Photoconversion of o-hydroxycinnamates to coumarins and its application to fluorescence imaging

(E)-o-Hydroxycinnamates were synthesized and their photochemical behavior was investigated in liquid and solid states. It was confirmed by H-1 NMR spectroscopy that the (E)-o-hydroxycinnamates converted into the corresponding coumarins via (Z)-o-hydroxycinnamate intermediates. The photoconversion was greatly accelerated in the presence of p-toluenesulfonic acid. The optical properties of the cinnamates were compared with those of the corresponding coumarins. Fluorescence imaging was successfully accomplished by photoirradiation of PMMA films containing the cinnamates. (C) 2009 Elsevier Ltd. All rights reserved.