Synthesis and optical properties of 4-(2-{[6-(1,1-dicyanoprop-1-en-2-yl)naphthalen-2-yl] (methyl)amino} ethoxy)-4-oxobutanoic acid fluorescent probe for β-amyloid

A novel 4-(2-{[6-(1,1-dicyanoprop-1-en-2-yl)naphthalen-2-yl](methyl)amino} ethoxy)-4-oxobutanoic acid ( 5 ) fluorescent probe for β-amyloids was synthesized by catalytic acylation using 4-dimethylaminopyridine between succinic anhydride and (1-{6-[(2-hydroxyethyl)(methyl) amino]-2-naphthyl}ethylidene)malononitrile ( 4 ). The structures of all compounds were identified by proton nuclear magnetic resonance spectroscopy, infrared spectroscopy, mass spectrometry, and ultraviolet–visible (UV–Vis) spectroscopy. The UV–Vis and fluorescence spectra of 1-{6-[(2-hydroxyethyl)(methyl) amino]-2-naphthyl}ethan-1-one ( 3 ), 4 , and 5 in solvents with different polarities were investigated, and the effects of solvent polarity on the optical properties of the three compounds were studied. The objective product 5 showed high binding affinities toward Aβ(1–40) aggregates in vitro ( K d  = 29.4 nmol/L) by fluorophotometry. This study provides a powerful fluorescent probe for the molecular diagnosis of Alzheimer’s disease.