Abstract
Bacterial resistance to fluoroquinolone has been increasing at an alarming rate worldwide. In an attempt to find more potent anti-bacterial agents, an efficient, straightforward protocol was performed to obtain a large substrate scope of novel ciprofloxacin and sarafloxacin analogues conjugated with 4-(arylcarbamoyl)benzyl 7a–ab. All prepared compounds were evaluated for their anti-bacterial activities against three gram-positive strains (Methicillin resistant staphylococcus aureus (MRSA), Staphylococcus aureus, and Enterococcus faecalis) as well as three gram-negative strains (Pseudomonas aeruginosa, Klebsiella pneumonia, and Escherichia coli) through three standard methods including broth microdilution, agar-disc diffusion, and agar-well diffusion assays. Most of the compounds exhibited great to excellent anti-bacterial potencies against MRSA and S. aureus. Among the targeted compounds, derivative 7n exhibited great antibacterial potency, which was noticeably more potent than parent ciprofloxacin. Subsequently, a molecular docking study was performed for this compound to find out its probable binding mode with the active site of S. aureus DNA gyrase (PDB ID: 2XCT).
Similar content being viewed by others
Explore related subjects
Discover the latest articles, news and stories from top researchers in related subjects.Avoid common mistakes on your manuscript.
Introduction
Nowadays, bacterial resistance originated from the excessive use of antibiotics has become a concerning issue all over the world, therefore, infectious diseases caused by multidrug resistant pathogens have been the noticeable threat leading to death over recent decades [1, 2]. Among them, the rate of fatalities owing to the methicillin-resistant Staphylococcus aureus (MRSA) has been remarkably more than other antibiotic-resistant pathogens [3]. Considering the difficulty of the treatment of MRSA infections, various antibiotics namely β-lactams [2], macrolides [4], glycopeptides [5], oxazolidinones [6], quinolones [5, 7, 8], and vancomycin have been frequently used. Quinolones are a group of antibiotics which tend to be prescribed for the treatment of a variety of bacterial infections such as hospital-acquired infections or other resistant pathogens including urinary tract infection, sexually transmitted disease, as well as gastrointestinal and abdominal infections [9, 10].
Since then, quinolones have become one of the most widely prescribed antibiotics. Their success might be contributed to their good bioavailability, low toxicity, favorable pharmacokinetics, enhanced tissue permeation, and good tolerability. However, the outbreak of quinolone-resistant and multi-drug-resistant bacteria have questioned the clinical use and efficacy of quinolone-based antibiotics [11, 12]. Therefore, discovery and development of new antimicrobial chemotherapeutic agents are highly demanding. Quinolones block DNA synthesis in bacteria through inhibition of two type-II bacterial topoisomerase enzymes named topoisomerase IV and DNA Gyrase, resulting into DNA synthesis and subsequently, the cell death. Topoisomerase-II plays a regulatory role on the topology and conformation of DNA during replication, transcription, and recombination of the strands of DNA in bacteria. Structurally, the role of quinolones to interfere with DNA synthesis in bacteria are attributed to their ability in formation of the hydrogen bonding interactions with single strand of DNA. As a result, this functionality is highly optimal and necessary for the antimicrobial activities of quinolones [13, 14].
In the quest for more effective quinolones, a fluorine atom has been introduced at the C-6 position, resulting into a remarkable breakthrough in the emergence and development of fluoroquinolones (FQ) which exhibit great effect on a wide spectrum of bacteria ranging from gram negative to positive bacteria. Structure-activity relationship studies of quinolones have demonstrated that the presence of fluorine atom improves metabolic characteristics through enhancing absorption and removing half-life of the quinolones [15]. Further ubiquitous and rational modifications leading to more effective fluoroquinolone analogues have proceeded through providing substituent at C-7 position, since studies have revealed that several properties including cell permeability, antibacterial spectrum, potency, safety and pharmacokinetics of fluoroquinolones are affected by C-7 side chains. Generally, 5 and 6-membered cyclic amines at the C-7 position are deemed as one of the most optimal substituents. Therefore, piperazin-1-yl moiety has been introduced at this position [16].
Overall, the presence of a fluorine atom at C-6 position and a piperazin-1-yl moiety at C-7 position of quinolone core structure have been remained, leading to find numerous potent drugs including pefloxacin, lomefloxacin, enrofloxacin, ofloxacin, levofloxacin, gatifloxacin, ciprofloxacin, and sarafloxacin, to name but a few [12, 17, 18]. The constructive role of piperazinyl are attributed to the transport of the fluoroquinolones into the bacteria and the inhibition of the target enzyme, type-II bacterial topoisomerase [19]. To afford more potent antimicrobial fluoroquinolone-based chemotherapeutic agents, numerous substituents conjugated with 7-piperazinyl moiety which were able to link with the special bulky substituents have been widely investigated [20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36].
According to the literature, there are several reasons to provide substituents on the 7-piperazinyl moiety. For example, the alteration of the serine amino acid and disruption of formed ternary complex within the performance of DNA gyrase cause bacterial resistance to fluoroquinolones [18, 37]. Making extra interaction with the named enzyme is one strategy to remove this resistance. Introducing substituents on the 7-piperazinyl led to obtain more potent compounds with great activities against broader spectrum of bacteria due to their abilities to make this noticeable extra-interaction [25, 38]. Moreover, structure activity relationship studies of quinolones revealed that unsubstituted 7-piperazine moiety induces convulsion [39]. Additionally, the presence of a diamine group in the piperazinyl moiety predisposes fluorquinolones to bacterial GSH-mediated modification and activity reduction [40]. Finally, acetylation of the unsubstituted nitrogen from 7-piperazinyl moiety is another mechanism of bacterial resistance to fluorquinolones; therefore, introducing substituents on this functionality resulted in find compounds with better efficacy against resistant species [12].
As a part of our long-term effort to find new, potential N-substituted piperazinyl fluoroquinolones [20, 21, 41, 42], herein, we present an efficient and straightforward synthetic route, antibacterial activity evaluation, and docking study to afford novel ciprofloxacin and sarafloxacin bearing various substituted 4-(arylcarbamoyl)benzyl 7a–ab moieties.
Results and discussion
Chemistry
The synthetic approach toward the desired fluoroquinolones including ciprofloxacin and sarafloxacin bearing different substituted 4-(arylcarbamoyl)benzyl 7a–ab is outlined in Scheme 1. This efficient protocol was initiated through reducing 4-formylbenzoic acid 1 using sodium tetraborohydride (NaBH4) in MeOH at ambient temperature to give 4-(hydroxymethyl)benzoic acid 2. Subsequently, this moiety underwent the chlorination with thionyl chloride (SOCl2) in DCM under the reflux conditions to afford 4-(chloromethyl)benzoyl chloride 3. This adduct went through the amidation with various substituted anilines 4a–n using TEA in acetone at the ambient temperature to afford corresponded 4-(chloromethyl)-N-arylbenzamide 5a–n. The structures of the isolated products were deduced on the basis of their 1H, and 13C NMR spectroscopy. Finally, the chloromethyl moiety underwent through the nucleophilic substitution with ciprofloxacin or sarafloxacin 6a,b in the presence of K2CO3 in DMF at 80 °C to obtain target compounds 7a–ab. The structures of these products were characterized on the basis of their IR, 1H and 13C NMR, as well as their elemental analyses and MASS spectroscopy. Partial assignments of these resonances are given in the Experimental Part.
Synthetic pathway for novel derivatives of ciprofloxacin and sarafloxacin bearing 4-(arylcarbamoyl)benzyl 7a–ab
Antibacterial activity
The figures in the antibacterial evaluation are reported as minimal inhibitory concentration (MIC, µM) values, showing the lowest concentration of each compound which inhibits visible growth of a bacterial culture under a defined set of experimental conditions. There are several routine methods used in many clinical microbiology laboratories for antimicrobial susceptibility testing to measure MIC values of antibiotic agents. In present study, our novel substituted ciprofloxacin and sarafloxacin derivatives 7a–ab were evaluated for their in vitro antibacterial activities through three standard methods including broth microdilution, agar-disc diffusion, and agar-well diffusion assays. Three gram-positive strains (Methicillin resistant staphylococcus aureus (MRSA), Staphylococcus aureus, and Enterococcus faecalis) as well as three gram-negative strains (Pseudomonas aeruginosa, Klebsiella pneumoniae, and Escherichia coli) were selected to evaluate the activities of our compounds against them.
Among various methods used to evaluate the antibacterial potencies, the most common and reliable one is “broth microdilution”. Considering its accuracy and clear results, this approach is the most valuable method used in clinical microbiology laboratories worldwide. Through this method, wells are filled with broth containing different concentrations of the antibiotic. Afterwards, they are inoculated with bacteria and incubated overnight. The next day, the figures for MIC could be measured [43]. To determine the antibacterial potencies of our fluoroquinolone analogues conjugated with 4-(arylcarbamoyl)benzyl 7a–ab through broth microdilution methods, various substituents either electron-donating group (EDG) or electron-withdrawing group (EWG) are provided on the 4-(arylcarbamoyl)benzyl in an effort to perform a comprehensive investigation about the role of this moiety on the anti-bacterial potencies of our fluoroquinolone analogues 7a–ab. In an attempt to provide better description of results and compare with parent drugs, compounds are divided into two categories: ciprofloxacin-derivative series 7a–n (Table 1) and sarafloxacin-derivative series 7o–ab (Table 2).
Regarding the anti-bacterial activities of the first series against gram-positive strains, there are almost similar trends about the MIC values against MRSA and S. aureus, while it seems different for E. faecalis. As it can be seen, all the synthesized compounds 7a–n showed good to excellent inhibitory activities with MIC values of 0.2 nM to 0.976 µM against MRSA and S. aureus in comparison with the parent drug (MIC MRSA = 0.488 µM and MIC S. aureus = 0.976 µM). To explain the structure and observed activity correlations against MRSA and S. aureus, the un-substituted 4-(phenylcarbamoyl)benzyl 7a showed the MIC values of 0.244 µM. Introducing a EDG including methyl and methoxy at C-4 position (compounds 7b and 7e) caused a decrease in anti-bacterial activity, whereas replacing these groups at C-3 position (compounds 7c and 7f) or C-2 position (compounds 7d and 7g) improved the potencies greatly. Moreover, it was found that introduction of an EWG like chlorine, fluorine, bromine, and trifluoromethyl at C-4 position (compounds 7h, 7k, 7l, and 7m, respectively) resulted into different anti-bacterial potencies. Although 4-Cl had a considerable deterioration in activity (7h, MIC values of 0.976 µM), other groups improved the potency remarkably. Providing a EWG at C-3 and C-2 positions (compounds 7i, 7j, and 7n) led to the significant increase in anti-bacterial activity. Therefore, the most potent compound in this series, 7n, was found as a probable, efficient antibiotic candidate with MIC values of 0.2 nM which was 2440 and 4880 times more potent than ciprofloxacin against MRSA and S. aureus, respectively.
None of the compounds 7a–n showed higher anti-bacterial activity than parent drug against E. faecalis. To provide a brief SAR description, the un-substituted 4-(phenylcarbamoyl)benzyl 7a demonstrated the moderate MIC value of 15.625 µM. The presence of methoxy group as EDG at C-3 or C-2 positions of 4-(arylcarbamoyl)benzyl moiety (compounds 7d, and 7g) as well as the cyano group as EWG at C-3 position (compound 7n) resulted into very good improvement on the observed activities.
In an attempt to provide a conclusion about the anti-bacterial activities of our ciprofloxacin analogues conjugated with 4-(arylcarbamoyl)benzyl 7a–n against gram-positive strains, all derivatives other than compound 7h demonstrated the very effective anti-bacterial activity against MRSA and S. aureus, since they were more potent than the parent drug. Moreover, the presence of methyl and methoxy as EDGs at C-2 position (compounds 7d and 7g) as well as the presence of cyano as EWG at C-3 position (compound 7n) could considerably improve the potency. In spite of excellent activities against MRSA and S. aureus, the synthesized compounds had low to moderate potencies against E. faecalis. To begin with the compound 7a, it demonstrated MIC value of 15.625 µM. Introducing methyl group at C-4 position of the phenyl ring caused a detrimental effect (compound 7b). Although moving this group to C-3 improved the potency noticeably (compound 7c with MIC value of 0.488 µM), moving to C-2 caused a weaker agent (compound 7d). The presence of methoxy group at any position resulted to more potent anti-biotic agents. For example, compounds 7f and 7g showed the MIC values of 0.122 µM which were the most potent derivatives in this strain. On the other hand, the presence of chlorine at any position of the phenyl ring (compounds 7h–j) had detrimental effects. Considering the role of other EWGs on the phenyl ring, the 3-cyano groups was the most efficient one (compound 7n with MIC value of 0.244 µM).
About the anti-bacterial activities of the first series against the gram-negative strains, all of the prepared ciprofloxacin analogues 7a–n demonstrated weaker potency than comparing with ciprofloxacin. About the strains of P. aeruginosa and K. pneumonia, compound 7a showed the MIC values of 0.976 µM and 31.25 µM, respectively. Introducing any groups whether EDGs or EWGs at any position of the phenyl ring on the 4-(arylcarbamoyl)benzyl moiety caused detrimental effects on the anti-bacterial potencies. About E. coli, the un-substituted 4-(phenylcarbamoyl)benzyl 7a had MIC value of 0.244 µM, and introducing methyl or methoxy at C-4 position of phenyl did not alter the anti-bacterial potency. Although the movement of this group from C-4 to whether C-2 or C-3 (compounds 7f and 7g) did not make any change on the activity, the movement of methyl led to noticeable change. The presence of 3-methyl enhanced the anti-bacterial activity (compound 7c with MIC value of 0.122 µM), while the presence of 2-methyl deteriorated the anti-bacterial potency (compound 7d with MIC value of 0.488 µM). To complete this study, various EWGs were introduced at different positions of the phenyl ring (compounds 7h–n), among which compounds 7j (bearing 2-Cl), 7l (bearing 4-Br), and 7n (bearing 3-CN) showed higher anti-bacterial potency (MIC values were 0.122 µM). Overall, against the gram-negative strains, the best results belonged to compounds 7j, 7l, and 7n with MIC values of 0.122 µM against E. coli.
