Asymmetric syntheses of β-phenylalanine, α-methyl-β-phenylalanines and derivatives

Abstract

A strategy of highly stereoselective conjugate additions of lithium (R)-(α-methylbenzyl)benzylamide to tert-butyl cinnamate and its 2-methyl derivative combined with appropriate tandem or sequential electrophilic quenches allows the asymmetric syntheses of β-phenylalanine (95% enantiomeric excess) and homochiral (2R, 3S)- and (2S, 3S)-α-methyl-β-phenylalanine and the corresponding β-lactams (3R, 4S)- and (3S, 4S)-3-methyl-4-phenylazetidinones.