Synthesis and anticoccidial activity of 3-(2-(benzofuran)-2-yl)-2- oxoethylquinazolinone derivatives

Article abstract of DOI:10.3184/174751912X13281900274006

In order to develop novel and effective anticoccidial compounds, a series of 3-(2-(benzofuran)-2-yl)-2-oxoethylquinazolinone derivatives were designed, synthesised and evaluated as potential anticoccidial drugs. The structures of these compounds were characterised by ¹H NMR, IR, HRMS spectra and elemental analysis. These compounds were tested for anticoccidial activities against Eimeria tenella according to the anticoccidial index method. 6-Chloro-3-(2-(benzofuran-2-yl)-2-oxoethyl) quinazolin-4-(3H)-one exhibited significant anticoccidial activities in the chicken's diet with a dose of 18 mg kg^-1.

Full text of DOI:10.3184/174751912X13281900274006

JOURNAL OF CHEMICAL RESEARCH 2012
RESEARCH PAPER 127
MARCH, 127–130
Synthesis and anticoccidial activity of 3-(2-(benzofuran)-2-yl)-2-
oxoethylquinazolinone derivatives
Ying Xina,b, Min Xiea, Li-Juan Zouc, Kui Niec and Yu-Liang Wanga*
aCollege of Chemistry, Sichuan University, Chengdu, Sichuan 610064, P. R. China
bPharmaecutical College of Chengdu Medical College, Chengdu, Sichuan 610083, P. R. China
cCollege of Animal Science andTechnology, Southwest University, Chongqi 6400715, P. R. China
In order to develop novel and effective anticoccidial compounds, a series of 3-(2-(benzofuran)-2-yl)-2-oxoethylquin-
azolinone derivatives were designed, synthesised and evaluated as potential anticoccidial drugs. The structures
1
of these compounds were characterised by H NMR, IR, HRMS spectra and elemental analysis. These compounds
were tested for anticoccidial activities against Eimeria tenella according to the anticoccidial index method. 6-Chloro-
3-(2-(benzofuran-2-yl)-2-oxoethyl) quinazolin-4-(3H)-one exhibited significant anticoccidial activities in the chicken’s
diet with a dose of 18 mg kg−1.
Keywords: 3-(2-(benzofuran)-2-yl)-2-oxoethylquinazolinone, anticoccidial activity, anticoccidial index method, Eimeria tenella
Coccidiosis is an intestinal infection caused by protozoan
parasites of the genus Eimeria, which can invade the intestinal
mucosa and induce a degree of epithelial cell damage and
inflammation. Intestinal lesions, diarrhoea, enteritis and death
can occur.1 Many anticoccidial drugs play an important role in
controlling the disease. However, because of drug-resistance
caused by both using anticoccidial medicine extensively and
the heredity of coccidia, the coccidial populations have been a
constant threat to the continued success of chemotherapy.2
Therefore, we have investigated the development of novel and
effective compounds.
Dichroa Febrifuge had been used as a traditional medicine
for the treatment of malaria and coccidiosis in China. Its active
components are confirmed as the quinazoline alkaloids, such
as febrifugine (1) and isofebrifugine (2) (Fig. 1).3 However, it
has not been used in anticoccidial drugs because of its side
effects of diarrhoea, vomiting and liver toxicity.4 Halofuginone
(3) (Fig. 1) (commercial name Stenorol) was designed and
synthesised based on the structure of febrifugine (1), It has
been a good anticoccidiostat at a dose of 3 mg kg−1 for a long
time.5 In contrast, the drug-resistance which led to the decline
in the effectiveness of halofuginone (3) has also been found.6
Furthermore, the synthesis of halofuginone (3) is very compli-
cated requiring both the synthesis of the quinazolinone ring
and the piperidine ring,7 resulting in expensive production
costs and limitations for broad-usage.
