Synthesis and in vitro evaluation of substituted phenyl-piperazinyl-phenyl oxazolidinones against Gram-positive bacteria

With the incidence of linezolid-resistant Enterococcus faecalis, E. faecium and Staphylococcus aureus, modification of linezolid at the 5- and/or 3-positions led to the development of a series of 3-(methoxyl-phenyl)-piperazinyl-phenyl oxazolidinone analogues. These compounds were tested in vitro against six gram-positive standard organisms (S. aureus, S. epidermidis, S. pneumoniae, S. albus, Streptococcus enteridis and S. nonhemolyticus). 5-acetylaminomethyl oxazolidinones bearing fluorine at 3'-position of phenyl ring showed activities against several gram-positive bacteria (MIC: 3.13-6.25 mug/mL). The position of methoxyl group on the phenyl ring of piperazine group affected antibacterial spectrum. 3-(4'- (para-methoxyl-phenyl)-piperazinyl)-(3'-fluoro)-phenyl-5-acetylaminomethyl oxazolidinone was found active against 5 gram-positive organisms except S. nonhemolyticus, whereas 3-(4'-(ortho-methoxyl-phenyl)-piperazinyl)-(3'-fluoro)-phenyl-5-acetylaminomethyl oxazolidinone was found active only against 2 gram-positive organisms, namely S. albus, S. enteridis.     

Conformational constraint in oxazolidinone antibacterials. Synthesis and structure-activity studies of (azabicyclo[3.1.0]hexylphenyl)oxazolidinones

The oxazolidinones are a new class of synthetic antibacterials effective against a broad range of pathogenic Gram-positive bacteria, including multi-drug-resistant strains. Linezolid is the first drug from this class to reach the market and has become an important new option for the treatment of serious infections, particularly those caused by methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enteroccocus faecium (VRE). In the search for novel oxazolidinones with improved potency and spectrum, we have prepared and evaluated the antibacterial properties of conformationally constrained analogues in which the morpholine ring of linezolid is replaced with various substituted azabicyclo[3.1.0]hexyl ring systems. Several classes of azabicyclic analogues were identified with activity comparable or superior to that of linezolid. These include analogues bearing hydroxyl, amino, amido, or carboxyl groups on the azabicyclic ring. The azabicyclic acid analogue 50 was 4 times more potent than linezolid against key Gram-positive and fastidious Gram-negative pathogens (S. aureus, Streptococcus pneumoniae, and E. faecalis MICs < or = 1 microg/mL; Haemophilus influenzae MIC = 4 microg/mL).     

Synthesis and in vitro antibacterial activity of some N-(5-aryl-1,3,4-thiadiazole-2-yl)piperazinyl quinolone derivatives

A series of N-[5-(1-methyl-5-nitro-2-imidazolyl)-1,3,4-thiadiazole-2-yl] and N-[5-(nitrophenyl)-1,3,4-thiadiazole-2-yl] piperazinyl quinolone derivatives (5a-c and 5d-l) were synthesized and evaluated for in vitro antibacterial activity against some Gram-positive and Gram-negative bacteria. The antibacterial data revealed that all nitroimidazole derivatives (5a-c) showed interesting activity against tested Gram-positive bacteria (minimum inhibitory concentration, MIC=0.008-0.03 microg/ml) while they did not show good activity against Gram-negative organisms. Despite the significant activity of nitroimidazole series, all nitrophenyl analogues (5d-l) were inactive against both Gram-positive and Gram-negative bacteria. Among all of the tested compounds, 5a (ciprofloxacin derivative in nitroimidazole series) exhibited excellent activity against Staphylococcus aureus and Staphylococcus epidermidis (MIC=0.008 microg/ml).     

