Reversal of Diastereoselectivity in a Masked Acyl Cyanide (MAC) Reaction: Synthesis of Protected erythro-β-Hydroxyaspartate Derivatives.

Using Garner's aldehyde as a substrate, one-pot MAC hydroxyhomologation reactions proceeded in good yields and with anti selectivity for the first time (dr up to 9:1). The products were used to prepare a panel of protected derivatives of erythro-β-hydroxyaspartic acid and erythro-β-hydroxyasparagine as single enantiomers in a few steps.