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Communication | Special issue | Vol 15, No. 1, 1981, pp.195-200
Published online, 1st January, 1970
DOI: 10.3987/S-1981-01-0195
Reversible Ring Opening of 3,9-Disubstituted Adenines : Effect of Substituents

Tozo Fujii,* Tohru Saito, and Tsuyoshi Nakasaka

*Faculty of Pharmaceutical Scicences, Kanazawa University, 13-1 Takara-machi, Kanazawa 920-0934, Japan


The equilibrium constants and the rates of ring opening and cyclization for equilibria between the 3,9-disubstituted adenines IVa-1 and the N-alkylformamidoimidazoles Va-1 in H2O at pH 8.98 and 25°C have been measured. It has been found that a bulky substituent at the 3-position of IV retards the ring opening to give V, whereas an electron-withdrawing group at the 3- or the 9-position accelerates it. A bulky alkyl group on the formamido nitrogen of V markedly retards the cyclization leading to IV, favoring the ring-opened form in the equilibrated mixture.