Synthesis of 3-substituted-5-(4-carb oxycyclohexylmethyl) - tetrahydro-2H-1,3,5-thiadiazine-2-thione derivatives as antifibrinolytic and antimicrobial agents

A series of 3-substituted-5-(4-carboxycyclohexylmethyl)-tetrahydro-2H-1,3,5thiadiazine-2-thione derivatives was prepared and examined for antifibrinolytic and antimicrobial activities. Their structures were elucidated by spectral methods. Antifibrinolytic activities of these compounds, were investigated in vitro and compared to tranexamic acid (CAS 1197-18-8). Among the synthesized compounds, 3-methyl-5-(4-carboxycyclohexylmethyl)-tetrahydro-2H-1,3,5-thiadiazine-2-thione (Ia) was the most prominent one (104%) when compared to tranexamic acid. Besides, 3-ethyl-5-(4-carboxycyclohexyl-methyl)-tetrahydro-2H-1,3,5-thiadiazine-2-thione (Ib), 3-iso-propyl-5-(4-carboxycyclohexylmethyl)-tetrahydro-2H-1,3,5-thiadiazine-2-thione (Id) and 3-isobutyl-5-(4-carboxycyclohexyl-methyl)-tetrahydro-2H-1,3,5-thiadiazine-2-thione (Ig) showed antifibrinolytic activity similar to tranexamic acid. Antibacterial activities of these compounds against Gram-positive bacteria (Staphylococcus aureus, Bacillus subtilis), Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa) and yeast-like fungi (Candida albicans, Candida tropicalis) were investigated by the micro-dilution method and compared with the activity of tranexamic acid, ofloxacin and fluconazole. By this way their minimal inhibitory concentration (MIC), minimal bactericidal concentration (MBC) and minimal fungicidal concentration (MFC) values were determined. Compound Ia exhibited almost equally potent activity against B. subtilis (MIC and MBC: 6.25 microg/mL). Compounds Ib-Id, If-Ig and In exhibited similar bactericidal activity against B. subtilis (MBC: 12.5 microg/mL). Compounds Ik and Im showed bacteriostatic activity against S. aureus. None of the compounds exhibited activity against Gram-negative bacteria. On the other hand, all compounds had potent antifungal activities against the yeast utilized. Among the synthesized compounds, 3-methyl-5-(4-carboxycyclohexylmethyl)-tetrahydro-2H-1,3,5-thiadiazine-2-thione (Ia) seems to be the most effective compound with antifibrinolytic and antimicrobial activity.     

Potent antibacterial activity of halogenated compounds against antibiotic-resistant bacteria

Common Gram-positive clinical pathogens are showing an increasing trend for resistance to conventional antimicrobial agents. New drugs with potent antibacterial activities are urgently needed to remediate this problem. Halogenated compounds isolated from several species of the red algae genus Laurencia were examined for their antibacterial activity against 22 strains of human pathogenic bacteria, 7 strains of which were antibiotic-resistant bacteria. Four phenolic sesquiterpenes and a polybrominated indole showed wide spectra of antibacterial activity against Gram-positive bacteria including methicillin-resistant Staphylococcus aureus (MRSA), penicillin-resistant Streptococcus pneumoniae, and vancomycin-resistant Enterococcus faecalis and E. faecium (VRE). In addition, laurinterol and allolaurinterol displayed potent bactericidal activity against three strains of MRSA at 3.13 microg mL(-1), and three strains of vancomycin-susceptible Enterococcus, at 3.13 microg mL(-1) and 6.25 microg mL(-1), respectively.     

Synthesis and in-vitro antibacterial activity of 5-substituted 1-methyl-4-nitro-1H-imidazoles

A series of 5-substituted 1-methyl-4-nitro-1H-imidazole derivatives were synthesized and evaluated for in-vitro antibacterial activity against a panel of microorganisms including Staphylococcus aureus, Staphylococcus epidermidis, Bacillus subtilis, Escherichia coli, Klebsiella pneumonia, Enterobacter aerogenes, and Helicobacter pylori using conventional agar dilution method. Among the test compounds, 1-methyl-4-nitro-5-(phenylsulfonyl)-1H-imidazole was the most potent against Gram-positive bacteria, with a MIC value of < or =8 microg/mL. All compounds showed no significant activity against Gram-negative bacteria at concentrations < or =64 microg/mL. The MIC values against 15 clinical isolates of H. pylori indicated that compounds 10 and 11 were the most active compounds in this series in terms of inhibiting the growth of H. pylori (MIC = 2 microg/mL). It was also demonstrated that their corresponding activities were four times larger than that of metronidazole.     

