SYNTHESIS OF 9-HYDROXYALKYL-SUBSTITUTED PURINES FROM THE CORRESPONDING 4-(C-CYANOFORMIMIDOYL)IMIDAZOLE-5-AMINES

The amino alcohols HO(CH2)nNH2 (n = 2, 3 and 5) react readily with ethyl (Z)-N-(2-amino-1,2-dicyanovinyl) formimidate 5 to give the amidines 6a-c, which cyclize in the presence of DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) to give the corresponding 4-(cyanoformimidoyl)imidazole-5-amines 7a-c, which can be isolated in the cases where n = 2 or 3. In the presence of aldehydes and ketones, the imidazoles 7a-d lead to the 6-carbamoyl-1,2-dihydropurines 9a-f which, in some cases, are oxidised to the corresponding 6-carbamoylpurines. The reaction of the imidate 5 with 2-methoxyethylamine leads to the amidine 6d and, on treatment with DBU, the reactive imidazole 7d which can be used directly for further reaction.