Synthesis, characterization, and antifungal activity of biaryl-based bis(1,2,3-triazoles) using click chemistry

Article abstract of DOI:10.1007/s00706-011-0652-x

Click chemistry was used to synthesize a series of biaryl-based bis(1,2,3-triazoles). Their antifungal activity was evaluated against three soil-borne plant pathogenic fungi, viz. Rhizoctonia bataticola, Sclerotium rolfsii, and Fusarium oxysporum, using the food poison technique at concentrations of 62.5-500 μg/cm³.

Full text of DOI:10.1007/s00706-011-0652-x

Monatsh Chem (2012) 143:283–288
DOI 10.1007/s00706-011-0652-x
ORIGINAL PAPER
Synthesis, characterization, and antifungal activity of biaryl-based
bis(1,2,3-triazoles) using click chemistry
•
Manoj Gaur Mayurika Goel L. Sridhar
•
•
•
Tara Devi S. Ashok S. Prabhakar
•
•
P. Dureja P. Raghunathan S. V. Eswaran
•
Received: 9 February 2010 / Accepted: 4 September 2011 / Published online: 22 October 2011
Ó Springer-Verlag 2011
Abstract Click chemistry was used to synthesize a series
of biaryl-based bis(1,2,3-triazoles). Their antifungal activ-
ity was evaluated against three soil-borne plant pathogenic
fungi, viz. Rhizoctonia bataticola, Sclerotium rolfsii, and
Fusarium oxysporum, using the food poison technique at
concentrations of 62.5–500 lg/cm3.
1,2,3-triazoles [1], but the reaction requires high temper-
ature, long reaction times, and is not regiospecific.
Copper(I)-catalyzed click chemistry discovered by
Sharpless and co-workers [2, 3] has put this reaction
center stage and since then it has become a reliable
method to synthesize 1,2,3-triazoles. The presence of
Cu(I) dramatically accelerates the rate and makes the
reaction highly regioselective, leading to only 1,4-disub-
stituted isomers [4]. Moreover, the reaction can be
performed at room temperature and under a variety of
conditions [5].
Keywords Biaryls ꢀ Antifungal ꢀ Click chemistry ꢀ
1,2,3-Triazoles
Introduction
1,2,3-Triazoles have attracted the interest of organic
chemists for development of new biologically active mol-
ecules owing to their stability, resistance to hydrolysis and
metabolic degradation, and capability to form hydrogen
bonds. 1,2,3-Triazoles have been shown to possess diverse
biological activities, e.g., they are antifungal and antibac-
terial agents, enzyme inhibitors [6–8], and are useful for
the treatment of various diseases [9, 10]. In spite of much
progress in diverse areas of research [11–13], the agro-
chemical potential of 1,2,3-triazoles has not been explored
fully so far. Plant pathogenic fungi are of concern as they
cause a substantial loss of crop. Among various pathogenic
fungi, which alone cause nearly 20% reduction in the yield
of major food and cash crops, Sclerotium rolfsii, Rhizoc-
tonia bataticola, and Fusarium oxysporum are soil-borne
fungi which devastate a wide range of hosts. These fungi
infect seeds, seedlings, and mature plants in the field
causing collar rot, wilt, damping off, dry root rot, and
spoilage [14–16]. To the best of our knowledge, reports of
antifungal activity of 1,2,3-triazoles against plant patho-
genic strains are scarce. Here, we report synthesis and
antifungal activity of a series of highly substituted biaryl-
based bis(1,2,3-triazoles) against three soil-borne patho-
genic strains.
Huisgen’s 1,3-dipolar cycloaddition reaction of azides
with substituted acetylenes is a well-established route to
Electronic supplementary material The online version of this
article (doi:10.1007/s00706-011-0652-x) contains supplementary
material, which is available to authorized users.
