A novel one-step diastereo- and enantioselective formation of trans- azetidinones and its application to the total synthesis of cholesterol absorption inhibitors

Article abstract of DOI:10.1021/jo990428k

An efficient and practical asymmetric process was developed for the synthesis of azetidinone-based cholesterol absorption inhibitors. Key to this synthesis was the discovery of a novel one-step diastereo- and enantioselective formation of trans β-lactams starting from commercially available 3(S)-hydroxy-γ-lactone. Various trans β-lactams can be prepared in good yields and with better than 95:5 enantio- and diastereoselctivity. A Lewis acid-catalyzed aldol condensation and a highly enantioselective oxazaborolidine-catalyzed chiral reduction completes the side chain.