A convenient route to α-amino acids with β-alkyne substituents from a serine derived aziridine

1-[(S)-1-(2-Nitrobenzenesulfonyl)-aziridin-2-yl]-4-methyl-2,6,7-trioxabicyclo[2.2.2]octane 5 was ring opened regioselectively with a variety of lithium acetylides to give α-amino acids bearing γ,δ-unsaturation in very good to excellent yields. The 2-nitrobenzenesulfonyl and OBO ester protecting groups were removed in excellent overall yield.