the synthesized compounds exist in DMSO solution in the 2-hydroxy-4-oxo form while in the crystal (at least for the case of the unsubstituted derivative) X-ray analysis shows that it occurs in the bipolar 2,4-dioxo form.Interest in 4-oxo-4H-pyrido[1,2-a]pyrimidine derivatives is principally due to their broad spectrum of biological activity. Based on this molecular system there have been synthesized bicyclic diaza sugars which inhibit β-glucosidase with high specificity [2]. 2-(Benzothiazol-2-yl) derivatives are novel, oral inhibitors of human leukocyte elastase suitable for treating chronic obstructive illnesses of the lungs, asthma, emphysema, cystic fibrosis, and various inflammatory reactions [3]. Substituted ethylenediamines containing the pyrido-[1,2-a]pyrimidine fragment are effective in the fight against microbacterial infection, not just tubercular [4]. 4-Oxo-4H-pyrido[1,2-a]pyrimidine-3-carboxamides find use as agents for the prophylaxis of gastric problems arising from the use of nonsteroidal anti-inflammatory agents [5]. 2-Amino-4H-pyrido[1,2-a]pyrimidin-4-ones actively inhibit the aggregation of human thrombocytes [6] and their analogs with a tetrazole fragment in position 3 the synthesis of leukotrienes [7].We have continued our work on preparative methods of synthesis and a study of the structure, chemical reactivity, and biological properties of 4-hydroxy-2-quinolinones and heterocycles related to them. This report concerns ethyl 2-hydroxy-4-oxo-4H-pyrido[1,2-a]pyrimidine-3-carboxylate.

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