الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 388 |  |  |
| | | from | 388 | | |
Abstract
This thesis describes the synthesis and characterization of some new nitrogen, oxygen or sulfur containing heterocyclic compounds to evaluate their biological activities as antimicrobial and antioxidant agents as well as LDHA and PDK-1 inhibitors and anti-colorectal agents against LoVo and HCT-116 cells. The target heterocyclic compounds were prepared using different approaches as follows:
First, certain new 4,5,6,7-tetrahydrobenzo[b]thiophene derivatives were synthesized through:
• The Schiff base 71b prepared by condensation of 5e with 4-hydroxy-3-methoxybenzaldehyde in ethanol and acetic acid (Scheme A).
Scheme A. Reagents and conditions: (i) EtOH, AcOH, reflux 12 h.
• Compound 71b was used as coating cap to prepare aldimine-Fe3O4 nanoparticles 71b’ and aldimine-Fe3O4/ SiO2nanoparticles 71b’’ (Fig. I).
.
Fig. I. Preparation of Nanoparticles
• Furthermore, Schiff base-like formamidine derivative 73 was obtained by reaction of 2-amino-4,5,6,7,tretahydrobenzo[b]thiophene 5g with DMF-DMA in dry xylene. Whereas, pyrroldinedione derivative 74 was obtained by treating 5g with succinic anhydride in the presence of sodium acetate at elevated temperature as shown in Scheme B.
Scheme B. Reagents and conditions: (i) Dry xylene, reflux 10 h; (ii) NaOAc, oil bath at 200 °C 2 h; (iii) reflux 10h, evaporation under reduced pressure; (iv) Dry CHCl3, 0 °C, TEA, RCOCl, stirring 1 h, warm up to r.t., reflux 16 h; (v) CH3OH, reflux 10 h.
• In addition, reactions of 5g and /or 5h with ethyl chloroformate and different acid chlorides produced the corresponding carbamates 75a,b, and amides 76a-e, respectively. Afterward, the reaction of chloroacetamides with the appropriate secondary amines produced the new acetamides conjugated with secondary amines 77a-c. (Scheme B).
• Heating 5e,g,h with formamide in acetic acid afforded thienopyrimidines 80a-c, which exist in tautomerism with structures 80’a-c. Thus, reaction of amino thienopyrimidine derivative 80’a with some aromatic aldehydes produced the corresponding Schiff bases 81a-c (Scheme C).
Scheme C. Reagents and conditions: (i) reflux 10 h; (ii) EtOH, AcOH, reflux 12 h.
Second, benzo[d]thiazole derivatives were synthesized as follows:
• Compounds 97, 98 and 101 were synthesized by reacting chloroacetamide 96 with ethyl thiogylcolate or 3,4,5-trimethoxyaniline and potassium thiocyante, respectively as depicted in Scheme D.
Scheme D. Reagents and conditions (i) Dry acetone, K2CO3, reflux 16 h; (ii) CH3OH, reflux 10 h; (iii) EtOH, reflux 16 h.
Finally, quinazolinone derivatives synthesized as follow:
• Condensation of 3-aminoquinazolinones 40i,l with excess of thio- phene-2-carbonyl chloride resulted in the formation of bis-carboxamides 111a,b , respectively as shown in Scheme E.
Scheme E. Reagents and conditions: (i) Dry CHCl3, 0 °C, TEA, stirring 1 h, warm up to r.t., reflux 16 h.
• Nucleophilic displacement of the chlorine atom in chloroacetamide 60b was carried out using excess amount of certain amines including, 3,4,5-
trimethoxyaniline, morpholine, and piperidine to give new acetamides 113a-c.
Scheme F. Reagents and conditions: (i) CH3OH, reflux 10 h; (ii) Dry acetone, K2CO3, reflux 16 h; (iii) EtOH, reflux 16 h.
• In addition, the nucleophilic substitution reaction of 60b using ethyl 2-mercaptoacetate afforded ethyl 2-((2-((6,7-dimethoxy-2-methyl-4-oxoquin- azolin-3(4H)-yl)-amino)-2-oxo-ethyl)thio) acetate 115.
• Finally, the heterocyclization reaction of chloroacetamide 60b was achieved by reaction with KSCN and yielded 6,7-dimethoxy-2-methyl-3-(4-oxo-4,5-dihydro-thiazol-2-yl-amino)-3H-quinazo-lin-4-one 116 as depicted in Scheme F.
