Antimicrobial evaluation of a set of heterobicyclic methylthiadiazole hydrazones: synthesis, characterization, and SAR studies.

To exploit the potential antimicrobial activities of azabicyclic skeleton based compounds, a set of 2r,4c-diaryl-3-azabicyclo[3.3.1]nonan-9-one-4-methyl-1,2,3-thiadazole-5-carbonyl hydrazones were synthesized. Unambiguous structural elucidation has been carried out by investigating IR, H(1), C(13) NMR, and elemental analysis. 2D NMR spectra ((1)H-(1)H COSY, HSQC, HMBC, and NOESY) were recorded for a representative compound, 12, to confirm the proposed structure for 9-15. Antimicrobial activity assessment of synthesized hydrazones 9-15 has been evaluated by screening against selective strains. Both bacteria and fungi of various forms along with standard drug have been taken for the analysis. Difference in the potency of activity against the strains has been evaluated on the basis of SAR, and it has been revealed that substitution of electron-withdrawing halogens (chloro, fluoro, and bromo) at para positions of the phenyl (10, 12, and 13) enhanced the antifungal and antibacterial activities against tested organisms compared to other hydrazone derivatives.

Synthesis, crystal and antibacterial studies of diversely functionalized tetrahydropyridin-4-ol.

In an effort to expand the spectrum of antibacterial activity associated with piperidin-4-one derivatives, we have synthesized two series of 3-carboxyethyl-2,6-diphenyl-4-hydroxy-Delta(3)-tetrahydropyridine derivatives bearing diversified heterocyclic and aromatic systems at the nitrogen atom through acetyl (6-18) and 2-propanoyl (9-31) linkers. Unlike acetyl derivatives, NMR spectral pattern of the propanoyl counterparts revealed the existence of pair of rotational isomers (syn and anti) in solution at room temperature due to the hindered rotation about N-CO bond. X-ray crystal studies of 9 and 24 clearly pointed out that all the compounds existed in only one form particularly, in stable syn form in solid state. Each of the compounds was screened for their in vitro antibacterial activity against nine human pathogenic gram-positive strains including multiple drug resistant organisms and seven problematic gram-negative strains. Among the various heterocycles examined here, imidazole substituted derivatives 12 and 25 exhibited antibacterial activity approaching that of Linezolid and Trovafloxacin drugs particularly against multiple resistant Enterococcus faecium-VanA phenotype strains.

A facile synthesis, antibacterial, and antitubercular studies of some piperidin-4-one and tetrahydropyridine derivatives.

The raise in clinical significance of multidrug-resistant bacterial pathogens has directed us to synthesize 2,6-diarylpiperidin-4-one and Delta(3)-tetrahydropyridin-4-ol based benzimidazole and O-arylsulfonyl derivatives. X-ray crystal structure of tetrahydropyridinol (23) confirmed a change in conformation and orientation of substituents upon amide formation. Antibacterial activities evaluated against a wide number of bacterial pathogens (both sensitive and multidrug-resistant) revealed that 19, 27 against Staphylococcus aureus, 27 against Enterococcus faecalis, and 19, 21, 23, and 27 against Enterococcus faecium are significantly good at lowest MIC(90) (16 microg/mL). Inhibitory power noticed by 23 against Vancomycin-Linezolid-resistant E. faecalis and 27 against Vancomycin-resistant E. faecium are onefold better than the standard Linezolid and Trovafloxacin drugs, respectively. Moreover, antitubercular activity for the selected compounds against Mycobacterium tuberculosis H37Rv revealed that compounds 23, 24, and 27 expressed onefold improved potency compared to the standard Rifampicin drug.