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Isocyanides-based multicomponent strategy for the construction of highly functionalized quinolones derivatives has been developed under mild conditions, in which few derivatives obtained in moderate to good yield. This is a mechanistic study of the carbonyl group of quinolone. A simple and convenient isocyanide-based multicomponent reaction for the construction of highly functionalized quinolones derivatives has been developed under mild conditions.

In search of potential therapeutics for tuberculosis, we describe here the synthesis and in vitro antitubercular activity of a novel series of thiazolone piperazine tetrazole derivatives. Among all the synthesized derivatives, four compounds (10, 14, 20 and 33) exhibited more potent activity (MIC = 3.08, 3.01, 2.62 and 2.51 μM) than ethambutol (MIC = 9.78 μM) and pyrazinamide (MIC = 101.53 μM) against Mycobacterium tuberculosis. Furthermore, they displayed no toxicity against Vero cells (C1008) and mouse bone marrow derived macrophages (MBMDMɸ). These investigated analogues have emerged as possible lead molecule to enlarge the scope of the study.

A series of novel 4-aminoquinolinyl and 9-anilinoacridinyl Schiff base hydrazones have been synthesized and evaluated for their antimalarial activity. All compounds were evaluated in vitro for their antimalarial activity against chloroquine-sensitive strain 3D7 and the chloroquine-resistant K1 strain of Plasmodium falciparum and for cytotoxicity toward Vero cells. Compounds 17, 20, and 21 displayed good activity against the 3D7 strain with IC50 values ranging from 19.69 to 25.38 nm. Moreover, compounds 16, 17, 21, 24, 32, and 33 exhibited excellent activities (21.64-54.26 nm) against K1 strain and several compounds displayed β-hematin inhibitory activity, suggesting that they act on the heme crystallization process such as CQ. Compounds were also found to be non-toxic with good selectivity index.

The World Health Organization has classified the leishmaniasis as a major tropical disease. The discovery of new compounds for leishmaniasis is therefore a pressing concern for the anti-infective research program. We have synthesized 19 compounds of triazine dimers as novel antileishmanial agents. Most of the synthesized derivatives exhibited better activity against intracellular amastigotes (IC50 ranging from 0.77 to 10.32 μM) than the control, pentamidine (IC50 = 13.68 μM), and are not toxic to Vero cells. Compounds 14 and 15 showed significant in vivo inhibition of 74.41% and 62.64%, respectively, in L. donovani/hamster model. Moreover, expansion of Th1-type and suppression of Th2-type immune responses proved that compound 14 stimulates mouse macrophages to prevent the progression of leishmania parasite. The molecular docking studies involving PTR1 protein PDB further validated the concepts involved in the design of these compounds. Among the investigated analogues, compound 14 has emerged as the potential one to enlarge the scope of the study.

The high potential of quinazolinone containing natural products and their derivatives in medicinal chemistry led us to discover four novel series of 53 compounds of quinazolinone based on the concept of molecular hybridization. Most of the synthesized analogues exhibited potent leishmanicidal activity against intracellular amastigotes (IC50 from 0.65 ± 0.2 to 7.76 ± 2.1 μM) as compared to miltefosine (IC50 = 8.4 ± 2.1 μM) and nontoxic toward the J-774A.1 cell line and Vero cells. Moreover, activation of Th1 type and suppression of Th2 type immune responses and induction in nitric oxide generation proved that 8a and 8g induce murine macrophages to prevent survival of parasites. Compounds 8a and 8g exhibited significant in vivo inhibition of parasite 73.15 ± 12.69% and 80.93 ± 10.50% against Leishmania donovani /hamster model. Our results indicate that compounds 8a, 8g, and 9f represent a new structural lead for this serious and neglected disease.

