252272-05-2Relevant academic research and scientific papers
Isomerization through cleavage and recombination of imidazolide linkage in the condensed tricyclic system related to hypermodified bases of phenylalanine transfer ribonucleic acids
Itaya, Taisuke,Kanai, Tae,Ohyama, Shin-Ichi,Shirasaki, Yoshihisa,Muramoto, Nobuhiro,Ono, Yukiko
, p. 1464 - 1472 (1999)
1-Benzyl-4,6-dimethyl-4,9-dihydro-1H-imidazo[1,2-a]purin-9-one bearing an alkyl, a 1-alkenyl, a hydroxymethyl, a methoxymethyl, or a formyl group at the 7-position (3a - e) underwent rearrangement through fission and recyclization of the pyrimidine ring, attaining equilibrium with the corresponding positional isomer 4a - e in MeONa-MeOH at 25 °C, whereas 7- methoxycarbonyl and 7-halogeno compounds 3f - i were irreversibly converted into the rearranged products 4f - i under identical conditions. The position of equilibrium appears to be affected by the electronic factor of the substituent rather than the steric one. The pseudo-first-order rate constants measured for the reactions of 3a,b,d,f - i suggest that the reaction is accelerated by the electron-withdrawing substituent. However, the reactions of this series of compounds do not always obey the Hammett equation. On the other hand, a linear free energy relationship (p = +3.2) was observed for the rates of rearrangement of a 6-demethyl series of compounds 9a,b,d,f,g, when σ(p/0) values were employed. The deviations from this relationship for the reactions with the 7-hydroxymethyl compound 9c and the 7-carbamoyl compound 9e are explicable in terms of the accelerative effect through intramolecular hydrogen bonding with the carbonyl oxygen at the 9-position.
