Used in solid-phase peptide synthesis to incorporate phosphorylated threonine residues into peptides. The Fmoc group allows for mild base deprotection, compatible with sensitive sequences. The benzyl (Bzl) protection on the phosphate group ensures stability during chain assembly and can be removed during final acidic cleavage. This building block is essential for synthesizing phosphopeptides used in studying cellular signaling pathways, kinase activity, and protein-protein interactions. Commonly applied in the development of peptide-based drugs, diagnostic tools, and biochemical probes.