Intramolecular H‐bonds and thioamide rotational isomerism in thiopeptides
- 1 August 1990
- journal article
- research article
- Published by Wiley in International Journal of Peptide and Protein Research
- Vol. 36 (2), 173-181
- https://doi.org/10.1111/j.1399-3011.1990.tb00963.x
Abstract
Mono- and dithionated N-acyl amino acid and dipeptide N''-methylamides were synthesized using Lawesson''s reagent and S-thioacetyl thioglycolic acid. The conformation of the thionated models was characterized by IR, 13C, and 1H NMR spectroscopy, including NOE experiments. The formation of .sbd.C.dbd.S...H.sbd.N.sbd.C.dbd.X (X = O or S) intramolecular H-bonds of the types 2 .fwdarw. 2, 1 .fwdarw. 3 and 1 .fwdarw. 4 was evidenced by the characteristic shifts of the IR stretching frequencies of the NH group. Act-Pro-NHCH3 (4) and Act-Prot-NHCH3 (5) were found to be present as mixtures of rotational isomers about the CS.sbd.N bond. 13C chemical shifts of the .gamma.- and .beta.-carbons of the proline ring elucidated the conformation (Z or E) the tertiary thioamide group. Our results suggest that the conformation of thiopeptides is determined by two factors: 1) the H-bond donating and accepting ability of the thioamide group and 2) the repulsion between the thiocarbonyl sulfur atom and the side chain groups of the neighbouring amino acid residues.Keywords
This publication has 24 references indexed in Scilit:
- Molecular and crystal structures of three monothiated analogues of the terminally blocked ala‐aib‐ala sequence of peptaibol antibioticsBiopolymers, 1988
- Stereochemistry of peptides containing a thioacyl groupInternational Journal of Peptide and Protein Research, 1987
- Comments on absorption in Takagi–Taupin equationsActa Crystallographica Section A Foundations of Crystallography, 1987
- Mean geometry of the thiopeptide unit and conformational features of dithiopeptides and polythiopeptidesBiochemical and Biophysical Research Communications, 1987
- Structure of the thiopeptide (Z)-Glyt-Gly-OBzlActa Crystallographica Section C Crystal Structure Communications, 1987
- Synthesis and biological activity of monothionated analogs of leucine‐enkephalinInternational Journal of Peptide and Protein Research, 1984
- Evidence of a peptide backbone contribution toward selective receptor recognition for leucine enkephalin thioamide analogsBiochemical and Biophysical Research Communications, 1984
- Synthesis and biological activities of pseudopeptide analogues of LH-RH: Agonists and antagonistsBiochemical and Biophysical Research Communications, 1980
- Stable conformations of dipeptidesBiopolymers, 1973
- Thiobenzoylation of Esters and Amides of alpha-Amino Acids.Acta Chemica Scandinavica, 1950