Nucleobases, Nucleosides and Nucleotides - Free-Radical-Induced DNA Damage and Its Repair - page 258

Table 10. 21. γ -Radiolysis if N 2 O-saturated aqueous solutions of MeOH (0.5 mol dm −3 ) in
the presence of 1,3Me 2 Ura (5 × 10 −4 mol dm −3 ). Products and their G values (unit: 10 −7 mol
J −1 ) at different dose rates (unit: Gy s −1 ; Schuchmann et al. 1986)

Product 0.18 0.026 0.0028

1,3-Dimethyl-6-hydroxymethyl-uracil 0.2 0.2 0.2

5,6-Dihydro-1,3-dimethyl-6-hydroxymethyluracil 0.85 1.7 2.1

5,6-Dihydro-5,6-di(hydroxymethyl)-1,3-dimethyluracil 0.95 0.7 0.6

0.45 a 0.68 a 0.95 a 5,5 ′ -Bi-(5,6-dihydro-6-hydroxymethyl-1,3-

dimethyl)uracilyl

Formaldehyde 0.7 1.1 n.d.

Ethylene glycol 0.95 0.8 ND

1,3-Dimethyluracil consumption 2.4 3.2

4 ± 1

n.d., Not determined
a G values in monomer units

Although the O 2 concentration prevailing under the experimental conditions
and other details such as products of competing reactions are not known exactly,
one can estimate that the rate of the C (5 C (6) addition must be around 10 5 s −1 .

This is the same order of magnitude as the addition of the C (5

′ ) →

′ ) radical to the

C (8) position in purines (see below).
The cyclonucleoside shown above has been synthesized and some of its prop-
erties such as piperidine stability were studied (Muller et al. 2002).
An interesting additional aspect offers the reaction of • CH 2 OH with
1,3Me 2 Thy (Schuchmann et al. 1986). Here, not only is an addition to the C (6)
position [reaction (197)] observed, but as much as 25% of • CH 2 OH abstract
an H atom from the methyl group [reaction (198); see also Leonov et al. 1973;
Livneh et al. 1982].