Synthesis and Photochemical Properties of a New Water-Soluble Coumarin,Designed as a Chromophore for Highly Water-Soluble and Photolabile Protecting Group

摘要

The absorption spectra and fluorescence spectra of a coumarin derivative (1),designed to be a water-soluble photo-labile protecting group for caged compounds,were successfully observed in aqueous buffer solutions at pH 2.0-12.5 for the first time.Coumarin 1 is highly soluble (>5 mM) in aqueous buffer at pH 7.2 and is stable in the dark at room temperature for up to a week.The pK_a value for the protonation of anilino nitrogen in coumarin 1 was determined to be 4.5.Coumarin 1 has a fluorescence lifetime of 2.0 ns and undergoes intersystem crossing to the triplet state.Therefore,compound 1 can be used for the light absorbing part of the new water-soluble caged compounds,such as caged amino acids or caged nucleotides,which can release free amino acids or nucleotides,respectively,by excitation in the visible region.