Publication Date:
2014-12-26
Description:
The title compound, cyclo(Phe1–d-Ala2–Gly3–Phe4–APO5), C26H32N4O5, is the minor diastereoisomer of a cyclic penta-peptidomimetic analogue containing a novel 2-aminopropyl lactone (APO) motif, which displays the same number of atoms as the native amino acid glycine and has a methyl group in place of the carbonyl O atom. The crystal structure presented here allows the analysis of the secondary structure of this unprecedented cyclic carbo-isosteric depsipeptide. The conformation of the central ring is stabilized by an intramolecular N—H...O hydrogen bond between the carbonyl O atom of the first residue (Phe1) and the amide group H atom of the fourth residue (Phe4). Based on the previously reported hydrogen bond and on the values of the torsion angles ϕ and ψ, the loop formed by the first, second, third and fourth residues (Phe1, d-Ala2, Gly3 and Phe4) can be classified as a type II′ β-turn. The loop around the new peptidomimetic motif, on the other hand, resembles an open γ-turn containing a weak N—H...O hydrogen bond between the carbonyl group O atom of the fourth residue (Phe4) and the amide unit H atom of the first residue (Phe1). In the crystal, the peptidomimetic molecules are arranged in chains along the b-axis direction. Within such a chain, the molecules of the structure are linked via N—H...O hydrogen bonds between the amide group H atom of the secondary residue (d-Ala2) and the carboxy unit O atom of the fourth residue (Phe4) in a neighboring molecule. The newly formed methyl stereocentre of the APO peptidomimetic motif (APO5) was obtained as the minor diastereoisomer in a ring-closing reductive amination reaction and adopts an R configuration.
Keywords:
crystal structuredepsipeptidepeptidomimeticcarbo-isosterβ-turnγ-turn
Electronic ISSN:
1600-5368
Topics:
Chemistry and Pharmacology
,
Geosciences
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