Isolation and Characterization of a New Product Produced by Ionizing Irradiation and Type I Photosensitization of 2′-deoxyguanosine in Oxygen-saturated aqueous Solution: (2S)-2,5′-anhydro-1-(2′-deoxy-β-d-erythro-pentofuranosyl)-5-guanidinylidene-2-hydroxy-4-oxoimidazolidine

A major product of the radiation-induced decompostion of 2′-deoxyguanosine in oxygen-saturated aqueous solution has been isolated by reverse phase high performance liquid chromatography and characterized by carbon and proton NMR spectroscopy, fast-atom bombardment mass spectrometry, and chemical analysis as (2S)-2,5′-anhydro-1-(2′-deoxy-β-d-erythro-pentofuranosyl)-5-guanidinylidene-2-hydroxy-4-oxoimidazolidine(d < G). This compound is stable in aqueous solution at room temperature but decomposes upon heating (45°C). The lesion is also observed following type I (riboflavin, benzophenone, and acetophenone) photosensitized irradiation of 2′-deoxyguanosine at 350 nm in oxygen-saturated aqueous solution. A similar reaction mechanism, involving a neutral guanine radical intermediate, is proposed to explain the generation of d < G following both types of irradiation.