Synthesis and antibacterial evaluation of series of novel tri-substituted-s-triazine derivatives

Two novel series of s-triazine derivatives (6a–e and 7a–f) were synthesized with various aromatic and heterocyclic amines. The synthesized compounds were subsequently evaluated for their in vitro antibacterial activity against three gram-positive viz. Bacillus subtilis (NCIM-2063), Bacillus cereus (NCIM-2156), Staphylococcus aureus (NCIM-2079) and gram-negative bacteria viz. Pseudomonas aeruginosa (NCIM-2036), Escherichia coli (NCIM-2065) and Klebseilla pneumoniae (NCIM-2706) by the broth dilution method as recommended by the National Committee for Clinical Laboratory Standards (NCCLS) using streptomycin as reference standard. Structures of the synthesized compounds were elucidated on the basis of elemental analyses and spectral data.     

Studies on pyrazine derivatives. XLVII. Synthesis and antibacterial activity of novel pyrazine derivatives with amidoxime moiety

The new pyrazine derivatives exhibiting an antibacterial activity have been synthesized. Initial amidoxime 1 was obtained in the reaction of pyrazinecarbonitrile with hydroxylamine. Upon treatment of amidoxime with methyl iodide O-methyl derivative 2 was formed. Both amidoximes were transformed into imidoyl chlorides 3, 4. Then the chloride atom in those derivatives was substituted with various secondary amines giving appropriate oximes 5-18 and O-methyl-oximes 19 and 20. The obtained compounds were tested in vitro for their tuberculostatic activity. The inhibiting concentration (MIC) values were within 25-100 microg/mL. Their activity towards 25 strains of anaerobic and 25 strains of aerobic bacteria was also studied. Three compounds exhibited activity against both types of bacteria.     

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     

Synthesis of novel isoxazolidine derivatives and their antifungal and antibacterial properties

The synthesis of some biologically interesting isoxazolidine derivatives has been accomplished by the cycloaddition reaction of C-(4-biphenyl)-N-(3-methylphenyl) nitrone and C-(4-biphenyl)-N-(3-chlorophenyl) nitrone to monosubstituted alkenes. The compounds were screened for their antibacterial and antifungal activities. Among the tested compounds 3a (ii), 3a (vii), 3a (viii), 3b (iv), 3b (vii), and 3b (viii) showed significant antifungal activity comparable with that of the standard drug Nystatin against Botrydiplodia theobromae.     

Aminothiazolylglycyl derivatives of carbacephems. I. Synthesis and antibacterial activity of novel carbacephems with substituted aminothiazolyl groups

A series of new carbacephem compounds which have substituted aminothiazolylglycyl side chain have been prepared starting from corresponding carbacephems with aminothiazolylmethoxyimino group. Among them, the compound having 3,4-dihydroxybenzoyl group showed very sharp activity against Pseudomonas aeruginosa. Moreover, the optical resolution of alpha carbon of aminothiazolylglycyl moiety was carried out through preparation of optically active side chain and the (S)-isomer (KT-4380) was found to be the most active against Pseudomonas sp. as well as other Gram-negative strains.     

Synthesis and antibacterial activity of various substituted oxadiazole derivatives

Some new 2-(2-(4(4-substitutedbenzoyl-2-methylphenoxy)acetyl)-N-(2-substitutedphenyl) hydrazinecarbothioamides (4a-4j) and (4-((5-(2-substitutedphenylamino)-1,3,4-oxadiazol-2-yl)methoxy)-3-substitutedphenyl)(phenyl)methanones (5a-5j) have been synthesized from 2-(4-(3-substitutedbenzoyl)-2-methylphenoxy)acetohydrazides (3a, 3b). These newly synthesized compounds (4a-4j and 5a-5j) were characterized by elemental and spectral (IR, (1)H-NMR and MS) analysis. All the synthesized compounds have been screened for their antibacterial activity against both types of Gram negative and Gram positive bacteria. The most potent antibacterial compound of this series was compound 5i which has the low MIC 3.75-0.9375 μg/mL value. Both minimal inhibitory concentration (MIC) and inhibition zones were determined in order to monitor the efficacy of the synthesized compounds. Certain compounds inhibit bacterial growth with low MIC (μg/mL) value.     

Synthesis and antibacterial evaluation of certain quinolone derivatives.

