Abstract A number of deaza analogues of adenosine were prepared and tested as inhibitors of platelet aggregation induced by ADP and collagen to investigate the structure-activity relationships in this class of nucleoside analogues. The results showed that the presence of a 6-amino group and nitrogen atoms at positions 3 and 7 of the purine moiety are required for inhibitory activity.
![3H-Imidazo[4,5-b]pyridine, 4-oxide Structure](https://image.chemsrc.com/caspic/098/6863-46-3.png)
![4-hydroxy-7-nitroimidazo[4,5-b]pyridine Structure](https://image.chemsrc.com/caspic/250/14432-11-2.png)