Synthesis of novel 1,3,4-oxadiazole derivatives and their nucleoside analogs with antioxidant and antitumor activities

Article abstract of DOI:10.1007/s10593-011-0847-4

A series of new (1,3,4-oxadiazol-2-yl)-1H-benzo[h]quinolin-4-one derivatives were synthesized, including glucose and xylose hydrazones that were obtained by the reaction of hydrazides with monosaccharides. Cyclization of the sugar hydrazones with acetic anhydride afforded substituted oxadiazoline derivatives. The newly synthesized compounds were evaluated for their antioxidant properties and cytotoxicity, and showed moderate to high activities.

Full text of DOI:10.1007/s10593-011-0847-4

Chemistry of Heterocyclic Compounds, Vol. 47, No. 7, October 2011 (Russian original Vol. 47, No. 7, July, 2011)
SYNTHESIS OF NOVEL 1,3,4-OXADIAZOLE DERIVATIVES
AND THEIR NUCLEOSIDE ANALOGS WITH ANTIOXIDANT
AND ANTITUMOR ACTIVITIES
1
2
3
A. A. Fadda , A. A.-H. Abdel-Rahman *, W. A. El-Sayed ,
1
4
T. A. Zidan , and F. A. Badria
A series of new (1,3,4-oxadiazol-2-yl)-1H-benzo[h]quinolin-4-one derivatives were synthesized, includ-
ing glucose and xylose hydrazones that were obtained by the reaction of hydrazides with monosaccha-
rides. Cyclization of the sugar hydrazones with acetic anhydride afforded substituted oxadiazoline de-
rivatives. The newly synthesized compounds were evaluated for their antioxidant properties and
cytotoxicity, and showed moderate to high activities.
Keywords: acyclic nucleosides, 1,3,4-oxadiazoles, sugar hydrazones, antioxidant activity, cytotoxicity.
A significant part of drug discovery efforts in the past few years has been focused on prevention or
treatment of cancer. This is not surprising because in most developed countries, and to an increasing extent,
cancer is among the three most common causes of death. Among the five-membered nitrogen heterocycles,
1
,3,4-oxadiazoles are associated with a broad spectrum of biological activities. The 1,3,4-oxadiazole ring has
been found in the structures of fungicidal, bactericidal, analgesic, antipyretic, antiphlogistic, anticompulsive,
anti-inflammatory, paralytic, hypnotic, and sedative agents [1–3]. Several 1,3,4-oxadiazole derivatives have
been shown to possess insecticidal, hypoglycemic, hypotensive, antiviral [4], as well as antitumor activities [5].
Certain 1,3,4-oxadiazoline-2(3H)-thiones are known to possess antibacterial, antifungal, antimicrobial, and
antiviral activities [4], as well as tyrosinase-inhibiting effect [6]. Nucleosides and their analogs possess a wide
range of medicinal properties, including antibiotic, antiviral, and antitumor activity [7–16]. Consequently, and
considering the possible enhancement of biological activity resulting from the attachment of carbohydrate
moieties to 1,3,4-oxadiazole heterocycles, our attention was turned to the synthesis of new 1,3,4-oxadiazole
derivatives and their nucleoside analogs [17, 18].
_
*
______
To whom correspondence should be addressed, e-mail: adelnassar63@hotmail.com.
1
Department of Chemistry, Faculty of Science, Mansoura University, Mansoura, Egypt.
Department of Chemistry, Faculty of Science, Menoufia University, Shebin El-Koam, Egypt.
Department of Photochemistry, National Research Center, El-Dokki, Cairo, Egypt; e-mail: wael-
2
3
shendy@gmail.com.
4
Department of Drugs, Faculty of Pharmacology, Mansoura University, Mansoura, Egypt.
_
_________________________________________________________________________________________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 1045–1054, July, 2011. Original
article submitted October 14, 2010. In revised form June 20, 2011.
56
0009-3122/11/4707-0856©2011 Springer Science+Business Media, Inc.
8

The starting 1-aminonaphthalene (1) was refluxed with diethyl ethoxymethylenemalonate in ethanol to
give 2-[(naphthalen-1-ylamino)methylidene]malonic acid diethyl ester (2) in high yield. Compound 2 underwent
intramolecular cyclization in boiling diphenyl ether to give 4-oxo-1,4-dihydrobenzo-[h]quinoline-3-carboxylic
acid ethyl ester (3). Treatment of ester 3 with hydrazine hydrate gave the corresponding acid hydrazide 4. Its
1
structure was proved by means of IR, H NMR, and mass spectra, which all agreed with the assigned structure.
Reaction of compound 4 with carbon disulfide in the presence of anhydrous potassium hydroxide gave
oxadiazole derivative 5 (Scheme 1).
