127820-75-1 1H-Pyrazolo[3,4-d]pyrimidine-3,4(2H,5H)-dione, 6-amino-1-b-D-ribofuranosyl- 6-Amino-3-oxo-1-.beta.-D-ribofuranosylpyrazolo[3,4-d]pyrimidin-4(5H)-one AIDS-001497 AIDS001497 Pyrazolopyrimidine nucleoside