Optimization and antifungal activity of amide analogues

Article abstract of DOI:10.14233/ajchem.2013.13895

Using salicylic acid as a lead compound, a series of its analogues (compounds 1-16) were designed and synthesized. Their activity of antipathogenic fungi of plants has been evaluated in the laboratory. The results showed that these compounds had certain antifungal activity against Sclerotinia sclerotiorum and Bipolaris maydis (Nisikado et Miyake) Shoem. Among them, the inhibition of growth for 2-(3- fluorophenylcarbamoyl)phenyl acetate (1) and 2-(3-chlorophenylcarbamoyl)phenyl acetate (2) reached 91.1 %, 92.8 % and 90.1 %, 90.1 % at a concentration of 100 mg L-1, respectively.

Full text of DOI:10.14233/ajchem.2013.13895

Asian Journal of Chemistry; Vol. 25, No. 7 (2013), 4029-4031
http://dx.doi.org/10.14233/ajchem.2013.13895
Optimization and Antifungal Activity of Amide Analogues
1
2
1
1
1
1
1
1,*
HUI FENG , LI LENG , JIA LIU , YUANMOU TANG , PENGCHENG TANG , CHIXIANG ZHANG , XIOARONG TANG and SHIRONG JIAO
1School of Bioengineering, Xihua University, Chengdu 610039, P.R. China
2School of Life Science, Sichuan University, Chengdu 610064, P.R. China
*Corresponding author: Tel: +86 13882002899; E-mail: huif2010@163.com
(Received: 12 April 2012;
Accepted: 23 January 2013)
AJC-12746
Using salicylic acid as a lead compound, a series of its analogues (compounds 1-16) were designed and synthesized. Their activity of anti-
pathogenic fungi of plants has been evaluated in the laboratory. The results showed that these compounds had certain antifungal activity
against Sclerotinia sclerotiorum and Bipolaris maydis (Nisikado et Miyake) Shoem. Among them, the inhibition of growth for 2-(3-
fluorophenylcarbamoyl)phenyl acetate (1) and 2-(3-chlorophenylcarbamoyl)phenyl acetate (2) reached 91.1 %, 92.8 % and 90.1 %, 90.1
% at a concentration of 100 mg L-1, respectively.
Key Words: Antifungal activity, Amide analogues, Synthesis.
sources unless specified otherwise. IR spectra were recorded
on a Thermofisher Nicolet-6700 spectrophotometer. 1H NMR
spectra were taken on a Varian Unity Inova-400 instrument
using deuteron chloro-form as the solvent.
INTRODUCTION
In agriculture, crop disease is the major issues in agricul-
tural production. Crop yields cutting down more than10 %
are caused by them. Meanwhile, fungal diseases are about 80 %
in the plant disease1,2. Many kinds of fungicides are chemical
fungicides. However, their over use has brought about side
effects, such as the contamination of the environment and occu-
rrence of resistance3. Botanical fungicides play an important
role in controlling pathogenic fungi of plants4-6. Nevertheless,
they have obvious drawbacks such as low yield, instability,
complex components and limited antifungal spectrum. Salicylic
acid (Fig. 1) is a natural compound existing in many plants. It
can help plants to disease resistance7-18. Thus, salicylic acid
used as a lead structure to synthesize new fungicides is mean-
ingful.
Synthesis of target compounds: The target compounds
were synthesized according to the route shown in Fig. 2 and
their yield was not optimized. Benzenamine or its derivatives
(30 mmol) and pyridine (30 mmol) were dissolved in CH2Cl2
(10 mL). The mixture was stirred and heated to 30 ºC. 2-
(Chlorocarbonyl)phenyl acetate or 2-methoxybenzoyl
chloride (30 mmol) were dissolved in CH2Cl2 (10 mL) and it
was slowly mix under stirring 3-5 h until the reaction was
complete. The precipitate was filtered and washed with distilled
water. The pure compounds 1-16 were obtained by re-crystalli-
zation in anhydrous ethanol.