Structure-based design of a macrocyclic inhibitor for peptide deformylase

A macrocyclic, peptidomimetic inhibitor of peptide deformylase was designed by covalently cross-linking the P1' and P3' side chains. The macrocycle, which contains an N-formylhydroxylamine side chain as the metal-chelating group, was synthesized from a diene precursor via olefin metathesis using Grubbs's catalyst. The cyclic inhibitor showed potent inhibitory activity toward Escherichia coli deformylase (K(I) = 0.67 nM) and antibacterial activity against both Gram-positive and Gram-negative bacteria (MIC = 0.7-12 microg/mL).     

In-vitro activity of panipenem against clinical isolates in 2006

The antimicrobial activity of various antibiotics against clinical bacterial isolates recovered from patients with infectious diseases at the medical facilities in the Kanto region between March and September 2006 was evaluated. A total of 1030 clinical isolates were available for susceptibility tests: 420 aerobic Gram-positive organisms, 520 aerobic Gram-negative organisms, 30 anaerobic Gram-positive organisms and 60 anaerobic Gram-negative pathogens. Antimicrobial susceptibility data for Streptococcus pneumoniae and Haemophilus influenzae isolates from pediatric and adult patients were analyzed separately. Panipenem (PAPM), imipenem (IPM), meropenem (MEPM), biapenem (BIPM), doripenem (DRPM), cefozopran (CZOP), cefepime (CFPM), and sulbactam/cefoperazone (SBT/CPZ) were used as test antibiotics. PAPM, IPM and DRPM exhibited excellent in vitro antibacterial activities against methicillin-susceptible Staphylococcus, with all isolates exhibiting a MIC of < or =0.06 microg/mL. Against Streptococcus including penicillin-resistant S. pneumoniae, PAPM demonstrated the strongest antibacterial activity among the carbapenems with a MIC range of < or =0.06 to 0.12 microg/mL. Against Enterobacteriaceae, MEPM showed the strongest antibacterial activity, and PAPM had comparable activity to IPM. Against the extended-spectrum beta-lactamase producing Escherichia coli, Klebsiella species and Proteus species, the MICs for the cephems were high, however, those for the carbepenems were low. Against H. influenzae, PAPM had comparable activity to IPM. With respect to anaerobes, each of the carbapenems tested demonstrated almost the same strong antibacterial activity. In conclusion, 13 years has passed since PAPM was launched in 1993, PAPM still maintains potent antibacterial activity and is considered an effective antimicrobial agent for various types of infectious diseases.     

Synthesis and in vitro antibacterial evaluation of novel imidazo[2',1':5,1]-1,2,4-triazolo[4,3-c]-quinazoline derivatives of 5-thioxo-1, 2, 4-triazole, 4-oxothiazolidine, and their open-chain counterparts

Two novel series of imidazo[2', 1':5, 1]-1, 2, 4-triazolo[4, 3-c]quinazolines bearing 5-thioxo-1, 2, 4-triazoles, 6a-f, and 4-oxothiazolidines, 7a-f, were synthesized from corresponding thiosemicarbazide derivatives, 5a-f. The stepwise methodology applied to the preparation of compounds 5a-f was initiated with reaction of the parent 3-amino-1, 2, 4-triazolo[4, 3-c]quinazolines, 2, with ethyl 2-chloroacetoacetate resulting in annelation of the imidazole ring to give esters, 3a-c. However, hydrazinolysis of these ester derivatives gave the corresponding acid hydrazides, 4a-c, which on reaction with the appropriate alkyl isothiocyanate yielded compounds 5a-f. In turn, compounds 5, were cyclized with potassium hydroxide or with ethyl bromoacetate to give the corresponding thioxotriazoles 6 and oxothiazolidines 7, respectively. All synthesized compounds were screened for their in vitro antibacterial activity against various Gram-positive and Gram-negative bacteria. Some test compounds were found to possess potent antibacterial activities. Compound, 7f, exhibited much higher potency than the reference standard ciprofloxacin, against both types of bacteria, particularly, Gram-positive organisms.     

In vitro antibacterial activity of FK041, a new orally active cephalosporin.