It could be obtained the similar SAR analysis results about the second series of our sarafloxacin-based derivatives 7o–ab against both gram-positive and gram-negative strains. For example, comparing with parent drug, sarafloxacin, all of the derivatives except compound 7o, 7p, and 7s showed better anti-bacterial activities against both MRSA and S. aureus (the MIC values were from 0.030 µM to 0.488 µM). To begin the description of SAR, the un-substituted 4-(phenylcarbamoyl)benzyl 7o had MIC values of 0.488 µM. Introducing a methyl group at C-4 position of phenyl (compound 7p) did not change the activity, whereas the presence of this moiety at C-3 or C-2 position (compound 7q and 7r, respectively) resulted to excellent anti-bacterial potency (the MIC values were 0.030 µM). Introducing methoxy at C-4 position of phenyl (compound 7s) caused a highly detrimental effects on the activity and the MIC values increased to 15.625 µM. However, the presence of this EDG at C-3 and C-2 positions (compound 7t and 7u, respectively) improved the results significantly. Additionally, the presence of EWGs at C-4 position (compounds 7v, 7y, 7z, and 7aa) led to noticeable anti-bacterial activity. Among them, 7z bearing 4-F showed the best potency with MIC values of 0.061 µM. Compounds 7w, 7x, and 7ab bearing EWGs at other positions resulted into the great activity with the same MIC values of 0.122 µM.
It was found that all of the derivatives except compound 7o, 7p, and 7s were more potent anti-biotic agents than sarafloxacin against MRSA and S. aureus. In particular, compounds 7q and 7r with MIC values of 0.030 µM were the most potent sarafloxacin analogues which were 16.3 and 32.5 times more potent than the parent drug against the strains of MRSA and S. aureus, respectively. However, some of the compounds including 7q, 7t, 7u, 7y, 7z, and 7aa showed better anti-bacterial activity against E. faecalis in comparison with parent drug. About this strain, the un-substituted phenyl derivative 7o demonstrated MIC value of 31.250 µM. Introducing a EDGs at various positions of phenyl (compounds 7p–u) led to better activities. It could be concluded that the presence of EDGs at C-2 or C-3 position was very helpful for the activity, for example, the MIC values for compounds 7q, 7t, and 7u decreased remarkably to 1.953 µM. Moreover, the presence of chlorine atom at any position of the phenyl ring (compounds 7v–x) caused a detrimental effect on the anti-bacterial activities; however, the presence of other EWGs improved the potency noticeably, for example, compounds 7z and 7aa showed the MIC values of 0.488 µM against E. faecalis.
Same as the previous series, none of the sarafloxacin derivatives 7o–ab were potent anti-biotic agents than the parent drug against the gram-negative strains. Among these strains, our flouroquinlones 7o–ab showed the worst activities against K. pneumonia, while their activities were low to moderate agents against P. aeruginosa and E. coli. In an attempt to provide a brief SAR description, the un-substituted 4-(phenylcarbamoyl)benzyl 7o exhibited the moderate MIC value of 7.812 µM against P. aeruginosa. Introducing any group whether EDGs or EWGs caused significant decrease for anti-bacterial activity. Moreover, the MIC value of compound 7o was 0.976 M, among various modifications on the phenyl ring, only the presence of 3-OCH3 (compound 7t), 4-Br (compound 7z), and 4-CF3 (compound 7aa) could retain the anti-bacterial activities against E. coli, while other attempts caused the potencies to decrease.
As it was described, in both ciprofloxacin-derivative series 7a–n (Table 1) and sarafloxacin-derivative series 7o–ab (Table 2), most of the derivatives other than 7h, 7o, 7p, and 7s were more potent than the corresponding standard drugs against MRSA and S. aureus, while none of them showed the better potencies comparing with positive controls against P. aeruginosa, K. pneumonia, and E. coli. Among the fluoroquinolone analogues conjugated with 4-(arylcarbamoyl)benzyl 7a–ab, 7n from first series as well as 7q and 7r from the second series exhibited the best anti-bacterial activities. Moreover, their aqueous solubility was high. Since, this is the most important pharmacokinetic property of fluoroquinolones, it might be possible to consider these compounds as the potential antibiotic candidates.
Additional confirmatory methods used to evaluate the anti-bacterial potency of our desired compounds against three gram-positive strains and three gram-negative strains were disk diffusion test or Kirby–Bauer test (which was performed on Mueller Hinton Agar (MHA)) and agar well diffusion. In the agar-disk diffusion test, also known as “Kirby-Bauer method”, there is a zone of inhibition to measure the antibiotic potency of compounds. To determine this zone, initially, agar plates are inoculated with a standardized inoculum of the test microorganism. Then, small filter paper disks containing antibiotic are placed on the agar surface, and the obtained plate is incubated. Finally, the zone of inhibition around each disk is determined. In the similar method, agar-well diffusion, the agar plate surface is inoculated by spreading a volume of the microbial inoculum. Subsequently, several holes with a diameter of 6 to 8 mm are punched aseptically with a sterile cork borer or a tip, and a volume (20–100 µL) of the antimicrobial agent at different concentration are introduced into the well. Afterwards, agar plates are incubated under suitable conditions depending upon the test microorganism. The antimicrobial agent diffuses in the agar medium and inhibits the growth of the tested microbial strain [43].
The inhibitory zone of the compounds 7a–ab as diameter in mm were summarized in Table 3 and 4. There is a great agreement between the results of broth microdilution with disk diffusion and well diffusion assays, particularly against MRSA and S. aureus. For example, all compounds other than 7h and 7s showed comparable or even better activity in comparison with the parent drugs against MRSA and S. aureus.
Based upon the disc diffusion assay results (Table 3), compound 7n from first series had a remarkable activity with inhibition zone of 32 and 28 mm. Additionally, the best results of second series were observed for compounds 7q and 7r, since the figures were 29 and 23 mm for 7q as well as 31 and 25 mm for 7r, which were better figures than those of the sarafloxacin.
According to the well diffusion assay results (Table 4), there is a similar trend, particularly against the strains of MRSA and S. aureus. Among the ciprofloxacin-based derivatives, compound 7n exhibited the inhibitory zone of 38 and 33 against MRSA and S. aureus, respectively, which was more than that of ciprofloxacin. Among the sarafloxacin-based derivatives, the highest zone of inhibition belonged to compounds 7q and 7r, confirming their excellent potencies in comparison with sarafloxacin.
Molecular docking
In order to gain more insight into the binding mode of the most promising compound 7n to the target protein, a molecular docking study was conducted using the crystal structure of a complex of DNA gyrase with ciprofloxacin (PDB ID: 2XCT). For validating the docking procedure, ciprofloxacin was redocked into the crystal structure of DNA gyrase. Ciprofloxacin's binding mode is similar to that of its co-crystallized ligand in X-ray structures, showing free binding energy of -8.29 kcal/mol. Ciprofloxacin's hydroxyl group participates in hydrogen bonding interactions with Ser1084 and the piperazine moiety interacts with Arg458 to stabilize the molecule. A metal carboxylate complex with manganese ion (Mn2+) was also observed, which increased ligand binding affinity (Fig. 1A).
Predicted binding mode at the binding site of crystal structure of S. aureus DNA gyrase for; A Ciprofloxacin using PDB ID: 2XCT [hydrogen bonds (green), hydrophobic interactions (pink), and metal bond (gray)], B Compound 7n [hydrogen bonds (green), hydrophobic interactions (pink), anion or cation-π (orange), and metal bond (gray)]
The docking results as shown in figure 1 and 2 revealed that there were similar binding modes for ciprofloxacin and compound 7n in the active site and the same coordination toward Mn+2 metal ions (figure 2). Compound 7n displayed important interactions with DNA gyrase with an affinity value of -7.96 kcal/mol (figure 1B). A hydrogen bond was formed between the carboxyl moiety of this compound and Ser 1084. The two phenyl rings of C-7 piperazine substituent were stabilized by cation-π and alkyl-π interactions with Arg458. Moreover, additional hydrogen bond interaction was formed between the amide moiety of this ligand and Asp 437. Interestingly, in spite of the elongation of this structure, the flexible methylene bridge created a U-shaped conformation that allowed the scaffold to be correctly positioned within the active area.
Proposed binding mode of compound 7n.
Conclusion
In conclusion, we have represented a study about the novel fluoroquinolone analogues conjugated with 4-(arylcarbamoyl)benzyl 7a–ab as potential anti-bacterial agents. Using an efficient, simple protocol from readily available starting materials and easy work-up without any need for chromatography purification processes led us to afford the targeted compounds in desired yields. Afterwards, the potencies of compounds were investigated through three reliable methods including broth microdilution, agar-disc diffusion, and agar-well diffusion assays against three gram-positive strains named MRSA, S. aureus, and E. faecalis as well as three gram-negative strains named P. aeruginosa, K. pneumonia, and E. coli. All derivatives demonstrated very good to excellent anti-bacterial activities against MRSA and S. aureus in comparison with the parent drugs, ciprofloxacin and sarafloxacin. However, they exhibited low to moderate potencies against other strains. It is more likely for these fluoroquinolones to have wider applications against other pathogens which could be investigated in further studies. Compound 7n bearing 3-cyano on the phenyl ring from the ciprofloxacin-based series showed remarkable potencies with MIC values of 0.2 nM against MRSA and S. aureus which was 2440 and 4880 times more potent than ciprofloxacin on the related strains. Compounds 7q and 7r from the second series, which demonstrated MIC values of 0.030 µM, were the most potent sarafloxacin analogues with the potency of 16.3 and 32.5 times more than that of the parent drug the strains of MRSA and S. aureus, respectively. Molecular docking to the active site of S. aureus DNA gyrase co-crystalized with ciprofloxacin-based compound 7n displayed appropriate fitting with relevant amino acids in the binding pocket with great score energy. Regarding the noticeable MIC value and solubility of these compounds, they could be considered as potential antibiotic candidates in further investigations.
Experimental
General procedures for the synthesis of compounds
All chemicals were purchased from Merck (Germany) and were used without further purification. Melting points were measured on an Electrothermal 9100 apparatus. Mass spectra were recorded on an Agilent Technologies (HP) 5973 mass spectrometer operating at an ionization potential of 20 eV. Elemental analyses for C, H and N were performed using a Heraeus CHN-O-Rapid analyzer. IR spectra were recorded on a Shimadzu IR-460 spectrometer. 1H and 13C NMR spectra were measured (DMSO-d6 solution) with Bruker DRX-300 (at 300.1 and 75.5 MHz) instrument.
General procedure for the preparation of 4-(hydroxymethyl)benzoic acid 2
To the stirred solution of 4-formylbenzoic acid 1 (15 g, 100 mmol) in dry methanol (50 ml) under the ice-bath conditions, sodium tetraborohydride (11.4 g, 300 mmol) was added gradually within almost 1h. The reaction mixture continued stirring for further 4h at ambient temperature. After completion of the reaction according to the TLC analysis, the mixture was quenched with saturated solution of NaHCO3 (60 ml) and extracted three times with EtOAc (3 × 120 mL). The combined organic extracts were washed with brine, dried over Na2SO4, and then totally concentrated. The residue was recrystallized in ethanol to afford pure compound 2 (12.31 g, 81%) as a white solid [44]. mp: 176-179 °C; 1H NMR (300 MHz, DMSO-d6): δ 14.30 (s, 1H, CO2H), 7.88 (d, J = 7.9 Hz, 2H, 2CH), 7.48 (d, J = 7.9 Hz, 2H, 2CH), 5.23 (s, 1H, OH), 4.57 (s, 2H, CH2). 13C NMR (75.1 MHz, DMSO-d6): δ 168.73 (C=O), 148.9, 130.69, 129.48, 129.26, 62.74 (CH2). ESI-MS m/ z: 153.62 [M + H]+.
General procedure for the preparation of 4-(chloromethyl)benzoyl chloride 3
A solution of 4-(hydroxymethyl)benzoic acid (12.31 g, 81 mmol) in dichloromethane (20 ml) was stirred under the ice-bath conditions at 0 °C for 30 min. Then, excess amount of thionyl chloride (8.71 ml, 120 mmol) was added dropwise over 5 min. The resulting mixture was refluxed under an argon atmosphere overnight. Afterwards, the reaction mixture was concentrated in vacuo to remove the excess amount of excess thionyl chloride and dichloromethane. The obtained pale yellow oil was pure enough to use in next step (11.94 g, 78%) [45]. 1H NMR (300.1 MHz, DMSO-d6): δ 7.94 (d, J = 8.1 Hz, 2H, 2CH), 7.53 (d, J = 8.1 Hz, 2H, 2CH), 4.80 (s, 2H, CH2). 13C NMR (75.1 MHz, DMSO-d6): δ 166.96 (C=O), 142.35, 130.64, 129.68, 128.92, 45.34 (CH2). ESI-MS m/ z: 187.48 [M]+.
