Enantioselective synthesis of fluorinated aromatic amino acids catalyzed by SPINOL-derived chiral quaternary ammonium salts†

Abstract

We report the synthesis of a new class of chiral quaternary ammonium salts featuring a rigid spirobiindane scaffold. These chiral quaternary ammonium salts were employed as catalysts in the phase-transfer catalytic asymmetric alkylation of tert‑butyl glycinate–benzophenone Schiff base with both fluorinated and non-fluorinated benzyl bromides. Under the established reaction conditions, a series of chiral fluorinated aromatic α-amino acid derivatives, some of which are key intermediates for biologically significant compounds, were obtained in high yields and enantioselectivities.