Synthesis of some quinoxaline derivatives containing indoline-2,3-dione or thiazolidinone residue as potential antimicrobial agents

The synthesis of some quinoxaline derivatives containing indoline-2,3-dione or thiazolidinone residue is described. The synthesized derivatives were screenedin vitro for their growth inhibitory activity against six species of bacteria, viz.Staphylococcus aureus, Streptococcus faecalis, Escherichia coli, Pseudomonas aeruginosa, Serratia marcescens andMycobacterium semegmatis. Most of the compounds exhibited antimicrobial activity especially those having indoline-2,3-dione moiety.     

Synthesis and antimicrobial activity of some indole derivatives

Bromination of 2,3-diphenyl-5-methylindole (I) (using 3 mol) with bromine gave the 4,6-dibromo derivative (II) which upon oxidation gave the corresponding 2-benzamido benzophenone derivative (III). Bromination (using 6 mol) with bromine afforded the tetrabromo derivative (IVa) which reated with amines to form the corresponding 5-substituted aminomethyl derivatives (IVb-d). Further bromination ofII using only 1 mol gave the tribromo derivative (Va) which in turn reacted with amines to formVb-g. The antimicrobial activities of compoundsI, IVa, IVc, Va, Ve, Vf andVg were studied.     

Synthesis and antimicrobial activity of new adamantane derivatives III

Some novel ester imides synthesised from trimellitic acid anhydride and 1-adamantanol or 2-adamantanol, were tested as antimicrobial compounds. Unfortunately, these agents showed a modest antibacterial activity (MIC > 6 microg/ml). However, a comparison of these N-substituted adamantylester imides with the series published previously, indicated that the incorporation of L-alanine and L-phenylalanine into the phthalimide moiety was the best choice regardless of the series and leads to antimicrobial activity against Staphylococcus aureus strains.     

Synthesis and antimicrobial activity of some pyridinyliminothiazoline derivatives

The synthesis of some pyridinyliminothiazoline derivatives starting from N-pyridine-N'-phenyl thiourea and alpha-halogenoacetophenones is described. The chemical structures of the compounds were elucidated. The prepared compounds were tested for antimicrobial activity.     

Synthesis and antimicrobial activities of some new benzimidazole derivatives

Some benzimidazolylbenzamides were synthesized and their antimicrobial activities against Staphylococcus aureus, Streptococcus faecalis, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa and Candida albicans evaluated. It was shown that the compound 14 exhibited the best activity against B. subtilis, P. aeruginosa and C. albicans.     

Synthesis and antimicrobial activity of some new 1-alkyl-2-alkylthio-1,2,4-triazolobenzimidazole derivatives

Some new derivatives of 1,2,4-triazolo[2,3-a]benzimidazoles were synthesized through the reaction of 1,2-diaminobenzimidazole with carbon disulfide. The resulting 1,2,4-triazolo-[2,3-a]benzimidazole-2-thione intermediate was reacted with one equivalent of alkyl halides to give the corresponding 2-alkylthio derivatives, which were further alkylated through the reaction with another one equivalent of different alkyl halides to afford the target compounds; 1-alkyl-2-alkylthio-1,2,4-traizolo[2,3-a]benzimidazoles. On the other hand, the 1,2-disubstituted derivatives with two identical alkyl substituents were prepared by the reaction of 1,2,4-triazolo[2,3-a]benzimidazole-2-thione with two equivalents of the alkyl halides. The structures of the new compounds were assigned by spectral and elemental methods of analyses. The synthesized compounds were tested for their antibacterial and antifungal activities. Most of the tested compounds proved comparable results with those of ampicillin and fluconazole reference drugs. The study indicated that, the antibacterial as well as the antifungal activities of the test compounds were improved with increase in the bulkiness of the introduced alkyl groups. Also, some active antibacterial compounds were tested for their antimycobacterial activity. All the test compounds showed equipotent antitubercular activity as that of INH as a reference drug.     

Synthesis and antimicrobial activity of some new N-substituted quinoline derivatives of 1H-pyrazole

A new series of 32 derivatives of 4-pyrazolyl-N-(hetero)arylquinoline 5a-p and 6a-p were synthesized by a one-pot base-catalyzed cyclocondensation reaction of 1-phenyl-3-(hetero)aryl-pyrazole-4-carbaldehyde 1a-h, malononitrile 2, and 3-(hetero)aryl-5,5-disubstitutedcyclohex-2-enone 3a-b or 4a-b, respectively. All the synthesized compounds were characterized by elemental analysis, FT-IR, (1) H-NMR, and (13) C-NMR spectral data. All the synthesized compounds were screened, against six bacterial pathogens, namely Bacillus subtilis, Clostridium tetani, Streptococcus pneumoniae, Salmonella typhi, Vibrio cholerae, Escherichia coli, and antifungal activity, against two fungal pathogens Aspergillus fumigatus and Candida albicans, using broth microdilution MIC method. Some of the compounds were found to be more or equipotent against most of the employed strains than commercially available drugs as evident from the screening data.     

