6
AFRADI ET AL.
δ, ppm): 1.36 (t, 9H, t‐Bu), 2.03 (s, 3H, CH3), 2.44 (s, 3H,
CH3), 5.28 (s, 1H, OH), 5.71 (s, 1H, H‐5), 6.79–7.67 (m,
8H, Ar‐H), 7.79 (s, 1H, exocyclic CH). 13C NMR
(100 MHz, DMSO‐d6, δ, ppm): 166.8 (C═O), 163.7
(N─C═O), 159.7 (C═N), 158.5, 153.7, 140.9, 140.3,
133.8, 127.5, 127.0, 126.4, 125.8, 125.1, 123.8, 120.7,
115.7, 114.0, 80.0, 50.6, 28.8, 19.9, 17.1.
126.0, 121.0, 119.6, 116.0, 112.9, 80.4, 56.5, 56.3,
29.1, 19.4.
3.3.10
| tert‐Butyl‐7‐methyl‐2‐(3‐nitrobenzylidine)‐5‐phenyl‐
3‐oxo‐2,3‐dihydro‐5H‐thiazolo[3,2‐a]pyrimidine‐6‐carboxylate
(7j)
IR (KBr, νmax, cm−1): 3031, 2861, 1714, 1701, 1593, 1576,
1
1210, 1196, 817, 700. H NMR (400 MHz, DMSO‐d6, δ,
ppm): 1.39 (t, 9H, t‐Bu), 2.35 (s, 3H, CH3), 5.72 (s, 1H, H‐
5), 7.12–8.14 (m, 9H, Ar‐H), 7.75 (s, 1H, exocyclic CH).
13C NMR (100 MHz, DMSO‐d6, δ, ppm): 166.3 (C═O),
165.2 (N─C═O), 159.7 (C═N), 154.2, 147.8, 142.7, 140.9,
134.1, 129.8, 127.3, 126.1, 125.4, 125.0, 121.7, 120.8,
119.1, 116.0, 79.6, 54.8, 29.1, 20.1.
3.3.6
| tert‐Butyl‐7‐methyl‐2‐(4‐chlorobenzylidine)‐5‐(4‐methyl-
phenyl)‐3‐oxo‐2,3‐dihydro‐5H‐thiazolo[3,2‐a]pyrimidine‐6‐
carboxylate (7f)
IR (KBr, νmax, cm−1): 3079, 2909, 1699, 1694, 1596, 1553,
1
1217, 1193, 848, 741, 711. H NMR (400 MHz, DMSO‐d6,
δ, ppm): 1.38 (t, 9H, t‐Bu), 1.94 (s, 3H, CH3), 2.32 (S, 3H,
CH3), 5.90 (s, 1H, H‐5), 7.18–7.48 (m, 8H, Ar‐H), 7.68 (s,
1H, exocyclic CH). 13C NMR (100 MHz, DMSO‐d6, δ,
ppm): 167.5 (C═O), 164.7 (N─C═O), 159.8 (C═N), 154,
139.6, 137.7, 135.1, 131.7, 131.0, 128.4, 128, 126.9, 125.7,
121.7, 116.6, 80.4, 56.3, 24.8, 29.3, 20.3.
3.4 | Biological assay
3.4.1
| In vitro antimicrobial assay
All synthesized compounds (4a–j and 7a–j) were tested for
antimicrobial activity against pathogenic strains by applying
the well diffusion assay method and MIC technique.
3.3.7
| tert‐Butyl‐7‐methyl‐2‐(4‐methylbenzylidine)‐5‐(3‐nitro-
phenyl)‐3‐oxo‐2,3‐dihydro‐5H‐thiazolo[3,2‐a]pyrimidine‐6‐
carboxylate (7g)
3.4.2
| Primary screening
IR (KBr, νmax, cm−1): 3078, 2843, 1725, 1698, 1587, 1551,
1244, 1201, 831, 687. H NMR (400 MHz, DMSO‐d6, δ,
The in vitro antimicrobial activities of 4a–j and 7a–j were
determined using the agar well diffusion method[1,29] against
a panel of microorganisms, namely S. aureus (ATCC 6538)
and S. epidermidis (ATCC 12228) as Gram‐positive bacteria,
E. coli (ATCC 8739) and P. aeruginosa (ATCC 9027) as
Gram‐negative bacteria, and A. niger (ATCC 16404) and C.
albicans (ATCC 10231) as fungus and yeast, respectively.