Experimental
Solvents and reagents were obtained from commercial sources with-
out further purification except salicylaldehyde which was purified
through redistilling and then kept at 0 °C. 1-(Benzofuran-2-yl)-ethanone
(1) was synthesised according to the literature.15 Quinazolin-4-(3H)-one
derivatives (3a–f) were synthesised according to the literature.9,16–18
Melting points were recorded using an XRC-1 apparatus and the
thermometer was uncorrected. Proton NMR spectra were recorded on
a Varian Unity Inova-400 spectrometer with CDCl3 as the solvent and
TMS as the internal standard, and the chemical shift values (δ) were
given in ppm. Mass spectra were recorded with an Agilent 6210
(DOF-MAS) spectrometer using ESI. IR spectra were recorded with
a Perkin-Elmer 16PC-FT instrument. Elemental analyses were carried
out by the Euro EA 3000 instrument (Euro Vector S.P.A., Italy).
Analytical TLC was determined with silica gel GF254, and spots were
visualised with UV light.
Synthesis of 2-bromo-1-(benzofuran-2-yl)-ethanone (2)19
A mixture of 1-(benzofuran-2-yl)-ethanone (1) (12.8 g, 80 mmol) in
CH2Cl2 (50 mL) was stirred vigorously at room temperature. A solu-
tion of bromine (12.8 g, 80 mmol) in CH2Cl2 (50 mL) was added in
small portions in such a way that the colour of bromine completely
disappeared before the next portion was added. Then HBr gas was
neutralised by the addition of sodium hydroxide solution. The reac-
tion mixture was adjusted to pH 7–8 with saturated NaHCO3 and the
organic layer was separated out and the aqueous layer was extracted
with CH2Cl2 (3×20 mL). The combined organic phases were washed
with saturated NaCl (3×40 mL), dried with anhydrous Na2SO4 and
concentrated under reduced pressure to give a crude product as a
brown yellow oil. A yellow crude solid was obtained by addition of
petroleum ether (20 mL) to the oil and yellow crystals were produced
by recrystallisation from petroleum ether. Yield: 80–85%; m.p. 83 °C
Our groups have been trying to find new and potential anti-
coccidial compounds,8–12 some of which were quinazolinone
derivatives. Here we describe the synthesis of six 3-(2-(benzo-
furan) -2-yl) -2 -oxoethylquinazolinone derivatives having
structures related to halofiginone (3) with the benzofuran
ring taking the place of piperidine ring. The synthetic route to
the target compounds (4a–f) is shown in Scheme 1. The anti-
coccidial activities of the novel compounds were evaluated
according to the anticoccidial index (ACI) method.13,14
1
(84.3 °C); H NMR spectrum (400 MHz, CDCl3) δ = 7.74 (d, J =
8.0 Hz, 1H), 7.66 (d, J = 8.0 Hz, 1H), 7.61–7.59 (m, 1H), 7.55–7.50
(m, 1H), 7.37–7.33 (m, 1H), 4.45 (s, 2H).
Synthesis of 3-(2-(benzofuran)-2-yl)-2-oxoethylquinazolinone
derivatives (4a–f); general procedure
In a three-necked flask with a thermometer and a condenser, a mixture
of (3a–f) (5 mmol), KI (0.37 g, 2.25 mmol) and NaH (0.24 g, 10 mmol)
Fig. 1 Structure of febrifugine (1), isofebrifugine (2) and halofuginone (3).
* Correspondent. E-mail: chemwang2000@163.com

128 JOURNAL OF CHEMICAL RESEARCH 2012
Scheme 1 General synthesis route for compounds 4a–f.
in DMSO (10 mL) was heated to 75 °C with stirring. Then a solution
of intermediate (2) (1.20 g, 5 mmol) in DMSO (10 mL) was added
dropwise. After 2–4 h, the mixture was cooled to room temperature
and washed with water (3 × 100 mL) giving much solid which was
dried and recrystallised from anhydrous ethanol to give (4a–f).
3-(2-(Benzofuran-2-yl)-2-oxoethyl) quinazolin-4-(3H)-one (4a):
1H),5.26 (s, 2H); IR (KBr, cm−1): 3428, 3071, 2932, 1692, 1669, 1609,
1551, 1448, 748. Anal. Calcd for C18H11ClN2O3: C, 63.82; H, 3.27; N,
8.27. Found: C, 63.79; H, 3.30; N, 8.31%; HR-MS (ESI): Calcd for
C18H11ClN2O3 (M + H+, isotopic peak): 339.0536, 341.0507; found:
339.0529, 341.0506 (3:1).