Scheme 1
CO Et
2
NH2
HN
CO Et
2
EtO–CH=C(CO Et)
Diphenyl ether
reflux
2
2
EtOH / reflux
1
2
COOEt
CONHNH2
HN
HN
.
N H H O
CS , KOH
2
4
2
2
O
O
EtOH, reflux
EtOH, reflux
3
4
H
N
N
O
N
N
O
S
SH
O
HN
HN
O
5
When compound 5 was deprotonated with sodium hydride in DMF it reacted with 2-chloroethyl methyl
ether at room temperature to afford 3-[5-(2-methoxyethylsulfanyl)-1,3,4-oxadiazol-2-yl]benzo[h]quinolin-
4
(1H)-one (6). The reaction of compound 5 with 2-chloroethoxyethanol in refluxing ethanolic sodium hydroxide
solution afforded 3-{5-[2-(2-hydroxyethoxy)ethylsulfanyl]-1,3,4-oxadiazol-2-yl}benzo[h]quinolin-4(1H)-one
7) in 94% yield. Compound 7 was acetylated with acetic anhydride in the presence of pyridine to give
(
compound 8. Compound 5 also reacted with 2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl bromide (9) in DMF in
the presence of TEA at room temperature. The reaction of the resulting β-thioglycoside 10 with methanolic
ammonia solution at room temperature afforded the corresponding deacetylated compound 11 (Scheme 2).
The reaction of oxadiazole derivative 5 with ethyl chloroacetate in DMF in the presence of anhydrous
1
K CO at room temperature afforded the corresponding thioacetate 12 (Scheme 3). The H NMR spectrum of
2
3
2
ester 12 showed the signal of SCH protons at 4.31 ppm. The reaction of the ester 12 with hydrazine hydrate in
ethanol at reflux temperature gave the corresponding hydrazide 13. The hydrazide 13 reacted with monosaccha-
rides galactose and xylose to give sugar hydrazones 14a,b. The IR spectra for hydrazones 14a,b showed
–
1
characteristic absorption bands at 3410–3415 cm corresponding to the free hydroxyl groups of sugar. The
sugar hydrazones 14a,b reacted with acetic anhydride in pyridine at room temperature to afford the correspond-
ing acetate derivatives 15a,b. The IR spectra of compounds 15a,b showed characteristic absorption bands at
–
1
1
737–1743 cm corresponding to the acetyl carbonyl groups, indicating the presence of O-acetyl group.
8
57

Scheme 2
5
Cl(CH ) O(CH ) OH, NaOH,
9, TEA,
Cl(CH ) OMe, NaH,
2 2
2 2
2
2
EtOH, reflux
DMF, rt
DMF, rt
HO
OMe
O
N
S
N
S
N
N
N
N
O
O
S
HN
HN
HN
O
O
O
OAc
O
O
AcO
6
7
OAcOAc
10
Ac O,
2
pyridine, rt
NH , MeOH,
3
rt
OAc
AcO
O
O
AcO
9
=
N
N
S
AcO
OAc
Br
N N
O
O
S
HN
HN
O
O
OH
O
HO
8
11
OH OH
1
The H NMR spectrum of compound 15a showed the signals of acetyl groups at 1.95–2.16 ppm. Sugar
hydrazones 14a,b were cyclized with acetic anhydride at reflux temperature to give 1,3,4-oxadiazoline
derivatives 16a,b (Scheme 3).
The synthesized compounds were tested for their antioxidant activity measured as the ability of the
newly synthesized compounds to react with the preformed radical cation of 2,2'-azino-bis(3-ethylbenzo-
thiazoline-6-sulfonic acid) (ABTS) [19]. L-Ascorbic acid was used as a control. The results of our preliminary
screening indicated that compounds 4, 12, and 13 showed the highest activity (inhibition of the radical cation)
among this series of tested compounds with an effective concentration of 0.2 µM, followed by compounds 5 and
1
1
6b. Compounds 10 and 11 showed moderate activity, while the other tested compounds 2, 3, 6–8, 15a,b, and
6a exhibited less activity (Table 1).
TABLE 1. Antioxidant Activity of Tested Compounds by ABTS Method
Compound
Inhibition, %
Compound
Inhibition, %
Compound
Inhibition, %
2
3
4
5
0.00
6.99
8
6.49
55.89
52.49
79.04
15a
15b
16a
16b
18.56
22.95
7.19
10
11
12
72.05
68.26
68.26
8
58

By relating of the antioxidant activity to the compound structure, we conclude that the carbohydrazide
or thioacetohydrazide residue attached to the benzo[h]quinolin-4-one, as well as (1,3,4-oxadiazol-2-yl)-
1
H-benzo[h]quinolin-4-one derivatives increase the antioxidant activity.
