3-(7-Methoxycoumarin-3-carbonyl)- and 3-(7-Dimethylaminocoumarin-3-carbonyl)-2-oxazolones as New Fluorescent Labeling Reagents for High-Performance Liquid Chromatography

3-(7-Methoxycoumarin-3-carbonyl)- and 3-(7-dimethylaminocoumarin-3-carbonyl)-2-oxazolones (IIa and IIb) were synthesized as fluorescent labeling reagents for high-performance liquid chromatography (HPLC). Treatment of 7-methoxy- and 7-dimethylaminocoumarin-3-carboxylic acids (Ia and Ib) with diphenyl 2-oxo-3-oxazolinylphosphonate in the presence of triethylamine in dichloromethane gave IIa and IIb in 45% and 26% yields, respectively. Compounds IIa and IIb reacted with primary and secondary amines at room temperature in chloroform to give the corresponding fluorescent 7-methoxy- and 7-dimethylamino-3-carboxamides (IIIa-i and IVa-i). A mixture of primary amines was labeled with IIa and chromatographed on a reversed-phase HPLC column (mobile phase : methanol-water) with a fluorescence detector. The detection limit of a test compound, benzylamine, was 19 fmol/100 μl by the use of IIa.