相間移動触媒を用いたシアノ酢酸エステル類への不斉アルキル化反応

抄録

α-Cyanoacetic acid esters are useful precursors for the synthesis of α- and β-amino acids, and α,α-disubstituted α-cyanoacetates can be valuable synthons for the synthesis of natural products which have a chiral quaternary carbon center. We have investigated asymmetric alkylation of α-cyanoacetates using chiral phase-transfer catalyst, and found that enantioselectivity was dependent on the type of ester group of substrate, solvent, and base. When the alkylation of α-substituted α-cyanoacetic acid t-butyl esters was carried out in ether solution using 1 mol% of phase-transfer catalyst(1), chiral α,α-dialkylated α-cyanoacetates were obtained in high yields with high enantioselectivities up to 94%. Application of the present reaction to the synthesis of a variety of β-amino acids and naturally occurring products, which have a chiral quaternary carbon center, is under investigation.

fig.1