General procedure for the preparation of 4-(chloromethyl)-N-arylbenzamides 5
A mixture of 4-(chloromethyl)benzoyl chloride 3 (1.19 g, 6.32 mmol), various substituted anilines 4a–n (7.58 mmol), and triethyl amine (1.32 mL, 9.48 mmol) in acetone (15 mL) was stirred within 16 to 18 h. After completion of the reaction which was monitored by TLC, the mixture was quenched with water, and the obtained precipitate was filtered and washed with Et2O to afford pure products 5 in great to excellent yields. Herein, the data of 4-(chloromethyl)-N-(4-methoxyphenyl)benzamide 5e is provided:
White solid; mp: 123-125 °C; 1H NMR (300 MHz, DMSO-d6): δ 10.99 (s, 1H, NH-amid), 7.94 (d, J = 8.1 Hz, 2H, 2CH), 7.65 (d, J = 7.6 Hz, 2H, 2CH), 7.34 (d, J = 8.1 Hz, 2H, 2CH), 6.91 (d, J = 7.6 Hz, 2H, 2CH), 4.58 (s, 2H, CH2), 3.86 (s, 3H, OCH3). 13C NMR (75.1 MHz, DMSO-d6) δ 165.96 (C=O, amid), 155.36, 141.66, 135.89, 130.61, 129.66, 128.92, 122.13, 114.22, 55.37 (OCH3), 45.32 (CH2).
General procedure for the preparation of ciprofloxacin and sarafloxacin bearing 4-(arylcarbamoyl)benzyl 7
A mixture of ciprofloxacin hydrochloride 6a (0.331 g, 1 mmol) or sarafloxacin hydrochloride 6b (0.385 g, 1 mmol) and K2CO3 (0.207 g, 1.5 mmol) was stirred in DMF (5 mL) at 80 °C for 30 min. Then, 4-(chloromethyl)-N-arylbenzamides 5a–n (1.2 mmol) was added portion by portion over 5 min. The resulting mixture was continued to heat under an argon atmosphere for 6 to 8 h. After completion of the reaction which was monitored by TLC, the mixture was cooled down to the ambient temperature. Afterwards, water (10 mL) was added to the mixture, and the precipitated product was filtered and washed with EtOH to afford pure desired products 7a–ab in great to excellent yields.
1-cyclopropyl-6-fluoro-4-oxo-7-(4-(4-(phenylcarbamoyl)benzyl)piperazin-1-yl)-1,4-dihydroquinoline-3-carboxylic acid (7a):
Milky solid; mp: 186-188 °C; IR (KBr) (νmax/cm–1): 3460–3000 (OH and NH), 1719, 1658, 1623 (3CO), 1598, 1496, 1411, 1356, 1288, 1169, 1023, 966, 847, 753, 706, 686, 633. 1H NMR (300.1 MHz, DMSO-d6): δ 14.92 (s, 1H, CO2H), 10.23 (s, 1H, NH-amid), 8.63 (s, 1H, CH-quinolone), 8.08-7.70 (m, 5H, 5CH), 7.64-7.40 (m, 5H, 5CH), 7.33 (t, J = 7.4 Hz, 1H, CH), 3.85-3.70 (m, 1H, CH-cyclopropyl), 3.64 (s, 2H, CH2), 3.32 (br. s, 4H, 2CH2-N), 2.59 (br. s, 4H, 2CH2-N), 1.35-1.10 (m, 4H, 2CH2-cyclopropyl). 13C NMR (75.1 MHz, DMSO-d6): δ 176.30 (C=O, ketone), 165.92 (CO2H), 165.17 (C=O, amid), 152.99 (d, 1JC-F = 249.5 Hz, C-F), 147.74 (d, 2JC-F = 28.7 Hz, C), 145.17, 136.52, 134.64, 132.56, 129.54, 129.34, 128.58, 127.76, 127.43, 120.31, 115.47, 110.89 (d, 2JC-F = 22.5 Hz, CH), 106.76, 101.62, 65.47 (CH2), 52.21 and 49.40 (2CH2-N), 35.83 (CH-cyclopropyl), 7.64 and 7.55 (2CH2-cyclopropyl). ESI-MS m/ z: 540.36 [M]+. Anal. Calcd. for C31H29FN4O4: C, 68.88; H, 5.41; N, 10.36.; found: C, 69.08; H, 5.72; N, 10.58 %.
1-cyclopropyl-6-fluoro-4-oxo-7-(4-(4-(4-tolylcarbamoyl)benzyl)piperazin-1-yl)-1,4-dihydroquinoline-3-carboxylic acid (7b):
White solid; mp: 211-212 °C; IR (KBr) (νmax/cm–1): 3228 (OH), 3096 (NH), 1715, 1669, 1609 (3CO), 1588, 1499, 1412, 1372, 1288, 1209, 1189, 1123, 1096, 989, 963, 839, 754, 685, 648. 1H NMR (300.1 MHz, DMSO-d6): δ 14.73 (s, 1H, CO2H), 10.15 (s, 1H, NH-amid), 8.64 (s, 1H, CH-quinolone), 7.97 (d, J = 8.6 Hz, 2H, 2CH), 7.87 (d, 3J H-F = 13.6 Hz, 1H, CH), 7.70-7.30 (m, 7H, 7CH), 3.89-3.70 (m, 1H, CH-cyclopropyl), 3.65 (s, 2H, CH2), 3.33 (br. s, 4H, 2CH2-N), 2.60 (br. s, 4H, 2CH2-N), 2.26 (s, 3H, CH3), 1.30-1.00 (m, 4H, 2CH2-cyclopropyl). 13C NMR (75.1 MHz, DMSO-d6): δ 176.30 (C=O, ketone), 165.91 (CO2H), 165.16 (C=O, amid), 152.97 (d, 1JC-F = 247.8 Hz, C-F), 147.72 (d, 2JC-F = 33.3 Hz, C), 145.07, 139.11, 134.68, 132.34, 129.53, 129.45, 129.32, 128.94, 127.81, 120.32, 118.51 (d, 3JC-F = 5.7 Hz, C), 111.18 (d, 2JC-F = 24.3 Hz, CH), 106.38, 101.51, 65.36 (CH2), 52.19 and 49.37 (2CH2-N), 35.82 (CH-cyclopropyl), 20.47 (CH3), 7.53 and 7.50 (2CH2-cyclopropyl). ESI-MS m/ z: 555.89 [M + H]+. Anal. Calcd. for C32H31FN4O4: C, 69.30; H, 5.63; N, 10.10.; found: C, 69.12; H, 5.88; N, 10.23 %.
1-cyclopropyl-6-fluoro-4-oxo-7-(4-(4-(3-tolylcarbamoyl)benzyl)piperazin-1-yl)-1,4-dihydroquinoline-3-carboxylic acid (7c):
White solid; mp: 178-181 °C; IR (KBr) (νmax/cm–1): 3441-2850 (OH and NH), 1723, 1648, 1612 (3CO), 1583, 1502, 1423, 1383, 1286, 1232, 1145, 1080, 988, 923, 899, 805, 726, 685, 656, 633. 1H NMR (300.1 MHz, DMSO-d6): δ 14.85 (s, 1H, CO2H), 10.39 (s, 1H, NH-amid), 8.62 (s, 1H, CH-quinolone), 8.10-7.87 (m, 3H, 3CH), 7.72 (d, J = 7.4 Hz, 1H, CH), 7.67-7.45 (m, 4H, 4CH), 7.12-7.00 (m, 2H, 2CH), 3.80-3.70 (m, 1H, CH-cyclopropyl), 3.64 (s, 2H, CH2), 3.32 (br. s, 4H, 2CH2-N), 2.59 (br. s, 4H, 2CH2-N), 2.14 (s, 3H, CH3), 1.35-1.00 (m, 4H, 2CH2-cyclopropyl). 13C NMR (75.1 MHz, DMSO-d6): δ 176.26 (C=O, ketone), 165.91 (CO2H), 165.16 (C=O, amid), 152.97 (d, 1JC-F = 247.8 Hz, C-F), 147.65 (d, 2JC-F = 35.0 Hz, C), 145.19, 139.09, 134.52, 132.75, 129.61, 129.53, 129.47, 129.33, 129.10, 128.90, 128.14, 127.79, 127.45, 118.57 (d, 3JC-F = 7.1 Hz, C), 110.86 (d, 2JC-F = 23.1 Hz, CH), 106.74, 101.33, 65.47 (CH2), 52.20 and 49.39 (2CH2-N), 35.77 (CH-cyclopropyl), 19.18 (CH3), 7.61 and 7.54 (2CH2-cyclopropyl). ESI-MS m/ z: 554.26 [M]+. Anal. Calcd. for C32H31FN4O4: C, 69.30; H, 5.63; N, 10.10.; found: C, 69.53; H, 5.43; N, 9.94 %.
1-cyclopropyl-6-fluoro-4-oxo-7-(4-(4-(2-tolylcarbamoyl)benzyl)piperazin-1-yl)-1,4-dihydroquinoline-3-carboxylic acid (7d):
Milky solid; mp: 168-169 °C; IR (KBr) (νmax/cm–1): 3432 (OH), 3348 (NH), 1718, 1652, 1634 (3CO), 1598, 1496, 1434, 1399, 1368, 1301, 1278, 1189, 1053, 1022, 994, 935, 899, 823, 752, 689, 643. 1H NMR (300.1 MHz, DMSO-d6): δ 15.13 (s, 1H, CO2H), 10.64 (s, 1H, NH-amid), 8.60 (s, 1H, CH-quinolone), 7.98 (d, J = 8.6 Hz, 2H, 2CH), 7.91 (d, 3J H-F = 11.3 Hz, 1H, CH), 7.65-7.40 (m, 5H, 5CH), 7.30-7.10 (m, 2H, 2CH), 3.80-3.70 (m, 1H, CH-cyclopropyl), 3.61 (s, 2H, CH2), 3.31 (br. s, 4H, 2CH2-N), 2.59 (br. s, 4H, 2CH2-N), 2.22 (s, 3H, CH3), 1.35-1.00 (m, 4H, 2CH2-cyclopropyl). 13C NMR (75.1 MHz, DMSO-d6): δ 176.24 (C=O, ketone), 167.47 (CO2H), 165.92 (C=O, amid), 152.96 (d, 1JC-F = 248.6 Hz, C-F), 147.64 (d, 2JC-F = 27.6 Hz, C), 145.20, 139.07, 134.73, 132.50, 129.54, 129.50, 129.31, 129.11, 128.79, 128.20, 127.78, 127.50, 118.54 (d, 3JC-F = 7.4 Hz, C), 110.84 (d, 2JC-F = 22.3 Hz, CH), 106.26, 101.24, 65.50 (CH2), 52.23 and 49.40 (2CH2-N), 35.81 (CH-cyclopropyl), 19.54 (CH3), 7.63 and 7.55 (2CH2-cyclopropyl). ESI-MS m/ z: 554.67 [M]+. Anal. Calcd. for C32H31FN4O4: C, 69.30; H, 5.63; N, 10.10.; found: C, 69.18; H, 5.95; N, 10.36 %.
1-cyclopropyl-6-fluoro-7-(4-(4-((4-methoxyphenyl)carbamoyl)benzyl)piperazin-1-yl)-4-oxo-1,4-dihydroquinoline-3-carboxylic acid (7e):
Pale yellow solid; mp: 221-224 °C; IR (KBr) (νmax/cm–1): 3320–2900 (OH and NH), 1726, 1640, 1618 (3CO), 1505, 1409, 1321, 1226, 1167, 1103, 1033, 898, 827, 749, 622. 1H NMR (300.1 MHz, DMSO-d6): δ 15.10 (s, 1H, CO2H), 10.23 (s, 1H, NH-amid), 8.61 (s, 1H, CH-quinolone), 8.00-7.80 (m, 3H, 3CH), 7.68 (d, J = 7.8 Hz, 2H, 2CH), 7.45-7.20 (m, 3H, 3CH), 6.98 (d, J = 7.8 Hz, 2H, 2CH), 4.11 (s, 3H, OCH3), 3.82-3.70 (m, 1H, CH-cyclopropyl), 3.63 (s, 2H, CH2), 3.37 (br. s, 4H, 2CH2-N), 2.59 (br. s, 4H, 2CH2-N), 1.38-1.05 (m, 4H, 2CH2-cyclopropyl). 13C NMR (75.1 MHz, DMSO-d6): δ 178.87 (C=O, ketone), 165.94 (CO2H), 164.60 (C=O, amid), 155.55, 153.26 (d, 1JC-F = 203.7 Hz, C-F), 147.85 (d, 2JC-F = 36.1 Hz, C), 145.65, 136.34, 134.85, 132.12, 129.62, 129.49, 129.04, 121.96, 118.08, 113.71, 110.89 (d, 2JC-F = 18.2 Hz, CH), 106.55, 101.19, 65.78 (CH2), 55.17 (OCH3), 52.30 and 49.72 (2CH2-N), 35.55 (CH-cyclopropyl), 7.71 and 7.54 (2CH2-cyclopropyl). ESI-MS m/ z: 570.38 [M]+. Anal. Calcd. for C32H31FN4O5: C, 67.36; H, 5.48; N, 9.82.; found: C, 67.58; H, 5.24; N, 10.12 %.
