Direct, visible light-sensitized benzylic C-H fluorination of peptides using dibenzosuberenone: selectivity for phenylalanine-like residues

A visible light-sensitized benzylic sp(3) C-H fluorination protocol using dibenzosuberenone (5 mol %) and Selectfluor is optimized for the direct functionalization of phenylalanine-like residues in short chain peptides. Amino acids, dipeptides, and tripeptides undergo benzylic fluorination with remarkable regioselectivity in the presence of protected basic, acidic, and nonpolar side chains (including those with tertiary sites). Additionally, protecting group compatibility, a gram scale application, and competition experiments were explored. (C) 2016 Published by Elsevier Ltd.