New insights into the water-solubilization of thiol-sensitive fluorogenic probes based on long-wavelength 7-hydroxycoumarin scaffolds

The synthesis and photophysical properties of novel water-soluble phenol-based fluorophores derived from 3-benzothiazolyl-7-hydroxycoumarin and emitting in the range 485-631 nm are described. Further conversion into thiol-sensitive fluorogenic probes through the chemical modification of their hydroxyl group was next investigated. Depending on the type of thiol-reactive quenching moiety used (2,4-dinitrobenzenesulfonyl ester, 2,4-dinitrophenyl ether or benzoquinone-type Michael acceptors) and the water-solubilizing group(s) pre-introduced into the coumarin core, dramatic differences in the thiol-induced fluorescence activation of these pro-fluorophores under physiological conditions were observed. Results for this comparative study provide valuable informations for the selection of the most suitable structural features for designing 7-hydroxycoumarin-based long-wavelength fluorescent probes for thiol bioimaging. (C) 2014 Elsevier Ltd. All rights reserved.