A concise synthesis of α-amino acid N-carboxy anhydrides of (2S,3S)-β-substituted serines

A general access to 3-hydroxy-4-(1-hydroxyalkyl)-β-lactams with a C4–C1′ relative configuration unlike is provided. The subsequent oxidative ring expansion of the corresponding 3-hydroxy β-lactam smoothly affords an α-amino acid N-carboxy anhydride (NCA) formally derived from (2S,3S)-β-substituted serine, which upon sequential peptide coupling furnishes the tripeptide segment 2, present in lysobactin.