scholarly journals Oxidation of caffeine by phosphate radical anion in aqueous solution under anoxic conditions

2000 ◽  
Vol 112 (5) ◽  
pp. 551-557 ◽  
Author(s):  
Maram Ravi Kumar ◽  
Mundra Adinarayana
Keyword(s):  
Aqueous Solution ◽  
Radical Anion ◽  
Anoxic Conditions

The SO4·̄induced Oxidation of 2′-Deoxyuridine-5′-phosphate, Uridine-5′-phosphate and Thymidine-5′-phosphate. An ESR Study in Aqueous Solution

1990 ◽  
Vol 45 (1-2) ◽  
pp. 47-58 ◽  
Author(s):  
Knut Hildenbrand
Keyword(s):  
Aqueous Solution ◽  
Radical Cation ◽  
Esr Spectroscopy ◽  
Radical Cations ◽  
Phosphate Group ◽  
Anoxic Conditions ◽  
Radical Site ◽  
Sugar Moiety ◽  
Type Radical ◽  
Phosphate Addition

Abstract Reactions of photolytically generated SO4·̄ with 2′-deoxyuridine-5′-phosphate (5′-dUMP), uridine-5′-phosphate (5′-UMP) and thymidine-5′-phosphate (5′-dTMP) were studied by ESR spectroscopy in aqueous solution under anoxic conditions. From 5′-dUMP and 5′-UMP the 5′,5-cyclicphosphate-6-yl radicals 10 and 11 were generated (pH 2 -11) whereas from 5′-dTMP at pH 3 -8 the 5,6-dihydro-6-hydroxy-5-yl radical 14 and at pH 7 -1 1 the 5-methylene-2′-deoxyuridine-5′-phosphate radical 15 was produced. In the experiments with 5′-UMP in addition to radical 11 the signals of sugar radicals 12 and 13 were detected. It is assumed that the base radical cations act as intermediates in the SO4·̄-induced radical reac­tions. The 5′-phosphate group adds intramolecularly to the C(5)−C(6) bond of the uraclilyl radical cation whereas the thymidyl radical cation of 5′-dTMP reacts with H2O at pH < 8 to yield the 6-OH-5yl adduct 14 deprotonates at pH > 7 thus forming the allyl-type radical 15. In 5′-UMP transfer of the radical site from the base to the sugar moiety competes with intramolecular phosphate addition.

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