Synthesis and antimicrobial activity of 2-alkenylchroman-4-ones, 2-alkenylthiochroman-4-ones and 2-alkenylquinol-4-ones

2-Alkenylchroman-4-ones, 2-alkenylthiochroman-4-ones, and 2-alkenylquinol-4-ones were prepared with very good regioselectivity by Me3SiOTf-mediated conjugate addition of alkenylmagnesium bromides and alkenyllithium compounds to chromones thiochromones, and quinol-4-ones. A number of products exhibit a considerable antimicrobial activity. The best activity, with respect to the spectrum of antimicrobial activity, was observed for 2-vinylchroman-4-ones containing an unsubstituted vinyl group and a chloride group located at the chromanone moiety.     

A convenient 'one-pot' synthesis and in vitro microbiological evaluation of novel 2,7-diaryl-[1,4] -diazepan-5-ones

A convenient method for the 'one-pot' synthesis of novel target molecule 2,7-diaryl-[1,4]-diazepan-5-ones from the respective 2,6-diaryl-piperidin-4-ones was catalyzed by NaHSO4.Al2O3 heterogeneous catalyst in dry media under microwave irradiation in solvent-free conditions. Moreover, the catalyst could be recovered and re-used up to 4 times after washing with ethyl acetate. They were evaluated for potential antibacterial activity against Staphylococcus aureus, beta-Haemolytic streptococcus, Vibreo cholerae, Salmonella typhii, Escherichia coli, Klebsiella pneumonia, Pseudomonas and antifungal activity against Aspergillus flavus, Aspergillus fumigatus, Mucor, Candida albicans and Rhizopus. Structure-Activity Relationship (SAR) led to the conclusion that, of all the compounds 25-32 tested, compound 30 exerted strong in vitro antibacterial activity against S. aureus, S. typhii, and Pseudomonas and all the compounds 25-32 were less active against E. coli, whereas all the compounds 25-32 displayed potent in vitro antifungal activity against all the fungal strains used, except compound 30, which was more effectual against Mucor.     

Synthesis and potent antimicrobial activity of some novel 2-phenyl or methyl-4H-1-benzopyran-4-ones carrying amidinobenzimidazoles

Series of flavones and methyl-4H-1-benzopyran-4-ones carrying mono or diamidinobenzimidazoles at different positions were synthesized and evaluated for antibacterial and antifungal activities against E. coli, S. aureus, MRSA (methicillin-resistant S. aureus), MRSE (methicillin-resistant S. epidermidis), S. faecalis and C. albicans, C. krusei. The results showed that while all diamidines are inactive, the compounds having monoamidinobenzimidazoles at the C-6 position of the 2-phenyl-4H-1-benzopyran-4-one have potent antibacterial activities, particularly, against Gram-positive bacteria. Compounds 23 and 22 exhibited the best inhibitory activity with MIC values of 1.56 microg/ml against S. aureus, MRSA, MRSE and 3.12 microg/ml against C. albicans, respectively.     

Substituted 3-((Z)-2-(4-nitrophenyl)-2-(1H-tetrazol-5-yl) vinyl)-4H-chromen-4-ones as novel anti-MRSA agents: synthesis, SAR, and in-vitro assessment

In search for a new antibacterial agent with improved antimicrobial spectrum and potency, we designed and synthesized a series of novel 3-((Z)-2-(4-nitrophenyl)-2-(1H-tetrazol-5-yl) vinyl)-4H-chromen-4-ones 7a-h by convergent synthesis approach. All the synthesized compounds were assayed for their in-vitro antibacterial activities against gram-negative and gram-positive bacteria. The preliminary structure-activity relationship, to elucidate the essential structure requirements for the antimicrobial activity that results into anti-MRSA (methicillin-resistant S. aureus) potential, has been described. Amongst the synthesized compounds 7d, 7e, 7f and 7h were found to possess activity against methicillin-resistant S. aureus in addition to the activity against other bacterial strains such as E. faecalis, S. pneumoniae, and E. coli.     

