Ultrasound-Promoted Enantioselective Decarboxylative Protonation of alpha-Aminomalonate Hemiesters by Chiral Squaramides: A Practical Approach to Both Enantiomers of alpha-Amino Esters
EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, v.2017, no.31, pp.4562 - 4565
Abstract
Herein, we report an ultrasound-promoted enantio-selective decarboxylative protonation reaction of alpha-aminomalonate hemiesters 1 in the presence of chiral cinchona-derived squaramide Bronsted bases under mild conditions, which afforded both the (S)- and (R)-enantiomers of alpha-amino acid derivatives 2 in excellent yields (>90 %) and excellent enantioselectivities (up to 98 % ee).