Synthesis of Fluorescent Derivatization Reagents: Reaction of Isatin with 3-Aryl- 7-diethylaminocoumarins and Their Fluorescent Properties

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Fluorescent derivatization reagents, 3-aryl-7-diethylaminocoumarin derivatives, were synthesized and reacted with isatin to give the adduct.Their fluorescent properties are discussed.Since isatin plays physiologically important roles in various biological systems, 2 there has been a demand for practical methods to determine the concentration of isatin.In the previous paper, we reported the synthesis of 4-tert-butyloxycarbonylaminooxybutyl [2-(7-diethylamino-2-oxo-2H-chromen-3-yl)thiazol-4-yl]acetate (DACT-ONH) as a fluorescent derivatization reagent for isatin (Figure 1). 1 However, it has been difficult to use DACT-ONH for determination of isatin by HPLC because of the formation of E and Z stereoisomers, and because the sensitivity in measuring the concentration of isatin was reduced to a half of fluorescence intensity of the reagent itself.The decreased sensitivity seems to be based on some interactions through a long linkage of the reacting group in DACT-ONH.In order to resolve the problems of stereoisomer formation and sensitivity, the reacting group with a short linkage will be preferable.