Synthesis and antimicrobial activity of some novel 2-(p-substituted-phenyl)-5-substituted-carbonylaminobenzoxazoles

A series of 2-(p-substituted-phenyl)-5-substituted-carbonylamino benzoxazole derivatives (5-22) was synthesized and their antimicrobial activities determined in comparison to several control drugs. The synthesized compounds were tested in vitro against Staphylococcus aureus, Streptococcus faecalis and Bacillus subtilis as Gram-positive, Pseudomonas aeruginosa and Escherichia coli as Gram-negative bacteria and the yeast Candida albicans. Microbiological results showed that the compounds possessed a diffuse spectrum of antibacterial activity against these microorganisms. Compound 9 which bears a phenylacetamido moiety at position 5 and a 4-fluorophenyl group at the 2-position of benzoxazole ring was the most active derivative against S. aureus, S. faecalis and P. aeruginosa with a MIC value of 12.5 microg/ml. Compound 11 provided higher potency than the other tested compounds against B. subtilis at a MIC value of 12.5 microg/ml. Compounds 5-22 showed antifungal activity against C. albicans with MIC values between 50 and 12.5 microg/ml.     

Synthesis, antimicrobial and anticancer activity of new thiosemicarbazone derivatives

Thiosemicarbazones of p-aminobenzoic acid (PABA) were synthesized and tested for their antimicrobial and anticancer activity. Hydroxamate derivatives 4a-4l were found to have better antimicrobial and anticancer activity than their acid counterpart. Compound 4d was found to have good antimicrobial activity against Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, Vibrio cholerae, and Bacillus subtilis with IC(50) value of about 1 μM. Compound 4f showed potent antifungal activity against Candida albicans (IC(50) = 1.29 μM) and compound 4h showed potent anticancer activity (IC(50) = 0.07 μM).     

Synthesis and antimicrobial activity of novel tetrahydrobenzothienopyrimidines

Due to the rapidly growing number of resistant strains of bacteria, the search for antibacterial agents with new modes of action will always remain an important and challenging task. Thus, the reaction of 2-substituted or unsubstituted-4-(4-acetylanilino)-5,6,7,8-tetrahydrobenzo[b]thieno[2,3-d]pyrimidine derivatives 1-3 with the hydrazine derivatives, semi and/or thiosemicarbazides, provided the corresponding hydrazones 4-6 and semi and/or thiosemicarbazones 7-9. Claisen-Schmidt condensation of compounds 1 or 2 with the appropriate aldehyde yielded the chalcones 10, 11 which, when treated with hydroxylamine hydrochloride gave rise to the isoxazoline-containing compounds 12, 13. Furthermore, reacting the respective chalcones 10, 11 with different hydrazines, urea and/or thiourea, furnished compounds 14, 15, 16, and 17 respectively. Representative compounds were tested for their antimicrobial activity against Candida albicans and certain gram-positive and gram-negative bacteria. Their MICs were then determined. Compound 15e, showed a broad spectrum of activity while most of the other compounds showed varying antimicrobial activity.     

Synthesis and antimicrobial activity of some new hydrazones of 4-fluorobenzoic acid hydrazide and 3-acetyl-2,5-disubstituted-1,3,4-oxadiazolines

A series of hydrazide hydrazones and 1,3,4-oxadiazolines of 4-fluorobenzoic acid hydrazide were prepared and evaluated as potential antimicrobial agents and were tested for their antibacterial and antifungal activities against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Candida albicans. From these compounds, 4-fluorobenzoic acid[(5-nitro-2-furanyl)methylene]hydrazide (1a) showed equal activity with ceftriaxone against S. aureus. In addition, the MIC values of compounds 1c, 1d and 2a for the same strain were in the range of those reported for ceftriaxone according to NCCLS 1997.     

Potential antimicrobial agents-I: Structural modifications and antimicrobial activity of some isatin derivatives

New isatin-3-isonicotinylhydrazones, isatinazine and its Mannich bases and spiro (indoline-3, 2'-thiadiazoline)-2-one have been synthesized. These compounds have been screened for their antibacterial activity against the Gram-positive and Gram-negative bacteria.     