Cytotoxicity was expressed as the concentration that caused approximately 50% loss of the cell
monolayer (IC ). The assay was used to examine the newly synthesized compounds. 5-Fluorouracil as a
5
0
standard anticancer drug was used for comparison [20–22]. The results of our preliminary screening indicated
that compound 5 showed a strong cytotoxicity. Compounds 4, 12, 13, and 16b showed moderate cytotoxicity,
while other compounds showed a weak to very weak cytotoxicity (Table 2).
Scheme 3
N
N
S
N
SCH CO Et
N
2
2
O
O
.
O
ClCH CO Et, K CO
N H H O
2
2
2
3
HN
2
4
2
HN
5
NH
EtOH, reflux
DMF, rt
O
H N
2
O
1
2
13
RCHO, AcOH,
EtOH, reflux
N
N
N
S
N
S
O
O
HN
O
Ac O, pyridine
2
HN
NH
CH
O
rt
O
O
N
R
NH
CH
N
1
5a,b
1
14a,b
R
Ac O, reflux
2
Ac
N
N
N
N
SCH2
1
R
HN
O
O
O
1
6a,b
H
HO
H
OH
H
H
AcO
H
OAc
H
H
OH
H
H
OAc
H
1
1
1
4a R =
b R = HO
15, 16 a R =
b R = AcO
OH
OH
OH
OAc
OAc
OAc
H
OH
OH
H
OAc
OAc
H
H
8
59

TABLE 2. Cytotoxicity of the Synthesized Compounds 2–8, 10–13,
1
5a,b, 16a,b on Different Cell Lines
IC50, μg/ml*
WI-38 VERO
Compound
HepG2
MCF-7
2
3
4
5
6
7
8
70.2
91.2
45.1
22.4
125.4
145.6
89.8
52.8
61.4
40.7
40.6
106.8
111.2
130.8
39.9
8.6
84.6
82.4
48.2
27.3
98.7
175.0
100.7
70.4
60.9
39.8
39.4
98.9
89.9
130.2
37.5
3.2
72.4
80.3
77.5
79.2
20.5
20.2
25.8
40.8
132.4
169.8
110.2
60.7
107.3
166.8
121.4
63.7
1
0
1
2
3
1
1
1
65.4
66.9
36.9
31.7
37.8
39.8
1
5a
5b
6a
6b
-Fluorouracil
109.9
100.7
150.8
40.5
170.9
109.9
140.8
42.6
1
1
1
5
6.5
2.3
_
*
______
IC50: 1–10 (very strong), 11–25 (strong), 26–50 (moderate), 51–100
(
weak), 100–200 (very weak), above 200 μg/ml (noncytotoxic).
By relating the antioxidant activity to the compound structure, we conclude that the carbohydrazide or
thioacetohydrazide residue attached to the benzo[h]quinolin-4-one, as well as (1,3,4-oxadiazol-2-yl)-
1
H-benzo[h]quinolin-4-one derivatives, increase the antioxidant activity.
Cytotoxicity was expressed as the concentration that caused approximately 50% loss of the cell
monolayer (IC ). The assay was used to examine the newly synthesized compounds. 5-Fluorouracil as a
5
0
standard anticancer drug was used for comparison [20–22]. The results of our preliminary screening indicated
that compound 5 showed a strong cytotoxicity. Compounds 4, 12, 13, and 16b showed moderate cytotoxicity,
while other compounds showed a weak to very weak cytotoxicity (Table 2).
In conclusion, new 1,3,4-oxadiazole acyclic nucleoside analogs were synthesized. Cyclization of the sugar
hydrazones with acetic anhydride afforded substituted oxadiazoline derivatives. The newly synthesized
compounds were evaluated for their antioxidant, cytotoxicity, and antitumor activities.
EXPERIMENTAL
The IR spectra were recorded on a Perkin-Elmer model 1720 FTIR spectrometer in KBr disc (com-
1
pounds 2, 3, 5–8, 10–14a,b, 15b, 16a,b) or thin film (compounds 4, 15a). The H NMR spectra were recorded
on a Varian Gemini 300 NMR spectrometer at 300 MHz in DMSO-d (internal standard TMS). EI mass spectra
6
were recorded on a Varian MAT 311A spectrometer. Elemental analyses were carried out at the Microanalytical
Center of Cairo University, Giza, Egypt. All melting points were determined with a Kofler block apparatus and
are uncorrected.The progress of the reactions was monitored by TLC using silica gel plates 60 F 245.
8
60

Diethyl 2-[(naphthalen-1-ylamino)methylidene]malonate (2) was synthesized by modifying a method
described in the literature [23]. Ethyl 4-oxo-1,4-dihydrobenzo[h]quinoline-3-carboxylate (3) was synthesized
following a published method [24].
