M. Rani

Synthesis, spectral, crystal structure and in vitro antimicrobial evaluation of imidazole/benzotriazole substituted piperidin-4-one derivatives.

Imidazole/benzotriazole analogues substituted piperidin-4-one derivatives (17-26) have been synthesized. Their chemical structures were characterized by IR, 1H NMR, 13C NMR and mass spectral analysis. In addition, single crystal X-ray diffraction has also been recorded for compounds 21 and 23. The synthesized compounds were subjected to their in vitro antibacterial and antifungal activities against pathogenic microbial strains. The results pointed out that compounds 19 & 24 against B. subtilis and 20 & 24 against E. coli were explored superior inhibition activity.

Design, synthesis and biological evaluation of novel 2-[(2,4-diaryl-3-azabicyclo[3.3.1]nonan-9-ylidene)hydrazono]-1,3-thiazolidin-4-ones as a new class of antimicrobial agents

New series of 2,4-diaryl-3-azabicyclo[3.3.1]nonan-9-one thiosemicarbazones (9-16) obtained from the corresponding 2,4-diaryl-3-azabicyclo[3.3.1]nonan-9-ones (1-8) upon cyclization with ethylbromoacetate in the presence of sodium acetate-acetic acid buffer afforded novel 2-[(2,4-diaryl-3-azabicyclo[3.3.1]nonan-9-ylidene)hydrazono]-1,3-thiazolidin-4-ones (17-24). The synthesized compounds have been characterized by their elemental, analytical and spectral studies. Besides, the reported compounds were screened for their antibacterial and antifungal activities against a spectrum of microbial organisms. These studies proved that compounds 11/18/20/23 against Staphylococcus aureus, 19/20/24 against Salmonella typhi show maximum inhibition potency at low concentration (6.25microg/ml) whereas 18/19 against Candida albicans and 19/20/21 against Rhizopus sp. showed beneficial antifungal activity at minimum concentration.

Efficient synthesis, spectral analysis and antimicrobial studies of nitrogen and sulfur containing spiro heterocycles from 2,4-diaryl-3-azabicyclo[3.3.1]nonan-9-ones.

Acetyl and propionyl group substituted thiadiazole derivatives (4a-4h, 5a-5h, 6a, 6b, 7a and 7b) have been synthesized by the cyclization of 2,4-diaryl-3-azabicyclo[3.3.1]nonan-9-one thiosemicarbazones (2a-2h, 3a and 3b) with acetic anhydride/propionic anhydride and were characterized by Elemental analysis, IR, (1)H NMR and (13)C NMR spectral analysis. Single crystal X-ray diffraction has also been recorded for compounds 4c and 5a. From the NMR and Single crystal X-ray diffraction analysis, compounds 4b-4d, 4f-4h, 5b, 5c, 5f-5h, 6a, 7a and 7b were found to adopt twin-chair conformations whereas compounds 4a, 4e, 5a, 5d, 5e and 6b adopt chair and boat conformation of cyclohexane and piperidine rings, respectively. Besides, the synthesized compounds were screened for antibacterial and antifungal activities using serial dilution method. The microbiological analysis showed that the electron withdrawing function substituted phenyl group at C-2 and C-4 of azabicyclononane based thiadiazoles 4c/4h and 5c/5h exposed significant antimicrobial activity against Salmonella typhi, Escherichia coli, Klebsiella pneumoniae, Aspergillus flavus, Aspergillus niger and Candida albicans at MIC of 6.25 μg/ml.

Synthesis, stereochemistry and in vitro antimicrobial evaluation of novel 2-[(2,4-diaryl-3-azabicyclo[3.3.1]nonan-9-ylidene)hydrazono]-4-phenyl-2,3-dihydrothiazoles.

2-[(2,4-Diaryl-3-azabicyclo[3.3.1]nonan-9-ylidene)hydrazono]-4-phenyl-2,3-dihydrothiazoles (3a-3k) have been synthesized by the cyclization of 2-[(2,4-diaryl-3-azabicyclo[3.3.1]nonan-9-one thiosemicarbazones with phenacyl bromide and characterized by analytical (melting point and elemental analysis) and spectral (IR, (1)H NMR, (13)C NMR, D(2)O exchange, NOESY and mass) techniques. The novel Hantzsch products (3a-3k) were screened for their in vitro antibacterial and antifungal activities against some selected microorganisms. Structure activity relationship (SAR) for the reported compounds was studied by comparing their MIC values with standard drugs (Streptomycin and Amphotericin B). The results show that 3e against Escherichia coli and Cryptococcus neoformans3i against Bacillus Subtilis, 3b against Aspergillus flavus, and 3k against Rhizopus sp. were found to show significant growth inhibition.

2-(2,4-Diphenyl-3-aza-bicyclo-[3.3.1]nonan-9-ylidenehydrazono)-1,3-thia-zolidin-4-one.

In the title compound, C23H24N4OS, the piperidine and cyclohexane rings adopt twin chair conformations and the phenyl groups occupy equatorial positions. The dihedral angle between the two benzene rings is 10.25 (12)°. The crystal structure is stabilized by intermolecular N—H⋯O hydrogen bonds with the formation of centrosymmetric dimers.

Ethyl 4-[2-(3,5-dimethyl-4-oxo-2,6-diphenyl-piperidin-1-yl)-2-oxoeth-yl]piperazine-1-carboxyl-ate.

In the title compound, C28H35N3O4, the piperidine ring adopts a boat conformation while the piperazine ring adopts a chair conformation with an equatorial orientation of the phenyl groups. The dihedral angle between the mean planes of the benzene rings is 74.14 (8)°. The molecular conformation is stabilized by a weak intramolecular C—H⋯N interaction and the crystal packing is stabilized by weak intermolecular C—H⋯O interactions.

1-Chloroacetyl-2,6-bis(2-chlorophenyl)-3,5-dimethylpiperidin-4-one oxime

In the title compound, C21H21Cl3N2O2, the piperidine ring adopts a distorted boat conformation. One of the chlorophenyl rings is almost perpendicular to the best plane through piperidine ring, making a dihedral angle of 88.7 (1)°, whereas the other ring is twisted by 71.8 (1)°. The crystal packing is stabilized by intermolecular C—H⋯O, C—H⋯Cl and O—H⋯O interactions.

1-Chloro­acetyl-2,6-bis­(2-chloro­phen­yl)-3,5-dimethyl­piperidin-4-one

In the title compound, C21H20Cl3NO2, the piperidin-4-one ring adopts a boat conformation. The two 2-chlorophenyl groups are approximately perpendicular to each other, making a dihedral angle of 74.07 (8)°.

2,6-Bis(3-fluoro­phen­yl)-3-isopropyl­piperidin-4-one

In the title compound, C20H21F2NO, the piperidine ring in each of the two independent molecules in the asymmetric unit adopts a normal chair conformation with an equatorial orientation of the 3-fluorophenyl groups. The dihedral angles between the two 3-fluorophenyl rings are 49.89 (7) and 50.35 (7)° in the two molecules.