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Paper | Regular issue | Vol 32, No. 9, 1991, pp.1719-1728
Published online, 1st January, 1970
DOI: 10.3987/COM-91-5752
Synthesis and Properties of Pyrimido[4,5-b][1,4]oxazin-7-one Derivatives. A Novel Heterocyclic System

Manuel Melguizo, Manuel Nogueras,* and Adolfo Sánchez

*Departamento de Química Orgánica, Facultad de Ciencias Experimentales de Jaén, 23071 Jaén, Spain


The synthesis of two pyrimido[4,5-b][1,4]oxazin-7-one derivatives (5 and 10) from 4,5-diaminopyrimidin-6(1H)-one derivatives (2 and 8) and ethyl pyruvate is reported. By treatment of a 5-amino-4-(xylosylamino)pyrimidine (2) with ethyl pyruvate, a 8-xyloxylpteridine derivative (4) or a 4-(xylosylamino)pyrimido[4,5-b][1,4]oxazin-7-one derivative (5) can be obtained depending on solvent employed. This solvent-dependent regioselectivity was rationalized on the basis of instability of compound 5 in hydroxylic media. This feature of instability is analized and conditions necessary for obtaining pyrimido[4,5-b][1,4]oxazin-7-one derivatives are reported.