The reactions between proline and several γ-oxo α,β-unsaturated esters have been studied in detail. The products isolated are in all cases derived from one molecule of proline and two molecules of the ester. The new polysubstituted pyrrolizidines result from the cycloaddition of an azomethine ylide to a second molecule of the unsaturated ester in a stereoselective manner. © 2002 Elsevier Science Ltd. All rights reserved.
- Azomethine ylides