Structural reinvestigation of two diastereoisomeric aspidosperma–eburnea type bis‐indoles by NMR methods. Detection of a ‘hidden’ exchange partner and implications in noe analysis

Csaba Szántay, Ádám Demeter, Katalin Honty, P. Kolonits, Csaba Szántay

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

Full 1H and 13C assignments are reported for two aspidosperma—eburnea type diastereoisomers. Homonuclear NOE difference measurements revealed that the previously reported configurational assignment of these compounds is in error. More interestingly, rotation about the bond connecting the two indole units is hindered in both molecules and gives a strongly biased two‐site chemical exchange system. At room temperature the exchange rates are slow on the chemical shift time‐scale with regard to certain 1H signals. In addition, the exchange rates are such that the signals due to the minor component are broadened to the extent that they escape detection in a conventional 1H spectrum, whereas only a very small amount of broadening is observed on the main signals. The presence of this ‘hidden’ exchange partner can give rise to peculiar effects in the NOE difference spectra. Such spurious effects can be the source of misinterpretation if the existence of the ‘silent partner’ goes unnoticed. Thermodynamic parameters are evaluated based on earlier work addressing the problem of the ‘hidden’ exchange partner.

Original languageEnglish
Pages (from-to)773-785
Number of pages13
JournalMagnetic Resonance in Chemistry
Volume31
Issue number8
DOIs
Publication statusPublished - 1993

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Chemical shift
Nuclear magnetic resonance
Thermodynamics
Molecules
Temperature
indole

Keywords

  • H NMR C NMR Aspidosperma–eburnea diastereoisomers
  • Conformational analysis Thermodynamic parameters
  • Molecular mechanics
  • NOE difference
  • Revised configuration
  • ‘Hidden’ exchange partner

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)

Cite this

Structural reinvestigation of two diastereoisomeric aspidosperma–eburnea type bis‐indoles by NMR methods. Detection of a ‘hidden’ exchange partner and implications in noe analysis. / Szántay, Csaba; Demeter, Ádám; Honty, Katalin; Kolonits, P.; Szántay, Csaba.

In: Magnetic Resonance in Chemistry, Vol. 31, No. 8, 1993, p. 773-785.

Research output: Contribution to journalArticle

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