Novel series of 7-piperazinylquinolones with tetrazole derivatives were synthesized and evaluated for their antibacterial activity against various strains of Staphylococcus aureus. All the synthesized compounds showed significant in vitro antibacterial activity against Gram-positive bacteria whereas some compounds displayed moderate activity against Gram-negative bacteria. Among all the synthesized compounds, compounds (6a-c, 6e-g, 6i-k, 6m, 6'f and 6'm) were found to be more effective with MIC ranging from (0.78-3.12 μg/mL) against S. aureus (ATCC-29213) than the control; ciprofloxacin (MIC = 25 μg/mL). Moreover, these analogues displayed no toxicity up to MIC = 0.39 μg/mL against mammalian cell line L-929. Furthermore, to correlate the biological activities of synthesized compounds with their 3D conformation, we attempted 3D-QSAR study.

Novel series of 7-piperazinylquinolones with tetrazole derivatives were synthesized and evaluated for their antibacterial activity against various strains of Staphylococcus aureus. All the synthesized compounds showed significant in vitro antibacterial activity against Gram-positive bacteria whereas some compounds displayed moderate activity against Gram-negative bacteria. Among all the synthesized compounds, compounds (6a-c, 6e-g, 6i-k, 6m, 6'f and 6'm) were found to be more effective with MIC ranging from (0.78-3.12 μg/mL) against S. aureus (ATCC-29213) than the control; ciprofloxacin (MIC = 25 μg/mL). Moreover, these analogues displayed no toxicity up to MIC = 0.39 μg/mL against mammalian cell line L-929. Furthermore, to correlate the biological activities of synthesized compounds with their 3D conformation, we attempted 3D-QSAR study.

Synthesis of novel 4-aminoquinoline-rhodanine hybrid using inexpensive starting materials via easy to operate methodology, and their biological activity is reported. All the compounds were screened for their in vitro antimalarial activity against chloroquine-resistant (K1) and chloroquine-sensitive (3D7) strains of Plasmodium falciparum, and their cytotoxicity toward VERO cell line. Compounds 9, 19, 21 and 23 exhibited excellent antimalarial activity with IC50 value ranging from 13.2 to 45.5 nM against chloroquine-resistant (K1) strain. Biochemical studies revealed that inhibition of hemozoin formation is the primary mechanism of action of these analogs for their antimalarial activity. Additionally, some derivatives (14, 18 and 26) of this series also exhibited the antimycobacterial activity against H37Rv strain of Mycobacterium tuberculosis with MIC value of 6.25 μM.

We have developed an efficient cyanuric chloride (2,4,6-trichloro-1,3,5-triazine, TCT) catalyzed approach for the synthesis of 2,3-dihydroquinazolin-4(1H)-one (3a–3x), 2-spiroquinazolinone (5, 7), and glycoconjugates of 2,3-dihydroquinazolin-4(1H)-one (10a, 10b) derivatives. The reaction allows rapid cyclization (8–20 min) with 10 mol % cyanuric chloride to give skeletal complexity in good to excellent yield. We believe that this novel procedure may open the door for the easy generation of new and bioactive quinazolinones.

Drug resistance to established antifungals such as azole derivatives (fluconazole and ketoconazole) is driving the rise in global mortality due to fungal infection. Identification of new molecular entities structurally unrelated to these may represent a valid strategy to overcome resistance to currently available drugs. In an effort to develop highly potent antifungal agents, we report herein a series of 27 compounds of dithiocarbamate and the rhodanine molecules containing pyridine moiety and their antifungal activity. Among the synthesized compounds, several analogues have shown potent antifungal activity. The potent compounds against Candida albicans strain were further tested for in vitro anticandidal activity and amphotericin B-resistant strain of Candida albicans. Several derivatives 4a–f, 6, and 7k–n were found to be more effective (MIC = 0.39 – 3.12 μg mL−1) against Candida albicans MTCC183 and further these compounds, except 4e, 4f, and 7m, showed significant activity against amphotericin B-resistant strain of Candida albicans than that of fluconazole. Moreover, these analogues did not exhibit any toxicity up to MIC 3.12 μg mL−1 against mammalian cell line L929. A molecular docking study was undertaken to understand the mode of action of the active compounds towards prospective target lanosterol 14α-demethylase (CYP-51).