Synthesis of pyrimidine-containing 3-aminobutenolides

An efficient synthesis of pyrimidine-containing butenolides is reported, starting from C-alkoxycarbonyl isoxazolidines. Two competitive reaction routes are operating: the pathway leading to homo-N,O-nucleosides, based on the reduction of an ester group at C3, and the reaction channel leading to butenolides promoted by the removal of the hydrogen atom at C3. The two reaction pathways can be easily controlled according to the adopted experimental conditions