Ultrasound Promoted Enatioselective Decarboxylative Protonation of α-Aminomalonate Hemiesters by Chiral Squaramides: A Practical Approach to Both Enantiomers of α-Amino Esters

Ultrasound promoted enantioselelctive decarboxylative protonation reaction of α-aminomalonate hemiesters 1 in the presence of chiral cinchona-derived squaramide Brønsted bases under mild conditions afforded both the (S) and (R) enantiomers of α-amino acid derivatives 2 in excellent yields (>90%) and excellent enantioselectivities (up to 98% ee).

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