Total Synthesis Of 1,5-Acrylodan As A Novel Fluorescent Probe For The Study Of Chemical Denaturation Dynamics In Human Serum Albumin

We report the succinct total synthesis of 1,5-Acrylodan, a novel solvatochromic fluorophore for the study of microenvironmental polarity in biological and biochemical systems. The reaction sequence proceeds via an aryllithium-directed nucleophilic addition, catalytic Kulinkovich cyclopropanation, and copper-catalyzed oxidative ring-opening to generate the critical acryloyl moiety. The identity of the carbonyl is set in a late-stage procedure; the functionalizable 5-bromo-1-dimethylaminonaphthalene intermediate can be isolated. All organic/catalytic reagents and naphthalic precursors are inexpensive and commercially available. The fluorescence characteristics of the unbound 1,5-Ac are reported, demonstrating strong fluorescence quenching in polar protic solvents. A mild conjugate addition procedure can be employed to afford fluorophore-labelled Human Serum Albumin, an important biomolecular system; the labelling procedure is both site-selective and singular. The 1,5-Ac-HSA complex can be applied to the study of environmental solvation as a function of molecular unfolding patterns; the fluorescence characteristics of the native-state and chemically denatured 1,5-Ac-HSA complex are reported and employed for the determination of denaturation dynamics.