esters with carbonyl compounds leads to simple generation of ester-stabilized azomethine ylides which are trapped by olefinic dipolarophiles as cycloadducts. Anti ylides are exclusively involved in the cycloadditions when N-substituted 2-amino esters are employed for the ylidegeneration, while syn ylides from N-unsubstituted 2-amino esters. Relative stability among all possible ylide isomers has been