title: Formation of 2'-deoxyoxanosine from 2'-deoxyguanosine and nitrous acid: mechanism and intermediates.
abstract: The reaction mechanism for the formation of 2'-deoxy-oxanosine from 2'-deoxyguanosine by nitrous acid was explored using methyl derivatives of guanosine and an isolated intermediate of the reaction. When 1-methylguanosine was incubated with NaNO(2)under acidic conditions, N (5) -methyloxanosine and 1-methylxanthosine were generated, whereas the same treatment of N (2), N (2)-dimethylguanosine generated no product. In a similar experiment without NO(2)(-), participation of a Dimroth rearrangement was ruled out. In the guanosine-HNO(2)reaction system, an intermediate with a half-life of 5.6 min (pH 7.0, 20 degrees C) was isolated and tentatively identified as a diazoate derivative of guanosine. The diazoate intermediate was converted into oxanosine and xanthosine at a molar ratio (oxanosine:xanthosine) of 0.26 at pH 7.0 and 20 degrees C. The ratio was not affected by the incubation pH between 2 and 10, but increased linearly with temperature from 0.22 (0 degrees C) to 0.32 (50 degrees C). The addition of acetone also increased the ratio up to 0.85 (98% acetone). Based on these results, a con-ceivable pathway for the formation of 2'-deoxyoxanosine from 2'-deoxyguanosine by HNO(2)is proposed.
authors.affiliation: Institute of Advanced Energy, Kyoto University, Gokasho, Uji 611-0011, Japan,
authors.forename: T
authors.initials: T
authors.lastname: Suzuki
authors.forename: H
authors.initials: H
authors.lastname: Ide
authors.forename: M
authors.initials: M
authors.lastname: Yamada
authors.forename: N
authors.initials: N
authors.lastname: Endo
authors.forename: K
authors.initials: K
authors.lastname: Kanaori
authors.forename: K
authors.initials: K
authors.lastname: Tajima
authors.forename: T
authors.initials: T
authors.lastname: Morii
authors.forename: K
authors.initials: K
authors.lastname: Makino
mesh_terms: D002412:Cations; D002851:Chromatography, High Pressure Liquid; D003849:Deoxyguanosine / Q000737:chemistry*; D003853:Deoxyribonucleosides / Q000138:chemical synthesis; D006868:Hydrolysis; D009682:Magnetic Resonance Spectroscopy; D009608:Nitrous Acid / Q000737:chemistry*
chemical_list: D002412:Cations; D003853:Deoxyribonucleosides; C042917:2'-deoxyoxanosine; D003849:Deoxyguanosine; D009608:Nitrous Acid