Used in the synthesis of modified oligonucleotides for antisense therapy and RNA interference (RNAi) applications. The 2'-O-methyl and 5-methyl modifications enhance nuclease resistance and improve binding affinity to complementary RNA strands. This phosphoramidite building block is essential in solid-phase oligonucleotide synthesis, particularly for creating stable and specific siRNA, miRNA, and antisense probes used in gene regulation studies and therapeutic development. Its modifications help reduce off-target effects and increase the in vivo stability of nucleic acid-based drugs.