Olcay Bekircan

Synthesis of new bis-1,2,4-triazole derivatives.

A series of new 1,2/1,3-bis[o-(N-methylidenamino-3-aryl-5-phenyl-4H-1,2,4-triazole-4-yl)phenoxy]ethane/propane derivatives 4 were prepared in good yields by treatment of 4-amino-3-aryl-5-phenyl-4H-1,2,4-triazoles 2 with certain bis-aldehydes 1.Compounds 4 were reduced with NaBH(4) to afford the corresponding 1,2/1,3-bis[o-(N-methylamino-3-aryl-5-phenyl-4H-1,2,4-triazole-4-yl)phenoxy]ethane/propane derivatives 5. All new compounds were characterized by IR, (1)H-NMR, (13)C-NMR and mass spectral data.

Carrier element-free coprecipitation (CEFC) method for the separation, preconcentration and speciation of chromium using an isatin derivative

A new, simple, rapid and sensitive separation, preconcentration and speciation procedure for chromium in environmental liquid and solid samples has been established. The present speciation procedure for Cr(III) and Cr(VI) is based on combination of carrier element-free coprecipitation (CEFC) and flame atomic absorption spectrometric (FAAS) determinations. In this method a newly synthesized organic coprecipitant, 5-chloro-3-[4-(trifluoromethoxy) phenylimino]indolin-2-one (CFMEPI), was used without adding any carrier element for coprecipitation of chromium(III). After reduction of chromium(VI) by concentrated H(2)SO(4) and ethanol, the procedure was applied for the determination of total chromium. Chromium(VI) was calculated as the difference between the amount of total chromium and chromium(III). The optimum conditions for coprecipitation and speciation processes were investigated on several commonly tested experimental parameters, such as pH of the solution, amount of coprecipitant, sample volume, etc. No considerable interference was observed from the other investigated anions and cations, which may be found in natural water samples. The preconcentration factor was found to be 40. The detection limit for chromium(III) corresponding to three times the standard deviation of the blank (N=10) was found 0.7 microg L(-1). The present procedure was successfully applied for speciation of chromium in several liquid and solid environmental samples. In order to support the accuracy of the method, the certified reference materials (CRM-TMDW-500 Drinking Water and CRM-SA-C Sandy Soil C) were analyzed, and standard APDC-MIBK liquid-liquid extraction method was performed. The results obtained were in good agreement with the certified values.

Synthesis of Schiff and Mannich Bases of Isatin Derivatives with 4-Amino-4,5-Dihydro-1H-1,2,4-Triazole-5-Ones

Ethyl imidate hydrochlorides 1 were prepared by passing HCl gas through solutions of substituted benzyl cyanides and absolute ethanol. Ethoxycarbonylhydrazones 2 were synthesized from the reaction of compounds 1 with ethyl carbazate. Treatment of 2 with hydrazine hydrate leads to the formation of substituted 4-amino-4,5-dihydro-1H-1,2,4-triazole-5-ones 3. Isatin and 5-chloroisatin were added to 3 to form Schiff bases 4 and N-Mannich bases 5 of these compounds were synthesized by reacting with formaldehyde and piperidine. Their chemical structures were confirmed by means of IR, 1H- and 13C-NMR data and by elemental analysis.

Microwave-assisted synthesis of new benzimidazole derivatives with lipase inhibition activity

Abstract A practical protocol has been used for the synthesis of benzimidazoles. The reaction of iminoester hydrochlorides of phenylacetic with 4,5-dichloro-1,2-phenylenediamine under microwave irradiation leads to the benzimidazole derivatives with good yields and in short reaction times. After the synthesis of benzimidazoles, we synthesized ester and hydrazide derivatives under microwave irradiation with good yields. All compounds were evaluated with regard to pancreatic lipase activity and 3b, 3c, 5a and 6a showed lipase inhibition at various concentrations.

Synthesis of Some New 1,2,4‐Triazole Derivatives Starting from 3‐(4‐Chlorophenyl)‐5‐(4‐methoxybenzyl)‐4H‐1,2,4‐triazol with Anti‐Lipase and Anti‐Urease Activities

In the present study, starting compound 4 was prepared by deamination of compound 2 in the presence of hypophosphorous acid and sodium nitrite. Treatment of compound 4 with ethyl bromoacetate produced ethyl[3‐(4‐chlorophenyl)‐5‐(4‐methoxybenzyl)‐4H‐1,2,4‐triazol‐4‐yl]acetate (5), which was converted to the hydrazide derivative (6) by treatment with hydrazine hydrate. The reaction of compound 6 with aromatic aldehydes resulted in the formation of arylidene hydrazides (7). Treatment of 6 with CS2 in the presence of potassium hydroxide (KOH), followed by cyclization with hydrazine hydrate, afforded 4‐amino‐5‐{[3‐(4‐chlorophenyl)‐5‐(4‐methoxybenzyl)‐4H‐1,2,4‐triazol‐4‐yl]methyl}‐2,4‐dihydro‐3H‐1,2,4‐triazole‐3‐thione (9). The condensation of 9 with appropriate aldehydes gave Schiff bases (10), which were converted into Mannich bases (11) in the presence of formaldehyde. All the synthesized compounds were screened for their anti‐lipase and anti‐urease activities. Compounds 7b, 7d, 11b, 11c, and 11d showed moderate‐to‐good lipase inhibitory effects compared to orlistat. Compounds 7b and 7d exhibited better anti‐lipase activity. Furthermore, among the compounds tested, 11a and 11d were found to show high inhibitory effect against urease with IC50 values of 12.39 ± 0.35 and 16.12 ± 1.06 µg/mL, respectively. Compound 11c showed moderate inhibitory activity. The Mannich base containing compound 11 may be a source of good leads for the synthesis of lipase and urease dual inhibitors.

