Manish P. Patel

Synthesis and identification of β-aryloxyquinolines and their pyrano[3,2-c]chromene derivatives as a new class of antimicrobial and antituberculosis agents.

A new class of β-aryloxyquinolines 3a-i and their pyrano[3,2-c]chromene derivatives 6a-r incorporating a validated molecular target has been synthesized via a nucleophilic displacement and a one-pot multicomponent reaction respectively. In vitro antimicrobial activity of the synthesized compounds were investigated against a representative panel of pathogenic strains specifically Bacillus subtilis, Clostridium tetani, Streptococcus pneumoniae, Escherichia coli, Salmonella typhi, Vibrio cholera, Aspergillus fumigatus and Candida albicans. Compounds 3c, 3e, 3g, 6f, 6l and 6q exhibited excellent antibacterial activity while compound 6p exhibited more potent antifungal activity than that of first line standard drugs. In vitro antituberculosis activity was evaluated against Mycobacterium tuberculosis H37Rv and compound 6f is emerged as the promising antimicrobial member with better antitubercular activity. Majority of the compounds appears to be better antimicrobials but poor antituberculars.

Microwave-assisted synthesis of 3′-indolyl substituted 4H-chromenes catalyzed by DMAP and their antimicrobial activity

A new series of indole-based chromene derivatives 4a–4p has been synthesized by one pot cyclocondensation reaction of 2-phenyl-1H-indole-3-carbaldehyde 1a–1h; malononitrile 2; and 1,3-cyclohexanedione/dimedone 3a/b under microwave irradiation catalyzed by an organocatalyst 4-(N,N-dimethylamino) pyridine. Easy experimental procedure, high yield, selectivity, and shorter reaction time are the imperative features of this method. All the compounds were screened against a representative panel of bacteria and fungi. Some of the compounds are found to be equipotent or more potent than that of standard drugs as evident from SAR study.

Microwave-assisted synthesis of some new tetrazolo[1,5-a]quinoline-based benzimidazoles catalyzed by p-TsOH and investigation of their antimicrobial activity

Keeping the objective to build up a new structural class of potent antimicrobials, a series of some new 4-Benzimidazol-2-yl tetrazolo[1,5-a]quinoline derivatives has been synthesized by reaction of tetrazolo[1,5-a]quinoline-4-carbaldehyde and o-phenylenediamine in the presence of an organocatalyst p-TsOH under the influence of microwave irradiation. The identity of all the compounds has been established by 1H NMR, 13C NMR, FTIR, and elemental analysis. The synthesized compounds were subjected to in vitro antimicrobial screening against a representative panel of pathogenic strains including three Gram-positive bacteria (Bacillus subtilis, Clostridium tetani, and Streptococcus pneumoniae) and three Gram-negative bacteria (Escherichia coli, Salmonella typhi, and Vibrio cholerae) as well as two fungal organisms (Aspergillus fumigatus and Candida albicans) by employing broth microdilution method. Of the compounds studied, compound 5e demonstrated significant activity against a Gram-positive bacteria Bacillus subtilis.

Design and synthesis of biquinolone-isoniazid hybrids as a new class of antitubercular and antimicrobial agents.

Twenty four biquinolone-isoniazid hybrids were designed based on molecular hybridization technique and synthesized via multicomponent cyclocondensation (MCC) approach. All the newly synthesized compounds were screened for their antimicrobial and antitubercular activities. The brine shrimp bioassay was carried out to study the cytotoxicity of the synthesized compounds. Hybrids 7f (MIC = 25 μg/mL); 7a, 7e and 7m (MIC = 50 μg/mL); 7g, 7h and 7k (MIC = 62.5 μg/mL) exhibited excellent antimicrobial activity as compared with standard drugs. Hybrids 7l and 7j displayed 99% inhibition against Mycobacterium tuberculosis bacteria with better LC50 values 35.39 and 34.59 μg/mL, respectively. These results indicate that the synthesized compounds can act as leads for the development of newer antimicrobial and antitubercular compounds.

One-Pot, Multicomponent Condensation Reaction in Neutral Conditions: Synthesis, Characterization, and Biological Studies of Fused Thiazolo[2,3-b]quinazolinone Derivatives

A new series of 12-(2-chloro-6-quinoline-3-yl)-3,3,8-substituted-2,3,4,12-tetrahydro-benzo[4,5]thiazolo[2,3-b]quinazolin-1-ones 4 was synthesized in one pot by condensing various 2-chloro-3-formylquinolines 1, 2-amino-6-substituted-benzothiazoles 2, and 1,3-cyclohexanedione 3 in ethanol. All the compounds were characterized by IR, 1H NMR, 13C NMR spectra and elemental analysis. All the synthesized compounds were screened for their antibacterial activity against Grampositive bacterial species Bacillus cereus and Bacillus substilus, Gram-negative bacterial species Escherichia coli, and their fungicidal activity against Aspergillus niger, Fuserium oxisporum, and Rhizopus species.

Microwave assisted synthesis and antimicrobial evaluation of new fused pyran derivatives bearing 2-morpholinoquinoline nucleus.

