New chiral phase-transfer catalysts possessing a 6,6′-bridged ring on the biphenyl unit: application to the synthesis of α,α-dialkyl-α-amino acids

A new chiral phase-transfer catalyst possessing a 6,6′-bridged ring on the biphenyl unit has been developed for the practical synthesis of α,α-dialkyl-α-amino acids. This catalyst shows very high activity for the asymmetric alkylation of an alanine derivative to give α,α-dialkyl-α-amino acid derivatives with high enantioselectivities.