M. Gaur ꢀ S. V. Eswaran (&)
St. Stephen’s College, University of Delhi, Delhi 110007, India
e-mail: sv.eswaran@gmail.com
M. Goel ꢀ P. Dureja
Division of Agricultural Chemicals, IARI, Pusa Road,
Delhi 110012, India
L. Sridhar ꢀ S. Prabhakar
National Centre for Mass Spectrometry, Indian Institute
of Chemical Technology, Hyderabad 500007, India
T. D. S. Ashok
University of Massachusetts Boston, Boston, MA, USA
P. Raghunathan
National Brain Research Centre, Manesar 122050, India
123

284
M. Gaur et al.
Results and discussion
and its ED50 values were 8.73, 11.78, and 10.34 lg/cm3
against R. bataticola, S. rolfsii, and F. oxysporum,
respectively. Further work on the synthesis and structure–
activity relationship is currently under progress.
The triazoles were synthesized in good yields (85–98%)
from three new bisazides obtained from their respective
amines. The position of the azide group was confirmed by
2D NMR spectroscopy of the corresponding nitro com-
pound. The reaction conditions were optimized by
examining the reaction of bisazide 1 with phenyl acetylene
in different solvents (Table 1), the best results being
obtained using t-butanol/water (3:1) and ethanol. However,
product isolation was found to be easier in the former case.
In the presence of acetonitrile several products were
formed, whereas the reaction in tetrahydrofuran (THF) was
not complete even after 3 days.
Experimental
Chemicals and solvents were purchased from Sigma-
Aldrich and E. Merck. Culture media (PDA) were pur-
chased from HiMedia. Reactions were monitored by thin-
layer chromatography (TLC) on fluorescent coated plates
purchased from E. Merck. Melting points were measured
on an electrothermal melting point apparatus. IR spectra
were recorded on a Spectrum BX series spectrophotometer
A series of compounds were synthesized bearing a
variety of substituents such as alkyl, aromatic, and het-
erocyclic groups (Table 2).
1
using KBr disks. H and 13C NMR spectra were recorded
on a Bruker 300 MHz spectrometer. TMS was used as the
internal standard in all cases. Mass spectra were recorded
on a Qstar XL instrument and processed using Analyst QS
software.
Studies on antifungal activity
The compounds were tested for their potential antifungal
activity using the food poison technique. The results
obtained in terms of percentage inhibition (mean of three
replicates) and ED50 values are shown in Table 3.
5,50-Diazido-2,20,3,30-tetramethoxy-1,10-biphenyl
(1, C16H16N6O4)
The diamine (260 mg, 0.73 mmol) was dissolved in 5 cm3
diluted HCl (1:1) and diazotized with 210 mg sodium
nitrite (0.03 mmol) below 5 °C. The solution was filtered
and added slowly to a freshly prepared solution of 150 mg
NaN3 (2.3 mmol) containing excess sodium acetate. The
reaction mixture was stirred for 2 h and the resulting solid
was filtered, washed with water, and dried. It was
recrystallized from petroleum ether to yield 120 mg
The newly synthesized triazoles showed moderate to
good antifungal activity. They were found to be more
effective against R. bataticola (55–100% inhibition) than
S. rolfsii and F. oxysporum at a concentration of
500 lg/cm3. ED50 values of most of these compounds were
in the range of 200–500 lg/cm3 against all three fungi. The
ED50 values of these compounds against R. bataticola
and S. rolfsii were in the range of *55–800 and
*350–875 lg/cm3, respectively. Except for compounds
1a and 2d, the ED50 values were 110–450 lg/cm3 against
F. oxysporum. Carboxin was used as a standard fungicide
ꢀ
(40%) 1. M.p.: 143–144 °C; IR: m = 2,939, 2,828, 2,111
(N3), 1,583, 1,488, 1,314, 1,246, 1,112, 1,038, 1,002,
954 cm-1; 1H NMR (CDCl3): d = 3.6 (s, 6H, –OCH3), 3.8
(s, 6H, –OCH3), 6.5 (s, 4H, Ar-H, J = 3 Hz) ppm; 13C
NMR (CDCl3): d = 55.9, 60.8, 103.4, 112.6, 132.8, 135.2,
144.0, 153.7 ppm.
