Theoretical investigations on the thiol–thioester exchange steps of different thioesters

As the rate-determining step in native chemical ligation reactions, the thiol–thioester exchange step is important in determining the efficiency of the ligations of peptides. In the present study, systematic theoretical calculations were carried out on the relationships between the structure of different thioesters and the free energy barriers of the thiol–thioester exchange step. According to the calculation results, the thiol–thioester exchange step is disfavored by the steric hindrance around the carbonyl center, while the electronic effect (i.e. conjugation and hyper-conjugation effects) becomes important when the steric hindrance is insignificant.

Graphical abstractThe structure–activity relationships of thiol–thioester exchange step in NCL reaction of different thioesters have been examined.Figure optionsDownload full-size imageDownload as PowerPoint slide