Nucleobases, Nucleosides and Nucleotides - Free-Radical-Induced DNA Damage and Its Repair - page 285

The C (4 ) radical has been generated specifically photolytically in the presence

of O 2 [reactions (290)−(293); Giese et al. 1995].

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The hydroperoxide (two isomers) is formed in high yield under these conditions
(the nature of the reduction equivalent that is required for this process is as yet
not known), and subsequent treatment with a base gives rise to glycolic acid and
the base propenal [Grob fragmentation; reaction (292); yields near 90%].
In the absence of O 2 and in the presence of Mn(III) acetate, the C (4 ) radical

is oxidized to the corresponding radical cation which in MeOH gives rise to the
acetal [reactions (294) and (295); Beyrich-Graf et al. 1998].

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To study the effect of a phosphate group at C (5 ), D -ribose-5-phosphate has been

investigated in some detail as a model system (Stelter et al. 1974, 1975a,b, 1976).
The phosphate group is a much better leaving group than the OH group, and its
elimination does not require proton catalysis. The data compiled in Table 10.29

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