Pteridines are a group of heterocyclic compounds with a wide variety of biological activities1 including anti-HIV,2 antimalarial,3 antiviral,4 anticancer5and also as a psychotropic agent.6They show aldose reductase inhibitor activities.7Additionally, pteridine structures are present in natural products such as folic acid, biopterin, neopterin,pterins and flavins. In this study, The reaction of 5-amino-3-(ethylthio)-1Hpyrazole-4-carbonitrile (1) with ethylacetoacetate in boiling acetic acid gave compound (2) which was brominated with molecular bromine in acetic acid at room temperature in order to obtain compound (3). Further treatment of compound (3) with various diamines gave the corresponding pyrazolo[1,5-a]pteridine derivatives 4(a-d) as major products in good yields.

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