Synthesis of 7H-1,2,4-triazolo[1,5-d](tetrazole acyclo C-nucleosides

Condensation of 1,5-diaminotetrazole I with 2,3,4,5,6-penta-O-acetyl-D-gluconoyl chloride 2 or 2,3,4,5-tetra-O-acetylgalactaroyl dichloride 6 gave the corresponding 2,3,4,5,6-penta-O-acetyl-D-gluconic-1-(5-aminotetrazole)amide 3 or 2,3,4,5-tetra-O-acetylgalactaric 1,6-bis[(5-aminotetrazole)amide] 7, respectively which upon dehydrative cyclization with phosphoryl chloride gave the corresponding 6-(1,2,3,4,5-penta-O-acetyl-D-gluco-pentitol-1-yl) 7H-1,2,4-triazolo[1,5-d] tetrazole 4 or 1,2,3,4-tetra-O-acetyl-1,4-bis(7H-1,2,4-triazolo[1,5-d]tetrazol-6-yl)galacto-tetritol 8, respectively. De-O-acetylation of the acyclo C-nucleoside peracetates 4 and 8 with methanolic ammonia or sodium ethoxide in ethanol gave the corresponding acyclo C-nucleosides 5 and 9.