Synthesis and antimicrobial evaluation of guanylsulfonamides

A series of guanylsulfonamides, 2-amino-9-[2-substituted-4-(4-substituted piperidin-1-sulfonyl)phenyl]-1,9-dihydropurin-6-ones, was synthesized by adopting reductive aminoformylation of 2-amino-5-nitro-6-[4-(piperidin-1-sulfonyl)phenylamino]-3H-pyrimidin- 4-one and subsequent intramolecular ring condensation as key steps. All the guanylsulfonamides were assayed for their in vitro antibacterial activities against Klebsiella pneumoniae, Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, Staphylococcus aureus, and Streptococcus faecalis, and their antifungal activities against Aspergillus flavus, Aspergillus niger, and Candida albicans. Of the guanylsulfonamides, 13e and 13f displayed better antibacterial activities than that of Norfloxacin against the bacterial strains S. aureus and S. faecalis except 13f against S. faecalis, which exhibited the activity similar to that of Norfloxacin. Against the fungal strains A. flavus and A. niger, 13g and 13h showed similar activities to that of Griseoflavin-16 except 13h against A. niger, which displayed a profound drop in the activity compared to that of Griseoflavin-16. The remarkable inhibition of the growth of the bacterial and fungal strains makes these substances promising microbial agents.     

Synthesis, structure, molecular docking, and structure-activity relationship analysis of enamines: 3-aryl-4-alkylaminofuran-2(5H)-ones as potential antibacterials

Thirty-one 3-aryl-4-alkylaminofuran-2(5H)-ones were designed, prepared and tested for their antibacterial activity. Some of them showed significant antibacterial activity against Gram-positive organisms, especially against Staphylococcus aureus ATCC 25923, but all were inactive against Gram-negative organisms. Out of these compounds, 3-(4-bromophenyl)-4-(2-(4-nitrophenyl)hydrazinyl)furan-2(5H)-one (4a11) showed the most potent antibacterial activity against S. aureus ATCC 25923 with MIC(50) of 0.42 μg/mL. The enzyme assay revealed that the possible antibacterial mechanism of the synthetic compounds might be due to their inhibitory activity against tyrosyl-tRNA synthetase. Molecular dockings of 4a11 into S. aureus tyrosyl-tRNA synthetase active site were also performed. This inhibitor snugly fitting the active site might well explain its excellent inhibitory activity. Meanwhile, this modeling disclosed that a more suitable optimization strategy might be to modify the benzene ring at 3-position of furanone with hydrophilic groups.     

N/C-4 substituted azetidin-2-ones: synthesis and preliminary evaluation as new class of antimicrobial agents

A series of 3-chloro-4-(3-methoxy-4-acetyloxyphenyl)-1-[3-oxo-3-(phenylamino)propanamido] azetidin-2-ones 3a-g and 3-chloro-4-[2-hydroxy-5-(nitro substituted phenylazo)phenyl]-1-phenylazetidin-2-ones 6a-h were synthesized using appropriate synthetic route. Structures of all the synthesized compounds were established on the basis of elemental analysis and spectroscopic data. The antimicrobial activity of the synthesized compounds was screened against several microbes. Several of these molecules showed potent antimicrobial activity against Bacillus anthracis, Staphylococcus aureus and Candida albicans and significant structure-activity relationship (SAR) trends.     

Novel non-nucleobase inhibitors of Staphylococcus aureus DNA polymerase IIIC

The preparation and biological evaluation of 5-substituted-6-hydroxy-2-(anilino)pyrimidinones as a new class of DNA polymerase IIIC inhibitors, required for the replication of chromosomal DNA in Gram-positive bacteria, are described. These new dGTP competitive inhibitors displayed good levels of in vitro inhibition and antibacterial activity against Staphylococcus aureus. A new class of dATP competitive inhibitors, 6-substituted-2-amino-5-alkyl-pyrimidin-4-ones, whose antibacterial activity was unaffected by serum, were identified.     

2-Phenylimidazo[2,1-i]purin-5-ones: structure-activity relationships and characterization of potent and selective inverse agonists at Human A3 adenosine receptors

