Synthesis of a Gln-Phe Hydroxy-ethylene Dipeptide Isostere

The protected Gln-Phe hydroxyethylene dipeptide isostere 1 was synthesized as a precursor for preparation of potential inhibitors of Botulinum neurotoxin B metalloprotease. The method allows for the synthesis of additional hydroxyethylene dipeptide isosteres such as 2 with functionalized P₁ side chains. The isosteres prepared were coupled with a dipeptide to produce protected pseudotetrapeptide derivatives.