Used in solid-phase oligonucleotide synthesis as a phosphoramidite building block for introducing a biotin-functionalized linker. Enables incorporation of biotin-modified nucleotides for downstream conjugation via streptavidin-biotin interactions, such as attaching fluorophores, enzymes, or other biomolecules. The N-1 position of biotin is protected with an acid-labile (4-methoxytrityl)methyl group to ensure stability during synthesis, allowing selective deprotection under mild acidic conditions to reveal the functional biotin moiety. Commonly applied in the preparation of probes for molecular diagnostics, antisense oligonucleotides, and nucleic acid therapeutics.