Author/Authors :
Raczy?ska، Ewa D. نويسنده Department of Chemistry, Warsaw University of Life Sciences (SGGW), 02-776 Warszawa, Poland , , Kami?ska، Beata نويسنده Department of Chemistry, Warsaw University of Life Sciences (SGGW), 02-776 Warszawa, Poland , , Szel?g، Ma?gorzata نويسنده Interdisciplinary Department of Biotechnology, SGGW, 02-776 Warszawa, Poland ,
Abstract :
Quantum-chemical calculations {DFT(B3LYP)/6-311+G**} were performed
for all possible nine tautomers of neutral purine (P) and its charged radicals, cation
(P+•) and anion (P-•), which may be formed in the presence of oxidizing or reducing
agents. Comparison of the stabilities orders for the neutral and charged forms shows
evidently that one-electron oxidation (P ? e ? P+•) has no important effect on the
tautomeric preferences. The NH tautomer containing the moving proton at the N9 atom
predominates for P+• (99.3%) as for P (99.8%). Dramatical changes take place for P-•.
One-electron reduction (P + e ? P-•) favors the C atoms for the moving proton,
particularly at the 6- (72.8%), 8- (26.2%) and 2-position (0.1%), and also the N3 atom
(0.9%). Preference of the CH tautomers in the tautomeric mixture of P-• may partially
explain synthesis and degradation reactions of purine derivatives.