Synthesis antimicrobial and antifungal activity of some new 3 substituted derivatives of 4-(2,4-dichlorophenyl)-5-adamantyl-1H-1,2,4-triazole

The synthesis of a series of substituted hydrazones and thiazolidinones is described, starting from N-[4-(2,4-dichlorophenyl)-5-adamantyl-1H-1,2,4-triazol-3-ylmercaptoacetyl]hydrazine. The new compounds were tested for antimicrobial and antifungal activity and some of them exhibited moderate activity against Candida albicans.     

Synthesis and antimicrobial evaluation of some novel 2-aminothiazole derivatives of 4-hydroxy-chromene-2-one

Syntheses of 2-aminothiazole derivatives of 4-hydroxy-chromene-2-one 2c-10c are reported in this paper. These compounds 2c-10c were prepared from 3-(2-bromoacetyl)-4-hydroxy-chromene-2-one 1 and corresponding thiourea derivatives 2b-10b using Hantzsch reaction. The structures of all compounds were confirmed by IR and( 1)H-NMR spectroscopy and elemental analyses. The molecules 2c-10c were evaluated for in vitro antimicrobial activity against ten bacteria and twelve fungi. All tested compounds exhibited antibacterial and antifungal activity.     

Synthesis and antibacterial activity of novel levofloxacin derivatives containing a substituted thienylethyl moiety

Background and the purpose of the study

Piperazinyl quinolones such as ciprofloxacin, ofloxacin and levofloxacin are an important group of quinolone antimicrobials which are widely used in the treatment of various infectious diseases. In the present study, we synthesized a new series of levofloxacin derivatives and evaluated their antibacterial activities.

Methods

The N-substituted analogs of levofloxacin 6a–j were prepared by nucleophilic reaction of N-desmethyl levofloxacin 11 with thienylethyl bromide derivatives 8 or 9. All target compounds were tested using conventional agar dilution method in comparison to levofloxacin and N-desmethyl levofloxacin and their MIC values were determined against a panel of Gram-positive and Gram-negative bacteria.

Results

All compounds showed significant antibacterial activities against Gram-positive bacteria (MIC = 0.04-6.25 μg/mL); however, the activity against Gram-negative bacteria was lower (MIC = 1.56–100 μg/mL). As is evident from the data, oxime derivatives 6e, 6h and 6i are superior in inhibiting the growth of Gram-positive bacteria (MIC = 0.04–0.19 μg/mL), and their activities were found to be 5–25 times better than N-desmethyl levofloxacin 11 and equal or better than levofloxacin 4.

Conclusion

We have designed and synthesized novel quinolone derivatives bearing functionalized thienylethyl moiety on the piperazine ring of levofloxacin. The results of antibacterial screening against Gram-positive and Gram-negative bacteria revealed that the introduction of functionalized thienylethyl moiety on the piperazine ring of levofloxacin can improve the activity against Gram-positive bacteria. Gram-positive bacteria are responsible for a wide range of infectious diseases, and rising resistance in this group is causing increasing concern. Thus, this study introduces structural features of levofloxacin scaffold for development of new candidates in the field of anti-Gram positive chemotherapy     

Studies on the synthesis of some new substituted benzylamino and phenyl-acrylamido-methyl flavone derivatives

The synthesis and biological activity of a new series of 2-{3-[substituted benzylamino-methyl)-phenyl]-4H-benzopyrane-4-one (IVa-e) and N-substituted benzyl-N-[3-(4-oxo-4H-benzopyrane-2-yl)benzyl]-3-phenyl-acrylamide (Va-e) derivatives are reported. The synthesized compounds were tested in vitro for antifungal and antibacterial activities. Compound IVa showed the best antifungal activity compared with miconazole (CAS 22916-47-8). Compound IVc indicated the best antibacterial activity compared with the control drug ampicillin (CAS 69-53-4).     

Synthesis and antimicrobial activity of new 4-thiazolidinone derivatives containing 2-amino-6-methoxybenzothiazole

A novel series of Schiff bases 5a–j and 4-thiazolidinones 6a–j have been prepared from the building blocks 2-chloro pyridine-3-carboxylic acid [1] and 2-amino-6-methoxy-benzothiazole [2]. All of the synthesized compounds have been confirmed by elemental analyses, IR, ¹H NMR and ¹³C NMR spectral data. These newly synthesized compounds were screened for their antimicrobial activity. Variable and modest activity was observed against the investigated strains of bacteria and fungi, however, compound 6h revealed significant antibacterial activity against Escherichia coli. Compounds 1, 2, 3, 5c, 5g and 5h, on the other hand, revealed potent antifungal activity against Candida albicans compared to the reference drug greseofulvin.     

