4:3-β-Naphthapyrone-4-acetic acid N-hydroxysuccinimidyl ester as a fluorescent labeling reagent for amino acids and oligopeptides in high-performance liquid chromatography

4:3-beta -Naphthapyrone-4-acetic acid N-hydroxysuccinimidyl ester (NPA-OSu) is a highly sensitive and moderately reactive derivatizing reagent with a naphthapyrone moiety as fluorophore and an N-hydroxysuccinimidyl active ester as reactive group toward amino compounds. It is readily prepared in two steps. The fluorescence properties of NPA-OSu and its hydrolysis product have been studied in detail, and the conditions for derivatization and separation of the NPA-OSu derivatives of some amino acids and oligopeptides have been investigated. At lambda (ex) = 352 nm and lambda (ex) = 422 nm the detection limits (signal-to-noise ratio = 3) for amino acids and oligopeptides reached fmol levels for injection of 20 muL; this sensitivity was comparable with that obtained by use of 7-(diethylamino)coumarin-3-carboxylic acid succinimidyl ester as derivatizing reagent in the analysis of amino acids by capillary electrophoresis with laser-induced-fluorescence detection.