Synthesis and Antioxidant Properties of Some New 3-(4-Chlorophenyl)-5- (pyridin-4-yl)-4H-1,2,4-triazole Derivatives

A series of new 3-(4-chlorophenyl)-5-(pyridin-4-yl)-4-(arylmethyleneamino)-4H-1,2,4-triazole derivatives 3 were prepared in good yields by treatment of 4-amino-3-(4-chlorophenyl)-5-(pyridine- 4-yl)-4H-1,2,4-triazole (2) with selected aldehydes. Compounds 3 were reduced with NaBH4 to afford the corresponding 3-(4-chlorophenyl)-5-(pyridin-4-yl)-4-(arylmethylamino)-4H-1,2,4-triazole derivatives 4. Eighteen new compounds were synthesized and characterized by elemental analyses, IR, 1H NMR and 13C NMR spectral data. The compounds were screened for their antioxidant and antiradical activities.

Synthesis and antioxidant activities of some new triheterocyclic compounds containing benzimidazole, thiophene, and 1,2,4-triazole rings

Abstract Various triheterocyclic compounds containing benzimidazole, thiophene, and 1,2,4-triazole rings (3–6) were synthesized and screened for their antioxidant activities. The structures of the synthesized compounds (2–6) were judged by 1H NMR, 13C NMR, elemental analysis, and LC-MS spectral data. Antioxidant activities of the synthesized compounds (2–6) were determined with CUPric Reducing Antioxidant Capacity (CUPRAC), ABTS (2,2-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)/persulfate, and DPPH (1,1-diphenyl-2-picrylhydrazyl) assays. Most of the compounds showed a significant antioxidant activity and especially, compound 5c showed very good SC50 value for DPPH method and compound 5h exhibited very high scavenging activity to ABTS method.

Synthesis of some novel heterocylic compounds derived from 2-[3-(4-chlorophenyl)-5-(4-methoxybenzyl)-4H-1,2,4-triazol-4-yl]acetohydrazide and investigation of their lipase and α-glucosidase inhibition

Abstract In the present study, 2-[3-(4-chlorophenyl)-5-(4-methoxybenzyl)-4H-1,2,4-triazol-4-yl]acetohydrazide (1) was used as starting compound for the synthesis of 2-{[3-(4-chlorophenyl)-5-(4-methoxybenzyl)-4H-1,2,4-triazol-4-yl]acetyl}-4-thiosemicarbazides (2a–c) and 5-{[3-(4-chlorophenyl)-5-(4-methoxybenzyl)-4H-1,2,4-triazol-4-yl]methyl}-1,3,4-oxadiazole-2-thione (5). The cyclization of compounds 2a–c in the presence of NaOH resulted in the formation of 5-{[3-(4-chlorophenyl)-5-(4-methoxybenzyl)-4H-1,2,4-triazol-4-yl]methyl}-4-alkyl/aryl-2,4-dihydro-3H-1,2,4-triazole-3-thiones (3a–c). Aminomethylation of compounds 3a–c and 5 with formaldehyde and N-methyl/phenylpiperazine furnished Mannich bases (4a–f and 6a–b). The newly synthesized compounds were well-characterized by IR, 1H NMR, 13C NMR, elemental analysis and mass spectral studies. They were also screened for their lipase and α-glucosidase inhibition. Among the tested compound 2c (IC50 = 2.50 ± 0.50 µM) showed the best anti-lipase activity and compounds 2c (IC50 = 3.41 ± 0.16 µM) and 6a (IC50 = 4.36 ± 0.10 µM) showed the best anti-α-glucosidase activity.

Synthesis and Pharmacological Activities of Some New 2-[1-Heptyl-3-(4- methoxybenzyl)-5-oxo-1,5-dihydro-4H-1,2,4-triazol-4-yl]acetohydrazide Derivatives

Abstract In the present investigation, the key intermediate acetohydrazide derivative 5 was synthesized starting from 3-(4-methoxybenzyl)-4-amino-4,5-dihydro-1,2,4-triazol-5-one (1) by a four-step reaction. Thiosemicarbazides 6a-f and arylidenehydrazide derivatives 8a-d were obtained from compound 5. The cyclization of compounds 6a-f in the presence of NaOH resulted in the formation of compounds 7a-f. The compounds were characterized by IR, 1H NMR, 13C NMR spectroscopy, elemental analysis and mass spectral studies. The compounds were tested for their anti-lipase, anti-α-glucosidase and anti-mycobacterial activities. Compounds 6b and 8c exhibited excellent anti-lipase activity, and compound 8d showed excellent anti-a-glucosidase activity. Compounds 3 and 4 exhibited good antituberculosis activity

A Novel Iron(III)-Selective Membrane Potentiometric Sensor Based on 5-Chloro-3-(4-(trifluoromethoxy) phenylimino) Indolin-2-one

A novel polyvinyl chloride (PVC) membrane sensor that is highly selective to Fe 3+ ions was prepared by using 5-chloro-3-(4-(trifluoromethoxy)phenylimino)indolin-2-one (CFMEPI) ionophore. The sensor exhibits a Nernstian response for Fe 3+ ions over a wide concentration range (1.0 ×10 -2 −1.0×10 -6 M) with a slope of 46.7±0.5 mV per decade. The sensor has a response time of 20s and can be used for at least 3 months without any measurable divergence in potential. It was concluded that the sensor response was pH independent in the range of 4.0-8.61. The sensor has some advantages such as short analysis time, particularly high se- lectivity towards iron (III). The sensor was used successfully for direct determination of Fe 3+ in several synthetic and real samples with satisfactory results.