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    Microwave-assisted and conventional synthesis of novel antimicrobial 1,2,4-triazole derivatives containing nalidixic acid skeleton
    (Walter De Gruyter Gmbh, 2016) Ceylan, Şule; Bayrak, Hacer; Özdemir, Serap Başoğlu; Uygun, Yıldız; Mermer, Arif; Demirbaş, Neslihan; Ülker, Serdar
    Carbothioamides 4a,b, obtained from nalidixic acid, were converted to the corresponding 1,3-thiazolidine derivatives 5a,b by cyclocondensation with 2-bromo-1-(4-chlorophenyl)ethanone. Treatment of 4a,b with base afforded 1,2,4-triazoles 6a,b. The synthesis of 1,3-oxazolidine 7 was performed by the reaction of compound 4a with ethyl bromoacetate. Treatment of 4a with acid produced 1,3,4-thiadiazole 8. The reaction of compounds 6a and 6b with several heterocyclic amines in the presence of formaldehyde gave the corresponding Mannich bases 9–15 containing various pharmacophore groups. Conventional and microwave-assisted methods were used for the synthesis. The effect of an acid catalyst on Mannich reactions was investigated. The structures of the newly synthesized compounds were elucidated on the basis of 1H NMR, 13C NMR, FTIR, EIMS techniques, and elemental analysis. All compounds were screened for their antimicrobial activity.
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    Microwave-assisted synthesis of some hybrid molecules derived from morpholine and investigation of their antimicrobial activities
    (Wiley-VCH Verlag GmbH, 2017) Cebeci, Yıldız Uygun; Özdemir, Serap Başoğlu; Ceylan, Şule; Bayrak, Hacer; Demirbaş, Ahmet; Alpay Karaoğlu, Şengül; Demirbaş, Neslihan
    2H-1,2,4-triazol-3(4H)-one compound was obtained starting from 4-(2-fluoro-4-nitrophenyl)morpholine via several steps. Then, these compounds were converted to the corresponding fluoroquinolone hybrids via one pot three component Mannich reaction. Moreover, the synthesis of eleven compounds, which can be considered as conazole analogues, was performed starting from 1,2,4-triazole-3-one compounds via three steps by either conventional or microwave mediated conditions. The effect of different solvents and microwave power on microwave prompted reactions was examined as well.
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    Novel microwave assisted synthesis and antimicrobial activity of new quinolone-hybrids
    (Bentham Science Publ Ltd, 2016) Ceylan, Şule; Bayrak, Hacer; Özdemir, Serap Başoğlu; Uygun, Yıldız; Mermer, Arif; Demirbaş, Neslihan; Ülker, Serdar
    Background: Carbo(thio)amid derivatives 4a, 4b were obtained starting from nalidixic acid in three steps. The acidic treatment of compound 4a generated the corresponding 1,3,4-oxadiazole (5), while the compound 4a gave 1,2,4-triazole derivatives 8a, 8b in basic media. The condensation of 4a with ethyl bromoacetate and 4-chlorophenacyl bromide afforded 1,3-oxazolidine, 6 and 1,3-thiazolidine, 7 derivatives. The synthesis of Mannich bases of 9-15 and 17-19 were achieved from the reaction of 1,2,4-triazoles, 8a, 8b and 1,3,4-oxadiazole, 16, with several heterocyclic amines that has biological activity. Methods: In this article, a series of triazole or 1,3,4-oxadiazole rings containing some novel biologically active quinolone derivatives. Conventional and microwave assisted methods were used for all syntheses. Moreover, the effect of acid catalyst on Mannich reactions was investigated. The structures of newly synthesized compounds were elucidated on the basis of H-1 NMR, C-13 NMR, FT IR, EI MS techniques and elemental analysis. All these compounds were screened in vitro for their antimicrobial activity against various gram-positive and gram-negative bacterial and fungal strains. Results: This study reports the successful synthesis of some new hybrid compounds starting from nalidixic acid. Two methods containing conventional and microwave assistance with/without catalyst were used to obtain the target compounds. Microwave assistance supplied more efficient way leading the formation of target compounds. Moreover, the effect of acid catalyst on Mannich reactions was investigated. The antimicrobial activity screening studies were also performed in the study. Conclusion: The antimicrobial screening suggests that the compounds containing norfloxacin (9a,b and 17), ciprofloxacin (10a,b and 18) or 7-aminocephalosporanic (12) acid nucleus displayed excellent antimicrobial activity. Moreover, some of them (5-7, 8-13, 15-18) displayed inhibition properties on Escherichia coli (Ec) and Mycobacterium smegmatis (Ms) better from ampicillin or streptomycin with the mic value 0.24 mu g/mL.