The in vitro activity of FK041, a new orally active cephem antibiotic, against a wide variety of clinical isolates of bacteria was investigated and compared with those of cefdinir (CFDN) and cefditoren (CDTR). FK041 exhibited broad spectrum activity against reference strains of Gram-positive and Gram-negative aerobes and anaerobes. FK041 was active against clinical isolates of Gram-positive organisms except Enterococcus faecalis with MIC90s less than 1.56 microg/ml. FK041 was more active than CFDN and CDTR against Staphylococcus aureus, Staphylococcus epidermidis, and Streptococcus agalactiae and was comparable to CFDN and CDTR against Streptococcus pyogenes and Streptococcus pneumoniae. FK041 had no activity against methicillin-resistant staphylococci, like CFDN and CDTR. FK041 showed moderate activity against penicillin-resistant S. pneumoniae with an MIC range of 0.05 approximately 3.13 microg/ml, and was superior to CFDN but inferior to CDTR. Against clinical isolates of many Gram-negative organisms such as Neisseria gonorrhoeae, Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis, FK041 had good activity comparable or superior to those of CFDN and CDTR. However, it was inferior to CDTR in activity against Moraxella catarrhalis, Haemophilus influenzae, Morganella morganii, and Serratia marcescens, and was inactive against Pseudomonas aeruginosa. With FK041 a small difference between MIC and MBC against S. aureus, E. coli, K. pneumoniae, and H. influenzae was found, indicating that its action is bactericidal against these species. FK041 was stable to group 2beta-lactamase hydrolysis but was unstable to group 1beta-lactamase hydrolysis. The stability of FK041 to these enzymes was similar to those of CFDN and CDTR. FK041 showed high affinity for the main penicillin-binding proteins (PBPs) of S. aureus (PBP 3, 2, and 1) and E. coli (PBP 3, 4, lbs, 2, and 1a).     

Comparative in vitro activity of gatifloxacin, grepafloxacin, levofloxacin, moxifloxacin and trovafloxacin against 4151 Gram-negative and Gram-positive organisms

Gatifloxacin, grepafloxacin, moxifloxacin and trovafloxacin are fluoroquinolones with enhanced Gram-positive activity while retaining broad-spectrum activity against Gram-negative pathogens. Levofloxacin and ciprofloxacin are older quinolones with broad activity against Gram-negative pathogens and borderline activity against some Gram-positive organisms. We compared the in vitro activity of these compounds against 4151 Gram-negative and -positive organisms. Gatifloxacin, grepafloxacin, moxifloxacin and trovafloxacin were highly active against penicillin sensitive and resistant Streptococcus pneumoniae, Staphylococcus aureus, Streptococcus pyogenes and Streptococcus agalactiae. Ciprofloxacin and levofloxacin were active but less potent. All compounds were highly active (overall) against Gram-negative pathogens with ciprofloxacin being the most active agent against Pseudomonas aeruginosa. Our data indicate that the advanced fluoroquinolones will be important compounds for treating infections caused by Gram-positive and Gram-negative pathogens.     

Synthesis and microbiological activity of some N-(o-hydroxyphenyl)benzamides and phenylacetamides as the possible metabolites of antimicrobial active benzoxazoles: part II

The synthesis of some N-(o-hydroxyphenyl)benzamides and benzacetamides (2a-2p) in order to determine their in vitro antimicrobial activity against two Gram-positive bacteria, three Gram-negative bacteria and the fungus Candida albicans is described. The new compounds were compared with several control drugs. The derivative 2g, 4-amino-N-(o-hydroxyphenyl)benzamide, was found active at an MIC value of 25 microg/ml against the Gram-negative microorganism Klebsiella pneumoniae. Most of the compounds exhibited antibacterial activity at an MIC value of 25 microg/ml against Pseudomonas aureginosa. For the antifungal activity against C. albicans, compounds 2e, 2h and 2m were found more active than the other derivatives (MIC 12.5 microg/ml). The antimicrobial activity of some of these benzamide and phenylacetamide derivatives (2a, 2b, 2f, 2g, 2h and 2k), possible metabolites of benzoxazoles, was also compared with that of the cyclic analogues 3-8. Compound 2f possesses two dilutions better antifungal activity than its cyclic analogue the benzoxazole derivative 5 against C. albicans, while having one dilution better antibacterial activity against Streptococcus faecalis and K. pneumoniae.     

