the azetidin-2-one ring. The most common strategy for the synthesis of 4-alkoxyazetidinons involves intramolecular nucleophilic substitution at C4 that leads to ring closure. Such a displacement proceeds via the flat intermediate that suppossedly has the structure of a mezomeric acyl ammonium cation. We herein report a novel and enantioselective, chiral Lewis acid mediated cyclization that affords the