A number of 7-substituted quinolone derivatives were synthesized and evaluated for antibacterial and cytotoxic activities. Preliminary results indicated that most compounds tested in this study demonstrated better activity against methicillin-resistant Staphylococcus aureus than norfloxacin. Among them, 1-(4-amino-2-fluorophenyl)-6-fluoro-1,4-dihydro-7-[4-[2-(4-methoxyphenyl)-2-hydroxyiminoethyl]-1-piperazinyl]-4-oxo-3-quinolinecarboxylic acid (11d) and its ketone precursor 10d exhibited significant activities against Klebsiella pneumoniae, methicillin-resistant S. aureus, erythromycin- and ampicillin-resistant Streptococcus pneumoniae, and vancomycin-resistant Enterococcus faecalis. Due to strong cytotoxicities of 11d (a mean log GI(50) of -5.40), compound 10d, with good antibacterial activities and low cytotoxicities (a mean log GI(50) of -4.67), is a more potential drug candidate.     

Sydnone derivatives. Part VII: Synthesis of some novel thiazoles and their pharmacological properties.

The synthesis of some 4-(arylsydnonyl)-2-(4-arylhydrazono-3-methyl-5-oxo-2-pyrazolin-1-yl)- thiazoles by reacting 1-thiocarboxamido-3-methyl-4-(aryihydrazono)-2-pyrazolin-5-ones with different 4-bromoacetyl-3-arylsydnones is described. A few compounds from this series were screened for their anti-inflammatory, analgesic, and CNS depressant activities. Among the tested compounds 6s, 6d, 6n, and 6u showed significant anti-inflammatory activity comparable with that of standard drug Ibuprofen. Compounds containing chlorine and carboxylic substituents are more active. 6f, 6r, and 6u showed marked analgesic activity and most of the compounds tested showed promising CNS depressant activity comparable with that of standard drug pentobarbitone.     

疟疾防治药物的研究——ⅩⅢ.3-取代氨基喹唑酮-4衍生物的合成

Twenty-five compounds of N³-amino substituted quinazolone-4 have been synthesized and screened for activities against Plasmodium berghei and P yoelii in mice. No activity was found in these compounds.     

Synthesis and antibacterial activity of 5- and 6-hydroxy substituted 4-aminoquinolines and derivatives

The synthesis and antimicrobial activity of 4-amino-8-methylquinolines 8, 11 substituted with a hydroxy- or methoxy-group at 5- and at 6-position have been investigated. The title compounds could be prepared by a six-step procedure according to the literature starting from commercially available anilines 1. The novel 4-aminoquinolines 8,11 exhibited slight antibacterial activity against Gram-positive and Gram-negative bacteria.     

Synthesis of variously substituted 1,8-naphthyridine derivatives and evaluation of their antimycobacterial activity

A series of 1,8-naphthyridine derivatives variously substituted in the 2, 3, 4 and 7 positions were synthesized for in vitro evaluation of antimycobacterial activity in accordance with an international program with the tuberculosis antimicrobial acquisition and coordinating facility (TAACF). Several compounds 4, 8, 12, 14, 19, 29 and 30, when tested at a concentration of 6.25 microg/ml against Mycobacterium tuberculosis H37Rv, showed an interesting activity with % inhibition in the range 38-96%. The most effective substituent in position 2, 4 or 7 of the 1,8-naphthyridine nucleus seem to be the piperidinyl group.     

Synthesis and antibacterial evaluation of 2-(substituted phenylureido)-4-thiocyanatobenzothiazoles

The synthesis and antibacterial evaluation of a number of 2-(substituted phenylureido)-4-thiocyanatobenzothiazoles are described. The more active compounds against the test organisms in vitro generally were those substituted with halogens on the phenyl and benzothiazole rings.     

Synthesis and biological evaluation studies of novel quinazolinone derivatives as antibacterial and anti-inflammatory agents

Some novel 6,8-diiodo-2-methyl-3-substituted-quinazolin-4(3H)-ones bearing sulfonamide derivatives (4–11) were synthesized in good yields and evaluated for their possible antibacterial, anti-inflammatory activities and acute toxicity. The structures of the synthesized compounds were confirmed on the basis of their spectral data and elemental analysis. Their antibacterial activities were evaluated by the agar well diffusion method while their anti-inflammatory activities were evaluated by the carrageenan-induced hind paw edema test. All the tested compounds showed considerable antibacterial activities and high to moderate anti-inflammatory activities that last for 12 h compared to ibuprofen. All the tested compounds showed no toxic symptoms or mortality rates 24 h post-administration at tested anti-inflammatory doses. In addition, LD₅₀ for all tested compounds was higher than that for ibuprofen implying their good safety margin. The obtained results showed that the most active compounds could be useful as a template for future design, modification and investigation to produce more active analogs.     

Synthesis of novel 4-substituted phenazone derivatives as potential antibacterial and antineoplastic agents

A new series of substituted phenazone derivatives has been prepared, through a series of reactions that are illustrated in Scheme I. The antibacterial and antineoplastic activities of the prepared compounds were evaluated. While none of the synthesized products showed marked antibacterial activity, all of them possessed a significant antitumor effect.