5'-O-[Bis(4-Methoxyphenyl)phenylmethyl]-thymidine 3'-[2-cyanoethyl N,N-bis(1-methylethyl)phosphoramidite] is a nucleotide and reactant used in the solid-phase synthesis of phosphorothioate oligonucleotides, and in the synthesis of lipophilic 5'-phosphoramidate derivatives of DNA and RNA oligonucleotides.