Diastereoselective and Enantioselective Synthesis of Unsymmetric <i>β,β</i>-Diaryl-α-Amino Acid Esters via Organocatalytic 1,6-Conjugate Addition of <i>para</i>-Quinone Methides

A novel strategy based on phase transfer catalysis for the diastereoselective and enantioselective direct assembly of unsymmetric β,β-diaryl-α-amino acid esters via 1,6-conjugate addition of para-quinone methides and glycine derivatives is described. This protocol also provides an alternative route to the synthetically interesting functionalized chiral tetrahydroisoquinoline and its analogues.