintain an average four actions vary.
hydrogen bond with the DNA gyrase. 10–15 Poses were
The variation in the bioactivity is mainly due to the
obtained for all the compounds and based on the top difference in the binding site. The activity study shows
score selected for each compound. Among all the com- that triazolylcoumarins 1–8 shows comparable results
pounds, synthesized triazolylcoumarins 4, 6 and 7 show with simocyclinone (D8) in the case of E. coli. It may
high binding affinity towards the DNA gyrase B and the be due to the fact that the binding sites of triazolyl-
results are compared with simocyclinone (D8), which coumarins are similar to that of the simocyclinone (D8)
was also docked with the DNA gyrase using a similar binding sites. The triazolylcoumarins 4, 6 and 7 show
protocol and the results are shown in table 2. Figure 2 interaction with the key residues of the receptors Arg
shows hydrogen bonding and hydrophobic interactions 91, Lys 42, Val 268, His 45, Arg 32, Gln 94 and Gln 114
of the triazolylcoumarins 1–8 with the DNA gyrase B, with Glide energy of −101.548 kcal mol−1, −101.002
Table 2. Binding free energy docking simulation results of triazolylcoumarins 1–8.
Hydrogen Bond
Compounds
Glide Score
Glide Energy (kcal/mol)
D-H. . .A
Distance(Å)
1
−10.291
−81.071
Lys N-H. . .N
Lys N-H. . .O
Arg N-H. . .N
Gln N-H. . .O
3.19
3.17
3.07
3.01
2
3
−8.963
−77.302
−83.188
Lys N-H. . .O
Ser O-H. . .O
3.29
2.89
−10.115
Ser O-H. . .O
Ser N-H. . .O
Tyr N-H. . .O
Asn N-H. . .O
Gln N-H. . .O
3.26
3.17
3.24
3.30
3.06
4
−10.238
−101.548
Arg N-H. . .O
Arg N-H. . .N
Arg N-H. . .O
Lys N-H. . .O
Val O-H. . .O
2.82
3.13
2.98
2.87
2.98
5
6
−9.705
−87.672
Lys N-H. . .N
Lys N-H. . .O
His N-H. . .N
Gly N-H. . .O
3.31
3.30
3.01
3.12
−11.057
−101.002
Lys N-H. . .N
His N-H. . .N
Arg N-H. . .O
Gln N-H. . .O
3.05
3.28
3.07
307
7
−10.238
−9.112
−6.565
−100.056
−80.123
−64.715
Lys N-H. . .O
Gln N-H. . .N
Arg N-H. . .O
3.06
3.21
305
8
Lys N-H. . .N
Ala N-H. . .O
Arg N-H. . .N
3.13
2.90
3.07
Simicyclinone
Asp N-H. . .O
Arg N-H. . .O
Gln N-H. . .O
Ala N-H. . .O
Ser N-H. . .O
Lys N-H. . .O
3.30
2.70
2.20
2.70
3.50
3.23

572
Chinnadurai Satheeshkumar et al.