5,50-Diazido-2,20,3,30,6,60-hexamethoxy-1,10-biphenyl
(2, C18H20N6O6)
Table 1 Effect of solvent on reaction of bisazide 1 and phenyl
acetylene
The diamino compound (500 mg, 1.3 mmol) was dissolved
in 2 cm3 conc. hydrochloric acid and cooled in ice bath. It
was diazotized by adding sodium nitrite solution (200 mg
in 1 cm3 water) slowly. The diazotized solution was
filtered and subsequently added to a stirred solution of
190 mg sodium azide and 10 cm3 sodium acetate in water.
The reaction mixture was stirred for 1 h, and the resulting
light yellow solid was filtered. Yield 478 mg (83.7%);
Solvent
Ratio
Yield/%
Time/h
Water
Neat
Neat
Neat
Neat
3:1
64
16
–
Acetonitrile
THF
Mixture
Incomplete
99
[72
14
14
12
12
14
Ethanol
Ethanol/water
t-Butanol
98.9
Neat
3:1
91.9
ꢀ
m.p.: 83–84 °C; IR: m = 2,942, 2,834, 2,104 (N3), 1,590,
t-Butanol/water
t-Butanol/water
99.9
1
1,482, 1,246, 1,046, 969, 816 cm-1; H NMR (CDCl3):
1:1
98.0
d = 3.6 (6H, s, –OCH3), 3.7 (6H, s, –OCH3), 3.9 (6H, s,
–OCH3), 6.6 (2H, s, Ar-H) ppm; 13C NMR (CDCl3):
d = 56.1, 60.7, 61.5, 104.1, 124.0, 127.9, 149.5 ppm.
The reaction was performed using the bisazide (0.05 mmol), alkyne
(0.1 mmol), sodium ascorbate (10-2 mmol), and CuSO4 (10-3 mmol)
123

Biaryl-based bis(1,2,3-triazoles)
285
Table 2 Synthesis of highly substituted biaryl-based bis(1,2,3-triazoles)
Bisazide
Alkyne
Product
Yield/%
97.7
O
O
N3
O
N
N
O
N
O
N
N3
O
1a
O
O
N
N
N
CH2OH
N
O
O
N
O
O
N3
O
OH
88.1
95.1
1b
N
O
O
N3
O
N
HOH2
C
N
N
N
O
O
O
O
O
N3
O
O
O
O
O
O
N
2a
2b
N3
N
O
N
N
N
CH2OH
N
O
O
O
O
O
N
O
O
O
O
O
N3
O
OH
87.0
N
O
N3
N
HOH2
C
N
N
COOC2H5
N
O
O
O
O
N
O
O
O
O
O
O
O
O
O
N3
O
COOC2H5
COOC2H5
85.0
89.3
2c
C2H5OOC
C2H5OOC
C2H5OOC
N
O
O
N3
O
N
N
N
N
O
O
O
O
N
N3
O
2d
N
O
N
O
N3
N
N
N
N
O
O
O
O
O
N3
O
O
N
O
O
N
93.1
2e
N
N3
O
O
O
N
N
N
N
N
N
O
O
N3
O
COOCH3
O
O
COOCH3
88.3
3a
H3COOC
O
O
H3COOC
N3
O
N
N
N
123

286
M. Gaur et al.
Table 3 Antifungal activity of
newly synthesized triazoles
Compound
Fungi
Inhibition (%) at different concentrations/lg cm-3
ED50/lg cm-3
500
250
125
62.5
1a
Rb
Sr
100
87.7
11.1
25.5
45.5
38.8
57.7
78.4
16.6
62.7
38.3
7.7
78.8
0
54.4
0
56.6
828.9
2,829.8
331.9
508.2
224.0
114.7
871.3
111.9
416.1
634.1
344.0
298.0
325.9
442.7
353.4
395.9
2,047.8
225.8
463.5
452.0
244.6
709.9
240.1
25.0
34.4
56.6
50.0
65.5
100
Fo
Rb
Sr
21.1
35.0
33.0
35.5
55.0
11.1
55.0
32.2
1.1
17.7
28.8
22.2
21.2
23.3
0
1b
2a
2b
2c
2d
2e
3a
Fo
Rb
Sr
32.2
73.8
54.4
36.6
55.0
65.5
66.1
51.0
55.0
54.4
34.4
70.5
54.4
52.7
74.2
34.4
67.7
Fo
Rb
Sr
38.3
20.2
0
Fo
Rb
Sr
45.5
50.5
43.2
37.7
41.6
38.3
21.1
53.8
14.4
38.8
48.3
21.6
45.5
36.6
16.4
12.2
23.3
38.3
12.2
18.8
31.6
0
26.1
8.3
0
Fo
Rb
Sr
8.8
13.8
0
Fo
Rb
Sr
13.3
21.1
0
Fo
Rb
Sr
30.5
28.3
7.3
21.6
13.6
0
Rb, Rhizoctonia bataticola; Sr,
Sclerotium rolfsii; Fo, Fusarium
oxysporum; no inhibition was
observed in dimethyl sulfoxide
(DMSO) used as control
Fo
38.8
24.4
Dimethyl 2,20-diazido-5,50,6,60-tetramethoxy-1,10-biphenyl-
3,30-dicarboxylate (3, C20H20N6O8)
monitored by TLC. After completion of the reaction (14–
48 h) the reaction mixture was diluted with water and the
resulting solid filtered. TLC showed that all compounds
were pure.