4
-Oxo-1,4-dihydrobenzo[h]quinoline-3-carbohydrazide (4). To a solution of compound 3 (2.67 g,
.01 mol) in ethanol (50 ml), hydrazine hydrate (1.5 g, 0.03 mol) was added. The reaction mixture was refluxed
for 12 h and cooled to room temperature. The precipitate was filtered off, dried, and recrystallized from ethanol
0
–
1
to give the benzoquinoline derivative 4. Yield 2.12 g (84%); mp 310–312°C. IR spectrum, ν, cm : 3340 (NH ),
3
(
2
1
279 (NH), 3178 (NH), 1677 (CONH), 1654 (C=O). H NMR spectrum, δ, ppm: 4.65 (2H, s, NH ); 7.82–8.27
2
+
6H, m, H Ar); 8.72 (2H, s, NH, H-2); 10.85 (1H, s, NH). Mass spectrum, m/z (Irel, %): 253 [M] (37), 222 (91),
1
66 (37), 139 (100), 76 (19). Found, %: C 66.36; H 4.38; N 16.43. C H N O . Calculated, %: C 66.40; H 4.38;
14 11 3 2
N 16.59.
3
-(5-Sulfanyl-1,3,4-oxadiazol-2-yl)benzo[h]quinolin-4(1H)-one (5). To a solution of compound 4
2.53 g, 0.01 mol) in absolute ethanol (50 ml), a solution of potassium hydroxide (0.56 g, 0.01 mol) in water
2 ml) was added. Carbon disulfide (5 ml) was then added, and the reaction mixture was refluxed for 20 h. The
(
(
solvent was evaporated, and the residue was dissolved in water. The solution was filtered and acidified with
dilute HCl. The precipitate was filtered, washed with water, and recrystallized from ethanol. Yield 2.45 g (83%);
–
1
1
mp 330–332°C. IR spectrum, ν, cm : 3139 (NH), 1629 (C=O), 1376 (C=S). H NMR spectrum, δ, ppm:
7
2
.75-8.27 (6H, m, H Ar); 8.55 (1H, s, H-2); 8.84 (1H, s, NH); 13.39 (1H, s, NH). Mass spectrum, m/z (Irel, %):
+
95 [M] (2), 267 (65), 221 (100), 193 (25), 149 (43). Found, %: C 61.00; H 3.07; N 14.21. C H N O S.
1
5
9
3
2
Calculated, %: C 61.01; H 3.07; N 14.23.
3
-[5-(2-Methoxyethylsulfanyl)-1,3,4-oxadiazol-2-yl]benzo[h]quinolin-4(1H)-one (6). To a solution of
compound 5 (2.95 g, 0.01 mol) in DMF (15 ml), NaH (0.24 g, 0.01 mol) was added. The mixture was stirred at
room temperature for 2 h. Chloroethyl methyl ether (0.95 g, 0.01 mol) was then added. The reaction mixture was
stirred at room temperature for 30 h, and then poured into ice water. The product was extracted using ethyl
acetate. The solvent was then evaporated under reduced pressure to give compound 6. Yield 0.96 g (27%); mp
–
1
1
2
00–202°C. IR spectrum, ν, cm : 3191 (NH), 1633 (C=O). H NMR spectrum, δ, ppm (J, Hz): 3.47 (3H, s,
CH
3
); 3.51 (2H, t, J = 5.5, CH
2
); 3.72 (2H, t, J = 5.5, CH
2
); 7.79–8.23 (6H, m, H Ar); 8.57 (1H, s, H-2); 8.87
(
1H, s, NH). Found, %: C 61.09; H 4.14; N 11.74. C H N O S. Calculated, %: C 61.18; H 4.28; N 11.89.
18
15
3
3
3
-{5-[2-(2-Hydroxyethoxy)ethylsulfanyl]-1,3,4-oxadiazol-2-yl}benzo[h]quinolin-4(1H)-one (7). To a
solution of compound 5 (2.95 g, 0.01 mol) in absolute ethanol (15 ml), NaOH (0.4 g, 0.01 mol) was added, and
the mixture was stirred at room temperature for 1 h. 2-(2-Chloroethoxy)ethanol (1.24 g, 0.01 mol) was then
added, and the reaction mixture was refluxed for 30 h. The solvent was evaporated under reduced pressure. The
–
1
resulting solid product was recrystallized from ethanol. Yield 3.60 g (94%); mp 80–82°C. IR spectrum, ν, cm :
1
3
3
400 (OH, NH), 1631 (C=O), 1588 (C=N), 1484 (C–O–C). H NMR spectrum, δ, ppm: 3.64 (4H, m, 2CH );
2
.79 (4H, m, 2CH ); 4.70 (1H, s, OH); 7.61–8.26 (6H, m, H Ar); 8.72 (1H, s, H-2); 9.02 (1H, s, NH). Mass
spectrum, m/z (Irel, %): 383 [M] (7), 279 (12), 167 (39), 149 (100). Found, %: C 59.48; H 4.33; N 10.84.
