Efficient synthesis of α-amino acid derivatives via phase-transfer-catalyzed directed reductive amination

An efficient phase-transfer-catalyzed directed reductive amination of α-keto esters was described using simple substituted benzyl amines as nitrogen source and K2CO3 as base at room temperature, giving a series of aliphatic α-amino acid derivatives in moderate to high yields(up to 99%). Preliminary study on this asymmetric process showed that cinchona-derived phase transfer catalyst was effective, affording the corresponding product in 13% e.e. and 40% yield.