The present invention generally relates to processes and methods of peptide and protein synthesis. The present invention also relates to specific compounds for use in such processes and methods. It is shown herein that peptides with a C-terminal tertiary N,N-bis(2-mercaptoethyl)-amide (BMEA) undergo N-to-S acyl transfer at weakly acidic pH to form a transient thioester which can be captured for direct ligation with a cysteinyl peptide. These C-terminal BMEA peptides are easily prepared with standard Fmoc solid-phase synthesis protocols, thus giving a very convenient access to the thioester components for native chemical ligation.