Obtention of two anomers of imidazolone during the type I photosensitized oxidation of 2 '-deoxyguanosine

The beta-furanose anomer of imidazolone (beta-dIz) is the main product of t he photosensitized oxidation of the natural 2'-deoxyguanosine in the presen ce of benzophenone, a type I photosensitizer, but the alpha-furanose anomer (alpha-dIz) is also formed through an imine intermediate during the photoc hemical reaction. This anomerization phenomenon has been confirmed by using the alpha-anomer of 2'-deoxyguanosine. In addition, the chemical oxidation of alpha- or beta-de by Mn-TMPyP-KHSO5 provides the alpha- or beta-furanos e anomers, respectively, in an almost quantitative yield, and thus represen ts a method of choice for the synthesis of both dIz stereoisomers.