Nucleophilic cyclopropanation of arylideneimidazolones possessing a peripheral chiral center and the subsequent fractionalcrystallization of diastereomers allows access to the compounds with an enantiomerically uniform configuration of the spirocyclic donor-acceptor cyclopropane fragment. They were used to study the mechanism of the cycloaddition reaction with aldehydes; it wasdemonstrated that stereochemical information from the cyclopropane fragment is lost during the reaction