The diamine (140 mg, 3 mmol) was dissolved in 2.5 cm3
conc. HCl and diazotized with 414 mg sodium nitrite
(6 mmol) below 5 °C. The solution was filtered and added
slowly to a freshly prepared solution of NaN3 (260 mg in
1 cm3 water) containing excess sodium acetate. The
reaction mixture was stirred for 2 h and left overnight in
the cold. The next day the white solid was filtered, dried,
and recrystallized from petroleum ether. Yield 103 mg
1,10-(5,50,6,60-Tetramethoxy-1,10-biphenyl-3,30-diyl)bis(4-
phenyl-1H-1,2,3-triazole) (1a, C32H28N6O4)
Yield 97.7%; m.p.: 132–134 °C; Rf = 0.45 (CHCl3); IR:
ꢀ
m = 3,435, 3,132, 2,941, 1,595, 1,498, 1,466, 1,420, 1,276,
1,233, 1,154, 1,054, 844 cm-1; 1H NMR (CDCl3): d = 3.8
(s, 6H, –OCH3), 4.0 (s, 6H, –OCH3), 7.4, 7.5, 7.9 (6H,
Ar-H), 8.2 (triazole-H) ppm; 13C NMR (CDCl3): d = 56.1,
60.9, 105.0, 113.9, 117.8, 125.6, 128.3, 128.8, 129.9,
131.9, 132.5, 146.8, 148.3, 153.6 ppm.
ꢀ
(92.2%); m.p.: 94–95 °C; IR: m = 3,099, 3,003, 2,947,
2,843, 2,125 (N3), 1,719, 1,588, 1,481, 1,427, 1,295, 1,211,
1,161, 1,025, 1,005, 794 cm-1; 1H NMR (CDCl3): d = 3.7
(s, 6H, –COOCH3), 3.9 (s, 6H, –OCH3), 4.0 (s, 6H,
–OCH3), 7.5 (s, 2H, Ar-H) ppm; 13C NMR (CDCl3):
d = 52.4, 56.1, 60.7, 115.1, 119.3, 124.8, 128.8, 133.2,
149.8, 150.9, 165.5 ppm.
1,10-(5,50,6,60-Tetramethoxy-1,10-biphenyl-3,30-diyl)-
bis(1H-1,2,3-triazole-4-methanol) (1b, C22H24N6O6)
Yield 88.1%; m.p.: 152–154 °C; Rf = 0.3 (ethyl acetate);
ꢀ
IR: m = 3,368, 2,939, 1,592, 1,490, 1,465, 1,417, 1,267,
1
1,238, 1,150, 1,066, 1,035, 872 cm-1; H NMR (acetone-
General procedure for the synthesis of triazoles [2]
d6): d = 3.7 (s, 6H, –OCH3), 4.1 (s, 6H, –OCH3), 4.8 (s,
4H, –CH2–), 7.4 (d, Ar-H, J = 2.1 Hz), 7.6 (d, Ar-H,
J = 2.1 Hz), 8.5 (triazole-H) ppm; 13C NMR (acetone-d6):
d = 56.6, 60.9, 105.7, 114.7, 121.3, 133.5, 133.7, 147.6,
154.5, 206.2, 206.5 ppm.