Structure-activity relationships of 2-phenyl-imidazo[2,1-i]purin-5-ones as ligands for human A(3) adenosine receptors (ARs) were investigated. An ethyl group in the 8-position of the imidazoline ring of 4-methyl-2-phenyl-imidazopurinone leading to chiral compounds was found to increase affinity for human A(3) ARs by several thousand-fold. Propyl substitution instead of methyl at N4 decreased A(3) affinity but increased A(1) affinity leading to potent A(1)-selective AR antagonists. The most potent A(1) antagonist of the present series was (S)-8-ethyl-2-phenyl-4-propyl-4,5,7,8-tetrahydro-1H-imidazo[2,1-i]purin-5-one (S-3) exhibiting a K(i) value of 7.4 nM at rat A(1) ARs and greater than 100-fold selectivity versus rat A(2A) and human A(3) ARs. At human A(1) ARs 2-phenylimidazo[2,1-i]purin-5-ones were generally less potent and therefore less A(1)-selective (S-3: K(i)=98 nM). 2-, 3-, or 4-Mono-chlorination of the 2-phenyl ring reduced A(3) affinity but led to an increase in affinity for A(1) ARs, whereas di- (3,4-dichloro) or polychlorination (2,3,5-trichloro) increased A(3) affinity. The most potent and selective A(3) antagonist of the present series was the trichlorophenyl derivative (R)-8-ethyl-4-methyl-2-(2,3,5-trichlorophenyl)-4,5,7,8-tetrahydro-1H-imidazo[2,1-i]purin-5-one (R-8) exhibiting a subnanomolar K(i) value at human A(3) ARs and greater than 800-fold selectivity versus the other AR subtypes. Methylation of 4-alkyl-2-phenyl-substituted imidazo[2,1-i]purin-5-ones led exclusively to the N9-methyl derivatives, which exhibited largely reduced AR affinities as compared to the unmethylated compounds. [35S]GTP gamma S binding studies of the most potent 2-phenyl-imidazo[2,1-i]purin-5-ones at membranes of Chinese hamster ovary cells expressing the human A(3) AR revealed that the compounds were inverse agonists at A(3) receptors under standard test conditions. Due to their high A(3) affinity, selectivity, and relatively high water-solubility, 2-phenyl-imidazo[2,1-i]purin-5-ones may become useful research tools.     

Stereoselective intramolecular cyclization to 4-(hydroxymethyl)-3-(1H-indolyl)oxazolidin-2-ones

A simple high-yield three-steps route to optically active 4-hydroxymethyl-3-(1H-indolyl)oxazolidin-2-ones from (S)-glycidol is described. The key intermediates (R)-oxiran-2-ylmethyl 1H-indol-4/-5-ylcarbamates are obtained in high yields from (S)-glycidol. These are readily transformed to oxazolidin-2-ones, very interesting building blocks in drug synthesis.     

Studies on heterocyclic compounds: 1,3-thiazolidin-4-one derivatives. IV. Biological activity of variously substituted 2,3-diaryl-1,3-thiazolidin-4-ones

The following 2,3-diaryl-1,3-thiazolidin-4-ones of general formula (A) were synthesized and screened for antimicrobial activity. (formula; see text) where: X = H (I, III, V, VII, IX, XI, XIII, XV, XVII, XIX, XXI, XXIII), CH3 (II, IV, VI, VIII, X, XII, XIV, XVI, XVIII, XX, XXII, XXIV); R = H (I, II, V, VI, VII, VIII, XI, XIII), 4-CH3 (XXI, XXII, XXIII, XXIV), 4-Br (III, IV, IX, X), 2-NO2 (XIII, XIV), 3-NO2 (XV, XVI), 4-NO2 (XVII, XVIII), 4-OCH3 (XIX, XX); R' = H (I, II, III, IV, XIII, XIV, XV, XVI, XVII, XVIII, XIX, XX, XXI, XXII), 4-CH3 (XXIII, XXIV), 3-Br (V, VI), 4-Br (VII, VIII, IX, X), 4-J (XI, XII). These compounds were prepared by the general synthetic procedure previously reported for the 1,3-thiazolidin-4-one derivatives already prepared and screened in this SARs program. The synthetic approach involves the cyclocondensation of the appropriate Schiff bases with alpha-mercaptoalkanoic acids. The prepared compounds were screened against S. aureus, S. beta-haemolititicus, B. subtilis, M. paratuberculosis 607, S. typhi, Kl. pneumoniae, E. coli Bb, Ps, aeruginosa, C. albicans, A. niger, S. cerevisiae by a disk-diffusion assay (Kirby-Bauer modified). The results obtained in this investigation showed that the prepared compounds exhibited varying degrees of antimicrobial activity. They were especially inhibitory toward Gram-positive bacteria, and fungi. 4-Nitroderivatives (XVII), (XVIII), and 2-nitroderivatives (XIV) and (XIII) possessed marked antimicrobial activity against S. aureus, S. beta-haemoliticus, and B. subtilis.(ABSTRACT TRUNCATED AT 250 WORDS)     

