Premium
Chemical Radiation Studies of 8‐Bromo‐2′‐deoxyinosine and 8‐Bromoinosine in Aqueous Solutions
Author(s) -
Russo Marialuisa,
Jimenez Liliana B.,
Mulazzani Quinto G.,
D'Angelantonio Mila,
Guerra Maurizio,
Miranda Miguel A.,
Chatgilialoglu Chryssostomos
Publication year - 2006
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200600040
Subject(s) - radiolysis , chemistry , radical , solvated electron , aqueous solution , yield (engineering) , reaction rate constant , redox , moiety , photochemistry , medicinal chemistry , stereochemistry , organic chemistry , kinetics , materials science , physics , quantum mechanics , metallurgy
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 CBr 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 1.4×10 5 and of 1.3×10 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 π*‐ and σ*‐radical anions.