title: Gamma-radiolysis DNA products: synthesis of 6-(alpha-thyminyl)-5,6-dihydro-4-thiothymine derivatives.
abstract: Far-UV photolysis of 4-thiothymidylyl(3'-5')thymidine led to the formation of three stable derivatives: one resulting from a combination between a 3'-end methylene radical and a 5'-end C(4) radical [4-(alpha-thyminyl) derivative] and two formed after a combination between a 3'-end methylene radical and a 5'-end C(6) radical [6-(alpha-thyminyl) derivative]. In the latter series, two stereochemical pathways took place during the reaction between the methylene and C(6) radicals. The major pathway occurred when the 5'-base glycosidic bond had an anti conformation leading to an S configuration of the C(6) Tp-end. The minor pathway, which had never been reported before in this series, involved a 5'-base in a syn conformation leading consequently to the R configuration at the C(6) Tp-end. The 5,6-dihydrothymine moiety of these two adducts presented a 5,6-trans diaxial substitution that resulted from the epimerization, at the 5,6-dihydropyrimidine 5-position, of a less stable cis-disubstituted intermediate.
authors.affiliation: Institut de Chimie des Substances Naturelles, CNRS, 1 Avenue de la Terrasse, 91198 Gif-sur-Yvette Cedex, France.
authors.forename: Javier Ulises
authors.initials: JU
authors.lastname: Ortiz Mayo
authors.forename: François-Yves
authors.initials: FY
authors.lastname: Dupradeau
authors.forename: Dominique
authors.initials: D
authors.lastname: Guillaume
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Fourrey
authors.forename: Pascale
authors.initials: P
authors.lastname: Clivio
mesh_terms: D004247:DNA / Q000528:radiation effects*; D005720:Gamma Rays; D015394:Molecular Structure; D010782:Photolysis; D011743:Pyrimidines / Q000737:chemistry; D013237:Stereoisomerism; D013941:Thymine / Q000031:analogs & derivatives* / Q000138:chemical synthesis*
chemical_list: D011743:Pyrimidines; D004247:DNA; D013941:Thymine