By the proposed Project stereoselective synthesis of chiral nonracemic aziridines and stereoselective opening of cyclic anhydrides is particularly examined. Chiral aziridines represent a very interesting and useful category of organic molecules; because of their specific reactivity they can be used as building blocks for the preparation of biological active compounds. Enantiomeric excesses (e.e.) of aziridines obtained by this original method represent the highest e.e. values ever observed. Stereoselective nucleofilic opening of cyclic meso-anhydrides (desymmetrization) is a key step for the preparation of valuable intermediates for the synthesis of biological active compounds starting from easily available substrates. Derived cyclic b- and g-amino acids (cispentacin, icofungipen, baclofen, pregabalin) are efficient antimikotics, anticonvulsants and antiepileptics.