الفهرس 
Metal catalyzed reactionsOnly 14 pages are availabe for public view
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Abstract
studying their biological activities as anti-tumor agents
PART (Ι)
Synthesis of biologically active some new heterocyclic
compounds containing nitrogen
The key precursor N-(1H-benzo[d]imidazol-2-yl)carbonohydrazonoyl
dicyanide (2) was prepared by diazo-coupling of 2-aminobenzimidazole (1)
with malononitrile in pyridine at 0-5 oC. Compound 2 was subjected to
react with different secondary amines namely, piperidine, morpholine,
piperazine, diphenyl amine, N-methylglucamine and diethanolamine in
refluxing ethanol to afford the corresponding 1:1 acyclic enaminonitrile
adducts 3-8, respectively
It has been found that, the behavior of nitrile derivative 2 towards
hydrazine hydrate led to the formation of the pyrazole ring. An equivalent
quantity of hydrazine hydrate and 2 were refluxed in ethanol to yield the
corresponding pyrazole compound 9 (Scheme 2).
In addition, it has been studied the utility of compound 2 as key
intermediate in the synthesis of pyridazine derivative of pharmacological
interest. Thus, compound 2 reacted with malononitrile in ethanolic solution
catalyzed with sodium ethoxide to give pyridazine derivative 11 via
structure 10 (Scheme 2).
In addition, the reaction of enaminonitrile 7 with malononitrile in
ethanolic sodium ethoxide solution afforded the corresponding
pyrimidine derivative 14 (Scheme 3).
Heating 7 in boiling acetic anhydride and pyridine afforded
(2R,3R,4R,5S)-6-(((1E)-2-((1-acetyl-1H-benzo[d]imidazol-2-yl)diazenyl)-
1-(N-acetylacetamido)-2-cyanovinyl)(methyl)amino)hexane-1,2,3,4,5-
pentayl pentaacetate (15) (Scheme 4). When compound 15 was subjected
for prolonged heating in refluxing DMF containing a catalytic amount of
TEA undergoes cyclization to give the corresponding pyridine derivative
16.
Moreover, the reaction of enaminonitrile 7 with triethyl
orthoformate in the presence of acetic anhydride afforded the
corresponding ethoxymethyleneamino derivative 17. Also, It has been
found that heating a mixture of 7 with DMF/DMA in anhydrous xylene
yielded compound 18 (Scheme 4)
Acid anhydride derivatives namely; phthalic anhydride, quinolinic
anhydride, pyromeltic anhydride, 1,2,4-benzene tricarboxylic anhydride, 4-
nitrophthalic anhydride, 3-nitrophthalic anhydride and tetrabromophthalic
anhydride was refluxed with compound 7 in DMF solution catalyzed with drops of acetic acid afforded the phthalimide derivatives 19-25,
respectively (Schemes 5 and 6).
Fusion of enaminonitrile derivative 7 with 3,4,9,10-perylenetetracarboxylic
dianhydride in the presence of freshly fused sodium acetate afforded
compound 26 (Scheme 7).
PHARMACOLOGICAL EVALUATION
PART (II)
Antioxidant activity ABTS
It was found that compounds 9 and 11 exhibited less than 50%
inhibition of the ABTS radical cation. The latter compounds have no
glucaminoid moiety and this is responsible for the low activity.
The other rest of compounds which having glucaminoid moiety
showed good to moderate inhibition of the ABTS radical cation. However,
compound 21, characterized by containing two glucaminoid moieties and
showed that it is the most active compound (79.79%) indicating that both
moieties proved to be effective.
Compound 16 showed that conversion of cyano group in
compound 15 to amino group enhanced greatly the antioxidant activity
indicating also that such group might have a role in trapping the ABTS free
radica
Antitumor testing
Cytotoxicity was expressed as the concentration that caused 50% loss of
the cell momolayer (IC50). The assay was used to examine the newly
synthesized compounds.
The synthesized compounds 4, 7, 8, 9, 11, 14-18, 19-26 were subjected to
antitumor testing by measuring their effect on the percentage viability of
four different cell lines: human heptacellular liver carcinoma cell line
(HepG2), human lung fibroblast cell line (WI-38), kidney epithelial cells
of the African green monkey (VERO), and human breast adenocarcinoma
cell line (MCF-7).
Interestingly, the results showed that compound 21 which exhibited
significantly higher ABTS scavenging, showed strong antitumor activity
than other derivatives.
In addition, it was found that compounds 20, 21, 23, 24 and 25 are very
strong while 8, 17, 18, and 19 are strong against WI-38 cell line.
Moreover, it was found also that compounds 20 and 21 are very strong
while 17, 19, 22, 23, 24 and 25 are strong against VERO cell lines. On
the other hand, compounds 14, 15, 16 and 21 are very strong while 4, 9,
11, 17, 18, 19, 20, 22, 23, 24 and 26 are strong against MCF-7 cell line
from the structure activity relationship (SAR’s) we can reach to the
following conclusion:
1- Compounds containing pyrazole, pyridine and/or pyrimidine
moieties which characterized by basic properties showed broad
spectrum of cytotoxicity against the four cell lines.
2- Compounds 21 showed high cytotoxic activity against all cell lines,
this may be attributed to glucaminoid moiety.
3- Introducing carbonyl group (electron withdrawing group) increased
the cytotoxicity activity markedly.
4- The presence or absence of glucaminoid attached to pyrazole ring
in compound 20 and compound 9 did not show any effect by
increasing or decreasing the cytotoxicity activity (Table 3).
Structure-activity relationship:
It is known that, DNA contains nucleotide moieties in its structure as
chemical building blocks. There are different types of nitrogen bases in
nucleotide structure: cytosine (C), guanine (G), thymine (T), adenine (A).
Usually, adenine and cytosine are linked together via hydrogen bond.
There are two factors18, 19 effect the cytotoxic activity toward the tumor
cell lines: (i) the presence of intramolecular hydrogen bond with DNA
bases (ii) the electrostatic attraction between the tested compounds and
cell wall. The structure activity relationship of the cytotoxicity of tested
compounds can be reported as follow:
1- Compounds 9 and 11 all of them displayed strong activity may be
due to the intramolecular hydrogen bonding of NH and NH2 groups
with one of the nucleobases of DNA and cases its damage.
2- Also, the presence of ester groups in compounds 15-17 and two
amidic carbonyl groups in compounds 19-26 act as strong electron
withdrawing groups, which lead to electrostatic attraction with DNA
nucleobases.
3- The presence of NH group in all tested compounds can form
intramolecular hydrogen bond with DNA nucleobases and causes its
damage.
4- The presence of pyrazole ring compound 9 showed cytotoxic
activity ranged from very strong to strong activity due to the
formation of hydrogen bond between NH of pyrazole with DNA
nucleobases, and causes its damage.