Solid-state structure of cyclic dipeptides: an X-ray and computational study of cis- and trans-diketo-piperazines of N-methyl-phenylalanine with the thia-pipecolic acids and thia-prolines

0483865 - ÚOCHB 2018 RIV GB eng J - Journal Article
Buděšínský, Miloš - Císařová, I. - Borremans, F. - Martins, J. C. - Pauwels, E.
Solid-state structure of cyclic dipeptides: an X-ray and computational study of cis- and trans-diketo-piperazines of N-methyl-phenylalanine with the thia-pipecolic acids and thia-prolines.
Acta Crystallographica Section B-Structural Science Crystal Engineering and Materials. Roč. 73, č. 6 (2017), s. 1179-1193. E-ISSN 2052-5206
Institutional support: RVO:61388963
Keywords : sulfur-containing cyclic dipeptides * X-ray crystal structures * DFT calculations * molecular flexibility
OECD category: Physical chemistry
Impact factor: 6.467, year: 2017

Ten new crystal structures of cis and trans bicyclic diketopiperazines (DKPs) of thia-pipecolic acid (with sulfur in the beta, gamma or delta position) or thia-proline (with sulfur in the beta or gamma position) and N-methyl phenylalanine [(NMe) Phe]: cyclo[(beta-S) Pip-(NMe) Phe], cyclo[(gamma-S) Pip-(NMe) Phe], cyclo[(delta-S) Pip-(NMe) Phe], cyclo[(beta-S) Pro-(NMe) Phe] and cyclo[(beta-S) Pro-(NMe) Phe] were determined with X-ray crystallography. Density functional theory calculations of these molecules in the gas phase succeed in reproducing the observed molecular conformations in the crystal remarkably well. This illustrates the weak to moderate impact of intermolecular packing forces in the absence of classical N-H center dot center dot center dot center dot O hydrogen bonds. The effect of sulfur on the geometry of the DKP ring and details of amide bond non-planarity are discussed. Molecular flexibility of the DKP ring, as estimated from the calculated deformation energies of its endocyclic ring torsion angles, is not in general the decisive factor for the occurrence of multiple symmetry independent molecules in the unit cell (Z' > 1), though in some cases a correlation is observed.
Permanent Link: http://hdl.handle.net/11104/0279033