Purines. LIX. An Alternative Synthesis of 7-Alkyl-1-methyladenines by Regioselective Alkylation, Fission, and Reclosure of the Adenine Ring

抄録

7-Alkyl-1-methyladenines (12a, b) have been synthesized from 1-alkyl-4-aminomidazole-5-carboxamides (5a, b) in two steps [hence from adenine (1) in six steps]. The synthesis started with dehydration (using POCl₃-HCONMe₂) of 5a, b, readily obtainable from 1 in four steps according to previously reported procedures, and proceeded through cyclization between the resulting 4-(dimethylaminomethyleneamino)imidazole-5-carbonitrile derivatives (8a, b) and MeNH₂. Similar cyclization between 1-benzyl-4-(ethoxymethyleneamino)imidazole-5-carbonitrile (11c) and MeNH₂ yielded 7-benzyl-1-methyladenine (12c).