1-cyclopropyl-6-fluoro-7-(4-(4-((3-methoxyphenyl)carbamoyl)benzyl)piperazin-1-yl)-4-oxo-1,4-dihydroquinoline-3-carboxylic acid (7f):
Milky solid; mp: 197-201 °C; IR (KBr) (νmax/cm–1): 3420-3161 (OH and NH), 1717, 1663, 1620 (3CO), 1593, 1499, 1445, 1413, 1354, 1278, 1229, 1156, 1044, 991, 936, 899, 833, 753, 737, 685, 660. 1H NMR (300.1 MHz, DMSO-d6): δ 15.12 (s, 1H, CO2H), 10.20 (s, 1H, NH-amid), 8.61 (s, 1H, CH-quinolone), 7.95 (d, J = 8.6 Hz, 2H, 2CH), 7.81 (d, 3J H-F = 12.1 Hz, 1H, CH), 7.42-7.16 (m, 6H, 6CH), 6.66 (d, J = 7.6 Hz, 1H, CH), 4.06 (s, 3H, OCH3), 3.84-3.72 (m, 1H, CH-cyclopropyl), 3.63 (s, 2H, CH2), 3.32 (br. s, 4H, 2CH2-N), 2.59 (br. s, 4H, 2CH2-N), 1.37-0.98 (m, 4H, 2CH2-cyclopropyl). 13C NMR (75.1 MHz, DMSO-d6): δ 176.27 (C=O, ketone), 165.91 (CO2H), 165.18 (C=O, amid), 156.22, 152.96 (d, 1JC-F = 247.1 Hz, C-F), 147.67 (d, 2JC-F = 28.8 Hz, C), 145.21, 136.25, 134.92, 132.70, 129.54, 129.34, 129.10, 127.78, 127.48, 118.55 (d, 3JC-F = 7.2 Hz, C), 112.49, 110.85 (d, 2JC-F = 22.5 Hz, CH), 106.74, 106.36, 101.50, 65.49 (CH2), 54.98 (OCH3), 52.22 and 49.44 (2CH2-N), 35.84 (CH-cyclopropyl), 7.87 and 7.56 (2CH2-cyclopropyl). ESI-MS m/ z: 571.64 [M + H]+. Anal. Calcd. for C32H31FN4O5: C, 67.36; H, 5.48; N, 9.82.; found: C, 67.14; H, 5.65; N, 9.66 %.
1-cyclopropyl-6-fluoro-7-(4-(4-((2-methoxyphenyl)carbamoyl)benzyl)piperazin-1-yl)-4-oxo-1,4-dihydroquinoline-3-carboxylic acid (7g):
Milky solid; mp: 174-176 °C; IR (KBr) (νmax/cm–1): 3400-3050 (OH and NH), 1733, 1676, 1618 (3CO), 1596, 1508, 1422, 1367, 1296, 1244, 1182, 1133, 1066, 996, 825, 755, 685, 639. 1H NMR (300.1 MHz, DMSO-d6): δ 15.19 (s, 1H, CO2H), 11.23 (s, 1H, NH-amid), 8.61 (s, 1H, CH-quinolone), 8.02 (d, J = 8.1 Hz, 2H, 2CH), 7.82 (d, 3J H-F = 12.9 Hz, 1H, CH), 7.68-7.28 (m, 4H, 4CH), 7.22 (d, J = 7.4 Hz, 1H, CH), 7.12-6.90 (m, 2H, 2CH), 3.98 (s, 3H, OCH3), 3.85-3.70 (m, 1H, CH-cyclopropyl), 3.63 (s, 2H, CH2), 3.31 (br. s, 4H, 2CH2-N), 2.59 (br. s, 4H, 2CH2-N), 1.40-1.05 (m, 4H, 2CH2-cyclopropyl). 13C NMR (75.1 MHz, DMSO-d6): δ 176.27 (C=O, ketone), 165.91 (CO2H), 165.19 (C=O, amid), 155.60, 152.97 (d, 1JC-F = 247.0 Hz, C-F), 147.75 (d, 2JC-F = 19.2 Hz, C), 145.08, 136.83, 134.20, 132.73, 129.55, 129.34, 129.12, 127.79, 127.49, 122.32, 118.57 (d, 3JC-F = 9.0 Hz, C), 113.23, 110.86 (d, 2JC-F = 17.3 Hz, CH), 106.76, 101.75, 65.49 (CH2), 54.53 (OCH3), 52.23 and 49.44 (2CH2-N), 35.80 (CH-cyclopropyl), 7.81 and 7.56 (2CH2-cyclopropyl). ESI-MS m/ z: 570.38 [M]+. Anal. Calcd. for C32H31FN4O5: C, 67.36; H, 5.48; N, 9.82.; found: C, 67.23; H, 5.73; N, 9.68 %.
7-(4-(4-((4-chlorophenyl)carbamoyl)benzyl)piperazin-1-yl)-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic acid (7h):
Milky solid; mp: 235-236 °C; IR (KBr) (νmax/cm–1): 3389 (OH), 2946 (NH), 1714, 1640, 1618 (3CO), 1497, 1455, 1266, 1176, 1098, 1014, 955, 843, 804, 756, 708, 630. 1H NMR (300.1 MHz, DMSO-d6): δ 15.19 (s, 1H, CO2H), 10.38 (s, 1H, NH-amid), 8.64 (s, 1H, CH-quinolone), 8.01 (d, J = 8.2 Hz, 2H, 2CH), 7.86 (d, 3J H-F = 13.4 Hz, 1H, CH), 7.74 (d, J = 8.6 Hz, 2H, 2CH), 7.68-7.30 (m, 5H, 5CH), 3.80-3.70 (m, 1H, CH-cyclopropyl), 3.64 (s, 2H, CH2), 3.33 (br. s, 4H, 2CH2-N), 2.60 (br. s, 4H, 2CH2-N), 1.40-1.00 (m, 4H, 2CH2-cyclopropyl). 13C NMR (75.1 MHz, DMSO-d6): δ 176.32 (C=O, ketone), 166.87 (CO2H), 165.89 (C=O, amid), 152.97 (d, 1JC-F = 248.9 Hz, C-F), 147.89 (d, 2JC-F = 13.3 Hz, C), 144.91, 139.12, 134.49, 133.84, 132.56, 129.61, 129.52, 129.35, 128.90, 121.80, 118.77, 110.89 (d, 2JC-F = 22.1 Hz, CH), 106.72, 101.45, 66.22 (CH2), 52.00 and 45.29 (2CH2-N), 35.87 (CH-cyclopropyl), 7.70 and 7.57 (2CH2-cyclopropyl). ESI-MS m/ z: 576.46 [M + H]+. Anal. Calcd. for C31H28ClFN4O4: C, 64.75; H, 4.91; N, 9.74.; found: C, 65.03; H, 5.18; N, 9.49 %.
7-(4-(4-((3-chlorophenyl)carbamoyl)benzyl)piperazin-1-yl)-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic acid (7i):
White solid; mp: 218-221 °C; IR (KBr) (νmax/cm–1): 3450-3100 (OH and NH), 1709, 1635, 1609 (3CO), 1595, 1495, 1396, 1373, 1297, 1254, 1186, 1071, 1010, 954, 877, 766, 729, 684, 649. 1H NMR (300.1 MHz, DMSO-d6): δ 15.13 (s, 1H, CO2H), 10.39 (s, 1H, NH-amid), 8.61 (s, 1H, CH-quinolone), 8.09-7.80 (m, 4H, 4CH), 7.81 (d, 3J H-F = 12.8 Hz, 1H, CH), 7.65-7.35 (m, 4H, 4CH), 7.13 (d, J = 7.8 Hz, 1H, CH), 3.85-3.71 (m, 1H, CH-cyclopropyl), 3.62 (s, 2H, CH2), 3.31 (br. s, 4H, 2CH2-N), 2.59 (br. s, 4H, 2CH2-N), 1.36-1.06 (m, 4H, 2CH2-cyclopropyl). 13C NMR (75.1 MHz, DMSO-d6): δ 176.23 (C=O, ketone), 165.90 (CO2H), 165.19 (C=O, amid), 152.95 (d, 1JC-F = 248.0 Hz, C-F), 147.70 (d, 2JC-F = 21.6 Hz, C), 145.05, 139.06, 134.94, 133.79, 132.72, 129.54, 129.48, 129.29, 129.10, 128.77, 127.77, 127.49, 118.54 (d, 3JC-F = 7.0 Hz, C), 110.84 (d, 2JC-F = 23.3 Hz, CH), 106.28, 101.47, 65.49 (CH2), 52.21 and 49.45 (2CH2-N), 35.80 (CH-cyclopropyl), 7.77 and 7.54 (2CH2-cyclopropyl). ESI-MS m/ z: 575.35 [M]+. Anal. Calcd. for C31H28ClFN4O4: C, 64.75; H, 4.91; N, 9.74.; found: C, 64.99; H, 5.23; N, 9.96 %.
7-(4-(4-((2-chlorophenyl)carbamoyl)benzyl)piperazin-1-yl)-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic acid (7j):
White solid; mp: 196-198 °C; IR (KBr) (νmax/cm–1): 3439 (OH), 3166 (NH), 1712, 1639, 1612 (3CO), 1594, 1496, 1378, 1298, 1234, 1180, 1122, 1038, 994, 939, 926, 803, 755, 686, 658, 634. 1H NMR (300.1 MHz, DMSO-d6): δ 14.72 (s, 1H, CO2H), 10.09 (s, 1H, NH-amid), 8.65 (s, 1H, CH-quinolone), 8.10-7.90 (m, 3H, 3CH), 7.65-7.35 (m, 6H, 6CH), 7.22 (d, J = 7.2 Hz, 1H, CH), 3.86-3.80 (m, 1H, CH-cyclopropyl), 3.77 (s, 2H, CH2), 3.36 (br. s, 4H, 2CH2-N), 2.61 (br. s, 4H, 2CH2-N), 1.36-0.90 (m, 4H, 2CH2-cyclopropyl). 13C NMR (75.1 MHz, DMSO-d6): δ 177.38 (C=O, ketone), 165.97 (CO2H), 165.07 (C=O, amid), 152.94 (d, 1JC-F = 251.3 Hz, C-F), 147.88 (d, 2JC-F = 16.5 Hz, C), 145.68, 139.81, 134.59, 133.62, 132.58, 129.92, 129.57, 129.39, 129.21, 127.84, 127.74, 127.70, 118.52, 110.98 (d, 2JC-F = 16.9 Hz, CH), 106.81, 101.13, 65.51 (CH2), 52.20 and 49.57 (2CH2-N), 34.83 (CH-cyclopropyl), 7.69 and 7.51 (2CH2-cyclopropyl). ESI-MS m/ z: 575.84 [M]+. Anal. Calcd. for C31H28ClFN4O4: C, 64.75; H, 4.91; N, 9.74.; found: C, 64.49; H, 4.76; N, 9.98 %.
1-cyclopropyl-6-fluoro-7-(4-(4-((4-fluorophenyl)carbamoyl)benzyl)piperazin-1-yl)-4-oxo-1,4-dihydroquinoline-3-carboxylic acid (7k):
Pale yellow solid; mp: 186-188 °C; IR (KBr) (νmax/cm–1): 3385-2900 (OH and NH), 1712, 1637, 1608 (3CO), 1599, 1504, 1437, 1410, 1370, 1294, 1245, 1174, 1144, 1078, 1029, 991, 944, 908, 836, 756, 729, 687, 642. 1H NMR (300.1 MHz, DMSO-d6): δ 15.15 (s, 1H, CO2H), 10.32 (s, 1H, NH-amid), 8.60 (s, 1H, CH-quinolone), 8.01 (d, J = 8.2 Hz, 2H, 2CH), 7.81 (d, 3J H-F = 13.4 Hz, 1H, CH), 7.68-7.30 (m, 5H, 5CH), 7.17 (t, J = 7.6 Hz, 2H, 2CH), 3.84-3.70 (m, 1H, CH-cyclopropyl), 3.63 (s, 2H, CH2), 3.31 (br. s, 4H, 2CH2-N), 2.59 (br. s, 4H, 2CH2-N), 1.29-1.02 (m, 4H, 2CH2-cyclopropyl). 13C NMR (75.1 MHz, DMSO-d6): δ 176.25 (C=O, ketone), 165.91 (CO2H), 165.20 (C=O, amid), 162.72 (d, 1JC-F = 281.5 Hz, C-F), 152.97 (d, 1JC-F = 249.3 Hz, C-F), 147.75 (d, 2JC-F = 16.1 Hz, C), 145.22, 134.43, 134.31, 132.67, 129.54, 129.47, 128.75, 122.12 (d, 3JC-F = 8.1 Hz, 2CH), 118.54 (d, 3JC-F = 6.3 Hz, C), 115.15 (d, 2JC-F = 21.7 Hz, 2CH), 110.85 (d, 2JC-F = 23.9 Hz, CH), 106.74, 101.61, 65.53 (CH2), 52.22 and 49.46 (2CH2-N), 35.81 (CH-cyclopropyl), 7.74 and 7.56 (2CH2-cyclopropyl). ESI-MS m/ z: 559.28 [M + H]+. Anal. Calcd. for C31H28F2N4O4: C, 66.66; H, 5.05; N, 10.03.; found: C, 66.82; H, 4.96; N, 9.79 %.
7-(4-(4-((4-bromophenyl)carbamoyl)benzyl)piperazin-1-yl)-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic acid (7l):
Yellow solid; mp: 234-237 °C; IR (KBr) (νmax/cm–1): 3520-3100 (OH and NH), 1722, 1665, 1613 (3CO), 1595, 1499, 1437, 1415, 1366, 1295, 1232, 1178, 1144, 1085, 1041, 992, 936, 833, 756, 740, 685, 655, 622. 1H NMR (300.1 MHz, DMSO-d6): δ 14.47 (s, 1H, CO2H), 10.36 (s, 1H, NH-amid), 8.60 (s, 1H, CH-quinolone), 7.99 (d, J = 7.6 Hz, 2H, 2CH), 7.80 (d, 3J H-F = 10.2 Hz, 1H, CH), 7.68-7.40 (m, 4H, 4CH), 7.35-7.28 (m, 3H, 3CH), 3.80-3.70 (m, 1H, CH-cyclopropyl), 3.62 (s, 2H, CH2), 3.31 (br. s, 4H, 2CH2-N), 2.58 (br. s, 4H, 2CH2-N), 1.30-1.00 (m, 4H, 2CH2-cyclopropyl). 13C NMR (75.1 MHz, DMSO-d6): δ 176.23 (C=O, ketone), 165.90 (CO2H), 165.16 (C=O, amid), 152.94 (d, 1JC-F = 247.2 Hz, C-F), 147.64 (d, 2JC-F = 27.2 Hz, C), 145.15, 136.82, 134.32, 132.60, 131.39, 129.64, 129.52, 129.11, 122.13, 120.76, 118.56, 110.85 (d, 2JC-F = 23.8 Hz, CH), 106.25, 101.46, 65.49 (CH2), 52.21 and 49.41 (2CH2-N), 35.79 (CH-cyclopropyl), 7.75 and 7.55 (2CH2-cyclopropyl). ESI-MS m/ z: 620.38 [M + H]+. Anal. Calcd. for C31H28BrFN4O4: C, 60.10; H, 4.56; N, 9.04.; found: C, 60.32; H, 4.38; N, 8.79 %.
