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licensee Molecular Diversity Preservation International, Basel, Switzerland. This article is an open-access article distributed under the terms and conditions of the Creative Commons Attribution license (http://creativecommons.org/licenses/by/3.0/).
The chemical structure of a) a pair of specifically-designed viscosity-dependent coumarin fluorescent probes (R = OH or CO2CH3); b) a coumarin-based amino acid probe; c) some iminocoumarins (R = NH or N(CO)OCH2CH3).