Asymmetric synthesis of novel quaternary α-Hydroxy-δ-lactam dipeptide surrogates

Application of the Sharpless AD protocol to a series of α-(E)-benzylidene-δ-lactam precursors followed by selective deoxygenation provided efficient synthetic routes to the chiral quaternary α-hydroxy-γ-lactam derivatives 4 and 5. These functionalized intermediates and the diol precursors 3 are regarded as novel types of D-Phe-Pro dipeptide surrogates that are useful as enzyme active site probes.