2- Methoxy-2,4-diphenyl-3 -furanone reagent

Two new chromophoric reagents, 2-methoxy-2,4-diphenyl-3(2/f)-furanone (MDPF) (49) and 4-phenylspiro[furan-2(3H)-r-phthalan]-3,3 -dione (fluorescamine, trade name Fluram) (50) were introduced for the correlation of... 

Methoxy-2-diphenyl-3(2//)-furanone, which is structurally related to fluorescamine, has the same unique properties. The reaction of MDPF with primary amines proceeds rapidly only above pH 9 (Weigele et al, 1973). Much higher reagent concentrations are often required, e.g., 10 mg/ml, in order to obtain nearly quantitative fluorophor formation (Wideman et al, 1978). This requirement is due to the more rapid hydrolysis of MDPF. In contrast with fluorescamine, MDPF dissolved in methanol is as stable and as reactive as when it is dissolved in acetone. The MDPF fluorophors also have excitation and emission maxima at 390 and 475 nm, respectively. Various peptide fluorophors have been found to be stable between pH 2 and 11, and it has been possible to lyophilize the fluorophors without any decomposition. The fluorescence intensity also varies with solvent composition, but not with pH. 

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