Synthesis of spiropyrrolidines and spiropyrrolizidines by 1,3-dipolar cycloadditions of azomethine ylides to substituted alpha-methylene-gamma-lactones

1,3-Dipolar cycloadditions of (E)- and (Z)-substituted alpha -methylene-gam ma -lactones with azomethine ylides derived from N-methyl glycine and L-pro line gave the corresponding spiropyrrolidine and spiropyrrolizidine cycload ducts in good to moderate yields with various extent of stereoselectivity a nd regioselectivity. Cycloadditions of the azomethine ylide derived from L- proline exhibited endo selectivity especially in the case of (Z)-isomers of starting methylene lactones. Reactivity and regioselectivity were rational ized by a comparison with quantum chemical calculations (AM1). Structures o f derivatives prepared were determined by NMR spectroscopy and by X-ray. (C ) 2001 Elsevier Science Ltd. All rights reserved.