Design of a Coumarin-Based Triketone as a Fluorescent Protecting Group for Primary Amines

A series of 3-acetyl-4-hydroxycoumarin and its derivatives were prepared and evaluated for their potential to function as a fluorescent primary amine protection group. When primary amines or amino acids react with the protecting group 3-acetyl-4-methoxy-7-N,N-dimethylaminocoumarin, the resulting compounds emit blue fluorescence with a quantum yield of 0.25−0.50 in methylene chloride. These protected compounds display satisfactory acid/base stability, and the protecting group can be removed with 5% hydrazine hydrate in DMF within 5 min at ambient temperature.