8-Bromo-6-chloro 3-(2-(benzofuran-2-yl)-2-oxoethyl) quinazolin-
4-(3H)-one (4e): Light grey flocculent solid; yield: 70.5%; m.p. 229–
230 °C. 1H NMR spectrum (400 MHz,CDCl3) δ = 8.25 (d, J = 2.4 Hz,
1H), 8.10 (s, 1H), 8.05 (d, J = 2.4 Hz, 1H), 7.77 (d, J = 8.0 Hz, 1H),
7.37 (d, J = 0.8 Hz, 1H), 7.64–7.56 (m, 2H), 7.38–7.36 (m, 1H), 5.44
(s, 2H); IR (KBr, cm−1): 3428, 3077, 2932, 1692, 1669, 1609, 1551,
1448, 748. Anal. Calcd for C18H10BrClN2O3: C, 51.77; H, 2.41; N,
6.71. Found: C, 51.81; H, 2.44; N, 6.68%; HR-MS (ESI): Calcd
for C18H10BrClN2O3 (M + H+, isotopic peak): 416.9642, 418.9621,
418.9612; found: 416.9628, 418.9616, 418.9607 (4:3:1).
1
Dark grey solid; yield: 40%; m.p. 204–206 °C; H NMR spectrum
(400 MHz,CDCl3) δ = 8.31 (d, J = 8.0 Hz, 1H), 8.04 (s, 1H), 7.82–
7.73 (m, 4H), 7.62 (d, J = 8.4 Hz, 1H), 7.57–7.51 (m, 2H), 7.42–7.32
(m, 1H), 5.44 (s, 2H); IR (KBr, cm−1) 3377, 3029, 2939, 1698, 1669,
1608, 1560, 1472, 1359, 1165, 1135, 782, 752. Anal. Calcd for
C18H12N2O3: C, 71.05; H, 3.97; N, 9.21. Found: C, 71.01; H, 3.99; N,
9.24%. HR-MS (ESI): Calcd for C18H12N2O3 (M + H+): 305.0926;
found: 305.0926.
6-Fluoro-3-(2-(benzofuran-2-yl)-2-oxoethyl) quinazolin-4-(3H)-
one (4b): Light pink flocculent solid; yield: 65.8%; m.p. 204–206 °C;
1H NMR spectrum (400 MHz, CDCl3) δ = 8.01 (s, 1H), 7.94 (dd,
J1 = 2.8 Hz, J2 = 8.4 Hz, 1H), 7.80–7.76 (m, 2H), 7.73(s, 1H), 7.62(d,
J = 8.4 Hz, 1H), 7.58-7.50 (m, 2H), 7.37 (t, J1 = J2 = 7.6 Hz, 1H),
5.44 (s, 2H); IR (KBr, cm−1): 3432, 3024, 2944, 1701, 1672, 1606,
1560, 1482, 1163, 1134, 843, 761. Anal. Calcd for C18H11FN2O3: C,
67.08; H, 3.44; N, 8.69. Found: C, 67.09; H, 3.48; N, 8.72%; HR-MS
(ESI): Calcd for C18H11FN2O3 (M + H+): 323.0832, 324.0866; found:
323.0827, 324.0860 (5:1).
8-Bromo-6-fluoro-3-(2-(benzofuran-2-yl)-2-oxoethyl) quinazolin-4-
(3H)-one (4c): Silver flocculent solid; yield: 68.5%; m.p. 240–241 °C;
1H NMR spectrum (400 MHz,CDCl3) δ = 8.09 (s, 1H), 7.95 (dd,
J1 = 2.8 Hz, J2 = 7.6 Hz, 1H), 7.85 (dd, J1 = 2.8 Hz, J2 = 8.0 Hz, 1H),
7.77 (d, J = 8.0 Hz, 1H), 7.73 (s, 1H), 7.62 (d, J = 8.4 Hz, 1H), 7.56
(t, J1 = J2 = 7.6 Hz, 1H), 7.37 (t, J1 = J2 = 7.6 Hz, 1H), 5.44 (s, 2H); IR
(KBr, cm−1): 3425, 3079, 2935, 1693, 1667, 1608, 1554, 1461, 1185,
1017, 862, 749. Anal. Calcd for C18H10BrFN2O3: C, 53.89; H, 2.51;
N, 6.98. Found: C, 53.93; H, 2.53; N, 6.95%; HR-MS (ESI): Calcd
for C18H10BrFN2O3 (M + H+, isotopic peak): 400.9937, 401.9971,
402.9917, 403.9950; found: 400.9935, 401.9971, 402.9917, 403.9949
(5:1:5:1).