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    Syntheses and biological activities of new hybrid molecules containing different heterocyclic moieties
    (Wiley-VCH Verlag GmbH, 2013) Ceylan, Şule; Bektaş, Hakan; Bayrak, Hacer; Demirbaş, Neslihan; Alpay Karaoğlu, Şengül; Ülker, Serdar
    4-Aryl-5-(pyridin-3-yl)-4H-1,2,4-triazole-3-(thi)oles 5-7, obtained starting from nicotinic acid hydrazide were converted to the corresponding Mannich bases 12-24 by the reaction with several heterocyclic amines in the presence of formaldehyde. The synthesis of S-alkylated compounds 8-11 was performed from the reaction of the corresponding triazol-5-thioles with various alkyl halides. The condensation of carbo(thio)amides 2-4 with 4-chlorophenacyl bromide afforded the corresponding 1,3-thia(oxa)zol-2(3H)-ylidene]pyridine-3-carbohydrazides 25-27. 1,3-Thia(oxa)zolidine derivatives 28-30 were obtained from the cyclization reaction between compounds 2-4 and ethyl bromoacetate. All newly synthesized compounds were screened for their antimicrobial, antiurease, and antilipase activities. The biological activity studies revealed that all the compounds screened showed good or moderate antimicrobial, antiurease, and/or antilipase activity.
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    Synthesis and antimicrobial activities of hybrid heterocyclic molecules based on 1-(4-fluorophenyl) piperazine skeleton
    (Bentham Science Publishers, 2017) Özdemir, Serap Başoğlu; Demirbaş, Neslihan; Cebeci, Yıldız Uygun; Bayrak, Hacer; Mermer, Arif; Demirbaş, Ahmet; Ceylan, Şule
    Background: The amine (2) was prepared starting from 1-(4-fluorophenyl) piperazine via two steps, and then converted to the corresponding hydrazide (4). The reaction of hydrazide (4) with carbon disulfide generated the corresponding 1,3,4-oxadiazole (5), while the treatment of hydrazide with ethyl bromoacetate produced 4-oxo-2-thioxo-1,3-thiazolidine compound (6). The four-component condensation of 4 with several aldehydes gave the corresponding 4-oxo-2-thioxo-1,3-thiazolidinglycinamides (7a-f). Methods: The synthesis of 4-oxo-1,3-oxazolidines (9a, b), 1,3-oxazoles (10a, b) and 1,3,4-triazoles (11a, b) was carried out starting from compounds 8a, b. Mannich bases (12a-d and 13a-f) were prepared using three component condensation of compounds 5 and 12a, b and corresponding amines. The synthesis of 16a-c, which were considered as the new analogues of azole class antifungals, was performed starting from the compound 14a via three steps. Results and Conclusion: All the reactions were examined under traditional and microwave irradiation conditions, and optimum conditions were defined. The antimicrobial activities of the newly synthesized compounds were screened and some of the tested compounds were displayed good-moderate antibacterial activity.
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    Synthesis and antimicrobial activity of new piperazine-based heterocyclic compounds
    (Walter De Gruyter Gmbh, 2017) Özdemir, Serap Başoğlu; Cebeci, Yıldız Uygun; Bayrak, Hacer; Mermer, Arif; Demirbaş, Ahmet; Karaoğlu, Sengül Alpay; Demirbaş, Neslihan; Ceylan, Şule
    The hydrazide 5, that was obtained from -1-(4-fluorophenyl) piperazine (1), was converted to the cor-responding carbothioamides 6a-c by the reaction with alkyl(aryl) isothiocyanates. The synthesis of conazole analogs 10a-f was performed via the intermediary of triazoles 7a-c. The condensation of triazoles 7a-c with -several -heterocyclic amines in the presence of formalde-hyde afforded the corresponding N-aminoalkylated tria-zoles 11-14. The effect of different catalysts and solvents on conventional and microwave (MW)-prompted reac-tions was examined. The synthesized compounds were screened for their antimicrobial activities.
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    Synthesis of some new hybride molecules containing several azole moieties and investigation of their biological activities
    (Maik Nauka/Interperiodica/Springer, 2014) Ceylan, Şule; Bayrak, Hacer; Demirbaş, Ahmet; Ülker, Serdar; Alpay Karaoğlu, Şengül; Demirbaş, Neslihan
    1,2,4-Triazole-3-one prepared from tryptamine was converted to the corresponding carbothioamides by several steps. Their treatment with ethyl bromoacetate or 4-chlorophenacyl bromide produced the corresponding 5-oxo-1,3-thiazolidine or 3-(4-chlorophenyl)-1,3-thiazole derivatives. Acetohydrazide derivative that was obtained starting from tryptamine, was converted to the corresponding Schiff basis and sulfonamide by the treatment with suitable aldehydes and benzensulphonyl chloride, respectively. 2-[(4-Amino-5-thioxo-4,5-dihydro-1H-1,2,4-triazole-3-yl)methyl]-4-[2-(1H-indole-3-yl)ethyl]-5-methyl-2,4-dihydro-3H-1,2,4-triazole-3-one was synthesized starting from hydrazide via the formation of the corresponding 1,3,4-oxadiazole compound, while the other bitriazole compounds were obtained by intramolecular cyclisation of carbothioamides in basic media. The treatment of 1,2,4-triazole or 1,3,4-oxadiazole compound with several amines generated the corresponding Mannich bases. Ethyl (2-amino-1,3-thiazole-4-yl)acetate was converted to the corresponding 1,3,4-oxadiazole derivative, arylidenehydrazides, 1,2,4-triazole-3-one and 5-oxo-1,3-oxazolidine derivatives by several steps. The structural assignments of new compounds were based on their elemental analysis and spectral (FT IR, H-1 NMR, C-13 NMR and LC-MS) data. The antimicrobial, antilipase and antiurease activity studies revealed that some of the synthesized compounds showed antimicrobial, antilipase and/or antiurease activity.