抄録
The rates of the three reactions in the system that produces the rearranged isomers 4a-d and the 5-aminoimidazole derivatives 6a-d from 1-benzyloxy- and 1-(modified benzyloxy)-9-methyladenine perchlorates (2a-d·HClO4) through the isolable ring-opened intermediates 3a-d have been determined at various pH's and ionic strength 1.0 at 40°C. Among four kinds of modified or unmodified benzyloxy groups in these compounds, the 4-nitrobenzyloxy group has been found to cause 2·HClO4 to open its adenine ring most rapidly, whereas it causes 3 to recyclize to 4 most slowly. The reaction of 9-methyladenine 1-oxide (5) with 4-nitrobenzyl bromide in AcNMe2 at room temperature and subsequent treatment of the product with NaClO4 produced 1-(4-nitrobenzyloxy)-9-methyladenine perchlorate (2a·HClO4) in 91% yield. Treatment of 2a·HClO4 with boiling pyridine gave 5 in 84% yield, and reduction of 2a·HClO4 with hydrogen and Pd-C afforded 9-methyladenine (1) in 72% yield, demonstrating the ease with which the 4-nitrobenzyl group can be removed. These results suggest the potential utility of the 4-nitrobenzyloxy group as a control synthon for the preparation of compounds of type 3, which are useful monocyclic intermediates for syntheses of a variety of substituted adenine derivatives.