Synthesis and antibacterial activity of nitroaryl thiadiazole-levofloxacin hybrids

Novel levofloxacin-containing hybrids carrying a 5-(nitroaryl)-1,3,4-thiadiazol-2-yl group were synthesized and evaluated in vitro against Gram-positive and Gram-negative bacteria. Preliminary data indicated that levofloxacin-nitrofuran and levofloxacin-nitroimidazole hybrids have a potent activity against Gram-positive organisms with enhanced anti-staphylococcal activity compared with the parent quinolone (N-desmethyl levofloxacin).     

Synthesis and antimicrobial activity of new 2-[p-substituted-benzyl]-5-[substituted-carbonylamino]benzoxazoles

A series of 23 new 2-[p-substituted-benzyl]-5-[p-substituted-phenyl/benzyl-carbonylamino]benzoxazole derivatives has been synthesized by reacting 5-amino-2-[p-substituted-benzyl]benzoxazoles with the appropriate carboxylic acid chlorides. The structures of the synthesized compounds were confirmed by IR and (1)H-NMR spectral data. Antimicrobial activities of the compounds were investigated using the twofold serial dilution technique against two gram-positive and two gram-negative bacteria and three Candida species in comparison with standard drugs. Microbiological results indicated that the newly synthesized 2-[p-substituted-benzyl]-5-[p-substituted-phenyl/benzyl-carbonylamino]benzoxazole derivatives (3-25) possessed a broad spectrum of activity, showing MIC values of 6.25-200 microg/mL against the gram-positive and gram-negative microorganisms tested. Moreover, they showed significant antifungal activity with MIC values of 3.12-100 microg/mL against the Candida species tested. Especially, with a MIC value of 3.12 microg/mL, 2-benzyl-5-[p-bromobenzyl-carbonylamino]benzoxazole 9 displayed the same activity against C. glabrata as the standard drug myconazol.     

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.     

Antitrypanosomal activity of 5'-deoxy-5'-(iodomethylene)adenosine and related 6-N-cyclopropyladenosine analogues

Treatment of the 6-N-cyclopropyl-2',3'-di-O-isopropylideneadenosine 5'-aldehyde with sulfone-stabilized phosphonate or fluorophosphonate reagents followed by stannyldesulfonylations and subsequent iodo- or protiodestannylation gave 6-N-cyclopropyl-5'-deoxy-5'-(iodomethylene)adenosine 8b or its 5'-fluoromethylene analogue 11. Treatment of the 5'-aldehyde with hydroxylamine or dibromomethylene- or cyanomethylene-stabilized Wittig reagents and deprotections gave the oxime 4b, 5'-cyanomethylene 5b, and 5'-dibromomethylene 13b analogues. Dehydrobromination of 13b gave acetylenic compound 14b. From the tested 6-N-cyclopropyladenosine analogues modified at the 5' carbon, the 5'-iodomethylene 8b had the most potent activity against Trypanosoma brucei in vitro with an IC50 of 12 microg/mL. The IC50 value was 19 microg/mL for both the 5'-fluoromethylene 11 and the 5'-cyanomethylene 5b compounds. The (E)-5'-deoxy-5'-(iodomethylene)adenosine 2a, a known inhibitor of AdoHcy hydrolase not modified with a cyclopropyl ring at 6-amino group, also inhibited T. brucei with an IC50 of 9 microg/mL. In contrast to some other adenosine analogues modified at C5', the 6-N-cyclopropyladenosine analogues described here do not exhibit an inhibitory effect on AdoHcy hydrolase and displayed only marginal antiviral activity.     

Antibacterial diterpenoids from Sagittaria pygmaea

There were five new diterpenoids, 18-beta-D-3',4'-diacetoxyxylopyranosyl-ent-kaur-16-ene (1), 18-beta-L-3',5'-diacetoxyarabinofuranosyl-ent-kaur-16-ene (2), 18-beta-D-3',6'-diacetoxyglucopyranosyl-ent-kaur-16-ene (3), ent-isopimar-8(14),15-dien-19-oic acid (4), and 5alpha-hydroxy-ent-rosa-15-en-18-oic acid (5), isolated from the whole herb of Sagittaria pygmaea. Their structures and relative configurations were established based on spectroscopic studies, chemical methods, and X-ray crystallographic analysis. Compound 2 exhibited significant antibacterial activity against the oral pathogens, Streptococcus mutans ATCC 25 175 and Actinomyces viscosus ATCC 27 044, with MIC values against both pathogens of 15.6 microg/mL. Compound 3 was active against only A. viscosus ATCC 27 044 with an MIC value of 62.5 microg/mL. Compounds 4 and 5 were active against S. mutans ATCC 25 175 and A. viscosus ATCC 27 044, with MIC values against both pathogens of 125.0 microg/mL.     

