Fig. 7. Proline-functionalised MA reacts with a thiol to form sulfide-MA. In the presence of strong oxidants, the sulfide-MA is activated towards nucleophilic attack via sulfone-MA, and proline-MA can be recovered (full cycle, light blue line). In the presence of weaker oxidants, two shunts open up, enabling the recovery of proline-MA via sulfoxide-MA (central pathway, purple line), as well as directly through sulfide-MA (left pathway, orange line), with different kinetics and side products compared to the full cycle. Experiments typically conducted in 9/1 0.5 M phosphate buffer (pH 7.0–8.0)/DMF.
