title: Formation of 13C-, 15N-, and 18O-labeled guanidinohydantoin from guanosine oxidation with singlet oxygen. Implications for structure and mechanism.
abstract: Guanosine labeled with 15N at N1, amino, and N7 and 13C at either C2 or C8 was oxidized by Rose Bengal photosensitization (singlet oxygen) in buffered aqueous solution. At pH > 7, spiroiminodihydantoin was the major product, while at pH < 7, guanidinohydantoin (Gh) was the principal product. 15N and 13C NMR studies confirmed that Gh was formed as a mixture of slowly equilibrating diastereomers. Experiments conducted in H218O indicated that Gh and Sp each contained one oxygen atom derived from O2 and one from H2O. Tandem mass spectrometry was used to identify the C4 carbonyl of Gh as the one labeled with 18O, supporting a mechanism involving attack of water at C5 of a dehydro-8-oxoguanosine intermediate.
authors: Department of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, UT 84112-0850, USA.
authors: Yu
authors: Y
authors: Ye
authors: James G
authors: JG
authors: Muller
authors: Wenchen
authors: W
authors: Luo
authors: Charles L
authors: CL
authors: Mayne
authors: Anthony J
authors: AJ
authors: Shallop
authors: Roger A
authors: RA
authors: Jones
authors: Cynthia J
authors: CJ
authors: Burrows
mesh_terms: D002247:Carbon Isotopes; D006146:Guanidines / Q000138:chemical synthesis* / Q000737:chemistry; D006151:Guanosine / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry; D006827:Hydantoins / Q000138:chemical synthesis* / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007553:Isotope Labeling / Q000379:methods; D009587:Nitrogen Isotopes; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods; D010084:Oxidation-Reduction; D010103:Oxygen Isotopes; D026082:Singlet Oxygen / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization; D013141:Spiro Compounds / Q000138:chemical synthesis / Q000737:chemistry
chemical_list: D002247:Carbon Isotopes; D006146:Guanidines; D006827:Hydantoins; D009587:Nitrogen Isotopes; D010103:Oxygen Isotopes; D013141:Spiro Compounds; C467338:guanidinohydantoin; C408822:spiroiminodihydantoin; D006151:Guanosine; D026082:Singlet Oxygen