1-(2'-O,4-C-Methylene-β-D-ribofuranosyl)thymine, with CAS number 206055-67-6, is a chemically modified nucleoside analog. Its structure features a methylene bridge between the 2'-O and 4'-C positions of the ribose sugar, creating a bicyclic "locked" sugar conformation. This modification imparts significant rigidity to the nucleoside structure compared to its natural counterparts. This compound is primarily utilized as a key intermediate in the research and development of novel nucleoside-based therapeutics. Its locked conformation is of particular interest in medicinal chemistry for the design of antisense oligonucleotides (ASOs) and small interfering RNA (siRNA) agents. The structural constraint can enhance binding affinity to target RNA sequences and improve metabolic stability against nucleases, which are critical factors for the efficacy of oligonucleotide drugs. It serves as a specialized building block for constructing advanced oligonucleotide sequences. As a modified nucleoside, it falls under the category of life science reagents and pharmaceutical intermediates. Its synthesis and application are geared towards advanced drug discovery programs, particularly in the fields of genetic medicine and antiviral research, where stable and high-affinity oligonucleotide analogs are essential.