R2
R2
OH
O
NH2
C
Cl
NH
C
O
Pyridine/CH2Cl2
R1
R1
C
O
OH
Fig. 2. Synthesis of target compounds 1-16
Fig. 1. Chemical structure of salicylic acid
Compound 1: White crystal, yield: 20 %, m.p. 116-117 ºC;
IR (KBr, νmax, cm-1): 3296, 3261, 3187, 3077, 1770, 1743, 1666,
1593, 1537, 1484, 1450, 1368, 1316, 1227, 1162, 1135, 785,
775, 751, 696, 680, 583; 1H NMR (400 MHz, CDCl3) δ (ppm):
2.32(s, 3H), 7.13 (t, J = 8.4 Hz, 2H), 7.26 (t, J = 8.0 Hz, 1H), 7.33
(t, J = 8.0 Hz, 1H), 7.40 (d, J = 8.0 Hz, 1H), 7.51 (t, J = 7.2 Hz,
1H), 7.74 (s,,1H), 7.79 (d, J = 8.0 Hz, 1H), 8.14 (s, 1H).
EXPERIMENTAL
Sclerotinia sclerotiorum and Bipolaris maydis (Nisikado
et Miyake) Shoem were obtained from the Chinese Academy
of Agricultural Sciences. They were preserved at 4 ºC. All
chemicals and solvents were purchased from commercial

4030 Feng et al.
Asian J. Chem.
Compound 2: White crystal, yield: 27 %, m.p. 126-
127 ºC; IR (KBr, νmax, cm-1): 3296, 3261, 3187, 3115, 3077,
1770, 1743, 1676, 1666, 1593, 1537, 1484, 1450, 1368, 1316,
Compound 10: White crystal, yield: 83 %, m.p. 66-67 ºC;
IR (KBr, νmax (cm-1): 3348, 3068, 3015, 2833, 1660, 1556,
1513, 1462, 1414, 1322, 1243, 1174, 1047, 1017, 833, 827,
753, 665, 600; 1H NMR (400 MHz, CDCl3): δ (ppm): 3.80 (s,
3H), 4.02 (s, 3H), 6.89 (d, J = 8.8 Hz, 2H), 7.01 (d, J = 8.4 Hz,
1H), 7.12 (t, J = 8.0 Hz, 1H), 7.45-7.49 (m, 1H), 7.57-7.60
(m, 2H), 8.27-8.29 (m, 1H), 9.69 (s, 1H).
1
1203, 1162, 1135, 785, 775, 751, 696, 583; H NMR (400
MHz, CDCl3) δ (ppm): 2.31 (s, 3H), 7.12 (t, J = 8.0 Hz, 2H),
7.23-7.27 (m, 1H), 7.31 (t, J = 8.0 Hz, 1H), 7.39 (d, J = 8.0
Hz, 1H), 7.49 (t, J = 8.0 Hz, 2H), 7.76 (t, J = 8.0 Hz, 1H), 8.18
(s, 1H).
Compound 11: Light purple solid, yield: 60 %, m.p. 77-
78 ºC; IR (KBr, νmax (cm-1): 3348, 3068, 2960, 2833,1660, 155,
1513, 1462, 1243, 1174, 1047, 1017, 833, 827, 753, 665, 600;
1H NMR (400 MHz, CDCl3): δ (ppm): 3.80 (s, 3H), 4.02 (s,
3H), 6.89 (d, J = 8.8 Hz, 2H), 7.01 (d, J = 8.4 Hz, 1H), 7.12 (t,
J = 8.0 Hz, 1H), 7.45-7.49 (m, 1H), 7.57-7.60 (m, 2H), 8.27-
8.29 (m, 1H), 9.69 (s, 1H).