2
+
C H N O S. Calculated, %: C 59.52; H 4.47; N 10.96.
1
9
17
3
4
2
-{2-[5-(4-Oxo-1,4-dihydrobenzo[h]quinolin-3-yl)-1,3,4-oxadiazol-2-ylsulfanyl]-ethoxy}ethyl Ace-
tate (8). To a solution of compound 7 (3.83 g, 0.01 mol) in pyridine (7 ml), acetic anhydride (1.02 g, 0.01 mol)
was added, and the reaction mixture was stirred at room temperature for 16 h. The resulting solution was poured
into crushed ice, and the product was filtered off, washed with water, and dried. Yield 2.30 g (54%);
–
1
mp 214–216°C. IR spectrum, ν, cm : 3184 (NH), 1735 (COCH ), 1629 (C=O), 1553 (C=N). Found, %:
3
C 59.14; H 4.39; N 9.71. C H N O S. Calculated, %: C 59.28; H 4.50; N 9.88.
2
1
19
3
5
3
-{5-[(2,3,4,6-Tetra-O-acetyl-β-D-glucopyranosyl)sulfanyl]-1,3,4-oxadiazol-2-yl}benzo[h]quinolin-
4
(1H)-one (10). To a solution of compound 5 (2.95 g, 0.01 mol) in DMF, compound 9 (4.11 g, 0.01 mol) and
TEA (0.5 ml) were added. The reaction mixture was stirred at room temperature for 30 h. The solution was
poured into crushed ice, and the product was filtered off, washed with water, and dried. Yield 3.94 g (63%);
–
1
1
mp 250–252°C. IR spectrum, ν, cm : 3226 (NH), 1751 (COCH ), 1635 (C=O), 1554 (C=N). H NMR
3
8
61

spectrum, δ, ppm (J, Hz): 1.90–2.06 (12H, m, 4COCH ); 4.07–4.19 (2H, m, H-6'); 5.04 (1H, m, H-5'); 5.07 (1H,
3
m, H-4'); 5.20 (1H, m, H-3'); 5.52 (1H, m, H-2'); 5.74 (1H, d, J = 9.8, H-1'); 7.69–8.22 (6H, m, H Ar); 8.50 (1H,
s, H-2); 8.76 (1H, s, NH). Found, %: C 55.54; H 4.35; N 6.60. C H N O S. Calculated, %: C 55.68; H 4.35;
29
27
3
11
N 6.72.
3
-{5-[β-D-Glucopyranosyl)sulfanyl]-1,3,4-oxadiazol-2-yl}benzo[h]quinolin-4(1H)-one (11). A
solution of compound 10 (6.25 g, 0.01 mol) in methanolic ammonia solution (methanol–34% ammonia,
0:50 ml) was stirred at room temperature for 10 h. The solvent was then evaporated under reduced pressure,
3
–
1
and the product was obtained as a solid powder. Yield 4.21 g (92%); mp 224–226°C. IR spectrum, ν, cm : 3373
OH, NH), 1632 (C=O), 1559 (C=N). Found, %: C 55.03; H 4.19; N 9.09. C21 S. Calculated, %:
C 55.14; H 4.19; N 9.19.
(
19 3 7
H N O
Ethyl {[5-(4-Oxo-1,4-dihydrobenzo[h]quinolin-3-yl)-1,3,4-oxadiazol-2-yl]sulfanyl}acetate (12). To a
solution of compound 5 (2.95 g, 0.01 mol) in DMF (10 ml), anhydrous K CO (1.38 g, 0.01 mol) was added and
2
3
the mixture was stirred at room temperature for 2 h. Ethyl chloroacetate (1.23 g, 0.01 mol) was then added, and
the reaction mixture was stirred at room temperature for 3 h. The resulting mixture was poured into crushed ice,
and the formed precipitate was filtered off, dried, and recrystallized from ethanol. Yield 3.51 g (92%); mp
–
1
1
2
04-206°C. IR spectrum, ν, cm : 3313 (NH), 1739 (COOEt), 1630 (C=O), 1587 (C=N). H NMR spectrum, δ,
ppm (J, Hz): 1.24 (3H, t, J = 5.5, CH ); 4.20 (2H, q, J = 5.5, CH ); 4.31 (2H, s, SCH ); 7.79–8.28 (6H, m, H Ar);
3
2
2
8
.69 (1H, s, H-2); 8.87 (1H, s, NH). Found, %: C 59.73; H 3.84; N 11.02. C19
H 3.96; N 11.02.
