127820-66-0 4H-Pyrazolo[3,4-d]pyrimidin-4-one, 6-amino-1,5-dihydro-3-methyl-1-b-D-ribofuranosyl- 6-Amino-3-methyl-1-.beta.-D-ribofuranosylpyrazolo[3,4-d]pyrimidin-4(5H)-one AIDS-001498 AIDS001498 Pyrazolopyrimidine nucleoside