4-alkoxy-3-arylfuran-2(5H)-ones as inhibitors of tyrosyl-tRNA synthetase: synthesis, molecular docking and antibacterial evaluation

A series of novel 4-alkoxy-3-arylfuran-2(5H)-ones as tyrosyl-tRNA synthetase inhibitors were synthesized. Of these compounds, 3-(4-hydroxyphenyl)-4-(2-morpholinoethoxy)furan-2(5H)-one (27) was the most potent. The binding model and structure-activity relationship indicate that replacement of morpholine-ring in the side chain of 27 with a substituent containing more hydrophilic groups would be more suitable for further modification. Antibacterial assay revealed that the synthetic compounds are effective against growth of Gram-positive organisms, and 27 is the most potent agent against Staphylococcus aureus ATCC 25923 with MIC(50) value of 0.23 μg/mL.     

Model of Staphylococcus aureus central venous catheter-associated infection in rats.

BACKGROUND AND PURPOSE: Staphylococcus aureus is an important cause of intravascular catheter-associated bacteremia. We developed a rat central venous catheter (CVC)-associated infection model to study pathogenesis and treatment. METHODS: A silastic lumen-within-lumen catheter and rodent-restraint jacket were designed. Subcutaneously tunneled catheters were inserted in the jugular vein of 20 male Sprague Dawley rats. Twelve rats (group 1) were inoculated with S. aureus via the CVC; three rats (group 2) were inoculated with S. aureus via the tail vein, five rats (group 3) served as uninfected controls; and three rats (group 4) were inoculated with S. aureus via the tail vein but did not undergo CVC insertion. Five to eight days after inoculation, animals were euthanized, CVCs were aseptically removed, and quantitative culture was done. Quantitative culture also was performed on blood, heart, liver, lungs, and kidneys. RESULTS: Infection, characterized by bacteremia and metastatic disease, was observed in all rats inoculated via the CVC with as few as 100 colony-forming units (CFU) of S. aureus. Rats of group 2 were not as likely to develop CVC-associated infection, and none of the animals of groups 3 or 4 developed infection. CONCLUSIONS: This model of CVC-associated infection should prove suitable for studying pathogenesis and treatment of the condition.     

Design,synthesis, and biological evaluation of a series of beta-lactam-based prodrugs

By use of pro-dual-drug concept the synthesis of 6-beta-[(R)-2-(clavaminio-9-N-yl)-2-(4-hydroxyphenylacetamido)]penicillanic acid (10), 6-beta-[(R)-2-(amino)-2-(4-(clavulano-9-O-yl)phenylacetamido)]penicillanic acid (13), (Z)-4-[2-(amoxycillin-4-O-yl)ethylidene]-2-(clavulano-9-O-yl)-3-methoxy-Delta(alpha,beta)-butenolide (19), and 3-[(amoxicillin-4-O-yl)methyl]-7-(phenoxyacetamido)-(1-oxo)-3-cephem-4-carboxylic acid (23) was accomplished. Unlike penicillin G, ampicillin, or amoxicillin, these four heretofore undescribed compounds 10, 13, 19, and 23 showed notable activity against beta-lactamase (betaL) producing microorganisms, Staphylococcus aureus A9606, S. aureus A15091, S. aureus A20309, S. aureus 95, Escherichia coli A9675, E. coli A21223, E. coli 27C7, Pseudomonas aeruginosa 18S-H, and Klebsiella pneumoniae A20634 TEM. In comparison with amoxicillin (9), alpha-amino-substituted compound 10 and butenolide derivative 19 showed a broadened spectrum of antibacterial activity; yet they were found to be less active than 13 and 23. Like clavulanic acid (7) or cephalosporin-1-oxide (21), the newly synthesized compounds 10, 13, 15, 16, 19, or 23 functioned as potent inhibitors of various bacterial betaLs.     