-{[5-(4-Oxo-1,4-dihydrobenzo[h]quinolin-3-yl)-1,3,4-oxadiazol-2-yl]sulfanyl}acetohydrazide (13). To a
H
15
N
3
O
4
S. Calculated, %: C 59.83;
2
solution of compound 12 (3.81 g, 0.01 mol) in ethanol (50 ml), hydrazine hydrate (1.5 g, 0.03 mol) was added,
and the mixture was refluxed for 7 h. The reaction mixture was left to cool. The formed solid product was
–
1
filtered off, dried, and recrystallized from ethanol. Yield 2.28 g (62%); mp 280–282°C. IR spectrum, ν, cm :
+
3
417 (NH
2
), 3199 (NH), 1689 (CONH). Mass spectrum, m/z (Irel, %): 367 [M] (19). Found, %: C 55.44; H 3.43;
N 19.06. C H N O S. Calculated, %: C 55.58; H 3.57; N 19.06.
17
13
5
3
Synthesis of Oxadiazole Sugar Hydrazone Derivatives 14a,b (General Method). To a solution of
compound 13 (3.67 g, 0.01 mol) in absolute ethanol (30 ml), the solution of the respective monosaccharide
(
2
0.01 mol) in water (2 ml) and glacial acetic acid (0.5 ml) were added. The reaction mixture was refluxed for
5 h, concentrated, and left to cool. The formed precipitate was filtered, washed with ethanol, dried, and
crystallized from ethanol to give compounds 14a,b.
N'-(D-Galactopentitolylmethylidene)-2-{[5-(4-oxo-1,4-dihydrobenzo[h]quinolin-3-yl)-1,3,4-oxadia-
–
1
zol-2-yl]sulfanyl}acetohydrazide (14a). Yield 4.23 g (80%); mp 320–322 °C. IR spectrum, ν, cm : 3415 (OH),
386 (NH), 1680 (CONH), 1527 (N=C). Found, %: C 52.07; H 4.23; N 13.12. C23 S. Calculated, %:
C 52.17; H 4.38; N 13.23.
-{[5-(4-Oxo-1,4-dihydrobenzo[h]quinolin-3-yl)-1,3,4-oxadiazol-2-yl]sulfanyl}-N'-(D-xylotetritolyl-
3
23 5 8
H N O
2
–
1
methylidene)acetohydrazide (14b). Yield 4.39 g (88%); mp 340–342 °C. IR spectrum, ν, cm : 3410 (OH,
NH), 1633 (CONH). Found, %: C 52.80; H 4.24; N 14.02. C H N O S. Calculated, %: C 52.90; H 4.24;
22
21
5
7
N 14.02.
Synthesis of Acetylated Oxadiazole Sugar Hydrazone Derivatives 15a,b (General Method). To a
solution of compounds 14a,b (0.01 mol) in pyridine (7 ml), acetic anhydride (0.01 mol) was added, and the
reaction mixture was stirred at room temperature for 40 h. The resulting solution was poured into crushed ice,
and the product was extracted using chloroform. The chloroform extracts were collected and evaporated under
reduced pressure to give compounds 15a,b.
2
-{[5-(4-Oxo-1,4-dihydrobenzo[h]quinolin-3-yl)-1,3,4-oxadiazol-2-yl]sulfanyl}-N'-(2,3,4,5,6-penta-
O-acetyl-D-galactopentitolylmethylidene)acetohydrazide (15a). Yield 5.40 g (73%); mp 350–352°C. IR
–
1
1
spectrum, ν, cm : 3448 (NH), 1743 (COCH ). H NMR spectrum, δ, ppm: 1.95, 2.02, 2.10, 2.13, 2.16 (15H, 5s,
3
5
CH CO); 4.09 (2H, m, OCH ); 4.50 (1H, m, H-5'); 4.60 (2H, s, SCH ); 4.71 (1H, m, H-4'); 5.18 (1H, m, H-3');
3 2 2
8
62

5
.48 (1H, m, H-2'); 7.40–7.79 (7H, m, H Ar, H-1'); 7.94 (1H, s, H-2); 9.35 (2H, s, 2NH). Found, %: C 53.48;
H 4.50; N 9.40. C H N O S. Calculated, %: C 53.58; H 4.50; N 9.47.
33
33
5
13
2
-{[5-(4-Oxo-1,4-dihydrobenzo[h]quinolin-3-yl)-1,3,4-oxadiazol-2-yl]sulfanyl}-N'-(2,3,4,5-tetra-
O-acetyl-D-xylotetritolylmethylidene)acetohydrazide (15b). Yield 5.00 g (75%); mp 325–327°C. IR
–
1
spectrum, ν, cm : 3430 (NH), 1737 (COCH ), 1632 (CONH). Found, %: C 53.86; H 4.33; N 10.35.
