The Direct Catalytic Asymmetric α-Alkylation Of Amino Esters By Aldehyde Via Imine Activation

Two types of BINOL-related chiral aldehydes are prepared and used as organocatalysts for the direct asymmetric α-alkylation of N-unprotected amino esters. The first chiral aldehyde catalyzed a-alkylation of 2-aminomalonates with 3-indolylmethanols via imine activation was reported. Various amino-free tryptophan derivatives are prepared in good yields and with high enantioselectivities. A reasonable mechanism is proposed and verified by HRMS.