Thr 88(A)
1)
2)
Val 44(A)
His 45(A)
Ala 84(A)
Arg 32(A)
C28
C29
Asp 87(A)
O3
C18
C30
O6
C17
C19
C31
N
Gly 170(A)
Val 176(A)
C16
C15
CA
Lys 42(A)
CG
C
Unk 999(Z)
O1
C13
CE
O
CB
3.19
C5
C8
NZ
CD
Asn 169(A)
C9
C4
C6
N
Ser 172(A)
3.17
N4
CB
N1
C1
C3
CG
CA
N3
C Arg 91(A)
O
NH1
C2
C32
CD
N6
C7
CZ
N5
Leu 98(A)
N2
NH2
3.07
NE
C10
C11
C25
C24
O2
O
Ser 97(A)
C26
C20
C14
C12
C
C27
C21
C23
Tyr 266(A)
CA
CB
O4
OE1
CD
N
C22
CG
O5
3.01
Gln 267(A)
NE2
Ile 112(A)
Phe 96(A)
Thr 219(A)
Gln 94(A)
Lys 42(A)
His 45(A)
3)
O
O
C
Ser 171(A)
OG
CB
C
Gly 40(A)
CA
CB
OG
Ser 172(A)
CA
N
N
C328.26
C27
Gly 170(A)
3.17
O4
Leu 102(A)
O5
C26
C22
C21
C23
Gly 170(A)
C24
4)
C25
Asn 169(A)
C27
C15
C28
Asn 165(A)
C26
O2
C22
C15
C13
C25
O4
Leu 98(A)
Asn 169(A)
Ser 97(A)
C21
C23
C12
O6
N5
C13
O
C
Thr 219(A)
C11
C24
2.87
N6
O
O2
C12
CB
C11
Ser 97(A)
CD
NZ
C
C1
N5
C6
N2
N2
Lys 42(A) CA
CG
CE
C7
C2
CE2
3.24
OH
C7
N
CD2
C2
CA
N6
Phe 96(A)
C5
Tyr 266(A)
N
CG
C3
C1
C6
C3
C4
Ile 112(A)
CZTyr 266(A)
ND2
CE1
His 45(A)
CB
CG1
C4
Val 268(A)
CG2
C8
Unk 999(Z)
O5
CD1
C8
2.82
N3
CB
3.13
C5
CB
2.98
N1
N
3.30
O
CA
N4
N1
N3
CG
O
N
C10
Ser 111(A)
Phe 96(A)
OD1
C10
C
CA
N4
C
Gln 94(A)
O
Asn 269(A)
C9
Unk 999(Z)
O1 C14
C32
C9
C14
C17
O
C31
C
O1
Arg 91(A)
NH2
C30
Gln 267(A)
C32
C16
C20
C
C31
C16
CZ
CA
Ile 112(A)
C17
O7
NE
C19
C29
CA
CB
CB
CG
NH1
Asp 87(A)
C30
C20
N
O3 C18
CD
CG
N
C19
2.98
Gly 114(A)
OE1
C18
Gly 114(A)
O3
Asp 115(A)
C29
Arg 91(A)
O6
Gln 267(A)
CD
NE2Gln 325(A)
3.06
Arg 272(A)
Val 44(A)
N
C
O
C
6)
O
O
5)
CA
CA
Lys 42(A)
C
N
CB
CG
CB
CA
N
CD
Arg 32(A)
NE
CG
CB
His 45(A)
CD2CG
Val 176(A)
CD
NZ
CZ
NH1
ND1
NH2
CE
NE2
O8
Pro 43(A)
CE1
3.07
3.18
C19
3.05
C20
C15
Ala 175(A)
O6
N4
C13
O5
N3
C18
C1
O2
C9
Ser 172(A)
C28
N1 C10
C2
C3
C17
C4
C25
C27
O1
Unk 999(Z)
Arg 91(A)
C6
C26
C5
Ser 97(A)
O3
Val 90(A)
C8
Tyr 266(A)
C11
C12
N2
C7
C31
C30
C29
N6
C32
C14
Gln 267(A)
C24
N5
O4
Asp 87(A)
Phe 96(A)
C23
Asn 269(A)
C16
OE1
O7
C21
3.07
NE2
CD
O
C22
Val 268(A)
CB
O9
C
CA
CG
Ser 116(A)
N
Gln 94(A)
Asp 115(A)
Gly 114(A)
Ser 111(A)
O
C
7)
CA
CB
His 45(A)
C34
C35
N
Lys 42(A)
CG
N
O6 C32
C36
CD
C
8)
O8
C31
C33C37
CA
CE
NZ
Arg 91(A)
CB
O
C30
C19
CG
Val 176(A)
Thr 88(A)
O1
C16
3.06
C42
O4
NE
CD
O7
C43
NH1
CZ
NH2
C11
NH2
CB
CD
N4
C
NZ
C24
N7
C10
C46
C23
C44
O
3.13
N6
O8
CZ
C25
C8
3.07
N5
Gln 94(A)
NE
C22
CA
NH1
CG
CE
3.05
O
N
C5
C4
CD
Lys 42(A)
Ala 33(A)
N1
C31
C13
C12
N2
C
C45
O6
C7
C21
C6
C17
C3
O3
Gly 114(A)
C30
CA
CG
C48
Ala 175(A)
C18
C32
CB
C1
C2
C34
O2
N
C19
Arg 32(A)
C26
C20
C47
N8
Phe 96(A)
CA
C9
C15
O
O1
C35
N
Ser 97(A)
O9
C27
C33
N9
C14
N8
C29
C37
3.21
