ChemInform Abstract: Preparation of Chiral 3‐Unsubstituted β‐Lactams from 3‐Hydroxy . beta.‐Lactams by Using the Alkoxyketene‐Imine Cycloaddition Reaction as an Approach to the Azetidinone Ring: A Formal Synthesis of the Carbapenem Antibiotic (+)‐PS‐5 (I). | Publicación