The bisazide (0.4 mmol) and the alkyne (0.4 mmol) were
added to a mixture of t-butanol/water (3:1). To the stirred
reaction mixture sodium ascorbate (0.04 mmol) and CuSO4
(0.004 mmol) were added. Completion of the reaction was
123

Biaryl-based bis(1,2,3-triazoles)
287
1,10-(2,20,5,50,6,60-Hexamethoxy-1,10-biphenyl-3,30-diyl)-
bis(4-phenyl-1H-1,2,3-triazole) (2a, C34H32N6O6)
ppm; 13C NMR (CDCl3): d = 56.2, 60.8, 61.2, 109.0,
115.0, 121.0, 122.8, 123.7, 125.0, 137.0, 144.0, 148.0,
148.1, 149.5, 149.9 ppm.
Yield 95.1%; m.p.: 120–122 °C; Rf = 0.40 (CHCl3); IR:
ꢀm = 3,435, 3,144, 2,935, 1,599, 1,478, 1,420, 1,226, 1,147,
Dimethyl 5,50,6,60-tetramethoxy-2,20-bis(4-phenyl-1H-
1,2,3-triazol-1-yl)-1,10-biphenyl-3,30-dicarboxylate
(3a, C36H32N6O8)
1,053, 831 cm-1 1H NMR (CDCl3): d = 3.3 (s, 6H,
;
–OCH3), 3.8 (s, 6H, –OCH3), 4.0 (s, 6H, –OCH3), 7.3, 7.4,
7.5, 7.9 (6X Ar-H), 8.4 (triazole-H) ppm; 13C NMR
(CDCl3): d = 56.3, 60.8, 61.2, 109.1, 121.3, 123.4, 125.8,
126.0, 128.3, 128.9, 130.3, 143.8, 147.9, 148.0, 149.5 ppm.
Yield 88.3%; m.p.: 128–130 °C; Rf = 0.55 (CHCl3/ethyl
ꢀ
acetate 9:1); IR: m = 3,444, 2,947, 1,718, 1,589, 1,479,
1
1,352, 1,216, 1,049, 997, 772 cm-1; H NMR (CDCl3):
1,10-(2,20,5,50,6,60-Hexamethoxy-1,10-biphenyl-3,30-diyl)-
bis(1H-1,2,3-triazole-4-methanol) (2b, C24H28N6O8)
Yield 87%; m.p.: 192–194 °C; Rf = 0.3 (ethyl acetate); IR:
d = 3.5 (s, 6H, –OCH3), 3.8 (s, 6H, –OCH3), 3.9 (s, 6H,
–OCH3), 7.3, 7.4, 7.8 (6X Ar-H), 8.3 (triazole-H) ppm; 13
C
NMR (CDCl3): d = 52.54, 56.07, 61.50, 114.95, 123.44,
124.00, 125.78, 125.94, 127.97, 128.75, 129.15, 130.49,
146.63, 149.57, 152.75, 164.77 ppm.
ꢀ
m = 3,411, 3,158, 2,941, 1,601, 1,492, 1,471, 1,418, 1,220,
1,054, 1,036, 840 cm-1; 1H NMR (DMSO-d6): d = 3.3 (s,
6H, –OCH3), 3.8 (s, 6H, –OCH3), 3.9 (s, 6H, –OCH3), 4.9
(s, 4H, –CH2–), 7.4 (s, 2H, Ar-H), 8.1 (triazole-H) ppm;
13C NMR (DMSO-d6): d = 54.8, 56.2, 59.7, 60.2, 60.9,
110.3, 122.8, 124.4, 125.6, 144.5, 147.4, 148.3, 148.7,
170.3 ppm.
Antifungal assay
Microorganisms and media used
The newly synthesized triazoles were tested for antifungal
activity against three soil-borne pathogenic fungi, namely
Sclerotium rolfsii (ITCC 5226), Rhizoctonia bataticola
(ITCC 0842), and Fusarium oxysporum (ITCC 2042), by
the food poison technique. These fungi were collected from
the Indian Type Culture, Division of Plant Pathology,
Indian Agricultural Research Institute (New Delhi, India)
and were maintained on potato dextrose agar (PDA) at
25 °C and were subcultured on PDA petri dishes for
5–6 days at 28 °C prior to use as inoculums.
