Protein chemical synthesis plays a crucial role in preparing protein with specific sequences and structures. Traditional solid-phase peptide synthesis encounters limitations due to the efficiency of stepwise amino acid coupling and deprotection reactions， posing challenges for synthesizing longer proteins in a single synthesis. Native chemical ligation and peptide hydrazide ligation have significantly facilitated protein synthesis by efficiently connecting unprotected peptide fragments. However， these ligation strategies rely on the relatively low abundance of cysteine in proteins， rendering them unsuitable for synthesizing proteins lacking cysteines or with inappropriate cysteine positions for ligation. The development of protein ligation-desulfurization has surmounted this hurdle by extending ligation sites to alanine and introducing thioamino acids. This innovation liberates protein synthesis from strict ligation site requirements. Moreover， advancements like VA044-based radical desulfurization and emerging desulfurization technologies such as photochemical desulfurization， P-B desulfurization， and iron-catalyzed desulfurization provide diverse options for protein chemical synthesis and expand its application scope. Overall， the chemical methods of protein ligation-desulfurization have undergone continuous evolution and innovation. This not only enriches synthetic methodology but also empowers in-depth investigations in protein engineering and chemical biology. This review provides a comprehensive overview of the development of ligation-desulfurization chemistry approaches in protein chemical synthesis in a timeline format. From the early native chemical ligation and peptide hydrazide ligation based on cysteine sites， to the breakthrough development of ligation-desulfurization strategies， to the exploration of thioamino acids and diversified desulfurization strategies， these techniques have not only enriched the strategies for peptide synthesis， but also demonstrated their broad application and development potential in protein synthesis. We expect that this review will provide insightful and valuable information for researchers in the field of protein chemical synthesis and stimulate further exploration and innovation in this field.
