Synthesis and antibacterial activity of N-[2-[5-(methylthio)thiophen-2-yl]-2-oxoethyl] and N-[2-[5-(methylthio)thiophen-2-yl]-2-(oxyimino)ethyl]piperazinylquinolone derivatives

3-(Bromoacetyl)coumarins: unraveling their synthesis, chemistry, and applications

This review emphasizes recent developments in synthetic routes of 3-(bromoacetyl)coumarin derivatives. Also, chemical reactions of 3-(bromoacetyl)coumarins as versatile building blocks in the preparation of critical polyfunctionalized heterocyclic systems and other industrially significant scaffolds are described. Recent advances of 3-(bromoacetyl)coumarins as attractive starting points towards a wide scale of five and six-membered heterocyclic systems such as thiophenes, imidazoles, pyrazoles, thiazoles, triazoles, pyrans, pyridines, thiadiazins as well as fused heterocyclic systems have been reported. Additionally, this review covers a wide range of analytical chemistry, fluorescent sensors, and biological applications of these moieties, covering the literature till May 2021.

N-substituted piperazinyl sarafloxacin derivatives: synthesis and in vitro antibacterial evaluation

Background

Fluoroquinolones (FQs) are compounds of major interest with broad antimicrobial activities against community and hospital-acquired infections such as respiratory tract infections (nosocomial pneumonia, chronic bronchitis and tuberculosis), skin and soft tissue infections, bone and joint infections, intra-abdominal infections and sexually transmitted diseases. This broad range of activities along with favorable pharmacokinetic and low toxicity introduced this class of compounds as important antimicrobial chemotherapy agents. The rapid increase in prevalence of FQs resistant microbes in environment motivated medicinal chemists to discover new quinolone-based compounds with potent activities against Gram-positive bacteria.

Methods

The designed compounds were prepared through the two-component reaction between aromatic α-haloketones or α-halooximes and sarafloxacin in the presence of NaHCO₃ in DMF, affording the corresponding N-[2-(aryl-3-yl) ethyl] piperazinyl quinolone derivatives in good yields. All synthesized compounds were evaluated for antibacterial activities against Gram-positive [Staphylococcus aureus ATCC 6538p, Micrococcus luteus, ATCC 1110, Staphylococcus epidermidis ATCC 12228 and Bacillus subtilis ATCC 6633] and Gram-negative [Escherichia coli ATCC 8739, Klebsiella pneumoniae ATCC 10031 Pseudomonas aeruginosa ATCC 9027 and Serratia marcescens PTCC 1111] bacteria.

Results

The antibacterial activities of 24 new compounds were reported as MIC values in comparison to sarafloxacin. The most active compound, 4 g, exhibited similar inhibitory activity against Gram-positive bacteria including S. aureus, S. epidermidis and B. subtilis compared to positive control. Furthermore, benzyloxime incorporated derivatives (4 s-4x) showed poor activity against all tested strains, except 4x.

Conclusion

The obtained results indicated that the synthesized compounds containing substituted piperazine moiety at the C-7 position displayed same or weak inhibitory activities compared to sarafloxacin.

Graphical abstract

Ciprofloxacin derivatives and their antibacterial activities

Bacterial infections represent a significant health threat globally, and are responsible for the majority of hospital-acquired infections, leading to extensive mortality and burden on global healthcare systems. The second generation fluoroquinolone ciprofloxacin which exhibits excellent antimicrobial activity and pharmacokinetic properties as well as few side effects is introduced into clinical practice for the treatment of various bacterial infections for around 3 decades. The emergency and widely spread of drug-resistant pathogens making ciprofloxacin more and more ineffective, so it's imperative to develop novel antibacterials. Numerous of ciprofloxacin derivatives have been synthesized for seeking for new antibacterials, and some of them exhibited promising potency. This review aims to summarize the recent advances made towards the discovery of ciprofloxacin derivatives as antibacterial agents and the structure-activity relationship of these derivatives was also discussed.

