Protein chemical synthesis usually relies on the use of native chemical ligation that couples peptide thioester with a Cys-peptide.A limitation of this method is the difficulty of finding an appropriate Cys ligation site in many synthetic targets.To overcome this problem,the ligation-desulfurization approach has been developed.This approach involves the use of a thiol-containing amino acid as the ligation partner.After the sequence assembly is completed,the thiol group is removed through a desulfurization reaction to generate the standard amino acids.Currently this strategy has been applied to the ligations at a number of amino acids including Ala,Phe,Val,Lys,Thr,Leu,Pro and Gln.The present article reviews the design and synthesis of these thiol-containing amino acids for native chemical ligation at non-Cys sites. Protein chemical synthesis usually relies on the use of native chemical ligation that couples peptide thioester with a Cys-peptide. A limitation of this method is the difficulty of finding an appropriate Cys Ligation site in many synthetic targets. To overcome this problem, the ligation- this approach involves the use of a thiol-containing amino acid as the ligation partner. After the sequence assembly is completed, the thiol group is removed through a desulfurization reaction to generate the standard amino acids. Currently this strategy has has applied to the ligations at a number of amino acids including Ala, Phe, Val, Lys, Thr, Leu, Pro and Gln. The present article reviews the design and synthesis of these thiol-containing amino acids for native chemical ligation at non- Cys sites.