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A new class of antimicrobial and antioxidant agents, based on thiourea and urea derivatives of 6-fluoro-3-(piperidin-4-yl)benzo[d] isoxazole were synthesized by adopting a simple and efficient method. Synthesized compounds were characterized by spectral data of IR, 1H, 13C NMR and mass spectra. The compounds were evaluated for their efficacy as antimicrobial and antioxidant agents. A few compounds showed good antibacterial, antifungal and antioxidant activity when compared to standard drugs and thus represent a new class of promising lead compounds.

A new class of methylthio linked pyrimidinyl 1,3,4-oxadiazoles, 1,3,4-thiadiazoles and 1,2,4-triazoles were prepared under conventional and ultrasound irradiation methods. All the compounds were obtained in higher yields and in shorter reaction times in ultrasound irradiation method when compared with the conventional method. The title compounds were tested for antimicrobial activity. The compounds 12c and 12f exhibited promising antibacterial activity against P. aeruginosa whereas the compounds 13c and 13f showed pronounced antifungal activity against A. niger.

A variety of bis heterocycles-heteroaryl pyrazoles (5) and pyrroles (6) were prepared from heteroaryl chalcones adopting 1,3-dipolar cycloaddition reaction and studied their antimicrobial activity. The compounds 5d and 5f having bromo and nitro substituents on the aromatic ring are the potent antimicrobial agents against Bacillus subtilis and Aspergillus niger.

A variety of bis heterocycles, oxazolyl/thiazolyl/imidazolyl oxadiazoles having a styryl sulfonylmethyl group at the 5-position of oxadiazole and tris heterocycles having a pyrrolyl/pyrazolyl sulfonylmethyl group at the 5-position of oxadiazole were prepared adopting simple and versatile synthetic methodologies. All the compounds were screened for their antioxidant activities. Compound 5b displayed radical scavenging activity in all the three methods greater than the standard ascorbic acid, whereas compounds 8b and 14b showed activities equal to the standard ascorbic acid.

Synthesis of a series of novel phosphorylated ganciclovir derivatives with bioactive amines/aminoacid esters as substituents was accomplished. These compounds were structurally characterized by IR, NMR (1H, 13C, 31P), mass spectra and CHN analysis. The compounds (5a–m) have been evaluated for its in vitro and in vivo immunomodulatory activities. The amino acid ester-substituted ganciclovir derivatives, especially the 5g and 5i, increased the intracellular killing activity of the stimulated neutrophils. The in vivo experiment results show that the administration of compounds 5g and 5i (8 mg/kg body weight) to diet-induced immune impaired obese rats ameliorated the significant increase in immune cell counts (lymphocytes, neutrophils and monocytes). In addition, TNF-α, IL-6 and IL-1 secretions were considerably restored to normal by the compounds 5g and 5i with regulation in the release of C-reactive protein suggesting their potentiating effect on immune system dysfunction. These in vitro and in vivo results suggest that the phosphorylated ganciclovir derivatives 5g and 5i are strong immunomodulators.

A series of diethyl/ethylphenyl {2-(benzo[d]thiazol-2-yl)phenylamino}phosphonates and phosphinates were synthesized under microwave irradiation and neat conditions via Kabachnik-Fields reaction in high yields (80%–93%). The compounds were screened for antimicrobial and antioxidant properties. A few compounds showed effective antibacterial and antifungal activities at MIC value 12.5 μg/mL as compared with the standard at MIC value 6.25 μg/mL.

New 2-amino-N-hydroxybenzamide derivatives (3a–j) have been synthesized in good to excellent yields from the reaction of isatoic anhydride with different hydroxamic acids. All the compounds of the series were screened against both Gram-positive and Gram-negative bacteria and fungi, and some of them have antibacterial and antifungal activities compared to the standard drugs.