p -Methoxybenzyl-Radical-Promoted Chemoselective Protection of sec -Alkylamides.

The hitherto difficult site-selective p -methoxybenzylation of secondary amides using p -methoxybenzylated alkylsilyl peroxides as a novel p -methoxybenzylation agent under copper catalysis is reported. The reaction proceeds under mild reaction conditions in a highly chemoselective manner. This approach was successfully applied to the site-selective p -methoxybenzylation of peptides.