1296
B. Tekiner-Gulbas et al. / European Journal of Medicinal Chemistry 42 (2007) 1293e1299
2
.3.6. Compound 8: 2-( p-chlorobenzyl)-5-[(3,4-
2.3. Microbiology
dimethylphenyl)carbonylamino]benzoxazole
C H ClN O , yield: 57, mp: 170e171 C.
ꢂ
For the antibacterial and antimycotic assays, the com-
pounds were dissolved in absolute ethanol (0.8 mg/ml). Fur-
ther dilutions of the compounds and standard drugs in the
test medium were prepared at the required quantities of 400,
200, 100, 50, 25, 12.5, 6.25, 3.12, 1.56, 0.78 mg/ml concentra-
tions with MuellereHinton broth and Sabouraud dextrose
broth. The minimum inhibitory concentrations (MIC) were de-
termined using the twofold serial dilution technique [32,33]. A
control test was also performed containing inoculated broth
supplemented with only ethanol at the same dilutions used
in our experiments and found inactive in the culture medium.
All the compounds were tested for their in vitro growth inhib-
itory activity against different bacteria and the yeasts Candida
albicans ATCC 10145, Candida krusei ATCC 6258, and
Candida glabrata (isolated ). Origins of bacterial strains are
Staphylococcus aureus ATCC 25923, Bacillus subtilis ATCC
2
3
19
2 2
1
H NMR (ppm): 2.05e2.20 (CH , 6H, s); 4.00e4.10 (CH ,
3
2
0
0
2
(
H, s); 7.00e7.10 (5 , 1H, d, J 00 00 ¼ 7.84 HZ); 7.10e7.45
5
,6
0 0 0 0 00
C-6, 7, 2 , 3 , 5 , 6 , 6 , 7H, m); 7.45e7.55 (C-4, 2H, d,
0
0
J4,6 ¼ 1.09 HZ); 7.85e7.90 (NH, 1H, s); 7.90e8.00 (C-2 , 1H,
d, J200 00 ¼ 2.40 HZ).
,6
ꢁ1
IR (cm ): 3303, 3083, 2932, 1671, 1556, 1487, 1270e
015, 966e688.
1
MS (70 eV) m/z: 392 (M þ 2), 391 (M þ 1), 390 (Mþ), 133
(
100%).
2
.3.7. Compound 9: 2-benzyl-5-[(3,4-dimethylphenyl)-
carbonylamino]benzoxazole
C H N O , yield: 55, mp: 177e178 C.
ꢂ
2
3 20 2 2
1
H NMR (ppm): 2.30e2.40 (CH , 6H, s); 4.20e4.30 (CH ,
3
2
0
0
0
0
0
00
00
00
2
7
H, s); 7.20e7.75 (C-6, 7, 2 , 3 , 4 , 5 , 6 , 2 , 5 , 6 , 10H, m);
.85e7.90 (NH, 1H, s); 7.90e8.00 (C-4, 1H, d, J ¼ 1.98 HZ).
6633 as Gram-positive and Escherichia coli ATCC 23556
4
,6
ꢁ
1
and Pseudomonas aeruginosa ATCC 10145 as Gram-negative
bacteria. ATCC strains of the microorganisms used in this
study were obtained from the culture collection of Refik
Saydam Health Institution of Health Ministry, Ankara, and
maintained at the Microbiology Department of Faculty of
Pharmacy of Ankara University.
Ampicillin, amoxycillin, tetracycline, streptomycin, cipro-
floxacine, gentamicin, miconazol, clotrimazole, and halopro-
gin were used as control drugs. The data on the
antimicrobial activity of the compounds and the control drugs
as MIC (mg/ml) values are given in Table 1.
IR (cm ): 3273, 3067, 2969, 1638, 1552, 1496e1420,
298e1022, 948e670.
1
MS (70 eV) m/z: 358 (M þ 2), 357 (M þ 1), 356 (Mþ), 133
(
100%).
2
.3.8. Compound 10: 2-( p-chlorobenzyl)-5-
[
(phenylthiomethyl)carbonylamino]benzoxazole
C H ClN O S, yield: 6, mp: 133e134.
