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The series of the β-ketoenoles (2 E ,5 Z ,7 E ,9 E )-2-(alkylamino)-6-hydroxy-10-phenyldeca-2,5,7,9-tetraen-4-ones with variation of the alkylamino tail groups was synthesized and studied as potential probes for the sensing of protein insoluble aggregates - amyloid fibrils. Depending on the structure of the alkylamino group, the dyes could increase their fluorescence intensity in the dozens of times in the presence of insulin fibrils. The compound with a 2-hydroxyethylamino substituent demonstrates the highest fluorescence response (up to 60 times) and good range of insulin fibril detection (1–50 μg/ml). In complexes with fibrils, the dyes possess fluorescence quantum yield values up to 15% and binding constant values of about 2 × 10 5 M −1 . The excitation and emission maxima of β-ketoenoles are located in the range 407–427 nm and 500–554 nm correspondingly. These compounds are weakly fluorescent when free and slightly sensitive to the native proteins insulin and bovine serum albumin. Thus β-ketoenoles are considered as prospective molecules for the fluorescent detection of amyloid aggregates of proteins. [ABSTRACT FROM AUTHOR]