Synthesis of Mannich bases of some 2,5-disubstituted 4-thiazolidinones and evaluation of their antimicrobial activities

5-Phenyl/methyl-5-morpholinomethyl/pyrrolidinomethyl-2-(5- aryl-1,3,4-oxadiazol-2-yl)imino]-4-thiazolidinones (5a-m) were synthesized by the reaction of 5-phenyl/methyl-2-[(5-aryl-1,3,4-oxadiazol -2-yl)imino]-4-thiazolidinones (4a-j) with formaldehyde and morpholine or pyrrolidine. The structures of the compounds were determined by analytical and spectral (IR, 1H-NMR, EIMS) methods. The antibacterial activities of the novel compounds against Staphylococcus aureus ATCC 6538, Staphylococcus epidermidis ATCC 12228, Escherichia coli ATCC 8739, Klebsiella pneumoniae ATCC 4352, Pseudomonas aeruginosa ATCC 1539, Salmonella typhi, Shigella flexneri and Proteus mirabilis and antifungal activity against Candida albicans ATCC 10231 were tested using the disk diffusion method. Compounds 5a, 5b, 5c, 5e, 5g, and 5h were found to be active against S. aureus ATCC 6538 (MIC: 312.5; 39; 19.5; 39; 156; and 78 micrograms/mL respectively) and compounds 5c and 5h against S. flexneri (MIC: both 312.5 micrograms/mL). The minimal inhibitory concentrations of these compounds were determined using the micro dilution method.     

Synthesis and antimicrobial activity of coordination compounds of some 3d-elements with Schiff bases

Translated from Khimiko-farmatsevticheskii Zhurnal, Vol. 23, No. 9, pp. 1098–1101, September, 1989.     

Synthesis of 4-aminoantipyrine Schiff bases and their antimicrobial activities

Various compounds of 4-aminoantipyrine Schiff bases (M₁–M₁₂) were synthesized via a condensation reaction of 4-aminoantipyrine with different benzaldehydes through a conventional method of refluxing the mixture for 3–4 h. The synthesizedSchiff bases were characterized by using elemental analyses, FT-IR, UV-Vis, Mass, ¹H and ¹³C NMR spectroscopy. The antimicrobial activity of the synthesized Schiff bases was investigated against 12 bacterial strains(Mycobacterium smegmatis, Bacillus cereus, Bacillus subtilis, Enterococcus faecalis, Staphylococcus epidermidis, Klebsiella pneumonia, Escherichia coli, Enterobacter cloacae,Klebsiella oxytoca, Proteus vulgaris, Enterobacter aerogenes, and Pseudomonas aeruginosa), and antifungal activities were tested against seven fungal strains (Aspergillus flavus, Aspergillus carbonarious, Aspergillus parasiticus, Aspergillus fumigatus,Aspergillus niger, Fusarium verticillioides and Fusarium proliferatum). The antimicrobial activities of the synthesized compounds were compared with standard streptomycin and nalidixicacid. The results obtained from antibacterial assay indicated that M₁–M₁₂ inhibited potential growth of Proteus vulgaris with minimum inhibitory concentrations (MICs) ranging from 15.6–250 µg/mL compared with the standard nalidixic acid with an MIC of 500 µg/mL. Moreover, we could conclude that most of the tested compounds experienced mild to low activities at 15.6 µg/mL. Their activities could be attributed to their low concentrations.The antifungal analysis showed that the tested fungi were not sensitive to the prepared Schiff bases at the prepared concentration of 500 µg/mL. Therefore, we recommended further analysis on both cytotoxicity and minimum bactericidal concentration (MBC) to ascertain their potential effects against human cells.     

Synthesis, spectroscopy, and antibacterial activity of some transition metal complexes with tridentate (ONS) and bidentate (NN) donor Schiff bases

The complexes of a series of transition metal ions including Mn(II), Co(II), Ni(II), Cu(II), Zn(II), and Cd(II) with salicylidene-o-aminothiophenol and bis(benzylidene)ethylenediamine or bis(acetophenone)ethylenediamine have been synthesized and characterized by elemental analyses, infrared spectra, reflectance spectra, magnetic measurements, and thermogravimetric analyses. All complexes have been screened for their antibacterial activity against bacterial strains using the disc diffusion technique. It is established that the complexes possess moderate antibacterial activity against Salmonella typhimurium, Escherichia coli, and Serratia marcescens, the effect being higher as compared to the action of individual ligands, metal chlorides, and control (DMSO), but lower than the action of the reference drug tetracycline. Published in Khimiko-Farmatsevticheskii Zhurnal, Vol. 40, No. 10, pp. 24–27, October, 2006.     