6-Chloro-3-(2-(benzofuran-2-yl)-2-oxoethyl) quinazolin-4-(3H)-one
(4d): White grey flocculent solid; yield: 60.2%; m.p. 229–230 °C;
1H NMR spectrum (400 MHz,CDCl3) δ = 8.27 (d, J = 1.2 Hz, 1H),
8.01 (s, 1H), 7.77 (d, J = 8.0 Hz, 1H), 7.73–7.72 (m, 3H), 7.62
(d, J = 8.4 Hz, 1H), 7.58–7.52 (m, 1H), 7.40–7.36 (t, J1 = J2 = 7.2 Hz,
6-Bromo-3-(2-(benzofuran-2-yl)-2-oxoethyl) quinazolin-4-(3H)-one
1
(4f): Light grey flocculent solid; yield: 45%; m.p. 212–214 °C; H
NMR spectrum (400 MHz,CDCl3) δ = 8.47 (d, J = 2.4 Hz, 1H), 8.21
(s, 1H), 7.92 (dd, J1 = J2 = 2.4 Hz, 1H), 7.80–7.72 (m, 3H), 7.65 (d,
J = 8.4 Hz, 1H), 7.60–7.54 (m, 1H), 7.42–7.38 (m, 1H), 5.51 (s, 2H);
IR (KBr, cm−1): 3436, 3072, 2929, 1694, 1670, 1609, 1549, 1465,
1175, 1029, 745. Anal. Calcd for C18H11BrN2O3: C, 56.42; H, 2.89;
N, 7.31. Found: C, 56.44; H, 2.93; N, 7.28%; HR-MS (ESI): Calcd for
C18H11BrN2O3 (M + H+, isotopic peak): 383.0031, 385.0011; found:
383.0027, 385.0009 (1:1).
Biological assay
The anticoccidial activities of the new compounds were evaluated
according to the anticoccidial index method, using the decoquinate
and diclazuril as reference drugs at a dose of 27 mg kg−1 and 1 mg kg−1,
respectively. Decoquinate is a highly sensitive drug to the coccidia,
but the diclazuril had been regarded as a good anticoccidiostat prior
to its use. The chickens that were used for testing were fed to 12-days-
old by a feedstuff that did not contain any anticoccidial drug.
Groups of these chickens were randomly housed in 10 cages with
15 in each. Groups 1–6 of 13-day-old chickens were fed the basal
starter diet with the compounds (4a–f) as 18 mg kg−1 until the end
of the test. Chickens in groups 7–8 were fed the basal starter diet
with decoquinate or diclazuril until the end of the test. Groups 1–9 of
14-day-old chickens were infected artificially with the Eimeria tenella
spores of the oocysts 100,000 and kept under observation for 9 days

JOURNAL OF CHEMICAL RESEARCH 2012 129
Table 1 Data for anticoccidial activities of compounds 4a–f against Eimeria tenella
Test groups
Test compounds Survival rate/%
/mg kg−1
Rate of relative
body weight gain
Lesion values Oocyst values OPG valuesd ×106
ACIa
1
2
4a (18e)
4b (18e)
93.33
100.00
93.33
100.00
93.33
93.33
100.00
93.33
80.00
100.00
53.97
50.00
65.48
72.22
53.17
60.00
71.65
53.54
62.99
100.00
17.14
15.00
14.64
14.29
18.00
23.00
13.00
20.00
28.00
0
1.00
1.00
10.00
10.00
10.00
20.00
0
20.00
40.00
0
0.14
0.80
1.25
1.16
1.16
6.45
0.01
6.22
19.34
0
129.16
134.00
134.17
147.93
118.50
110.33
158.65
106.87
74.99
3
4c (18e)
4
4d (18e)
5
4e (18e)
6
4f (18e)
7
Decoquinate(27e)
Diclazuril (1e)
INGb
8
9
10
NNGc
200.00
a Anticoccidial activity index.
b Infected non-medicated group.
c Non-infected non-medicated group.
d Occyst per gram.
e The dose of tested compounds 18 mg kg−1, 27 mg kg−1, 1mg kg−1.
after infection. The weight gain, mortality, lesion scores and oocysts’
counts of the chickens were recorded and then the ACI was calculated.
