Improved methods of native chemical ligation are provided. The methods involve reacting a thioacid (e.g. a peptide thioacid) with an aziridinyl compound (e.g. an aziridinyl peptide) under mild conditions without the use of protecting groups, and without requiring that a cysteine residue be present in the ligation product. Initial coupling of the thioacid and the aziridinyl compound yields a ligation product which contains an aziridinyl ring. Subsequent opening of the aziridinyl ring (e.g. via a nucleophilic attack) produces a linearized and modified ligation product.
ligation site. The aziridine-mediated peptide ligation concept is exemplified using H(2)O as the nucleophile, producing a Xaa-Thr linkage (where Xaa can be an epimerizable and hindered aminoacid). The overall process is compatible with a variety of unprotectedaminoacid functionality, most notably the N-terminal and Lys side chain amines.