Tetraethyl 1,10-(2,20,5,50,6,60-hexamethoxy-1,10-biphenyl-
3,30-diyl)bis(1H-1,2,3-triazole-4,5-dicarboxylate)
(2c, C34H40N6O14)
Yield 85%; m.p.: 140–142 °C; Rf = 0.62 (CHCl3/ethyl
ꢀ
acetate 9:1); IR: m = 3,104, 2,981, 2,943, 1,747, 1,602,
1,560, 1,489, 1,421, 1,376, 1,350, 1,284, 1,225, 1,085,
1,021, 841 cm-1 1H NMR (CDCl3): d = 1.2 (t, 3H,
;
CH3), 1.4 (t, 3H, CH3), 4.2 (q, 4H, –CH2), 4.5 (q, 4H,
–CH2), 3.2 (s, 6H, –OCH3), 3.8 (s, 6H, –OCH3), 3.9 (s,
6H, –OCH3), 7.2 (s, 2H, Ar-H) ppm; 13C NMR (CDCl3):
d = 13.7, 14.2, 56.2, 60.8, 61.3, 61.5, 61.8, 62.6, 110.3,
123.0, 124.5, 133.3, 138.7, 145.1, 149.1, 149.5, 158.4,
159.7 ppm.
Food poison technique
The ready-made PDA medium (39 g) was suspended in
distilled water (1,000 cm3) and heated to boiling until
completely dissolved. The medium and petri dishes were
autoclaved at 120 °C for 30 min. The compounds were
tested at concentrations of 500, 250, 125, and 62.5 lg/cm3.
A stock solution of 1,000 lg/cm3 was prepared, which was
further diluted with DMSO to give the required concen-
trations. DMSO (1 cm3) was used as the control. These
solutions were added to the media (65 cm3) contained in
conical flasks to obtain the desired concentrations of the
test compounds in the media. The medium was poured into
a two petri dishes (90 cm in diameter) under aseptic con-
ditions in a laminar flow hood. The plates were kept under
UV light in the laminar flow chamber for solidification of
the media. After solidification, a 5-mm mycelial plug cut
from the actively growing front of a 2-week-old colony of
the desired pathogenic fungus was then placed with the
inoculum side down in the center of each treatment plate,
aseptically. Treated petri dishes were then incubated at
28 °C until the fungal growth was almost complete in the
control plates.
1,10-(2,20,5,50,6,60-Hexamethoxy-1,10-biphenyl-3,30-diyl)-
bis(4-hexyl-1H-1,2,3-triazole) (2d, C34H48N6O6)
Yield 89.3%; m.p.: 54–56 °C; Rf = 0.65 (CHCl3/ethyl
ꢀ
acetate 9:1); IR: m = 2,929, 2,855, 1,601, 1,496, 1,421,
1,221, 1,143, 1,059, 839 cm-1; 1H NMR (CDCl3): d = 0.8
(s, 6H, CH3), 1.3 (s, 12H, CH2), 1.7 (s, 4H, CH2), 2.8 (s,
4H, CH2), 3.2 (s, 6H, –OCH3), 3.7 (s, 6H, –OCH3), 3.9 (s,
6H, –OCH3), 7.4 (s, 2H, Ar-H), 7.8 (triazole-H) ppm; 13C
NMR (CDCl3): d = 13.9, 22.5, 25.5, 28.7, 29.3, 29.6, 31.4,
56.1, 60.7, 60.8, 109.1, 122.4, 123.3, 126.2, 143.7, 147.5,
148.6, 149.4 ppm.