Biological Evaluation:
In this thesis, the newly synthesized 4,5,6,7-tetrahydrobenzo[b] thiophene, thiazole and benzothiazole derivatives were evaluated as antimicrobial, and antioxidant agents as well as LDHA and PDK-1 inhibitors and anti-colorectal agents against LoVo and HCT-116 cells.
• The enzymatic inhibitory potencies of the synthesized derivatives were determined against both PDK1 and LDHA and compared to the inhibition efficiencies of the reference inhibitors sodium dichloroacetate and sodium oxamate, respectively. The results of PDK1-assays revealed that compounds 71f and 71i were the most active derivatives with inhibition percentages of 94.65 and 91.00 relative to 100% by dichloroacetate inhibitor. Similarly, compounds 91a demonstrated the highest inhibitory percentage against LDHA with 92.60 as compared to 100% inhibition by sodium oxamate. In the view of these results, the IC50 (µg/mL) values of the most active derivatives 71f and 81c were determined to be 52.5 ± 2.12 and 57.15 ± 3.04 against PDK1 and LDHA, respectively.
• The antioxidant activities were assessed using DPPH radicals via determination of the percentages of scavenging activities of the studied compounds and butylated hydroxy toluene (BHT), which was used as the reference antioxidant drug. These experiments revealed that compounds (5g, 81c and 93b) exerted the strongest free-radical scavenging activities with efficiencies of (95.10 ± 1.27, 92.45 ± 1.34 and 92.25 ± 1.77 %). Whereas, the IC50 values were 110 ± 14.14, 62.50 ± 3.54 and 77.00 ± 9.90 µg/mL) in order as compared to 95.3 ± 0.42 %, and 54 ± 5.66 µg/mL by BHT.
• The antibacterial evaluations were performed by determination of IC50 (µg/mL) against Bacteroides fragilis (ATCC 25285), Enterococcus faecalis (ATCC 29122) and E. coli (ATCC 25922) using ampicillin as the reference antibiotic, which exhibited values of; 16.15 ± 1.20, 12.75 ± 1.06 and 20.25 ± 1.77 against the tested strain, respectively. The results indicated that the tested bacterial strains demonstrated varied sensitivities to the studied compounds, so compounds 91a, 71f and 81c displayed stronger potency than ampicillin with IC50 (µg/mL) value of 13.40 ± 1.27, 13.60 ± 0.85 and 16.10 ± 0.99 against B. fragilis. Likewise, the measured IC50 (µg/mL) values against E. faecalis showed that compounds (81c and 93b) exhibited the smallest values of 13.15 ± 1.20 and 14.25 ± 1.06 µg/mL, respectively. Last, compounds 91e and 95b were the most active against E. coli, wherein they displayed stronger potency than ampicillin with IC50 (µg/mL) value of 13.25 ± 1.06 and 18.40 ± 1.98.
• The antifungal activity results indicated that compounds 91e and 91a were the most effective ones with IC50 (µg/mL) values of 4.30 ± 0.56 and 4.90 ± 0.56 against A. niger. Also, compounds 93a and 91a displayed the smallest values of 4.85 ± 0.49 and 5.03 ± 0.42 µg/mL against P. digitatum strain corresponding to cycloheximide that exhibited values of 2.65 ± 0.21 and 3.15 ± 0.21.
• Last, the compounds, which demonstrated promising results in the previous biological screening, were further evaluated as cytotoxic agents against HCT-116 and LoVo cell lines of colorectal cancer. Thus, the percentages of cells viability of each compound were determined. The obtained results indicated that compounds (80b, 91e and 71b’) exhibited the lowest cell viability percentages of 11.75 ± 1.06, 13.25 ± 1.77 and 15.75 ± 1.06 against HCT-116 and 7.75 ± 1.06, 18.75 ± 1.77 and 11.75 ± 1.06 against LoVo cell line, respectively. Accordingly, the IC50 (µg/mL) values of these potential cytotoxic agents were determined and they were found to be 52.80 ± 3.96, 58.65 ± 2.33, and 57.15 ± 2.47 µg/mL against LoVo cell and 59.20 ± 1.41, 53.8 ± 1.83 and 60.35 ± 2.76 µg/mL against HCT-116 cell, respectively.