Synthesis of a complete set of l-difluorophenylalanines, l-(F2)Phe, as molecular explorers for the CH/π interaction between peptide ligand and receptor

A complete set of difluorophenylalanines in the l -configuration [ l -(F 2 )Phe] (namely, l -(2,3-F 2 )Phe, l -(2,4-F 2 )Phe, l -(2,5-F 2 )Phe, l -(2,6-F 2 )Phe, l -(3,4-F 2 )Phe, l -(3,5-F 2 )Phe) was prepared and incorporated into the thrombin receptor-tethered ligand peptide SFLLRNP to identify the phenyl hydrogens of the Phe-2 residue involved in the CH/π receptor interaction.