Simple and Stereocontrolled Preparation of Benzoylated Phenylalanine Using Friedel–Crafts Reaction in Trifluoromethanesulfonic Acid for Photoaffinity Labeling

Simple and stereocontrolled preparation of benzoylated phenylalanine derivatives from optically pure phenylalanine using Friedel Crafts reaction in trifluoromethanesulfonic acid (TfOH) is reported; these derivatives are useful for photoaffinity labeling. Protected or unprotected phenylalanine derivatives were converted to benzoyl derivatives in TfOH at room temperature in a short time without loss of optical purity. The reaction condition was applied to synthesize novel photoreactive phenylalanine derivative, which has two photophores (benzophenone and diazirine). The detail analysis of photo-irradiation for two different photophores contained phenylalanine derivative was also investigated.