Synlett 2025; 36(13): 1847-1867
DOI: 10.1055/a-2594-9636
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Advances in Chemical Conjugation of Natural Cysteine: Techniques and Applications

Kaibo Xu
a   Henan Linker Technology Key Laboratory, College of Advanced Interdisciplinary Science and Technology, Henan University of Technology, Zhengzhou, 450001, P. R. of China
,
Jinling Li
a   Henan Linker Technology Key Laboratory, College of Advanced Interdisciplinary Science and Technology, Henan University of Technology, Zhengzhou, 450001, P. R. of China
,
Zhenguo Zhang
a   Henan Linker Technology Key Laboratory, College of Advanced Interdisciplinary Science and Technology, Henan University of Technology, Zhengzhou, 450001, P. R. of China
,
a   Henan Linker Technology Key Laboratory, College of Advanced Interdisciplinary Science and Technology, Henan University of Technology, Zhengzhou, 450001, P. R. of China
b   Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 637371, Singapore, Singapore
› Author Affiliations

Distinguished University Professor grant (Nanyang Technological University) and the Agency for Science, Technology, and Research (A*STAR) under its MTC Individual Research grant (M21K2c0114) and RIE2025 MTC Programmatic Fund (M22K9b0049) for T.-P.L.


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Abstract

This review examines recent progress in chemical modification of natural cysteine residues, emphasizing biomedical and biotechnological applications. Capitalizing on the distinctive thiol group of cysteine (-SH) and natural scarcity in proteins, researchers have developed selective modification strategies operating under physiological conditions. The analysis systematically compares single thiol functionalization techniques (maleimide conjugation, cyclooctyne reactions) and disulfide rebridging approaches (phosphonamidate/allenamide linkers), evaluating their respective merits and limitations. Current applications span targeted drug delivery, biosensor development, and protein engineering innovations. The discussion highlights increasing attention toward disulfide bond manipulation for enhanced bioconjugation stability and diversity. While acknowledging the transformative potential of the field, the review identifies key challenges in the optimization of reaction specificity, product stability, and biological compatibility that will guide future research directions.

1 Introduction

2 Single Thiol Functionalization of Cysteine

3 Disulfide Functionalization of Cysteine

4 Conclusion



Publication History

Received: 07 April 2025

Accepted after revision: 25 April 2025

Accepted Manuscript online:
25 April 2025

Article published online:
17 June 2025

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