4-Quinolone derivatives and their activities against Gram positive pathogens

Gram-positive bacteria are responsible for a broad range of infectious diseases, and the emergency and wide spread of drug-resistant Gram-positive pathogens including MRSA and MRSE has caused great concern throughout the world. 4-Quinolones which are exemplified by fluoroquinolones are mainstays of chemotherapy against various bacterial infections including Gram-positive pathogen infections, and their value and role in the treatment of bacterial infections continues to expand. However, the resistance of Gram-positive organisms to 4-quinolones develops rapidly and spreads widely, making them more and more ineffective. To overcome the resistance and reduce the toxicity, numerous of 4-quinolone derivatives were synthesized and screened for their in vitro and in vivo activities against Gram-positive pathogens, and some of them exhibited excellent potency. This review aims to outlines the recent advances made towards the discovery of 4-quinolone-based derivatives as anti-Gram-positive pathogens agents and the critical aspects of design as well as the structure-activity relationship of these derivatives. The enriched SAR paves the way to the further rational development of 4-quinolones with a unique mechanism of action different from that of the currently used drugs to overcome the resistance, well-tolerated and low toxic profiles.

Synthesis of Oxadiazolyl, Pyrazolyl and Thiazolyl Derivatives of Thiophene-2-Carboxamide as Antimicrobial and Anti-HCV Agents

Introduction:

Three series of pyrazole, thiazole and 1,3,4-oxadiazole, derivatives were synthesized starting from 5-amino-4-(hydrazinocarbonyl)-3-methylthiophene-2-carboxamide (2).

Methods:

All compounds were investigated for their preliminary antimicrobial activity. They were proved to exhibit remarkable antimicrobial activity against Pseudomonas aeruginosa with insignificant activity towards Gram positive bacterial strains and fungi.

Results:

In-vitro testing of the new compounds on hepatitis-C virus (HCV) replication in hepatocellular carcinoma cell line HepG2 infected with the virus utilizing the reverse transcription polymerase chain reaction technique (RT-PCR) generally showed inhibition of the replication of HCV RNA (–) strands at low concentration, while, eight compounds; 3a, 6, 7a, 7b, 9a, 9b, 10a and 11b proved to inhibit the replication of HCV RNA (+) and (–) strands at very low concentration range 0.08-0.36 μg/mL.

Conclusion:

Compounds 7b and 11b displayed the highest anti-HCV and antimicrobial activities in this study.

Microwave-assisted and conventional synthesis of novel antimicrobial 1,2,4-triazole derivatives containing nalidixic acid skeleton

Carbothioamides

Piperazine scaffold: A remarkable tool in generation of diverse pharmacological agents

Piperazine is one of the most sought heterocyclics for the development of new drug candidates. This ring can be traced in a number of well established, commercially available drugs. Wide array of pharmacological activities exhibited by piperazine derivatives have made them indispensable anchors for the development of novel therapeutic agents. The review herein highlights the therapeutic significance of piperazine derivatives. Various therapeutically active piperazine derivatives developed by several chemists are reported here.

Synthesis, Antibacterial Evaluation and QSAR of α-Substituted-N₄-Acetamides of Ciprofloxacin and Norfloxacin