1-cyclopropyl-6-fluoro-4-oxo-7-(4-(4-((4-(trifluoromethyl)phenyl)carbamoyl)benzyl)piperazin-1-yl)-1,4-dihydroquinoline-3-carboxylic acid (7m):
Yellow solid; mp: 189-201 °C; IR (KBr) (νmax/cm–1): 3450-2900 (OH and NH), 1715, 1648, 1612 (3CO), 1588, 1512, 1463, 1388, 1289, 1233, 1184, 1123, 1087, 1010, 936, 901, 821, 755, 736, 686, 639. 1H NMR (300.1 MHz, DMSO-d6): δ 15.15 (s, 1H, CO2H), 10.58 (s, 1H, NH-amid), 8.60 (s, 1H, CH-quinolone), 7.91 (d, J = 7.8 Hz, 2H, 2CH), 7.80 (d, 3J H-F = 13.2 Hz, 1H, CH), 7.69 (d, J = 8.2 Hz, 2H, 2CH), 7.58-7.30 (m, 5H, 5CH), 3.80-3.70 (m, 1H, CH-cyclopropyl), 3.62 (s, 2H, CH2), 3.32 (br. s, 4H, 2CH2-N), 2.59 (br. s, 4H, 2CH2-N), 1.40-0.98 (m, 4H, 2CH2-cyclopropyl). 13C NMR (75.1 MHz, DMSO-d6): δ 176.26 (C=O, ketone), 165.89 (CO2H), 165.16 (C=O, amid), 152.96 (d, 1JC-F = 248.1 Hz, C-F), 147.63 (d, 2JC-F = 28.9 Hz, C), 145.21, 140.75, 134.10, 133.24, 132.02, 129.49, 129.30, 128.78, 125.85, 124.37, 120.05, 118.52 (d, 3JC-F = 7.8 Hz, C), 110.84 (d, 2JC-F = 23.2 Hz, CH), 106.73, 101.46, 65.49 (CH2), 52.23 and 49.45 (2CH2-N), 35.83 (CH-cyclopropyl), 7.79 and 7.56 (2CH2-cyclopropyl). ESI-MS m/ z: 608.49 [M]+. Anal. Calcd. for C32H28F4N4O4: C, 63.15; H, 4.64; N, 9.21.; found: C, 63.38; H, 4.88; N, 9.43 %.
7-(4-(4-((3-cyanophenyl)carbamoyl)benzyl)piperazin-1-yl)-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic acid (7n):
White solid; mp: 211-214 °C; IR (KBr) (νmax/cm–1): 3500-3000 (OH and NH), 2258 (CN), 1719, 1633, 1615 (3CO), 1596, 1492, 1475, 1399, 1313, 1294, 1246, 1149, 1072, 1046, 1011, 913, 832, 760, 655. 1H NMR (300.1 MHz, DMSO-d6): δ 15.12 (s, 1H, CO2H), 10.55 (s, 1H, NH-amid), 8.61 (s, 1H, CH-quinolone), 8.08-7.86 (m, 4H, 4CH), 7.81 (d, 3J H-F = 13.0 Hz, 1H, CH), 7.75-7.30 (m, 5H, 5CH), 3.86-3.70 (m, 1H, CH-cyclopropyl), 3.62 (s, 2H, CH2), 3.31 (br. s, 4H, 2CH2-N), 2.59 (br. s, 4H, 2CH2-N), 1.38-1.02 (m, 4H, 2CH2-cyclopropyl). 13C NMR (75.1 MHz, DMSO-d6): δ 176.25 (C=O, ketone), 165.90 (CO2H), 165.15 (C=O, amid), 152.95 (d, 1JC-F = 248.2 Hz, C-F), 147.65 (d, 2JC-F = 25.5 Hz, C), 145.20, 141.88, 134.82, 133.29, 132.16, 130.02, 129.49, 129.32, 128.78, 125.51, 122.20, 119.19, 118.54 (d, 3JC-F = 6.8 Hz, C), 117.34, 110.83 (d, 2JC-F = 22.9 Hz, CH), 106.74, 101.68, 65.46 (CH2), 52.21 and 49.39 (2CH2-N), 35.80 (CH-cyclopropyl), 7.91 and 7.53 (2CH2-cyclopropyl). ESI-MS m/ z: 566.38 [M]+. Anal. Calcd. for C32H28FN5O4: C, 67.95; H, 4.99; N, 12.38.; found: C, 67.78; H, 5.12; N, 12.64 %.
6-fluoro-1-(4-fluorophenyl)-4-oxo-7-(4-(4-(phenylcarbamoyl)benzyl)piperazin-1-yl)-1,4-dihydroquinoline-3-carboxylic acid (7o):
Milky solid; mp: 184-187 °C; IR (KBr) (νmax/cm–1): 3350-2900 (OH and NH), 1718, 1656, 1612 (3CO), 1597, 1462, 1378, 1299, 1216, 1199, 1156, 1093, 984, 899, 797, 746, 668, 624. 1H NMR (300.1 MHz, DMSO-d6): δ 14.27 (s, 1H, CO2H), 10.23 (s, 1H, NH-amid), 8.62 (s, 1H, CH-quinolone), 8.02 (d, J = 8.0 Hz, 2H, 2CH), 7.97 (d, 3J H-F = 12.4 Hz, 1H, CH), 7.75 (d, J = 8.0 Hz, 2H, 2CH), 7.70-7.10 (m, 10H, 10CH), 3.58 (s, 2H, CH2), 3.05 (br. s, 4H, 2CH2-N), 2.72 (br. s, 4H, 2CH2-N). 13C NMR (75.1 MHz, DMSO-d6): δ 177.26 (C=O, ketone), 168.53 (CO2H), 165.70 (C=O, amid), 162.21 (d, 1JC-F = 265.7 Hz, C-F), 153.19 (d, 1JC-F = 202.6 Hz, C-F), 148.51 (d, 2JC-F = 23.4 Hz, C), 146.31, 136.64, 135.67, 133.36, 131.56 (d, 4JC-F = 1.9 Hz, C), 130.46 (d, 3JC-F = 6.7 Hz, 2CH), 129.83, 129.52, 128.63, 127.76, 127.40, 120.36, 118.14 (d, 3JC-F = 6.8 Hz, C), 117.21 (d, 2JC-F = 24.4 Hz, C-F), 110.95 (d, 3JC-F = 26.7 Hz, CH), 107.84, 102.33, 66.65 (CH2), 52.13 and 49.05 (2CH2-N). 0ESI-MS m/ z: 595.34 [M + 1]+. Anal. Calcd. for C34H28F2N4O4: C, 68.68; H, 4.75; N, 9.42.; found: C, 68.44; H, 4.99; N, 9.21 %.
6-fluoro-1-(4-fluorophenyl)-4-oxo-7-(4-(4-(4-tolylcarbamoyl)benzyl)piperazin-1-yl)-1,4-dihydroquinoline-3-carboxylic acid (7p):
White solid; mp: 208-207 °C; IR (KBr) (νmax/cm–1): 3500–3100 (OH), 3066 (NH), 1721, 1640, 1628 (3CO), 1510, 1467, 1385, 1336, 1301, 1262, 1178, 1102, 1018, 946, 891, 834, 763, 706, 634, 588, 550, 514, 467. 1H NMR (300.1 MHz, DMSO-d6): δ 14.81 (s, 1H, CO2H), 10.16 (s, 1H, NH-amid), 8.62 (s, 1H, CH-quinolone), 8.03 (d, J = 7.6 Hz, 2H, 2CH), 7.94 (d, 3J H-F = 13.1 Hz, 1H, CH), 7.70-7.20 (m, 9H, 9CH), 7.14 (t, J = 7.8 Hz, 2H, 2CH), 3.56 (s, 2H, CH2), 3.03 (br. s, 4H, 2CH2-N), 2.72 (br. s, 4H, 2CH2-N), 2.26 (s, 3H, CH3). 13C NMR (75.1 MHz, DMSO-d6): δ 177.87 (C=O, ketone), 168.62 (CO2H), 165.73 (C=O, amid), 162.45 (d, 1JC-F = 246.7 Hz, C-F), 153.55 (d, 1JC-F = 147.6 Hz, C-F), 148.69 (d, 2JC-F = 15.4 Hz, C), 146.39, 139.11, 134.68, 133.79, 131.58, 130.54 (d, 3JC-F = 9.9 Hz, 2CH), 129.84, 129.52, 129.29, 128.95, 127.75, 120.32, 118.50, 117.24 (d, 2JC-F = 22.6 Hz, 2CH), 110.99 (d, 2JC-F = 23.9 Hz, CH), 107.51, 102.11, 65.47 (CH2), 52.05 and 49.07 (2CH2-N), 20.47 (CH3). ESI-MS m/ z: 609.74 [M + H]+. Anal. Calcd. for C35H30F2N4O4: C, 69.07; H, 4.97; N, 9.21.; found: C, 68.88; H, 5.14; N, 8.98 %.
6-fluoro-1-(4-fluorophenyl)-4-oxo-7-(4-(4-(3-tolylcarbamoyl)benzyl)piperazin-1-yl)-1,4-dihydroquinoline-3-carboxylic acid (7q):
Milky solid; mp: 189-192 °C; IR (KBr) (νmax/cm–1): 3500-3200 (OH), 3098 (NH), 1723, 1648, 1613 (3CO), 1598, 1474, 1399, 1323, 1276, 1191, 1095, 994, 839, 754, 685, 648. 1H NMR (300.1 MHz, DMSO-d6): δ 14.94 (s, 1H, CO2H), 10.61 (s, 1H, NH-amid), 8.61 (s, 1H, CH-quinolone), 7.95 (d, J = 7.2 Hz, 2H, 2CH), 7.89 (d, 3J H-F = 10.8 Hz, 1H, CH), 7.65-7.26 (m, 8H, 8CH), 7.20-7.00 (m, 3H, 3CH), 3.55 (s, 2H, CH2), 3.04 (br. s, 4H, 2CH2-N), 2.72 (br. s, 4H, 2CH2-N), 2.15 (s, 3H, CH3). 13C NMR (75.1 MHz, DMSO-d6): δ 177.88 (C=O, ketone), 168.23 (CO2H), 165.73 (C=O, amid), 162.47 (d, 1JC-F = 247.3 Hz, C-F), 152.97 (d, 1JC-F = 246.2 Hz, C-F), 148.42 (d, 2JC-F = 25.7 Hz, C), 146.45, 139.13, 135.86, 133.72, 131.59 (d, 4JC-F = 2.3 Hz, C), 130.40 (d, 3JC-F = 6.4 Hz, 2CH), 129.84, 129.53, 129.48, 129.27, 129.01, 128.71, 127.76, 127.48, 118.52, 117.25 (d, 2JC-F = 23.1 Hz, 2CH), 110.99 (d, 2JC-F = 24.1 Hz, CH), 107.48, 102.14, 65.46 (CH2), 52.06 and 49.12 (2CH2-N), 21.11 (CH3). ESI-MS m/ z: 608.32 [M]+. Anal. Calcd. for C35H30F2N4O4: C, 69.07; H, 4.97; N, 9.21.; found: C, 69.26; H, 4.68; N, 9.46 %.
6-fluoro-1-(4-fluorophenyl)-4-oxo-7-(4-(4-(2-tolylcarbamoyl)benzyl)piperazin-1-yl)-1,4-dihydroquinoline-3-carboxylic acid (7r):
White solid; mp: 168-169 °C; IR (KBr) (νmax/cm–1): 3500-3100 (OH and NH), 1719, 1664, 1622 (3CO), 1594, 1444, 1377, 1283, 1189, 1123, 1068, 991, 957, 843, 790, 753, 645, 623. 1H NMR (300.1 MHz, DMSO-d6): δ 15.00 (s, 1H, CO2H), 10.90 (s, 1H, NH-amid), 8.61 (s, 1H, CH-quinolone), 8.02 (d, J = 7.7 Hz, 2H, 2CH), 7.90 (d, 3J H-F = 12.5 Hz, 1H, CH), 7.65-7.25 (m, 6H, 6CH), 7.20-7.00 (m, 5H, 5CH), 3.54 (s, 2H, CH2), 3.02 (br. s, 4H, 2CH2-N), 2.72 (br. s, 4H, 2CH2-N), 2.17 (s, 3H, CH3). 13C NMR (75.1 MHz, DMSO-d6): δ 177.41 (C=O, ketone), 167.32 (CO2H), 165.77 (C=O, amid), 162.48 (d, 1JC-F = 245.9 Hz, C-F), 152.88 (d, 1JC-F = 247.2 Hz, C-F), 148.45 (d, 2JC-F = 18.8 Hz, C), 146.67, 139.11, 135.83, 133.70, 131.05 (d, 4JC-F = 2.9 Hz, C), 130.62 (d, 3JC-F = 4.2 Hz, 2CH), 129.85, 129.55, 129.30, 129.02, 128.72, 127.76, 127.48, 118.53 (d, 3JC-F = 5.3 Hz, C), 117.29 (d, 2JC-F = 23.3 Hz, 2CH), 110.99 (d, 2JC-F = 25.4 Hz, CH), 107.51, 102.21, 65.39 (CH2), 52.07 and 49.11 (2CH2-N), 20.57 (CH3). ESI-MS m/ z: 608.48 [M]+. Anal. Calcd. for C35H30F2N4O4: C, 69.07; H, 4.97; N, 9.21.; found: C, 69.16; H, 5.23; N, 9.57 %.
