An oxazol-5(4H)-one from benzyloxy­carbonyl-(Aib)₄-OH

Benzyl N-[8-(4,4-dimethyl-5-oxo-4,5-dihydrooxazol-2-yl)-2,5,5,8-tetra­methyl-3,6-dioxo-4,7-diazanon-2-yl]­carbamate, C₂₄H₃₄N₄O₆, an oxazol-5(4H)-one from N-α-benzyloxycarbonyl-(Aib)₄-OH (Aib = α-amino­isobutyryl) represents the longest peptide oxazolone so far characterized by X-ray diffraction. The overall geometry of the oxazolone ring compares well with literature data. The Aib(1) and Aib(2) residues are folded into a type III β-bend, while the conformation adopted by Aib(3), preceding the oxazolone moiety, is semi-extended. The disposition of the oxazolone ring relative to the preceding residue is stabilized by C—­H⋯N and C—H⋯O intramolecular interactions.