3
C
30
H
29
N
5
O
11S. Calculated, %: C 53.97; H 4.38; N 10.49.
Synthesis of Oxadiazole–oxadiazoline Derivatives 16a,b (General Method). A solution of 14a,b
0.01 mol) in acetic anhydride (15 ml) was refluxed for 30 h. The resulting solution was poured into crushed ice,
and the product was extracted using chloroform to afford compounds 16a,b.
-[5-({[4-Acetyl-5-(1,2,3,4,5-penta-O-acetyl-D-galactopentitolyl)-4,5-dihydro-1,3,4-oxadiazol-2-yl]-
methyl}sulfanyl)-1,3,4-oxadiazol-2-yl]benzo[h]quinolin-4(1H)-one (16a). Yield 5.23 g (67%); mp 300-302°C.
(
3
–
1
1
IR spectrum, ν, cm : 3434 (NH), 1745 (COCH ), 1628 (C=O), 1505 (C=N). H NMR spectrum, δ, ppm (J, Hz):
3
1
.95, 1.96, 2.01, 2.10, 2.19, 2.39 (18H, 6s, 6CH CO); 3.87 (2H, s, SCH ); 3.98–4.05 (2H, m, OCH ); 4.96 (1H,
3 2 2
m, H-4'); 5.16 (1H, m, H-3'); 5.20 (1H, m, H-2'); 5.37 (1H, dd, J = 3.2, J = 6.2, H-1'); 5.95 (1H, d, J = 6.2,
oxadiazoline H-5); 7.04 (1H, s, H-2); 7.71–7.80 (6H, m, H Ar); 8.70 (1H, s, NH). Found, %: C 53.66; H 4.40;
N 8.91. C H N O S. Calculated, %: C 53.77; H 4.51; N 8.96.
3
5
35
5
14
3-[5-({[4-Acetyl-5-(1,2,3,4-tetra-O-acetyl-D-xylotetritolyl)-4,5-dihydro-1,3,4-oxadiazol-2-yl]methyl}-
sulfanyl)-1,3,4-oxadiazol-2-yl]benzo[h]quinolin-4(1H)-one (16b). Yield 3.83 g (54%); mp 323–325°C. IR
–
1
spectrum, ν, cm : 3430 (NH), 1739 (COCH ), 1503 (C=N). Found, %: C 54.09; H 4.40; N 9.77. C H N O S.
3
32 31
5
12
Calculated, %: C 54.16; H 4.40; N 9.87.
Antioxidant Screening Assay Method [19]. For each of the investigated compounds, 2 ml of ABTS
solution (60 mM) was added to MnO suspension (25 mg/ml), all prepared in phosphate buffer (pH 7, 0.1 M).
2
The mixture was shaken, centrifuged, and filtered, and the absorbance (Acontrol) of the resulting green-blue
solution (ABTS radical solution) was adjusted to ~0.5 at λ 734 nm. Then, 50 µl of (2 mM) solution of the test
compound in spectroscopic grade methanol/phosphate buffer (1:1) was added. The absorbance (A ) was
test
measured, and the reduction in color intensity was expressed as % inhibition, which was calculated for each
compound from the following equation:
Inhibition = (Acontrol – Atest/ Acontrol)×100%
Ascorbic acid was used as standard antioxidant (positive control). A blank sample was run without
ABTS and using methanol–phosphate buffer (1:1) instead of the sample. A negative control sample was run
with methanol–phosphate buffer (1:1) instead of the tested compound.
Cytotoxic Activity [20–22]. RPMI-1640 medium (Sigma Co., St. Louis, USA), Fetal bovine serum
(
GIBCO, UK) and the cell lines from ATCC were used.
The cytotoxic activity of the synthesized compounds was tested against human hepatocellular liver car-
cinoma cell line (HepG2), human lung fibroblast cell line (WI 38), human Caucasian breast adenocarcinoma cell
line (MCF-7), and normal adult African green monkey kidney cell line (VERO). The stock samples of the
compounds were diluted with RPMI-1640 medium to desired concentrations ranging from 10 to 1000 µg/ml.
The final concentration of DMSO in each sample did not exceed 1% v/v.
