Practical one-step synthesis of ethynylglycine synthon from Garnerʹs aldehyde

A simple, efficient and practical synthesis of (R)-2,2-dimethyl-3-(tert-butoxycarbonyl)-4-ethynyloxazolidine (ethynylglycine synthon) is described. The method involves in situ formation of dimethyl 1-diazo-2-oxopropyl phosphonate from dimethyl 2-oxopropyl phosphonate and 4-acetamidobenzene sulfonyl azide and one-pot reaction on Garnerʹs aldehyde. The reaction has been extended to other aminoaldehydes.