An Fe-catalyzed highly regio- and diastereoselective reaction of 4-ethynyloxetan-2-ones with different Grignard reagents affording alkynes 3 in good yields with absolute configuration of the β-carbon atom completely inverted has been developed. The optically active acids may be easily converted to esters, which may easily undergo desilylation and highly diastereoselective allenylation to afford optically active 4,5-allenoates with two chiral centers and one axial allene chirality.