Synthesis and evaluation of new phenolic derivatives as antimicrobial and antioxidant agents
reflux for 2 h. The reaction mixture was then concentrated
to half its volume under reduced pressure and set aside to
attain room temperature. The reaction mixture was grad-
ually poured onto stirred crushed ice to decompose the
excess unreacted acetic anhydride and left in a refrigerator
for an overnight. The separated products were filtered,
washed with water, air dried, and crystallized from the
selected solvent.
4-Acetoxy-2-[4-acetyl-5-(4-acetoxy-3-ethoxyphenyl)-4,5-dihy-
dro-1,3,4-oxadiazol-2-yl]phenyl acetate (3d, C24H24N2O9)
Crystallized from ethanol. Yield 85%; m.p.: 165–166 °C;
1H NMR (300 MHz): d = 1.28 (t, 3H, J = 6.9 Hz,
OCH2CH3), 2.23 (s, 3H, COCH3), 2.25, 2.26 (2 s, 9H,
OCOCH3), 3.79 (s, 3H, OCH3), 4.05 (q, 2H, J = 6.9 Hz,
OCH2CH3), 7.00 (dd, 1H, J = 8.1, 1.8 Hz), 7.12 (s, 1H),
7.15 (d, 1H, J = 8.1 Hz), 7.19 (d, 1H, J = 1.8 Hz), 7.35
(d, 1H, J = 8.7 Hz), 7.41 (dd, 1H, J = 8.7, 2.7 Hz), 7.60
(d, 1H, J = 2.7 Hz) ppm; 13C NMR (100 MHz): d = 14.8,
20.7, 21.1, 21.2, 21.8, 64.7, 91.4, 112.6, 118.7, 119.0,
122.8, 123.7, 125.7, 126.8, 135.4, 141.2, 146.3, 148.6,
150.7, 151.6, 167.3, 168.8, 169.5, 169.7 ppm; IR (KBr):
4-Acetoxy-2-[4-acetyl-5-(4-acetoxyphenyl)-4,5-dihydro-
1,3,4-oxadiazol-2-yl]phenyl acetate (3a, C22H20N2O8)
Crystallized from ethanol. Yield 57%; m.p.:
147–148 °C; 1H NMR (300 MHz): d = 2.25 (s, 3H,
COCH3), 2.26, 2.27 (2 s, 9H, 3OCOCH3), 7.16 (s, 1H),
7.21 (d, 2H, J = 8.7 Hz), 7.36 (d, 1H, J = 9 Hz), 7.41
(dd, 1H, J = 9, 2.7 Hz), 7.50 (d, 2H, J = 8.4 Hz), 7.60
(d, 1H, J = 2.7 Hz) ppm; 13C NMR (100 MHz):
d = 21.1, 21.2, 21.3, 21.7, 91.1, 118.8, 122.8, 122.9,
126.0, 126.8, 128.5, 134.2, 146.3, 148.5, 151.5, 152.0,
ꢀ
m = 1762 (C=O ester), 1670 (C=O amide), 1625 (C=N),
1210, 1044 (C–O–C) cm-1
.
4-Acetoxy-2-[4-acetyl-5-(3,4-dimethoxyphenyl)-4,5-dihydro-
1,3,4-oxadiazol-2-yl]phenyl acetate (3e, C22H22N2O8)
Crystallized from ethanol. Yield 80%; m.p.: 115–116 °C;
1H NMR (300 MHz): d = 2.23 (s, 3H, COCH3), 2.25, 2.26
(2 s, each 3H, 2OCOCH3), 3.76, 3.77 (s, 3H, 2OCH3), 6.96
(d, 1H, J = 9 Hz), 7.00 (s, 1H), 7.01 (d, 1H, J = 8.1 Hz),
7.06 (s, 1H), 7.35 (d, 1H, J = 8.7 Hz), 7.40 (dd, 1H,
J = 8.7, 2.4 Hz), 7.58 (d, 1H, J = 2.4 Hz) ppm; 13C NMR
(100 MHz): d = 21.1, 21.2, 21.8, 55.9, 56.0, 91.9, 110.3,
112.1, 119.1, 119.6, 122.6, 125.7, 126.7, 129.1, 146.3,
148.5, 149.3, 150.5, 151.5, 167.1, 169.5, 169.6 ppm; IR
(KBr): mꢀ = 1762 (C=O ester), 1672 (C=O amide), 1612
ꢀ
167.3, 169.4, 169.5, 169.7 ppm; IR (KBr): m = 1765
(C=O ester), 1661 (C=O amide), 1616 (C=N), 1209,
1048 (C–O–C) cm-1
.