Compound 3: White crystal, yield: 30 %, m.p. 119-
120 ºC; IR (KBr, νmax, cm-1): 3293, 3258, 3118, 3076, 1768,
1742, 1666, 1609, 1589, 1480, 1449, 1367, 1318, 1192, 1134,
1
1095, 783, 774, 751, 703, 679, 583; H NMR (400 MHz,
CDCl3) δ (ppm): 2.31 (s, 3H), 7.13 (d, J = 8.0 Hz, 1H), 7.19 (t,
J = 8.0 Hz, 1H), 7.26 (t, J = 6.4 Hz, 1H), 7.31 (t, J = 8.0 Hz,
1H), 7.45-7.52 (m, 2H), 7.77 (d, J = 8.0 Hz, 1H), 7.87 (s, 1H),
8.15 (s, 1H).
Compound 12: White needle crystal, yield: 88 %, m.p.
144-145 ºC; IR (KBr, νmax (cm-1): 3351, 3071, 3032, 2940,
1669, 1587, 1534, 1485, 1463, 1408, 1319, 1272, 1186, 1126,
Compound 4: White solid, yield: 32 %, m.p. 147-148 ºC;
IR (KBr, νmax, (cm-1): 3325, 3272, 3130, 3099, 1737, 1675,
1608, 1524, 1487, 1446, 1353, 1333, 1229, 1199, 1134, 814,
1
1023, 823, 755, 654, 592; H NMR (400 MHz, CDCl3): δ
(ppm): 2.59 (s, 3H), 4.08 (s, 3H), 7.05 (d, J = 8.8 Hz, 1H),
7.15 (t, J =7.2 Hz, 1H), 7.50-7.55 (m, 1H), 7.78 (d, J = 8.8 Hz,
2H), 7.97 (d, J = 8.8 Hz, 2H), 8.27-8.29 (m, 1H), 10.05 (s,
1H).
1
758, 737, 677, 590; H NMR (400 MHz, CDCl3): δ (ppm):
2.35 (s, 3H), 7.17 (d, J = 8.0 Hz, 1H), 7.35 (t, J = 8.0 Hz, 1H),
7.50-7.56 (m, 2H), 7.80 (t, J = 6.8 Hz, 2H), 7.81 (d, J = 8.0
Hz, 1H), 8.34 (s, 1H), 8.45 (s, 1H).
Compound 13: :Light yellow powder, yield: 85 %, m.p.
68-69 ºC; IR (KBr, νmax (cm-1): 3447, 3392, 3072, 3029, 2847,
1669, 1604, 1 492, 1457, 1326, 1243, 1146, 1072, 1016, 768,
746, 680; 1H NMR (400 MHz, CDCl3): δ (ppm): 4.05 (s, 3H),
6.79-6.84 (m, 1H), 7.03 (d, J = 8.4 Hz, 1H), 7.11-7.15 (m,
1H), 7.25-7.29 (m, 2H), 7.48-7.52 (m, 1H), 7.67-7.70 (m, 1H),
8.26-8.28 (m, 1H), 9.89 (s, 1H).
Compound 5: White solid, yield: 75 %, m.p. 95-96 ºC;
IR (KBr, νmax (cm-1):3338, 3200, 3074, 3000, 2838, 1651, 1597,
1524, 1465, 1323, 1250, 1185, 1184, 1102, 1028, 753, 690,
595; 1H NMR (400 MHz, CDCl3): δ (ppm): 4.05 (s, 3H), 7.03
(d, J = 8.4 Hz, 1H), 7.11-7.15 (m, 2H), 7.36 (t, J = 8.0 Hz,
2H), 7.47-7.51 (m, 1H), 7.68 (d, J = 8.0 Hz, 2H), 8.28-8.30
(m, 1H), 9.81(m, 1H).
Compound 14: White needle crystal, yield: 87 %, m.p.