Twenty six α-substituted N₄-acetamide derivatives of ciprofloxacin (CIPRO) and norfloxacin (NOR) were synthesized and assayed for antibacterial activity against Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus and Bacillus subtilis. The derivatives were primarily more active against Gram-positive bacteria. The CIPRO derivatives, CD-7 (Ar = 3-chlorophenyl), CD-9 (Ar = 2-pyrimidyl) and CD-10 (α-phenyl, Ar = 2-pyrimidyl), exhibited lower MIC values, 0.4–0.9 μM, against Staphylococcus aureus than CIPRO, while only compound CD-10 exhibited better activity, 0.1 μM, against Bacillus subtilis than CIPRO. In addition, compounds CD-5 (Ar = 2-methoxyphenyl), CD-6 (α-phenyl, Ar = 2-methoxyphenyl), CD-7 (Ar = 3-Chlorophenyl), CD-8 (α-phenyl, Ar = 3-chlorophenyl) and CD-9 (Ar = 2-pyrimidyl) showed MIC values below 1.0 μM against this strain. The NOR derivatives showed lower activity than NOR itself against Staphylococcus aureus, although ND-6 (α-phenyl, Ar = 2-methoxyphenyl) and ND-7 (Ar = 3-chlorophenyl) showed MIC values less than 2 μM. Two NOR derivatives, ND-7 and ND-6, exhibited MIC values of 0.7 and 0.6, respectively, which were comparable to that of NOR against Bacillus subtilis, while compounds ND-8 (α-phenyl, Ar = 3-chlorophenyl) and ND-10 (α-phenyl, Ar = 2-pyrimidyl) exhibited MIC values less than 1.0 μM against the same strain. QSAR revealed that while polarity is the major contributing factor in the potency against Staphylococcus aureus, it is balanced by lipophilicity and electron density around the acetamide group. On the other hand, electron density around the introduced acetamide group is the major determining factor in the activity against Bacillus subtilis, with a lesser and variable effect for lipophilicity.

Microwave assisted synthesis of some hybrid molecules derived from norfloxacin and investigation of their biological activities

Norfloxacin was converted to 7-(4-amino-2-fluorophenyl)piperazin derivative (2) via the formation of nitro compound. The synthesis of the norfloxacin derivatives containing 1,3-thiazole or 1,3-thiazolidin moiety was performed from the reaction of 4-chlorophenacylbromide or ethyl bromoacetate with compounds 4-7 obtained starting from 2. 3-Fluoro-4-[4-(2-methoxyphenyl)piperazin-1-yl]aniline (14), 5-{[4-(2-methoxyphenyl)piperazin-1-yl]methyl}-4-phenyl-4H-1,2,4-triazole-3-thiol (18) and {[4-(2-methoxy phenyl)piperazin-1-yl]methyl}-1,3,4-oxadiazol-2-thiol (19) were obtained starting from 1-(2-methoxyphenyl)piperazine by several steps. The treatment of hydrazide (16) with several aldehydes afforded N'-[(2-hydroxyphenyl)methylen]- (20), N'-[(3-hydroxy-4-methoxy phenyl)methylen]- (21) or N'-[1H-indol-3-ylmethylene]-2-[4-(2-methoxyphenyl)piperazin-1-yl]acetohydrazide (22). Then, compounds 14, 18, 19 and 22 were condensed with 7-[4-(chloroacetyl)piperazin-1-yl]-1-ethyl-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic acid (3) that was obtained from norfloxacine. All newly synthesized compounds were screened for their antimicrobial activities and some of them exhibited excellent activity. Moreover, one compound was found to have antiurease activity.

Medicinal potential of ciprofloxacin and its derivatives

Ciprofloxacin (CP) is a fluoroquinolone that is highly active against diverse microorganisms. At concentrations less than 1 µg/ml it is active against a diverse types of bacteria, including Staphylococcus aureus, Staphylococcus epidermidis, Bacillius subtilius, Escherichia coli and Mycobacterium tuberculosis. In addition, it has shown to be effective against other diseases such as malaria, cancer and AIDS. The extended antimicrobial activity, lack of plasmid-mediated resistance, large volume of distribution and minimal adverse effects of CP are therapeutically advantageous. In the pursuit of increasing their effectiveness against these diseases and prevent unwanted resistance, researchers have begun to synthesize a class of organic, inorganic and organometallic derivatives, which have displayed interesting activities. This review describes the development and recent advances on the evaluation of CP and its derivatives as a new class of drugs with potential for clinical development.

