Native chemical ligation derived method for recombinant peptide/protein C-terminal amidation

C-terminal amidation is often a requisite structural feature for peptide hormone bio-activity. We report a chemical amidation method that converts peptide/protein thioesters into their corresponding C-terminal amides. The peptide/protein thioester is treated with 1-(2,4-dimethoxyphenyl)-2-mercaptoethyl auxiliary (1b) in a native chemical ligation (NCL) reaction to form an intermediate, which upon removal of the auxiliary with TFA, yields the peptide/protein amide. We have demonstrated the general utility of the approach by successfully converting several synthetic peptide thioesters to peptide amides with high conversion rates. Preliminary results of converting a recombinant peptide thioester to its amide form are also reported.