Stability of N-glycosidic bond of (5'S)-8,5'-cyclo-2'-deoxyguanosine.

8,5′-Cyclopurine deoxynucleosides are unique tandem lesions containing an additional covalent bond between the base and the sugar. These mutagenic and genotoxic lesions are repaired only by nucleotide excision repair. The N-glycosidic (or C1′-N9) bond of 2′-deoxyguanosine (dG) derivatives is usually susceptible to acid hydrolysis, but even after cleavage of this bond of the cyclopurine lesions, the base would remain attached to the sugar. Here, the stability of the N-glycosidic bond and the products formed by formic acid hydrolysis of (5′S)-8,5′-cyclo-2′-deoxyguanosine (S-cdG) were investigated. For comparison, the stability of the N-glycosidic bond of 8,5′-cyclo-2′,5′-dideoxyguanosine (ddcdG), 8-methyl-2′-deoxyguanosine (8-Me-dG), 7,8-dihydro-8-oxo-2′-deoxyguanosine (8-Oxo-dG), and dG was also studied. In various acid conditions, S-cdG and ddcdG exhibited similar stability to hydrolysis. Likewise, 8-Me-dG and dG showed comparable stability, but the half-lives of the cyclic dG lesions were at least 5-fold...