Antibacterial and anticoagulant activities of coumarins isolated from the flowers of Magydaris tomentosa

The phytochemical investigation of the acetone and methanol extracts of the flowers of Magydaris tomentosa (Desf.) DC afforded six known coumarins as well as (+)-meranzin hydrate (7), not previously reported as a natural product. The antibacterial activity of umbelliprenin (1), osthol (2), imperatorin (3), citropten (4) and (+)-meranzin hydrate (7) was tested against Gram-positive and Gram-negative bacteria. All coumarins (1-7) isolated in this study inhibited growth of all bacterial strains tested (MIC between 16 and 256 microg/mL), the most active being imperatorin (3) (MICs between 32 and 128 microg/mL) and citropten (4) (MICs between 16 and 256 microg/mL). The anticoagulant activity of compounds 1-4 and 7 was also evaluated.     

Conformational movement of F251 contributes to the molecular mechanism of constitutive activation in the C5a receptor

Some novel chemically synthesized 2,4,5-trisubstituted imidazoles from aryl aldehydes and 1,2-diketones or alpha-hydroxyketone were screened against eight different human pathogenic bacteria and fungi. Seven compounds were found to be active against different bacteria. These compounds showed variation in activity and were found to be active against Gram-positive as well as Gram-negative bacteria. Compound 4-(4,5-diphenyl-1H-imidazol-2-yl)-phenol, 3d was the only compound which showed activity against Klebsiella pneumoniae while rest of the compounds did not show significant activity against this micro-organism. Minimum inhibitory concentrations of the compounds were in the range of 0.50 to 6.1 microg/mL and minimum bactericidal concentration ranges from 1.11 to 12.9 microg/mL. The candidature of active compounds to be an effective and novel drug was examined based on Lipinski's rule of Five which explained ClogP, LogS, H-bond acceptors, H-Bond donors and rotational bonds. Compounds 3a-d and 3f satisfies Lipinski's rule of Five and could be proposed as potent new antibacterial drugs.     

Substituent effects on the antibacterial activity of nitrogen-carbon-linked (azolylphenyl)oxazolidinones with expanded activity against the fastidious gram-negative organisms Haemophilus influenzae and Moraxella catarrhalis

A series of new nitrogen-carbon-linked (azolylphenyl)oxazolidinone antibacterial agents has been prepared in an effort to expand the spectrum of activity of this class of antibiotics to include Gram-negative organisms. Pyrrole, pyrazole, imidazole, triazole, and tetrazole moieties have been used to replace the morpholine ring of linezolid (2). These changes resulted in the preparation of compounds with good activity against the fastidious Gram-negative organisms Haemophilus influenzae and Moraxella catarrhalis. The unsubstituted pyrrolyl analogue 3 and the 1H-1,2,3-triazolyl analogue 6 have MICs against H. influenzae = 4 microgram/mL and M. catarrhalis = 2 microgram/mL. Various substituents were also placed on the azole moieties in order to study their effects on antibacterial activity in vitro and in vivo. Interesting differences in activity were observed for many analogues that cannot be rationalized solely on the basis of sterics and position/number of nitrogen atoms in the azole ring. Differences in activity rely strongly on subtle changes in the electronic character of the overall azole systems. Aldehyde, aldoxime, and cyano azoles generally led to dramatic improvements in activity against both Gram-positive and Gram-negative bacteria relative to unsubstituted counterparts. However, amide, ester, amino, hydroxy, alkoxy, and alkyl substituents resulted in no improvement or a loss in antibacterial activity. The placement of a cyano moiety on the azole often generates analogues with interesting antibacterial activity in vitro and in vivo. In particular, the 3-cyanopyrrole, 4-cyanopyrazole, and 4-cyano-1H-1,2,3-triazole congeners 28, 50, and 90 had S. aureus MICs 相似文献