A β-lactam-based stereoselective access to β,γ-dihydroxy α-amino acid-derived peptides with either α,β-like or unlike configurations

A concise access to alpha,beta -dihydroxy alpha -amino acid-derived N-carboxy anhydrides (NCAs) with either like or unlike relative configuration is described. The key steps of the synthetic route are the preparation of the nonracemic Li-alkenyl beta -lactams, through either Horner-type olefination of a common 4-formyl beta -lactam or the Corey-Winter alkene synthesis applied to 4-dihydroxyalkyl beta -lactams, followed by the Sharpless AD reaction, and a subsequent ring expansion of the corresponding 4-substituted 3-hydroxy beta -lactams promoted by TEMPO. The opening of thus-prepared NCAs upon treatment with different O- and N-nucleophiles, including alpha -amino esters which lead to peptides, has also been studied under various reaction conditions.