Design, synthesis, spectral and biological evaluation of novel 1-allyl substituted 2,6-diphenylpiperidin-4-ones and its derivatives of oximes/oxime ethers

A series of 1-allyl-2,6-diphenylpiperidin-4-one oximes 17-24 and 1-allyl-2,6-diphenylpiperidin-4-one O-benzyloximes 25-32 were synthesized from respective 1-allyl-2,6-diphenylpiperidin-4-ones 9-16. The structure and the conformations have been investigated for all the synthesized compounds 9-32 by analytical and spectral techniques (IR, Mass, 1H, 13C, 2D NMR and X-ray Diffraction). Based on the proton NMR analysis, all the synthesized compounds 9-32, exposed chair conformation except compounds 22 and 30 (twist boat conformation). For all the synthesized compounds 9-32 antimicrobial activity has been carried out against a panel of selected bacterial and fungal strains using Streptomycin and Amphotericin B as standards. Antibacterial and antifungal activity of compounds 19, 21, 23 (allyl oximes) 25-29, 31, 32 (allyl oxime ethers) and 11, 13 (ketones) exerted moderate to excellent activity against Staphylococcus aureus, Bacillus subtilis, Salmonella typhi bacterial strains and Penicillium chrysogenum, Aspergillus niger, Fusarium oxysporum fungal strains. The MIC results of all the synthesized compounds revealed that most of the oxime ether compounds exhibit excellent activity against selected bacterial and fungal strains.