Results of the tests are shown in Table 1.
Compared with 80.00 (the infected non-medicated group), all
the tested drugs could obviously protect the chickens from
death. Compared with the infected non-medicated group,
two of the tested compounds were advantageous for the growth
of the chickens. According to the infected non-medicated
group (62.99), the relative rate of weight gain is better when
(4c) (65.48) and (4d) (72.22) were used respectively.
Briefly, three of these compounds exhibited higher anticoc-
cidial activities against Eimeria tenella with ACI of 134.00
(4b), 134.17 (4c) and 147.93 (4d), and other compounds (4a)
(129.16), (4e) (118.50) and (4f) (110.33) exhibited certain
anticoccidial activities. We selected only one concentration at
random to test the anticoccidial activity of the synthesised
compounds, without considering the optimal concentration to
obtain the best ACI.
Results and discussion
When the chickens were infected by coccidia, their survival
rates would reduce, bodyweight gain would diminish, lesions
would be found in the cecum and the oocyst of the next
generation would be produced. The ACI was calculated as
follows:
ACI = (relative rate of weight gain + rate of survival) −
(lesion value + oocyst value)
Based on the literature of Johnson and Reid,14 the lesion of
chickens was ranked in five classes and the related lesion score
was recorded as 0-4. The lesion score of each group was the
average value for chickens in each team. And the lesion value
was calculated as below:
Conclusion
Six novel 3-(2-(benzofuran)-2-yl)-2-oxoethylquinazolinone
derivatives have been synthesised and the anticoccidial activi-
ties of these compounds were evaluated according to the ACI
method. The results indicated that all of compounds have
biological activities. Especially, (4d) (ACI of 147.93) had
significant anticoccidial activities against Eimeria tenella at
a dose of 18 mg kg−1 and might be developed as an anticoc-
cidial drug when the coccidian-increased resistance to older
compounds, such as decoquinate, increases.
Lesion value = lesion score × 10
Table 2 shows the relation between oocyst counts of per
gram and the oocyst value.20
The data for anticoccidial activities of the compounds
(4a–f) are shown in Table 1. In the positive control group, the
coccidiosis in chickens is serious with an ACI of 74.99. By
contrast, the negative control group showing no coccidiosis in
chickens has an ACI of 200. Thus the control was set up.
Lesion values could evaluate the effect of Eimeria to chick-
en’s caecum. The lesion values in all groups of compounds
(4a–f) were 17.14, 15.00, 14.64, 14.29, 18.00 and 23.00 which
are lower than the value 28.00 of the infected non-medicated
group. It clearly indicated that all the tested compounds could
control the effect of Eimeria tenella on the chickens’ caecum.
The oocyst value data ranges from 0 to 40 reflecting the
amount of oocysts per gram, which are produced by the elder
generation of coccidian. The oocyst value data in Table 1 are
1.00 (4a, 4b), 10.00 (4c, 4d, 4e) and 20.00 (4f), respectively,
and they are significantly lower than the value 40.00 of the
infected-untreated group. They showed that all the tested com-
pounds could effectively suppress the generation of oocysts.
Survival rate and the relative rate of weight gain indicated
the affect of drugs or coccidia on the birds’ growth. The
survival rate data are 93.33 (4a, 4c, 4e, 4f) and 100.00 (4b, 4d).
We appreciate the financial support from the National Science
1
Foundation of China (Nos. 21072135) and H NMR analysis
by Sichuan University Analytical & Testing Center.
Received 28 November 2011; accepted 16 January 2012
Paper 1101010 doi: 10.3184/174751912X13281900274006
Published online: 22 March 2012
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