C-C Bond Formation at C-5 Position of Dimethyluracil Derivatives Using SmI₂

It has been demonstrated that the reaction of 5-iododimethyluracil with carbonyl compounds in the presence of SmI₂ can provide the C-5-substituted pyrimidines in moderate to good yields. This methodology will facilitate the development of pyrimidine nucleosides substituted at the 5-position, biologically important molecules, by the introduction of the α-hydroxyalkyl group at C-5 position, whose hydroxy moiety can be transformed to a variety of other functional groups. Derivation of purine and pyrimidine nucleosides has attracted much attention because of potent antitumor or antiviral activity. Pyrimidine nucleosides substituted at the C-5 position constitute a class of biologically significant molecules. The well-known cancer chemotherapeutic 5-fluorouracil and antiviral agents, such as 5-iodo-2'-deoxyuridine and 5-(trifluoromethyl)-2'-deoxyuridine, have been in clinical use for several years. Meanwhile, in recent years, there have been significant interests in the potential usages of the C-5-substituted pyrimidine nucleosides in synthetic oligonucleotide probes as a tether site for linking reporter groups to nucleic acids