6-fluoro-1-(4-fluorophenyl)-7-(4-(4-((4-methoxyphenyl)carbamoyl)benzyl)piperazin-1-yl)-4-oxo-1,4-dihydroquinoline-3-carboxylic acid (7s):
Yellow solid; mp: 236-239 °C; IR (KBr) (νmax/cm–1): 3500-3150 (OH), 3068 (NH), 1722, 1635, 1612 (3CO), 1598, 1548, 1391, 1368, 1297, 1188, 1079, 997, 935, 897, 752, 668, 623. 1H NMR (300.1 MHz, DMSO-d6): δ 14.36 (s, 1H, CO2H), 10.12 (s, 1H, NH-amid), 8.43 (s, 1H, CH-quinolone), 7.93 (d, J = 7.8 Hz, 2H, 2CH), 7.89 (d, 3J H-F = 10.4 Hz, 1H, CH), 7.84-7.28 (m, 7H, 7CH), 7.13 (t, J = 7.8 Hz, 2H, 2CH), 6.91 (d, J = 8.4 Hz, 2H, 2CH), 3.73 (s, 3H, OCH3), 3.56 (s, 2H, CH2), 2.98 (br. s, 4H, 2CH2-N), 2.77 (br. s, 4H, 2CH2-N). 13C NMR (75.1 MHz, DMSO-d6): δ 177.77 (C=O, ketone), 168.42 (CO2H), 166.42 (C=O, amid), 162.43 (d, 1JC-F = 273.7 Hz, C-F), 155.51, 152.78 (d, 1JC-F = 210.8 Hz, C-F), 148.58 (d, 2JC-F = 22.3 Hz, C), 146.90, 136.55, 134.38, 133.79, 132.21 (d, 4JC-F = 5.2 Hz, C), 129.98 (d, 3JC-F = 8.9 Hz, C), 129.58, 129.23, 128.62, 121.92, 118.86, 117.22 (d, 2JC-F = 23.1 Hz, 2CH), 113.69, 111.41 (d, 2JC-F = 12.3 Hz, CH), 108.35, 102.55, 64.89 (CH2), 55.15 (OCH3), 52.11 and 49.27 (2CH2-N). ESI-MS m/ z: 625.36 [M + H]+. Anal. Calcd. for C35H30F2N4O5: C, 67.30; H, 4.84; N, 8.97.; found: C, 67.14; H, 5.06; N, 9.12 %.
6-fluoro-1-(4-fluorophenyl)-7-(4-(4-((3-methoxyphenyl)carbamoyl)benzyl)piperazin-1-yl)-4-oxo-1,4-dihydroquinoline-3-carboxylic acid (7t):
Pale yellow solid; mp: 212-215 °C; IR (KBr) (νmax/cm–1): 3500-2900 (OH and NH), 1718, 1648, 1614 (3CO), 1596, 1511, 1497, 1346, 1287, 1192, 1153, 1084, 997, 835, 776, 658, 635. 1H NMR (300.1 MHz, DMSO-d6): δ 14.59 (s, 1H, CO2H), 10.21 (s, 1H, NH-amid), 8.62 (s, 1H, CH-quinolone), 8.12-7.80 (m, 3H, 3CH), 7.70-7.00 (m, 10H, 10CH), 6.67 (d, J = 7.4 Hz, 1H, CH), 3.74 (s, 3H, OCH3), 3.62 (s, 2H, CH2), 3.03 (br. s, 4H, 2CH2-N), 2.78 (br. s, 4H, 2CH2-N). 13C NMR (75.1 MHz, DMSO-d6): δ 178.84 (C=O, ketone), 168.33 (CO2H), 165.17 (C=O, amid), 162.46 (d, 1JC-F = 244.7 Hz, C-F), 155.43, 152.87 (d, 1JC-F = 249.3 Hz, C-F), 148.44 (d, 2JC-F = 19.2 Hz, C), 146.63, 136.16, 134.59, 133.68, 131.16 (d, 4JC-F = 1.9 Hz, C-F), 129.87, 129.53, 129.51 (d, 3JC-F = 5.1 Hz, 2CH), 129.28, 129.00, 127.75, 127.46, 118.63, 117.26 (d, 2JC-F = 23.6 Hz, 2CH), 112.49, 110.99 (d, 2JC-F = 22.7 Hz, CH), 107.49, 106.36, 102.39, 65.48 (CH2), 54.96 (OCH3), 52.05 and 49.08 (2CH2-N). ESI-MS m/ z: 624.58 [M]+. Anal. Calcd. for C35H30F2N4O5: C, 67.30; H, 4.84; N, 8.97.; found: C, 67.56; H, 4.54; N, 8.78 %.
6-fluoro-1-(4-fluorophenyl)-7-(4-(4-((2-methoxyphenyl)carbamoyl)benzyl)piperazin-1-yl)-4-oxo-1,4-dihydroquinoline-3-carboxylic acid (7u):
Pale yellow solid; mp: 192-195 °C; IR (KBr) (νmax/cm–1): 3500-3000 (OH), 2968 (NH), 1728, 1656, 1618 (3CO), 1578, 1532, 1432, 1397, 1292, 1188, 1132, 1095, 989, 933, 844, 732, 684, 625. 1H NMR (300.1 MHz, DMSO-d6): δ 14.34 (s, 1H, CO2H), 10.10 (s, 1H, NH-amid), 8.61 (s, 1H, CH-quinolone), 7.98 (d, J = 8.0 Hz, 2H, 2CH), 7.90 (d, 3J HF = 12.1 Hz, 1H, CH), 7.65-7.28 (m, 8H, 8CH), 7.20-6.80 (m, 3H, 3CH), 3.87 (s, 3H, OCH3), 3.60 (s, 2H, CH2), 3.03 (br. s, 4H, 2CH2-N), 2.86 (br. s, 4H, 2CH2-N). 13C NMR (75.1 MHz, DMSO-d6): δ 178.97 (C=O, ketone), 167.65 (CO2H), 165.89 (C=O, amid), 162.43 (d, 1JC-F = 263.3 Hz, C-F), 155.13, 152.99 (d, 1JC-F = 249.0 Hz, C-F), 148.53 (d, 2JC-F = 20.4 Hz, C), 146.18, 136.15, 134.18, 133.11, 132.41, 131.47 (d, 4JC-F = 1.3 Hz, C), 129.94, 129.59 (d, 3JC-F = 4.3 Hz, 2CH), 128.83, 127.85, 127.55, 122.63, 118.59, 117.33 (d, 2JC-F = 22.2 Hz, 2CH), 113.15, 111.08 (d, 2JC-F = 20.6 Hz, CH), 107.52, 102.42, 65.45 (CH2), 54.40 (OCH3), 52.10 and 49.16 (2CH2-N). ESI-MS m/ z: 625.56 [M + H]+. Anal. Calcd. for C35H30F2N4O5: C, 67.30; H, 4.84; N, 8.97.; found: C, 67.68; H, 5.12; N, 9.23 %.
7-(4-(4-((4-chlorophenyl)carbamoyl)benzyl)piperazin-1-yl)-6-fluoro-1-(4-fluorophenyl)-4-oxo-1,4-dihydroquinoline-3-carboxylic acid (7v):
White solid; mp: 268-270 °C; IR (KBr) (νmax/cm–1): 3500-2900 (OH and NH), 1719, 1652, 1618 (3CO), 1602, 1445, 1422, 1398, 1277, 1252, 1129, 1098, 1032, 988, 928, 848, 776, 729, 687, 635. 1H NMR (300.1 MHz, DMSO-d6): δ 15.09 (s, 1H, CO2H), 10.40 (s, 1H, NH-amid), 8.63 (s, 1H, CH-quinolone), 7.98 (d, J = 7.4 Hz, 2H, 2CH), 7.89 (d, 3J HF = 11.8 Hz, 1H, CH), 7.78 (d, J = 8.5 Hz, 2H, 2CH), 7.68-7.00 (m, 9H, 9CH), 3.55 (s, 2H, CH2), 3.08 (br. s, 4H, 2CH2-N), 2.88 (br. s, 4H, 2CH2-N). 13C NMR (75.1 MHz, DMSO-d6): δ 177.43 (C=O, ketone), 168.23 (CO2H), 165.63 (C=O, amid), 162.47 (d, 1JC-F = 246.8 Hz, C-F), 152.89 (d, 1JC-F = 238.6 Hz, C-F), 148.26 (d, 2JC-F = 18.4 Hz, C), 146.18, 136.15, 135.08, 133.68, 132.98, 131.74, 129.87, 129.53 (d, 3JC-F = 3.6 Hz, 2CH), 128.89, 128.50, 127.98, 121.98, 118.41, 117.25 (d, 2JC-F = 21.7 Hz, 2CH), 110.99 (d, 2JC-F = 23.6 Hz, CH), 107.36, 102.48, 65.57 (CH2), 52.47 and 49.53 (2CH2-N). ESI-MS m/ z: 630.43 [M + H]+. Anal. Calcd. for C34H27ClF2N4O4: C, 64.92; H, 4.33; N, 8.91.; found: C, 65.13; H, 4.58; N, 9.18 %.
7-(4-(4-((3-chlorophenyl)carbamoyl)benzyl)piperazin-1-yl)-6-fluoro-1-(4-fluorophenyl)-4-oxo-1,4-dihydroquinoline-3-carboxylic acid (7w):
White solid; mp: 236-239 °C; IR (KBr) (νmax/cm–1): 3500-3200 (OH), 3062 (NH), 1724, 1647, 1629 (3CO), 1595, 1498, 1472, 1349, 1258, 1263, 1149, 1085, 1035, 972, 948, 885, 784, 738, 625. 1H NMR (300.1 MHz, DMSO-d6): δ 14.36 (s, 1H, CO2H), 10.41 (s, 1H, NH-amid), 8.62 (s, 1H, CH-quinolone), 8.10-7.80 (m, 5H, 5CH), 7.70-7.30 (m, 6H, 6CH), 7.25-7.00 (m, 3H, 3CH), 3.55 (s, 2H, CH2), 3.04 (br. s, 4H, 2CH2-N), 2.88 (br. s, 4H, 2CH2-N). 13C NMR (75.1 MHz, DMSO-d6): δ 177.37 (C=O, ketone), 168.17 (CO2H), 165.73 (C=O, amid), 162.28 (d, 1JC-F = 219.7 Hz, C-F), 153.03 (d, 1JC-F = 231.1 Hz, C-F), 148.72 (d, 2JC-F = 16.3 Hz, C), 146.54, 139.15, 135.15, 133.86, 133.51, 131.40 (d, 4JC-F = 1.2 Hz, C), 129.87, 129.51 (d, 3JC-F = 5.2 Hz, 2CH), 129.25, 128.70, 128.55, 127.78, 127.76, 127.48, 119.44, 117.25 (d, 2JC-F = 31.1 Hz, 2CH), 111.02 (d, 2JC-F = 27.2 Hz, CH), 107.49, 102.34, 65.48 (CH2), 52.07 and 49.15 (2CH2-N). ESI-MS m/ z: 629.48 [M]+. Anal. Calcd. for C34H27ClF2N4O4: C, 64.92; H, 4.33; N, 8.91.; found: C, 64.78; H, 4.14; N, 9.14 %.
7-(4-(4-((2-chlorophenyl)carbamoyl)benzyl)piperazin-1-yl)-6-fluoro-1-(4-fluorophenyl)-4-oxo-1,4-dihydroquinoline-3-carboxylic acid (7x):
Milky solid; mp: 198-201 °C; IR (KBr) (νmax/cm–1): 3450-3000 (OH and NH), 1724, 1635, 1612 (3CO), 1599, 1506, 1436, 1348, 1294, 1233, 1172, 1061, 990, 898, 831, 786, 686, 635. 1H NMR (300.1 MHz, DMSO-d6): δ 15.08 (s, 1H, CO2H), 10.06 (s, 1H, NH-amid), 8.62 (s, 1H, CH-quinolone), 7.95 (d, J = 7.6 Hz, 2H, 2CH), 7.89 (d, 3J HF = 12.8 Hz, 1H, CH), 7.80-7.20 (m, 9H, 9CH), 7.15 (t, J = 7.8 Hz, 2H, 2CH), 3.57 (s, 2H, CH2), 3.04 (br. s, 4H, 2CH2-N), 2.72 (br. s, 4H, 2CH2-N). 13C NMR (75.1 MHz, DMSO-d6): δ 176.65 (C=O, ketone), 167.31 (CO2H), 165.76 (C=O, amid), 162.49 (d, 1JC-F = 245.9 Hz, C-F), 152.83 (d, 1JC-F = 238.8 Hz, C-F), 148.59 (d, 2JC-F = 7.9 Hz, C), 146.30, 139.17, 135.02, 133.61, 132.70, 131.22 (d, 4JC-F = 3.1 Hz, C), 129.88, 129.53 (d, 3JC-F = 4.3 Hz, 2CH), 129.33, 128.92, 127.96, 127.80, 127.72, 127.49, 118.64, 117.27 (d, 2JC-F = 23.7 Hz, 2CH), 111.02 (d, 1JC-F = 23.2 Hz, CH), 107.43, 102.26, 65.52 (CH2), 52.07 and 49.13 (2CH2-N). ESI-MS m/ z: 628.63 [M]+. Anal. Calcd. for C34H27ClF2N4O4: C, 64.92; H, 4.33; N, 8.91.; found: C, 64.68; H, 4.09; N, 8.76 %.
