Stereodivergent Approach to β-Hydroxy α-Amino Acids from C₂-Symmetrical Alk-2-yne-1,4-diols

A new stereodivergent route to erythro- and threo-β-substituted serines from a common C₂-symmetrical alk-2-yne-1,4-diol is described. Stereocontrol in such an acyclic system is achieved by taking advantage of symmetry. Stereoselective alkyne reduction to either (Z)- or (E)-olefin allows selection of the stereochemistry of α-carbon in the final amino acid by using a Pd(0)-catalyzed process. This strategy has been applied to the synthesis of (2S,3S)-3-hydroxyleucine.