title: Chemical radiation studies of 8-bromo-2'-deoxyinosine and 8-bromoinosine in aqueous solutions.
abstract: The reactions of hydrated electrons (e(aq) (-)) with 8-bromo-2'-deoxyinosine (8) and 8-bromoinosine (12) have been investigated by radiolytic methods coupled with product studies and have been addressed computationally by means of BB1K-HMDFT calculations. Pulse radiolysis revealed that one-electron reductive cleavage of the C--Br bond gives the C8 radical 9 or 13 followed by a fast radical translocation to the sugar moiety. Selective generation of a C5' radical occurs in the 2'-deoxyribo derivative, whereas in the ribo analogue the reaction is partitioned between the C5' and C2' positions with similar rates. Both C5' radicals undergo cyclizations, 10-->11 and 14-->15, with rate constants of 1.4 x 10(5) and of 1.3 x 10(4) s(-1), respectively. The redox properties of radicals 10 and 11 have also been investigated. A synthetically useful photoreaction has also been developed as a one-pot procedure that allows the conversion of 8 to 5',8-cyclo-2'-deoxyinosine in a high yield and a diastereoisomeric ratio (5'R)/(5'S) of 4:1. The present results are compared with data previously obtained for 8-bromoadenine and 8-bromoguanine nucleosides. Theory suggests that the behavior of 8-bromopurine derivatives with respect to solvated electrons can be attributed to differences in the energy gap between the pi*- and sigma*-radical anions.
authors.affiliation: ISOF, Consiglio Nazionale delle Ricerche Via P. Gobetti 101, 40129 Bologna, Italy.
authors.forename: Marialuisa
authors.initials: M
authors.lastname: Russo
authors.forename: Liliana B
authors.initials: LB
authors.lastname: Jimenez
authors.forename: Quinto G
authors.initials: QG
authors.lastname: Mulazzani
authors.forename: Mila
authors.initials: M
authors.lastname: D'Angelantonio
authors.forename: Maurizio
authors.initials: M
authors.lastname: Guerra
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Miranda
authors.forename: Chryssostomos
authors.initials: C
authors.lastname: Chatgilialoglu