6-fluoro-1-(4-fluorophenyl)-7-(4-(4-((4-fluorophenyl)carbamoyl)benzyl)piperazin-1-yl)-4-oxo-1,4-dihydroquinoline-3-carboxylic acid (7y):
White solid; mp: 228-231 °C; IR (KBr) (νmax/cm–1): 3500-3300 (OH), 2987 (NH), 1717, 1652, 1620 (3CO), 1575, 1511, 1485, 1327, 1254, 1082, 1046, 945, 823, 766, 628. 1H NMR (300.1 MHz, DMSO-d6): δ 14.11 (s, 1H, CO2H), 10.26 (s, 1H, NH-amid), 8.62 (s, 1H, CH-quinolone), 7.96 (d, J = 7.8 Hz, 2H, 2CH), 7.87 (d, 3J HF = 12.1 Hz, 1H, CH), 7.68-7.20 (m, 7H, 7CH), 7.18 (t, J = 7.6 Hz, 2H, 2CH), 7.07 (t, J = 7.4 Hz, 2H, 2CH), 3.59 (s, 2H, CH2), 3.05 (br. s, 4H, 2CH2-N), 2.86 (br. s, 4H, 2CH2-N). 13C NMR (75.1 MHz, DMSO-d6): δ 177.01 (C=O, ketone), 167.43 (CO2H), 165.78 (C=O, amid), 162.35 (d, 1JC-F = 258.3 Hz, C-F), 162.02 (d, 1JC-F = 261.0 Hz, C-F), 152.83 (d, 1JC-F = 243.6 Hz, C-F), 148.44 (d, 2JC-F = 23.6 Hz, C), 146.79, 135.27, 134.75, 133.60, 131.17, 129.89, 129.47 (d, 3JC-F = 1.8 Hz, 2CH), 128.65, 127.89, 122.18 (d, 3JC-F = 3.4 Hz, 2CH), 118.65, 117.54 (d, 2JC-F = 19.3 Hz, 2CH), 115.20 (d, 2JC-F = 18.7 Hz, 2CH), 110.83 (d, 2JC-F = 21.8 Hz, CH), 107.63, 102.53, 65.56 (CH2), 52.08 and 48.32 (2CH2-N). ESI-MS m/ z: 612.49 [M]+. Anal. Calcd. for C34H27F3N4O4: C, 66.66; H, 4.44; N, 9.15.; found: C, 66.94; H, 4.69; N, 8.89 %.
7-(4-(4-((4-bromophenyl)carbamoyl)benzyl)piperazin-1-yl)-6-fluoro-1-(4-fluorophenyl)-4-oxo-1,4-dihydroquinoline-3-carboxylic acid (7z):
Pale yellow solid; mp: 262-266 °C; IR (KBr) (νmax/cm–1): 3400-2900 (OH and NH), 1718, 1636, 1613 (3CO), 1595, 1434, 1345, 1293, 1233, 1145, 1061, 995, 846, 789, 748, 647, 623. 1H NMR (300.1 MHz, DMSO-d6): δ 14.91 (s, 1H, CO2H), 10.37 (s, 1H, NH-amid), 8.61 (s, 1H, CH-quinolone), 7.95 (d, J = 7.6 Hz, 2H, 2CH), 7.89 (d, 3J HF = 12.8 Hz, 1H, CH), 7.76 (d, J = 8.4 Hz, 2H, 2CH), 7.70-7.10 (m, 9H, 9CH), 3.56 (s, 2H, CH2), 3.04 (br. s, 4H, 2CH2-N), 2.88 (br. s, 4H, 2CH2-N). 13C NMR (75.1 MHz, DMSO-d6): δ 177.75 (C=O, ketone), 167.37 (CO2H), 165.74 (C=O, amid), 162.44 (d, 1JC-F = 248.3 Hz, C-F), 152.88 (d, 1JC-F = 252.4 Hz, C-F), 148.51 (d, 2JC-F = 13.8 Hz, C), 146.34, 136.15, 134.30, 133.41, 131.38, 129.83, 129.50 (d, 3JC-F = 3.3 Hz, 2CH), 129.29, 128.69, 127.75, 122.13, 121.45, 118.62, 117.28 (d, 2JC-F = 22.9 Hz, 2CH), 110.98 (d, 2JC-F = 23.2 Hz, CH), 107.59, 102.38, 65.47 (CH2), 52.04 and 49.06 (2CH2-N). ESI-MS m/ z: 672.58 [M]+. Anal. Calcd. for C34H27BrF2N4O4: C, 60.63; H, 4.04; N, 8.32.; found: C, 60.88; H, 3.76; N, 8.66 %.
6-fluoro-1-(4-fluorophenyl)-4-oxo-7-(4-(4-((4-(trifluoromethyl)phenyl)carbamoyl)benzyl)piperazin-1-yl)-1,4-dihydroquinoline-3-carboxylic acid (7aa):
White solid; mp: 278-280 °C; IR (KBr) (νmax/cm–1): 3500-3000 (OH and NH), 1722, 1646, 1612 (3CO), 1602, 1482, 1453, 1371, 1285, 1253, 1198, 1045, 939, 879, 755, 695, 644, 623. 1H NMR (300.1 MHz, DMSO-d6): δ 15.13 (s, 1H, CO2H), 10.54 (s, 1H, NH-amid), 8.63 (s, 1H, CH-quinolone), 7.97 (d, J = 7.8 Hz, 2H, 2CH), 7.89 (d, 3J HF = 12.1 Hz, 1H, CH), 7.78 (d, J = 8.0 Hz, 2H, 2CH), 7.68-7.40 (m, 5H, 5CH), 7.38 (d, J = 8.0 Hz, 2H, 2CH), 7.15 (t, J = 7.6 Hz, 2H, 2CH), 3.58 (s, 2H, CH2), 3.05 (br. s, 4H, 2CH2-N), 2.72 (br. s, 4H, 2CH2-N). 13C NMR (75.1 MHz, DMSO-d6): δ 177.40 (C=O, ketone), 168.34 (CO2H), 166.56 (C=O, amid), 162.52 (d, 1JC-F = 270.0 Hz, C-F), 153.26 (d, 1JC-F = 234.1 Hz, C-F), 148.54 (d, 2JC-F = 22.3 Hz, C), 146.90, 140.69, 133.77, 133.40, 131.58, 129.88, 129.50 (d, 3JC-F = 5.8 Hz, 2CH), 128.75, 127.82, 125.89, 124.55, 121.10, 118.50, 117.50 (d, 2JC-F = 13.8 Hz, 2CH), 110.68 (d, 2JC-F = 27.9 Hz, CH), 107.82, 102.88, 64.28 (CH2), 52.08 and 49.78 (2CH2-N). ESI-MS m/ z: 663.24 [M + H]+. Anal. Calcd. for C35H27F5N4O4: C, 63.44; H, 4.11; N, 8.46.; found: C, 63.89; H, 3.93; N, 8.23 %.
7-(4-(4-((3-cyanophenyl)carbamoyl)benzyl)piperazin-1-yl)-6-fluoro-1-(4-fluorophenyl)-4-oxo-1,4-dihydroquinoline-3-carboxylic acid (7ab):
Milky solid; mp: 221-224 °C; IR (KBr) (νmax/cm–1): 3450-2900 (OH and NH), 2249 (CN), 1721, 1648, 1622 (3CO), 1598, 1494, 1455, 1399, 1343, 1298, 1242, 1176, 1128, 1096, 1038, 915, 826, 795, 759, 736, 689, 655. 1H NMR (300.1 MHz, DMSO-d6): δ 14.14 (s, 1H, CO2H), 10.54 (s, 1H, NH-amid), 8.62 (s, 1H, CH-quinolone), 8.03 (d, J = 7.5 Hz, 2H, 2CH), 7.87 (d, 3J HF = 11.2 Hz, 1H, CH), 7.76 (s, IH, CH), 7.70-7.30 (m, 8H, 8CH), 7.12 (t, J = 7.6 Hz, 2H, 2CH), 3.57 (s, 2H, CH2), 3.04 (br. s, 4H, 2CH2-N), 2.88 (br. s, 4H, 2CH2-N). 13C NMR (75.1 MHz, DMSO-d6): δ 177.39 (C=O, ketone), 167.25 (CO2H), 165.72 (C=O, amid), 162.45 (d, 1JC-F = 243.8 Hz, C-F), 153.23 (d, 1JC-F = 202.1 Hz, C-F), 148.44 (d, 2JC-F = 26.6 Hz, C), 146.34, 141.82, 135.37, 133.83, 133.03, 131.47, 130.65, 130.06, 129.50 (d, 3JC-F = 4.8 Hz, 2CH), 128.69, 127.77, 125.70, 122.62, 119.98, 118.56, 117.96, 117.24 (d, 3JC-F = 22.7 Hz, 2CH), 110.99 (d, 3JC-F = 27.4 Hz, CH), 107.37, 102.75, 65.48 (CH2), 52.03 and 49.10 (2CH2-N). ESI-MS m/ z: 620.58 [M + H]+. Anal. Calcd. for C35H27F2N5O4: C, 67.84; H, 4.39; N, 11.30.; found: C, 68.12; H, 4.64; N, 11.18 %.
Antibacterial assays
panel of selected standard bacterial strains, including gram-positive (MRSA ATCC 12493, Staphylococcus aureus ATCC 29213 and Enterococcus faecalis ATCC 29212) and gram-negative (Pseudomonas aeruginosa ATCC 27853, Klebsiella pneumonia ATCC 11706, Escherichia coli ATCC 25922) were utilized to evaluate the antibacterial activities of synthesized compounds 7a–ab using three methods, including broth microdilution, well diffusion and disc diffusion assays.
Broth microdilution
In order to determine the MIC of compounds 7a–ab, broth microdilution assay was performed as described previously [19]. Briefly, the starting concentrations of compounds were 100 μg/mL and they were prepared by dissolving the compounds in DMSO (1 mL), dilution with water (9 mL). The turbidity of the bacterial solution was adjusted by using McFarland as 0.5 which corresponded 107 CFU/mL and then, two-fold dilution was made. After adding bacterial solutions (1–5 × 105 CFU/mL) into the 96-well plate, the plate incubated at 35–37 °C aerobically. After 18 h, MICs were characterized as the lowest concentration of an agent which can prevent the visible growth on the plate.
Well diffusion assay
Antibacterial activities of compounds 7a–ab were assessed using well diffusion assay on MHA as described previously [46]. Preparing the bacterial suspension was done by adjusting the turbidity of the solution as 0.5 McFarland. After the inoculation of bacterial strains on MHA agar plates, 50 μl of the targeted compound solutions poured into the wells (diameter = 6 mm) and incubated at 37 °C. After 24 h, the growth inhibition zones were determined in diameter. The zones of inhibition were given in millimeters (mm).
Disk diffusion assay
Agar disk-diffusion assay was performed on MHA, as explained previously [46]. In summary, each bacterium was cultured in MHA and incubated at 37 °C. After 24 h, in order to prepare a suspension of 105 CFU/mL, the bacteria were suspended in saline solution, in accordance with the McFarland protocol (0.5 McFarland). Fresh stock solutions of compounds 7a–ab were prepared in DMSO. Then, the different concentrations were produced by dilution of the stock solution of each test compound. The discs (6.0 mm diameter) were injected with the different concentrations of the test compound and inoculated on the MHA. After incubation of the plates at 37 °C for 18 h, the antibacterial activity of each compound was characterized by the formation of an inhibitory zone, which reported in mm.
Molecular docking study
Based on the crystal structure of topoisomerase II DNA gyrase cocrystallized with ciprofloxacin (PDB ID: 2XCT, https://www.rcsb.org), docking study was employed to explore the binding mode of 7n in comparison with ciprofloxacin in the active site of the enzyme. Using AutoDock 4.2.1, the protein-DNA complex was prepared as a pdbqt file. In the 2XCT structure, the chains 'S, U, V, W, X, and Y' were choosen, CPF 1020 bound to Mn2001 was deleted, and the grid was created at coordinates x = 41.533, y = 45.643, z= -18.864, and 40 × 40 × 40 A. Redocking of cocrystallized ligand ciprofloxacin within the active site of topoisomerase II DNA-gyrase was performed to assess the docking accuracy. With a RMSD of 0.21 A, AutoDock reproduced ciprofloxacin's binding position successfully. The 3D structure of 7n was generated by MarvineSketch 5.8.3, 2012, ChemAxon (www.chemaxon.com) and converted to pdbqt format by AutoDock Tools. Each docked system was carried out by 100 runs by the Lamarckian genetic algorithm. The results were displayed using Discovery Studio 4.0 Client [47].
Data availability
The authors confirm that the data supporting the finding of this study are available within the manuscript.
