Used in peptide synthesis as a protected selenocysteine derivative, enabling the incorporation of selenium-containing amino acids into peptides for structural and functional studies. The Fmoc group allows for solid-phase synthesis, while the 4-methoxybenzyl selenoether protects the selenium functionality during assembly. After chain assembly, the protecting group can be selectively removed to enable formation of selenol groups or selenide bridges, useful in designing redox-active peptides, enzyme mimics, and stable peptide structures through Se–Se bonds. Also applied in the development of selenopeptides with potential antioxidant or catalytic properties.