Synthesis and antimicrobial activity of new 5-(2-thienyl)-1,2,4-triazoles and 5-(2-thienyl)-1,3,4-oxadiazoles and related derivatives

New 5-(2-thienyl)-1,2,4-triazoles and 5-(2-thienyl)-1,3,4-oxadiazoles namely, N-[3-mercapto-5-(2-thienyl)-1,2,4-triazol-4-yl]-N'-arylthioureas 4a–e, 2-arylamino-5-(2-thienyl)-1,2,4-triazolo[3,4-b][1,3,4]thiadiazoles 5a–e, 3-arylaminomethyl-5-(2-thienyl)-1,3,4-oxadiazoline-2-thiones 7a–e, 3-(N-substituted anilinomethyl)-5-(2-thienyl)-1,3,4-oxadiazoline-2-thiones 8a, b and 3-(4-substituted-1-piperazinylmethyl)-5-(2-thienyl)-1,3,4-oxadiazoline-2-thiones 9a–f, were prepared. The synthesized compounds were tested for in vitro activities against certain strains of Gram-positive and Gram-negative bacteria and the yeast-like pathogenic fungus Candida albicans. Compound 9a displayed marked broad spectrum antibacterial activity, while compounds 4d, 5e, 7b, 7c, 7d, 9b, 9c and 9d were highly active against the tested Gram-positive bacteria. None of the synthesized compounds were proved to be significantly active against Candida albicans.

Synthesis and antibacterial activity of quinolone-based compounds containing a coumarin moiety

A new series of quinolone-based compounds containing a coumarin moiety have been synthesized and studied for their antibacterial activity against a panel of gram-positive and gram-negative bacteria, including methicillin-resistant Staphylococcus aureus (MRSA). The results of the antibacterial evaluation of N-[2-(coumarin-3-yl)ethyl]piperazinyl quinolone derivatives in comparison with parent quinolones (norfloxacin, ciprofloxacin, and enoxacin) indicated that N-[2-(coumarin-3-yl)-2-oxoethyl]ciprofloxacin derivative (compound 8b) showed comparable or more potent antibacterial activity with respect to the reference drugs against the test strains. Generally, in both gram-positive and gram-negative bacteria, better results are obtained with cyclopropyl at the N-1 position of the quinolone ring and 2-oxo- on the ethyl spacer of coumarin and piperazine rings.

Synthesis and antibacterial activity of 4,5,6,7-tetrahydro-thieno[3,2-c]pyridine quinolones

Synthesis and antibacterial activity of a number of substituted 4,5,6,7-tetrahydro-thieno[3,2-c]pyridine quinolones is reported. The antibacterial activities were evaluated in standard in vitro MIC assay method. Some of the compounds showed in vitro (MIC) antibacterial activity comparable to those of Gatifloxacin, Ciprofloxacin, and Sparfloxacin.

Synthesis and antibacterial activity of levofloxacin derivatives with certain bulky residues on piperazine ring

A number of levofloxacin analogues carrying a 2-aryl-2-oxoethyl or a 2-aryl-2-oxyiminoethyl moiety attached to the piperazine ring at C-10 position have been prepared and evaluated as antibacterial agents against a series of Gram-positive and Gram-negative bacteria. Some of them exhibited significant inhibitory activity against Gram-positive bacteria.

Synthesis and Antibacterial Activity of New N-[2-(Thiophen-3-yl)ethyl] Piperazinyl Quinolones

As a part of continuing search for potential antibacterial agents in the quinolones field, we have synthesized novel quinolone agents bearing N-[2-(thiophen-3-yl)ethyl] piperazinyl moiety in the 7-position of the quinolone ring. In vitro antibacterial evaluation of the target compounds showed that N-[2-(thiophen-3-yl)ethyl] group attached to piperazine ring served as promising C-7 substituent for piperazinyl quinolone antibacterials. Among these derivatives, ciprofloxacin analogues, containing N-[2-(thiophen-3-yl)-2-hydroxyiminoethyl] or N-[2-(thiophen-3-yl)-2-methoxyiminoethyl] residue provided a high inhibition against all the tested Gram-positive organisms including methicillin-resistant Staphylococcus aureus comparable or superior with respect to the reference drugs norfloxacin and ciprofloxacin.