Microbial colonies were prepared in 5 ml of tripticase soya
broth from a fresh isolation plate. The broth was incubated
for 6 h at 37 °C to observe obvious growth. A 0.5 McFarland
standard was prepared by mixing 0.05 ml of 0.1% (w/v)
BaCl2⋅2H2O in phosphate buffer saline (PBS) with 9.95 ml
of 1% (v/v) sulfuric acid in PBS. The turbidity of all six cul-
tures using sterile PBS was controlled to 0.5 McFarland tur-
bidity standard to obtain a 108 cfu ml−1 suspension. To
prepare incolums of yeast and fungi including 106 cfu ml−1
suspension, the 108 cfu ml−1 suspension was diluted 102
times in trypticase soya broth. All the examined compounds
and ciprofloxacin as antibacterial standard and clotrimazole
as antifungal standard were prepared by dissolving 50 mg
of each compound in 1 ml of DMSO. So DMSO was applied
as a negative control for all the experiment samples.
1
ppm): 1.19 (t, 9H, t‐Bu), 1.86 (s, 3H, CH3), 2.18 (s, 1H,
CH3), 5.75 (s, 1H, H‐5), 7.09–8.14 (m, 8H, Ar‐H), 7.82 (s,
1H, exocyclic CH). 13C NMR (100 MHz, DMSO‐d6, δ,
ppm): 166.3 (C═O), 165.1 (N─C═O), 160.0 (C═N), 153.7,
147.6, 142.8, 141.0, 138.9, 134.0, 130.7, 130.0, 128.4,
127.5, 121.8, 120.4, 117.8, 116.0, 81.0, 55.4, 29.3, 25.4,
20.3.
3.3.8
| tert‐Butyl‐7‐methyl‐2‐(4‐chlorobenzylidine)‐5‐(2‐nitro-
phenyl)‐3‐oxo‐2,3‐dihydro‐5H‐thiazolo[3,2‐a]pyrimidine‐6‐car-
boxylate (7h)
IR (KBr, νmax, cm−1): 3075, 2879, 1720, 1693, 1590, 1541,
1
1266, 1210, 841, 723, 695. H NMR (400 MHz, DMSO‐d6,
δ, ppm): 1.40 (t, 9H, t‐Bu), 2.25 (s, 3H, CH3), 5.43 (s, 1H,
H‐5), 7.39–8.14 (m, 8H, Ar‐H), 8.05 (s, 1H, exocyclic CH).
13C NMR (75 MHz, DMSO‐d6, δ, ppm): 166.8 (C═O),
163.9 (N─C═O), 159.6 (C═N), 153.9, 145.9, 140.3, 135.8,
133.1, 131.7, 131.1, 129.9, 128.3, 127.9, 127.0, 120.9,
118.4, 116.6, 79.9, 51.4, 28.7, 19.9.
3.3.9
|
tert‐Butyl‐7‐methyl‐2‐(2‐nitrobenzylidine)‐5‐(4‐
An amount of 100 μl of suspension containing
1 × 108 cfu ml−1 of each examined bacterial strain and
1 × 106 cfu ml−1 of yeast and fungus was mixed with
20 ml of Mueller–Hinton agar and Sabouraud dextrose agar,
respectively, and transferred into sterilized Petri plates. Wells
of 8 mm in diameter were punched in the solidified agar
plates and 100 μl of test solution was charged to individual
wells. The loaded plates were preserved for incubation at
37 °C for 24 h for bacteria and 48 h at 28 °C for fungi. After
the incubation time, the antimicrobial activity of each sample
methoxyphenyl)‐3‐oxo‐2,3‐dihydro‐5H‐thiazolo[3,2‐a]pyrimi-
dine‐6‐carboxylate (7i)
IR (KBr, νmax, cm−1): 3057, 2878, 1704, 1697, 1574, 1546,
1
1286, 1224, ,811, 697. H NMR (400 MHz, DMSO‐d6, δ,
ppm): 1.37 (t, 9H, t‐Bu), 2.26 (s, 3H, CH3), 3.72 (s, 3H,
OCH3), 5.72 (s, 1H, H‐5), 7.06–8.15 (m, 8H, Ar‐H), 8.31
(s, 1H, exocyclic CH). 13C NMR (100 MHz, DMSO‐d6, δ,
ppm): 166.4 (C═O), 164.7 (N─C═O), 159.8 (C═N), 156.4,
153.9, 144.8, 140.1, 135.3, 133.7, 130.8, 129.3, 126.8,