Chiroptical properties and solution conformations of protected endothiodipeptide esters

M. Kajtár, M. Hollósi, J. Kajtár, Zs. Majer, K. Kövér

Research output: Contribution to journalArticle

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Abstract

The syntheses and CD spectra in different solvents are described for four series of N-benzyloxycarbonyl-endothiodipeptide esters of types a-d with Ala, Val, Phe and Pro residues. Difference 1H NOE and IR measurements were also performed on selected models. The spectroscopic evidence pointed to the existence of two main conformers in solution. Conformation A, predominating in nonpolar solvents, can be characterized as a folded C7C5 form with a bifurcated system of intramolecular H-bonds formed by the thioamide N-H and the CO groups of the N-terminal urethane and the C-terminal ester moieties. Conformation B, the major conformation in H-bond-accepting solvents such as DMSO, is more extended and flexible in the N-terminal region and assumes a "proline-like" rotamer state (φ2 ~ -60°) at the C-terminus. The sign and magnitude of the Cotton effect due to the n →π* transition (near 350 nm) can be rationalized with an octant-like sector rule. The optical activity of the π→π* transition is determined in part by exciton interaction of the thioamide with the urethane and/or ester chromophores. Through application of the sector rule, finer details of the correlation between the chiroptical properties and the conformation can be explained.

Original languageEnglish
Pages (from-to)3931-3942
Number of pages12
JournalTetrahedron
Volume42
Issue number14
DOIs
Publication statusPublished - 1986

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Thioamides
Conformations
Esters
Urethane
Optical Rotation
Carbon Monoxide
Dimethyl Sulfoxide
Proline
Chemical bonds
Chromophores
Cotton

ASJC Scopus subject areas

  • Biochemistry
  • Organic Chemistry
  • Drug Discovery

Cite this

Chiroptical properties and solution conformations of protected endothiodipeptide esters. / Kajtár, M.; Hollósi, M.; Kajtár, J.; Majer, Zs.; Kövér, K.

In: Tetrahedron, Vol. 42, No. 14, 1986, p. 3931-3942.

Research output: Contribution to journalArticle

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