(E)-2-Benzylidenecyclanones: Part XX. Reaction of Cyclic Chalcone Analogs with Cellular Thiols. Unexpected Increased Reactivity of 4-Chromanone- Compared to 1-Tetralone-Analogs in Thia-Michael Reactions [1]

In vitro cancer cell cytotoxicity (IC50 values) of (E)-3-(4’-methylbenzylidene)-4-chromanone (IIIb) showed >50.0 decreases in comparison to those of the respective tetralone derivative (IIIc). On the other hand, such a decrease was not observed in the analogous 4-OCH3 (IIc and IIIc) derivatives. Since the compounds can be considered cyclic chalcone analogs, kinetics and diastereoselectivity of non-enzyme catalyzed reactions with reduced glutathione (GSH) and N-acetylcysteine (NAC) of IIIb and IIIc were investigated to assess the possible role of thiol-reactivity in the increased cytotoxicity of IIIb. Reactivity of the compounds and stereochemical outcome of the reactions were evaluated using high-pressure liquid chromatography-mass spectrometry (HPLC-MS). Molecular modeling calculations were performed to rationalize the observed differences in the thiol-reactivities of the chromanones (III) and the previously investigated tetralones (II). The results indicated possible role of spontaneous thiol-reactivity of compounds III in their recorded biological effects.