Efficient and stereoselective synthesis of (S)-α-propargylglycine derivatives from allenylboronic acid

The Petasis–Mannich reaction of allenylboronic acid with glyoxylic acid and (S)-1-phenylethylamine diastereoselectively leads to N-substituted propargylglycine of high optical purity in good yield. This product can be further subjected to esterification followed by bioconjugate synthesis using Cu^I-catalyzed alkyne–azide 1,3-dipolar cycloaddition reaction (‘click reaction’).