Synthesis and biological activity of novel Schiff bases derived from metronidazole

A number of novel Schiff bases (5a–i) and (7a–d) derived from metronidazole were synthesized. Reaction of 2-(2-methyl-5-nitro-imidazol-1-yl)-ethyl ester toluene-4-sulfonate with 4-hydroxybenzaldehyde and with 3-hydroxybenzaldehyde in the presence of a base afforded 4-(2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethoxy)benzaldehyde (5) and 3-(2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethoxy)benzaldehyde (7), respectively. The reaction of aldehydes 5 and 7 with a number of primary aromatic amines produced Schiff bases 5a–i and 7a–d, respectively. Structures of these compounds were confirmed through different spectroscopic methods such as ¹H-NMR, ¹³C-NMR, mass spectrometry, and also by elemental analyses. The prepared compounds were evaluated in vitro for their antigiardial, anti-trichomonal, antibacterial, and antifungal activities. Compounds 5e, 5g, 5i, 7a, 7b, 7c, and 7d exhibited remarkable antigiardial activity and were found to be more active than metronidazole with IC₅₀ of 7.2, 3.3, 1.5, 5.8, 4.5, 2.9, and 3.8 µg/mL, respectively. Compounds 5a and 5c also exhibited antigiradial activity with similar IC₅₀ values compared to the reference drug metronidazole with IC₅₀ of 7.2 µg/mL. The other compounds 5b, 5d, 5f, and 5 h also showed antigiardial activity but with higher IC₅₀ compared to the reference drug. Compounds were also tested for their anti-trichomonal activity, they, however, exhibited higher IC₅₀ compared to the reference drug metronidazole (7.4 µg/mL), except for compound 5a which exhibited anti-trichomonal activity with an IC₅₀ of 6.3 µg/mL. On the bases of preliminary screening, the newly synthesized compounds exhibited moderate to potent antimicrobial activities. Compound 5e inhibited the growth of Methicillin resistant Staphylococcus aureus (MRSA) and Bacillus cereus and compound 5c inhibited Candida Pathogenic fungus at 50 μg/mL compared with the positive control (Nystatin) which inhibits Candida at 25 μg/mL.     

Synthesis and antibacterial activity of some new hydrazones

New hydrazone derivatives were synthesized by the condensation of some selected heteroaromatic hydrazines with appropriate aromatic ketones at high temperature (100 °C). The structures of the synthesized compounds were established by elemental (CHN) and spectral (IR, ¹HNMR, and Mass) analysis. The synthesized compounds were screened for their antibacterial (Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Salmonella typhi, Proteus mirabilis) activities, which reveal that all the compounds possess activity against all the tested organisms.     

Synthesis, characterization and biological activity of Schiff bases derived from metronidazole

A series of novel Schiff bases; compounds 3a–j were prepared by reacting 1-(2-aminoethyl)-2-methyl-5-nitroimidazole dihydrochloride monohydrate (1) with different aldehydes. The structures of these compounds were confirmed through different spectroscopic methods such as ¹H-NMR, ¹³C-NMR and mass spectrometry and also by elemental analyses. The prepared compounds were evaluated in vitro for their antigiardial, antibacterial and antifungal activities. Compounds 3h, 3b and 3d showed remarkable antigiardial activities and were found to be more active than metronidazole with IC₅₀ of 0.83, 1.36 and 1.83?μM, respectively. Other compounds also exhibited antigiardial activity and were as good as or even more potent than metronidazole. Some of the newly synthesized Schiff bases exhibited more antifungal activities than the parent drug. In addition, a few of the prepared compounds exhibited modest antibacterial activity but were not as active as metronidazole.     

Synthesis, structure and antibacterial activity of some alkyltriazenopyrazoles

A series of bis-beta-chlorethyl-, dimethyl- and diethyltriazenopyrazoles (I-IV) were synthesized. By the method of IR spectroscopy the most probable transformation form of I was shown. The compounds were tested as antibacterial agents on a series of bacterial species. It was established that only one of them (VI) possessed a low inhibitory effect. All the rest inhibited strongly the growth of Staphylococcus aureaus 209 and E. coli 387.     

