Synthesis and biological activities of 2,6-diaryl-3-methyl-4-piperidone derivatives.

In the present study, a new series of 2,6-diaryl-3-methyl-4-piperidones was synthesized by Mannich reaction (condensation) of ethyl-methyl ketone, substituted aromatic aldehydes and ammonium acetate. Oximes and thiosemicarbazone derivatives of 2,6-diaryl-3-methyl-4-piperidones were synthesized by reaction with hydroxylamine hydrochloride and thiosemicarbazide respectively. The chemical structures were confirmed by means of IR, 1H-, 13C-NMR and mass spectral data. The compounds were screened for acute toxicity, analgesic, local anaesthetic and antifungal activity. 2-(4-Methylphenyl)-3-methyl-6-(4-chlorophenyl)-piperidin-4-one 2 exhibited the highest analgesic and local anaesthetic activity. The oximes and thiosemicarbazones were completely devoid of analgesic and local anaesthetic activity. 2-(4-Methylphenyl)-3-methyl-6-(4-hydroxyphenyl)-piperidin-4-oxime 21 and 2-(4-methoxyphenyl)-3-methyl-6-(4-chlorophenyl)-piperidin-4-oxime 17 exhibited potent antifungal activity against Aspergillus niger. Antifungal activity against Candida albicans was observed only with 2-(4-dimethylaminophenyl)-3-methyl-6-(4-chlorophenyl)-piperidin-4-oxime 20. 2,6-Diaryl-3-methyl-4-piperidones did not exhibit antifungal property.