Design, Synthesis and Tumour-Selective Toxicity of Novel 1-[3-{3,5-Bis(benzylidene)-4-oxo-1-piperidino}-3-oxopropyl]-4-piperidone Oximes and Related Quaternary Ammonium Salts

A novel series of 1-[3-{3,5-bis(benzylidene)-4-oxo-1-piperidino}-3-oxopropyl]-4-piperidone oximes 3a–h and related quaternary ammonium salts 4a–h were prepared as candidate antineoplastic agents. Evaluation against neoplastic Ca9-22, HSC-2 and HSC-4 cells revealed the compounds in series 3 and 4 to be potent cytotoxins with submicromolar CC(50) values in virtually all cases. In contrast, the compounds were less cytocidal towards HGF, HPLF and HPC non-malignant cells revealing their tumour-selective toxicity. Quantitative structure–activity relationships revealed that, in general, both cytotoxic potency and selectivity index figures increased as the magnitude of the Hammett sigma values rose. In addition, 3a–h are cytotoxic towards a number of leukemic and colon cancer cells. 4b,c lowered the mitochondrial membrane potential in CEM cells, and 4d induced transient G2/M accumulation in Ca9-22 cells. Five compounds, namely 3c,d and 4c–e, were identified as lead molecules that have drug-like properties.