Asymmetric synthesis of homochiral differentially protected bis-β-amino acid scaffolds

A strategy for the asymmetric synthesis of homochiral [(R,R)- or (S,S)-], or meso-(R,S) bis-β-amino acid scaffolds, formally resulting from the stepwise conjugate addition of two differentially protected homochiral lithium amides to two α,β-unsaturated esters attached to a central arene, is demonstrated. Further manipulation enables the efficient synthesis of orthogonally protected pseudo-meso or pseudo-C2 symmetric scaffolds via selective N-benzyl or N-allyl deprotection, enabling regio-, stereo- and chemoselective functionalisation.