新型5-氯水杨醛Schiff碱还原胺的合成及其抗菌活性研究

目的设计合成5-氯水杨醛Schiff碱还原胺并研究其抗菌活性。方法以具有很好的药物活性的5-氯水杨醛为原料,设计并合成一系列新型5-氯水杨醛的Schiff碱还原胺衍生物,通过晶体结构、1H-NMR、MS及元素分析对所合成的目标化合物进行结构表征,并对其生物活性进行了初步筛选。结果初步生物活性测试结果表明,大部分化合物表现出一定的抗菌活性,其中化合物3b和3g具有较强的抗菌活性。结论以5-氯水杨醛Schiff碱还原胺为先导化合物研发新型抗菌药物具有很好的应用前景。     

Synthesis, antimalarial-, and antibacterial activity evaluation of some new 4-aminoquinoline derivatives

Some new 4-aminoquinoline derivatives were synthesized, characterized by their analytical and spectral data (IR, ¹HNMR, ¹³CNMR and MS), and screened for in vitro antimalarial activity against a chloroquine-sensitive strain of Plasmodium falciparum (3D7). Results clearly reveal that all the synthesized compounds possess in vitro antimalarial activity at the tested dose which, however, was considerably less than that of the standard reference drug, chloroquine. From results, it could be assumed that the presence of an aromatic bulky group with optimal lipophilicity at 1,3-thiazinan-4-one ring system might be an important requirement for the antimalarial activity of synthesized compounds, 6a–g. In addition to the evaluation of antimalarial activity, the synthesized compounds were also screened for antibacterial activity against six different strains of Gram-positive (Bacillus subtilis, Bacillus cereus, and Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae). All the compounds at the tested doses were found to be active against all the tested organisms, but were less active as compared to the standard drug, ofloxacin. Results of antibacterial study indicate that aromatic bulky substituents have greater contributing effect than the aliphatic non-bulky group toward the antibacterial activity of the prepared 4-aminoquinoline derivatives.     

Synthesis and antimicrobial activity of coordination compounds of 3d-elements with Schiff bases obtained from 5-nitrofurfurol and some sulfanilamides

Translated from Khimiko-farmatsevticheskii Zhurnal, Vol. 25, No. 3, pp. 37–39, March, 1991.     

Synthesis and antimicrobial study of fluoroquinolone-based 4-thiazolidinones

The title compounds 2-substituted phenyl-3-{1-cyclopropyl-6-fluoro-7-[4-(4-methoxyphenylpiperazin-1-yl]-4-oxo-1,4-dihydroquinoline} carboxamido-1,3-thiazolidin-4-ones 6a–j have been synthesized from lead molecule 7-chloro-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic acid 1; this reacted with thionyl chloride to give acid chloride 2 and with hydrazine hydrate to afford hydrazide 3. The hydrazide 3 on condensation with substituted aromatic aldehydes a–j gave Schiff base; these on reaction with N-(4-methoxyphenyl) piperazine and thioglycolic acid furnished title compounds 6a–j. All of the synthesized compounds have been established by elemental analysis. IR and NMR spectral data and have been screened for antifungal and antibacterial activities.     

Synthesis and antifungal activity of oxovanadium(IV) complexes with Schiff bases

A series of preparations are reported representing complexes between a range of ligands [KHL = potassium salt of salicylidene-β-alanine, A¹ = 2,2′-bipyridylamine, A² = bis(benzylidene)ethylenediamine, A³ = thiophene-o-carboxaldene-aniline, A⁴ = thiophene-o-carboxaldene-p-toluidine, A⁵ = bis(benzylidene)-1,8-diaminonaphthalene, A⁶ = bis(acetophenone)ethylenediamine] and oxovanadium(IV) ion. Relevant electronic (UV), infrared (IR) spectra, thermogravimetric analyses, elemental analyses, and magnetic measurements are reported and interpreted in terms of the metal ion coordination geometry and, where appropriate, the likely octahedral structures of the compounds. The complexes are paramagnetic in nature. The antifungal activity of the complexes against A. niger, F. oxysporum, and A. flavus species is reported. All the tested complexes show higher antifungal activity as compared to free ligands, vanadyl sulfate, and the control (DMSO), but moderate activity as compared to the reference fungicides bavistin and emcarb. Published in Khimiko-Farmatsevticheskii Zhurnal, Vol. 40, No. 9, pp. 32–35, September, 2006.