78-79 ºC; IR (KBr, νmax, cm-1):3446, 3333, 3082, 3049, 2839,
1669, 1593, 1484, 1456, 1316, 1230, 1128, 1048, 1024, 791,
747, 684, 606; 1H NMR (400 MHz, CDCl3): δ (ppm): 4.06 (s,
3H), 7.03 (d, J = 8.4 Hz, 1H), 7.10 (t, J = 6.0 Hz, 1H), 7.14 (d,
J = 8.0 Hz, 1H), 7.48-7.53 (m, 2H), 7.80 (s, 1H), 8.26-8.28
(m, 1H), 9.85 (s, 1H).
Compound 6: Light yellow needle crystal, yield: 70 %,
m.p. 97-98 ºC; IR (KBr, νmax, cm-1): 3329, 3284, 3075, 3027,
2842, 1647, 1601, 1579, 1464, 1317, 1287, 1210, 1181, 1094,
1
1022, 831, 759, 638, 591; H NMR (400 MHz, CDCl3): δ
(ppm), 4.05 (s, 3H), 7.02-7.07 (m, 3H), 7.13 (t, J = 8.0 Hz,
1H), 7.48-7.52 (m, 1H), 7.62-7.65 (m,2H), 8.27-8.29 (m, 1H),
9.78 (s, 1H).
Compound 15: White needle crystal, yield: 85 %, m.p.
79-80 ºC; IR (KBr, νmax, cm-1): 3438, 3341, 3069, 2843, 1665,
1598, 1485, 1458, 1311, 1236, 1181, 1129, 1068, 1016, 779,
756, 681; 1H NMR (400 MHz, CDCl3): δ (ppm): 4.06 (s, 3H),
7.03 (d, J = 8.4 Hz, 1H), 7.13 (t, J = 8.0 Hz, 1H), 7.18-7.26
(m, 2H), 7.48-7.53 (m, 1H), 7.58-7.60 (m, 1H), 7.92 (d, J =
1.6 Hz, 1H), 8.25-8.28 (m, 1H), 9.84 (s, 1H).
Compound 7: White needle crystal, yield: 80 %, m.p.
92-93 ºC; IR(KBr, νmax, cm-1): 3345, 3107, 3031, 2983, 2843,
1670, 1650, 1593, 1463, 1399, 1316, 1245, 1181, 1022, 1014,
825, 759, 689, 619, 590; 1H NMR (400 MHz, CDCl3): δ (ppm):
4.05 (s, 3H), 7.03 (d, J = 8.4 Hz, 1H), 7.13 (t, J = 8.0 Hz, 1H),
7.30 (t, J = 8.8 Hz, 2H), 7.48-7.52 (m, 1H), 7.63 (d, J = 8.8
Hz, 2H), 8.26-8.28 (m, 1H), 9.83 (s, 1H).
Compound 16: Light yellow crystal, yield: 80 %, m.p.
145-146 ºC; IR (KBr, νmax, cm-1): 3312, 3203, 3123, 2986,
2843, 1669, 1552, 1531, 1486, 1467, 1340, 1258, 1236, 1130,
1073, 1020, 804, 750, 738, 676; 1H NMR (400 MHz, CDCl3):
δ (ppm): 4.11 (s, 3H), 7.07 (d, J = 8.4 Hz, 1H), 7.16 (t, J = 8.0
Hz, 1H), 7.49-7.56 (m, 2H), 7.95-7.97 (m, 1H), 8.27-8.30 (m,
1H), 8.49 (t, J = 2.0 Hz, 1H), 10.07 (s, 1H).
Compound 8: White powder, yield: 65 %, m.p. 124-
125 ºC; IR (KBr, νmax, cm-1): 3334, 3080, 3006, 2932, 2835,
1655, 1589, 1518, 1465, 1316, 1248, 1163, 1025, 1013, 819,
757, 629, 618; 1H NMR (400 MHz, CDCl3): δ (ppm): 4.05 (s,
3H), 7.03 (d, J = 8.4 Hz, 1H), 7.13 (t, J = 7.2 Hz, 1H), 7.46 (t,
J = 6.8 Hz, 2H), 7.49-7.52 (m, 1H), 7.58 (d, J = 8.8 Hz, 2H),
8.26-8.28 (m, 1H), 9.83 (s, 1H).
