Free radical chemistry of nucleosides and nucleotides. Ring opening of C4'-radicals

Article abstract of DOI:10.1016/S0040-4020(97)10262-9

It is demonstrated that nucleotide C4' radicals may be generated from a C4'-thiolester on treatment with tributyltin hydride. When the reaction is conducted in benzene at reflux the C4' radical expels the C3'-phosphate group to give a radical cation. This species undergoes deprotonation to an allylic radical which suffers cleavage of the deoxyribose ring. Similar reactions are observed when the reaction is conducted with tris(trimethylsilyl)silane in place of the stannane. In methanolic benzene the radical cation is trapped by methanol to give a new C4' radical which is quenched before ring opening. The behavior of C4' radicals toward ring opening is discussed in terms of the conformations imposed by the substituents at C3'.