Synthesis of hydrazides of heterocyclic amines and their antimicrobial and spasmolytic activity

Un unsolvable issue of a significant number increase of drug multi resistant strains of microorganisms including Mycobacterium tuberculosis force researchers for continuous design novel pharmaceuticals.The purpose of the study is the establishment of the correlation between the structure of novel heterocyclic hydrazide derivatives and their biological activity. Several hydrazide derivatives of N-piperidinyl and N-morpholinyl and propionic acids and N-piperidinyl acetic and their derivatives were synthesized via condensation of corresponding esters with hydrazine hydrate.The structure of synthesized compounds were confirmed by the use of FTIR, H1NMR, Mass-spectroscopy and element analysis. Investigation of synthesized substances using PASS software was carried out to predict probability of pharmacological activity in silico. The antibacterial, antifungal and spasmolytic activity as well as acute toxicity of obtained compounds were evaluated in vivo. 2-(N-piperidinyl)acetic acid hydrazide and 2-methyl-3-N-piperidinyl)propanacid hydrazide revealed antibacterial and spasmolytic activities comparable to the model drugs (drotaverin) in vitro study. Synthesized compounds in in vivo experiment showed significantly low acute toxicity (LD50 520–5750 mg/kg) compared to commercially available drugs (streptomicine, ciprofloxacinum and drotaverin LD50 100–215 mg/kg). The structure- activity relationship was established that the increasing of the length of the linker between heterocyclic amine and hydrazide group results in a decrease of antimicrobial activity against studied strains (Escherichia coli, Salmonella typhymurium, Salmonella choleraesuis, Staphylococcus aureus).     

Synthesis of 2,4-dihalogenofluorobenzenes and their antimicrobial and antifungal activity studies

The aim of this study was to synthesize and identify 2,4-dihalogenofluorobenzene (or trihalogenobenzene) derivatives by spectroscopic means, ¹H-NMR and ¹⁹F-NMR. The 2,4-dihalofluorobenzene derivatives considered were 2,4-dichlorofluorobenzene (1), 2-bromo-4-chlorofluorobenzene (2), 2-iodo-4-chlorofluorobenzene(3), 2,5-dichlorofluorobenzene (4), 2-bromo-5-chlorofluorobenzene (5), 2-iodo-5-chlorofluorobenzene (6). The in vitro antibacterial and antifungal activities of trihalogenobenzene derivatives were studied against the bacteria Staphylococcus aureus ATCC 25923 Gram(+), Bacillus cereus ATCC 6633 Gram(+), Micrococcus flavus (clinical isolate) Gram(+), Morgenella morganii (clinical isolate) Gram(-), Escherichia coli ATCC 27853 Gram(-) and fungus Candida albicans (clinical isolate), obtained from the biology departments of the Pamukkale and Gazi Universities. The antibacterial and antifungal activities were measured by minimum inhibition concentration (MIC) method and the disc-diffusion method used to measure zone diameter against Gram-positive and Gram-negative bacteria and fungi. All these bacteria and fungi were studied against antibiotics to compare the zone diameters with the results from our treatments.     

Synthesis and antimicrobial activity of some 1,3,4-oxadiazole derivatives

Six new 5-(1-/2-naphthyloxymethyl)-1,3,4-oxadiazole-2(3H)-thione, 2-amino-5-(1-/2-naphthyloxymethyl)-1,3,4-oxadiazole, 5-(1-/2-naphthyloxymethyl)-1,3,4-oxadiazole-2(3H)-one derivatives have been synthesized from 1-and/or 2-naphthol. The structures of the compounds were confirmed by IR and 1H NMR spectral data and microanalysis. The antimicrobial properties of the compounds were investigated against Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa, Candida albicans, C. krusei and C. parapsilosis using microbroth dilution method. 2-Amino-5-(2-naphthyloxymethyl)-1,3,4-oxadiazole and 5-(2-naphthyloxymethyl)-1,3,4-oxadiazole-2(3H)-one show significantly (32 microg/ml), compounds 5-(1-/2-naphthyloxymethyl)-1,3,4-oxadiazole-2(3H)-thione, 2-amino-5-(1-naphthyloxymethyl)-1,3,4-oxadiazole and 5-(1-naphthyloxymethyl)-1,3,4-oxadiazole-2(3H)-one moderately (64 microg/ml) active against C. krusei. All the compounds were active against S. aureus, E. coli, P. aeruginosa, C. albicans, and C. parapsilosis at 64-256 microg/ml concentration.