Synthesis of s-triazine-based thiazolidinones as antimicrobial agents

A novel series of thiazolidinone derivatives, namely 4-{4-dimethylamino-6-[4-oxo-2-phenyl-5-(4-pyridin-2-yl-piperazin-1-ylmethyl)-thiazolidin-3-yl]-[1,3,5]-triazin-2-yloxy}-1-methyl-1H-quinolin-2-ones, have been synthesized from the key intermediate 4-(4-amino-6-dimethylamino-[1,3,5]-triazin-2-yloxy)-1-methyl-1H-quinolin-2-one (5). Compound 5 was condensed with various aldehydes to give Schiff base derivatives, which after cyclization gave thiazolidinones that were linked with 1-pyridin-2-yl-piperazine to obtain the target compounds. The newly synthesized compounds were evaluated for their antimicrobial activity against eight bacteria (Staphylococcus aureus, Bacillus cereus, Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, Salmonella typhi, Proteus vulgaris, Shigella flexneri) and four fungi (Aspergillus niger, Candida albicans, Aspergillus fumigatus, Aspergillus clavatus).     

2,6-disubstituted pyran-4-one and thiopyran-4-one inhibitors of DNA-Dependent protein kinase (DNA-PK)

6-aryl-2-morpholin-4-yl-4H-pyran-4-ones and 6-aryl-2-morpholin-4-yl-4H-thiopyran-4-ones were synthesised and evaluated as potential inhibitors of the DNA repair enzyme DNA-dependent protein kinase (DNA-PK). Several compounds in each series exhibited superior activity to the chromenone LY294002, and were of comparable potency to the benzochromenone NU7026 (IC(50)=0.23 microM). Importantly, members of both structural classes were found to be selective inhibitors of DNA-PK over related phosphatidylinositol 3-kinase-related kinase (PIKK) family members. A multiple-parallel synthesis approach, employing Suzuki cross-coupling methodology, was utilised to prepare libraries of thiopyran-4-ones with a range of aromatic groups at the 3'- and 4'-positions on the thiopyran-4-one 6-aryl ring. Screening of the libraries resulted in the identification of 6-aryl-2-morpholin-4-yl-4H-thiopyran-4-ones bearing naphthyl or benzo[b]thienyl substituents at the 4'-position, as potent DNA-PK inhibitors with IC(50) values in the 0.2-0.4 microM range.     

RAPID DETECTION of STAPHYLOCOCCUS AUREUS IN FOOD BY FLOW CYTOMETRY

This report describes the detection of Staphylococcus aureus in buffer and in several kinds of food by flow cytometry. Fluorescein isothiocyanate conjugated anti-protein A antibodies were used in a 4-h procedure to label cells, 10⁵-10⁶ cells/mL are needed. the use of single parameter, green fluorescence, enabled specific differentiation of S. aureus from other bacteria including 11 Staphylococcus species. the flow cytometric method can detect S. aureus in food samples after 48-h enrichment in trypticase soy broth with 10% NaCl. As low as 2 S. aureus cells present in 10 mL enrichment broth could grow to a population density detectable by the flow cytometric method after enrichment. This method was faster and less laborious than the conventional BAM (Bacteriological Analytical Manual) or AOAC (Association of Official Analytical Chemists) methods, and could be automated for analysis of S. aureus in food.     

A Staphylococcus aureus mouse keratitis topical infection model: cytokine balance in different strains of mice

Staphylococcus is a leading cause of the potentially blinding disease microbial keratitis. Even with the use of antibiotic therapy, the host inflammatory response continues to damage the cornea, which may lead to blindness. Manipulation of the host response may help improve patient outcome from this devastating disease. We aim to understand the contribution of the host response to Staphylococcus aureus infection. A S. aureus keratitis mouse model was developed in both C57BL/6 and BALB/c mice using two different strains of S. aureus (8325-4 and Staph 38). Twenty-four hours postinfection, mice were killed and eyes were harvested for enumeration of bacteria, polymorphonuclear leucocytes, chemokines and cytokines. The laboratory strain 8325-4 was not as virulent as the clinical isolate Staph 38. In vitro data showed a 250-fold increase in invasion of human corneal epithelial cells by Staph 38 compared to 8325-4. BALB/c mice were susceptible to S. aureus infection whereas C57BL/6 mice were resistant. The resistant C57BL/6 mice were polarized towards a Th2 response, which may be protective for these mice. IL-4, IL-10 and IL-6 were elevated significantly in C57BL/6 mice infected with Staph 38 (P < 0.05). Macrophage inflammatory peptide (MIP)-2 was also significantly elevated in C57BL/6 mice (P < 0.001). The susceptible BALB/c mice had a muted cytokine response, which suggests that S. aureus might be 'walled off' during infection and might avoid host defences. IL-4, IL-10 and IL-6 cytokines may be protective during Gram-positive corneal infection and therefore may be useful for adjunct therapies in the treatment of this disease.