Cycloaddition reactions of N-allyl substituted polycyclic derivatives of isoindole-1,3-dione with nitrones proceeds regio- and stereoselectively on the double bond of the N-allyl substituent giving substituted isoxazolidines with good yields. Regioselectivity of the cycloaddition of this dipolarophiles with nitrile oxides depends on the structure of unsaturated hydrocarbon scaffold and the reaction selectively leads to adducts on endocyclic or the double bond of the N-allyl substituent. DFT calculations were used to investigate the reasons of the selectivity.