3
The cells were batch-cultured for 10 days, then seeded in 96-well plates of 10×10 cells/well in fresh
complete growth medium in 96-well microtiter plastic plates at 37°C for 24 h under 5% CO using a water-
2
jacketed carbon dioxide incubator (Shedon.TC2323.Cornelius, OR, USA). The medium (without serum) was
added, and cells were incubated either alone (negative control) or with different concentrations of the sample to
give final concentrations of 1000, 500, 200, 100, 50, 20, and 10 µg/ml. Cells were suspended in RPMI-1640
4
4
medium, 1% antibiotic-antimycotic mixture (10 µg/ml penicillin potassium, 10 µg/ml streptomycin sulfate and
2
9
5 µg/ml amphotericin B) and 1% L-glutamine in 96-well flat bottom microplates at 37°C under 5% CO
6 h of incubation, the medium was again aspirated; the trays were inverted onto a pad of paper towels, and the
2
. After
8
63

remaining cells rinsed carefully with medium and fixed with 3.7% (v/v) formaldehyde in saline for at least
0 min. The fixed cells were rinsed with water. The % viability of cells was examined visually as described
2
previously [25].
REFERENCES
1
.
A. A. El-Azzouny, Y. A. Maklad, H. Bartsch, W. A. Zaghary, W. M. Ibrahim, and M. S. Mohamed, Sci.
Pharm., 71, 331 (2003).
2
3
.
.
C. Loetchutinat, F. Chau, and S. Mankhetkorn, Chem. Pharm. Bull., 51, 728 (2003).
Z. Amtul, M. Rasheed, M. I. Choudhary, R. Supino, K. M. Khan, and Atta-ur-Rahman, Biochem.
Biophys. Res. Commun., 319, 1053 (2004).
4.
5.
6.
A. A. El-Emam, A. O. Al-Deeb, M. Al-Omar, and J. Lehmann, Bioorg. Med. Chem., 12, 5107 (2004).
H. Liszkiewicz, M. W. Kowalska, J. Wietrzyk, and A. Opolski, Ind. J. Chem., B42, 2846 (2003).
M. T. H. Khan, M. I. Choudhary, M. K. Khan, M. Rani, and Atta-ur-Rahman, Bioorg. Med. Chem., 13,
3
385 (2005).
7.
8.
9.
A. Larsson, S. Alenius, N.-G. Johnsson, and B. Öberg, Antiviral Res., 3, 77 (1983).
R. J. Remy and J. A. Secrist, Nucleosides, Nucleotides, Nucleic Acids, 4, 411 (1985).
C. K. Chu and S. J. Cutler, J. Heterocycl. Chem., 23, 289 (1986).
10.
11.
12.
13.
14.
15.
A. Holy, Nucleosides, Nucleotides Nucleic Acids, 6, 147 (1987).
E. S. H. El Ashry and Y. El Kilany, Adv. Heterocycl. Chem., 67, 391 (1996).
E. S. H. El Ashry and Y. El Kilany, Adv. Heterocycl. Chem., 68, 1 (1997).
E. S. H. El Ashry and Y. El Kilany, Adv. Heterocycl. Chem., 69, 129 (1997).
G. M. Makara and G. M. Keseru, J. Med. Chem., 40, 4154 (1997).
P. Franchetti, L. Cappellacci, G. Abu Sheikha, H. N. Jayaram, V. V. Gurudutt, T. Sint, B. P. Schneider,
W. D. Jones, B. M. Goldstein, G. Perra, A. De Montis, A. G. Loi, P. La Colla, and M. Grifantini,
J. Med. Chem., 40, 1731 (1997).
1
1
6.
7.
F. Hammerschmidt, B. Peric, and E. Öhler, Monatsh. Chem., 128, 183 (1997).
W. A. El-Sayed, F. A. El-Essawy, O. M. Ali, B. S. Nasr, M. M. Abdalla, and A. A.-H. Abdel-Rahman,
Monatsh. Chem., 141, 1021 (2010).
18.
19.
20.
21.
22.
23.
24.
25.
W. A. El-Sayed, N. M. Fathy, W. A. Gad, and E. S. H. El-Ashry, J. Carbohydr. Chem., 27, 357 (2008).
E. A. Lissi, B. Modak, R. Torres, J. Escobar, and A. Urzua, Free Radical Res., 30, 471 (1999).
C. K. Lee, H. Jiang, and A. M. J. Scofield, J. Carbohydr. Chem., 16, 49 (1997).
H. A. Abdel-Aziza, B. F. Abdel-Wahab, and F. A. Badria, Arch. Pharm., 343, 152 (2010).
B. Hegazi, H. A. Mohamed, K. M. Dawood, and F. A. Badria, Chem. Pharm. Bull., 58, 479 (2010).
A. Ilangovan and R. G. Kumar, Chem. Eur. J., 16, 2938 (2010).
R. E. Foster, R. D. Lipscomb, T. J. Thompson, and C. S. Hamilton, J. Am. Chem. Soc., 68, 1327 (1946).
T. Fouad, C. Nielsen, L. Brunn, and E. B. Pederson, Sc. J. Az. Med. Fac. (GIRLS), 19, 1173 (1998).
8
64