P. Cysewski et al., Structure and tautomeric properties of cytosine derivatives generated by ahydroxyl radical in aerobic conditions, THEOCHEM, 459(1-3), 1999, pp. 1-14
The tautomeric properties of four hydroxyl radical cytosine derivatives wer
e characterised by an ab initio quantum chemistry method. 5,6-dihydroxycyto
sine (I), 5,6-dihydroxyuracil (2), isodialuric acid (3) and uracil glycol (
4) were characterised based on 6-311G** full gradient geometry optimisation
and single point MP2(6-311G**) energy calculation. Solvent effects were es
timated on the basis of the SCI-PCM(6-311G**) model. The most stable tautom
er of 5,6-dihydrocytosine (I) is in keto-amino form. The most probable stru
cture of the remaining studied derivatives corresponds to a diketo tautomer
. No significant impact of environment polarity on the tautomer succession
was observed for all studied derivatives. The most probable isomers in vacu
um remained the most preferred in water and other solvents. Due to the stab
ility of major tautomeric forms, the coding ability of 5,6-dihydroxycytosin
e (I) may be described as (+ - -) (acceptor-donor-donor). The formal coding
abilities of the other studied derivatives correspond to a (- + -) scheme
(donor-acceptor-donor). (C) 1999 Elsevier Science BV. All rights reserved.