A new series of fused pyran derivatives 5a-x bearing 2-morpholinoquinoline nucleus has been synthesized under microwave irradiation by a reaction of 2-morpholinoquinoline-3-carbaldehyde 2a-c, malononitrile 3 and compounds 4a-h in presence of NaOH as basic catalyst. All the compounds were screened against three Gram positive bacteria (Streptococcus pneumoniae, Clostridium tetani, Bacillus subtilis), three Gram negative bacteria (Salmonella typhi, Vibrio cholerae, Escherichia coli) and two fungi (Aspergillus fumigatus, Candida albicans) using broth microdilution MIC (Minimum Inhibitory Concentration) method. Of the compounds studied, compounds 5b, 5f, 5k, 5m, 5q, 5s and 5v have found to be most efficient members of the series.

Synthesis and Antimicrobial Activity of Some New N-Substituted Quinoline Derivatives of 1H-Pyrazole

A new series of 32 derivatives of 4‐pyrazolyl‐N‐(hetero)arylquinoline 5a–p and 6a–p were synthesized by a one‐pot base‐catalyzed cyclocondensation reaction of 1‐phenyl‐3‐(hetero)aryl‐pyrazole‐4‐carbaldehyde 1a–h, malononitrile 2, and 3‐(hetero)aryl‐5,5‐disubstitutedcyclohex‐2‐enone 3a–b or 4a–b, respectively. All the synthesized compounds were characterized by elemental analysis, FT‐IR, 1H‐NMR, and 13C‐NMR spectral data. All the synthesized compounds were screened, against six bacterial pathogens, namely Bacillus subtilis, Clostridium tetani, Streptococcus pneumoniae, Salmonella typhi, Vibrio cholerae, Escherichia coli, and antifungal activity, against two fungal pathogens Aspergillus fumigatus and Candida albicans, using broth microdilution MIC method. Some of the compounds were found to be more or equipotent against most of the employed strains than commercially available drugs as evident from the screening data.

Microwave-assisted CAN-catalyzed solvent-free synthesis of N-allyl quinolone-based pyrano[4,3-b]chromene and benzopyrano[3,2-c]chromene derivatives and their antimicrobial activity

A new series of pyrano[4,3-b]chromene and benzopyrano[3,2-c]chromene derivatives have been synthesized via microwave-assisted one-pot, three-component reaction of N-allyl quinolones, cyclic β-diketones, and 4-hydroxy-6-methyl-2H-pyran-2-one/4-hydroxy coumarin in the presence of catalytic amount of ceric ammonium nitrate under solvent-free condition. The protocol offers expeditious and solvent-free synthesis with excellent yield to furnish fused chromenes for their antimicrobial activity. The chemical structures of the synthesized compounds were elucidated by 1H NMR, 13C NMR, FT-IR, elemental analysis, and mass spectral data. All the compounds were screened against a representative panel of pathogenic strains by broth micro dilution minimum inhibitory concentration method. Among these derivatives, compounds 6i, 6k, 6l, and 6m were found to have admirable activity when compared to the standard drugs.

Synthesis and antimicrobial screening of pyrano[3,2-c]chromene derivatives of 1H-pyrazoles

AbstractA new series of twenty four derivatives of pyrano[3,2-c]chromene IVa-x bearing 1H-pyrazole were synthesized by a one pot, base-catalyzed cyclocondensation reaction of 1H-pyrazole-4-carbaldehyde Ia-l, malononitrile II and 4-hydroxycoumarin IIIa-b. All the synthesized compounds were characterized by elemental analysis, FT-IR, 1H NMR and 13C NMR spectral data. All the synthesized compounds were screened against six bacterial pathogens, namely B. subtilis, C. tetani, S. pneumoniae, S. typhi, V. cholerae, E. coli and for antifungal activity against two fungal pathogens, A. fumigatus and C. albicans using the broth microdilution MIC method. Some of the compounds were found to be equipotent or more potent than commercial drugs against most of employed strains, as evident from the screening data.

Synthesis and Antimicrobial Evaluation of New Pyrano[4,3‐b]pyran and Pyrano[3,2‐c]chromene Derivatives Bearing a 2‐Thiophenoxyquinoline Nucleus

A new series of pyrano[4,3‐b]pyran 4a–i and pyrano[3,2‐c]chromene 6a–r derivatives bearing a 2‐thiophenoxyquinoline nucleus were synthesized by reaction of 2‐(4‐(un)‐substituted thiophenoxy)quinoline‐3‐carbaldehydes 2a–i with 6‐methyl‐4‐hydroxypyran‐2‐one 3 and 4‐hydroxy‐6‐(un)‐substituted‐2H‐chromen‐2‐one 5a–b respectively and malononitrile at room temperature in the presence of KOH as a basic catalyst. All the compounds were screened against three Gram‐positive bacteria (Streptococcus pneumoniae, Bacillus subtilis, Clostridium tetani), three Gram‐negative bacteria (Salmonella typhi, Escherichia coli, Vibrio cholerae) and two fungi (Candida albicans, Aspergillus fumigatus) using the broth microdilution MIC (minimum inhibitory concentration) method. Upon antimicrobial screening, it was observed that the majority of the compounds were found to be active against Bacillus subtilis, Clostridium tetani and Candida albicans as compared to standard drugs.