Enhancing Reactivity and Site-Selectivity in Hydrogen Atom Transfer from Amino Acid C-H Bonds via Deprotonation.

A kinetic study on the reactions of the cumyloxyl radical (CumO•) with N-Boc-protected amino acids in the presence of the strong organic base DBU has been carried out. CO2H deprotonation increases the electron density at the α-C-H bonds activating these bonds toward HAT to the electrophilic CumO• strongly influencing the intramolecular selectivity. The implications of these results are discussed in the framework of HAT-based aliphatic C-H bond functionalization of amino acids and peptides.