2
2
17
2 2
1
H NMR (ppm): 3.50e3.70 (CH , 2H, s); 4.00e4.10 (S-
2
CH , 2H, s); 7.00e7.70 (aromatic protons, 11H, m); 7.60e
2
7
.65 (C-4, 1H, d, J ¼ 2.60 HZ); 8.40e8.50 (NH, 1H, s).
4
,6
ꢁ
1
IR (cm ): 3258, 3056, 2360, 1660, 1575e1534, 1485,
263e1015, 977e690.
2.4. Antibacterial and antifungal assay
1
MS (70 eV) m/z: 410 (M þ 2), 409 (M þ 1), 408 (Mþ), 407
The cultures were obtained from MuellereHinton broth
Difco) for all the bacterial strains after 24 h of incubation at
(
100%).
(
ꢂ
3
7 ꢀ 1 C. C. albicans, C. krusei and C. glabrata were main-
2
.3.9. Compound 11: 2-benzyl-5-[(phenylthiomethyl)-
carbonylamino]benzoxazole
C H N O S, yield: 19%, mp: 171e172 C.
tained in Sabouraud dextrose broth (Difco) after incubation for
ꢂ
2
4 h at 25 ꢀ 1 C. Testing was carried out in MuellereHinton
ꢂ
2
1
18
2
2
broth and Sabouraud dextrose broth (Difco) at pH 7.4 and the
twofold serial dilution technique was applied. The final inoc-
5
ulum size was 10 CFU/ml for the antibacterial assay and
1
only inoculated broth was used as controls. For the antibacte-
1
H NMR (ppm): 3.80e3.90 (CH , 2H, s); 3.90e4.00 (S-
2
CH , 2H, s); 7.00e7.70 (aromatic protons, 13H, m); 8.50e
2
8
.60 (NH, 1H, s).
1
4
0 CFU/ml for the antifungal assay. A set of tubes containing
ꢁ
IR (cm ): 3278, 3061, 2958e2911, 1648, 1549, 1497e
480, 1244e1024, 991e636.
1
ꢂ
rial assay after incubation for 24 h at 37 ꢀ 1 C and after incu-
MS (70 eV) m/z: 373 (M ꢁ 1), 372 (M ꢁ 2), 43 (100%).
ꢂ
bation for 48 h at 25 ꢀ 1 C for the antifungal assay, the last
tube with no growth of microorganism and/or yeast was re-
corded to represent the MIC expressed in mg/ml. Every exper-
iment in the antibacterial and antifungal assays was replicated
twice.
2
.3.10. Compound 12: 2-benzyl-5-[(4-nitrophenylmethyl)-
carbonylamino]benzoxazole
C H N O , yield: 35, mp: 204e206 C.
ꢂ
2
0 17 3 4
1
H NMR (ppm): 4.00e4.10 (CH , 2H, s); 4.40e4.50 (CH ,
2
H, s); 7.50e7.70 (C-4, 6, 7, 2 , 3 , 4 , 5 , 6 , 2 , 6 , 10H, m);
.90e8.00 (NH, 1H, s); 8.30e8.45 (C-3 , 5 , 2H, dd,
2
0
0
0
0
0
00
00
00
2
7
3. Results and discussion
00
J300 00 ¼ 8.73 HZ, J 00 00 ¼ 8.63 HZ).
Some of the new 2-(benzyl/p-chlorobenzyl)-5-[(substituted-
thienyl/phenyl/phenyl-thiomethyl/benzyl)carbonylamino]ben-
zoxazole derivatives (3e12) have been synthesized by using
three-step procedure as shown in Scheme 1. All the derivatives
,2
5 ,6
ꢁ
1
IR (cm ): 3320, 3050e3090, 1650, 1510e1560, 1480,
050e1230, 960e690.
1
MS (70 eV) m/z: 389 (M þ 2), 388 (M þ 1), 387 (Mþ), 91
1
(
100%).
(3e12) were supported by spectral data. The IR, H NMR and