4-Acetoxy-2-[4-acetyl-5-(4-acetoxy-3-methoxyphenyl)-4,5-di-
hydro-1,3,4-oxadiazol-2-yl]phenyl acetate (3b,C23H22N2O9)
Crystallized from ethanol. Yield 71%; m.p.: 155–156 °C;
1H NMR (300 MHz): d = 2.23 (s, 3H, COCH3), 2.25,
2.26 (2 s, 9H, 3OCOCH3), 3.79 (s, 3H, OCH3), 7.09 (s,
1H), 7.16 (d, 1H, J = 8.1 Hz), 7.20 (d, 1H, J = 2.7 Hz),
7.33 (dd, 1H, J = 8.1, 2.7 Hz), 7.37 (d, 1H, J = 8.7 Hz),
7.41 (dd, 1H, J = 8.7, 2.7 Hz), 7.58 (d, 1H, J = 2.4 Hz)
ppm; 13C NMR (100 MHz): d = 20.8, 21.1, 21.2, 21.8,
56.4, 91.2, 113.3, 118.8, 121.5, 122.8, 125.8, 125.9,
126.8, 129.2, 139.8, 146.3, 148.5, 151.4, 152.6, 167.3,
(C=N), 1207, 1023 (C–O–C) cm-1
.
4-Acetoxy-2-[4-acetyl-5-(3,4,5-trimethoxyphenyl)-4,5-dihy-
dro-1,3,4-oxadiazol-2-yl]phenyl acetate (3f, C23H24N2O9)
Crystallized from methanol. Yield 85%; m.p.: 131–132 °C;
1H NMR (300 MHz): d = 2.22 (s, 3H, COCH3), 2.27 (s,
6H, 2OCOCH3), 3.67, 3.78 (2 s, 9H, 3OCH3), 7.06 (s, 1H),
6.74 (s, 2H), 7.35 (d, 1H, J = 8.7 Hz), 7.41 (dd, 1H,
J = 8.7, 2.7 Hz), 7.59 (d, 1H, J = 2.7 Hz) ppm; 13C NMR
(100 MHz): d = 21.0, 21.2, 21.8, 56.4, 60.4, 92.0, 104.3,
118.9, 122.8, 125.6, 126.8, 132.2, 139.1, 146.3, 148.5,
ꢀ
168.9, 169.5, 169.6 ppm; IR (KBr): m = 1764 (C=O
ester), 1664 (C=O amide), 1619 (C=N), 1212, 1051 (C–
O–C) cm-1
.
4-Acetoxy-2-[4-acetyl-5-(3-acetoxy-4-methoxyphenyl)-4,5-di-
hydro-1,3,4-oxadiazol-2-yl]phenyl acetate (3c,C23H22N2O9)
Crystallized from methanol. Yield 83%; m.p.:
135–136 °C; 1H NMR (300 MHz): d = 2.23 (s, 3H,
COCH3), 2.26, 2.27 (2 s, 9H, 3OCOCH3), 3.79 (s, 3H,
OCH3), 7.02 (dd, 1H, J = 8.1, 1.8 Hz), 7.13 (s, 1H),
7.16 (d, 1H, J = 8.1 Hz), 7.21 (d, 1H, J = 1.5 Hz), 7.35
(d, 1H, J = 8.7 Hz), 7.41 (dd, 1H, J = 8.7, 2.7 Hz), 7.60
(d, 1H, J = 2.7 Hz) ppm; 13C NMR (100 MHz):
d = 20.8, 21.1, 21.2, 21.8, 56.3, 91.4, 111.6, 118.8,
119.1, 122.8, 123.9, 125.7, 127.0, 135.7, 140.9, 146.4,
148.5, 151.5, 151.6, 167.3, 168.9, 169.5, 169.6 ppm; IR
ꢀ
151.7, 153.6, 167.3, 169.5, 169.6 ppm; IR (KBr): m = 1770
(C=O ester), 1664 (C=O amide), 1625 (C=N), 1209, 1053
(C–O–C) cm-1
.
4-Acetoxy-2-[4-acetyl-5-(2-acetoxy-1-naphthalenyl)-4,5-dihy-
dro-1,3,4-oxadiazol-2-yl]phenyl acetate (3g, C26H22N2O8)
Crystallized from ethanol. Yield 82%; m.p.: 247–248 °C
(decomp.); 1H NMR (300 MHz): d = 2.16 (s, 3H,
COCH3), 2.19, 2.22, 2.32 (3 s, each 3H, 3OCOCH3),
3.79 (s, 3H, OCH3), 7.35 (d, 1H, J = 8.7 Hz), 7.41 (s, 1H),
7.42 (d, 1H, J = 2.1 Hz), 7.55–7.68 (m, 3H), 8.02–8.05
(m, 2H), 8.09 (d, 1H, J = 9 Hz), 8.30–8.40 (m, 1H) ppm;
13C NMR (100 MHz): d = 21.0, 21.1, 21.2, 21.5, 86.4,
ꢀ
(KBr): m = 1763 (C=O ester), 1670 (C=O amide), 1625
(C=N), 1208, 1041 (C–O–C) cm-1
.
123