Cyclo(l-leucyl-α,β-dehydro-phenyl-alanine): the first diketopiperazine containing an α,β-dehydro-phenyl-alanine residue

Abstract

The title compound (systematic name: 3-benzyl-idene-6-iso-butyl-piperazine-2,5-dione), C₁₅H₁₈N₂O₂, an α,β-dehydro-phenyl-alanine containing diketopiperazine, crystallizes in the space group P1 with two mol-ecules in the asymmetric unit arranged antiparallel to one another. The α,β-dehydro-phenyl-alanine (ΔPhe) residue in this cyclic peptide retains its planarity but deviates from the standard conformations observed in its linear analogues. Each type of mol-ecule forms a linear chain with mol-ecules of the same type via pairwise N-H···O hydrogen bonds, while weaker C-H···O inter-actions link the chains together to form a three-dimensional network.