C41
C
N3
C16
O5
C14
N3
C2
C4
N9
N4
C36
C40
Asp 82(A)
C28
C38
C15
C9
N5
C11
C10
C18
O3
C39
C1
Asp 115(A)
C21
Ile 112(A)
C22
Unk 999(Z)
N2
Val 44(A)
C45
C25
Ser 172(A)
C6 C7
C3
C23
O7
C44
C24
C5
O4
Ser 111(A)
Asp 87(A)
Asn 165(A)
C43
C42
2.90
C8
N
Tyr 266(A)
Thr 88(A)
Gln 267(A)
CB
N7
N1
CA
Unk 999(Z)
Ala 117(A)
Ala 84(A)
N6
C
C12
O
Leu 98(A)
His 45(A)
Leu 102(A)
Asn 269(A)
C13
C17
O2
Leu 41(A)
Arg 91(A)
C41
Val 268(A)
Asn 169(A)
C40
C20
Met 92(A)
C26
Arg 272(A)
C29
C39
C28
Gln 94(A)
Ser 116(A)
Asp 115(A)
C27
Phe 96(A)
C38
O9
O5
Leu 273(A)
Gly 170(A)
Ser 111(A)
Gln 325(A)
Lys 276(A)
Figure 2. Interaction of triazolylcoumarins 1–8 with DNA gyrase B.

Synthesis, anti-microbial activity and molecular docking studies
573
Table 3. Theoretical ADMET properties of triazolylcoumarins 1–8.
Hydrogen Bonding
Compounds
CNSa
SASAb
Donor
Acceptor
QPlogSc
1
2
3
4
5
6
7
8
−2
−2
−2
−2
−2
−2
−2
−2
−
962.55
970.04
1010.42
1023.68
1187.89
958.69
1010.09
1010.91
641.47
514.69
0
0
0
1
0
0
0
0
2
1
12
11
−6.546
−7.212
−7.715
−8.206
−10.753
−2.91
11.5
12.25
11.5
17.25
17.25
17.25
7.5
−3.884
−3.9
Tetracylcine
Flucanacole
−4.53
+/−
6
−3.740
aPredicted central nervous system (CNS) activity on a −2 (inactive) to +2 (active) scale.
bTotal solvent accessible surface area (SASA) in square Angströms using a probe with a 1.4 Å radius.
cPredicted aqueous solubility, log S. S. in moles/liter is the concentration of the solute in a saturated
solution that is in equilibrium with the crystalline solid (QplogS).
kcal mol−1 and −100.056 kcal mol−1, respectively. The
Acknowledgements
activity study clearly reveals that all the synthesized
The authors thank the Council of Scientific and Indus-
trial Research (CSIR), New Delhi, India for the finan-
cial support and the DST-FIST New Delhi, India
for providing the NMR facility for the Department
of Organic Chemistry, University of Madras, Guindy
Campus, Chennai.
triazolylcoumarins 1–8 show excellent results compara-
ble with that of simocyclinone (D8). Hence, the dock-
ing studies would of great help in the design of the novel
triazolylcoumarins drug targets of bacterial proteins.
Further, the theoretical prediction of the ADMET
properties based on the numbers of hydrogen donors
and acceptors have been studied for compounds 1–8
and the results are presented in table 3. The ADMET
parameter shows that the reported triazolylcoumarins
have good oral absorption and do not affect the central
nervous systems (CNS) and hence could be favourable
drug candidates after a systematic in vivo analysis.
