Stereoselective syntheses of fluorescent non-natural aromatic amino acids based on asymmetric Michael additions.

Four fluorescent non-natural aromatic amino acids have been synthesized based on a key stereoselective Michael addition reaction. S-1-phenylethylamine was employed as both the source of amine and the stereoselectivity controller. The overall yields were moderate (30-50%). Fluorescent properties of some of the fluorophores were also investigated. It was found that compounds with a dimethylamino group bonded to the aromatic ring display intramolecular charge transfer fluorescence.