TICL4-MEDIATED REACTIONS OF SILYL KETENE ACETALS DERIVED FROM N-METHYLEPHEDRINE ESTERS - ASYMMETRIC-SYNTHESIS OF BETA-LACTAMS

TiCl4 mediated addition of silyl ketene acetals derived from N-methylephedrine esters to various aldehydes and imines was used as the key-step in the enantio- and diastereo-controlled synthesis ofβ-lactams. Thus 3,4-trans and cis substituted-2-azetidinones were synthesized in good yield and high enantiomeric purity, and transformed by using established methods to known precursors of carbapenem antibiotics.