A Convenient Synthesis of Fluorinated Pyrazolo[3,4-b]pyridine and Pyrazolo[3,4-d]pyrimidine Nucleosides

Starting from 5-amino-1-(2,3-O-isopropylidene-beta-D-ribofuranosyl)-1H-pyrazole, fluorine-containing 1,3-CCC-, 1,3-CNC-dielectrophiles and 2,4,6-tris(trifluoromethyl)-1,3,5-triazine, a set of fluorinated pyrazolo[3,4-b]pyridine and pyrazolo[3,4-d]pyrimidine nucleosides was obtained. Synthetic access to stable 4-(polyfluoroalkyl)-4,7-dihydro-1H-pyrazolo[3,4-b]pyridin-4-ole was elaborated, which can be considered to be mimetics of the putative transition state involved in adenosine deaminase activity.