SYNTHESIS AND PROPERTIES OF OLIGONUCLEOTIDES CONTAINING 3′-O,4′-C-ETHYLENEOXY-BRIDGED 5-METHYLURIDINES

A phosphoramidite of 3'-O,4'-C-ethyleneoxy-bridged 5-methyluridine (3',4'-EoNA-T) was successfully incorporated into oligonucleotides, and their abilities to form duplexes with RNA and DNA as well as triplexes with double-stranded DNA were evaluated. The stabilities of the duplexes formed between RNA and 3',4'-EoNA-modified oligonucleotides were only slightly lower than those of the natural DNA RNA duplex, while the duplexes formed between 3',4'-EoNA-modified oligonucleotides and DNA were drastically less stable than the natural DNA-DNA duplex. Moreover, under the same conditions as the UV-melting experiments of the duplexes, 3',4'-EoNA-modified oligonucleotides were unable to form triplexes with dsDNA. These results showed that oligonucleotides containing 3',4'-EoNA-T had excellent RNA selectivity.