Asymmetric synthesis of beta-lactams and pseudopeptides via stereoselective conjugate additions of lithium (alpha-methylbenzyl)-allylamide to alpha,beta-unsaturated iron acyl complexes

Lithium (alpha-methylbenzyl)allylamide 2 undergoes stereoselective conjugat e additions to alpha,beta-unsaturated iron acyl complexes 3a-c to afford be ta-amino iron acyl adducts 5a-c and 6a-c. These adducts may be deallylated smoothly using palladium(0) catalysis providing the corresponding homochira l secondary amines 7a-c which, upon oxidative decomplexation with bromine o r N-bromosuccinimide, undergo direct beta-lactam ring formation. The diaste reoselectivity for the conjugate addition to 3a may be further improved by the use of magnesium amide 10. Oxidative decomplexation of one of the beta- amino iron acyl adducts 5b in the presence of alpha-amino esters provides p seudopeptide fragments comprising an alpha-amino acid coupled to a beta-ami no add.