References
1. Riveiro M E, Moglioni A, Vazquez R, Gomez N,
Facorro G, Piehl L, de Celis E, Shayo C and Davio C
2008 Bioorg. Med. Chem. 16 2665
2. Symth T, Ramachandran V N and Smyth W F 2009 Int.
J. Antimicrob. Agents 33 421
3. Shikishima Y, Takaishi Y, Honda G, Ito M, Takfda Y
Kodzhimatov O K, Ashurmetov O and Lee K H 2001
Chem. Pharm. Bull. 49 877
4. Conclusions
4. Kontogiorgis C A, Savvoglou K and Hadjipavlou-Litina
D J 2006 J. Enzyme Inhib. Med. Chem. 21 21
5. Yeh J Y, Coumar M S, Horng J T, Shiao H Y, Kuo F M
Lee H L, Chen I C Chang C W Tang W F Tseng S N
Chen C J Shih S R Hsu J T A Liao C C, Chao Y C, Hsieh
H P 2010 J. Med. Chem. 53 1519
6. Kontogiorgis C A, Hadjipavlou-Litina D J 2005 J. Med.
Chem. 48 6400
7. Lee Y, Lee S, Jin J and Yun-Choi H 2003 Arch. Phar-
macal. Res. 26 723
8. Grimm E, Brideau C, Chauret N, Chan C, Delorme D,
Ducharme Y, Ethier D, Falgueyret J, Friesen R and Guay
J 2006 Bioorg. Med. Chem. Lett. 16 2528
9. Fylaktakidou K, Hadjipavlou-Litina D, Litinas K and
Nicolaides D 2004 Curr. Pharm. Des. 10 3813
10. Wu P, Feldman A K, Nugent A K, Hawker C J, Scheel
A, Voit B, Pyun J, Frechet J M, Sharpless K B and Fokin
V V 2004 Angew. Chem. Int. Ed. 43 3928
We have synthesized a series of triazole based coumarin
derivatives by the click chemistry approach. The anti-
microbial activity showed that the coumarin deriva-
tives 4 and 6 could be developed as potential anti-
bacterial agents against B. subtilis, S. aureus, K. pneu-
monia, P. mirabilis and also anti-fungal agents against
C. krusei and C. tropicalis. The molecular docking
studies also revealed that compounds 4 and 6 may be
good inhibitors of the DNA gyrase B enzyme and also
showed strong hydrogen bonding with key residues of
chain A of the enzyme dimer DNA gyrase B with novel
binding conformation.
Supplementary Information
11. Himo F, Demko Z P, Noodleman L and Sharpless K B
2002 J. Am. Chem. Soc. 124 12210
12. Demko Z P and Sharpless K B 2001 Org. Lett. 3 4091
NMR and Mass data are available at www.ias.ac.in/
chemsci.

574
Chinnadurai Satheeshkumar et al.
13. Howell L A, Howman A, O’Connell M A, Mueller A 20. Eldridge M D, Murray C W, Auton T R, Paolini G V and
and Searcey M 2009 Bioorg. Med. Chem. Lett. 19 5880 Mee R P 1997 J. Comput.- Aided Mol. Des. 20 11
14. Pericherla K, Khedar P, Khungar B and Kumar A 2012 21. (a) Thomas W and Colin K http://www.gnuplot.info/
Tetrahedron Lett. 53 6761
15. Liu X, Yang X, Fu Y, Zhu C and Cheng Y 2011
Tetrahedron 67 3181
16. Xue J L, He X P, Yang J W, Shi D T, Cheng C Y, Xie J,
Chen G R and Chen K 2012 Carbohydr. Res. 363 38
17. Kosiova I, Kovackova S and Kois P 2007 Tetrahedron
63 312
18. Arjun P, Priya S M, Saranya Sivan P S, Krishnamoorthy
M and Balasubramanian K 2012 J. Acad. Indus. Res. 1 15
19. Schrödinger Glide version 2009 LLC, New York, NY 18
2008; (b) Wallace A C, Laskowski R and Thornton J M
1995 LIGPLOT: Protein Engineering 8 127
22. (a) Thomas J R, Liu X and Hergenrother P J 2005 J. Am.
Chem. Soc. 127 12434; (b) Rajakumar P, Satheeshkumar
C, Ravivarma M, Ganesan S and Maruthamuthu P 2013
J. Mater. Chem. A 1 13941
23. Edwards M J, Flatman R H, Mitchenall L A, Stevenson
C E M, Le T B K, Clarke T A, Mckay A R, Fiedler H P,
Buttner M J, Lawson D M and Maxwell A 2009 Science
326 1415