Assay of antifungal activity: All the synthesized comp-
ounds were screened for their activity against Sclerotinia
sclerotiorum and Bipolaris maydis(Nisikado et Miyake) Shoem
using the plate growth rate method19.
Compound 9: Golden yellow crystal, yield: 58 %, m.p.
157-159 ºC; IR (KBr, νmax, cm-1): 3280, 3256, 3074, 2987, 2842,
1668, 1580, 1464, 1425, 1343, 1273, 1148, 1118, 1045, 1014,
826, 745, 741, 686; 1H NMR (400 MHz, CDCl3): δ (ppm): 4.14
(s, 3H), 7.06 (d, J = 8.0 Hz, 1H), 7.12 (t, J = 8.0 Hz, 1H), 7.17-
7.21 (m, 1H), 7.51-7.56 (m, 1H), 7.64-7.68 (m, 1H), 8.19-8.21
(m, 1H), 8.26-8.28 (m, 1H), 8.98-9.00 (m, 1H), 12.12 (s, 1H).
Each tested compound and carbendazim (purity 90 %)
were dissolved in dimethyl sulfoxide, respectively. They were
added to the sterile culture medium (PDA) at 45 ºC, mixed to
homogeneity and transferred to sterile Petri dishes to solidify.

Vol. 25, No. 7 (2013)
Optimization and Antifungal Activity of Amide Analogues 4031
For primary screening, each compound was used at a concen-
tration of 100 mg L-1.A mycelium agar disc (5 mm in diameter)
of the target fungi was placed in the center of PDA plates.
They were incubated at 28 ºC in the dark until the target fungi
used as the controls covered the surface of these plates. Control
groups were treated with the corresponding solutions without
the tested compound or carbendazim. The diameter of the fungi
in the cultures was measured and the inhibition of growth was
calculated according toAbbott’s formula. Each compound was
replicated three times.
A series of analogues of amide have been successfully
synthesized and tested for their antifungal activity against
Sclerotinia sclerotiorum and Bipolaris maydis (Nisikado et
Miyake) Shoem. The preliminary results suggested that the
design and synthesis of these compounds may be conducive
to the antifungal activity of analogues of amide. They are also
promising and beneficial to further studies in developing new
and more effective fungicides in the agricultural chemistry
field. However, there is more work to be done. A number of
analogues of amide should be further synthesized for screening
and surveying quantitative structure-activity relationships so
as to find novel fungicides with high effect and low toxicity.
The structural modification and optimization of compound 1
and compound 2 need to be done. Meanwhile, its mode of
action and its safety to humans and non-target organisms also
need to be investigated.
RESULTS AND DISCUSSION
All the synthesized analogues of amide were screened
for their activity against Sclerotinia sclerotiorum and Bipolaris
maydis (Nisikado et Miyake) Shoem. The results are presented
in Table-1. Some of them were active against the two different
pathogenic fungi at a concentration of 100 mg L-1. Among
them, the inhibition rate of compound 1 and compound 2
reached 91.1 %, 92.8 % and 90.1 %, 90.1 %, respectively,
which was close to carbendazim.
ACKNOWLEDGEMENTS
This project was supported by the Scientific Research
Fund of Sichuan Provincial Education Department (No.
09ZA158 ) and the Key Scientific Research Fund of Xihua
University (No. R0820501).
TABLE-1
ANTIFUNGAL ACTIVITY AGAINST Sclerotinia sclerotiorum AND
Bipolaris maydis(Nisikado et Miyake) Shoem 1-16 AT 100 mg L−1
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