References
Armstrong GL, Conn LA, Pinner RW (1999) Trends in infectious disease mortality in the United States during the 20th century. Jama 281:61–66. https://doi.org/10.1001/jama.281.1.61
Chambers HF (2005) Community-associated MRSA—resistance and virulence converge. N Engl Med 352:1485–1487. https://doi.org/10.1056/nejme058023
Song R, Wang Y, Wang M, Gao R, Yang T, Yang S, Yang C-G, Jin Y, Zou S, Cai J (2020) Design and synthesis of novel desfluoroquinolone-aminopyrimidine hybrids as potent anti-MRSA agents with low hERG activity. Bioorg Chem 103:104176. https://doi.org/10.1016/j.bioorg.2020.104176
Moran GJ, Krishnadasan A, Gorwitz RJ, Fosheim GE, McDougal LK, Carey RB, Talan DA (2006) Methicillin-resistant S. aureus infections among patients in the emergency department. N Engl J Med 355:666–674. https://doi.org/10.1016/j.annemergmed.2007.07.004
Moran GJ, Amii RN, Abrahamian FM, Talan DA (2005) Methicillin-resistant Staphylococcus aureus in community-acquired skin infections. Emerg Infect Dis 11:928. https://doi.org/10.3201/eid1106.040641
Wilson P, Andrews J, Charlesworth R, Walesby R, Singer M, Farrell D, Robbins M (2003) Linezolid resistance in clinical isolates of Staphylococcus aureus. J Antimicrob Chemother 51:186–188. https://doi.org/10.1093/jac/dkg104
Frazee BW, Lynn J, Charlebois ED, Lambert L, Lowery D, Perdreau-Remington F (2005) High prevalence of methicillin-resistant Staphylococcus aureus in emergency department skin and soft tissue infections. Ann Emerg Med 45:311–320. https://doi.org/10.1016/j.annemergmed.2004.10.011
Fridkin SK, Hageman JC, Morrison M, Sanza LT, Como-Sabetti K, Jernigan JA, Harriman K, Harrison LH, Lynfield R, Farley MM (2005) Methicillin-resistant Staphylococcus aureus disease in three communities. N Engl J Med 352:1436–1444. https://doi.org/10.1097/01.aog.0000170861.29348.64
Hooper DC (1998) Clinical applications of quinolones. Biochim Biophys Acta BBA 1400:45–61. https://doi.org/10.1016/S0167-4781(98)00127-4
Owens RC Jr, Ambrose PG (2000) Clinical use of the fluoroquinolones. Med Clin N Am 84:1447–1469. https://doi.org/10.1016/S0025-7125(05)70297-2
Drlica K, Hiasa H, Kerns R, Malik M, Mustaev A, Zhao X (2009) Quinolones: action and resistance updated. Curr Top Med Chem 9:981–998. https://doi.org/10.2174/156802609789630947
Aldred KJ, Kerns RJ, Osheroff N (2014) Mechanism of quinolone action and resistance. Biochemistry 53:1565–1574. https://doi.org/10.1021/bi5000564
Dougherty TJ, Beaulieu D, Barrett JF (2001) New quinolones and the impact on resistance. Drug Discov Today 6:529–536. https://doi.org/10.1016/s1359-6446(01)01760-3
Timsit Y (2011) Local sensing of global DNA topology: from crossover geometry to type II topoisomerase processivity. Nucleic Acids Res 39:8665–8676. https://doi.org/10.1093/nar/gkr556
Zhang G-F, Zhang S, Pan B, Liu X, Feng L-S (2018) 4-Quinolone derivatives and their activities against Gram positive pathogens. Eur J Med Chem 143:710–723. https://doi.org/10.1016/j.ejmech.2017.11.082
Domagala JM (1994) Structure-activity and structure-side-effect relationships for the quinolone antibacterials. J Antimicrob Chemother 33:685–706. https://doi.org/10.1093/jac/33.4.685
Emami S, Shafiee A, Foroumadi A (2006) Structural features of new quinolones and relationship to antibacterial activity against Gram-positive bacteria. Mini Rev Med Chem 6:375–386. https://doi.org/10.2174/138955706776361493
Redgrave LS, Sutton SB, Webber MA, Piddock LJ (2014) Fluoroquinolone resistance: mechanisms, impact on bacteria, and role in evolutionary success. Trends Microbiol 22:438–445. https://doi.org/10.1016/j.tim.2014.04.007
Peterson LR (2001) Quinolone molecular structure-activity relationships: what we have learned about improving antimicrobial activity. Clin Infect Dis 33:S180–S186. https://doi.org/10.1086/321846
Letafat B, Emami S, Mohammadhosseini N, Faramarzi MA, Samadi N, Shafiee A, Foroumadi A (2007) Synthesis and antibacterial activity of new N-[2-(thiophen-3-yl) ethyl] piperazinyl quinolones. Chem Pharm Bull 55:894–898. https://doi.org/10.1002/chin.200748152
Emami S, Foroumadi A, Faramarzi MA, Samadi N (2008) Synthesis and antibacterial activity of quinolone-based compounds containing a coumarin moiety. Arch Pharm 341:42–48. https://doi.org/10.1002/ardp.200700090
Kumar R, Kumar A, Jain S, Kaushik D (2011) Synthesis, antibacterial evaluation and QSAR studies of 7-[4-(5-aryl-1, 3, 4-oxadiazole-2-yl) piperazinyl] quinolone derivatives. Eur J Med Chem 46:3543–3550. https://doi.org/10.1016/j.ejmech.2011.04.035
Emami S, Ghafouri E, Faramarzi MA, Samadi N, Irannejad H, Foroumadi A (2013) Mannich bases of 7-piperazinylquinolones and kojic acid derivatives: synthesis, in vitro antibacterial activity and in silico study. Eur J Med Chem 68:185–191. https://doi.org/10.1016/j.ejmech.2013.07.032
Sharma PC, Jain A, Yar MS, Pahwa R, Singh J, Goel S (2015) Synthesis and antibacterial evaluation of novel analogs of fluoroquinolones annulated with 6-substituted-2-aminobenzothiazoles. Arab J Chem 8:671–677. https://doi.org/10.1016/j.arabjc.2011.04.008
Dileep K, Polepalli S, Jain N, Buddana SK, Prakasham R, Murty M (2018) Synthesis of novel tetrazole containing hybrid ciprofloxacin and pipemidic acid analogues and preliminary biological evaluation of their antibacterial and antiproliferative activity. Mol Diversity 22:83–93. https://doi.org/10.1007/s11030-017-9795-y
Soleimani E, Torkaman S, Sepahvand H, Ghorbani S (2019) Ciprofloxacin-functionalized magnetic silica nanoparticles: as a reusable catalyst for the synthesis of 1 H-chromeno [2, 3-d] pyrimidine-5-carboxamides and imidazo [1, 2-a] pyridines. Mol Diversity 23:739–749. https://doi.org/10.1007/s11030-018-9907-3
Seliem IA, Panda SS, Girgis AS, Nagy YI, George RF, Fayad W, Fawzy NG, Ibrahim TS, Al-Mahmoudy AM, Sakhuja R (2020) Design, synthesis, antimicrobial, and DNA gyrase inhibitory properties of fluoroquinolone–dichloroacetic acid hybrids. Chem Biol Drug Design 95:248–259. https://doi.org/10.1111/cbdd.13638
Yang P, Luo J-B, Wang Z-Z, Zhang L-L, Xie X-B, Shi Q-S, Zhang X-G (2022) Synthesis and in vitro antibacterial activity of N-acylarylhydrazone-ciprofloxacin hybrids as novel fluoroquinolone derivatives. J Mol Struct 1262:133007. https://doi.org/10.1016/j.molstruc.2022.133007
Tan Y-M, Li D, Li F-F, Ansari MF, Fang B, Zhou C-H (2022) Pyrimidine-conjugated fluoroquinolones as new potential broad-spectrum antibacterial agents. Bioorg Med Chem Lett 73:128885. https://doi.org/10.1016/j.bmcl.2022.128885
Ibrahim NM, Fahim SH, Hassan M, Farag AE, Georgey HH (2022) Design and synthesis of ciprofloxacin-sulfonamide hybrids to manipulate ciprofloxacin pharmacological qualities: potency and side effects. Eur J Med Chem 228:114021. https://doi.org/10.1016/j.ejmech.2021.114021
Kumar N, Khanna A, Kaur K, Kaur H, Sharma A, Bedi PMS (2022) Quinoline derivatives volunteering against antimicrobial resistance: rational approaches, design strategies, structure activity relationship and mechanistic insights. Mol Diversity. https://doi.org/10.1007/s11030-022-10537-y
Mohammed HH, Ali DME, Badr M, Habib AG, Mahmoud AM, Farhan SM, Gany SSHAE, Mohamad SA, Hayallah AM, Abbas SH (2022) Synthesis and molecular docking of new N 4-piperazinyl ciprofloxacin hybrids as antimicrobial DNA gyrase inhibitors. Mol Diversity. https://doi.org/10.1007/s11030-022-10528-z
Allaka TR, Kummari B, Polkam N, Kuntala N, Chepuri K, Anireddy JS (2022) Novel heterocyclic 1, 3, 4-oxadiazole derivatives of fluoroquinolones as a potent antibacterial agent: synthesis and computational molecular modeling. Mol Diversity 26:1581–1596. https://doi.org/10.1007/s11030-021-10287-3
Aziz HA, El-Saghier AM, Badr M, Abuo-Rahma GE-DA, Shoman ME (2022) Thiazolidine-2, 4-dione-linked ciprofloxacin derivatives with broad-spectrum antibacterial, MRSA and topoisomerase inhibitory activities. Mol Diversity 26:1743–1759. https://doi.org/10.1007/s11030-021-10302-7
Abdel-Aziz SA, Cirnski K, Herrmann J, Abdel-Aal MA, Youssif BG, Salem OI (2023) Novel fluoroquinolone hybrids as dual DNA gyrase and urease inhibitors with potential antibacterial activity: design, synthesis, and biological evaluation. J Mol Struct 1271:134049. https://doi.org/10.1016/j.molstruc.2022.134049
Cardoso-Ortiz J, Leyva-Ramos S, Baines KM, Gómez-Durán CFA, Hernández-López H, Palacios-Can FJ, Valcarcel-Gamiño JA, Leyva-Peralta MA, Razo-Hernández RS (2023) Novel ciprofloxacin and norfloxacin-tetrazole hybrids as potential antibacterial and antiviral agents: targeting S. aureus topoisomerase and SARS-CoV-2-MPro. J Mol Struct 1274:134507. https://doi.org/10.1016/j.molstruc.2022.134507
Marc G, Araniciu C, Oniga SD, Vlase L, Pîrnău A, Nadăș GC, Novac CȘ, Matei IA, Chifiriuc MC, Măruțescu L (2019) Design, synthesis and biological evaluation of new piperazin-4-yl-(acetyl-thiazolidine-2, 4-dione) norfloxacin analogues as antimicrobial agents. Molecules 24:3959. https://doi.org/10.3390/molecules24213959
Mustaev A, Malik M, Zhao X, Kurepina N, Luan G, Oppegard LM, Hiasa H, Marks KR, Kerns RJ, Berger JM (2014) Fluoroquinolone-gyrase-DNA complexes: two modes of drug binding. J Biol Chem 289:12300–12312. https://doi.org/10.1074/jbc.M113.529164
Akahane K, Sekiguchi M, Une T, Osada Y (1989) Structure-epileptogenicity relationship of quinolones with special reference to their interaction with gamma-aminobutyric acid receptor sites. Antimicrob Agents Chemother 33:1704–1708. https://doi.org/10.1128/aac.33.10.1704
Goswami M, Mangoli S, Jawali N (2014) Importance of chemical modification at C-7 position of quinolones for glutathione-mediated reversal of antibacterial activity. Int J Antimicrob Agents 43:387–388
Jazayeri S, Moshafi MH, Firoozpour L, Emami S, Rajabalian S, Haddad M, Pahlavanzadeh F, Esnaashari M, Shafiee A, Foroumadi A (2009) Synthesis and antibacterial activity of nitroaryl thiadiazole–gatifloxacin hybrids. Eur J Med Chem 44:1205–1209. https://doi.org/10.1016/j.ejmech.2008.09.012
Norouzbahari M, Salarinejad S, Güran M, Şanlıtürk G, Emamgholipour Z, Bijanzadeh HR, Toolabi M, Foroumadi A (2020) Design, synthesis, molecular docking study, and antibacterial evaluation of some new fluoroquinolone analogues bearing a quinazolinone moiety. DARU J Pharm Sci 28:661–672. https://doi.org/10.1007/s40199-020-00373-6
Balouiri M, Sadiki M, Ibnsouda SK (2016) Methods for in vitro evaluating antimicrobial activity: a review. J Pharm Anal 6:71–79. https://doi.org/10.1016/j.jpha.2015.11.005
Okada Y, Tsuda Y, Tada M, Wanaka K, Okamoto U, Hijikata-Okunomiya A, Okamoto S (2000) Development of potent and selective plasmin and plasma kallikrein inhibitors and studies on the structure-activity relationship. Chem Pharm Bull 48:1964–1972. https://doi.org/10.1248/cpb.48.1964
Liu Y-F, Wang C-L, Bai Y-J, Han N, Jiao J-P, Qi X-L (2008) A facile total synthesis of imatinib base and its analogues. Org Process Res Dev 12:490–495. https://doi.org/10.1021/op700270n
Khan SA, Saleem K, Khan Z (2008) Synthesis, structure elucidation and antibacterial evaluation of new steroidal-5-en-7-thiazoloquinoxaline derivatives. Eur J Med Chem 43:2257–2261. https://doi.org/10.1016/j.ejmech.2007.09.022
Temiz-Arpaci O, Zeyrek CT, Arisoy M, Erol M, Celik I, Kaynak-Onurdag F (2021) Synthesis, quantum mechanical calculations, antimicrobial activities and molecular docking studies of five novel 2, 5-disubstituted benzoxazole derivatives. J Mol Struct 1245:131084. https://doi.org/10.1016/j.molstruc.2021.131084
Funding
This work was supported and funded by Tehran University of Medical Sciences (TUMS); Grant Nos. 9211266096 and 9123120022.
Author information
Authors and Affiliations
Contributions
Prof. AF designed the study and conducted the experiments. Dr. FP, TS, and MN synthesized the targeted compounds. Dr. FP, Dr. MGD, and Dr. HRB wrote the manuscript and analyzed the characterization data. Dr. LF and Dr. ZE carried out the docking studies. Dr. MN, Dr. MG, and GŞ performed the biological evaluations. Dr. MBT revised the manuscript. All authors read and approved the final manuscript.
Corresponding authors
Ethics declarations
Competing interests
The authors declare no competing interests.
Ethical approval
This study did not involve human subjects and/or animals.
Additional information
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Supplementary Information
Below is the link to the electronic supplementary material.
Rights and permissions
Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.
About this article
Cite this article
Peytam, F., Norouzbahari, M., Saadattalab, T. et al. Novel fluoroquinolones analogues bearing 4-(arylcarbamoyl)benzyl: design, synthesis, and antibacterial evaluation. Mol Divers 28, 1577–1596 (2024). https://doi.org/10.1007/s11030-023-10676-w
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s11030-023-10676-w