Fused pyrimidine derivatives R 0515 Transformations of Diethyl 2-[(Dimethylamino)methylene]-3-oxopentanedioate. A Simple Synthesis of Substituted 2-Amino-5-oxo-5,6-dihydropyrido[4,3-d]pyrimidine-8-carboxylates. -Diethyl acetonedicarboxylate (I) is used as building block for the synthesis of title compounds (VIII) and (IX). -(ZUPANCIC, S.; SVETE, J.; STANOVNIK*, B.; Heterocycles 77 (2009) 2, 899-908; Fac. Chem.