Misonidazole, after reduction to the hydroxylamine derivative, was found to react with guanosine in aqueous solution at pH 7. The guanosine product was isolated and was assigned a structure having a new 5-membered ring with a -CHOH-CHOH-linkage between the N-1 and N-2 positions of guanine. Removal of the sugar residue from the guanosine product by acid hydrolysis resulted in the corresponding g...