The catalytic enantioselective epoxidation of the isoflavones 1a-f has been performed by the Mn(III)salen complexes (R,R)-3 and (S,S)-3 as catalysts and dimethyldioxirane as the oxygen-atom source to afford optically active isoflavone epoxides 2a-f, The absolute configuration of the nonracemic epoxides 2 have been determined by X-ray diffraction analysis. Our present results constitute the first examples of the preparation of optically active isoflavone epoxides. (C) 1998 Elsevier Science Ltd. All rights reserved.