Two routes for the synthesis of 6-substituted 8-azaguanosine analogues are described. 2, 5, 6-Triamino-4 (3H)-pyrimidinethione (1) was converted by methylation, nitrosation, and acetylation to N-acetyl-7-(methylthio)-3H-1, 2, 3-triazolo [4, 5-d] pyrimidin-5-amine (5). The reaction of 5 with 2, 3, 5-tri-O-acetyl-D-ribofuranosyl chloride gave a mixture of the 7-, 8-, and 9-(2, 3, 5-tri-0-acetyl-@-~-ribofuranosyl)-8-azapurines 4a-c which was converted to 8- ...