An enantioselective approach to bis-α-amino acids

In this paper, we describe details of a study into the asymmetric synthesis of bis-α-amino acids via alkylation of a benzophenone-derived glycine imine under phase-transfer conditions. By employing chiral quaternary ammonium salts derived from cinchona alkaloids it was found that the target bis-amino acids can be produced in good overall yield, and with high levels of stereoselectivity.