Raymond C. F. Jones, Gurdip Bhalay, Paul A. Carter, Kathryn A. M. Duller and Stephen H. Dunn
1,3-Dipolar cycloaddition of nitrile oxides, formed in situ by dehydration of primary nitro compounds, with pyrrolidine enamines of protected γ- or δ-amino-β-keto esters affords isoxazole-4-carboxylates; these undergo lactam formation and N–O bond cleavage to afford 3-acyltetramic acids and 3-acyl-4-hydroxypyridin-2-ones.