Anthrols 2-7 were synthesized and their photochemical reactivity investigated by irradiations in aq CHOH. Upon excitation with visible light (λ > 400 nm) in methanolic solutions, they undergo photodehydration or photodeamination and deliver methyl ethers, most probably via quinone methides (QMs), with methanolysis quantum efficiencies Φ = 0.02-0.3. Photophysical properties of 2-7 were determined by steady-state fluorescence and time-correlated single photon counting. Generally, anthrols 2-7 are highly fluorescent in aprotic solvents (Φ = 0.5-0.9), whereas in aqueous solutions the fluorescence is quenched due to excited-state proton transfer (ESPT) to solvent. The exception is amine 4 that undergoes excited-state intramolecular proton transfer (ESIPT) in neat CHCN where photodeamination is probably coupled to ESIPT. Photodehydration may take place via ESIPT (or ESPT) that is coupled to dehydration or via a hitherto undisclosed pathway that involves photoionization and deprotonation of radical cation, followed by homolytic cleavage of the alcohol OH group from the phenoxyl radical. QMs were detected by laser flash photolysis and their reactivity with nucleophiles investigated. Biological investigation of 2-5 on human cancer cell lines showed enhancement of antiproliferative effect upon exposure of cells to irradiation by visible light, probably due to formation of electrophilic species such as QMs.

Within this work we describe the synthesis of versatile substituted 2-phenyl benzothiazole 3–10 and 2-phenylbenzimidazole 12–19 derivatives bearing amidino groups. Furthermore, the synthesized compounds were explored for their antiproliferative activity in vitro on three cancer cell lines. Tested compounds showed moderate to strong antiproliferative activity. Furthermore, the type of the attached amidino group on benzazole nuclei has the significant impact on the antiproliferative activity only within benzimidazole derivatives with 2-imidazolinyl substituted derivatives being more active in comparison to amidino substituted analogues. All obtained results revealed that this type of benzothiazole derivatives have a great potential for further optimization and development of more efficient potential antiproliferative agents.