Abstract
Methylation of N6-methoxyadenine (3) with an excess of Mel in AcNMe2 at 40°C was found to give the 3-methylated product 8 (17% yield), 9-methylated product 4 (2%), N6, 9-dimethylated product 5 (9%), 7, 9-dimethylated product 6 (27%). 3, 7-dimethylated product 7 (10%), and N6, 3-dimethylated product 9 (11%). Similar treatment of N6-benzyloxyadenine (12) with Mel also afforded a mixture of several products, from which the 7, 9-dimethylated product 13 (X=1) was isolated in 30% yield. Similar methylation of N6-methyladenine (17), prepared in 65% yield from 1-methyladenine (16) by a Dimroth-type rearrangement. gave the 3-methylated product 18 (82% yield), 9-methylated product 20 (1.3%), 3, 7-dimethylated product 19 (1.8%), and 1, 9-dimethylated product 21 (0.3%). On methylation under similar reaction conditions, 18 furnished the 9-methylated product 22 (15% yield) as well as the 7-methylated product 19 (29%), and 20 produced 22 (17%) and 21 (11%). The probable pathways to the six methylated products from 3 and those to the four methylated products from 17 are discussed.