1,10-(2,20,5,50,6,60-Hexamethoxy-1,10-biphenyl-3,30-diyl)-
bis[4-(2-pyridinyl)-1H-1,2,3-triazole] (2e, C32H30N8O6)
Yield 93.1%; m.p.: 98–100 °C; Rf = 0.22 (CHCl3); IR:
ꢀ
m = 3,424, 2,924, 2,837, 1,606, 1,492, 1,469, 1,425, 1,221,
1,149, 1,058, 1,028, 930 cm-1; 1H NMR (CDCl3): d = 3.3
(s, 6H, –OCH3), 3.8 (s, 6H, –OCH3), 3.9 (s, 6H, –OCH3),
7.4, 7.8, 8.2, 8.6 (Ar-H and pyridine-H), 8.7 (triazole-H)
123

288
M. Gaur et al.
Department of Chemistry, Brown University, Providence, RI, USA
under a St. Stephen’s College–Brown University exchange program.
One of the authors (LS) thanks UGC, New Delhi for the award of
junior research fellowship.
Calculation of ED50 values
The mycelial growth of fungus (cm) in both treated and
control petri dishes was measured diametrically. The mean
and standard errors were calculated from the three repli-
cates of each treatment, and the percentage inhibition of
growth (I) was calculated using the following equation:
References
C ꢁ T
Ið%Þ ¼
ꢂ 100
ð1Þ
1. Huisgen R (1963) Angew Chem Int Ed 2:565
2. Kolb HC, Finn MG, Sharpless KB (2001) Angew Chem Int Ed
40:2004
3. Rostovtsev VV, Green LG, Fokin VV, Sharpless KB (2002)
Angew Chem Int Ed 41:2596
4. Rozkiewicz DI, Janczewski D, Verboom W, Ravoo BJ, Rein-
houdt DN (2006) Angew Chem Int Ed 45:5292
5. Binder WH, Kluger C (2006) Curr Org Chem 10:1791
6. Bock VD, Speijer D, Hiemstra H, van Maarseveen JH (2007) Org
Biomol Chem 5:971
C
where C is the diameter of fungal growth in the control and
T is the diameter fungal of growth in the treated plates.
For calculation of ED50 values (effective dose required
for 50% inhibition of growth), the percentage inhibition
was converted to corrected inhibition by using Abbott’s
formula:
7. Reck F, Zhou F, Girardot M, Kern G, Eyermann CJ, Hales NJ,
Ramsay RR, Gravestock MB (2005) J Med Chem 48:499
8. Whiting M, Muldoon J, Lin YC, Silverman SM, Lindstrom W,
Olson AJ, Kolb HC, Finn MG, Sharpless KB, Elder JH, Fokin
VV (2006) Angew Chem Int Ed 45:1435
%I ꢁ CF
Corrected inhibition ð%Þ ¼
ꢂ 100
ð2Þ
100 ꢁ CF
where CF is the correction factor [(9 - C)/C]. ED50 values
were calculated (effective dose for 50% inhibition, lg/cm3)
for inhibition of growth using the Basic LD50 program,
version 1.1 [17].
9. Kadaba PK (1986) US Patent 4,610,994
10. Carini DJ, Duncia JJV, Wells GJ (1992) US Patent 5,081,127
11. Prakash S, Long TM, Selby JC, Moore JS, Shannon MA (2007)
Anal Chem 79:1661
12. Moses JE, Moorhouse AD (2007) Chem Soc Rev 36:1249
13. Binder WH, Sachsenhofer R (2007) Macromol Rapid Commun
28:15
14. Chattapadhyay TK, Dureja P (2006) J Agric Food Chem 54:2129
15. Sharma P, Raina A, Dureja P (2007) Arch Phytopath Plant Prot 1
16. Fravell D, Olivain C, Alabouvette C (2003) New Phytol 157:493
17. Trevors JT (1986) Bull Environ Contam Toxicol 37:18
Acknowledgments We thank the Principal of St. Stephen’s Col-
lege, Delhi for providing facilities. We thank the Defence Research
Development Organisation (DRDO) and University Grants Com-
mission (UGC), Govt. of India, New Delhi for the grant for research
projects. We are grateful to Dr. Vairmani, Head, Chemical &
Instrumental Analysis, IICT, Hyderabad for mass spectrometric
studies. We thank Prof. Amit Basu for introducing click chemistry to
one of us (SVE) during a visit to Prof. David Cane’s laboratory in the
123