Scheme 12.

Copper-catalyzed oxidative cleavage of protein backbone: (A) General reaction scheme. The cleavage site is highlighted with a red arrow. (B) Ser-selective cleavage by a copper complex (top) and site-selective cleavage of lysozyme through reactive oxygen species (ROS) generation with a copper- and tungsten-based cluster (Cu-WD). The imide intermediate of the Ser-selective cleavage can be hydrolyzed at both imide C═O groups (blue and pink), but only one of the two possible hydrolysis products is shown for the sake of simplicity. The image of ROS-mediated cleavage was reprinted with permission.^[172] Copyright 2023, American Chemical Society (https://pubs.acs.org/doi/10.1021/jacsau.3c00011).