Adenosine kinase inhibitors. 2. Synthesis, enzyme inhibition, and antiseizure activity of diaryltubercidin analogues

In the preceding article (Ugarkar et al. J. Med. Chem. 2000, 43) we reported that analogues of tubercidin are potent adenosine kinase (AK) inhibitors with antiseizure activity in the rat maximum electroshock (MES) model. Despite the discovery of several highly potent AK inhibitors (AKIs), e.g., 5'-amino-5'-deoxy-5-iodotubercidin (1c) (IC50 = 0.0006 mu M), no compounds were identified that exhibited a safety, efficacy, and side effect profile suitable for further development. In this article, we demonstrate that substitution of the tubercidin molecule with aromatic rings at the N4- and the C5-positions not only retains AKI potency but also improves in vivo activity. Synthesis of such compounds entailed transformation of 4-arylanlino-5-iodotubercidin analogues to their corresponding 5-aryl derivatives via the Suzuki reaction. Alternatively, 4-N-suylamino-5-arylpyrrolo[2,3-d]pyrimdine bases were constructed and then glycosylated with appropriately protected alpha-ribofuranosyl chlorides using a phase-transfer catalyst. Several compounds exhibited potent activity in the rat MES seizure assay with ED(50)s less than or equal to 2.0 mg/kg, ip, and showed relatively mild side effects.