Reaction of appropriatel protected purine nucleosides (adenosine and guanosine) with leadtetra-acetate results in the formation of the corresponding 5′-O,8-cyclopurine nucleosides (2), whereas that of the protected pyrimidine nucleosides (uridine and cytidine) give predominantly 5-acetoxy-5′-O,6-cyclo-5,6-dihydrouridine(4).
Intramolecular Cyclization of Purine Nucleosides by N-Halogenosuccinimides/Acetic Acid. A Mechanistic Aspect on the C(8)-Halogenation of Purine Nucleosides