Purines. LXVIII. Trifluoroperoxyacetic Acid Oxidation of N⁶-Benzyladenine : Formation of the N(3)-Oxide and N(7)-Oxide, and Their Cytokinin Activities

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Treatment of N⁶-benzyladenine (2) with 15% aqueous H₂O₂ in trifluoroacetic acid at 65-70°C for 1 h was found to give the N(3)-oxide (3) and the N(7)-oxide (4) in 4% and 4% yields, respectively. The structure of 3 was established by its identity with a sample prepared from 6-chloropurine 3-oxide (6) and benzylamine, and the structure of 4 by its identity with a sample obtained from 1-benzyladenine 7-oxide (8) by Dimroth rearrangement. The N-oxides 3 and 4, together with previously reported N⁶-benzyladenine 1-oxide (1), were tested for cytokinin activity in the tobacco callus bioassay. Each of the three N-oxides was active at 4 μM concentration, being less active than the parent base 2 by a factor of 40.