The pyrazolo [3, 4-b] pyridine ring system [1] is present in a number of pharmaceutically important compounds targeted to inhibit VEGFR/PDGFR kinases [2] or GSK-3 [3]. In a current project aimed at the synthesis, design, and biological evaluation of new GSK-3 inhibitors, we have recently synthesized a series of known and new 3, 6-diamino-1H- pyrazolo [3, 4-b] pyridines [4](A)(Chart 1). To carry out basic SAR studies, we decided to ...