PURINES .59. AN ALTERNATIVE SYNTHESIS OF 7-ALKYL-1-METHYLADENINES BY REGIOSELECTIVE ALKYLATION, FISSION, AND RECLOSURE OF THE ADENINE RING

7-Alkyl-1-methyladenines (12a, b) have been synthesized from 1-alkyl-4 -aminoimidazole-5-carboxamides (5a, b) in two steps [hence from adenin e (1) in sir; steps]. The synthesis started with dehydration (using PO Cl3-HCONMe(2)) of 5a, b, readily obtainable from I in four steps accor ding to previously reported procedures, and proceeded through cyclizat ion between the resulting 4-(dimethylaminomethyleneamino)imidazole der ivatives (8a,b) and MeNH(2). Similar cyclization between l-4-(ethoxyme thyleneamino)imidazole-5-carbonitrile (11c) and MeNH(2), yielded 7-ben zyl-1-methyladenine (12c).