1,3-Dipolar cycloaddition reactions of nitrones with vinylacetic olefins in the racemic series and synthesis of δ-lactams via isoxazolidines

A study of the cycloaddition behavior of a series of esters and nitriles α-chloro- and α-hydroxyvinyl-acetic dipolarophiles with C-aryl-N-alkylnitrones has been carried out. Regiospecific cycloadditions are observed; the reactions lead to a mixture of 5-substituted isoxazolidines either erythro or threo, wherever the nitrone is involved. We report the synthesis of some δ-lactams in which isoxazolidines are used as latent synthons.