Used in the synthesis of oligonucleotides, particularly in solid-phase DNA synthesis. Acts as a phosphoramidite building block for incorporating a modified nucleobase, specifically 5-ethynyluracil, into nucleic acid chains. The compound enables the introduction of specific protecting groups, such as the DMTr group at the 5'-position and the phosphoramidite at the 3'-position, that enhance coupling efficiency and selectivity during automated synthesis. Its structure supports high-yield oligonucleotide assembly, making it valuable in the production of primers, probes, and antisense molecules for research, diagnostics, and therapeutic applications. The 5-ethynyl modification allows for further functionalization, such as via click chemistry, enabling applications in labeling and bioconjugation.