Synthesis and Pro-apoptotic activity of Arylidene-Cyclo-Alkanones

Screening of a small chemical library (the Developmental Therapeutics Program-National Cancer Institute "challenge set") on cells expressing mutated caspase-9, allowed the identification of two compounds, named G5 (3,5-bis(4-nitro-benzyliden)-tetrahydrothiapyran-4-one-1,1-dioxide) and F6 (3,5-bis(4-methyl-benzyliden)-4-piperidone hydrochloride) (Fig. 1), capable of activating caspases and to induce cell death with an apoptosome-independent apoptotic pathway. G5 and F6 are typified by a cross-conjugated ?,?-unsatured dienone with two sterically accessible electrophilic ?-carbons , a determinant that confers isopeptidase (DUBs) inhibitory activity. G5 and F6 inhibit isopeptidases (DUBs) by reacting with the sulfhydryl group of the catalytic cysteine with the olefinic carbon atoms. Infact compounds with 1,5-diaryl-3-oxo-1,4-pentadienyl pharmacophore react preferentially with thiols rather than hydroxy and amino group, so these conjugated enones may lack the genotoxic effects associated with currently used anticancer alkylating agents However it is likely that these compounds may exert their bioactivities by interacting with a number of different molecular target. Compounds wit 1,5-diaryl-3-oxo-1,4-pentadienyl pharmacophore are analogues of the natural product Curcumin, a yellow pigment obtained from the indian spice turmeric, that exhibits numerous biological activities, including anti-cancer, anti-inflammatory, anti-angiogenesis, anti-viral, anti-oxidant properties. Curcumin is selective towards neoplastic cell and it do not show toxicity in vivo. The present work consist of the studies of the synthesis and the evaluation of cytotoxic activity of a small focused library of symmetrical and non-simmetrical bis-arylidene-cycloalkanones and mono-arylidene-cycloalkanones. The aim of this work was to find a compound with a greater pro-apoptotic activity than G5. Besides a representative compound, 2f (2,6-bis(4-nitro-benzylidene)-4-hydroxy-cyclohexanone), was selected for further development and conjugated to PEG5000 to improve water solubility with the aim to start in vivo studies.