An efficient method of synthesis of isoxazolidine-fused β-lactams via base-promoted cyclization-ring opening of carbamoyl-spirocyclopropane isoxazolidines

摘要

1,3-Dipolar cycloadditions of dialkyl-substituted 2- benzylidenecyclopropane-1,1-dicarboxylates and a number of C-carbamoyl nitrones proceed with high efficiency and selectivity with the formation of single isomeric spiro[cyclopropane-1,4-isoxazolidine] cycloadduct. Obtained cycloadducts easily undergo cyclopropyl ring opening-cyclization to form new β-lactams fused with isoxazolidine ring in high yields.