Glycogen phosphorylase (GP) plays a crucial role in the conversion of glycogen to glucose-1-phosphate (and in turn glucose) and is a promising target for therapeutic intervention in diabetes. In this study we synthesized new derivatives of 2-oxo-1,2-dihydropyridin-3-yl amides using a facile aminolysis reaction, in which different alkyl and aryl esters and amides are substituted at N-1 and C-3 of the heterocyclic ring. The in vitro inhibitory activity of compounds against glycogen phosphorylase was evaluated. From this series the most potent compound exhibits good GPa inhibition (IC(50)=6.3 microM). A preliminary study of these compounds showed that anti-GP activity was decreased by the incorporation of a C3-N carbonyl group and favored by increased lipophilicity.